Investigating Thermophysical Properties Under Microgravity: A Review

Abstract

The advancement of metallic alloys is generally driven by alloy development, but furthermore requires the development of suitable production and processing routines. Almost all metallic products are formed through the solidification processing from the liquid phase. Although the solid-state is not influenced by gravitational effects, the processing of liquids is strongly impacted by earth's gravity-this influences interface phenomena, momentum, heat, and mass transport and, consequently, the solidification events. Experiments on liquid metallic alloys in microgravity avoid these influences and therefore allow benchmark experiments. This allows, for example, to obtain reliable thermophysical properties, improve the understanding of nucleation, phase selection, crystal growth, and other basic features of the liquid phase and the liquid-solid transition. The basic methodology, as well as a number of recent results obtained in the long-duration microgravity environment on board the international space station, are presented and discussed.

Structural Changes in Metallic Glass-Forming Liquids on Cooling and Subsequent Vitrification in Relationship with Their Properties

“…For example, from the viscosity data for Zr 58.5 Cu 15.6 Ni 12.8 Al 10.3 Nb 2.8 (Vit106a) BMG forming liquid plotted in Figure 4 a [ 76 ] by two tangents one can obtain T A = 1219 K. The reported values of T A , and T g are 1360 and 672 K, respectively, (or 1276 and 668 K, respectively, from Ref. [ 84 ]) while T l is 832 °C or 1105 K [ 85 ]. If both high temperature and low temperature limits of the viscosity slope are used then the estimated T A is only 909 K, which is below T l ( Figure 4 b).…”

Electromagnetic levitation containerless processing of metallic materials in microgravity: thermophysical properties

“…For these reasons, electromagnetic levitation 19 – 24 is currently the most important levitation technique 21 , 31 for electrically conducting metallic samples and the vast majority of commercial alloys, which are prone to evaporation or naturally contain “impurities” like Oxygen, Sulphur, Magnesium, Manganese, Carbon, and others.…”

“…Electromagnetic levitators on parabolic flights and on ground are typically restricted to certain noble-gas atmospheres, in order to achieve a sufficient cooling rate. The longer process durations, as well as the better microgravity quality on the ISS clearly improves the measurement precision 23 , 31 . Consequently, the long-duration microgravity environment on board the ISS allows materials science investigations that cannot be done otherwise.…”

“…A compact overview can be found in Refs. 23 , 25 , 27 , 31 , 38 , 39 . These methods allow the direct measurement of the following surface and volume-dependent thermophysical properties: Surface tension – using the oscillating drop method 40 Viscosity – using the oscillating drop method 40 Mass density – optically and inductively 25 , 41 , 42 Specific heat, thermal conductivity, and total hemispherical emissivity – using AC calorimetry 32 Electrical resistivity – using measurements of the samples coupling to the electromagnetic field 41 …”

“… a on a parabolic flight, ~10 s in the liquid phase ( b ) in the ISS-EML on board the ISS, about 30 s. in the liquid phase. Reproduced under the terms of the CC BY 4.0 license 31 . Copyright 2020, Wiley.…”