Atomistic analyses of fracture in α, β and lamellar α -

Sunil Rawat,Alankar Alankar

In this work, molecular dynamics simulations are employed to investigate crack growth behavior and related microstructural evolution in α-Ti, β-Ti, and lamellar-Ti single crystals under plane strain conditions. It is observed that the crack growth is independent of the initial crack length in α-Ti while it depends on the initial crack length in β-Ti and lamellar-Ti. The crack growth in β-Ti increases monotonically with an increase in initial crack length. However the crack growth in lamellar-Ti does not increase monotonically with respect to the initial crack length since the crack tip of different initial cracks may lie in α-phase, β-phase, or α−β interface in lamellar-Ti. Significant structural changes (α to β phase transformation) due to the applied deformation are not observed in α-Ti. For both β-Ti and lamellar-Ti, the β-phase is transformed into different variants of the α-phase. Dislocation density is the largest for lamellar-Ti followed by β-Ti and α-Ti. The critical strain energy release rate is the largest for β-Ti and it is lowest for α-Ti. The Gc for α-Ti decreases with an increase in initial crack length and does not appear to be much sensitive to the initial crack length. In the case of β-Ti and lamellar-Ti, Gc shows a strong dependence on the initial crack length and the variation of Gc relative to the initial crack length can be well described by an exponentially decaying function.