Optimizing Strength and Electrical Conductivity of 6201 Aluminum Alloy Wire Through Rotary Swaging and Aging Processes

Age-hardened 6201 aluminum alloy wires utilized in high-voltage transmission lines need to have high strength, high conductivity and high ductility. However, simultaneously obtaining high values for the above three parameters remains a challenge, as there are trade-off relationships between strength and ductility, strength and conductivity. In this article, we employed solid solution, under-aging and peak-aging treated 6201 aluminum alloys as initial samples, then performed rotary swaging (RS) on them equally and subsequent aging at different temperatures. Performance testing found that RS plus aging improved the strength and conductivity of all three samples. The best combinations of electrical conductivity and ultimate tensile strength are 50.6 %IACS and 363 MPa, 51.7 %IACS and 352 MPa, which were obtained through under-aged (550 ℃/3 h + 175 ℃/2 h) + RS + re-aging (160 ℃/4 h) and peak-aged (550 ℃/3 h + 175 ℃/8 h) + RS + re-aging (160 ℃/4 h). Quantitative analysis show that precipitation strengthening is the main strengthening mechanism, contributing about 50 % of the yield strength. Grain boundary strengthening and dislocation strengthening contribute comparable amounts of 25 % and 20 %, respectively. The theoretical model can well predict the yield strength of RSed Al alloys based on the microstructure. The conductivity increase was caused mainly by the precipitation of solid solutions and fiber grain boundaries. In addition, RS reduced the tensile ductility to 6–10 % and subsequent aging regain it up to 10–13 % due to decrease of dislocation density and precipitation hardening. Our results indicate that high strength, high conductivity and high ductility of aging-hardened alloys can be achieved through optimizing deformation and aging processes.