Influence of tool geometry in friction stir welding

In this article we highlight the results of a recent study undertaken to understand the influence of tool geometry on friction stir welding (FSW) of an aluminum alloy with specific reference to microstructural development, defect formation, and mechanical response. The welding trials were made on 4.4mm thick sheets using tools made of die steel and having different diameters of the shoulder and the pin, and the profile of the pin. Throughout the welding operation, the rotational speed, traverse speed, and tool axial tilt were held constant at 1400rpm, 80mm/minute, and 0 degrees, respectively. For a shoulder diameter of 20mm and a pin diameter of 6mm, the severity of defects in the weld was found to be the least and the resultant tensile strength of the weld was high. For the welds that were made using a tool having a shoulder diameter of 10mm and a pin diameter of 3mm the tensile strength of the weld was the least since the degree of defects observed were higher.