Simulation of martensitic microstructural evolution in zirconium

Abstract

A twinned microstructure is frequently observed after a martensitic phase transition. In this paper we investigate the atomic-level processes associated with the twin formation in a model system, using a many-body potential parametrized to represent zirconium. Molecular-dynamics simulations of the martensitic phase transition from bcc to hcp in zirconium show the evolution of a laminated twinned microstructure. Plastic deformation also occurs, creating basal stacking faults. The plastic deformation is such as to cause a rotation of the twins. This alters the twinning angle to the $61.5\ifmmode^\circ\else\textdegree\fi{}$ angle of the low-energy $(10\overline{1}{1)}_{\mathrm{hcp}}$ twins. These are thus identified as a cause of microscopic irreversibility in the transition.