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A study on nanocrystallization of alloy Fe73Cu1Nb1.5V2Si13.5B9 by high-energy ball milling
Journal of Alloys and Compounds 448 (2008) 234–237
A study on nanocrystallization of alloy Fe73Cu1Nb1.5V2Si13.5B9 by high-energy ball milling Boqu Chen a,b , Sha Yang a,b , Xingxing Liu a,b , Biao Yan a,b,∗ , Wei Lu b a
b
School of Materials Science and Engineering, Tongji University, Shanghai 200092, China Shanghai Key Laboratory of D&A for Metal-Functional Materials, Tongji University, Shanghai 200092, China Received 29 January 2007; received in revised form 18 March 2007; accepted 20 March 2007 Available online 24 March 2007
Abstract In order to lower the price of Finemet alloy, a new nanocrystalline alloy was developed, in which Nb was partly replaced by V. This paper focused on the study of its nanocrystallization induced by high-energy ball milling. It was shown that after milling for 3 h or so, uniformly distributed nanocrystalline phase ␣-Fe(Si, B, V, Nb, Cu) began to form. The milling time required for the nanocrystallization of the amorphous alloy upon ball milling depended very much on milling intensity. The higher the intensity, the shorter the milling time. After full crystallization a complex solid solution ␣-Fe(Si, B, V, Nb, Cu) was obtained. The crystallization process is polymorphous and not primarily observed during conventional thermal annealing. The kinetics of the mechanically induced crystallization of amorphous Fe73 Cu1 Nb1.5 V2 Si13 B9 alloy may be described by JMA model. The value of Avrami exponent n was 1.53, implying a zero-nucleation rate and crystals growth in all shapes from very small dimensions; the intrinsic factors of controlling the mechanically induced crystallization of the amorphous alloy Fe73 Cu1 Nb1.5 V2 Si13 B9 may be the deformation and local temperature rise. © 2007 Elsevier B.V. All rights reserved. Keywords: Crystallization kinetics; Nanocrystallization; Soft magnetic; Amorphous alloy
1. Introduction It has been known that Finemet alloy (Fe73.5 Cu1 Nb3 Si13.5 B9 ) is one of soft magnetic nanocrystalline materials of important technical interest [1–3]. But it contains Nb element which is very expensive. So, the present authors developed a new alloy in which Nb was partly replaced by V element, i.e., Fe73 Cu1 Nb1.5 V2 Si13.5 B9 . The magnetic properties of the new alloy could be comparable with those of Finemet alloy (Patent No. 200410053070.X). This paper focused on the microstructural evolution and nanocrystallization kinetics for the new alloy created by means of high-energy ball milling instead of the conventional thermal activating. 2. Experimental procedure The alloy used, whose composition was Fe73 Cu1 Nb1.5 V2 Si13.5 B9 , was first prepared as amorphous ribbons by the melt spinning technique, which were cut
∗
Corresponding author. E-mail address: [email protected] (B. Yan).
0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2007.03.087
into 1 cm × 1 cm pieces. The pieces were then sealed in an agate vial with agate balls in a high-energy ball mill and ground into powders. The grinding was carried out in Ar atmosphere. The ball-to-powder weight ratio was 10:1. X-ray diffractometry (XRD) with Cu K␣ radiation and transmission electron microscope (TEM) were employed to examine the microstructural change of the new alloy.
3. Results 3.1. XRD The XRD pattern for the Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy is given as a function of milling time in Fig. 1. The as-quenched ribbon showed the usual board peak of amorphous state. After 3 h milling, some new peaks appeared and became more and more clean. The phase corresponding to these peaks may be suggested to be a complex solid solution ␣-Fe(Si, B, V, Nb, Cu), instead of ␣-Fe(Si) by the conventional thermal induced primary crystallization of the same metallic glasses. This is because of relatively low temperature of the crystallization process, only a short-range diffusion takes place and the crystallization process is polymorphous and not primary normally observed at
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Fig. 2. Variation of average grain size D with milling time t for milled Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy. Fig. 1. XRD patterns of the Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy milled for different time.
