Effect of Thermal Treatment (T5) on Microstructure and Tensile Properties of Vacuum High Pressure Die Cast Al–Si–Mg Alloy

Abstract

In this work, a modified Al–Si–Mg (A356) alloy was prepared by vacuum-assisted high pressure die casting processes (V-HPDC). To release residual stresses, various thermal treatment schemes over a wide range of temperatures between 120 and 350 °C were experimented to the as-cast V-HPDC alloy, in an effort of understanding the effect of thermal treatment on tensile properties of V-HPDC modified Al–Si–Mg (A356) alloy. The morphology of eutectic silicon has a sound effect on the tensile properties of the tested alloy. The content of magnesium-based intermetallic phase, their morphology, and distribution throughout the matrix affect the tensile properties as well. The reduction in the strengths of the alloy treated at 350 °C for two hours should be at least attributed partly to the absence of the magnesium-based intermetallic phase. However, the presence of sufficient amount of magnesium intermetallic phase plays an important role in strengthening the alloy thermally treated at 200 °C.