Viscosity of high-entropy melts in Cu-Sn-Pb-Bi-Ga, G-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 (t hom) leads to the appearance of viscosity hysteresis, which indicates a variation in the structural state of the HEM. The values of t hom for all studied samples are in limits of 925–1185°C. It is found that heating the HEM to definite temperatures (t*) leads to a variation in the activation energy of viscous flow (E) and entropy multiplier (A) in the Arrhenius equation: ν = Aexp[E/(RT)]. Entropy of viscous flow (ΔS #) for studied HEMs 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 rheological characteristics of HEMs allow us to consider these melts promising functional materials: solders, heat carriers, and electric contacts.