(07A736) Studies of sintered MRE-Fe-B magnets by DyF_3 addition or diffusion treatment (MRE = Nd + Y + Dy)

摘要

Sintered MRE_2(Fe, Co)_(14)B magnets by DyF_3 blending or diffusion treatment were investigated. "Base-line" magnets with a thickness of 1.5 mm were coated (painted) with DyF_3 powder and heated to promote Dy diffusion at 800-900 °C, i.e., "Diffusion" magnets. For comparison, the magnet alloy powder for making Base-line magnets was blended with 3-5 wt.% DyF_3 powder and then made into sintered magnets, i.e., "Blended" magnets. The coercivity and (BH)_(max) of Base-line magnets were 9.7 kOe and 32.7 MGOe, respectively, while the coercivity of Diffusion magnets was increased to 15 kOe and the (BH)_(max) was nearly unchanged at 31.4 MGOe. Blended magnets with 5 wt% DyF_3 had a coercivity of 17.8 kOe, but the (BH)_(max) was reduced to 25.4 MGOe, due to a considerable reduction of remanence. The total Dy concentration in the MRE_2(Fe, Co)_(14)B Diffusion magnets with a β value of -0.5%/°C was 5.3 wt%, while typical commercial Nd-based Nd_2Fe_(14)B magnets require at least 7.5 wt% Dy to achieve the same β. Therefore, the MRE_2(Fe, Co)_(14)B Diffusion magnets exhibited better temperature stability.