National Physical Laboratory

A phase-field model of solidification of ITS-90 fixed points

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Published: 24 October 2013

Authors: Matt Large & Jonathan Pearce

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We present a 2D axisymmetric phase-field model of thermo-solutal solidification in ITS-90 fixed-point cells. The model is applied to understand the effect of experimental parameterssuch as initiation technique and furnace homogeneityon the measured freezing curve.

Results show that Scheil-like freezing curves can be obtained with a specific furnace temperature profile, and provided that the freeze is of long duration the results are consistent with previous 1D models and experiments. Morphological instability is observed with the inner mantle initiation technique, causing the interface to adopt a cellular structure.

This elevates the measured temperature, in accordance with the Gibbs-Thomson effect. In addition, under certain circumstances, de-wetting behaviour is observed when the inner mantle is initiated. These are new findings. Directions for further investigation are described.

Last Updated: 24 Oct 2013
Created: 22 Aug 2013