环境条件对NdFeB合金烧结和回火的影响

Effects of Environmental Conditions on Sintering and Tempering for NdFeB Alloys

研究了Ar保护和真空条件对NdFeB合金烧结的影响以及真空度条件对烧结NdFeB磁体回火的影响。研究发现,与真空烧结相比,采用Ar保护烧结时磁体的密度、磁能积和剩磁相对较低,矫顽力较高,磁体中形成的孔洞较多,孔径较大,并有明显的显微缩松存在,富Nd相的数量明显较多,且主要呈块状和片状沿晶界分布。与烧结态磁体采用高真空回火不同,低真空回火后磁体的密度、磁能积和剩磁上升,磁体中的孔洞既少也小,线状晶界缺陷明显较少,富Nd相更细小,分布也更均匀。结果表明,真空烧结和低真空回火分别是NdFeB合金烧结和回火较好的环境介质条件。

The effects of argon protection and vacuum on NdFeB alloy sintering and the effects of vacuum conditions on tempering of sintered NdFeB magnets were studied. It is found that, compared with the vacuum sintering, the magnet sintering at argon protection has lower density, magnetic-energy product and remanence, but coerciveforces are higher. The magnet has more and bigger pores, and there obviously exist loose microstructure, the Nd-rich phases are clearly distributed along the grain boundaries mainly in the shape of lumpish and lamelliform. It is different from the magnets with high vacuum tempering, the density, magnetic- energy product and remanence of magnets with low vacuum tempering become higher, the pores in the magnets are less and smaller, the linear grain boundary defects are obviously fewer, and the Nd-rich phases are smaller and distribute more uniformly. These results indicate that vacuum sintering and low vacuum tempering are relatively better environmental medium conditions of sintering and tempering for NdFeB alloys.