Novel weld composition to improve mechanical properties of 2219-T8 aluminum alloy joint using double-wire TIG welding

The composition of weld is one of the determining factors for the microstructure and mechanical properties of the joint. In this study, a novel weld composition was designed for 2219-T8 aluminum alloy TIG joint and achieved by Al-Cu and Al-Mg double-wire welding. The relationships between composition, microstructure, and mechanical properties of weld were investigated, and the strengthening mechanisms were discussed. The results show that Al-5.8Cu-0.5Mg was the desired weld composition with defect-free and improved mechanical properties. The microstructure of Al-5.8Cu-0.5Mg weld mainly consisted of rod-shaped alpha + theta eutectic and nanoprecipitates S phase. Compared with the Al-6.2Cu weld, the yield strength of Al-5.8Cu-0.5Mg weld increased by about 80 MPa, which was the result of precipitation strengthening of S phase. The average tensile strength of the joint with Al-5.8Cu-0.5Mg weld was increased by 25 MPa (about 8.6%) than that of the joint with Al-6.2Cu weld.