Coercivity of the Nd–Fe–B hot-deformed magnets diffusion-processed with low meltingtemperature glass forming alloys

Nd- and Pr-based alloys with bulk glass forming ability and low melting temperatures,Nd60Al10Ni10Cu20 and Pr60Al10Ni10Cu20, were used for grain boundary diffusion process toenhance the coercivity of hot-deformed magnets. The coercivity increment was proportional tothe weight gain after the diffusion process. For the sample with 64% weight gain, the coercivityincreased up to 2.8 T, which is the highest value for bulk Nd–Fe–B magnets that do not containheavy rare-earth elements, Dy or Tb. Approximately half of the intergranular regions wereamorphous and the remaining regions were crystalline. Magnetic isolation of the Nd2Fe14Bgrains by the Nd-rich amorphous/crystalline intergranular phases is attributed to the largecoercivity enhancement. The coercivity does not change after the crystallization of theintergranular phase, indicating that the coercivity is not influenced by the strain at theinterface with the crystalline intergranular phase.

This work was in part supported by JST, CREST. UMRS thanks ESICMM for post-doctoral fellowship.