DOI: https://doi.org/10.30970/jps.27.1601
VISCOSITY OF Cu-BASED BINARY ALLOYS
Yu. Plevachuk 
, L. Romaka
Ivan Franko National University of Lviv
8, Kyrylo & Mefodiy St., Lviv, UA–79005, Ukraine
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Journal of Physical Studies 27(1), Article 1601 [6 pages] (2023)
DOI: https://doi.org/10.30970/jps.27.1601 VISCOSITY OF Cu-BASED BINARY ALLOYS
Yu. Plevachuk
Ivan Franko National University of Lviv
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High-entropy alloys are alloys containing at least five main metallic elements in equiatomic proportions from 5 to 35 at. %. The main feature of high-entropy alloys is the formation of a single-phase thermodynamically stable solid solution mainly with bcc and fcc lattices. Stabilization of the solid solution and prevention of the intermetallic phases formation during the solidification is ensured by the high entropy of mixing of the components. The highest value of entropy is achieved with an equiatomic ratio of components, and, according to the Boltzmann hypothesis, the configurational entropy increases with an increase in the number of elements.
Along with the characteristics typical of metal alloys, such materials have unique and unusual properties inherent, for example, in metal ceramics: high hardness and resistance at high temperatures, positive temperature hardening coefficient, resistance to corrosion and oxidation, good wear resistance and a number of other properties. The continuous expansion of practical applications of high-entropy alloys shows that the deviation of one or more elements from equiatomic proportions can even improve some specific properties.
The main experimental difficulties in extreme thermodynamic conditions of the liquid state are related to the high melting temperatures of the elements. Therefore, it is helpful to study similar multicomponent alloys with lower melting points of the elements. Information about the properties of such low-temperature systems, as well as their subsystems with a smaller number of components, which can be considered as model systems, is necessary for further study of the high-temperature alloys' characteristics and for their industrial production.
In this work, temperature dependence of viscosity for Cu-Bi, Cu-Ga, Cu-Pb and Cu-Sn binary alloys with chemical compositions deviating from equiatomic ones was investigated. These alloys are subsystems of the high-entropy five-component Bi-Cu-Ga-Sn-Pb system. Based on the obtained results, the activation energy of the viscous flow and the configurational entropy of mixing were calculated. The obtained negative values of entropy of mixing indicate structural ordering in the system.
Key words: metals, high-entropy alloys, entropy, viscosity.