The interaction of dislocations and hydrogen-vacancy complexes and its importance for deformation-induced proto nano-voids formation in α-Fe

By using molecular dynamics and cluster dynamics simulations, we probed the role of hydrogen-vacancy complexes on nucleation and growth of proto nano-voids upon dislocation plasticity in α-Fe. Our atomistic simulations reveal that, unlike a lattice vacancy, a hydrogen-vacancy complex is not absorbed by dislocations sweeping through the lattice. Additionally, this complex has lower lattice diffusivity; therefore, it has a lower probability of encountering and being absorbed by various lattice sinks. Hence, it can exist metastably for a rather long time. Our large-scale molecular dynamics simulations show that when metals undergo plastic deformation in the presence of hydrogen at low homologous temperatures, the mechanically driven out-of-equilibrium dislocation processes can produce extremely high concentrations of hydrogen-vacancy complex (10−5 ∼ 10−3). Under such high concentrations, these complexes prefer to grow by absorbing additional vacancies and act as the embryos for the formation of proto nano-voids. The current work provides one possible route for the experimentally observed nano-void formation in hydrogen embrittlement of steels and bridges atomic-scale events and damage with macroscopic failure. •By using multi-scale simulation techniques, we probed the role of hydrogen-vacancy complexes on proto nano-voids formation due to dislocation plasticity in α-Fe during hydrogen embrittlement.•Our atomistic and coarse-grained cluster dynamics simulations show that the concentration of hydrogen-vacancy complexes can reach extremely high levels during dislocation plasticity in the presence of hydrogen, and these hydrogen-vacancy complexes prefer to aggregate by absorbing additional vacancies and act as nuclei for nano-voids.•The current work provides the link between hydrogen-vacancy complexes at the atomic scale to macroscopic failure by nano-void coalescence in hydrogen embrittlement.