Thermodynamic Modeling of Aluminum and Nickel Ternary Alloy Systems

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The objective of this research is to develop a thermodynamic description for the free energy of each phase as a function of composition and temperature in ternary aluminum and nickel base alloys. 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 transitions 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 SETARAM 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 that find application in technologies requiring high temperature structural alloys. Such data on Al and Ni-base alloy systems are scarce or non-existent. The experimental results will be used to compute the minimum in free energy for a particular composition at a given temperature. Such thermodynamic modeling of phase diagrams provides an opportunity to approach the phase equilibria aspects of alloy development in a more efficient manner. The improved database will be used to compute several isothermal sections in each of the ternary alloy systems using THERMOCALC. 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. The work finds application in the design of multi-component nickel and aluminum based alloys that are used in many technologies as structural materials. The experimental results of the study will provide the needed data for phase diagram calculations using CALPHAD methodology that is far more efficient than the currently available techniques. These experimental data are not available and this will be the only facility in USA that has the expertise to fill the need. From a fundamental viewpoint, the project will advance a largely uncharted area of research that is concerned with multi-component, multi-phase systems with varied phases. These systems find application in many technologies that require high temperature structural materials.