Dendritic solidification in undercooled Ni-Zr-Al melts: Experiments and modeling

The kinetics of dendritic solidification in a ternary Ni98Zr1Al1 alloy is investigated experimentally in a range of melt undercoolings 40 K <= Delta T <= 320 K. The growth velocity is measured for samples processed by the electromagnetic levitation technique using a highspeed video camera. With Delta T less than or similar to 220 K the measured growth rates are the same as those of a binary Ni99Zr1 alloy. In the regime of rapid solidification, especially within the regime of thermal dendritic growth at Delta T greater than or similar to 220 K, growth rates are decreased. Sharp-interface modeling predicts growth rates over the whole range of undercooling. Phase-field simulations give quantitative predictions for the dendritic growth velocity in the solute-controlled growth regime. Results show that the composition and temperature dependency of the thermodynamic data, e.g. liquidus slope and solute partition coefficient, are important for describing the alloys. Our findings give improved sharp-interface model predictions compared to calculations based on an approximation of the thermodynamic data derived from binary phase diagrams. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.