Investigation of columnar–equiaxed transition and equiaxed growth of aluminium based alloys by X-ray radiography

Among solidification processes, the columnar to equiaxed transition (CET) and equiaxed growth are still raising issues both from the metallurgical point of view and for the understanding of the fundamental related physical phenomena. The phenomena involved are complex and most of the time intimately related to the dynamical events happening during the solidification. Bridgman solidification of Al–Ni alloys is performed at the ID19 beamline of the European Synchrotron Radiation Facility (ESRF) in Grenoble. The use of a third generation synchrotron X-ray source allows for in situ and real-time observation of the solid–liquid interface, in particular at the CET. To provoke the CET, refined alloys are used and the pulling rate is increased following several profiles. The experiments give direct access to specific behaviours and enable the measurement of several key parameters during the CET and equiaxed growth, which can be discussed.