In situ 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 delta-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.