Crystallization Behavior and Magnetic Properties of Nanocrystalline Sm(Co0.9Cu0.1)5 Alloy

The nanocrystalline SmCo₅ permanent magnet alloy demonstrates exceptional magnetic properties owing to its distinctive nanoscale microstructure. In this study, leveraging crystallization annealing to regulate the SmCo₅ amorphous alloy microstructure, a systematic temperature-time-controlled strategy was proposed to optimize its nanocrystalline microstructure. The effects of the annealing time and temperature on the crystallization, phase evolution, and magnetic properties of this alloy were systematically studied. Sm(Co_0.9Cu_0.1)₅ nanocrystalline alloys were obtained via high-energy ball milling (HEBM) and then annealed at 550–700°C. The amorphous phase initially transformed into metastable Sm(Co,Cu)₇ phase, followed by the gradual transition to the Sm(Co,Cu)₅ main phase and Sm₂(Co,Cu)₁₇-R trace phase. Upon annealing at 550°C for 30 min, ~ 15-nm nanocrystals were formed in the alloy, with coercivity (H_c) = 5.4 kOe and remanence (M_r) = 28.5 emu/g. H_c gradually increased with increasing annealing temperature, while M_r increased slightly at 600°C and then gradually decreased. After annealing at 650°C for 4 h, the alloy exhibited uniform grains with moderate sizes and clear grain boundaries. Furthermore, H_c substantially increased to 31.1 kOe and M_r rose to 35.2 emu/g. These results contribute to elucidate the role of the amorphous-to-crystallization mechanism in improving the magnetic properties of SmCo₅-based or similar alloys.