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

Abstract

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. (C) 2016 Elsevier B.V. All rights reserved.