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A Phase Field Model for Grain Refinement in Deeply Undercooled Metallic Melts

Published online by Cambridge University Press:  21 March 2011

A.M. Mullis  and
R.F. Cochrane
A.M. Mullis
Affiliation:
Department of Materials, University of Leeds, Leeds LS2 9JT, UK.
R.F. Cochrane
Affiliation:
Department of Materials, University of Leeds, Leeds LS2 9JT, UK.
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Abstract

We present the results of phase field simulations of dendritic growth into pure undercooled melts, at growth velocities up to 35 m s−1. We find that, at low growth velocities, dendrite morphologies are broadly self-similar with increasing growth velocity. However, above ≈ 15 m s−1 the initiation of side-branching moves closer to the dendrite tip with increasing growth velocity. This appears to be related to the level of kinetic undercooling at the tip. Once side- branch initiation begins to occur within 1-2 radii of the tip, profound morphological changes occur, leading to severe thinning of the dendrite trunk and ultimately repeated multiple tip- splitting. This process can be invoked to explain many of the observed features of spontaneous grain refinement in deeply undercooled metallic melts.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 677: Symposium AA – Advances in Materials Theory and Modeling–Bridging Over Multiple-Length and Time Scales , 2001 , AA7.15
Copyright
Copyright © Materials Research Society 2001

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