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Vibration assisted welding (VAW) has emerged as a successful replacement for heat treatments and post-weld vibration treatments of arc welds to reduce residual stresses and distortions and thus to improve its mechanical properties. This review paper tries to create a knowledge platform for such a next generation research by consolidating the findings, merits, demerits and shortfalls identified hitherto in the field of VAW. This paper presents a review on the various techniques and processes of applying vibration to the welding system and their effects on microstructure, mechanical properties and residual stress of welds, and the directions for future research are presented. Vibration of workpiece during welding, oscillation of weld pool, oscillation of molten droplet, oscillation of welding arc and vibration of welding electrode were identified from the literature as the possible ways of imparting vibration. The advancement in the direction of computational work is also observed.

Dissimilar friction stir welds of aluminium alloys AA 5083 and AA2219 were investigated in a view to get defect free welds by varying process parameters. An attempt has been made to develop a mathematical model to predict sound welds. Design of experiments with three parameters and five levels were used to optimize the effectiveness of process parameters. Analysis of variance and response surface methodology were used to determine the significance and optimal level for each parameter to minimize % area of volumetric defect. The experimental and predicted values of % area of defect were in good agreement. The effects of process parameters and tool-offset on the extent of intermixing of materials and to minimize % area of volumetric defects are analyzed in detail by employing different methods such as macrostructural analysis and electron probe micro analysis. The defect free dissimilar weldments were characterized for transverse tensile properties. The observed tensile strength values were correlated with reference to the extent of intermixing of materials in the stir/nugget zone. Established mathematical models which have depicted a good prediction of relationship between the investigated FSW process parameters and the % area of defect of the welds. It is understood # Co-corresponding Author ## Corresponding Author that the mixing pattern in nugget zone and further joint strength are primarily affected by the tool offset and welding parameters.

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