Orientation-induced anisotropy of plasticity and damage behavior in monocrystalline tantalum under shock compression

In this work, the role of crystallographic orientation on dynamic mechanical response in single-crystalline tantalum subjected to impact loading is investigated using non-equilibrium molecular dynamics simulations. Interestingly, the correlation of spall strength with void distribution is characterized statistically. Moreover, it is discovered that the entanglement of dislocation lines plays an important role in void nucleation, and then high dislocation density is beneficial to the increase in potential void nucleation sites. Oppositely, the movement of dislocation lines is deteriorated by voids, and then the dislocation density within the spall region dramatically drops after void nucleation in each orientation. There is a strong sensitivity of dislocation line evolution to void growth and coalescence in the later stage of cavitation. For [100], fewer potential void nucleation sites are found to occur in narrower spall zone, and then the existing voids are easier to be aggregated. Consequently, dislocation lines cannot be absorbed by surrounding voids. In contrast, the void distribution area is wider enough to facilitate to annihilate more dislocation lines through voids in [110]. Particularly, the decrease of dislocation density is inclined to the fact that the space for dislocation line survival is preoccupied by void nucleation sites along the [111] direction.