It was noted that, under creep conditions, the microstructural behavior of lamellar TiAl was different to that of other materials. In the as-received state, the initial number of dislocations was very high and intrinsic dislocations, with b = <110>, existed in lamellar interfaces with an irregular morphology. In the early primary stage, the dislocation density in the γ matrix rapidly decreased. These dislocations glided in the lamellar interface during primary creep. When they reached the interface ledge, atomistic deformation caused by the gliding dislocations could change the stacking sequence and the composition of α2 ledges. As a result, the α2 was transformed into γ. During this phase transformation, a new unstable phase (Ti2Al) was observed. This new phase was an intermediate disordered phase between the α2 and γ ordered phases.

Investigation of α2/γ Phase Transformation Mechanism under the Interaction of Dislocations with Lamellar Interfaces in the Primary Creep of Lamellar TiAl Alloys. S.J.Yang, S.W.Nam: Materials Science and Engineering A, 2002, 329-331, 898-905