The structure and mechanical properties of heat treated Al-Zn-Cu-Mg type alloy

The results of precipitation hardening 7075 type cold worked alloy are presented. The aim of the study was to elaborate an Al-Zn-Cu-Mg type light alloy for special application. The most important was to propose the heat treatment parameters which would allow reach the extremely high tensile properties with good ductility. These properties was as follow: tensile strength > 640MPa, Rp, 02 > 600MPa and A5 no less than 8%. To meet these properties we propose the solution heat treatment at the temperature 520 °C with cooling in cold water. The temperature 125°C was chosen for aging. The different aging time was applied for the specimen after solution heat treatment followed with quenching in cold water. The mechanical properties of heat treated specimens were tested in tension and using hardness measurement. Besides the conventional Metallography, scanning (SEM) and transmission electron microscopy (TEM) were applied for structure observations. In case of the last one we used either microscopy observations where tilting experiment was used and selected area electron diffraction (SAD).