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MEASUREMENT OF DENDRITE GROWTH ON Al-Ni ALLOYS IN REDUCED GRAVITY

Lengsdorf, Roman und Galenko, Peter und Herlach, Dieter (2009) MEASUREMENT OF DENDRITE GROWTH ON Al-Ni ALLOYS IN REDUCED GRAVITY. In: Proceedings of the 19th ESA Symposium on European Rocket and Balloon Programmes and Related Research, ESA SP-671, Seiten 355-360. 19th ESA Symposium on European Rocket and Balloon Programmes and Related Research, 7.-11. Juni 2009, Bad Reichenhall. ISBN 978-92-9221-235-3.

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Kurzfassung

It is well known that the growth kinetics in metallic melts controls microstructure evolution. If the melt is cooled below its equilibrium melting temperature prior to solidification, the state of a metastable undercooled melt is created. An undercooled melt possesses an enhanced free energy that enables the liquid to choose solidification pathways into various metastable solids of properties being different to their stable counterparts. A very efficient method to undercool a metallic liquid is the application of containerless processing a liquid drop such that heterogeneous crystal nucleation on container walls is completely avoided. Electro-magnetic levitation is a power-full technique to produce a freely suspended drop without any contact to a solid or liquid medium with the extra benefit that it is accessible for direct observation of solidification far from equilib-rium by proper diagnostic means. Under terrestrial conditions, strong electromagnetic fields are needed to compensate the gravitational force. That, in turn, causes forced convection inside the liquid drop and influences mass and heat transport, and consequently, crystal growth in undercooled melts. If the reduced gravity environment is utilized the forces to compensate residual accelerations are several orders of magnitude smaller than the levitation force on Earth. In the present paper we report on results obtained in the Earth laboratory, during parabolic flight missions and during TEXUS 44 flight in 2008 using the TEMPUS facility for containerless processing of metals in space. The results are discussed within dendrite growth theory and give evidence for strong effects of gravitational driven effects in the solidification dynamics.

Dokumentart:Konferenzbeitrag (Vortrag, Paper)
Titel:MEASUREMENT OF DENDRITE GROWTH ON Al-Ni ALLOYS IN REDUCED GRAVITY
Autoren:
AutorenInstitution oder E-Mail-Adresse der Autoren
Lengsdorf, RomanRuhr-Universität Bochum
Galenko, Peterpeter.galenko@dlr.de
Herlach, Dieterdieter.herlach@dlr.de
Datum:September 2009
Erschienen in:Proceedings of the 19th ESA Symposium on European Rocket and Balloon Programmes and Related Research, ESA SP-671
Referierte Publikation:Ja
In ISI Web of Science:Nein
Seitenbereich:Seiten 355-360
ISBN:978-92-9221-235-3
Status:veröffentlicht
Stichwörter:Undercooling, containerless processing
Veranstaltungstitel:19th ESA Symposium on European Rocket and Balloon Programmes and Related Research
Veranstaltungsort:Bad Reichenhall
Veranstaltungsart:internationale Konferenz
Veranstaltungsdatum:7.-11. Juni 2009
Veranstalter :European Space Agency
HGF - Forschungsbereich:Verkehr und Weltraum (alt)
HGF - Programm:Weltraum (alt)
HGF - Programmthema:W FR - Forschung unter Weltraumbedingungen (alt)
DLR - Schwerpunkt:Weltraum
DLR - Forschungsgebiet:W FR - Forschung unter Weltraumbedingungen
DLR - Teilgebiet (Projekt, Vorhaben):W - Vorhaben Materialforschung unter Mikro-g (alt)
Standort: Köln-Porz
Institute & Einrichtungen:Institut für Materialphysik im Weltraum
Hinterlegt von: Dieter Herlach
Hinterlegt am:02 Mär 2010 11:29
Letzte Änderung:12 Dez 2013 20:54

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