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Synthesis and magnetic properties of Cu-based amorphous alloys made by mechanical alloying
Intermetallics 12 (2004) 1115–1118 www.elsevier.com/locate/intermet
Synthesis and magnetic properties of Cu-based amorphous alloys made by mechanical alloying Kou Shengzhonga,*, Feng Liua, Ding Yutiana, Xu Guangjia, Ding Zongfua, La Peiqingb a
State Key Laboratory of Gansu Advanced Nonferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050, China b China Academy of Sciences, The Institute of Chemical and Physics, Lanzhou 730050, China Available online 13 July 2004
Abstract Advanced Cu-based amorphous powders are synthesized by mechanical alloying with different milling time and weight ratios of ball to powder and examined by X-ray diffraction, scanning electron microscope and transmission electron microscope. Magnetic hysteresis loops at room temperature are measured by a vibration sample magnetometer. According to the present experiment, Cu-based amorphous powders are synthesized after being milled for 8, 10, and 12.5 h, respectively. If the time is more than 12.5 h, amorphous phase will transform into crystalline one again; otherwise, if less than 8 h, amorphous phase cannot be formed completely. Cu-based amorphous powders show hard magnetic properties. In addition, their hard magnetic properties are lower than Nd-based amorphous alloys. q 2004 Elsevier Ltd. All rights reserved. Keywords: A. Intermetallics, miscellaneous; B. Magnetic properties; C. Mechanical alloying and milling
1. Introduction Cu-based amorphous alloys are advanced materials that have been developed in recent years. Their super high mechanical properties have attracted considerable interests. At present, Cu-based bulk amorphous alloys are mainly made by conventional casting techniques. During the process, the cooling rate of molten metal must be larger than critical cooling rate of forming amorphous alloys. So the size of bulk amorphous alloys is limited greatly [1]. Another technique applied for bulk amorphous alloys preparation is consolidation of amorphous powders between glass transition temperature ðTg Þ and crystalline temperature ðTx Þ: Amorphous powders could be produced by solid reaction without passing through the liquid state. It is the premise of making Cu-based bulk amorphous pieces, so it is very important to understand the transformation kinetic from crystalline to amorphous in the milling process. It is also very useful to determine the optimum milling process in industrial production. The aim of the present work is to study the effect of milling parameters (milling time and weight ratio of balls to powders) on the formation kinetics and properties of Cu-based amorphous alloy * Corresponding author. Tel.: þ 86-931-2757285; fax: þ 86-9312756034. E-mail address: [email protected] (K. Shengzhong). 0966-9795/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.intermet.2004.04.007
powders used to consolidate it into bulk amorphous alloys and study their magnetic properties.
2. Experimental procedure The alloy system researched in the work is Cu47Ti34Zr11Ni8. Mechanical alloying is performed in a QM-1SP planetary high-energy ball miller with different weight ratios of ball to powder and milling time under ultra-high pure argon atmosphere. Elemental powders of Cu (99.9%), Ti (99.9%), Zr (99.9%) and Ni (99.9%) are accurately weighed according to the designed compositions. The preweighed powder mixtures are then mixed into the stainless containers together with the steel balls. It is noted that the stainless containers must be sealed completely in order to avoid oxidation during milling process. The whole mechanical alloying process is carried out for different hours and interrupted every hour. Each interval time lasts 30 min to make the containers cool down. The powders are milled until they meet the demanded time and extracted to examine if they are amorphous phase [2 – 4]. The X-ray diffraction is performed by Rigakku D/Max-2400 Japan with Cu Ka radiation and the powder morphologies are examined by JSM-5600LV. The magnetic properties are measured with 7304 vibrating sample magnetometer.
