Impact of the Friction Stir Welding Process on the Microstructure and Surface Reactivity of Aluminum-Copper Alloys
Abstract: Welding processes are increasingly used in the aerospace industry, particularly to replace mechanical fasteners, which saves time, reduces weight, and lowers fuel consumption. The friction stir welding (FSW) process has attracted significant interest in recent decades, particularly due to its ability to overcome the limitations encountered when fusion-welding aluminum alloys. Among the aluminum alloys used in aerospace, the 2xxx series (based on the Al-Cu system) is valued for its mechanical properties, which can be enhanced through precipitation heat treatment. Its poor weldability in fusion welding—particularly due to its susceptibility to hot cracking during solidification—makes it an ideal candidate for solid-state processes such as FSW.
However, the severe thermomechanical cycles characteristic of FSW generate significant microstructural gradients that profoundly alter the corrosion susceptibility of the welded zones. Appropriate surface protection is therefore necessary to protect FSW-welded zones against corrosion. This doctoral dissertation investigates the impact of the FSW process on the microstructure and surface reactivity of the AA2219 alloy in order to evaluate the effectiveness of surface protection systems designed for welded zones. A multiscale understanding of the relationship between FSW metallurgy, surface electrochemical behavior, and the effectiveness of tartaric-sulfuric anodizing sealed with boiling water is thus established.
Keywords: Friction stir welding, AA2219, microstructure, corrosion
Impact of Friction Stir Welding on the Microstructure and Surface Reactivity of Al-Cu Binary Alloys
Abstract: Welding processes are increasingly used in the aerospace industry, particularly to replace mechanical fasteners, which saves time, reduces weight, and lowers fuel consumption. The solid-state Friction Stir Welding (FSW) process has attracted significant interest in recent decades due to its ability to overcome the limitations encountered in the fusion welding of aluminum alloys. Among the aluminum alloys used in aircraft, the 2xxx series (based on the Al-Cu system) is valued for its mechanical properties, which can be enhanced through precipitation heat treatment. Its poor weldability during fusion welding—particularly due to its susceptibility to solidification hot cracking—makes it an ideal candidate for solid-state processes such as FSW.
However, the severe thermomechanical cycles inherent in FSW generate sharp microstructural gradients that profoundly alter the local corrosion susceptibility of welded zones. Appropriate surface treatments are therefore necessary to protect FSW areas from corrosion. This doctoral thesis focuses on the impact of the FSW process on the microstructure and surface reactivity of the AA2219 alloy to evaluate the effectiveness of surface protection schemes intended for welded zones. A multiscale understanding of the relationship between FSW metallurgy, surface electrochemical behavior, and the protective efficiency of tartaric-sulfuric acid (TSA) anodization sealed via hydrothermal hot water sealing (HWS) is established.
Keywords: FSW, AA2219, microstructure, corrosion
