FREE DENDRITE GROWTH IN UNDERCOOLED MELTS: EXPERIMENTS AND MODELING

摘要

Essential progress of modeling of free dendrite growth in undercooled melts was achieved by the "classic" work of Wilfried Kurz et al. In the present paper, recent developments in experimental methods are described to measure the dendrite growth dynamics in undercooled metallic melts, which are containerlessly processed by electromagnetic levitation technique. Results of essentially improved accuracy in measuring the dendrite growth velocity as a function of undercooling are presented for "nominally" pure nickel. In parallel, the sharp interface dendrite growth theory is extended to include effects both of melt convection and electromag-netically induced stirring of the levitation processed liquid. The analysis of the results indicate that fluid flow causes an enhancement of the dendrite velocity in the small undercooling range. Also, small amounts of impurities in nickel can lead to an increase of the growth velocity but with a temperature characteristics being different from that of the effect by fluid flow. This allows to discriminate between both contributions as it is shown by experimental investigations and modeling within the extended sharp interface model and phase-field modeling as well.