Influence of Copper Addition on Microstructure, Mechanical and Thermal Properties of Al-Zn-Mg Alloys

In this research paper, the effect of the addition of copper (0.02 to 3.32 wt.%) on microstructure, mechanical and thermal properties of Al-Zn-Mg alloy are studied using an optical microscope, scanning electron microscope (SEM), X-ray diffractometer (XRD), Vicker’s microhardness tester, universal testing machine (UTM) and differential scanning calorimeter (DSC). Precipitates (η-MgZn 2 phases) are present in as-cast Al-Zn-Mg alloy. SEM and XRD analyses have shown the presence of η (MgZn 2 ) and θ (Al 2 Cu) precipitate in the as-cast Al-Zn-Mg-Cu alloy. Micro-Vickers hardness increases from 121.3 HV1 to 153.1 HV1 for the initial increase in copper content (0.02 to 1.54 wt.%) and then decreases to 137.3 HV1 (3.32 wt.% copper). The melting point decreases continuously with increased copper content from 619.8 °C (0.02 wt.% Cu) to 608.5 °C (3.32 wt.% Cu). Peak compressive stress, absorbed energy per unit volume, yield stress is observed to increase by 43.6%, 75.4%, and 59.3%, respectively, for the rise in copper content (0.02 wt.% to 1.54 wt.%) in the alloy.