X-ray visualisation of solidifying GaIn-alloys in the presence of melt convection

X-ray radioscopic methods enable the in-situ real-time observation of solidification processes in metal alloys with a spatial resolution of a few microns. Visualisation of bottom up directional solidification of a Ga-25wt%In binary metal alloy contained in a capillary slit container was conducted. The solidification is obviously affected by natural thermosolutal melt flow patterns. Externally forced melt convection was superimposed by means of a magnetic stirrer in form of a rotating wheel equipped with permanent magnets. The electromagnetic flow provokes a considerable redistribution of the solutal boundary layers around the solidifying dendrites, and influences therewith the formation of the microstructure.