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3. Experimental results The morphologies of the powders are examined by SEM. Fig. 1 shows the morphologies of the powders milled for different time. The mixed elemental powders undergo repeated cold welding, fracturing and become amorphous phase finally. Cold welding makes the size of the particles increase, resulting in alloying in the interface of multicomponents, while fracturing makes the size decrease, fresh interfaces are formed. When the process attains amorphous stage, the size is stable [5 – 7]. It is noticed that the powders if not milled is irregular, After being milled for 4 h, the size of the powders has grown much larger, at this time, cold welding plays the main role. Four elements, Cu, Zr, Ti and Ni, are dissolved through interfacial reaction. From 4 to 6 h, fracturing dominates the key function, the size is getting smaller. Until the amorphous stage, the size of the powders is constant basically. Fig. 2 shows the XRD patterns of the powders milled for different milling time. In the experiment, the weight ratio of balls to powders is 20. According to the first curve after 6.5 h of ball milling, the Bragg peaks have been broadened, it could be deduced that the alloy powders have been amorphized, but there still exists crystalline phase. Another four curves in the middle after 8, 10, 11, 12.5 h of ball milling indicate that all the crystalline peaks have disappeared, only leaving a broad diffraction peak, which demonstrate that Cu47Ti34Zr11Ni8 powders have been amorphized completely at the end of the ball milling. But the curve’s Bragg peaks for powders milled 15 h appear again, indicating that amorphous phase begins to transform into crystal phase. Fig. 3 shows the effect of weight ratio of balls to powders on the formation of amorphous phase. The milling time is set to 10 h. When the weight ratio is 5:1, the Bragg peak
is sharp, which shows alloy powders are in crystalline phase completely. The curve in the middle, whose weight ratio is 10:1, the Bragg peak has not been broadened, which indicates the powders have transformed from crystalline to amorphous phase mostly, but still have a little of crystalline phase. The top curve shows a broad diffraction peak, it implies that the powders have been completely transformed into amorphous phase. From above experiments, it could be concluded that the weight ratio of balls to powders has greatly influenced the transformation from crystalline powders to amorphous powders. In the fixed milling time, higher weight ratio of balls to powders shows larger ability to form amorphous state. The TEM images for Cu47Ti34Zr11Ni8 powders with different milling time are shown in Fig. 4. The powders milled for 4 h are polycrystalline; amorphous phase has not appeared yet. After being milled for 6.5 h, some amorphous phases have formed, but most of them still exist in the form of crystalline phases. On the other hand, in Fig. 4(c), we can see a halo pattern, which is characteristic of a fully amorphous structure. It is in agreement with the XRD patterns presented in Fig. 2. The magnetic properties of Cu-based amorphous alloys with different time have been studied at room temperature. Fig. 5 displays the magnetic hysteresis loops of amorphous alloys powders for Cu47Ti34Zr11Ni8. Fig. 5 indicates that with the milling time increasing, coercivity ðHc Þ and ds increases gradually.
4. Discussion Fig. 3 shows that the milling time is one of the most important parameters for synthesizing copper-based amorphous powders. If the time is less than required, the powders cannot be amorphized completely. While too long milling time, amorphous powders result in crystallization again. So, the milling time involves a suitable time range in present experimental condition. The results can be interpreted from the point of thermodynamics. Thermodynamic formula of transformation from crystalline to amorphous state can be given as follow: DG ¼ DH 2 TDS
Fig. 1. Powder morphologies of Cu47Ti34Zr11Ni8 milled for different milling time.
ð1Þ
Here, DG refers to Gibbs free energy; DH stands for formation enthalpies in an alloy system; DS means formation entropies. It is well known that when DG is lower, the glass forming ability is higher. That is, if the amorphous phase forms, DH must be smaller and DS must be larger simultaneously. During the ball milling process, because of atomic disorder state, DS increases gradually. According to the results of Inoue [8,9], the temperature of MA increases first until it attains the maximum value, then decreases and be stable finally. On the other hand, DH decreases to the minimum, and then increases again with
K. Shengzhong et al. / Intermetallics 12 (2004) 1115–1118
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Fig. 2. XRD profiles for Cu47Ti34Zr11Ni8 powders with different milling time.
