new era of high–entropy alloys · -5 0 5 10 15 20 25 30 35 40 100 200 300 400 500 600 700 fcc...
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New Era of High–Entropy Alloys
Jien-Wei Yeh Professor
Department of Materials Science and Engineering National Tsing Hua University
Hsinchu, Taiwan
高熵合金新紀元
Outline
New alloy concept: high-entropy alloys
Four core effects of high-entropy alloys New developments on high-entropy alloys Summary
New Alloy Concept
●“High-entropy alloys” have been explored since 1995 by my group at Tsing Hua Univ., Taiwan.
● High-entropy alloys have at least 5 major metallic
elements (n ≧ 5), each having an atomic percentage between 5 % and 35 %.
Equimole: AlCoCrCuFeNi Nonequimole: AlCo0.5CrCuFe1.5Ni1.2
Minor element addition: AlCo0.5CrCuFe1.5Ni1.2B0.1C0.15
Birth of High-Entropy Alloys
Ashby M.F Materials Selection in Mechanical Design, fourth edition, Butterworth-Heinemann, Elsevier, Oxford, UK, 2011, pp. 1-13
Why use the name of high-entropy? Consider an equimolar alloy with n elements at
its liquid state or regular solid solution state, Configurational entropy △Sconf = Rln(n) Mixing entropy △Smix= △Sconf + △Svibration + △Sdipole + △Selec ~ △Sconf
n 1 2 3 4 5 6 7 8 9 10 11 12 13
ΔSconf 0 0.69R 1.1R 1.39R 1.61R 1.79R 1.95R 2.08R 2.2R 2.3R 2.4R 2.49R 2.57R
Richards’ rule for metals’ fusion: Sliquid - Ssolid = △S = R
low medium high entropy 1.0R 1.5R
Most alloys has low entropy, and some concentrated alloys has medium entropy.
System Alloy ∆Sconf. at liquid state Low-alloy steel 4340 0.22R low
Stainless steel 304 0.96R low
316 1.15R medium
High speed steel M2 0.73R low Mg alloy AZ91D 0.35R low
Al alloy 2024 0.29R low 7075 0.43R low
Cu alloy 7-3 brass 0.61R low
Ni-base superalloy Inconel 718 1.31R medium Hastelloy X 1.37R medium
Co-base superalloy Stellite 6 1.13R medium
BMG Cu47Zr11Ti34Ni8 1.17R medium
Zr53Ti5Cu16Ni10Al16 1.30R medium
HEA System Examples AlCoCrCuFeNi AlCoCrCuFeNiMox
AlCoCrCuNiTiYx
AlCoCrCuFeNiTi, AlCoCrCuFeNiMn, AlCoCrCuFeNiTiV AlCoCrFeNi AlCoCrFeNiTix
AlCoCrFeMoNi AlCrFeMnNi AlTiNiMnBx
AlCuCrFeNi, CuCrFeMoNi, CuCrFeMnNi, CuCrFeNiZr Alx(TiVCrMnFeCoNiCu)100-x
CoCrCuFeNiTix
CoCrFeNiTi CrCuFeMnNi WNbMoTaV
Alloys world
R: gas constant
1. Thermodynamics – high entropy 2. Kinetics – sluggish diffusion 3. Structure – severe-lattice-distortion 4. Properties – cocktail effect
Core Effects of High-Entropy Alloys
-- Thermodynamics --
High Entropy Effect Enhance the formation of multi-element solid solutions
Entropy effect is often ignored in the phase prediction of conventional alloys
Because conventional alloys are based on one major elements, their phases would have quite small mixing entropies. Thus
△Gmix ~ △Hmix
The equilibrium phases mainly result from the competition between the mixing enthalpies of competing phases. However, the mixing entropies of solid solution phases are much higher in HEAs and should be considered in predicting equlibrium phases.
