HIGH-RESOLUTION SCANNING ELECTRON-MICROSCOPY STUDY ON SINTERED AND CAST NDFEB MAGNETS

By using a field-emission gun scanning electron microscope, the micros tructural details in sintered and cast NdFeB magnets can be revealed e ither at high resolution (below 50 nm) or at low magnification (100 X) to view a larger area. In all sintered NdFeB based magnets, we found many Nd2O3 particles about 1 mum in diameter. The Nd-rich phase is not limited to the Nd2Fe14B (2-14-1) grain boundaries; some areas of this phase have dimensions similar to those of the 2-14-1 grains. rhe micr ostructure of cast NdFeB-based alloys strongly depends on the doping e lements. An alloy containing Co and V shows a dendritic Fe-V primary p hase with long thin 2-14-1 grains, while an alloy containing Co and Nb shows larger 2-14-1 grains with all phases in the ingot corresponding to phases in the sintered magnets.