Influence of silicon content and heat treatment parameters on mechanical properties of cast Al-Si-Mg alloys

The influence of silicon content and solution and aging temperature on microstructure and mechanical properties, and mode of fracture of cast Al-(4-20)Si-0.3Mg alloys is reported. Alloys were prepared by controlled melting, casting and heat treatment. Increasing solution temperature from 450 to 550 degrees C and aging temperature from 150 to 230 degrees C increased the tensile strength of all the Al-Si-Mg alloys. High solution temperatures produce greater refinement and distribution of eutectic silicon grains than low temperatures. Scanning electron microscopy of tensile fracture surfaces showed that the fracture surface of specimens treated at higher solution and aging temperatures is characterised by finer, equaixed dimples than that of specimens heat treated at lower temperatures.