Investigation of tensile properties and microstructure in dissimilar AA2219–AA2014 friction stir welded aluminium alloys

Friction stir welding (FSW) of dissimilar aluminium alloys provides significant advantages in aerospace applications. However, the microstructural variation and its influence on mechanical properties in dissimilar AA2219–AA2014 welds have not been sufficiently investigated. In this study, the tensile properties of dissimilar AA2219–AA2014 friction stir welded joints are examined across room temperature and cryogenic temperatures (77 K and 20 K). A miniature tensile test was conducted to study the local tensile behaviour of the stir zone in similar and dissimilar FSW welds. To corroborate the tensile behaviour, hardness evaluation was done across the weld regions. A detailed microstructural analysis was conducted at various regions of the dissimilar weld using optical microscopy, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) techniques. The results brought out a logical correlation between the tensile properties and microstructural data, including grain evolution, particle redistribution, and dislocation density. The dissimilar weld joint exhibited a UTS of 348 MPa and a YS of 195 MPa at RT, yielding a joint efficiency of 73%. It was evident that the weaker base material, AA2219 alloy, largely determined the tensile properties at RT, 77 K and 20 K.