Liu Meihong ^* Qing Lvjun

• Xi'an Aeronautical University, Xi'an, China

Abstract: The TC17 titanium alloy is widely used in aero-engine production due to its remarkable strength, exceptional fracture toughness, and hardenability. Vacuum electron beam welding is commonly employed for TC17 welding. However, defects can occur during welding, manufacturing, and use of actual components, affecting the overall performance of TC17 welded structural components. In terms of this issue, experiments were conducted to determine the fatigue crack propagation rate of both the base metal and the welded metal. A finite element model was developed to analyze titanium alloy welded joints with initial cracks. The study involved calculating the variation of J-integral during crack propagation at low-stress levels. Subsequently, the stress intensity factor K and the crack propagation rate of the welded joint were determined using the Paris formula. The research findings indicate that as the crack propagates from the base metal to the welded metal in TC17 titanium alloy joints, the crack propagation rate decreases at the interface of the two metals but increases with the crack length. During the process of crack propagation along the interface of two materials, the crack propagation rate falls between the fatigue crack propagation rates of each material. The differing mechanical properties of welding joint materials result in discontinuous stress distribution at the crack tip and stress on the interface between the two materials. Fatigue crack expansion in TC17 titanium alloy electron beam welding joints depends on various factors, including mechanical performance distribution characteristics, initial crack position, and welding joint materials. Variations exist in the fatigue cracking extension between base metal and welded metal, warranting a comprehensive analysis when evaluating fatigue crack propagation life.