Viscosity measurements of metallic melts using the oscillating drop technique

Abstract

By means of benchmarking reduced gravity experiments, we have verified the measured viscosity of binary Zr-Ni glass forming liquids utilizing the oscillating drop technique combined with ground-based electrostatic levitation (ESL). Reliable viscosity data can be obtained as long as internal viscous damping of a single oscillation mode of a levitated drop dominates external perturbations. This can be verified by the absence of a sample mass dependence of the results. Hence, ESL is an excellent tool for studying the viscosity of metallic glass forming melts in the range of about 10–250 mPa s, with sample masses below 100 mg. To this end, we show that, for binary Zr-Ni melts, the viscosity is qualitatively controlled by the packing density.

Industrial grade versus scientific pure: Influence on melt properties

“…% can lead to a supposed difference in viscosity by a factor of 2. 8 Our ESL and EML experiments in contrast proved that the viscosity barely changes at an increased oxygen and/or impurity content. The significance of these findings is based on the fact that viscosity is an important material parameter, e.g., in casting processes or fragile-tostrong 17 and liquid-liquid transitions.…”

“…Further information is given in Ref. 8. The results displayed here always include measurements with different sample masses, and no mass dependence was observed.…”

“…Viscosities were measured in the equilibrium and undercooled melt by Couette rheometry and electrostatic and electromagnetic levitation (ESL 7 and EML) experiments in combination with the oscillating drop technique. 8,9 EML measurements were conducted under reduced gravity (lg) conditions in the TEMPUS facility (Tiegelfreies Elektromagnetisches Prozessieren Unter Schwerelosigkeit). The ESL technique was also used to study density 10,11 and undercooling ability of the alloy melts.…”

“…After stopping this induced oscillation, the damping time s of the oscillation amplitude was determined. 8 With this information, the viscosity g can be calculated as…”

“…14 Here, EML is combined with the oscillating drop method and viscosities are determined during %20 s of reduced gravity of a level of %0.01 g. Samples possess a diameter of 6-8 mm and accordingly a weight of approximately 1.5 g. In the TEMPUS facility, levitation and heating processes are decoupled by employing a two coil system. 8 Surface oscillations are induced via a single rectangular pulse of a tenth of a second executed by the heating coil. The decay behavior was monitored with a camera system.…”