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

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 center dot m(-1), 75.69% higher than that of Pr-Cu-free magnet (723 kA center dot 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 center dot m(-1), and 419.8 kJ center dot m(-3), respectively, and those of the sample with 4.0% Pr85Cu15 alloy addition are 1.30 T, 1271 kA center dot m(-1), and 330.0 kJ center dot m(-3), respectively.