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Intermetallics 69 (2016) 47e53

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Intermetallics

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Microstructure and phase transformations in a liquid immiscibleFe60Cu20P10Si5B5 alloy

Krzysztof Ziewiec a, *, Mirosława Wojciechowska a, Grzegorz Garzeł b, Tomasz Czeppe b,Artur Błachowski c, Krzysztof Ruebenbauer c

a Institute of Technology, Pedagogical University of Cracow, Podchora _zych 2, 30 084 Krak�ow, Polandb Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Reymonta 25, 30 059 Krak�ow, Polandc M€ossbauer Spectroscopy Division, Institute of Physics, Pedagogical University, Podchora _zych 2, 30 084 Krak�ow, Poland

a r t i c l e i n f o

Article history:Received 20 July 2015Received in revised form16 September 2015Accepted 17 October 2015Available online xxx

Keywords:Metallic glassesMicrostructureSegregationDifferential scanning calorimetryScanning electron microscopyM€ossbauer spectroscopy

* Corresponding author.E-mail address: kziewiec@up.krakow.pl (K. Ziewie

http://dx.doi.org/10.1016/j.intermet.2015.10.0100966-9795/© 2015 Elsevier Ltd. All rights reserved.

a b s t r a c t

This work presents a study of the microstructure formed in a liquid immiscible Fe60Cu20P10Si5B5 alloyduring moderate cooling on a copper plate and melt-spinning. The alloy ingot was re-melted on a copperplate and observed while cooling using a mid-wave infra-red (MWIR) camera. The heating and coolingcharacteristics of the melt-spun ribbon were studied using differential scanning calorimetry (DSC). Themorphology and chemical composition of the ingot as well as the melt-spun ribbon were analyzed usingscanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The compositions of theingot and the ribbon were investigated using X-ray diffraction (XRD). M€ossbauer spectroscopic mea-surements showing the influence of adding Cu to the FeeSiePeB alloy were also analyzed.

The IR images from the MWIR camera enabled direct observation and identification of the liquid statetransformations of the alloy. The DSC trace of the melt-spun ribbon showed crystallization of theamorphous matrix and confirmed that high temperature transformations occurred when the alloy was inthe liquid state. Observations of the microstructure of the ingot revealed crystalline surface fractalstructures formed by the Fe-rich eutectic constituent and Cu-rich fcc spherical precipitates. Themorphology of the precipitates indicated that the precipitates formed in the miscibility gap. Themicrostructure of the melt-spun ribbon is composed of an amorphous Fe-rich matrix and elongated Cu-rich fcc precipitates. The observations based on the study of the microstructure are supported byM€ossbauer spectroscopy.

© 2015 Elsevier Ltd. All rights reserved.

1. Introduction

Liquid immiscibility could be an interesting concept to explorewhen considering the issue of controlling the microstructure ofcomposite materials. It is well known that liquid immiscible alloyssuch as AlePb, AleBi and CuePb are potential materials foradvanced bearings in the automotive industry. There are recentreports on the formation of two-phased glassy composites in anNieNbeY system [1,2], YeTieAleCo system [3], AlePbeNieYeCosystem [4], iron-based FeeCueNieSieSneBeY system [5],FeeCueNiePeSieB system [6,7] and FeeCuePeSieB [8] amor-phous/crystalline composite. In the latter alloys, it has been shownthat the morphology of the composites can be changed by varying

c).

the temperature prior to ejection.Phase transformations and structure development in alloys

processed in the liquid state are important for controlling the finalmicrostructure and properties of the alloys, and as such, should bebetter investigated and understood. Up to this time, the only re-ports on liquid immiscibility in metal alloys were based on ther-mocouple [9], pyrometer [10,11], differential thermal analysis (DTA)[12] and DSC [13,14] measurements. In Ref. [8], the studies of theFe60Cu20P10Si5B5 amorphous/crystalline alloy prove that itsmicrostructure depends on the temperature of ejection from thecrucible, and that the temperature at which the liquid separates canbe found using indirect pyrometric and DTA measurements. Thispresent work provides further evidence for this through directobservation of thermal images made by a MWIR camera. Theseimages are verified by DSC analysis and microstructural studiesusing SEM/EDS and XRD.

FeePeSieB alloys are known for their ability to form glass and

Fig. 1. Scanning electron microscope microstructure of the Fe60Cu20P10Si5B5 arc-meltingot and results of the EDS analysis.

