Papers by Author: Adeline Buffet

Abstract: The columnar to equiaxed transition (CET) has been widely studied for many years [1] because this phenomenon is observed in metallurgical applications like castings. In non refined alloys, detachment of dendrite fragments is the most probable mechanism responsible for the formation of an equiaxed microstructure [1]. In this frame, melt convection influences the grain structure evolution by playing a role in the fragmentation phenomena [2].

Abstract: In the present study, we report on an image analysis procedure, which enables to extract from synchrotron radiographs the long range solute profiles in the whole sample and in both phases (solid and liquid). This image analysis is based on the measurement of local density differences, and is applied to study the directional solidification of Al - 4wt% Cu alloy, from planar to onset of the initial instability. Dedicated experiments were carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble (France). In order to validate this analysis the value of a key solidification parameter, namely the partition coefficient, was experimentally determined during the planar solidification, and a very good agreement was found with value found usually in the literature. On a further step, the evolution of the microstructure and solute profile during the initial transient of solidification was analysed in detail.

Abstract: X-ray diffraction imaging allows the investigation of a large area of a polycrystalline specimen in a single shot. Dynamic processes like recystallization can, therefore, be studied without prior knowledge of where they occur. Even early stages of nucleation can be traced back using the information from images taken from the fully recrystallized specimen. Experiments performed at HASYLAB beamline G3 on cold rolled Cu and Al showed nucleation and growth behaviour that cannot be explained by classical models.