Pierre GUERIN – Effect of recycling impurities on the formability of automotive aluminum alloys: influence of intermetallic particles studied by process variation and data-driven approaches

Jury

Mr. Warren POOLE : Full professor, The University of British Columbia (UBC), Reviewer
Mme. Mathilde LAURENT-BROCQ : Chargée de recherche HDR, Institut de chimie et des matériaux (ICMPE), Reviewer
Mme. Aude SIMAR : Professeure, Université catholique de Louvain (UCL), Examiner
Mr. Thilo MORGENEYER : Directeur de recherches, Mines de Paris (PSL), Examiner
Mr. Alexis DESCHAMPS : Professeur, Université Grenoble Alpes (UGA), Thesis supervisor
Mme. Fanny MAS : Ingénieure docteure, Constellium C-TEC, Invited

Abstract

The use of aluminum alloys for automotive applications is growing rapidly, as they help to reduce the weight of cars and hence their greenhouse gas (GHG) emissions. These aluminum alloys are bound to contain an increasing proportion of recycled metal to reduce their carbon footprint, leading to variations in alloy composition, particularly regarding impurities. In alloys of the 6000 family (Al-Mg-Si), the increased presence of low-solubility elements such as Mn and Fe can have a significant impact on their formability.

The aim of this thesis is to gain a better understanding of the effect of microstructural parameters characterizing Fe- and Mn-based intermetallic phases on the formability properties of these alloys. The first step was to develop experiments to quantify the properties of intermetallics and dispersoids, based on compositional and process variations. Local ductility criteria measured under two loading modes were defined and compared with traditional criteria and industry-standard tests such as bending. These steps made it possible to link process parameters to microstructural and mechanical properties in the T4 condition, and thus to build up a database. The latter was exploited by statistical study and machine learning tools, enabling us to identify the parameters relating to intermetallic particles that govern fracture in a uni-axial loading mode and in plane strain deformation, both in tension and in bending, and thus to propose ways of mitigating the adverse effects of impurities.