Statistical-thermodynamic description of the order-disorder transformation of D0_(19)-type phase in Ti-Al alloy

摘要

Within the framework of the self-consistent field approximation and the static concentration waves approach, a statistical-thermodynamic description of D0_(19)-type superstructure in Ti-Al alloy is developed. A model of order-disorder phase transformation is applied for the non-stoichiometric intermetallic Ti_3 Al phase. Interatomic-interaction parameters are estimated for both approximations. One model supposes temperature-independent interatomic-interaction parameters, while the other includes the temperature dependence of mixing energies. The partial phase diagrams (equilibrium compositions for the coexistent ordered alpha_2-phase and disordered a-phase) are evaluated for both cases.