Columnar-EquiaxedTransition inSolidification processing: The ESA-MAP CETSOL project

Abstract

Many castings are the result of a competition between the growth of columnar and equiaxed grains. Indeed, microstructures are at the center of materials science and engineering, and solidification is the most important processing route for structural materials, especially metals and alloys. Presently, microstructure models remain mostly based on diffusive transport mechanisms so that there is a need of critical benchmark data to test fundamental theories of microstructure formation, which often necessitates to have recourse to solidification experiments in the reduced-gravity environment of space. Accordingly, the CETSOL (Columnar-Equiaxed Transition in SOLidification processing)-MAP project of ESA is gathering together European groups with complementary skills to carry out experiments and model the processes, in particular in view of the utilization of reduced-gravity environment that will be afforded by the International Space Station (ISS) to get benchmark data. The ultimate objective of the CETSOL research program is to significantly contribute to the improvement of integrated modeling of grain structure in industrially important castings. To reach this goal, the approach is devised to deepen the quantitative understanding of the basic physical principles that, from the microscopic to the macroscopic scales, govern microstructure formation in solidification processing under diffusive conditions and with fluid flow in the melt. Pending questions are attacked by well-defined model experiments on technical alloys and/or on model transparent systems, physical modeling at microstructure and mesoscopic scales (e.g. large columnar front or equiaxed crystals) and numerical simulation at all scales, up to the macroscopic scales of casting with integrated numerical models.