Julien Guénolé

Julien Guénolé
University of Lorraine | UdL · LEM3 - Laboratoire d’Etude des Microstructures et de Mécanique des Matériaux

Ph.D

About

50
Publications
10,025
Reads
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544
Citations
Additional affiliations
January 2018 - present
RWTH Aachen University
Position
  • Group Leader
January 2014 - December 2017
Friedrich-Alexander-University of Erlangen-Nürnberg
Position
  • PostDoc Position
February 2013 - July 2013
Université de Poitiers
Position
  • ATER
Education
October 2009 - December 2012
Université de Poitiers
Field of study
  • Physique des matériaux

Publications

Publications (50)
Preprint
Full-text available
Oxide glasses with a network structure are omnipresent in daily life. Often, they are regarded as isotropic materials; however, structural anisotropy can be induced through processing in mechanical fields and leads to unique materials properties. Unfortunately, due to the lack of local, atomic-scale analysis methods, the microscopic mechanisms lead...
Preprint
In Laves phases, synchroshear is the dominant basal slip mechanism. It is accomplished by the glide of synchro-Shockley dislocations. However, the atomic-scale mechanisms of motion of such zonal dislocations are still not well understood. In this work, using atomistic simulations, two 30{\deg} synchro-Shockley dislocations with different Burgers ve...
Article
Complex intermetallic materials known as MAX phases exhibit exceptional properties from both metals and ceramics, largely thanks to their nanolayered structure. With high-resolution scanning transmission electron microscopy supported by atomistic modelling, we reveal atomic features of a nano-twist phase in the nanolayered Ti3AlC2. The rotated hexa...
Article
This paper describes atomistic simulations of deformation and fracture of Al reinforced with carbon nanotubes (CNTs). We use density functional theory (DFT) to understand the energetics of Al-graphene interfaces and gain reference data for the parameterization of Al-C empirical potentials. We then investigate the load transfer between CNTs and Al a...
Preprint
Full-text available
Sharp texture after thermal processing is one of the biggest barriers restricting the wide usage of magnesium alloys. Rare earth elements (e.g., neodymium and gadolinium) can essentially weaken and modify the texture of magnesium alloys. However, the underlying mechanisms for texture modification by rare earth elements remain debated. Here, we use...
Preprint
Full-text available
This paper describes atomistic simulations of deformation and fracture of Al reinforced with carbon nanotubes (CNTs). We use density functional theory (DFT) to understand the energetics of Al-graphene interfaces and gain reference data for the parameterization of Al-C empirical potentials. We then investigate the load transfer between CNTs and Al a...
Article
Full-text available
The identification of defects in crystal structures is crucial for the analysis of atomistic simulations. Many methods to characterize defects that are based on the classification of local atomic arrangement are available for simple crystalline structures. However, there is currently no method to identify both, the crystal structures and internal d...
Preprint
Full-text available
The identification of defects in crystal structures is crucial for the analysis of atomistic simulations. Many methods to characterize defects that are based on the classification of local atomic arrangement are available for simple crystalline structures like face-centered cubic or body-centered cubic crystals. However, there is currently no metho...
Article
Full-text available
The mechanical behaviour of MgAl alloys can be largely improved by the formation of an intermetallic Laves phase skeleton, in particular the creep strength. Recent nanomechanical studies revealed plasticity by dislocation glide in the (Mg,Al)2Ca Laves phase, even at room temperature. As strengthening skeleton, this phase remains, however, brittle a...
Preprint
Full-text available
The mechanical behaviour of Mg-Al alloys can be largely improved by the formation of an intermetallic Laves phase skeleton, in particular the creep strength. Recent nanomechanical studies revealed plasticity by dislocation glide in the (Mg,Al)$_2$Ca Laves phase, even at room temperature. As strengthening skeleton, this phase remains, however, britt...
Article
The control of complex nanostructures is one of the most promising strategy for designing tailored property materials. Ti2AlC, as nanolayered ternary materials combining both ceramics and metals properties, could efficiently reinforce metal matrix composite by its decomposition into nano-Ti2C particles. However, the comprehensive description of the...
Article
Full-text available
The elastic-to-plastic transition during the deformation of a dislocation-free nanoscale volume is accompanied by displacement bursts associated with dislocation nucleation. The dislocations that nucleate during the so-called “pop-in” burst take the form of prismatic dislocation loops (PDLs) and exhibit characteristic burst-like emission and plasti...
Article
Full-text available
In atomistic simulations, pseudo-dynamical relaxation schemes often exhibit better performance and accuracy in finding local minima than line-search-based descent algorithms like steepest descent or conjugate gradient. Here, an improved version of the fast inertial relaxation engine (fire ) and its implementation within the open-source atomistic si...
Article
Exploring the reasons for the initiation of Al-O-Al bond formation in alkali-earth aluminosilicate glasses is a key topic in the glass-science community. Evidence for the formation of Al-O-Al and Al-NBO bonds in the glass composition 38.7 CaO - 9.7 MgO - 12.9 Al2O3 - 38.7 SiO2 (CMAS, mol%) has been provided based on Molecular Dynamics (MD) simulati...
Preprint
In atomistic simulations, pseudo-dynamics relaxation schemes often exhibit better performance and accuracy in finding local minima than line-search-based descent algorithms like steepest descent or conjugate gradient. Here, an improved version of the fast inertial relaxation engine (FIRE) and its implementation within the open-source code LAMMPS is...
Article
Two different mechanisms have been reported in previous ab initio studies to describe basal slip in complex intermetallic Laves phases: synchroshear and undulating slip. To date, no clear answer has been given on which is the energetically favourable mechanism and whether either of them could effectively propagate as a dislocation. Using classical...
Article
The mechanical properties of Mg-Al alloys are greatly influenced by the complex intermetallic phase Mg17Al12, which is the most dominant precipitate found in this alloy system. The interaction of basal edge and 30∘ dislocations with Mg17Al12 precipitates is studied by molecular dynamics and statics simulations, varying the inter-precipitate spacing...
