Direct simulation of a directional solidification experiment observed in situ and real-time using X-ray imaging

It has been shown in the last decade that in situ and real-time observation of metallic alloy solidification is possible by using X-ray monitoring conducted at third generation synchrotron sources. A detailed analysis of a Bridgman experiment carried out at ESRF with an Al - 3.5 wt% Ni alloy was presented earlier [1]. This article proposes a direct simulation of the solidification of the entire sample for this experiment, in which all the dendritic grains are individually represented as they nucleate and grow in the experiment. This is possible by extracting from the radiographs a list of all the nucleated grains, including the positions and orientations of their main trunks. Simulation is performed using a two-dimensional (2D) Cellular Automaton (CA) – Finite Element (FE) model. As a result of the coupling between the CA and FE methods, consequences of the macroscopic transport of heat, liquid momentum and solute mass on the development of the dendritic grain structure are accounted for, and vice versa. The macroscopic deformation of the columnar front observed during the experiment is reproduced, as well as the columnar-to-equiaxed transition. The influence of flow patterns on macrosegregation is also discussed.