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Concentration dependent growth velocities in undercooled Al-rich Al-Ni alloy systems

Ehlen, Georg and Wang, Haifeng and Herlach, Dieter M. (2014) Concentration dependent growth velocities in undercooled Al-rich Al-Ni alloy systems. Materials Science Forum, 790, pp. 485-490. Trans Tech Publications. DOI: doi:10.4028/www.scientific.net/MSF.790-791.485 ISSN 0255-5476

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Abstract

Dendrite growth velocity as a function of undercooling on the Al-rich side of the Al-Ni system has recently been measured by electromagnetic levitation. The results have shown an anomalous behaviour, which so far cannot be theoretically described. The present work uses two simplified qualitative models of sharp interface theory, one of them treating the forming AlNi (B2) phase as a solid-solution, one treating it as an intermetallic phase, to investigate the influence of the phase diagram on the growth velocities. The results imply that the concentration dependent growth behaviour is a superposition of at least two effects: (1) A strong decrease of the total growth velocity level for increasing Al concentrations. (2) An increase of growth velocities with increase of Al concentration at medium and low undercoolings. The present work is able to explain the first effect, namely the concentration dependent reduction of velocities. Results are compared to experimental data. In both models the properties of the phase diagram lead to an increase of the constitutional undercooling�� when the Al content increases. This reduces the fraction left for kinetic undercooling�� which is responsible for interface migration and which determines the growth velocity. Neither of the models can reproduce the second effect.

Item URL in elib:https://elib.dlr.de/89243/
Document Type:Article
Title:Concentration dependent growth velocities in undercooled Al-rich Al-Ni alloy systems
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Ehlen, Georggeorg.ehlen (at) dlr.deUNSPECIFIED
Wang, Haifenghaifeng.wang (at) dlr.deUNSPECIFIED
Herlach, Dieter M.dieter.herlach (at) dlr.deUNSPECIFIED
Date:2014
Journal or Publication Title:Materials Science Forum
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:No
Volume:790
DOI :doi:10.4028/www.scientific.net/MSF.790-791.485
Page Range:pp. 485-490
Publisher:Trans Tech Publications
ISSN:0255-5476
Status:Published
Keywords:dendrite growth velocity, kinetic undercooling, constitutional undercooling, Al-rich Al-Ni, concentration dependence
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Materialforschung unter Mikro-g (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space > Scientific Experiments MP
Deposited By: Gegner, Jan
Deposited On:26 May 2014 08:40
Last Modified:06 Sep 2019 15:22

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