High entropy Al0.5CrMoNbTa0.5 alloy: Additive manufacturing vs. casting vs. CALPHAD approval calculations

This paper reports on a temperature-dependent microstructural examination of a BCC-based High Entropy Alloy (HEA) Al_0.5CrMoNbTa_0.5, produced by arc-melting and electron beam melting. Subsequent heat treatments were performed in a protective atmosphere at temperatures of 1000 and 1300 °C for 24 h. SEM/EPMA and HR-SEM/EBSD, XRD, and TEM have been used for the characterization of the resulting microstructure and phase content. A notable Aluminum loss throughout the applied production processes was found. Both cast and EBM-built samples consisted primarily of a BCC-solid solution. The cast samples also contained small amounts of C14 Laves phase and a newly-found complex cubic (FCC-type) intermetallic phase with a lattice parameter of 11.5 Å. The obtained experimental results were compared with CALPHAD thermodynamic simulations, applied for the prediction of the equilibrium phase content. Good correlation between the experimental and predicted results was found.