Optimization of Heat Treatment, Mechanical and Microstructural Characterization of Recycled Aluminum-Silicon Alloys

The study focuses on heat treatment optimization and the mechanical and microstructural characterization of prototype castings produced using recycled aluminum alloys. Aluminum is widely employed in many industrial sectors thanks to its excellent properties, such as mechanical strength and corrosion resistance, combined with a low density, which makes it ideal for structural lightening. However, the production of primary aluminum requires a high energy input, making the use of recycled aluminum crucial to reducing the environmental impact and preserving natural resources. This research involved the production of gravity die castings using AlSi7Mg alloys, supplied by Raffmetal S.p.a., with different recycling contents. Heat treatment was optimized following a mechanical–energetic approach, aiming to balance the best mechanical properties with the lowest possible energy consumption. The optimization was based on aging curves, which track the evolution of hardness for various combinations of temperature and treatment duration. Tensile tests were performed on samples selected according to the most promising aging conditions, extracting key parameters such as yield strength, ultimate tensile strength, and elongation. Mechanical results were then correlated with the most relevant microstructural parameters and analysed through optical microscopy and scanning electron microscopy. Results highlighted the capability of recycled aluminum alloys to achieve properties suitable for high-performance automotive components.