PhD Thesis (CIFRE) - Damage in recycled Al-alloys H/F/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’s subject:

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

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, 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. So, it is interesting to massively use recycled aluminium, meaning remelting used Al to make new ingots. Operating a significant shift from primary synthesis (ore reduction) to secondary synthesis (scrap melting) require designing new alloys, able to tolerate more impurities. 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). Due to their low solubility in aluminium, these elements 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. 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…).

Methodology:

• Fabrication of tailored Al-alloy grades with different microstructures (variations in Fe content, intermetallics size and spatial distribution, 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 for the same time 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
• Crystal plasticity 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 both experimental techniques and simulation/modelling
• Knowledge in tomography, image analysis, artificial intelligence, finite element modelling would be a plus
• Strong digital skills would be a plus e.g. experimental data analysis using e.g. R, Python or statistical packages
• Ability to work/interact with both academic and industrial teams
• Strong analytical skills
• The PhD student is expected to self-motivated, creative, and capable of critical thinking

Starting date: from October 2023

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 Paristech)

Industrial supervision: Fanny MAS (Constellium C-TEC)