Microstructure evaluation of dissimilar AA2024 and AA7050 aluminum joints made by corner stationary-shoulder friction stir welding

Abstract

Fillet welds made by the corner stationary-shoulder friction stir welding process between AA7050-T7451 and AA2024-T4 sheets were characterized using different metallographic techniques and mechanical testing. Robotic welds of an aircraft’s skin-to-internal stiffeners were examined using Barker’s electrolytic and Keller’s etching techniques and correlated with electron backscattered diffraction results and energy-dispersive microprobe analysis. The composition and grain orientation maps and material flow lines demonstrated excellent weld quality in spite of the apparent inhomogeneities in the stir zone where mechanical mixing was complete. Welded joint efficiencies were in the 85–92% of the base metals and were acceptable in terms of resistance to crack initiation and propagation and corrosion resistance, even with softening of the heat-affected zones. It was concluded that several optical and electron microscopy techniques are needed to characterize these dissimilar aluminum welds fully and that post-weld mechanical and thermal treatments could even further improve their quality.

Effect of Process Parameters on Friction Stir Welded Joints between Dissimilar Aluminum Alloys: A Review

“…Mertinger at al. [30] study the corner stationary shoulder friction stir welding process between AA7050-T7451 and AA2024-T4 sheets for aerospace applications with the aim to replace approximately 500,000 rivets on an Airbus A350 plane.…”

Technologies for Joining and Forming Thin-Walled Structures in the Construction of Transportation Vehicles

“…In this case, it is particularly advantageous to use solid-state welding processes, e.g., variants of friction welding, in particular friction stir welding (FSW) [ 9 , 10 , 11 ]. In the last decade, FSW is being increasingly employed in the construction of, e.g., aircraft and automotive structures [ 12 , 13 ]. The growing interest in this method of joining is fully justified due to a number of advantages, such as the low energy consumption of the process and the possibility of joining different metals, plastics or composites [ 14 , 15 ].…”