Effect of Li on Mechanical Properties and Electrical Conductivity of the Al-Zn-Cu-Mg Based Alloys.

In this study, changes in the microstructure, mechanical properties, and electrical conductivity of cast and extruded Al-Zn-Cu-Mg based alloys with the addition of Li (0, 0.5 and 1.0 wt.%) were investigated. The Al-Zn-Cu-Mg-xLi alloys were cast and homogenized at 570 °C for 4 hours. The billets were hot extruded into rod that were 12 mm in diameter with a reduction ratio of 38:1 at 550 °C. As the amount of Li added increased from 0 to 1.0 wt.%, the average grain size of the extruded Al alloy increased from 259.2 to 383.0 µm, and the high-angle grain boundaries (HGBs) fraction decreased from 64.0 to 52.1%. As the Li content increased from 0 to 1.0 wt.%, the elongation was not significantly different from 27.8 to 27.4% and the ultimate tensile strength (UTS) was improved from 146.7 to 160.6 MPa. As Li was added, spherical particles bonded to each other, forming an irregular particles. It is thought that these irregular particles contribute to the strength improvement.