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The paper focuses on developing a novel decision-making model, to select the best welding parameters for friction stir welding of dissimilar aluminium to copper plates. A set of 21 experiments are carried out based on a d-optimal design matrix. Apart from considering the rotational speed and traverse speed as input variables, the position of aluminium and copper either in the advancing or retreating side is also considered as an input variable. On the successful fabrication of joints, the ultimate tensile strength, elongation, hardness and impact energy are estimated experimentally which are considered as performance parameters. The proposed decision-making process is categorized under multi-criteria decision-making (MCDM) methods. In the first phase, the novel MCDM model is applied to select the best welding parameters. The concept of the model is to minimize the risk of not attaining the global best result. The results obtained by the MCDM method is justified by carrying out a sensitivity analysis and finally validated with the results obtained from the fuzzy logic decision-making approach. The second phase is related to the computation of optimized values for the joining process that reports the development of a mathematical model by response surface methodology to predict different performance parameters. This is followed by conducting a trade-off analysis by developing a multi-objective response surface methodology (MORSM) that computes the optimal welding parameters. Finally, a confirmatory test is carried out for validation of the proposed MORSM model.

The aim of the study is to investigate the consequences of tool traverse speed on force and torque distribution of friction-stirwelded third-generation Al-Cu-Li alloy joints. The microstructure and corresponding mechanical properties of the joints are investigated on force and torque perspective. Thus, the contribution of the present work lies in establishing the relation between traverse speed and mechanical properties of the AA2050-T84 joint. Four welds have been considered at varying traverse speeds from 1 to 4 mm/s at constant tool rotational speed and tool tilt angle of 1400 rpm and 2°, respectively. A tool of H13 steel having a tapered screw-threaded pin profile was used. The investigation reveals that with the increase in traverse speed, longitudinal force (X-force), vertically downward force (Z-force) and spindle torque also increase. The grain size of the nugget zone reduces from 19.84 to 14.86 µm as traverse speed increases. It has been found that the mechanical strength of the joint increases as the traverse speed increases. The Vickers microhardness value increases from 115 HV 0.1 to 131 HV 0.1 in the nugget zone as traverse speed increases from 1 to 4 mm/s. The maximum tensile strength, % elongation and joint efficiency are 403.2 MPa, 7.2% and 75.5% for traverse speed of 4 mm/s. The tensile fracture samples are analyzed by scanning electron microscope and reveal ductile mode of fracture.

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