Correlation of solidification microstructure refining scale, Mg composition and heat treatment conditions with mechanical properties in Al-7Si-Mg cast aluminum alloys

Analysis of solidification conditions, compositions and heat treatment parameters and their mutual interaction on the microstructure evolution is of great importance for designing components with desired mechanical properties. The present paper aims at widening the knowledge on the correlation of solidification microstructure refining scale, Mg composition and heat treatment parameters with the mechanical properties in Al-7Si-Mg cast aluminum alloys. The results reveal that the advantage of fine solidification microstructure can be inherited after heat treatment, with the finer microstructure being characterized by higher tensile properties. Furthermore, with the solidification microstructure refining, the fracture mode transforms from quasi-cleavage to dimple and fracture path transforms from transgranular to intergranular. With the increase of Mg composition, both yield strength and ultimate tensile strength increase, while the elongation decreases. Higher artificial aging temperature can decrease the peak strength. Different solution treatment can produce the different tensile properties because of the different microstructures and composition. A yield strength model using an experiment-based term ∆σ0 to account the effect of solidification and solution treatment is proposed, and the relationship between yield strength and ultimate tensile strength is described using an empirical equation.