Mathilde Laurent-Brocq

• PhD
• Researcher at Institut de Chimie et des Matériaux Paris-Est

Solid state recycling of aluminium chips is a promising technique to reduce environmental impacts of secondary production. As the recycling process induces a highly oriented microstructure, this study aims to quantify the mechanical properties of extrudates and identify the role of chip boundaries in the fracture behavior. Tensile and shear tests a...

Solid state recycling of aluminium chips is a promising technique to reduce environmental impacts of secondary production. As the recycling process induces a highly oriented microstructure, this study aims to quantify the mechanical properties of extrudates and identify the role of chip boundaries in the fracture behavior. Tensile and shear tests a...

In this study, we report the experimental coarsening kinetics at 850, 900 and 950°C of four complex concentrated alloys in the Al-Ti-Cr-Fe-Co-Ni senary system with different chemical compositions but a similar γ' (L12) volume fraction (~35 % at 950°C) in a face-centered cubic (γ, FCC) matrix. The selected alloys were specifically designed to invest...

The composition and stratification of the passive oxide films formed on three Cr-Fe-Co-Ni(-Mo) multi-principal element alloys by electrochemical anodic passivation in sulfuric acid electrolyte containing 0.2 and 4.7 M NaCl were investigated, combining X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry surface analys...

Surface analysis by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry was applied to investigate the origin of the enhanced surface passivity and resistance to a chloride-induced breakdown provided by the protective ultrathin oxide films formed on Cr–Fe–Co–Ni–Mo single-phase fcc multi-principal element alloys. A bi...

X‐ray photoelectron spectroscopy analysis was applied to investigate the thermal stability under ultra‐high vacuum environment of the surface oxide film formed by electrochemical passivation of a newly‐designed Cr15Fe10Co5Ni60Mo10 (at. %) multi‐principal element alloy and providing the alloy superior localized corrosion resistance compared to conve...

Extensive thermodynamic calculations exploring the large composition space of the Cr-Fe-Co-Ni-Mo system were performed in order to design new multi-principal element single-phase fcc alloys with enhanced passivity and resistance to localised corrosion. This presentation will cover several aspects from design to production, passivation, surface anal...

The vast composition space of the Cr-Fe-Co-Ni-Mo system was explored by massive thermodynamic calculations in order to design and characterize multi-component single-phase fcc alloys optimized in Cr and Mo content and having enhanced passivity. Adding up to 15 at.% Mo while retaining the fcc single-phase is possible, which is unprecedented. Cr is c...

Chemically architectured alloys are a new concept of microstructure in which two phases are separated by a 3D network of fluctuations of composition, which is called interphase, and which induces a strengthening. Chemically architectured alloys were processed by spark plasma sintering of a mixture of pure Ni and CoCrFeMnNi high entropy alloy with v...

The study of the transition from high-entropy alloys (HEAs) to conventional alloys (CAs) composed of the same alloying components is apparently important, both for understanding the formation of HEAs and for proper evaluation of their potential with respect to that of the corresponding CAs. However, this transition has thus far been studied in only...

Ce compte instagram, animé par Mathilde Laurent-Brocq et moi-même présente l'avancée d'un projet de recherche sur un nouveau procédé de recyclage des alliages d’aluminium. A destination des jeunes adultes en orientation professionnelle, mais aussi plus généralement de toutes les personnes intéressées par la science et les curieux des autres métiers...

The aim of this paper is to investigate the contribution of the mixing enthalpy to the stability of the faced-centered cubic (fcc) phase of the Co–Cr–Fe–Mn–Ni system. For this purpose, systematic first principles calculations on Special Quasirandom Structures (SQS) were performed in a comprehensive manner on the fcc solution in every \(\left( {\beg...

Effects of solutes on saturation grain size and mechanical properties are investigated for the Cantor alloy and Ni-enriched variations ((CrMnFeCo)xNi1-x) with x=0.8, 0.4, 0.08 and 0. Indentation on coarse-grained and severely deformed states shows increasing hardness with increasing alloying content due to higher solid solution strengthening and Ha...

New face-centered cubic (FCC) multicomponent alloys designed through the high-entropy (HEA) concept and strengthened with L1 2 ordered precipitates are promising material solutions for high temperature (HT) structural applications. However, as the design strategy is based on multi-principal elements, the research of alloy compositions exhibiting a...

