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Phase transformation and magnetic properties of annealed Fe52.2Co46V1.8 alloy
ARTICLE IN PRESS
Vacuum 75 (2004) 33–38
Phase transformation and magnetic properties of annealed Fe52.2Co46V1.8 alloy Fangzhen Zhua, Xiaofang Bia,*, Shanqing Zhangb, Shengkai Gonga, Huibin Xua a
Materials Science and Engineering Department, Beijing University of Aeronautics and Astronautics, Beijing 100083, China b Beijing Institute of Aeronautical Materials, Beijing 100095, China Received 15 October 2003; received in revised form 30 December 2003; accepted 2 January 2004
Abstract In this work, FeCoV alloys were annealed in vacuum at various temperatures for different time, with and without applying an external magnetic field, respectively. The effect of the annealing on their magnetic properties has been investigated in regard with microstructural characterizations. X-ray diffraction analysis shows that the alloy is characterized of a-Fe bcc structure. It has been found that an order–disorder phase transformation took place locally in the surface around 993 K. In addition, a2g phase transformation occurs at the same temperature at which the Curie point is observed in the TG curve. Coercivity is decreased with increasing annealing temperatures, and changed from about 3.2 kA/m to 78 A/m when the annealing temperatures are increased to 1173 K. Microstructural observations show that the decrease of coercivity after annealing is contributed mainly by grain growth. The coercivity of the alloy is further decreased by 32 A/m after magnetic field annealing at 1033 K. Hysteresis loops of the alloys after field annealing at 1033 K featured more rectangular shape with smaller coercivity, compared with those after vacuum annealing. r 2004 Elsevier Ltd. All rights reserved. Keywords: FeCo alloy; Vacuum annealing; Magnetic properties; Order–disorder transition
1. Introduction The FeCo alloys, which are known as soft magnetic materials with maximum saturation magnetization (Ms ) and high Curie temperature (Tc ), have been an interesting research topic [1–3]. It is well known that the alloys are used for the stator and rotor of the generator, and its weight and performance are dependent largely on the magnetic properties of the alloys. Generally *Corresponding author. Tel.: 86-10-82315999; fax: 86-1082314871. E-mail address: [email protected] (X. Bi).
speaking, the total power losses of the generator could be divided into three parts: hysteresis loss, eddy current loss and relaxation loss, in which the third one is usually neglected because of its mild contribution to the total loss. The eddy current loss can be successfully reduced by increasing the electrical resistance of materials and decreasing the thickness of the laminations. On the other hand, hysteresis loss is a function of the coercivity of the magnetic materials used for generator [4,5]. Therefore, it is of great importance to decrease coercivity from the practical point of view. According to the Fe–Co phase diagram [6], a disorder to long-range order transition (A2 2B2 )
0042-207X/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2004.01.002
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F. Zhu et al. / Vacuum 75 (2004) 33–38
occurs around 1003 K in the ideal binary FeCo alloys with a weight ratio of cobalt from 30% to 70%. A recent research has revealed that the A22B2 transition only occurred in the surface of the alloy when the alloy was annealed in air atmosphere [7]. This transition is believed to increase its brittleness and deteriorate its mechanical workability, which is hereby suppressed by adding a moderate amount (E2%) of third element vanadium to the binary system. Previous work has placed much attention on the phase transformation, annealing process or the grain growth [3,7–11]. However, the relationship of those parameters and magnetic properties are required to be studied in order to improve the soft magnetic properties of the alloys. Many things still remain unclear regarding the effect of annealing on the magnetic properties [12,13]. In this work, the effect of vacuum annealing and field annealing on soft magnetic properties has been investigated and discussed in terms of the corresponding microstructural variations.
a heating rate of 20 K/min and cooling rate of 20 K/min (DSC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to investigate structure and microstructural characterizations. As to the specimen preparation for SEM observation, specimens were polished, and then they were etched with a chemical solution composed of 5 g copper chloride, hydrochloric acid, ethanol and water 20 ml, respectively.
