Demonstration of the effect of stirring on nucleation from experiments on the International Space Station using the ISS-EML facility

TL;DR

This study investigates how fluid stirring influences crystal nucleation in supercooled liquids under microgravity conditions on the ISS, revealing alloy-dependent effects consistent with the coupled-flux model.

Contribution

It demonstrates the effect of controlled stirring on nucleation temperatures in microgravity, providing experimental validation of the coupled-flux model for different alloys.

Findings

Maximum nucleation temperatures increased with stirring for Vit106.

Nucleation temperatures remained nearly unchanged for CuZr and TiZrNi.

Results support the coupled-flux model predictions.

Abstract

The effect of fluid flow on crystal nucleation in supercooled liquids is not well understood. The variable density and temperature gradients in the liquid make it difficult to study this under terrestrial gravity conditions. Nucleation experiments were therefore made in a microgravity environment using the Electromagnetic Levitation facility on the International Space Station on a bulk glass-forming Zr57Cu15.4Ni12.6Al10Nb5 (Vit106), as well as Cu50Zr50 and the quasicrystal-forming Ti39.5Zr39.5Ni21 liquids. The maximum supercooling temperatures for each alloy were measured as a function of controlled stirring by applying various combinations of radio frequency positioner and heater voltages to the water-cooled copper coils. The flow patterns were simulated from the known parameters for the coil and the levitated samples. The maximum nucleation temperatures increased systematically with increased fluid flow in the liquids for Vit106, but stayed nearly unchanged for the other two. These results are consistent with the predictions from the coupled-flux model for nucleation.