In this paper, dual laser-beam bilateral synchronous welding (DLBSW) technology is performed to fabricate 2219 aluminum alloy T-joint. The cryogenic axial tensile strength of the DLBSW T-joint in the direction parallel to the weld at −182℃ is tested. The microstructure of T-joint, the cryogenic axial tensile strength, fracture location and tensile fracture morphology are comprehensively investigated to explore the cryogenic axial tensile mechanism. The average value of cryogenic axial tensile strength of T-joint is 415 MPa, 76.9% of base metal (BM). Under the axial tensile force, the grain deformation and intergranular cracks are respectively generated in weld seam (WS) and heat affected zone (HAZ) near the fracture location. It is found that the cryogenic axial tensile fracture mechanism of the T-joint is intergranular ductile fracture, contains cleavage fracture and microvoid coalescence fracture. The degradation of cryogenic axial tensile property is attributed to multiple factors, such as impurity phases, pores, eutectics.

本文采用双激光束双边同步焊接（DLBSW）技术制造2219铝合金T型接头。测试了DLBSW T型接头在-182℃平行于焊缝方向的低温轴向拉伸强度。综合研究T型接头的微观结构、低温轴向拉伸强度、断裂位置和拉伸断裂形貌，探索低温轴向拉伸机理。T型接头低温轴向抗拉强度平均值为415 MPa，占母材（BM）的76.9%。在轴向拉力作用下，断口附近的焊缝（WS）和热影响区（HAZ）分别产生晶粒变形和晶间裂纹。发现T型接头的低温轴向拉伸断裂机制为沿晶韧性断裂，包括解理断裂和微孔聚结断裂。低温轴向拉伸性能的下降归因于多种因素，如杂质相、孔隙、共晶。