Comprehensively improved magnetic performance of Nd-Fe-B magnets with high-efficiency grain boundary diffusion of heavy rare earth

Comprehensively improved magnetic performance Nd-Fe-B magnets with extremely limited amount of Heavy Rare Earth (HRE) elements are obtained to meet the increasingly demanding applications. In this work, Tb-Co thin film with uniform distribution, flat surface and strong adhesion is successfully prepared by magnetron sputtering, and the effects of Tb-Co film thickness on the magnetic properties are investigated. The magnets with optimal magnetic properties are achieved when the film thickness is about 3.5 mu m, the coercivity of 1284.81 kA/ m, the remanence of 1.48 T, and the maximum magnetic energy product of 437.32 kJ/m3, compared with the original magnets, enhancing by 47.9 %, 0.4 % and 5.7 %, respectively, so the magnetic properties have been comprehensively improved using little amount of HRE and Co elements. HRTEM and EPMA results revealed that Tb-rich shell distributed around the Nd2Fe14B grain. The mechanisms of the remanence and coercivity simultaneous enhancement of Nd-Fe-B magnets is elaborated in detail. Besides, the diffusion of Tb-Co thin film can enhance thermal stability of the magnets.