Molecular Dynamics Research of Crack Propagation of Single Crystal γ-TiAl Alloy along the Different Crystalline Phases

The different crystallographic orientation extension of the prefabricated micro-crack in the process of uniaxial tension of the single crystal gamma-TiAl was investigated using molecular dynamics simulations. The different forms of mechanical behavior and extension were analyzed at the crystallographic orientation of [100], [110] and [111]. The results show that the micro crack stress value of the three crystallographic orientation is 5.766, 6.26, and 6.57 GPa, respectively and their strength is enhanced in turn. The micro crack of the [100] crystal orientation exhibits brittleness cleavage extension completely, and the stress is always focused on the crack tip and decreases with increasing time. The micro crack of the [110] crystal orientation exhibits brittleness cleavage extension in the early stage and passivation phenomenon appears due to atomic staggering and dislocation emission, subsequently the sub crack initiates whose plane is different from that of the main crack, the stress always concentrates on the crack tip and decreases with increasing time; the main crack and the sub crack connect to constitute the step touch fracture crack. The micro crack of the [111] crystal orientation extends for launching slip dislocation and producing twins, and presents the obvious orientation effect, so the strength of materials is enhanced; the stress is always focused on the crack tip and twinning planes and it decreases with loading; the micro crack extension has fully different characteristics in the different crystallographic orientations.