回火处理对烧结Nd-Fe-B磁体结构与磁性能的影响

Effects of tempering on the microstructure and magnetic properties of sintered Nd-Fe-B magnets

应用常规粉末冶金工艺制备(Pr-Nd)32Dy0.60FebalNb0.75Cu0.20Al0.55B1.15烧结磁体,分析了回火处理对磁体显微组织、取向度、磁性能的影响。结果表明,回火处理之后,显微组织中富Nd相分布较为均匀,不存在薄层状富Nd相的晶粒边界数量减少,同时富B相数量增加,磁体取向度稍有提高,磁体内禀矫顽力显著上升,而其剩磁则表现出比较明显的下降。显微组织中形成较多数量富B相是烧结状态磁体回火处理之后剩磁降低的主要原因。

（Pr-Nd）32Dy0.60FebalNb0.75Cu0.20A10.55B1.15 sintered magnets were prepared with conventional powder metallurgy technique. Effects of tempering on microstructure, orientation degree and magnetic properties of these magnets were analyzed. As a consequence of tempering, Nd-rich phase becomes uniformly distributed, Nd2FeI4B grain boundaries without a thin layer of Nd-rich phase between them are reduced, and the amount of B-rich phase is increased, orientation degree of NdEFel4B grains is slightly enhanced, the intrinsic coercivity is greatly improved and the remanence is obviously decreased. It was found that the formation of relatively large amounts of B-rich phase in the microstructure was the main reason for the obvious decrease in remanence after the sintered magnets are tempered.