2219-T651铝合金激光摆动焊接接头微观组织和力学性能

Microstructure and properties of 2219-T651 aluminum alloywelded joint by laser oscillating welding

采用激光摆动焊接技术对2219-T651铝合金进行了不同摆动幅度和频率下的焊接试验,研究了摆动工艺参数、焊缝气孔率和宏观成形、接头组织和性能之间的内在联系.结果表明,与无摆动焊接相比,激光摆动焊接可以降低焊缝气孔率,尤其随着摆动幅度的增加,当摆动幅度为2.5 mm时,气孔率降至1.66%.与母材相比,热影响区和熔化区发生软化.靠近焊缝的热影响区,由于沉淀强化作用的变弱,硬度逐渐降低,直至出现“平台”.而由α(Al)基体以及枝晶间和晶界α(Al)+θ(Al2Cu)共晶相组成的熔化区,因铜的偏析导致固溶强化效果被削弱,表现出最低的硬度.此外,部分摆动参数下焊缝晶粒尺寸有所细化,这引起了其硬度的略微升高.当摆动频率为150 Hz和摆动幅度为2.5 mm时,接头的抗拉强度高达318 MPa,约为母材抗拉强度的69.4%,接头抗拉强度与断口孔洞面积占比呈线性负相关关系,焊缝气孔率是影响焊态接头抗拉强度的主要因素.

Laser oscillating welding technology was applied to 2219-T651 aluminum alloy under different oscillating frequency and amplitude.The corresponding relationships between the oscillating parameters,the weld porosity,the joints formation,the microstructures and properties of the welded joints were revealed.The results show that compared with laser welding,laser oscillating welding can reduce weld porosity.When oscillating amplitude is set at 2.5 mm,the weld porosity can be decreased to 1.66%.In comparison with base metal,the heat-affected zone and the fusion zone are softened.Due to the weakening of the precipitation strengthening effect,the microhardness in the heat-affected zone near the weld gradually decreases until a“platform”appears.Meanwhile,the fusion zone is composed ofα(Al)matrix,α(Al)+θ(Al2Cu)eutectic phase distributed between dendrites and grain boundaries.Because of the diminished solid solution strengthening effect caused by Cu segregation,the microhardness in the fusion remain the lowest.Additionally,the grain sizes of the welds are refined under some oscillating parameters,leading to slight increase in the microhardness.The tensile strength of the welded joint reach the highest 318 MPa under the oscillating frequency of 150 Hz and the oscillating amplitude of 2.5 mm,which is approximately 69.4%of that of the base metal.The tensile strength of the welded joint shows negative linear correlation for the area proportion of fracture pores.The weld porosity is the main factor to affect the tensile strength of the welded joint.