Effect of tool diameter on the joint properties of AA6061 hollow panels using a novel one-step double-acting Friction Stir Weld method

Hollow aluminum panels are designed to be both rigid and lightweight, making them ideal for structural applications where material efficiency is critical. However, reliable welding techniques are essential to join these panels effectively. A common challenge during welding is the formation of porosity defects, caused by the varying solubility of hydrogen gas as aluminum transitions between liquid and solid states. While solid-state welding methods like Friction Stir Welding (FSW) are effective in minimizing porosity, they present difficulties when applied to thick materials such as extrusion panels. Thick structures often require multiple welding passes, resulting in increased production time and higher costs. To address these challenges, this study investigates the potential of an innovative one-step double-acting FSW technique. This novel method uses two tools operating simultaneously, providing dual sources of frictional heat and compressive force, a concept unexplored in traditional FSW methods. The research focuses on the influence of shoulder diameter—a critical parameter—on the physical and mechanical properties of AA6061 hollow aluminum panels. Experiments were conducted using shoulder diameters of 20, 22, and 24 mm, with process parameters set at a transverse speed of 30 mm/min, a rotational speed of 1500 rpm, and a tilt angle of 2°. The findings demonstrate that increasing the shoulder diameter significantly enhances the mechanical performance of the welded joints. The specimen welded with a 24 mm shoulder diameter achieved the best results, with a hardness value of 71.73 HVN, a load capacity of 15.51 kN, and a bending strength of 4.7 MPa. These results underline the effectiveness of the one-step double-acting FSW technique in improving the quality and efficiency of welding hollow aluminum panels, offering a practical solution to the limitations of conventional FSW in thick-structured materials.