Investigating the effects of pre-deformation and aging conditions on mechanical properties and SCC resistance of aluminium alloy 7075 via slow strain rate testing and electrochemical polarisation

In this study, the effects of pre-deformation on mechanical properties and stress corrosion cracking behaviour of 7075 alloy was investigated with SSRT and electrochemical polarization. The 10% pre-deformation substantially improves the SCC resistance of the 7075 alloys. The strain induced dislocations act as diffusion shortcuts and result in enhanced precipitation and early appearance of GBPs in the naturally aged 7075-T3. For artificial aging, pre-deformation causes rapid over-aging as larger precipitates are found in both matrix and GBs of the 7075-T8. The substitution of Cu for Zn in the GBPs and the larger GBPs acting as hydrogen traps are possible explanations for the improved SCC resistance of 7075-T8. Further improvements in SCC resistance can be found in the RRA treated 7075 alloys, while a more ductile behaviour can be seen in the pre-deformed 7075 alloy. Additionally, results of electrochemical testing are in high correlation with the SSRT results.