Effect of 0.12wt%Sr Addition on Structural, Mechanical and Tribological Properties of Al-12Si+10wt%Zn Alloy

The effects of 0.12wt%Sr additive on some material properties of Al-12Si+10wt%Zn alloy were examined in this study. Al-12Si+10wt%Zn and Al-12Si+10wt%Zn+0.12wt%Sr alloys were manufactured by permanent mold casting. Microstructures of these alloys were examined with both optic and scanning electron microscopes. Phases in the alloys were identified by energy-dispersive spectroscopy and X-ray diffraction analyses. Hardness measurements were performed with the Brinell method. Mechanical and tribological properties of the alloys were investigated with tensile and friction-wear tests, respectively. The microstructure of the Al-12Si+10wt%Zn alloy consists of alpha-Al, eutectic Al-Si mixture, primary Si and beta phases. Al-12Si+10wt%Zn+0.12wt%Sr alloy includes the Al-Zn-Fe-Si and Sr-Al-Si phases in addition to phases observed in the Al-12Si+10wt%Zn alloy. Sr addition resulted in the eutectic silicon particles becoming thinner and a spherical-like shape. The Sr addition to the Al-12Si+10wt%Zn alloy caused the hardness, yield strength and tensile strength to increase from 97 HBN to 138 HBN, 163 MPa to 233 MPa and 215 MPa to 240 MPa, respectively. The addition of Sr also caused coefficient of friction and wear volume of the Al-12Si-10Zn alloy to decrease from 0.5189 to 0.4621 and 4.488 mm3 to 4.025 mm3, respectively. Effects of Sr additive on the material properties of the Al-12Si+10wt%Zn alloy were discussed based on the microstructural changes.