Phase composition tailoring and coercivity mechanism of high-performance high-abundance rare-earth sintered magnets

The widespread adoption of Nd-Fe-B magnets with abundant and cheap Ce substitution for Nd is significantly constrained by the inherently inferior magnetic properties exhibited by Ce-Fe-B. In this study, high-performance Nd-Ce-Fe-B sintered magnets with Nd-Fe-B + Ce-Fe-B (N-C-type) and Nd-Fe-B + (Nd, Ce)-Fe-B (N-NC-type) compositions are successfully developed through the design of dual-alloy components, which facilitate precise control over the distribution of rare-earth (RE) elements in the dual-main-phase grains. The N-C-type exhibits higher remanence ( B _r) and magnetic energy product [( BH) _max], whereas the N-NC-type demonstrates higher coercivity ( H _cj). The magnetic properties of the as-sintered magnet with 20 wt.% of Ce over the total RE content are optimized via B _r of 14.25 kG, H _cj of 8.6 kOe, and ( BH) _max of 48.6 MGOe. After annealing, H _cj increases to greater than 10 kOe and ( BH) _max remains at 47 MGOe. Through the implementation of reasonable composition design and the optimization the preparation processes in these grains, the RE elements exhibit a clear stepwise heterogeneity of the chemical composition in their core-shell structure, whereas the shell structures of these grains display a homogeneity of chemical composition. The results provide a reference for the composition design and development of high-performance high-abundance RE sintered magnets for enhancing the utilization of high-abundance RE elements in permanent magnetic materials and contributing to a more balanced exploitation of RE resources.