△Gmix = △Hmix - T△Smix
Ni-Sn-Zn Phase Diagram
Experimental isothermal section of the Ni-Sn-Zn system at 873 K (axes units: at%). Numbers from 1 to 6 represent the ternary phases; light grey areas indicate the binary solid solution extension; shaded areas represent the two phase field; estimated phase field boundaries and liquidus are shown by dashed lines.
873 K
Possible combinations and compounds between 80 metal elements
Mackay’s Statistical Distribution of Inorganic Crystal Structures
1. There is a sharp limit to complexity. 2. Many of the structures with large number of elements contain solid solutions, different elements occupying the same sites.
Mackay, “On Complexity”, Crystallography Reports, Vol. 46, 2001.
N≧5, high entropy effect
Enhancing the formation of solid solutions.
~1090 structures
~19000 structures
Extended Crystal Structures of Solid Solutions
Conventional crystal structure can be extended for multi-principal-element solid solutions.
J. W. Yeh, et al. Metall. Mater. Trans., Vol. 35, 2004.
-- Kinetics --
Sluggish Diffusion Effect 1. Lower diffusion rate 2. Lower phase transformation rate
Fine Precipitation in Cast Alloys
Many high-entropy cast alloys have nano or submicron precipitates in the matrix.
TEM microstructures of as-cast equimolar AlCoCrCuFeNi alloy
Kinetics Explanation The formation of new phases require cooperative diffusion
of many different kinds of atoms to accomplish the partitioning (re-distribution) of composition.
But the vacancy concentration is limited, 1. A vacancy is competed by multi-elements during diffusion. 2. The slowest-diffusion element determines the overall rate.
New phase
Vacancy
Assume the same atom size for simplicity
When heating the assembly, the HEA samples will be compressed to weld with each other and form diffusion couple due to the smaller CTE of Mo (5 ppm/K).
Design for the HEA Diffusion Couple
Mo Mo
Alumina
HEA1 HEA2
Mo
Argon-filled quartz tube
Use single FCC system of CoCrFeMnNi. Only two of the five elements had concentration
difference across the interface.
21
Composition of Diffusion Couples
Couple Alloy Composition (at.%)
Co Cr Fe Mn Ni
Cr−Mn 1 22 29 22 5 22
2 22 17 22 17 22
Fe−Co 3 33 23 11 11 22
4 11 23 33 11 22
Fe−Ni 5 23 24 30 11 12
6 23 24 12 11 30
Calculated Diffusivities
Diffusion coefficient: Mn > Cr > Fe > Co > Ni
0 exp QD DRT
= −
Evidence for Sluggish Diffusion
Low-entropy
Medium-entropy
high-entropy
HEAs have the highest Q/Tm!
Diffusion coefficients of Cr, Mn, Fe, Co, and Ni in different matrices
Ref. K.Y. Tsai, M.H. Tsai, J.W. Yeh, “Sluggish diffusion in Co–Cr–Fe–Mn–Ni high-entropy alloys”, Acta Materialia, 61(2013), pp. 4887-4897.
Advantages of Sluggish Diffusion
Slow down phase transformation Easy to get supersaturated state and fine precipitates Raise recrystallization temperature Slow down grain growth Slow down particle coarsening improve creep resistance
These advantages might benefit microstructure and property control!
-- Structure --
Severe-Lattice-Distortion Effect
Severe-Lattice-Distortion Effect Lattice distortion affects properties and
reduces the thermal vibration effect: Hardness and strength Temp. coefficient Electrical conductivity Temp. coefficient Thermal conductivity Temp. coefficient XRD peak intensity Temp. coefficient
e-
phonon
X-ray
Mechanical properties from Ni to NiCoFeCrMn
As N increases, YS, UTS, and EL significantly increase. This suggests solution hardening in FCC HEAs is superior than many hardening mechanisms..
Both strength and ductility of CoCrFeMnNi increase as temperature decreases
B. Gludovatz, A. Hohenwarter, D. Catoor, E.H. Chang, E. P. George, R.O. Ritchie, “A fracture-resistant high-entropy alloy for cryogenic applications”, Science, 345(2014), pp. 1153-1158.
