Search for a solute-drag effect in dendritic solidification

Abstract

We report the results of an indirect experimental test for the solute-drag effect in alloy solidification by fitting the data of Eckler et al. for NiB dendrite tip velocities vs undercooling to models in several ways. The unknown equilibrium partition coefficient, k e, was varied as a fitting parameter. When we combine the dendrite growth model of Boettinger et al. with the Continuous Growth Model (CGM) of Aziz and Kaplan “with solute drag”, we cannot fit the data for any value of k e. When we combine dendrite growth theory with the CGM “without solute drag”, we obtain a reasonable fit to the data for k e = 4 × 10 −6. When we combine dendrite growth theory with a new “partial-solute-drag” interpolation between the “with-solute-drag” and the “without-solute-drag” versions of the CGM, we obtain a still better fit to the data for k e = 2.8 × 10 −4. This result points out the possibility of partial solute-drag during solidification and the importance of an independent determination of k e in order to distinguish between models.