A Research on the Effect of Retrogression and Re-Aging Heat Treatment on Hot Tensile Properties of AA7075 Aluminum Alloys

Aluminum alloys are preferred in most industries due to the functional properties they provide. It is known that alloys that can be processed with heat treatments show better mechanical properties. 7xxx series alloys can be processed via heat treatments and are often used in environmental conditions such as extreme temperatures and corrosive environments. Corrosive sensitivities such as stress corrosion cracking can be observed with the effect of working conditions. It is known that retrogression and re-aging heat treatment provide corrosion resistance and decrease the stress corrosion cracking velocity. The purpose of this study is to examine the tensile behavior of annealed and retrogression-re-aging heat-treated AA7075 alloys at elevated temperatures. The mechanical properties of the alloys were investigated by conducting tensile tests at room temperature, 100, 200, and 300 °C. Hardness tests were performed at room temperature on the samples that were taken from tensile test specimens after tensile tests. The potential effects of test temperature on mechanical and microstructural properties were examined. The annealed and RRA heat-treated alloys were characterized by scanning electron microscope and X-ray diffraction analysis. As a result, an increase in strength and hardness of the retrogression-re-aging treated AA7075 alloys was observed. The ductility of the retrogression-re-aging treated alloy was lower compared to the annealed AA7075 alloy. Fracture surface examinations showed that there was a semi-ductile fracture below 200 °C and ductile fracture at temperatures of 200 and 300 °C. Ductility was observed to increase with increasing temperature.