The role of residual stress and heat affected zone properties on fatigue crack propagation in friction stir welded 2024-T351 aluminium joints

The effects of weld residual stress and heat affected zone on the fatigue propagation of cracks parallel and orthogonal to the weld direction in friction stir welded (FSW) 2024-T351 joints were investigated. Crack propagation behaviour was sensitive to both weld orientation and the distance of the crack from the weld line. Growth rates both faster and slower than in the parent material were observed, depending on the crack orientation and distance from the weld. Weld residual stress was mechanically relieved and the effects on crack propagation observed. A comparative analysis of the results indicated that crack growth behaviour in the FSW joints was generally dominated by the weld residual stress and that microstructure and hardness changes in FSWs had a minor influence.