ISSN: 2603-4018 eISSN: 2603-4646

INTERNATIONAL JOURNAL

for science, techniques and innovation for non-destructive inspection

and material evaluation for the industries

NDT DAYS

Volume II / Issue 2 Year 2019

Published by Bulgarian Society for Non-Destructive Testing Member of ICNDT and EFNDT

International Journal “NDT Days”

ISSN: 2603-4018, eISSN: 2603-4646

PUBLISHER: Bulgarian Society for NDT (BG S NDT)

FOUNDERS: Bulgarian Society for NDT, Institute of Mechanics at the Bulgarian Academy of Sciences The scope of the journal is aimed to all methods and techniques of non-destructive and destructive testing, as well as evaluation of materials and structures in all areas of technical activities. It is an opportunity to publish research and development results, together with good practices and recommendations for standardization. Submitted manuscripts should not have been published previously and should not be currently under consideration for publishing elsewhere. They should be prepared in accordance with the Instructions for Authors, published on the journal site. The articles appearing in the Journal are indexed in NDT Net.

THEMATIC FIELDS

1. Non-destructive inspection methods - Non-destructive testing methods (ultrasonic, penetrant, magnetic, visual,

infrared thermography, radiography, leek, etc.); - Non-destructive and destructive inspection of the integrity, structure and

physico-mechanical properties of materials; - Application of non-destructive and destructive testing methods for

inspection in energy, transport, engineering, construction, chemical industry, etc.;

- Structural health monitoring of equipment and structures with non-destructive testing methods (vibration diagnostics, acoustic emission, infrared thermography, etc.);

- Advanced non-destructive testing methods and techniques (phased array, TOFD, computer and digital radiography, tomography, automatic system for inspection, shearography, etc.);

- Training, certification, accreditation and standardization in scope of non-destructive inspection and conformity assessment of materials, equipment and structures.

2. Techniques for material processing and condition monitoring of equipment - Design and construction; - Life cycle condition monitoring; - Material sciences; - Manufacturing, exploitation, maintenance and repair; - Innovation methods and techniques for modernization; - Metal casting, welding, soldering bonding, machining, surface

treatment; - Mathematical modeling of technological processes; - Load treatment and deformation; - Training.

OFFICIAL LANGUAGES: Bulgarian, English and Russian

EDITORIAL BOARD

EDITOR IN CHIEF Mitko MIHOVSKI, President of BG S NDT, Sofia, Bulgaria

DEPUTY EDITOR IN CHIEF Peter DJONDJOROV, Institute of Mechanics at the Bulgarian Academy of Sciences, Sofia, Bulgaria

SCIENTIFIC SECRETARIES Yordan MIRCHEV, Institute of Mechanics at the Bulgarian Academy of Sciences, Sofia, Bulgaria Krassimira IVANOVA, Institute of Mathematics and Informatics at the Bulgarian Academy of Sciences, Sofia, Bulgaria

MEMBERS Victor CHIRIKOV, Technical University of Varna, Varna, Bulgaria Pavel CHUKACHEV, Multitest Ltd., Varna, Bulgaria Dimitar DIMOV, University of Architecture, Civil Engineering and Geodesy, Sofia, Bulgaria Hristo DRAGANCHEV, Technical University – Varna, Varna, Bulgaria Grigorii DYMKIN, Emperor Alexander I St. Petersburg State Transport University, Saint-Petersburg, Russia Borislav GENOV, Defence Institute “Prof. Tsvetan Lazarov”, Sofia, Bulgaria Ivan GEORGIEV, Institute of Information and Communication Technologies at the Bulgarian Academy of Sciences, Sofia, Bulgaria Eduard GORKUNOV, Institute of Engineering Science, Ural Branch of the Russian Academy of Science, Ekaterinburg, Russia Janez GRUM, University of Ljubljana, Slovenia Yonka IVANOVA, Institute of Mechanics at the Bulgarian Academy of Sciences, Sofia, Bulgaria Vasil KAVARDJIKOV, Institute of Mechanics at the Bulgarian Academy of Sciences, Sofia, Bulgaria Ivan KOLAROV, Todor Kableshkov University of Transport, Sofia, Bulgaria Vladimir KOSTIN, M.N. Mikheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences; Yekaterinburg, Russia

Vadim KOVTUN, Gomel Branch of the University of Civil Protection of the Ministry for Emergency Situations of the Republic of Belarus, Gomel, Belarus Sergey KRIVOSHEEV, Peter the Great Polytechnic University, Saint Petersburg, Russia Emil MANOAH, Institute of Mechanics at the Bulgarian Academy of Sciences, Sofia, Bulgaria Svetozar MARGENOV, Institute of Information and Communication Technologies at the Bulgarian Academy of Sciences, Sofia, Bulgaria Boris MIHAYLOV, SPECTRI Ltd, Sofia, Bulgaria Giuseppe NARDONI, International Academy on NDT, Brecia, Italy Alexander NAZARYTHEV, Federal State Educational Establishment “PEIPK”, Saint Petersburg, Russia Amos NOTEA, Technion, Israel Institute of Technology, Haifa, Israel Anna POVOLOTSKAYA, Institute of Engineering Science, Ural Branch of the Russian Academy of Science, Ekaterinburg, Russia Vladimir PROHOROVICH, ITMO University, Saint Petersburg, Russia Nikolay RAZYGRAEV, State Reseach Center of Russian Federation CNIITMASH, Moscow, Russia Vladimir SERGIENKO, V.A. Belyi Metal-Polymer Research Institute of the NAS of Belarus”, Gomel, Belarus Yossi SHOEF, Israeli National Society for NDT, Tel Aviv, Israel Alexandar SKORDEV, Certification Center for NDT Personnel at the Bulgarian Society for NDT, Bulgaria Marin STOYCHEV, Institute of Metal Science, Equipment, and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski”, Sofia, Bulgaria Maciej SULOWSKI, AGH University of Science and Technology, Krakow, Poland Alexey TADJIBAEV, Federal State EducationalEstablishment “PEIPK”, Saint Petersburg, Russia Vasiliy TITKOV, Peter the Great Polytechnic University, Saint Petersburg, Russia Vladimir TROITSKY, E. O. Paton Electric Welding Institute of the NAS of Ukraine, Kiev, Ukraine Valeriy VENGRINOVICH, Institute of Applied Physics of the NAS of Belarus, Minsk, Belarus

EDITORIAL OFFICE: International Journal “NDT Days”

Institute of Mechanics, Bulgarian Academy of Sciences Acad. G. Bonchev Str., Block 4, Sofia – 1113, Bulgaria phone: +359 2 9797120 e-mail: ndtdays@abv.bg http://www.bg-s-ndt.org/journal.html

Publishing of Volume II (2019) of the International Journal “NDT Days” is partially financed by TU-Varna under the project NF-2/2019

123

Table of Contents

Possibilities of Optimizing the Processing of Metallic Radioactive Waste ........................... 125 Yavor LUKARSKI, Christo ARGIROV

Structural Researches on Wear-Resistant Steels Using the Centrifugal Metal Cast Method ................................................................................................................................... 134

Hristo ARGIROV, Ivan GEORGIEV, Yavor LUKARSKI Структурни изследвания на износоустойчиви стомани, произведени по метода на центробежното металолеене

Христо АРГИРОВ, Иван ГЕОРГИЕВ, Явор ЛУКАРСКИ

Thermo-mechanical Study of the Cu-Zr Ribbon with 2% V Addition for Amorphous-nano Crystalline Composites .................................................................................................. 141

Georgi STEFANOV, Tomasz CZEPPE, Stoyko GYUROV, Katarzana JANIK, Anna WIERZBICKA-MIERNIK

Obtaining of ZrNiCuAl Alloys with Nano-microcrystalline Structure in Argon-arc Furnace ................................................................................................................................... 153

Mihail KOLEV, Lyudmil DRENCHEV, Georgi STEFANOV, Stoyko GYUROV, Yordan GEORGIEV Получаване на ZrNiCuAl сплави с нано-микрокристална структура в аргоно-дъгова пещ

Михаил КОЛЕВ, Людмил ДРЕНЧЕВ, Георги СТЕФАНОВ, Стойко ГЮРОВ, Йордан ГЕОРГИЕВ

Application of ZrO2 and ZrO2-TiO2 Coatings as Corrosion Barriers: Surface Composition and Structure .......................................................................................................................... 160

Irina STAMBOLOVA, Ognian DIMITROV, Stancho YОRDANOV, Lyuben LAKOV, Bojidar JIVOV, Sasho VASSILEV, Vladimir BLASKOV, Maria SHIPOCHKA

Magnetron Deposition of the Thin Coatings with High Dielectric Permeability on the Alloy Steel .............................................................................................................................. 165

Lyuben LAKOV, Mihaela ALEKSANDROVA, Petio IVANOV, Timur NURGALIEV Магнетронно разпрашаване на тънки слоеве с висока диелектрична проницаемост върху подложка от легирана стомана

Любен ЛАКОВ, Михаела АЛЕКСАНДРОВА, Петьо ИВАНОВ, Тимур НУРГАЛИЕВ

Technology for Production and Experimental Furnace for Hitting of Article "Yellow Bricks" .................................................................................................................................... 169

Marieta GACHEVA, Lyuben LAKOV, Krasimira TONCHEVA

Analysis of the Test Results of the Installation for Receiving the Foam Glass Continuous Tape and Suggestion for its Improvement ............................................................................. 173

Krasimira TONCHEVA, Lyuben LAKOV

124

Technology for the Preparation of White and Colored Petrurgical Materials on the Basis of Sedimentary Rocks ............................................................................................................ 182

Marieta GACHEVA, Lyuben LAKOV, Bojidar JIVOV, Kamelya MARINOVA, Stancho YORDANOV, Stefan RAFAILOV

Технология за получаване на бели и цветни петрургични материали на база седиментни скали

Мариета ГАЧЕВА, Любен ЛАКОВ, Божидар ЖИВОВ, Камелия МАРИНОВА, Станчо ЙОРДАНОВ, Стефан РАФАИЛОВ

Composite Materials Obtained from Foamed Silicate Products ............................................ 188 Lyuben LAKOV, Bojidar JIVOV, Yonka IVANOVA, Stancho YORDANOV, Marin MARINOV, Stefan RAFAILOV

Композитни материали получени от разпенени силикатни продукти Любен ЛАКОВ, Божидар ЖИВОВ, Йонка ИВАНОВА, Станчо ЙОРДАНОВ, Марин МАРИНОВ, Стефан РАФАИЛОВ

Phase Composition of TRIP-Steels after Aging ..................................................................... 195 Margarita ILIEVA, Stoyan PARSHOROV

Austenite Stability of TRIP-Steels ......................................................................................... 199 Stoyan PARSHOROV, Peter PETROV, Stefan VALKOV

Behavior of the High-temperature Background of Internal Friction by Martensite Phase Transformation in Fe-20% Ni ................................................................................................ 205

Ivan PARSHOROV, Stoyan PARSHOROV

Study the Influence of the Limit Contents of Alloying Elements and Heat Treatment on the Mechanical Properties and Structure, in Characteristic Areas of Automobile Wheels from AlSi7Mg0.3 Alloy, Cast under Low Pressure ............................................................... 210

Lenko STANEV, Anna MANEVA, Sergey STANEV, Mihail GEORGIEV Изследване влиянието на граничните стойности на легиращите елементи и термичната обработка върху механичните свойства и структурата в характерни зони на автомобилни колела, отляти под ниско налягане от сплав AlSi7Mg0.3

Ленко СТАНЕВ, Анна МАНЕВА, Сергей СТАНЕВ, Михаил ГЕОРГИЕВ

Material Science – Chemical Analysis and K-test with Zone Melting of Metals and Alloys ..................................................................................................................................... 217

Anna MANEVA, Stefan BUSHEV

Foundry-Gas Pressing Method ............................................................................................... 224 Angel VELIKOV, Stefan BUSHEV

Material Science – Mathematics and Mathematical Physics in Alloys and Other Materials for Foundry ............................................................................................................................. 230

Stefan BUSHEV

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

125

Possibilities of Optimizing the Processing of Metallic Radioactive Waste

Yavor LUKARSKI, Christo ARGIROV Institute of metal sciences, equipment and technologies with hydro and aerodynamics centre “Acad. A. Balevski,

Bulgarian Academy of Sciences Sofia 1574, Shipchenski prohod 67, Bulgaria,

e-mail: lukarski@ims.bas.bg, h.argirov@ims.bas.bg Abstract These instructions have been prepared to assist authors in the preparation of papers for reproduction in Journal NDT Days. The instructions should be followed in all matters of format including section headings, capitalisation, punctuation, table and figure headings and their placement within the text. These guidelines are to ensure maximum uniformity of style and reproduction without further modifications – please try to follow them as closely as possible. Keywords metallic radioactive waste, radioactivity, waste optimization, hydrometallurgical treatment, pyrometallurgical deactivation 1. Introduction The recycling of radioactive waste (RAW) from operating and closed units of nuclear facilities is an extremely complex environmental and, at the same time, technological problem. The main problem to solve in the utilization of such wastes is to reduce the radioactivity degree with the aim of their possible future use. In case that this is impossible, these wastes should be compacted, so that they do not occupy much space during their ground disposal. This is due to the fact that the decommissioned metals are with different dimensions and configurations – thin and thick sheets, tubes with various diameters and wall thickness, V-shaped and other forms of the metal elements, used in the construction of nuclear units. Reduction in volume is achieved only by remelting the metallic waste and casting the liquid metal in crucibles of appropriate volume and shape. Thus the amount of metal deposited for storage is diminished from 20 to 50 times. The following methods for MRAW deactivation are known:

− Mechanical deactivation. The process is called “blasting” and is carried out in closed chambers by jet crushing machines. The fragments of the radioactive waste are treated with small cast iron balls (pellets), sand or other mineral materials, which are shot under pressure by the jet machine. Here the problem consists in the utilization of the radioactively contaminated wastes and their possible return to the chamber;

− Hydrometallurgical methods. They include the use of concentrated or dilute solutions of various reagents, in which radioactively contaminated preliminary segmented parts of metal, covered by organic coatings – lacquer, paint, etc., are immersed. The desired degree of deactivation is achieved by controlling the time of sojourn of the contaminated metal in the solution. The criticism on the methods for chemical deactivation is directed to the complicated technology of processing of solutions and slurries obtained after decontamination and the further utilization of solid radioactive waste and polluted radioactive water. A variaty of chemical deactivation is the electrochemical one, which is considered as a variant of chemical deactivation in an electric field.

126

− Pyrometallurgical methods. They include cutting and fragmentation of MRAW with subsequent melting, treatment with fluxes and casting in crucible molds.

At the present stage in many of the countries with advanced nuclear power generation researches are carried out on the development of technologies and installations for MRAW processing with the aim of reducing the volume of solid radioactive waste subjected to ground disposal, as well as utilizing part of the metal for its secondary use. An optimal solution of the utilization problem, providing the return of metal in industry for reuse, is to apply at the last stage of MRAW processing the method of remelting in various types of furnaces and to obtain metal blocks as the final product. Depending on the residual contamination of the metal, these blocks can be used in industry without any restrictions or with restrictions as protective screens, containers for RAW, etc. Another possibility for MRAW utilization is their storage in special repositories till the final decay of the radionuclides in them. One of the main advantages of MRAW deactivation by remelting is the redistribution of heavy radionuclides between the metal blocks, slag and filter dust. Table 1 shows the distribution of the major part of the radioactive isotopes found in MRAW between the molten metal, slag and dust from air purging filters [1].

Table 1. Distribution of radioactive isotopes between the metal, slag and dust from air purging filters.

Nuclide Metal, % Slag, % Dust, %

Mn54 24-100 1-75 0-5 Co60 20-100 0-1 0-80 Zn65 0-20 0-1 80-100 Sr90 0-20 95-100 0-10 Cs137 0 0-5 95-100

U 0-1 95-100 0-5 Pu 0-1 95-100 0-5

Am241 0-1 95-100 0-5 The rest part represents heavy isotopes such as Cs137, Ru106, Sr90, etc. [2]. The studies of specialists from MRAW utilization companies [2, 3] show that the removal (completely or partially) of heavy nuclides is achieved by introducing flux additives in the molten metal in the amount of 2 to 10%. 2. Specific instructions Three types of melting aggregates are usually applied for the metallurgical deactivation of MRAW: 2.1 Electro resistive furnaces They are mainly used for compaction of non-ferrous metal waste. These are cables, insulation screens, sheathings of aggregates and pipes, etc. Their maximum operation temperature is 1250°C and they can usually process up to 600 kg of metal waste. Fig. 1 shows a drawing of such a furnace. Its bottom should be movable.

127

Fig. 1. Scheme of an electro resistive furnace with a movable bottom. 1 – furnace carriage; 2 – door; 3 – furnace insulation;

4 – heaters; 5 – rails for the carriage

Once the above described processes are completed, the furnace is switched off, the container moves out of it and the block is cooled. The container is opened, the slag is removed and the block is taken out. It is subjected to radiation control and depending on the degree of radioactive contamination it is shipped according to the existing scheme. 2.2 Electric arc furnaces These are metallurgical aggregates, in which the heat for melting is produced by an electric arc, formed by graphite electrodes and the introduced scrap. As a rule they are used for remelting of steel RAW. These furnaces are not very suitable for remelting of MRAW due to the difficult access to the furnace because of the complex construction of its lid and the restricted possibilities of introducing refining fluxes. The scheme of such a furnace is shown in Fig. 2. The refining processes in the electric arc furnaces proceed usually in an additional vessel. 2.3 Induction crucible furnaces These are the most commonly used aggregates in the metallurgical deactivation of MRAW. The induction crucible furnaces find wide application in the industry of remelting ferrous and non-ferrous metals in air, vacuum and protective atmosphere. The induction crucible furnaces are used mainly for melting high-quality steels and other special alloys, requiring especial purity, structural homogeneity and precise chemical composition. They are used for melting both steel elements from nuclear facilities and elements of copper and copper alloys. A scheme of such a furnace is shown in Fig. 3. The crucible induction furnaces have the following disadvantages:

− Relatively low temperature of the slag. The relatively cold slags hamper the proceeding reactions between the metal and slag and hence, hamper the refining processes. This is not a problem in the metallurgical deactivation of MRAW in the induction furnace because the amount of the slag obtained is small (3-5% of the metal mass);

− Relatively high cost of the equipment. However, this applies only to furnaces with a frequency above 50 Hz. The aggregates used at present for metallurgical deactivation generally do not exceed this frequency.

128

The combination of such advantages and disadvantages of the induction crucible furnaces determines the scope of their application, namely: melting of alloyed and non-alloyed steels, cast iron, heavy and light non-ferrous metals and alloys, rare and precious metals. This makes them extremely convenient for use in the metallurgical deactivation of MRAW from nuclear power plants.

Fig. 2. Scheme of a three-phase electric arc furnace 1 – lower metal casing of the furnace;

2 – launder for pouring the liquid metal; 3 – scrap; 4 – casing; 5 – refractory masonry;

6 – furnace lid; 7 – wire lines; 8 – devices feeding electric current to the electrodes;

9 – electrodes; 10 – slag pouring opening; 11 – device for tilting the furnace and pouring the

metal; 12 – refractory packing at the furnace bottom.

Fig. 3. Induction furnace, used by the Siempelkamp company:

1 – inductor; 2 – crucible; 3 – liquid metal; 4 – scheme for electromagnetic vortexing of

the metal; 5 – slag layer; 6 – furnace insulation.

3. Equipment for MRAW recycling in Europe Since 1989 the technological department of the Siempelkamp engineering division in Germany has operated CARLA, an enterprise for recycling low-level RAW [3]. The equipment processes the metal waste with lower activity by blasting (to remove surface contamination) or remelting. The contaminated residues are recycled to new products in the nuclear industry. If the release requirements are met, the metal can be placed on the free market. Both after the surface treatment and remelting of the metal, a small volume of radioactive residue remains, which is returned to the shipper for ground disposal. Characteristics of the installation of Siempelkamp, Germany

− Furnace capacity – 3,2 t; − Ingot weight – 1 t; − Allowed quantity of metal for remelting – 4000 t/yr.

Criteria for acceptance of metals in the Siempelkamp installation, Germany: Specific design activity 200 Bq/g; increased in 2008 to 1000 Bq/g (total for α-, β-, γ- radiation); up to 10 000 Bq/g are allowed for Fe55, Ni63, C14 and H3 β- radiation, released materials

129

(U233, U235, Pu239, Pu241) < 15 g/100 kg of scrap, NORM (Ra226, U238, Th232) – 1,000 Bq/g. Some of the facilities and the metal blocks obtained by leading companies are given in Figs. 4, 5. Figs. 4 show moments of the operation on the deactivation process in the Siempelkamp company (Germany) and Fig. 6 presents the process of manual feeding of fluxes in the induction furnace of the Studsvik company, Sweden. This facility has a licensed capacity of 5 000 t/yr, of which no more than 1 000 t may be lead. The technical capacity of the melting installation is about 8 000 t/yr. Except for the melting of metal, it has unique installations for cutting of large gauge facilities, as for example, steam generators. It can process aluminum and zinc plated metals.

Table 2. Characteristics of the production capacity and the field of metal application after the processing

Company Furnace type

Capacity, t Type of metal Production Field of metal

application

Siempelkamp, Germany Induction 3,2

Ferrous, stainless steel, aluminum,copper

Ingots, screens, containers

60% reuse in nuclear facilities; 40% unlimited use

Studsvik, Sweden

Induction for steel, electric arc for aluminum

3 Ferrous, stainless steel, aluminum Ingots

77%-intermediate storage; 13% -free use

INFANTE, Marcoule, France

Electric arc 12 Ferrous, stainless

steel

Ingots, screens, containers

100% – storage and reuse in nuclear facilities

BNFL, Great Britain

Electric arc, induction

3 Ferrous, stainless steel, aluminum Ingots Unlimited use

SEG, USA Induction 20 Ferrous, stainless steel, aluminum

Ingots, screens, containers

Reuse in nuclear facilities

МSС, USA Vacuum, induction 4

Ferrous, stainless steel, non-ferrous metals

Ingots, screens, containers

40% – reuse in nuclear facilities; 60% – unlimited use

Duratek, USA Induction 6 Ferrous, stainless steel, non-ferrous metals

Screens, physical protection

Reuse in nuclear facilities

EKOMET-S, Russia

2number induction furnaces

2,5 0,45

Ferrous, stainless steel, non-ferrous metals

Ingots Ingots

86% – unlimited use; 14% – intermediate storage

Cost of MRAW processing: 4 300 – 6 300 €/t The secondary RAW are returned back to the shipper.

130

The results reported in the presentations of Studsvik Rad Waste [4] prove that the company has a developed technology for remelting radioactively contaminated metals, according to which 80% of the intended for remelting radioactively contaminated metal is deactivated in a form, suitable for unlimited use. This is done by remelting of the metal in induction furnaces and its processing with special fluxes. The latter are bound to the radioactive isotopes forming stable compounds, which pass into the slag.

Fig. 4. Slag scraper appliance used in MRAW remelting by the Siempelkamp company

Fig. 5. Manual feeding of fluxes in an induction furnace of the Studsvik company, Sweden

The Nukem German company is also involved in MRAW remelting. The metals are crushed and surface deactivated prior to remelting. Liquids, flammable and explosive materials, hazardous components, zinc and lead are removed. The elements with closed volumes are cut. Table 3 gives the characteristics of the installation.

Table 3. Characteristics of the installation of Nukem, Germany

VIM 200-NSR Furnace capacity 1,5 t Installed capacity of the furnace AC 400 V, 50 Hz, 1000 kVA Crucible, 1.5 t Diameter=600 x 800 mm

Volume of the bath for spilled metal collection 250 lProductivity 800 t/yr Dimensions of the premises(L*B*H) 24 m x 10 m x 7,5 m

The ECOMET-C company, Russia, presents the following activity [5]: The technology developed in the enterprise for complex processing and utilization of MRAW allows significant diminution of solid radioactive waste volume (20 to 50 times) shipped for storage, returning large part of the metal to industry for unlimited use and substantial reduction of the total costs for processing and disposal. The technology is based on the application of the method for remelting and casting the metal in crucibles at the final stage of MRAW processing.

131

ECOMET-C has its own production capacities mostly for processing MRAW with low levels of activity up to 30 µSv/h and a park of certified metal containers for transport and storage. Characteristics of the installation of ECOMET-C, Russia:

− Furnace capacity – 2.5t; Ingot weight – 0,5 t; − Installed capacity up to 1000 V – 2024 kW; up to 6000 V- 1600 kW; − Consumption of recirculating cooling water – 50 m3/h.

The radiation characteristics of the metal for remelting in ECOMET-C are shown in Table 4.

Table 4. Radiation characteristics of the metal for remelting of ECOMET-C, Russia

Nuclide Mn54 Co60 Sr90 Zn65 Ru106 Cs134 Cs137 Ce144 Eu154

Average specific activity, Bq/g 40 15 10 55 150 20 50 50 30

4. Facilities for MRAW recycling outside Europe The production of the MRAW recycling enterprises in the USA reached its maximum in 1995, when 13 600 t of carbon and stainless steel were recycled. This is, however, less than 1 % of the total volume of radioactive waste in the USA. DOE has estimated that the adhering to the policy leads to the retention of over 14 000 t of non-contaminated scrap in the units of DOE by 2014. Within a period of five years between 2000 and 2004 DOE recycled 710 t of lead for use in protective products and shipping containers, which saved approximately 2,5 million Euros. Regardless of the mentioned difficulties, metallurgical deactivation is applied for the further use of metals in nuclear industry. The metal with lower activity is decontaminated and recycled to obtain shields, screens, waste containers, safety barriers and transport containers, used in nuclear industry. The main facility for metal processing in the USA is that of Energy Solutions “Bear Creek” in Oak Ridge, Tennessee, where various types of radioactive waste may be processed. The capacity of metal melting is used to process lead and other low-contaminated metals from the decommissioning of nuclear reactors. Between 1994 and 2007 54 000 t of metal were treated. MSC is among the enterprises with high capacity of producing metals, suitable for unlimited reuse. This company disposes of technologies and technical possibilities to perform mechanical surface deactivation in order to obtain such metals. The application of the jet crushing machine of the PANGBORN company with capacity of 5 t/24 h allows to produce metal for unlimited reuse in industry. The output of such metal is about 60 % of the initial amount of MRAW. The metal, which is not fit for unlimited use is sent for subsequent metallurgical processing. MSC has an induction furnace, two rolling mills for cold and hot rolling, equipment for metal welding and cutting and turning machines for metal mechanical processing. These aggregates are used mainly for the production of barrels and containers for RAW storage. At this stage Duratek is the enterprise offering a complete set of services for acceptance and processing of MRAW, including conditioning and storage. It has branches in many states, a large park of containers and transport vehicles for RAW shipping, including MRAW from large-dimension equipment (steam generators, heat exchangers). While Japan operates an LLWR-center for waste disposal in Rokkasho-Mura, in Asia there are restricted number of facilities for deactivation and limited possibilities of waste treatment. China, Japan, Korea and Taiwan face up-coming challenges in nuclear reactor

132

decommissioning. The Asian nuclear operators look for information in Europe and USA on best practices and recycling by remelting in order to minimize the volumes for ground disposal. The companies involved in the waste management and deactivation also look at the emerging Asian market. Studsvik and Kobe Steel Ltd established a new Japanese joint venture Kobelco Studsvik to provide solutions for radioactive waste management of the nuclear industry of Japan. The Japanese Atomic Energy Agency (JAEA) has built an advanced facility, in which high ratio of MRAW volume reduction is achieved, and homogenization and stabilization by processes of remelting or super-compacting for low-level radioactive solid waste [6]. It will produce waste packaging for final decontamination and will reduce the volume of ground disposed waste by for low-level solid waste with a surface dose rate less than 2 mSv h. This facility consists of a block for waste size reduction and storage (WSRSF) and waste volume reduction (WVRF). The former has installations for cutting large-size waste and the latter – for melting and super-compacting. Since July 1999 the processed radioactive waste have amounted to 750 m3, and the ratio of volume reduction is within the range of 1,7 to 3,7 times. Conclusions Since MRAW, yielded during the operation and decommissioning of nuclear capacities are constantly growing, the operators of these capacities all over the world have to cope with the challenges of their accumulation and utilization. New and innovative approaches will be probably developed in the course of acquiring expert knowledge on reactor decommissioning. The world practice proves that specialized companies are involved in MRAW processing. Their establishment allows the solution of a whole complex of issues related to MRAW processing at a scientific and high-tech level. The following conclusions can be drawn from the review of the various technologies and facilities for utilization of radioactively contaminated metallic waste:

− All over the world there are built and efficiently operated a considerable number of installations for remelting of radioactively contaminated metals. They are mainly in Sweden, Germany, USA, Japan, Russia, etc.;

− With convenient sorting according to the degree of radioactive contamination and remelting of the radioactive steel waste, deactivation can be achieved with subsequent release from radiation monitoring of up to 50% of the remelted metal, which is transformed into a raw material for metallurgical production. This result is subject to additional comments and verification.

Recommendation On the basis of the study of world experience it is proved that the metallurgical deactivation by remelting and treatment of the molten metal with special fluxes is a prospective method for MRAW utilization. At present an installation for laser incineration of RAW is in operation on the site of the Kozloduy NPP. An installation for hydro deactivation with a section for metal cutting is also in a process of commissioning. If an installation for metallurgical deactivation is to be established, it can be operated together with the installation for hydro deactivation with the aim of complete deactivation of MRAW from the closed units of the plant. In case that two 2 t induction furnaces are installed at the site of the facility for metallurgical deactivation, the capacity of the installation will amount to about 800 t of metal per year in a two-shift operation mode.

133

References 1. Lidar, P., M. Lindberg et al. Nuclide Distribution in the Metal Recycling Process. Studsvik

Nuclear AB 2014. 2. Slaveykova, M., E. Demireva, G. Simova. Predicted estimate of the flows of discharged

materials from the decommissioning of Units 1 and 2 of the Kozloduy NPP. Annual conference of the Bulgarian Nuclear Society, October 10-13, 2012, Hisarya.

3. Björkvall, J., G. Ye, M. Lindberg. Technical Possibilities to Support Separation of Radioactive Elements from Metallic Waste. https://www.oecd-nea.org/rwm/wpdd/studsvik2014/documents/C-1__technical_possibilities__G-Ye.pdf.

4. Recycling of contaminated metals for free release. Studsvik, WM’99 Conf., February 28–March 4, 1999.

5. Andreev, D. E., A. B. Gelbutovskii et al. Existing practices and economic aspects of the issues of metallic radioactive waste management. ZAO ECOMET-C, 07.10.2005.

6. Nakashio, N., H. Higuchy et al., Saoryvenie za LLW in JAEA, Vestnik po qdrena nauka I tehnologiya, 44: 3, 441-447.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

134

Structural Researches on Wear-Resistant Steels Using the Centrifugal Metal Cast Method

Hristo ARGIROV, Ivan GEORGIEV, Yavor LUKARSKI

Institute of metal sciences, equipment and technologies with hydro and aerodynamics centre “Acad. A. Balevski,

Bulgarian Academy of Sciences Sofia 1574, Shipchenski prohod 67, Bulgaria,

e-mail: h.argirov@ims.bas.bg, ivan_georgiev@abv.bg, lukarski@ims.bas.bg Abstract Pipes of wear-resistant steels are produced by centrifugal metal cast method. Structural investigation of the steels is carried out. It is established that radial laying macrostructure and formed microstructure guarantees high operating live-time of the products. It is proved that heat and thermo mechanical treatments additionally improve on the hardness, the wear-resistant and the resistant to chemical aggressive mediums. Optimum regimes for heat and thermo mechanical treatments (ionic nitriding) of the investigated alloys guaranteed reliable work in the operating conditions are defined. Keywords: centrifugal metal cast method, wear-resistant steels, structural researches

Структурни изследвания на износоустойчиви стомани, произведени по метода на центробежното металолеене

Христо АРГИРОВ, Иван ГЕОРГИЕВ, Явор ЛУКАРСКИ

1. Увод

В химичната и металургична промишленост (при реформингови, сяровъглеродни, пиролизни инсталации и други) се използват детайли, възли и съоръжения, които следва да осигуряват нормална работа при тежки условия на експлоатация: висока температура, налягане и високи натоварвания. Процесите в такова оборудване протичат в условията на агресивна среда, при високи температури от порядъка от 750ºС до 1150ºС и при налягане на работната среда до 40 МРа. Това предполага използването на сплави с определен химичен състав, които да издържат на агресивни работни среди при високи температури и налягане. Максималната проектна якост на леярските топлоустойчиви сплави при продължителна работа при високи температури е ограничена от напрежението, което предизвиква разрушаване след определено време на експлоатация. Такива сплави са със съдържание на основните легиращи елементи хром от 20 до 30% и никел от 20 до 48%, като свойствата им се определят от комбинирания ефект на всички легиращи елементи. Известно е, че хромът подобрява твърдостта, устойчивостта към корозия и навъглеродяване (цементация); никелът спомага за металургичната стабилност, подобрява пластичността при стайна температура и устойчивостта към цементация; въглеродът повишава якостта при повишени температури; силицият подобрява устойчивостта към окисляване и цементация.

