Effect of heterogeneous microstructure on magnetization reversal mechanism of hot-deformed Nd-Fe-B magnets |
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| Affiliation: | 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. 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. Daido Steel Co., Ltd., Nagoya 457-8545, Japan;4. Center for Integrated Sensor Systems, Danube University Krems, Krems, Austria;1. Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba 305-0047, Japan;2. CREST, Japan Science and Technology Agency, Japan;3. Toyota Motor Corporation, Advanced Material Engineering Div., Susono 410-1193, Japan;4. St. Pölten University of Applied Science, St. Pölten, Austria;1. Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, People’s Republic of China;2. Ningbo University of Technology, Ningbo 315211, People’s Republic of China;3. University of Dayton, Dayton, OH 45469, USA;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. CREST, Japan Science and Technology Agency, Japan;4. Daido Steel Co. Ltd., Nagoya 457-8545, Japan;5. St. Pölten University of Applied Science, St. Pölten, Austria |
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| Abstract: | The hot-deformed(HD) Nd-Fe-B magnets show heterogeneous microstructure composed of coarse and fine grain regions. It is significant to fully understand the influence of this complex microstructure on the magnetization reversal process which can give the guidance for the enhancement of the magnetic properties. In this paper, the heterogeneous microstructure of the(HD) Nd-Fe-B magnets were characterized from the morphology, size, macro-texture and micro-structure. In addition, the magnetization reversal process of the HD Nd-Fe-B magnets was systematically analyzed by magnetic measurement, insitu domain evolution observation and micromagnetic simulation. The results indicate that the HD NdFe-B magnets mainly consist of fine grain regions(FGRs) and coarse grain regions(CGRs). The FGRs show plate-like grains with fine grain size and strong c-axis texture, while the CGRs show equiaxial grains with large grain size and weak c-axis texture. In particular, it is worth noting that the texture in homogeneity exists not only between FGRs and CGRs, but also inside both the FGRs and CGRs. The dominant coercivity mechanism of the HD Nd-Fe-B magnets is domain wall pinning. Also, the experimental analysis shows that the reverse domain is formed and expanded in the CGRs at low reverse applied field, while the reverse domain occurs in the FGRs at higher reverse applied field. The micromagnetic simulation results also confirm the above magnetization reversal process. In addition, micromagnetic simulation results also show that the orientation of the grains also affects the pinning strength, besides the grain size. |
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| Keywords: | Hot-deformed Nd-Fe-B magnet Heterogeneous microstructure Magnetization reversal Coercivity mechanism Rare earths |
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