Single and poly- crystal elastic constants of nickel and NiHx alloys at finite temperature from experiments and first principles calculations

International audienc

Influence de l’hydrogène sur les mécanismes élémentaires de plasticité du nickel : contribution de l’hydrogène aux propriétés d’élasticité

Comptes rendusInternational audienc

Characterization and oxidation resistance of additive manufactured and forged IN718 Ni-based superalloys

International audienc

The influence of hydrogen on cyclic plasticity of <001> oriented nickel single crystal. Part I: dislocation organisations and internal stresses

The present paper discussed the impact of hydrogen on the mechanical response of cyclically strained nickel single crystal oriented for multi-slips at different length scales. At macroscale, as a function of the plastic strain, the hydrogen seems to induce competition between softening and hardening of the metal. Then, by separating internal stresses induced by long-range and short-range interactions between dislocations (represented by back and effective stresses, respectively), we noted that hydrogen reduces the effective stress but has a more complex behaviour with the back stress. Therefore, observations with transmission electron microscope and nano-indentation tests have been performed on cyclically pre-strained nickel single crystal with and without hydrogen. The dislocation organisation induced by the cyclic tests is similar for nickel with and without hydrogen. In both cases, the dislocation arrangement can be affiliated to a composite structure with a wall phase containing mainly edge dislocation dipoles and a channel structure where the mobility and cross-slip events of screw dislocations occurred. From both approaches, we observed that hydrogen hardens the wall phase while it softens the channel phase. These results are discussed on the base of plasticity mechanisms

Multiscale analysis of hydrogen-induced softening in f.c.c. nickel single crystals oriented for multiple-slips: elastic screening effect

International audienc

Dissolution and passivation of aluminide coatings on model and Ni-based superalloy

International audienc

A multi-scale analysis of the different interactions between defects and hydrogen: A review on the contribution of the elastic fields

International audienc

The Influence of Hydrogen Flux on Crack Initiation in Martensitic Steels

AbstractUnderstanding hydrogen transport and trapping phenomena is a key feature to revisit the hydrogen embrittlement (HE) models proposed in the literature. Both aspects can be affected by stress-strain states at different microstructural scales. Elastic distortion and plastic strain are both aspects of the mechanical states associated with defects (vacancies, dislocations), metallurgical elements (grain boundaries, precipitates), internal stresses and applied stresses, which can modify the diffusion and solubility of hydrogen. In the present work we first explore the effects of a tensile stress applied on martensitic steel membrane on the hydrogen concentration and mobility. In a second part, we analyse the impact of mobile and trapped hydrogen on HE using local approach of fracture under hydrogen flux

Consequence of the diffusive hydrogen contents on tensile properties of martensitic steel during the desorption at room temperature

International audienc