Effects of the filler wire composition on the structures and mechanical performance of 2195 Al-Li alloy TIG joints

The mechanical properties of Al-Li alloy joints are closely related to the composition of the welding consumables. The present study aims to improve the mechanical properties of 2195 Al-Li alloy joints by adjusting the filler wire composition. The 2195 Al-Li alloy filler wire (same composition welding, SCW) and a self-designed filler wire (dissimilar composition welding, DCW) are used for the TIG welding of 2195 Al-Li alloy sheets in this study. The results reveal that increasing Cu concentration in the filler wire leads to more eutectic formation in the DCW weld, and the possible solidification crack can be healed in time by the liquid metal in the final solidification stage; significant grain refining in the DCW weld is caused by adding Ti and Zr into the filler wire, the refined grains enable the joint to tolerate more plastic deformation and reduce the continuity of the eutectics along the grain boundaries. The positive effects of filler wire composition adjustment on the joint mechanical properties are verified by the mechanical tests. The plastic deformation is concentrated in the weld, and the weld elongation of the DCW joint is much higher than the SCW joint. In addition, the solidification crack can be observed in the SCW joint but not in the DCW joint. These findings can guide the design of subsequent filler wires matched to 2195 Al-Li alloy.