High-strength, high-conductivity hypoeutectic Al–Si conductor wires via lamellar ultrafine-grained structures and Si nanoprecipitation

Achieving a favorable balance between mechanical strength and electrical conductivity (EC) remains a major challenge for hypoeutectic Al–Si conductor alloys. In this work, a simplified route combining Properzi continuous casting–rolling, cold wire drawing, and direct low-temperature post-annealing is applied to AA4043 conductor wires to overcome the conventional strength–conductivity trade-off. Cold drawing to 86.2% area reduction produces a lamellar ultrafine-grained structure with high dislocation density, yielding an ultimate tensile strength (UTS) of 292 MPa but an EC of only 50.2% IACS, below the industrial threshold of 52.5% IACS. Subsequent post-annealing at 90–300 °C for 1–24 h raises EC into the industrial range through microstructural regimes governed by recovery, Si nanoprecipitation and coarsening, recrystallization, and grain growth, as characterized by EBSD and TEM. Annealing at 150 °C for 4 h promotes uniformly distributed Si nanoprecipitates, reducing Si in solid solution and improving EC while largely preserving the deformed lamellar structure and high dislocation density. This condition yields an optimal combination of UTS (266 MPa) and EC (57.0% IACS). At ≥200 °C, dislocation annihilation, recrystallization, grain growth, and precipitate coarsening progressively reduce strength and increase EC, reaching 133 MPa and 60.3% IACS after 300 °C for 4 h. The property evolution is interpreted by correlating dislocation density, grain structure, Si precipitation, and solute depletion using semi-quantitative strengthening and resistivity models. Overall, low-temperature post-annealing provides an industrially practical route to improve the strength–conductivity balance of AA4043 wires within existing Properzi-based production lines while avoiding complex thermomechanical processing.