Phase transformation and equation of state in Ti–45Al alloy under high pressure

The phase transformations and pressure-volume dependencies of the Ti–45Al alloy with respect to pressure have been investigated by means of in-situ observation using multi anvil-type high-pressure devices and synchrotron radiation. Under hydrostatic compression from 0 to 10.1 GPa, about 2.3 vol % of γ transforms continuously to α2. Lattice parameters as well as volume fractions of these two phases have been determined as functions of pressure. Bulk moduli estimated using Birch-Murnaghan's equation of state are 146.2 GPa for the γ phase, 136.7 GPa for the α2 phase, and 145.6 GPa for their two-phase mixture of Ti–45Al alloy. First-principles have also applied to investigate bulk moduli of two single phases, and the deviation between calculations and measurements is discussed and attributed to mainly phase transformation. The present study provides useful insights into thermodynamics of α2 and γ phases under high pressure.