Abstract
The surface tension of molten Zircaloy (Zry–2 and
Zry–4), a Zr–1 at% Sn model alloy, and pure zirconium with
varying hafnium content was measured using the oscillating
droplet method with electromagnetic levitation in atmospheres
with controlled oxygen partial pressure (𝑃𝑃O2
). The surface
tension of molten zirconium was not significantly affected by
the presence of hafnium impurities in the 0.05–2.3 at% range.
When the 𝑃𝑃O2
was buffered at low levels (≤ 10−4 Pa) using Ar
He–H2–CO2 gas, oxygen gradually dissolved into the molten
Zr–1 at% Sn alloy, resulting in a time-dependent decrease in surface tension. In contrast, under Ar–He gas (𝑃𝑃O2
≈ 10−2 Pa),
both oxygen content and surface tension remained nearly constant over time due to kinetic limitations in
gas-phase transport. The surface tension of molten Zry–2 and Zry–4 decreased linearly with increasing
temperature and was nearly identical to that of the molten Zr–1 at% Sn alloy under the Ar–He atmosphere.
These values were consistently lower than those of pure molten zirconium. These experimental results,
along with Butler model analysis, indicate that tin plays a dominant role in reducing surface tension
through surface segregation. The maximum expanded uncertainty was within ±1%, confirming the
reliability of the measurements.
