Columnar-to-Equiaxed Transition in Solidification Processing (CETSOL) - 11.22.16

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Hey, do me a solid? Researchers solidifying refined and unrefined alloys under normal and micro-gravity observed a transition from columnar crystals (those with one direction of longer growth) to equiaxed crystals (equal growth in all directions). This transition, more pronounced in the refined alloy, was affected by temperature gradient and the presence or absence of grain refiner. That grain effect could occur because crystal fragments that are less dense than the melted alloy detach, float upward, and serve as a nucleus for equiaxed grains. Another way to say that is new crystals nucleate and grow directly in the undercooled melt ahead of the columnar crystals. The data may improve the modelling of solidification structures, useful in producing solar cells, thermoelectrics, and other materials.

The following content was provided by Gerhard Zimmermann, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.
Experiment Details

OpNom:

Principal Investigator(s)
Gerhard Zimmermann, Ph.D., ACCESS e.V., Aachen, Germany

Co-Investigator(s)/Collaborator(s)
Charles-Andre Gandin, Ph.D., Ecole de Mines de Paris, ARMINES-CEMEF (CETSOL), Sophia Antipolis, France
Bernard Billia, Ph.D., Aix-Marseille Universite´, Marseille, France
David John Browne, Ph.D., University College Dublin, Dublin, Ireland
David Poirier, Sc.D.,, University of Arizona, Tucson, AZ, United States
Robert Erdmann, Ph.D., University of Arizona, Tucson, AZ, United States
Christoph Beckermann, University of Iowa, Iowa City, IA, United States
Alain Karma, Ph.D.,, Northeastern University, Boston, MA, United States
Henry Nguyen-Thi, Ph.D., Aix-Marseille Universite´, Marseille, France
Shaun McFadden, Trinity College Dublin , Dublin, Ireland
Peter W. Voorhees, Ph.D., Northwestern University, Evanston, IL, United States
Andras Roosz, Ph.D., University of Miskolc, Miskolc, Hungary
Nils Warnken, University of Birmingham, Birmingham, United Kingdom

Developer(s)
Transvalor S.A., Mougins, France
HYDRO Aluminium Rolled Products GmbH, Bonn, Germany
Incaal GmbH, Nörvenich, Germany
ArcelorMittal Industeel France, Saint-Denis, France
Alcoa-Köfem Kft, Szekesfehervar, Hungary
Nemak Györ Kft., Győr, Hungary
INOTAL Aluminiumfeldolgozo, Varpalota, Hungary

Sponsoring Space Agency
European Space Agency (ESA)

Sponsoring Organization
Information Pending

Research Benefits
Information Pending

ISS Expedition Duration
October 2009 - September 2010

Expeditions Assigned
21/22,23/24

Previous Missions
Information Pending

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Experiment Description

Research Overview
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Description
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Applications

Space Applications
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Earth Applications
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Operations

Operational Requirements and Protocols
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Decadal Survey Recommendations

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Results/More Information

On the ISS, within the Material Science Laboratory (MSL), Aluminum-Silicon alloys were directionally solidified under different conditions.  The alloys came in two types: refined and unrefined.  The analysis of the samples confirmed the transition from crystals that have one direction of growth that is longer than others (columnar) to crystals that have directions of growth that are about the same length (equiaxed).  This transition is confirmed especially in the refined alloy (Zimmermann 2011).
 
Temperature evolution, and grain-structure analysis provide critical values for the position, temperature gradient, and solidification velocity, at the point of transition from columnar to equiaxed. Scientists detected a sharp transition when the rate of solidification increased.  In contrast, progressive transition was seen when lowering the temperature gradient (Zimmermann 2014, Liu 2014).  The transition appears to be more difficult to start in the absence of grain refiner since none of the corresponding samples showed that happening (Mirihanage 2012).  Whereas, the transition was found in a sample processed on the ground under similar conditions. This effect is potentially due to the detachment of fragments of dendrites that are less dense than the melted alloy. They then float up towards regions where they serve as nucleation sites for equiaxed grains.  These unique data are used to improve modelling of both solidification microstructures, and grain structure on different lengths scales (McFadden 2010, Sturz 2012, Liu 2015).
 

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Related Publications

    Ludwig A, Mogeritsch J, Kolbe M, Zimmermann G, Sturz L, Bergeon N, Billia B, Faivre G, Akamatsu S, Bottin-Rousseau S, Voss D.  Advanced solidification studies on transparent alloy systems: A new European solidification insert for material science glovebox on board the International Space Station. JOM Journal of the Minerals, Metals and Materials Society. 2012 September; 64(9): 1097-1101. DOI: 10.1007/s11837-012-0403-4.

    Liu DR, Mangelinck-Noel N, Gandin C, Zimmermann G, Sturz L, Thi HN, Billia B.  CAFE simulation of columnar-to-equiaxed transition in Al-7wt%Si alloys directionally solidified under microgravity. IOP Conference Series: Material Science and Engineering. 2016 March; 117. DOI: 10.1088/1757-899X/117/1/012009.

    McFadden S, Browne DJ, Sturz L, Zimmermann G.  Analysis of a microgravity solidification experiment for columnar to equiaxed transitions with modeling results. Materials Science Forum. 2010 May; 649: 361-366. DOI: 10.4028/www.scientific.net/MSF.649.361.

    Liu DR, Mangelinck-Noel N, Gandin C, Zimmermann G, Sturz L, Nguyen-Thi H, Billia B.  Simulation of directional solidification of refined Al–7wt.%Si alloys – Comparison with benchmark microgravity experiments. Acta Materialia. 2015 July; 93: 24-37. DOI: 10.1016/j.actamat.2015.03.058.

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