2A14铝合金VPTIG焊交叉焊缝组织与力学性能

Study on Microstructure and Mechanical Properties of 2A14 Aluminum Alloy VPTIG Welded Cross Joint

采用变极性钨极氩弧焊(单面两层,VPTIG打底+VPTIG盖面)工艺对2A14-CS态δ6 mm铝合金进行VPTIG1+VPTIG2交叉焊缝焊接试验,对比研究交叉焊缝与单一VPTIG焊缝的微观组织和力学性能。结果表明,交叉焊缝相较单一VPTIG焊缝拉伸性能下降,其抗拉强度下降5.4%~6.6%,断后延伸率下降19.2%~23.6%,塑性下降更明显。交叉焊缝硬度与单一VPTIG焊缝硬度规律一致,从母材到焊缝中心硬度均呈现先下降后局部上升再下降的趋势,但交叉焊缝焊缝区及靠近焊缝的部分热影响区硬度较单一VPTIG焊缝明显下降。交叉焊缝微观组织呈树状枝晶和胞状枝晶形态,其打底层焊缝相较单一VPTIG焊缝晶粒更粗大且大小不均匀分布,导致交叉焊缝的力学性能下降。交叉焊缝断裂机制与单一VPTIG接头断裂机制一致,为混合型断裂机制,即以晶界韧性断裂为主,并伴随有微裂纹源受力扩展开裂、微孔聚合型断裂。交叉焊缝断口相较单一VPTIG接头断口呈现韧窝少且浅、微裂纹源受力扩展开裂更明显的特征。

In this paper,the welding test of VPTIG1+VPTIG2 cross joint of 2A14-CS stateδ6mm 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 in‐creasing 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 micro‐porous 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.