Advanced REE Magnets require new thermal process technologies

The development of next-generation rare earth element (REE) magnets—particularly NdFeB-based systems—relies increasingly on innovative thermal process technologies to improve efficiency, sustainability, and material performance. Among these, hydrogen decrepitation (HD) has emerged as a critical enabler for both primary production and recycling of REE magnets. This paper examines the pivotal role of HD in transforming coarse-grained cast alloys into fine, friable powders with controlled particle morphology and minimal oxidation, providing an ideal precursor for subsequent sintering and grain boundary diffusion treatments. The HD process not only reduces energy consumption and processing time compared to mechanical pulverization but also enables selective separation pathways in magnet recycling, contributing to circular economy strategies. We analyze key parameters such as hydrogen pressure, temperature profiles, and alloy composition to optimize decrepitation kinetics and magnetic properties. Furthermore, the integration of HD with advanced thermal cycles—including low-oxygen sintering and targeted annealing—is shown to significantly enhance coercivity, thermal stability, and microstructural uniformity. This paper concludes that a redefinition of thermal processing around hydrogen-based techniques is essential for scaling the production and sustainability of advanced REE magnets for electric mobility, wind energy, and high-performance applications.