ON INCREASING PRODUCTIVITY OF MICRO-FRICTION STIR WELDING WITH AID OF TOOL SHOULDER MICRO-FEATURES

Prior investigations on micro-friction stir welding (micro-FSW) of 0.5 mm thick aluminium alloy 6061-T6 sheets have shown that increasing the tool travel speed above 200 mm/min, at a fixed tool rotational speed (1900 rpm) and shoulder penetration (0.10 mm), results in lack of penetration defect in the welds. This limits the production rate and may distract the interest of industries which aim at utilizing micro-FSW for joining of micro-mechanical components. The present work investigates the utilization of micro-features on tool shoulder face to solve this issue. A spiral shape of micro-feature having a unique cross-section was employed on the tool shoulder and welding was performed at a tool travel speed of 1000 mm/min at two plunge depths (0.10 and 0.14 mm). The forces, temperature and material distribution 'during welding' and the surface finish, microstructure, microhardness and tensile property of the weld obtained 'post welding' were analyzed and compared with that of the welds obtained with featureless tool shoulder. It was found that low temperature welding with better surface finish and tensile property could be achieved with micro-featured tool shoulder at 0.14 mm plunge depth even at high tool travel speed of 1000 mm/min.