Remarkable undercooling capability and metastable thermophysical properties of liquid Nb_84.1Si_15.9 alloy revealed by electrostatic levitation in outer space

The stable manipulation, high undercooling, and thermophysical property measurement of the liquid Nb_84.1Si_15.9 refractory alloy were successfully achieved by the electrostatic levitation technique on board the China Space Station. By controlling the superheating temperature, a maximum liquid undercooling up to 421 K (0.18 T_L) was obtained in the space environment, and two distinct solidification paths with different recalescence features were realized at metastable undercooled states. The liquid density and the ratio of specific heat to emissivity were measured in a wide temperature range from 1841 to 2346 K, which displayed linear and quadratic relations vs temperature, respectively. The liquid emissivity was further deduced from the specific heat of the liquid alloy calculated by molecular dynamics simulation. In addition, both the density and structural characteristics of the undercooled liquid alloy were also analyzed by MD calculations.