Shock-induced structural phase transformations studied by large-scale molecular-dynamics simulations

Shock waves in martensitic Fe (bcc) induce a complex relaxation mechanism behind the shock front. Non-equilibrium multimillion-atom molecular-dynamics simulations demonstrate that for shock strengths above the threshold for plastic deformation, small grains of austenite (hcp, fcc) nucleate in the martensite matrix. The subsequent growth and orientation of the austenitic grains strongly depend on the crystallographic shock direction and the shock strength. Crystallographic orientational relationships between the unshocked and shocked material are quite similar to that found in the temperature-driven structural transformations (i.e. martensitic and austenitic transformations) in iron-based alloys. The influence of the specific potential on the qualitative and the quantitative results of the simulations will be discussed.