Dynamic properties of structural transition in iron under uniaxial compression

By using molecular dynamics simulations, we have successfully simulated the bcc hcp structural transition in single-crystal iron under isothermal compression along the [001] direction. The results reveal a distinct softening of C₃₃ and a hardening of C₃₁ (or C₃₂) prior to the transition and an over-relaxation of the stress after transition. Above the critical stress the morphology evolution of structural transition is analyzed, which can be divided into four stages: hcp homogeneously nucleated, columnar grains formed, nuclei competed and merged, and a laminar structure formed along {110} planes. Besides, our simulations demonstrate that in mixed phases the hcp phase has negative shear stress and the potential of the hcp phase is higher than the bcc phase, and the shear stress of the system keeps a linear decrease with hcp mass fraction. The effect of temperature on the structural transition is also discussed.