Recycled AlSi7Mg0.3 alloys with different iron content: Heat treatment and tensile properties

Recycled aluminum-silicon alloys offer environmental advantages by reducing raw materials consumption and carbon emissions. However, heat treatment response and corresponding mechanical behavior remain insufficiently characterized, limiting their applicability. This study investigates two secondary AlSi7Mg0.3 alloys, containing 76 % and 97 % recycled aluminum, focusing on the influence of increased iron content on aging and mechanical properties. A primary alloy was used as a benchmark. Specimens were produced by gravity die-casting and subjected to T6 heat treatment, involving solutionizing at 535°C for 4.5 h, water quenching, and artificial aging at temperatures from 160°C to 190°C for durations up to 184 h. Aging curves revealed that secondary alloys responded similarly to primary alloy, achieving higher hardness values. Four aging conditions were selected for tensile characterization. Aging condition of 160°C for 4.5 h was identified as optimal, yielding a strength-ductility balance in peak-aged specimens (YS up to 268 MPa, UTS up to 310 MPa, and elongation no less than 4.3 %). Minor differences were observed between primary and secondary alloys, with a clear trade-off: increased Fe content improved strength but reduced ductility. Mechanical behavior was interpreted through microstructural characterization, defect analysis, and fractographic examination, all of which confirming the suitability of recycled alloys for high-performance applications.