Microstructure and properties of precipitation-hardened Zr and Zn-Zr based aluminum alloys

New aluminum alloys with improved durability and thermal resistance are desired to improve the performance of high-voltage power transmission lines. These improvements must not significantly reduce the electrical conductivity of the Al alloys currently used for this application to maintain current levels of power transmission efficiency. Precipitation-hardened binary Al-Zr alloys have been shown to have promising electrical conductivity and strength. However, there is room for improving the alloy strength, while maintaining a relatively high electrical conductivity by controlled additions of Zn. The objective of this study is to experimentally examine the addition of Zn to Al-Zr alloys with subsequent heat treatment to improve mechanical properties via controlled precipitation hardening. Vickers microhardness and conductivity measurements, tensile test, scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and selected area electron diffraction are used to measure the properties and determine the microstructure of Al-Zr-Zn alloys for a wide range of aging conditions. As expected, the results indicate that Al-Zr-Zn alloys have improved mechanical properties and slightly reduced electrical conductivity relative to Al alloys currently used for power transmission. However, it is determined that the addition of Zn is unable to improve the heat resistance of Al-Zr alloys. (c) 2019 Elsevier B.V. All rights reserved.