A Fast and Robust Method for Predicting the Phase Stability of Refractory Complex Concentrated Alloys Using Pairwise Mixing Enthalpy

The ability to predict the composition- and temperature-dependent stability of refractory complex concentrated alloys (RCCAs) is vital to the design and discovery of high-temperature structural alloys. Here, we present a model based on first-principles calculations to predict the thermodynamic stability of multicomponent solid solutions in a high-throughput manner and apply it to screen over 20,000 compositions. We develop a database that contains pairwise mixing enthalpy of 17 refractory metals using density-functional-theory (DFT)-based total energy calculations. To these, we fit thermodynamic solution models that can accurately capture the mixing enthalpy of multicomponent BCC solid solutions. By comparing their energy with DFT-calculated intermetallic enthalpies obtained from the Materials Project database and using convex hull analyses, we identify the ground state phase for any multi-component alloy composition as a function of temperature. The predicted phase diagrams for NbTiZr-V-(Mo, Ta, Cr) systems agree well with prior experimental observations. We apply our model to predict the phase evolution in NbVZr-Ti_x (0 &lt; <i>x &lt; </i>1), which are confirmed using laser-based alloy library deposition. With this method, we provide a fast and accurate way to estimate the microstructure of new RCCAs system and expedite experimental discovery. This method can also be adapted for multi-cation high entropy compounds.