Slower nucleation kinetics with stirring in a supercooled Zr₈₀Pt₂₀ liquid—Terrestrial and microgravity experiments on the International Space Station.

This article investigates the effect of stirring on nucleation kinetics in a eutectic Zr₈₀Pt₂₀ metallic liquid using containerless processing via electrostatic levitation (ESL) on Earth and electromagnetic levitation (EML) aboard the International Space Station (ISS). Contrary to predictions from the Coupled-Flux Model (CFM), which suggests stirring should have little or positive effect on nucleation in eutectic systems, the study finds that increased stirring slows nucleation kinetics of a metastable icosahedral quasicrystal phase (i-phase) that nucleates prior to the equilibrium eutectic phases. Statistical analysis of hundreds of nucleation cycles reveals that nucleation is heterogeneous, occurring on a limited number of catalytic sites whose number decreases with stirring, possibly due to disruption of surface patches or impurity-related sites, though their exact nature remains uncertain. The findings highlight that stirring influences nucleation differently depending on alloy composition and nucleating phase, underscoring the complexity of nucleation mechanisms in metallic liquids.