Abstract: An addition of Nb up to 2 at.-% into(Nd,Dy)-(Fe,Co)-B alloy causes the formation of dendrite Fe_2Nb and the precipitates in hard magnetic grains.Both increases with increasing Nb content.During sintering,part of Fe_2Nb dissolves within the 2:14:1 grains, and the Fe_2Nb along grain boundaries hinders the growth of 2:14:1 grains.During an- nealing,the dissolved Nb in(?)-phase precipitates out,and this nearby the grain boundary diffuses into Nd-rich phase to form new granular Fe_2Nb and to increase the Nb content in Nd-rich phase,this results in a precipitate-free zone in the(?)-grain near Nd-rich phase.

Key words: NdFeB, rare earth permanent magnet, microstructure