University of Cambridge > Talks.cam > Structural Materials Seminar Series > In situ synchrotron X-ray characterisation of microstructure formation during solidification of Al-based alloys

In situ synchrotron X-ray characterisation of microstructure formation during solidification of Al-based alloys

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The primary microstructure formed during the solidification step has a major influence on the properties of materials processed by major techniques (casting, welding…). In situ and real-time characterisation by synchrotron X-ray imaging is the method of choice to unveil the dynamical formation of the solidification microstructure in metallic alloys, and thus provide precise data for the validation of the theoretical predictions that is needed for advancement of modelling and numerical simulation. After a description of the experimental procedure used at the European Synchrotron Radiation Facility (ESRF), dynamical features occurring during the formation of the columnar and equiaxed grain structure in Al-based alloys are presented. Convective flows initiated by residual transverse temperature gradients are amplified by the solute rejection during the solidification process. Beyond fluid flow interaction, earth gravity induces stresses, deformation and fragmentation in the dendritic mush. Settling of dendrite arms and equiaxed grains thus occurs, in particular in the columnar to equiaxed transition (CET). Quantitative analysis of the grey level in radiographs enables the analysis of solute segregation, which noticeably results in solutal poisoning of growth when equiaxed grains are interacting. Finally, the extension of such investigation to the study of materials with a high melting point such as superalloys will be discussed.

This talk is part of the Structural Materials Seminar Series series.

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