The effect of ultrasonic rolling on the fatigue performance of laser-welded TC4 titanium alloy joints

Abstract In order to improve the fatigue performance of TC4 titanium alloy laser welded joints, ultrasonic rolling treatment was adopted in this study, and different passes of rolling process were used. The research results show that the ultrasonic rolling treatment significantly improves the fatigue limit and fatigue life of the weldment. At room temperature, the fatigue strength of the weldment increases by 2.04–4.58%, and the corrosion fatigue life increases by 1.71 to 3.05 times. This study also deeply analyzed the significant effects of ultrasonic rolling treatment on surface morphology, microstructure, surface residual stress and microhardness to reveal its strengthening mechanism. It was found that the ultrasonic rolling treatment shifted the crack initiation point to the subsurface and formed a hard layer with high residual stress on the surface by applying significant static pressure input and multiple treatments. This change makes the fatigue stripes narrower and denser. Compared with the traditional weld surface treatment method, ultrasonic rolling treatment significantly improves the surface quality and fatigue performance of TC4 titanium alloy laser welded joints.