Evaluation of local constitutive properties of Al2024 friction stir-welded joints using digital image correlation method

Abstract

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.