time prolonging. In the present experiment, when the milling time is less than 6.5 h, Gibbs free energy is larger and not suitable to the transformation into amorphous phase; when the milling time is between 6.5 and 8 h, there are amorphous phase and crystalline one coexisting. Up to 8 h, the temperature is much higher and the enthalpies are smaller, according to thermodynamic formula, the Gibbs free energy would become smaller, which is favorable to the transformation from crystalline to amorphous phase. In fact, many other parameters including alloy components, milling speed, the weight ratios to ball to powder, etc. have effects on transforming crystalline into amorphous
phase. Among them, the weight ratio of balls to powders and atmosphere are very important factors to synthesize amorphous powder. The weight ratio of balls to powders effects the energy transmitted into powders from mechanical energy. The formation of amorphous needs a critical energy, as the amorphous phase cannot be synthesized if the power is below the critical energy. So, higher energy ball milling is necessary to alloying and transformation into amorphous phase. Fig. 4 demonstrates the result, that different weight ratios with the same time get different phases. Atmosphere is another important factor to fabricate amorphous powders. Once one of the alloy elements is oxidized, the amorphous
Fig. 3. XRD profiles for Cu47Ti34Zr11Ni8 powders milled for 10 h with various weight ratio of balls to powders.
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Fig. 4. TEM images of mechanical alloyed Cu47Ti34Zr11Ni8 powder for (a) 4 h, (b) 6.5 h, (c) 11 h.
During the MA process, the milling time is an important parameter, there is a suitable time range for synthesizing amorphous alloys. According to the present experiment results, Cu-based amorphous powders can be obtained after being milled from 8 to 12.5 h. If the time is more than 12.5 h, amorphous phase is transformed into crystalline one again; if shorter, amorphous phase cannot be formed completely. In addition, the steel vial should be sealed tightly to avoid oxidation. Magnetic properties at room temperature are measured. Cu-based amorphous powders exhibit hard magnetic properties. Hc , Ms increase with the time of milling prolonging. Compared with Nd-based amorphous alloys, their hard magnetic properties are lower.
Acknowledgements The authors are grateful for the financial support of this work by the State Key Lab of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, P.R. China.
References
Fig. 5. Magnetic hysteresis loops of amorphous alloys for Cu47Ti34Zr11Ni8 amorphous alloys powders with 8, 10, and 11 h.
phase would not be formed regardless of changing other process parameters. During our experiment, the powders are protected by Ar gas from oxidation. Fig. 5 shows that the magnetic hysteresis loops of Cu47Ti34Zr11Ni8 powders. In the figure, Hc is , 26.9, , 31.8, , 32.4 and ds is , 0.1758, , 0.1787, , 0.2020 emu/g, respectively, in the order of 8, 10, 11 h. It could be seen that Hc is between 26 and 32 kA/M and ds is between 0.17 and 0.20 emu/g. The values of Hc are all larger than 1 kA/m, it also shows that Cu47Ti34Zr11Ni8 powders with different milling time are hard magnetic materials. The Hc of Nd60Fe30Al10 is 260 kA/M [10 –13]. So according to the present experimental data, Cu-based amorphous alloys show lower hard magnetic properties compared with Ndbased amorphous alloys. The most interesting is magnetic properties have evident changes with different milling time. The Hc and Ms increase with the milling time prolonging.
5. Conclusion Advanced Cu-based amorphous alloys are synthesized by mechanical alloying with different milling time and weight ratio of balls to powders, which indicates the Cu47Ti34Zr11Ni8 powders have higher glass forming ability.
