Likhatskyi I. Development of casting high-entropy alloys with increased aluminium content and technologies for their production

The dissertation is devoted to the solution of the scientific and technical problem of developing cast high-entropy alloys with increased aluminium content, substantiating their chemical composition and production technologies, investigating the regularities of structure and phase formation, and establishing relationships between chemical composition, processing conditions, and casting, mechanical, and corrosion properties. Based on theoretical and experimental studies, the regularities governing the influence of chemical composition, increased aluminium content, and technological parameters of melting and casting on the formation of structure, phase composition, and properties of cast high-entropy alloys have been established. It is shown that the formal value of configurational entropy of mixing is not a sufficient criterion for predicting the phase state, while the decisive role is played by the combined effect of enthalpic interactions, valence electron concentration, crystal-chemical factors, microsegregation, and solidification conditions. The influence of phase formation on fluidity, mechanical properties, and corrosion resistance of the investigated alloys has been determined, and promising compositions with increased aluminium content have been identified. The obtained results extend the understanding of the regularities of structure formation, phase composition, and properties of cast high-entropy alloys with increased aluminium content, confirm the feasibility of using aluminium as an effective means for density reduction and phase stability control, and can be used for further design of multicomponent casting systems, selection of melting and casting regimes, prediction of structural state, and preliminary identification of promising alloy compositions.