higher temperatures [4]. The lattice parameters of the phase versus the milling time were calculated to be a constant value basically (Table 1), which supports the above suggestion. As milling time increased, the intensity of the peaks of ␣-Fe(Si, B, V, Nb, Cu) increased, indicating that the residual amorphous phase decreased and continued to crystallize to ␣-Fe(Si, B, V, Nb, Cu) phase. Further milling the sample to 70 h, it was seen that the sample consisted of the ␣-Fe(Si, B, V, Nb, Cu) only and the amorphous phase disappeared, meaning that the alloy was fully crystallized. The study of mechanical crystallization of amorphous Fe78 Si9 B13 using low-energy ball milling exhibited that the amorphous alloy did not crystallize after milling for 80 h at room temperature [5]. Guo and Wei reported the mechanical crystallization of amorphous FeMoSiB using planetary ball mill at room temperature and found that the amorphous FeMoSiB alloy began to crystallize into ␣-Fe(Mo, Si) solid solution after milling for 65 h [6]. But in the present experiment, because of using highenergy ball milling, the amorphous Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy began to crystallize only after milling for 3.5 h. The present and previous experimental results [5,6] indicated that microstructural changes occurring in amorphous solids upon mechanical milling depend very much on milling intensity. The higher the milling intensity, the shorter the milling time required for the crystallization of the amorphous alloy. The average grain size D of ␣-Fe(Si, B, V, Nb, Cu) was estimated with the aid of Scherrer formula β = 0.9λ/D cos θ, where β is the full width at half maximum of peak, λ the wavelength of the X-ray, and θ Bragg angle. Fig. 2 showed the D of ␣-Fe(Si, B,
V, Nb, Cu) in the milled powders as a function of the milling time t. The D increased from ∼2 nm after 3 h of milling to ∼10.5 nm after 70 h. When milling for more than 70 h, there was no further growth in the ␣-Fe(Si, B, V, Nb, Cu) grains. 3.2. TEM Fig. 3 showed a bright-field TEM picture with its selected area electronic diffraction pattern for the alloy after 30 h of milling. It was seen that a distribution of very small crystallites highly dispersed in the amorphous matrix. The mostly complete rings were the characteristic of the presence of numerous randomly oriented crystals. The D of the crystallites was about 5 nm. With
Table 1 Lattice parameter vs. milling time Milling time (h) Lattice parameter (nm)
7 0.2856
20 0.2857
50 0.2852
70 0.2863 Fig. 3. TEM pictures of Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy milled for 30 h.
236
B. Chen et al. / Journal of Alloys and Compounds 448 (2008) 234–237
milling time up to 70 h, the alloy was fully crystallized and the sizes of the precipitates increased to about 10 nm except for a few abnormal large particles. The D of the crystallites measured by TEM was in good agreement with the one estimated from the XRD analysis. 4. Discussion 4.1. About crystallization kinetics The kinetics of the mechanically induced crystallization of Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy was studied by the crystalline volume fraction (Vc ) calculated from XRD data: Vc = Ic /(Ic + kIa ), where Ic and Ia are the integral intensities of peaks of the crystalline phase and amorphous phase, respectively, and k a constant (1.06) obtained by the experiment [7]. Its calculation error was less than ±5%. Fig. 4 showed the Vc as a function of milling time t. We tried to use Johnson–Mehl–Avrami (JMA) equation Vc = 1 − exp[−(Kt)n ] [8] which is based on the steady state nucleation model, to simulate the crystallization. In the equation, K is a rate constant, which depends on temperature, nucleation rate and the speed of growth of crystallites and n is the Avrami exponent, which is related to the growth mechanism. The ln[−ln(1 − Vc )] versus ln t was plotted in Fig. 5. The linear relationship indicated that the primary crystallization induced by the ball milling met the nucleation model of steady state. The fitted value of Avrami exponent n was 1.53, which closed to 1.5, indicating a zero-nucleation rate and crystals growth in all shapes from very small dimensions [8]. 4.2. About the factors of affecting nanocrystallization during ball milling Some earlier publications [9–11] pointed out that the mechanical crystallization is different from the thermal one. Several
Fig. 4. Change of crystallite volume fraction Vc with milling time t.
