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

Aiming to improve the corrosion resistance of Nd–Fe–B sintered magnets, Nd 6 Co 13 Cu powders are introduced into a near-stoichiometric Nd 2 Fe 14 B 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 H cj above 12.5 kOe, remanence B r 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 Nd 2 Fe 14 B grains.