Effect of two-stage deformation on magnetic properties of hot-deformed Nd–Fe–B permanent magnets

The effect of pre-straining at and below 823 K prior to hot forging at 973 K on the magnetic properties of hot-deformed Nd–Fe–B magnets was examined. Nd–Fe–B alloys prepared in this study could be hot-forged, even at 723 K. Both the squareness and the coercivity of the magnetization curves at room temperature were improved by pre-straining at 773 K or below, owing to the suppression of the formation of non-aligned coarse Nd2Fe14B grains.