The French Alternative Energies and Atomic Energy Commission (CEA) is a key player in research, development and innovation in several areas including fundamental research in the physical sciences. The CEA-DAM is established in nine centers spread throughout France. It works in partnership with many other research bodies, local authorities and universities. Bruyères le Châtel center hosts 2000 research scientists and engineers with expertise in environmental monitoring, large instruments (accelerators, lasers), materials and high performance supercomputing.
Interested candidates must send an e-mail to the correspondent supervisor with the following documents: 1) Letter of interest for the position; 2) Short CV containing academic degrees, publications, and the documents showing expertise in the field and 3) letters of recommendation.
Opportunity 1: Modeling inheritance of crystal plasticity during the temperature-induced phase transitions in iron
The mechanical properties of crystals strongly depend on their internal microstructure, in terms of crystal phases and relative orientations, solid/solid interface migration as well as plastic deformation that is mainly driven by the movement and multiplication of dislocations. Our phase field method for martensites developed to capture successive (reconstructive) transformations has demonstrated that plasticity is playing a key role, e.g., for the reversion process in iron. To understand the evolution of microstructures under various thermodynamical environments, a coupling between our phase field method and dislocation-based crystal-plasticity is the next step toward a comprehensive and predictive modeling of the martensitic transformations.
To establish a thermodynamical and numerical framework that couples the phase field method with dislocation-based constitutive relations for the FCC and BCC phases of iron under temperature change. A high pressure-induced phase field framework is already available as well as the Taylor-like relations for which the material-dependent coefficients of both FCC and BCC phases have been calibrated by dislocation dynamics simulations. To complete the framework, the question of inheritance of plastic deformation and hardening during phase transformations, e.g., the transition of the plastic slip from a well-defined system of the mother phase to systems of the newly-formed crystal structures after the passing of mobile (coherent/semi-coherent) solid-solid interfaces, will be addressed. The forward and reverse martensitic phase transformations in presence of interface dislocations will be considered. Discussions and interactions with specialists of digital image correlation will be motivated to compare simulations with experimental investigations.
A PhD in materials science and a background in mechanics / constitutive laws are required to apply. The development will be done in a non-classified massively parallel (finite element) code.
Aurélien Vattré (firstname.lastname@example.org) and Christophe Denoual (email@example.com)
Opportunity 2: “Micro”-Tensile testing in a Diamond Anvil Cell
The diamond anvil cell is an elegant device used to generate high pressures (up to 4 million atmospheres) over small samples that allows reproducing in the lab extreme conditions encountered in natural systems such as the Earth’s core. The pressure modifies the onset and mobility of defects such as dislocations and affects mechanical behavior (elastic limit, plastic behavior). The goal of this project is to quantify this effect by performing elementary mechanical tests under high pressure conditions.
You first task will be to design, with a finite element Code, "micro-tensile testing machines" in diamond anvil cells. This machine will take advantage of the difference in compressibility between the specimen material and the diamond to generate a controlled differential stress on the specimen during pressure increase. You will make this machine by machining/welding with femtosecond laser/focused ion beam at CEA-DAM. You will carry out tensile tests using synchrotron X-ray diffraction diagnostics at sources such as European Synchrotron Radiation Facility (Grenoble, France) or abroad.
Your work will be guided by experts in mechanics and diamond anvil cell/synchrotron experiments at CEA-DAM
A PhD in physics/materials science and a background in mechanics are required to apply. Experience with synchrotron facilities will be appreciated. The working language will be English.
Agnès Dewaele (firstname.lastname@example.org) and Christophe Denoual (email@example.com)