γ ↔ α2 Phase transformation in fractured high temperature stress rupture Ti-48Al-2Nb(at.%).

The γ ↔ α₂ phase transformation in fractured high temperature stress rupture Ti-48Al-2Nb(at.%) alloy has been studied by analytical electron microscopy. α₂ and γ phases were found at grain boundaries. α₂ layers that suspended in γ layers and interfacial ledge higher than 2 d_(111)γ at γ/α₂ interfaces were observed in the lamellar grains. These facts indicated that γ ↔ α₂ phase transformation and dynamic recrystallization have occurred during high temperature stress rupture deformation. It can be concluded that deformation induced γ ↔ α₂ phase transformation and dynamic recrystallization resulted in the presence of γ particles at grain boundaries. A structural and compositional transition area between deformation-induced α₂(or γ) and its adjacently original γ(or α₂) phases was found by HREM and EDS and is suggested as a way to transform between γ and α₂ phase during high temperature stress rupture deformation. The transition area was formed by slide of partial dislocations on close-packed planes and diffusion of atoms. [ABSTRACT FROM AUTHOR]