Effect of Nd-Ho-Al-Ga diffusion on coercivity and thermal stability of hot-deformed PrNd-Fe-B magnets

In this study,to enhance the coercivity and high-temperature stability of hot-deformed PrNd-Fe-B magnets,the NdHoAlGa alloy was utilized as a diffusion source and a dual-alloy diffusion process was employed to enhance the room temperature coercivity from 1.72 to 2.28 T.For the magnet doped with7 wt% Nd72.3Ho13.8Al2.3Ga11.7,within the temperature range from 20 to 200℃,the remanence temperature coefficient a increases from-0.16%/℃ to-0.14%/℃,and the coercivity temperature coefficient βincreases from-0.49%/℃ to-0.43%/℃.By controlling grain boundary（GB） phases and optimizing the main phase simultaneously,Ga was induced to motivate the formation of non-ferromagnetic GB phases,reducing the size of grains and intergranular exchange coupling.Additionally,Ho was diffused into the main phase,forming（Pr,Nd,Ho）-Fe-B phase,which enhances the magnetic crystalline anisotropy field of the main phase grains at high temperatures.