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Modulating the crystallization process of Fe82B12C6 amorphous alloy via rapid annealing
Journal of Alloys and Compounds 785 (2019) 328e334
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Modulating the crystallization process of Fe82B12C6 amorphous alloy via rapid annealing L. Zhu, H. Zheng, S.S. Jiang, Y.G. Wang* College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 December 2018 Received in revised form 2 January 2019 Accepted 17 January 2019 Available online 18 January 2019
Crystallization is a uniform behavior for amorphous alloys while it can be fairly complex. For Fe-B-C alloys with high Fe content, the precipitation of a-Fe is ahead of the Fe-metalloid compounds with temperature increasing. It is found that the crystallization products of Fe-B-C amorphous alloys with Fe content lower than 82% can be modulated by appropriate annealing. The Fe82B12C6 alloy is eutectoidally crystallized with the simultaneous precipitation of a-Fe and Fe-metalloid compounds under conventional annealing. It is a diffusion controlled three-dimensionally growth with a constant nucleation rate. However, only a-Fe nanocrystals with a low volume fraction form under rapid annealing, which is evidenced by the results of X-ray and electron diffractions along with the magnetometry. The transmission electron microscopy bright-field images show that the a-Fe nanocrystals obtained by rapid annealing have two different morphologies. One is dendritic with a large characteristic length and the other is equiaxed-like. © 2019 Elsevier B.V. All rights reserved.
Keywords: Amorphous materials Crystal structure Phase transitions Thermal analysis
1. Introduction An amorphous alloy will gradually transform into a crystalline one upon heating due to its thermodynamically metastable nature. Crystallization is a uniform behavior for amorphous alloys while it can be fairly complex. It is widely accepted that Cu atoms cluster in the early stage of the crystallization and provides nucleation sites for a-Fe leading to a high nucleation rate in Cu-containing Fe-based amorphous alloys [1e3]. The impurities such as oxygen can also induce the formation of nuclei and trigger the subsequent crystallization [4]. Inspired by the asymmetry in the crystallization behavior during constant heating and cooling, the existence of the quenched-in nuclei is suggested [5]. Sharma et al. claimed the role of these so-called pre-existing nuclei/compositional fluctuation to the crystallization of Fe-Si-B-P-Cu alloys during which the preexisting nuclei grow in size with annealing time and lead to a nearly constant volume fraction of a-Fe at relatively low temperature [6]. In addition to the complexity in the crystallization mechanism, the crystallization of the amorphous alloys can be easily altered by processing history, for instance, increasing the heating rate [7e10],
* Corresponding author. E-mail address: [email protected] (Y.G. Wang). https://doi.org/10.1016/j.jallcom.2019.01.209 0925-8388/© 2019 Elsevier B.V. All rights reserved.
employing two-step annealing [11], applying preliminary deformation [12] and so on. The sensitivity of the onset crystallization temperature to the heating rate differs from that of the glass transition temperature [13]. Rapid annealing has been proved to be effective in grain refinement of the Fe-based amorphous alloys, because the onset temperature of crystallization is raised to the vicinity of the glass transition temperature under high heating rates [10]. Moreover, Kosiba et al. found that when heating a Cu-Zr-Al-HfCo bulk amorphous alloy at a sufficient high rate, the crystallization reaction changes from eutectoid to polymorphic, that is, the glass precipitated Cu10Zr7 and CuZr2 at low heating rate whereas only metastable B2-CuZr crystals formed at high rates [14]. This suggests that the rapid annealing is capable to modulate the crystallization products of an amorphous alloy. In the present work, a structure with only a-Fe nanocrystals dispersing in the amorphous matrix is successfully obtained via rapid annealing in an Fe82B12C6 alloy whose crystallization under conventional annealing is eutectoid, and the absence of Fe-metalloid compounds results in a drastic reduction in the coercivity. 2. Material and methods The Fe-B-C alloy ingots with nominal composition of Fe84(x ¼ 0e4) were prepared by arc-melting in a Ti-gettered argon atmosphere, after which the amorphous ribbons with a
xB10þxC6
L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
thickness of ~25 mm were produced by single roller spinning method. Thermal properties of the melt-spun ribbons were analyzed by differential scanning calorimetry (DSC, Netzsch DSC 404 F3). The structure of the melt-spun and annealed ribbons was characterized using X-ray diffraction (XRD, Rigaku Smartlab9) with Cu-Ka and transmission electron microscopy (TEM, Tecnai G2 T20). Magnetic hysteresis loop measurements were conducted using a DC BeH loop tracer (MATS-2010SD) with the magnetic field applied parallel to the longitudinal direction of ribbons. Before the measurements, the DC B-H loop tracer was calibrated using an Fe-Ni permalloy sample. All the annealing was carried out in a furnace that can heat a sample up to a rate of 100 K/s. A continual argon flow was applied during the annealing to prevent the possible oxidation. 3. Results and discussion XRD and TEM were performed to investigate the structure of the melt-spun Fe-B-C alloy ribbons and the results for Fe84B10C6 are shown in Fig. 1 for representation. All the samples show typical amorphous features with (1) a broad diffraction peak in XRD pattern; (2) featureless contrast in the TEM bright-field image; and (3) one obvious diffuse halo ring in the selected area electron diffraction (SAED) pattern. Therefore, it is concluded that all the melt-spun ribbons are in amorphous state.
329
Fig. 2(a) displays the DSC curves for the melt-spun Fe-B-C alloy ribbons. When Fe is no more than 82%, the DSC curves are characterized by a single exothermic peak, while a secondary peak followed by the primary peak can be observed in the DSC curves for the alloys with Fe 83%. The primary exothermic peak is generally related to the a-Fe precipitation and the second one is the result of the formation of Fe-metalloid compounds for Fe-based amorphous alloys [15,16]. To check this, Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloy ribbons were selected and isothermally annealed with a heating rate of 20 K/min and a duration time of 180 s. Fig. 2(b) shows the XRD patterns for these annealed Fe82 and Fe84 samples. Although the annealing temperature for Fe82 is slight lower than its onset crystallization temperature determined by DSC, crystallization does occur by isothermal duration time. Consistent with DSC, the XRD patterns reveal that the crystallization for Fe84 occurs through the process of amorphous / amorphous þ a-Fe / amorphous þ a-Fe þ Fe-metalloid compounds phases, whereas Fe82 is eutectoid with the simultaneous precipitation of a-Fe and Fe-metalloid compounds. The crystallization products can be identified as a-Fe, Fe2B, Fe3B and Fe3C for Fe82 and Fe84 alloys. The metastable phase Fe23(B,C)6 that has been reported previously [17,18] is absent in the present study. A comprehensive study of the crystallization behavior of Fe82 and Fe84 alloys are conducted through thermal analyses. Fig. 3(a) shows the DSC curves of Fe82 and Fe84 alloys at various heating
Fig. 1. (a) XRD pattern and (b) TEM bright-field image for Fe84B10C6 melt-spun ribbons. Inset in (b) is the corresponding SAED pattern.