Low stacking fault energy enhances nanotwinning deformation with decreasing temperature, which results in continuous steady strain hardening.
-- Properties --
Cocktail Effect
Rule of mixture
Excess properties due to mutual interactions
Come from the basic features and mutual interactions among all constituent elements in a solution phase.
Cocktail Effect
-5 0 5 10 15 20 25 30 35 40
100
200
300
400
500
600
700
BCC phaseFCC + BCC phasesFCC phase
Hard
ness
(Hv)
Al content (at.%)
Ex. AlXCoCrCuFeNi alloys
Importance of the Four Core Effects
Four core effects are much more pronounced in HEAs as compared with traditional alloys.
It would become easier to understand HEAs
through these four core effects. Four core effects are useful guidelines for
alloy design of HEAs.
New Developments on High-Entropy Alloys and Ceramics
Spray-deposition HEAs Elevated-temperature HEAs Highly-workable HEAs Carbides and cermets with HEA binders High-entropy nitride, carbide, and oxide
coatings
For protective coatings on heat exchangers and high-temperature components
1. Spray-Deposition HEAs
304 substrate HV150
AlCoCrFeNiSiTi HV800
2. Refractory HEAs
Senkov, Wilks, Scott, and Miracle, Intermetallics, 2011, Vol. 19, pp. 698-706.
Developed by US Air Force Research Laboratory
Nb25Mo25Ta25W25 and V25Nb25Mo25Ta25W25
At 1600℃, YS can be around 460 MPa.
3. Highly-Workable HEA AlCrFeMnNi When cold-rolled by a four-high rolling mill, the rolling
extension is up to 4900%. For 304 stainless steel with a similar hardness of HV160, the
rolling extension is only 1543%. Possible applications : 3C housing, golf head.
70μm-thick foil
4. Carbides and Cermets with HEA Binders
For dies, molds, and cutting tools
SEM image: TiC + 20% CoCrFeNiTi
Based on 12 strong binary nitrides Binary nitrides Crystal structure Lattice constant (nm) Hardness (GPa)
TiN FCC (B1 NaCl) 0.4249 19.9 ZrN FCC 0.4577 15.0 HfN FCC 0.4392 16.3 VN FCC 0.4136 15.0
NbN FCC 0.4392 18.3
TaN Hexagonal a = 0.519
c = 0.291 24.0 FCC 0.4330
CrN FCC 0.4149 11.0 Mo2N Cubic 0.4169 13.8 W2N Cubic 0.4126 24
AlN Hexagonal a = 0.3114 c = 0.3896 17.7
Si3N4 Hexagonal a = 0.7608 c = 0.29107 16-18
BN Hexagonal a = 0.2504
c = 0.3615 0.08-0.09
Cubic 0.661 29.9-43.1
5. High-Entropy Nitrides
HE Nitrides Hardness (GPa)
Modulus (GPa)
(AlCrMoTaTiZr)N 40 379
(AlCrTaTiZr)N 36 360
(AlCrMoSiTi)N 35 325
(AlCrSiTiV)N 31 300
(AlBCrSiTi)N 25 260
(AlCrNbSiTiV)N 42 350
(AlCrSiTaTiZr)N 34 343
(AlMoNbSiTaTiVZr)N 37 350
HE Nitride Coating Examples All HE nitrides have simple FCC structure. The FCC structure is stable even after 1100 ℃-5h vacuum annealing.
Strengthening mechanisms:
1. Strong bonding
2. Nanograin structure
3. Solid solution hardening
4. Residual stress
AlN+CrN+TaN+TiN+ZrN (AlCrTaTiZr)N
Si
HEA nitride
Cu
Cu (300 nm)
Si Substrate
HEA Barrier (10 nm)
Superior HEA Diffusion Barriers
Barrier Material Thickness (nm) Performance
TaN 50 750 °C 60 min
ZrN 100 800 °C 60 min
Ta36Si14N50 120 850 °C 30 min
Ti34Si23N43 120 850 °C 30 min
TiB2 60 600 °C 30 min
Ta 50 550 °C 60 min
(AlCrTaTiZr)N 10 900 °C 30 min
Shou-Yi Chang and Dao-Sheng Chen, Applied Physics Letters, 2009, 94, 231909.
