Friction Stir Welding (FSW) is an innovative solid-state joining process, which is gaining a great deal of
attention in several applicative sectors. The opportune definition of process parameters, i.e. minimizing residual stresses,
is crucial to improve joint reliability in terms of static and dynamic performance. Longitudinal residual stresses, induced
by FSW in AA2024-T3 butt joints, have been inferred by means of a recently developed technique, namely the contour
method. Two approaches to stress measurement have been adopted; the former is based on the assumption of uniform
material properties, the latter takes into account microstructural effects and material properties variations in the welding
zones. The influence of process parameters, namely rotating and welding speeds, on stress distribution is also discussed.