Microstructure evolution and coercivity enhancement in Pr_(50)Dy_(20)Cu_(15)Ga_(15)-doped hot-deformed Nd-Fe-B magnets

摘要

To improve the coercivity (H_(cj)) and thermal stability of hot-deformed (HD) Nd-Fe-B magnets, Pr_(50)Dy_(20)Cu_(15)Ga_(15) (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 Pr_(50)Dy_(20)Cui_5Ga_(15) alloy powders are investigated. The H_(cj) of the HD magnets is enhanced from 1242 kA/m to 1595 kA/m by doping 3 wt.% Pr_(50)Dy_(20)Cu_(15)Ga_(15) alloy powders. The thermal stability of the doped HD magnet is also improved at high temperatures. The better isolation of Nd_2Fe_(14)B grains by rare earth-rich (RE-rich) phases and the formation of local high-anisotropy (Nd, Pr, Dy)_(2Fe_(14)B hard magnetic phases are the main reasons for the increase of H_(cj). 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.