A Rapid Consolidation Route for Recycled NdFeB Powders and the Role of Particle Shape in Grain Growth

The recycling of NdFeB magnets is essential to reduce reliance on critical rare earth elements and mitigate the environmental burden of virgin magnet production. Hydrogen Processing of Magnetic Scrap (HPMS) offers an efficient method to extract magnet powders from end-of-life (EOL) products, yet oxidation and microstructural degradation during powder preparation limit the magnetic performance of recycled magnets. In this work, rapid Radiation-Assisted Sintering (RAS) was systematically evaluated for the first time as a consolidation route for HPMS-derived powders. Magnets prepared via RAS exhibited performance comparable to those obtained by conventional sintering. When oxygen uptake during milling was prevented, the addition of 1 wt.% NdH₃ to the already oxygen-burdened recycled powder improved the intrinsic coercivity and squareness of the demagnetization curve. The best-performing samples achieved B_r = 1.18 T, (BH)_max = 263 kJ/m³, and H_ci = 742 kA/m at 100 °C, surpassing the properties of the original EOL magnets. Furthermore, the study revealed that, when the HPMS powder fragments preferentially break along grain boundaries, the resulting near-equilibrium powder particles exhibit limited growth, thereby restraining grain coarsening. These findings highlight the strong potential of RAS for more energy-efficient magnet-to-magnet recycling and provide new insight into optimizing HPMS powder processing to achieve enhanced magnetic performance.