Optimization and characterization of dissimilar friction stir welded DP600 dual phase steel and AA6082-T6 aluminium alloy sheets using TOPSIS and grey relational analysis

Abstract

In the present investigation, dissimilar Dual Phase (DP) 600 Steel and aluminium alloy AA6082-T6 of 2 mm thickness were butt joined by friction stir welding process. The experimental runs were planned according to Taguchi’s L9 orthogonal array, with four process variables such as tool rotational speed, tool travel speed, tool tilt angle and tool pin offset towards aluminium side. The response variables such as tensile strength, yield strength, percentage elongation, and average hardness in the weld nugget zone and impact energy were considered as performance characteristics. Technique for order of preference by similarity to ideal solution (TOPSIS) and Grey relational analysis (GRA) approaches were used to determine the optimum set of input parameters. ANOVA a statistical technique was used to identify optimum levels and percentage contribution of each individual process parameter. Experimental validation was also conducted using an optimal set of process parameters which were found to be identical for both the techniques. The microstructural evolution was carried out for the joints using an optical microscope and Scanning electron microscopy (SEM). Energy dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) analysis were employed to analyse the composition of the optimized welded joint interface and fractography was conducted to evaluate the mode of failure. The main aim of the present research is to establish a decision support system with a robust design that helps weld engineers to eliminate defects and achieve sound weld joints.