Application of Imaging Techniques to Determine the Post-Yield Behaviour of the Heterogeneous Microstructure of Friction Stir Welds

Abstract Background Friction Stir Welding (FSW) causes intense plastic deformation and consequent thermomechanical interactions resulting in a localised heterogeneous microstructure. To understand the weld mechanical behaviour, it is necessary to identify each microstructural sub-region weld. Objective Determine relationship between local microstructure behaviour of different regions FSW. Methods Scanning electron microscopy (SEM) identified sub-regions an FSW joint. A novel High-Resolution Digital Image Correlation (HR-DIC) methodology enabled determination full-field strain response provide sub-regions. X-ray computed tomography (CT) geometry material composition. Results The grain morphology varied stir zone with fine structure nugget larger grains affected (TMAZ); were retreating side (RS) compared advancing (AS). Tungsten deposits found attributed tool wear. properties subregions showed that had greater yield strength than base RS was much more ductile AS side. tungsten distributions correlated behaviour. Conclusions developed combines observations HR-DIC enabling, for first time, be related inclusions caused by