We are recruiting a highly motivated PhD student to constrain the feedback between strain localization and microstructure evolution during ductile (viscous) deformation in rocks, ice and metals, using experiments with in situ monitoring of strain field and microstructure evolution. He/she should have a solid grounding in solid mechanics, knowledge of crystalline plasticity, and a keen interest in experimentation and analysis of physical data. Previous experience in physical experimentation will be a real plus. Solid methodological and scientific programming skills are also essential. Knowledge of geophysics or geology is a plus, not a prerequisite.
In-situ experimentation to constrain feedbacks between strain localization and microstructure evolution in rocks, metals and ice (ERC RhEoVOLUTION)
The aim of this thesis is to constrain the feedbacks between strain location and microstructure evolution during ductile deformation through experiments. These experiments will combine in situ monitoring of strain field evolution, by digital image correlation (DIC), and of microstructure, by indexing electron backscatter diffraction (EBSD) patterns. The experiments will be carried out on AZ31 magnesium alloys. These alloys are excellent analogous materials for studying the high-temperature deformation of rocks and ice, but unlike the latter, they deform ductibly and recrystallize under conditions (150-250°C and ≤ l atm) enabling in-situ measurement of the evolution of the microstructure and deformation field in a scanning electron microscope or under high-resolution optical microscopy.
An initial series of experiments, carried out as part of a thesis due to end in September 2024, has highlighted the fundamental role of dynamic recrystallization on the evolution of microstructure (see figure opposite) and texture, and the softening effect of these evolutions on the mechanical behavior of the sample.
The next step, which is the aim of the present PhD thesis, is to couple DIC monitoring of the evolution of the deformation field in high-resolution optical microscopy with that of the microstructure. This coupling will enable us to constrain the feedback between dynamic recrystallization and strain localization. The results of these experiments will be compared with the predictions of medium- and full-field crystal plasticity models, such as self-coherent viscoplastic approaches or finite element or FFT simulations, in order to quantify the relative contributions of the various processes to mechanical behavior at local and global scales.
This PhD thesis is part of the ERC RhEoVOLUTION project, which aims to develop new approaches for the self-consistent simulation of deformation localization at different scales in the Earth or glacier flows. The experiments planned in the present PhD project will play a key role in the RhEoVOLUTION ERC, as they will provide essential physical constraints for the development of numerical models, such as: (1) quantification of feedbacks between deformation localization and microstructural evolution, (2) quantification of the evolution of mechanical behavior heterogeneity during deformation, and (3) evolution laws for microstructure and mechanical behavior. The PhD student will work with other members of the RhEoVOLUTION team to integrate the results into numerical models simulating the spatial and temporal evolution of strain and stress distributions in a polycrystalline material with evolving rheology.
Contact: Andréa Tommasi (andrea.tommasi@umontpellier.fr) & Maurine Montagnat (maurine.montagnat@univ-grenoble-alpes.fr)