The properties of typical β/ω and β/α" heterophase interfaces in β-Ti alloys from a first-principles insight

The nucleation, growth, evolution, morphology, volume size, and distribution of omega and alpha" phases significantly predominate various properties of beta-Ti alloys. Therefore, the heterophase interfaces of beta/omega and beta/alpha" are both common and very important since they essentially dominate the whole process from nucleation to distribution of omega and alpha" product phases. In this study, the heterophase interfaces of beta/omega and beta/alpha" in beta-Ti alloys are carefully studied using first-principles method. The favorable local microstructures of beta/omega and beta/alpha" interfaces are explicitly determined. The calculations show the intermediate state at interface can smooth the structure changes across interface, thereby reducing the interfacial energy. Then the interfacial energies of the favorable interfaces functioned with the types and concentrations of the typical beta-stabilizers such as Mo, Nb, and V are investigated. Furthermore, the effects of beta-stabilizers on the nucleation morphologies of omega and alpha" phases are described from the perspective of interfacial energies and interfacial anisotropy, which show that the omega, alpha" embryos tend to be strip- and cube-like, respectively. Lastly, the most favorable beta/omega and beta/alpha" interfaces are discussed from the viewpoint of reducing interface strain. The present studies provide deep and explicit insights into beta/omega and beta/alpha" interfaces and a theoretical basis not only for the further study of microstructure evolution using phase field simulations, but also for further investigation on alloying effects of beta-stabilizers, so as to eventually achieve the bottom-up design of beta-Ti alloys.