Effect of Laser Shock Peening on AA2219 Friction Stir Weld Joint: Temperature Dependent Tensile Properties

AA2219 is an age hardenable, high-strength aluminium alloy used for manufacturing propellant tanks in launch vehicles with Friction Stir Welding (FSW). Surface treatment methods such as shot peening, laser shock peening etc., are widely used to improve the fatigue performance of metallic materials and weld joints. This study focuses on the effect of laser shock peening on the tensile properties of AA2219 T87 FSW joint at various temperatures. Specimens were laser shock peened on the crown (top) and root (bottom) sides of the weld joint, and tensile behaviour was studied at room temperature, cryogenic temperature (77 K), and high temperature (423 K). At room temperature, laser shock peening increased yield strength by 7, 10 and 14% with single, three and six layers of peening, respectively. A similar increase (5%—single layer, 7%—three layers, 12%—six layers peening) is observed in cryo temperature also. At 423 K, an increase of 1-7% in yield strength is noticed. However, LSP does not influence ultimate tensile strength and elongation properties significantly. Due to LSP, a high-energy laser pulse impacts the specimen and induces compressive stress on the surface, increasing dislocation density and improving yield strength. Laser shock peening also increased the hardness in all the weld zones. In the Weld nugget region, an increase of 7%, 17% and 20% is observed with single, three and six-layers of peening, respectively, in average microhardness on the crown side of the weld. Irrespective of the number of layers of peening and test temperatures, the failure was found in the thermo-mechanically affected zone due to the dissolution and coarsening of Al 2 Cu strengthening precipitates.