Diminishing residual stress and distortion by in-situ rolling tensioning to increase fatigue performance of friction stir welded AA2024-T3 joints

In this research, local mechanical tensioning treatment in the form of in-situ rolling tensioning (ISRT) was applied during friction stir welding of AA2024-T3 sheets. Two types of roller configurations were used. First, a single roller located at the rear of the tool which passed over the weld region and secondly, two rollers were located next to the weld zone symmetrically. Subsequently, several experiments comprising residual stress, distortion and fatigue crack growth (FCG) measurements were carried out combined with microstructure, texture, hardness and tensile tests. Results demonstrated that a single roller ISRT effectively diminished residual stress in the nugget zone (NZ) from + 11.7 MPa to −45.3 MPa accompanied by better weld FCG resistance. Apart from residual stress reduction, the improved weld fatigue performance was likely correlated with the modifications of weld microstructure and texture due to rolling tensioning.