Effect of the roughness of crucible on viscosity of liquid Pb38.1Sn61.9 alloy

The viscosity of the eutectic Pb38.1Sn61.9 alloy has been measured by a torsional oscillation viscometer using three different crucibles which are made of the materials of highly sintered alumina (Al2O3), quartz (SiO2), and graphite (C) respectively. The roughness of crucibles has effect on the viscosity. The viscosity data obtained for SiO2 and C crucibles were concentrated in the narrow range of about 0.5% and showed almost the same activation energy. However, the viscosity obtained using Al2O3 crucible with the maximal roughness is higher than that using the other two crucibles. The discrepancy of viscosity obtained using those crucibles increases with the viscosity. In addition, the viscosity obtained using three kinds of crucibles in our work has a breakpoint at 488 K, which is approximate with the results of electrical conductivity and thermopower measurements reported by Plevachuk et al., which indicates the microstructure in melt changes before solidification.