Gas Tungsten Arc Welding of Ti2AlNb Based Alloy Sheet

Butt welding of a Ti-18Al-22Nb-O. 4Mo alloy was carried out employing gas tungsten arc welding on 1. 0-mm-thick cold rolled sheet. No crack was observed within the fusion zone and its associated heat affected zones. Two-step post-weld heat treatments at different temperature for the first stage were applied to improve the mechanical properties of the weldment. The results showed that only metastable ordered p phase (namely B2 phase) was detected in the fusion zone before the heat treatment, and though the room temperature ductility was excellent, the elevated temperature tensile strength was low with brittle failure. Widmanstatten microstructure was formed with precipitation at different scales after the heat treatment. The precipitates generated in the original B2 were predominantly acicular O phase as confirmed by X-Ray diffraction. The higher the temperature at the first stage, the coarser the O phase became. The room temperature and elevated temperature tensile strengths were improved after the heat treatment. The ductility of the weld joints with coarser Widmanstatten microstructure was better than that of joints with a finer one, at both room and elevated temperature.