TRIBOLOGICAL AND MECHANICAL PROPERTIES IMPROVEMENT THROUGH REINFORCEMENT BY USING FRICTION STIR PROCESSING

Abstract

This research work focuses on a comparative study on weld quality of dissimilar aluminum alloys incorporated with three different volume fractions and two different sizes of reinforcement particles using friction stir processing (FSP) technique. Aluminum alloys AA7075 and AA6061 plates of thickness 6 mm were used as base materials to fabricate dissimilar FSPed composite joints and, micro and nano-sized Al2O3 particles were used as reinforcing candidates. Tool rotational speed (700-1100 rpm), traverse speed (40-60 mm/min) and different volume fraction of reinforcement particles (4-10%) were used as input process parameters for response output such as, tensile strength, %elongation, micro hardness and wear behavior. Central composite face-centered design (CCFCD) under response surface methodology (RSM) is employed to develop the design matrix for conducting the experiments. Microstructural characterization is carried out using optical microscopy and scanning electron microscope (SEM) equipped with energy-dispersive X ray spectroscopy (EDS). Tensile fractured surfaces were also examined by SEM. Multi response mathematical model is established for prediction of response parameters. This model is proficient to forecast the main effects and interactive effects of three levels of the opted process parameters. Results show that increasing the tool rotational speed and decreasing the traverse speed, leads to improve the dispersion pattern of reinforcing particles of Al2O3 (micro and nano) in the stir zone of FSPed composite joints. The large dimples and quasi cleavage with a sharp edge and various depths were found on the fractured tensile specimen surface of low tool rotational speed whereas fine dimples were found at high tool rotational speed of FSP composite joints. The maximum tensile strength (241.35 MPa), microhardness (157.5 HV) and minimum wear weight loss (10.3 mg) for FSPed composite joints incorporated with Al2O3 microparticles were observed at rotational speed of 1100 rpm, traverse speed of 40 mm/min with 10% volume fraction of Al2O3 particles. The optimized value of tensile strength, % elongation, micro-hardness and wear (weight loss) at the stir zone are 227.80 MPa, 19.31, 147.97 HV and 10.474 mg respectively, whereas the optimized value of tool rotational speed, traverse speed and volume fraction of Al2O3 particles are 1096.76 rpm, 55.59 mm/min and 8.64 % respectively was found for Al2O3 microparticles. The maximum tensile strength (254.9 MPa) and microhardness (169.1 HV) for FSPed composite joint incorporated with Al2O3 nanoparticles were observed at rotational speed of 1100 rpm, traverse speed of 40 mm/min with 10% volume fraction of Al2O3 particles. Whereas, minimum wear weight loss (8.97 mg) for FSPed composite joint incorporated v with Al2O3 particles was observed at rotational speed of 1100 rpm, traverse speed of 60 mm/min with 10% volume fraction of Al2O3 particles. The optimized value of tensile strength, %elongation, micro-hardness and wear (weight loss) at stir zone are 240.45 MPa, 24.95%, 157.89 HV, and 9.17 mg, respectively, whereas the optimized value of tool rotational speed, traverse speed and volume fraction of Al2O3 particles are 1089.40 rpm, 58.09 mm/min, and 8.74% respectively was found for Al2O3 nanoparticles.