Successful prediction of the elastic properties of multiphase high entropy alloys in the AlTiVCr-Si system through a novel computational approach

High-Entropy Alloys (HEAs) are a novel class of materials that can potentially enable novel high-stiffness lightweight alloy design through their exceptional chemical diversity. Most computational techniques for assessing the elastic properties of HEAs are restricted to relatively simple, single phase systems. In this research we present a computational approach capable of assessing the elastic properties of multiphase HEAs and verify it experimentally. Our computational approach involved the combination of several predictive techniques; Thermodynamic Modelling with Thermo-Calc for phase property prediction, Density Functional Theory (DFT) simulations with CASTEP to derive the elastic properties of the phases present in the alloy and Finite Element Modelling (FEM) with ABAQUS to homogenise the elastic properties of each phase into a unified material. The applicability of this methodology is alloy-universal and solely depends on the accuracy of each individual modelling technique used. For verification, the equiatomic AlTiVCr and AlTiVCr-Si7.2 high entropy alloys were manufactured through Vacuum Arc Melting (VAM) and were then heat-treated at 1200 °C for 8 h, followed by air-cooling to room temperature. The samples were characterised by Optical and Scanning Electron Microscopy (OM, SEM), X-Ray Diffraction analysis (XRD), together with elastic properties measurements through depth-sensing nanoindentation and microindentation testing. Our approach managed to successfully predict the elastic properties of both materials, yielding a deviation of 10% for the AlTiVCr alloy and only 2% for the AlTiVCr-Si7.2 alloy.