135

2. Теория

Един от утвърдените начини за подобряване на високотемпературната устойчивост на сплавите е чрез легиране, т.е. употреба и добавяне на легиращи елементи за уякчаване на твърдия разтвор. Структурно представлява внедряване на чужди атоми в кристалната решетка, което предизвиква локални деформации на решетката, възпрепятстващи високотемпературните деформации. Това обикновено се осъществява чрез добавяне на легиращи елементи като волфрам, ниобий, кобалт подобряващи якостта на сплавите. Размерът на зърната оказва съществено влияние върху продължителната якост на сплавите при високи температури. За разлика от деформируемите сплави, размерът на зърната при сплавите, получени чрез леене, в частност по метода на центробежното металолеене, е по-голям, в следствие на което се подобрява устойчивостта срещу пълзене и разрушаване. При определяне на химичния състав на такива сплави се отчита, че основните им свойства следва да отговарят на условията на работа: висока механична якост при високи температури; устойчивост към пълзене и разрушаване; задоволителна пластичност при стайна и високи температури; устойчивост срещу въздействие на окисляващи и навъглеродяващи работни среди. При избора на оптимална сплав, освен якостта и времето за работа при високи температури и налягане на работната среда, следва да се отчита и икономическата страна. Имайки пред вид високото съдържание на хром и никел в състава с постоянно нарастващите им цени на международните пазари, следва да се търсят и разработват сплави с оптимално съдържание на тези легиращи елементи за гарантиране на експлоатационния им ресурс [1, 2, 3].

Устойчивостта срещу разрушаване при пълзене е определящ фактор при избора на дебелината на стената на изделията в процеса на проектиране на съоръженията и конфигурацията на отделните конструктивни елементи. В процеса на непрекъсната работа в следствие на приложените термични и механични натоварвания при високи температури намалява пластичността. Например, при използването на сплав от типа на 40Cr25Ni20Si2 (DIN WrNr 1.4848; ASTM HK 40), устойчива на високи температури (Табл. 1) са установени два механизма, чрез които пластичността при опънови натоварвания може да намали стареенето: формиране на сигма-фаза и отлагане на карбид.

Когато сплавта работи при температури в границите от 650 до 870ºС феритът се превръща в сигма-фаза. При лятите сплави феритът се получава в следствие на утаяването на карбидни частици, променящи състава на матрицата. Микроструктурата на сплавта е напълно аустенитна в лято състояние. В процеса на стареене се образуват карбиди, които намаляват никеловия еквивалент и приближават състава до границата аустенит/ферит (съгласно диаграмата на Шефлер [4]). Диаграмата на Шефлер показва фазовите съставни на една принципна топлоустойчива сплав, използвана в конструкцията на пиролизните пещи. Съдържанието на въглерод в тази сплав е в границите 0,30-0,45% за намаляване до минимум ефекта от сигма-фазата (Фиг. 1). Другите високо топлоустойчиви сплави, представени в Табл. 1, са разположени далеч от границата аустенит-ферит и не се увреждат от сигма-фазата. Отлагането на фини карбидни частици по границите на зърната, повишаващи устойчивостта срещу разрушаване при пълзене, води до влошаване на пластичността. Предполага се, че при повишаване на температурата, отлагащият се карбид се уедрява ускорено вътре в обема на зърната, увеличавайки тяхната якост като по границите на зърната образува непрекъсната мрежа, която намалява пластичността. За осигуряване на надеждна и ефикасна работа при високите температури и налягане на работната среда с минимални разходи за поддръжка производителите се стремят към разработване на нови сплави. Изискванията към качеството на изделията могат да се постигнат чрез избор на подходящ

136

химичен състав на високолегираните хромникелови сплави чрез фиксиране на стабилна базова матрица на съставните фази от микроструктурата. Уякчаването на базовата матрица при високи температури може да се постигне чрез добавяне на карбидообразуващи легиращи елементи като ниобий, волфрам, алуминий, титан и други. Микролегирането с малки количества топлоустойчиви добавки като Тi подобрява устойчивостта към разрушаване при пълзене, както и устойчивостта към окисляване и навъглеродяване без съществено увеличаване на разходите.

Таблица 1. Марки високо топлоустойчиви стомани

No

ОзначениеМеханични показатели

EN 10295 DIN WNr. ASTM

Якостна

опънRm, MPa

Граница на

провлачване Rp0.2, MPa

Относително удължение

А5, %

1 GX25CrNiSi 18-9 1,4825 - 440 210 102 GX40CrNiSi 25-12 1,4837 A 297 HH 450 220 6

3 GX40CrNiSi 25-20 1,4848 A 297 HK40 440 220 8 4 GX40CrNiSiNb24-24 1,4855 IN 519 440 220 8 5 GX40NiCrSi 38-19 1,4865 - 420 220 6 6 GX10NiCrSiNb 32-20 1,4859 A351 Ct15C 440 180 207 GX40NiCrSi 35-26 1,4857 A 297 HP 440 220 8 8 GX40NiCrSiNb 35-26 1,4852* A 297 HP 440 220 8 9 G-NiCr28W 2,4879 - 400 220 3

10 - 1,4840 - 440 205 1511 - 1,4856 - 440 230 8 12 - 1,4868 - 440 220 6

Фиг. 1. Решетка на аустенит и дефекти от легиране. ○ – Fe, ● – аустенито-стабилизиращ легиращ елемент (Me23C6) за СЦК, където (Me са: Ni, Mn и др.), – C;

1 – тетрагонален дефект, 2 – орторомбичен дефект (диаграма на Шефлер)

137

За повишаване на устойчивостта на високо топлоустойчивите сплави към навъглеродяване (цементация), същите се легират с алуминий, който образува предпазно покритие от оксид [5]. Добавянето на по-големи количества алуминий оказва влияние върху заваряемостта и разрушаването при пълзене. Изборът и производството на материал с желания химичен състав определя търсенето на технологични решения за формиране на подходяща структура на заготовките като форма, размери и разположение на зърната, образувани в процеса на първична обработка, както и ограничаване до пълно изключване на дефекти в макро- и микроструктурата (шупли, пори, пукнатини, различни примеси и други). Получаването на ротационни заготовки чрез центробежно или стационарно металолеене има редица предимства пред другите методи за металообработка (пластична деформация и други). Получаването на аустенитна базова матрица от съставните фази на материала, както и ограничаването или пълното изключване на дефектите на микро- и макроструктурата се реализира успешно чрез метода на центробежното металолеене. Това е специален леярски процес с редица предимства в сравнение с другите методи за първична обработка: конвенционални методи на леене, топло валцоване, студено валцоване и други.

Цел на настоящата работа е експериментално изследване в лабораторни условия на процеса на центробежно формообразуване на тръбни заготовки от високо топлоустойчиви и износоустойчиви сплави. Изследване на макро- и микроструктурата на произведените сплави за прогнозиране на тяхната устойчивост в реалните условия на експлоатация. 3. Експериментална част

За целите на настоящото изследване на инсталация за центробежно металолеене са произведени различни марки износоустойчиви и високоустойчиви стомани. Металната стопилка с определен химичен състав и с необходимото количество е получена в индукционна пещ, синтерована с основна набивна маса RB10. За получаване на качествена стопилка е легирано с нисковъглероден ферохром FeCr 006 и високолегиран ферохром FeCr 800 A, а разкисляването е извършено с разчетни количества 75% феросилиций. От получените отливки са изработени пробни образци за металографски изследвания, механични изпитвания и за изследване на износоустойчивостта. По-долу са представени получените експериментални резултати за някои от изследваните марки износоустойчиви стомани. 2.1 Стомана GX 120 Mn12

Известната класическа износоустойчива сплав GX 120 Mn12, разработена през

1882г. от Роберт Хадфилд, се използва широко и днес. Поради високия процент на легиране с манган-13%, понижаващ значително температурата на полиморфно превръщане на желязото, хадфилдовата стомана е стомана от аустенитен клас. При охлаждане до стайна температура аустенитът не претърпява евтектоиден разпад. Формираната структура е съставена от аустенитна матрица с разположена по границата на зърната карбидна мрежа от легиран с манган цементит, което я прави крехка. За повишаване на жилавостта стоманата се подлага на закаляване чрез нагряване до високи температури от 900-1100ºС с цел разтваряне на отделената карбидна мрежа. Времето за задържане обезпечава разтварянето на карбидната мрежа, а в същото време следва да бъде възможно най-малко поради склонността на стоманата към обезвъглеродяване. Охлаждането възпрепятства отделянето на свободни карбиди, особено в критичния температурен интервал 800-850ºС. Получава се днофазна аустенитна структура с ниска

138

твърдост (НВ=180-200) и износоустойчивост. Аустенитът се наклепва и твърдостта се повишава. Високата износоустойчивост се дължи на голямото изкривяване на кристалната решетка на аустенита и формиращата се в процеса на деформиране дисперсна мозаечна структура. Ако процесът на износване не е съпроводен със създаване на натискови напрежения в аустенитната структура и наклепване на последната, сплавта се износва лесно [1, 2, 5]. 2.2. Стомани с приложение в целулозната, хартиената и химическата индустрии

За целите на настоящата работа са произведени ротационни отливки от такива

специални износоустойчиви стомани по метода на центробежното металолеене. Условията на работа са сложни и разнообразни: абразивна работна среда, налягане на полиестерна смола при определена работна температура, ударно натоварване съчетано с абразивно износване и други. Химичният състав на изследваните марки стомани е показан в Табл. 2.

Таблица 2. Химичен състав на стоманите, % по маса.

Марка стомана C Mn Si Cr Mo V Ni S,P

38CrMoAl 0,41 0,65 0,25 1,58 0,53 - - 0,020 0,016

35CrMnMoNi2 0,34 0,93 0,10 0,85 0,41 - 1,9 0,015

Cr12 1,89 0,34 0,25 12,40 - 0,01 O,30 0,016 0,014

Cr12WV 1,94 0,41 0,24 12,30 - 0,23 0,24 0,017 0,019

Cr12Mo 1,63 0,32 0,30 11,62 0,45 0,23 0,25 0,022 0,025

Cr5MoV 0,88 0,72 0,26 4,83 0,67 0,28 0,14

9Cr18 0,94 0,65 0,45 17,87 - - - 0,021 0,017

Забележка: ст. 38CrMoAl: 0,95 % Al; ст. Cr12: 0,19% W; ст. Cr12WV: 0,76 % W.

Допълнителното легиране с никел, молибден и ванадий повишава износоустойчивостта на центробежно летите детайли. Центробежно летите заготовки от стомана 35CrMnMoNi2 се подлагат на допълнителна термична обработка. Първоначално се отгряват при 900ºС, след което следва закаляване при температура от 870ºС в масло и отвръщане при температури между 300-400ºС. След изотермично отгряване при 650ºС в продължение на 4 часа стоманата има твърдост HRC=35, а след 8 часа отгряване e отчетена твърдост HRC=27. Получената микроструктура на стоманата е ферит и зърнест перлит, като се наблюдава и пластинчат перлит.(Фиг. 2).

След закаляване от 860ºС във вода стомана 35CrMnMoNi2 има мартензитна структура, а след отвръщане при 200ºС структурата й е отвърнат мартензит и остатъчен аустенит, също претърпял отвръщане (Фиг 3). След отвръщане при 500ºС стоманата има сорбитообразна структура (фино-дисперсна смес от ферит и перлит)-Фиг. 4 и 6. След закаляване на стоманата при температура от 860ºС в масло структурата е мартензитна, а след отвръщане при 200ºС – биструктурен мартензит и ферит (Фиг. 5).

139

Фиг.2. Микроструктура на стомана 35CrMnMoNi2 след изотермично отгряване

Фиг.3. Микроструктура-отвърнат мартензит и остатъчен аустенит

Фиг. 4. Фино дисперсна смес от ферит и перлит Фиг.5. Структура – биструктурен мартензит и ферит

Фиг.6. Сорбитообразна структура след отвръщане при 500ºС.

140

4. Изводи

Произведени са тръбни заготовки от износоустойчиви стомани чрез метода на центробежното металолеене. Проведени са структурни изследвания на стоманите.

Установено е, че радиално насочената макроструктура и формираната микроструктура гарантират висок експлоатационен ресурс на изделията. Доказано е, че термичната и химико-термичната обработка допълнително подобряват твърдостта, износоустойчивостта и устойчивостта към химични агресивни работни среди.

Определени са оптимални режими на термична обработка на изследваните сплави, гарантиращи надеждна работа в условията на експлоатация. Уякчаването на базовата матрица при високи температури се постига чрез допълнително легиране с ниобий, волфрам, титан и азот. Литература 1. Геллер Ю. А. Инструментальньıe стали, Москва, Металлургия, 1983. 2. Георгиев И. С., Н. Станев. Центробежно леене-формообразуване и кристализация.

Научни известия на НТСМ. Сборник доклади. Международна конференция "Дни на безразрушителния контрол 2012", год. XX, бр. 1 (133), юни 2012, 178-182, ISSN 1310-394.

3. Вълков В, И. Георгиев, М. Илиева. Центробежно леене на дебелостенни отливки от азотно легирана сплав 45АФЛ с приложение в индустрията. НКМУ „Дефектоскопия” 2008, Доклади, 386÷390, гр. Созопол, ISSN 1310-3946.

4. Drury B. G. Metals and Materials, October 1986. 5. Rashev Тs., G. Todorov. Production of wear-resistant carbidic austempered ductile iron,

International scientific conference, UNITECH’ 10, 19-20 November, 2010, Gabrovo, II 225-227.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

141

Thermo-mechanical Study of the Cu-Zr Ribbon with 2% V Addition for Amorphous-nano Crystalline Composites

Georgi STEFANOV1, Tomasz CZEPPE2, Stoyko GYUROV1,

Katarzana JANIK2, Anna WIERZBICKA-MIERNIK2

1 Institute of Metal Science, Equipment, and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski” at Bulgarian Academy of Sciences,

67 "Shipchenski prohod" St., Sofia 1574, Bulgaria, e-mail: stefanov.g@gmail.com 2 Institute of Metallurgy and Materials Sciences Polish Academy of Sciences,

Reymonta 25 St. 30-059 Krakow, Poland, e-mails: t.czeppe@imim.pl, k.janik@imim.pl, a.wierzbicka-miernik@imim.pl

Abstract The structure, thermal stability and dynamic viscosity of the CuZrV amorphous alloy around Tg were studied. This kind of amorphous alloys are potential amorphous-crystalline composites with the lowered glass forming ability and increased ability for the nano-crystallization. The structure and thermal properties of amorphous alloys were determined. To determine the dynamic viscosity the mechanical properties and GFA were studied in an amorphous state of the material in the form of ribbons using multiplied tensile tests experiments. The results of the experimental viscosity were interpreted on the base of the free volume model (FVM). The obtained values of the parameters were used to estimate glass forming ability (GFA) in terms of the Angell parameter mA and characteristic temperatures measured by DSC as well as to determine dynamic viscosity and flow defect concentration. Keywords: CuZrV amorphous alloys, viscous flow, glass transition, glass forming ability, Free Volume Model Introduction Amorphous metallic alloys (glassy metals) represent new class materials in materials science. Recently most studies concern amorphous alloys revealing high glass forming ability (GFA), which can easily form metallic glasses by suction casting sizing from several mm to several cm [1, 2]. The other leading subject concerns formation and properties of the composite, amorphous-crystalline structures which should reveal enhanced mechanical properties, especially avoiding catastrophic fail in the tensile tests due to local plasticity introduced by the deformable crystalline particles [3, 4]. In that range of investigations the Cu-Zr alloys with different additions stabilizing the deformable β phase are of a special interest [5]. One of the less known addition to the amorphous Cu-Zr alloys are small V additives. During the heat treatment of metallic glasses, they undergo fine changes of a short range atomic ordering leading to the decrease of the internal free energy of the system. Extremely sensitive to the structural relaxation are the coefficients of atomic transport, especially the viscosity η. This is why one of the most important characteristics of amorphous phase of the metallic glasses is the temperature dependence of their coefficient of viscous flow [6] which drastically decreases at the glass transition temperature Tg and further decreases until the primary crystallization temperature Tx is reached. The mechanical properties of the glassy alloys have inspired great interest. Commonly, metallic glasses reveal high strength but their applicability depends on the ductility, which at low temperatures is commonly the weakest point of most compositions [7]. Large, homogenous deformation at the temperature range between 0.8Tg and primary crystallization Tx1, that is in the range of Newtonian flow remains the most promising way of the amorphous alloys

142

processing. This is why the study of viscosity in its connection to the application properties is of great importance from both scientific and practical point of view [6]. Many methods could be applied to measure viscosity from the equilibrium melt down to undercooled liquid near Tg, such as parallel-plate rheometry, beam bending and capillary flow method [8–12]. In this work, we study the thermal stability and viscosity around Tg using tensile tests equipment what determined the required form of the investigated samples to be the thin ribbons of the Cu40Zr58V2 nominal composition. At the presented stage of the investigations the study concerns seldom the glassy state of the alloy. For the interpretation of the results the Russew Free Volume Model was applied [6]. A short theoretical background of the applied model is as follows. The basic assumption of the free volume model (FVM) used for interpretation of the viscosity experimental data is that viscous flow takes place through thermally activated events at specific sites in the structure, called flow defects (cf). The most generalized temperature dependence of the viscosity (η) of an amorphous alloy can be represented as [13]:

(1)

Here Qη is the activation energy for the viscous flow, η0 is a pre-exponential factor and cf is the concentration of the flow defects. The equilibrium concentration of flow defects cf,eq(T) is given by Zhu et all. [14]:

(2)

where B and T0 are two model parameters, which can be related to the empirical constants BVFT, and T0,VFT in the classical empirical Vogel-Fulcher-Tammann equation. Combining equation (1) and (2), the so-called ‘hybrid’ temperature dependence of quasi-equilibrium viscosity ηeq is obtained [14]:

(3)

Equation (3) describes the change of viscosity of glass forming undercooled (metallic) melts in the structural state, where the flow defect concentration follows immediately the changes of temperature. Taub and Spaepen, [15] were the first, who have found, that the defect concentration changes cause linear increase of glassy metals viscosity along with increasing the time of isothermal annealing far from their metastable equilibrium. In that case, it follows from eq. (4), that the concentration cf of flow defects decreases inversely proportional to the time of annealing, e.g.:

(4)

Duine et al. [16] have shown that alloy Pd40Ni40P20 possess a very high thermal stability around its glass transition temperature thus a term taking into account the production of flow defects should be included in (5):

(5)

Russew et al. [6,17] have transform equation (5) to dcf/dt = (dcf/dT)q in order to describe the change of cf in the glassy alloy with temperature under non-isothermal conditions and at a constant heating rate, q in the temperature range around the glass transition temperature Tg. The solution becomes to equation (6):

η η η=

0

1T

QRT cf

exp

−

−=0

, exp)(TT

BTc eqf

η η ηeq T T

QRT

BT T

( ) exp exp=

−

0

0

2fr

f ckdt

dc−=

)( 2,

2eqffr

f cckdt

dc−−=

143

(6)

where , νr is the attempt frequency,

Qr is activation energy of relaxation, cf,0 is the initial defect concentration and R is the universal gas constant. Combining equation (1) with equation (6) one obtains the temperature dependence of viscosity η in the high temperature range near Tg. The Free Volume Model interpretation of the viscosity experimental data allows specifying the model parameters ηo, Qη, νr , Qr , cf,0 , B and T0 in equations (1) and (6) by using multi-parameter regression analysis. This is an equation of Bernoulli [18] of the 2nd order. Angell [19] has pointed out also that not the absolute value of the melt viscosity but the rate of viscosity change at Tg is the most important factor determining the glass forming ability of different substances including classical silicate glasses and amorphous metallic alloys. This is mathematically presented as (7):

(7)

where mA is the melt fragility number of Angell and can be used as a measure of the glass forming ability (GFA). Equation (7) bases on the assumption that the melt viscosity of glass forming substances follows Vogel-Fulcher-Tammann (VFT) temperature dependence. In the case of FVM interpretation, the viscosity temperature dependence should be presented by the “hybrid” eq.(3). In this case:

(8)

The Free Volume Model interpretation of the experimental data allows to specify the parameters in eq. (6) Qη, B and To, and Tg is easily interpreted as the temperature at the cross point of ηnonequilibrium and ηquasiequilibrium. Experiments The alloys were prepared by the arc melting from the high purity at least 99,99 components. The ribbons were made by the typical melt spinning method with the solidification on the brass disc of the 300 mm diameter in the controlled atmosphere of Ar. The rotation speed was 33 m/s. The ribbons were 5 mm wide and 20-30 μm thick. For comparison also massive samples were prepared by the melt suction method 1-3 mm in diameter. The structure and composition was controlled with the SEM/EDS FEI QUANTA 3D FEGSEM scanning, electron microscope (SEM) equipped with the EDAX EDXS XRD detector. Further, the structure both ribbons and massive samples was investigated by XRD. The diffraction patterns were collected using diffraction of high-energy synchrotron radiation (87.1 keV) in transmission geometry at the HZG materials science beamline P07B at DESY in Hamburg, Germany. To ensure a good statistics and to get rid of texture effect, the sample was continuously rotated 180° around the ω-axis. Such an approach allowed to obtain data from the whole measured volume. Afterwards, the obtained 2D patterns were integrated employing the Fit2D software and showed in a graph of relative intensity vs. 2Theta angle. The beam of

′′

′

′′−′−=

′−−

T

T

T

T

T

Tfhighf TdTPTddTTPTQcqTc

o 00

)(exp")(exp)(),( 10,

1,

,exp)(0

−

−−−=TT

BRTQ

qTP rrν

−−=

RTQ

qTQ rr exp)( ν

( )gTTg

A TTddm

=

=

/)(logη

( )

−+

−= 1434.0 2

gog

gA RT

QTT

BTm η

144

photons was limited to 0.5 × 0.5 mm2. The detector was placed at a distance of 1100 mm from the sample. The Plexiglas support was used to fit the ribbon samples. To determine thermal stability of the amorphous ribbons the DSC 404 F1 Pegasus (Netzsch company) and DuPont 910 were used in the temperature range 473- 1400 K, with the heating rate 20 K/min and with the controlled Ar gas atmosphere. The ceramic Al2O3 cups were used and to avoid possible oxidation the low vacuum was made before controlled atmosphere was introduced to the measuring cell. Several measurements was performed on the different parts of the ribbons to avoid differences resulting from the slightly different cooling rates. The temperature dependence of η were investigated by Perkin Elmer thermo-mechanical device TMS-2- shown in Fig. 1 with a home-made silica glass assembly for high temperature measurements.

Fig. 1 Lower part of the Perkin-Elmer TMS-2 analyzing unit with the home-made

silica glass assembly.

Fig. 2 Tool for setting the ribbons on wedge shaped grips, and some ribbons.

In Fig. 1 the supporting silica glass tube (rigid frame) (1), silica glass probe with a hook at the end where the load is applayed (and connecting moving grip to LVDT) (2), furnace (3), unmovable wedge shaped grip of Invar alloy (4), stationary silica glass hook (5), specimen of fixed initial length of 4 mm (6), unmovable wedge shaped grip of Inver alloy (7) and the thermocouple (8) are shown. The special tool, where the ribbon is set to wedge shaped grips with fixed length is shown more clear at Fig. 2. The measurements were carried out under loads ranging between 50 g and 130 g. The temperature accuracy (±1K) of the TMS-2 was calibrated by using the strips of pure Sn, Pb, Zn and Al of known melting points.

145

Results Structure and crystallization process of the ribbons The experimental composition of the ribbon in wt.%, verified with the EDS is shown in Tab.1.

Table 1 Chemical composition of the investigated alloy in weight %.

elements Ribbon

Experimental composition, wt. %Cu Zr V

1 41.9 56.9 1.2 As was established the V content 1.9 at.% is very near to the assumed 2 at.%, while the Cu/Zr proportion 50.4/47.7 (in at.%) was shifted in the Cu direction, suggesting in case of crystallization the two phase CuZr + Cu10Zr7 composition at high temperatures while below 988 K CuZr phase should decompose into Cu10Zr7 and CuZr2 phases (Fig.3).

Fig 3. Equilibrium Phase diagram of the Cu-Zr binary system [20].

Fig.4 Microstructure on the polished edge section of the investigated ribbon. SEM, BSE mode, magnification 5000x.

146

The general view of the ribbon in the SEM/BSE technique from the edge side is shown in Fig. 4. At the SEM magnification no crystalline phase was detected. As a powerful tool for the crystalline nano-phase determination the XRD with use of the synchrotron radiation was used (Fig. 5). Two XRD curves are compared in the figure, the upper concerning the investigated ribbon and the bottom the massive, moustly crystalline sample prepared also by the suction method. As is visible from the upper curve the sample reveals amorphous microstructure however very small amount of crystalline phase, marked by arrows in the Fig. 5, were also present. Due to the bottom curve, the nanoparticles may be identified as the CuZr phase. There is no method to estimate the amount of the crystalline phase, however, it’s amount is below 1 vol.%.

Fig. 5. XRD on the investigated ribbon (upper curve) revealing amorphous character of the sample and from the “suction cast” massive 3 mm in diameter sample (lower curve) revealing predominant

crystallization of the CuZr and Cu10Zr7 phases. Synchrotron radiation.

Fig. 6a. Glass transition and crystallization process in the investigated ribbon containing 2 at.% of V. DSC DuPont 910.

147

Fig. 6b. Glass transition, crystallization process and phase transitions in the investigated ribbon containing 2 at.% of V. DSC Netzsch F1.

The heat flow DSC curves are presented in Fig. 6a and b. The effects observed are typical for the metallic glasses. After small relaxation effect the increase of the heat capacity related to the glass transition takes place at 729 K (Fig. 6a insert). The large, primary crystallization effect at 766 K proceeded by the additional exothermic transition which may be related to the growth of the existing nano-crystals of CuZr phase at 747 K (Fig. 6a). The endothermic effect at 1014 K relates to the Cu10Zr7 + CuZr2 → CuZr transition (Fig. 6b). Melting starts at Tm 1156 K (Fig. 6b). Liquidus temperature Tl was assumed to be at the peak temperature at 1167.9 K. The characteristic temperatures are given in Tab. 2. Some parameters recognised as related to the glass forming ability are also given in Tab. 2. As is known, there is no universal one. The following parameters were calculated: ΔTrg related rather to the stability of the amorphous phase of the glass, Trg connected to the resistivity for the crystallization of the kinetic character and an universal GFA parameter for many glass-forming systems γ = Tx/(Tg+Tl).

Table 2 Characteristic parameters detected from the DSC heat flow signals. Heating rate 20 K/min.

Amorphous ribbon

Parameter Temperature[K]

Interpretation

V2

Tg [K] 729.0 devitrification Tx1 [K] 746.6 first crystallization effect Tx2 [K] 766.2 dominant crystallization effect

ΔH [J/g] 43.5 glass crystallization enthalpy Tp [K] 1014.0 Cu10Zr7 + CuZr2 → CuZr peak transitionTm [K] 1155.5 melting temperature Tl [K] 1167.9 liquidus temperature

GFA ΔTrg=Tx-Tg 17.6 glassy phase stability Trg= Tg/Tl 0.624 stability against crystallization

γ=Tx/(Tg+Tl) 0.394 calculated glass forming ability

148

Dynamic viscosity investigations – Experimental procedure Typical experimental elongation (l(T)-lo) temperature (time) curves for the amorphous alloys are shown in Fig. 7.

Fig. 7 Experimental elongation (l(T)-lo) versus temperature curves in various loads for Cu40Zr58V2 glassy alloy at heating rate at 20 K/min.

The overall strain of a glassy alloy ribbon reached at temperature T under applied tensile stress at continuous heating conditions is given by:

(9) where l0 and l(T) are the initial length and the current length of the specimen at temperature T, respectively, is the elastic strain of the ribbon divided by Young’s modulus

of the material . It is worth adding that represents the possible anelastic

contribution to the overall strain, takes into account the contribution of any relaxation

effects to the overall strain, represents the contribution of the thermal expansion to the

overall strain, while takes into account the viscous flow contribution to the overall strain. It is shown that the subtraction of the strains obtained at different loads gives:

(10) where is caused by the effective stress . Applying the Newtonian relation for viscous flow and taking into account that the shear stress one obtains

(11)

where is difference of the strain rates and , caused by the differenet applied shear stresses and , while . The typical temperature dependences of the strain rates caused by the shear stresses

difference are shown in Fig. 8. These curves are obtained by numerical

differentiation of the temperature dependences of the strain differences.

( ) ( )[ ] ( ) ( ) ( ) ( ) ( )TTTTTllTlT vfterelanelσσσσσ εεεεεε ++++=−= 00 /

( ) ( )TETel /σεσ =

( )TE ( )Tanσε

( )Trelσε

( )Tteσε

( )Tvfσε

( ) ( ) ( ) ( ) ( )TTTTT vfvf21212,1 σσσσ εεεεε −≅−=Δ

( )T2,1εΔ 212,1 σσσ −=Δετη /= 3/στ =

( ) ( )TT

ητ

ε 2,12,1

Δ=Δ

( ) ( ) ( )TTT 212,1 εεε −=Δ 1ε 2ε

1τ 2τ 212,1 τττ −=Δ)(TεΔ

( )2121 31 σστ −=Δ −

149

Fig. 8 Temperature dependence of the strain rates obtained at different load differences (100 g -50 g (1); 130 g – 50 g (2), 130-100 g (3)) for Cu40Zr58V2 glassy alloy at 20 K/min.

The strain rates increase smoothly up to approximately 730 K for the CuZrV alloy. On reaching these temperatures, a rapid increase in the strain rates is observed because of reaching Tg of the alloy studied. A passage over a maximum is observed after reaching the onset temperature of crystallization. Fig. 9 illustrates the shear viscosity values calculated in accordance with eq. (11) (points) from strain rates (Fig. 8). The solid line represents the best- fit curve of all data, obtained at the different load differences.

Fig. 9 Viscosity temperature dependence Cu40Zr58V2 glassy alloys at 20 K/min. The solid line represents the best-fit curve of all data, obtained at the different load differences (100 g -50 g; 130 g – 50 g; 130 g –

100 g ).

A common feature of the viscosity curves, obtained by measuring under a constant heating rate, is the presence of two almost linear parts and curved transitional portion between them. The steeper part of the temperature dependence is approaching the quasi-equilibrium structural state of under-cooled liquid of the alloys described by the “hybrid” equation (3). The other one in the lower temperature region is the non-equilibrium viscosity of the vitrified alloy. In the temperature range of crystallization beginning, the viscosity values are influenced by the increasing volume fraction of crystallized regions.

150

In Fig. 10 experimental data (points) are presented together with the viscosity values calculated using the Free Volume Model equations (solid line) for the studied alloys.

Fig. 10 Experimental viscosities of the CuZrV glassy alloys at 20 K/min (points). Solid curve – fitted viscosity versus 1/T dependencies according to the free volume model (eqs. (1) and (4). Steep broken line –

temperature dependence of the quasi-equilibrium viscosity ηeq, calculated according to eq. (3).

