Anisotropic shock response of titanium: Reorientation and transformation mechanisms

We investigate shock-induced phase transformations in titanium (α-Ti) single crystals induced by shock loading along the [0 0 0 1], [101̄0] and [121̄0] 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)α//( _101̄0)ω and [_101̄0]α//[ _112̄3]ω between parent and product phases are observed, which differs from that previously reported for Ti. For shock compression along the [101̄0] and [121̄0] directions, there is a reorientation of the hexagonally close-packed α phase before the α → ω 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.