Residual stress in friction stir-welded Al sheets

Friction stir welding (FSW) is a relatively new joining technique particularly for aluminum alloys that are difficult to fusion weld. Although FSW is as a solid-state joining process which produces low-distortion welds of high quality, significant levels of residual stresses can be present in the weld after fabrication. These residual stresses can influence the service performance of the welded components with respect to fatigue and corrosion properties. Therefore, attempts were made to reduce tensile residual stresses in the weld region. The residual stress states of FSW joints in 6.3 and 3.2 mm thick Al-sheets (AA2024) that have been welded under mechanical tensioning were analysed. The results show that large compressive stress can be induced in the weld by applying mechanical tensioning during welding. (C) 2004 Elsevier B.V. All rights reserved.