Understanding thermophysical properties such as surface tension (σ), total hemispherical emissivity (ε), specific heat capacity (cp) and viscosity (η) as a function of temperature is essential for optimizing the vitrification of bulk metallic glasses (BMGs). In this study, the thermophysical properties of liquid Vit106a were measured aboard the International Space Station (ISS) using the electromagnetic levitator (EML). The surface tension σ exhibited a similar value with other Zr-based BMG, with a weak temperature dependence described by σ(T) = 1.557–4.36 ×10−5 × (T - 1106) N.m−1. The viscosity temperature-dependence η(T) was analyzed using the Vogel–Fulcher–Tammann (VFT) equation, yielding a kinetic fragility parameter of D* = 9.8 at high temperature, compared to D* = 21.6 at low temperature, that indicates a fragile-to-strong transition characteristic of Zr-based metallic glass formers. XRD analysis confirms full crystallization of the sample, despite being cooled at a rate of 16 K.s⁻¹, over nine times faster than the critical cooling rate of 1.75 K.s⁻¹ reported in the literature. The crystallized sample reveals a heterogeneous distribution of binary intermetallic phases, including ZrAl3, Zr2Cu, Zr2Ni, ZrAl and Nb2Ni. These findings provide insights into the thermophysical behavior of liquid Vit106a for large-scale manufacturing but also raise important questions regarding its good glass-forming ability for larger casting thickness.

Abstract A series of 54 experiment cycles were performed on an FeCr21Ni19 (at. %) sample in vacuum, He and Ar gas atmospheres using the Electromagnetic Levitation facility onboard the International Space Station (ISS-EML). Evaporation control is a critical facility resource that limits processing time and must be tracked to ensure astronaut safety. Species specific evaporation during this test has been estimated using a mathematical model based on thermodynamic assessment and Langmuir’s equation to track the dynamic mass loss during each thermal cycle. The findings from this study were validated using post-mission SEM-EDX evaluations. The predicted mass loss and elemental distribution from the evaporation model was consistent with experimental observations. Based on facility geometry, deposit layer thicknesses at various locations have also been calculated and results showed excellent agreement with near-real-time predictions using software developed by the German Space Agency (DLR) Microgravity User Support Center (MUSC).

Evaporation control is a critical facility resource during solidification experiments that limits processing time and must be tracked to ensure facility health. A thermodynamic analysis was performed on a ternary FeCrNi sample processed onboard the International Space Station (ISS) using ESA Electromagnetic Levitation (EML) facility in a microgravity environment. A non-ideal solution-based mathematical model was applied for the overall sample mass loss prediction during this study. The overall sample mass loss prediction is consistent with the post-flight mass loss measurements. The species-specific findings from this study were validated using post-mission SEM-EDX surface evaluations by three different facilities. The bulk composition prediction was validated using SEM-EDX and wet chemical analysis. The non-ideal solution model was then applied to predict the composition of the dust generated during EML testing. The thicknesses of the deposited layer on the EML coil at various locations were also calculated using the geometry of the facility and results were validated with near-real-time dust layer predictions from toxicity tracking software developed by the German Space Center (DLR) Microgravity User Support Center (MUSC).

Titanium alloys combine low mass densities and high strength. The high-temperature stability makes them important materials for aerospace and space applications. The high biocompatibility of several Ti-based alloys makes them applicable for biomedical implant applications. The high melt reactivity makes the precise measurement of thermophysical with container-based methods impossible. Hence, the containerless measurement of thermophysical properties using containerless methods is mandatory.

Abstract Thermophysical properties of the γ-TiAl alloy Ti-48Al-2Cr-2Ni in the liquid phase were investigated with a containerless electromagnetic processing device on board the International Space Station. Containerless processing is warranted by the high liquidus temperature T liq = 1 776 K and the high dissolution reactivity in the liquid phase. Thermophysical properties investigated include the surface tension and viscosity, density, specific heat capacity and the electrical resistivity. The experiments were supported by magnetohydrodynamic fluid flow calculations. The Ti-48Al-2Cr-2Ni alloy could be stably processed over extended times in the stable and undercooled liquid phase and exhibited an exceptional degree of undercooling before solidification. Experimental processes and thermophysical properties so obtained will be described. The experiments demonstrate the broad experimental capabilities of the electromagnetic processing facility on the International Space Station for thermophysical investigations in the liquid phase of metallic alloys not achievable by other methods.

