Parameter-free test of alloy dendrite-growth theory

In rapid alloy solidification the dendrite-growth velocity depends sensitiv ely on the deviations from local interfacial equilibrium manifested by kine tic effects such as solute trapping. The dendrite tip velocity-undercooling function was measured in dilute Ni(Zr) over the range 1-25 m/s and 50-255 K using electromagnetic levitation techniques and compared to theoretical p redictions of the model of Trivedi and colleagues for dendritic growth with deviations from local interfacial equilibrium. The input parameter to whic h the model predictions are most sensitive, the diffusive speed V-D charact erizing solute trapping, was not used as a free parameter but was measured independently by pulsed laser melting techniques, as was another input para meter, the liquid diffusivity D-L. Best-fit values from the pulsed laser me lting experiment an V-D = 26 m/s and DL = 2.7 x 10(-9) m(2)/s. Inserting th ese values into the dendrite growth model results in excellent agreement wi th experiment with no adjustable parameters. [S0163-1829(99)02101-3].