Effect of cooling rate on the properties of multicomponent alloys of Al-Cu-Fe-Ni-Si system

Purpose. This work is dedicated to establish the effects of the composition and the melt cooling rate on microhardness, phase composition and parameters of the fine structure of high-entropy alloys (HEA) of Al-Cu-Fe-Ni-Si system in the as-cast and rapid quenched state. Metodology. As-cast alloy samples were obtained using a copper mold (cooling rate ~ 102 K/s). Quenching from a liquid state was carried out by a known technique of splat-quenching (SQ). Cooling rate estimated by foil thickness was ~ 105-106 K/s. The X-ray diffraction analysis was carried out with use of the DRON-2.0 diffractometer. Microhardness was measured on the PMT-3 microhardnessmeter. Selection of components of the studied HEAs was carried out on the basis of the criteria adopted in the literature for the HEA composition based on calculation of the entropy and enthalpy of mixing, as well as the difference between the atomic radii of the components. Findings. It was found that the studied alloys of Al-Cu-Fe-NiSi is a multiphase HEAs, with the structure consisting of disordered solid solutions of BCC and FCC. Confirmed that the leading role in determining the type of solid solution formed in the studied HEAs plays an element with the highest melting point. It was found that an increase in the structure of the investigated HEAs volume fraction of the solid solution of BCC type leads to an increase I microhardness. Confirmed the positive effect o f microstrains and dislocation density to the level o f mechanical properties of the studied HEAs. It was found that the as-cast HEAs of Al-Cu-Fe-Ni-Si system are characterized by higher values of microhardness than SQ alloys, which is obviously due to their more multi-phase equilibrium state. Originality. At present work were first obtained and studied HEAs of Al-Cu-Fe-Ni-Si system in the as-cast and splat-quenched state. Practical value. The alloys of this system are characterized by the absence of expensive components, such as Co, V, Mo, Cr, usually used for the HEAs production while their characteristics are not inferior to those of the more expensive alloys. The study of thin films obtained by using quenching from the liquid state is also of great practical interest, since one of the promising applications of HEAs are thin film coatings.