Developing CALPHAD databases for High Entropy Alloys.

CALPHAD modeling of High Entropy Alloys presents unique challenges compared with that of conventional alloys due to the lack of a single principal element. It requires an accurate description for the entire composition range rather than just in the vicinity of the base element.

Here we describe the approach taken in developing the TCHEA thermodynamic database, which contains 26 elements, where almost all underlying binary and over 500 ternary systems have been critically evaluated to capture the composition and temperature dependence. We also present the corresponding MOBHEA mobility database.

The CALPHAD approach to describe composition and temperature dependence can also be extended to many other thermochemical or thermophysical properties such as density, viscosity, surface tension, thermal conductivity, and electrical resistivity. All these properties are modelled in the TCHEA database.

Validation with experimental data for various HEAs and application examples will also be given.