A combination of equations (1) and (4) is used to obtain the non-equilibrium viscosity curve and eq. (3) – for obtaining the quasi-equilibrium viscosity curve (steeper curve –broken line). The intersection of the non-equilibrium and quasi-equilibrium curves for studied alloy determines the glass transition temperature Tg. The glass transition temperature, Tg and the value of the viscosity at Tg, η(Tg), the values of the model parameters in eq.(1), eq.(3) and eq.(4), νr, Qr , cf,о , Tо, Qη, B and ηо, obtained by the regression analysis of the experimental data are given in Table 3.

Table 3 Glass transition temperature Tg, calculated mAngel and FVM parameters of the CuZrV metallic glass.

CuZrV dimensionν 9,49E+16 1/sQr 120,296 kJ/molcf,o 2,92E-7 -R 8,31451 J/molKTo 510 KdT 0,25 KQη 255,254 kJ/mol B 5221 K

q-value 0.33334 K/sηo 2,33E-21 Pa s/K

mAngel 34,56 -Tg 727 K

η(Tg) 9E+10 Pa s

151

The GFA of the studied alloy was determined on the bases FVM interpreted by the Angell melt fragility number and is given in Table 3. Summary and Discussion The composition of the sample revealed to be very near to the nominal one, at the equilibrium state and high temperature the alloy should be composed with the CuZr and Cu10Zr7 phases. This was also the phase composition revealed in the rapidly solidified samples 3 mm in diameter, prepared by the melt suction method and should be expected as well in the case of the crystallization of the ribbons from the glassy state. The XRD measurements with use of the synchrotron intensive beam revealed very small amount of the crystalline nano- particles of the CuZr structure. Such small content of the crystalline phase should not have any influence on the amorphous phase properties, e.g. a dynamic viscosity, however proves that even a small V addition may promote crystallization of the CuZr phase from the melt. Lack of the CuZr2 phase should suggest also stabilizing influence of the V on the CuZr (β) phase at low temperature range. DSC results revealed two-step crystallization proceeded by the glass transition at 729 K (Tab. 2) what remains in a very good agreement with the Tg determined at 727 K by the rheometric experiments (Tab. 3). The parameters related to GFA presented in Tab. 2 suggest quite large potential for the glassy phase formation [21] in spite of the fact, that the massive samples could not be produced amorphous. Conclusions 1. The ribbons made from the Cu40Zr58V2 alloy by the melt-spoon method revealed amorphous

structure. 2. The V addition promotes crystallization of the CuZr (β) ductile phase from the melt and

stabilizes it at a low temperature range. 3. The glass transition temperatures Tg for the investigated alloy determined by the DSC and

FVM by the thermomechanical analysis are very close at 729 and 727 K respectfully proving the high precision and reliability of the model.

4. The parameters related to GFA determined by FVM model suggest quite large potential for the metallic glassy phase formation.

Acknowledgements: The work was done in the frame of the bilateral cooperation program EBR between PAS and BAS at 2018-2020. The experimental work was partially done in the Laboratories of the IMIM PAS accredited by PCA and partially in Laboratories of the IMSET BAS. The Authors want to express thanks to prof R. Chulist from IMMS PAS for the synchrotron XRD experiments and dr. A Sypien for the SEM/EDS analysis. References 1. Inoue A., Takeuchi A., Recent progress in Bulk Glassy Alloys, Mater. Trans., 43(8) (2002)

1892-1906. 2. Inoue A., Stabilization of Metallic Supercooled Liquid and Bulk Amorphous Alloys, Acta

Mater. 48 (2000) 279–306. 3. Fan C., Inoue A., Improvement of mechanical properties by precipitation of nanoscale

comp[ound particles in Zr-Cu-Pd-Al amorphous alloys, Mater. Trans. JIM 1997, 38, 1040-1046;

152

4. Hays C.C., Kim C.P., Johnson W.L., Improved mechanical behaviour of bulk metallic glasses containing in situ formed ductile phase dendrite dispersions, Mater. Sci. Eng. A 2001,304, 650-655;

5. Sopu D., Yuan X., Moitzi F., Stoica M, Eckert J, Structure-Property Relationships in Shape Memory Metallic Glass Composites, Materials 2019, 12, 1419;

6. Russew K., Stojanova L.. Glassy Metals, Springer, 2016, ISBN 978-3-662-47881-3. 7. Nieh T.G., Deformation Behavior, in: M. Miller, P. Liaw (Eds.), Bulk Metallic Glasses,

2008, 147-167. 8. Busch R., The thermophysical properties of bulk metallic glass-forming liquids, JOM 52

(2000) 39–42, http://dx.doi.org/10.1007/s11837-000-0160-7. 9. Heilmaier M., J. Eckert, The synthesis and properties of Zr-based metallic glasses and glass-

matrix composites, JOM 52 (2000) 43–47, http://dx.doi.org/10.1007/s11837-000-0161-6. 10. Waniuk T.A., R. Busch, A. Masuhr, W.L. Johnson, Equilibrium viscosity of the

Zr41•2Ti13.8Cu12•5Ni10Be22.5 bulk metallic glass-forming liquid and viscous flow during relaxation, phase separation, and primary crystallization, Acta Mater. 46 (1998) 5229–5236, http://dx.doi.org/10.1016/S1359-6454(98)00242-0.

11. Busch R., E. Bakke, W.L. Johnson, Viscosity of the supercooled liquid and relaxation at the glass transition of the Zr46•75Ti8.25Cu7•5Ni10Be27.5 bulk metallic glass forming alloy, Acta Mater. 46 (1998) 4725–4732, http://dx.doi.org/10.1016/S1359-6454(98)00122-0.

12. Bakke E., R. Busch, W.L. Johnson, The viscosity of the Zr46•75Ti8.25Cu7•5Ni10Be27.5 bulk metallic glass forming alloy in the supercooled liquid, Appl. Phys. Lett. 67 (1995) 3260–3263, http://dx.doi.org/10.1063/1.114891.

13. Van den Beukel A, Huizer E, Mulder AL, van der Zwaag S., Change of viscosity during structural relaxation of amorphous Fe40Ni40B20, Acta Metall, 1986; 34:483.

14. Zhu S.L., Wang X.M., Inoue A., Glass-forming ability and mechanical properties of Ti-based bulk glassy alloys with large diameters of up to 1 cm, Intermetallics 16 (2008) 1031–1035, doi:10.1016/j.intermet.2008.05.006

15. Taub A.I., Spaepen F., The kinetics of structural relaxation of a metallic glass Acta Metall (1980) 28:1781-1788.

16. Duine P.A., Sietsma J., Van den Beukel A., Characterization of free volume in atomic models of metallic glasses. Acta Metall. Mater., 1992, 40, 743-751.

17. Russew K., B. J. Zappel and F. Sommer, Nonisothermal viscous flow behavior of Pd40Ni40P20 glassy alloy considered as a free volume related phenomenon, Scripta Metall. Mater., 32 (1995) 271.

18. Korn GA, Korn T.M., Mathematical Handbook for Scientist and Engineers: Definitions, Theorems and Formulas for Reference and Review. ISBN-13: 978-0486411477, ISBN-10: 0486411478.

19. Angell CA, Formation of glasses from liquids and biopolymers, Science, 267(5206), 1995, 1924-1035.

20. Wang N., Li C., Du Z., Wang F., Zhang W.; The thermodynamic re-assessment of the Cu–Zr system; CALPHAD, 30 (2006) 461-469;

21. Lu Z.P., Liu Y., Liu C.T., Evaluation of glass-forming ability in: Bulk Metallic Glasses, eds. M. Miller, P. Liaw, Springer 2008, pp.93-95;

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

153

Obtaining of ZrNiCuAl Alloys with Nano-microcrystalline Structure in Argon-arc Furnace

Mihail KOLEV, Lyudmil DRENCHEV, Georgi STEFANOV,

Stoyko GYUROV, Yordan GEORGIEV

Institute of Metal Science, Equipment, and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski” at Bulgarian Academy of Sciences,

67 "Shipchenski prohod" St., Sofia 1574, Bulgaria, e-mail: stefanov.g@gmail.com Abstract The preparation of amorphous and microcrystalline Zr65Ni10Cu17.5Al7.5 alloy is considered in this work. The amorphous ribbon was obtained by Planar Flow Casting and the microcrystalline alloy was obtained by melting in argon-arc furnace. Keywords: Amorphous ribbons, microcrystalline alloy

Получаване на ZrNiCuAl сплави с нано-микрокристална структура в аргоно-дъгова пещ

Михаил КОЛЕВ, Людмил ДРЕНЧЕВ, Георги СТЕФАНОВ,

Стойко ГЮРОВ, Йордан ГЕОРГИЕВ 1. Увод

Едни от най-новите и интензивно изследвани материали са аморфните метални сплави, известни също така като метални стъкла. Благодарение на уникалното атомно подреждане в структурата им в сравнение с кристалните материали, аморфните сплави притежават изключителни механични свойства, като висока граница на провлачване (~ 2 GPA) [1] и широк диапазон на якост на разрушаване (2000-5500 MPa) [2, 3]. Тези уникални свойства ги правят изключително интересни нови материали, радващи се на огромен интерес от страна на изследователите през последните две десетилетия. Освен така наречените "двумерни" метални стъкла, чиято дебелина не надхвърля 30 µm, в последните десетилетия бяха получени и обемни аморфни сплави с дебелина до няколко сантиметра. Днес сплавта Pd43Ni10Cu27P20 може да бъде получена в аморфно състояние при критична скорост на охлаждане от порядъка на 0.33 K/s [4] и с диаметър до 8 см [5].

Металните пени като цяло намират все повече инженерни приложения. Това до голяма степен се дължи на относително високата якост, комбинирана с много ниско специфично тегло. Тази уникална комбинация от свойства прави пените атрактивен конструкционен материал, който имитира механичните характеристики на някои природни материали като например дърво или кости [6]. Обемните аморфни метални пени могат да се превърнат в едно ново поколение конструкционни материали. Получаването на аморфни или нанокристални пени минава през два етапа: синтез на подходящи сплави; и последващото им разпенване. Ето защо получаването на обемни аморфни и нанокристални сплави, и охарактеризирането им е задача от огромен интерес от страна на изследователите.

154

Известно е [7, 8], че обемни метални стъкла се получават от многокомпонентни системи (три и повече компоненти). Успешно получаване на аморфни метални пени досега е постигано с ограничен брой паладиеви сплави от рода на Pd43Cu27Ni10P20 [9] и Pd42.5Cu30Ni7.5P20 [10]. Всички те съдържат фосфор като застъкляващ елемент, който позволява получаване на аморфен метал дори от трикомпонентна сплав при ниски скорости на охлаждане от порядъка на 102-103 °С/s.

Сплави от системата паладий фосфор са изключително трудни за получаване поради високия парен натиск при температурите на сплавяване. Освен това фосфорът е опасен за работа – лесно се възпламенява и е токсичен. Ето защо е необходимо да се изследват възможностите за синтез на други сплави несъдържащи фосфор и проверена способността им да се застъкляват.

Цел на работата е получаване и охарактеризиране на аморфна или нанокристална метална пяна от ZrNiCuAl сплав в аргоно- дъгова пещ. 2. Опитна постановка

Получена е плътна заготовка от ZrNiCuAl сплав в лабораторна аргоно- дъгова пещ, показана на фиг. 1.

Фиг. 1 Аргоно- дъгова пещ (1), вакуумна установка СНИ-3 (2)

Лабораторната аргоно- дъгова пещ е свързана с вакуумната система на СНИ-3 (три

канална система за напускане на изотопи) към масспектрометър МИ-1201В. За получаване на аморфна сплав под формата на лента е използвана установка за леене в плосък поток (Planar Flow Casting), снабдена с високочестотен генератор ГИ-25.

Рентгеноструктурният анализ е проведен с прахов рентгенов дифрактометър апарат Bruker D8 Advance с СuКα лъчение (Ni филтър) и регистрация на LynxEye в твърдотелен позиционно чувствителен детектор. Качествения фазов анализ е проведен с помощта на базата данни PDF-2 (2009) на Международния център за дифракция на данни (ICDD) с помощта на софтуерния пакет DiffracPlusEVA. Рентгеновият микроанализ е проведен чрез сканиращ електронен микроскоп Carl Zeiss EVO 10 с микроанализатор Bruker.

2

1

155

Фазовите промени при нагряване на лента от сплав ZrNiCuAl бяха проследени в система за термичен анализ TGA, DTA, DSC с компютъризирана термична инсталация SETSYS 2400, на фирмата SETARAM, Франция.

Микроструктурата на образците е изследвана с помощта на оптичен металографски микроскоп Reichert MeF-2 и регистрирана чрез цифров фотоапарат Panasonic DMC-FZ38. 3. Резултати и дискусия

Според литературни данни Inoue получава плътни аморфни заготовки с цилиндрична форма до 16 mm от Zr65Al7,5Ni10Cu17,5 сплав [11]. За експериментите бе подбрана сплав с подобен химически състав от системата ZrNiCuAl. Сплавта е синтезирана чрез многократно претопяване на 3,7436g Zr; 0,1279g Al; 0,3706g Ni и 0,7035g Cu, в аргоно- дъгова пещ в атмосфера от пречистен чрез гетериране аргон 99,999. Полученият образец има лещообразна форма с диаметър около 16 милиметра с тегло след сплавяването 4,9482g и е показан на фиг. 2.

На Фиг. 3 е показана микроструктурата от сплав № 1. Наблюдава се кристална структура на образеца, като се виждат различните фази в него.

Фиг. 2. Образец № 1 от сплав ZrNiCuAl Фиг. 3. Микроструктура на образец № 1 от сплав

Следваща стъпка за получаване на заготовка, готова за разпенване е стопяването

на образец № 1 от сплав ZrNiCuAl в установка за синтез на аморфни и нанокристални метални материали в ИМСТЦХ „Акад. А. Балевски“ [12]. Полученият след стопяване в индукционна пещ в атмосфера от аргон 99,999 образец № 2 е показан на фиг. 4.

Размерите на получения след закаляване във вода образец № 2 са около 10

милиметра в диаметър и дължина около 12 милиметра. След направен рентгеноструктурен и металографски анализи се установи, че образеца има микрокристална структура, но не и аморфна такава – фиг. 5 и фиг. 6. В изследвания образец се наблюдават две фази- Zr6NiAl2 и CuZr2.

156

Фиг. 4. Образец № 2 след стапяне и закаляване Фиг. 5. Микроструктура на образец № 2 от сплав ZrNiCuAl

Фиг. 6. Рентгенограма на образец № 2 от сплав ZrNiCuAl

Предполагаме, че това се дължи на факта, че химическият състав на получената

сплав се различава от този в литературата [11]. За да проверим дали получената сплав може да се аморфизира, ние подложихме образец № 2 на бързо закаляване от стопилка на установка за леене в плосък поток (Planar Flow Casting) чрез индукционно нагряване. Лентата е получена при скорост на въртене на охлаждащия меден диск от 3900 min-1 до

Aluminum Nickel Zirconium

03-065-2647 (D) - Copper Zirconium - CuZr2 - Y: 53.28 % - d x by: 1. - WL: 1.5406 - Tetragonal - a 3.22040 - b 3.22040 - c 11.18320 - alpha 90.000 - beta 90.000 - gamma 90.000 - Body-centered - I4/mmm (139) - 00-054-0402 (*) - Aluminum Nickel Zirconium - Zr6NiAl2 - Y: 18.22 % - d x by: 1. - WL: 1.5406 - Hexagonal - a 7.91560 - b 7.91560 - c 3.37320 - alpha 90.000 - beta 90.000 - gamma 120.000 - Primitive - P-62m (18Operations: Background 1.000,1.000 | ImportFile: ZrNiCuAl f12-shiroka kiuveta.raw - Type: 2Th/Th locked - Start: 10.000 ° - End: 89.807 ° - Step: 0.020 ° - Step time: 70. s - Temp.: 25 °C (Room) - Time Started: 10 s - 2-Theta: 10.000 ° - Theta: 5.000 ° - Chi: 0.

Lin

(Cou

nts)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

2-Theta - Scale10 20 30 40 50 60 70 80

157

4000 min-1 и налягане на аргон над стопилката от 0,4 atm. Лентата е с размери широчина от около 3-4 милиметра и дължина до 2 метра. На Фиг. 7 е показана лента от сплав № 2. Лентата бе подложена на рентгеноструктурен анализ, и получената рентгенограма е показана на фиг. 8. От рентгенограмата се вижда, че лентата е аморфна- не се наблюдават ясно изразени пикове на фази.

Фиг. 7. Аморфна лента от образец № 2 от сплав ZrNiCuAl

Фиг. 8. Рентгенограма на аморфна лента от образец № 2

От проведения DSC анализ, показан на фиг. 9, е установена температурата на

топене на изследваната сплав, която е 874,3 оC, и е много близка до тази от литературните данни (Tтоп= 872 оC)

Фиг. 9. DSC анализ на аморфна лента от образец № 2

На фиг. 10 е показан SEM анализ на аморфната лента, а в табл. 1 е даден химическият състав на лентата.

500

1000

1500

2000

2500

3000

10 30 50 70 90 110

2-Theta-Scale

Lin

(cou

nts)

158

Фиг. 10 SEM анализ на аморфна лента от образец № 2

Таблица 1 Химичен състав на аморфна лента

Елемент тегловни % атомни % Inoue сплав, атомни % [11] Zr 77,45 67,16 65 Cu 13,55 16,87 17,5 Ni 6,58 8,86 10 Al 2,42 7,11 7,5

От Табл. 1 се вижда, че съставът на изследваната сплав се различава малко от тази,

получена от Inoue. Възможно е именно на тази малка разлика да се дължи факта, че не можем да получим плътна аморфна заготовка от изследваната сплав дори при по- малък диаметър на заготовката (около 10 милиметра). На фиг. 11 е показана микроструктурата на аморфната лента чрез използване на SEM.

Фиг. 11. SEM анализ на аморфна лента от образец № 2

От фиг. 11 се вижда матрица без други отделяния в нея, виждат се също така и някои дефекти в лентата.

0 2 4 6 8 10 12 14 16keV

10-3

10-2

10-1

1

10

cps/eV

Al Cu Cu Ni Ni

Zr Zr Zr

159

3. Изводи

Получени са пробни тела от сплав Zr67,16Ni8,86Cu16,87Al7,11 в лабораторна аргоно-дъгова пещ.

Получени са пробни тела от сплав Zr67,16Ni8,86Cu16,87Al7,11 с микрокристална структура след претопяване в кварцова ампула и закалени във вода.

Получена е аморфна сплав със нов състав Zr67,16Ni8,86Cu16,87Al7,11 след бързо закаляване от стопилка.

Аморфната сплав е охарактеризирана и са получени оригинални данни за термичното ѝ поведение. Благодарности

Настоящото изследване е финансирано от Фонд Научни Изследвания Министерството на Образованието и Науката, по проект МОН-02-16/3. Литература 1. Bruck HA, Christman T, Rosakis AJ, Johnson WL. Quasi-Static Constitutive Behavior of

Zr41.25Ti13.75Ni10Cu12.5Be22.5 Bulk Amorphous-Alloys. Scr. Metall. Mater. 30 (1994) 429.

2. Lowhaphandu P, Lewandowski JJ. Fracture toughness and notched toughness of bulk amorphous alloy: Zr-Ti-Ni-Cu-Be. Scr. Mater. 1998; 38:1811.

3. Gilbert CJ, Ritchie RO, Johnson WL. Fracture toughness and fatigue-crack propagation in a Zr-Ti-Ni-Cu-Be bulk metallic glass Appl. Phys. Lett. 1997; 71:476.

4. Schroers J, Johnson WL, Busch R. Crystallization kinetics of the bulk-glassforming Pd43Ni10Cu27P20 melt. Appl. Phys. Lett. 2000; 77:1158.

5. Telford M. The case for bulk metallic glass. Mater. Today 2004; 7:36. 6. Drenchev L., Sobczak J. J., Self-healing materials as biomimetic smart structures, Foundry

Research Institute, Krakov, 2014, ISBN 978-83-88770-98-2. 7. Johnson WL, Bulk amorphous metal – An emerging engineering material, JOM 54 (2002),

40. 8. Akihisa Inoue, Bulk Glassy Alloys: Historical Development and Current Research,

Ingineering 2015, 1(2): 185–191, DOI 10.15302/J-ENG-2015038 9. Schroers J., Veazey C., Johnson WL., Appl Phys Lett 2003;82:370 10. Wada T., Inoue A., Mater Trans 2003; 44:2228 11. A. Inoue, T. Zhang, N. Nishiyama, K. Ohba, T. Masumoto: Mater. Trans., JIM 34 (1993),

1234-1237. 12. Михаил Колев, Георги Стефанов, Тони Спасов, Людмил Дренчев, „Получаване и

охарактеризиране на нанокристална метална пяна от паладиеви сплави “, Созопол, Дни на БК 2018

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

160

Application of ZrO2 and ZrO2-TiO2 Coatings as Corrosion Barriers: Surface Composition and Structure

Irina STAMBOLOVA1, Ognian DIMITROV2, Stancho YОRDANOV3, Lyuben LAKOV3,

Bojidar JIVOV3, Sasho VASSILEV2, Vladimir BLASKOV1, Maria SHIPOCHKA1

1 Bulgarian Academy of Sciences, Institute of General and Inorganic Chemistry, Acad G. Bonchev Blvd., bl 11, 1113 Sofia, Bulgaria, e-mail: stambolova@yahoo.com

2 Bulgarian Academy of Sciences, Institute of Electrochemistry and Energy Systems, G. Bonchev Blvd., bl 10, 1113 Sofia, Bulgaria, e-mail: ognian@labatscience.com; sasho.vassilev@mail.ru

3 Bulgarian Academy of Sciences, Institute of Metal Science, Equipment and Technologies with Hydro and Aerodynamics Centre “Acad. A. Balevski”, 67 Shipchenski prohod st., 1574 Sofia, Bulgaria.

e-mail: stancho14@abv.bg Аbstract Two types of zirconium oxide sol gel coatings: pure ZrO2 and ZrO2/TiO2 composites were deposited by sol-gel method on stainless steel substrates. The morphology and surface features were examined by Scanning electron microscopy (SEM) and X ray photoelectron spectroscopy (XPS). X-ray diffraction analyses (XRD) was applied to investigate the phase composition. The corrosion resistances of the coatings were studied by evaluation of the weight loss in NaCl medium. According to XRD the ZrO2 coatings treated at 400oC and 500oC crystalized in cubic phase, while the Zr-Ti composites are amorphous after treatment at these temperatures. The surfaces of ZrO2/TiO2 coatings are smoother than those of ZrO2 films. The composite coatings deposited on stainless steel have zero weight loss in corrosive medium, while ZrO2 coatings exhibited lower corrosion resistance. This could be explained by the amorphous structure of the composites, which deteriorates the ion and electron conduction of the films due to the absence of grain boundaries. Keywords: corrosion resistances, sol-gel technology, zirconia and zirconia-titania films 1. Introduction The corrosion processes can damage many metal constructions such as: bridges, automobiles, airplanes, industrial plants, petrochemical, desalination, pharmaceutical, etc. which leads to a decrease in their efficiency and loss of useful or productive life. Corrosion prevention is performed through different techniques, and choosing the right one should be done while optimising between process cost, process performance, and corrosion effects. Coating is the most widely used method for preventing corrosion. The nanocoatings possess improved thermal, mechanical, physical, chemical, magnetic, electronic, and optical properties [1]. The fine sizes of oxide nanocoatings form a uniform physical barrier on the surface of the material and could be successfully used as corrosion barriers. For this purpose ZrO2, TiO2, Al2O3, SiO2 and their composites are the most effective protective materials against corrosion. The system ZrO2-TiO2 is very promising due to the interesting physicochemical properties of the individual oxides and was investigated in different areas. It was revealed that the mixed titania-zirconia particles prepared via UV (Ultraviolet rays)-induced crosslinking polymerization possess high refractive index, high transparency, good thermal stability and mechanical properties [2]. Srivastava et al. have successfuly applied titania–zirconia nanocomposite as urea detectors [3]. The addition of ZrO2 into TiO2 leads to improved photocatalytic activity as a result of decreased band gap and recombination rate. [4]. ZrO2/TiO2 porous coatings doped with zinc (Zn-ZrO2/TiO2) were prepared on titanium alloy. The biological experiments indicated that the coatings exhibit excellent antibacterial properties,

161

favorable cytocompatibilit and the corrosion resistance in the simulated body fluids [5]. Al Lateef et al. have prepared anticorrosive ZrO2–TiO2 nanocomposite coatings with different ZrO2 loading for carbon steel. The high protection efficiency of composite coatings have explained by the mutual influence of TiO2 and ZrO2 films [6]. The aim of this article is deposition and investigation of anticorrosion properties of ZrO2 and ZrO2/TiO2 composite coatings on stainless steel. 2. Experiment 2.1. Coatings preparation The zirconium precursor was 0.25M ethanol solution of ZrOCl2.8H2O, (р.а) with small quantity of nitric acid, acetylacetone as complexing agent and 0.4 ml polyethylene glycol (PEG) Mw=400. The steel substrates were ultrasonically cleaned in ethanol and acetone. Then the substrateswere immersed and withdrawn at a speed of 30 mm/min. Then, the samples are dried in air first at 100°C and 300°C for 1 hour consecutively. The procedures were repeated 5 times, after that the samples were treated at 400оС и 500 оС and denoted as Z1 и Z2, respectively. Titanium solution was prepared using titanium butoxide; Ti(OC4H9)4 and AcAc dissolved in 2-propanol. The resulting solution was mixed with zirconium solution in atomic ratio Zr:Ti=1:1. Then the deposition-drying procedures and final treatment followed the scheme described deposition of pure ZrO2 coatings. The samples were treated at 400оС и 500 оС and denoted as ZT1 and ZT2, respectively. 2.2. Sample characterization and estimation of the anticorrosion properties The phase compositions of the samples were studied by X-ray diffraction (XRD) with CuKα-radiation (Philips PW 1050 apparatus). A scanning electron microscope (SEM) Philips 515 was used for morphology observations of the films. X-ray photoelectron spectroscopy (XPS) was applied to investigate the chemical composition and electronic structure of the films surface. The measurements were carried out on AXIS Supra electron- spectrometer (Kratos Analitycal Ltd.) using achromatic AlKα radiation with a photon energy of 1486.6 eV and charge neutralisation system. The binding energies (BE) were determined with an accuracy of ±0.1 eV, using the C1s line at 284.6 eV (adsorbed hydrocarbons). The chemical composition in the depth of the films was determined monitoring the areas and binding energies of C1s, O1s, Ti2p and Zr3d photoelectron peaks. The corrosion resistance of the investigated samples and uncoated stainless steel (reference sample) estimated by weight loss were studied using salty corrosive solution of 3.5% NaCl at 25°C (EN ISO10289/2006). The temperature of the solution and the air temperature were controlled by calibrated thermometers. The mass weight loss was determined after 650 hours of corrosion attack. 3. Results and Discussion X-ray diffraction revealed a formation of ZrO2 cubic crystallographic phase after thermal treatment of zirconia Z1 coatings (Fig.1). The patterns of the samples ZT1 and ZT2 were not revealed any peaks of crystalline ZrO2, so the structures are amorphous. Similar results were presented by Guo et al. [7]. This research group have established that the structure of the TiO2/ZrO2 sol gel membranes is still in amorphous phase up to 500 °C and that the crystallization temperature of the mixed TiO2/ZrO2 powder has been significantly increased compared with the pure oxides. The amorphous structure of the composites suggests the high thermal stability.

162

25 30 35 40 45 50

steel

x

x

PDF N 650461

Inte

nsity

, a.u

.

2Θ, degrees

steel

Fig.1 XRD pattern of ZrO2 (Z1) sample

Fig 2 Morphology of fresh coatings Z1(a), Z2 (b) and after corrosion Z1 (c); Z2(d)

Fig. 3 Morphology of fresh coatings ZT1(a), ZT2 (b) and after corrosion ZT1 (c); ZT2(d)

163

The SEM photographs of Z1 and Z2 fresh samples are presented in Fig. 2. The coatings, annealed at 400oC and 500oC have island surface morphology with shallow microcracks. After corrosion test the surface of Z1 remains its characteristics, while the morphology of Z2 exhibits some visible signs of the acid attack: pits, cracks etc. The samples ZT1 and ZT2 exhibit smoother surface, than Z1 and Z2. The main surface features do not change significantly after the immersion in salt medium.

Fig. 4 Deconvolution of O1s; Zr3d and Ti2p core level spectra of fresh composites ZT1 and ZT2

Fig 5. Weight loss of the samples after corrosion attack

The XPS analyses were performed and show peaks of C1s, O1s, Zr3d and Ti2p on the surface of the films (Fig. 4). The O1s peaks are wide and asymmetric and could be deconvoluted by Lorentzian–Gaussian curve fitting into two components. The first ones at ~529.7 eV are assigned to lattice oxygen in TiO2 and ZrO2. The second peaks at ~531.1 eV are attributed to adsorbed hydroxyl groups. The Ti2p spectra have a peaks at ~458.3 eV for Ti2p3/2 and ~464.0 eV for Ti2p1/2. The doublet separation between the 2p3/2 and 2p1/2 peaks of ~5.7 eV and the registered binding energies are characteristic of TiO2 (Fig. 4). The Zr3d5/2 peaks have a maximum at 182.0 eV, typical for Zr4+ oxidation state. The corrosion test by weight loss method in Neutral Salt Spray Chamber showed that pure ZrO2 definitely have lower corrosion

0.00E+001.00E-052.00E-053.00E-054.00E-055.00E-056.00E-057.00E-058.00E-059.00E-05

Z1 Z2 ZT1 ZT2

Wei

ght l

oss (

g/m

2 )

164

resistance than the ZrO2/TiO2 composite coatings. (Fig. 4). This result probably is due to the more pronounced crystallization of of the samples Z1/Z2 (as can be seen from the Fig. 1). It could be supposed that the increased crystallization leads to deeper and more pronounced boundaries between individual grains, which accelerate the intercrystalline corrosion processes between the grains. It was established for TiO2–CeO2 composite films that the amorphous structure deteriorates their ion/electron conduction, thus improving the barrier properties [8]. Conclusions Zirconia and zirconia-titania films have been prepared by sol-gel technology and were studied as protective barriers against corrosion. Pure zirconia films exhibit cubic phase, while the composites are amorphous. The samples possess relatively dense structure with shallow microcracks. The pure zirconia coatings treated at higher temperatures (500oC) manifested lower corrosion stability than those treated at 400oC. It was established that the ZT1 and ZT2 composite samples, treated at 400oC and 500oC manifested better stability to corrosion attack than Z1 and Z2 probably due to their amorphous structure. Acknowledgements The authors are grateful to the financial support of Bulgarian National Science Fund at the Ministry of Education and Science, Contract No DN07/2 (14.12.2016) References 1. Bashir, S.; Liu, J. L., Nanomaterials and Their Application. In Advanced Nanomaterials

and Their Applications in Renewable Energy; Elsevier Inc.: Amsterdam, The Netherlands, 2015; pp. 1–50, ISBN 9780128017081

2. Nakayama, N., T. Hayashi, Preparation and characterization of TiO2–ZrO2 and thiol-acrylate resin nanocomposites with high refractive index via UV-induced crosslinking polymerization Composites Part A: 38(2007) 1996-2004

3. Srivastava S., Md. A. Ali, P. R. Solanki, P. M. Chavhan, M. K. Pandey, A. Mulchandani, A. Srivastava, B. D. Malhotra, Mediator-free microfluidics biosensor based on titania–zirconia nanocomposite for urea detection, RSC Adv.,Vol 3, 2013, pp. 228-235.

4. Pirzada, B M., N. A. Mir, N. Q. Owais, M. S. Sabir, M. Muneer, Synthesis, characterization and optimization of photocatalytic activity of TiO2/ZrO2 nanocomposite heterostructures, Materials Science and Engineering: B, Vol. 193, 2015, pp. 137-145

5. Wang, R., X. He, Y. Gao, X. Zhang, Х. Yao, B.Tang, Antimicrobial property, cytocompatibility and corrosion resistance of Zn-doped ZrO2/TiO2 coatings on Ti6Al4V implants, Mater. Sci. Eng. C, Vol. 75, 2017, pp. 7-15.

