Measurement of Surface Tension of Cu–5Sn by an Oscillating Drop Technique

Abstract

The surface tension of liquid Cu–5Sn (copper with ${5}\,{\hbox {wt} \%}$ tin) in the temperature range from ${1290}\,\hbox {K}$ to ${1560}\,\hbox {K}$ was measured by an oscillating drop technique combined with electromagnetic levitation. The levitation device uses an inhomogeneous radiofrequency electromagnetic field inside a levitation coil to position and to heat metallic material. Eddy currents are induced in a specimen to heat it to the liquid phase and to exert a Lorentz force, pushing it against gravity towards regions of lower field strength. The levitating liquid specimen takes the shape of a sphere, which is rotating and oscillating. The oscillations are recorded by a high-speed camera at $600\,\hbox {fps}$; the temperature of the specimen is measured by a fast near-infrared pyrometer. A linear fit to the measured surface tension $\gamma$ of Cu–5Sn as a function of temperature T in Kelvin is given by:

$$\gamma (T)({\hbox {mN}\cdot \mathrm{m}^{-1}})=1195-0.052\cdot (T-1318).$$