[1] Yulai G, Jun S, Jianfei S, et al. Consolidation of amorphous powders: a new technique for bulk amorphous alloy. Mater Rev 2002;16(10): 32. [2] Lee PY, Lin CK, Chen GS, Louh RF, Chen KC. Formation of Cu –Zr–Ti amorphous alloys with significant supercooled liquid region by mechanical alloying. Mater Sci Forum 1999;312–314:68. [3] Eckert J. Mechanical alloying of bulk metallic glass forming systems. J Metastable Nanocryst Mater 1999;312–314:3. [4] Eckert J. Mechanical alloying of highly processable glassy alloys. Mater Science Eng 1997;A226–228:365–8. [5] Lee P-Y, Hung S-S, Hsieh J-T, et al. Consolidation of amorphous Ni– Zr–Ti–Si powders by vacuum hot-pressing method. Intermetallics 2002;10:1278. [6] Mendez H, Mancha MM, Cisneros MM, et al. Structure of a Fe– Cr–Mn–Mo –N alloy processed by mechanical alloying. Metall Mater Trans A 2002;33A(10):3274. [7] Lin CK, Liu SW, Lee PY. Preparation and thermal stability of Zr – Ti – Al – Ni – Cu amorphous powders by mechanical alloying technique. Metall Mater Trans A 2001;32A(7):1778–80. [8] Sherif El-Eskandarany M, Inoue A. Solid-state crystalline-glassy cyclic phase transformations of mechanically alloyed Cu33Zr67 powders. Metall Mater Trans A 2002;33A(1):141–2. [9] Inoue A. Bulk amorphous alloys—preparation and fundamental characteristics. Switzerland: Trans Tech; 1998. p. 4. [10] Ortega-Hertogs RJ, Inoue A, Rao KV. Evolution from random-axis ising to Stoner– Wohlfarth type of hysterisis loops of the cluster glass Fe3Nd phase in bulk glassy Nd60Fe30Al10 hard magnets. Scripma Mater 2001;44:1334–6. [11] Fan GJ, Loser S, Roth S, Echert J, Schultz L. Glass-forming ability and magnetic properties of Nd702xFe20Al10Cox alloys. J Mater Res 2000;15(7):1558. [12] Chiriac H, Lupu N. Structure and magnetic properties of some bulk amorphous materials. J Non-Crystall Solids 1999;250–252:752. [13] Abdul Khadar M, Bihu V, Inoue A. Effect of finite size on the magnetization behavior of nanostructured nickel oxide. Mater Res Bull 2003;38:1343 –4.
Synthesis and magnetic properties of Cu-based amorphous alloys made by mechanical alloying Kou Shengzhonga,*, Feng Liua, Ding Yutiana, Xu Guangjia, Ding Zongfua, La Peiqingb a
State Key Laboratory of Gansu Advanced Nonferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050, China b China Academy of Sciences, The Institute of Chemical and Physics, Lanzhou 730050, China Available online 13 July 2004
Abstract Advanced Cu-based amorphous powders are synthesized by mechanical alloying with different milling time and weight ratios of ball to powder and examined by X-ray diffraction, scanning electron microscope and transmission electron microscope. Magnetic hysteresis loops at room temperature are measured by a vibration sample magnetometer. According to the present experiment, Cu-based amorphous powders are synthesized after being milled for 8, 10, and 12.5 h, respectively. If the time is more than 12.5 h, amorphous phase will transform into crystalline one again; otherwise, if less than 8 h, amorphous phase cannot be formed completely. Cu-based amorphous powders show hard magnetic properties. In addition, their hard magnetic properties are lower than Nd-based amorphous alloys. q 2004 Elsevier Ltd. All rights reserved. Keywords: A. Intermetallics, miscellaneous; B. Magnetic properties; C. Mechanical alloying and milling
1. Introduction Cu-based amorphous alloys are advanced materials that have been developed in recent years. Their super high mechanical properties have attracted considerable interests. At present, Cu-based bulk amorphous alloys are mainly made by conventional casting techniques. During the process, the cooling rate of molten metal must be larger than critical cooling rate of forming amorphous alloys. So the size of bulk amorphous alloys is limited greatly [1]. Another technique applied for bulk amorphous alloys preparation is consolidation of amorphous powders between glass transition temperature ðTg Þ and crystalline temperature ðTx Þ: Amorphous powders could be produced by solid reaction without passing through the liquid state. It is the premise of making Cu-based bulk amorphous pieces, so it is very important to understand the transformation kinetic from crystalline to amorphous in the milling process. It is also very useful to determine the optimum milling process in industrial production. The aim of the present work is to study the effect of milling parameters (milling time and weight ratio of balls to powders) on the formation kinetics and properties of Cu-based amorphous alloy * Corresponding author. Tel.: þ 86-931-2757285; fax: þ 86-9312756034. E-mail address: [email protected] (K. Shengzhong). 0966-9795/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.intermet.2004.04.007
powders used to consolidate it into bulk amorphous alloys and study their magnetic properties.
