This paper has studied the deformation-induced γ→DI-α2 phase transformation of TiAl alloys using high-resolution electron microscopy. Studies revealed that the deformation-induced γ→DI-α2 phase transformation could occur in the regions where a deformation twin was blocked during both high-temperature and room-temperature deformations. Though the deformation conditions were completely different, these phase transformations have not exhibited any difference. High-resolution image observations of the deformation-induced DI-α2 phase suggested that the orientation relationship between the DI-α2 and γ phases remained the typical one： （0001）DI-α2//{111}γ, 11 20DI-α2// 〈 110 〉 γ- The conversion of stacking sequence from ordered FCT to ordered non-equilibrium HCP structure was accomplished by the movement of a/6 〈 11 2 Shockley partial dislocations on every other {111}γ plane. Compositional analysis based on X-ray energy dispersive spectroscopy （EDS） revealed that the DI-α2 phase had the same composition as the matrix γ phase and no compositional diffusion occurred. The strong stress concentration in the intersection region was the major force to induce the γ→DI-α2 phase transformation.
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