Recycling of Sintered NdFeB Magnet Wastes Using Nd85Al15 Alloy Diffusion

In this paper, the regenerated NdFeB magnets were fabricated by Nd85Al15 alloy diffusion, and the influence of alloy content and diffusion temperature on the properties and microstructure was systematically studied. The recovery mechanism of magnetic properties was discussed based on the analyses using scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electron probe microanalysis (EPMA) observation. The results indicate that the coercivity (Hcj) increases significantly with both alloy addition and temperature, reaching the maximum value of 1087 kA/m (80.9% enhancement) compared with the non-diffused magnet (601 kA/m). The maximum remanence (Br) and maximum energy product (BHmax) of the diffused magnet are 0.99 T and 184.7 kJ/m3, which are 8.8% and 5.9% lower than those (1.085 T and 196.3 kJ/m3) of the non-diffused magnet. The density and compressive strength of the diffused magnet are enhanced by 8.2% (7.25 g/cm3) and 67.47% (628 MPa), respectively. As the compensation of Nd85Al15 melt, the density, Br and BHmax are improved via the liquid filling into pores. Simultaneously, the Hcj is enhanced through the repair of grain boundary defects and the formation of continuous Nd-rich phases.