氧含量对烧结NdFeB磁体晶界调控的影响

Influence of Oxygen Content on Grain Boundary Control of Sintered NdFeB Magnet

晶界扩散技术经过近些年的发展,研究人员对晶界扩散技术的涂覆化合物种类、涂覆方式、热处理工艺等进行了系统的研究。O元素是烧结NdFeB磁体生产环节中重要的影响因素,但对晶界扩散的影响却很少被研究。通过调节磁体制备工艺,获得不同O含量的NdFeB磁体,并对磁体分别进行Tb4O7和TbHx晶界扩散。得出当涂覆增重小于7 mg·cm^-2时,两种化合物对磁体矫顽力的提升幅度基本一致。当涂覆增重为11 mg·cm^-2时,随着基体中O含量的增加,两种化合物对矫顽力的提升都有不同程度的减弱。EPMA结果显示:Tb4O7晶界扩散后O,Tb元素主要分布于三角晶界处,呈团聚状态。TbHx晶界扩散后Tb元素分布相对弥散,浓度梯度不明显。在高O基体中,相同涂覆量条件下,TbHx晶界扩散后对矫顽力提升幅度比Tb4O7晶界扩散后高1.6 kOe。

A large number of research works were involved in the Grain boundary diffusion(GBD)process.The influences of parameters,such as the types of coating compound,coating method and annealing technology on the GBD process,were investigated.However,there are few reports focusing on the influence of oxygen content in magnets on the effect of GBD process.In this work,influence of different oxygen contents in initial magnets on the effect of GBD process was studied by using Tb4O7 and TbHx as coating compounds,respectively.The coercivity(Hcj)increment of Tb4O7/TbHx GBD treated magnets is similar when Tb increment value is lower than 7 mg·cm^-2.If Tb increment value is 11 mg·cm-2,the Hcj increment of TbHx GBD treated magnet is obviously higher than that of Tb4O7 GBD treated magnet.From EPMA mappings,it can be obviously seen that the O and Tb of magnet diffused by Tb4O7 are more centralized than that of magnet diffused by TbHx.If Tb increment value is 11 mg·cm^-2,the Hcj increment of TbHx GBD treated magnet(3060×10^-6)is obviously higher than that of Tb4O7 GBD treated magnet.