6. Abd Al Lateef, H. M., M. Khalaf, Corrosion resistance of ZrO2–TiO2 nanocomposite multilayer thin filmscoated on carbon steel in hydrochloric acid solution, Mater. Characteriz., Vol. 108,2015, pp. 29–41

7. Guo, H., S. Zhao, X. Wu, H. Qi,, Fabrication and characterization of TiO2/ZrO2 ceramic membranes for nanofiltration, Microporous and Mesoporous Materials, Vol. 260, 2018, pp. 125–131.

8. Ghasemi,T., A. A. Shahrabi, H. O. Hassannehad, S. Sanjabi, Effect of heat treatment on corrosion properties of sol–gel titania–ceria nanocomposite coating, J. Alloys Comp. Vol. 504, 2010, pp. 237-242.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

165

Magnetron Deposition of the Thin Coatings with High Dielectric Permeability on the Alloy Steel

Lyuben LAKOV1, Mihaela ALEKSANDROVA1, Petio IVANOV1, Timur NURGALIEV2

1Institute of Metal Science Equipment and Technology with Hydro-aerodynamic center “Acad. A. Balevski”-

BAS, Sofia, Bulgaria 2Academician Emil Djakov Institute of Electronics Bulgarian Academy of Sciences

e-mail: mihaela.krasimirova@mail.bg Abstract In the present work, ceramic titanium phases with high dielectric permeability were synthesized. The synthesis is carried out by a sol-gel method. Particular attention has been paid to magnetron deposition as it allows the deposition of metals, alloys, ceramic on a wide range of substrate materials. At the same time, the article is the development of corrosion resistant coatings, solid ceramic coatings with desirable properties useful for creating a supercapacitor. Keywords: sol-gel, magnetron deposition, coatings, alloy steel

Магнетронно разпрашаване на тънки слоеве с висока диелектрична проницаемост върху подложка от легирана стомана

Любен ЛАКОВ, Михаела АЛЕКСАНДРОВА, Петьо ИВАНОВ, Тимур НУРГАЛИЕВ

1. Въведение

Известни са редица методи за изработване на многокомпонентни керамики подходящи за изработване на изделия със специфични технически характеристики. Получаването на тънки ВТСП (високотемпературни свръхпроводници) в голяма степен се определя от материала и кристалната структура на подложката. От друга страна структурата и устойчивостта им се определят от методите за синтез и методи на отлагане. Най-подходящите подложки са монокристалните от стронциев титанат, магнезиев оксид и циркониев двуокис.[1,2]

Високочестотните тънки слоеве (ВЧТС) се получават чрез йонно разпрашаване. Предпочитат се магнетронните системи поради по-голямата скорост на отлагане (до 10 nm/мин) и простотата на оборудването в сравнение с йонно-лъчевите източници. Разпрашават се постояннотоково или високочестотно керамични мишени с диаметри от 50 до 100 cm (2-4 инча), в смес от аргон и кислород.[1-5]

Диелектриците на базата на BaTiO3-BaSnO3 намират широко приложение в електрическата и електронната промишленост поради високата си диелектрична константа (ɛr). В зависимост от използваните подготвителни условия, тънките филми от BaTiO3 показват широк диапазон на диелектрично поведение. Ниска стойност на ɛr приблизително 12, се получава, когато BaTiO3 се отлага при температура на подложката приблизително 23°С [1]. Въпреки това, за да се постигне стойност на ɛr по-голяма от 1000 е необходимо филмът от BaTiO3 да се отлага при температура на носителя до 1000°С [5-7].

166

Диелектричната проницаемост може да бъде дори по-висок от 7000, ако отлагането протича при температура, по-висока от 580°С достигаща до 1200°С за няколко часа [1]. Установено е, че тази стойност е пряко свързана с размера на кристалите на филмите BaTiO3 или BaSnO3. Аморфният филм има склонност да дава по-ниско ɛr, докато по-висок ɛr се получава, ако филмът има поликристален характер. Теоретично, висок и регулируем капацитет на единица площ може да бъде реализиран чрез използване на BaTiO3 като изолационен материал. На практика, някои проблеми възпрепятстват използването на BaTiO3 в хибридни материали с тънки покрития. Един от основните проблеми в тенденцията за разработване на ВТСП филми е наличието на висока електропроводимост [8-10].

Jia и колектив разглеждат еднослойни структури от аморфен или поликристален BaTiO3 тънкослоен кондензатор. Аморфните тънки филми на BaTiO3 показват добри изолационни свойства, но също и ниско ɛr. Стойност на ɛr в диапазона 12-20 се съобщава, когато филмът се отлага при стайна температура или при температура на субстрата под 700°С [1, 4, 7]. Поликристалните BaTiO3 тънки филми показват сравнително висока Er, но също така и висока стойност на ơ. Отчетено е, че увеличаването на ɛr от 16 до 400 е придружено с нарастване плътността на протичащия ток при напрежение 5 V от 10 -13 A cm-2 до 10-3A cm-2 [6,7,8,9]. Разбира се, плътността на протеклия ток също е функция на дебелина на филма. Въпреки това, с увеличаване дебелината на диелектрика намалява капацитета на единица площ. В литературата са описани изследвания на някои нови структури, които могат да запазят природата на поликристалния BaTiO3 с висок ɛr, но също така са изследвани и характеристиките на аморфен BaTiO3 и BaSnO3 с ниска ơ. Филмите се отлагат като се използва RF магнетронно разпрашване. Изследваните кондензаторни структури включват конвенционални конструкции от еднослоен аморфен или еднослоен поликристален материал. За да се постигнат по-добри характеристики на тънкослойните кондензатори от BaTiO3 и BaSnO3, бяха изследвани кондензаторни структури, отложени върху легирана стомана.[11-16]. 2. Експериментална част

Чрез зол-гелен метод бяха синтезирани титанатни фази на основата на BaTiO3 (ВТО) и BaSnO3(ВSO). Изходните прекурсори се хомогенизират на магнитна бъркалка модел ТК 22 Techno Kartell в продължение на 3 часа. Полученият гел старее при температура на околната среда. Суши се в продължение на 24 часа в сушилня на 60ОС.

За отлагането на слоевете от ВТО (BaTiO3) и ВSO (BaSnO3) бяха използвани подложки от легирана стомана с размери 5x10mm2 и 10x10mm2. Изследвано е влиянието на температурата на подложката и естествения окисен слой върху качеството на отлагане на тънки слоеве от BaTiO3 и BaSnO3. Разработени са пет серии образци при различни температури на подложката.(Таблица.1)

Таблица1: Серии образци при различни обработки на подложката

Серия № I II III IV V Обработка на окисния

слой

Без обработка

С обработка Двуетапно отлагане

С обработка пасивация

С обработка пасивация

С обработка пасивация

Ar:O2 10:1 10:1 10:1 10:1 1:1700оС ВаSn1 ВаSn1а ВаSn1в ВаSn1д ВаSn1ж750оС BaSn2 BaSn2б BaSn2г BaSn2е BaSn2з800оС BaTi 1 BaTi 1а BaTi 1б BaTi 1в BaTi 1г

167

Сериите се отличават по обработката на подложките. Химическата обработка се

осъществява непосредствено преди началото на отлагането. Предварително са третирани подложките в разтвори на сярна киселина и флуороводород.

От получената кристална фаза е изготвена мишена, която се използвана за магнетронно нанасяне на тънки слоеве върху подложки от стомана. Високочестотният магнетрон, функциониращ на честота 13,56 MHz, e монтиран във вакуумен универсален пост ВУП-5. Остатъчното налягане във вакуумната камера преди пускане на работния газ Ar(50%)/O(50%) е не по-голямо от 2.10-4 Torr, като нанасянето на тънки слоеве е извършено при работно налягане ~5.10-2 Torr. Преди всяка процедура на нанасяне е направена кратковременна „тренировка” – разпрашване (~10 мин.) на мишена при затворена заслонка, при което разпрашени от мишената частици не попадат върху подложката. С отваряне на заслонката започва процедурата на отлагане на слоя, която продължава от 1 до 4 часа. Отлагането е извършено при постъпваща и отразена мощност на магнетрона съответно ~ 80W и 26W, и при индуцирано напрежение на мишената ~280V. 3. Резултати и дискусии

Чрез зол-гел метод бяха получени фази BaTiO3 и BaSnO3. И двете фази са получени при значително по-ниски температури в сравнение с традиционните методи за синтез и на двете фази. Отложени бяха върху подложка от легирана стомана. На рентгенограмите са изобразени получените кристални фази като на фиг. 1 нямаме термично третиране. Поради този факт в шихтата е установено присъствие на BaCO3. На фиг. 2 е представена фаза без наличие на бариев карбонат след третиране при 600оС.

Фиг. 1. Зол-гел синтез преди накаляване на пробата.

Фиг. 2. Зол-гел синтез след накаляване на пробата при 600ОС.

Експериментално беше установено, че температурата на носителя влияе върху кристалната структура и това оказва въздействие върху ɛr – колкото по-висока е температурата на субстрата по време на разпрашването, толкова по-висока е ɛr. Съпоставката на събраните литературни данни и експериментални резултати дават добра основа за по-нататъшните изследвания в областта и възможност за разработване на модул за суперкондензатор.

Barium Titanium Oxide

00-044-1487 (D) - Witherite, syn - BaCO3 - Y: 9.03 % - d x by: 1. - WL: 1.5406 - Orthorhombic - a 5.31280 - b 8.90380 - c 6.43350 - alpha 90.000 - beta 90.000 - gamma 90.000 - Primitive - Pmcn (62) - 4 - 304.331 01-070-9165 (*) - Barium Titanium Oxide - Ba(TiO3) - Y: 108.53 % - d x by: 1. - WL: 1.5406 - Cubic - a 4.00940 - b 4.00940 - c 4.00940 - alpha 90.000 - beta 90.000 - gamma 90.000 - Primitive - Pm-3m (221) - 1 - 601-072-3822 (*) - Barium Titanium Oxide - Ba(Ti2O5) - Y: 75.44 % - d x by: 1. - WL: 1.5406 - Monoclinic - a 16.89900 - b 3.93500 - c 9.41050 - alpha 90.000 - beta 103.103 - gamma 90.000 - Base-centered - C2 (5) Operations: Background 1.000,1.000 | ImportFile: 3.2 800oC.raw - Type: 2Th/Th locked - Start: 5.300 ° - End: 79.984 ° - Step: 0.029 ° - Step time: 52.5 s - Temp.: 25 °C (Room) - Time Started: 9 s - 2-Theta: 5.300 ° - Theta: 2.650 ° - Chi: 0.00 ° - Phi: 0.00 ° - X:

Lin

(Cou

nts)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

2-Theta - Scale8 10 20 30 40 50

Barium Titanium Oxide

01-079-2263 (*) - Barium Titanium Oxide - Ba(TiO3) - Y: 80.80 % - d x by: 1. - WL: 1.5406 - Cubic - a 4.00600 - b 4.00600 - c 4.00600 - alpha 90.000 - beta 90.000 - gamma 90.000 - Primitive - Pm-3m (221) - 1 - 64.01-072-3822 (*) - Barium Titanium Oxide - Ba(Ti2O5) - Y: 40.56 % - d x by: 1. - WL: 1.5406 - Monoclinic - a 16.89900 - b 3.93500 - c 9.41050 - alpha 90.000 - beta 103.103 - gamma 90.000 - Base-centered - C2 (5) Operations: Background 1.000,1.000 | ImportFile: Proba 3.4.raw - Type: 2Th/Th locked - Start: 5.300 ° - End: 79.984 ° - Step: 0.029 ° - Step time: 52.5 s - Temp.: 25 °C (Room) - Time Started: 11 s - 2-Theta: 5.300 ° - Theta: 2.650 ° - Chi: 0.00 ° - Phi: 0.00 ° - X

Lin

(Cou

nts)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

2600

2-Theta - Scale6 10 20 30 40 50 60 70

168

4. Заключение

Кондензаторите със двуслойна и трислойна структура имат някои обещаващи предимства за електрически и електронни приложения. Трислойният кондензатор може да бъде един от най-добрите възможности за избягване на рязката промяна на електрическото поле от поликристална област в аморфна област. Сравнителните електрически параметри на пробивно напрежение и електропроводимост на трислойната с тези на еднослойната аморфна структура, но сравнително висока диелектрична константа също правят трислойния кондензатор по-привлекателен за промишлена употреба. Литература 1. Q. X. Jia, Z. Q. Shi and W. A. Anderson, „BaTiO3 thin film capacitors deposited by r.f.

magnetron sputtering”, Thin Solid Films, 209 (1992) 230 -239. 2. K. Sreenivas, A. Mansingh and M. Sayer, J. Appl. Phys., 62 (1987) 4475. 3. Y. Shintani and O. Tada, J. Appl. Phys., 41 (1970) 2376. 4. T. L. Rose, E. M. KeUiher, A. N. ScoviUe and S. E. Stone, J. AppL Phys., 55 (1984) 3706. 5. I. H. Pratt and S. Firestone, J. Vac. Sci. Technol., 8 (1972) 256. 6. C. A. T. Salama and E. Siciunas, J. Vac. Sci. Technol., 9 (1971) 91. 7. J. K. G. Panitz and C. C. Hu, J. Vac. Sci. Technol., 16(1979) 315. 8. J. C. Olsen, D. T. Stevison and I. Bransky, Ferroelectrics, 37 (1981) 685. 9. E. P. Kashchieva, V. D. Ivanova, B. T. Jivov and Y. B. Dimitriev, „Nanostructured borate

glass ceramics containing PbMoO4”, Physics and Chemistry of Glasses, 41 (6), 2000, pp. 355-357.

10. Elena P. Kashchieva, Vanya D. Ivanova, Bojidar Tzv. Jivov, Plamen K. Petkov, Yanko B. Dimitriev, „Structure-Property Correlation in Lead-Borate Composites with Participation of PbMoO4”, In: Proceedings of the 13th Conference on Glass and Ceramics, 29 September – 1 Oktober 1999, Varna, Bulgaria, Vol. 1 (Glass), Varna, Eds B. Samuneva et al. (Science Invest, Sofia, 1999), pp. 159-164.

11. V. D. Ivanova, E. P. Kashchieva, B. T. Jivov, Y. B. Dimitriev, „Electron Microscopic Study of Lead-Borate Composites Containing PbMoO4 Nanocrystals”, Nanostructured Materials Application and Inovation Transfer, Heron Press Science Series, Sofia, 2001, pp 30-32.

12. St. I. Yordanov, A. D. Bachvarov-Nedelcheva, R. S. Iordanova, “Influence of ethylene glycol on the hydrolysis-condensation behavior of Ti(IV) butoxide”, Bulgarian Chemical Communications, Special Issue A, Volume 49, 2017, pp 265-270.

13. Li, H. D.; Feng, C. D.; Yao, W. L. MaterialLetter.2004, 58, 1194. 14. Xu, Q.; Chen, M.; Chen, W.; Liu, H. X.; Kim, B. H.; Ahn, B.-K. ActaMaterialia. 2008, 56,

642. 15. Lee, J.-K.; Yi, J. Y.; Hong, K. S. Journal of Applied Physics. 2004, 96, 1174. 16. Yasuda, N.; Konda, J. Applied Physics Letters. 1993, 62, 535.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

169

Technology for Production and Experimental Furnace for Hitting of Article "Yellow Bricks"

Marieta GACHEVA, Lyuben LAKOV, Krasimira TONCHEVA

Bulgarian Academy of Sciences, Institute of Metal Science, Equipment and Technologies

with Hydro- and Aerodynamics Centre “Acad. A. Balevski”, 67, “Shipchenski Prohod” Blvd, 1574 Sofia, Bulgaria, e-mail: mvgacheva@abv.bg

Abstract In the laboratory, prototypes of yellow pavements for street pavement have been prepared by creating and testing technology for their production from Bulgarian raw material based on sedimentary marble rocks. On the basis of the technological parameters a design assignment was prepared a thermal furnace for production of yellow paving stones was designed to cover experimental sections from the center of Sofia, aiming at continuous testing and proving in real conditions their tribological indicators.

Keywords: Mergel rocks, yellow pavers, “Clam” thermal furnaces. 1. Introduction Bulgaria has a variety of deposits of sedimentary rocks (marble rocks) suitable for the development of recipe compositions and technology for the production of yellow pavers. The elaborated prototype technology is based on the classical methods [1-3] used in the silicon industry, which enables the rapid organization of production with available standard equipment. The indicators of the finished samples are consistent with the requirements for this type of ceramic flooring and the existing standard [4]. Based on this experience and material from sedimentary rocks (marble), a production table for the petrochemical material was developed and tested in an experimental technological line and yellow pavers were produced, equivalent in color to the so-called yellow pavers, which were paved at the center of Sofia, but which excelled them in physic and mechanical, climatic and tribological indicators, introduced at the beginning of the last century. Works have been reported at international conferences and published in collections and journals [5-8]. The use of heat treatment is a widely used technological method for the synthesis of various phases characterized by a diverse structure [5-11]. For this reason, it is of interest to construct new furnaces, equipment and aggregates tailored to the specifics of the final products. An experimental plot has been set up for the production of yellow paving stones based on sedimentary rocks in the Firm “Parent idustry” of town Popovo. What is missing for a small production of new products – the paving, not dependent on the natural raw material, is a furnace with a homogeneous temperature field and temperature programming for conducting high temperature liquid phase synthesis of a newly created original petrographic color material. 2. Aim The aim of the present work is the creation of a therm and technical facility with a homogeneous temperature field with the possibility of programming a temperature regime of firing with a performance of 20-24 pavements per day and the development of technology for production of artificially created compositions for yellow and other colored paving stones – white, green, brown and others.

170

The conditions for achieving the objective are to create a white base composition which, by modifying with various additives, achieves the listed colors and qualities of the paving material from natural raw materials. 3. Experimental technology The elaborated prototype technology is based on a patent – protective base composition of washed kaolin, hydrated lime powder, magnesium oxide and colorants in a specified ratio. The mixture is homogenized in a mixture, plasticized with a humidity of 18-20%, left to stand for 2 days and pressed into paving molds. Sizes of the press for plastic pressing. The resulting blanks are dried in a vacuum drier to 1-2 % residual moisture and processed according to the selected temperature regime for the respective composition and color. The thermal treatment is carried out in a "Mida" furnace with a programmable process regulator for programmed process guidance.

− Heat rate: 1 – 2 to 3 – 4 oC / min; − Temperatures, time and number of inhibitions according to the chosen composition

and color; − Maximum working temperature up to 1220 oC up to 5 hours depending on composition

and color; − The cooling rate is also 6 – 7 to 8 – 10 oC / min.

The new samples are also characterized by about 80 times lower surface porosity and 19 times lower water absorption compared to the original yellow pavers. The following characteristics of prototypes were found:

− compressive strength – 2900-3000 kg / cm2, − wear resistance – 0.05 g / cm2, − micro-hardness – 760-800 kg / mm2, − thermal resistance of 30 °C (500 to 20 °C).

Fig. 1. Mounting drawing of a "Mida" furnace

171

4. Construction characteristics of population furnace – type "Mida" Technical specifications for a setting for the furnace design are the next parameters:

− Useful working area of the furnace 900 x 600 x 250 mm; − Heaters – heater A1 2 x 7 pieces with common power 20 kW two-sided; − Maximum firing temperature up to 1250°C; − Programmer for execution of the temperature regime of synthesis; − Hair homogeneity with 2 thermocouples with possibility to place two more pieces; − Isolation of the working space – high temperature corundum wadding plates.

The furnace was created and tested for working capacity. 5. Technical data regarding the temperature regulations The temperature is controlled by a temperature controller "TC – 3L. The temperature increases linearly. The supply voltage is 220 V AC, -15% / + 10%. Supported types of thermocouples are: (nickel – chromium – nickel) or S (platinum – rhodium – platinum); non-volatile memory of all programs, points and parameters; number of programs up to 9; number of retention points in each program – 9; retention time: from 1 to 1000 minutes at resolution: 1 min; a rise time of 1 to 1000 minutes. If the maximum allowed temperature is exceeded, the furnace switches off automatically. Operating ambient temperature range 0 to 55 оС. The furnace has three multifunction control buttons.

Fig. 2. Pictures of the manufactured and tested "Mida" furnace

Conclusion 1. Paving prototypes of a new, patent-patented base composition with modifiers and additives for colored paving stones including yellow without the use of sedimentary marble rocks have been prepared. Colorful pavers with stable colors are obtained. 2. Technological regimes for firing paving of different colors were created. 3. A high temperature furnace with a homogeneous temperature field and a programmable setting of the temperature regime was created, made and tested. Acknowledgement The authors express their gratitude to the Fund „Science Research” of the Ministry of Finance for Research project (Contract no № КП-06-ОПР03/4 of 14.12.2018), won in a competition for the financing of fundamental research in public Challenges – 2018.

172

References 1. Hlavac J. The technology of glass and ceramics, Oxford, 1983. 2. Zhechkov G., L. Konstantinova et al., "A Reference on Building Ceramics", Sofia,

Technika, 1986. 3. Gerasimov E., A. Gerasimov, A. Atanasov, V. Toshev, D. Petkov, D. Ivanov, L. Georgieva,

L. Pavlova, H. Drenska, P. Vinarov, P. Petrov, S. Bachvarov, S. Panova, S. Bagarov, S. Serbezov, S. Stefanov, S. Dzhambazov, T. Stojkova, T. Datskova, H. Berlinov., "Technology of Ceramic Products and Materials", Edited by Prof. Bachvarov S. Saraswati press, Sofia, 2003.

4. Ceramic paving standard, BDS EN 1344: 2014, Ceramic paving, Requirements and test methods.

5. Encheva Sv., P. Petrov, D. Yanakieva, L. Lakov, K. Yankova, "Why are the yellow bricks yellow?" – In: Proc. National Conf. of Bulg.Geol.Soc. "GEOSCIENCES 2016", Sofia, BGS, pp. 25-26.

6. Lakov, L., N. Stoimenov, P. Tsonev, V. Vasilev, B. Jivov, Kr. Toncheva, "Physic and Chemical, Mechanical Properties and Tomographic Analysis of New" Yellow Pavements" of Petrographic Material, Collection of Papers, International Scientific Conference" Design and Construction of Buildings and Facilities ", DCB 2016 September 15-17, 2016, Bulgaria, pp. 115-120.

7. Lakov L., St. Encheva, P. Tsonev, V. Vasilev, B. Jivov, Kr. Toncheva, "Technology for Production, Chemical and Phase Composition of New" Yellow Paving "Based on Sedimentary Rocks", Collection of Reports, International Scientific Conference "Design and Construction of Buildings and Facilities", DCB 2016, 5-17 September 2016 Varna, Bulgaria, pp. 121-127.

8. Kandeva M., L. Lakov, P. Tsonev, V. Vasilev, Kr. Toncheva, "Tribological research of new Bulgarian" yellow pavers", HTCM Scientific Notifications, Days of Nondestructive Control 2016, issue. 1 (187), 2016, pp. 235-240.

9. Ilieva D., B. Jivov, D. Kovacheva, Ts. Tsacheva, Y. Dimitriev, G. Bogachev, Ch. Petkov, „FT-IR and Raman Spectra of Gd Phosphate Crystals and Glasses”, Journal of Non-Crystalline Solids, 293-295 (1), 2001, pp. 562-568.

10. Ilieva D., B. Jivov, G. Bogachev, Ch. Petkov, I. Penkov, Y. Dimitriev, „Infrared and Raman Spectra of Ga2O3-P2O5 Glasses”, Journal of Non-Crystalline Solids, 283 (1-3), 2001, pp. 195-202.

11. Ivanova V. D., E. P. Kashchieva, B. T. Jivov, Y. B. Dimitriev, „Electron Microscopic Study of Lead-Borate Composites Containing PbMoO4 Nanocrystals”, BAS, Nanoscience & Nanotechnology: Nanostructured Materials Application and Innovation Transfer, Eds E. Balabanova and I. Dragieva (Heron Press Science Series, Sofia, 2001), pp 30-32.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

173

Analysis of the Test Results of the Installation for Receiving the Foam Glass Continuous Tape and Suggestion for its Improvement

Krasimira TONCHEVA, Lyuben LAKOV

Institute of Metal Science, Equipment and Technologies,

with Hydro-and Aerodynamics Center "Acad. A. Balevski ", Bulgarian Academy of Sciences, Sofia, Bulgaria krasiton4@abv.bg

Abstract Based on the experience gained in the creation, experimentation and study of an equipment and a technology for the production of foam glass from household waste glass based on Bulgarian patents No 65718/24.11.2004 and No 65745 /26.05.2006, an idea was developed for a new device for which a patent application has also been filed and is now acknowledged. The basic operational concept of the previous device is preserved, but some deficiencies discovered during the experimentation have been corrected. Keywords: Foam glass, device for the production of foam glass. I. Introduction Obtaining foam glass at the Institute of Metal Science, Equipment and Technologies “Acad. Angel Balevski” with Center of Hydro- and Aerodynamics at the Bulgarian Academy of Sciences (IMSETHC-BAS) [1] is related to the development of a new technology and an installation for the manufacturing of continuous band and blocks of foam glass using a vertical (Bulgarian) method which differs from the traditional methods for obtaining these products. The new installation was tested under a project entitled “Study of the technological processes in the production of thermal insulation material – foam glass obtained in a model of a frothing unit of a new vertical production device.” The project was funded by the Bulgarian Ministry of Education and Science within a program of the Bulgarian National Science Fund (BNSF) – Contract No DTK-02/72 of 17.12.2009, as well as under Bulgarian patents Nos. 65718/24.11.2004 and 65745/26.05.2006 “Model of a vertical installation for manufacturing of continuous band of foam glass”. In Table 1 are shown the technical characteristics of the foam glass material produced using the new equipment. The completed project tasks, as reflected in the literature [3,4,5] form the basis for the testing and analysis of an experimental device for the production of bands or blocks (at greater width of the band – up to 200 mm) of foam glass using household waste glass.

Table 1. Technical characteristics of the foam glass material produced in Bulgaria with the new equipment

Property Value Density, kg/m3 from120 to 300 and more (at the customer’s request)Water absorption, % max 3 (practically 0) Thermal conductivity, W/m.K from 0.032 to 0.093Compressive strength, MРa from 1.9 to 4.2 (up to 8 with modifiers)

174

Due to the limited resources (reduction of the project budget for Stage 2 by BGN 100,000), the experimental program was not implemented as originally planned and the funds used for the implementation of the program up to that stage could not provide the return needed to generate sufficient experimental results for the required qualitative assessment. II. Analysis of the test results for the device for the production of a continuous band of foam glass 1. Organizing the construction of the device and its installation on a test site The development and the study of the vertical device for the production of band of foam glass, protected by Bulgarian patents [6,7], and the design of a technology for working with the device include several major tasks: organization of a test site, assembling and testing of the individual aggregates and nodes of the model device, wiring of the elements to form the heating system, building a control unit, putting the equipment into operation and running it for a certain amount of time to prove its functionality. The tested device is shown in Fig. 1 and Fig. 2. A test site of the required size was provided on the site of Promstroyproject Ltd. – Sofia. The firm was also the contractor for the mechanical structure of the device. The biggest difficulty was the shortage of funds for detailed testing and for the development of a working technology necessary to achieve product quality consistency (continuous band of foam glass). During the testing of the device it became clear that in order to ensure its proper and continuous operation, its construction required a number of modifications which could not be have been predicted in advance. Some deficiencies were eliminated while other changes requiring more funds were left for a later stage. The shortage of funds also affected the experimental work, especially the lack of funds for electricity costs and for the modification of some units of the system. Owing to this, the planned experiments involving the production of foam glass bands with varying thickness were curtailed.

Fig. 1. Diagram of the device a) Longitudinal section of the device

(b) Top view of the device Fig. 2. Picture of the device

175

Despite the difficulties, the model of the device, which is an 8-meter-high facility featuring 5 heating sections with a total of 43 heating elements and a furnace space capable of producing a continuous foam glass band, was launched and technological experiments were carried out. Experimental samples were obtained from which test samples were made in accordance with the requirements of the relevant standards and test procedures.

Fig. 3. Picture of the feed unit Fig. 4. Picture of the roller block

Fig. 5. Picture of the control unit Fig. 6. Diagram of the external heaters

The mechanical structure of the device was tested off site after being manufactured, which ensures its correct operation when mounted on site. Subjected to testing were the most important units: the mechanical support frame; all basic units of the mechanical structure such as the batch supply system – the feed unit (Fig. 3), the system for shaping the ingot by means of metal strips – roller blocks with tension springs (Fig. 4), a pull-out mechanism for ensuring uniform drawing of the finished plate of foam glass, pressing and cooling rollers, a ratchet mechanism for driving the strips and other smaller elements. The following elements were also produced and then tested separately:

− The control unit (Fig. 5), which can control and test the important units of the device; − The internal heater (Fig. 7 and Fig. 8) and the external heaters (Figures 6, 9 and 10)

located along the height of the structure – a total of 16 heaters located on 4 levels; all heating elements are mounted in boxes isolated from the non-working area using wadding and cardboard made of ceramic fibers. The boxes contain the thermocouples

176

controlling the temperature processes. The heating elements are wired using power and control wires, compensating wires and all other necessary operational elements;

− The hydro system located at the top of the device that drives all actuating mechanisms. 2. Organizing experimental work and conducting technological experiments. The organization of the experimental work of the model of the device for the production of bands of foam glass includes manufacturing and assembly of the different units and elements of the system, preparation of the feedstock, glass granules in this case, mobilizing human resources for the fulfillment of all tasks, and creating a precise plan, i.e. a scenario for carrying out the experimental work.

Fig. 7. Diagram of the internal heater Fig. 8. Picture of the internal heater

The technological process includes the following sequence of operations: 2.1. Processing of the necessary basic and auxiliary materials for the production of foam glass from household glass waste. The preparation of the feedstock for the device (Fig. 11 and Fig. 12) comprises grinding the glass waste in a large 2-ton ball mill with non-metallic insulation, micro granulation (with a size from 0.3 to 0.6 mm) of the groundеd and homogenized waste glass with the addition of a foamer consisting of 1% glycerin and 3% water glass, granulation of the obtained raw material to pellets with a size from 5 to 9 mm using a specialized granulator, hardening the granules obtained in a drying oven at 100-120 °C for 1-2 hours and sifting the granules using two types of sieves to separate them into two fractions with dimensions respectively up to 0.3 mm and up to 10 mm.

177

Fig. 9. Diagram of the external heaters Fig. 10. Picture of the external heaters

Due to the limited resources (reduction of the project budget for Stage 2 by BGN 100,000), the experimental program could not be implemented as originally planned.

Fig. 11. Picture of the feedstock used in the device Fig. 12. Obtaining raw granules with a granulator

2.2. Conducting of the technological experiments: putting the device into working mode Successive industrial experiments were conducted after the preparation of the various mechanisms and of the feedstock in order to obtain bands with a thickness of 60 mm and 160 mm. Test reports were issued for these experiments. From the material obtained from these experiments, samples were made and tested (Fig. 13) at the Department of Silicate Materials at the University of Chemical Technology and Metallurgy in Sofia, Partner No 1 in the Project, and at the Department of Building Materials and Insulations at the University of Architecture, Civil Engineering and Geodesy in Sofia, Partner No 2 in the project.

178

3. Analysis of the technological tasks and of the construction as a whole. The program of the project includes the fulfillment of the following tasks:

− Preparation of the feedstock in the form of granules (not in powder form, as in the case of the conventional production of foam glass) – accomplished.

− Exploration of the speed of movement (the ingot residence time in the different technological zones). This task requires extensive tests with different speeds of movement of the foam glass ingot towards the mechanism which cuts it into separate plates – partially accomplished.

− Developing of technological procedures for different types of foam glass (for plates of various thicknesses: 60, 100, 160 and 200 mm) – accomplished.

− Evaluation of the results of the planned technological experiments, conclusions and determination of the parameters for a future industrial model using the theory of similarity. In this task, it was intended to made adjustments to the documentation and to make a new constructive assignment for a following industrial model of the device – accomplished.

− Study of the physical and mechanical properties of the obtained samples of foam glass such as compressive strength, bending strength, density, apparent porosity, thermal expansion coefficient, heat resistance and others – accomplished.

− Conducting of climate tests, examination of the coefficient of heat conduction and sound insulation in order to assess the product’s ability to fulfill its intended purpose, which is the rehabilitation of buildings and the construction of supporting partition walls – partially accomplished.

