Offres de Thèses

Compréhension des mécanismes de déformation et d’endommagement de fils composites Cu-Al architecturés

Dans le domaine des matériaux métalliques, l’optimisation conjointe de différentes propriétés telles que la résistance mécanique, la conductivité, la résistance à la corrosion, la masse volumique ou le coût n’est que rarement possible dans le cas de microstructures homogènes et monophasées. La communauté scientifique s’est donc assez rapidement penchée sur l’élaboration de matériaux dit architecturés, soit en proposant des matériaux multiphasés, principalement dans le cas des aciers (Dual-Phase, Duplex...), ou en cherchant à obtenir une microstructure hétérogène (taille de grains, texture cristallographique/morphologique).

 

Au sein de la littérature, de nombreux auteurs se sont intéressés au comportement mécanique de matériaux composites métalliques tricouches CuAl obtenus par laminage. Ces différents travaux ont mis en évidence une forte modification du comportement mécanique (écrouissage et ductilité) en fonction des différents traitements thermiques et ce du fait du rôle endommageant de l’interface , elle-même dépendante de l’épaisseur d’intermétalliques.

A partir de ces résultats et des différences de microstructures entre les échantillons laminés et les échantillons co-étirés dans le cadre de ce projet, plusieurs questions peuvent être soulevées:
- quelle est la contribution des différentes phases en présence du point de vue de la distribution des contraintes ?

- quel est le rôle de la fraction volumique et de la distribution spatiale de ces phases sur le comportement mécanique ?
- quel va être le rôle de l’interface entre le cuivre et l’aluminium sur la réponse mécanique globale (transfert de la charge mécanique entre phases, influence sur les mécanismes d’écrouissage et d’endommagement) ?

- comment quantifier expérimentalement la contrainte de cisaillement à l’interface ?
- la formation d’intermétalliques lors de traitements thermiques va-t-elle modifier les caractéristiques de l’écrouissage des phases ? les mécanismes d’endommagement ?
- comment quantifier les contraintes résiduelles engendrées lors de l’élaboration, notamment lors de la réalisation d’un traitement thermique post-élaboration ?

Cette thèse ambitionne ainsi de répondre à ces différentes questions.

 

Contact : Clément Keller - clement.keller@insa-rouen.fr

 Benoit Vieille - benoit.vielle@insa-rouen.fr

Fundamental understanding of the sensitivity of radiation hardening to nickel content and temperature in RPV materials

Nuclear power plants (NPP) provide about 10% of the world’s electricity. Scenarios consistent with the goal of less than 2°C temperature increase, foresee a steady increase of this proportion. In Europe, USA and Japan, it requires to extend NPP operations beyond their original design lifetimes.

The lifetime limiting component for current generation NPP is the reactor pressure vessel (RPV). Its integrity must be guaranteed at any time and in any circumstance. However, RPV steels are long known to undergo hardening and embrittlement caused by irradiation. Knowledge and understanding of the vessel’s mechanical degradation istherefore critical for ensuring the safety of NPP.

The objectives of the project are to investigate the effect of Ni on the radiation microstructure of RPV steels, and how it is influenced by temperature, up to high neutron doses (15-20×1019n/cm2). For that purpose, samples available from the RADAMO-8 irradiation campaign will be analyzed by APT. The observed solute rich clusters will be characterized in terms of size, density and composition.

Student holder of a master degree or equivalent in the domain of material sciences,good knowledge in physical metallurgy (phase transformation, solid state diffusion...)and good experimental ability.

