Highly thermally stable Nd0.6Y0.4-Fe-B magnet with a spontaneous shell-strengthened structure by Tb alloying

Abstract

Thermally stable Nd0.6Y0.4-Fe-B magnet with 0.83 at% Tb alloying was yielded with a coercivity of 1.58 T and a temperature coefficient (β20–120 ℃) of − 0.531%/°C. Microstructure analyses showed that the aggregation of Y in the core region essentially dominated the heterogeneous distribution of rare earth (RE) elements in the matrix phase grains, leading to the enrichment of Pr, Nd and Tb in the outer layers of matrix grains. The preferred regulation of Y for Tb distribution contributed to the spontaneous Tb-rich shells with strengthened anisotropy field, significantly mitigating the inevitable degradation of coercivity caused by the high Y-substitution. Continuous non-ferromagnetic grain boundary phases were also constructed to isolate the adjacent grains. The synergistic effect of above microstructural modification presents a reliable new strategy to compensate for the magnetic dilution effect of Y and promote the effective utilization of Tb.