Controlling Fe-Rich Intermetallic Phase Morphology in Recycled Aluminum for Automotive Wire Applications

Upcycling of post-consumer aluminum scrap into high-quality wire conductors, such as those used in modern electric vehicle applications, is severely constrained by iron (Fe) accumulation, which may induce wire breakage during high-speed drawing. To define the metallurgical limits for the utilization of secondary 1xxx-series aluminum, this study systematically investigates Fe enrichment behavior, intermetallic phase evolution, and the relationship between phase morphology and mechanical reliability. For this purpose, Fe content was systematically increased from 0.079 to 1.789 wt% by controlled liquid-state diffusion, showing a strong dependence of Fe uptake on holding time and temperature. Microstructural analysis demonstrated a progressive transition from fine dispersed Fe-containing particles at low Fe levels to elongated needle-/plate-like β-Al 5 FeSi-type intermetallic phases at elevated Fe concentrations. Furthermore, aluminum derived from used beverage cans (UBCs) revealed the formation of a more compact α-Al(Fe,Mn)Si-type morphology due to the combined influence of Fe, Si, and Mn. While passive sedimentation at 600–615 °C yielded only modest Fe reduction (from 1.789 to 1.31 wt%), the persistence of elongated Fe-rich phases after treatment demonstrated that gravity-based separation alone is not sufficient to achieve the microstructural requirements for conductor-grade aluminum. Subsequent metallurgical treatment by the addition of Al5B master alloy was therefore investigated as a potential approach for grain refinement and modification of Fe-containing intermetallic phases. The treatment improved the mechanical response but showed limited capability for transforming existing precipitate morphologies under the investigated conditions. Mechanical characterization coupled with Weibull reliability analysis established that 0.2% proof stress (Rp0.2) increased from approximately 20 to 30–40 MPa, while ultimate tensile strength increased from approximately 40 to ~100 MPa, potentially due in part to second-phase strengthening. However, this strength improvement was accompanied by a reduction in elongation at fracture from ~60 to ~30%. The findings demonstrate that the successful recycling of aluminum scrap for electrical conductor applications requires not only impurity reduction but also effective control of the morphology, size, and distribution of Fe-rich intermetallic phases. A successful approach would provide a metallurgical pathway to increase recycled content in aluminum conductor applications while maintaining the mechanical reliability required for wire production.