Mécanique

ISMME - Ingénierie des Systèmes, Matériaux, Mécanique, Énergétique

MORGENEYER Thilo

Centre des Matériaux

09/12/2023

Circular economy, damage nucleation

Circular economy, damage nucleation, intermetallic particles, tomography, plane strain, image correlation

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The PhD project aims at understanding and modeling the damage mechanisms operating in recycled aluminium alloys when loaded in plane strain mode. .Recycling aluminium allows both energy savings and a drastic reduction of GHG emissions, because only 5% of the energy required for primary synthesis (ore reduction) is needed to remelt aluminium scrap. In comparison with reference alloys currently used in transport and packaging sectors, these alloys have a higher content in impurities, especially iron, which often leads to decreasing mechanical performance. Its main objective is to predict the impact of microstructural features related to intermetallic particles (size, morphology, nature, spatial distribution) and their environment (matrix' hardness, crystallographic orientations of grains) on ductility and formability by combining in-situ 3D synchrotron characterizations at different resolutions and multi-scale simulations.

Due to its low density, aluminium (Al) is a key material for sustainability as it allows lightweighting. In the transportation industry, it means fuel consumption reduction and thus lower CO2 emissions, or increased autonomy for electrical vehicles. However, producing primary Al from bauxite ore is very energy intensive, especially the electrolysis step in which alumina oxide is refined and transformed into metal aluminium. So, it is interesting to massively use recycled aluminium, meaning remelting used Al to make new ingots. Indeed, only 5% of the energy required to produce primary Al is needed to remelt Al scrap. Among the most widely used materials, Al has the largest energy gap between primary and secondary synthesis. In principle, Al is infinitely recyclable. However, only one third of Al produced today is made from scrap, resulting in significant greenhouse gas emissions. Increasing this ratio in the coming decades and operating a significant shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) require designing new alloys, able to tolerate more impurities [Raabe 2021]. As finished goods are often complex and multi-materials, recycling loops operating in a circular economy will systematically bring some contaminants, the main one being iron (Fe). These elements have a low solubility in aluminium and form intermetallic particles negatively impacting product properties such as formability and in service ductility. The current challenge lies in finding solutions to mitigate this detrimental effect, in order to meet demanding properties in spite of higher impurities contents, allowing reduced CO2 emissions for vehicles fabrication and use.

The project aims at determining the particle-related microstructural features (sizes, morphology, nature, spatial distribution…) but also the environment-related features (matrix strength, crystallographic orientations…) that have to be tuned to extend the fields of application of recycling friendly Al alloys. For that, it is key to better understand and predict damage nucleation and growth from intermetallic particles in industrially relevant loading cases (plane strain tension, bending/unbending…).
For that, it is key to better understand and predict damage nucleation and growth from intermetallic particles in industrially relevant loading cases: plane strain tension, as the lowest ductility is found under this strain state. Given the micrometric size of the particles and the nanometric size of the voids in the first stages of nucleation together with the 3D environment to be considered, cutting edge Xray instruments are required to observe and quantify the relation between microstructure and damage. Development of innovative numerical approaches is also needed to tackle the multi-scale aspect of the problem, going from damage at individual particles coupled with the deformation field of the surrounding grains, up to formability and failure prediction on real parts. Currently, our modeling tools do not take into account any intermetallic- or texture-related microstructural aspects into the damage criteria.

Directeur de thèse : Thilo MORGENEYER - Centre des Matériaux
Co-directeur de thèse : Henry PROUDHON - Centre des Matériaux
Co-encadrant externe : Fanny MAS - Constellium

Ingénieur et/ou Master recherche - Bon niveau de culture générale et scientifique. Bon niveau de pratique du français et de l'anglais (niveau B2 ou équivalent minimum). Bonnes capacités d'analyse, de synthèse, d'innovation et de communication. Qualités d'adaptabilité et de créativité. Capacités pédagogiques. Motivation pour l'activité de recherche. Projet professionnel cohérent.

Pré-requis (compétences spécifiques pour cette thèse) :
Le(la) candidat(e) recherché(e) aura suivi un enseignement de haut niveau en mécanique des matériaux et métallurgie. Il(elle) aura un goût développé pour à la fois le travail expérimental, la caractérisation métallurgique et la modélisation micromécanique.

Pour postuler : Envoyer votre dossier à recrutement_these@mat.mines-paristech.fr comportant
• un curriculum vitae détaillé
• une copie de la carte d'identité ou passeport
• une lettre de motivation/projet personnel
• des relevés de notes L3, M1, M2
• 2 lettres de recommandation
• les noms et les coordonnées d'au moins deux personnes pouvant être contactées pour recommandation
• une attestation de niveau d'anglais

Engineer and / or Master of Science - Good level of general and scientific culture. Good level of knowledge of French (B2 level in french is required) and English. (B2 level in english is required) Good analytical, synthesis, innovation and communication skills. Qualities of adaptability and creativity. Teaching skills. Motivation for research activity. Coherent professional project.

Prerequisite (specific skills for this thesis):

PhD candidate should have excellent skills in mechanics and physical metallurgy and ability for both experimental work and micro-mechanical modelling.


Applicants should supply the following :
• a detailed resume
• a copy of the identity card or passport
• a covering letter explaining the applicant's motivation for the position
• detailed exam results
• two references : the name and contact details of at least two people who could be contacted
• to provide an appreciation of the candidate
• Your notes of M1, M2
• level of English equivalent TOEIC
to be sent to recrutement_these@mat.mines-paristech.fr

Insight into damage nucleation kinetics as a function of stress and strain is expected. In addition, information about damage nucleation as a function of particle size and spacing should be provided. The damage mechanisms for each alloy shall be studied for the different alloys. Digital image and volume correlation techniques will provide insight into the strain fields within material bulk. They also provide boundary conditions for Full field FE modelling. For selected cases the 3D grain structure will be correlated with local strain fields and damage nucleation kinetics.

On the scientific point of view, the project will provide new avenues for testing materials (including plane strain which is completely new) at extremely high resolution with in situ nano-imaging [Hurst2023], which can be further used for many different other applications. This new method has the aim to elucidate damage nucleation as a function of microstructural parameters. Different material grades with different impurity/particle content, shape and spacing as well as texture will be produced for the present study. Based on this unprecedented experimental data, new and existing damage nucleation laws will be tested and validated. Combining correlative techniques such as DCT for the polycrystalline structure, in situ nanotomography together with digital image correlation techniques [Buljac 2018], a wealth of complementary information will be gathered to inform or validate full-field numerical approaches. From a numerical point of view, the PhD project is a perfect opportunity to demonstrate the interest of using advanced full-field modelling at the microstructure scale to feed ML-based damage models.

[Raabe2022] D. Raabe, Prog. Mater. Sci., vol. 128, p. 100947, Jul. 2022.
[Hurst2023] M. Hurst et al., Sci. Rep., vol. 13, no. 1, pp. 1–11, Jan. 2023.
[Buljac2018] A. Buljac, F. Hild, L. Helfen, and T. F. Morgeneyer, Acta Mater., vol. 149, pp. 29–45, May 2018.
[Kobayashi2022] M. Kobayashi et al., Acta Mater., vol. 240, Nov. 2022.
[Buljac2017] A. Buljac et al., Comput. Mech., vol. 59, no. 3, pp. 419–441, Mar. 2017.

CIFRE ANRT

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