Study of the welding parameters effect on the tunnel void area during friction stir welding of 1060 aluminum alloy

Friction stir welding is a relatively novel solid state method which produces ultra fine-grained microstructure and promoted mechanical properties due to the severe plastic deformation induced during welding. These features, of course, would be obtained if the welding parameters have been justified so that the welding zone becomes free of any defect specially tunnel cavity. This defect was primarily caused by an insufficient heat input during welding. In this study, a mathematical model has been presented to estimate the heat input generation during welding pertaining to the frictional work dissipated between the tool/workpiece interface, and moreover, the heat produced by the mechanical stirring of the plastically deformed material around the pin. The aim was to correlate the heat input generation and the tunnel void area. Aluminum plates with commercial purity were used for experimental efforts. During friction stir welding, a thermal camera was utilized to measure the maximum temperature of the material. After welding, samples cut through the transverse direction and examined for the area of tunnel cavity, and the extent of thermo-mechanically affected zone, as well. Comparison among the tunnel cavity areas with the heat input generations showed that to eliminate the tunnel cavity, at least a minimum heat input of about 800 J mm(-1) was required.