Shear deformation in TiAl: Atomic dynamic and static simulations

The dynamic shear deformation process and the related stacking fault transitions in TiAl have been systematically investigated using both the molecular dynamics and ab initio methods. The details of the dislocation initiation and microstructural evolution are presented, and the concomitant potential energy variation and the radial distribution functions have been analyzed. The results show, interestingly, that some deformation-induced hexagonal close-packed (hcp) structures are metastable, and that a higher velocity field promotes more hcp segments. The phenomena are interpreted based on ab initio calculations of the detailed energy variation at the different fault transition stages, i.e., superlattice intrinsic stacking fault (SISF) → TWIN, SISF → hcp, and hcp → TWIN. The intrinsic factor that governs the deformation process is discussed. The results promote new understanding of the stress-induced interfaces and dislocation behaviors in experimental observations.