Fig. 2. (a) DSC curves of the melt-spun Fe-B-C alloy ribbons at a heating rate of 20 K/min. (b) XRD patterns of annealed Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloy ribbons.
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the characteristic temperature, R is the ideal gas constant (8.314 J K1 mol1) and E represents the activation energy. Fig. 3(b) displays the plots of ln(T2/b) versus 1000/T for Kissinger method of the Fe82 and Fe84 alloys. Note that the activation energy of a-Fe precipitation for Fe84 alloy gets a relatively small value, implying the amorphous structure of Fe84 can be easily transformed into a mixture with amorphous and a-Fe phases. With a slight reduction in Fe content (i.e. Fe82), the crystallization becomes quite different and changes into a eutectoid mode. Moreover, the activity energy for the eutectoid reaction of Fe82 alloy is comparable with that for the Fe-metalloid compounds precipitation of Fe84 in magnitude. The crystallization mechanism can be understood with JMA analysis, in which the crystallized volume fraction x(t, t) follows the equation x(t, t) ¼ 1-exp[k(tiso-t)n], where k is the rate constant, t is the incubation time and n denotes the Avrami exponent that reflects the nucleation rate and the growth mode. Accordingly, the Avrami exponent n equals to the slope of the ln[-ln(1-x)] versus ln(tiso-t) curve. Fig. 4(a) depicts the plots of crystallized volume fraction x with respect to isothermal time for Fe82 and Fe84 alloys. The inset in Fig. 4(a) is the isothermal DSC curves. When calculating the Avrami exponent n, only the data in the region of 0.1 < x < 0.9 are used to minimize the experimental error and the results are plotted in Fig. 4(b). According to the related literatures [20e22], n ¼ 2.5 reflects that the crystallization process is the diffusion controlled three-dimensional growth with a constant nucleation rate. And n ¼ 1.9 corresponds to a diffusion-controlled growth with pre-existing nuclei. As for the Fe-metalloid compound precipitation, n equals to 3.2 manifesting an interface-controlled growth. In short, from the thermal analyses, we have found that the crystallization of Fe82 alloy is diffusion controlled and the activation energy needed to trigger the eutectoid reaction is relatively high. The question is that can one obtain a structure with only a-Fe nanocrystals precipitation for the eutectoidally crystallized Fe-B-C alloys (for instance, Fe82) through appropriate treatment. A series of annealing treatment with a duration time of 10 s were conducted so as to modulate the crystallization products of the Fe82 alloy. Fig. 5(a) shows the B-H curves of melt-spun and 733 K annealed Fe82 alloy ribbons with partially enlarged drawing inserted. The B-H curve of the melt-spun sample is characterized by a low coercivity and a large permeability showing typical features of soft magnetic materials. After annealing at a low heating rate (i.e. 1 K/s), the coercivity increases drastically, while it drops down with a heating rate of 40 K/s. The magnetic properties of the Fe-based amorphous alloys are closely related to their microstructure. It is known that the Fe-metalloid compounds are usually hard magnetic phases and will result in a large coercivity. Therefore, the coercivity can be used as a signature for the precipitation of Fe-metalloid compounds. The plots of coercivity as a function of heating rate and annealing temperature are depicted in Fig. 5(b). Interestingly, higher heating rates favor lower coercivity suggesting that there is no Fe-metalloid compound precipitation for the Fe82 alloy at high
Fig. 3. (a) DSC curves of Fe82 and Fe84 alloys at various heating rates. (b) The plots of ln(T2/b) versus 1000/T for Kissinger method of the Fe82 and Fe84 alloys.
rates. As can be seen, characteristic temperatures whose absolute value are listed in Table I in the DSC curves increase with heating rates increasing. The primary exothermic peak related to a-Fe becomes more prominent at higher heating rate, a similar phenomenon with the Fe-Si-B alloy [19], which suggests that the a-Fe precipitation of Fe-based amorphous alloys is favored at high heating rate. The apparent activation energies of nucleation (Ex) and growth (Ep) processes can be calculated by the Kissinger equation ln(b/T2) ¼ -E/RTþConst, where b is the heating rate, T is
Table 1 Thermodynamic parameters for the Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloys obtained from the thermal analyses. Alloys
Heating Rates (K/min)
Tx (K) ±0.5
Fe82B12C6
10 20 30 40 10 20 30 40
720.9 725.9 733.3 737.4 665.8 678.3 683.6 686.7
Tx1
Fe84B10C6
Tp (K) ±0.5 Tx2
Tp1
761 768.9 773.9 776.1
745.5 749.8 753.4 760.6 692.4 705.3 717.8 720.4
Ex (kJ/mol) Tp2
Ex1
Ep (kJ/mol) Ex2
340 ± 16
772.5 778.8 787.6 789.5
235 ± 15
Ep1
n Ep2
408 ± 24
427 ± 20
180 ± 20
n1
n2
2.5
365 ± 19
1.9
3.2
L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
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magnetic properties may be simply attributed to the structural relaxation since the change in the saturation magnetic flux density among all the annealed samples is small. In addition, the coercivity increases to a high level again with annealing temperature further increasing to 783 K. In this case, XRD measurements for the samples annealed with a heating rate of 40 K/s at various annealing temperatures (Fig. 6) were performed. One can see from the XRD patterns that the rapid annealing increases the crystallization temperature. A weak crystalline peak arises at 753 K, higher than the crystallization temperature with slower heating rate and longer duration time [Fig. 2 (b)], suggesting the beginning of crystallization. The appearance of three Bragg peaks identified as (110), (200) and (211) planes for a-Fe indicates the precipitation of a-Fe phase for Fe82 alloy. But the peak intensities are relatively low via rapid annealing (40 K/s), meaning that the volume fraction of these precipitates is small. Fig. 7(a) is the TEM bright-field image for the Fe82 alloy rapidly annealed at 753 K with a heating rate of 40 K/s. A few dark regions with a diameter less than 10 nm, as marked by the white circle, can
Fig. 4. (a) Plots of crystallized volume fraction versus isothermal time, inset is the isothermal DSC curves. (b) JMA curves of Fe82 and Fe84 alloys.
heating rates. But the possibility of that the sample still remains in amorphous state cannot be ruled out and the differences in
Fig. 6. XRD patterns of Fe82 alloy ribbons annealed at various temperatures with a heating rate of 40 K/s.
