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Le Cuivre nanostructuré massif : élaboration par métallurgie des poudres et étude du comportement mécanique

Abstract : Fully dense nanostructured metals are mainly studied for their exceptional mechanical properties. The reduced grain size prevents the interactions between dislocations, resulting in the development of new deformation mechanisms responsible for the increase of the flow stress.
We show in this study that powder metallurgy can succeed in the engineering of a fully dense nanostructured copper with large dimensions. Fabrication steps are i) nanocrystalline powder synthesis, ii) compaction, iii) sintering, iv) differential hydrostatic extrusion. The microstructures at each stage are detailed by mean of X-Ray diffraction, scanning and transmission electron microscopy. The caracterisation after extrusion reveals that the deformation is accommodated by dislocation activity.
We studied the mechanical properties by tensile and compression tests. It appears that during the tensile tests, the flow stress is around 400 MPa. The deformation is homogeneous without necking. Failure occurs after 12 % with a ductile rupture surface. Strain rate sensitivity has been studied in compression. The flow stress is highly dependant on the strain rate, in comparison with microstructured copper. This trend is confirmed by nanoindentation experiments.
The microstructure after mechanical tests is studied by transmission electron microscopy. Dislocation activity is reported, mainly at the grain boundaries. Dislocation sources seem to be located at the grain boundaries. The microstructural features identified result in a rough outline of a new deformation mechanism.
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Contributor : Cyril Langlois <>
Submitted on : Friday, December 10, 2004 - 3:01:55 PM
Last modification on : Tuesday, June 25, 2019 - 11:16:04 AM
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Cyril Langlois. Le Cuivre nanostructuré massif : élaboration par métallurgie des poudres et étude du comportement mécanique. Matériaux. Université Paris XII Val de Marne, 2003. Français. ⟨tel-00007715⟩

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