Effects of the interface curvature on cellular and dendritic microstructures

International audienceWe study the solidification of succinonitrile-based alloys contained in cylindrical glass crucibles. In such samples, the solid–liquid interface iscurved as the latent heat generated upon solidification is mainly evacuated through the crucible wall of higher thermal conductivity. This createsradial thermal gradient which drives some important modifications in solute macrosegregation and of the microstructure array. A facility dedicatedto the in situ and real time characterization of solid–liquid interface morphology during directional solidification of bulk samples has been developedby CNES (French Space Agency) in the frame of the DECLIC project. The effects on microstructure dynamics of fluid flow driven by the radialthermal gradient associated to curvature have already been pointed out, but other effects of curvature – function of the type of structure developed– are here presented. For a cellular microstructure, curvature is at the origin of advection that manifests in observation by the gliding of cells fromthe border to the centre of the interface. For a dendritic microstructure, a strong dependence of dendrite growth direction on the curvature appearsthat alters the columnar structure