Article
Full-text available
Hydrogen pickup leading to hydride formation is often observed in commercially pure Ti (CP-Ti) and Ti-based alloys prepared for microscopic observation by conventional methods, such as electro-polishing and room temperature focused ion beam (FIB) milling. Here, we demonstrate that cryogenic FIB milling can effectively prevent undesired hydrogen pic...
Preprint
Full-text available
The mechanical properties of Mg-Al alloys are greatly influenced by the complex intermetallic phase Mg$_{17}$Al$_{12}$, which is the most dominant precipitate found in this alloy system. The interaction of basal edge and 30{\deg} dislocations with Mg$_{17}$Al$_{12}$ precipitates is studied by molecular dynamics and statics simulations, varying the...
Preprint
Full-text available
Two different mechanisms have been reported in previous ab initio studies to describe basal slip in complex intermetallic Laves phases: synchroshear and undulating slip. To date, no clear answer has been given on which is the energetically favourable mechanism and whether either of them could effectively propagate as a dislocation. Using classical...
Article
The focused ion beam (FIB) technique has established itself as an indispensable tool in the material science community, both to analyze samples and to prepare specimens by FIB milling. In combination with digital image correlation (DIC), FIB milling can, furthermore, be used to evaluate intrinsic stresses by monitoring the strain release during mil...
Article
Focused ion beam (FIB) machining has become a standard tool for sample preparation and in combination with digital image correlation (DIC) for the evaluation of local intrinsic stresses by measuring strain relaxation. However, FIB milling always leads to irradiation damage of the material. Current models for the formation of irradiation damage and...
Article
Full-text available
Eigenstrain offers a versatile generic framework for the description of inelastic deformation that acts as the source of residual stresses. Focused ion beam (FIB) milling used for nanoscale machining is accompanied by target material modification by ion beam damage having residual stress consequences that can be described in terms of eigenstrain. D...
Article
The interaction of dislocations with precipitates is an essential strengthening mechanism in metals, as exemplified by the superior high-temperature strength of Ni-base superalloys. Here we use atomistic simulation samples generated from atom probe tomography data of a single crystal superalloy to study the interactions of matrix dislocations with...
Article
The interaction of dislocations with precipitates is an essential strengthening mechanism in metals, as exemplified by the superior high-temperature strength of Ni-base superalloys. Here we use atomistic simulation samples generated from atom probe tomography data of a single crystal superalloy to study the interactions of matrix dislocations with...
Article
The interaction of dislocations with precipitates is an essential strengthening mechanism in metals, as exemplified by the superior high-temperature strength of Ni-base superalloys. Here we use atomistic simulation samples generated from atom probe tomography data of a single crystal superalloy to study the interactions of matrix dislocations with...
Article
Full-text available
A new parametrization of the widely used Stillinger-Weber potential is proposed for silicon, allowing for an improved modelling of defects and plasticity-related properties. The performance of the new potential is compared to the original version, as well as to another parametrization (Vink et al 2001 J. Non-Cryst. Solids, 282 248), in the case of...
Article
Full-text available
Experimentally the silicon nanowires or nanopillars are naturally recovered by a thin oxide layer as soon as they are exposed to the air or present an amorphous layer of silicon when they are milled by focused ion beam (FIB) techniques. Here we investigate the role of the silicon amorphous shell on the plasticity of Si nanowires (NWs), thanks to mo...
Article
We have performed molecular dynamics simulations and first-principles calculations to investigate the first stages of plasticity in single-crystalline silicon nanostructures free of initial defects, under compressive and tensile strain along the [001] axis. In compression especially, we observe the activation of {011} planes, both in nanowires and...
Article
Full-text available
The effect of various parameters such as temperature or surface state on the very first stages of plasticity in semiconductor nanowires has been investigated by molecular dynamics simulations. In particular, the role of edge and surface reconstructions has been analyzed and discussed in detail. To this end, square nanowires with the [0 0 1] and [1...
Article
Full-text available
Recent theoretical investigations of the properties of dislocation cores in silicon are reviewed. New results, obtained from numerical simulations for the non-dissociated screw and 60° dislocations, are presented and discussed in relation with experiments.
Article
Full-text available
We have performed molecular dynamics simulations on silicon nanowires (Si-NW) with [001] axis and square section. The forces are modeled by well-tested semi-empirical potentials. First we investigated the edge reconstruction of Si nanowires. Then, we studied the behavior of the NW when submitted to compression stresses along its axis. At low temper...
Article
Full-text available
The non-dissociated screw dislocation in a model covalent material like silicon is known to exist in three possible stable core configurations. We performed calculations combining the nudged elastic band technique and a semi-empirical description in order to determine mechanisms and activation parameters for transforming one core into another. Our...

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Projects (2)
Project
Eigenstrain offers a versatile generic framework for the description of inelastic deformation that acts as the source of residual stresses. Focused Ion Beam (FIB) milling used for nanoscale machining is accompanied by target material modification by ion beam damage having residual stress consequences that can be described in terms of eigenstrain. Due to the lack of direct means of experimental determination of residual stress or eigenstrain at the nanoscale we adopt a hybrid approach that consists of eigenstrain abstraction from molecular dynamics simulation, its application within a finite element simulation of a flexible silicon cantilever, and satisfactory comparison of the prediction with experimental observation.