A. Palasyuk
Ames National Laboratory,
United States
Keywords: cerium, samarium, cobalt, gap magnet, price, performance
Summary:
In commercial permanent magnets, ferrites and NdFeB occupy 90% of the current permanent magnet market. The main reason for this is their price/performance of ~ 2 $/kg per MGOe (or ~ 12 $/m3 per MGOe), that is acceptable for mass market manufacturing. While ferrite magnets are less costly, they cannot accommodate the size requirements of many magnetic assemblies. Due to these size constraints, NdFeB magnets have gained popularity and use, resulting in increased consumption of critical elements such as neodymium (Nd) and dysprosium (Dy). However, for the vast variety of applications, these magnets are stronger than they need to be. There is a disconnect, i.e., the gap between those two polar cases as there is no middle performance magnet satisfying similar price/performance characteristics. Intensification of the magnet processing by avoiding typical powder routes may facilitate better price/performance, especially for the commercially available niche market magnets like SmCo. Being superior in resistance to demagnetization, temperature performance and corrosive environments, these magnets are manufactured using fine powders, which builds up to 30 – 40 % to their total market price. Efficient processing, accompanied by usage of noncritical cerium (Ce) and reduced amounts of cobalt (Co), as well as novel magnesium (Mg) alloying techniques, significantly reduces processing cost and creates an opportunity for the new SmCo-derivative magnets with middle strength and performance characteristics suitable for the mass market. Our experiments show that these magnets easily achieve energy products (BH)max. beyond 20 MGOe, whereas their unique intra-granular coercivity mechanism does not require typical powder metallurgy. Preliminary, the mechanism is regulated by the 2:7/5:19-type stacking faults and/or spinodal decomposition that appear in the matrix. This opens potential for simple processing and/or advanced manufacturing. Our casting experiments show that (BH)max. beyond 20 MGOe, with Curie temperatures of >500 oC, remanent magnetizations > 9 kG and coercivities > 6.5 kOe, are achievable in one-step procedure that includes vacuum induction melting of kg-scale ingots with precisely controlled cooling process. Acknowledgement: This work was supported by the Critical Materials Innovation Hub, funded by the U.S. Department of Energy. The work was performed at Ames National Laboratory, operated for the U.S. Department of Energy by Iowa State University of Science and Technology.