3. Results and discussion Fig. 1 show XRD patterns for the alloys before and after annealing at 1033 and 1123 K for (a) 1 h and (b) 2 h. It is revealed that the alloy is characterized of a-Fe bcc structure. Three peaks of 1 1 0, 2 0 0 and 2 1 1 are observed for the alloys before annealing, and it can be seen that 2 0 0 texture appears after annealing at 1033 K for 2 h
2. Experimental procedures The main chemical composition of the specimens was Fe52.2Co46V1.8, examined by energy dispersive spectroscopy (EDS). The specimens were machined into 10 2 0.2 (mm) sheets. The magnetization (Ms ) and coercivity (Hc ) for the cold-rolled alloys were 240 emu/g and 3.2 kA/m, respectively. The specimens were subjected to annealing in a vacuum of 10 3 Pa at various temperatures. The cooling rate was set about 250 K/h [2,13]. In field annealing, a directional current (DC) field was applied along the longitudinal direction of the specimens in the plane before cooling processes started. After annealing, the magnetic properties and the micro-hardness of the specimens were measured at room temperature using vibrating sample magnetometer (VSM) and HXZ-1000 sclerometer, respectively. The experimental results are the average of three samples to ensure repetition. Differential scanning calorimetry (DSC) curves along TG curves were measured in an argon atmosphere, at
Fig. 1. The XRD profiles of the specimens after various annealings.
ARTICLE IN PRESS F. Zhu et al. / Vacuum 75 (2004) 33–38
Fig. 2. (a) DSC curves for the alloy and (b) the corresponding TG curves. Solid line—heating process; and Dash dot—cooling process.
and 1123 K for 1 h. The texture vanished again when annealing at higher temperatures or for a longer holding time. The structural variation with annealing temperatures indicates that second recrystallization occurred for the alloys during the annealing process. From the XRD result, it can be obtained that a higher temperature and/or longer holding time should be demanded for the occurrence of recrystallization. Fig. 2 displays DSC analysis along with TG curves for the as-alloy during heating and cooling processes, respectively. From the DSC curves, a discontinuous point can be observed at 993 K, implying that a second-order phase transformation took place around the temperature. It can be inferred from quasi-binary Fe–Co phase diagram [12] that the transient point corresponds to order– disorder phase transformation, although it was not detected by XRD profiles in this work. The result
35
seemed to be different from the previous results that no A2–B2 transition could be observable for the alloy after annealing in vacuum [7]. This can be explained as following. Since the DSC analysis was performed in a base vacuum lower than 10 3 Pa, it is considerable that the surface might be slightly oxidized, which would cause a change in composition in the surface. It has been reported in the previous work [14] that a short-range ordering, that is, A2–B2 transition occurred locally in the surface layer around 993 K, induced by the different compositions or activities of the atoms between the surface and interior of the alloy. The failure to detect the change by XRD profiles is thoughtful to be ascribed by small amount of oxide layers and order phase in the surface. In addition, a sharp peak is also observed at 1240 K in the heating curve, and shifted to a lower temperature in the cooling curve. The peak was attributed to the phase transformation from a to g; based on the Fe–Co phase diagram. It should be noted that the a2g phase transformation occurs at the same temperature at which the Curie point is observed in the TG curve, indicating that the ferromagnetism and para-ferromagnetism transition is associated closely with the a2g phase transformation. The different position of the peak in the heating and cooling curves, as shown in Fig. 2(a), is caused simply by a delay in phase transformation because the cooling rate was not slow enough. We can also observe a delay for magnetic transition in the TG curve during the cooling process, corresponding to the result from DSC curves. The change of magnetic properties was also investigated with annealing process in this work. Fig. 3 shows the hysteresis loops for the alloys before and after annealing at the temperatures of 823 and 1033 K. It has been seen that magnetic properties are becoming softer with increasing annealing temperatures. Hysteresis area for the alloy annealed at 1033 K is dramatically reduced compared to the others. The variation of coercivity with annealing temperatures is demonstrated in Fig. 4. We can find that the coercivity begins to abruptly decrease at a certain point with increasing the annealing temperatures to around 1073 K, and shows only a little decline with further increasing
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Fig. 3. The hysteresis loops of the alloy: (a) before annealing; (b) after annealing at 823 K for 2 h; (c) annealing at 1033 K for 2 h.
