Observation of dendritic growth and fragmentation in Ga-In alloys by X-ray radioscopy


Observation of dendritic growth and fragmentation in Ga-In alloys by X-ray radioscopy

Boden, S.; Willers, B.; Eckert, S.; Gerbeth, G.

Capabilities of the X-ray attenuation contrast radioscopy were utilised to provide a real-time diagnostic technique for observations of dendritic growth and fragmentation during solidification of a Ga-30wt%In alloy. The solidification process was visualised by means of a microfocus X-ray tube providing shadow radiographs at spatial resolutions of about 10 µm. Experiments have been carried out to solidify the Ga-In alloy unidirectional either starting from the bottom or the top of the specimen. The first case is significantly affected by solutal convection, which governs a redistribution of solute concentration. A detachment of dendrite side arms, which is unambiguously caused by melt flow, was not observed. Dendritic fragmentation occurs during the solidification in the reverse top-down direction. Variations of the applied cooling rate excited a transition from a columnar to an equiaxed dendritic growth (CET).

Keywords: solidification; X-ray radioscopy; dendrite growth; dendrite fragmentation

  • International Journal of Cast Metals Research 22(2009), 30-33

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Publ.-Id: 11461