Phase composition and magnetic properties of SmCo5/Fe nanocomposite powder prepared by cryomilling

Ball milling temperature is a significant factor influencing the phase composition and magnetic properties of ball-milled powders. We compare the morphology, phase composition and magnetic properties of SmCo ₅ and SmCo ₅/Fe powders produced through cryomilling and conventional milling techniques. Our findings indicate that cryomilling effectively inhibits cold welding and phase transformations, reduces contamination, and enhances the magnetic properties of powders compared with conventional ball milling. Larger sized particles formed due to cold welding were observed in conventional milled powders, while better dispersion was observed in cryomilled powders. Sm ₂Co ₁₇ phase appeared in the SmCo ₅ powder after 12 h of conventional ball milling, while only an amorphous phase was found in the cryomilled one. When ball milling time was extended from 2 h to 12 h, the Fe content in the conventional milled SmCo ₅ powder increased from 4.6 wt% to 7.9 wt%, which was much higher than that in the cryomilled SmCo ₅ powder (from 1.4 wt% to 2.2 wt%). After 8 h of ball milling, the coercivity of the cryomilled SmCo ₅ powder reached 3.01 kOe, representing a 64.48 % increase compared with that of the conventional milled powder. The saturation magnetization of cryomilled SmCo ₅/Fe composite powder was 122.89 emu/g, which is 4.34 % higher than that of the conventional milling. As the annealing temperature increases from 500 °C to 700 °C, the main phase of the hard magnetic phase in the SmCo ₅/Fe nanocomposite powders transformed from SmCo ₃ phase to Sm ₂Co ₁₇ phase, and the content of the soft magnetic Fe(Co) phase is decreasing, and the coercivity is increasing. SmCo ₅/Fe cryomilled magnetic powder annealed at 550 °C possesses a M _r of 79.63 emu/g, a M _r/M _s of 0.71, a H _c of 6.16 kOe, which are much higher than that of the conventional milled SmCo ₅/Fe powder annealed at 550 °C. This work provides a ball milling process optimization strategy for the preparation of high performance nanocomposite magnets.