Effect of Thermal Treatment on Tensile Properties of a Vacuum Die Cast Hypoeutectic Al-Si Alloy

摘要

Vacuum assisted high pressure die casting processes appear to gain popularity in automotive industry. A number of thermal treatment schemes have been experimented in an effort to understand the effect of thermal treatment on tensile properties of vacuum die cast modified AA365 alloy. The results of tensile testing indicate that, high temperature treatments have an observable effect on tensile properties. The average ultimate tensile strength of about 286 MPa is achieved at 200˚C thermal treatment for 90 minutes. However, the ductility has reduced to 7.8% from 10.7% in as-cast condition. The morphology of eutectic silicon and magnesium-based phase has sound effect on the tensile properties of the tested alloy. The reduction in the strengths of the alloy treated at 350˚C for 120 minutes should be at least attributed partly to the absence of the magnesium-based phase and change of eutectic Si morphology.