Experimental validation of semi-empirical parameters for phase prediction in rapid-quenched and as-cast high-entropy alloys

Анотація

Predicting phase formation in high-entropy alloys remains a significant challenge due to the complex interplay of thermodynamic, atomic size, electronic, and kinetic factors. Nowadays, various empirical and semi-empirical criteria are proposed with this end in view, relying on parameters such as atomic size difference, mixing enthalpy and entropy, valence electron concentration, electronegativity difference, and electron-to-atom ratios. This study evaluates several widely used criteria by comparing their phase predictions with actual phase compositions observed experimentally in 29 high-entropy alloys produced by casting and rapid quenching. Results show that while many criteria capture general trends, none are universally accurate. Electronic criteria based on valence electron concentration and related parameters generally predict crystal structures well for 3d transition metal-based alloys but are less reliable for alloys containing non-transition elements or oxidized phases. Thermodynamic and atomic size-based criteria frequently fail to predict intermetallic and amorphous phase formation accurately. Increased cooling rates suppress intermetallic compounds and favor metastable phases, including amorphous structures; however, some criteria only partially capture this behavior. Discrepancies between predictions and observations are linked to temperature dependence of criteria, kinetic constraints, nanoscale phase inclusions, and alloy-specific chemical effects.