Observation of side arm splitting studied by high resolution X-ray radiography

Abstract

Abstract The local dynamics of dendritic side arms during the growth stage were studied by in-situ radiography observations at high spatial resolution of better than 1 μm. A flat sample of a Ga–In alloy was solidified top-down applying a vertical temperature gradient. The evolving dendritic microstructure was visualized using synchrotron X-ray imaging at the beamline ID19 (ESRF, France). The experimental investigations on the dendrite evolution revealed a transition from a four-fold symmetry to a hyperbranched dendritic morphology. Both the side arm-splitting phenomenon – responsible for this morphological transition – as well as the arm growth dynamics were characterized using image processing.