Investigation on Microstructure and Residual Stress Distribution in Dissimilar AA3105/AA2024 Friction Stir Joints

The microstructure, mechanical properties and residual stress of dissimilar AA3105/ AA2024 friction stir welds have been investigated. The formation of voids was observed at high rotational speeds and low transverse speeds due to the high weld heat input and abnormal stirring. The precipitate fragmentation was noticeable at higher tool rotational speed. The highest hardness was obtained at the AA2024 side of the joints due to the presence of precipitates. The results showed that the welding transverse speed has more effect on UTS than the rotational speed. Tensile residual stresses were found at the AA2024-T6 side and the welding line; while residual stresses at the AA3105 side were compressive.