Fig. 5. ln[−ln(1 − Vc )] vs. ln t.
explanations were suggested, such as oxidation, contamination, some element segregation, deformation, local temperature rise, but a unique explanation of mechanical nanocrystallization has not yet been reached until now [11–16]. No doubt, these explanations are probably correct and reasonable depending on their own alloy system and processing conditions used. According to the present result, however, some of them seem to be phenomenological and, therefore, not universally applicable. For example, the present authors successfully prepared nanocrystallized Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy using agate vial and balls under Ar gas. A chemical analysis exhibited that the oxidation and contamination in the alloy were negligible. The proposal in connection with the elemental segregation fails in interpreting the nanocrystallization of the alloys containing the elements that are not easily segregated. The truly intrinsic explanation, we think, should be by means of a combination of the deformation and a local temperature rise owing to ball milling. As we know, during ball milling, the as-spun amorphous ribbons are trapped and repeatedly collide with the balls. In general, the colliding force has both compression and shear components, which causes a severe and heterogeneous deformation of the ribbons. And the local temperature at the sites of collision at the exact moment the collision is happening will certainly rises even if liquid nitrogen surrounds the powders being milled. For this case, the deformation leads to the lowering of the potential barrier of part of the atoms to move, facilitating the diffusion of the atoms. Chakk et al. [17] suggested that the atomic mobility may be enhanced during the deformation process. However, without a thermal fluctuation, the atoms may still not be activated. Perhaps, it is the local temperature rise by milling that makes it possible for the atoms to be activated and subsequently diffuse, resulting in subsequent nucleation and grain growth. Simultaneously, the severe deformation also leads to the increasing of the potential barrier of other atoms in the alloy to move and is obstacle for diffusing, especially for long-range diffusion, restricting the grain growth with the result that fine grains, i.e. nanocrystallites form. In the present experiment, during the initial stage of nanocrystallization, only short-range atomic diffusion is needed because of the ultrafine ␣-Fe(Si, B, V, Nb, Cu) crystals (∼2 nm). When the
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crystals grow to about 5 nm (milling for about 20 h), long-range atomic diffusion will be needed for the following growth. But the severe deformation, as well as point and line defects induced by ball milling is obstacle to the long-range atomic diffusion, so the following growth of ␣-Fe(Si, B, V, Nb, Cu) nanocrystals is restricted. In short, oxidation, contamination, element segregation, and so on are not the main factors of affecting nanocrystallization during mechanical milling. The dominating factors may be the deformation and local temperature rise created by ball milling.
(4) The intrinsic factors of controlling the mechanically induced crystallization of the amorphous alloy Fe73 Cu1 Nb1.5 Si13 B9 V2 were the deformation and local temperature rise.
