Structures and energetics of semicoherent interfaces of precipitates in hcp/bcc systems: A molecular dynamics study

Abstract

α/β (hcp/bcc) interfaces are of great importance in the microstructure development and the mechanical properties of titanium and zirconium alloys. This work contributes to the study of interface energetics and interfacial structures of the precipitate in the hcp/bcc system based on a simulation study using molecular statics (MS) and molecular dynamics (MD). The input orientation relationship (OR) was calculated based on the O-line criterion. Based on the energy of the interfaces containing the invariant line (IL), two preferred facets were determined by the Wulff construction, which explained the observed orientations of the habit plane (HP) and the side facet (SF). The deviation of the observed precipitate morphology from the equilibrium shape was discussed in terms of interface kinetics. The structures of the interfaces surrounding a three-dimensional (3D) precipitate, including the preferred facets and the end face, were obtained at the atomic level. The simulated dislocation structures and atomic structures in these interfaces are in good agreement with those of the experimental observations for Ti-Cr alloys. A method was suggested for modifying the O-cell structure with the guidance of the relaxed structure, yielding consistency between the calculated dislocation structure based on the generalized O-element approach and the simulation results.