− Preparation of a standardization document for the release of the product on the market using the laboratories of the Department of Building Materials and Insulations at the University of Architecture, Civil Engineering and Geodesy in Sofia, and of the Building Research Institute in Sofia or of another authorized body (the Bulgarian branches of LLOYD England or Germany) – not accomplished.

The fulfillment of each of the above-mentioned tasks was analyzed precisely, the results were summed up and conclusions were drawn. Particular attention was paid to analyzing the effectiveness of the technological and constructive solutions. The tasks were divided into 2 groups: qualitative and quantitative. The results from the analysis were presented using a special methodology with a ten-point scale for each technological and constructive task: For the first group – qualitative tasks:

− efficient utilization of glass waste – 10; − effective heating of the granule shaped batch material in order to froth it – 6; − obtaining a quality exterior surface and a different color range of the finished product

(ingot of foam glass), by moving the forming surfaces (metal strips) and coating them to avoid contact between them and the foam glass band, without scrap and losses – 8.

For the second group – quantitative tasks:

− Creating of formulations (recipes) for a batch made of waste glass and production of granules of specified sizes – 10;

− Investigation of the process of pore growth and testing of various foaming agents to determine the quantitative balance for optimal frothing according to the type of glass waste and the size of the granules – 10;

179

− Study of the thermal balance of the frothing process and creation of different thermal modes for the production of foam materials of various density – 8;

− Determination of the heating and cooling speeds in the frothing area and in the stabilization zone – 8;

Fig. 13. Test samples obtained from a 160 mm thick band

− Determination of the motion modes of the metal strips to obtain a quality ingot of foam

glass – 8; − Determination of the type and thickness of the coating on the boundary between the

ingot and the metal surface, as well as the optimal intervals of coating to obtain a quality surface of the ingot – 8 (6).

The constructional solutions of the frothing system of the device have also been analyzed and evaluated and methodologies have been developed to test them. This includes a block diagram of the system, constructive solutions for the different system units implementing specific technological functions and development of test methods for the different units. The evaluations for the different units are as follows:

− The feedstock installation supplying the device with granular material – 10; − The unit for heating the batch to frothing temperature combined with a process

monitoring and controlling system – 6; − The unit for fixation of the foamed structure – 8; − The unit for stabilization and subsequent cooling of the foamed material -8; − The driving unit for the ingot – 6; − The system for synchronization and control of the technological parameters of

frothing, fixing and stabilization of the speed of movement of the side strips, and hence of the ingot of foam glass – 10.

4. Summary of the results of the implementation of the project "Study of the technological processes in the production of thermal insulation material – foam glass obtained in a model of a frothing unit of a new vertical production device". The work that was carried out was complex and considerable. It covers a variety of creative activities: formulating conceptual solutions, implementing them through specific constructions and technologies, organizational activities and using research methods and analytical assessments to solve diverse complex tasks. Despite the cutting of the project budget, the results are very good. Further work is still to be done to turn the model into an operating facility suitable for commercialization. III. Solutions for improving the construction of the existing device by creating a new one with improved performance The main improvements of the existing and tested device are as follows:

180

1. In the existing device (Fig. 1) the quality of the middle layer of the monolithic ingot is not quite satisfactory due to the adherence of the foamed material to the housing of the heating unit since the batch frothing takes place at the lower end of the wedge-shaped heating unit which has ribs on its outer surface. The purpose of this positioning of the heating unit was to maximize the use of froth-forming energy by supplying it in the middle of the band or block being processed. This hinders the technological process and the finished product does not achieve the desired quality. In the new device (Fig. 14) [8] the concept for the internal heater has changed. The adhesion to the surface of the inner heater is eliminated by moving the heaters to the upper part of the ingot which is formed by accumulating granules so that the contact of the ingot with the walls and the ribs of the heater is minimal. In the new installation the lower surface of the vertical inner prismatic heating block is the heating roof of a rectangular furnace with a homogeneous temperature. Additionally, during the construction stage the inner wall of the rectangular furnace will be required to have minimal contact with the softened batch. Also, minimal clearance must be sustained between the inclined wall of the rectangular furnace and the movable metal strips which form the side walls of the foam glass band. 2. In the existing installation the metal strips which get expanded by the temperature and due to the pulling of the propelling rollers located at the top of the device. This affects adversely the performance of the device. In the new solution the propelling of the metal strips will be carried out by the lower rollers of the installation, designated in Fig. 14 as both driving and pulling. This allows the metal strips to stay tightened. As a result, the working efficiency of the device improves considerably.

Fig. 14. Scheme of the new system – Bulgarian patent 66903/19.12.2014

3. In order to obtain better homogenization of the temperature field, the width of the narrower heaters in the thermal heating zones is symmetrically extended from 200 mm to 350 mm and the additional expansion space is filled with insulating wool. The overlapping thus obtained

181

provides for the closing of the joints (left for free movement of the metal strips) which causes heat loss, as a result of which the frothing at the corners of the forming foam band is improved. 4. It was planned to investigate the possibility to use a composition of a coating that would prevent the foam glass material sticking to the walls of the internal heater, but because of the cuts in the project budget this task was not implemented. The new solution minimizes the contact of the frothed granules to the cooler metal surfaces. Only the well-heated walls of the furnace that have a minimum area of contact remain. It is desirable to seek a metal alloy with water glass dampness for these walls and with good insulation. The metal strips are coated each time before entering the heating zone, so that with them the problem of sticking does not occur. Conclusions An experimental study and an analysis of the working technology and the constructive solution of the installation for the production of foam glass band has been carried out. In order to avoid some shortcomings, a new construction of the device is proposed for which a patent application has also been filed and is now acknowledged. The following conclusions are derived: 1. With the help of the new and improved technical solution, an important optimization task is solved – the efficiency of the system is improved. 2. The proposed new construction for the frothing unit of the installation for forming a continuous band of foam glass in a vertical manner guarantees low energy consumption and avoids the problem of the material sticking to the inner heater by means of moving the inner heater to the upper part of the frothing section of the device. 3. The main goal is achieved – the heating and the frothing of the feedstock and the obtaining of a quality product. 4. The technological decision for the type of feedstock – in the form of granules – remains unchanged. References 1. Project NF-00-92 / 05.05.2005 for a preliminary study on the topic “Study for the

development of technology and equipment for introduction in the production of energy-saving insulation (foam glass) from waste glass”.

2. NSF – MES “Study of the technological processes in the production of heat insulating material – a foam glass obtained in a model of a frothing section of a new vertical production installation” under the contract with MES No DTK-02/72.

3. Toncheva Kr., L. Lakov, Technologies and Structures for Foam Glass Production – Overview, Scientific Conference RU & SU'10, 29-30.10.2010, Ruse, Series 1.2, pp. 25-33

4. Toncheva Kr., L. Lakov, I. Chorbov, Construction of the Model of the Organization for the Manufacture of Penthouse on Patent, 65718 / 24.11.2004, International Scientific Conference to commemorate the 65th Anniversary of the Technical University of Sofia – Sofia and the 100th anniversary of the birth of Acad. Angel Balevski, 13-16.09.2010, Sozopol, pp. 108-113.

5. Lakov L. Kr. Toncheva, Y. Georgiev, P. Zlatev, “Technology and equipment for the production of energy-saving materials from recycled glass materials”, Journal of the Bulgarian Academy of Sciences, vol. 3, 2012, pp. 38-45.

6. Bulgarian Patent No. 65718 / 24.11.2004, “Device for the production of foam glass”. 7. Bulgarian Patent No. 65745 / 26.05.2006, “Device for the production of foam glass”. 8. Bulgarian Patent No. 66903 / 19.12.2014, “A device for obtaining a foam glass”.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

182

Technology for the Preparation of White and Colored Petrurgical Materials on the Basis of Sedimentary Rocks

Marieta GACHEVA1, Lyuben LAKOV1, Bojidar JIVOV1, Kamelya MARINOVA2,

Stancho YORDANOV1, Stefan RAFAILOV1

1 Bulgarian Academy of Sciences, Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski”,

67 "Shipchenski Prohod" Blvd, 1574 Sofia, Bulgaria, e-mail: mvgacheva@abv.bg 2 University of Mining and Geology “St. Ivan Rilski” Sofia

Abstract Colored petrurgical materials obtained on the basis of sedimentary rocks are investigated. Develop a base composition to produce white specimens and a series of compositions applicable to the synthesis of materials characterized by different colors and shades. The starting batch is made with the participation of kaolin, silicate glass (in powder form, obtained from household glass waste) and varying the quantity of the introduced ceramic dyes (2-6%). The prepared formulations were subjected to thermal treatment at 1200°C. The color characteristics of the resulting sample bodies are determined on the Munsell scale. Keywords: Рetrurgical materials, ceramic dyes

Технология за получаване на бели и цветни петрургични материали на база седиментни скали

Мариета ГАЧЕВА, Любен ЛАКОВ, Божидар ЖИВОВ, Камелия МАРИНОВА,

Станчо ЙОРДАНОВ, Стефан РАФАИЛОВ 1. Увод

Седиментните скали намират приложение при изготвяне на различни традиционни строителни материали и същевременно представляват подходяща изходна суровина за разработване на нови такива с разнообразни характеристики. Разработени са рецептурни състави за получаване на петрургични материали, характеризиращи се с еквивалентен жълт цвят с предоставени сравнителни еталони от автентична паважна настилка с историческа стойност [3-6]. Съществен недостатък на тези състави, базирани предимно на природни суровини (без въвеждане на допълнителни оцветители), е ограничената цветна палитра при крайните продукти – главно в рамките на жълтата и червената гама. Поради това, интерес предствалава изследването на възможностите за получаване на серия цветни петрургични материали чрез въвеждане в изходните рецептурни състави на различни оцветители. Използваните оцветители са типични и широко употребявани в силикатната промишленост за изготвяне на строителни, опаковъчни, художествено-декоративни и други изделия от керамика и стъкло [1]. Въведените технологични добавки представляват специални неорганични пигменти с висока термична стабилност и подходяща химическа устойчивост. Към керамичните пигменти съществуват някои основни изисквания: да запазват цвета на тона си след прилагане на съответната термична обработка и да проявяват устойчивост спрямо разтворимото действие на

183

силикатните стопилки, с които влизат в контакт. Обикновено голяма част от оцветителите проявяват стабилност до 1200°C, а в някои случаи и при по-високи температуратурни стойности. Въвеждането на различни оцветители към базовите съставите предизвиква сложни химични процеси при повишаване на температурата и взаимодействие между изходните компоненти и приложените оцветяващи агенти, което оказва влияние на цветовите характеристики на образците. Използваното количество пигмент се обуславя от неговата специфика и необходимият интензитет на цвета на получаваните крайни продукти. Една от основните предпоствки за създаване на естетично и функционално изделие е определянето на оптимални състави и технологични условия на получаване.

Цел на настоящата работа е разработването на бял базов състав и серия рецептурни състави, подходящи за получаване на петрургични продукти с различни цветови характеристики. Материалите се разглеждат като потенциално приложими при изпълнение на инфраструктурни и архитектурни обекти, изготвяне на художествено-декоративни изделия и други. 2. Експериментална част

На база седиментни суровини, добити от находища на територията на страната, е разработен базов състав за получаване на образци с бял цвят и серия състави за синтез на цветни петрургични материали. Пробните образци са изготвени чрез употреба на следното оборудване: лабораторна везна Sartorius А210 Р-0 D1 (Germany) за измерване на отделните компоненти на шихтите, топковаова мелница, стандартен комплект лабораторни сита, матрица с диаметър 20 мм., механична преса за отпресоване на образците. Термичната обработка на образците е извършена в програмируема пещ, оборудвана с програматор за задаване на скоростта на нарастване и понижаване на температурата и определяне времето за провеждане на изотермична задръжка.

За синтез на основния състав са използвани следните компоненти: промит каолин от находище Каолиново със състав (в тег.%): SiO2 -54,07; Al2O3 – 32,09; Fe2O3 – 0,79; TiO2

– 0,24; CaO – 0,07; MgO – 0,15; K2O – 0,89; Na2O – 0,12 – до 80 тегл.% и фино смлени битови стъклени отпадъци в количество със състав (в тег.%): SiO2 – 72,7; Al2O3 – 1,2; CaO – 8,1; MgO – 2,7; NaO – 15,2 – до 20 тегл.%. Изборът на промит каолин (за целите на изследването) при разработване на съставите се дължи на неговата висока природна белота, висока огнеупорност и устойчивост на цветовите му характеристики при високи температури.

След хомогенизиране шихтата е пресована във формата на таблетки. Необходимата термична обработка на получените образци е извършена в програмируема пещ при температура 1100оС.

Към разработения базов състав са въведени различни количества керамични багрила (2-6 %) самостоятелно или в комбинация. Точната дозировка се определя експериментално.

Оцветителите са произведени във форма подходяща за смилане съвместно с изготвената по рецептурен състав маса. Приложената степен на смилане може да окаже въздействие на наситеността на цвета. Всяка партида е тествана в Отдела по котрол на качеството съгласно задължителните методи за тестване и Наръчник за осигуряване на качеството в съответствие с EN ISO 9001. Параметрите които се тестват са:

− размер на частиците (Malvern); − отклонение на цвета спрямо мостра-стандарт (Chromameter Minolta); − влажност. Използваните оцветители са представени в таблица 1.

184

За получаване на образци с еквивалентен жълт цвят с предоставени сравнителни еталони от автентична паважна настилка към базовия състав са въведени различни количества Fe2O3 и MgO. Високотемпературният синтез е осъществен при 1100-1200оС и задръжка от 1- 2 часа.

При отделните състави експериментално е установена зависимостта на цвета на опитните образци от вида и количеството на приложените оцветители. Определянето на цветните характеристики на пробните тела е извършено по системата Munsell [2].

Таблица. 1. Използвани оцветители

№ Наименование на цвета Химична система 1 К24111 (Черно) Cr Co Fe Ni Mn 2 K22611 (Светло синьо) Zr Si V 3 K22811 (Тъмно синьо) Co Cr Zn 4 К22011 (Синьо-зелено) Co Cr Al 5 К22640 (Зелено) Zr Si Co 6 К22211 (Турско синьо) Co Cr Zn 7 К23011 (Пепел от Рози) Sn Si Cr 8 К23411 (Розово) Mn Al 9 К22411 (Оранжево) Zr Si Cd S Se 10 К22311 (Жълто) Z Si Pr 11 К22180 (Бежово) Fe Cr Ni 12 К23111 (Кафяво) Fe Cr Al

3. Резултати и дискусия

Класифицирането на цвета на образците е извършено по карта на Munsells Soil Color, като изпитваните образци са поставени директно зад отвора, разделящ най-близките цветни определители в картата. Получените резултати са представени на фигура 1 и фигура 2. № А В С № А В С

1

6

2

7

3

8

185

4

9

5

10

Фигура. 1. Цветна палитра на петрургичен материал

Образците, получени чрез добавка на оцветител в количество 1,5 тегл.% към

базовия състав, при термична обработка от 1100о С и задръжка 1 час, притежават устойчиви и интензивни цветове (фигура 1).

Таблица. 2. Цветова характеристика на петрургични образци

№ A (Hue Value Chrom)

B (Hue Value Chrom)

C (Hue Value Chrom)

1 10 Y 8/2 10 Y 8/3 10 Y 8/6 2 10 B 8/2 10 B 8/4 10 B 8/6 3 2.5 R 7/2 2.5 R 7/4 2.5 R 6/4 4 5 G 6/2 5 G 4/3 5 G 4/4 5 10 R 5/3 10 R 4/3 10 R 4/4 6 2.5 R 8/2 2.5 R 7/4 2.5 R 6/4 7 5 R 8/2 5 R 8/4 5 R 6/6 8 10 R 8/2 10 R 7/3 10 R 6/3 9 5 PB 6/1 5 PB 5/1 5 PB 4/1 10 10 Y 8/1 10 Y 8/1 10 Y 8/1

Записването на цвета, определен по номенклатурата на Munsells се означава с

нюанс (hue), стойност (value), цвят (chroma). Цветовите характеристики на образците са представени в таблици 2.

Образец 11 Образец 12 Образец 13

Фигура. 2. Цвят на изследваните образци

186

За постигане на еквивалентен жълт цвят с еталона на автентичната паважна настилка, към базовия състав са въведени Fe2O3 и MgO в различни количества. Проби 11 и 12 са подложени на високотемпературен синтез от 1100оС и задръжка 1час, а термичната обработка на образец 13 се осъществява при 1200оС и 2 часа задръжка.

Табл. 3. Цветова характеристика на петрургични образци

№ Hue Value Chroma

11 10YR 6/6 brownish yellow

12 10YR 5/6 yellowish brown

13 10YR 6/6 brownish yellow

Резултатите показват, че определеният цвят на керамични проби с номера 11, 12 и 13 се различава от този на получените прототипи и предоставения еталон на „жълти павета“, които са определени до момента, а именно – 2,5Y 5/6 light brown. Пробите попадат в жълто-червената гама, а предходните материали изцяло в жълтата. Цветовите характеристики на образците са представени в таблици 3. 4. Изводи

Разработен е базов рецептурен състав за изготвяне на образци с бял цвят и серия модифицирани състави (на негова баз) за получаване на продукти с различни цветови характеристики. Експерименталните шихти са подготвени от промит каолин, силикатно стъкло (в прахообразно състояние, получено от стъклени отпадъци) и въвеждане на различни количества керамични багрила (2-6 %) самостоятелно или в комбинация.

При разработените състави е определена зависимостта на цвета на получените крайни продукти от вида и количеството на въведените оцветители. По системата Munsell са установени цветовите характеристики на изготвените пробни тела. Получените резултати позволяват извършването на допълнителни корекции на изходните рецептурни състави, с цел изготвяне на продукти със зададени цветни характеристики.

Въз основа на анализираните експериментални данни са определени оптималните технологични условия за изготвяне на образци и подходящ режим на термична обработка (до 1200oC и изотермични задръжки).

Разработените цветни петрургични материали са потенциално приложими за изготвяне на декоративни изделия (пана, мозайки и др.) за интериорна и екстериорна украса на архитектурни обекти и при изпълнение на различни градоустройствени дейности. Acknowledgement The authors express their gratitude to the Fund „Science Research” of the Ministry of Finance for Research project (Contract no № КП-06-ОПР03/4 of 14.12.2018), won in a competition for the financing of fundamental research in public Challenges – 2018.

187

References 1. Gerassimov E., A. Gerasimov, A. Atanasov, V. Toshev, D. Petkov, D. Ivanov, L.

Georgieva, L. Pavlova, N. Drenska, P. Vinarov, P. Petrov, S. Bachvarov, S. Panova, S. Bagarov, S. Serbezov, S. Stefanov, S. Djambazov, T. Stoykova, T. Datskova, H. Berlinov, "Technology of Ceramic Products and Materials", "Sarasfati", Sofia, 2003.

2. Kulev I.. "Archeometry", University Edition – "St. Kliment Ohridski " – Sofia, 2012, 839. 3. Lakov L., Sv. Encheva, P. Conev, V. Vasilev, B. Jivov and Kr. Toncheva, Manufacturing

technology, chemical and phase composition of new “yellow brick”, obtained on the base of sedimentary rocks”, in: Proceedings of the International Conference on Civil Engineering Design and Construction (Science and Practice), DCB 2016, 15–17 September, 2016, Varna, Bulgaria, pp. 121–127 (in Bulgarian).

4. Conev P., L. Lakov and V. Vasilev, Patent Application No. 112274/1304, 2016, Petrurgical material (in Bulgarian).

5. Gerasimov E. and S. Bachvarov, Techology of ceramic products, State Publishing House „Technica“, pp. 252-527.

6. Encheva S., P. Petrov, D. Yanakieva, L. Lakov and K. Yankova, “Why are the yellow bricks yellow?”, In: Proc. National Conf. of Bulg. Geol. Soc. “GEOSCIENCES 2016”, Sofia, BGS, 2016, pp. 25-26.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

188

Composite Materials Obtained from Foamed Silicate Products

Lyuben LAKOV1, Bojidar JIVOV1, Yonka IVANOVA2,3, Stancho YORDANOV1, Marin MARINOV1, Stefan RAFAILOV1

1 Bulgarian Academy of Sciences, Institute of Metal Science, Equipment and Technologies

with Hydro- and Aerodynamics Centre “Acad. A. Balevski”, 67, “Shipchenski Prohod” Blvd, 1574 Sofia, Bulgaria, e-mail: b_jiv@abv.bg

2 Bulgarian Academy of Sciences, Institute of Mechanics, “G. Bonchev” str., Bl. 4, Sofia 1113, Bulgaria, e-mail: yonivanova566@gmail.com

3 Sofia University "St. Kl. Ohridski", Faculty of Physics, “James Boucher” Blvd. 5, Sofia, Bulgaria. Abstract From waste silicate materials and technological additives at thermal treatment up to 900oC, foam products with specific characteristics are produced. With the participation of various fractions of the foamed silicate materials (with diameter up to 20 mm) experimental samples with composite structure and prototype of insulating panel were obtained. A technological method has been developed for the production of finished products or of various composites, liable to additional technological processing, according to their functional purpose. Keywords: foamed silicate materials, composites

Композитни материали получени от разпенени силикатни продукти

Любен ЛАКОВ, Божидар ЖИВОВ, Йонка ИВАНОВА, Станчо ЙОРДАНОВ, Марин МАРИНОВ, Стефан РАФАИЛОВ

1. Увод

Композитните материали представляват специфични технологични продукти, които съчетават характеристиките на изграждащите ги два или повече различни компоненти и същевременно притежават по-благоприятни експлоатационни показатели от тях [1-13]. Композитите са формирани от т. н. матрица (в аморфно или кристално състояние), изградена от фаза непрекъсната в обема на образците, армираща фаза, равномерно разпределена в материала и обособена междуфазова граница.

Физикохимичните характеристики на отделните компоненти и съществуващата междуфазова граница определят протичането на различни дифузионни реакции, процеси на фазообразуване, структорни изменения и други [1, 7]. Якосните показатели на композитните материали и механизма на тяхното разрушаване се обуславя от спецификата на компонентие, структурата на композита, вида на приложеното армиране, адхезията между фазите (матрица-армираща фаза), присъствието на различни дефекти, наличието на пори, възникването и разпространението на пукнатини, типа и скоростта на натоварване при експлоатация [1, 7]. Механичното разрушаване на композитите е последица от разрушаване на компонентите, изграждащи образците или от настъпило разслояване на съществуващата междуфазова граница между армиращата фаза и матрицата. При композитните материали, поради наличието на армираща фаза

189

съществува изразена вътрешна разделна повърхност, което ограничава разпространението на пукнатините.

Въз основа на съществуващите данни за свойствата на изходните компоненти е възможно създаването на нови композитни материали с подходящи целеви характеристики, съобразени с предвидените условия на експлоатация. Строителният бранш представлява една от основните сфери на приложение на разнообразни композитните продукти [1, 7]. Повишените нива на шум в големите градове, индустриалните райони и зоните около транспортната инфраструктура изискват разработването и приложението на ефективни звукоизолационни материали и системи [14]. Прилагането на адекватна звукоизолационна система при изграждането на нови сгради и реконструкцията на стари архитектурни обекти осигурява съществено намаляване на акустичните въздействия от околната среда [14]. Същевременно при проектирането на сгради и експлоатацията на вече съществуващия сграден фонд, основен проблем представлява осигуряването на подходяща енергийна ефективност. Монтажът на ефективна топлоизолация на жилищните и производствени постройки намалява необходимия разхода от енергия за поддържане на подходящи температурни стойности през отоплителния сезон. В настоящия момент в строителството намират приложение разнообразни материали с изолационни свойства: експандиран пенополистирол (EPS), екструдиран пенополистирол (XPS), депрон, минерални вати (стъклена, каменна, шлакова), полистиролбетон, газобетон, пенобетон, полиуретан, дървесно-влакнести плочи, коркови плочи, каучукови листа, пеностъкло и др. Същевременно интерес представлява създаването на нови алтернативни изолационни материали, приложими в строителството.

След проучване на преобладаващите в строителството звуко- и топлоизолационни изделия е разработен композитен материал с участие на силикатни пенопродукти, (получени от рециклируеми суровини) и хидравлично свързващо вещество. Цел на настоящата работа е изследване в лабораторни условия на акустичните и механични характеристики на експериментални образци, изготвени от получения композитен материал. 2. Експериментална част

За целите на изследването са получени пеностъклени гранули чрез прилагане на следните последователни технологични етапи: смилане на отпадъчно силикатно стъкло (с произход битови отпадъци), подготвяне на шихти с участие на полученото прахообразно стъкло и разпенващ агент (глицерин или CaCO3), гранулиране на съставите до суров гранулат и разпенване (при температури до 900oC) до получаване на пеностъклени гранули.

При изготвяне на експерименталните композитни образци е използвано хидравлично неорганично свързващо вещество (портланд цимент CEM I 52.5 R, производител Холсим България). Към първоначално изготвен циментов разтвор при непрекъснато разбъркване е добавена фракция пеностъклените гранули (с диаметър от 5 до 20 мм) до пълно омокряне на тяхната контактна повърхност. След изследване на серия рецептурни състави експериментално е установено подходящо (оптимално) количествено съотношение на използваните компоненти. Получената смес е положена в предварително подготвени кофражни форми с перфорирано дъно, което позволява отделяне на излишната течна фаза. С цел по-ефективно и ускорено отделяне от системата на течната фаза и оптимално разпределение на различните фракции пеногранули в обема на образците е приложена вибрационна обработка чрез поставяне на кофражните форми на вибростенд (до 50 мин). След престой от 24 h в кофражните матрици заготовките са

190

декофрирани и след допълнителен технологичен престой от 6 денонощия образците са подложени на окончателна обработка до необходимите крайни размери. Изготвени са стандартни експериментални образци (кубчета и призми) и композитен панел 60x55x8 cm.

За определяне на изолационната способност на композитните материали е използван коефициента на звукоизолация R, който представлява отношение на звуковото налягане на падащата звукова вълна към звуковото налягане на вълната, преминала през преграда [15-18].

Използва се метода на двете камери, между които се поставя изпитвания образец (фиг.1).

Фигура 1. Блок схема на апаратура за измерване на коефициент на звукоизолация.

На стената на първата камера е монтиран високоговорител, който създава звуково

поле, а в центъра е поставен микрофон, който измерва интензитета на създаденото поле. Прието е да се нарича „Source room”. В другата камера се разполага микрофон, който приема преминалия през изпитвания образец звук. Нарича се „receiving room”. Обемът на камерите е 0.125 m3. Камерите имат дебели стени и са облицовани със звукопоглъщащи материали. Предаването на звук извън изследвания панел е намалено до минимум. Режимът на работа е стационарен.

Високоговорителят VK 0829/38 (честотна лента 80- 16000 Hz) излъчва звукови вълни, които се възбуждат с генератор тип MS-9160. Микрофоните в камерата с източника и приемащата камера са от клас измерител, тип ECM-999 (честотна област 20 Hz-20кHz). Като измерително устройство се използва 16 битова компютъризирана измерителна система в реално време „Sound Level Meter System“ VT RTA и двуканална звукова карта тип ASIO (тип Focusrite Scarlett 2i2. Софтуерът за измерване е Multi-Instrument Software 3.8 [www.virtins.com]. С апаратурата се измерва звуковото налягане на падащата звуковата вълна в първата камера и на преминалата през образеца. С осцилоскоп се наблюдават сигналите и техните честотни характеристики. Анализът е направен в терцоктавни честоти.

Измерванията на звуковото налягане в двете камери се провеждат по два начина: 1. При използване на синусоидален сигнал, подаван към високоговорителя на

отделни честоти и измервания при всяка фиксирана честота. 2. С използване на бял шум в честотния диапазон от 20 до 20000 Hz и измервания

на звуковото налягане на падащата и преминалата през образеца-преграда звукова вълна. Коефициентът на звукоизолация се определя като разлика на измерените звукови

налягания [15-18] съответно в камерата с източник на звук и приемащата камера. 𝑅 = 𝐿 − 𝐿 , dB

191

Където LS и LR са звуковите нива, съответно на падащата и преминалата през образеца звукова вълна.

При извършените механични изследвания е използвана машина за изпитване чрез натоварване на опън, натиск и огъване “Amsler”. 3. Резултати и дискусия

При проведените лабораторни изследвания са извършени измервания на звуковите налягания при фиксирани честоти. В таблица 1 са представени средните стойности и стандартните отклонения.

Таблица 1. Средните стойности и стандартните отклонения.

Frequency f,Hz

Коефициент на звукоизолация R, dB

50 Average St Dev63 10.53 0.4280 15.17 3.75100 22.21 3.57125 27.97 3.75160 30.57 2.43200 25.41 4.75250 19.52 2.64315 24.86 6.39400 23.11 5.97500 25.28 5.68630 33.97 5.77800 34.46 2.031000 37.52 5.121250 45.85 6.461600 45.07 8.072000 41.09 5.542500 44.13 6.023150 42.36 2.604000 43.67 4.395000 49.50 2.79

На фигури 2 и 3 са представени резултатите от извършените акустични измервания

за изготвения експериментален панел, измерени на отделни терцоктавни честоти (фиг. 2) и при използване на бял шум и измервания на звуковите нива в целия честотен диапазон ( фиг. 3).

На фиг. 4 са представени усреднените стойности на коефициентите на

звукоизолация получени при лабораторни измервания на разработения композитен материал и на газобетон. Регистрирани са средна стойност на звукоизолация за изготвения експериментален композитен панел R≈33 dB (в целия честотен диапазон) и R=33 dB за итонг.

192

Фиг 2. Коефициенти на звукоизолация от честотата за композитен панел с пеностъклени

гранули

Фиг 3. Коефициент на звукоизолация от честотата за композитен панел при използване на бял шум и измервания на звуковите нива в

целия честотен диапазон

Фигура 4. Коефициенти на звукоизолация от честотата за газобетон и за композитен панел с пеностъклени гранули, измерени с показаната на фигура 1 експериментална установка.

Съобразно приложеното време на вибриране, използваните фракции гранули и

тяхното разпределение в образците, обемната плътност на продукта варира в различни граници. При употреба на няколко фракции гранули с различни размери по-малките попадат в образуваните празнините между гранули с по-големи размери, което понижава кухинността на образците. С нарастване на въведеното количество гранули с по-малък диаметър нараства обемната плътност и специфичната повърхност на продукта. Прилагането на непрекъснат зърнометричен състав се разглежда като по-оптимален вариант при изготвяне на композитни материали.

0.00

10.00

20.00

30.00

40.00

50.00

60.00

0 2000 4000 6000

R, dB

Frequency f, Hz

1 measurement 2 measurement

3 measurement Average R, dB

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000

R, dB

Frequency f,Hz

0

10

20

30

40

50

60

0 1000 2000 3000 4000 5000 6000

R, dB

Frequency f, Hz

газобетон composite panel

193

При извършените предварителни лабораторни изпитвания на стандартни пробни тела са констатирани средна стойност за якост на натиск 1,08 MPa, средна стойност за якост на опън при огъване 0,56 MPa и средна стойност на плътност 0,36 g/cm3.

Констатират се неизбежни отклонения при стойностите на якостните показатели при изпитване на отделните експериментални образци от изследваната серия композитни пробни тела, поради наличие на микронееднородности, разнообразни микропукнатини и различни структурни дефекти, образувани в процеса на първоначалното технологично изготвяне на заготовките и окончателната дообработка на пробните тела до стандартни размери.

Приложеният технологичен подход е подходящ за изготвяне на различни крайни изделия или заготовки подлежащи на допълнителна технологична обработка. Нанасянето на покрития с подходящи характеристики, съобразени с конкретните условия на приложение повишават ефективността на продукта. Композитният материал е потенциално приложим за получаване на изделия с различно функционално предназначение: звуко- и топлоизолационни неносещи панели, плочи, разнообразни профили и др. Алтернативна възможност представлява съчетаването на разработения композит с други негорими материал с изолационни характеристики (минерални вати и други) под формата на краен продукт изграден от няколко слоя. 4. Изводи

Изследвани са акустичните и механични характеристики на композитен силикатен материал, получен на база портландцимент (CEM I 52.5 R) и пеностъклени материали. При проведените предварителни лабораторни изпитвания на експериментален композитен панел е констатирана средна стойност на звукоизолация R≈33 dB. Регистрирана е средна стойност за якост на натиск 1,08 MPa и средна стойност за якост на опън при огъване 0,56 MPa при изпитваните пробни тела. Установена е средна стойност на плътност 0,36 g/cm3.

