Atomic simulation of the orientation effects on crack tip behavior in titanium single crystal

Abstract

This work presents atomic simulations of crack tip behavior in HCP titanium single crystal with center crack under mode I loading condition. The simulation results show that the crack tip plasticity in most of the studied crack orientations is attributed to the activation of basal or prismatic 〈a〉 slips, which is in accordance with the slip characteristics analysis. Comparing the increment of crack tip advance with the applied strain under different conditions, it is found that brittle mode has the highest crack propagation rate, following by twinning dominated crack tip behavior and the latter is dislocation slip dominated crack tip behavior. The above toughness difference is further explained from the perspective of the atomic stress distribution in front of the crack tip. Finally, the simulation results are compared with theoretical predictions based on the linear elastic fracture mechanics. Besides, the observed crack kinking phenomenon is attributed to the preference of cleavage along the plane with lower critical stress intensity factor. In general, the simulation results indicate that titanium is an intrinsically ductile metal as plastic deformation can be observed in the vicinity of the crack tip for most of the studied crack orientations, though some slip modes that have relatively Schmid factors are suppressed by the applied boundary condition.