Thermodynamic modelling of phase diagram provides an opportunity to approach the phase equilibria aspects of alloy development in a more efficient manner than experimentally determining the phase equilibria in large numbers of alloys at many temperatures. The basic approach is to develop a thermodynamic description for the free energy of each phases as a function of composition and temperature and then to compute the minimum in free energy for a particular composition at a given temperature. In this way the phase diagram can be mapped in a matter of minutes or hours rather than the months involved with experimental methods of phase diagram determination. The accuracy of the computed diagram is dependent on the accuracy of the thermodynamic data used in the free energy description of the phases. Such data on Al and Ni-base alloy systems are scarce or non-existent. For this reason it is common to utilize and existing phase diagram for the development of the thermodynamic models. Such models may not be unique and may not correctly reflect the underlying thermodynamics of the system.

For reliable thermodynamic models it is essential to have some thermodynamic data on a system. In the project the author proposes to determine the heats of formation of a number of ternary Aluminum-Nickel-base alloy phases including the composition dependence for phases with substantial composition ranges. The heats of formation are determined using a custom built high temperature reaction calorimeter with a typical accuracy of ±1kJ/mole. In addition differential thermal analysis will be used to determine melting points and other phase transformations and differential scanning calorimetry will be used to determine heat capacity of selected alloys as a function of temperature. The DTA and DSC experiments will be performed in a new SETRAM 1750°C calorimeter.

The data determined from the experiments will be used to develop an improved, self-consistent thermodynamic database for Aluminum-Nickel-base alloys in collaboration with Professor Zi-Kui Liu, Penn State, Professor Bo Sundman, Division of Computational Thermodynamics, Royal Institute of Technology, Stockholm, Sweden and Professor Zhanpeng Jin, Department of Materials Science & Engineering, Central South University, ChangSha, China. The improved database will be used to compute several isothermal sections in each of the ternary alloy systems using ThermocalcTM. The data will also be used to validate various extrapolation models from the literature for the prediction of heats of formation of ternary compounds from binary data.