Zr and Si co-substitution for SmCo7 alloy with enhanced magnetic properties and improved oxidation and corrosion resistances

Abstract The effects of Zr and Si co-substitution on the magnetic properties, oxidation and corrosion resistances of TbCu 7 -type Sm–Co alloys have been investigated. Zr addition is very effective in promoting the formation of TbCu 7 -type structure and it contributes to the most of the coercivity enhancement. The largest coercivity of 1389 kA/m was obtained for SmCo 6.3 Zr 0.4 Si 0.3 alloy. Si addition can significantly improve the oxidation resistance. After exposure in air at 500 °C for 90 h, the thickness of the oxidation layer was just 106 μm for as-cast SmCo 6.4 Zr 0.3 Si 0.3 alloy compared to 230 μm for the SmCo 6.7 Zr 0.3 alloy. The room temperature coercivity of SmCo 6.4 Zr 0.3 Si 0.3 ribbon is as high as 884 kA/m after exposure at 300 °C in air for 10 min. The improved corrosion resistance for Si added alloys was also confirmed by polarization curve measurement. Zr and Si co-substitution provides a good approach for enhancing both the coercivity and resistances to oxidation and corrosion of the TbCu 7 -type Sm–Co alloy.