Developing Structural Die-Cast Alloys from Automotive Aluminum Scrap Materials

Abstract In this investigation, microalloying additions of Mn, Cr, Sr, and Ce were used to modify and refine detrimental intermetallic phases formed in secondary alloys with high Fe content. Three secondary Al-Si-based alloys were designed based on Fe content (0.5–0.6 wt.%) in the twitch scrap and die cast alongside the primary C611 alloy (0.1 wt.% Fe). The results suggest the addition of Mn and/or Cr can effectively suppress the formation of detrimental β-AlFeSi phase, with predominantly α-Al(Fe,Mn)Si in the die-cast microstructure of the secondary alloys. Sr additions (30–40 ppm) refined the eutectic silicon, and a small Ce addition (0.15 wt.%) led to the formation of Ce-intermetallics that functioned as sinks for Cu and Mg. Average elongations between 7 and 9% were achieved in as-cast conditions for three secondary alloys while exhibiting improvements in strength over the primary C611 alloy. A T7 treatment further improved the mechanical properties (up to 220 MPa ultimate tensile strength and 13% elongation).