PhD Thesis (CIFRE) - Better understanding of precipitation mechanisms in low-density Al-Cu-Li alloys

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:

Better understanding of precipitation mechanisms in low-density Al-Cu-Li alloys for aerospace application

Context: Al-Cu-Li alloys have experienced a strong development in the last 15 years for aerospace application. In addition to their low density, they offer an excellent corrosion resistance and a combination of specific yield strength, damage tolerance properties, weldability and formability, that is not achieved in conventional alloys. To further decrease the density of Al-Cu-Li alloys in order to lighten the aircraft, it would be beneficial to increase the Li content. However, the thermal stability of Al-Cu-Li alloys with high Li content is a challenge due to the significant precipitation of δ’ (Al3Li) precipitates during simulated in service thermal exposure at 70-85°C. This precipitation can lead to a decrease in toughness. Moreover, precipitation sequences during the ageing of this alloy family is complex and the interactions between the Cu-rich and δ’ precipitates still need to be better understood to improve the thermal stability.

Objective: The objective of the Ph.D. is to better understand the precipitation mechanisms during the ageing and the simulated thermal exposure in service of low-density Al-Cu-Li alloys in order to improve their thermal stability.

Methods: The microstructure and, more precisely, the precipitation mechanisms in Al-Cu-Li alloys will be investigated in depth. The influence of process parameters (solution heat treatment, stretching, ageing…) on the precipitation during the ageing and the simulated in service thermal exposure will be studied. To characterize the precipitation of δ’, GP zones, θ’, T1, S’… microstructures will be investigated using advanced techniques such as atom probe tomography (APT), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Some mechanical tests (hardness, tensile and toughness) will be also performed to study the effect of the precipitation on the mechanical properties.

We are looking for a highly-motivated individual with a Master or Engineer degree in materials science. An aptitude for experimental work will be appreciated.

Starting date: October 2024      Duration: 3 years

Host laboratories: SIMaP (80-90%) and Constellium C-TEC (10-20% with possible adjustment during the different phases of the thesis)

Academic supervision (SIMaP): Frédéric De Geuser, Alexis Deschamps, Isabelle Mouton

Industrial supervision (Constellium C-TEC): Hélène Godin, Marion Bellavoine, Christophe Sigli

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