Strain induced structure transition in hot deformed γ+α dual-phase titanium aluminide

Strain induced structure transition (SIST) during hot deformation in TiAl alloy was investigated by high-resolution transmission electron microscopy (TEM). Various non-equilibrium asymmetrical twin boundaries with a large number of ledges were found. Special non-equilibrium tilt and asymmetrical γ/α interfaces were also illustrated. The normal crystal relation between γ and α can be changed. The 1/3 [111] Frank partial dislocations often appear at these non-equilibrium interfaces. It is also reported that the strain induced phase transitions, including γ→α, α→γ and γ→9R structure, commonly occur during hot deformation; the strain induced phase transitions are closely related to interface structure. The dislocation reactions and mechanisms for SIST are discussed.