Table 1Calculated enthalpies of mixing DHmix for equiatomic liquids containing Fe, Cu, P, Siand B in binary systems, kJ/mole [18,19].

Fe Cu P Si B

Fe e þ13 �31 �18 �11Cu e �17,5 �10 þ16

K. Ziewiec et al. / Intermetallics 69 (2016) 47e5348

their magnetic properties [15e17]. However, alloying with a liquidimmiscible element can ruin both glass formation and themagneticproperties. M€ossbauer spectroscopic study can show changes in themicrostructure and magnetic properties introduced by alloyingFeePeSieB with Cu. Thus, it is worth investigating how alloyinginfluences the hyperfine field, quadrupole interaction and isomershift.

Fig. 2. X-ray diffraction pattern of the Fe60Cu20P10Si5B5 arc-melt ingot; FeBP stands forFe3B0.36P0.64 compound.

2. Experimental

The five-component Fe60Cu20P10Si5B5 alloy was prepared by arcmelting the following precursors: 99.95 wt. % Fe, 99.95 wt. % Cu,99.95 wt. % Si and FeeP and FeeB ferroalloys in a protective at-mosphere, using Ti as a getter. Analysis of the microstructure andchemical composition of the ingot was performed using a JEOL6610 scanning electron microscope with an Oxford X-Ray micro-analyzer. The 2 g ingot was re-melted in the arc furnace andobserved with an MWIR FLIR SC7650 camera while it cooled on acopper plate. The sample-to-camera distance was 300 mm, trans-missivity of the window in the electric arc furnace was 70% and theroom temperature was 20 �C. The areas for temperature mea-surement were selected in order to avoid the narcissus effect andreflection from the hot tungsten electrode. The alloy was melt-spunin a helium atmosphere with a linear velocity of 33 m/s, an ejection

pressure of 150 kPa, a crucible and hole diameter of 0.7 mm and anejection temperature of 1434 K. The microstructure of the melt-spun ribbons was investigated using scanning electron micro-scopy (SEM). The ribbonwas also investigated using a Perkin ElmerDSC7 differential scanning calorimeter at a heating rate of 40 K/min. XRD measurements of the ribbons as well as the ingot wereperformed using a DRON-3 diffractometer and CuKa radiationfiltered by the bent single crystal LiF linearly focusing mono-chromator on the detector side. The scattering angle of 2Q wasvaried between 30 and 80� with a constant step of 0.05�. Scanswere done in the Q� 2Q mode. M€ossbauer spectroscopy mea-surements were performed on the Fe60Cu20P10Si5B5 alloy as an arc-molten ingot and melt-spun ribbon and the Fe80P10Si5B5 melt-spunribbon in transmission geometry at room temperature using aRENON MsAa-3 spectrometer equipped with a LND Kr-filled pro-portional detector and HeeNe laser based interferometer used tocalibrate a velocity scale. A commercial 57Co(Rh) sourcewas appliedfor 14.41-keV resonant transitions in 57Fe. Spectra were fitted to adistribution of hyperfine fields for magnetically ordered compo-nents including electric quadrupole interaction to the first order.Magnetically unsplit components were fitted with a doubletresulting from the electric quadrupole interaction. Spectral shiftswere reported versus shifts in a-Fe at room temperature.

3. Results and discussion

Microstructural SEM observations of the arc-molten 2 g ingotshowed that the microstructure basically consists of brighterglobular precipitations within the darker matrix (Fig. 1). EDSmapping indicates that the globular areas were Cu-rich liquiddepleted in iron. The globular areas contained a significantlysmaller quantity of phosphorus than the matrix. However, thecontent of silicon in the globular regions was only slightly lowerthan in the Fe-base matrix.

Boron was not detected by the analysis. Nevertheless, it can beexpected that due to negative enthalpy of mixing for FeeB (�11 kJ/mol) and positive enthalpy of mixing for CueB (þ16 kJ/mol)(Table 1) [18,19], boron is strongly attracted to the Fe-based matrix.

Table 2The values of TS, TCu and TE registered in areas A, B and C.

Area Temperature [K]

TS TCu TE

A 1571 1291 1002B 1482 1243 915C 1306 1216 880

Fig. 3. The course of the free cooling for Fe60Cu20P10Si5B5 on the three areas of arc-melt ingot; a) IR images of the cooled sample; b) cooling curves from the areas “A”, “B” and “C”; c)initial sections of the cooling curves from 0 s to 0.5 s; sample weight 2 g.

