Deformation-induced γ↔α2 phase transformation in a hot-forged Ti–45Al–10Nb alloy

Deformation-induced γ→α2 and α2→γ phase transformations in a hot-forged Ti–45Al–10Nb alloy have been investigated by using high-resolution transmission electron microscopy (HREM). The γ→α2 transformation is an interface-related process, which involves the emission of the interfacial superdislocations from the misoriented semi-coherent α2/γ interface. These superdislocations further react with each other or with the moving dislocations in γ phase and results in the formation of α2 phase. On the other hand, the deformation-induced α2→γ phase transformation nucleates either at the α2/γ interfaces or at the stacking faults on the basal plane of α2 phase. The growth of γ plate is accomplished by the moving of a/6<101̄0> Shockley partials on alternate basal plane (0001)α2. The interfaces as well as the crystallographic orientation relationship between the as-cast or deformation-induced α2 and γ phase have been analyzed. The mechanisms for the deformation-induced γ→α2 and α2→γ phase transformations were also discussed.