Magnetic properties, corrosion resistance, and microstructure of Nd–Fe–B sintered magnets with Tb6Fe13Cu addition

We investigated the magnetic properties, corrosion resistance, and microstructure of Tb6Fe13Cu-added Nd–Fe–B sintered magnets through the magnetic measurement device, electrochemical method, and microstructure analysis. The results show that doping Tb6Fe13Cu can not only effectively improve the intrinsic coercivity but also significantly improve the corrosion resistance of the magnet. An intrinsic coercivity from 15.01 to 21.40 kOe is achieved in magnet by increasing the additive amounts of Tb6Fe13Cu to 3 wt%, while the remanence and the maximum energy product decreased slightly. It was also found that as the amount of addition increases, the corrosion potential of the magnet gradually becomes positive. Further investigations reveal that the remarkable enhancement in coercivity and corrosion resistance was owing to the formation of a Tb-rich (Nd, Pr, Tb)2Fe14B shell structure, the optimization in distribution/morphology of intergranular phases, and the more stable RE-rich phase.