应变速率条件下第二相对7A52铝合金搅拌摩擦焊焊缝应力腐蚀性能的影响

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

摘要: 采用慢应变速率拉伸试验,结合扫描电镜、能谱分析仪研究了第二相对7A52铝合金搅拌摩擦焊(FSW)焊缝应力腐蚀性能的影响.结果表明,FSW焊缝在3.5%NaCl溶液中,应力腐蚀开裂(SCC)均发生在后退侧的热影响区,断裂位置与显微硬度曲线中硬度最低区域相对应.焊缝的SCC敏感性在1×10^-6s^-1条件下最高,在1×10^-5s^-1条件下最低,不同第二相对FSW焊缝应力腐蚀裂纹形核和扩展的影响是不同的:Al₉Fe_0.84Mn_2.16Si容易引发裂纹的萌生和扩展,Mg₂Si被腐蚀留下的点蚀坑引发的裂纹相对较小.

Abstract: 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.