Microstructure and Mechanical Characterization of an Al-Zn-Mg Alloy after Various Heat Treatments and Room Temperature Deformation

In this study, the effect of various solution and aging treatments on microstructure and mechanical properties of an as cast Al-5.5Zn-1.2Mg alloy has been investigated by optical microscopy, hardness measurements and room temperature tensile test. The solution heat treatments performed at temperatures between 400 and 490°C have little effects on hardness while electrical conductivity values increased at the lower temperature because of dissolved atoms and vacancy rich clusters. Concerning aging, only T6 improves mechanical properties of the undeformed alloy, while aging performed on tensile tested samples results in a decrease of hardness due to accelerated kinetics and heterogeneous nucleation of equilibrium phase stimulated by dislocation network. Tensile tested samples of the as cast alloy exhibits the fastest recrystallization time during annealing because of the absence of fine precipitates and the high strain hardening.