Parametric optimization of friction stir welding parameters of marine grade aluminium alloy using response surface methodology

Friction stir welding between AA5052-H32 aluminium plates is performed by central composite design technique of response surface methodology. It is found that the welding parameters such as tool pin profile, tool rotational speed, welding speed, and tool tilt angle play a major role in deciding the joint characteristics. The joints fabricated using tapered square pin profile tool with a tool rotational speed of 600 r/min, welding speed of 65 mm/min, and tool tilt angle of 1.5° result in an unexpected weld efficiency of 93.51%. Mathematical models are developed to map the correlation between the parameters and responses (ultimate tensile strength and elongation) and these models are optimized to maximize the ultimate tensile strength of the friction stir welded joint. Response plots generated from the mathematical models are used to interpret the interaction effects of the welding parameters on the response variables. Adequacy of the developed models is validated using analysis of variance (ANOVA) technique. Results from the confirmatory experiments plotted in scatter diagram show a good agreement with predicted models. Different grain structures in various zones of the weld are examined by observing the micro and macro structures of the weld.