Titanium implants are widely used in dental and orthopedic surgeries. Osseointegration phenomena lead to direct contact between bone tissue and the implant surface. The quality of the bone-implant interface (BII), resulting from the properties of newly formed bone, determines the implant stability. This study investigates the BII properties using a...

Tracer diffusion of all constituting elements is studied at various temperatures in a series of (CoCrFeMn)100−xNix alloys with compositions ranging from pure Ni to the equiatomic CoCrFeMnNi high-entropy alloy. At a given homologous temperature, the measured tracer diffusion coefficients change non-monotonically along the transition from pure Ni to...

The chemically architectured alloys were proposed as a new concept of microstructure, with a multi-scale architecturation. They are composed of a solid-solution at the atomic scale, grain boundaries and composition gradients at the micronic scale and finally a 3D network of gradients at the mesoscale. Composition gradients are between two phases wi...

Tracer diffusion of all constituting elements is studied at various temperatures in a series of (CoCrFeMn)$_{100-x}$Ni$_x$ alloys with compositions ranging from pure Ni to the equiatomic CoCrFeMnNi high-entropy alloy. At a given homologous temperature, the measured tracer diffusion coefficients change non-monotonically along the transition from pur...

XPS and ToF-SIMS analysis have been combined with electrochemical measurements to determine the corrosion behavior of the equiatomic CoCrFeMnNi high entropy alloy. An XPS methodology based on analysis of the 3p core level spectra was developed to determine the composition and thickness of oxide films. Both native oxide (∼1.4 nm) and passive films (...

A silver-based nanoporous material was produced by dealloying (selective chemical etching) of an Ag38.75Cu38.75Si22.5 crystalline alloy. Composed of connected ligaments, this material was imaged using a scanning electron microscope (SEM) and focused ion-beam (FIB) scanning electron microscope tomography. Its mechanical behavior was evaluated using...

Single-phase multi-component alloys exist for a very wide range of composition, which is still mostly unexplored. To determine the mechanical properties of one new medium entropy alloy (MEA) and to assess the potential of an accelerated testing strategy, the compositions CoCrFeMnNi, (CoCrFeMn)40Ni60 and (CoCrFeMn)8Ni92 were studied. They were proce...

The mechanical properties due to solid solution strengthening are explored within the single phase face-centered cubic (fcc) domain of the Co–Cr–Fe–Mn–Ni high entropy alloy (HEA) system. This is achieved by combining an efficient and reproducible metallurgical processing of alloys to X-ray diffraction and nanoindentation characterization techniques...

A specific copper complex is used here for the development of new antibacterial coatings against two different bacteria strains i.e. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Remarkably, the cationic polymerization of a glycerol-derived monomer was performed using an efficient Cu complex as a photoinitiator. The synthesized...

Powder metallurgy is a promising processing path to produce high entropy alloys (HEA) with improved mechanical properties. According to this, a bulk CoCrFeMnNi alloy was milled with a wide range of conditions. It was shown that a powder which is micronic, approximately spherical and with nanometric crystallites could be produced by a cryo-milling w...

Tracer diffusion of Co, Cr, Fe and Ni is measured at 1373 K in Co20Cr20Fe20Mn20Ni20, Co10Cr10Fe10Mn10Ni60 and Co2Cr2Fe2Mn2Ni92 alloys. Diffusion retardation in the high-entropy Co20Cr20Fe20Mn20Ni20 alloy is most prominent in comparison to the Co2Cr2Fe2Mn2Ni92 solid solution, however the concept of ‘sluggish’ diffusion cannot be used as a blanket st...

Static recrystallization kinetics, at 300 °C, of a hot rolled commercial purity aluminum alloy AA1050 has been investigated using high temperature nanoindentation. Annealing treatments were achieved inside a nanoindentation device to measure corresponding hot nanohardness versus time. Clear evidences of recrystallization phenomenon were deduced fro...

Le but de ce travail est d’évaluer les méthodes et procédures permettant de mesurer en indentation et de comprendre la relaxation mécanique des matériaux solides proche de leur surface. Dans un premier temps, la relaxation du Poly(Méthacrylate de Méthyle) – PMMA – a été étudiée par indentation à température ambiante. L’effet, sur les mesures, de la...

The phase stability of the fcc solid solution in the Co-Cr-Fe-Mn-Ni system was theoretically and experimentally investigated. Using the Calphad approach and a new database (TCHEA1) devoted to high entropy alloys (HEA), the stable phases of 10 626 compositions could be calculated, depending on the temperature. 11 alloys were also processed and chara...

