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

Abstract The grain boundary diffusion process was applied to the commercial sintered Nd–Fe–B magnets using Pr 68 Cu 32 , Dy 70 Cu 30 and Pr 35 Dy 35 Cu 30 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 Pr 68 Cu 32 , higher than 1402.7 kA/m by Dy 70 Cu 30 . Microstructural investigations showed that the evident coercivity enhancement for the sample by Pr 68 Cu 32 was mainly attributed to continuous intergranular layers isolating Nd 2 Fe 14 B grains. Nevertheless, the coercivity enhancement of the sample by Dy 70 Cu 30 was mainly resulted from the magnetic strengthening of the extensive layers in Nd 2 Fe 14 B grains.