VISCOSITY OF HIGH-ENTROPY MELTS IN CU–SN–PB–BI–GA, CU–SN, CU–PB, CU–GA, AND CU–BI EQUIATOMIC COMPOSITIONS

Abstract

Temperature dependences of kinematic viscosity of high-entropy melts (HEM) of the composition, at %: Cu–20Sn–20Pb–20Bi–20Ga, Cu–50Sn, Cu–50Pb, Cu–50Ga, and Cu–50Bi are investigated in a temperature range from 1550 to 1300 °C. It is shown that melt overheating above a definite temperature (thom) leads to the appearance of viscosity hysteresis, which indicates the variation in the structural state of the HEM.  Values of thom for all studied samples are in limits of 925–1185 °C. It is found that heating of the HEM to definite temperatures (t*) leads to the variation in activation energy of viscous flow (Е) and entropy multiplier (A) in the Arrhenius equation: v = Aexp[E/(RT)]. Entropy of viscous flow (ΔS≠) for studied HEM is investigated in terms of the Airing theory. It is revealed that the magnitude of ΔS≠ for a five-component Cu–Sn–Pb–Bi–Ga melt in a cooling mode is smaller than during heating by a factor of 2,6. The found rheological characteristics of HEMs allow us to consider these melts as promising functional materials: solders, heat carriers, electric contacts.