Advanced REE Magnets Require New Thermal Process Technologies

Abstract Developing 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. Compared to mechanical pulverization, the HD method uses less energy and takes less processing time. It also makes selected separation paths possible in magnet recycling, which supports circular economy initiatives. To maximize decrepitation kinetics and magnetic characteristics, we examine important variables such as alloy composition, temperature profiles, and hydrogen pressure. Furthermore, the integration of HD with advanced thermal cycles—including low-oxygen sintering and targeted annealing—is shown to enhance coercivity, thermal stability, and microstructural uniformity significantly. 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. Experimental work of high quality is expensive, much more so than multiscale computational modeling, physics- and data-informed. This shift of paradigm toward using much more computational work, constructing digital twins, and modern AI/ML technologies will dramatically accelerate the process of improving the fundamental properties of REE magnets. They will result in the rapid discovery of new materials and industrial processes of their production, including sophisticated novel heat treatments.