A videographic and numerical study of nonisothermal oscillation process for electrostatically levitated liquid Nb–Si alloy

Li, M.X.; Wang, H.P.; Zheng, Chenhui; Wang, Qing; Wei, Baogang

doi:10.1016/j.ijthermalsci.2023.108197

“…Thus, the solidified alloys exhibit as spheres for small undercoolings. However, for large undercooling conditions, the liquid viscosity at a large undercooling is nearly increased by 300 % compared with viscosity at T E , [52][53] leading to a greatly decreasing of the mass transportation. Meanwhile, based on the experimental data on the ground, at a large undercooling of 437 K, the migration velocity of the liquid-solid interface is beyond 100 mm s À 1 , approximately 40 times greater than the 2.5 mm s À 1 observed at a small undercooling of 87 K. The mass transportation could not meet the growth of solid phase, which results in the initially generated solid phase exhibiting a large curvature compared with original droplet edge in nucleation process.…”

Section: Resultsmentioning

confidence: 97%

“…However, the flow field of levitated droplet on the ground is almost two orders larger than that in the microgravity environment. [52] Under the microgravity condition, the disturbances caused by gravity and electrostatic field significantly diminish, resulting in a weaker internal flow within droplet. It is therefore possible to increase the undercooling values of the droplet.…”

Section: Resultsmentioning

confidence: 99%

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

Wang,

Hu,

Xie

et al. 2024

Angewandte Chemie

1

0

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The metastable liquid properties and chemical bonds beyond 2000 K remain a huge challenge for ground‐based research on liquid materials chemistry. We show the strong undercooling capability, metastable liquid properties and surface wave patterns of refractory Nb‐Si and Zr‐V binary alloys explored in space environment. The floating droplet of Nb82.7Si17.3 eutectic alloy superheated up to 2388 K exhibited an extreme undercooling of 437 K, approaching the 0.2TE threshold for homogenous nucleation of liquid‐solid reaction. The microgravity state endowed alloy droplets with nearly perfect sphericity and thus ensured the high accuracy to determine metastable undercooled liquid properties. A special kind of swirling flow was induced for liquid alloy owing to Marangoni convection, which resulted in the spiral microstructures on Zr64V36 alloy surface during liquid‐solid phase transition. The coupled impacts of surface nucleation and surface flow brought in a novel olivary shape for these binary alloys. Furthermore, the chemical bonds and atomic structures of high temperature liquids were revealed to understand the liquid properties in outer space circumstances.

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“…The simulated maximum flow velocity at the melting point in our model is consistent with Li's results. [31] The r--u curve describes the change of flow velocity along directions r a and r b (r a represents the direction from the center of the droplet to the surface position where the flow velocity is the maximum, while r b represents the direction which is the minimum). The solid fraction (area) changes with time at different temperature transition intervals 𝛿T are studied through a 2D model (Figure 2c).…”

Section: Freezing Shrinkage Dynamics Coupled With Microgravity Flow M...mentioning

confidence: 99%

Freezing Shrinkage Dynamics and Surface Dendritic Growth of Floating Refractory Alloy Droplets in Outer Space

Wang,

Liao,

Hu

et al. 2024

Advanced Materials

8

0

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The freezing shrinkage and dendritic growth are of great importance for various alloys solidified from high temperature liquids to solids since they dominate microstructure patterns and follow‐up processing. However, the microgravity freezing shrinkage dynamics is scarcely explored on the ground as it is hard to suppress the strong natural convection inside liquid alloys. Here, we conduct a series of in‐orbit solidification experiments aboard China Space Station with a long‐term stable 10−5 g0 microgravity condition. A highest temperature up to 2265 K together with substantial liquid undercoolings far from thermodynamically stable state are attained for both Nb82.7Si17.3 and Zr64V36 refractory alloys. Furthermore, we simulate the freezing shrinkage of a droplet without gravity to reveal the liquid‐solid interface migration, temperature gradient, and flow field. It is found that microgravity solidification process leads to freezing shrinkage cavities and distinctive surface dendritic microstructure patterns. The combined effects of shrinkage dynamics and liquid surface flow in outer space result in the dendrites growing not only along the tangential direction but also along the normal direction to the droplet surface. These space experimental results contribute to a further understanding of solidification behavior of liquid alloys under a weaker convection condition, which is often masked by gravity on the ground.This article is protected by copyright. All rights reserved

show abstract

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

Wang,

Hu,

Xie

et al. 2024

View full text Add to dashboard Cite

The metastable liquid properties and chemical bonds beyond 2000 K remain a huge challenge for ground‐based research on liquid materials chemistry. We show the strong undercooling capability, metastable liquid properties and surface wave patterns of refractory Nb‐Si and Zr‐V binary alloys explored in space environment. The floating droplet of Nb82.7Si17.3 eutectic alloy superheated up to 2388 K exhibited an extreme undercooling of 437 K, approaching the 0.2TE threshold for homogenous nucleation of liquid‐solid reaction. The microgravity state endowed alloy droplets with nearly perfect sphericity and thus ensured the high accuracy to determine metastable undercooled liquid properties. A special kind of swirling flow was induced for liquid alloy owing to Marangoni convection, which resulted in the spiral microstructures on Zr64V36 alloy surface during liquid‐solid phase transition. The coupled impacts of surface nucleation and surface flow brought in a novel olivary shape for these binary alloys. Furthermore, the chemical bonds and atomic structures of high temperature liquids were revealed to understand the liquid properties in outer space circumstances.

show abstract

A videographic and numerical study of nonisothermal oscillation process for electrostatically levitated liquid Nb–Si alloy

Cited by 4 publications

References 35 publications

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

Freezing Shrinkage Dynamics and Surface Dendritic Growth of Floating Refractory Alloy Droplets in Outer Space

Metastable Liquid Properties and Surface Flow Patterns of Ultrahigh Temperature Alloys Explored in Outer Space

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