Coercivity enhancement of hot-deformed Nd–Fe–B magnets with Pr–Cu alloy addition

Abstract

Effects of low-melting Pr–Cu alloy addition on the microstructure and magnetic properties of the hot-deformation Nd–Fe–B magnets were investigated. A small amount of Pr–Cu addition enhances the coercivity of the hot-deformation Nd–Fe–B magnets obviously. The coercivity of the hot-deformation Nd–Fe–B magnets with 4.0 wt% Pr85Cu15 addition increases to 1271 kA·m−1, 75.69% higher than that of Pr–Cu-free magnet (723 kA·m−1), and then decreases with 5 wt% Pr85Cu15 addition. It is observed that there a uniform RE-rich phase is formed wrapping the Nd2Fe14B main phase in the sample with 4.0% Pr85Cu15 addition by scanning electron microscopy (SEM), which promotes the coercivity. The angular dependence of coercivity for the hot-deformation Nd–Fe–B magnets indicates that the coercivity mechanism is nucleation combined with domain wall pinning. The domain wall pinning is weakened, while the nucleation is enhanced after Pr–Cu addition. The remanence, intrinsic coercivity, and maximum magnetic energy product of the original Nd–Fe–B magnet are 1.45 T, 723 kA·m−1, and 419.8 kJ·m−3, respectively, and those of the sample with 4.0% Pr85Cu15 alloy addition are 1.30 T, 1271 kA·m−1, and 330.0 kJ·m−3, respectively.