High cycle fatigue and crack growth rate of 30 mm thick TC4 titanium alloy electron beam welded joint

High cycle fatigue properties of 30 mm thick TC4 titanium alloy electron beam welded joints and base material were compared and studied in this paper, it was found that high cycle fatigue performance of welded joints was very close to that of base material. Under the experimental conditions, high cycle fatigue strength of electron beam welded joints was 474 MPa when number of cycles was 2 ×10⁶, reaching 94.2% of base material. By observing high cycle fatigue fracture morphology of welded joints and base material, it was found that fatigue sources were located on the samples’ surface of welded joints and base material. Fatigue cracks were found in the fatigue crack growth area. Under the same load condition, spacing of scratches in the high cycle fatigue fracture of base material was smaller, about 1.49 μm, and spacing of the adjacent scratches of electron beam welded joints was 2.14 μm. A large number of dimples were found in the final tensile fracture area of welded joints and base material, showing characteristics of ductile fracture. Fatigue crack propagation rate of base material, heat affected zone and weld zone was also compared in this paper, and it was found that fatigue crack propagation resistance of heat affected zone was the weakest. It was concluded that high hardness of heat affected zone was an important reason for its weaker anti-fatigue crack growth performance than other areas.