Waste Nd-Fe-B Sintered Magnet Recycling by Doping With Rare Earth Rich Alloys

Waste sintered Nd-Fe-B permanent magnets were recycled via doping (Nd₂₀Dy₈₀)₇₆Co₂₀Cu₃Fe₁ special alloy (SA) powders. The effect of the SA on the microstructure and magnetic properties of the recycled magnets has been studied. The SA additives between 0.0 and 2.0 wt% have little effect on the remanence (B_r) of the recycled magnet. When the additive content is more than 2.0 wt%, the remanence (B_r) begins to decrease. The coercivity of recycled magnet increases gradually as the SA additive increases. Compared with the properties of the original waste sintered magnet, a magnet recycled with 2.0 wt% SA recovers 97.5%, 92.4%, and 93.1% of B_r, H_cj and (B_H)_max, respectively. The volume fraction of the Nd-rich phase reaches a maximum of 7.4 vol% for 2.0 wt% SA, which is nearly equal to that of the original waste magnet. The average grain size of all the recycled magnets is larger than that of the original waste magnet. It is our conclusion that currently 2.0 wt% SA additive is the best content for recovering the properties of the waste magnets.