Използваният технологичен метод за изготвяне на образците се характеризира с редица предимства: оползотворяване на отпадъчни суровини (неразградими в естествена среда), употреба на широко достъпни материали с относително ниска цена (портландцимент и др.), използване на прости технологични процеси при изготвяне на заготовките и тяхната окончателна дообработка, получаване на незапалими, негорими, водоустойчиви, екологични, дълготрайни крайни продукти. Разработеният композитен материал е потенциално приложим за получаване на звуко- и топлоизолационни неносещи панели, разнообразни профили, плочи и др. References 1. Boydjieva Hr., “Composite silicate materials”, Sofia, MNP, 1989, (in Bulgarian). 2. Markgraaff J., “Overview of new developments in composite materials for industrial and

mining applications”, The Journal of The South African Institute of Mining and Metallurgy, March/April 1996, pp. 55-65.

3. Harris B., “Engineering composite materials”, The Institute of Materials, London, 1999. 4. Jones R. M., “Mechanics of composite materials”, Second edition, Taylor & Francis, 1999. 5. Boydjieva Hr., “Composite materials”, Sofia, Nasko, 2000, (in Bulgarian). 6. Daniel I. M., I. M. Daniel, “Engineering mechanics of composite materials”, Second

edition, New York, Oxford, Oxford University Press, 2006. 7. Yoleva A., G. Chernev, “Guides for exercise in composite materials based on inorganic

binders”, UCTM, Sofia, 2009, (in Bulgarian).

194

8. Nijssen R. P. L., “Composite materials an introduction”, 1st English edition, based on 3rd Dutch edition, A VKCN publication, Inholland University of Applied Sciences, 2015.

9. Gupta G., A. Kumar, R. Tyagi, S. Kumar, “Application and Future of Composite Materials: A Review”, International Journal of Innovative Research in Science, Engineering and Technology, Vol. 5, Issue 5, 2016, pp. 6907-6911.

10. Sai M. K. S., “Review of Composite Materials and Applications”, International Journal Latest Trends in Engineering and Technology, vol. 6, Issue 3, 2016. pp. 129-135.

11. Nagavally R. R., “Composite materials – history, types, fabrication techniques, advantages, and applications”. International Journal of Mechanical and Production Engineering, Vol. 5, Issue 9, 2017, pp. 82-87.

12. De Luca A., F. Caputo, “A review on analytical failure criteria for composite materials”, Review, AIMS Materials Science, 4 (5), 2017, pp. 1165-1185.

13. Subramani N., J. Ganesh Murali, P. Suresh, V. V. Arun Sankar, “Review on Hybrid Composite Materials and its Applications”, International Research Journal of Engineering and Technology (IRJET), Vol. 04, Issue 02, 2017, pp. 1921-1925.

14. D. Nazarski, Building Insulations, Publishing House “St. Naum “, Sofia, 2004, (in Bulgarian).

15. Fahy F., Foundation of Engineering Acoustics, Elsevier Academic Press, San Diego, 2005. 16. Samoylenko N., V. Didkovskiy, The Evaluation of the Sound Insulation of Partition in

Expanded Frequency Range, Journal of Physical Science and Application 3 (4), 2013, pp. 249-255

17. Farina A., P. Fausti, R. Pompoli, F. Scamoni, Intercomparison of laboratory measurements of airborne sound insulation of partitions, InterNoise 96, Liverpool England, pp. 537-1003.

18. Höller C., Review and Comparison of ASTM and ISO Standards on Sound Transmission in Buildings, Conference Paper August 2018, https://www.researchgate.net/publication/ 327920232.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

195

Phase Composition of TRIP-Steels after Aging

Margarita ILIEVA, Stoyan PARSHOROV

Institute of Metal Science, Equipment, and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski” at Bulgarian Academy of Sciences,

67 "Shipchenski prohod" St., Sofia 1574, Bulgaria, e-mail: s_parshorov@ims.bas.bg Abstract. The aim of the present study is to investigate the influence of various elements (carbon, nitrogen, manganese and chromium) on the phase composition after aging of four carbon and nitrogen austenitic-unstable TRIP-manganese and chromium-manganese steels. The results showed that: after aging, manganese austenitic-unstable steels, both carbon and nitrogen, form chemical compounds that destabilize austenitie and particularly transformed into martensite. When aging, chromium-manganese austenitic steels do not form martensite but only produce nitride or carbonitride phases. In the process of aging of carbon austenite, mixed carbides of cementite type and of the type Me23C6 are released. Keywords: phase composition, aging, TRIP-steels, XRD. 1. Introduction Austenitic-unstable steels are group of steels characterized in that the deformation and the thermal treatment sharply change their phase composition. After quenching, they have a virtually austenitic structure. When cooling to sub-zero temperatures, the steels form the so-called thermal martensite, at low degrees of deformation epsilon-martensite is obtained, and at higher degrees of deformation – deformational martensite. These properties are mainly due to their balanced chemical composition. In austenitic – unstable steels, the aging processes have a major impact on their tendency towards martensite formation in thermal and deformation influence. The formation of new phases during aging is due to the presence of carbide and nitride-forming elements in the solid solution, stabilizing of the austenite and formation of martensite at temperatures above room temperature. Aim of the present work is to investigate the influence of the different elements (carbon, nitrogen, manganese and chromium) on the phase composition after aging in four carbon and nitrogen austenite- unstable manganese and chromium- manganese steels. 2. Materials and methods The object of the study is four austenitic-unstable steels of chemical composition, shown in Table 1.

Table 1. Chemical composition – wt. %

Steel C% N% Mn% Cr% X30Mn12 0,32 - 12,42 -XA25Mn 0,04 0,246 12,84 -

X30CrMn10.10 0,37 - 10,43 10,73 X20A20CrMn10.10 0,22 0,237 10,77 10,56

196

The above compositions are selected from austenitic – unstable steels which after quenching have a virtually austenitic structure and show a good propensity for martensitic deformation. Test specimens of the investigated steels are preliminarily quenched from a temperature of 1150 ° C in water. Aging is carried out for two hours at 800 °C, where previous studies have shown that the aging processes are most intense. The samples tested were pretreated in a H2SO4 solution to purify from the oxide coating preventing the identification of the carbide and nitride phases. The thus-cleaned samples are subjected to electrolytic dissolution in a salt-acid solution at a current density of 0,05А/см2 after which X-ray phase analysis (XRD) was performed on the treated anode sludge. 3. Experimental results and discussion X-ray diffraction studies of solid samples and extracted anode sludge showed the following results – Table 2:

Table 2. Results of X-Ray analysis

Steel Phase composition after quenching

Phase composition after aging

X30Mn12 austenite+5% martensite austenite+15% martensiteXA25Mn austenite+10% martensite austenite+30% martensite

X30CrMn10.10 austenite austenite+(Cr,Mn)23C6 + (Fe,Mn)3C

X20A20CrMn10.10 austenite austenite+Mn5C2+Cr2N The experimental curves obtained on the "Леко TN-314" apparatus from the quantitative nitrogen assay in the anode sludge of samples of the nitrogen-alloyed alloys – XA25Mn and X20A20CrMn10.10 are shown in Fig.1.

Fig.1. Experimental decomposition results of Leko TN-314 nitrides [5]

197

The heating temperature is recorded in the abscissa, and the ordinate is the amount of nitrogen released at the respective temperature. The apparatus allows automatic recording of the set sum values of the quantities of nitrogen evaporated at the appropriate temperature intervals from decomposition of the available nitride or carbonitride phases as well as the total amount of nitrogen in the entire sludge. The results are shown in Table 3.

Table 3. Results from the quantitative analysis of nitrogen sludge

Alloy designation Nitrogen content in the sample %

Nitrogen content (in wt%) in anode sludge

Nitrogen content (in mass%) in the

maximum

XA25Mn 0,246 1,577 1,36

X20A20CrMn10.10 0,190 0,95 0,88 As it can be seen from the experimental results, the XRD analysis shows that in nitrogen and carbon steels alloyed with manganese only, no evidence of carbide or nitride phase presence is observed after aging. Undoubtedly, the processes of aging in these steels have occurred, as destabilization of austenite occurs from the release of manganese from the solid solution, the formation of new phases, and the transformation of part of austenite into martensite. Furthermore, there is a nitride phase in XA25Mn which is demonstrated by the thermal curve of "Леко TN314" in Fig.1, where the maximum of the manganese nitride alone is clearly outlined. Probably this is stable Mn3N2, as the presence of this nitride is found in our other studies in steels with similar compositions [1, 2]. Stoichiometric studies show that, with the available nitrogen content in the XA25Mn melt, provided that all of the nitrogen is bound in manganese nitride, the total nitride content cannot exceed 1.56% by mass, which cannot be detected by the XRD method. Similar calculations for the carbon alloy show the presence of, for example, Мn5C2, of not more than 2.8% by weight, which is also difficult to be detected by XRD method. The larger amount of martensite formed in the nitrogen-alloy after aging is due to the fact that nitrogen austenite has a lower stacking fault energy (SFE) compared to that of the carbon austenite and from there they are more prone to martensite formation [3]. XRD analysis of alloys containing 10% of chromium shows that austenite remains stable and does not form thermal martensite when aging, and from it phases typical of chromium-manganese austenitic steels are formed- Table 2. Carbon austenite (X20A20CrMn10.10) after aging forms both types carbides- (Cr,Mn)23C6 and (Fe,Mn)3C. It is known that manganese, as well as chromium, can replace a significant amount of the iron atoms in the cementite and the solubility of the alloying element in the cementite is as large as the closer it is to the iron in the periodic table of the elements [4]. The presence of Mn5C2 and Cr2N is observed in the nitrogen-alloyed chromium-manganese austenitic-unstable steel- X20A20CrMn10.10. The presence of only one nitride Cr2N is also confirmed by the nitrogen maximum of the thermal decomposition curve in Fig.1. This, of course, is easily explained, knowing that nitrogen is preferentially bonded to Cr in the C, Mn, Cr, Fe system i.е. the affinity of nitrogen in the direction of Cr, Mn, and Fe decreases [5]. The difference in the thermodynamic potential of Cr2N and that of manganese nitride at the aging temperature which for Cr2N is (-12,12 kcal/mol), and for Mn3N2 is (-9,17 kcal/mol) is very small [6] as it can be seen on Fig.2.

198

Fig.2. Temperature dependence of the isobar-isothermal nitride formation potential [5]

4. Conclusions 1. Upon aging, manganese the austenitic-unstable steels, both carbon and nitrogen- alloyed, form compounds that destabilize austenite, and it is partially transformed into martensite. This destabilization is significantly greater in the nitrogen austenite, which has a lower stacking fault energy (SFE) than that of the carbon one. 2. On aging, chromium-manganese austenitic steels do not form martensite but release nitride or carbonitride phases. 3. In the process of aging of carbon austenite, mixed carbides of cementite type and of the type Ме23С6 are formed. Acknowledgements The authors are grateful to the financial support of Bulgarian National Science Fund at the Ministry of Education and Science, Contract No DN17/17 /12.12.2017/. References 1. Ilieva М., I. Parshorov, I.Panchovski, Coference “Defectoscopy -96”, p.177. 2. Petrov U., Defecti i bezdifusionne prevrashtenija v stali”, Kiev, 1978. 3. Lahtin M., Leontieva P., Materialovedenie, Moskva, Mashinostroenie, М, 1972. 4. Lashko N., Zaslavskaja P., Kozlova M., and all, Fiziko-Chemicheskij fazovoj analiz stalej

I splavov, Metalurgija, 1978. 5. Averin V., Revjanin V., and all, Azot v metalah (Азот в метталах), Moskva, Metalurgija,

1976.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

199

Austenite Stability of TRIP-Steels

Stoyan PARSHOROV1, Peter PETROV2, Stefan VALKOV2

1 Institute of Metal Science, Equipment, and Technologies with Hydro- and Aerodynamics Centre “Acad. A. Balevski” at Bulgarian Academy of Sciences,

67 "Shipchenski prohod" St., Sofia 1574, Bulgaria, e-mail: s_parshorov@ims.bas.bg

2 Institute of Electronics of Bulgarian Academy of Sciences, Sofia, Bulgaria Abstract. The stability of austenite in TRIP-steel was investigated at uniaxial strain deformation. It has been found that by alloying, plastic deformation and aging, using the Shaeffler’s diagram, the phase composition of the solid solution can be controlled and predicted. The relationship between the composition of the solid solution, the micro-structural parameters of austenite and its stability is shown. The studies allow a new understanding of the applicability of TRIP-steel. Keywords: TRIP-steel, plastic deformation, Shaeffler’s diagram, phase composition 1. Introduction The steels of the austenite-martensite class known in publications as “steels of controlled transformation” or the so called TRIP-steels are characterized by plasticity provided by phase transformation as a result of deformation. This plasticity is accompanied by high strength characteristics and impact ductility. The TRIP-steels have a balanced chemical composition that provides they are austenite after quenching and after certain thermal treatments (aging at high temperatures of the order of 800ºC or cooling below room temperature) or after deformation at temperatures of the order of 100-150ºC a large part of the austenite transforms into martensite [1-3]. The aim of the present study is to investigate the dependence of the stability of austenite in TRIP-steels from alloying, aging and plastic deformation processes. 2. Material and method The investigations reported in publications show that austenite unstable steels contain carbon plus nitrogen in the range of 0.1-0.7% wt and austenite stabilizing elements, such as manganese above 10%, part of it being possibly replaced by nickel. The additional alloying with ferrite stabilizing elements in definite limits can render a positive effect on the austenite tendency to deformation martensite formation [1-7]. The Institute of Metal Science at the Bulgarian Academy of Sciences has developed and investigated more than 80 alloys with unstable structure. We subjected to detailed study 12 TRIP-steels of selected compositions meeting certain requirements – after quenching they have austenite phase composition and no more than 5% martensite (with the exception of alloy No. 10 which serves as a comparison) and after deformation to fracture of the samples they have maximum tendency to form deformation martensite of the order of 50-60%, Table 1. In order to study martensite transformation during tensile deformation a specialized installation is developed, described in details in [8], the registration of the transformation being performed

200

in magnetometric way. The installation permits to investigate the transformation of austenite in deformation martensite at room temperatures. The specimens are preliminary quenched from temperature of 1100ºC in quartz tubes in water. The size of the inherited austenite grain of all alloys is in the limits of 7-8 rating. For some more characteristic alloys presented in Table 1 X-ray diffraction analyses of the austenite microstructure parameters are made in compliance with a method described in details in [9-11]. It is based on the principle that each microstructure parameter of the martensite introduces its share in the extension of every one of the crystal lattice reflection lines. The relation between the coefficients of Fourier order describing the reflection line and its width as sum effect allows obtaining dependencies connecting in certain way the influence of every microstructure parameter on this width. The major parameters describing austenite microstructure are shown in Table 1.

Table 1. Chemical and phase composition of the investigated alloys

Alloy Chemical composition, %wt. Phase composition

No. C N Cr Mn Other After quenching

After plastic deformation

1. 0.10 0.203 9.13 10.85 Si=1.15 A A + 50% Md

2. 0.26 - 9.90 10.44 Si=1.09 A A + 49% Md

3. 0.38 - 4.80 11.20 Si=1.02 À A + 56% Ìd

4. 0.29 0.140 5.10 11.70 Si=0.93 À À + 58% Md

5. 0.30 - 4.80 11.26 V= 1.54 Si=1

À A + 50% Md

6. 0.21 - 7.63 2.36 Ni = 7,9Ìî=2.3 Si=4

A A + 63%Md

7. 0.33 - 5.02 11.19 Ìî=1.58 Si=1.12

A A + 52% Md

8. 0.36 0.07 9.08 12.76 Ìî=2.55 Si=1.5

À À + 54% Md

9. 0.36 0.246 4.78 13.03 Si=2.03 À À + 55% Md

10. 0.29 - - 11.62 Si=1.3 À + 20%Mt

À + 34% Md

11. 0.036 0.246 - 16.78 Si=2 À À + 50.6% Md

12. 0.073 0.234 - 20.18 Si=1.75 À À + 47.8% Md Designations: A-austenite; Md-deformation martensite; Mt-initial martensite D- domain of crystal, ε- lattice micro-deformation and α- concentration of stacking faults. The results of the investigations are shown in Table 2.

201

Table 2. Microstructure parameters of the austenite of the investigated alloys

N Alloy Microstructure parameters of the austenite after quenching

ε.103 α.104 Lm. 108 cm

1. Х10А20CrMn10.10 0.30 31.5 396 2. Х30CrMn10.10 0.83 38.4 344 3. Х40CrMn5.12 1.42 46.5 275 4. Х30А15CrMn5.12 0.83 58 335 5. Х30CrMnV5.12.2 - - - 6. Х20CrMnNiMo8.3.8.2 0.64 62 456 7. Х30CrMn5.12 - - - 8. Х40CrMnMo5.12.3 0.63 72 465 9. Х40А25CrMn5.13 - - - 10. Х30Mn12 0.36 87 489 11. Х0А25Mn16 0.22 96 534 12. Х0А25Mn20 - - -

3. Experimental Results and Discussion Fig. 1 shows as an illustration instrumental records of the performed investigations on specimens of some of the alloys, carried out at room temperature. It is also shown the instrumental curve of alloy No 10 in which there is initial martensite as well as that of alloy No.6 after aging. It is seen that the aging of alloys results in austenite stabilizing components removal out of the solid solution and transformation of part of the austenite into martensite. The further deformation of aged austenite shows that it is stabilized and possesses low predisposition towards martensite formation during plastic deformation. Similar stability of austenite, as seen in Fig. 1, is observed also in alloys with present initial martensite, alloy No 10. In this case probably the austenite stability is due to exhausting the points for initiation and growth of deformation martensite. In order to have general criteria of comparability for the individual TRIP-steels compositions we have used the well-known Schaeffler’s diagram [12]. The diagram compares the austenitic stabilizing and austenitic stabilizing role of each element to those of chromium and nickel with a corresponding coefficient, e.g. chromium and nickel equivalents. Fig. 2 shows Schaeffler’s diagram with written in it values of the equivalents for the considered by us 11 alloys (without these of alloy 10). It is seen that after quenching all of them enter the two phase zone of the diagram – austenite and martensite. The analysis of the locations both of the chromium free alloys and of those additionally alloyed with molybdenum shows that the application of Schaeffler’s dependencies to TRIP-alloys requires further definition of some coefficients. In compliance with our concept the coefficient of molybdenum ferrite stabilizing ability can be accepted to be 0.6 instead of 1. It could be said in analogy that the manganese austenite stabilizing ability is higher than that in the diagram and the coefficient in front of this element can be accepted to be of the order of 0.8 instead 0.5.

202

Fig.1. Dependence of the deformation martensite quantity on the deformation rate

Fig. 2. Schaeffler’s diagram applied to the studied TRIP-compositions

203

Conclusion The results and Schaeffler’s diagram presented could be a basis for developing new TRIP-steel compositions where the influence of every element is taken into account. Resulting of it some more important practical conclusions follow:

− Manganese and nitrogen are elements that favour the formation of deformation martensite. This is related to the lower energy and higher concentration of stacking faults in the solid solution containing these elements, Table 1. In these alloys a decrease of micro-deformations and increase the lengths of crystal domain is observed which favours the movement of the partial dislocations enclosing the stacking faults that are major bearers of nucleation and deformation martensite.

− Chromium, despite being a ferity-stabilizing element, favours the deformation martensite formation associated with the reduction of the critical germ of the martensite.

− The increase of chromium in these alloys to 10% by weight slightly affects their tendency to deformation martensite formation.

− Molybdenum has a favourably affect on deformation martensite formation as it improves the plastic properties of alloys and eases the growth processes of martensite nucleation.

− Vanadium is a strong carbide and nitride forming element and the formation of difficult to dissolve nitrides and carbides results on the one hand in removal of inclusion atoms from the solid solution and austenite destabilization and on the other hand it refines the austenite grain which increases the stacking faults energy and austenite stabilization. In this connection alloying with certain quantities of vanadium should be well balanced.

Schaeffler’s diagram is valid at condition that the alloys are quenched from sufficiently high temperature and the alloying elements are in the solid solution. Any cause related to removal of the alloying elements from the solid solution strongly affects its stability. In that sense, the diagram shows that depending on the quenching temperature, solubility of the alloying elements in the austenite, the energy of respective carbides and nitrides formation, different quantities of alloying elements can be fixed in the solid solution and they will determine its stability. Therefore, the temperature cross-sections of the triple diagrams of Fe-Me-C condition at quenching temperatures typical for austenite steels at 1000-1100ºC should be used as subsidiary diagrams [13]. Me designates the various carbide forming elements. It is obvious from the triple Fe-Me-C systems that the whole quantity of alloying elements determined by the concentration limits shown above, in which the TRIP-steels are defined, can dissolve in the austenite at these temperatures. As the alloying of the austenite determines its stability then by the aging processes its phase composition and properties could be affected. That is verified by the presented deformation dependence of aged specimen martensite, Fig. 1, and our published investigations of carbide and carbonitride phase analyses of these and similar alloys [14] The results showed that austenitic aging altered the stability of austenite at deformation – fig. 1, as it reduced the amount of carbide forming elements in the solid solution. Acknowledgements The authors are grateful to the financial support of Bulgarian National Science Fund at the Ministry of Education and Science, Contract No DN17/17 /12.12.2017/.

204

References 1. Bogachoff N., Austenitno-nestabilnie stali.-Moskva,”Tehnika”, 1977. 2. Schumann H., J. Kristall und Technik, 1974, 9, s. 1141-1152. 3. Petroff Y.N. Defekti I bezdifuzionnoe prevrastenie v stali.-Kiev, “Naukova dumka”, 1978. 4. Bouaziz O., N. Guelton, Modelling of TWIP effect on work-hardening, Materials Science

and Engineering: A, Volumes 319–321, December 2001, p. 246-249. 5. Grässel O., L. Krüger, G. Frommeyer, L. W. Meyer, High strength Fe–Mn–(Al, Si)

TRIP/TWIP steels development-properties-application, International Journal of Plasticity, Volume 16, Issues 10–11, 2000, p. 1391-1409.

6. Hamada A.S., L.P. Karjalainen, M.C. Somani, The influence of aluminum on hot deformation behavior and tensile properties of high-Mn TWIP steels, Materials Science and Engineering: A, Volume 467, Issues 1–2, 15 October 2007, p. 114-124.

7. Huang B.X., X.D. Wang, Y.H. Rong, L. Wang, L. Jin, Mechanical behavior and martensitic transformation of an Fe–Mn–Si–Al–Nb alloy, Materials Science and Engineering: A, Volumes 438–440, 25 November 2006, p. 306-311.

8. Mitchew W, T., Stojchev, Internationales Symposium Metallkunde und Warmebechandlung, 1/4-1, Karl-Marx-Stadt, 1975, 217-220.

9. Sturm F., Zeitschrift fuer angewandte Physik, 27, 2, 1969, 100. 10. Sturm F., Archiv fuer Eisenhuettenwesen, 41, 4, 1970, 369. 11. Parshoroff I, Tz.Banova, Tehnicheska misal, XXXVI, 3-4, 1999, 117. 12. Schaeffler A.L., Metall Progress, 56, 1, 1949, 680. 13. Saito T., Sacuma T., Nishiwa S., Transaction of the JIM, 21, 8, 1980, 471. 14. Margarita Ilieva, Stoyan Parshorov, Phase composition of TRIP-steel after aging, Journal

“NDT Days”, 2019, ISSN: 2603-4018 (in press).

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

205

Behavior of the High-temperature Background of Internal Friction by Martensite Phase Transformation in Fe-20% Ni

Ivan PARSHOROV, Stoyan PARSHOROV

Institute of Metal Science, Equipment, and Technologies with Hydro-

and Aerodynamics Centre “Acad. A. Balevski” at Bulgarian Academy of Sciences, 67 "Shipchenski prohod" St., Sofia 1574, Bulgaria,

e-mail: s_parshorov@ims.bas.bg Abstract. The aim of the present study is to investigate the behavior of the high temperature background of internal friction in phase martensite transformations. The energy of activation against the internal friction background is close to that of the martensite transform, calculated on the maximum rate of the solid phase reaction. This confirms the dislocation mechanism of initiation and growth of the martensitic phase. There is a wide distribution of relaxation times, defining the energy of activation against the internal friction, which at the respective temperature defines the course of the martensite transformation process Keywords: high temperature background, internal friction, martensite phase transformation, TRIP-steels, XRD. 1. Introduction This paper presents studies of the relationship between the temperature dependence of the internal friction background and the structural states accompanying the processes of martensitic phase transformations in a high nickel alloy. 2. Material and methods The Fe-20% Ni alloy is produced /cast, rolled and annealed/ in IMSETHC-BAS. The temperature dependencies of the dynamic relaxation spectra /internal friction/ were investigated with a computerized apparatus for the study of internal friction in metals and alloys built on the principle of the equilibrium pendulum pendulum of Ke. The investigations were conducted at working frequency of 1-3 Hz with heating and cooling in the temperature interval 20 – 1100 oC at heating rates of 10 and 20 deg/min. Data is processed with Origin. 3. Experimental results and discussion Other studies of the same alloy [1-2] showed that at room temperature it has a martensite phase composition. Under heating, according to the state diagrams, the martensite is transformed into austenite. With cyclic heating and cooling in Fe-20% Ni the right and reverse reaction of the martensite αγ-conversion occurs. These phase reactions are reflected as maximums on the temperature dependence of internal friction of the alloy – fig.1. Characteristic of the right reaction α↔γ is that the conversion occurs in the vicinity or in the high-temperature background of internal friction, where the mobility of the dislocation structure is greatest. According to the literature, the investigated alloy has low stacking faults energy, the order of 50 erg / cm2, which guarantees the martensitic γ-α transformation. In this sense, the dislocation structure of the high-alloy alloy is easily movable and consists of wide-spaced partial dislocations surrounding large areas with stacking faults [3-5].

206

Several models describing the relationship between the internal friction value and the phase conversion parameters show [6-8] that the height of the internal friction peak is proportional to the rate of phase conversion and the rate of heating. The numerical integration of the experimentally obtained maxima represents the kinetics of the martensitic reaction under non-isothermal conditions. The investigation shown in fig. 2 is an attempt to obtain information about the initial stage of development of the martensite transformation process. Then the primary role is played by the dislocation mechanisms of origin and growth of the new phase, and the internal friction method is sensitive to dislocation mobility. That is why the samples are heated only to the temperatures typical of the initial stage of the martensitic reaction before reaching the maximum of the conversion rate as shown in the figure.

200 400 600 800 10000

20

40

60

80

100

γ − α

α − γ

Q-1.1

000

T [oC]

Fig.1. Temperature dependence of internal friction on heating and cooling – 10 deg/min [1]

200 400 600 800 10000

20

40

60

80

100

120

Q-1 .

1000

T [ oC ]

Fig.2. Temperature dependence of internal friction on heating and cooling – 10 deg/min [1]

207

Fig. 3 and 4 show experimental temperature dependencies of internal friction background after subtraction of relaxation maxima. According to the Maxwell rheological model, refined by Weller [9] and Schaller [10], the temperature dependence of the internal friction background Q-1f is described by the dependence:

Q-1f = A.exp (-H/RT), where – A is an empirical constant. The equation refers to the ideal case of a rheological model characterized by a single relaxation time. In reality, there is a distribution in relaxation times, in which the above equation is transformed into:

Q-1f = [A.exp (-H/RT)] n, where “n” is a constant describing the distribution of relaxation times of the process. At n = 1, the above equations are identical. To determine the energy of activation, the experimental data was approximated with the top function – Fig. 3-4, using the program product "Origin 6.0". The results are automatically plotted as shown in the figures. For clarity, the values obtained are shown in Table 1. The experimental results are approximated and at a set value for one relaxation time n=1. The values of the energy of activation corresponding to one relaxation time, as well as the magnitude of its values for heating and cooling, are given in Table 2. The average energy value and the energy distribution are also shown in the table.

400 600 800 10000,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14Data: RES2104FILT_frictionfilModel: user1Chi^2 = 0.00002P1 15352.47945 ±2374.1518n 1 ±0P3 12542.62497 ±164.67378H=25084 cal/mol

Data: RES2104FILT_frictionfilModel: user2Chi^2 = 0.00002P1 515200.05168n 0.77326P3 16973.94416H=33947 cal/mol

Fe-20%-Ni - heating(10 deg/min)

Q-1

f. 10

00

T [K]

Fig.3. Temperature dependence of the internal friction background on heating

208

400 600 800 10000,00

0,02

0,04

0,06

0,08

0,10

0,12Data: RES2104FILT_frictionfilModel: user2 0,013+(P1^P2)*(exp(-P3/x))^P2Chi^2 = 7.7206E-6P1 1587151.82679 ±254586567566.2226n 1.35838 ±14546.14902P3 13621.0527 ±196110185.71239H=26242 cal/mol

Data: RES2104FILT_frictionfilModel: user1Chi^2 = 0.00014P1 118232.90947 ±79536.5435n 1 ±0P3 14546.20797 ±702.57123H=29092 cal/mol

Fe-20%-Ni - cooling(10 deg/min)

Q-1

f . 10

00

T [K]

Fig.4. Thermal dependence of the internal friction background on cooling

Table 1. Activation energy values H [kcal/mol] and n

Conditions H [kcal/mol] n 10 degrees / min Heating 33.9 0,77 10 degrees / min Cooling 26.2 1.36 20 degrees / min Heating 33.4 0,77 20 degrees / min Cooling 27.4 1,138 Average values Heating and cooling 30,33 1,0095

Table 2. Values and mean value of activation energy distribution H [kcal/mol] at n = 1

Conditions H [kcal/mol] ΔH [kcal/mol] 10 degrees / min Heating 25.9 -8.0 10 degrees / min Cooling 29.1 +2.9 20 degrees / min Heating 25,4 -8.0 20 degrees / min Cooling 29.4 +2.0 Average values Heating and cooling 27,45 -5.55

The results showed that:

− The activation energy against the internal friction – Table 2 is close to that of the martensitic transformation, which confirms the dislocation mechanism of origin and growth of the martensitic phase.

209

− There is a wide distribution of relaxation times that determine the energy of activation against the background friction, which at the appropriate temperature defines the course of the martensite transformation process. The spread of this distribution is in the order of 10 [kcal / mol].

− The difference in activation energies against the internal friction with heating and cooling, determined by the thermal dependence of the energy of the defects in the arrangement, defines the parameters of the martensitic right and the reverse reaction.

− In the mechanism of germ formation in low-energy alloys of the defects in the arrangement defining the temperature dependence of the latter. It is known that it depends heavily on the temperature and changes jump from it. This fact also determines the existing high temperature hysteresis between the straight and reverse martensitic reactions observed in these alloys.

4. Conclusions Studies have shown that there is a widespread distribution of relaxation times that determine the energy of activation against the internal friction, which at the corresponding temperature defines the course of the martensite transformation process. The spread of this distribution is in the order of 10 [kcal / mol] and for the full and accurate description of a martensitic reaction this fact needs to be taken into account. Acknowledgements The authors are grateful to the financial support of Bulgarian National Science Fund at the Ministry of Education and Science, Contract No DN17/17 /12.12.2017/. References 1. Parshorov S., I.Parshorov, E.Machev, Kinetic and Phase Transformation Mechanism of Fe-

20%Ni and Fe-12%Mn Binary Alloys, Junior euromat 2004, 6-9.09.2004, Lausanne, Switzerland, www.junior-euromat.fems.org

2. Hansen M.,Constitution of Binary alloy. Mc. 1958. 3. Petrov U., UFJournal, 16, 9,1971, p. 1409. 4. Cohen M., MetallTrans., 3, 1972, 1095. 5. Nebel T., D.Eifler, International Congress on Advanced Materials, their Processes and

Applications, Materialsweek 2000, Muenchen, 2000, CD-ROM, H2-P10. 6. Dejonghe W., L.Delaey, O.Mercier, Zeitschrift Metallkunde, 70, 8, 1979, 486. 7. Morin M., G.Guenin, P.Gobin, Internal Frrction and and ultrasonic attenuation in solids,

Proceedings of the Third european Conference University of Manchester, England, 18-20 July, 1980, 275.

