PhD offer (M/F). Micro-mechanics of fracture : how do voids nucleate in metals ?

Job Description

Thesis Subject

PhD thesis offer (funded by ANR)

"Micro-mechanics of fracture : how do voids nucleate in metals ?"

Keywords: physics of crystalline defects, atomistic simulations, small scale mechanics.

Context:
Clarifying the process leading to void formation in metals will be useful for a number of applications such as ductile fracture, fatigue [3], damage related to hydrogen storage, dewetting of thin films, cavitation by electromigration in microelectronics...
Fracture initiation is qualitatively well understood in metallic alloys which contain micron size inclusions. It occurs by decohesion of either the inclusion itself or its interface with the matrix. The voids grow by emitting dislocations and finally the ligaments between them break by plastic thinning. On the contrary, the mechanism is still controversial when the particles are in the nanometer range or when the alloy is pure [2]. Recent experiments [4] have shown that voids appear preferentially at the dislocation boundaries formed during straining. However they are detected only when they are already relatively large, 20 to 50 nm in diameter, and few information is known on the first stages of their formation within the dislocation boundaries.

The question is to determine if these voids can nucleate by vacancy condensation.

Objective:
In this research project, we propose to study void nucleation in various well chosen crystalline defects to unravel the mechanism of void formation. The methods used will be atomic scale simulations (Monte Carlo [5] and Machine Learning interatomic potentials). The work is part of an ANR project and therefore will benefit from interactions with partners having complementary competences. In particular, the atomistic simulations will have inputs from micro-mechanics simulations (stress levels from 3D discrete dislocation dynamics [6] performed at CEA) and from experiments (observations of microstructures produced by deformation, such as the one in Fig. 1a, and voids location) performed at PIMM Arts et Métiers Paris Tech, as well as at iLM (tensile tests within SEM, FIB slicing).

Applicant skills :
Strong background in condensed matter physics or materials science, some knowledge of C programming (or equivalent). The applicant should include a CV, a statement of interest and master's degree transcript (marks and ranking if available).

Bibliography:

[2] “Void nucleation during ductile rupture of metals: A review” P. J. Noell et al. Prog. Mat. Sci. 135 101085 (2023)
[3] “Fatigue damage of ultrafine-grain copper in very-high cycle fatigue region” P. Lukáš et al. Mat. Sci. Eng. A 528 (2011) pp. 7036-7040
[4] “Nanoscale conditions for ductile void nucleation in copper: Vacancy condensation and the growth-limited microstructural state” P. J. Noell et al. Acta mater 184 (2020) pp. 211-224
[5] “Sampling vacancy configurations with large relaxations using Smart Darting” D. Tanguy Phys. Rev. Mat. 8 033604 (2024)
[6] “On the role of cross-slip and collinear annihilation in dynamic recovery annihilation” R. Madec, B. Devincre and L. Kubin, Modelling Simul. Mater. Sci. Eng. 33 015010 (2025)

Your Work Environment

The Institut Lumière Matière (iLM) is a joint research unit of the CNRS and Université Claude Bernard Lyon 1, located on the LyonTech-La Doua campus. With a staff of 310 members, including approximately one third PhD students and postdoctoral researchers, iLM is a center of excellence in physics and chemistry in the Auvergne-Rhône-Alpes region and enjoys international recognition for the quality of its research.

The institute structures its approach around a continuum linking fundamental research, responses to societal challenges, and innovation. This approach is accompanied by a collective commitment to scientific excellence, ethics, and responsibility in research.

The scientific activities of iLM are organized around six main thematic areas:

Advanced materials and optics
Complex Matter and Out-of-Equilibrium Systems
Nanosciences
Optics, dilute media, and ultrafast processes
Theory and modeling
Living Systems, Health, and Environment

The PhD project will be hosted by the MMCI team (modeling of condensed matter and interfaces), 12 permanent staff, member of the "Theory and Modeling" axis.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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