Process parameter optimization in underwater Friction Stir welding of dissimilar aluminium alloy butt joints by design of experiment

Abstract

Friction Stir Welding (FSW) is a nontraditional joining method that is used for the attachment of similar and divergent substances, which are comparatively difficult to be welded by fusion techniques. They are extensively used for joining metals in different applications. Also, this welding is more energy-competent and eco-responsive when contrasted with traditional fusion methods. The FSW has various degrees of prevalence when compared with conventional fusion. Generally, the mechanical properties of heat-treatable alloys are reduced due to thermal cycles and the roughening of the reinforcing expeditions in the FSW, resulting in joint softening. The Underwater Friction Stir Welding (UWFSW) is a preferred methodology to prevail over these problems. This procedure is appropriate for the heat treatable materials which are responsive to thermal activities throughout the fusion cycle. In this work, the UWFSW was carried for welding dissimilar alloys AA7075 and AA6082 with dimensions of 150 × 100 × 6 mm. The Hot work steel H13 was used as a tool material. Also, the influence of the fusion characteristics, including tool rotational speed, tool traverse speed, and tool tilt angle on the micro-arrangement and tensile characteristics of the UWFSW joints of AA7075 and AA6082 alloy, were investigated using Taguchi’s method. The S/N fraction scrutiny revealed that the optimum mechanical rigidity was attained at a tool rotational speed of 1200 rpm, tool fusion speed of 40 mm/min, and tool tilt angle of 1°. In accordance with the ANOVA method, the maximum input of parameters were analyzed for the objective functions, including the UTS (MPa), % of elongation, and micro hardness in the different zones (NZ, TMAZ, HAZ).