Study on the influence of FSSW process parameters on tensile strength of dissimilar materials joint (AA2014/AA7075)

Abstract Friction Stir Spot Welding (FSSW) belongs to the category of solid-state welding process and is most suitable for joining lightweight materials. For obtaining highly efficient spot welds with good structural integrity, there is a need to optimize the process parameters involved in the FSSW process. This work is aimed at optimizing the process parameters for the spot welds fabricated in the AA2014-AA7075 alloy via the FSSW process. With the aid of Box-Behnken design, the sequence of experimental trials was performed at three levels along with the results obtained from the ANOVA methodology. The empirical modeling was established via Response Surface Methodology (RSM) and compared with the experimental trials. Results showed that the tool rotating speed serves as the most influential parameter followed by the tool shoulder diameter, plunge depth and dwell time. With the effect of response, contour and desirability plots, the optimal process parametric values were found and these values were correlated with the 7th experimental trial which was based on the maximum tensile strength offered by the spot weld. Further, the optical micrograph captured at the weld zone of the 7th trial specimen was rich in equiaxed grains with intermetallic phases. This grain refinement and intermetallic phases contributed to a higher hardness of the spot welds and thus offering maximum tensile strength with good structural integrity.