8. Carrad M., C.Prioul, J.Plusquellec, P.Azou, Internal Frrction and and ultrasonic attenuation in solids,Proceedings of the Third european Conference University of Manchester, England, 18-20 July, 1980, 281.

9. Weller M., A.Chatterjee, G.Haneczok, H.Clemens, Internal Friction of gama-TiAl- Alloys at high temperature, J. Alloys and Compounds, 310, 2000, 134.

10. Schaller R.,G. Fantozzi, Study of the brittle-Ductile transition in ceramics and cermets by mechanical spectroscopy, J.Physical Aspects of Fracture, 2001,111-121.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

210

Study the Influence of the Limit Contents of Alloying Elements and Heat Treatment on the Mechanical Properties and Structure, in Characteristic

Areas of Automobile Wheels from AlSi7Mg0.3 Alloy, Cast under Low Pressure

Lenko STANEV, Anna MANEVA, Sergey STANEV, Mihail GEORGIEV

Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Center „Acad. A.

Balevski“ at the Bulgarian Academy of Science, Sofia, Bulgaria e-mails: stanev@ims.bas.bg, anna13@abv.bg, geo131@gmail.com, mngeorgiev@gmail.com

Abstract The properties and structure, in characteristic areas, of castings for automotive wheels, cast under low-pressure from AlSi7Mg0.3 alloy was investigated. Alloy compositions have been with limit contents of alloying elements and have been undergone of T6 regime of heat treatment. It is shown the effect of alteration the contents of Si and Mg, within the standard limits, on the basic mechanical properties and some parameters of the structure, in characteristic zones, of the casting. It was found that, the change in the contents of Si and especially of Mg most substantially influences on the hardness and plasticity of the casting’s material. Changes in the microstructure, shown by the changes in of SDAS values, mainly depend on the conditions of crystallization in the different zones and to a lesser extent on the content of the alloying elements. Keywords: aluminum alloy wheels, low pressure casting, AlSi7Mg0.3

Изследване влиянието на граничните стойности на легиращите елементи и термичната обработка върху механичните свойства и

структурата в характерни зони на автомобилни колела, отляти под ниско налягане от сплав AlSi7Mg0.3

Ленко СТАНЕВ, Анна МАНЕВА, Сергей СТАНЕВ, Михаил ГЕОРГИЕВ

1. Въведение

Производството на алуминиеви колела за леки автомобили, през последните 20-30 години, нараства непрекъснато и вече успешно конкурира производството на класическите стоманени джанти. Основен процес за производство на алуминиеви колела е леенето под ниско налягане. Значително по-рядко се използват леене с газово противоналягане, кокилно леене, полутечно щамповане и други леярски процеси [1,2]. Известно количество алуминиеви колела се произвеждат чрез пластична деформация (горещо щамповане, щанцоване, спининговане и други процеси). Делът на лятите, спрямо общия брой алуминиеви колела, надхвърля 80-85 % за Европа и 85-93% за САЩ и Япония [1].

Освен намалената маса водеща до намален разход на гориво и въглеродни емисии, лятите алуминиеви колела позволяват голяма свобода в дизайна на колелата. Леенето под ниско налягане е широко разпространен метод и при производството на алуминиеви колела осигурява висока производителност, точност на размерите, отлично качество на

211

повърхността, добри механични свойства и сравнително ниски разходи за екипировка [2,3].

При производството на ляти алуминиеви колела се използват сплави от системата Al-Si-Mg, като в 95 % от случаите това е сплав AlSi7Mg0.3, обработена по режим Т6 [4]. Сплав AlSi7Mg0.3 се е наложила в производството на ляти колела поради добрите си леярски свойства, добрите механични свойства в термообработено състояние, висока устойчивост срещу уморни натоварвания и не на последно място отлична корозионна устойчивост [2,3].Конкретният режим на термообработка производителите избират в зависимост от конкретните условия – метод на производство, конструкция и маса на отливката, оборудване, изисквания и т.н [5]. По рядко се използват нетермообработваеми сплави от типа на AlSi12, AlSi11Mg.

Влиянието на основните легиращи елементи върху структурата и свойствата на моделни отливки с проста форма от сплав AlSi7Mg0.3 в термообработено състояние е добре известно [2,6,7], но слабо е изучено върху конкретни сложни по форма и произведени по различни методи отливки, което е и предмет на настоящата работа. 2. Експериментална процедура

В настоящата работа са изследвани структурата и свойствата на отливки за автомобилни колела, получени в промишлени условия, чрез леене под ниско налягане. Отливките са произведени от сплав AlSi7Mg0.3 със състав: Si 6.5÷7.5%; Mg 0.30÷0.45 %; Fe<0.12%; Cu<0.1%; Mn<0.05%; Ti<0.2% и термообработени по режим Т6. На изследване са подложени 4 плавки, с вариране на основните легиращи елементи в горна и долна граница в рамките на стандарта, Таблица 1.

Таблица 1. Вариране на процетното съдържание на легиращите елементи

Плавка № Химичен състав, % Si Mg Fe Mn Sr Ti

1 6.52 0.30 0.065 0.001 0.0015 0.027 2 6.43 0.46 0.070 0.002 0.0006 0.029 3 7.24 0.30 0.070 0.0003 0.0015 0.027 4 7.60 0.46 0.080 0.003 0.0006 0.03

Като първа стъпка за по-широко изследване, при настоящата работа сплавта не е

подложена на обичайно прилаганото модифициране и издребняване на структурата. Основните технологични параметри при производството на алуминиеви джанти под ниско налягане са:

− Температура на метала -710±3ºC; − Начална температура на формата:

Горна полуформа.- 320-330ºC; Долна полуформа – 330-360ºC; Странични части на формата – 280-300ºC

− Разликата в налягането (ΔP) се реализира на два етапа: първи етап – от 0 до 450 mbar за 30 s и втори – от 450 до 1200 mbar за 30 s.

Отливките са подложени на 100% рентгенов контрол и са обработени по два

варианта на режим Т6 на термообработка, Таблица 2.

212

Таблица 2. Т6 режим на термична обработка

Режим Хомогенизация Изкуствено стареене

Режим I

535±3°C/6h, закаляване във вода (45÷50°C), не по-късно от 10s след изваждане от пещта; естествено стареене 10÷12h при стайна температура

145±3°C/5h; охлаждане на въздух

Режим II

535±3°C/6h, закаляване във вода (45÷50°C), не по-късно от 10s след изваждане от пещта; естествено стареене 10÷12h при стайна температура

170±3°C/3h; охлаждане на въздух

Структурата и механичните свойства на получените отливки са изследвани в 3

характерни области (център, ребро и легло на гумата), Фиг.1. От посочените области са изрязани проби за микроструктурен анализ и пробни тела за измерване на твърдостта и изпитване на опън (по 3 броя).

Фиг.1. Общ вид на получените отливки и схема на местата за вземане на проби за изследване

3. Резултати и обсъждане

На Фиг.2 са показани микроструктури на колела от плавки № 1 и 2 в трите изследвани области. Микроструктурата на изследваните отливки се състои от дендритен α- твърд разтвор и евтектика. Установено е наличието на микродефекти (микропори), дължащи се на обемен дефицит, незабележими при рентгеновия контрол, разположени предимно в областта на леглото на гумата и по-рядко в областта на центъра и ребрата. В областта на леглото на гумата се наблюдават и зони обогатени с евтектика. Може да се счита, че това е доказателство за ефективното действие на налягането, което се състои в запълване с нискотопима евтектика на образуващите се при затвърдяването дефекти от свиването.

213

Фиг.2. Микроструктури в характерни зони на отливки от плавка 1 и плавка 2

214

Разстоянието между вторичните дендритни оси (SDAS) e основна количествена характеристика на микроструктурата, показваща условията на затвърдяване на отливката и пряко свързана с механичните свойства на материала. Измерените стойности на SDAS за четирите плавки, в трите характерни области са показани в Таблица 3.

Таблица 3. Измерени стойности на SDAS

Плавка № Режим на ТОSDAS, µm

Център Ребро Легло

1 I (145оС/5h) 43.06 40.37 23.46 II (170oC/3h) 41.55 40.58 16.85

2 I (145оС/5h) 47.98 46.87 25.24 II (170oC/3h) 44.35 31.44 26.08

3 I (145оС/5h) 41.08 33.6 23.50 II (170oC/3h) 42.89 46.33 21.90

4 I (145оС/5h) 48.50 31.90 24.90 II (170oC/3h) 49.45 30.13 22.70

Резултатите показват закономерно намаляване на разстоянието между вторичните

дендритни оси от центъра през ребрата към леглото на гумата и не зависят съществено от състава и термичната обработка, а основно от условията на затвърдяване, обусловени от дебелината на сечението и условията на леене.

На Фиг. 3 и 4 в графичен и табличен вид са показани осреднените резултати от изпитването на основните механични свойства в изследваните области в зависимост от състава и термичната обработка на отливките от плавки с №№ 1÷4, за двата варианта на режим Т6 на термообработка.

Фиг.3 Режим I на термообработка (1-център; 2- ребро; 3-легло на гумата)

215

Фиг. 4. Режим II на термообработка (1-център; 2- ребро; 3-легло на гумата)

От резултатите се вижда, че увеличаването на съдържанието на Mg на горна

граница на стандарта, при съдържание на Si 6.5%, най-общо води до известно увеличаване на границата на провлачане Rp02 и незначително на якостта на опън Rm, като същевременно нараства съотношението Rp02/Rm. Основният ефект от увеличаване съдържанието на Mg се изразява в съществено намаляване на показателя на пластичността А5.

При съдържание на Si на горна граница на стандарта (7.5%), увеличаването съдържанието на Mg води до по-съществено увеличаване на границата на провлачане Rp02, твърдостта, както и на съотношението Rp02/Rm, за сметка на запазване на якостта на опън Rm. Пластичността, както и в първия случай намалява значително.

Същият ефект се наблюдава и при втория вариант на Т6 режим на термообработка. При едно и също съдържание на Mg, увеличаването на Si от долна на горна граница

не води до осезаем ефект върху механичните свойства и при двата режима на термична обработка.

Увеличаването на температурата на изкуствено стареене при едновременно намаляване времето на стареене води до изравняване на механичните свойства на отливките при двата режима на термообработка. 4. Заключение

Въз основа на проведеното изследване на автомобилни колела, ляти под ниско налягане в промишлени условия от сплав AlSi7Mg0.3 и термообработени по режим Т6 е установено:

− Изменението на съдържанието на основните легиращи елементи Si и Mg в рамките на границите на стандарта не води до съществено изменение на структурата в характерните зони на отливките;

MPа %

216

− Разстоянието между вторичните оси на дендритите SDAS зависи в по-голяма степен от условията на кристализация отколкото от състава и термичната обработка;

− Изменението на съдържанието на Mg от долна в горна граница, при едно и също съдържание на Si, води до незначително нарастване на якостта на опън Rm, по-забележително нарастване на границата на провлачане Rp02 и съотношението Rp02/Rm, като същевременно показателят на пластичността А5 намалява значително.

− Увеличаването на съдържанието на Si от долна на горна граница при едно и също съдържание на Mg, не води до осезаем ефект върху механичните свойства и при двата режима на термична обработка.

Литература 1. Weeks G. Aluminium alloy wheels manufacturing process, materials and design, 16th July 2012.

https://www.engineeringclicks.com/aluminium-car-wheels/ 2. Applications – Chassis & Suspension – Wheels, Version 2011, European Aluminium Association

(auto@eaa.be) https://www.european-aluminium.eu/media/1563/aam-applications-chassis-suspension-3-wheels.pdf

3. Çetinel M., Investigation and Development of the Quality Control of Al-Wheel Rim Production Process. Dissertation submitted to the Graduate School in Partial Fulfillment of the requirements for the degree of Master of Science, Mechanical Engineering Department, İzmir Institute of Technology, İzmir, Turkey, October, 2001.

4. Aluminum Alloy A356 T6 https://www.newarctech.com/cm/dpl/downloads/content/69/A356_Aluminum_Wheel_Facts.pdf

5. Frost F. F., A Study of Heat Treatment of Aluminium Wheel Castings. Thesis submitted as a requirement for the completion of Master of Engineering Science Degree in Manufacturing Engineering. University of Tasmania, July, 1997.

6. Aluminum and Aluminum alloys, ASM Specialty Handbook, 1994. 7. Kaufman G. J., L. R. Elwin, Aluminum Alloy Castings: Properties, Processes, and Applications,

ASM International, 2004.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

217

Material Science – Chemical Analysis and K-test with Zone Melting of Metals and Alloys

Anna MANEVA, Stefan BUSHEV

Institute of Metal Science, Equipment and Technologies With Hydro- and

Aerodynamics Center „Acad. A. Balevski“ at the Bulgarian academy of sciences Sofia 1574, 67 „Shipchenski prohod“ blvd. Bulgaria

e-mail: anna13@abv.bg; stbushev@abv.bg Abstract Mathematical experiments are presented for the first-order phase transition process in the formation of test bodies for chemical melt analysis and K-test. The effect of the initial temperature of the mold is shown. It is suggested that the two approaches be used to evaluate the technological process of a first-stage phase transition in a small volume. Keywords: first-order phase transition, chemical test of liquids, K-test, little volume 1. Introduction – material science by special Stefan-Schwartz tasks Figure 1 presents the general methodological idea of using data from powerful tool not only for scientific but also for technological research mathematical experiments through Stefan-Schwartz's tasks for describing the temperature field of a first-order phase transition. The idea of the methodology is based on the fundamental knowledge in Physical Metallurgy and Materials Science [1 and 2]. Foundry with the main scientific and technological processes is presented in [3 and 4]. Standard practices for good casting quality were taken on samples for [3]: chemical analysis very important test; K-test for use of secondary alloy [12]; zoning to purify by refining and obtaining fresh material [3]. Chemical analysis is the most important for the formation of the casting structure in a first-order phase transition [4 and 12]. The K-test is important for the use of secondary metal (alloy) [12]; The process of refining by zoning is used to clean secondary metals and alloys. For good casting quality were taken on samples for [3]: chemical analysis very important test; K-test for use of secondary alloy [12]; zoning to purify by refining and obtaining fresh material [3]. Under modern circumstances, the mathematical experiment is a new essential tool for research not only in scientific but also in engineering studies. The mathematical experiment is very important in modifying a material or article. An example of a mathematical experiment is any software for solving Stephan type problems. For example, Stephen-Schwartz's 3D task allows to calculate the solidification technology, i.e. technology first-order phase transition. The mathematical experiment is a complex set of mathematical models, mathematical theories, mathematical physics, theoretical physics, computational mathematics, and physics. Formed in the structure of the new phase, it is necessary to evaluate such parameters of the foundry process, which can be considered technological parameters. In Fig. 2 we present such performance parameters [3, 1, 2, 10, 11 and 13]; for example the local solidification time in a small characteristic volume.

218

a) Stefan-Schwarz's specific tasks for obtaining material data 10 such as: standard first-order phase transition processes and low volume crystallization – chemical analysis and K-test with Zone-melt;

b): b, 1) Fundamental science (engineer) mathematical experiment on the base of date 10 from (a) for technological process of 3D first-order phase transition (on macro-level solidification) in simple geometry (3D

cylindrical symmetry); b, 2) The obtaining results from (b, 1)) are date for little volume which should be repeated in every little volumes Δυcorr of casting with complex geometry.

Fig.1 General methodological idea is Stefan-Schwarz tasks and mathematical experiments for technological first-order phase transition.

219

Fig. 2 Technological patameters for first-order phase transition [3].

2. Specific instructions preparation of melt casting Technological parameters (Fig. 2) are in Stefan-Schwarz's 3D task and the information about them is extracted by mathematical experiments – the 3D phase transition phase field of first order in the above mentioned tasks. The following results of mathematical experiments are presented in the paragraph [4, 3, 7 and 12]: influence of the initial temperature of the mold on the type of the first-order phase transition temperature field 2.1 Chemical analysis – mathematical experiment is solidification of sample [4, 3 and 12]

Fig. 3. The cast of sample for chemical analysis is disk. Geometric kind of the open thermodynamic (cast and mold and boundaries W, Γ) system for chemical analysis (OTS, CA) with numerical calculated

temperature field of solidification by the task of Stefan-Schwarz in the moment of time t=0,0259 s and coefficient of heat transfer at the surface cast-mold α = 3400 w/m2 K.

220

The most important part of the process is the formation of the disk (the chemical sample). Phase conversion parameters are determined by the staging of each end of the disk volume. Then, chemical analysis in the volume may allow experimental testing of the chemical composition in the sample material volume. The link between the parameters in the mathematical task and the search for the most sensible possibility of easy research is clearly stated. 2.2 K-test – mathematical experiment solidification of sample The temperature test through a mathematical experiment in the K-test is interesting with much more complex geometry and observation through chemical analysis. The combination between the two methods will much better address the question of the permissible use of secondary alloys with competitive and safe application.

Fig. 4. K-test: cross section of the mod and the open thermodynamic (cast and mold and boundaries W, Γ) system (OTS, Kt). High intensity of heat exchange: αW = 56000 w/m2 K αΓ = 28000 w/m2 K. Numerical

calculated temperature field of solidification by Stefan-Schwartz task at two different initial temperatures of the mold.

Chemical analysis primarily determines a limitation on the use of secondary metals and alloys, or the possibility of mixing with primary (fresh) materials to achieve beneficial use without compromising safety. Chemical analysis also allows the use of refining by zonal melting. K-test and first-order phase transition at maximum heat exchange αW = 56000 w/m2 K; and data from mathematical experiments also allows for a limit assessment for the use of secondary materials, which is linked to an optimal number of consecutive refinements. 3. Numerical results of preparation of melt casting and methodology The influence of the initial temperature of the form is one of the factors with its influence and capabilities. Forming the casting structure in the chemical analysis sample depends on the feed of the disk from the dead head. This is the natural organization of the foundry process. The influence of initial mold temperatures of 20оC to 500оC is investigated.

221

Initials temperature 20, 50, 70, 100, 150 and 200оC;

Initials temperature 300, 400 and 500оC

Fig. 5. Influence of the initial temperature of the chemical analysis mold

Fig. 6. Influence of the initial temperature of the K-test mold.

222

Fig. 7. Heat conduction equation (1), boundary condition of heat transfer at boundary WC|M, boundary condition of heat transfer ΓM|E environment are base of the Stefan-Schwartz task. (4) Latent heat of

melting Qm with function of heat source SF. Interesting is the interaction of the first-order phase transition processes and the crystallization processes in the volume of one final element and the correlation volume

as υFE > or >> Δucorr.

From Fig. 7 we have complex interaction for mathematical description of first – order phase transition processes in at υFE > or >> Δucorr.

Fig. 8. Mathematical experiment: Technological first-order phase transition only by the initial

temperature field.

223

The results of the mathematical experiments are presented methodologically based on: physics of metals and solid state physics [5 and 6]; metal science and solid state physics [7 and 8]; machines and technology created in the institute of [9]; quantum mechanics for atoms with one and two electrons [14 and 15]. Conclusions Mathematical experiments describing the first-order phase transition through Stefan-Schwarz's problem in the formation of probes for chemical analysis and K-test are presented. The joint mathematical examination of the melt chemical analysis and the K-test allows to define a first-order technological transition. Natural linkage exists between the methods of chemical analysis of melt, K-test and refining by zone crystallization. References 1. R. E. Smallman, R. J. Bishop, Modern Physical Metallurgy and Materials Engineering, sixth edition,

Butterworth-Heinemann, Oxford, 1999. ISBN 0 7506 4564 4 2. W. Callister, Jr., David G. Rethwisch Materials Science and Engineering, an introduction, John

Wiley & Sons, Inc., Hoboken, 2014. 3. M. Flemings, Solidification Processing, Peace, Moscow, 1977. (In Russian) 4. J. Campbell, Castings Practice: The 10 Rules of Castings, Butterworth-Heinemann, Oxford, 2004.

ISBN 07506 4791 4 5. G. Schulze, Physics of metals, Peace, Moscow, 1971, (In Russian) 6. J. Blakemore, Solid state physics, Metallurgy, Moscow, 1972. (In Russian) 7. A. Balevski, Metalscience, Technics, Sofia, 1962. (In Bulgarian) 8. M. Borisov, K. Marinova, Introduction of physics of the solid body part I, Science and Art, Sofia,

1977. (In Bulgarian) 9. Y. Arsov, E. Momchilov, K. Daskalov, G. Bachvarov, Theoretical and technological fundamentals

of gas counter-pressure casting, Academic publishing house, Sofia, 2007. ISBN 978-954-322-199-8

10. S. Bushev, These of PhD, Controllability problems of crystallization process in casting, TU – Sofia, 1993.

11. S. Bushev, G. Moumdjian, A possibility to influence the dynamics of a phase transition of first order during casting in open thermodynamic systems, Comptes rendus de l’Académie bulgare des Sciences, Tome 46, No 7, p.27-30, 1993.

12. A. Maneva, These of PhD, Investigation of the structure and properties of castings from subeutectic aluminum alloys depending on the ratio of primary and secondary alloys, Bulgarian academy of sciences, Institute of metal science, equipment and technology with hydro- and aerodynamic center „acad. A. Balevski“, Sofia, 2013. (In Bulgarian)

13. S. Bushev, Theoretical model of structure formation in die casting, XXII International scientific technical conference „FOUNDRY 2015“, 16-17 April 2015 Pleven, Bulgaria (In Bulgarian)

14. L. Landau, E. M. Lifshitz, Quantum mechanics, 1960. 15. Hans A. Bete, Edwin E, Solpiter, Quantum mechanics of One- and Two-Electron Atoms, Springer

Berlin Heidelberg, 1957.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

224

Foundry-Gas Pressing Method

Angel VELIKOV, Stefan BUSHEV

Institute of Metal Science, Equipment and Technologies with Hydro- and Aerodynamics Center „Acad. A. Balevski“ at the Bulgarian academy of sciences

Sofia 1574, 67 „Shipchenski prohod“ Blvd. Bulgaria e-mail; stbushev@abv.bg

Abstract The developed methodology for fundamental research of the casting process with IMSETCHA "Acad. Angel Balevski ". Data from preliminary experiments is used. A mathematical framework for mathematical modeling of the first-order phase transition in the „Gas Pressing“ method is proposed. Below are links to important casting parameters. Keywords: Mathematical Framework, First-order phase transition, Macro-Level, Parameters 1. Introduction In IMETCHA „Acad. Angel Balevski“ has been established „Foundry Industry“ in three directions: 1. Foundry machines based on the Balevski-Dimov counter-casting method [1 and 2]; 2. Pressure metallurgy also based on the Balevski-Dimov back pressure casting method [1 and 3]; 3. Theoretical research led by Correspondent member prof. I. Dimov and prof. D.Sc. I. Nedyalkov from the Institute for Nuclear Researches and Nuclear Energy (INRNE) at the Bulgarian Academy of Sciences. Prof. D.Sc. I. Nedyalkov heads a section: "Mathematical Modeling in Physics and Engineering" at INRNE at the Bulgarian Academy of Sciences. Fundamental experiments and results are presented in many works, some of them being [4, 5, 6, 7 and 8]. The results obtained, apart from articles, were formed in non-commercial mathematical computational products: 1D and 2D products based on the finite difference method and 3D computational products using the finite element method. It is known that the boundary condition of the cast|mold is of the 4-th order (ideal contact) and depends only on the thermal conduction of the cast (C) and the mold (M) (Boundary Ideal Contact, C|M is Heat Flow from Cast to Mold) 𝑴𝛁𝑻(𝒙, 𝒚, 𝒛, 𝒕)𝑴𝑾 = 𝑪𝛁𝑻(𝒙, 𝒚, 𝒛, 𝒕)𝑪𝑾, (ICC|M) where λ, ∇ and T are coefficient of conductivity and temperature gradient (heat flow) at boundary C|M of the cast and mold materials, and index W is work surface of the mold. That's why in the Stefan-Schwartz task the contact temperature is determined. In [4] a new type of bonding is made in the open thermodynamic system (cast-shape) between: the non-stationary temperature field with the stress and deformation fields by the non-stationary thermal resistance of the contact edge cast|mold (work surface of the mold). Boundary Real Contact cast|mold (BRC, C|M) is 𝑴𝛁𝑻(𝒙, 𝒚, 𝒛, 𝒕)𝑴𝑾 = [𝜶(𝑻𝑪 − 𝑻𝑴)](𝒙, 𝒚, 𝒛, 𝒕)𝑪|𝑴𝑾 = 𝑪𝛁𝑻(𝒙, 𝒚, 𝒛, 𝒕)𝑪𝑾, (RCC|M) where we have complex non stationary function [𝛼(𝑇 − 𝑇 )](𝑥, 𝑦, 𝑧, 𝑡) | ; the coefficient of the real contact of heat transfer α [5] is 𝜶(𝒕) = 𝜹𝟎

𝟎 + 𝝅𝝆()𝟐 + ∑ 𝑹𝒍𝑭𝒌 + 𝜹𝒍𝒌𝒍𝒌𝟐𝒊 𝟏 𝟏 + (𝟏 − ) 𝜶𝑪 + 𝜶𝑹 𝜹𝟎

𝟎 + 𝜹𝒙𝒙 + + ∑ 𝑹𝒍𝑭𝒌 + 𝜹𝒍𝑴

𝒍𝑴𝟐𝒊 𝟏 𝟏, (RCC|M)

η is relative contact area; δ0 and λ0 are thickness and thermal conductivity of the protective coating; 𝜹𝒍𝒌(𝑴) and 𝒍𝒌(𝑴) are the thickness and thermal conductivity of the oxide layers; ψ(η) is

225

the contraction coefficient; ρ is the radius of contact spot; λμ is the geometric mean of the heat conducting materials; αc is the coefficient of convective heat exchange; αR is the radiation heat transfer coefficient; 𝑹𝒍𝑭𝒌 is the thermal resistance of the phonon heat transfer between the cast or mold material and the corresponding oxide layer (l=1, 2). η is a complex function of statistical distribution, geometry of irregularities and normal tensions in the contact area. An indirect method [6] for evaluation of the coefficient heat exchange on the mold work surface in the cyclic foundry process. In [7] it has been proven that contact pressure and gap are determining factors for contact heat exchange at the cast|mold boundary. Mathematical simulation by Stefan-Schwartz's 3D task and the finite element method of a rapid solidification of metallic eutectic melt from Al-Cu is presented in [8]. The curing front movement speed was obtained for selected values of the heat transfer coefficient at the limit (metal melt)/cooler. On Fig. 1 shows the general geometric scheme of a gas pressing (GP) method.

Fig. 1. General geometric scheme of the gas pressing (GP) method: cylindrical CAST, MOLD and boundaries surfaces W (working) and external Γ (mold/environment); P is pressure [9, 10].

To account for the influence of pressure on the crystallization process in "GP" method [9, 10] proposes we use the Clausius–Clapeyron equation (CCE) 𝒅𝒑 𝒅𝑻⁄ = 𝑸𝒎 [𝑻(𝒗𝟐 − 𝒗𝟏)]⁄ , (CCE) where p is pressure; T is temperature; Qm is the latent heat of melting; v1(2) – relative volume corresponding to a unit mass of phases 1 and 2. The aim of this work is to create a mathematical model of the processes of solidification in casting with the "GP" method. 2. Mathematical model of solidification on the base of the heat conductivity theory by Stefan-Schwartz problem -3D nonstationary equation of the heat conductivity 𝑐 𝜌 = + + in 𝑉 (𝑥, 𝑦, 𝑧) = 𝑉 (𝑥, 𝑦, 𝑧) ∪ 𝑉 (𝑥, 𝑦, 𝑧), (1, 1)

-initial conditions at τ=0 TC(x, y, z, 0)=const1 и TM(x, y, z, 0)=const2, (1, 2)

226

-boundary conditions at surfaces W and Γ for τ≥0 𝑊 | : − ∇T ⃗ = 𝛼 | [𝑇 (𝑥, 𝑦, 𝑧, 𝑡) − 𝑇 (𝑥, 𝑦, 𝑧, 𝑡)] = − ∇T ⃗, (1, 3, W) |Е: − ∇T ⃗ = 𝛼 | [𝑇 (𝑥, 𝑦, 𝑧, 𝑡) − 𝑇 ] (1, 3, Γ) -with the conditions for the heat physical coefficients of the cast as follows: CCC --- , ρ , c

, ρ , c , ρ , c +Q [ ( )] forforfor T (τ)T (τ)T (τ) >∈< T + ∆[T -∆, T + ∆]T -∆ 0 < ∀τ < ττ ∈ ∆τ∀τ > ∆τ + τ , (1, 4, a)

three time intervals for the state of material of each finite element: liquid time [0÷τL]; time of solidification ∆𝝉𝑳𝑺; time of solid state τ > ∆τ + τL; , 𝜌 , 𝑐 for 𝑇 (𝜏) ∀𝜏, (1, 4, b) -the function of the heat source is approximated by δ-type function 𝑆 (𝑇) = √ 𝑒 at (T-Tm) ∈ ΔT(τ) = [Tm-Δ, Tm+Δ], (1, 5) and the condition 𝑆 (𝑇)𝑑𝑇∆∆ = 1 𝑒𝑟𝑓 ∆

and at ∆

> 2. (1, 5, 1) Here of the open thermodynamics system (OTS) we have: the heat coefficients λ, c, ρ – thermal conductivity, heat capacity and density for the cast (C) and mold (M); L and S – liquid and solid parts of pure Al; x, y, z – coordinates of (OTS); αW and αΓM are heat transfer coefficients at the work (W) and external (Γ ) surfaces of the mold; Tm – temperature of firs-order phase transition; T-Tm – temperature interval of Tm; σ – dispersion of the function SF; Δ is the associated temperature interval with SF; TEnv. is temperature of environment; VOTS = VC + VM is of the sum of cast and mold volumes. 2.1 Technological solidification methodology on the base on [4, 5, 6, 7 and 8] and Fig.2 1. 1D Stefan-Schwartz and termo-elastic tasks are solved in [4], but here we not solved thermo-elastic task, and only solved Stefan-Schwarz's 3D task; 2. The filling process of the cavity mold is not accounted; 3. Apply the same (thermal resistances at the work (W) and external (Γ ) surfaces of the mold) i. e. by a heat transfer coefficient αW = constW at (W) and αΓ = constΓ at (Γ ) and with condition αW ≠ αΓ; 4. For the real coefficient of heat transfer in [5] we here prepare identification based on works [6 and 7]. I. The information gathered from many experiments is the basis of mathematical models for the Institute's needs. Mathematical models were captured in the 3D case for all of the foundry machines created in our institute. II. Measurement of the non-stationary phase transition temperature field of first order (solidification) with thermocouples placed in the open thermodynamic system (OTC) cylindrical cast|press-mold (Fig. 2). The use of thermocouples and other sensors in a pressurized volume has been a major challenge, creating an interesting scientific technology. III. For works [4, 5, 6 and 7] a methodology and developed technology for fundamental physics experiments in counter-pressure die-casting was developed. In Fig. 2 a) is presented the basic idea of fundamental physical experiments on a gas-pressure casting machine VP-type; Fig. 2 b) is the closed chamber system of the mold/press-mold thermodynamic system and the furnace of the machine and the molten pure Al crucible; In Fig. 2 c) show the spatial points of the thermocouple peaks;

227

Fig. 2. General geometric scheme of the methodology and technology for fundamental physical experiments in open thermodynamics system (OTS) of cylindrical CAST, MOLD.

