The microsegregation inherited from the directional solidification and quenching (DSQ) of an experimental third generation single crystal superalloy is characterised using electron probe microanalysis (EPMA). A statistical treatment of the data is used to estimate the composition of the solid in the mushy zone. Comparison of the experimental data with the predictions from a numerical model indicates that the results cannot be rationalised without acknowledging that back diffusion is occurring; it is demonstrated that the magnitudes of the diffusion coefficients which need to be invoked are consistent with recent experimental measurements of the coefficients deduced from diffusion couples.
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