Effects of secondary phases on stress corrosion property of friction stir welded seam of 7A52 aluminum alloy under different strain rates

The effects of secondary phases on stress corrosion property of friction stir welded (FSW) seam of 7A52 aluminum alloy were investigated with SEM-EDS during low stress rate test (SSRT). The experimental results indicate that the stress corrosion cracking (SCC) occurred on the retreating side of HAZ in FSW seam in 3. 5% NaCl solution. The fracture position was corresponding to the position of minimum microhardness value in FSW seam. The SCC susceptibility of FSW seam was highest at strain rate of 1×10^{- 6} s^-1 and lowest at 1×10^-5 s^-1. Different secondary phases had different effects on the initiation and growth of stress corrosion cracks. Al9Fe0.84Mn2.16Si easily induced the initiation and growth of cracks,however,the pitting resulted from the dissolved Mg₂Si could only initiate small cracks.