Atomistic analyses of fracture in α, β and lamellar α - β Ti single crystals

In this work, molecular dynamics simulations are employed to investigate crack growth behavior and related microstructural evolution in alpha-Ti, beta-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 alpha-Ti while it depends on the initial crack length in beta-Ti and lamellar-Ti. The crack growth in beta-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 alpha-phase, beta-phase, or alpha - beta interface in lamellar-Ti. Significant structural changes (alpha to beta phase transformation) due to the applied deformation are not observed in alpha-Ti. For both beta-Ti and lamellar-Ti, the beta-phase is transformed into different variants of the alpha-phase. Dislocation density is the largest for lamellar-Ti followed by beta-Ti and alpha-Ti. The critical strain energy release rate is the largest for beta-Ti and it is lowest for alpha-Ti. The G(c) for alpha-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 beta-Ti and lamellar-Ti, G(c) shows a strong dependence on the initial crack length and the variation of G(c) relative to the initial crack length can be well described by an exponentially decaying function.

Automated summary

Molecular dynamics simulations were used to investigate crack growth behavior and microstructural evolution in different Ti single crystals. It was found that crack growth in alpha-Ti was independent of initial crack length, while it depended on initial crack length in beta-Ti and lamellar-Ti. Structural changes were observed in beta-Ti and lamellar-Ti, where the beta-phase transformed into variants of the alpha-phase. The critical strain energy release rate was largest in beta-Ti and lowest in alpha-Ti, and it showed a strong dependence on initial crack length in beta-Ti and lamellar-Ti.