  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.
