M.S. Kesler, M.J. Thompson, A. Palasyuk, O. Palasyuk, M.A. McGuire
Oak Ridge National Laboratory,
United States
Keywords: permanent magnets, thermomagnetic processing, Cerium Gap Magnet, rare-earth-free
Summary:
The reliance on critical materials for key technologies poses a national security threat. Of particular concern is the need for critical rare earths for fabricating magnets. Currently, NdFeB-based magnets fill a large application space. Many of these applications do not require the high performance of sintered NdFeB magnets, so it is diluted to form a bonded magnet with polymers like nylon. These bonded magnets generally fill a performance regime whose substitute magnet material candidates are referred to as ‘gap’ magnets. As of yet, there are no practical substitute gap magnet materials that can make a significant impact affecting criticality. CeCuCo-based alloys are a promising critical rare-earth-free magnet material system to fill the gap. This material forms a hard magnet upon casting which is an important factor for scalability and, thus, market impact. However, a lack of crystallographic and magnetic alignment in these cast structures limits performance. In the current work, casting and a subsequent homogenization and annealing heat treatment in the applied magnetic field, of the monolithic material, results in a more complete transformation into the target hard magnetic phase leading to improvements in magnetization and coercivity, even over their powdered and magnetically aligned counterparts. This enables a scalable approach of obtaining fully dense, anisotropic, critical rare-earth-free gap magnets, which eliminates the costly and hazardous powder processing steps typically needed for modern rare-earth magnet production.