Metall. Res. Technol.
Volume 111, Number 5, 2014
Topical Issue on Solidification
|Page(s)||295 - 303|
|Published online||14 May 2014|
Kinetics of dendrite growth and dendritic fragmentation in the undercooled Co81.2 Cu18.8 alloy’s melt
Friedrich-Schiller-Universität Jena, Physikalisch-Astronomische Fakultät, Löbdergraben
2 Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51147 Köln, Germany
3 Institut für Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
Accepted: 4 April 2014
The growth velocity during solidification of an undercooled melt of a Co-Cu alloy processed by electromagnetic levitation was measured using a high speed video camera. Applying a model of local non-equilibrium solidification, theoretical predictions of dendrite growth velocity and dendritic growth radii are compared with high-accuracy measurements of the growth kinetics. As the undercooling ΔT reaches a critical value consistent with the dendrite growth velocity being equal to the atomic diffusion speed VD in bulk liquid, ΔT = ΔT(VD), the velocity-undercooling relationship exhibits a break-point. A distinct change in the dendritic growth mechanism exists with the onset of complete solute trapping and chemically partitionless solidification of the core of the main stems of the dendrites occurs. A complete transition to the thermally controlled growth of dendrites occurs at ΔT = ΔT(VD) that leads to essential changes in the microstructure of dendritic patterns The phenomenon of dendritic fragmentation in Co-Cu melts, solidifying at ΔT < ΔT(VD), is discussed.
Key words: undercooling / dendrite growth / solidification / modeling
© EDP Sciences 2014
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