The titanium alloy Ti–6Al–4V (Ti64) is a very widely applied alloy with extreme importance in the fields of aerospace, automotive, and biomedicine. For a large range of manufacturing methods that involve the liquid phase, such as casting, metal injection molding, thermal spraying, and additive manufacturing, process simulations are an important tool for the optimization and development of the fabrication process. Reliable thermophysical property data of Ti64 in the solid and the liquid phase are necessary inputs to such models. Due to the high melt reactivity of titanium alloys with container materials, measurements performed using conventional thermophysical equipment are usually impossible. Precise benchmark measurement of thermophysical properties (surface tension, viscosity, specific heat, total hemispherical emissivity, thermal conductivity, electrical resistivity, mass density) of Ti64 is presented in the undercooled liquid phase using containerless electromagnetic levitation on board the International Space Station (ISS). The obtained values are compared with predictive models that can help to analyze the data for other compositions of the alloy system. The property values are applied to simulations of industrial fabrication processes, to optimize these processes and thus the product quality.

Pure, low-oxygen zirconium samples have been observed to nucleate a solid phase under conditions during which the sample was expected to remain liquid. This phenomenon was first seen during Spacelab Mission MSL-1R (materials science laboratory) experiments and has since also been observed in the International Space Station (ISS) electromagnetic levitation (EML) facility on a different sample. Current work has been able to replicate these anomalous solidification events under a range of conditions in the ISS MSL-EML facility. The solidification events are not well explained by classical homogeneous or heterogeneous nucleation. The current theory is that collapsing voids in the melt create a local region of high pressure that results in local material being deeply undercooled and a strong driving force for solidification.

Advanced nickel‐based superalloys combine excellent high‐temperature mechanical strength, creep resistance, and toughness, and therefore find applications in next‐generation aircraft engines and turbines for land‐based power generators. The related fabrication processes are complex, time consuming, and costly, making it necessary to perform supporting computer simulations of the heat and material flow in the melt before and during crystallization. Such models are based on reliable thermophysical property data in the solid and liquid phase. However, measurements of surface‐ and volume‐dependent properties, such as liquid surface tension, viscosity, and specific heat of these complex liquid metal alloys, are very challenging, due to the melts high chemical reactivity at temperatures of interest. The method of choice is electromagnetic levitation, a containerless method. The measurements of surface tension, viscosity, mass density, and specific heat capacity, performed in the electromagnetic levitator (EML) on board the Space Laboratory Columbus in the International Space Station (ISS), are presented and discussed.

The present study is an overview of the surface properties of liquid Al-Ni alloys, which are of great importance for the design and development of new Al-Ni and Ni-based industrial alloys, widely used as functional and structural materials. The solidification and thus, the microstructural evolution are directly dependent on the interface/surface properties of metallic melts. Therefore, numerical simulation of microstructure evolution requires reliable property data as input to such models. Taking into account the experimental difficulties related to a high reactivity of liquid Al-Ni alloys and the effects of impurities on their surface properties, the surface tension over the whole concentration range has been determined in the frameworks of three international research projects. Namely, the surface tension measurements have been carried out by both traditional container-based and as an alternative, containerless methods within the ESA-MAP ThermoProp and ESA-MAP Thermolab Projects and also under the EU FP6-IMPRESS Project. The obtained datasets were analysed and subsequently compared with the model predicted values as well as with the literature data. A strong exothermic mixing characterises the Al-Ni system and the presence of a few intermetallic compounds in the solid state leads to the formation of short range ordered elements or complexes in the liquid phase, at least near the melting temperature, which significantly affects the surface properties of alloy melts. Aiming to estimate the effects of short range ordering on these properties, the Compound Formation Model (CFM) and the Quasi Chemical Approximation (QCA) for regular solution were applied.

