The grain boundary diffusion process of Pr-Al-Cu at various temperatures has been applied in the sintered Nd-Fe-B magnets. Detailed evolution of the grain boundary phases and its influence on the magnetic properties were investigated. Microstructure analysis showed that the shell morphology rich in Pr and Al was significantly formed in the diffusion process at 700 °C, which was determined as (Pr,Nd)₂(Fe,Al)₁₄B phase, while Al is homogeneous in the 900 °C diffused magnets. After the annealing treatment, continuous grain boundary phases were generated in the 700 °C diffused magnet to isolate the neighbouring grains even at the depth of 1000 µm, whereas that in the 900 °C diffused magnet were scarce. Thus a pronounced enhancement of coercivity from 16.21 kOe to 21.36 kOe was yielded in the annealed 700 °C diffused magnet. Transmission electron microscopy showed that the thickness of the Pr and Al rich shell in the matrix phase grains was dramatically decreased during the annealing process. The absent shell layers facilitate the formation of (Pr,Nd)₆(Fe,Al,Cu)₁₄ phase in the intergranular regions. Also the residual diffusion source on the surface of the diffused magnets was supposed to promote the development of continuous grain boundary phases during the annealed process. Based on these results, the temperature-dependent microstructure and magnetic properties evolution was detailedly discussed.

Pr-Al-Cu 在不同温度下的晶界扩散工艺已应用于烧结 Nd-Fe-B 磁体。研究了晶界相的详细演变及其对磁性能的影响。显微组织分析表明，在700℃扩散过程中明显形成富含Pr和Al的壳形貌，确定为(Pr,Nd) ₂ (Fe,Al) ₁₄B 相，而 Al 在 900 °C 扩散磁体中是均匀的。退火处理后，700℃的扩散磁体中产生连续的晶界相，即使在1000μm的深度也将相邻的晶粒隔离，而900℃的扩散磁体中则很少。因此，在退火的 700 °C 扩散磁体中，矫顽力从 16.21 kOe 显着提高到 21.36 kOe。透射电子显微镜显示，在退火过程中，基体相晶粒中富含 Pr 和 Al 的壳层的厚度显着降低。缺少的壳层有利于 (Pr,Nd) ₆ (Fe,Al,Cu) _14的形成相在晶间区。此外，扩散磁体表面上的残余扩散源被认为促进了退火过程中连续晶界相的发展。基于这些结果，详细讨论了温度相关的微观结构和磁性能演变。