Mechanism and microstructure evolution of high temperature oxidation of end-of-life NdFeB rare earth permanent magnets

Abstract The behaviour of rare earth permanent magnets during oxidation profoundly determines the high temperature recycling processes. This current study analysed the microstructure evolution of end-of-life, coated NdFeB rare earth permanent magnets after oxidization at 973-1473 K under ambient air conditions. Four distinct categories of microstructure evolution were observed at the temperatures of 973 K, 1073 K, 1173-1273 K, and 1373-1473 K. The presence of a Ni/Cu/Ni coating was found to significantly affect the oxidation mechanism. The distinct oxide morphologies developed at these temperatures have different implications for designing strategies for the recycling process.