Numerical simulation and experimental investigation on electron beam welding of Ti-22Al-25Nb alloy with electron beam oscillation

Ti-22Al-25Nb (at%) alloy with the thickness of 3.5 mm is welded by using electron beam welding (EBW) based on electron beam oscillation. Numerical simulation analysis of EBW process, and microstructure and mechanical properties of welded joint are systematically investigated. Microstructure analysis shows that base metal consists of phases α 2, B2 and O. The fusion zone (FZ) of joint in as-welded condition consists of single phase B2. During EBW process, the transformation from phase B2 to phase α 2 or phase O is restrained in FZ due to the rapid cooling rate. Results of numerical simulation demonstrate the thermal change in EBW process and verify the microstructural evolution of weldment. Electron beam oscillation can stir the molten pool and stabilize the keyhole, thus the mechanical properties of welded joint are greatly improved. Under the experimental condition, the ratio of joint tensile strength varies from 85.2% to 91.9% and the failed locations of joints are in FZ or heat-affected zone (HAZ). Tensile fracture morphology of joint presents the pattern of quasi-cleavage fracture.