PhD Thesis (CIFRE) - Damage in recycled Al-alloys studied by correlative 4D experiments

C-TEC IS RECRUITING 

PhD Thesis (CIFRE) F/H/X

Constellium is a world leader in the development and manufacture of high value-added aluminum products and solutions for a wide range of markets and applications, focusing in particular on aerospace, automotive and packaging. Our Research and Technology Center, C-TEC Constellium Technology Center employs about 240 people, mainly dedicated to research in the fields of casting, aluminum transformation and surface treatment. We are committed to minimizing the environmental impact of our operations and improving the environmental footprint of aluminum throughout the value chain.

Thesis subject:

Damage in recycled Al-alloys studied by correlative 4D experiments

Context of the project and associated challenges:

Due to its low density, aluminium (Al) is a key material for sustainability as it allows lightweighting. In the transportation industry, this enables fuel consumption reduction and thus lower CO₂ emissions, or increased range for electric vehicles. On the material side, however, producing primary Al from bauxite ore is very energy intensive. Since recycling reduces by 95% the energy needed to produce an Al ingot, it is interesting to massively use recycled material. As finished goods are often complex and multi-material, scrap material coming from the circular economy will systematically bring some contaminants. Hence, operating a significant shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) requires designing new alloys, able to tolerate more impurities, the main one being iron (Fe). Due to its low solubility in aluminium, this element 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.

The PhD 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. In-situ synchrotron experiments will be performed to get unprecedented detailed data about the mechanisms occurring at the damage initiation step during plane strain and bending loadings.

The PhD work is part of the larger project RECYCAL, which involves Finite Element (FE) modelling on full 3D microstructures as well as Artificial Intelligence approaches to link microstructural features to plane strain and bending performance. The experimental results obtained during the PhD will feed these approaches. Significant interactions with the other partners will be needed to succeed in transferring the experimental knowledge into efficient models.

Methodology:

• Selection and characterization of tailored Al-alloy grades with different microstructures (variations in Fe content, intermetallic sizes and spatial distributions, crystallographic textures…) to be submitted to plane strain tension (the loading state leading to most of the failure during stamping of automotive parts).
• Microlaminography and nano-tomography experiments performed at the European synchrotron ESRF or KIT (Germany) to obtain high and very high resolution 3D imaging during in situ testing.
• Post-treatment of resulting data to link the local strain fields, the spatial and morphological distribution of second phase particles and the damage evolution during straining.
• Characterization of the complete initial polycrystalline structure for selected cases using laboratory diffraction contrast tomography (DCT carried out at Xnovotech, Denmark)
• Combined analysis of the grain orientations, local strain field heterogeneities and locations of particles leading to damage initiation in order to identify the governing mechanisms.
• Identification of the macroscopic constitutive behavior of the materials, accounting for their macroscopic anisotropy and hardening.
• 3D FE simulations and comparison with experimental strain fields.
• Generation of input data (both microstructure and boundary conditions) for micro-scale FE simulations of representative volume elements (RVE) loaded in plane strain tension to be conducted in cooperation with CEMEF (Mines ParisTech, Sophia Antipolis).

Key words: Recycling, Circular economy, damage nucleation, intermetallic particles, tomography, image correlation, finite element simulations

Your Profile:

• Masters-level degree or graduate of Engineering school (Mines, Centrale, INSA, INPs, UTC…) in Mechanics or Materials Science

• Strong motivation for advanced experimental techniques, data analysis methods, and simulation/modelling
• Strong analytical skills
• Ability to work/interact with both academic and industrial teams
• Knowledge in tomography, image analysis, artificial intelligence, finite element modelling would be a plus
• Digital skills would be a plus (e.g. experimental data analysis using R, Python or statistical packages)
• The PhD student is expected to be self-motivated, creative, and capable of critical thinking

Starting date:  October 2024 or earlier

Duration: 3 years

Research laboratory and Location : Centre des Matériaux – Pierre-Marie Fourt (psl.eu), Centre des Matériaux, Evry (90%)

Academic supervision: Thilo MORGENEYER, Henry PROUDHON (Mines Paris - PSL)

Industrial supervision: Erembert NIZERY, Fanny MAS (Constellium C-TEC)

Interested? Please send your application to C-Tec-RH@constellium.com