Analysis of gravity effects during binary alloy directional solidification by comparison of microgravity and Earth experiments with in situ observation.

Under terrestrial conditions, solidification processes are influenced to a large degree by the gravity effects such as natural convection or buoyancy force, which can dramatically modify the final characteristics of the grown solid. In the last decades, the coupling of in situ observation of growth from the melt, that enables the study of microstructure formation dynamics, and microgravity experimentation, that allows to approach diffusive conditions, has been implemented for both transparent and metallic materials. The results of these investigations enable to test the validity of advanced solidification theories, to validate or develop numerical models and sometimes to reveal unexpected phenomena. The aim of this paper is to present a selection of conclusive experiments obtained with this combined approach in our group to highlight the gravity effects by a comparative study of experiments carried out on earth and in microgravity conditions.