Microstructural characteristics of two-phase titanium aluminides

The microstructural characteristics of two-phase α 2 + γ 1 conventional and XD-processed, titanium aluminides were investigated by transmission electron microscopy. The observed microstructures show that the two-phase material composition promotes the formation of alternating lamellae of α 2 and γ corresponding to twin-related γ laths. The microstructures of XD materials suggest that the influence of excess boron dissolved from TiB 2 particles was to reduce the α 2− γ interfacial mismatch. The microstructural results demonstrate that deformation which occurs via the formation of α 2 layers and twin-related γ laths, rather than via large populations of mobile dislocations, plays the primary role in the deformation behavior of the two-phase titanium aluminides and show that twin-related γ lath formation was very important to the capability of two-phase materials for continuous deformation.