5. Summary
References
A study of nanocrystallization by high-energy ball milling was completed for a new developed Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy using XRD and TEM techniques. It was summarized as follows:
[1] G. Herzer, IEEE Trans. Mag. Mag. 26 (1990) 1397. [2] J.F. Loffler, H.B. Braun, W. Wagner, G. Kostorz, A. Wiedenmann, Mater. Sci. Eng. A 304–306 (2001) 1050. [3] R. Alben, J.J. Becker, M.C. Chi, J. Appl. Phys. 48 (1978) 1653. [4] T. Kulik, J. Non. Sol. 287 (2001) 145. [5] J. Xu, M. Atzmon, Appl. Phys. Lett. 73 (13) (1998) 1805. [6] F.Q. Guo, W.Z. Wei, Chin. J. Mater. Res. 9 (4) (1995) 311. [7] W. Lu, L. Yang, B. Yan, B. Lu, W. Huang, J. Mag. Mag. Mater. 292 (2005) 299. [8] J.W. Christian, in: D.W. Hopkins (Ed.), The Theory of Transformations in Metals and Alloys, Part I, Pergamon, Oxford, 1981, p. 256. [9] U. Herr, K. Samwer, Mater. Sci. For. 179–181 (1995) 85. [10] M.L. Trudeau, J.Y. Huot, et al., Phys. Rev. B45 (1992) 4626. [11] M.L. Trudeau, D. Dussault, A. Van Nestle, R. Schulz, Phys. Rev. Lett. 64 (1990) 99. [12] M.L. Trudeau, L. Dignard-Bailey, R. Schulz, D. Dussault, A. Van Nestle, Nanostruct. Mater. 2 (1993) 361. [13] H. Chen, Y. He, G.J. Shiflet, S.J. Poon, Nature 367 (1994) 541. [14] D. Oleszak, H. Matayja, J. Mater. Sci. 29 (1994) 4070. [15] B. Huang, H.G. Jiang, R.J. Perez, S.R. Nutt, E.J. Lavernia, Nanostruct. Mater. 11 (1999) 1009. [16] Suryanarayana, Intermetallics 3 (1995) 153. [17] Y. Chakk, S. Berger, B.Z. Weiss, E. Brook-Levinson, Acta Metall. Mater. 42 (1994) 3679.
(1) After milling for more than 3 h, uniformly distributed nanocrystalline ␣-Fe(Si, B, V, Nb, Cu) began to form. The milling time required for the mechanical crystallization of amorphous alloys upon ball milling depended very much on milling intensity. The higher the intensity, the shorter the milling time. (2) After full crystallization a complex solid solution ␣-Fe(Si, B, V, Nb, Cu) was obtained The crystallization process is polymorphous and not primary observed during conventional thermal annealing. (3) The kinetics of mechanically induced crystallization of amorphous Fe73 Cu1 Nb1.5 Si13 B9 V2 alloy may be described by JMA model. The value of Avrami exponent n was 1.53, implying a zero-nucleation rate and crystals growth in all shapes from very small dimensions;
Acknowledgement This work was partly supported by Shanghai Science and Technology Committee (Grant No: 0352nm057 and 04DZ05616).
A study on nanocrystallization of alloy Fe73Cu1Nb1.5V2Si13.5B9 by high-energy ball milling Boqu Chen a,b , Sha Yang a,b , Xingxing Liu a,b , Biao Yan a,b,∗ , Wei Lu b a
b
School of Materials Science and Engineering, Tongji University, Shanghai 200092, China Shanghai Key Laboratory of D&A for Metal-Functional Materials, Tongji University, Shanghai 200092, China Received 29 January 2007; received in revised form 18 March 2007; accepted 20 March 2007 Available online 24 March 2007
Abstract In order to lower the price of Finemet alloy, a new nanocrystalline alloy was developed, in which Nb was partly replaced by V. This paper focused on the study of its nanocrystallization induced by high-energy ball milling. It was shown that after milling for 3 h or so, uniformly distributed nanocrystalline phase ␣-Fe(Si, B, V, Nb, Cu) began to form. The milling time required for the nanocrystallization of the amorphous alloy upon ball milling depended very much on milling intensity. The higher the intensity, the shorter the milling time. After full crystallization a complex solid solution ␣-Fe(Si, B, V, Nb, Cu) was obtained. The crystallization process is polymorphous and not primarily observed during conventional thermal annealing. The kinetics of the mechanically induced crystallization of amorphous Fe73 Cu1 Nb1.5 V2 Si13 B9 alloy may be described by JMA model. The value of Avrami exponent n was 1.53, implying a zero-nucleation rate and crystals growth in all shapes from very small dimensions; the intrinsic factors of controlling the mechanically induced crystallization of the amorphous alloy Fe73 Cu1 Nb1.5 V2 Si13 B9 may be the deformation and local temperature rise. © 2007 Elsevier B.V. All rights reserved. Keywords: Crystallization kinetics; Nanocrystallization; Soft magnetic; Amorphous alloy
1. Introduction It has been known that Finemet alloy (Fe73.5 Cu1 Nb3 Si13.5 B9 ) is one of soft magnetic nanocrystalline materials of important technical interest [1–3]. But it contains Nb element which is very expensive. So, the present authors developed a new alloy in which Nb was partly replaced by V element, i.e., Fe73 Cu1 Nb1.5 V2 Si13.5 B9 . The magnetic properties of the new alloy could be comparable with those of Finemet alloy (Patent No. 200410053070.X). This paper focused on the microstructural evolution and nanocrystallization kinetics for the new alloy created by means of high-energy ball milling instead of the conventional thermal activating. 2. Experimental procedure The alloy used, whose composition was Fe73 Cu1 Nb1.5 V2 Si13.5 B9 , was first prepared as amorphous ribbons by the melt spinning technique, which were cut
∗
Corresponding author. E-mail address: [email protected] (B. Yan).
