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The objective of this study was to investigate the influences of the main parameters of friction stir welding (FSW) on the residual stresses remained in the FSW of Al 2024-T6. The main parameters were tool rotational speed and tool transverse speed. The effect of these parameters on the residual stresses was studied in both finite element simulation and hole drilling strain gauge measurement. The results showed a good agreement between the numerical results and the experimental outcomes. The change in transverse speed from 25 to 31.5 mm/min resulted in increase of longitudinal residual stresses in welding centerline in which the longitudinal residual stress was increased at the tool rotational speed of 1120 rpm and 1600 rpm about 12.5% and 2.67%, respectively. The results showed that at the low rotational speed, the strain rate had the most effect on the residual stresses whereas at the high rotational speed, some residual stress was released due to the generated heat in the weld zone.

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The intense applied thermal gradients during the welding process leads to the variation in the properties of the weld zone and its surrounding areas. In this regard, determining the local mechanical properties and evolved microstructures of the weld and its surrounding zones are essential in the evaluation of welded structures. In this study, the local mechanical properties of Al2024 friction-stir-welded joints were precisely examined. Digital image correlation (DIC) technique using uniform stress (USM) and virtual field methods (VFM) were utilized to evaluate the local mechanical properties. The local stress-strain curves were plotted for different weld regions using local strain from the DIC technique. It was observed that the advancing side of the thermo-mechanically affected zone (TMAZ) had the lowest values of Young’s modulus and yield strength (YS), approximately 9% and 31% of the base metal, respectively. Effects of welding parameters, such as tool rotational and traverse speeds, were also taken into account. The plotted local stress-strain curve for the fractured region of welded specimens at lower rotational speed illustrated a higher strength and elongation. Furthermore, lower rotational and also higher traverse speeds resulted in the reduction of the grain size.