Directional solidification of inclined structures in thin samples

We address the directional solidification of inclined structures by combining numerical and experimental studies performed in situations capable of yielding a detailed relevant comparison between them. We especially seek to determine the growth directions and the stability of microstructures at various Péclet numbers when the crystal axes and the thermal gradient involve a misorientation. For this we perform experiments and simulations in the closest possible conditions referring to similar physical parameters and to a monocrystal growing in a thin sample by a single layer of homogeneously spaced microstructures. Implementing a 3D phase-field numerical code proves necessary to accurately model the solidification structures. A quite satisfactory agreement, both on qualitative and quantitative grounds, is found between experiments and 3D simulations, on both the growth directions of microstructures and the transition to the degenerate mode. This agreement provides a confirmation of the growth direction law evidenced experimentally and a fine validation of the 3D phase-field numerical model.