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 Nb 82.7 Si 17.3 eutectic alloy superheated up to 2338 K exhibited an extreme undercooling of 437 K, approaching the 0.2 T E threshold for homogeneous 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 Zr 64 V 36 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.