Role of Crystal Orientation on Dislocation Nucleation in Zr: A Molecular Dynamics Study

Abstract

Plastic deformation is known to be highly orientation sensitive. This orientation sensitivity of deformation gets further accentuated in case of hexagonal materials. Present study is an attempt to bring out the role of crystal orientation on the dislocation nucleation behavior of Zr (hcp material). Molecular dynamics simulations have been performed on single-crystal Zr with different orientations covering entire fundamental zone of orientations. Simulations have brought out high degree of orientation sensitiveness in dislocation nucleation stresses and considerable asymmetry of critical stresses of homogenous nucleation of dislocation in tension and compression. It was shown that it is easier to nucleate < a > type dislocations than < c > type. This is in agreement with the experimental observation of higher density of < a > type dislocations in comparison to < c > type in Zr. While a majority of the orientations have resulted in the formation of dislocations, certain orientations have resulted in the homogenous nucleation of nanotwins during the deformation. The simulations indicated, consistent with experimental evidence, larger density of < a > type dislocations in prismatic planes in comparison to the basal planes of Zr and dominance of prismatic slip in the deformation behavior of Zr.