Stored energy in plastically deformed metals

Texture and microstructure are two important characteristics that influence the physical properties of metallic alloys. In practice, the recipe of obtaining the required physical properties of a polycrystalline material for a given application is not easy to establish and usually it is obtained via a large number of tests. The reason is the lack of a theory that takes into account complex microscopic processes acting during heat treatment such as recovery and recrystallization. The state of the art reveals the influence of geometrical (ex. the grain shape) and microstructural parameters (such as the stored strain-energy of lattice defects) and there is a debate among the scientists on the degree of their contribution to the recrystallization process. Stored energy is classically determined by X-ray line profile analysis (LPA) and backscatter electron diffraction (EBSD). LPA gives a single value for a grain. On the other hand, EBSD delivers spatially resolved results, but only on the fraction of the stored energy associated to lattice tilt. Recently a new technique has been developed at synchrotron source, the scanning three dimensional X-ray diffraction (S3DXRD), which could combine LPA and EBSD into one single technique. Developing this method will allow for the first time coupling the 3D grain geometry with the locally stored strain-energy, a groundbreaking result permitting more realistic modeling of recrystallization in a full-field approach. Modeling will be done by our partners (MINES Paristech) in this ANR project and will finally answer the debate on the degree of contribution of these parameters to recrystallization.

S3DXRD experiments are planned at the European Synchrotron Radiation Facility (ESRF) in Grenoble and at the Advanced Photon Source (APS) in Chicago with the aim of determining the grain structure of a polycrystal and the spatially resolved stored energy using the a new version of S3DXRD, which will be developed within the frame of this PhD.

Required skills and knowledge of the candidate: Python programming language (data evaluation will be done with Python scripts developed at ESRF). Good background in physical metallurgy or physics, as well as basic knowledge in crystallography and lattice defects could be an advantage.

École Nationale Supérieure des Mines de Saint-Étienne is a graduate engineering school and research institute aka « Grande École d’Ingénieurs » founded in 1816. Our range of career-focused diplomas will open doors to some of the best careers in the field of engineering and enable you to build your own international network.

The candidate should have a good background in materials science or physics

The knowledge of Python programming language is necessary