Determining the range of process parameters for friction stir welding using steepest ascent approach

Abstract In the present research work, friction stir welding (FSW) of dissimilar aluminium alloy series (i.e., 7xxx and 8xxx) is performed at various rotational speeds (1900–2500 rpm), welding speeds (60–80 mm min −1 ), and tilt angle (1.8°–2.4°) to find out the optimal ranges of process parameters for main experiments. The experiments are designed as per the steepest ascent approach by using three factors two-level fractional factorial design. The tensile strength is considered as an output parameter for deciding the optimal levels of process parameters. The graphical analysis of the steepest ascent provides the optimal ranges of process parameters, i.e., 1818 to 2104 rpm for rotation speed, 42 to 63 mm min −1 for tool travel speed and 0.9 to 1.8° for tool tilt angle. Furthermore, microstructural and fractography analyses are also carried out to study the morphology and nature of joints. The microstructure shows the different welding zones such as the nugget zone, thermomechanical affected zone, and heat affected zone. The fractography analysis reveals the ductile nature of joint.