静轴肩FSW铝合金6061-T4板的T形接头组织特征及动静载特性研究

利用自主开发的静止轴肩焊接工具及工装,在不同的焊接参数下均获得到了外观成形良好、无焊接缺陷的T形接头,并对接头内部成形、显微组织、硬度、静载强度和疲劳性能及疲劳失效机制进行了研究.研究结果表明铝合金静止轴肩搅拌摩擦焊T性接头内部质量良好,无缺陷,接头表面存在表面超细晶区,且焊核区内部由于流动状态不同导致组织及硬度存在一...

Microstructure Characteristics,Static and Fatigue Properties of Stationary Shoulder Friction Stir Welded T-joint of AA6061-T4

T-joints of AA6061-T4 were fabricated by self-made stationary shoulder friction stir welding tool. Defect-free T-joints with good appearance were obtained under different welding parameters. The weld formation,microstructure,micro-hardness,static performance and fatigue properties of the T-joint were evaluated. The weld surface was characterized by super fine equiaxed grains. Microstructure and hardness distribution in weld nugget vary due to the material flow condition. The hardness in the skin and stringer decreased at different levels compared to that of the base material. T-joints failed at the heat affected zone during the tensile tests in both skin and stringer direction. Using optimized welding parameter,the characterized fatigue strength was 101 MPa at the cycle of 2×10⁶. Fatigue crack initiated at the corner of skin and stringer,the failure mechanism in fatigue tests was transgranular fracture for T-joints at low welding speed and a mixture of intergranular and transgranular fracture for T-joints at high welding speed. The study of microstructures and mechanical properties of defect-free T-joint provides basic technical support for the manufacturing of the next-generation light-weight spacecraft structure.