 

To candidate :

▪ Motivation letter
▪ Curriculum vitae
▪ Copy of the last diploma
▪ Statement rating of the last diploma

Contact : Philippe PAREIGE - philippe.pareige@univ-rouen.fr

 Bertrand RADIGUET - bertrand.radiguet@univ-rouen.fr

Mise au point d’une Imagerie corrélative SIMS/MET pour identifier, localiser et quantifier des nanoparticules dans des tissus biologiques (NanoCoSIMSTEM)

La thèse que nous proposons est un programme de recherche pluridisciplinaire à l’interface de la physique des matériaux et de la biologie. Il repose sur l’identification, la localisation et la quantification d’élément métallique à l’échelle nano par imageries électronique (microscopie électronique à transmission, MET) et ionique (Secondary Ion Mass Spectrometry, SIMS). L’accent sera porté tout particulièrement sur 1) la corrélation entre l’imagerie électronique et l’imagerie ionique (au NanoSIMS50) ; 2) la distribution et la quantification des NPs dans des tissus biologiques et 3) le traitement d’images pour obtenir une image 3D de la distribution des NPs dans les tissus.

 

Le candidat devra de préférence avoir obtenu un master ou diplôme d’ingénieur à dominantes physiques ou biologiques abordant des techniques d’imageries, dont la microscopie électronique (MET), appliquées à l'étude des nanomatériaux ou à l’imagerie cellulaire. Des compétences en traitement d’image et programmation sont souhaitées et une expérience de manipulation en laboratoire (manipulation de produits chimiques, préparation d’échantillons pour étude microscopique etc.) sera un atout pour le candidat.

Le candidat devra fournir un CV détaillé, un relevé de notes L3, M1, M2 ou équivalent école d’ingénieur, une lettre de motivation et 2 Lettres de recommandation dont une du maître de stage ou les coordonnées de deux responsables de la dernière formation suivie par le candidat avant le 31 mai 2019.

 

Contact : Armelle.cabin@univ-rouen.fr

Nanofibres et Analyse Thermique Avancée

Le travail de thèse consiste donc à caractériser la microstructure semi-cristalline denanofibres polymères par l’utilisation d’appareils analyse thermique avancée. Diverspolymères seront étudiés : PAN, polyamide, ... Une forte interaction avec l’équipe américainequi conçoit et analyse mécaniquement ces matériaux sera mise en place. Une réunion mensuelle aura lieu par visioconférence.

Le candidat sera titulaire d'un Master de physique, chimie ou Matériaux avec une bonne connaissance en sciences de la matière et des matériaux. La connaissance des propriétés physiques des polymères et de l'analyse thermique sera un plus.
Niveau d'anglais requis: Intermédiaire: Vous pouvez parler et écrire la langue de manière compréhensible et cohérente.

 

Contact : eric.dargent@univ-rouen.fr

Improvement and Development of a New Process for Magnet Recycling

A 36-months doctoral position, project RAP, funded by the ANR

 

Successful candidate will have a master degree in material science (Chemistry of materials, Physics of Materials), a good background in chemistry of materials (synthesis, crystallography, magnetic properties, characterization techniques...), an ability to communicate effectively, a willingness to work in a team. Previous experience in one or more of the specific techniques or related fields described in the following would be an asset: synthesis, nanostructured materials, magnets, electron microscopy, Mossbauer spectroscopy, XRD, recycling techniques

 

Contact :

Associate Professor Virginie NACHBAUR (virginie.nachbaur@univ-rouen.fr)

Closing date for application: 05/07/2018

Cyclic behavior of metallic materials: effect of temperature and strain path on the strain hardening memory.

The overall objective of the PhD is to better understand the memory effect linked to the pre-hardening test and, in particular, the influence of the dislocation slip characteristics and the thermomechanical loadings. This understanding of the origin of the memory effect will help to improve the modelling of the cyclic behavior of the metallic materials.

The applicant should be graduated with a master degree in material science or in mechanics of materials. Skills in mechanical testing and electron microscopy will be appreciated. Fluent english (written and oral) is needed.

