Coercivity enhancement of nanocrystalline hot-deformed Nd-Fe-B magnets by low-melting eutectic MM-Cu(MM=La,Ce,Pr,Nd) alloys addition |
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| Affiliation: | 1. CAS Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, 315201, China;2. School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;4. University of Dayton, Dayton, OH, 45469, USA;1. Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan;2. Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571, Japan;3. Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193, Japan;1. Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, Tsukuba 305-0047, Japan;2. Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577, Japan;3. Toyota Motor Corporation, Advanced Material Engineering Div., Susono 410-1193, Japan;4. Center for Integrated Sensor Systems, Danube University Krems, Krems, Austria;1. Jiangxi Key Laboratory for Rare Earth Magnetic Materials and Devices/Institute for Rare Earth Magnetic Materials and Devices (IREMMD), Jiangxi University of Science and Technology, Ganzhou 341000, People''s Republic of China;2. Faculty of Materials, Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, People''s Republic of China;1. Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba, 305-0047, Japan;2. Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8577, Japan;3. Institute for Solid State Physics, University of Tokyo, Kashiwa-no-ha 5-1-5, Kashiwa, 277-8581, Japan;1. Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China;2. Anhui Key Laboratory of Metal Materials and Processing, School of Materials Science and Engineering, Anhui University of Technology, Maanshan 243002, China |
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| Abstract: | MM85Cu15 (MM = La, Ce, Pr, Nd) eutectic alloys were added into the hot-deformed Nd-Fe-B magnets to enhance the coercivity. It is found that three endothermic peaks occur on the differential scanning calorimetry curve of the MM-Cu melt-spun ribbons at 432.2, 451.1 and 516.5 °C. The peaks substantially correspond to three types of MM-Cu low-melting eutectic phase. The coercivity of magnets increases when the MM-Cu content is lower than 4 wt%, and then keeps almost no change with the content further increasing to 5 wt%. The coercivity of the hot-deformed magnets with 4 wt% and without MM-Cu addition is 948 and 683 kA/m, respectively. Nearly all the platelet-shaped grains are isolated by the thickened intergranular phase after MM-Cu addition. Moreover, the average grain size of the magnets with MM-Cu addition decreases compared with that of the magnet without MM-Cu addition. Scanning electron microscopy images show that the areal fraction of the RE-rich grain boundary phase increases from 8.6% to 15.1% after MM-Cu addition. The La, Ce together with Cu and Ga aggregate at the grain boundary regions separating neighboring grains and smoothing the grain boundaries. Therefore, both the thickened grain boundary and decreased mean grain size result in the enhancement of coercivity after MM-Cu eutectic alloy addition. |
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| Keywords: | Hot deformation Nd-Fe-B Coercivity MM-Cu eutectic alloy Rare earths |
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