Wetting of grain boundaries in hard-magnetic Nd-Fe-B alloys

Samples of Nd-Fe-B alloys, which have been the main hard-magnetic materials with the highest magnetic energy since the end of the 1980s, are investigated. Magnets based on them are obtained by liquid-phase sintering or spin coating. In this article, wetting of the Nd2Fe14B grains by the neodymium-enriched liquid phase is investigated. The microstructure of the Fe-12.3 at %Nd-7.6 at %B alloy quenched after annealing at T = 700-1100A degrees C in the presence of a neodymium-enriched melt is studied. The acquired data indicate that the transition from incomplete to complete wetting of grain boundaries occurs as the temperature increases. The results are compared with the reference data for alloys of the Nd-Fe-B system obtained by liquid-phase sintering. The relation between the wetting phase transition of grain boundaries and magnetic properties is also discussed.