合金化元素Al和Cu的微量添加对铽晶界渗透的影响

Influence of(Al+Cu)Micro-adding on Tb Boundary Diffusion in Nd-Fe-B Sintered Magnet

研究了(Al+Cu)质量分数为0.23%、0.3%、0.35%和0.55%时烧结钕铁硼Tb晶界扩散对磁性能、外观和微区成分的影响。随着(Al+Cu)含量的增加,大尺寸产品(宽度大于20 mm)表面的麻坑现象越来越严重,H提高的幅度越来越小。微观EDS分析发现,当(Al+Cu)含量增加时,晶界扩散后晶界内Tb含量减少。(Al+Cu)形成的共晶化合物主要分布在晶界处,在高温扩散时,增加了扩散通道的液相浸润性,少量时有利于晶界扩散,而(Al+Cu)含量较高时,对于Tb置换出来的Nd形成的新的富钕相的延展具有阻碍作用,不利于渗透;这种液相的富足也是导致外观不良主要诱因。

The influence of(Al+Cu)micro-adding on sintered NdFeB with Tb grain boundary diffusion are investigated on magnetic properties,appearance and microdomain composition with the(Al+Cu)mass fractions 0.23%,0.3%,0.35%and 0.55%.With the increase of(Al+Cu)content,the pitting phenomenon on the surface of large-size products(the width is no more than 20 mm)is more and more serious,and the increasing of Hcj becomes smaller and smaller.Microscopic EDS analysis found that when the(Al+Cu)content increased,the Tb content in the grain boundaries decreased after grain boundary diffusion process.The eutectic compound formed by(Al+Cu)is mainly distributed at the grain boundary.When diffusing at high temperature,the liquid phase wettability of the diffusion channel is increased.A small content is beneficial to the grain boundary diffusion.When the content of(Al+Cu)is too high,it has a hindering effect on the extension of the new neodymium-rich phase formed by Nd replaced by Tb,which is not conducive to diffusion;the abundance of this liquid phase is also the main cause of poor appearance.