 

Contact :

Clément Keller, Clement.Keller@insa-rouen.fr, +33 2 32 95 98 65

Lakhdar Taleb, lakhdar.taleb@insa-rouen.fr, +33 2 32 95 97 65

Analysis of the cyclic behavior of metallic materials with bimodal grain size distribution

Grain size refinement is one of the most promising solution to improve the mechanical properties of metal alloys. Ultrafine or nanocrystalline materials exhibit, hence, larger yield stress or irradiation resistance. However, these materials generally show a lack of ductility which may be detrimental to their potential industrial applications. Several solutions have been considered to improve the ductility of ultrafine grain materials: grain boundary engineering, precipitation or grain size distribution. The first way is linked to the increase in twin boundary density through thermomechanical processes, which, in turn, improve the ductility due to the coherent character of these particular grain boundaries. The second way is based on the increase of the production of dislocations by anchoring on the precipitates. Thanks to this mechanism, the strain hardening capacity is increased even for the low grain sizes. The third way focuses on introducing a second population of coarse grains inside an ultrafine grain matrix to increase ductility.

 

This PhD project is focused on this third way. A first PhD revealed the interest of a bimodal distribution of grain size for a material with industrial vocation - steel 316L. This first work validated the powder metallurgy as a convenient elaboration route to develop alloys with bimodal grain size distribution. The mechanical tests showed a significant increase in ductility for a given yield stress for a bimodal grain size distribution. Numerical simulations in crystalline plasticity on polycrystals with an explicit representation of the microstructure were also performed with different grain size distributions and spatial coarse grain arrangements. These simulations revealed the influence of the grain size distribution on the stress and strain fields.

 

Contact :

Clément Keller, Clement.Keller@insa-rouen.fr, +33 2 32 95 98 65

Fabrice Barbe, Fabrice.Barbe@insa-rouen.fr, +33 2 32 95 97 60

Influence of Fe doping on the MagnetISm of ThERmoelectric sulfide compounds (MISTER project)

This PhD subject focuses on the study of iron-based thermoelectric sulfide compounds in the search for new materials for energy hardvesting. The objectives are to investigate the influence of iron doping, magnetism, but also chemical disorder on the thermoelectric efficiency of these compounds. For this purpose, several characterization techniques of the structural and physical properties will be used, including SQUID measurements and 57Fe Mössbauer spectrometry as a local probe of the chemical, electrical and magnetic environments of iron sites. The results obtained at various temperatures and external magnetic fields should provide a better understanding of the thermoelectric properties to optimize them for applications.

The work will be made in close collaboration with the CRISMAT laboratory in Caen in the framework of Labex “COVATIS”, Réseau d’Intérêt Normand “TEMPO” and Institut Carnot “MASTER” research programs.

 

This full-time position is funded by the « Région Normandie » and the European Union. Europe invests in Normandy with the European Regional Development Fund (ERDF).

Contact : jean.juraszek@univ-rouen.fr

Effect of Cu, P, Ni and Mn content, individually and synergistically, on the microstructure of irradiated chemically-tailored RPV steels

Context :


Nuclear power contributes about 13% of the electricity supply worldwide [1]. If this major source of carbon-free energy is to be sustained, life extension of the current fleet of light water reactors will be required to bridge the gap to new plant builds [2]. Life extension will require clear demonstration of large safety margins and reliable and economic long-term plant operation. A key challenge is understanding materials aging and degradation issues for reactor internals and pressure steels [3,4]. Thus, extensive aging research is conducted to support extending plant life from 40 (the original license) and 60 years (the first license extension), and now to 80 years, or more, based on a second license extension.
One critical life extension issue is neutron irradiation embrittlement of reactor pressure vessels (RPVs). RPVs are massive, thick-walled, permanent structures, whose primary function is to pressurize water to 14 MPa (for Pressurized Water Reactors, PWRs), thereby permitting reactor operating temperatures around 290 °C [5]. RPVs are also an important barrier to the release of radioactivity in the event of a core damaging accident. Regulations require very low RPV failure probabilities by crack propagation, both for normal operation and postulated low probability accident events. In the unirradiated condition, low alloy RPV steels are very tough, and vessel fracture probabilities are negligibly small, representing no significant risk. However, neutrons leaking from the reactor core cause irradiation hardening and embrittlement, manifested as upward shifts in the ductile-to-brittle transition temperature that may challenge continued vessel operation for some plants during extended life. The sources of embrittlement include formation of precipitates, stable and unstable matrix defects, and segregation to dislocations and grain boundaries [5–7].

