The influence of nonlinear friction stir welding (FSW) tool control on joints' mechanical properties was investigated. Although FSW is widely applied to linear joints, it is impossible for five-axis FSW machines to maintain all FSW parameters in optimum conditions during nonlinear welding. Nonlinear FSW joints should be produced according to an order of priority for FSW parameters. Tensile test results of butt joints with rectangular change in the welding direction on the plate plane (L-shape butt joints) change with various welding parameters. Results show that a turn to the retreating side is encouraged when the welding direction changes. The method of zero inclination tool angles is effective for nonlinear and plane welding.
