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

doi:10.3901/JME.2021.20.108

Abstract

Abstract: 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.

Key words: aluminum alloy, stationary shoulder friction stir welding, T-joint, fatigue, failure mechanism

CLC Number:

TG453

LI Dongxiao, YANG Chun, HUANG Xin, XING Guangqiang, YANG Xinqi. Microstructure Characteristics,Static and Fatigue Properties of Stationary Shoulder Friction Stir Welded T-joint of AA6061-T4[J]. Journal of Mechanical Engineering, 2021, 57(20): 108-116.

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