烧结钕铁硼(Al+Cu)含量对晶界扩散的影响

本研究对(Al+Cu)含量分别为0.25%的钕铁硼基体和0.5%基体进行Dy晶界扩散,并分析了矫顽力、Dy含量分布和微观结构。通过比较两种磁体的成分、性能发现,在Dy增加量基本相同的情况下,高(Al+Cu)磁体扩散后的矫顽力提高量相较于低(Al+Cu)磁体高37kA/m~43kA/m。进一步进行成分、矫顽力的梯度分析发现,基体的(Al+Cu)含量变化并没有改变扩散后磁体内部Dy元素随扩散深度的浓度分布,但是矫顽力梯度分析结果显示高(Al+Cu)的各片层矫顽力提升量均比低(Al+Cu)片层高40 kA/m~80 kA/m。后续的EPMA的Dy面分布图显示,高(Al+Cu)基体扩散后Dy在晶界处富集条纹更清晰、连续,而TEM的EDX分析结果也显示高(Al+Cu)样品中晶界附近Dy含量更高。(Al+Cu)含量的提高,使得晶界相的流动性增强,Dy更加连续包裹主相晶粒,使得Dy增加量相同的情况下进一步提升矫顽力。

Influence of (Al+Cu) content on grain boundary diffusion in Nd-Fe-B sintered magnet

In the present work, Nd-Fe-B base magnets with 0.5% and 0.25% (Al+Cu) were treated by Dy grain boundary diffusion process and the coercivity distribution, Dy content distribution and microstructure were analyzed. By comparing the composition and properties of the two types of magnets, it was found that the coercivity increment of high (Al + Cu) magnet is 37 kA/m ~ 43kA/m higher than that of low (Al + Cu) magnet in spite of the same Dy increment. Further gradient analysis of composition and coercivity showed that the change of (Al + Cu) content does not change Dy distribution versus to the diffusion depth, but the coercivity increments of high (Al+Cu) magnet slices were 40kA/m~ 80kA/m higher than those of low (Al+Cu) slices. The subsequent EPMA Dy mapping images showed that Dy-rich shells were distributed more clearly and continuously at the high (Al+Cu) magnet, and the TEM EDX analysis results also showed Dy concentration near the grain boundary region is higher in the high (Al+Cu) magnet. With the increase of (Al + Cu) content, the fluidity of grain boundary phase is enhanced and Dy-rich shell wraps the main phase grains more continuously, which further enhances the coercivity with the same Dy increment.