Enhancement of thermal stability of Nd–Fe–B sintered magnets with tuned Tb-diffused microstructures via temperature control
Enhancement of thermal stability of Nd–Fe–B sintered magnets with tuned Tb-diffused microstructures via temperature control
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DOI：
10.1016/j.jallcom.2020.157478
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发表时间：
2021-02
影响因子：
6.2
通讯作者：
Sumin Kim;H. Lee;W. Nam;Donghwan Kim;W. Shin;J. Roh;Wooyoung Lee
中科院分区：
文献类型：
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作者：
Sumin Kim;H. Lee;W. Nam;Donghwan Kim;W. Shin;J. Roh;Wooyoung Lee
我们研究了在不同晶界扩散温度和附加热处理温度下制备的 Tb 扩散 Nd-Fe-B 磁体的磁性能和热稳定性。这些热处理工艺提高了 Tb 扩散 Nd-Fe-B 磁体比基础磁体的矫顽力。研究发现扩散温度在控制磁热稳定性方面发挥着关键作用；温度变化引起磁体中解耦铽扩散微结构的精确变化。在高扩散温度下制造的磁体在室温下表现出最好的矫顽力，但热稳定性较差。这是由于在较高温度下扩散过程中形成了富Tb (Tb, Nd)2Fe14B 相，该相具有高磁晶各向异性，并且在晶粒内部产生了较少的核壳结构。在较低扩散温度下制备的磁体观察到最好的热稳定性。该磁体比其余磁体具有更良好的核壳结构。通过使用电子显微镜和微磁方程分析其微观结构，发现具有扩散 Tb 原子的解耦微观结构主要负责更好的热磁稳定性。本文获得的结果表明优化的扩散温度可以提供具有良好热稳定性的磁体。
We investigate the magnetic properties and thermal stability of Tb-diffused Nd–Fe–B magnets prepared at various grain-boundary diffusion temperatures and additional heat-treatment temperatures. These heat-treatment processes improved the coercivity of Tb-diffused Nd–Fe–B magnets than that of the base magnets. The diffusion temperature was found to play a key role in controlling the magnetic thermal stability; temperature variations induced precise changes in the decoupled Tb-diffused microstructures in the magnets. The magnet fabricated at a high diffusion temperature showed the best coercivity at room temperature but poor thermal stability. This was due to the formation of Tb-rich (Tb, Nd)2Fe14B phases with high magnetocrystalline anisotropy produced inside the grains and less core–shell structures during diffusion at a higher temperature. The best thermal stability was observed for the magnet prepared at a lower diffusion temperature. This magnet had more well-formed core–shell structures than the remaining magnets. By analyzing its microstructure, using electron microscopy and a micromagnetic equation, it was found that a decoupled microstructure with diffused Tb atoms was mainly responsible for the better thermal magnetic stability. Results obtained herein suggest that an optimized diffusion temperature can provide a magnet with good thermal stability.