Outstanding properties of HEA Film For CIGS solar cell, HEA film as back electrode could provide
thermal stable amorphous structure, diffusion barrier, higher reflectivity and conductivity.
Efficiency is improved by 9% as compared with Mo back electrode.
41 Glass / Stainless Steel / Polymer Substrate
CIGS (1.5~2μm)
Mo (0.5~1.5μm) Back electrode
Absorption layer
CdS(0.05μm) Buffer layer
i-ZnO(0.05μm) Pure ZnO TCO (ZnO:Al)(0.5~1.5μm) TCO of ZnO:Al
Top electrode Ni / Al
Sputtering method
•Vacuum method •Non-Vacuum method
Chemical bath deposition
Sputtering method
(AlCrTaTiZr)-Si-N coatings on carbide inserts
Film thickness is 1 μm. (AlCrTaTiZr)-Si-N has better flank-wear
resistance than that of TiN and TiAlN commercial coatings.
High cutting performance of multi-layer HEA/HEN coating
WC-Co I-TiAlN I1-200N I-TiN
Workpiece: 304 stainless steel
Multi-functional HEA coatings Hard, abrasive, dent-resistant, anti-corrosion, anti-fingerprint, anti-bacteria, anti-static, and colorful liquid metal
A
Materials World (based on mixing entropy)
Growing Interest Worldwide in HE Materials
At least 300 individual research groups have started to explore this new field.
1038 papers have been published from 2004 to 2015.
First HEA paper
Anyone who does HEA research knows MSE of NTHU, Taiwan!!
MSE, NTHU
47
International Symposiums Symposium of BMGs and HEAs IUMRS-ICA Conference, Qingdao, China, Sep. 25-28, 2010. IUMRS-ICA Conference, Taipei, Taiwan, Sep. 19-22, 2011. IUMRS-ICA Conference, Busan, Korea, Aug. 26-31, 2012. IUMRS-ICAM Conference, Qingdao, China, Sep. 22-28, 2013.
Symposium of HEAs MS&T-2012 Meeting, Pittsburgh, PA, USA, Oct. 7-11, 2012 - TMS-2013 Annual Meeting, San Antonio, Texas, USA, March
3-7, 2013 ---- HEAs(I) TMS-2014 Annual Meeting, San Diego, CA, USA, Feb. 16-20,
2014 ---- HEAs(II) TMS-2015 Annual Meeting, Orlando Florida, USA, March 15-
19, 2015 ---- HEAs(III) TMS-2016 Annual Meeting, Nashville, Tennessee, Feb. 14 –
18, 2016 ---- HEAs(IV)
Workshop on HEAs in India 2015
International Conference on High-Entropy Materials
(ICHEM 2016) November 6th – 9th 2016,
National Tsing Hua University, Hsinchu, Taiwan Chairs: J.W. Yeh, P.K. Liaw, O.N. Senkov
Topics of interest: Materials design Physical metallurgy Processing development Structure characterization Mechanical, physical, and chemical properties Surface and structural stability Simulation and modeling Applications
