Friction Stir Welding of Dissimilar Aluminum Alloys

Dissimilar aluminum alloy plates of 2017A-T451 and 7075-T651 with 6 mm thickness were friction stir butt welded. Numerous trials were conducted to determine the conditions that produce the highest weld quality. These parameters were found to be a welding speed of 112 mm/min, a rotation speed of 355 rev/min and a vertical force of 32,8 kN. The weldability and blending of the two materials were evaluated by using macro- and microstructural analysis as well as EDS mapping to show the distribution of main alloying elements within the weld. The effect of material locations, either on the advancing or retreating sides, on the microstructure and mechanical properties was also investigated. Hardness profiles differ substantially for different weld configurations. Regardless of the position of a particular alloy, the weld microstructure was composed of alternating layers of both materials. However, the layers of the 7075 alloy always exhibited smaller grain size and a larger number of secondary phase particles.