In this paper, the welding test of VPTIG,1,+VPTIG,2, cross joint of 2A14-CS state δ 6mm aluminum alloy is carried out by single-side two-layer welding (argon arc backing+argon arc capping) process, and the microstructure and mechanical properties of the cross joint and single VPTIG welded joint are compared. The results show that the tensile strength of cross joint decreases by 5.4%~6.6% compared with that of single VPTIG welded joint; the elongation after fracture decreases by 19.2%~23.6%, and the plasticity decreases more significantly. The hardness of cross joint is consistent with that of single VPTIG welded joint; from the base metal to the weld center, the hardness shows a trend of first decreasing, then locally increasing and then decreasing, but the hardness of the weld zone of the cross joint and the part of the heat affected zone near the weld is significantly lower than that of the single VPTIG welded joint. The microstructure of the cross joint is in the form of dendrite and cellular dendrite. Compared with the single VPTIG welded joint, the grain size of the backing layer cross weld is thicker and unevenly distributed, which leads to the decline of the mechanical properties of the cross joint. The fracture mechanism of cross joint is the same as that of single VPTIG joint, which is a mixed fracture mechanism; that is, grain boundary ductile fracture is the main fracture, accompanied by microcrack source stress propagation crack and microporous polymerization fracture. However, compared with single VPTIG joint, the fracture of cross joint has fewer dimples and is shallow, and the microcrack source has more obvious characteristics of stress propagation cracking.
ZHAO Y J， MENG Z X， SUN G D， al. Microstructure and mechanical properties of 2A14 aluminum alloy intersection joints by tig welding and friction stir welding［J］. Aerospace Materials & Technology， 2020（4）： 97-102.