Improving the performance of recycled EN 45500: a sustainable approach through heat treatment optimization

This study investigates the performance and environmental impact of a 100% recycled EN 45500 aluminum alloy subjected to T6 heat treatment, using its primary counterpart as a benchmark. Both alloys were produced by gravity die casting under controlled laboratory conditions and subsequently characterized from a microstructural and mechanical standpoint. The recycled alloy exhibited a higher iron content, promoting the formation of Fe- based intermetallic compounds, which increased defect density and reduced ductility compared to the primary alloy. Heat treatment parameters were optimized to balance mechanical performance with energy efficiency. Tensile testing revealed that the recycled alloy achieved mechanical properties comparable to those of the peak- aged primary alloy when aged at 160 ◦C for 4.5 h, a less energy-intensive condition than the 180 ◦C for 4.5 h required by the primary alloy. The environmental impact analysis demonstrated a significant reduction in carbon footprint, from 19.6 kgCO2eq/kgAl for the primary alloy to 2.47 kgCO2eq/kgAl for the recycled one. For 100% recycled EN 45500 alloy, the heat treatment, including solution treatment and aging, accounted for 92.3% of CO2eq emissions, underscoring the relevance of heat treatment optimization. Overaging tests demonstrated that the recycled EN 45500 retained copper-driven thermal stability. Overall, the findings highlight the capability of recycled aluminum to meet both mechanical performance and sustainability requirements to produce advanced automotive applications.