2195-T8铝锂合金激光填丝双面焊熔池行为与接头力学性能研究

Study on welding pool behavior and joint mechanical properties of 2195-T8 Al-Li alloy by laser wire filling double-sided welding

铝锂合金以其质轻、高强、耐腐蚀等优势成为新一代航空航天应用材料,与其他铝锂合金相比,2195-T8铝锂合金焊接性能最优。基于液体火箭贮箱连接处的焊接需求,采用激光填丝双面焊接可以获得质量较好的接头。针对焊接过程中熔池内流体流动与温度的变化,建立了热-流耦合数学模型,通过数值模拟的方法对2195-T8铝锂合金焊接过程进行了研究,而后开展了接头轴向拉伸强度测试实验,阐明了焊接速度与填丝速度对熔池成形、流动与热输入的影响,并得到了不同焊接工艺参数下的最高接头强度。研究结果表明:4组不同焊接工艺参数下,第一面焊接与第二面焊接的熔池内流体流动趋势基本一致,主要为熔池左侧的顺时针涡流与右侧的逆时针涡流;提高焊接速度或填丝速度可以改善熔池成形质量,降低熔池热输入,细化焊缝熔合区中以柱状晶为代表的晶粒,进而有效提升接头力学性能;通过对4组不同焊接工艺参数的数值模拟与实验结果进行对比分析,最终得到熔池成形质量最好、热输入最小的焊缝,其接头轴向拉伸强度高达426.4 MPa,为母材强度的72.6%,对应的焊接速度与填丝速度分别为50 cm/min、1.8 m/min。

Al-Li alloy has become a new generation of aerospace application materials with its advantages of light weight, high strength and corrosion resistance. Compared with other Al-Li alloys, 2195-T8 Al-Li alloy has the best welding performance. Based on the welding demand of liquid rocket tank joint, better joint quality can be gotten with laser wire filling double-sided welding. For the fluid flow and temperature change in the molten pool in the welding process, heat-flow coupling mathematical model is established. By using the method of numerical simulation, the welding process of 2195-T8 Al-Li alloy is studied, and then the joint axial tensile strength test is carried out. The effect of welding speed and wire filling velocity of the molten pool on the flow and heat input is illustrated. The maximum joint strength under different welding parameters is obtained. The results show that under four different welding parameters, the fluid flow trend in the molten pool is basically the same between the first welding side and the second welding side, which is mainly clockwise eddy current on the left side and counterclockwise eddy current on the right side. Increasing welding speed or wire filling speed can improve the forming quality of the molten pool, reduce the heat input of the molten pool, refine the grain represented by columnar crystal in the welding fusion zone, and effectively improve the mechanical properties of the joint. By comparing and analyzing the numerical simulation and experimental results of 4 groups of different welding process parameters, the weld with the best forming quality and the smallest heat input is finally obtained. The axial tensile strength of the joint is up to 426.4 MPa, which is 72.6% of the base metal strength. The corresponding welding speed and wire filling speed are 50 cm/min and 1.8 m/min respectively.