Tb扩散对NdFeB磁体微观组织和性能的影响

Effects of Tb Diffusion on Microstructure and Properties of Nd Fe B Magnets

利用直流磁控溅射技术在烧结NdFeB磁体的单极面镀不同厚度Tb膜,并进行热扩散及退火处理,研究了不同厚度Tb膜及热处理工艺对磁体的影响。结果表明,3.137μm膜厚对磁体内禀矫顽力提升最明显,并在850℃×7 h+500℃×2 h热处理条件下,获得的磁性能最佳,其内禀矫顽力从872.36 kA/m提升到1305.67 kA/m;20~160℃的剩磁温度系数α从-0.1226%/℃减小至-0.1230%/℃,略有降低,但矫顽力温度系数β从-0.5534%/℃明显增大至-0.52967%/℃。利用SEM观测Tb扩散磁体的近表面及深处的微观结构,可以发现明显的(Nd,Tb)_(2)Fe_(14)B核壳结构及分布较均匀的富Nd相,这是磁体磁性能提升的主要原因。

DC magnetron sputtering technology were used to coat Tb films of different thicknesses on the unipolar surface of sintered NdFeB magnets,and the thermal diffusion and annealing treatment were carried out.The results show that,3.137μm film thickness is the most coercivity of magnet most obviously,and under the heat treatment conditions of 850℃×7h+500℃×2 h,the best magnetic properties are obtained,and its coercivity increases from 872.36 kA/m to 1305.67 kA/m,the temperature coefficient of remanenceαat 20-160℃decreases from-0.1226%/℃to-0.1230%/℃,which are slightly lower,but the temperature coefficient of coercivityβincreases from-0.5534%/℃to-0.5297%/℃.The microstructure of the near surface and deep part of the Tb diffusion magnet is observed by SEM,it can be found that the obvious(Nd,Tb)_(2)Fe_(14)B core-shell structure and the more uniform distribution of rich Nd phase are the main reasons for the improvement of the magnetic properties of the magnet.