Investigating the impact toughness properties and influential factors of titanium alloy joints

Double-sided symmetric MIG welding can significantly enhance welding efficiency for thick titanium alloys and holds promising engineering applications. However, the use of high currents and deposition rates in this process not only boosts welding efficiency but also impacts joint performance, particularly its impact toughness. In this study, the Charpy impact performance of double-sided double-arc MIG welded joints in each region was studied via oscillometric impact tests, and the main factors affecting the impact of joints were revealed. Scanning electron microscope was used to observe the fractures, and the microstructure characteristics and grain orientation of the impact crack propagation path were observed and analysed via metallurgical microscopy and EBSD. In addition, the microstructure of each region of the joint was observed via metallographic microscopy and transmission electron microscopy, which revealed the microstructure characteristics of different regions of the joint and clarified the effects of microstructure and grain orientation in different regions of the welded joint on the impact performance of each region of the double-sided, double-arc MIG welded joint. The results show that the crack initiation energy across different regions of joints typically ranges between 18 and 20 J, with minimal variations. Crack propagation plays a pivotal role in determining impact toughness, which is influenced both by microstructural features and orientation. This provides guidance for subsequent adjustments and improvements to the impact performance of the joint.