Utilizing thermomagnetic processing to optimize rare-earth content and resultant properties in Nd2Fe14B-based bonded magnets

Z.P. Tener, X. Liu, I. Nlebedim, M.J. Kramer, M.A. McGuire, M.S. Kesler
Oak Ridge National Laboratory,
United States

Keywords: rare-earth, magnetism, processing, recycling


Thermomagnetic processing is a relatively underutilized technique that alters both the temperature and magnetic field parameter space of standard processes, and can have far reaching benefits. Performing HDDR (hydrogenation, disproportionation, desorption, recombination) on Nd2Fe14B feedstock reduces the microstructural grain size towards the theoretical single magnetic domain, and is utilized in the production of anisotropic, hard magnetic powders, as well as a recycling pathway for end-of-life magnets. By utilizing concurrent thermomagnetic processing with HDDR, we show how we can produce anisotropic Nd2Fe14B powders with improved magnetic properties relative to samples processed without an applied field. Furthermore, we investigate the dependence of the magnetic properties of the resultant powder by discretely and sequentially altering the strength of the applied DC fields. Finally, we compare the values obtained post-TMP-HDDR between a lab-synthesized feedstock and commercially-attained sintered magnet utilizing X-ray diffraction, magnetometry, and electron microscopy. This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.