Scientific and Industrial context:

Recycling loops in the Al industry are undergoing a massive change, with the expected end of combustion engines (Al-Si foundry alloys) and the development of Al-based car-bodies, both being aimed at reducing the carbon imprint of car transportation. In parallel the post-consumer recycled rate in automotive alloys must be maximised, as the use of recycled aluminium generates 90% less greenhouse gas emissions than the use of primary aluminium. All this implies that recycling-compatible automotive Al based alloys are bound to contain more and more impurities, such as Fe, which is a challenge for the formability of rolled sheets.

In the Al industry, Constellium is one of the leading companies in the automotive market[1]. It is Constellium’s ambition to pull all the levers to tailor microstructure generation so as to mitigate the detrimental effect of impurities in microstructures. There are basically two main levers: at the process level, and on the alloy composition. The latter is at the heart of the proposed project.

Solidification determines the distribution of Fe-bearing intermetallic phases in the microstructures, thus their harmfulness. Solidification microstructures are controlled by diffusion phenomena in the liquid phase, which are themselves determined by the Short Range Order (SRO) which prevails in the alloy melt. The more Icosahedral SRO, the lower the diffusivity of species in the melt, which is what is sought after. In multiconstituent alloys, even minor additions may have a large influence on the ISRO, probably leading to the formation of icosahedral Medium Range Order (IMRO). The problem is so complex that ab initio molecular dynamics (AIMD) reaches the limits of computation capacity when there are more than 3 atom species. Hence the need for a renewed approach.

Scientific challenge:  

From a fundamental point of view, researchers are still facing challenges in the understanding of the atomic organization and dynamic properties of melts. There is now some evidence that structural features not only at the local atomic scale (SRO) but also in the medium range (MRO) might govern the early stages of crystal nucleation and/or phase selection, which implies capturing multiconstituent effects.

The main objective is to use the strongly developing tools based on the use of Artificial Intelligence to identify empirical potentials from ab initio calculations that will allow for Quantum Engineering of Multiconstituent Alloy Melts through Molecular Dynamics, so as to accelerate alloy design.

Work to be done:

The recruited person will be responsible for the ab initio calculations of model alloys used as a basis for automotive alloys, namely Al-Mg, Al-Si, and Al-Mg-Si systems, and the same with additions of specific transition metals. In addition, he/she will use and extend the tools developed in the framework of the Chair of Materials of the Multidisciplinary Institute of Artificial Intelligence (MIAI) which uses unsupervised structural identification of atomic clusters constituting the short-range order in supercooled liquid alloys. The tool will be applied to his/her own alloy calculations as well as to alloys previously calculated (mainly Al-Zn, Al-Zn-Cr, Al-Cu-Li).

Working environment:

This project will benefit from C-TEC's knowledge and modelling capabilities in the field of aluminium alloy solidification, SIMaP's expertise in the field of Quantum Engineering applied to liquid metals, as well as from the strong links with specialists of Machine Learning under the auspices of MIAI. This project is hosted by the Common Laboratory recently created between C-TEC and SIMAP.

Application:

Applicants should be proficient in chemistry, physics and processing of materials, as well as in the modelling approaches at different scales (quantum mechanics, ab initio) the kinetic modelling techniques up to phase transformations (from statistical physics to materials science). Strong interest in computer science is required. The applicants must have obtained their PhD in France during the academic years 2019-20 or 2020-21 and send a detailed CV, publication list, motivation letter, and names and contact of at least two references for recommendation letters.

Duration:

This is a two-year position starting before December, 31, 2021

Contact:

Noel JAKSE, Professor, Univ. Grenoble Alpes.  SIMAP Lab: [email protected]

Philippe JARRY, Senior Scientist, C-TEC Constellium,  [email protected]

References

Ph. Jarry and M. Rappaz: Recent advances in the metallurgy of aluminium alloys. Part I: Solidification and casting - ScienceDirect  (2018)

A. Pasturel, N. Jakse. Atomic-scale structural signature of dynamic heterogeneities in metallic liquids. npj Computational Materials 3, 1 (2017

[1] The project is fully in line with the national low-carbon strategy (SNBC = Stratégie Nationale Bas Carbone) insofar as it aims at promoting the recycling of end-of-life vehicles. Constellium is also committed to achieve carbon neutrality by 2050. The project is consistent with the law on circular economy published in 2020, which aims at promoting eco-design through the incorporation of recycled materials.