Microstructure and Magnetic Properties of Grain Boundary Diffused Nd-Ce-Fe-B Magnets with Different Cerium Contents
The Ce elements with high-abundance partially replacing Nd in the Nd-Fe-B magnets can achieve high quality utilization of Ce elements,which is a hot research topic in the field of rare earth permanent mag-nets.Effects of grain boundary diffusion process and Ce content on the microstructure and magnetic properties of grain boundary diffused(GBD)Nd-Ce-Fe-B magnets were investigated using Tb-Al-Ga alloy as the diffusion source.It is shown that in the grain boundary diffused magnets with lower Ce content,Tb elements mainly form shell structure with high magneto-crystalline anisotropy field surrounding main phase grains,and Al elements wrap the main phase grains as non-magnetic phase,isolating exchange coupling between adjacent main phase grains.Therefore,the coercivity of the grain boundary diffused magnets increases substantially.In the grain boundary diffused magnets with higher Ce content,the thickness of Tb-rich shell is increasing.Al elements dif-fuse into the main phase grains resulting in remanence in decreasing and can not form non-magnetic phase to isolate the main phase grains leading to the decrease of coercivity.
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