Fabrication of an Al-4Si-1.1Mg-0.13Zr-0.06Cu-0.15Sc Alloy with Excellent Electrical Conductivity and Mechanical Properties

Improving the strength of Al conductive alloys while maintaining high electrical conductivity (EC) remains a long-standing challenge, as conventional strengthening strategies usually degrade electrical performance. Although multi-element microalloying has been explored for Al-Si alloys in the prior literature, most existing studies fail to achieve the simultaneous refinement of eutectic Si and controlled precipitation of multi-scale nanoprecipitates, often leading to a strength–conductivity trade-off. In this work, a novel Al-4Si-1.1Mg-0.13Zr-0.06Cu-0.15Sc conductive alloy was designed, integrating trace Mg/Zr/Cu/Sc microalloying with hot extrusion and tailored heat treatment. The results reveal that the individual addition of these alloying elements greatly raises alloy hardness but inevitably reduces EC. The combined hot extrusion and heat treatment solves this dilemma: eutectic Si particles are refined to ~200 nm with a uniform distribution, while nano-sized Mg2Si (~15 nm) and Al4Zr(Sc)3Si5 (~50 nm) precipitates are formed. The synergistic strengthening of these multi-scale precipitates enables prominent mechanical enhancement without sacrificing electrical conductivity, which distinguishes this work from many previous Al-Si alloy reports. After the optimized two-step heat treatment (500 °C/4 h + 200 °C/48 h), the alloy achieves excellent comprehensive performance: yield strength of 164.0 MPa, ultimate tensile strength of 364.0 MPa, hardness of 106.0 HV, elongation of 9.0%, and EC of 50.8% IACS. This work provides a feasible microstructure engineering strategy for designing high-performance conductive aluminum alloys by precise multi-component composition control.