Effect of Pr-Ga dual-alloys diffusion on magnetic properties and thermal stability of hot-deformed PrNd-Fe-B magnets

Abstract To investigate the influence of the addition of Pr-Ga alloys on magnetic properties and morphology of materials, the hot-deformed PrNd-Fe-B magnets were prepared by the addition of Pr-Ga alloys using a dual-alloys diffusion. The room-temperature coercivity of the hot-deformed PrNd-Fe-B magnets increased substantially from 1.68 to 2.34 T, while the remanence decreased from 1.42 to 1.24 T, by the addition of 5 wt% Pr-Ga alloys. Moreover, the thermal stability of coercivity improved from –0.46%/oC to –0.42%/oC. Two types of grain boundary phases (PrNd-rich and PrNd-Ga-rich) were generated at grain boundaries by microstructural analysis, resulting in the decrease of Fe element concentration from more than 60% to about 10% at grain boundaries. The decrease of ferromagnetic element concentration at grain boundaries and the refinement of grain are considered to the main reasons for the improvement of coercivity and thermal stability.