Boundary structure modification and magnetic properties enhancement of Nd-Fe-B sintered magnets by diffusing (PrDy)-Cu alloy

The grain boundary diffusion process was applied to the commercial sintered Nd-Fe-B magnets using Pr68Cu32, Dy70Cu30 and Pr35Dy35Cu30 ribbons as direct diffusion source. The coercivities increased from 1114.4 kA/m for the original magnet to 1642.8 kA/m for the processed magnet by Pr68Cu32, higher than 1402.7 kA/m by Dy70Cu30. Microstructural investigations showed that the evident coercivity enhancement for the sample by Pr68Cu32 was mainly attributed to continuous intergranular layers isolating Nd2Fe14B grains. Nevertheless, the coercivity enhancement of the sample by Dy70Cu30 was mainly resulted from the magnetic strengthening of the extensive layers in Nd2Fe14B grains.