Fracture toughness of TA31 titanium alloy joints welded by electron beam welding under constrained condition

Abstract Electron beam welding (EBW) of titanium alloy was carried out by simulating the constraint conditions in actual welding. The fracture toughness of welded joints was studied. It is found that the fracture toughness decreases a lot, only 70% of the fracture toughness of base metal. The fracture surface was mainly ductile fracture mechanism with a large number of dimples by SEM. It was found that the crack propagation path was straight and mixed mode of intergranular and transgranular fracture by OM. OM and TEM observations show that the weld is mainly composed of fine and disordered acicular martensite with a large number of dislocations and twins. The grain size of restrained weld is finer and more disorderly than that of non-restrained weld, and there is no obvious grain orientation observed by EBSD. The crack propagation behavior of restrained weld was analyzed by the model.