Effect of strain rates on stress corrosion sensitivity of 7085-T7452 thick-plate friction stir welding joint

Abstract

The stress corrosion behavior of 7085-T7452 high-strength aluminum alloy base material (BM) and its friction stir welding (FSW) joints under varying strain rates during slow strain rate tensile (SSRT) was investigated. The results show that the stress corrosion sensitivity (I_SSRT) of both the BM and FSW joints decreases with the increase of strain rate from 10⁻⁷ s⁻¹ to 10⁻⁵ s⁻¹. Moreover, the BM demonstrates lower I_SSRT than the joints. The cracks in the joints exhibit dendritic paths along grain boundaries, with evidence of crack arrest marking (CAM) at localized areas in 3.5 wt% NaCl solution, suggesting both anodic dissolution and hydrogen-induced cracking simultaneously govern the propagation of stress corrosion cracks. There is the forced more test time in the slower strain rate, and the accumulation of stress corrosion coupling damage accelerates with the time, eventually leading to the greater degradation in the stress corrosion resistance and the higher I_SSRT.