0925-8388/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2007.03.087
into 1 cm × 1 cm pieces. The pieces were then sealed in an agate vial with agate balls in a high-energy ball mill and ground into powders. The grinding was carried out in Ar atmosphere. The ball-to-powder weight ratio was 10:1. X-ray diffractometry (XRD) with Cu K␣ radiation and transmission electron microscope (TEM) were employed to examine the microstructural change of the new alloy.
3. Results 3.1. XRD The XRD pattern for the Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy is given as a function of milling time in Fig. 1. The as-quenched ribbon showed the usual board peak of amorphous state. After 3 h milling, some new peaks appeared and became more and more clean. The phase corresponding to these peaks may be suggested to be a complex solid solution ␣-Fe(Si, B, V, Nb, Cu), instead of ␣-Fe(Si) by the conventional thermal induced primary crystallization of the same metallic glasses. This is because of relatively low temperature of the crystallization process, only a short-range diffusion takes place and the crystallization process is polymorphous and not primary normally observed at
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235
Fig. 2. Variation of average grain size D with milling time t for milled Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy. Fig. 1. XRD patterns of the Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy milled for different time.
higher temperatures [4]. The lattice parameters of the phase versus the milling time were calculated to be a constant value basically (Table 1), which supports the above suggestion. As milling time increased, the intensity of the peaks of ␣-Fe(Si, B, V, Nb, Cu) increased, indicating that the residual amorphous phase decreased and continued to crystallize to ␣-Fe(Si, B, V, Nb, Cu) phase. Further milling the sample to 70 h, it was seen that the sample consisted of the ␣-Fe(Si, B, V, Nb, Cu) only and the amorphous phase disappeared, meaning that the alloy was fully crystallized. The study of mechanical crystallization of amorphous Fe78 Si9 B13 using low-energy ball milling exhibited that the amorphous alloy did not crystallize after milling for 80 h at room temperature [5]. Guo and Wei reported the mechanical crystallization of amorphous FeMoSiB using planetary ball mill at room temperature and found that the amorphous FeMoSiB alloy began to crystallize into ␣-Fe(Mo, Si) solid solution after milling for 65 h [6]. But in the present experiment, because of using highenergy ball milling, the amorphous Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy began to crystallize only after milling for 3.5 h. The present and previous experimental results [5,6] indicated that microstructural changes occurring in amorphous solids upon mechanical milling depend very much on milling intensity. The higher the milling intensity, the shorter the milling time required for the crystallization of the amorphous alloy. The average grain size D of ␣-Fe(Si, B, V, Nb, Cu) was estimated with the aid of Scherrer formula β = 0.9λ/D cos θ, where β is the full width at half maximum of peak, λ the wavelength of the X-ray, and θ Bragg angle. Fig. 2 showed the D of ␣-Fe(Si, B,
V, Nb, Cu) in the milled powders as a function of the milling time t. The D increased from ∼2 nm after 3 h of milling to ∼10.5 nm after 70 h. When milling for more than 70 h, there was no further growth in the ␣-Fe(Si, B, V, Nb, Cu) grains. 3.2. TEM Fig. 3 showed a bright-field TEM picture with its selected area electronic diffraction pattern for the alloy after 30 h of milling. It was seen that a distribution of very small crystallites highly dispersed in the amorphous matrix. The mostly complete rings were the characteristic of the presence of numerous randomly oriented crystals. The D of the crystallites was about 5 nm. With
Table 1 Lattice parameter vs. milling time Milling time (h) Lattice parameter (nm)
7 0.2856
20 0.2857
50 0.2852
70 0.2863 Fig. 3. TEM pictures of Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy milled for 30 h.
