High-efficiency utilization of Tb in enhancing the coercivity of Nd-Fe-B magnets by multicomponent Tb70-xPrxCu10Al10Zn10 (x=0-30) film diffusion

The effect of multicomponent Tb70-xPrxCu10Al10Zn10 (x = 0-30) film diffusion on microstructure and magnetic properties of sintered Nd-Fe-B magnets was investigated in this paper through magnetron sputtering system. The coercivity increased significantly from 11.5 kOe to 17.5 kOe, 18.8 kOe, 19.8 kOe, and 17.8 kOe for the processed samples by Tb40Pr30Cu10Al10Zn10, Tb60Pr10Cu10Al10Zn10, Tb(70)Cu10Al(10)Zn(10) and Tb, respectively. The remanence and the maximum magnetic energy product of multicomponent film diffused magnets were all higher than those of Tb diffused magnet. Particularly, compared with Tb diffused magnet, the Delta H-cj/wt%Tb (the coercivity enhancement per wt% Tb usage) of Tb40Pr30Cu10Al10Zn10, Tb60Pr10Cu10Al10Zn10 and Tb70Cu10Al10Zn10 diffused samples increased by 105%, 63.4% and 57.5%, respec-tively. It is obviously that the Tb utilization in multicomponent diffusion sources has a higher efficiency in coercivity enhancement. The quantitative analysis of Tb distribution was characterized for comparison. The extra addition of Cu/Al/Zn elements in Tb70Cu10Al10Zn10 diffusion source would enter into the rare earth-rich (RE-rich) grain boundary phases, and an easy diffusion channel was formed to promote the infiltration of Tb element. The results show that improved distribution uniformity of the Tb-rich shell, deeper shell-core structure and the increased local grain boundary phases are the key factors for the significant enhancement of coercivity in multicomponent diffusion magnet. In addition, on one hand, the easily combination of Tb and Cu/Al/Zn elements effectively prevented Tb from entering the main phases. On the other hand, the thinner shell-core structure was observed due to the uniform distribution of Tb in Tb70Cu10Al10Zn10 diffused magnet. These two factors jointly lead to the increase of remanence. This work puts forward that using multicomponent alloy as diffusion sources provides a composition diversity and cost-effective way to enhance the magnetic properties of sintered Nd-Fe-B magnets, while reducing the consumption of Tb. (C) 2022 Published by Elsevier B.V.