Subject of the PhD:
In the 2014 irradiation campaign at SCK•CEN, the RADAMO-13 irradiation program was performed on 36 different RPV steels including 23 chemically-tailored RPV steels as well as commercial RPV steels. Tensile specimens as well as microstructural bars were irradiated at 290°C to various neutron fluence levels ranging between 1 1019 and 6 1019 n/cm², E>1MeV.
The chemically-tailored steels were obtained from the reference material ASTM A533B. The chemical composition was then varied by changing only one variable (low, medium, high content) at a time and keeping all others elements similar. Of course, the aim is not to cover all possible alternatives but to investigate only relevant cases where information is missing.
It is known that Cu, Ni, P and eventually Mn play an important role in irradiation damage accumulation. In particular, under irradiation, Cu diffuses extremely rapidly to form the so-called Cu-rich precipitates (CRPs) that impede dislocation motion thereby increasing hardening and embrittlement. This phenomenon was extensively investigated in literature. P can also precipitate to form phosphorus-rich precipitates but this is less investigated. Indeed, the P-content in most materials remains very low, typically lower than 0.015%. The question that can be addressed is how these two elements, namely Cu and P, precipitate under irradiation and how they are affecting each other. Moreover, the CRPs contain a large proportion of Ni, Mn, Si and P. Therefore, in order to clarify the role of Cu in the precipitation process, irradiated steels with no Cu as well as up to 0.30%-content are available. Similarly, Ni and Mn synergy will be investigated. Ni is known to dominate the hardening/embrittlement kinetics at high fluence levels. However, characterization of irradiation defects shows that it is often associated with Mn and this association is not well understood. Therefore, nine irradiated steels will be available for investigation covering from nearly 0% to 1.8% Ni/Mn-content combinations.
All tensile test results to determine the irradiation hardening were already performed. Only microstructural examination must be carried out using different techniques including transmission electron microscopy (TEM) and Atom Probe Tomography (APT). TEM measurements can be performed at SCK•CEN and APT at GENESIS - GPM Rouen. The irradiation defects for the relevant neutron fluence levels cannot be observed by TEM but could provide information on the microstructure of the materials.
Objectives:
The RADAMO-13 programs allows to have access to a unique worldwide materials data base where 9 different chemically tailored A533B-type steels are available for the study of the effect of Ni and Mn contents, 12 materials with various Cu and P contents, two materials with respectively high and low Cu/Ni/Mn/P contents and 14 materials representatives of RPV forgings or welds. All these materials have been neutron irradiated with three different neutron fluences, at the same temperature and neutron flux.
The first part of this large project is to select among these materials (chemically tailored and RPV representatives) a small set that will allow the understanding on the materials ageing of the effect of one or two pairs of chemical elements and their synergetic effects.
At the end of this study, the main objective is to support the mechanical behavior (tensile strength) with the microstructural changes after irradiation. A combination of TEM and APT will be used to characterize the microstructure of irradiated steels. The radiation damage modeling tools used for RPV steels can therefore be updated to take into account the results of these investigations.
The combination of mechanical behavior (hardening) and microstructure (nature, size and number density of the nano-size defects) will help understanding the influence and interaction of these key elements (Cu/P and Mn/Ni) and in developing reliable irradiation damage tools that can be used to predict the post-irradiation behavior of RPV steels, not only those irradiated in the BR2 reactor (SCK•CEN reactor) but also those irradiated in surveillance programs (real RPV from nuclear plants) and applicable directly to surveillance programs.
Schedule:
• First year: Basic knowledge on radiation damage in RPV materials with particular attention on the microstructure. Training on various microstructure observation techniques. Visits to partner labs (GPM/ SCK•CEN).
• First year - Second year: Analyzing available RADAMO-13 mechanical data (SCK•CEN), selection of microstructural specimens and further examination with techniques (SCK•CEN -GPM). Follow-up of microstructure examination.
• Second year - Third year: Microstructural data analysis (GPM) and further examination where required (SCK•CEN -GPM). Additional tests after post-irradiation annealing where necessary (SCK•CEN -GPM). Performing radiation damage modeling adjustments where required (SCK•CEN -GPM).
• Third year: Finalization of the work and writing of the thesis (GPM).
References:
[1] S. Chu, A. Majumdar, Opportunities and challenges for a sustainable energy future, Nature, 488 (2012), pp. 294-303
[2] Technology Roadmap - Nuclear Energy. Nuclear Energy Agency (2015)
[3] J.T. Busby, P.G. Oberson, C.E. Carpenter, M. Srinivasan, Expanded Materials Degradation Assessment    Executive Summary of EMDA Process and Results, vol. 1, Office of Nuclear Regulatory Research (2013)
[4] J.T. Busby, P.G. Oberson, C.E. Carpenter, M. Srinivasan, Expanded Materials Degradation Assessment,     Aging of Reactor Pressure Vessels, vol. 3, Office of Nuclear Regulatory Research (2013)
[5] G.R. Odette, G.E. Lucas, Embrittlement of nuclear reactor pressure vessels, J. Miner., Metals Mater. Soc. (TMS), 53 (2001), pp. 18-22
[6] K. Fukuya, Current understanding of radiation-induced degradation in light water reactor structural materials, J. Nucl. Sci. Technol., 50 (2013), pp. 213-254
[7] J.E. Zelenty, Understanding thermally induced embrittlement in low copper RPV steels utilising atom probe tomography, Mater. Sci. Technol., 31 (2015), pp. 981-988

