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

The surface tension of liquid Cu–5Sn (copper with 5 wt % 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 γ of Cu–5Sn as a function of temperature T in Kelvin is given by: γ ( T ) ( mN · m - 1 ) = 1195 - 0.052 · ( T - 1318 ) .