elib
DLR-Header
DLR-Logo -> http://www.dlr.de
DLR Portal Home | Imprint | Contact | Deutsch
Fontsize: [-] Text [+]

Dendrite growth in undercooled melts of Al–Ni alloys solidified on Earth and under reduced gravity

Holland-Moritz, Dirk and Galenko, Peter and Hartmann, Helena and Lengsdorf, Roman and Reutzel, Sven and Herlach, Dieter M. (2011) Dendrite growth in undercooled melts of Al–Ni alloys solidified on Earth and under reduced gravity. ISPS 4, 11.-15. Juli 2011, Bonn, Deutschland.

Full text not available from this repository.

Abstract

Fluid flow decisively influences the heat and mass transport during solidification of melts and consequently the properties of the as-solidified materials. In this work we present investigations on the influence of convection on the non-equilibrium solidification of different undercooled Al-Ni alloy melts. The dendrite growth velocities in Al-Ni melts containerlessly processed by electromagnetic levitation have been measured on Earth and under the conditions of reduced gravity. While under terrestrial conditions strong electromagnetic fields are required for levitation against gravity, the fields necessary to compensate disturbing accelerations under reduced gravity conditions are smaller by orders of magnitude. Consequently, convective fluid flow induced by electromagnetic stirring effects is significantly decreased in experiments performed under reduced gravity. Comparative experiments on congruently melting Al50Ni50 alloys revealed that the dendrite growth velocities measured at small undercoolings in the electromagnetic positioning facility TEMPUS during parabolic flight campaigns are significantly lower as compared to terrestrial results [1]. At elevated undercoolings, when the growth velocity is exceeding the fluid flow velocity, the influence of convection becomes negligible. Finally, at very high undercoolings and growth velocities a transition from growth of the ordered superlattice structure of the intermetallic AlNi phase to solidification of a disordered superlattice structure due to the nonequilibrium effect of disorder trapping is observed for Al50Ni50 [2]. This transition is associated with a strong rise of the growth velocity. The growth velocity - undercooling relation measured on Earth and during parabolic flight, respectively, is well described by modelling of the dedrite growth using a sharp interface approach with and without considering convective fluid flow. While on the Ni-rich side of the Al-Ni phase diagram and around the equiatomic composition the growth velocity during non-equilibrium solidification is increasing with increasing undercooling, Al-rich Al-Ni alloys show an unusual decrease of the growth velocity with increasing undercooling in terrestrial investigations. The comparison with complementary microgravity experiments performed during the sounding rocket mission TEXUS 44 suggests that the anomalous growth behavior of Al-rich Al–Ni alloys may be caused by fluid-flow related processes [3]. Support by ESA within contract numbers 15236/02/NL/SH (NEQUISOL), by DLR Space Agency under contract number 50 WM 036, by Deutsche Forschungsgemeinschaft (DFG) under contract number HE1601/18 and by the European Commission EC under contract FP6-500635-2 (IMPRESS) is gratefully acknowledged. References: [1] S. Reutzel, H. Hartmann, P.K. Galenko, S. Schneider, and D.M. Herlach, Appl. Phys. Lett. 91, 041913 (2007). [2] H. Hartmann, D. Holland-Moritz, P.K. Galenko, and D.M. Herlach, Europhys. Lett. 87, 40007 (2009). [3] R. Lengsdorf, D. Holland-Moritz, and D.M. Herlach, Scripta Materialia 62, 365 (2010).

Document Type:Conference or Workshop Item (Speech)
Title:Dendrite growth in undercooled melts of Al–Ni alloys solidified on Earth and under reduced gravity
Authors:
AuthorsInstitution or Email of Authors
Holland-Moritz, Dirkdirk.holland-moritz@dlr.de
Galenko, Peterpeter.galenko@dlr.de
Hartmann, HelenaDLR, Institut für Materialphysik im Weltraum
Lengsdorf, RomanDLR, Institut für Materialphysik im Weltraum
Reutzel, SvenDLR, Institut für Materialphysik im Weltraum
Herlach, Dieter M.dieter.herlach@dlr.de
Date:13 July 2011
Status:Published
Keywords:dendrite growth, Al-Ni, reduced gravity
Event Title:ISPS 4
Event Location:Bonn, Deutschland
Event Type:international Conference
Event Dates:11.-15. Juli 2011
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W FR - Forschung unter Weltraumbedingungen (old)
DLR - Research area:Space
DLR - Program:W FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):W - Vorhaben Materialforschung unter Mikro-g (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Dr.rer.nat. Dirk Holland-Moritz
Deposited On:20 Jul 2011 08:50
Last Modified:20 Jul 2011 08:50

Repository Staff Only: item control page

Browse
Search
Help & Contact
Informationen
electronic library is running on EPrints 3.3.12
Copyright © 2008-2012 German Aerospace Center (DLR). All rights reserved.