Thermochemistry of multi principal element alloys

With the introduction of the high entropy alloy (HEA) concept about 13 years ago, new ideas have stimulated the exploration of the vast composition space offered by multi-principal element alloys (MPEA). Understanding the thermodynamics of such MPEA is crucial to addressing their synthesis, properties, stability, materials compatibility, and technological applications. While the thermodynamics of binary and ternary alloys are relatively well investigated both experimentally and theoretically in the last five decades, this is not the case for multi-component (> 4 elements) alloys. Unfortunately, the methods used for alloys have limitations for application to multicomponent alloys containing a variety of elements with different chemical properties. They are not general but must be tailored carefully to the specific system of interest, and sometimes are simply inadequate. A more flexible and general calorimetric approach is needed. In the present talk, a new methodology for measuring the enthalpy of formation and mixing of metals will be introduced. This new calorimetric technique is designed for a new and broad class of materials and to increased understanding of the thermodynamics of MPEA, especially to address questions of local ordering and phase transition which may influence their thermodynamic and physical properties, as well as the generation of data to constrain phase diagram calculations.