Super-high coercivity NdFeB magnet fabricated with double Tb-rich/lean shells by double alloy method and grain boundary diffusion

In this work, the high performance NdFeB magnet were fabricated by double alloy method and grain boundary diffusion Tb70Cu20Ga10 alloys. The maximum energy product (BH)max and coercivity Hcj of the magnet are 45.33 MGOe and 35.46 kOe, respectively. The reversible temperature coefficients of coercivity of the diffusion magnets improve from − 0.456%/°C to − 0.412%/°C at the range of 22 °C −180 °C. The magnetostatic loss of NdFeB magnet was analyzed in high temperature applications by general finite element method (FEM). The RE-(Fe,CuGaO) grain boundary phases and double Tb-rich/lean shells improve the utilization rate of heavy rare earths and coercivity of magnets after diffusion. The magnetization reversal mechanism of double core-shell microstructures had been discussed. This work may shed light on developing coercivity above 30 kOe of NdFeB magnet with low heavy rare earth through modified microstructure.