Unveiling the microstructural evolution and magnetic properties of NdCeFeB magnets prepared by hot-pressed sintering

Improving Ce utilization is an important measure for the sustainable and balanced utilization of rare earth permanent magnets. In this work, Nd-Pr-Fe-B and Nd-Ce-Fe-B ribbons, along with low-melting-point PrCu alloy powders, were uniformly mixed and subsequently hot-pressed to fabricate a nanocrystalline magnet with high Ce content. The results indicate that raising the temperature enhances PrCu alloy diffusion into grain interiors but also stimulates grain growth, thereby constraining further coercivity enhancement. To overcome this challenge, we have devised a two-step sintering process that effectively promotes PrCu diffusion while inhibiting excessive grain growth, resulting in a high coercivity of 1515 kA/m. Furthermore, microstructure evolution and its correlations with magnetic properties were systematically examined, showing that the enhancement in coercivity is attributed to the strengthened magnetic isolation and the formation of a Pr-containing shell. This suggests that the proposed two-stepped hot-pressed process is a feasible method for enhancing coercivity. • A non-heavy rare earth PrCu alloy is selected as the diffusion source for grain boundary diffusion. • A two-step hot-pressing process was developed to enhance PrCu alloy diffusion while suppressing grain growth. • A well-defined Pr-containing shell improves the coercivity by enhancing the reversed domain nucleation field. • The relationship between the evolution of microstructure and its magnetic properties was elucidated.