primary spacing evolution during microstructure formation in 3D directional solidification: microgravity experiments conducted in the declic-dsi

Paper number

IAC-16,A2,6,4,x32979

Coauthor

Mr. Jorge Pereda, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Coauthor

Mr. Younggil Song, Northeastern University, United States

Coauthor

Dr. Fatima Mota, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Coauthor

Prof. Bernard Billia, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Coauthor

Prof. Jean-Marc Debierre, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Coauthor

Prof. Rahma Guérin, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Coauthor

Prof. Alain Karma, Northeastern University, United States

Coauthor

Prof. Rohit Trivedi, Ames Laboratory US-DOE & Iowa State University, United States

Coauthor

Dr. Nathalie Bergeon, IM2NP - Aix-Marseille Université & CNRS UMR 7334, France

Year

2016

Abstract

The study of solidification microstructure formation is of utmost
importance for the design and processing of materials, as solid-liquid
interface patterns largely govern mechanical and physical properties.
Pattern selection occurs under dynamic conditions of growth in which
the initial morphological instability evolves nonlinearly and undergoes
a reorganization process. This dynamic and nonlinear nature renders
in situ observation of the solid-liquid interface an invaluable tool
to gain knowledge on the time-evolution of the interface pattern.
In this framework, the materials of choice for direct visualization
of interface dynamics are transparent organic analogs that solidify
like metallic alloys. Extensive ground-based studies of both metallic
and organic bulk samples have established the presence of significant
convection during solidification processes that alters the formation
of cellular and dendritic microstructures. The reduced-gravity environment
of Space is therefore mandatory for fluid flow elimination in bulk
samples. \\


Over a hundred days of experiments were carried out in the Directional
Solidification Insert (DSI) of the Device for the Study of Critical
Liquids and Crystallization (DECLIC), developed by the French Space
Agency (CNES) in collaboration with NASA and installed onboard the
International Space Station. The DSI offered the unique opportunity
to observe in situ and characterize the entire development of the
microstructure in extended 3D patterns under diffusive growth conditions,
using bulk samples of transparent organic alloys. Analysis and interpretation
of our experiments is considerably enhanced by corresponding phase-field
computational modelling. \\


A selection of some of our most striking results will be presented.
These focus on crystal grain competition and the dynamics of primary
spacing selection, highlighting the effects of crystal orientation,
grain boundary configurations, solidification front velocity, and
macroscopic interface curvature. We will also discuss selected quantitative
comparisons of the experiments with phase-field simulations that shed
light on fundamental mechanisms of interface pattern selection. \\


This project is supported by the French Space Agency CNES (Microstructures
de solidification 3D - MISOL3D \textendash{} project) and NASA (grant
NNX16AB54G and Spatiotemporal Evolution of Three-Dimensional Dendritic
Array Structures - SPADES \textendash{} project).
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