Mechanical properties of squeeze-cast Al-7Si-0.3Mg alloys with Sc-modified Fe-rich intermetallic compounds

Iron (Fe) has a low solid solubility in aluminum (Al), and it usually forms Fe-rich intermetallic compounds. Scandium (Sc) is an element that can act as a grain refiner, modify the eutectic silicon and change the morphology of Fe-rich intermetallic compounds at the same time. The present work was conducted to study the effect of Sc on the mechanical properties of Al-7Si-0.3Mg. The alloy was prepared by squeeze casting at two levels of Fe (0.2 and 0.4 wt%) and three levels of Sc (0 wt%, 0.2 wt% and 0.4 wt%). Sc is found to increase the mechanical properties of the alloy, including its hardness, yield strength and ultimate tensile strength. At 0.2 wt% Fe, adding Sc increases the strength while maintaining good elongation. At 0.4 wt% Fe, adding Sc increases the strength but decreases the elongation slightly. The distributions and morphologies of intermetallic compounds and eutectic silicon affect the elongation. Both Fe-rich intermetallic compounds and Sc-rich intermetallic compounds act as crack initiation sites. The 0.2 wt% Fe + 0.2 wt% Sc alloy has the lowest amount of these intermetallic compounds, and eutectic silicon is small and fibrous. So, it has the highest elongation.