Improved Tensile Strength and Electrical Conductivity of the Electrical Conductor Aluminum Alloy 6201

Abstract

The aluminum-magnesium-silicon alloy 6201-T81 is a popular electrical conductor, widely used for overhead and distribution lines. Its light weight makes its mass conductivity twice that of copper. Aluminum conductors however experience creep, corrosion, power loss, and other drawbacks. Therefore, it has become a necessity for manufacturers to improve mechanical and electrical properties. The alloy 6201-T81 is an age hardenable alloy, in which a controlled precipitation of Mg2Si is performed through two different successive heat treatments: Solution heat treatment and precipitation heat treatment. ∅ 3.5 mm wires of the alloy were solution heat treated at 510 °C for an hour, quenched in ice water, and precipitation heat treated at the temperature range 150–200°C for the time range 2–24 h. Results show that strength and hardness increase with aging time at the precipitation heat treatment temperatures 150 °C, 165 °C, and 175 °C, but decreased with aging time at 185 °C and 200 °C. The increase was due to the precipitation of finely and uniformly coherent needle-like Mg2Si precipitates, β″. The decrease was due to the precipitation of the semi-coherent and incoherent rod-like Mg2Si precipitates β′ and β, respectively. Electrical conductivity increases with the aging temperature and time. Maximum conductivity was 60 %IACS obtained after treatments (185°C, 18h), (200 °C, 13h), and (200 °C, 24h. Optimum mechanical properties were obtained after the treatment (165 °C, 18 h) (313 MPa, 8%, 95 HV, and 57.7 %IACS). Optical micrographs verified the correlation between the microstructural grain size and both the mechanical and electrical properties.