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

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Title: The interaction of dislocations and hydrogen-vacancy complexes and its importance for deformation-induced proto nano-voids formation in α-Fe.
Authors: Li, Suzhi1,2,3, Li, Yonggang2,4, Lo, Yu-Chieh2, Neeraj, Thirumalai5 neeraj.s.thirumalai@exxonmobil.com, Srinivasan, Rajagopalan5, Ding, Xiangdong1, Sun, Jun1, Qi, Liang2, Gumbsch, Peter3,6, Li, Ju1,2 liju@mit.edu
Source: International Journal of Plasticity. Nov2015, Vol. 74, p175-191. 17p.
Subjects: Vacancy-dislocation interactions, Deformations (Mechanics), Voids (Crystallography), Molecular dynamics, Nucleation, Crystal lattices
Abstract: 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. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract: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. [ABSTRACT FROM AUTHOR]
ISSN:07496419
DOI:10.1016/j.ijplas.2015.05.017