Retrieval of three-dimensional spatial information from fast in situ two-dimensional synchrotron radiography of solidification microstructure evolution

In situ synchrotron X-ray radiography of columnar dendritic growth in Al-15 wt.% Cu-9 wt.% Si-0.015 wt.% Sr alloy has been carried out with the temporal and spatial resolutions of 100 ms and 0.65 μm, respectively. Two-dimensional (2-D) projected images have been processed and analysed to retrieve three-dimensional (3-D) spatial information on the growing dendrite network, through X-ray transmission contrast differences that account for solute-composition variations in the liquid and thickness variations in the growing dendrites. The analysis elucidates the way in which gravity-driven natural convection and solute sedimentation can result in solid fractions that deviate markedly from Scheil and Lever-rule-based models, which could alter mushy zone permeability. Furthermore, the ability to render 3-D spatial details may lead to future opportunities to use 2-D radiography in the development and validation of more sophisticated 3-D models of dendritic growth.