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M: Metallphysik
M 21: Intermetallische Phasen II
M 21.5: Talk
Saturday, March 5, 2005, 12:00–12:15, TU H2038
Solidification of Undercooled Intermetallic Forming Systems — •Hamid Assadi1,2 and Dieter M. Herlach1 — 1DLR, Institut für Raumsimulation, 51147 Köln — 2On leave from: Tarbiat Modarres University, Tehran, Iran
Intermetallics exhibit unique solidification behaviour due to their chemical long-range order. This inclues, for instance, generally slow solidification kinetics, and in some cases, a characteristically sharp change of slope in the corresponding relation between crystal growth velocity and undercooling. The present work uses a phase-field approach to illustrate this behaviour, and further to predict an entire microstructure in an intermetallic forming system. The phase field model is derived from a thermodyanamic formulation, and is assessed qualitatively against the sharp-interface theory of disorder trapping by Boettinger and Aziz (Acta Metall. 1989). A quantitative assessment of the model is provided with respect to the measured growth velocity - undercooling data for various Ni-Al alloys, obtained from electromagnetic levitation experiments.
(Support by the Alexander von Humboldt-Foundation is gratefully acknowledged.)