Strength-conductivity synergy in hypoeutectic Al-Si conductors via ultrafine-grained embedded Si nanoprecipitates

Abstract

Hypoeutectic Al–Si alloys are promising candidates for novel Al conductor cables; however, their limited electrical conductivity (EC) and mechanical strength hinder their widespread industrial applications. This study investigates the influence of two thermomechanical processing routes—conventional (C-TMP) and modified (M-TMP)—on the microstructural evolution and the resulting enhancements in mechanical and electrical properties of hypoeutectic AA4043 Al alloy. The C-TMP method improved the ultimate tensile strength from 180.7 MPa to 289.8 MPa and slightly increased the EC from 50.1 to 51.4 % IACS, however, it still remained below the industrial requirement threshold of 52.5 % IACS. In contrast, the M-TMP method successfully overcame the strength-EC trade-off by achieving simultaneous improvements in both properties: the UTS reached 231.4 MPa, while the EC increased to 59.2 % IACS, which represent enhancements of 28.1 % and 18.2 %, respectively, over the as-rolled (AsR) rod condition. The substantial improvement in the EC was attributed to the depletion of solute Si from the Al matrix through the formation of Si nanoprecipitates during pre-annealing. Microstructural analysis of the M-TMP sample revealed the development of an ultrafine-grained (UFG) structure containing embedded Si nanoprecipitates, with a lower dislocation density compared to the C-TMP sample. The underlying mechanisms contributing to the strength-EC synergy are discussed using constitutive models, focusing on Si nanoprecipitates, dislocation density, and grain refinement. These results demonstrate that M-TMP effectively resolved the strength-EC trade-off and yielded a high-strength, high-EC Al-Si conductor that is suitable for advanced electrical wiring applications.