Fig. 5. (a) B-H curves of melt-spun and 733 K annealed Fe82 alloy ribbons with partially enlarged drawing inserted. (b) Variation of the coercivity as a function of heating rates and annealing temperature.
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L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
Fig. 7. (a) Variation of the coercivity as a function of heating rates and annealing temperature for Fe82 alloy ribbons. (b) XRD patterns of Fe82 alloy ribbons annealed at various temperatures with a heating rate of 40 K/s.
be observed in the TEM image. This indicates the initial stage of the crystallization, which is consistent with the XRD result. With annealing temperature increasing to 773 K, a small number of distinct precipitates emerge in the amorphous matrix [Fig. 7(b)]. There are two different morphologies of the precipitates. One is dendritic with a large characteristic length and the other is equiaxed-like that is widely observed in Fe-based nanocrystallization alloys [23], as shown in Fig. 7(c) and (e). The SAED and convergent beam electron diffraction (CBED) patterns taken
from the two different nanocrystals are depicted in Fig. 7(d) and (f). The diffraction spots (discs) are indexed as {110} and {211} based on their geometry and the electron beam directions are along ½113 and ½111, respectively. In other words, these diffraction spots (discs) evidence that the nanocrystal has a body-centered cubic (bcc) symmetry, further demonstrating the a-Fe precipitation. The formation of dendrites has been previously reported in an Fe-Si-B amorphous system, which is thought to result from constitutional supercooling due to the composition difference between the
L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
amorphous matrix and crystals [24]. Macroscopically, amorphous alloys are uniform and isotropic, but there are compositional or structural fluctuations at angstrom or nano scales [6,25]. Crystallization nucleation of a-Fe thus can be achieved through transient short-range atomic diffusion in the amorphous structure with compositional fluctuation [26]. That is why the Fe84 alloy yields a low value of activation energy and a small Avrami exponent of 1.9. However, it may be not applicable for the alloy systems with low Fe content (82% in the present case). Instead, a eutectoid precipitation is more free-energy favored for Fe82 alloy under conventional annealing treatment. The high heating and cooling rates (estimated to be ~20 K/s above 473 K) may magnify the compositional or structural fluctuations, causing an effect similar to the structural rejuvenation [27]. Moreover, the formation of Fe-metalloid compounds that contain a high concentration of metalloid atoms involves the long-range diffusion of metalloid atoms, which may be restricted by the short duration time at high temperature. Therefore, the crystallization of Fe82 alloy under rapid annealing prefers the precipitation of a-Fe. The steady-state nucleation rate, Iss, can be described as Iss ¼ Ah expð DGÞ, where A is a proportionality constant, kT
h is the viscosity, DG is the enthalpy of forming a critical nucleus, k is the Boltzmann constant and T is the temperature. Since the viscosity of an amorphous system decreases drastically by many orders of magnitude when approaching the glass transition temperature, the nucleation rate reaches its maximum near the glass transition temperature for most amorphous alloys. Meanwhile, the role of the viscous flow to the nucleation kinetics sets in and results in the large number density of nuclei [10]. Furthermore, for a real system, a certain time is needed to attain its constant steady-state nucleation rate at a given annealing temperature. The transient nucleation rate Itrans follows the equation of Itrans ¼ Iss þ ðIin Iss Þexpð t=tÞ, where Iin corresponds to the initial nucleation rate, t is the time and t is the relaxation time of transient nucleation rate [28]. In the present work, the annealing temperature is expected to be lower than the actual glass transition temperature of Fe82 alloy so the dynamic of the system is limited. Therefore, the short annealing time as well as the transient effects may be responsible for the low volume fraction of a-Fe in the annealing temperature range we studied.
4. Conclusion In summary, we investigated the crystallization behaviors of the Fe-B-C amorphous alloys. When the content of Fe is high, with the annealing temperature increases the crystallization occurs in the sequences of amorphous / amorphous þ a-Fe / amorphous þ aFe þ Fe-metalloid compounds. However, the alloys with low Fe content (e.g. Fe82) are eutectoidally crystallized with the simultaneous precipitation of a-Fe and Fe-metalloid compounds. According to the JMA analyses, the crystallization mechanism for Fe82 is diffusion-controlled three-dimensional growth with a constant nucleation rate. When annealing the Fe82 alloy with a heating rate of 40 K/s and duration time of 10 s, a single a-Fe phase precipitation for Fe82 alloy is successfully achieved as evidenced by the XRD, electron diffraction and magnetometry as well. The TEM brightfield images illustrate that the nanocrystals obtained by rapid annealing has two different morphologies. One is dendritic with a large characteristic length and the other is equiaxed-like. A plausible explanation that the rapid annealing may magnify the compositional or structural fluctuations and restrict the long-rang diffusion thus prefers the a-Fe precipitation is proposed.
