First-principles based calculation of the macroscopic α/β interface in titanium

The macroscopic α/β interface in titanium and titanium alloys consists of a ledge interface (112)β/(01-10)α and a side interface (11-1)β/(2-1-10)α in a zig-zag arrangement. Here, we report a first-principles study for predicting the atomic structure and the formation energy of the α/β-Ti interface. Both component interfaces were calculated using supercell models within a restrictive relaxation approach, with various staking sequences and high-symmetry parallel translations being considered. The ledge interface energy was predicted as 0.098 J/m2 and the side interface energy as 0.811 J/m2. By projecting the zig-zag interface area onto the macroscopic broad face, the macroscopic α/β interface energy was estimated to be as low as ∼0.12 J/m2, which, however, is almost double the ad hoc value used in previous phase-field simulations.