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

Abstract 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–30In (wt-%) 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 unidirectionally 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).

[1]  G. Gerbeth,et al.  X-Ray Radioscopic Visualization of the Solutal Convection during Solidification of a Ga-30 Wt Pct In Alloy , 2008 .

[2]  P. Bleuet,et al.  Crystal fragmentation and columnar-to-equiaxed transitions in Al-Cu studied by synchrotron X-ray video microscopy , 2006 .

[3]  G. Zouhar,et al.  The columnar-to-equiaxed transition in Pb–Sn alloys affected by electromagnetically driven convection , 2005 .

[4]  R. Mathiesen,et al.  X-ray radiography observations of columnar dendritic growth and constitutional undercooling in an Al–30wt%Cu alloy , 2005 .

[5]  A. Kazimirov,et al.  Real-time observation of dendrite coarsening in Sn-13%Bi alloy by synchrotron microradiography. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[6]  K. Umetani,et al.  Direct observation of stray crystal formation in unidirectional solidification of Sn Bi alloy by X-ray imaging , 2004 .

[7]  Timm Weitkamp,et al.  Time Resolved X-Ray Imaging of Dendritic Growth in Binary Alloys , 1999 .

[8]  Andrew M. Mullis,et al.  Grain refinement and the stability of dendrites growing into undercooled pure metals and alloys , 1997 .

[9]  S. Lu,et al.  Dendrite fragmentation and the effects of fluid flow in castings , 1997 .

[10]  W. Kaukler,et al.  Real-Time X-Ray transmission microscopy of solidifying Al-In Alloys , 1996 .

[11]  Schwarz,et al.  Physical mechanism of grain refinement in solidification of undercooled melts. , 1994, Physical review letters.