Structural Die Cast Alloy Development from Scrap Aluminum

The use of secondary (recycled) aluminum for structural components in the transportation industry is limited by its high Fe contents which often result in the formation of brittle β-Al₅FeSi phase and reduce the ductility of aluminum castings. We have developed a structural die cast alloy with high Fe content (about 0.5wt.%) from scrap aluminum for die casting applications, based on CALPHAD modeling and experimental validation. Manganese was added to obtain a designed Fe-to-Mn ratio of 2 which successfully suppressed the formation of β-Al₅FeSi phase, by forming α-Al₁₅(Fe,Mn)₃Si₂ phase with rounded or hexagonal morphology. Additionally, a fine needle-like π-Al₈FeMg₃Si₂ phase was also formed to provide additional strengthening effects. The new recycled alloy showed comparable mechanical properties in as-cast and heat treated (T5 and T6) conditions to a typical primary die cast alloy (≤ 0.2wt.%) with similar composition. This new alloy provides a promising path for increasing usage of recycled aluminum in structural die castings for transportation applications.