SILA - Segregation at Interfaces in Lightweight Alloys towards Tailored Mechanical Properties

Duration: 01/2023 - 12/2026 (36 months)
Funding (ANR): 285,000 euros by the french agency for scientific research (ANR).
Funding (DFG): 330,000 euros by the german research fundation (DFG).
Participants (CNRS, Metz, France): Dr. Thiebaud RICHETON, Dr. Julien GUÉNOLÉ, Dr. Stéphane BERBENNI, Dr. Antoine GUITTON.
Participants (RWTH, Aachen, Germany): Dr.-Ing. Zhuocheng XIE, Dr.-Ing. Talal AL-SAMMAN.
Abstract: Greenhouse gas reductions and fuel efficiency associated with energy generation and transportation have led to increased interest in the development of lightweight alloys in recent years. Following this trend, sustainable materials involving recycling have become of crucial importance. Magnesium alloy is a major candidate to achieve this goal but suffers from poor ductility at ambient temperature, making the processing and forming challenging and costly and preventing widespread applications. Understanding the mechanisms of plasticity in such alloy containing desired and undesired solute elements is the necessary step towards the design of lightweight alloys with tailored mechanical properties.
The project SILA proposes to contribute to this challenge by the improvement and development of continuum models able to predict solute segregation at grain boundaries and its impact on mechanical properties, supported by experimental and atomistic results. A unique French-German collaboration between the LEM3 in Metz, the leader in the continuum modelling of mechanics and crystalline defects, and the IMM in Aachen, the leader in the experimental characterization of Mg alloys, proposes to employ atomistic simulations to bridge the gap between atomic-scale experiments and continuum models.
SILA will consider bi- and tri-crystals of Mg with Zn or Y solute elements. Atomic-scale experimental characterisation by atom probe tomography will be used to validate molecular statics/dynamics simulations of the segregated interfaces. The atomistic details of the simulations will feed novel continuum models based on the excess of interfacial free energy able to capture the chemo-mechanical processes at interfaces, including complex interactions between present defects at grain boundaries. Experimental and numerical nano-mechanical tests will explore the mechanical response of the Mg alloys, including the interaction with dislocations, and describe the role of solute segregation at interfaces.
SILA aims at an accurate, experiment-based, continuum description of grain boundaries with segregated elements, to improve constitutive models for strain-aged alloys. This is of prime importance for engineering alloys and recycled alloys whose segregated solutes at interfaces impact largely mechanical properties.

Atomistic simulation and micromechanical modeling of chemo-mechanical couplings in the presence of crystal defects

Duration: 10/2022 - 09/2025 (35 months)
Funding: 110,000 euros by Université de Lorraine (French research ministry).
Participants: Dr. Thiebaud RICHETON, Dr. Julien GUÉNOLÉ, Dr. Stéphane BERBENNI.
Abstract: In this thesis, we propose to simulate the chemo-mechanical couplings in the presence of defects in one (dislocation) or two (grain boundary) dimensions. In particular, we wish to evaluate at the atomic scale the discrete effects of the presence of solute atoms on the excess energies and elastic fields of crystal defects. We will rely on molecular statics, nudge elastic band (NEB) [3,4] and molecular dynamics methods that allow the study of interactions between defects and interfaces. The continuous representation of these same effects with micromechanical approaches will be undertaken in parallel and the constitutive parameters of these approaches will be identified by the discrete methods mentioned above. The continuous approaches concerned by the project are the Stroh methods in 2D anisotropic elasticity, the Eshelby inclusion methods with the theory of eigenstrains or dipoles, and the thermodynamic method of Gibbs splitting surface to calculate the excess energy at grain boundaries but this time in the presence of solutes. These methods will be enriched and validated by discrete (atomistic) simulations.

AtoUum - Atomistic fundamentals of plasticity at interfaces in lightweight complex alloys and transfer to continuum models

09/2021 - 08/2025 (48 months).
Funding: 231,049 euros by the french agency for scientific research (ANR).
Participants: Dr. Julien GUÉNOLÉ (Project coordinator), Dr. Vincent TAUPIN.
Abstract: Lightweights metallic materials with outstanding mechanical properties are of uttermost importance for the scientific and environmental challenges ahead. Such alloys commonly exhibit complex microstructures responsible for their peculiar mechanical behavior. The long-standing research question of the plastic deformation of materials and components is intrinsically related to the propagation of slip across interfaces such as grain boundaries or phase boundaries. Despite intense work, mechanisms of slip transfer remain to date fundamentally unclear. The primary objective of this project is to reveal the discrete features at the atomic scale associated with slip transfer in a representative selection of alloys, by using state-of-the-art atomistic simulations. This project will then identify and assess key parameters that can be transferred from our discrete approach to continuum models capable of considering dislocation-interface interactions at larger scale.

PlaTra - Discrete Atomic Scale Characterization of Plasticity at Interfaces in Lightweight Complex Alloys and Transfer to Continuum Models: Defect Engineering for Energy Performance

Duration: 11/2021 - 10/2024 (36 months)
Funding: 110,000 euros by LabEx DAMAS and Région Grand-Est.
Participants: Dr. Vincent TAUPIN, Dr. Julien GUÉNOLÉ.
Abstract: Lightweight metallic materials with outstanding mechanical properties are of utmost importance for future scientific and environmental challenges. Despite intensive work, their deformation mechanisms remain fundamentally unclear to date. The main objective of this project is to develop defect engineering for energy performance by revealing the discrete characteristics of defects at the atomic scale in light metals, and to transfer this information to continuum models.