The viscosity change in solidifying Sn-Pb and Al-Si alloys was investigated using a torsional transduccr forced to oscillate at a resonance frequency. Since the amplitude of vibration was only 1
μ and the skin depth was less than a few millimeter in this viscometer, it has only a very small stirring effect on the melt. Therefore, the features of solidification of melts were reflected well in the results of viscosity measurements with this apparatus.
There was a rapid increase in viscosity at the beginning of solidification in the supercooled melt. In the eutectic alloy, the beginning of viscosity increase at the eutectic temperature was delayed, but once the change began the viscosity increased sharply. Viscosity increase was more rapid in alloys with wide freezing range than in those with narrow freezing range. Viscosity increase was more rapid in alloys which primary phases crystallize dendritically than in alloys which those crystallizes planarly. Viscosity increase was more rapid in alloys which crystallize many small primary solids than in alloys which crystallize only a few large solids.
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