Weldability of a titanium aluminide

The authors report the weldability of an alpha-two titanium auuminide, Ti-13.5 wt-%Al-21.5 wt-%Nb (Ti-24 at.-%Al-11 at.-%Nb), investigated from a perspective of developing relationships between the weld cooling rate, microstructure, mechanical properties and fracture behavior. Dilatometry studies performed over a range of cooling rates from 1 degree to 150 degrees C/s(1.8 degrees to 270 degrees F/s) show a continuous decrease in the body-centered cubic (BCC) to hexagonal close-packed (HCP) transformation start temperature. Water quenching from above the beta transus temperature provided a rapid cooling rate of 750 degrees C/s(1350 degrees F/s), which promoted complete retention of BCC beta phase. Implications of the continuous-cooling phase transformation study on the joining of Ti-13.5 wt-%Al-21.5 wt-%Nb using alternate welding processes are discussed