Effectof grain boundary diffusion with DyH2 and DyH2+Cu on Nd-Ce-Fe-B sintered magnets
The sintered Nd-Ce-Fe-B magnet with cerium accounting for 40.6％of the total rare earth weight was prepared using a dual-main phase sintering process,followed by grain boundary diffusion using DyH2 and DyH2+Cu,respectively.The coercivity has been improved at a cost of slight reduction of the remanence and maxi-mum magnetic product.Under the same diffusion process conditions,the enhancement effect of DyH2+Cu dif-fusion on the coercivity of magnets is higher than that of DyH2 diffusion.In DyH2+Cu diffusion magnets,Dy atoms can diffuse to deeper parts of the magnet,and core-shell structure can exist at deeper positions.Cu aided DyH2 diffusion makes grain boundary phase be more continuous.This is related to the increased fluidity of the grain boundary phase by Cu atoms.The micromagnetic simulation results confirm that the grain boundary diffu-sion of Dy can enhance the coercivity of the magnet.
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