Effect of welding wires on the microstructures and mechanical properties of TIG-welded Al-Cu-Mg alloys

• A low-cost and high-performance welding method was proposed for welding 2024-T4 aluminum alloy. • The scientific basis for the compatibility of different welding wire compositions and base materials was analyzed from a microscopic perspective. • The mechanisms of weld defect reduction, weld fracture, and weld reinforcement were discussed. • The factors influencing the elongation of 2024-T4 weld were clarified. Welding wire composition and porosity defects are two key factors affecting the performance of aluminum alloy welds. In this study, three commercial wires (ER2319, ER4043, ER5356) and TIG welding with/without pulse mode were employed to weld 2024-T4 alloy, aiming to clarify the scientific basis for matching wire composition to the base material (BM), reveal mechanisms of porosity reduction, weld strengthening, and fracture, and achieve low-cost and high-performance welding. Wire composition significantly influences its compatibility with the BM by altering the type and content of solute atoms, eutectic phase fraction, and grain size, with ER2319 wire achieving the optimal solution strengthening effect, the least amount of eutectic phase, and the smallest grain size, leading to a tensile strength of ∼340 MPa and an elongation of 6.8 %, with performance superior to ER4043 and ER5356. Pulse mode reduces porosity defects by stirring the molten pool and suppressing the formation of columnar crystals, decreasing the porosity by 92.69 % to 0.11 % and thereby increasing the elongation by 240 %. In addition, strain localization causes the weakest weld zone (WZ) to determine the elongation of joints, while the eutectic phase and porosity can accelerate joint failure, resulting in a severe reduction in the elongation.