Effects of Cu nanopowders addition on magnetic properties and corrosion resistance of sintered Nd–Fe–B magnets

Sintered permanent magnets have been prepared by blending Nd–Fe–B jet-milled powders with Cu nanopowders (0, 0.05, 0.1 and 0.2 wt%) before pressing in a perpendicular magnetic field. Permanent magnetic properties, Curie temperature ( T c ), microstructures and corrosion resistance of the sintered magnets were investigated. Microstructural characterization revealed that the grain size of Nd 2 Fe 14 B phase was refined and more homogeneous, and the grain boundaries became clear and smooth by the addition of Cu nanopowders, resulting in the improvement of coercivity H c j . Moreover, the corrosion resistance of Nd–Fe–B magnets was also improved. However, T c remained nearly unchanged with Cu addition, which was consistent with the elemental analysis results. Cu was not detected in the matrix phase Nd 2 Fe 14 B, but concentrated in the intergranular region.