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

Deformation-induced γ→α₂ and a₂→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 < 1010 > 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. © 1997 Elsevier Science S.A.