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Center for Nonlinear Studies |
Modelling hydrogen diffusion including the effect of traps at different length scales is a fundamental first step towards the understanding and prediction of hydrogen embrittlement. In this study a multiscale approach is developed to study hydrogen diffusion in alpha-iron crystals containing dislocations. At the nanoscale, DFT simulations are performed to obtain the energy barriers to move hydrogen between different lattice sites including the effect of other hydrogen atom, vacancies and external stress. At the microscale this information is used in an object kinetic Monte Carlo model (OkMC) which aims to evolve the arrangement of a large set of hydrogen atoms into the iron lattice considering point defects and the presence of dislocations. The OkMC model also accounts for the elastic interactions between hydrogen and different defects using an FFT-based approach which considers the defect full elastic field in an anisotropic medium. Dislocations are introduced through a phase-field dislocation approach, enabling an accurate representation of the dislocation core. As an outcome of the model, the hydrogen diffusivity tensor is obtained as a function of local stress, temperature, and dislocation distribution.
Bio: Dr. Javier Segurado is a Full Professor at Universidad Politécnica de Madrid and Senior Researcher at IMDEA Materials Institute (since 2008). His research activity is focused on the simulation of the behavior of materials at different length scales and the coupling of the scales using multiscale approaches. His work uses computational micromechanics, atomistic methods, dislocation dynamics and FFT based solvers to predict how microstructure influences the behavior and fracture of heterogeneous materials. He has published more than 110 papers (H index 51, ~9,000 citations). A Fulbright Scholar and former UCLA visiting professor, he is ranked in Stanford University’s ranking in the top-2% of researchers worldwide since 2021.
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