Magnetic properties and microstructures of Sm2Co17type magnets produced by cycle-aging

Effects of aging treatments of a precipitation hardened type magnetic alloy, Sm(Co0.67Fe0.21Cu0.08Ni0.02Zr0.02)7.6, were investigated with regard to their coercivity and their magnetization process. It was found that repeated continuous coolings from starting temperature of 1053K to final temperature of 673K are very effective means to induce a high coercivity in this material together with a good square I-H loop. For example, the magnetic properties of the magnet obtained by three cycles of continuous coolings are as follows; Br =1.08T,bHc=693kA/m, iHc =820kA/m, Hk=637kA/m and(BH){\max} =223kJ/m³. It was observed that this magnet has a finer multiphase structure in comparison with the magnet of about the same iHc value which is produced by the well-known single continuous cooling from higher starting temperatures. The relationships between microstructures and magnetic properties of magnets of this cycle-aging are also discussed.