Microstructure evolution and coercivity enhancement in Pr50Dy20Cu15Ga15-doped hot-deformed Nd-Fe-B magnets

To improve the coercivity (Hcj) and thermal stability of hot-deformed (HD) Nd-Fe-B magnets, Pr50Dy20Cu15Ga15 (at.%) alloy powders with minor heavy rare earth (HRE) are introduced. The magnetic properties, thermal stability and microstructure of the HD magnets with different amounts of Pr50Dy20Cu15Ga15 alloy powders are investigated. The Hcj of the HD magnets is enhanced from 1242 kA/m to 1595 kA/m by doping 3 wt.% Pr50Dy20Cu15Ga15 alloy powders. The thermal stability of the doped HD magnet is also improved at high temperatures. The better isolation of Nd2Fe14B grains by rare earth-rich (RE-rich) phases and the formation of local high-anisotropy (Nd, Pr, Dy)2Fe14B hard magnetic phases are the main reasons for the increase of Hcj. Notably, the non-uniform aggregation of RE-rich phases results in the inhomogeneity of magnetic anisotropy, which eventually leads to the large openness of the recoil loops. This study gives an intuitive view on the relationship between microstructure evolution and magnetic properties of the HD magnets.