<i>In situ</i>observation of solidification phenomena in Al–Cu and Fe–Si–Al alloys

Synchrotron radiation enables the observation of solidification in metallic alloys. In situ observations of solidification for Al–Cu alloys (5, 10 and 15 wt-%Cu) are reported. Nucleation and fragmentation of dendrite arms were often observed in the 15 and 10%Cu alloys when unidirectional solidification was performed from the planar interface. In contrast, nucleation and fragmentation were rarely observed in the 5%Cu alloys. The nucleation ahead of the solidifying front and the fragmentation in the mushy region strongly depended on alloy composition. This paper also presents in situ observation of solidification of Fe–10Si–0·5Al (at-%) alloys. The dendritic growth of δ-Fe was clearly observed using this technique. The development of X-ray imaging techniques enables the solidification of various conventional cast alloys such as Al, Ni and Fe alloys to be observed and will be increasingly used to investigate solidification phenomena.