Enhancement of Metallurgical Properties on the ۴۰۰۹ Aluminum Alloy Joint by Underwater Friction Stir Welding (UFSW)

Underwater Friction Stir Welding (UFSW) is one of the modern and constantly evolving technologies of solid state joining and it is used for welding a wide range of materials. The technique used to the ۴۰۰۹ aluminum alloy joint and it has been demonstrated to be an effective method to improve the mechanical properties of joints. To illuminate the characteristics of underwater FSW, the microstructural evolution and its effect on mechanical performance of anunderwater joint were investigated in the present paper. This work compared the parameters of friction stir welding (FSW) and underwater friction stir welding (UFSW) on the weld joint .In this investigating friction stir welding (FSW) used in underwater environment, for this operations research pin covered and shielded from contact water by hollow shaft spin (HSS), the HSS controlled the heat conduction of pin and disconnect with water, applying for the firsttime a novel underwater FSW technique developed at marine structures. The metallographic exams indicate that weld nugget grain size has been decreased. The mechanical testing illustrated that hardness and tensile strength have been increased, on the other hand the percentage of elongation and impact energy have been diminished.