Improvements in mechanical and stress corrosion cracking properties in Al-alloy 7075 via retrogression and reaging

Aluminum alloy 7075 has been widely studied, due to its excellent mechanical properties developed by age hardening and their extensive uses in the aircraft structure. Tensile test specimens were tested in various preaging conditions (100, 120, 140 °C) and various retrogression temperatures T7 (160, 180, 200 °C) in order to evaluate the effect of heating cycles on the mechanical as well as corrosion properties. The optimum condition was preaging at T6 120 °C and retrogressing at T7 200 °C, which gave the highest hardness and tensile properties. rrosion behavior of three-point-loaded specimens after 7 days of immersion in 3.5% NaCl solution, using modified electrochemical cell, was studied. The most resisting condition for SCC was preaging at T6 = 100 °C and retrogression at T7 = 160 °C for 250 min. Specimens retrogressed at 200 °C for 8 min showed low resistance to stress corrosion cracking.