钕铁硼基体镝含量对晶界扩散磁性能的影响

Effect of Dy Content in Base Nd-Fe-B Magnets on Magnetic Properties after Grain Boundary Diffusion

摘要: 文章对含量分别为0 wt.%、1 wt.%和4 wt.%的3种钕铁硼基体进行了Dy晶界扩散，并分析比较了其磁性能。结果显示，所有样品在经过Dy扩散后均提升3 kOe~4 kOe的矫顽力，矫顽力提升幅度与基体初始Dy含量未发现单调或线性关联。电子探针Dy元素面分布图显示，无论基体中原有的Dy含量多与少，经过晶界扩散后Dy含量均显著增加。1 Dy和4 Dy样品中的晶界扩散，是将原有晶界Dy富集浓度进一步提高；而0 Dy样品中的晶界扩散，是磁体的晶界附近区域实现从无重稀土到高浓度重稀土覆盖的过程。对比三种样品的各向异性场，4 Dy样品的各向异性场增量只有5.33 kOe，小于0 Dy和1 Dy样品，验证了已含有Dy的磁体中进行扩散后各向异性场的增加幅度会小于0 Dy磁体。

Abstract: In this work, grain boundary diffusion of Dy was performed on three types of Nd-Fe-B substrates with Dy contents of 0 wt.%, 1 wt.%, and 4 wt.%, and their magnetic properties were analyzed and compared. The results indicate that the coercivity of all samples increases by 3 kOe to 4 kOe after Dy diffusion, and no obvious correlation is observed between the enhancement magnitude of coercivity and the initial Dy content of the substrates. Elemental mapping of Dy obtained by electron probe microanalysis (EPMA) reveals that the Dy concentration rises remarkably in all samples after grain boundary diffusion, regardless of the initial Dy content in the substrates. For the 1 Dy and 4 Dy samples, grain boundary diffusion further elevates the pre-existing Dy enrichment at grain boundaries. In contrast, grain boundary diffusion in the 0 Dy sample realizes the coverage of heavy rare earth elements with high concentration near grain boundaries, where heavy rare earths were originally absent. By comparing the anisotropy field of the three samples, the 4 Dy sample only presents an anisotropy field increment of 5.33 kOe, which is lower than that of the 0 Dy and 1 Dy samples. This finding verifies that the increase in anisotropy field caused by grain boundary diffusion is less significant for Nd-Fe-B magnets initially containing Dy than for Dy-free magnets.