Re-exchange of Fe and Cu at the interface in sintered Nd–Fe–B magnets: A method to eliminate Fe precipitation at grain boundaries |
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| Authors: | YuQi Yang HengGang Si Hao Yang Lan Zhang DongFang Huang BaiYi Chen Fang Xu YongMei Hu BaoJun Han |
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| Institution: | 1. School of Material Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China;2. Center of Analysis and Testing, Jiangxi University of Science and Technology, Ganzhou 341000, China;3. Gannan Normal University, Ganzhou 341000, China |
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| Abstract: | According to the decoupling hypothesis for magnetic grains, the coercivity in sintered Nd–Fe–B magnets is increased after Cu doping, which is due to the formation of non-magnetic grain boundaries. However, this method partially fails, and ferromagnetic Fe-segregation occurs at the grain boundary. We discovered both experimentally and through calculation that the Fe content at the grain boundaries can be tuned across a wide range by introducing another element of Ag. Segregated Fe at high temperature at the grain boundary re-dissolves into Nd2Fe14B grains during annealing at low temperature. Both configurable and magnetic entropies contribute a large driving force for the formation of nonmagnetic grain boundaries. Almost zero Fe content could be achieved at the grain boundaries of sintered Nd–Fe–B magnet. |
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| Keywords: | Nd–Fe–B Grain boundaries Magnetic materials First-principle calculation |
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