Coercivity enhancement in hot-pressed Nd-Fe-B permanent magnets with low melting eutectics

Nd-Fe-B melt-spun ribbons with optimized composition for hot workability have been hot-compacted together with low melting DyCu, DyNiAl, NdCu, and NdAl powders to enhance coercivity. Annealing at 600 degrees C leads to an interdiffusion of Dy and Nd at the interfaces between the Nd-Fe-B flakes and the Dy-rich phase. This modifies the grain boundary phase and thus further enhances coercivity without decreasing remanence. The higher coercivity for DyCu compared to DyNiAl was attributed to the lower melting point obtained by differential scanning calorimetry. For NdCu and NdAl, annealing was found to be ineffective.