| Thermodynamic phase calculation and its experimental confirmation were made on a series of wrought Ni base superalloys. The Gibbs free energy of the constituent phases such as γ, γ`, σ, etc can be expressed by applying the Sublattice model. Minimum Gibbs free energy condition was selected as the criteria for determining the equilibrium state. The calculated phase fraction and the transition temperature were experimentally validated by comparing the calculated value with the measured one. Isothermal aging treatment followed by electrochemical extraction and quantitative X-ray diffraction was employed for experimental validation of the calculated phase fraction, and the differential thermal analysis for the phase transition temperature. The calculated values for both phase fraction and transition temperature are well matched with the measured values. The calculated phase diagrams offer lots of useful information such as solution treatment temperature, TCP(Topologically Close Packed) phase formation, γ` phase fraction and driving force for precipitation, etc. |
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