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Acknowledgements This work is supported by National Natural Science Foundation of China (No. 51571115), the Six Talent Peaks Project of Jiangsu Province, China (2015-XCL-007) and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. References [1] Y.M. Chen, T. Ohkubo, M. Ohta, Y. Yoshizawa, K. Hono, Three-dimensional atom probe study of FeeB-based nanocrystalline soft magnetic materials, Acta Mater. 57 (2009) 4463e4472. [2] K. Hono, D.H. Ping, M. Ohnuma, H. Onodera, Cu clustering and Si partitioning in the early crystallization stage of an Fe73.5Si13.5B9Nb3Cu1 amorphous alloy, Acta Mater. 47 (1999) 997e1006. [3] K.G. Pradeep, G. Herzer, P. Choi, D. Raabe, Atom probe tomography study of ultrahigh nanocrystallization rates in FeSiNbBCu soft magnetic amorphous alloys on rapid annealing, Acta Mater. 68 (2014) 295e309. [4] C.T. Liu, M.F. Chisholm, M.K. Miller, Oxygen impurity and microalloying effect in a Zr-based bulk metallic glass alloy, Intermetallics 10 (2002) 1105e1112. [5] J. Schroers, A. Masuhr, W.L. Johnson, R. Busch, Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid, Phys. Rev. B 60 (1999) 11855e11858. [6] P. Sharma, X. Zhang, Y. Zhang, A. Makino, Competition driven nanocrystallization in high Bs and low coreloss FeeSieBePeCu soft magnetic alloys, Scr. Mater. 95 (2015) 3e6. [7] L. Morsdorf, K.G. Pradeep, G. Herzer, A. Kov acs, R.E. Dunin-Borkowski, I. Povstugar, G. Konygin, P. Choi, D. Raabe, Phase selection and nanocrystallization in Cu-free soft magnetic FeSiNbB amorphous alloy upon rapid annealing, J. Appl. Phys. 119 (2016) 124903. [8] K. Suzuki, R. Parsons, B. Zang, K. Onodera, H. Kishimoto, A. Kato, Copper-free nanocrystalline soft magnetic materials with high saturation magnetization comparable to that of Si steel, Appl. Phys. Lett. 110 (2017), 012407. [9] X.B. Zhai, Y.G. Wang, L. Zhu, C.C. Cao, Y.D. Dai, J.K. Chen, F.M. Pan, Effect of heating rate on atom migration, phase structure and magnetic properties of the Fe82Si2B11P4Cu1 alloy, J. Non-Cryst. Solids 499 (2018) 337e343. [10] K. Suzuki, R. Parsons, B. Zang, K. Onodera, H. Kishimoto, T. Shoji, A. Kato, Nano-crystallization of amorphous alloys by ultra-rapid annealing: an effective approach to magnetic softening, J. Alloys Compd. 735 (2018) 613e618. [11] J.C. Tang, X.Y. Mao, S.D. Li, W.L. Gao, Y.W. Du, Effects of two-step annealing on the microstructures and soft magnetic properties of nanocrystalline Fe86Zr7B6Cu1 ribbons, J. Alloys Compd. 375 (2004) 233e238. [12] A. Aronin, D. Matveev, E. Pershina, V. Tkatch, G. Abrosimova, The effect of changes in Al-based amorphous phase structure on structure forming upon crystallization, J. Alloys Compd. 715 (2017) 176e183. [13] W.L. Johnson, G. Kaltenboeck, M.D. Demetriou, J.P. Schramm, X. Liu, K. Samwer, C.P. Kim, D.C. Hofmann, Beating crystallization in glass-forming metals by millisecond heating and processing, Science 332 (2011) 828e833. [14] K. Kosiba, S. Scudino, R. Kobold, U. Kühn, A.L. Greer, J. Eckert, S. Pauly, Transient nucleation and microstructural design in flash-annealed bulk metallic glasses, Acta Mater. 127 (2017) 416e425. [15] A. Urata, M. Yamaki, M. Takahashi, K. Okamoto, H. Matsumoto, S. Yoshida, A. Makino, Low core loss of non-Si quaternary Fe83.3B8P8Cu0.7 nanocrystalline alloy with high Bs of 1.7 T, J. Appl. Phys. 111 (2012), 07A335. [16] T. Gheiratmand, H.R.M. Hosseini, Finemet nanocrystalline soft magnetic alloy: investigation of glass forming ability, crystallization mechanism, production techniques, magnetic softness and the effect of replacing the main constituents by other elements, J. Magn. Magn. Mater. 408 (2016) 177e192. [17] T. Hibino, T. Bitoh, Ternary Fe-B-C and quaternary Fe-B-C-Si amorphous alloys with glass transition and high magnetization, J. Alloys Compd. 707 (2017) 82e86. [18] H.Y. Jung, S. Yi, Nanocrystallization and soft magnetic properties of Fe23M6 (M: C or B) phase in Fe-based bulk metallic glass, Intermetallics 49 (2014) 18e22. [19] K. Chrissafis, M.I. Maragakis, K.G. Efthimiadis, E.K. Polychroniadis, Detailed study of the crystallization behaviour of the metallic glass Fe75Si9B16, J. Alloys Compd. 386 (2005) 165e173. [20] M.J. Duarte, A. Kostka, D. Crespo, J.A. Jimenez, A.C. Dippel, F.U. Renner, G. Dehm, Kinetics and crystallization path of a Fe-based metallic glass alloy, Acta Mater. 127 (2017) 341e350. [21] S. Ranganathan, The three activation energies with isothermal transformations: applications to metallic glasses, J. Mater. Sci. 16 (1981) 2401e2404. [22] P. Gong, X. Wang, K. Yao, Effects of alloying elements on crystallization kinetics of TieZreBe bulk metallic glass, J. Mater. Sci. 51 (2016) 5321e5329. [23] C.C. Cao, Y.G. Wang, L. Zhu, Y. Meng, X.B. Zhai, Y.D. Dai, J.K. Chen, F.M. Pan, Local structure, nucleation sites and crystallization behavior and their effects on magnetic properties of Fe81SixB10P8-xCu1 (x ¼ 0~8), Sci. Rep. 8 (2018) 1243. [24] Y.R. Zhang, R.V. Ramanujan, A study of the crystallization behavior of an amorphous Fe77.5Si13.5B9 alloy, Mater. Sci. Eng. A Struct. 416 (2006) 161e168. [25] F. Zhu, A. Hirata, P. Liu, S. Song, Y. Tian, J. Han, T. Fujita, M. Chen, Correlation
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between local structure order and spatial heterogeneity in a metallic glass, Phys. Rev. Lett. 119 (2017) 215501. [26] K. Sato, H. Murakami, W. Sprengel, H.E. Schaefer, Y. Kobayashi, Nanocrystallization mechanism of amorphous Fe78B13Si9, Appl. Phys. Lett. 94 (2009) 171904. [27] S.V. Ketov, Y.H. Sun, S. Nachum, Z. Lu, A. Checchi, A.R. Beraldin, H.Y. Bai,
W.H. Wang, D.V. Louzguine-Luzgin, M.A. Carpenter, A.L. Greer, Rejuvenation of metallic glasses by non-affine thermal strain, Nature 524 (2015) 200e203. [28] A. Ziabicki, B. Misztal-Faraj, L. Jarecki, Kinetic model of non-isothermal crystal nucleation with transient and athermal effects, J. Mater. Sci. 51 (2016) 8935e8952.
