Comparison of Friction Stir Welded and Stationary Shoulder Friction Stir Welded Dissimilar AA 2024 / AA 7050 Butt Joints with Comparable Energy Inputs

Comparison of Friction Stir Welded and Stationary Shoulder Friction Stir Welded dissimilar AA 2024 / AA 7050 butt joints with comparable energy inputs

The work at hand describes a comparison of Friction Stir Welded (FSW) dissimilar aluminium alloys AA 2024 and AA 7050 in butt joint configuration using two different variants of the FSW process. The standard FSW process and the Stationary Shoulder FSW (SSFSW) process have been employed and benchmarked through mechanical characterisation and chemical analysis at a comparable energy input levels. Aim of the work was to establish a robust parameter window for both FSW variants for the material combination commonly employed in the aircraft industry as well as to benchmark and ameliorate the SSFSW process and technology.

Characterization of these welds has been carried out by macrographic overviews, Energy Dispersive X-ray Spectroscopy analysis (EDX), three point root bending, micro-hardness as well as transverse tensile tests.

The results have shown that through thickness heat distribution in the welds are more uniform using SSFSW. At higher energy inputs, varying the positioning of materials on to the advancing side (AS) or retreating side (RS), seems to have less impact on the mechanical performance of the welds regardless of the FSW process variant employed. With higher welding speeds (lower energy input per unit length) tensile strength for both variants of the FSW process increases. Comparable energy inputs lead to higher tensile strength results for the SSFSW process variant. EDX analysis shows diffusion zones between interweaving patterns of dissimilar materials in the stir zones.