Exploring the distinctive role of REFe2 (RE=rare earth) phase in sintered and hot-deformed Ce-containing Nd-Fe-B magnets

The distinct role of REFe2 (RE = rare earth) phase in Ce-containing Nd-Fe-B magnets remains a topic of debate. In this study, we investigated the correlation between the REFe2 phase and the magnetic properties of sintered and hot-deformed magnets. The results reveal that the REFe2 phase with a melting point lower than sintering temperature plays a positive role in promoting the liquid-phase sintering of magnets and helps to form continuous grain boundary (GB) layers. This paramagnetic REFe2 phase can act as GB layers like the RE-rich phase, which can magnetically decouple the ferromagnetic RE2Fe14B grains and ultimately improves the coercivity of sintered magnets. However, the REFe2 phase cannot melt during hot-deformation process, thus negatively impacting the formation of c-axis texture and remanence. Furthermore, the accumulation of the REFe2 phase reduces the RE-rich GB layers and promotes the formation of misaligned coarse RE2Fe14B grains, ultimately deteriorating the coercivity in hot-deformed magnets.