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Modulating the crystallization process of Fe82B12C6 amorphous alloy via rapid annealing L. Zhu, H. Zheng, S.S. Jiang, Y.G. Wang* College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 December 2018 Received in revised form 2 January 2019 Accepted 17 January 2019 Available online 18 January 2019
Crystallization is a uniform behavior for amorphous alloys while it can be fairly complex. For Fe-B-C alloys with high Fe content, the precipitation of a-Fe is ahead of the Fe-metalloid compounds with temperature increasing. It is found that the crystallization products of Fe-B-C amorphous alloys with Fe content lower than 82% can be modulated by appropriate annealing. The Fe82B12C6 alloy is eutectoidally crystallized with the simultaneous precipitation of a-Fe and Fe-metalloid compounds under conventional annealing. It is a diffusion controlled three-dimensionally growth with a constant nucleation rate. However, only a-Fe nanocrystals with a low volume fraction form under rapid annealing, which is evidenced by the results of X-ray and electron diffractions along with the magnetometry. The transmission electron microscopy bright-field images show that the a-Fe nanocrystals obtained by rapid annealing have two different morphologies. One is dendritic with a large characteristic length and the other is equiaxed-like. © 2019 Elsevier B.V. All rights reserved.
Keywords: Amorphous materials Crystal structure Phase transitions Thermal analysis
1. Introduction An amorphous alloy will gradually transform into a crystalline one upon heating due to its thermodynamically metastable nature. Crystallization is a uniform behavior for amorphous alloys while it can be fairly complex. It is widely accepted that Cu atoms cluster in the early stage of the crystallization and provides nucleation sites for a-Fe leading to a high nucleation rate in Cu-containing Fe-based amorphous alloys [1e3]. The impurities such as oxygen can also induce the formation of nuclei and trigger the subsequent crystallization [4]. Inspired by the asymmetry in the crystallization behavior during constant heating and cooling, the existence of the quenched-in nuclei is suggested [5]. Sharma et al. claimed the role of these so-called pre-existing nuclei/compositional fluctuation to the crystallization of Fe-Si-B-P-Cu alloys during which the preexisting nuclei grow in size with annealing time and lead to a nearly constant volume fraction of a-Fe at relatively low temperature [6]. In addition to the complexity in the crystallization mechanism, the crystallization of the amorphous alloys can be easily altered by processing history, for instance, increasing the heating rate [7e10],
* Corresponding author. E-mail address: [email protected] (Y.G. Wang). https://doi.org/10.1016/j.jallcom.2019.01.209 0925-8388/© 2019 Elsevier B.V. All rights reserved.
employing two-step annealing [11], applying preliminary deformation [12] and so on. The sensitivity of the onset crystallization temperature to the heating rate differs from that of the glass transition temperature [13]. Rapid annealing has been proved to be effective in grain refinement of the Fe-based amorphous alloys, because the onset temperature of crystallization is raised to the vicinity of the glass transition temperature under high heating rates [10]. Moreover, Kosiba et al. found that when heating a Cu-Zr-Al-HfCo bulk amorphous alloy at a sufficient high rate, the crystallization reaction changes from eutectoid to polymorphic, that is, the glass precipitated Cu10Zr7 and CuZr2 at low heating rate whereas only metastable B2-CuZr crystals formed at high rates [14]. This suggests that the rapid annealing is capable to modulate the crystallization products of an amorphous alloy. In the present work, a structure with only a-Fe nanocrystals dispersing in the amorphous matrix is successfully obtained via rapid annealing in an Fe82B12C6 alloy whose crystallization under conventional annealing is eutectoid, and the absence of Fe-metalloid compounds results in a drastic reduction in the coercivity. 2. Material and methods The Fe-B-C alloy ingots with nominal composition of Fe84(x ¼ 0e4) were prepared by arc-melting in a Ti-gettered argon atmosphere, after which the amorphous ribbons with a
xB10þxC6
L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
thickness of ~25 mm were produced by single roller spinning method. Thermal properties of the melt-spun ribbons were analyzed by differential scanning calorimetry (DSC, Netzsch DSC 404 F3). The structure of the melt-spun and annealed ribbons was characterized using X-ray diffraction (XRD, Rigaku Smartlab9) with Cu-Ka and transmission electron microscopy (TEM, Tecnai G2 T20). Magnetic hysteresis loop measurements were conducted using a DC BeH loop tracer (MATS-2010SD) with the magnetic field applied parallel to the longitudinal direction of ribbons. Before the measurements, the DC B-H loop tracer was calibrated using an Fe-Ni permalloy sample. All the annealing was carried out in a furnace that can heat a sample up to a rate of 100 K/s. A continual argon flow was applied during the annealing to prevent the possible oxidation. 3. Results and discussion XRD and TEM were performed to investigate the structure of the melt-spun Fe-B-C alloy ribbons and the results for Fe84B10C6 are shown in Fig. 1 for representation. All the samples show typical amorphous features with (1) a broad diffraction peak in XRD pattern; (2) featureless contrast in the TEM bright-field image; and (3) one obvious diffuse halo ring in the selected area electron diffraction (SAED) pattern. Therefore, it is concluded that all the melt-spun ribbons are in amorphous state.
329
Fig. 2(a) displays the DSC curves for the melt-spun Fe-B-C alloy ribbons. When Fe is no more than 82%, the DSC curves are characterized by a single exothermic peak, while a secondary peak followed by the primary peak can be observed in the DSC curves for the alloys with Fe 83%. The primary exothermic peak is generally related to the a-Fe precipitation and the second one is the result of the formation of Fe-metalloid compounds for Fe-based amorphous alloys [15,16]. To check this, Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloy ribbons were selected and isothermally annealed with a heating rate of 20 K/min and a duration time of 180 s. Fig. 2(b) shows the XRD patterns for these annealed Fe82 and Fe84 samples. Although the annealing temperature for Fe82 is slight lower than its onset crystallization temperature determined by DSC, crystallization does occur by isothermal duration time. Consistent with DSC, the XRD patterns reveal that the crystallization for Fe84 occurs through the process of amorphous / amorphous þ a-Fe / amorphous þ a-Fe þ Fe-metalloid compounds phases, whereas Fe82 is eutectoid with the simultaneous precipitation of a-Fe and Fe-metalloid compounds. The crystallization products can be identified as a-Fe, Fe2B, Fe3B and Fe3C for Fe82 and Fe84 alloys. The metastable phase Fe23(B,C)6 that has been reported previously [17,18] is absent in the present study. A comprehensive study of the crystallization behavior of Fe82 and Fe84 alloys are conducted through thermal analyses. Fig. 3(a) shows the DSC curves of Fe82 and Fe84 alloys at various heating
Fig. 1. (a) XRD pattern and (b) TEM bright-field image for Fe84B10C6 melt-spun ribbons. Inset in (b) is the corresponding SAED pattern.
