晶界扩散深度对烧结Nd-Fe-B磁体磁性能影响的实验与计算分析,Journal of Alloys and Compounds

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晶界扩散深度对烧结Nd-Fe-B磁体磁性能影响的实验与计算分析
Journal of Alloys and Compounds ( IF 5.8 ) Pub Date : 2024-04-03 , DOI: 10.1016/j.jallcom.2024.174320
Jie Wang , Suxin Lu , Fugang Chen , Zhong Lei , Yong Zhao , Juan Fu , Yingang Wang , Lanting Zhang

晶界扩散工艺（GBDP）已被广泛应用于提高Nd-Fe-B磁体的矫顽力。采用富 Dy/Tb 扩散源的 GBDP 后，2:14:1 主相晶粒外延层上形成的富 Dy/Tb 壳的厚度从磁体表面向中心减小。然而，富Dy/Tb壳梯度分布对磁性能的影响尚未得到深入研究。在这项工作中，烧结 Nd-Fe-B 磁体在 860°C 下使用 PrTbCu 合金进行 GBDP 不同的扩散时间（3 小时、6 小时和 9 小时）。 GBDP 3 h 后，矫顽力从 884 kA/m（无 GBDP）迅速提高到 1533 kA/m。随着扩散时间增加至 6 小时，矫顽力进一步增加至 1741 kA/m。但进一步将扩散时间延长至9 h只能获得边际矫顽力增强（升至1803 kA/m）。微观结构分析表明，较长的扩散时间导致表面晶粒粗化，从而降低了扩散效率。同时，微磁模拟表明，当磁体中心富Tb壳厚度小于4 nm时，随着富Tb壳厚度均匀性的增强，矫顽力显着增加。但如果磁体中心富Tb壳的厚度高于4 nm，则进一步提高富Tb壳的厚度均匀性无法有效提高矫顽力。这项工作的结果阐明了磁性能依赖于扩散时间的机制，并有助于将来优化 GBDP 参数。

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Experimental and calculational analysis about the influence of the grain boundary diffusion depth on the magnetic properties of a sintered Nd-Fe-B magnet

The grain boundary diffusion process (GBDP) has been widely applied to increase the coercivity of Nd-Fe-B magnets. After GBDP with Dy/Tb-rich diffusion sources the thickness of the Dy/Tb-rich shell formed on the epitaxial layer of the 2:14:1 main phase grain decreases from the magnet surface to the center. However, the influence of the Dy/Tb-rich shell gradient distribution on magnetic properties has not been thoroughly studied. In this work, a sintered Nd-Fe-B magnet was subjected to GBDP with PrTbCu alloy at 860°C for various diffusion times (3 h, 6 h and 9 h). The coercivity improves rapidly from 884 kA/m (without GBDP) to 1533 kA/m after GBDP of 3 h. The coercivity further increases to 1741 kA/m with increased diffusion time to 6 h. But only marginal coercivity enhancement (rising to 1803 kA/m) can be obtained by further prolonging the diffusion time to 9 h. Microstructure analysis indicates that the long diffusion time leads to the surface grain coarsening, which degrades the diffusion efficiency. Meanwhile, micromagnetic simulation indicates that if the thickness of the Tb-rich shell in magnet center is less than 4 nm, the coercivity increases significantly with the enhanced thickness uniformity of the Tb-rich shell. But if the thickness of the Tb-rich shell in magnet center is higher than 4 nm, the coercivity cannot be improved effectively by further increasing the thickness uniformity of the Tb-rich shell. The results in this work clarify the mechanism of the magnetic property dependence on the diffusion time and help to optimize the GBDP parameters in the future.

更新日期：2024-04-03

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