Magnetic Properties and Microstructures of Spark Plasma Sintered Sm-Co-Fe-Cu-Zr-Hf Magnets Under Various Heat Treatment Conditions

A spark plasma sintering technique was applied to fabricate full dense and fine-grain Sm 24.6 Co 50 Fe 17.4 Cu 5.7 Zr 1.3 Hf 1.0 magnetic alloys. The microstructure, phase constituents, and magnetic performance were systematically studied by applying various treatment conditions. It is observed that the single 1:7H phase exists in the solution-treated magnet and then decomposes into the 1:5H phase and 2:17R phase during the isothermal aging treatment and slow cooling treatment. The remanence ( J r ) of 0.55 T, intrinsic coercivity ( H cj ) of 870 kA/m, and maximum magnetic energy product (( BH ) max ) of 45 kJ/m 3 are obtained for the final state magnet prepared with optimal conditions. The investigated alloys showed excellent thermal stability in the temperature range of 300 to 673 K. As the heat treatment progressed, the distribution of Cu element tends to be more uniform. Completed cellular structure and lamellar phase are observed in the magnets. The current research work might be a potential reference for further research and development work on Sm 2 Co 17 -based permanent magnets by the short process.