Application of synchrotron X-ray imaging to the study of directional solidification of aluminium-based alloys

Third generation synchrotron X-ray sources like ESRF (European Synchrotron Radiation Facility) have enhanced the capabilities of in situ and real-time X-ray imaging so that it is possible to follow the solid-liquid interface dynamics on metallic alloys with improved spatial and time resolution. In this paper, we focus on the solidification patterns of Al-based alloys, visualised by absorption and phase contrast radiography at ESRF. Two metallic systems were selected for this study: (i) Al-3.5 wt% Ni (with and without refiners) for the analysis of columnar growth and equiaxed growth, and the influence of the refiners on the columnar to equiaxed transition (CET), which is a key point in solidification processing, (ii) Al72.4Pd20.5Mn7.1 for the analysis of interface shape of growing quasicrystals (QCs). For both alloys, striking features were observed and a preliminary discussion is presented. Those results demonstrate the high potential of ESRF Synchrotron source for the characterisation of the dynamical formation of the solid microstructure in materials processing.