K. Ziewiec et al. / Intermetallics 69 (2016) 47e53 49

One can assume that before solidification, the Fe-rich matrix wasalso enriched with phosphorus and probably boron. The siliconcontent seemed to be slightly higher in the Fe-richmatrix, althoughdue to a small difference in enthalpies of mixing and a small siliconcontent in the alloy (5 at.%), the distribution between Cu-richprecipitates and the Fe-rich matrix was similar.

The XRD pattern for the arc-molten ingot are shown in Fig. 2.The XRD peaks observed on the diffraction can be attributed to fourcrystalline phases: the fcc Cu-based solid solution (space group:Fm-3m, a: 3.625 Å, PDF 01-070-3038), the bcc Fe-based solid so-lution (space group: Im-3m, 2.8664 Å, PDF 00-006-0696), thetetragonal Fe3B0.36P0.64 compound (space group I4, a ¼ 8.98 Å,c ¼ 4.427 Å, PDF 04-006-5538), and the tetragonal Fe3P compound(space group I4, a ¼ 9.1 Å, c ¼ 4.4592 Å, PDF 00-019-0617).

Through comparison of the SEM/EDS observations and the XRD

measurements, it can be noticed that the microstructure of theingot consists of fcc Cu-based precipitates and a fine eutectic matrixconsisting of the three crystalline phases, i.e. the bcc Fe-based solidsolution and compounds isomorphic with the tetragonalFe3B0.36P0.64 and Fe3P compounds that also contain Si as an elementthat substitutes P and B.

Fig. 4. Scanning electron microscope microstructure of the Fe60Cu20P10Si5B5 melt-spun ribbon after ejection at 1434 K and results of the EDS analysis.

K. Ziewiec et al. / Intermetallics 69 (2016) 47e5350

Fig. 3a presents the snapshots from the MWIR camera takenwhile the ingot was cooling on a copper plate. These snapshots arepresented for five times: t1¼0.04 s, t2¼ 0.12 s, t3¼ 0.16 s, t4¼1.6 sand t5 ¼ 2.7 s. At the beginning of the cooling sequence, just afterswitching off the electric arc which had been heating the sample,the alloy droplet was highly overheated and in a uniform liquid

Fig. 5. X-ray diffraction patterns for Fe60Cu20P10Si5B5 melt-spun ribbons obtained byejecting the master alloy at 1434 K.

phase (Fig. 3a). Comparison of IR images from t1 and t2 revealschanges that are visible in areas “A”, “B” and “C”. For area “A”, thereis an oval-shaped region (indicated by an arrow). A similar regioncan also be seen on the left of area “A” (indicated by an arrow). Forareas “B” and “C”, a distinct change in brightness can be observed.These changes in the IR images can be attributed to the decom-position of the initially uniform liquid into a mixture of liquids. Thismoment corresponds to the beginning of a steeper drop in tem-perature, which is marked as Ts in Fig. 3b. The very beginning of thecooling curves up to 0.5 s is presented in Fig. 3c. Formation ofglobular-shaped liquid phase colonies has also been noticed in themicrostructure of ingots of the Fe60Cu20P10Si5B5 alloy [8]. Suchdevelopment of the microstructure of liquid immiscible alloys hasalso been reported in other works [5e7,20]. Liquid globular-shapedCu-rich regions crystallize at a lower temperature, TCu, forming anfcc Cu-based solid solution.

After crystallization of the Cu-rich liquid at TCu, there is asegment of continuous cooling that finally leads to the crystalliza-tion of the matrix at TE, where a plateau on all of the cooling curvescan be observed (Fig. 3b). Due to the overheating of the droplet, therecalescence effect can also be observed on the curves for areas “A”and “B”. The temperatures of separation in the liquid state Ts,crystallization of the Cu-based solid solution TCu, and eutecticcrystallization of the matrix TE vary depending on the location ofthe area where temperature was measured (Table 2). The highesttemperatures were recorded at the top of the droplet (area “A”)because, while cooling, this area had the lowest degree of under-cooling. A moderate degree of undercooling was observed at area“B” and the highest degree of undercooling was at area “C”. This canbe explained by the strong cooling influence of the massive coppersubstrate plate.

