Torsional vibration measurement of the viscosity of a metallic melt

The liquid Co 91 B 9 alloy is used as an example to study the influence of boundary conditions at the upper melt boundary on the results of viscosity measurements using torsional vibrations. Specific features related to film effects and wetting phenomena are shown to appear in the temperature dependence of logarithmic decrement. To exclude the influence of these effects and phenomena, viscosity measurements should be performed under the experimental conditions where the melt to be studied is in closed volume and the internal crucible walls are fully wetted. The temperature dependence of the kinematic viscosity of the Co 91 B 9 melt that is obtained under such experimental conditions has a monotonic character.