Modeling and Experimental Characterization of the Microstructure and Grain Structure of Al-7wt%Si Directionally Solidified

Paper number

IAC-10.A2.2.12

Author

Dr. Nathalie Mangelinck-Noel, CNRS, France

Coauthor

Dr. Kleber Sabat Da CRUZ, IM2NP UMR CNRS 6242, France

Coauthor

Dr. Charles-André Gandin, Center for Materials Forming, MINES ParisTech, France

Coauthor

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

Year

2010

Abstract

Controlling the solidification microstructure of metallic materials is the main objective of several researches developed nowadays due to its strong influence on the mechanical properties. During the solidification process, the natural convection in the liquid metal caused by the action of the gravitational field and sedimentation can produce important changes in the final structural morphology, from microstructural up to macrostructural scales. 
The objective of this study is to analyze the evolution of the microstructure and grain structures of an Al - 7 wt% Si refined alloy under the presence of natural convection. The experiments of directional solidification were carried out on ground at IM2NP in a Bridgman- Stockbarger type directional solidification furnace. During the experiments, the temperature profile inside the furnace is fixed. The varying parameter is the pulling rate of the crucible. Using this procedure with a refined alloy (added particles acting as nucleation sites), a transition from columnar grains (oriented in the vertical direction of the temperature gradient) to equiaxed grains is expected for increasing pulling rate. Columnar or equiaxed grain growth generates different grain sizes, to which correspond different repartitions of the eutectic. Such mesoscopic scale distribution of phases is expected to have consequences on the final properties of the cast structure. The experimental results are compared to numerical simulations performed using the R2Sol-CA code developed at CEMEF which combines the finite element method with the cellular automaton method to simulate the development of the structure and segregation. Eutectic fraction, grain size and spacing were measured to achieve the quantitative analysis of the experimental results and to deepen the comparison between simulations and experiments.
These ground experiments and associated simulations are part of a Microgravity Application Programme from the European Space Agency named Columnar to Equiaxed Transition in Solidification processing. In the frame of this project, experiments have been performed in the Materials Science Laboratory of the International Space Station on the same alloy. In a subsequent step, results of the microgravity experiments will be compared to the preparatory ground experiments presented here and simulations will be extended to microgravity experiments.

Abstract document

IAC-10.A2.2.12.brief.pdf

Manuscript document

IAC-10.A2.2.12.pdf (🔒 authorized access only).

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