The SEM observations and EDS mapping of the melt-spun rib-bon obtained by ejection at 1434 K is presented in Fig. 4. Theelongated lamellar Cu-rich regions a few microns thick are sur-rounded by the Fe-rich matrix. While the Cu-enriched regions areimpoverished in the other alloying elements, the matrix containsthe majority of the alloying elements such as P, Si and B. Further-more, the matrix contains small submicron-sized particles of Cu-based precipitates. According to earlier work [8], the microstruc-ture of the melt-spun ribbons depends on ejection temperature.The lamellar microstructure that can be observed in the presentcase was obtained after ejection of the alloy within the miscibilitygap, where the liquid consisted of two phases [8].

The XRD pattern for the melt-spun ribbon ejected at 1434 K ispresented in Fig. 5. There are peaks near the dhkl values corre-sponding to {111}, {200} and {220} fcc copper (PDF-4 no.: 03-065-9743). The broad and shallow peak between 40� and 50� (2Q) is dueto scattering in the amorphous matrix of the alloy.

With reference to the microstructure of the arc-molten ingotcomposed of microstructural components with the morphology ofa liquid immiscible alloy (i.e. a fine eutectic and Cu-based solidsolution) it is possible to state that the composition of the melt-spun ribbon derives from this microstructure. It is worth notingthat similar microstructures of liquid immiscible alloys have alsobeen observed in other systems [14,21]. Spherical morphologyderives from a liquid phase, mainly due to the natural tendency ofimmiscible liquids to reduce surface energy. Liquid phase separa-tion is also possible in a metallic glass liquid even with strongnegative enthalpies of mixing [22e25]. However, in the latter case,both immiscible liquids can form amorphous/amorphous micro-structures. Rapid cooling of the highly alloyed Fe-rich eutecticliquid transforms the liquid into a glassy matrix, and rapid coolingof immiscible Cu-rich poorly alloyed melt crystallizes the melt.Such microstructures can be expected based on the enthalpy ofmixing (Table 1). The explanation for this is the high positive

Fig. 6. DSC trace for heating and cooling; the hatched areas show the thermal effects from transformations for which enthalpy was determined from the DSC measurement.

K. Ziewiec et al. / Intermetallics 69 (2016) 47e53 51

enthalpy of mixing between Fe and Cu and the fact that theenthalpy of mixing for CueP, CueSi and CueP are substantiallyhigher than the corresponding values for FeeP, FeeSi and FeeP.Therefore, in an FeeCuePeSieB system, a Cu-based liquid at atemperature lower than Ts forms poorly alloyed constituents.However, Fe, P, Si and B below Ts mainly form a second liquid that,depending on the cooling rate, forms a fine eutectic constituent orglass. In the present experiment involving theMWIR camera, it waspossible to observe the whole sequence of transformations startingfrom a uniform liquid, to separation of the liquids at TS, to crys-tallization of a Cu-rich liquid at TCu, and finally to crystallization ofan FeePeSieB-rich eutectic liquid at TE.

Fig. 6 shows the DSC trace for the heating and cooling of theFe60Cu20P10Si5B5 alloy starting from the as-melt-spun state. Thetemperatures and heat of transformations determined from theDSC measurements are presented in Table 3 and Table 4, respec-tively. There are three thermal effects that can be observed afterheating (Fig. 6, Table 3). The first is exothermic, with its onset atTx ¼ 765 K and peak at TC ¼ 776 K. This is due to the crystallizationof the amorphousmatrix. Further, there are two endothermic peaksthat are associated with the melting sequence. The melting of thealloy starts at Tm ¼ 1288 K and terminates at Tl ¼ 1373 K. The twopeaks, i.e. TE ¼ 1312 K and TCu ¼ 1358 K, correspond to the meltingof the products formed from the amorphous matrix and the coppersolid solution, respectively. The deviation from the baseline ends atTS¼ 1676 K due to themixing of the twomelts and formation of theuniform liquid solution. During cooling, the temperature of sepa-ration in the liquid state TS is observed at 1621 K. In further cooling,three exothermic peaks are recorded. The first of these peaks can beattributed to the crystallization of the copper solid solution atTCu ¼ 1302 K. However, the position of the second and third peaksare TE1¼1264 K, and TE2¼ 1199 K, respectively. Therefore, there aretwo peaks in contrast to the one peak present during the heating ofthe initially uniform sample. However, it is worth noting that due tothe separation of the liquid state, the chemical composition isbasically is not uniform across the sample [5e8,20]. Consequently,the transformations occurring at TE1 and TE2 may refer to liquids ofslightly different chemical compositions. Furthermore, the split inthe crystallization peaks upon cooling may result from the sepa-ration of the droplet into two parts, which actually was observed.This could result in a slightly different degree of undercooling for

