Microstructure of Ti-45Al-8.5Nb-0.2W-0.03Y electron beam welding joints

High Nb containing TiAl alloys showed susceptibility to cold cracking when welding was performed without preheating and post-heating; however, crack-free welds could be made with pre- and post-heating. The room-temperature strength of the crack-free welds was 480 MPa, and failure occurred in the base metal. The fusion zone obtained at a beam current of 7 mA mainly comprised coarse β/B2-phase grains, with acicular α₂ and γ phases distributed at the grain boundaries. The fusion zone obtained at 13 mA mainly contained fine γ- and α₂-phase grains. The fusion zone obtained with pre- and post-heating was dominated by the acicular α phase, reticular β/B2 phase, and blocky γ phase. The heat-affected zone could be divided into two characteristic regions according to the morphologies of the α₂ and γ phases. Changes in microhardness were analyzed with respect to the phase composition and microstructural morphology.