Contactless measurement of temperature-dependent viscosity and surface tension of liquid Al69.1Cu12.8Ag18.1 eutectic alloy under microgravity conditions using the oscillating-drop-method
Mitja Beckers, Marc Engelhardt and Stephan Schneider
Thermophysical properties of the Al69.1Cu12.8Ag18.1 eutectic liquid alloy are of particular interest for support of self-and inter-diffusion studies. In the presented work, Al69.1Cu12.8Ag18.1 -samples were processed contactlessly by electromagnetic levitation under microgravity conditions using the TEMPUS facility. The measurements were performed onboard the Airbus A310 Zero-G in parabolic flight campaigns. The oscillating drop method (ODM) was used for measurements of the viscosity via oscillations damping and surface tension via oscillations frequency. These were determined for temperatures in the range of 900-1500 K by analysis of the oscillation spectrum obtained from the electrical impedance. The latter was measured using the Sample Coupling Electronics. An Arrhenius-law η(𝑇)∝η∞ exp(𝐸η⁄𝑅𝑇) was used to fit the temperature-dependent viscosity data. The resulting fit parameters were η∞ = (0.632±0.160)mPas and activation energy of viscous flow 𝐸η = (2.344±0.233)⋅104 J/mol. A linear law γ(𝑇) = γ𝑙 + γ𝑇 (𝑇-𝑇𝑚 ) was fit to the surface tension data yielding γ𝑙 = (0.9013±0.02625) 𝑁𝑚-1 and γ𝑇 = —(0.7462±0.2675)⋅10-4𝑁𝑚-1𝐾-1. The Kozlov-model was applied to determine the enthalphy of mixing as Δ𝐻𝑚𝑖𝑥 = —(18.576±0.018) kJ/mol.
Keywords: ODM, viscosity, ternary alloy, eutectic, AlCuAg, EML, TEMPUS, surface tension, Arrhenius, parabolic flight