The Development and Validation of a New Thermodynamic Database for Ni-based Alloys ................................... 803

Abstract

Thermodynamic databases developed using the CALPHAD method has been successfully applied to the modeling and simulation of Ni based superalloys for more than fifteen years. Such databases when combined with suitable software, such as Thermo-Calc, can be used for accelerating alloy design as well as improving understanding of existing alloys in terms of their processing and in-service behavior. Additionally, such databases are also essential to the modeling of microstructural evolution using methods such as phase field or mean field approaches.A new thermodynamic database, TCNI6, has been developed for Ni-based superalloys based on the critical evaluation, using the CALPHAD method, of all the constituent binary systems across their full range of composition and many of the ternary systems containing Ni, as well as a number of other key ternary systems. The database has also been validated where possible against higher order systems as well.Together with the new mobility database, MOBNI3, which contains descriptions for the atomic mobility for respectively the γ (A1), γ' (L1 2 ), α (A2), β (B2) and liquid phases, TCNI6 can be used with software such as DICTRA to predict different kinetic aspects taking all relevant phases into account, e.g. the simulation of interdiffusion across Ni-based coatings.A new user friendly computational tool, TC-PRISMA, which simulates the kinetics of precipitation processes, is demonstrated utilizing these new databases and combined with interface property data. Engineering applications of precipitation modelling are validated against experimental data.