Investigation of α2/γ phase transformation mechanism under the interaction of dislocation with lamellar interface in primary creep of lamellar TiAl alloys

Under creep condition, the microstructural behavior of lamellar TiAl alloy is different from that of general materials. At as-received state, the amount of initial dislocations is very high and intrinsic dislocations, b→=〈110〉, are existed in lamellar interface with irregular interface morphology. In early primary stage, the amount of dislocation density in γ matrix is rapidly decreased. These dislocations are gliding on lamellar interface during primary creep. When they reach interface ledge, atomistic deformation caused by gliding dislocations can change the stacking sequence and the composition of α2-ledge. As a result of this process, α2 is transformed to γ phase. During this phase transformation process, a new unstable phase, Ti2Al, is observed. This new phase is intermediate and disordered phase between α2 and γ ordered phases. The atomistic model for α2→Ti2Al→γ phase transformation process is newly proposed.