Deformation-induced γ ↔ α2 phase transformation in TiAl alloy compressed at room temperature

Deformation-induced γ ↔ α2 phase transformation in a Ti–47Al–2Cr–2Nb–0.2Y (at.%) alloy compressed at room temperature was investigated by high-resolution transmission electron microscopy (HREM) and energy dispersive spectrum (EDS). The deformation-induced (DI) γ → α2 phase transformation occurred in a twin intersection region. On the other hand, the deformation-induced α2 → γ transformation nucleated at the stacking faults of α2 phase. The composition analysis of the γ and α2 laths by EDS suggested that composition of some laths deviated much from their equilibrium values. These composition deviations promoted the deformation-induced γ ↔ α2 phase transformation to occur; EDS results also suggested that there was no composition difference between the DI-γ plate and the primary γ phase. Based on the HREM and EDS experimental results, the mechanism of the deformation-induced γ ↔ α2 phase transformation has been discussed.