Effect of porosities on tensile properties of laser-welded Al-Li alloy: an experimental and modelling study

Aluminium-lithium (Al-Li) alloys are very attractive for aerospace applications due to their outstanding properties, such as high specific strength, high rigidity and good resistance to corrosion and fatigue, compared to conventional aluminium alloys. The butt joints of Al-Li 2A97-T3 alloy sheet produced by fibre laser welding with ER2319 filler wire were investigated in this paper. Uniaxial tensile tests have been performed to determine the nominal mechanical properties of the joints with and without porosities. In addition, a defect zone was defined in the welded specimens to investigate the effects of porosity on the joint tensile behaviour. The post-weld strength prediction (PWSP) model in a previous study has been extended by including the effects of the porosity in the welds to predict the overall response of the butt joints. The experimental and the modelling results show a good agreement, with the yield strength having a deviation lower than 5%. Both the yield strength and the ductility of the tensile specimens were observed to have decreased with the presence of porosities. The porosities aggravated the inhomogeneous deformation in the weld zone. Higher strain rate was found in the defect area than the remaining weld zone during plastic deformation, as the porosity in the specimen caused inhomogeneous deformation. It was found that this accelerated the failure of the specimen and lowered the global ductility significantly.