SEMIEMPIRICAL EQUATIONS FOR PRESSURE COMPOSITION TEMPERATURE CURVES OF THE TI-H SYSTEM

Semi-empirical equations were developed for the pressure-composition-t emperature (PCT) curves of the alpha, beta, delta and epsilon phases i n the Ti-H system. Past PCT data were correlated within a practical ac curacy using a difference in the excess chemical potential of hydrogen in Ti. The excess chemical potential difference in the alpha phase wa s calculated based on the ideal one-site model. The excess chemical po tential difference in the beta phase was evaluated by assuming that th e partial molar enthalpy and entropy increase linearly with hydrogen c ontent and for that in the delta and epsilon phases by assuming that t he partial molar enthalpy is constant.