Abstract：The coercivity of a sintered Nd-Fe-B magnet is not only related to the magneto-crystalline anisotropy field (HA), also depends severely on the microstructure. There are very important influence on the coercivity of the grain boundary (GB) phases with only a few nanometer thickness existed between two Nd2Fe14B grains, and the larger size of GB phases at the triple junctions of grains. However for a long time, the thin GB phases and triple junction phases are vaguely called as "Nd-rich phases". In the paper, the study results in the early stage, including phase structures, microstructure characteristics, and the coercivity of sintered magnets, are first briefly reviewed; next, combining with the latest research progress, the phase identification, chemical composition, magnetism of GB, and the influence of added elements are emphatically analyzed; at last, considering the Nd-Fe-B phase diagram, the current problems in the research field are discussed, and the research trends of GB fine structure in Nd-Fe-B magnets are pointed out.
2022, Vol. 29 