High Entropy Alloys (HEA) can be classified in three domains according to their e/a and r values, with e/a, the number of itinerant valence electrons and r the average radius for a 12 nearest atoms neighborhood. The phase composition, thermal stability and possible phase transformations of a series of HEA alloys, CoCrzFeNi-XY (with X and Y = Al, Cu, Pd, Ru, Ti and z = 0 or 1), selected according to their e/a ratio were investigated in cast conditions (TO), after 3 h homogenization at 1100 degrees C (TI) and after 3 h annealing at 700 degrees C (T3). When observing the behavior of the different Domains of HEAs as classified by electronic structure it is observed that for the alloys from Domain I which contain fcc structures, the microstructure transforms from multi-to almost single-phase under homogenization (T1). In Domain III alloys containing cubic (bcc and/or B2) structures, very small multi-structural changes are observed. Alloys in Domain II have a mixed structure, i.e. several different structures in the diffraction pattern, which changes during heat treatments. (C) 2020 Elsevier B.V. All rights reserved.

Here we present measurements of surface tension and viscosity of the bulk glass-forming alloy Pd43Cu27Ni10P20 performed during containerless processing under reduced gravity. We applied the oscillating drop method in an electromagnetic levitation facility on board of parabolic flights. The measured viscosity exhibits a pronounced temperature dependence following an Arrhenius law over a temperature range from 1100 K to 1450 K. Together with literature values of viscosity at lower temperatures, the viscosity of Pd43Cu27Ni10P20 can be well described by a free volume model. X-ray diffraction analysis on the material retrieved after the parabolic flights confirm the glassy nature after vitrification of the bulk samples and thus the absence of crystallization during processing over a wide temperature range.

The effect of severe plastic deformation by high-pressure torsion (HPT) on the structure and plastic tensile properties of two Zr-based bulk metallic glasses, Zr55.7Ni10Al7Cu19Co8.3 and Zr64Ni10Al7Cu19, was investigated. The compositions were chosen because, in TEM investigation, Zr55.7Ni10Al7Cu19Co8.3 exhibited nanoscale inhomogeneity, while Zr64Ni10Al7Cu19 appeared homogeneous on that length scale. The nanoscale inhomogeneity was expected to result in an increased plastic strain limit, as compared to the homogeneous material, which may be further increased by severe mechanical work. The as-cast materials exhibited 0.1% tensile plasticity for Zr64Ni10Al7Cu19 and Zr55.7Ni10Al7Cu19Co8.3. Following two rotations of HPT treatment, the tensile plastic strain was increased to 0.5% and 0.9%, respectively. Further testing was performed by X-ray diffraction and by differential scanning calorimetry. Following two rotations of HPT treatment, the initially fully amorphous Zr55.7Ni10Al7Cu19Co8.3 exhibited significantly increased free volume and a small volume fraction of nanocrystallites. A further increase in HPT rotation number did not result in an increase in plastic ductility of both alloys. Possible reasons for the different mechanical behavior of nanoscale heterogeneous Zr55.7Ni10Al7Cu19Co8.3 and homogeneous Zr64Ni10Al7Cu19 are presented.

The viscosities of Cu50Zr50 melt from 1250 K to 1435 K were measured in a containerless electromagnetic levitator under microgravity. The viscosity in the investigated temperature range can be expressed by an Arrhenius temperature dependencerg eta(T) = eta(0) exP(E-A/k(B)T),with eta(0) = (0.08 +/- 0.02) mPa.s and E-A = (0.58 +/- 0.03) eV. We find a correlation between the fraction of closer neighboring atoms, f, and viscosity, which is described by eta = exp(n) f(m), where n = 1.746/Delta pe(c)-4.478, m = -0.374/Delta pe(c) + 0.440, and Delta pe(c) is the excess potential energy, indicating that the temperature dependent viscosity during cooling is controlled by the fraction of closer neighboring atoms. (C) 2019 Elsevier B.V. All rights reserved.

