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A plan of measurement of interfacial tension between Cu-rich and Fe-rich immiscible liquid phases in undercooled molten Cu-Fe alloy, using an oscillating droplet method using electromagnetic levitation, is in progress at the International Space Station. In this work, numerical simulations of an oscillating composite droplet composed of core and shell phases were performed using OpenFOAM. To determine the proper composition of the CuFe alloy to measure interfacial tension, oscillations at two specific frequencies caused by the surface and interfacial tensions appearing on the surface of the droplets have been investigated in this study. Numerical results indicate that the narrow compositional variation can be permitted as a suitable condition for determining the interfacial tension. The suitable composition of Cu for measurement of interfacial tension is 21-27at% or 67-76 at % at 1550 K - 1650 K. Especially in the case of Cu25Fe75 alloy, interfacial tension can be measured at only approximately 1600 K. [ABSTRACT FROM AUTHOR]

The surface tension of molten nickel was measured under a reducing gas atmosphere of Ar-He-5 vol% H $$_{2}$$ by an oscillating droplet method using electromagnetic levitation. The influence of the temperature dependence of the oxygen partial pressure of the gas on the surface tension was investigated. The surface tension of molten nickel was successfully measured over the very wide temperature range of 750 K, which included undercooling conditions. The temperature dependence of the surface tension did not exhibit a linear relationship but had a peculiar kink at around 1600 K, due to competition between the temperature dependence of the oxygen partial pressure and that of the oxygen adsorption equilibrium constant. [ABSTRACT FROM AUTHOR]

• A new experimental set up is presented to measure surface tension of liquid metals by aerodynamic levitation. • A linear variation of surface tension for pure iron is pointed out under Ar-2.5 %vol. H 2. • A nonlinear relationship for the 304L stainless steel is highlighted under argon and Ar-2.5 %vol. H 2. • Chemical reactions between the atmosphere and the molten metal are limited by the short experimental time. In this paper, the surface tension of molten pure iron and 304L stainless steel is measured under different gas mixtures (pure argon and Ar-2.5 %vol. H 2). Measurements are realized by aerodynamic levitation with an acoustic excitation. The surface tension is measured between 1756 K and 2227 K. The addition of H 2 in the surrounding gas is supposed to create a desorption of oxygen and modify surface tension. The effect of oxygen on surface tension is then analyzed. Measurements show a linear variation of surface tension with temperature for pure iron under Ar-2.5 %vol. H 2 and a nonlinear relationship for the 304L stainless steel even when an active gas is used. This phenomenon can be explained by the short time at high temperature which does not allow oxygen desorption. Increasing the time at high temperature may change the surface tension but at the risk of evaporation of some alloy elements. The intensification of the evaporation would also disturb the surface tension measurements. In this study, the time spent at the liquid state is equivalent to that of welding and additive manufacturing processes, allowing to determine the thermocapillary coefficient (Marangoni effect) for both metals considered in these conditions. The comparison between our measurements and different data are consistent. [ABSTRACT FROM AUTHOR]

Abstract: When a static magnetic field was applied to a Si droplet levitated by an electromagnetic force, only one peak was observed to remain in the frequency spectrum. It was the objective of this work to clarify whether this peak can be assigned to the m =±2 oscillation or to the rotation of the droplet. By analyzing the behavior of the deflection angle of the droplet in a top view, we conclude that this peak is not due to the surface oscillation of the droplet but to the droplet rotation. [Copyright &y& Elsevier]