Re-designing A380 Secondary Aluminum Die Cast Alloys from Automotive Twitch Scrap

Abstract A380 alloy containing 3–4% Cu and less than 0.1% Mg is the workhorse secondary aluminum alloy used for non-structural die casting applications. However, the production of this alloy from end-of-life automotive Twitch scrap involves expensive Mg removal (de-mag chlorination) and Cu additions. In this paper, new secondary alloys, labeled as NS-X, have been designed to have considerably lower Cu (1.8%) and higher Mg (0.4%) than A380 alloy, to better match the Twitch scrap composition. Furthermore, microalloying additions such as Sr, Cr, and Ca were made to a baseline Al–7Si–1.8Cu–0.4 Mg alloy (designated NS-3) to improve mechanical properties. The NS-1 alloy with Sr and Cr additions featured refined eutectic silicon and coarse sludge phases that reached up to ~ 60 µm. The microstructure of NS-2 alloy with Ca microalloying showed fully modified eutectic silicon, far fewer sludge particles than NS-1, and especially refined β-AlFeSi (β-phase) needles in 3-mm-thick cast plate samples. Tensile tests demonstrated that each of these three alloys had essentially equivalent yield strengths as A380 (150–160 MPa) while having better ductility. These results show a successful “re-designing” of A380 with compositions more closely resembling the Twitch scrap stream. These redesigned alloys provide lower-cost alternatives to A380, essentially eliminating de-mag operations and associated environmental impact in scrap recycling and secondary alloy production. Graphical Abstract