The contribution of non-linear fluid flow effects to the damping of surface oscillations in the oscillation drop method was investigated in a series of experiments in an electromagnetic levitation device installed on the International Space station, ISS-EML. In order to correctly evaluate the damping time constant from measured surface oscillation decays the effect of a modulated signal response on measured surface oscillation decay curves was investigated. It could be shown that various experimentally observed signal patterns could be well represented by a modulated response. The physical origin of such modulations is seen in rotation and precession. Over a temperature range of 220 K covered by different surface oscillation excitation pulses with an initial sample shape deformation of 5 – 10% the amplitude of surface oscillations as a function of time could be very well represented by a Lamb type damping with a temperature dependent viscosity. A direct comparison of surface oscillation decay times measured in the same temperature range but for different oscillation amplitudes showed no non-linear contribution to the damping time constant with a confidence level better 10%.

The surface tension and viscosity of equilibrium and supercooled liquids of Cu50Zr50 were measured in the containerless electromagnetic levitator ISS-EML in the European space laboratory Columbus on board the International Space Station (ISS) under microgravity using high-speed camera recordings. From 1250 K to 1475 K, the surface tension follows the relation σ(T) = (1.58 ± 0.01) N/m – (3.1 ± 0.6) · 10−4 N/m · K · (T – 1209 K). A frequency shift correction was applied to remove the influence of sample rotation on the measured surface tension. Within the investigated temperature range, the viscosity can be expressed by an Arrhenius temperature dependence η(T) = η0 · exp(EA/kBT), with η0 = (0.08 ± 0.02) mPa·s and EA = (0.58 ± 0.03) eV.

Bulk metallic glasses are of critical interest for a wide range of applications, including their use in spacecraft gearboxes and mechanisms due to their excellent low-temperature, unlubricated wear resistance. Also of interest, is the potential for in-space manufacturing of metal alloys and the use of microgravity to determine fundamental thermophysical properties to inform ground-based modeling and experimentation. In this work, a Zr-based bulk metallic glass was processed in the electromagnetic levitator ISS-EML to determine undercooling, electrical resistivity, specific heat capacity, surface tension, and viscosity. A 6.5 mm sphere was vitrified during the processing, resulting in the first bulk metallic glass manufactured on board the international space station (ISS).

Recent experiments using electromagnetic levitation in reduced gravity have confirmed prior observations of anomalous nucleation of the solid in undercooled melts under specific conditions. All indications are that this effect is dynamical, not chemical: the same sample undercools over 300 °C before and after the anomalous event, but maintains the liquid state for only a few seconds when held at a more modest undercooling in the range of 0–50 °C. The new experimental results and related modeling will be examined in comparison to the hypothesis that the solidification is triggered by cavitation in the melt. This platform may provide data relevant to a better quantitative understanding of the effect of ultrasonic processing on grain refinement of terrestrial castings.

The temperature dependent viscosities of stable and undercooled liquid zirconium (Zr) have been studied by the electromagnetic levitation (EML) experiments on the International Space Station ISS together with molecular dynamics (MD) simulations. Oxygen additions of about 1.2 ± 0.5 at.% in EML experiments increases the viscosity of undercooled liquid Zr. MD simulations reveal a Vogel-Fulcher-Tammann-type temperature dependent viscosity for pure Zr in the temperature range of 1600–2700 K. The evolution of the internal energy and the nearest neighboring coordination numbers show crossovers at about 2000 K, indicating a local structural change when stable liquid Zr is cooled into undercooled liquid state. This local structural change is reflected by a slight drop of fraction of the <0,3,6,4> cluster, and the nonlinear temperature dependent evolution of icosahedral-like, bcc-like and tetrahedral-like short-range order. The temperature dependent fraction of mobile atoms with high potential energy exhibits a strong anti-correlation with the temperature dependent viscosity. The decrease of these mobile atoms reduces the potential energy and increases the high-coordinated clusters with strong spatial correlations upon cooling, resulting in an increase of the local stability and viscosity of stable and undercooled liquid Zr. All results obtained here will promote the research activities of the thermophysical properties and structural evolution of metallic liquids.