236
B. Chen et al. / Journal of Alloys and Compounds 448 (2008) 234–237
milling time up to 70 h, the alloy was fully crystallized and the sizes of the precipitates increased to about 10 nm except for a few abnormal large particles. The D of the crystallites measured by TEM was in good agreement with the one estimated from the XRD analysis. 4. Discussion 4.1. About crystallization kinetics The kinetics of the mechanically induced crystallization of Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy was studied by the crystalline volume fraction (Vc ) calculated from XRD data: Vc = Ic /(Ic + kIa ), where Ic and Ia are the integral intensities of peaks of the crystalline phase and amorphous phase, respectively, and k a constant (1.06) obtained by the experiment [7]. Its calculation error was less than ±5%. Fig. 4 showed the Vc as a function of milling time t. We tried to use Johnson–Mehl–Avrami (JMA) equation Vc = 1 − exp[−(Kt)n ] [8] which is based on the steady state nucleation model, to simulate the crystallization. In the equation, K is a rate constant, which depends on temperature, nucleation rate and the speed of growth of crystallites and n is the Avrami exponent, which is related to the growth mechanism. The ln[−ln(1 − Vc )] versus ln t was plotted in Fig. 5. The linear relationship indicated that the primary crystallization induced by the ball milling met the nucleation model of steady state. The fitted value of Avrami exponent n was 1.53, which closed to 1.5, indicating a zero-nucleation rate and crystals growth in all shapes from very small dimensions [8]. 4.2. About the factors of affecting nanocrystallization during ball milling Some earlier publications [9–11] pointed out that the mechanical crystallization is different from the thermal one. Several
Fig. 4. Change of crystallite volume fraction Vc with milling time t.
Fig. 5. ln[−ln(1 − Vc )] vs. ln t.
explanations were suggested, such as oxidation, contamination, some element segregation, deformation, local temperature rise, but a unique explanation of mechanical nanocrystallization has not yet been reached until now [11–16]. No doubt, these explanations are probably correct and reasonable depending on their own alloy system and processing conditions used. According to the present result, however, some of them seem to be phenomenological and, therefore, not universally applicable. For example, the present authors successfully prepared nanocrystallized Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy using agate vial and balls under Ar gas. A chemical analysis exhibited that the oxidation and contamination in the alloy were negligible. The proposal in connection with the elemental segregation fails in interpreting the nanocrystallization of the alloys containing the elements that are not easily segregated. The truly intrinsic explanation, we think, should be by means of a combination of the deformation and a local temperature rise owing to ball milling. As we know, during ball milling, the as-spun amorphous ribbons are trapped and repeatedly collide with the balls. In general, the colliding force has both compression and shear components, which causes a severe and heterogeneous deformation of the ribbons. And the local temperature at the sites of collision at the exact moment the collision is happening will certainly rises even if liquid nitrogen surrounds the powders being milled. For this case, the deformation leads to the lowering of the potential barrier of part of the atoms to move, facilitating the diffusion of the atoms. Chakk et al. [17] suggested that the atomic mobility may be enhanced during the deformation process. However, without a thermal fluctuation, the atoms may still not be activated. Perhaps, it is the local temperature rise by milling that makes it possible for the atoms to be activated and subsequently diffuse, resulting in subsequent nucleation and grain growth. Simultaneously, the severe deformation also leads to the increasing of the potential barrier of other atoms in the alloy to move and is obstacle for diffusing, especially for long-range diffusion, restricting the grain growth with the result that fine grains, i.e. nanocrystallites form. In the present experiment, during the initial stage of nanocrystallization, only short-range atomic diffusion is needed because of the ultrafine ␣-Fe(Si, B, V, Nb, Cu) crystals (∼2 nm). When the
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crystals grow to about 5 nm (milling for about 20 h), long-range atomic diffusion will be needed for the following growth. But the severe deformation, as well as point and line defects induced by ball milling is obstacle to the long-range atomic diffusion, so the following growth of ␣-Fe(Si, B, V, Nb, Cu) nanocrystals is restricted. In short, oxidation, contamination, element segregation, and so on are not the main factors of affecting nanocrystallization during mechanical milling. The dominating factors may be the deformation and local temperature rise created by ball milling.
