T. J. Lienert, W. L. Stellwag, Los Alamos National Laboratory, Los Alamos, NM

Summary: Results of the microstructural and process characterization will be employed to explain microstructural evolution in the stir zone and TMAZ.Peak temperatures above the beta transus for the stir zone were corroborated by microstructural evidence. Strain rates in the stir zone during welding were estimated using a simple kinematic analysis and using the Zener-Holloman parameter. Temperature and strain rate estimates were then used to describe microstructural evolution in the stir zone. Evidence indicated that temperatures do not exceed the beta transus temperature in the TMAZ. The data on phase fraction in the TMAZ was used to estimate the distribution of peak temperatures in the TMAZ. Microstructural evolution in the TMAZ was discussed with the aid of pseudo-binary sections of the of the Ti-Al-V phase diagram.