MICROSTRUCTURE FORMATION IN CASTING OF TECHNICAL ALLOYS UNDER DIFFUSIVE AND
MAGNETICALLY CONTROLLED CONVECTIVE CONDITIONS (MICAST)
Research Area: Materials Science
Expedition(s): 21 - 26
Principal Investigator(s): ● Lorenz Ratke, German Aerospace Center, Cologne, Germany
● Eckhard Müller, German Aerospace Center, Cologne, Germany
● Yves Fautrelle, Centre National de la Recherche Scientifique,
Grenoble, France
● Andras Roosz, University of Miskolc, Miskolc, Hungary
● Gerhard Zimmermann, ACCESS e.V., Aachen, Germany
● Jacques Lacaze, Centre National de la Recherche Scientifique
(CNRS), Cirimat, Toulouse, France
● Sadik Dost, University of Victoria, Victoria, British Columbia,
Canada
● David Poirier, University of Arizona, Tucson, Arizona,
RESEARCH OBJECTIVES
MICAST identifies and controls experimentally the fluid-flow patterns that affect microstructure
evolution during casting processes, and to develop analytical and advanced numerical models.
The microgravity environment of the International Space Station (ISS) is of special importance
to this project because only there are all gravity-induced convections eliminated and well-
defined conditions for solidification prevail that can be disturbed by artificial fluid flow being
under full control of
the experimenters.
Design solutions
that make it
possible to improve
casting processes
and especially
aluminum alloys
with well-defined
properties will be
provided.
RESULTS
Preliminary data
indicates the
samples are homogeneously distributed under purely diffusive conditions, the longer
precipitates appear clearly accumulated in the center of the sample when a rotating magnetic
field is applied. The size and distribution of the precipitates as a function of the solidification
velocity and the controlled flow of melt imposed by the magnetic field are produced by 3D
tomographic reconstruction. The enrichment in Si and Fe resulting from the convective flows in
the central part of the sample clearly lead to the formation of larger precipitates.
These 2 pictures resulting from the treatment of images of the cross-section of samples
processed in space, provide the sought for quantitative evidence of the influence of
convection on the distribution of the precipitates in the solidified alloy.