Real-time observation of dendrite coarsening in Sn-13%Bi alloy by synchrotron microradiography.

An improved synchrotron microradiography technique is being used to study dendrite growth and coarsening in Sn-13%Bi alloy in real time. The morphology of growing dendrites can be well resolved with reasonable image contrast. Dendrite arm remelting, coalescence, and fragmentation have been observed in a real alloy and in real time during solidification under controlled thermal gradients and cooling rates. This research opens a different window to the study of alloy solidification and enables unambiguous understanding of solidification processes in optically opaque, metallic alloys.