Effect of WS2/Al co-doping on microstructural and magnetic properties of Nd−Fe−B sintered magnets

The effect of WS2 (0-1.2 wt.%) and Al (0.3 wt.%) doping on microstructural and magnetic properties of Nd2Fe14B sintered magnets was investigated. Grain growth in WS2-doped magnets was inhibited by the grain boundary (GB) pinning resulting in increased magnet coercivity. Al co-doping (0.3 wt.%) produced continuous Nd-rich grain boundary phases (GBPs), in which fine WFeB precipitates were distributed selectively at the grain boundaries due to the higher fluidity of the liquid phases. 0.6 wt.% WS2/Al co-doped magnets are characterized by the optimum magnetic properties because of the smaller grain sizes and formation of continuous Nd-rich GB phases. When the WS2 content exceeds 0.6 wt.%, magnetic properties of the resulting magnets deteriorate due to the reduction in magnet density and relatively large WFeB precipitates formed inside the main phase and at the GBs.