Enhancement of coercivity of hot-deformed Nd–Fe–B anisotropic magnet by low-temperature grain boundary diffusion of Nd60Dy20Cu20 eutectic alloy

The coercivity of a hot-deformed Nd–Fe–B magnet was enhanced from 1.6 to 2.6 T by a low-temperature grain boundary diffusion process using a Nd60Dy20Cu20 near-eutectic alloy. The alloy melt infiltrates into the magnet through grain boundaries at the processing temperature of 650 °C. The composition of ferromagnetic elements in the intergranular phase parallel to the c-planes decreases substantially and thin Dy-rich shell surrounds the Nd2Fe14B phase grains after the diffusion process, which explains the large enhancement in coercivity.