Microstructure evolution and stress corrosion cracking sensitivity of friction stir welded high strength AA7085 joint

• Published in: Materials & design 2021-12, Vol.212, p.110297, Article 110297
• Main Authors: Xu, W.F., Lu, H.J., Li, X.H., Wang, M., Ma, J., Luo, Y.X.
• Format: Article
• Language: English
• Subjects: AA7085-T7452; Friction stir welding; Microstructure evolution; Stress corrosion cracking sensitivity
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2021.110297

[Display omitted] •The order of coarsening degree of precipitates is: SS-60 HAZ > SS-120 HAZ > DS-First HAZ > DS-Second HAZ.•Both the SCC sensitivity of the SS-60 and the bottom of joints is higher than that of the SS-120 and the top, respectively.•The decrease of Cu content and spacing of GBPs lead to the highest SCC sensitivity in HAZ. Influence of welding process parameters on stress corrosion cracking (SCC) sensitivity through thickness of 12 mm thick AA7085-T7452 joints by single-sided and double-sided friction stir welding (FSW) was investigated via the slow strain rate tensile (SSRT). The corrosion morphology of joint indicates that the coarse precipitates distributed on the grain boundary acts as corrosion cathode, causing the dissolution of the surrounding matrix which acts as anode and forming a corrosion crack initiation site under tensile stress. Different weld zones exhibit diversity in corrosion resistance and the heat affected zone (HAZ) has the largest SCC sensitivity compared with other microstructural zones. The reduction of Cu content in FSW joints increases the SCC sensitivity. The decrease spacing of grain boundary precipitates (GBPs) for the SS-60 joint and in HAZ from the top to bottom with the higher thermal cycle enhance the SCC sensitivity of FSW joints. Combined actions of the above three factors lead to the characteristic of SCC sensitivity for FSW high strength AA7085 joint.