Special Issues on High-Entropy Alloys
1. High-Entropy Alloys, Annales de Chimie Science des Matériaux, Vol. 31, 2006.
2. High-Entropy Alloys, Entropy, Vol. 15, 2013.
3. High-Entropy alloys, Journal of Metals, Vol. 65, 2013.
4. Progress in High-Entropy alloys, Journal of Metals, Vol. 67, 2015.
5. High-Entropy alloys, Materials Science and Technology, Vol.31, 2015.
6. High-Entropy alloy Coatings, Coatings, Feb. 2016.
7. High-Entropy Alloys, Entropy, Vol. 18, 2016.
8. High-Entropy Alloys, Metals, Dec. 2016.
9. Concentrated Solid Solution Alloys, Current Opinion in Solid State & Materials Science, 2016
High-Entropy Alloys By B.S. Murty, Jien-Wei Yeh, S. Ranganathan This book provides a complete review of the current state of the art in the field of high entropy alloys (HEA). The conventional approach to alloy design is to select one principal element and add elements to it in minor quantities in order to improve the properties. In 2004, Professor J.W. Yeh and his group first reported a new approach to alloy design, which involved mixing elements in equiatomic or near-equiatomic proportions, to form multi-component alloys with no single principal element. These alloys are expected to have high configurational entropy and hence were termed as "high entropy alloys." HEAs have a broad range of structures and properties, and may find applications in structural, electrical, magnetic, high-temperature, wear-resistant, corrosion-resistant, and oxidation-resistant components. Due to their unique properties, high entropy alloys have attracted considerable attention from both academics and technologists. This book presents the fundamental knowledge present in the field, the spectrum of various alloy systems and their characteristics studied to date, current key focus areas, and the future scope of the field in terms of research and technological applications.
Published in June, 2014
• Introduces and explains the source of high-entropy alloys, their advantages and weakness, and advances in understanding this class of materials including their industrial applications • Explains all aspects of high-entropy alloys including formation rules, processing, physical metallurgy, mechanical behavior, functional properties, prediction of the structure using various ab initio methods, thermodynamics and elasticity, liquid structure and solidification, CALPHAD modeling, and future prospects • Details computational procedures for high-entropy alloys and the latest computational development of high-entropy alloys
High-Entropy Alloys Fundamentals and Applications
Editors: Gao, M.C., Yeh, J.W., Liaw, P.K., Zhang, Y.
XiaoZhi Lim, ”多元金屬合成的更強更韌更延合金”, 自然,第533卷,第7603期,5月19日, 2016年, 第306-307頁
Summary High-entropy alloys have four core effects: high
entropy, sluggish diffusion, severe-lattice-distortion and cocktail effects and provide a wide spectrum of properties.
The concept and core effects of high-entropy
alloys could be applied to other high-entropy materials.
High-entropy materials have promising
applications such as elevated-temperature components, carbide tools, cermet tools, thermal spray coatings, and functional coatings.
Thank you for your attention!
開拓人煙未至的新世界
沒有參考書及論文 取名稱,做定義 提出核心效應及基本原理 擴展到高熵陶瓷及高熵高分子材料 開馬路,打先鋒,做示範 (1)鑄造成型 (2)加工成型及熱處理 (3)粉末冶金成型 (4)鍍膜 (5)各種結構及特性探討 (6)發展應用
高熵合金的應用
傳統材料應用在嚴苛的地方,若性能不足,壽命不長,正是高熵合金展現身手的機會。近12年的發展,已看到了解決的機會,指日可待。例如:
1.高速切削且無切削液 (1)車刀、銑刀:耐磨、耐溫,提高數倍壽命 (2)超硬鍍膜:再提高耐溫、耐磨,提高數倍壽命 2.噴射引擎葉片:耐溫 > 極限1150℃,原效率增10%以上 3.現今核能廠燃料管由400℃提至900℃,以免福島氫爆重演 4.下世代核能反應爐直接可耐900℃耐輻照損傷的材料 5.大溫度範圍極低電阻溫度係數的薄膜電阻,-60~+200℃ 6.室溫或更高溫的超導材料,目前高壓下-120℃ 7.抗沾黏鍍膜,不沾鍋不沾模 8.塑膠射出機的螺桿的耐溫耐磨耐蝕鍍層 9.採礦、鑽油井等耐溫耐磨耐蝕的高熵合金及超硬高熵合金 10.手機美觀耐磨多功能的保護層
金屬的調合學 更強、更韌、更延:冶金學家以新配方正在創造新一代性能顯著的合金
XIAOZHI LIM 撰
高熵合金可用於噴射引擎高溫段的葉片
XiaoZhi Lim, ”多元金屬合成的更強更韌更延合金”, 自然,第533卷,第7603期,5月19日, 2016年, 第306-307頁
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