Establishing a role of composition and applied stress in behavior of hydrogen near crystal defects in Fe-Cr and Fe-Ni alloys.

• Applicant: Daria Smirnova, Ph.D.
• Subject Area: Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545344573

Main goal of the project is to relate composition and applied stresses to the characteristics of hydrogen diffusion and segregation on crystal defects in Fe-Cr and Fe-Ni alloys. The project is motivated by open questions regarding individual mechanisms of hydrogen embrittlement in Fe-containing alloys. Here Fe-containing alloys with two different lattice types (bcc and fcc) are chosen as prototypes. Parallel consideration of fcc and bcc alloys addresses existing questions on fundamental differences in H behavior. The study will be done by means of atomistic modeling: DFT calculations, classical Monte-Carlo method and large-scale molecular dynamics simulations. The project plan encompasses development of a classical interatomic potential for Fe-Ni-Cr-H system. The potential will allow extensive theoretical simulations of hydrogen diffusion and segregation in Fe-Ni and Fe-Cr binary alloys, with extension to elaborate Fe-Ni-Cr alloys. Intended results include H diffusion coefficients and equilibrium concentrations at various isolated crystal defects. Following types of defects will be considered: vacancies, edge and screw dislocations, tilt grain boundaries. Hydrogen concentrations and diffusion will be studied for different temperatures, stressed conditions, and specified compositions of H and alloying elements. Calculated H diffusion coefficients will be combined with H concentration at defect related to H concentration in bulk. It will provide an estimate for H fluxes through various diffusion channels depending on temperature and alloy composition. Information on H diffusion at isolated defects will be especially beneficial for development of a unified hydrogen embrittlement model considering behavior of diffusing hydrogen.

• DFG Programme: Research Grants