Fig. 2. shows general geometric scheme of the methodology and technology for fundamental physical experiments in open thermodynamics system (OTS) of cylindrical CAST, MOLD. Methodology – measurement of 3D temperature field of the first-order phase transition: 1. the filling process of the cavity mold with liquids of pure metal or Alloy; a) VP-type gas counter-pressure casting machine. We use the created fundamental methodological, technological and manufacturing experience; b) Geometrical scheme of the physical experiment: Geometric bodies for fundamental experiments in foundry are: plate, cylinder and sphere. In the figure we present our choice – a cylindrical cast. An important point is the mathematical experiment based on precisely constructed mathematical models (Stefan Schwarz's 3D task (1)). It is known that the technological factor in the foundry is the initial temperature field of the press-form and thermal resistance at the work surface W. A mathematical experiment is a major tool for developing and modifying technological processes. In the foundry the main process is the phase transition from the first genus, creating the structure of the new solid phase; c) A fundamental experiment in the foundry is the study of the temperature field of a first-order phase transition at the macro level; – thermocouples are used for this purpose. The figure to point at the center of the cross are given places of the tops of thermocouples. Other sensors are also used, which we do not consider here. The information about casting formation is the thermocouples in the mold cavity. Each thermocouple is recorded continuously and a time-temperature curve is obtained with three consecutive time intervals: 1 – change in the temperature of the liquid phase; 2 – retention at the melting point until the end of the first-order

228

phase transition; 3 – cooling the solid phase. The more thermocouples are in the cast, the more informative the experiment is. Important possibility for identification of the local thermal resistance at the surface W is shown by . 2.2 Mathematical experiment in Foundry The basic mathematical experiment of foundry is presented in Fig. 3

Fig. 3. Mathematical experiments on the base of mathematical model of the theory of heat conductivity Stefan-Schwartz’s 3D problem in physics and engineering Foundry. Initial temperature field is show on

(Fig.2 b) and with simple condition αW = constW at (W) and αΓ = constΓ at (Γ ) and with condition αW ≠ αΓ. Technological process of solidification is obtained through the initial temperature field of the press mold.

Description of the physical first-order phase transition process at the macro level on Fig.3 is clearly reveals the possibilities for mathematical experiment foundries. Using the possibilities of the mathematical experiment in the gas-pressure casting method is more than necessary. The description of the interfacial boundary surface is necessarily to describe their geometry, which is related to physics, the equilibrium temperature is influenced by the curvature. This connectivity is represented by Stefan's well known classical boundary condition 𝜌𝑄 𝑉 = | − | ,

and the Clapeyron-Clausius equation (see CCE) as [12, 13 and 14] ( ) = 𝛾 ∇ ∙ 𝑛,

where Te is set to the adjusted equilibrium temperature, which takes into account the differences in pressure and density; γSL is the difference in energy (deposited material)/matrix; ∇⋅n is the local curvature.

229

Conclusion The article introduced a mathematical framework for the use of mathematical experiments in the Gas Pressing Method (GP) and with different methodological approaches. References 1. A. T. Balevski, I. D. Nikolov, The first Bulgarian Patent for the counter-pressure casting process №

187/1961 year. 2. Y. Arsov, E. Momchilov, K. Daskalov, G. Bachvarov, Theoretical and technological fundamentals

of gas counter-pressure casting, Academic publishing house „Prof. Marin Drinov“, Sofia, 2007. 3. Ts. Rashev, High Nitrous Steels. Pressurized metallurgy. Publishing House of BAS "Prof. Marin

Drinov ", 1995. (In Bulgarian) 4. S. Bushev, G. Georgiev, I. Dimov, I. Nedyalkov. Thermoelastic model of a two-phase system of

bodies with cylindrical symmetry, taking into account the effect of counterpressure. Yearbook of a Higher Education Institution, Technical Physics, 16, 1979, No.1, 77-90. (In Bulgarian)

5. S. Bushev, G. Georgiev, I. Dimov, I. Nedyalkov. Mathematical model of the thermo-physics of casting with counter pressure of cylindrical castings, taking into account the phenomena of heat transfer of the boundary cast-mold. Technique Thought, 21, 1984, No.3, 99-103. (In Bulgarian)

6. S. Bushev, G. Georgiev. Indirect method for determining the coefficient of heat transfer on the work surface of a metallic form under the conditions of a cyclic casting process. Technical Thought, 25, 1988, No.3, 103-108. (In Bulgarian)

7. S. Bushev, G. Georgiev, I. Dimov, L. Drenchev, I. Nedyalkov, L. Stanev, Exploring an option for determining the heat transfer cast-mold as a function of the state of the system. Technical Thought, 21, 1984, No.5, 93-101. (In Bulgarian)

8. S. Bushev, N. Stoichev, M. Dimitrov, N. Miloshev. Mathematical Model the Metals Rapid Solidification Applied Al-Cu Eutectic, Proc. of Fifth International Congress Mechanical Engineering Technologies’06, September 20-23.2006, Varna, Bulgaria, p. 12-14.

9. A. Velikov, S. Stanev, A. Maneva, R. Dikov, Experimental mold for pressure test on heat exchange between cast and mold in the casting process by gas pressing („GP-PROCESS“). Mezinarodni Vedechcko-Prakticka Konference, Praha, 2012, 28-32. (In Russian)

10. G. Georgiev, A. Velikov, S. Stanev, A. Maneva, Thermal Processes in The Formation of Aluminum Casting As Per The "GP" Method, Proceedings of: XXII International Scientific Technical Conference „FOUNDRY’2015“, 16-17. April 2015 Pleven, Bulgaria, Year XXIII, ISSUE 3, (166), April 2015, pp 52-54. ISSN 1310-3946 (In Bulgarian)

11. E. Femi, Thermodynamics, New York, Prentice-Hall, INC, 1937; Second Stereotype Edition, Kharkov University Publishing House, 1973. (In Russian)

12. C. Meyer, Solidification of Fluids Lecture Notes, www.people.seas.harvard.edu/~colinrmeyer/Solidification%20of%20Fluids%20Notes.pdf

13. Gibbs-Thomson effect, https://en.wikipedia.org/wiki/Gibbs–Thomson_equation 14. R. E. Smallman, R. J. Bishop, Modern Physical Metallurgy and Materials Engineering, Sixth

edition, Butterworth-Heinemann, Linacre House, Jordan Hill, Oxford OX2 8DP, 1999.

Bulgarian Society for NDT International Journal “NDT Days” Volume II, Issue 2, Year 2019

ISSN: 2603-4018eISSN: 2603-4646

230

Material Science – Mathematics and Mathematical Physics in Alloys and Other Materials for Foundry

Stefan BUSHEV

Institute of Metal Science, Equipment and Technologies With Hydro- and

Aerodynamics Center „Acad. A. Balevski“ at the Bulgarian academy of sciences Sofia 1574, 67 „Shipchenski prohod“ blvd. Bulgaria

e-mail: stbushev@abv.bg Abstract This article examines the methodology and philosophy of complete knowledge in terms of: history of science and the individual sciences from antiquity to the present; fundamental results and their applications; development guidelines. This approach is applied when considering the historical development from metal science to material science with all the knowledge known today. In the technological revolution 4.0, material science is also the subject of a knowledge transfer industry. Keywords: Methodology and philosophy of science, metal science, material science, technology revolution 1. Introduction – methodology [1-8] and philosophy of the science The term philosophy is from Greek φιλοσοφια it means: φιλεῖν – love and σοφία – wisdom. The system of principles of philosophy are in constant evolution and change to respond to the intense dynamics of reality. The definition is [1]:

Philosophy is the study of general and fundamental questions concerning man and the world, with mine areas and objects research. (PHILOSOPHY) On the table 1 are:

Table 1. Fundamentals of philosophy

METAPHYSIC Nature and origin of the existing and the world ONTOLOGY Being

EPISTEMOLOGY Knowledge of nature and possibility of cognitive process ETHICS Morality how to act human, correct behavior and „good live“

POLITICAL PHYLOSOPHY Governance and respect for human and communities to the state

AESTHETICS Beautiful, sublime, art, pleasure LOGIC (mathematical and Philosophical) – Forms and lows of thinking

PHILOSOPHY OF LANGUAGE Beginning, development, use and attitudes towards of thinking

SCIENTIFIC METHODOLOGY

(academic disciplines) – Grounds and subject science; history; mathematics; physics; psychology; anthropology; etc.

231

Philosophy [1] – in its earliest years, philosophy encompasses empirical knowledge and their description in the then accumulated knowledge. Knowledge is accumulated in the various fields of philosophy and explanations and logical connections are sought in each of them. Philosophy also separates the individual sciences, and the first separates mathematics, after that separates physics, etc. [1]. Philosophy of science has its historical roots in the history of science, methodology of science, scientific methods of research [2, 3, 4 and 5]. The history of science is closely linked to the history of philosophy, because science is separated from the latter [2]. The philosophy of science deals with all hypotheses, foundations, methods, results and the use of science and the use and contribution of science [3]. The philosophy of science is an old discipline used by Plato and Aristotle; on the nature of science, its knowledge and methods, and today on rational life and industrial progress [4]. The history of philosophy of science also has a strong educational significance [5]. The demarcation line in the philosophy of knowledge is "science/pseudo-science", but often "wrong demarcation lines" are introduced. For example (rationality/intuition): in [6] consider the phenomenology of the theory of strong interactions, quantum chromodynamics (QCD) of Standard Model processes in the experiments of the Large Hadron Collider LHC CERN. Theoretical calculations for predictions in the theory of disturbances for observations of large quantities of highly interacting particles, quarks, and gluons are presented. Such calculations form the most important class of correction for solving New Physics at LHC. Heuristics means the approach to solving scientific problems when there are no other (tried and tested) ways or means to solve them [7]. Heuristics is something like the anti-thesis of standard thinking and there is no sharp line between non-heuristic and heuristic thinking; there is a connection and transition between these two approaches. Heuristics have a connection with the problem of artificial intelligence. The most complete heuristic methods are presented – Tong [7]: 1. Breaking down the problem of "small" parts with a goal and sub-goal organization of behavior; 2. Using behavioral indicators to identify among a large number of alternatives valuable to the program; 3. Use of recursive procedures so that sub-problems are solved with the same set of lumps as the problem itself; 4. Absence of a guarantee for obtaining a satisfactory solution, and often a decision at all. Heuristic rules, general approach of successive phases – Code [7]: 1. Preparatory, explaining the history of the problem, its formulation and the means available for its study; 2. Study phase covering analysis and synthesis, possibly reformulation, new analysis and synthesis (which may be repeated several times). A significant factor here is the time to be reckoned with; 3. The final phase, which consists of proposing a decision or decisions. The term "methodology" is related to a whole group of concepts [8]: theory of science, logic of science, philosophy respectively theory of knowledge, philosophy of science, heuristics and so on. Relations between logic (L), methodology (M) and philosophy of science (P): independent concepts (≠); matching (≡) or roughly matching (≈); two cases of inclusion (⊃, ⊂); excision (∩) or union (∪) i. e. that is, algebraic relations between fuzzy sets. If we take the concept of methodology as a starting point, we may have the following relationships: the methodology covers or partially covers philosophy; the methodology covers heuristics; methodology comes down to the logic of science. In [9] presents a discussion of the concept of "complicated" from the perspective of Quantum Mechanics-Complexity-Biology. It is suggested that the language of quantum mechanics is probably useful or very essential at the cellular level, but it is not known how to apply it. Work [10] is an essay with a response from the authors on "The theory of everything?". Work [10] is an essay with a response from the authors on "the theory of everything". Gerard'T Hoof (Utrecht University, Netherlands, 1999 Nobel Laureate): The most striking difficulty is the

232

reconciliation of general theory of relativity with quantum mechanics; Leonard Susskind (Stanford University, CA, USA): The more you learn about cosmology and string theory, the less likely it is that string theory will describe our world; Eduard Witten (Institute for Advanced Research, Princeton, NJ, USA): Physicist theorists seem to find what looks like a unified field theory, but it continually puzzles them; Masataka Fukugita (Space Beam Institute, Tokyo University, Tokyo, Japan): Cosmology does not make much of a contribution to building a theory of everything; Lisa Randall(Harvard University, Cambridge, MA, USA): I believe that we will continue to make greater progress towards understanding fundamental laws of nature; Lee Smolin (Perimeter Institute, Waterloo, Ontario, Canada): One next step: finding a common source for the geometry of space-time and quantum phenomena, so that they can really be combined; John Stachel (Faculty of Physics, Boston University, Boston, MA, USA): Attempts to create a quantum theory of gravity run into the following problem: do we have to give up background independence to quantize gravity?; Carlo Rovelli (Center for Theoretical Physics, University of Marseille, Marseille, France): The big theoretical question is how to formulate quantum field theory so that it is consistent with what we have learned from general relativity, namely background independence; George Ellis (Faculty of Mathematics at the University of Cape Town, South Africa): The ultimate goal of the quest for "force and particle theory" is to unambiguously formulate a fundamental theory without any free parameters in it; Steven Weinberg (Faculty of Physics, University of Texas at Austin, Texas, USA. Nobel Laureate, 1979): The term "theory of everything" implies that there is some theory that will solve all scientific problems, there is no such thing. But there may be a "definitive" theory that will lead us as far as we can; Roger Penrose (Institute of Mathematics, University of Oxford, Oxford, UK): However, there is at least one significant gap in modern physical theory. In an essay [11], the author considers the origin of Europe and culture as a region/continent "geographically" and Hellenic civilization with its identity cultural identity as a science, a philosophy at the heart of European civilization. The second part of the essay „Esprit de géométrie“ i. e. especially based on the science of Geometry. For us, another essential part of European civilization is Roman civilization. Judeo-Christian culture must be added here. Geometry or mathematics is an essential part of science. For a complex process, we use the W. Corfield model [12]. It is known that quantum mechanics was created to describe the properties of metals, which are the largest part of the periodic system of chemical elements of Mendeleev. In [13], in addition to the Kossel–Stranski–Volmer–Kaishev theory, quantum mechanics is also presented. In [14] is the theory of solid state physics. These two books [13 and 14] are an important part of the history of not only metal science but also material science. It has long been known that the sciences interact [7, 8], but one generalized approach to description is the synergetic that H. Haken calls a simple union of sciences [15]. Mathematics plays a huge role in science. It is well known that a field of knowledge becomes a science if and only when mathematics is applied. The first science to be separated from philosophy is mathematics. In [16] is presents the history of mathematics. Math does not need experiments. The math just expands and nothing falls away from it. The history of mathematics [16] shows its extension and the capabilities of the human mind. Metal science [17] and solid state physics [18] are methodologically completely overlapped. The fundamental solidification results [19] are also methodologically overlaid with the engineering solutions in [21]. Metal science [17] methodologically overlaps with the curing processes [19]. Then, in our opinion, there is a common methodological scientific field [17, 18, 19 and 21] is the area of physical metallurgy [20] that is, following [7 and 8] it is the methodological field [17, 18, 19 and 21] is subdomain of [20] or [17, 18, 19 and 21] ⊂ [20].

233

Work [22] is a technological realization of the bulk and surface formation of non-ferrous and ferrous metal castings based on theoretical and experimental studies of the gas counter-pressure casting method. The methodology of technological solutions of the basic casting and heat treatment processes in [22] covers technological solutions except for metals as well as for ceramic materials and plastics, i. e. for material science. Therefore we have

[17, 18, 19, 21 and 22] ⊂ [20]. (A) A. Balevski's definition of the working properties of alloys (material) is the basic [17]: Such a combination of mechanical and technological (and in some cases physical and chemical) properties that no pure metal possesses no matter what mechanical and thermal treatment it is subjected to. (Working Properties Material) The working properties of each article include: the working properties of the material and the working properties of the macro-volume with its geometric complexity. Following the methodological (A) definition is obtained for the working properties of the product – cast: Such a combination of mechanical and technological (and in some cases physical and chemical) properties that no pure metal casting possesses, no matter what mechanical and thermal treatment it undergoes. (Working Properties Cast) The fundamental sciences are formed historically first – mathematics, physics, chemistry, biology, history, economics, etc., and are called monodisciplinary sciences – a set of objects and methods of research. The object (the source of the problem) is located in one, and the methodology (approaches, principles, etc.) is in the other (s). Their borders usually coincide with those of the united sciences, and their development goes in the same basic sciences. Scientific development in the 20th century has removed the boundaries between the various sciences and in the 21st, this tendency is: the separation of integrative sciences – interdisciplinary and classified according to the source of interdisciplinarity: 1. Interdisciplinary sciences with a source аn central concept defining the subject (problematic) is generally located in a very wide range of fundamental sciences and their methodologies. Interdisciplinary Science with a Central Concept of Self-Organization is Synergetics: Synergy is a relationship in which the effect obtained is different or greater than the sum of the individual effects. Origin of the Greek word συνέργια meaning "work together". Characteristic of synergetic is: it arises from physics (nonequilibrium thermodynamics, nonlinear processes, collective phenomena in many-particle systems – lasers, superconductivity, etc.). It quickly covers areas with processes of spontaneous structure formation – from chemical batch reactions, crystallization, etc.; 2. Another type of source of interdisciplinary is the central issue – interdisciplinary sciences with a source of central issue defining the interdisciplinary situation. Examples of central issues are global problems (environment, greenhouse effect, ozone hole, population explosion, energy and raw materials, population nutrition, etc.). Examples of global research problems that determine the interdisciplinary situation: the Large Hadron Collider, the Fusion Reactor, the Neutrino Experiment, Space Research, the development of global science and technology projects, and more. The implementation of these projects requires large budgets, the cooperation of huge teams of specialists from different fields. Due to their huge scope, integrative sciences lead to a natural unification of knowledge – natural, technical and social sciences.

234

Central Concepts of Interdisciplinary Sciences – Chaos (C) and Order (O) [23, 28 and 29]: The concepts of chaos (C) and order (O) in these sciences place a dual (dichotomous) character – thesis and antithesis. Examples: simplicity and complexity, symmetry and antisymmetry.

Fig. 1. Science and methodology – general scheme of [7 and 8] on the dependence of one science on factors: one examines the science of Sr with two other sciences Sq and St, and their methodologies Mr, Mp and Ms; Definition of complexity using the W. Corfield model [12]; Interdisciplinarity [15, 28, 29, 30, 31

and 32] Synthesis of Open Systems and an Open Technology System [28].

235

The chaos of physics came with the concept of "gas" by Van Helmon in the 17th century. Chaos and order as thesis and antithesis enters physics with the ideas of entropy (R. Clausius, 1865). Entropy is a quantitative measure of chaos in a system. For this reason, entropy quantifies chaos and joy. Symmetry describes the order in a system, the more ordered a system is, the lower its symmetry. At the end of the 20th century, physics distinguished several types of chaos [23]: 1. Non-deterministic chaos (NDC) – complex and random behavior in systems of many elements. It is due to random external or internal factors. A quantitative measure of this kind of chaos is entropy; 2. Deterministic chaos (DC) – irregular behavior of dynamic systems having the properties of a random process. It is due to a strong sensitivity to the initial conditions. For example, the random number generator; 3. Deterministic causes (O) and consequences (O) are associated with order; with chaos – random causes (C) and consequences (C). Deterministic causes give rise to deterministic or random consequences. Accidental causes give rise to deterministic causes or accidental consequences. The O→C transition is described by the (interdisciplinary!) Theory of deterministic chaos. The C→O transition is described by the interdisciplinary science of synergetic or the theory of dissipative structures. The four types of transitions are:

Order → Order; Order → Chaos; Chaos → Chaos; Chaos → Order. (B)

An important feature of the interdisciplinary sciences is that they generate new connections in the field of knowledge.

The development of integrative sciences of great, even critical importance, is the role of scientific schools, which always grow thanks to leading figures. Such examples from Bulgaria are: N. Obreshkov – Mathematics; I. Stransky – R. Kaishev – Physic chemistry; L. Krastanov – meteorology; A. Balevski – I. Dimov – metal science, counter pressure casting; I. Kostov – crystallography; I. Todorov – theoretical physics. The great difficulty is in integrating integrative sciences into existing scientific knowledge.

In [27 and 28], a scientific methodology was established for the two main processes of material science: foundry and heat treatment and shows on Fig. 1

It can be said that the development is from metal science to material science. The first-order phase transition in the foundry and the second-order phase transition in the heat treatment require their full description i.е. full knowledge of material science. The reasons are: 1. These processes are essential for obtaining macro- and micro-structures, carriers of working properties and require a multi-scale description approach; 2. Another reason for stepping outside the field of metal science is that all possible materials are already cast: metals, alloys, glasses, plastics and composites are easy to create.

The aim of this article is the need for material science and working with full modern knowledge.

2. Historical development from metal science to material science and full known knowledge We present the science used in our institute through the classification and historical approach presented in the following two periods:

236

Algorithm Classification "POLICAR" – Historical Approach

Institute of Metal Science and Metal Technology – Bulgarian Academy of Sciences

Angel BALEVSKI, Ivan DIMOV

Technological research Counter-pressure casting. Species

Metallurgy under Pressure Heat treatment Welding Plastic

deformation Electro-Magnetic

StudiesAnalyzes and structural investigations of metals and alloys

PATENTSINNOVATIONApplied research

Machine building Transport: Road; Rail-road; Air Transport. Space Energy Special applications

Institute of Metal Science, Equipment and Technologies With Center of Hydro-and Aerodynamics – Varna "Acad. Angel Balevski" – Bulgarian Academy of Sciences

Stefan VODENICHAROV

Physics of metals

Physics-chemistry

Phase transitions Metal science Physics Solid

Body Experiment

Daskalov; distribution on

sciences sections

Mathematical modelling

Hydro- Aero-dynamics

Counter-pressure casting. Species

Metallurgy under Pressure Heat treatment Welding Plastic

deformation

Electro-Magnetic Studies

Analyzes; Structures

Hydro- aerodynamic technologies

Thin layers and technologies Special investigation, alloys, materials and technologiesPATENTS

INNOVATIONApplied research

Machine building Transport: Road; Rail-road; Air Transport. Space Energy Special applications

The history of scientific, technological development and economic realization can be summarized as follows:

INTERDISCIPLINARY SCIENTIFIC FOUNDATION – MATERIAL SCIENCE

Mathematics Theoretical Physics

Physics Solid Body

Chemistry Applied Mathematics

Hydro- Aerodynamics

Physical and technological experiments.

Important conclusion: the scientific classification, it is clear to us that an implicit transition is made metal science → material science naturally through the applications based on the first-order and second-order phase transitions. The scientific foundation is the full knowledge.

Scientific foundations

Physics of metals

Physics-chemistry

Phase transitions

Metal science

Physics Solid Body Experiments

Balevski – Dimov –

Nedyalkov Mathematical

modelling

237

3. Material Science, Technological revolution The history of mathematics at the institute is mathematical modeling. The Institute was invited by the Institute of Nuclear Research and Nuclear Energy Prof. I. Nedialkov, Head of the Section "Mathematical Modeling in Physics and Engineering". Mathematical modeling topics were managed by A. Balevski, I. Dimov and I. Nedyalkov. In the next historical stage the Department of Mathematical Modeling in Physics and Engineering was headed by K. Daskalov. There is a huge hunger for mathematics at the institute and for this reason the members of this scientific section have been distributed to different scientific departments.

Why should mathematics be developed at our institute? Because the development of material science is based on complete knowledge: mathematics; crystallization, nucleation theory, mathematical physics; theoretical physics; chemistry, quantum mechanics, quantum physics.

In [27] outlines the fundamental idea of the Industrial Revolution 4.0 – Knowledge transfer in the economic. This requires a new competitive environment – a knowledge economy. If knowledge is a subject of commerce, then the work of specialists must first know it in detail and secondly know where to apply it. The only science that doesn't need experiments and is only expanding is mathematics. In the field of material science, the needs are full knowledge, i. e. first of all mathematics with mathematical physics and theoretical physics.

It is well known that there is no universal mathematics and one must always keep in mind Gödel's theorems. It is therefore always necessary to: observe: the demarcation line science / pseudoscience; the boundaries between the interacting sciences are blurred, the interaction between methodologies every science; continuous lifelong learning; very dynamic programs in education from child to scientist.

Demarcation Line required: (Fundamental Research/Applied Research) is identical to (Fundamental Research/Knowledge Transfer in Industry 4.0). Fundamental research is with possible result. An example of "theory of everything": there is hope, but work continues, despite the great difficulties, etc. Industrial Research: Fundamental knowledge is known – the physical experiment confirms the theoretical result. Industrial research is already the subject of company institutes and high-tech companies. An set of (sciences with their methodologies, {(Sq, Mp), (Sr, Mr), (St, Ms)}) interact through (heuristics, complexity, interdisciplinary, multiscale) seems like this (see Fig.1): 𝑆 ; 𝑀 ⎯⎯⎯⎯⎯ 𝑆 ; 𝑀 ⎯⎯⎯⎯⎯ 𝑆 ; 𝑀 ⎯⎯⎯⎯⎯ 𝑆 ; 𝑀 . (C)

The relations (A), (B), (C) with (Heuristics (rules, methods), complexity, interdisciplinary, multiscale) for us are a generalized idea of interaction at dynamics at different speeds in 3D (X, Y, Z, t) space-time i. e. hierarchy with respect to the three axes in time. The relations (A), (B), (C) with (Heuristics (rules, methods), complexity, interdisciplinary, multiscale) for us are a generalized idea of interaction at dynamics at different speeds in 3D (X, Y, Z, t) space-time i. e. arrangement between close currents with respect to the three axes in time. On the based work [27] of Fig. 2, we present a general scheme of an office for knowledge transfer

238

Fig. 2. Knowledge transfer office for Micro-foundry assistance. Design of products and micro-structures of material. Scientific services are obtained from a higher level: for example, from a branch organization and membership fees. Full knowledge Wites and innovation ideas + areas of our transfer are the

grays; Full analysis of generated innovation.

4. Conclusion „Mathematical Modeling in Physics and Engineering“ to be changed to „Mathematics in Physics and Material Science“, which is a job for a sub-institute for the purpose of: covering the whole subject of the institute. Example: Many materials are cast at the Institute: alloys, ceramics, plastics and composites, which requires MATERIAL SCIENCE with it’s the sciences based: {Mathematic}; {Metal science [17], Theory of solid body [18]}; {Theory of crystallization [24], Nucleation [25], Crystal growth and epitaxy [26]}; {Solidification [19], First-order phase transition in casting [32]}; {Software for calculating the properties of materials from first principles. [33]}. The main proposal is to create an economy-wide Knowledge Transfer Industry (ITS) (Fig.3) and the Bulgarian Academy of Sciences (BAS) expertly works and studies the fundamental knowledge of the world.

239

Fig. 3. Knowledge transfer for MATERIAL SCIENCE in Industry 4.0.

Material science in Industry 4.0 requires much more basic knowledge than the sciences cited above, because in describing the properties of modern materials, new ideas and new interactions of sciences are required; development of mathematics and physic. Institute to become a Center for Materials Science: Institute of Materials Science, Equipment and Technology with the Hydro and Aerodynamic Center “Acad. A. Balevski ”at the Bulgarian Academy of Sciences. The interaction of BAS with ITZ is most effective. The knowledge transfer industry is high-tech with offices throughout the economy; interacts with the Bulgarian Academy of Sciences and with large high-tech companies. References 1. https://bg.wikipedia.org/wiki/Философия; https://bg.wikipedia.org/wiki/ 2. A. Rosenberg, Philosophy of science, Routledge Taylor & Frances Group, New York and

London, 2005. ISBN 0-203-08706-2 3. https://web.stanford.edu/class/symsys130/Philosophy%20of%20science.pdf 4. The Blackwell Guide to the Philosophy of Science, P. Machamer and Michael Silberstein,

Blackwell Publishers Inc., 2002. ISBN 0-631-22107-7 5. B. Ellis, R. Home, D. Oldroyd, R. Nola, H. Sankey, K. Hutchison, N. Thomason, J. Wilkins,

J. Forge, P. Catton, and R. Barton, https://www.researchgate.net/.../278702723_History_and_Philosophy_of_Science

6. M. A. Lim, Thesis of PhD, Quantum chromodynamics and the precision phenomenology of heavy quarks, University of Cambridge, 2018.

7. A. Polikarov, Methodology of scientific knowledge, Science and Art, Sofia, 1972. (In Bulgarian)

8. A. Polikarov, Essays on Methodology of Science, Science and Art, Sofia, 1981. (In Bulgarian)

9. R. Rosen, H. H. Pattee, R. L. Somorjai, A Question оf Physics: Conversations in Physics and Biology, Routledge & Kegan Paul, London and Henley, London, 1979. ISBN07100 03I3 7

10. F. Tampoia, The Origin of Europe and the esprit de geometrie https://philpapers.org/rec/TAMTOO-3

11. Gerard’T Hooft; Leonard Susskind; Eduard Witten; Masataka Fukugita; Lisa Randall; Lee Smolin; John Stachel; Carlo Rovelli; George Ellis; Steven Weinberg; Roger Penrose; A

240

theory of everything? In. NATURE. 2005; Vol. 433, No. 7023. pp. 257-259. Translation by M. Bushev, World of Physics – 4, 2005, pages 391-399. (In Bulgarian)

12. W. Corfield, PhD. Thesis, Queensland University of Technology Brisbane, Australia, 2006. 13. G. Schulze, Physics of metals, Peace, Moscow, 1971, (In Russian) 14. J. Blakemore, Solid state physics, Metallurgy, Moscow, 1972. (In Russian) 15. G. Gaglioti and H. Haken, Proc. of the International School of Physics Enrico Fermi,

Sinergetitics and Dynamic Instabilities, 24 June – 4 July, 1986. 16. U. C. Merzbach and Carl B. Boyer, A History of Mathematics, Third Edition, John Wiley

& Sons, Inc., ISBN 978 0 470 52548 7 17. Balevski A., Metalscience, Technics, Sofia, 1962. (In Bulgarian) 18. M. Borisov, K. Marinova, Introduction of physics of the solid body part I, Science and Art,

Sofia, 1977. (In Bulgarian) 19. M. Flemings, Solidification Processing, Peace, Moscow, 1977. (In Russian) 20. R. E. Smallman, R. J. Bishop, Modern Physical Metallurgy and Materials Engineering, sixth

edition, Butterworth-Heinemann, Oxford, 1999. ISBN 0 7506 4564 4 21. J. Campbell, Castings Practice: The 10 Rules of Castings, Butterworth-Heinemann, Oxford,

2004. ISBN 07506 4791 4 22. Y. Arsov, E. Momchilov, K. Daskalov, G. Bachvarov, Theoretical and technological

fundamentals of gas counter-pressure casting, Academic publishing house, Sofia, 2007. ISBN 978-954-322-199-8

23. М. Bushev, The world of physics, 2/2010, 220-227. (In Bulgarian) 24. R. Kaishev, Selected Works, “Prof. Marin Drinov”, BAS, Sofia, 1980. (In Bulgarian) 25. D. Kashchiev, Nucleation: Basic Theory with Applications, Butterworth-Heinemann,

Oxford, 2000. ISBN 0750646829 26. I. Markov, Crystal Growth for Beginners: Fundamentals of Nucleation, Crystal Growth,

and Epitaxy, 2nd Edition, World Scientific Publishing Co. Pte. Ltd., New Jersey, London, Singapore, Hon Kong, 2004. ISBN 981-238-245-3

27. S. Bushev, Knowledge transfer Industry 4, International Scientific Journal, „INDUSTRY 4.0“, Yare I, ISSUE 1 / 2016, 51-54. ISSN 2543-8582

28. S. Bushev, These of PhD, Controllability problems of crystallization process in casting, TU – Sofia, 1993.

29. S. Bushev, G. Moumdjian, A possibility to influence the dynamics of a phase transition of first order during casting in open thermodynamic systems, Comptes rendus de l’Académie bulgare des Sciences, Tome 46, No 7, p.27-30, 1993.

30. St. Bushev, Modelling and Numerical Estimates for Phase Transitions in Metal Alloys, Institute of Metal Science, Equipment and Technologies With Hydro- and Aerodynamics Center „Acad. Angel Balevski“ at the Bulgarian academy of sciences, Sofia 1574, 67 „Shipchenski prohod“ blvd. Bulgaria, 2011.

31. St. Bushev, Modeling and Prediction of Phase Transitions in Metal Alloys, Institute of Metal Science, Equipment and Technologies With Hydro- and Aerodynamics Center „Acad. Angel Balevski“ at the Bulgarian academy of sciences, Sofia 1574, 67 „Shipchenski prohod“ blvd. Bulgaria, 2014.

32. S. Bushev, Theoretical model of structure formation in die casting, XXII International scientific technical conference „FOUNDRY 2015“, 16-17 April 2015 Pleven, Bulgaria (In Bulgarian)

33. CASTEP, www.tcm.phy.cam.ac.uk/castep/oxford/castep.pdf