Small scale plasticity

Materials that have at least one of their characteristic length scale reduced (bulk nanostructured materials, nanocrystalline fibers or films) exhibit different mechanical properties than their equivalent counterparts. We study these size effects from both an experimental by performing in-situ Transmission Electron Microscopy (TEM) experiments but also with numerical and analytical approaches. We study especially: coupling between grain boundary migration and plastic strain, dislocation nucleation processes and dislocation/grain boundaries interactions.

  • Grain boundary based plasticity in nanocristalline metals. Collaborations: M. Legros, N.Combe, D. Caillard (CEMES), D. Molodov (RWTH, Aachen), J. Sharon, K.Hemker (Johns Hopkins Univ, Baltimore) (A. Rajabzadeh thesis 2010-2013).

  • Plastic deformation of sub-micron monocrystalline fibers. Collaborations: M.Legros, D. Caillard (CEMES), D. Gianola (U. Penn, Philadelphia), A. Sedlmayr, O. Kraft (KIT, Karlsruhe)

  • French National Agency project: ANR HighS-Ti (High Mechanical Strength Ti based Harmonic Microstructures: Processing and and Properties) (PI: G. Dirras, LSPM, Villetaneuse). Collaborations: Institu Pprime, Institut Jean Lamour, LSPM, RITS Ritsumeikan University ((cf HighSTi)

Elementary plasticity mechanisms for nuclear materials

For a better understanding of long term irradiation impact on the mechanical behavior of different structural materials (steels for vessels, fuel cladding), it is crucial to dispose of a solid understanding of elementary mechanisms of plastic deformation. In that purpose, we perform in-situ TEM experiments at high temperature (operating temperature) on both irradiated Zircalloy and ferritic steels reinforced by oxide dispersion (ODS steels). These experiments are coupled with mechanical tests and numerical modelling.

  • Plastic deformation of ODS steels (coll. J. Malaplate, SRMA/CEA-Saclay) (M. Praud thesis 2009-2012)

  • Interaction dislocations-irradiation loops in Zr alloys (Coll. F. Onimus, L. Dupuy, SRMA/CEA-Saclay)(J. Drouet thesis 2011-2014).

Instrumentation for TEM

We contribute to the development of dedicated holders for in-situ TEM.

  • ESTEEM1 and ESTEEM2 (Enabling Science and Technology through European Electron Microscopy) projects.