烧结态NdFeB磁体基体相和富B相的微观组织分析

Microstructure Analysis of Matrix Phase and Boron-rich Phase in Sintered NdFeB Magnets

制定了一种机械抛光加振动抛光,适合NdFeB磁体的EBSD试样制备方法。采用扫描电镜(SEM)、能谱仪(EDS)和电子背散射衍射(EBSD)装置对烧结态NdFeB材料的显微组织进行研究。结果表明,试验用烧结NdFeB主要由基体相(Nd,Pr)_(2)Fe_(14)B,富Nd、Pr相和富B相组成,合金基体相具有强烈的晶体学c轴方向平行于磁场取向轴的择优取向,大部分基体相的晶粒尺寸为2~7μm,平均晶粒尺寸约为4μm。在低加速电压(5 kV)下富B相的背散射电子成像衬度优于高电压(20 kV)的。能谱分析表明,合金中的方块状的富B相主要由Fe、Nb和B元素组成。可在5 kV加速电压下应用虚拟标样库对富B相进行微区成分定量分析。

The EBSD specimen preparation method suitable for NdFeB magnets was set up,which was composed of mechanical polishing and vibration polishing.Microstructures of sintered NdFeB materials were investigated by scanning electron microcopy(SEM)、energy dispersive spectrum(EDS)and electron backscatter diffraction(EBSD)equipment.The results indicate that sintered NdFeB magnets are composed of matrix phases(Nd,Pr)_(2)Fe_(14)B,Nd-rich,Pr-rich phases and boron-rich phases.The EBSD results reveal that the matrix phases of alloy have strong preferred crystallographic orientation that c axis runs parallel to magnetic orientation axis.The grain size of most matrix phases is 2~7μm,and the average size is around 4μm.The BSE contrast of boron-rich phase at low electron accelerating voltage(5 kV)is superior than that at 20 kV.Energy spectrum analysis proves that blocky boron-rich phase is mainly composed of Fe,Nb and B,of which the micro zone can be analyzed quantitatively using virtual standard specimen library at electron accelerating voltage of 5 kV.