(4) The intrinsic factors of controlling the mechanically induced crystallization of the amorphous alloy Fe73 Cu1 Nb1.5 Si13 B9 V2 were the deformation and local temperature rise.
5. Summary
References
A study of nanocrystallization by high-energy ball milling was completed for a new developed Fe73 Cu1 Nb1.5 V2 Si13.5 B9 alloy using XRD and TEM techniques. It was summarized as follows:
[1] G. Herzer, IEEE Trans. Mag. Mag. 26 (1990) 1397. [2] J.F. Loffler, H.B. Braun, W. Wagner, G. Kostorz, A. Wiedenmann, Mater. Sci. Eng. A 304–306 (2001) 1050. [3] R. Alben, J.J. Becker, M.C. Chi, J. Appl. Phys. 48 (1978) 1653. [4] T. Kulik, J. Non. Sol. 287 (2001) 145. [5] J. Xu, M. Atzmon, Appl. Phys. Lett. 73 (13) (1998) 1805. [6] F.Q. Guo, W.Z. Wei, Chin. J. Mater. Res. 9 (4) (1995) 311. [7] W. Lu, L. Yang, B. Yan, B. Lu, W. Huang, J. Mag. Mag. Mater. 292 (2005) 299. [8] J.W. Christian, in: D.W. Hopkins (Ed.), The Theory of Transformations in Metals and Alloys, Part I, Pergamon, Oxford, 1981, p. 256. [9] U. Herr, K. Samwer, Mater. Sci. For. 179–181 (1995) 85. [10] M.L. Trudeau, J.Y. Huot, et al., Phys. Rev. B45 (1992) 4626. [11] M.L. Trudeau, D. Dussault, A. Van Nestle, R. Schulz, Phys. Rev. Lett. 64 (1990) 99. [12] M.L. Trudeau, L. Dignard-Bailey, R. Schulz, D. Dussault, A. Van Nestle, Nanostruct. Mater. 2 (1993) 361. [13] H. Chen, Y. He, G.J. Shiflet, S.J. Poon, Nature 367 (1994) 541. [14] D. Oleszak, H. Matayja, J. Mater. Sci. 29 (1994) 4070. [15] B. Huang, H.G. Jiang, R.J. Perez, S.R. Nutt, E.J. Lavernia, Nanostruct. Mater. 11 (1999) 1009. [16] Suryanarayana, Intermetallics 3 (1995) 153. [17] Y. Chakk, S. Berger, B.Z. Weiss, E. Brook-Levinson, Acta Metall. Mater. 42 (1994) 3679.
(1) After milling for more than 3 h, uniformly distributed nanocrystalline ␣-Fe(Si, B, V, Nb, Cu) began to form. The milling time required for the mechanical crystallization of amorphous alloys upon ball milling depended very much on milling intensity. The higher the intensity, the shorter the milling time. (2) After full crystallization a complex solid solution ␣-Fe(Si, B, V, Nb, Cu) was obtained The crystallization process is polymorphous and not primary observed during conventional thermal annealing. (3) The kinetics of mechanically induced crystallization of amorphous Fe73 Cu1 Nb1.5 Si13 B9 V2 alloy may be described by JMA model. The value of Avrami exponent n was 1.53, implying a zero-nucleation rate and crystals growth in all shapes from very small dimensions;
Acknowledgement This work was partly supported by Shanghai Science and Technology Committee (Grant No: 0352nm057 and 04DZ05616).