Grain structure and segregation in microgravity castings
Résumé
The main objective of this MAP project is the investigation of the formation of the transition from columnar to equiaxed macrostructure that takes place in casting. Indeed, grain structures observed in most casting processes of metallic alloys are the result of a competition between the growth of several arrays of dendrites that develop under constrained and unconstrained conditions, leading to the columnar to equiaxed transition. A dramatic effect of buoyancy-driven flow on the transport of equiaxed crystals on Earth is acknowledged. This leads to difficulties in conducting precise investigations of the origin of the formation of the equiaxed crystals and their interaction with the development of the columnar grain structure. Consequently, critical benchmark data to test fundamental theories of grain structure formation are required, which benefit from microgravity investigations. These objectives are of direct interest to the project's industrial partners.