Study on stress corrosion properties of aviation aluminum alloy friction stir welded joint at the different strain rate

Abstract

Aviation aluminum alloy welded structures are subjected to stresses at different strain rates in corrosive environments such as the ocean. Studying the stress corrosion properties of aviation aluminum alloy Friction Stir Welding (FSW) structures is essential. Therefore, this paper focuses on the study of 12 mm thick 7085-T7452 high-strength aviation aluminum alloy FSW joints under different strain rates of stress corrosion properties changes and the impact of welding process parameters. The main conclusions of this thesis are as follows: For the base material (BM) and the aluminum alloy FSW joints, when the strain rate increased from 10−7 s−1 to 10−5 s−1, the stress corrosion strength increased, and the stress corrosion cracking (SCC) sensitivity index ISSRT decreases. The SCC sensitivity at the same strain rate: SS-400-120 > SS-300-60 > SS-300-120 > BM. After the Slow strain rate tensile (SSRT) test, the FSW joint fracture in the air is a transgranular ductile fracture. Meanwhile, the fracture is a ductile-brittle hybrid fracture in 3.5% NaCl solution, and the number of secondary cracks along the grain boundary increased significantly, showing obvious SCC sensitivity. The BM fracture after SSRT is ductile, showing lower SCC sensitivity.