2. Experimental procedure The alloy system researched in the work is Cu47Ti34Zr11Ni8. Mechanical alloying is performed in a QM-1SP planetary high-energy ball miller with different weight ratios of ball to powder and milling time under ultra-high pure argon atmosphere. Elemental powders of Cu (99.9%), Ti (99.9%), Zr (99.9%) and Ni (99.9%) are accurately weighed according to the designed compositions. The preweighed powder mixtures are then mixed into the stainless containers together with the steel balls. It is noted that the stainless containers must be sealed completely in order to avoid oxidation during milling process. The whole mechanical alloying process is carried out for different hours and interrupted every hour. Each interval time lasts 30 min to make the containers cool down. The powders are milled until they meet the demanded time and extracted to examine if they are amorphous phase [2 – 4]. The X-ray diffraction is performed by Rigakku D/Max-2400 Japan with Cu Ka radiation and the powder morphologies are examined by JSM-5600LV. The magnetic properties are measured with 7304 vibrating sample magnetometer.
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3. Experimental results The morphologies of the powders are examined by SEM. Fig. 1 shows the morphologies of the powders milled for different time. The mixed elemental powders undergo repeated cold welding, fracturing and become amorphous phase finally. Cold welding makes the size of the particles increase, resulting in alloying in the interface of multicomponents, while fracturing makes the size decrease, fresh interfaces are formed. When the process attains amorphous stage, the size is stable [5 – 7]. It is noticed that the powders if not milled is irregular, After being milled for 4 h, the size of the powders has grown much larger, at this time, cold welding plays the main role. Four elements, Cu, Zr, Ti and Ni, are dissolved through interfacial reaction. From 4 to 6 h, fracturing dominates the key function, the size is getting smaller. Until the amorphous stage, the size of the powders is constant basically. Fig. 2 shows the XRD patterns of the powders milled for different milling time. In the experiment, the weight ratio of balls to powders is 20. According to the first curve after 6.5 h of ball milling, the Bragg peaks have been broadened, it could be deduced that the alloy powders have been amorphized, but there still exists crystalline phase. Another four curves in the middle after 8, 10, 11, 12.5 h of ball milling indicate that all the crystalline peaks have disappeared, only leaving a broad diffraction peak, which demonstrate that Cu47Ti34Zr11Ni8 powders have been amorphized completely at the end of the ball milling. But the curve’s Bragg peaks for powders milled 15 h appear again, indicating that amorphous phase begins to transform into crystal phase. Fig. 3 shows the effect of weight ratio of balls to powders on the formation of amorphous phase. The milling time is set to 10 h. When the weight ratio is 5:1, the Bragg peak
is sharp, which shows alloy powders are in crystalline phase completely. The curve in the middle, whose weight ratio is 10:1, the Bragg peak has not been broadened, which indicates the powders have transformed from crystalline to amorphous phase mostly, but still have a little of crystalline phase. The top curve shows a broad diffraction peak, it implies that the powders have been completely transformed into amorphous phase. From above experiments, it could be concluded that the weight ratio of balls to powders has greatly influenced the transformation from crystalline powders to amorphous powders. In the fixed milling time, higher weight ratio of balls to powders shows larger ability to form amorphous state. The TEM images for Cu47Ti34Zr11Ni8 powders with different milling time are shown in Fig. 4. The powders milled for 4 h are polycrystalline; amorphous phase has not appeared yet. After being milled for 6.5 h, some amorphous phases have formed, but most of them still exist in the form of crystalline phases. On the other hand, in Fig. 4(c), we can see a halo pattern, which is characteristic of a fully amorphous structure. It is in agreement with the XRD patterns presented in Fig. 2. The magnetic properties of Cu-based amorphous alloys with different time have been studied at room temperature. Fig. 5 displays the magnetic hysteresis loops of amorphous alloys powders for Cu47Ti34Zr11Ni8. Fig. 5 indicates that with the milling time increasing, coercivity ðHc Þ and ds increases gradually.
