Papers by Author: P. Cloetens

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Authors: Alexandre Velhinho, Francisco Manuel Braz Fernandes, S.C. Ferreira, L.A. Rocha, Gerard Vignoles, P. Cloetens
Abstract: This paper provides a brief overview of the possibilities offered by X-ray computed microtomography, and particularly synchrotron radiation X-ray microtomography, regarding metal matrix composite characterization, emphasis being placed in the case of Al-based functionally graded materials. Examples are provided concerning the characterization of the reinforcement population, interfacial properties, in-situ transformation and damage evolution. The specific needs of the technique and limitations to its widespread use are mentioned.
Authors: Alexandre Velhinho, Gerard Vignoles, P. Cloetens, X. Thibault, Elodie Boller, Francisco Manuel Braz Fernandes, L.A. Rocha, José D. Botas
Abstract: Reliability of functionally graded metal matrix composites (FGMMCs) for automotive components is still dependent on the detailed knowledge of the mechanisms of the microstructural build-up, for instance on the mechanisms leading to the distribution and relative positions of the reinforcing particles. In order to assess the influence of the SiC particle size on the 3-D inter-particle connectivity in functionally graded Al/SiCp composites produced by centrifugal casting, X-ray microtomography experiments were performed at the ID19 beamline in ESRF (European Synchrotron Radiation Facility). The FGMMCs consisted of an Al-10Si-2Mg alloy matrix, reinforced by an average SiC particle volume fraction of 0.10; two different average sizes were used: 37 µm and 12 µm. The holographic modification of the X-ray CMT (Computer Micro- Tomography) method allowed to obtain neatly contrasted images, as opposed to classical CMT.Good agreement was found between the particle size evaluated by CMT and by laser interferometry. Particle clustering has been evaluated in number and volume, showing that a lower mean particle size is related to more clustering. Such an adverse effect relies on the importance of particle/liquid alloy surface tension. Also, the mean particle size has been evaluated as a function of particle number within a cluster: as expected, the larger a cluster, the larger the particles inside it.
Authors: Éric Maire, Jean Yves Buffière, R. Mokso, P. Cloetens, Wolfgang Ludwig
Abstract: This paper generally presents different techniques available to image the microstructure of materials in three dimensions (3D) at different scales. It then focuses on the use of the more versatile of these techniques for aluminum alloys : X-ray tomography. The paper describes the recent improvements (spatial and the temporal resolution, grain imaging). Electron tomography is also presented as a promising technique to improve the spatial resolution.
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