The Influence of Cu Powders Doping on Magnetic and Mechanical Properties of Sm2Co17 Permanent Magnets

In this work, the influence of Cu powders doping on the magnetic and mechanical properties of Sm2Co17 permanent magnets is systematically investigated. For high-energy-product Sm2Co17 (low initial Cu content), the intrinsic coercivity is significantly improved from 11.7 to 25.7 kOe with 1 wt.% Cu powders doping. The flux loss (soaking at 300 degrees C for 2 h) is reduced from 7.4% to 3.8%, and the average flexure strength is improved from 60.2 to 74.1 MPa. For high-temperature-resistant Sm2Co17 (high initial Cu content), the intrinsic coercivity is slightly reduced from 39.2 to 38.3 kOe with 1 wt.% Cu powders doping. The flux loss (soaking at 300 degrees C for 2 h) is increased from 1.4% to 3.4%, and the average flexure strength is improved from 86.7 to 93.2 MPa. The differences in magnetic properties change of these two Sm2Co17 permanent magnets are closely related with their initial Cu content. The doped Cu is prone to diffuse into intragranular cell boundaries in magnet with low initial Cu content. The increased Cu content in intragranular cell boundaries benefits the improvement of intrinsic coercivity, thus enhancing the thermal stability and reducing the flux loss. Doping Cu powders may increase the Cu-rich phase around ground boundaries, which will hinder the grain growth during heat treatment. The decrease of grain size will enhance the flexure strength, while it will increase the flux loss.