the transformations occurring in each particular separated dropletof the alloy. It is worth noting that in spite of the different sequenceof the peaks, when comparing the heating and the cooling, the totalheat absorbed during melting (�200.2 J/g) and absolute value ofthe heat released during solidification (195.6 J/g) are very close. Dueto the higher cooling rates on the copper plate compared to the DSCfurnace, the observed transformation temperatures are substan-tially lower. Thus, the corresponding transitions are undercooled byDTs¼ 50 K, DTCu¼ 11 K, DTE1¼262 K and DTE1¼197 K. Comparisonof the DSC trace for cooling and heating shows that there is no peakin the low temperature range that corresponds to the one observedduring heating at TC ¼ 776 K, which confirms the irreversibletransformation of a metastable constituent such as an amorphousmatrix.

Fig. 7 shows the M€ossbauer spectra with the correspondinghyperfine field distributions for magnetically split components. Theessential results are summarized in Table 5. The copper-free samplein the form of a ribbon is characterized by a smooth hyperfine fielddistribution, negligible quadrupole interaction and a relatively highelectron density at the iron nuclei (low isomer shift). The sample ismagnetically ordered at room temperature. The addition of copperleads to significant phase separation on the semi-macroscopic scaleas far as the ingot is concerned. The fraction corresponding to theCu-rich phase practically does not contain iron except for isolatedatoms and small atomic clusters dissolved in the copper matrix.One can hardly obtain a M€ossbauer spectrum for this fraction, andtraces of iron are found as is typical for solid solution of iron in thecopper (the spectrum is not shown). There is no magnetic order atroom temperature.

The second fraction, corresponding to the Fe-rich phase, ismagnetically ordered at room temperature with a hyperfine fielddistribution indicating a variety of regions with different averagehyperfine fields. The hyperfine field of metallic a-Fe is locatedwithin this distribution confirming the presence of a-Fe found bythe XRD. Low negative (in fact effective) quadrupole interaction isdue to disorder in the iron atoms. The average electron density atthe iron nuclei is lower in comparison with the copper-free mate-rial, which indicates a much higher disorder with the possiblepresence of vacancies. The same material prepared as rapidlycooled ribbons is even more disordered on the semi-macroscopicscale as the average hyperfine field is lower, the absolute value of

Table 3The values characteristic for transformation temperatures determined from the DSCmeasurements; Tx e crystallization onset; Tc e crystallization peak, Tm e meltingpoint, TE e eutectic transition, Tl e liquidus temperature, Ts e demixingtemperature.

Portion of DSC trace Temperature [K]

Tx Tc Tm TE TCu Tl TS

Heating 765 776 1288 1312 1358 1373 1676Cooling e e 1184 1: 1264

2: 11991302 1312 1621

Table 4The values of enthalpy for derived from DSC measurements; DHC e crystallizationenthalpy for glassy matrix, DHE e crystallization/melting eutectic, DHCu e crystal-lization/melting of Cu-based constituent.

Portion of DSC trace Heat of transformation [J/g]

DHC DHE DHCu DHEþDHCu

Heating 28.5 �166.7 �33.5 �200.2Cooling e DHE1þDHE2 ¼ 152.3 43.3 195.6

Table 5M€ossbauer parameters for Fe80P10Si5B5 melt-spun ribbons, Fe60Cu20P10Si5B5 arc-melt ingot and melt-spun ribbons. The symbol A denotes relative contribution ofthe given iron site to thewhole spectrum. The symbol IS stands for the isomer (total)shift of the particular sub-spectrum versus room temperature a-Fe, while QS de-notes the absolute value of the quadrupole splitting for magnetically unsplit com-ponents and the first order correction due to the electric quadrupole interaction formagnetically split components. The symbol <B> stands for the average magnetichyperfine field.

