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 degrees C) and various retrogression temperatures T-7 (160, 180, 200 degrees C) in order to evaluate the effect of heating cycles on the mechanical as well as corrosion properties. The optimum condition was preaging at T-6 120 degrees C and retrogressing at T-7 200 degrees C, which gave the highest hardness and tensile properties. The corrosion 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 T-6 = 100 degrees C and retrogression at T-7 = 160 degrees C for 250 min. Specimens retrogressed at 200 degrees C for 8 min showed low resistance to stress corrosion cracking. (C) 2007 Elsevier B.V. All rights reserved.