 

Nature du financement : contrat doctoral – Région Haute Normandie

desired profile or skills:

Physical metallurgy, Irradiation effects in metals, Atom probe Tomography, Transmission electron microscopy, DualBeam Focused Ion Beam-Scanning Electron Microscope 

 

Contact : philippe.pareige@univ-rouen.fr

 

Atomic-scale correlative microscopy for the study of nanostructural defects, structural and functional properties of individual nano-objects

Description of the project :

The aim of this thesis is to propose for the investigation of nanometric defects and nano-objects a set of methodological and instrumental means for combining three-dimensional structural and chemical information. This project is part of an advanced instrumentation approach for materials, especially for advanced materials such as semiconductor nanowires and high temperature aluminum alloys for the transport of electrical energy. The proposed methods are based on the correlation of scanning transmission electron microscopy (STEM) corrected of spherical aberrations and tomographic atom probe (APT). Fields of investigation are related to various topics of materials sciences ranging from current issues in physical metallurgy (stress-precipitation relationships, coupling between defects, structures and composition of stable or metastable precipitates and their precursors) to nanomaterials related topics or nanostructured materials (semiconductor heterostructures). The areas of interest are therefore structural materials, energy transport or conversion, and energy efficiency.

The characterization work will be undertaken on a very high level experimental platform, including state-of-the-art transmission electron microscopes and a set of tomographic atomic probes. This project is a continuation of two ANR Young Researcher projects led by the two supervisors of this thesis.

 

Required skills:

The candidate must have a master's degree in research or engineering. A curriculum of materials physicist is sought. Prior experience in transmission electron microscopy or tomographic atom probe is an advantage but is not required. The candidate must demonstrate the ability to work in a team, demonstrate initiative and be able to quickly work independently on complex instruments. Special skills in algorithmic or image processing would be appreciated but are not mandatory.

 

Contact : williams.lefebvre@univ-rouen.fr

Contact : lorenzo.rigutti@univ-rouen.fr