An investigation on semi-solid Al-7Si-0.3Mg alloy produced by mechanical stirring

In this research an aluminum alloy Al-7Si-0.3Mg (A356.1) was cast by a semi-solid casting technique. The parameters like stirring time, temperature and heat treatment conditions on mechanical properties were investigated and obtained optimum conditions. The cylindrical specimens with a height of 40 mm and a diameter of 160 mm were cast in a permanent mould. Mechanical properties plus fracture surfaces of specimens were identified as brittle or ductile fracture. Results showed that the optimum temperature and time for semi-solid cast A356.1 aluminum alloy, with 700-rpm shear rate were 590 °C and 20 min, respectively. The most appropriate heat treatment cycle, to achieve the best tensile properties was annealing at 520 °C for 6 h, followed by quenching in 40 °C water and then aging at 160 °C for 6 h. The most important feature of this study was the conversion of fracture mechanism mode from brittle to ductile in result of changing the morphology of globules and the matrix.