4. Discussion Fig. 3 shows that the milling time is one of the most important parameters for synthesizing copper-based amorphous powders. If the time is less than required, the powders cannot be amorphized completely. While too long milling time, amorphous powders result in crystallization again. So, the milling time involves a suitable time range in present experimental condition. The results can be interpreted from the point of thermodynamics. Thermodynamic formula of transformation from crystalline to amorphous state can be given as follow: DG ¼ DH 2 TDS
Fig. 1. Powder morphologies of Cu47Ti34Zr11Ni8 milled for different milling time.
ð1Þ
Here, DG refers to Gibbs free energy; DH stands for formation enthalpies in an alloy system; DS means formation entropies. It is well known that when DG is lower, the glass forming ability is higher. That is, if the amorphous phase forms, DH must be smaller and DS must be larger simultaneously. During the ball milling process, because of atomic disorder state, DS increases gradually. According to the results of Inoue [8,9], the temperature of MA increases first until it attains the maximum value, then decreases and be stable finally. On the other hand, DH decreases to the minimum, and then increases again with
K. Shengzhong et al. / Intermetallics 12 (2004) 1115–1118
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Fig. 2. XRD profiles for Cu47Ti34Zr11Ni8 powders with different milling time.
time prolonging. In the present experiment, when the milling time is less than 6.5 h, Gibbs free energy is larger and not suitable to the transformation into amorphous phase; when the milling time is between 6.5 and 8 h, there are amorphous phase and crystalline one coexisting. Up to 8 h, the temperature is much higher and the enthalpies are smaller, according to thermodynamic formula, the Gibbs free energy would become smaller, which is favorable to the transformation from crystalline to amorphous phase. In fact, many other parameters including alloy components, milling speed, the weight ratios to ball to powder, etc. have effects on transforming crystalline into amorphous
phase. Among them, the weight ratio of balls to powders and atmosphere are very important factors to synthesize amorphous powder. The weight ratio of balls to powders effects the energy transmitted into powders from mechanical energy. The formation of amorphous needs a critical energy, as the amorphous phase cannot be synthesized if the power is below the critical energy. So, higher energy ball milling is necessary to alloying and transformation into amorphous phase. Fig. 4 demonstrates the result, that different weight ratios with the same time get different phases. Atmosphere is another important factor to fabricate amorphous powders. Once one of the alloy elements is oxidized, the amorphous
Fig. 3. XRD profiles for Cu47Ti34Zr11Ni8 powders milled for 10 h with various weight ratio of balls to powders.
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Fig. 4. TEM images of mechanical alloyed Cu47Ti34Zr11Ni8 powder for (a) 4 h, (b) 6.5 h, (c) 11 h.
During the MA process, the milling time is an important parameter, there is a suitable time range for synthesizing amorphous alloys. According to the present experiment results, Cu-based amorphous powders can be obtained after being milled from 8 to 12.5 h. If the time is more than 12.5 h, amorphous phase is transformed into crystalline one again; if shorter, amorphous phase cannot be formed completely. In addition, the steel vial should be sealed tightly to avoid oxidation. Magnetic properties at room temperature are measured. Cu-based amorphous powders exhibit hard magnetic properties. Hc , Ms increase with the time of milling prolonging. Compared with Nd-based amorphous alloys, their hard magnetic properties are lower.
Acknowledgements The authors are grateful for the financial support of this work by the State Key Lab of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, P.R. China.
