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

The surface tension of liquid Cu-5Sn (copper with 5wt% tin) in the temperature range from 1290 K to 1560 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 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)(mN . m(-1)) = 1195 - 0.052 . (T - 1318).