Effect of Dy2O3 intergranular addition on thermal stability and corrosion resistance of Nd-Fe-B magnets

Sintered Nd-Fe-B magnets with and without Dy2O3 were prepared by powder blending method. The temperature-dependent magnetic properties, thermal stability, microstructure and corrosion resistance of sintered magnets were investigated. The temperature-dependent magnetic properties revealed that with intergranular addition of Dy2O3, the reversible temperature coefficients β and α in the range of 293-373 K were both lowered, indicating that the thermal stability was effectively improved. This was also verified by the decreased irreversible flux loss (hirr) and the increased maximum operating temperature (MOT). Moreover, the electrochemical and accelerated corrosion results clearly evidenced that the corrosion resistance of Nd-Fe-B magnet was also modified by addition of Dy2O3. Furthermore, the related mechanisms on improved thermal stability and corrosion resistance were systematically discussed.