Doe applied to microstructural and mechanical properties of Al-Si-Cu-Mg casting alloys for automotive applications

Mechanical properties and microstructural features of an aluminium alloy are affected by several parameters, such as alloy composition, solidification rate and heat treatment. The analysis of the effects of each variable and their reciprocal interaction on the alloy behaviour plays a key role in determining its potential for the development of a component with improved performance. The use of the design of experiment (DOE) methodology and the analysis of variance (ANOVA) can be a useful instrument to reach this objective. In this study, DOE and ANOVA have been applied to assess the concurring effects of the Cu content, the grain refinement, the solidification rate and the heat treatment on microstructural and mechanical properties of a secondary AlSi7CuMg foundry alloy for engine block application. The results indicate that the size of eutectic Si is controlled by the solidification time and by the interaction between Ti and Cu content, while the eutectic Si morphology depends mainly on the heat treatment process. The grain size is affected by the solidification time, the Ti content and the interaction between Cu and Ti. While the strength of the alloy increases with increasing Cu amount, cooling rate and heat treatment, the ductility decreases as the Cu amount and the solidification time increase.