Anisotropic shock response of titanium: Reorientation and transformation mechanisms

We investigate shock-induced phase transformations in titanium (alpha-Ti) single crystals induced by shock loading along the [0001], [10 (1) over bar0] and [12 (1) over bar0] directions using molecular dynamics simulations. We find a significant dependence of the microstructure evolution on the crystallographic shock direction, providing insight into the nature of the coupling between deformation and phase transformation. For shock along the c-axis, the orientation relationships (ORs) (0001)(alpha)//(10 (1) over bar0)(omega) and [10 (1) over bar0](alpha)//[11 (2) over bar3](omega) between parent and product phases are observed, which differs from that previously reported for Ti. For shock compression along the [10 (1) over bar0] and [12 (1) over bar0] directions, there is a reorientation of the hexagonally close-packed alpha phase before the alpha -> omega martensitic transformation, and the OR is consistent with the previously proposed Silcock relationship. We associate the reorientation with a shuffle and shear mechanism and suggest that shear stress is an underlying factor for the anisotropic phase transformation sensitivity. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.