5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

The microstructure formed during the solidification processing from the melt is a critical issue for industrial applications. Most of the mechanical properties of alloys are a result of these microstructures. Understanding and predicting both the microstructure formation and evolution are crucial for the development of performant materials. Since microstructures are strongly influenced by the history of the solid-liquid interface evolution during the solidification process, in situ observation of the interface patterns is an important tool to gain knowledge on microstructure formation. To study the fundamental physical mechanisms in the dynamical formation of two-dimensional arrays under diffusive growth conditions, two experimental campaigns of directional solidification in a model transparent alloy - succinonitrile–camphor - have been conducted onboard the International Space Station using the Directional Solidification Insert (DSI) of DECLIC (Device for the Study of Critical Liquids and Crystallization) facility. This facility was developed by the French Space Agency (CNES) in collaboration with NASA. The solute concentration was changed between the two experimental campaigns so that both cellular and dendritic regimes could be explored up to highly-branched structures. The combination of in situ observation on transparent systems and microgravity environment which allows solidification experiments of unprecedented duration offered a very unique possibility to study solidification and the dynamics of patterns. This possibility puts us on the path to produce benchmark data needed to validate and develop theoretical and numerical models. Experimental observations, supported by 3D phase-field simulations, demonstrate the influence of subgrain-boundary, misorientations and macroscopic heterogeneities of the thermal field on the primary spacing selection and pattern organization. Some of the most striking results from both campaigns regarding the pattern selection will be presented.