Mechanical performance and material characterization of secondary aluminum alloys for automotive megacasting

Sammanfattning

The transition toward sustainable automotive manufacturing has intensified interestin using recycled materials without compromising mechanical performance. Thisthesis investigates the feasibility of applying secondary aluminum alloys in highpressuredie casting (HPDC), specifically within the megacasting process for largestructural components. Four alloy batches were analyzed: one primary aluminumused as the reference (A4), one secondary aluminum with similar chemical composition(B1), and two secondary aluminum variants with different levels of Fe, Cu, Zn,and V (B2–B3). Mechanical performance was evaluated through tensile, three-pointbending, and hardness testing, while microstructural analysis, including optical microscopy,metallography, SEM, and X-ray was used to identify shrinkage, porosity,and intermetallic phases.The results show that recycled aluminum with up to 90% secondary content (B1) canachieve comparable mechanical properties to primary aluminum (A4) when chemicalcomposition remains unchanged. Batches with higher Fe content (B2, B3) exhibitedincreased yield strength due to solid solution and precipitation strengthening butshowed reduced ductility and bending toughness, particularly in regions with greatershrinkage. Comparing the results with historical trials can separate the impact ofcast processing and raw material. Microstructural analysis confirmed that castingposition influences defect formation and performance. In HPDC, areas farther fromthe ingate (e.g. F3) generally experience longer flow paths and therefore tend toform more shrinkage and intermetallic phases. Building on this context, this workdemonstrates that, with optimized chemistry and process parameters, secondaryaluminum alloys can achieve mechanical performance compared with primary alloys,thereby offering a sustainable megacasting solution for the automotive industry.