Coercivity strengthening mechanism of Nd(-Ce)-Fe-B magnet by grain boundary diffusing Pr-Tb-Al-Ga alloy
The coercivity of sintered Nd-Fe-B magnets can be improved and the cost can be reduced when light rare earth is used as the diffusion source to replace part of heavy rare earth.In this paper,the heavy rare earth Tb in Tb-Al-Ga alloy was partially replaced by low-cost light rare earth Pr.The effects of Pr substitution on the magnetic properties and microstructure of sintered dual-main-phase Nd-Ce-Fe-B magnets and sintered single-main-phase Nd-Fe-B magnets were studied,and the coercivity strengthening mechanism was revealed.With Pr60Tb20Al10Ga10 as the diffusion source,the coercivity of the grain boundary diffusion magnet increases obvi-ously.Compared with the single main phase magnet,the diffusion depth of the double main phase magnet is sig-nificantly increased.Pr with low melting point preferentially enters the magnet and improves the wettability of grain boundary phase.This causes more Tb elements to enter more deeply in magnet,forming a shell structure with high magneto-crystalline anisotropy field surrounding main phase grain,and then improving the coercivity of GBDed magnet.
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