Fig. 4. The dependence of coercivity on the annealing temperatures: (a) 1 h, (b) 2 h, and (c) 4h.
temperatures. The point at which the coerecivity began to change has been shifted to lower annealing temperature regions when annealing time was increased. The coercivity decreases from 131 to 117 A/m when increasing annealing time from 1 to 4 h at 1033 K, showing a slight decline with increasing annealing time. The minimum coercivity of 78 A/m was obtained in this work after annealing at 1173 K for 4 h. The changes in magnetic properties for the annealed alloys can be expected to be associated closely with microstructural characterizations. It seems, however, that a slight amount of order–disorder phase transformation has only a limited affect on the change of soft magnetic properties for the alloys after annealing. Fig. 5 shows SEM micrographs for the alloys before and after various annealing. It can be found that recrystallization did not take place after annealing at the temperatures below 923 K. The grain growth started at temperatures above 923 K, and the grain size is about 10–15 and 20–30 mm after annealing at 1033 and 1123 K, respectively.
Fig. 5. The micromorphology of the FeCoV alloy after annealing: (a) at 823 K for 1 h; (b) at 923 K for 1 h; (c) at 1033 K for 1 h; (d) at 1033 K for 2 h; (e) at 1123 K for 1 h; and (f) at 1123 K for 2 h.
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Fig. 6. The change of microhardness with the annealing temperatures.
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Fig. 7 shows the change of coercivity with applied magnetic field during annealing process at 1033 K. It can be seen that coercivity was further decreased by 32 A/m as the applied field increases to 200 Oe, followed by a plateau range with further increasing the field. Hysteresis loops of the alloys after field annealing at 1033 K showed that magnetic field annealing has made the loops more rectangular with smaller coercivity, compared with those after vacuum annealing. On the contrary, it is not observed that coercivity was decreased with increasing magnetic field at 873 K, which is lower than the order–disorder transition temperature. It can be considered that the effect of magnetic field on coercivity should be linked with the order– disorder transition.
4. Conclusions
Fig. 7. The dependence of coercivity on the applied magnetic field.
From the change of micro-hardness with annealing temperatures, as shown in Fig. 6, it is found that the micro-hardness first increases by 100 Hv after annealing at around 823 K before it starts to decrease, and shows a value of 220 Hv after annealing at 1123 K. The grain growth induced by annealing at higher temperatures leads to the decrease in micro-hardness. From the results of SEM observations and micro-hardness, we can obtain that the decrease of coercivity after annealing was contributed mainly by the grain growth. Effect of field annealing on the magnetic properties has also been investigated in this work.
In this work the change of microstructure and magnetic properties for Fe–Co–V alloys has been investigated after vacuum annealing with and without applied magnetic field. XRD analysis showed that the alloy was characterized of a-Fe bcc structure. It has been found that an order– disorder phase transformation took place locally in the surface around 993 K. The coercivity begins to abruptly decrease at an annealing temperature for a given holding time. The low coercivity of 78 A/m was obtained for the alloy after annealing at 1173 K for 4 h. From the results of SEM observations and micro-hardness, we can obtain that the decrease of coercivity after annealing was contributed mainly by grain growth. The coercivity of the alloy was further decreased by 32 A/m after magnetic field annealing at 1033 K. Hysteresis loops after field annealing at 1033 K were more rectangular with smaller coercivity, compared with those after vacuum annealing.
Acknowledgements The research is sponsored by Aviation Science Foundation of China (Grant No. 02H51012).
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References [1] Richard BC, editor. Soft magnetic materials, Simens. Berlin, Munich: Aktiengesellschaft; 1979. [2] Wang X, Gao GS. Met Funt Mater 1999;6:168. [3] George EP, Gubbi AN, Baker I, Robertson L. Mater Sci Eng 2002;A329–331:325. [4] Tebble RS, Craik DJ. Magnetic materials. London: WileyInterscience; 1969. [5] Ma XL, Wan DF, editors. Ferromagnetics. Beijing: Electronic Industry, 1999. p. 401. [6] Wohlfarth EP, editor. Ferromagnetic materials II: a handbook on the properties of magnetically ordered substances [M], 1982.
[7] Ustinovshikov Y, Tresheva S. Mater Sci Eng A 1998; 248:238. [8] Orehotsky J, Shroder K. Phys F 1974;4:196. [9] Buckley RA. Met Sci 1975;9:243. [10] Seehra MS, Silinsky P. Phys Rev 1976;B13:5183. [11] Glazyrina MU. Fiz Met Metalloved 1983;56:733. [12] Soft Metallic Group. A handbook of soft magnetic alloy [M]. Beijing: Metallurgical Industry, 1975. p. 204. [13] He KY, editor. Material science and technology on fine alloys, Beijing, 1991. p.77. [14] Mrozek P, Menyhard M, Jablonski A, Tyuliev G. Phys Status Solidi 1988;a110:495.
