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

SZ Li and YG Li and YC Lo and T Neeraj and R Srinivasan and XD Ding and J Sun and L Qi and P Gumbsch and J Li, INTERNATIONAL JOURNAL OF PLASTICITY, 74, 175-191 (2015).

DOI: 10.1016/j.ijplas.2015.05.017

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 alpha-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) similar to 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. (C) 2015 Elsevier Ltd. All rights reserved.

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