DIS-SIMILAR FRICTION STIR WELDED JOINT QUALITY IMPROVEMENT THROUGH REINFORCEMENT AND PROCESS PARAMETER OPTIMIZATION

Abstract

This research work focuses on a comparative study on weld quality of reinforced friction stir welded joints of dissimilar aluminum alloys AA5083 and AA6061 incorporated with two different types of reinforcement particles. To fabricate dissimilar reinforced FSWed joints, AA5083 and AA6061 plates of thickness 6 mm were used as base materials and micro-sized Al2O3 and SiC particles were used as reinforcing candidates. Response surface methodology (RSM) based full factorial face-centered central composite design using three process parameters along with their three levels was employed to develop the design of experiments. Different tool rotational speed (750-1150 rpm), traverse speed (25-45 mm/min) and number of FSW passes (1-2) were considered as process parameters to multi-optimize the output response parameters (tensile strength, %elongation and microhardness) using desirability function in Response surface methodology. Multi-response mathematical model was developed to predict the response output parameters. To analyze the tensile strength, %elongation and microhardness of reinforced FSWed joints of AA6061 and AA5083, empirical relationships were developed at 95% confidence level. Microstructural characterization is carried out using optical microscopy and Field emission scanning Electron Microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The results showed that increasing rotational speed, decreasing the traverse speed and increasing numbers of FSW passes leads to improve the dispersion pattern of reinforcing particles of (Al2O3 and SiC) in the SZ of reinforced FSWed joints. The highest tensile strength (254.42 MPa), %elongation (30.9%) and micro-hardness (124.2 HV) for Al2O3 microparticles reinforced FSWed joints were observed at rotational speed of 950 rpm, traverse speed of 35 mm/min after three passes of FSW. The optimum value of tensile strength, %elongation and micro-hardness at the SZ are 258.09 MPa, 31.3% and 124.69 HV respectively, whereas the optimum value of rotational speed, traverse speed and number of FSW passes are 995.38 rpm, 29.79 mm/min and 3 passes, respectively was found for Al2O3 microparticles reinforced FSWed joints. The highest tensile strength (266.97 MPa), %elongation (32.7 %) and microhardness (128.4 HV) for SiC microparticles reinforced FSWed joint were observed at rotational speed of 950 rpm, traverse speed of 35 mm/min after three passes of FSW. The v optimum value of tensile strength, %elongation and micro-hardness at the SZ are 269.62 MPa, 32.75 % and 128.47 HV, respectively, whereas the optimum value of rotational speed, traverse speed and number of FSW passes are 994.57 rpm, 29.40 mm/min, and 3 passes, respectively was found for SiC microparticles reinforced FSWed joints.