Research on microstructure deformation mechanism of crack tip in titanium under tension along different orientations

The deformation process of titanium with an initial crack was simulated under uniaxial tension by the molecular dynamics method. The effect of [0001], and orientations on the microstructure deformation mechanisms at the crack tip was investigated using embedded atom method potentials. In the simulation, various deformation evidence were clearly observed, such as dislocation nucleation and movement, stacking faults formation, deformation twinning and phase transformation. The stress-strain curves showed that orientations had a greater influence on the plastic stage and less on the elastic stage. By applying uniaxial tension with a constant strain rate along different orientations, microstructure deformation at the crack tip was analysed. When loading along [0001] orientation, twinning was the main deformation mechanism and stacking fault occurred and expanded along slip system with the increase in strain. Applying uniaxial tension along orientation, an abnormal 'secondary increase' phenomenon was observed in the stress-strain curve. At the same time, dislocation loops appeared at the crack tip and they expanded, merged with the increase in strain. The massive phase transformation from HCP to BCC was observed in the model when loading along orientation, which was caused by multiple Shockley incomplete dislocations under the size limitation.