Phase-field simulation of coherent BCC/B2 microstructures in high entropy alloys

This present work simulated the coherent BCC/B2 microstructures existing in body-centered-cubic (BCC)-based Al-Ni-Co-Fe-Cr high entropy alloys (HEAs) in light of the phase-field method. These coherent BCC/B2 microstructures contain spherical or cuboidal nanoprecipitates, or exhibit a weave-like spinodal decomposition in experiments. Based on the Chan-Hilliard equation, a two-dimensional phase field model was established using the COMSOL Multiphysics software to reveal the coherent microstructural evolutions of the present HEAs. It was found that the simulations of spherical/cuboidal nanoprecipitations and weave-like spinodal decomposition are well consistent with the experimental results. Both the lattice misfit and the anisotropy difference of Young's moduli between the precipitated phase and matrix phase affect the precipitate morphology, in which the cuboidal nanoprecipitation is especially susceptible to the modulus anisotropy. The coarsening behavior of precipitates is also discussed with the aid of the simulation results. The phase-field simulation will provide an important technique to predict the microstructural evolution and to assist the composition design of new HEAs. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.