Shear deformation in TiAl: Atomic dynamic and static simulations

The dynamical shear deformation-induced HCP → FCC process in Ti3Al was systematically investigated using both molecular dynamics (MD) and ab initio methods. The details of the dislocation initiation, the microstructure evolution and the velocity field effect were presented and discussed. The MD simulation reveals that, with the increment of the velocity field, the deformation-induced dislocation slide may happen by three modes based on the nucleation of an initial FCC core, i.e. the continued fault slipping may initiate every other three layers, every other one and then three layers and every other one atomic layer. The corresponding transformed structure is an alternate existence of the single FCC and HCP plate, 18R fault, and the FCC plate containing three ABC units or more. The mechanism was further explored based on ab initio calculations of the detailed energy variation at different fault transition modes. The results promote systematic understanding of the stress induced fault transition mechanism in experimental observations. (Some figures in this article are in colour only in the electronic version)