Effects of the friction stir welding process variants on residual stress

A high-strength aerospace aluminium alloy, 25?mm thick plate, has been friction stir welded using four different process variants. The process variants used were stationary shoulder single pass, conventional shoulder single pass, stationary shoulder dual pass and conventional shoulder dual pass. The goal of the reported work was to investigate effects of different process variants on residual stress. Defect-free welds were produced by all process variants. Through thickness average, longitudinal, residual stress in both as-welded and post-weld heat-treated conditions is reported.