Enhancing the grain boundary diffusion efficiency of Nd-Fe-B magnet by synergistic diffusion of multi-component alloy: A review

Nd-Fe-B permanent magnets with excellent magnetic performance have been extensively employed in various fields. The rapid development of downstream industry also puts higher requirements on the magnetic properties of the Nd-Fe-B magnets. Heavy rare-earth elements (HRE) such as Dy and Tb are generally introduced into the magnets to significantly enhance their coercivity, but it also leads to a considerable deterioration in remanence. The grain boundary diffusion (GBD) process has been developed to improve the coercivity of Nd-Fe-B magnet with reduced consumption of HRE. Considering the scarcity and high cost of HREs, the researchers have explored various methods to improve the diffusion efficiency of HREs during GBD process, among which multi-alloy synergistic diffusion has attracted much attention. Based on the latest research progress and the research work of the author's team, this paper summarizes the mechanism of elemental synergistic effect on improving the diffusion efficiency and service performance of sintered Nd-Fe-B magnets by multi-component alloy diffusion sources. The effects of multiple elements and composite diffusion sources are described and discussed. An outlook on the future development of synergistic GBD process is also presented.