This research combines experimental measurements of reaction kinetics in titanium aluminide-based intermetallic alloys with detailed quantitative transmission electron microscopy to study massive phase transformations. Changes in atomic configuration occurring during phase transformation are examined and the associated kinetic, thermodynamic, and crystallographic features are explored. Novel experimental techniques incorporating a computer interfaced for control and high speed data acquisition provide in situ measurements of K and electrical resistivity. Controlled gas quenching permits variation in cooling rate. The experimental measurements are incorporated in quantitative thermodynamic models to establish mechanisms of interface migration. %%% New alloys based on the titanium aluminide alloy system are of great importance for applications in high temperature aerospace systems because of their unique combinations of properties. Design of these alloys depends on understanding the phase transformations and phase equilibria that control mechanical properties.