Fig. 2. (a) DSC curves of the melt-spun Fe-B-C alloy ribbons at a heating rate of 20 K/min. (b) XRD patterns of annealed Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloy ribbons.
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the characteristic temperature, R is the ideal gas constant (8.314 J K1 mol1) and E represents the activation energy. Fig. 3(b) displays the plots of ln(T2/b) versus 1000/T for Kissinger method of the Fe82 and Fe84 alloys. Note that the activation energy of a-Fe precipitation for Fe84 alloy gets a relatively small value, implying the amorphous structure of Fe84 can be easily transformed into a mixture with amorphous and a-Fe phases. With a slight reduction in Fe content (i.e. Fe82), the crystallization becomes quite different and changes into a eutectoid mode. Moreover, the activity energy for the eutectoid reaction of Fe82 alloy is comparable with that for the Fe-metalloid compounds precipitation of Fe84 in magnitude. The crystallization mechanism can be understood with JMA analysis, in which the crystallized volume fraction x(t, t) follows the equation x(t, t) ¼ 1-exp[k(tiso-t)n], where k is the rate constant, t is the incubation time and n denotes the Avrami exponent that reflects the nucleation rate and the growth mode. Accordingly, the Avrami exponent n equals to the slope of the ln[-ln(1-x)] versus ln(tiso-t) curve. Fig. 4(a) depicts the plots of crystallized volume fraction x with respect to isothermal time for Fe82 and Fe84 alloys. The inset in Fig. 4(a) is the isothermal DSC curves. When calculating the Avrami exponent n, only the data in the region of 0.1 < x < 0.9 are used to minimize the experimental error and the results are plotted in Fig. 4(b). According to the related literatures [20e22], n ¼ 2.5 reflects that the crystallization process is the diffusion controlled three-dimensional growth with a constant nucleation rate. And n ¼ 1.9 corresponds to a diffusion-controlled growth with pre-existing nuclei. As for the Fe-metalloid compound precipitation, n equals to 3.2 manifesting an interface-controlled growth. In short, from the thermal analyses, we have found that the crystallization of Fe82 alloy is diffusion controlled and the activation energy needed to trigger the eutectoid reaction is relatively high. The question is that can one obtain a structure with only a-Fe nanocrystals precipitation for the eutectoidally crystallized Fe-B-C alloys (for instance, Fe82) through appropriate treatment. A series of annealing treatment with a duration time of 10 s were conducted so as to modulate the crystallization products of the Fe82 alloy. Fig. 5(a) shows the B-H curves of melt-spun and 733 K annealed Fe82 alloy ribbons with partially enlarged drawing inserted. The B-H curve of the melt-spun sample is characterized by a low coercivity and a large permeability showing typical features of soft magnetic materials. After annealing at a low heating rate (i.e. 1 K/s), the coercivity increases drastically, while it drops down with a heating rate of 40 K/s. The magnetic properties of the Fe-based amorphous alloys are closely related to their microstructure. It is known that the Fe-metalloid compounds are usually hard magnetic phases and will result in a large coercivity. Therefore, the coercivity can be used as a signature for the precipitation of Fe-metalloid compounds. The plots of coercivity as a function of heating rate and annealing temperature are depicted in Fig. 5(b). Interestingly, higher heating rates favor lower coercivity suggesting that there is no Fe-metalloid compound precipitation for the Fe82 alloy at high
Fig. 3. (a) DSC curves of Fe82 and Fe84 alloys at various heating rates. (b) The plots of ln(T2/b) versus 1000/T for Kissinger method of the Fe82 and Fe84 alloys.
rates. As can be seen, characteristic temperatures whose absolute value are listed in Table I in the DSC curves increase with heating rates increasing. The primary exothermic peak related to a-Fe becomes more prominent at higher heating rate, a similar phenomenon with the Fe-Si-B alloy [19], which suggests that the a-Fe precipitation of Fe-based amorphous alloys is favored at high heating rate. The apparent activation energies of nucleation (Ex) and growth (Ep) processes can be calculated by the Kissinger equation ln(b/T2) ¼ -E/RTþConst, where b is the heating rate, T is
Table 1 Thermodynamic parameters for the Fe82B12C6 (Fe82) and Fe84B10C6 (Fe84) alloys obtained from the thermal analyses. Alloys
Heating Rates (K/min)
Tx (K) ±0.5
Fe82B12C6
10 20 30 40 10 20 30 40
720.9 725.9 733.3 737.4 665.8 678.3 683.6 686.7
Tx1
Fe84B10C6
Tp (K) ±0.5 Tx2
Tp1
761 768.9 773.9 776.1
745.5 749.8 753.4 760.6 692.4 705.3 717.8 720.4
Ex (kJ/mol) Tp2
Ex1
Ep (kJ/mol) Ex2
340 ± 16
772.5 778.8 787.6 789.5
235 ± 15
Ep1
n Ep2
408 ± 24
427 ± 20
180 ± 20
n1
n2
2.5
365 ± 19
1.9
3.2
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magnetic properties may be simply attributed to the structural relaxation since the change in the saturation magnetic flux density among all the annealed samples is small. In addition, the coercivity increases to a high level again with annealing temperature further increasing to 783 K. In this case, XRD measurements for the samples annealed with a heating rate of 40 K/s at various annealing temperatures (Fig. 6) were performed. One can see from the XRD patterns that the rapid annealing increases the crystallization temperature. A weak crystalline peak arises at 753 K, higher than the crystallization temperature with slower heating rate and longer duration time [Fig. 2 (b)], suggesting the beginning of crystallization. The appearance of three Bragg peaks identified as (110), (200) and (211) planes for a-Fe indicates the precipitation of a-Fe phase for Fe82 alloy. But the peak intensities are relatively low via rapid annealing (40 K/s), meaning that the volume fraction of these precipitates is small. Fig. 7(a) is the TEM bright-field image for the Fe82 alloy rapidly annealed at 753 K with a heating rate of 40 K/s. A few dark regions with a diameter less than 10 nm, as marked by the white circle, can
Fig. 4. (a) Plots of crystallized volume fraction versus isothermal time, inset is the isothermal DSC curves. (b) JMA curves of Fe82 and Fe84 alloys.
heating rates. But the possibility of that the sample still remains in amorphous state cannot be ruled out and the differences in
Fig. 6. XRD patterns of Fe82 alloy ribbons annealed at various temperatures with a heating rate of 40 K/s.
