Viscosity of Al–Cu liquid alloys: measurement and thermodynamic description

Abstract

In the present work a high temperature oscillating cup viscometer has been used to measure the viscosities of liquid binary Al-Cu alloys. The dependence of viscosity on temperature is well described by the Arrhenius law. For constant temperature, the viscosity as a function of copper concentration exhibits a maximum at a mole fraction x Cu = 0.7. This might be due to a pronounced chemical short range order in the liquid phase at this composition. As the comparison of existing phenomenological models describing viscosity as a function of composition to the experimental data is unsatisfactory, a new model for the viscosity has been developed within this work based only on a few assumptions and using the enthalpy of mixing as input parameter which is easily accessible. The agreement between model calculation and experimental data is excellent.

Structure and chemistry of liquid Al–Cu alloys: molecular dynamics study versus thermodynamics-based modelling

“…The average total CN for the investigated liquid Al-Cu alloys increases with increasing Cu content, and importantly, and such trend is compatible to that displayed by AIMD simulations for Al 80 Cu 20 and Al 60 Cu 40 liquid alloys [16,18]; however, it is less pronounced. A significant rise in total coordination number obtained by performing MEAM-MD simulations can signify the occurrence of structural changes in atomic packing of liquid Al-Cu alloys with Cu content growth.…”

“…Thermophysical properties of liquid Al-Cu alloys also caught scientific interest [19][20][21][22], including experimental and modelling contributions, which altogether build a solid background and open up a field for discussion of the new data presented in this paper. Schick et al [20] experimentally determined viscosity for a series of liquid Al-Cu alloy compositions, excluding only the liquid Al 60 Cu 40 alloy, using a high-temperature oscillating-cup viscometer method and supplementing it with thermodynamicsbased modelling analyses.…”

“…A recent parametrization of the modified embedded atom model (MEAM), given by Trybula [5] [16] (AIMD) and experimental [20,22,35] results. Herein, we validate this MEAM parametrization for structure and transport properties investigations over a broad Cu concentration range.…”

“…Schick et al [20] experimentally determined viscosity for a series of liquid Al-Cu alloy compositions, excluding only the liquid Al 60 Cu 40 alloy, using a high-temperature oscillating-cup viscometer method and supplementing it with thermodynamicsbased modelling analyses. As a result, a pronounced maximum in viscosity was observed for Al-Cu alloy composition close to intermetallic phases existing in the solid state of the Al-Cu system, which could suggest ''associates'' influence.…”

“…This issue has not been discussed in the literature with regard to structure and diffusivity investigations. The latter ones include the determination of the self-diffusion coefficient of Cu and of the mutual diffusion coefficient using neutron scattering [21] or X-ray radiography [22] for liquid Al-rich alloys, namely Al 90 Cu 10 , Al 83 Cu 17 , Al 80 Cu 20 and Al 75 Cu 25 .…”