Magnetic properties and microstructure of sintered Nd–Fe–B magnets with intergranular addition of Ni powders

This paper aims to improve the magnetic properties of sintered Nd–Fe–B magnet. Ni powders were added to the Nd–Fe–B magnet through intergranular addition, and their effects on the microstructure and magnetic properties of the magnet were investigated. By adding a proper amount of Ni (0.3 wt%), the intrinsic coercivity H_cj of Nd–Fe–B magnet is significantly improved with only a slight decrease in the remanence B_r and the maximum energy product (BH)_max. The microstructural and compositional analyses reveal that Ni atoms not only enter the matrix phase but also concentrate in the intergranular regions either as Ni-containing Nd-rich phase or as Ni particles. This is consistent with the thermodynamic calculation results. Furthermore, a sintering mechanism of magnet with intergranular addition of Ni powders is tentatively proposed. These results may provide a reference for improving the magnetic properties of sintered Nd–Fe–B magnets.