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

Abstract

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.

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

“…Both the International Space Station (ISS) and CSS are supplied with experimental equipment to study the alloy solidification under microgravity and containerless conditions. [12,13] Electrostatic levitation (ESL) has been widely used in solidification experiments, most of which are carried out by ground-based ESL equipment, [14][15][16][17] while a small number of which are carried out on ISS. [18] Compared to electromagnetic levitation, ESL lacks electromagnetic stirring within the molten materials, which is advantageous for studying deep undercooling and rapid solidification of liquid alloys.…”