Improved corrosion resistance of low rare-earth Nd–Fe–B sintered magnets by Nd6Co13Cu grain boundary restructuring

•Nd6Co13Cu is introduced into a near-stoichiometric Nd2Fe14B magnet.•More comprehensive corrosion resistance is obtained in the restructured magnets.•Electrode potential difference between intergranular phase and matrix is reduced.•Good magnetic property is obtained due to the optimized microstructure.

Aiming to improve the corrosion resistance of Nd–Fe–B sintered magnets, Nd6Co13Cu powders are introduced into a near-stoichiometric Nd2Fe14B magnet by grain boundary restructuring. The restructured magnet containing only 28.46 wt% (Pr, Nd) shows much better corrosion resistance against hot/humid, acidic and saline environments than the un-restructured magnet with equivalent rare earth content (REC). It results mainly from the formation of higher electrode potential Co-rich phase and Cu-rich interface layers in the intergranular regions. Besides, magnetic properties of the restructured magnet are well retained with coercivity Hcj above 12.5 kOe, remanence Br above 14.0 kGs and maximum magnetic energy product (BH)max above 48.5 MGOe respectively. It can be ascribed to the formation of more continuous grain boundary phase that isolates well the neighboring Nd2Fe14B grains.