Preliminary Investigation on the Use of Recycled A356 Alloy for Semi-Solid Processing

The continuous demand for lightweighting vehicles leads to a significant increase in the use of aluminium alloys in the automotive sectors. The Al-Si-Mg aluminium alloys are widely applied in foundry processes to produce structural components, due to their high specific mechanical properties combined with good castability and corrosion resistance. Primary (from bauxite) alloys are often used to ensure the highest quality of such parts, nevertheless their production route causes high CO2 emissions. With the goal of reducing cradle-to-grave emissions of vehicles secondary (from recycling) Al-Si-Mg alloys are often used for cast products, however their percentage of impurities is considered too high for structural components. Lately, some Al-Si-Mg recycled alloys with a low content of Fe are available on the market as an alternative to primary alloys. Alongside the traditional foundry processes, semi-solid techniques are known to be able to increase the performance of Al-Si alloys. In this paper, a preliminary microstructural and mechanical characterization of secondary A356 alloys, manufactured by the ultrasound semi-solid method, was performed. In detail, both high Fe and low Fe recycled A356 alloys were investigated in comparison to the traditional primary one. The effect of the T6 heat treatment was also taken into account.