Effect of Casting Microstructure on the Mechanical Performance of Recycled EN AC-43200 Al-Si Alloy

Nowadays, the automotive industry is moving toward the reduction of CO2 emissions implementing different strategies. Beyond the direct reduction of emissions from the vehicles, an important role is played by the production of parts made with recycled materials. This is particularly relevant for automotive components (e.g., brake calipers and steering knuckles) produced using cast Aluminium-Silicon (Al-Si) alloys, whose primary production from bauxite is highly energy-intensive. However, recycled cast Al-Si alloys could have different mechanical performances with respect to their primary counterparts, due to the presence of impurity elements from the recycling process. For this reason, it becomes fundamental to study the effect of different casting parameters (e.g., molten alloy temperature, sprue design and mould temperature) on the solidification microstructure of recycled, cast Al-Si alloys and, as a consequence, on the mechanical performances of the material. In this context, this work investigates the effect of the casting process, i.e., the casting microstructure, on the mechanical performance of a recycled EN AC-43200 Al-Si alloy. Three sets of samples with different microstructural features (i.e., SDAS and porosity) are obtained by carefully modulating pouring and in-mould cooling conditions. Specimens are then characterized in terms of tensile and high-cycle fatigue performance at room temperature coupled with microstructural (i.e., X-ray computed tomography and metallography) and fracture surface analyses. A strong correlation between microstructural features and mechanical performance is demonstrated, thus providing insights on the interplay existing between casting parameters and final performance of recycled Al-Si alloys. These results pave the way for smart design of cast automotive components made with recycled Al-Si alloys.