Fig. 5. (a) B-H curves of melt-spun and 733 K annealed Fe82 alloy ribbons with partially enlarged drawing inserted. (b) Variation of the coercivity as a function of heating rates and annealing temperature.
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Fig. 7. (a) Variation of the coercivity as a function of heating rates and annealing temperature for Fe82 alloy ribbons. (b) XRD patterns of Fe82 alloy ribbons annealed at various temperatures with a heating rate of 40 K/s.
be observed in the TEM image. This indicates the initial stage of the crystallization, which is consistent with the XRD result. With annealing temperature increasing to 773 K, a small number of distinct precipitates emerge in the amorphous matrix [Fig. 7(b)]. There are two different morphologies of the precipitates. One is dendritic with a large characteristic length and the other is equiaxed-like that is widely observed in Fe-based nanocrystallization alloys [23], as shown in Fig. 7(c) and (e). The SAED and convergent beam electron diffraction (CBED) patterns taken
from the two different nanocrystals are depicted in Fig. 7(d) and (f). The diffraction spots (discs) are indexed as {110} and {211} based on their geometry and the electron beam directions are along ½113 and ½111, respectively. In other words, these diffraction spots (discs) evidence that the nanocrystal has a body-centered cubic (bcc) symmetry, further demonstrating the a-Fe precipitation. The formation of dendrites has been previously reported in an Fe-Si-B amorphous system, which is thought to result from constitutional supercooling due to the composition difference between the
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amorphous matrix and crystals [24]. Macroscopically, amorphous alloys are uniform and isotropic, but there are compositional or structural fluctuations at angstrom or nano scales [6,25]. Crystallization nucleation of a-Fe thus can be achieved through transient short-range atomic diffusion in the amorphous structure with compositional fluctuation [26]. That is why the Fe84 alloy yields a low value of activation energy and a small Avrami exponent of 1.9. However, it may be not applicable for the alloy systems with low Fe content (82% in the present case). Instead, a eutectoid precipitation is more free-energy favored for Fe82 alloy under conventional annealing treatment. The high heating and cooling rates (estimated to be ~20 K/s above 473 K) may magnify the compositional or structural fluctuations, causing an effect similar to the structural rejuvenation [27]. Moreover, the formation of Fe-metalloid compounds that contain a high concentration of metalloid atoms involves the long-range diffusion of metalloid atoms, which may be restricted by the short duration time at high temperature. Therefore, the crystallization of Fe82 alloy under rapid annealing prefers the precipitation of a-Fe. The steady-state nucleation rate, Iss, can be described as Iss ¼ Ah expð DGÞ, where A is a proportionality constant, kT
h is the viscosity, DG is the enthalpy of forming a critical nucleus, k is the Boltzmann constant and T is the temperature. Since the viscosity of an amorphous system decreases drastically by many orders of magnitude when approaching the glass transition temperature, the nucleation rate reaches its maximum near the glass transition temperature for most amorphous alloys. Meanwhile, the role of the viscous flow to the nucleation kinetics sets in and results in the large number density of nuclei [10]. Furthermore, for a real system, a certain time is needed to attain its constant steady-state nucleation rate at a given annealing temperature. The transient nucleation rate Itrans follows the equation of Itrans ¼ Iss þ ðIin Iss Þexpð t=tÞ, where Iin corresponds to the initial nucleation rate, t is the time and t is the relaxation time of transient nucleation rate [28]. In the present work, the annealing temperature is expected to be lower than the actual glass transition temperature of Fe82 alloy so the dynamic of the system is limited. Therefore, the short annealing time as well as the transient effects may be responsible for the low volume fraction of a-Fe in the annealing temperature range we studied.
4. Conclusion In summary, we investigated the crystallization behaviors of the Fe-B-C amorphous alloys. When the content of Fe is high, with the annealing temperature increases the crystallization occurs in the sequences of amorphous / amorphous þ a-Fe / amorphous þ aFe þ Fe-metalloid compounds. However, the alloys with low Fe content (e.g. Fe82) are eutectoidally crystallized with the simultaneous precipitation of a-Fe and Fe-metalloid compounds. According to the JMA analyses, the crystallization mechanism for Fe82 is diffusion-controlled three-dimensional growth with a constant nucleation rate. When annealing the Fe82 alloy with a heating rate of 40 K/s and duration time of 10 s, a single a-Fe phase precipitation for Fe82 alloy is successfully achieved as evidenced by the XRD, electron diffraction and magnetometry as well. The TEM brightfield images illustrate that the nanocrystals obtained by rapid annealing has two different morphologies. One is dendritic with a large characteristic length and the other is equiaxed-like. A plausible explanation that the rapid annealing may magnify the compositional or structural fluctuations and restrict the long-rang diffusion thus prefers the a-Fe precipitation is proposed.
