PhD candidate (M/F) : Mechanical correlative microscopy by nanoindentation for high-throughput microstructural characterizations

Job Description

Thesis Subject

High speed nanoindentation mapping (HSNM) is becoming very effective in evaluating the mechanical properties of materials from correlative measurements, such as lattice orientation by EBSD or local chemical composition by EDX [1]. For instance, an original protocol based on Bayesian inference was recently co-developed by LEM3 and ICA to determine the single-crystal elastic constants of cubic crystals from HSNM and EBSD correlative measurements [2]. Such a mechanical correlative microscopy approach was also used to study the effect of oxygen content on titanium's elastic properties [3,4]. The present PhD aims to fully exploit the potential of the HSNM technique on materials with gradients of microstructures and properties. The objective is twofold: first, provide fruitful data to calibrate physics-based crystal plasticity models and inform them with key parameters (e.g., variation of single-crystal elastic constants and critical resolved shear stresses with microstructural features, interfaces strengths), secondly, gain a better understanding of the mechanisms leading to strain localization which has a determinative role in influencing the suitability of a given material for an intended structural application. To conduct this study, a nickel-based superalloy (Inconel 718) will be used as a model material because of its broad industrial applicability and its remarkable metallurgical modularity, enabling the elaboration of specimens with gradients of microstructural states (from solid solution to precipitation hardened) directly influencing its strain localization. The PhD research will notably involve:
• Preparation of INCONEL 718 specimens having a gradient of precipitation along the tensile direction (1), chemically-graded specimens for controlled gradients in Nb and/or Al content (2), and pre-deformed samples (3).
• Application of high-speed nanoindentation maps combined with EBSD and/or EDX measurements that allows for data merging/correlative measurements to subsequently extract mechanical properties.
• Statistical analysis of slip bands around indents and stress drops occurring during nanoindentation tests [5] with respect to lattice orientation, chemical composition, metallurgical state, and distance to grain or twin boundary.
• Study of the strength of grains and twin boundaries and the constraint of plasticity by interfaces from the deviation of classical indentation size effect (ISE) [6] obtained in nanoindentation tests carried out in continuous stiffness measurement (CSM) mode close to interfaces.

REFERENCES:
[1] Rossi, E., Wheeler, J. M., & Sebastiani, M. (2023). High-speed nanoindentation mapping: A review of recent advances and applications. Current Opinion in Solid State and Materials Science, 27(5), 101107
[2] Idrissi, Y., Richeton, T., Texier, D., Berbenni, S., & Lecomte, J. S. (2024). Robust determination of cubic elastic constants via nanoindentation and Bayesian inference. Acta Materialia, 281, 120406
[3] Texier, D., Richeton, T., Proudhon, H., Dziri, A., Sirvin, Q., & Legros, M. (2024). Increase in elastic and hardness anisotropy of titanium with oxygen uptake due to high temperature oxidation: A multimodal framework using high speed nanoindentation mapping. Materials Characterization, 216, 114244
[4] Dziri, A., Ammar, K., Forest, S., Proudhon, H., Sirvin, Q., Richeton, T., & Texier, D. (2025). Effect of oxygen content on elastic properties of an oxygen-graded titanium: Experimental and computational analyses. Materials & Design, 114801
[5] Jullien, M., Legros, M., Calvat, M., Stinville, J. C., & Texier, D. (2025). Quantifying the impact of oxidation on the mechanical properties of Alloy 718 using local mechanical testing techniques. Materials & Design, 114669
[6] Nix, W. D., & Gao, H. (1998). Indentation size effects in crystalline materials: a law for strain gradient plasticity. Journal of the Mechanics and Physics of Solids, 46(3), 411-425

Your Work Environment

This is a fully funded PhD position for 3 years (2300 € (gross) per month) supported by the PEPR DIADEM program. The PhD candidate will be recruited in the framework of the AMMETIS (AI-assisted Simulations of Microstructure driven Mechanical properties from high Throughput and multiscale analysIS) project which is based on an effective collaboration between LEM3, ICA, PIMM and CEA. The PhD candidate will be mainly located at LEM3 in Metz, while making long stays at ICA in Toulouse at the beginning of the thesis to perform experimental campaigns. He will be involved in the AMMETIS'team composed of experienced researchers from CNRS, UL, Arts et métiers, IMT and CEA, as well as several PhD students and post-doctoral researchers, working on high-throughput material characterization and micromechanical modelling, both assisted by AI. The PhD candidate will have access to state-of-the-art research facilities and computational resources. He will be offered the opportunity to participate in in international conferences, workshops, and training events.

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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