Sample A (%) IS (mm/s) QS (mm/s) <B> (T)

Fe80P10Si5B5 melt spun ribbon 100 0.12 0 24.8Fe60Cu20P10Si5B5 arc-molten ingot 100 0.19 �0.07 26.7Fe60Cu20P10Si5B5 melt-spun ribbon 93 0.22 �0.10 24.8

7 0 0.22 e

K. Ziewiec et al. / Intermetallics 69 (2016) 47e5352

the quadrupole interaction is higher, and the electron density islower in comparisonwith thematerial in the form of ingot. One cansee some paramagnetic fractions at room temperature as well,which are caused by the regions with an enhanced concentration ofphosphorus and boron. Iron dissolved in the copper precipitates(see the XRD pattern) is so rare that it is invisible on the largebackground due to the amorphous phase.

4. Conclusions

1. The final morphology of the arc-molten ingot results from theimmiscibility of the alloy in the liquid state. Due to the separa-tion of the liquid state, the microstructure is composed of a fineeutectic constituent formed by phases rich in Fe, P, Si and Bisomorphic with the tetragonal Fe3B0.36P0.64 and Fe3P com-pounds, the bcc Fe-base solid solution and the fcc Cu-basedspherical precipitates. The M€ossbauer spectroscopic measure-ments reflect the separation phase as well as the presence ofregions with different average hyperfine fields. Disorder in Featoms was also observed.

2. During the rapid cooling of the Fe60Cu20P10Si5B5 alloy, the Fe-rich highly alloyed eutectic liquid is able to transform into aglassy matrix, and the immiscible Cu-rich poorly alloyed meltcrystallizes. This is due to the separation of the liquid state thatcan be attributed to the high positive enthalpy of mixing be-tween Fe and Cu and the enthalpy of mixing for CueP, CueSi andCueP, which are substantially higher than the correspondingvalues for FeeP, FeeSi and FeeP. The similar values of the hy-perfine field <B>¼24.8 T for the Fe80P10Si5B5 and Fe60Cu20-P10Si5B5 melt-spun ribbons derived from M€ossbauerspectroscopic measurements confirm that adding Cu does notchange the magnetic properties of the amorphous matrix in theFe60Cu20P10Si5B5 alloy.

3. The DSC trace confirms the presence of an exothermic irre-versible transformation at Tc¼ 776 K due to the crystallization ofthe amorphous matrix. The melting of the alloy occurs betweenTm ¼ 1288 K and Tl ¼ 1373 K with strong endothermic peaks at

Fig. 7. 57Fe M€ossbauer spectra for Fe80P10Si5B5 melt-spun ribbons, Fe60Cu20P10Si5B5 arc-melt ingot and melt-spun ribbons. A distribution of the hyperfine field is shown formagnetically split component for each spectrum.

K. Ziewiec et al. / Intermetallics 69 (2016) 47e53 53

TE ¼ 1312 K and TCu ¼ 1358 K for the melting of the eutecticconstituent and the melting of the Cu-rich precipitates. Theproducts are immiscible liquids that coexist up to TS ¼ 1676 K,where the uniform liquid state is obtained. At the DSC trace forcooling, separation of the liquid state is observed at TS ¼ 1621 K,which results in a sequence of three peaks. The first can beattributed to the crystallization of the copper solid solution atTCu ¼ 1302 K. However the second and the third peaks atTE1 ¼ 1264 K and TE2 ¼ 1199 K can be attributed to the solidi-fication of the near-eutectic liquids. The deviation from theuniform eutectic liquid mixture is probably due to the separa-tion of the liquid state.

4. The experiment involving the MWIR camera enabled directobservation of the whole sequence of transformations startingfrom a uniform liquid, to separation of the liquids at TS, tocrystallization of a Cu-rich liquid at TCu and finally to crystalli-zation of an FeePeSieB-rich eutectic liquid at TE.

5. The thermal effects observed from the MWIR camera may beassociated with the microstructure of the arc-molten ingot.Thus, the separation of the liquid state into Fe-rich and Cu-richregions occurs at Ts. The effect at TCu can be attributed to thecrystallization of the Cu-rich globular precipitates and TE is thecrystallization of the Fe-rich eutectic liquid. Due to the strongcooling influence of the massive copper substrate plate, thetransformations occur at higher degrees of undercooling. This isthe reason why the Ts, TCu, and TE values are lower in theneighborhood of the plate.

Acknowledgments

The work described in this paper was supported by a grant fromthe National Science Centre (NCN) (Project No. 2012/05/B/ST8/02644).

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