In order to explore precipitation hardening, carbonitrides precipitates are formed within a CrMnFeCoNi high entropy alloy (HEA). The matrix and the precipitates are independently characterized by electron probe microanalysis, atom probe tomography, transmission electron microscopy, and nanoindentation. The matrix is a face-centered cubic multi-comp...

Depth variation at constant load in instrumented nano-indentation was used to measure activation volume controlling shear band formation in the Mg65Cu12.5Ni12.5(Ce75La25)10metallic glass. A series of measurements revealed a large scattering of the data spanning from 100 Å3 to 800 Å3. The distribution of values, which is not following a normal one,...

A model, which takes into account the indentation size effect, was proposed to relate hardness and its standard deviation to the quality of the sample surface, i.e., the roughness and the tilt. Stainless steel samples were mechanically polished so as to obtain various roughness and tilt. Then the quality of the surface and the hardness were measure...

In order to study the thermodynamics of high entropy alloys, the evolution of the structure and microstructure of the equimolar CrMnFeCoNi high entropy alloy was investigated during processing under varying conditions (cooling rate and annealing duration). For the very first time, a true solid-solution down to the atomic scale was evidenced in an H...

A novel low-temperature plasma method, using Pt acetylacetonate as a precursor, was used for the first time to produce Pt/carbon black catalysts for polymer electrolyte membrane fuel cells. Catalysts were prepared under various plasma conditions and characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectro...

The characteristics of strengthening nanoclusters (NCs) have a major influence on the mechanical properties of oxide dispersion strengthened (ODS) steels. To determine how to control NC formation, ODS powders are synthesized in different ball-milling and annealing conditions, then characterized by electron probe micro-analysis and small angle neutr...

In our past work, the commercial ferrtic oxide dispersion strengthened alloy MA957 had at least two types of nanometer-sized oxide particles: non-stoichiometric Y-, Ti-, O-enriched clusters (Y/Ti <1) and stoichiometric Y(2)Ti(2)O(7) particle. Non-stoichiometric clusters had a much higher number density and smaller sizes than Y(2)Ti(2)O(7) particles...

Reactive high energy ball-milling has known a growing interest from both fundamental and applied point of view. We focus here on the specific system Fe-Y2O3 metal-oxide nanocomposite because of its potential application to the synthesis of oxide dispersion strengthened steels, which are promising materials for nuclear applications. YFe3 and Fe2O3 w...

Reactive-inspired ball-milling is proposed as a new production route for oxide dispersion strengthened (ODS) steels. So a Fe–14Cr–2W–1Ti–0.8Y–0.2O (wt.%) ODS steel is elaborated by ball-milling of FeCrWTi and YFe3 plus Fe2O3 powders instead of Y2O3 and then by annealing at 800 °C for 5 min. Characterizations by Electron Probe MicroAnalysis and Atom...

In the framework of ODS (Oxide Dispersion Strengthened) steels development for application as core materials in future nuclear reactors, a new process based on a reactive-inspired ball-milling, which consists in using YFe3 and Fe2O3 instead of Y2O3, and the influence of synthesis conditions on nano-oxides features were studied. To do so, ODS steels...

Reactive ball milling and annealing is proposed as a new production method for oxide dispersion strengthened (ODS) steels. A highly concentrated Fe–38 atm.% Y2O3 ODS model alloy was processed by reactive ball milling and annealing of YFe3 and Fe2O3 powders so as to induce the chemical reaction 2YFe3 + Fe2O3 → 8Fe + Y2O3. The model alloy was charact...

Threshold stress of COS (Oxide Dispersion Strengthened) alloy is well known as a value which can quantitatively shows the effect of oxide dispersion strengthening. However, the threshold stress cannot be clearly observed in the result of creep tests for the commercial ODS alloy MA957. In this work, the threshold stress of MA957 was carefully evalua...

ODS (oxide dispersion strengthened) alloys have superior creep properties. As it is well known, these excellent creep properties result from very fine oxide particles dispersed with the matrix. However, there is no common understanding about the nature of the very small oxide particles. Two hypotheses arise from the literature, 1: non-stoichiometri...

In our past work, two types of nanometer-sized oxide particle were found in the commercial ODS (Oxide Dispersion Strengthened) ferritic alloy MA957. They were nonstoichiometric Y-, Ti-, O-enriched clusters (2 ̃ 15 nm) and stoichiometric Y 2Ti 2O 7 (15 ̃ 35 nm). The particles which have an important role for the strengthening were confirmed to be no...