烧结NdFeB永磁合金的边界显微结构与磁硬化

BOUNDARY MICROSTRUCTURE AND MAGNETIC HARDENING OF SINTERED NdFeB MAGNET

用TEM观察了烧结NdFeB永磁合金的内边界显微结构,发现该合金存在4种类型的边界。回火前后前三类边界的形貌没有变化,而第4类边界的显微结构发生了显著的变化。用SAED和AES分析了第4类边界的成分与结构,该边界由两个区域组成,即富Nd相区和Nd_2Fe_(14)B晶粒的外延层。回火时,由于原子的扩散和物质迁移,Nd_2Fe_(14)B晶粒的外延层发生了磁硬化,因而合金的矫顽力得到提高。

The boundary microstructure of the sintered alloy Nd_(15.5)Fe_(77)B_(7.5) hasbeen studied by TEM, ASE and SAED. It may distinguish the boundaries into 4types. The first three types remain the same during annealing, and the 4th changesits microstructure remarkably. The 4th type of boundary microstructure is composedof two different regions, i. e., the central Nd-rich phase and the epitaxial layer ofthe Nd_2Fe_(14)B grains. Owing to the atomic diffusion and other types of masstransport,magnetic hardening occurred in the epitaxial layers, thus the coercivity of the alloywill be improved.