References
Fig. 5. Magnetic hysteresis loops of amorphous alloys for Cu47Ti34Zr11Ni8 amorphous alloys powders with 8, 10, and 11 h.
phase would not be formed regardless of changing other process parameters. During our experiment, the powders are protected by Ar gas from oxidation. Fig. 5 shows that the magnetic hysteresis loops of Cu47Ti34Zr11Ni8 powders. In the figure, Hc is , 26.9, , 31.8, , 32.4 and ds is , 0.1758, , 0.1787, , 0.2020 emu/g, respectively, in the order of 8, 10, 11 h. It could be seen that Hc is between 26 and 32 kA/M and ds is between 0.17 and 0.20 emu/g. The values of Hc are all larger than 1 kA/m, it also shows that Cu47Ti34Zr11Ni8 powders with different milling time are hard magnetic materials. The Hc of Nd60Fe30Al10 is 260 kA/M [10 –13]. So according to the present experimental data, Cu-based amorphous alloys show lower hard magnetic properties compared with Ndbased amorphous alloys. The most interesting is magnetic properties have evident changes with different milling time. The Hc and Ms increase with the milling time prolonging.
5. Conclusion Advanced Cu-based amorphous alloys are synthesized by mechanical alloying with different milling time and weight ratio of balls to powders, which indicates the Cu47Ti34Zr11Ni8 powders have higher glass forming ability.
[1] Yulai G, Jun S, Jianfei S, et al. Consolidation of amorphous powders: a new technique for bulk amorphous alloy. Mater Rev 2002;16(10): 32. [2] Lee PY, Lin CK, Chen GS, Louh RF, Chen KC. Formation of Cu –Zr–Ti amorphous alloys with significant supercooled liquid region by mechanical alloying. Mater Sci Forum 1999;312–314:68. [3] Eckert J. Mechanical alloying of bulk metallic glass forming systems. J Metastable Nanocryst Mater 1999;312–314:3. [4] Eckert J. Mechanical alloying of highly processable glassy alloys. Mater Science Eng 1997;A226–228:365–8. [5] Lee P-Y, Hung S-S, Hsieh J-T, et al. Consolidation of amorphous Ni– Zr–Ti–Si powders by vacuum hot-pressing method. Intermetallics 2002;10:1278. [6] Mendez H, Mancha MM, Cisneros MM, et al. Structure of a Fe– Cr–Mn–Mo –N alloy processed by mechanical alloying. Metall Mater Trans A 2002;33A(10):3274. [7] Lin CK, Liu SW, Lee PY. Preparation and thermal stability of Zr – Ti – Al – Ni – Cu amorphous powders by mechanical alloying technique. Metall Mater Trans A 2001;32A(7):1778–80. [8] Sherif El-Eskandarany M, Inoue A. Solid-state crystalline-glassy cyclic phase transformations of mechanically alloyed Cu33Zr67 powders. Metall Mater Trans A 2002;33A(1):141–2. [9] Inoue A. Bulk amorphous alloys—preparation and fundamental characteristics. Switzerland: Trans Tech; 1998. p. 4. [10] Ortega-Hertogs RJ, Inoue A, Rao KV. Evolution from random-axis ising to Stoner– Wohlfarth type of hysterisis loops of the cluster glass Fe3Nd phase in bulk glassy Nd60Fe30Al10 hard magnets. Scripma Mater 2001;44:1334–6. [11] Fan GJ, Loser S, Roth S, Echert J, Schultz L. Glass-forming ability and magnetic properties of Nd702xFe20Al10Cox alloys. J Mater Res 2000;15(7):1558. [12] Chiriac H, Lupu N. Structure and magnetic properties of some bulk amorphous materials. J Non-Crystall Solids 1999;250–252:752. [13] Abdul Khadar M, Bihu V, Inoue A. Effect of finite size on the magnetization behavior of nanostructured nickel oxide. Mater Res Bull 2003;38:1343 –4.