采用摆动光纤激光-CMT电弧复合焊接方式对高速列车用带锁底6A01-T5铝合金型材进行焊接工艺试验。采用优化的焊接参数得到了表面成形均匀、外观无缺陷的良好接头,并对接头进行了气孔分布特征、显微组织和力学性能试验。研究结果表明:摆动激光复合焊缝成形优良,内部横、纵截面上气孔率的平均值分别为0.63%、0.06%,且以形状规则、直径小于50.0 μm的圆形气孔为主,与光束不摆动时相比,焊缝内的工艺性气孔得到了明显抑制;焊缝中心为树枝晶组织,二次枝晶明显弱化;焊缝区和热影响区的硬度值低于母材,为软化区;复合焊接接头的极限疲劳强度为105.0 MPa,抗拉强度平均值为223.19 MPa,抗拉强度达到了母材的84.22%;接头拉伸断口呈韧窝状,具有典型的韧性断裂特征。

In this paper, the 6A01-T5 aluminum alloy hollow extrusion profiles with lock bottom for high-speed trains was welded by oscillating fiber laser-CMT arc hybrid welding. With optimized welding parameters, joints with uniform surface formation and without defects were obtained. Furthermore, the porosity distribution characteristics, microstructure and mechanical properties of the joint were investigated.The experimental results show that the joint formed by the oscillating laser hybrid welding has excellent forming quality. The average porosity rate of cross-section and longitudinal section is 0.63% and 0.06%, respectively. The round porosities with regular shape and diameter less than 50.0 μm are dominant, and the technological porosities in the weld bead are obviously restrained, compared to the non-oscillating laser hybrid welding. The central microstructure of the weld bead is dendrites, and the secondary dendrite is obviously weakened along the weld centerline. The microhardness of the fusion zone and heat affected zone is lower than that of base metal, which means the two zones are the softening zone.The fatigue limit of the hybrid joints is 105.0 MPa and the average tensile strength of joints is 223.19 MPa, while the tensile strength is up to 84.22% of the base metal. The tensile fracture shows an obvious dimple shape, which is the typical characteristic of ductile fracture.