The effect of TIG welding techniques on microstructure, properties and porosity of the welded joint of 2219 aluminum alloy

2219 aluminum alloy was mainly used in the propellant tanks of domestic aerospace vehicles. Porosity was often observed during the VPTIG welding joint of the 2219 aluminum alloy. The new welding technology under condition of direct current electrode negative A-TIG (DCEN A-TIG) welding using a special active agent (AlF₃, LiF, KF-AlF₃, K₂SiF₆) had eliminated the welding porosity of 2219 aluminum alloy. DCEN A-TIG welding and VPTIG welding of 2219 aluminum alloy were performed. Compared with VPTIG welding, the current decrease of DCEN A-TIG welding had greatly reduced thermal effect on base metal and heat-affected zone. The DCEN A-TIG technology had prevented welding porosity, while VPTIG welding had contained numerous macro and micro porosity. The weakest part of the DCEN A-TIG welding joint was the fusion zone, however, the VPTIG joint mainly ruptured in the weld zone due to significant porosity defect. The grain sizes of the welding zone in VPTIG welding were coarser than those in DCEN A-TIG welding, which can reach the same mechanical performance index with VPTIG welding. - Highlights: • The direct current electrode negative A-TIG (DCEN A-TIG) welding using a special active agent was realized. • DCEN A-TIG welding had eliminated the welding porosity of 2219 aluminum alloy. • DCEN A-TIG welding had removed the oxide film of 2219 aluminum alloy. • VPTIG welding had contained numerous macro and micro porosity and had increased thermal effect on base metal. • DCEN A-TIG welding can reach the same mechanical performance index with VPTIG welding.