Three-point bending fatigue life prediction of TC4 titanium weld joints based on tungsten inclusion defects

The lightweight alloy of titanium is gradually used in armored vehicles, the shell plates of which are often subjected to dynamic fatigue loads such as bending and torsion during their service. However, the mechanism of the influence of tungsten inclusion defects on the bending fatigue properties of titanium weld joint is still unclear. To solve this problem, the TC4 titanium weld joint specimens with and without the tungsten inclusion defects were prepared in this study, and the three-point bending fatigue properties of two different specimens were studied. The results indicate that the fatigue life of the specimens without defects is higher than that of the specimens with defects under the high stress amplitude, and the difference of fatigue life between them increases with the decrease of stress amplitude. The fatigue crack initiation sites of TC4 titanium weld joint without tungsten inclusion defects are mainly located at the edge or the corner position. For the TC4 titanium weld joints with tungsten inclusion defects, the fatigue crack mainly initiated at edges and corners under the low stress amplitude, and the initiation cracks are mainly located near the defects under the high stress amplitude. A model of the relationship model between the fatigue life of TC4 titanium weld joint and its equivalent projected area of tungsten inclusion defects under the stress amplitude of 275 MPa is established, the correction determination coefficient of the model equation is ~98.50%. The work can provide important clues for the fatigue performance optimization of the welded metallic components.