烧结Nd-Fe-B磁体的晶界精细结构研究进展

Research progress on fine structure of grain boundary in sintered Nd-Fe-B magnets

烧结Nd-Fe-B磁体的矫顽力不仅与其各向异性场(HA)有关,同时严重依赖磁体的微观组织结构。只有几纳米厚的富Nd晶界薄层,以及存在于晶界角隅处的尺度较大的富Nd晶界相,对Nd-Fe-B磁体的矫顽力有重要影响。长期以来,Nd-Fe-B磁体中晶界相被含糊地称为“富钕相”。首先简要回顾了相关领域早期的研究结果,包括:烧结钕铁硼磁体的相组成、微结构特点及其与磁体矫顽力的关系;然后结合最新的研究进展,重点对磁体的晶界相组成和晶界成分、晶界磁性质、添加元素的影响、以及回火以后晶界显微结构的演变和微磁学模拟结果进行综合分析。最后,结合Nd-Fe-B相图研究结果,对目前研究中存在的问题进行探讨,指出今后需要努力的方向。

The coercivity of a sintered Nd-Fe-B magnet is not only related to the magneto-crystalline anisotropy field(HA), also depends severely on the microstructure. There are very important influence on the coercivity of the grain boundary(GB) phases with only a few nanometer thickness existed between two NdFeB grains, and the larger size of GB phases at the triple junctions of grains. However, for a long time, the thin GB phases and triple junction phases are vaguely called as "Nd-rich phases". The study results of the early stage, including phase structures, microstructure characteristics, and the coercivity of sintered magnets, werefirst briefly reviewed. Next, combining with the latest research progress, the phase identification, chemical composition, magnetism of GB, and the influence of added elements were emphatically analyzed. At last, considering the Nd-Fe-B phase diagram, the current problems in the research field were discussed, and the research trends of GB fine structure in Nd-Fe-B magnets were pointed out.