Viscous and acoustic properties of AlCu melts
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Viscous and Acoustic Properties of AlCu Melts R. M. Khusnutdinoffa, b*, A. V. Mokshina, b**, S. G. Menshikovac, A. L. Beltyukovc, and V. I. Ladyanovc a Kazan
b Landau
Federal University, Kazan, 420008 Russia Institute of Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia c Physicotechnical Institute, Ural Branch, Russian Academy of Sciences, Izhevsk, 426000 Russia *e-mail: [email protected]; **e-mail: [email protected] Received September 26, 2015
Abstract—The atomic dynamics of the binary Al100 – xCux system is simulated at a temperature T = 973 K, a pressure p = 1.0 bar, and various copper concentrations x. These conditions (temperature, pressure) make it possible to cover the equilibrium liquid Al100 – xCux phase at copper concentrations 0 ≤ x ≤ 40% and the supercooled melt in the concentration range 40% ≤ x ≤ 100%. The calculated spectral densities of the time correlation functions of the longitudinal C L (k, ω) and transverse CT (k, ω) currents in the Al100 – xCux melt at a temperature T = 973 K reveal propagating collective excitations of longitudinal and transverse polarizations in a wide wavenumber range. It is shown that the maximum sound velocity in the vL(x) concentration dependence takes place for the equilibrium melt at an atomic copper concentration x = 10 ± 5%, whereas the supercooled Al100 – xCux melt saturated with copper atoms (x ≥ 40%) is characterized by the minimum sound velocity. In the case of the supercooled melt, the concentration dependence of the kinematic viscosity ν(x) is found to be interpolated by a linear dependence, and a deviation from the linear dependence is observed in the case of equilibrium melt at x < 40%. An insignificant shoulder in the ν(x) dependence is observed at low copper concentrations (x < 20%), and it is supported by the experimental data. This shoulder is caused by the specific features in the concentration dependence of the density ρ(x). DOI: 10.1134/S1063776116040166
1. INTRODUCTION Owing to their unique physicochemical properties, aluminum-containing copper alloys (copper-based duralumins and aluminum alloys–aluminum bronzes) are widely used in mechanical engineering and aircraft industry [1]. For example, apart from a small weight and a high strength, aluminum–copper alloys are characterized by a high plasticity and a high corrosion resistance. Their physical properties (thermal conductivity, viscosity, electrical resistivity, magnetic susceptibility, etc.) are mainly determined by the ratio of the concentrations of their components, namely, Al and Cu atoms [2–5]. A binary Al100 – xCux aluminum alloy is characterized by a complex phase diagram, which has a melt at temperatures T ≥ 820 K (at a pressure p = 1.0 bar and a copper concentration x ≈ 17.5%) and an extended field containing various crystalline phases (see the phase diagram of the Al100 – xCux melt in Fig. 1). As was shown in [5–7], aluminum-containing alloys have a high glass-forming ability. Viscosity is one of the most important character
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