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Acknowledgements This work is supported by National Natural Science Foundation of China (No. 51571115), the Six Talent Peaks Project of Jiangsu Province, China (2015-XCL-007) and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. References [1] Y.M. Chen, T. Ohkubo, M. Ohta, Y. Yoshizawa, K. Hono, Three-dimensional atom probe study of FeeB-based nanocrystalline soft magnetic materials, Acta Mater. 57 (2009) 4463e4472. [2] K. Hono, D.H. Ping, M. Ohnuma, H. Onodera, Cu clustering and Si partitioning in the early crystallization stage of an Fe73.5Si13.5B9Nb3Cu1 amorphous alloy, Acta Mater. 47 (1999) 997e1006. [3] K.G. Pradeep, G. Herzer, P. Choi, D. Raabe, Atom probe tomography study of ultrahigh nanocrystallization rates in FeSiNbBCu soft magnetic amorphous alloys on rapid annealing, Acta Mater. 68 (2014) 295e309. [4] C.T. Liu, M.F. Chisholm, M.K. Miller, Oxygen impurity and microalloying effect in a Zr-based bulk metallic glass alloy, Intermetallics 10 (2002) 1105e1112. [5] J. Schroers, A. Masuhr, W.L. Johnson, R. Busch, Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid, Phys. Rev. B 60 (1999) 11855e11858. [6] P. Sharma, X. Zhang, Y. Zhang, A. Makino, Competition driven nanocrystallization in high Bs and low coreloss FeeSieBePeCu soft magnetic alloys, Scr. Mater. 95 (2015) 3e6. [7] L. Morsdorf, K.G. Pradeep, G. Herzer, A. Kov acs, R.E. Dunin-Borkowski, I. Povstugar, G. Konygin, P. Choi, D. Raabe, Phase selection and nanocrystallization in Cu-free soft magnetic FeSiNbB amorphous alloy upon rapid annealing, J. Appl. Phys. 119 (2016) 124903. [8] K. Suzuki, R. Parsons, B. Zang, K. Onodera, H. Kishimoto, A. Kato, Copper-free nanocrystalline soft magnetic materials with high saturation magnetization comparable to that of Si steel, Appl. Phys. Lett. 110 (2017), 012407. [9] X.B. Zhai, Y.G. Wang, L. Zhu, C.C. Cao, Y.D. Dai, J.K. Chen, F.M. Pan, Effect of heating rate on atom migration, phase structure and magnetic properties of the Fe82Si2B11P4Cu1 alloy, J. Non-Cryst. Solids 499 (2018) 337e343. [10] K. Suzuki, R. Parsons, B. Zang, K. Onodera, H. Kishimoto, T. Shoji, A. Kato, Nano-crystallization of amorphous alloys by ultra-rapid annealing: an effective approach to magnetic softening, J. Alloys Compd. 735 (2018) 613e618. [11] J.C. Tang, X.Y. Mao, S.D. Li, W.L. Gao, Y.W. Du, Effects of two-step annealing on the microstructures and soft magnetic properties of nanocrystalline Fe86Zr7B6Cu1 ribbons, J. Alloys Compd. 375 (2004) 233e238. [12] A. Aronin, D. Matveev, E. Pershina, V. Tkatch, G. Abrosimova, The effect of changes in Al-based amorphous phase structure on structure forming upon crystallization, J. Alloys Compd. 715 (2017) 176e183. [13] W.L. Johnson, G. Kaltenboeck, M.D. Demetriou, J.P. Schramm, X. Liu, K. Samwer, C.P. Kim, D.C. Hofmann, Beating crystallization in glass-forming metals by millisecond heating and processing, Science 332 (2011) 828e833. [14] K. Kosiba, S. Scudino, R. Kobold, U. Kühn, A.L. Greer, J. Eckert, S. Pauly, Transient nucleation and microstructural design in flash-annealed bulk metallic glasses, Acta Mater. 127 (2017) 416e425. [15] A. Urata, M. Yamaki, M. Takahashi, K. Okamoto, H. Matsumoto, S. Yoshida, A. Makino, Low core loss of non-Si quaternary Fe83.3B8P8Cu0.7 nanocrystalline alloy with high Bs of 1.7 T, J. Appl. Phys. 111 (2012), 07A335. [16] T. Gheiratmand, H.R.M. Hosseini, Finemet nanocrystalline soft magnetic alloy: investigation of glass forming ability, crystallization mechanism, production techniques, magnetic softness and the effect of replacing the main constituents by other elements, J. Magn. Magn. Mater. 408 (2016) 177e192. [17] T. Hibino, T. Bitoh, Ternary Fe-B-C and quaternary Fe-B-C-Si amorphous alloys with glass transition and high magnetization, J. Alloys Compd. 707 (2017) 82e86. [18] H.Y. Jung, S. Yi, Nanocrystallization and soft magnetic properties of Fe23M6 (M: C or B) phase in Fe-based bulk metallic glass, Intermetallics 49 (2014) 18e22. [19] K. Chrissafis, M.I. Maragakis, K.G. Efthimiadis, E.K. Polychroniadis, Detailed study of the crystallization behaviour of the metallic glass Fe75Si9B16, J. Alloys Compd. 386 (2005) 165e173. [20] M.J. Duarte, A. Kostka, D. Crespo, J.A. Jimenez, A.C. Dippel, F.U. Renner, G. Dehm, Kinetics and crystallization path of a Fe-based metallic glass alloy, Acta Mater. 127 (2017) 341e350. [21] S. Ranganathan, The three activation energies with isothermal transformations: applications to metallic glasses, J. Mater. Sci. 16 (1981) 2401e2404. [22] P. Gong, X. Wang, K. Yao, Effects of alloying elements on crystallization kinetics of TieZreBe bulk metallic glass, J. Mater. Sci. 51 (2016) 5321e5329. [23] C.C. Cao, Y.G. Wang, L. Zhu, Y. Meng, X.B. Zhai, Y.D. Dai, J.K. Chen, F.M. Pan, Local structure, nucleation sites and crystallization behavior and their effects on magnetic properties of Fe81SixB10P8-xCu1 (x ¼ 0~8), Sci. Rep. 8 (2018) 1243. [24] Y.R. Zhang, R.V. Ramanujan, A study of the crystallization behavior of an amorphous Fe77.5Si13.5B9 alloy, Mater. Sci. Eng. A Struct. 416 (2006) 161e168. [25] F. Zhu, A. Hirata, P. Liu, S. Song, Y. Tian, J. Han, T. Fujita, M. Chen, Correlation
334
L. Zhu et al. / Journal of Alloys and Compounds 785 (2019) 328e334
between local structure order and spatial heterogeneity in a metallic glass, Phys. Rev. Lett. 119 (2017) 215501. [26] K. Sato, H. Murakami, W. Sprengel, H.E. Schaefer, Y. Kobayashi, Nanocrystallization mechanism of amorphous Fe78B13Si9, Appl. Phys. Lett. 94 (2009) 171904. [27] S.V. Ketov, Y.H. Sun, S. Nachum, Z. Lu, A. Checchi, A.R. Beraldin, H.Y. Bai,
W.H. Wang, D.V. Louzguine-Luzgin, M.A. Carpenter, A.L. Greer, Rejuvenation of metallic glasses by non-affine thermal strain, Nature 524 (2015) 200e203. [28] A. Ziabicki, B. Misztal-Faraj, L. Jarecki, Kinetic model of non-isothermal crystal nucleation with transient and athermal effects, J. Mater. Sci. 51 (2016) 8935e8952.