Surfaces – Interfaces and Materials under Stress – SIMAC

Permanent people: Eric Le Bourhis (PR UP), Pierre Godard (MdC UP), Philippe Goudeau (DR CNRS), Pierre-Olivier Renault (PR UP), Pascale Valat-Villain (MdC UP)

Context et objectives

One of the major objectives of this axis is to obtain a better understanding of the mechanical behavior of thin polycrystalline or even monocrystalline films of a few tens of nm thick deposited by spraying on polymers, and to highlight the size effects, microstructure and architecture. The thin film - polymer composite is mechanically stressed using a very original biaxial deformation machine allowing to follow in situ by X-ray diffraction the microstructural evolutions in the film, the deformation at the crystalline level and the macroscopic deformation by correlation. digital images. The experimental set-up makes it possible to measure very low relative changes in deformation (of the order of 10_-5) and makes it possible to reproduce the complex deformation fields encountered by these materials in the various fields of application. The adhesion, the modes of cracking or the physical mechanisms at the origin of plasticity can be studied.

 

This action revolves around three research activities:

• • • • Effect of microstructure on the mechanical behavior of thin metallic films
      • Study of the relaxation of thin films
      • Plasticity of thin monocrystalline films

 

These synchrotron activities were developed within the framework of an ANR Pnano Cmonano which associated Soleil and the LSPM (formerly LPMTM) of Villetaneuse for polycrystalline modeling. They come within the framework of the GDRi Mecano.

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Recent papers

P. Godard, D. Faurie and P. O. Renault, Strain ratio effects in mechanical properties of supported thin films, J. Appl. Phys. 127, 105103 (2020)

 

D. Faurie, F. Zighem, P. Godard, G. Parry, T. Sadat, D. Thiaudière, P.-O. Renault, In situ x-ray diffraction analysis of 2D crack patterning in thin films, Acta Materialia 165, 177-182 (2019)

 

Job offer

PhD candidate - Propriétés physiques de films minces fonctionnels sous contrainte

Permanent people: J. Colin (PR), C. Coupeau (PR), J. Grilhé (PR Emerit), J. Durinck (MdC), A. Cimetière (PR Emerit), L. Vernisse (MdC)

Context et objectives:

This axis is centered on studies of surface evolutions under mechanical stress fields. We aim to understand the phenomena related to buckling, delamination, the decohesion of thin films or even related to the reconstruction of surfaces. Our experimental research is based on a unique experimental tool (Nanoplast). This device in an ultra-high vacuum environment allows to monitor in situ by AFM / STM microscopy the evolution of the surface of materials under varying stresses and temperatures. The current studies are focused on two themes, understanding of the elementary plasticity mechanisms of crystalline materials, from the slip traces generated at the atomic scale on the surface, and  piloting nanostructures and reconstructions of surfaces by mechanical nanoengineering under stress. The experimental approaches are closely associated with numerical simulations or models. Thus, theoretical studies on the growth kinetics of nano-objects deposited on substrates and on the evolution of delamination are undertaken in correlation with the experimental observations of the team or through external collaborations (national and international).

 

We are exploring five paths:

• • • • Effect of plasticity on thin film buckling
      • Plasticity of nanostructures
      • Morphological evolution of alloys under stress
      • Buckling of hyperelastic materials
      • Surface nanoengineering

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Recent papers

Colin, J., Effect of stiffness contrast on the dislocation equilibrium positions in a multi-layered structure, International Journal of Solids and Structures 185, 234-235 (2022).

 

Chauraud, D.; Durinck, J. ; Vernisse, L. ; Smalley, S. ; Drouet, M. ; Coupeau, C., External stress as a way to control Au (111) reconstruction, Surface Science 162, 714 (2021)

 

Bertin, B.; Durinck, J.; Grihlé, J.; Colin, J., Grain boundary-induced plasticity during thin film buckling, Surface and Coatings Technology 162, 408(2021)

Permanent people : L. Pichon (Pr), J.B. Dubois (MCF), M. Drouet (IR)

Coll. DPMM-axe ENDO: P. Villechaise, J. Cormier

Context and objectives:

We are interested in surface modifications by thermochemical treatments assisted by low pressure plasma and / or by ion implantation. We have a main (but not exclusive) objective of improving mechanical properties by creating layers of compounds (nitrides, oxides, etc.) or solid insertion solutions (nitrogen, oxygen, carbon, etc.). These studies are based on two original reactors: URANOS, a treatment reactor assisted by low pressure plasma and TAPIIR, a plasma based ion implantation reactor (PBII). The aim is to understand, in connection with the processing conditions, the mechanisms of chemical and microstructural modifications and to relate them to the induced properties of interest. Employed analytical techniques enable the chemical study of surfaces and the microstructural characterization at different scales. The properties of interest are then tested  within P’ or as part of external national or international collaborations.   Following the first successes of nitriding at moderate temperature (<450 ° C) obtained on various FCC austenitic g-phase alloys (ASS316L, CoCrMo), the treatment of various nickel-based superalloys was undertaken from 2011 to 2018. The low temperature nitriding is today applied to the new High Entropy Alloys (HEA) containing chemical elements found in the previous studied alloys (Fe, Co, Ni, Cr…) Since 2018, plasma assisted thermochemical treatments are applied on Titanium based alloys in order to obtain thick layer of multi-interstitials (N, O, C) solid solutions as mechanical support for the very hard surface layer, within wear resistance objectives.  

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Recent papers

M. Drouet, E. Le Bourhis, Low Temperature Nitriding of Metal Alloys for Surface Mechanical Performance. Materials, 16, 4704 (2023) V. Parry, E. Le Bourhis, L. Pichon, M. Drouet, Relation between Mechanical Hardening and Nitrogen Profile of PBII Nitrided Titanium Alloy. Materials,15, 9028 (2022)   M. Drouet, L. Pichon, Y. Vallet, E. Le Bourhis, T. L. Christiansen Surface engineering of titanium alloy TiAl6V4 by multi-interstitial diffusion using plasma processing European Journal of Materials 1 (2022)