Influence of In-Process Cryogenic Cooling on Mechanical Performance of Friction Stir T6 – AA 2900 Alloy Weldments

Al-Li-Cu alloy Al2195-T84 is used extensively in the aerospace launch vehicle external fuel tank structures. Aerospace components are generally joined using aluminium alloy materials, which increases the overall payload capacity of the launch vehicle. In this context, friction stir welding (FSW) process could be a potential solution. In this research work, Al2900-T6 specimens hot extruded were welded by FSW, using different parametric combinations of tool rotation and welding speed. In process cryo cooling was employed to dissipate the heat generated during the FSW. Microstructure and mechanical properties of the weldments were examined for both in-process cryo cooling and normally cooled conditions. It was observed that the grain size of the nugget zone (NZ) got refined because of the in-process cryogenic cooling during FSW. It was also discovered that microhardness was more in case of in-process cryo-cooled weldments as compared to naturally cooled weldments. Micro-hardness of the NZ was observed to be highest due to formation of finer grains because of the in-process cryogenic cooling. In-process cryogenic cooling has also improved tensile properties such as yield strength and % elongation of the FSW weldments.