Orientational anisotropy in energy dissipation of shocked Nb crystals

A plethora of energy-dissipation mechanisms are observed in single crystals that are subjected to shock loading. Considering a specific flyer velocity, the study demonstrates orientational anisotropy for Nb single crystals using atomistic simulations. For all the cases of crystal orientations, the α to ω and α″ phase transformations occur along with {112} twins and dislocation slips. The magnitude and intensity of the observed energy-dissipation mechanisms are different for shock loading along different directions. The spall occurs for shock loading along ⟨100⟩ and ⟨011⟩ directions while incipient spall occurs for shock loading along the ⟨111⟩ direction. The variation in spall strengths for different crystal orientations is consistent with the experimental trends. Overall void volume fraction and population of voids vary with different directions of loading. A comprehensive study of competing energy-dissipation mechanisms in a shock-loaded Nb crystal along different directions is presented, which can be extended to other types of crystal structures.