Due to the increased use of wind turbines and electric vehicle motors the amount of FeNdB magnets increases and these magnets are a valuable resource that must be preserved at the end of the systems’ life-cycles. There are different ways of recycling waste magnets. By means of direct or alloy recycling, FeNdB based powders are obtained from the waste magnets, which are afterwards reprocessed into recycled magnets. In contrast to elemental recycling, no problematic chemicals and less energy is needed. The recyclate powders, which are recovered by hydrogen embrittlement and milling are mixed with additional RE-rich alloy powder and sintered again. Usually some amount of new material is necessary to compensate for the loss of RE-rich phase due to oxidation during the powder metallurgical recycling process of the magnets.
In this contribution recyclate powders of commercial magnets with high remanence as new (>N50) are used to synthesize recycled magnets. HRE-free alloy powder with a Nd content of 26 at% is added to allow formation of new grain boundary phase. For ecological and economic reasons the amount of new material is kept as low as possible. Depending on the manufacturer of the commercial magnets amounts of 0-20 wt% of RE-rich alloy are necessary to fully restore or even exceed the coercivity of the original magnets by ~40%, with only minor reduction of remanence. The microstructure and the phase fractions of the recycled magnets are determined by means of quantitative microstructure analysis. The microstructural features are related to the magnetic properties.