Vacuum 75 (2004) 33–38
Phase transformation and magnetic properties of annealed Fe52.2Co46V1.8 alloy Fangzhen Zhua, Xiaofang Bia,*, Shanqing Zhangb, Shengkai Gonga, Huibin Xua a
Materials Science and Engineering Department, Beijing University of Aeronautics and Astronautics, Beijing 100083, China b Beijing Institute of Aeronautical Materials, Beijing 100095, China Received 15 October 2003; received in revised form 30 December 2003; accepted 2 January 2004
Abstract In this work, FeCoV alloys were annealed in vacuum at various temperatures for different time, with and without applying an external magnetic field, respectively. The effect of the annealing on their magnetic properties has been investigated in regard with microstructural characterizations. X-ray diffraction analysis shows that the alloy is characterized of a-Fe bcc structure. It has been found that an order–disorder phase transformation took place locally in the surface around 993 K. In addition, a2g phase transformation occurs at the same temperature at which the Curie point is observed in the TG curve. Coercivity is decreased with increasing annealing temperatures, and changed from about 3.2 kA/m to 78 A/m when the annealing temperatures are increased to 1173 K. Microstructural observations show that the decrease of coercivity after annealing is contributed mainly by grain growth. The coercivity of the alloy is further decreased by 32 A/m after magnetic field annealing at 1033 K. Hysteresis loops of the alloys after field annealing at 1033 K featured more rectangular shape with smaller coercivity, compared with those after vacuum annealing. r 2004 Elsevier Ltd. All rights reserved. Keywords: FeCo alloy; Vacuum annealing; Magnetic properties; Order–disorder transition
1. Introduction The FeCo alloys, which are known as soft magnetic materials with maximum saturation magnetization (Ms ) and high Curie temperature (Tc ), have been an interesting research topic [1–3]. It is well known that the alloys are used for the stator and rotor of the generator, and its weight and performance are dependent largely on the magnetic properties of the alloys. Generally *Corresponding author. Tel.: 86-10-82315999; fax: 86-1082314871. E-mail address: [email protected] (X. Bi).
speaking, the total power losses of the generator could be divided into three parts: hysteresis loss, eddy current loss and relaxation loss, in which the third one is usually neglected because of its mild contribution to the total loss. The eddy current loss can be successfully reduced by increasing the electrical resistance of materials and decreasing the thickness of the laminations. On the other hand, hysteresis loss is a function of the coercivity of the magnetic materials used for generator [4,5]. Therefore, it is of great importance to decrease coercivity from the practical point of view. According to the Fe–Co phase diagram [6], a disorder to long-range order transition (A2 2B2 )
0042-207X/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.vacuum.2004.01.002
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F. Zhu et al. / Vacuum 75 (2004) 33–38
occurs around 1003 K in the ideal binary FeCo alloys with a weight ratio of cobalt from 30% to 70%. A recent research has revealed that the A22B2 transition only occurred in the surface of the alloy when the alloy was annealed in air atmosphere [7]. This transition is believed to increase its brittleness and deteriorate its mechanical workability, which is hereby suppressed by adding a moderate amount (E2%) of third element vanadium to the binary system. Previous work has placed much attention on the phase transformation, annealing process or the grain growth [3,7–11]. However, the relationship of those parameters and magnetic properties are required to be studied in order to improve the soft magnetic properties of the alloys. Many things still remain unclear regarding the effect of annealing on the magnetic properties [12,13]. In this work, the effect of vacuum annealing and field annealing on soft magnetic properties has been investigated and discussed in terms of the corresponding microstructural variations.
a heating rate of 20 K/min and cooling rate of 20 K/min (DSC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to investigate structure and microstructural characterizations. As to the specimen preparation for SEM observation, specimens were polished, and then they were etched with a chemical solution composed of 5 g copper chloride, hydrochloric acid, ethanol and water 20 ml, respectively.
