Impact de l’hétérogénéité de déformation plastique sur la diffusion et la ségrégation de l’hydrogène – DISHYDRO

The project aims better identification and understanding of the mechanisms of interaction between hydrogen and the plasticity of f.c.c. metal at intra-granular scale. This issue is fundamental if you will, ultimately, ensure the integrity of structures in contact with hydrogen (watery environments, cathodic protection, production and storage of hydrogen, ...). In the case of the crack tip (high hydrostatic pressure, plasticity), hydrogen interacts with the crystal structure and crystal defects (density and distribution of dislocations) in the plastic zone. Many mechanisms are proposed to describe the effects of hydrogen which in particular: the reduction of cohesion energy, increased of dislocations mobility, a slip localization. In parallel, the presence of crystalline defects affects adsorption and absorption of hydrogen on the surface, then its diffusion and particularly encourages segregation on preferential sites In crack tip all these phenomena occurs in synergy. This complex, multidisciplinary course requires a good understanding of the mechanisms of cracking, plastic deformation, and adsorption and transport of hydrogen. While many studies have focused in recent years to study the damaging nature of hydrogen, it is not the same for understanding the role played by crystalline defects on the processes of absorption, transport and segregation of hydrogen. This fundamental and original goal is at the heart of the project. The proposed study aims to provide a significant impetus to an ambitious scientific break with the traditional routes of research are conducted in France (ANR PAN-H) or internationally (HYDROGENIUS Institute in Japan) that aim for the most part to identify the mechanical behavior of materials in the presence of hydrogen. Thus, it is proposed a different investigative strategy incorporating all the scientific and technical partners (f.c.c. plasticity of metals and distribution of hydrogen) which is to identify the location of hydrogen in terms of distribution of mobile and stored dislocations. In particular, the intersection between scientific communities remote: physicochemical-electrochemistry and mechanisms of plasticity is a strong point of the project. The aim of the study is to demonstrate the relevance of the strategy proposed in the case of a model material (single crytal)-medium (in aqueous cathodic polarization). The prospects of the approach are to extend the analysis to more complex situations typically encountered in industry (polycrystalline alloys, multiphase, complex environments ...). Better knowledge of the physical premises involved in the interaction between metals and hydrogen, should eventually enable us to glimpse the damage models most relevant in the presence of hydrogen.