Development of high-strength and high-electrical-conductivity aluminum alloys for power transmission conductors

Abstract

Using the current processing methods for aluminum conductors, any addition to mechanical strength negatively impacts their electrical conductivity (EC). This trade-off can be seen in common aluminum conductors such as AA1350-H19 which has a relatively high EC (~61%IACS), but low tensile strength (~180 MPa), as opposed to AA6201-T81 having a lower EC (~52.5%IACS) and higher tensile strength (~330 MPa). Presented in this work is the development of new low-cost, scalable 6000-series aluminum conductors with superior combination of mechanical strength and electrical conductivity. By optimizing the thermo-mechanical processing of the aluminum alloy, a synergetic strengthening from precipitation and strain hardening mechanisms is achieved, while the EC loss is minimized. The formation of the strengthening Mg- and Si-rich phase is significantly improved by controlling the Mg and Si concentrations as well as adding inoculant elements to accelerate precipitation kinetics, thus also increasing the alloy’s strength. Two alloys stand out in particular: (i) Al-0.7 Mg-0.3Si-0.08Bi aged at 200 °C for 7 h (ultimate tensile strength = 426 MPa and EC = 52.7%IACS); and (ii) Al-0.7 Mg-0.3Si-0.01Sn aged at 200 °C for 4 h (ultimate tensile strength = 445 MPa and EC = 48.2%IACS).