3. Results and discussion Fig. 1 show XRD patterns for the alloys before and after annealing at 1033 and 1123 K for (a) 1 h and (b) 2 h. It is revealed that the alloy is characterized of a-Fe bcc structure. Three peaks of 1 1 0, 2 0 0 and 2 1 1 are observed for the alloys before annealing, and it can be seen that 2 0 0 texture appears after annealing at 1033 K for 2 h
2. Experimental procedures The main chemical composition of the specimens was Fe52.2Co46V1.8, examined by energy dispersive spectroscopy (EDS). The specimens were machined into 10 2 0.2 (mm) sheets. The magnetization (Ms ) and coercivity (Hc ) for the cold-rolled alloys were 240 emu/g and 3.2 kA/m, respectively. The specimens were subjected to annealing in a vacuum of 10 3 Pa at various temperatures. The cooling rate was set about 250 K/h [2,13]. In field annealing, a directional current (DC) field was applied along the longitudinal direction of the specimens in the plane before cooling processes started. After annealing, the magnetic properties and the micro-hardness of the specimens were measured at room temperature using vibrating sample magnetometer (VSM) and HXZ-1000 sclerometer, respectively. The experimental results are the average of three samples to ensure repetition. Differential scanning calorimetry (DSC) curves along TG curves were measured in an argon atmosphere, at
Fig. 1. The XRD profiles of the specimens after various annealings.
ARTICLE IN PRESS F. Zhu et al. / Vacuum 75 (2004) 33–38
Fig. 2. (a) DSC curves for the alloy and (b) the corresponding TG curves. Solid line—heating process; and Dash dot—cooling process.
and 1123 K for 1 h. The texture vanished again when annealing at higher temperatures or for a longer holding time. The structural variation with annealing temperatures indicates that second recrystallization occurred for the alloys during the annealing process. From the XRD result, it can be obtained that a higher temperature and/or longer holding time should be demanded for the occurrence of recrystallization. Fig. 2 displays DSC analysis along with TG curves for the as-alloy during heating and cooling processes, respectively. From the DSC curves, a discontinuous point can be observed at 993 K, implying that a second-order phase transformation took place around the temperature. It can be inferred from quasi-binary Fe–Co phase diagram [12] that the transient point corresponds to order– disorder phase transformation, although it was not detected by XRD profiles in this work. The result
35
seemed to be different from the previous results that no A2–B2 transition could be observable for the alloy after annealing in vacuum [7]. This can be explained as following. Since the DSC analysis was performed in a base vacuum lower than 10 3 Pa, it is considerable that the surface might be slightly oxidized, which would cause a change in composition in the surface. It has been reported in the previous work [14] that a short-range ordering, that is, A2–B2 transition occurred locally in the surface layer around 993 K, induced by the different compositions or activities of the atoms between the surface and interior of the alloy. The failure to detect the change by XRD profiles is thoughtful to be ascribed by small amount of oxide layers and order phase in the surface. In addition, a sharp peak is also observed at 1240 K in the heating curve, and shifted to a lower temperature in the cooling curve. The peak was attributed to the phase transformation from a to g; based on the Fe–Co phase diagram. It should be noted that the a2g phase transformation occurs at the same temperature at which the Curie point is observed in the TG curve, indicating that the ferromagnetism and para-ferromagnetism transition is associated closely with the a2g phase transformation. The different position of the peak in the heating and cooling curves, as shown in Fig. 2(a), is caused simply by a delay in phase transformation because the cooling rate was not slow enough. We can also observe a delay for magnetic transition in the TG curve during the cooling process, corresponding to the result from DSC curves. The change of magnetic properties was also investigated with annealing process in this work. Fig. 3 shows the hysteresis loops for the alloys before and after annealing at the temperatures of 823 and 1033 K. It has been seen that magnetic properties are becoming softer with increasing annealing temperatures. Hysteresis area for the alloy annealed at 1033 K is dramatically reduced compared to the others. The variation of coercivity with annealing temperatures is demonstrated in Fig. 4. We can find that the coercivity begins to abruptly decrease at a certain point with increasing the annealing temperatures to around 1073 K, and shows only a little decline with further increasing
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Fig. 3. The hysteresis loops of the alloy: (a) before annealing; (b) after annealing at 823 K for 2 h; (c) annealing at 1033 K for 2 h.
Fig. 4. The dependence of coercivity on the annealing temperatures: (a) 1 h, (b) 2 h, and (c) 4h.
temperatures. The point at which the coerecivity began to change has been shifted to lower annealing temperature regions when annealing time was increased. The coercivity decreases from 131 to 117 A/m when increasing annealing time from 1 to 4 h at 1033 K, showing a slight decline with increasing annealing time. The minimum coercivity of 78 A/m was obtained in this work after annealing at 1173 K for 4 h. The changes in magnetic properties for the annealed alloys can be expected to be associated closely with microstructural characterizations. It seems, however, that a slight amount of order–disorder phase transformation has only a limited affect on the change of soft magnetic properties for the alloys after annealing. Fig. 5 shows SEM micrographs for the alloys before and after various annealing. It can be found that recrystallization did not take place after annealing at the temperatures below 923 K. The grain growth started at temperatures above 923 K, and the grain size is about 10–15 and 20–30 mm after annealing at 1033 and 1123 K, respectively.
