Microstructures and properties of welded joints of a Ti alloy

Abstract

Titanium alloy Ti-6Al-4V is commonly used in aircraft structure. However, the material will result in defect after prolonged usage, such as pitting due to corrosion. To save cost from changing the whole structure, TIG beam-on-plate welding was used in this project to study the feasibility of using it to repair the defect. TIG welding is the most used fusion welding process for reactive metal such as titanium alloy, as it provides a shielding gas to prevent interstitial elements from reacting with the titanium alloy. The 3 mm thick annealed plate of Ti-6Al-4V with TIG beam-on-plate welding and tensile tested was used as the received material and the microstructure of the material was seen using optical microscope. Scanning electron microscope was used to observed the fracture surface after the tensile test. Shearing of the material and ductile fracture were seen when investigating the fracture surface. Scanning electron microscope was also used to observe microstructure at a higher magnification and microcracks were seen to be developed mostly at the α phase or α/β interface.