Ultra-high strength and thermally stable Al-Mg-Si-Cu conductors microalloyed with Sc and Zr: Balancing strength and electrical conductivity

This study examines the effects of Sc and Zr microalloying on the strength, electrical conductivity (EC), and thermal stability of Al-Mg-Si-Cu alloys developed for high-temperature conductor applications. Two alloy compositions were investigated: Alloy A (Al-Mg-Si-Cu base alloy free of Sc or Zr) and Alloy B (with 0.07 wt% Sc and 0.086 wt% Zr). Both alloys were subjected to a tailored thermomechanical treatment involving pre-aging at 120 °C, post-aging at 140 °C and 160 °C, and over-aging at 300 °C for 5 h. Alloy B was further processed using solution treatments at 500 °C (BS500) and 530 °C (BS530). The BS530 condition, post-aged at 160 °C, achieved the highest tensile strength of 518 MPa but exhibited relatively low electrical conductivity (45.0 %IACS). The BS500, over-aged at 300 °C, exhibited the best overall thermal stability due to forming finer and thermally stable Al 3 (Sc,Zr) dispersoids, and reached the highest EC (54.1 %IACS) with reasonably high strength (290 MPa). This strength value greatly surpasses the IEC 62004 AT2 requirement of 225 MPa, although conductivity fell slightly below the target of 55 % IACS. In contrast, the base alloy (A) achieved a maximum EC of 55.1 %IACS but significantly lower strength and thermal-resistant performance. Overall, the Sc and Zr microalloying, combined with tailored thermomechanical processing, enabled balanced combinations of strength, EC, and long-term thermal resistance—supporting the design and processing of next-generation aluminum conductors for elevated-temperature applications.