Three-Dimensional in Situ Observations of Solidification Microstructure Formation Aboard the ISS and Comparison With in Silico Modeling

From traditional casting to additive manufacturing, the microstructures formed during the solidification process determine the properties of a wide range of structural alloys. In a microgravity environment, microstructural pattern formation can be studied without the added complexity of buoyancy-driven convection. To characterize the dynamical formation of three-dimensional arrays of dendrites under diffusive growth conditions, a series of experiments using a transparent succinonitrile – 0.46 wt% camphor model alloy was carried out under low gravity in the DECLIC Directional Solidification Insert onboard the International Space Station. These experiments monitor in situ the dynamics of the solid-liquid interface during microstructural pattern formation, thereby yielding new fundamental insights into this dynamics and, at the same time, providing unique benchmark data to validate the predictions of in silico models. This talk will report quantitative comparisons of in situ observations and in silico modeling spanning three orders of magnitude of microstructural length scales from the dendrite tip radius to the sample scale. The results shed new light on the crucial role of the combined effects of the macroscopic curvature of the solidification front and the crucible wall geometry on grain structure selection and spatial ordering of intragrain dendritic arrays.