Fig. 5. The micromorphology of the FeCoV alloy after annealing: (a) at 823 K for 1 h; (b) at 923 K for 1 h; (c) at 1033 K for 1 h; (d) at 1033 K for 2 h; (e) at 1123 K for 1 h; and (f) at 1123 K for 2 h.
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Fig. 6. The change of microhardness with the annealing temperatures.
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Fig. 7 shows the change of coercivity with applied magnetic field during annealing process at 1033 K. It can be seen that coercivity was further decreased by 32 A/m as the applied field increases to 200 Oe, followed by a plateau range with further increasing the field. Hysteresis loops of the alloys after field annealing at 1033 K showed that magnetic field annealing has made the loops more rectangular with smaller coercivity, compared with those after vacuum annealing. On the contrary, it is not observed that coercivity was decreased with increasing magnetic field at 873 K, which is lower than the order–disorder transition temperature. It can be considered that the effect of magnetic field on coercivity should be linked with the order– disorder transition.
4. Conclusions
Fig. 7. The dependence of coercivity on the applied magnetic field.
From the change of micro-hardness with annealing temperatures, as shown in Fig. 6, it is found that the micro-hardness first increases by 100 Hv after annealing at around 823 K before it starts to decrease, and shows a value of 220 Hv after annealing at 1123 K. The grain growth induced by annealing at higher temperatures leads to the decrease in micro-hardness. From the results of SEM observations and micro-hardness, we can obtain that the decrease of coercivity after annealing was contributed mainly by the grain growth. Effect of field annealing on the magnetic properties has also been investigated in this work.
In this work the change of microstructure and magnetic properties for Fe–Co–V alloys has been investigated after vacuum annealing with and without applied magnetic field. XRD analysis showed that the alloy was characterized of a-Fe bcc structure. It has been found that an order– disorder phase transformation took place locally in the surface around 993 K. The coercivity begins to abruptly decrease at an annealing temperature for a given holding time. The low coercivity of 78 A/m was obtained for the alloy after annealing at 1173 K for 4 h. From the results of SEM observations and micro-hardness, we can obtain that the decrease of coercivity after annealing was contributed mainly by grain growth. The coercivity of the alloy was further decreased by 32 A/m after magnetic field annealing at 1033 K. Hysteresis loops after field annealing at 1033 K were more rectangular with smaller coercivity, compared with those after vacuum annealing.
Acknowledgements The research is sponsored by Aviation Science Foundation of China (Grant No. 02H51012).
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References [1] Richard BC, editor. Soft magnetic materials, Simens. Berlin, Munich: Aktiengesellschaft; 1979. [2] Wang X, Gao GS. Met Funt Mater 1999;6:168. [3] George EP, Gubbi AN, Baker I, Robertson L. Mater Sci Eng 2002;A329–331:325. [4] Tebble RS, Craik DJ. Magnetic materials. London: WileyInterscience; 1969. [5] Ma XL, Wan DF, editors. Ferromagnetics. Beijing: Electronic Industry, 1999. p. 401. [6] Wohlfarth EP, editor. Ferromagnetic materials II: a handbook on the properties of magnetically ordered substances [M], 1982.
[7] Ustinovshikov Y, Tresheva S. Mater Sci Eng A 1998; 248:238. [8] Orehotsky J, Shroder K. Phys F 1974;4:196. [9] Buckley RA. Met Sci 1975;9:243. [10] Seehra MS, Silinsky P. Phys Rev 1976;B13:5183. [11] Glazyrina MU. Fiz Met Metalloved 1983;56:733. [12] Soft Metallic Group. A handbook of soft magnetic alloy [M]. Beijing: Metallurgical Industry, 1975. p. 204. [13] He KY, editor. Material science and technology on fine alloys, Beijing, 1991. p.77. [14] Mrozek P, Menyhard M, Jablonski A, Tyuliev G. Phys Status Solidi 1988;a110:495.