Prediction of tensile properties of cast Al-Si-Mg automotive components

The main limitation of Al-Si-Mg castings is the considerable influence of the solidification and heat treatment conditions on the final microstructure and, consequently, mechanical properties. This generally leads to a wide scatter in their values in different parts of complex-shaped cast components, with detrimental consequences on the design phase. In this work, a microstructural and mechanical characterisation of specimens extracted from A356-T6 gravity cast automotive components was carried out. This activity aimed to develop empirical models to successfully predict the local tensile properties of the castings, from the knowledge of the main microstructural parameters. Among the microstructural parameters, the secondary dendrite arm spacing, the shape and size of the eutectic Si, the grain size and the percentage area fraction of defects were taken into account. The effect of the T6 heat treatment was evaluated by hardness measurements. The proposed empirical models were implemented in a commercial casting simulation software, to predict the local tensile properties of some A356 T6 gravity castings. The developed equations allow the designer to evaluate the local tensile properties (YS, UTS, E%) without any tensile tests. This permits, in a co-engineered design approach, a direct link of the post-processing results of the casting simulation software with the pre-processing phase of the structural ones, with consequent costs and time-to-market reductions.