Hydrogen–vacancy–dislocation interactions in<i>α</i>-Fe

Tehranchi, Ali; Zhang, X; Lü, Gang

doi:10.1088/1361-651x/aa52cb

Cited by 31 publications

(10 citation statements)

References 34 publications

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“…Hydrogen embrittles metallic materials by lowering the bond energy between metal atoms, which translates into a reduction of the fracture resistance. A number of authors have employed Density Functional Theory (DFT) to investigate the decohesion of fracture surfaces with varying hydrogen coverage (see, e.g., [27][28][29] and references therein). For example, Alvaro et al [28] computed the change in ideal fracture energy in the presence of hydrogen atoms at Σ3 and Σ5 grain boundaries in nickel.…”

Section: Hydrogen-dependent Surface Energy Degradationmentioning

confidence: 99%

A phase field formulation for hydrogen assisted cracking

Martínez‐Pañeda

Golahmar

Niordson

2018

Computer Methods in Applied Mechanics and Engineering

307

197

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We present a phase field modeling framework for hydrogen assisted cracking. The model builds upon a coupled mechanical and hydrogen diffusion response, driven by chemical potential gradients, and a hydrogen-dependent fracture energy degradation law grounded on first principles calculations. The coupled problem is solved in an implicit time integration scheme, where displacements, phase field order parameter and hydrogen concentration are the primary variables. We show that phase field formulations for fracture are particularly suitable to capture material degradation due to hydrogen. Specifically, we model (i) unstable crack growth in the presence of hydrogen, (ii) failure stress sensitivity to hydrogen content in notched specimens, (iii) cracking thresholds under constant load, (iv) internal hydrogen assisted fracture in cracked specimens, and (v) complex crack paths arising from corrosion pits. Computations reveal a good agreement with experiments, highlighting the predictive capabilities of the present scheme. The work could have important implications for the prediction and prevention of catastrophic failures in corrosive environments. The finite element code developed can be downloaded from www.empaneda.com/codes

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Section: Hydrogen-dependent Surface Energy Degradationmentioning

confidence: 99%

A phase field formulation for hydrogen assisted cracking

Martínez‐Pañeda

Golahmar

Niordson

2018

Computer Methods in Applied Mechanics and Engineering

307

197

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“…Continuum theories and simulations have shown that in the presence of hydrogen, the solute drag force exerted on a moving dislocation adds resistance to dislocation motion 14,15 and no shielding of dislocation–dislocation interactions by hydrogen can be found in atomic simulations 16 . Hydrogen segregation to grain boundaries and interactions with vacancies also play important roles in HE 17–19 . A recent study suggested that vacancies can interact with hydrogen and lock dislocations motion in aluminum 20 .…”

Section: Introductionmentioning

confidence: 99%

Hydrogen embrittlement in metallic nanowires

et al. 2019

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Although hydrogen embrittlement has been observed and extensively studied in a wide variety of metals and alloys, there still exist controversies over the underlying mechanisms and a fundamental understanding of hydrogen embrittlement in nanostructures is almost non-existent. Here we use metallic nanowires (NWs) as a platform to study hydrogen embrittlement in nanostructures where deformation and failure are dominated by dislocation nucleation. Based on quantitative in-situ transmission electron microscopy nanomechanical testing and molecular dynamics simulations, we report enhanced yield strength and a transition in failure mechanism from distributed plasticity to localized necking in penta-twinned Ag NWs due to the presence of surface-adsorbed hydrogen. In-situ stress relaxation experiments and simulations reveal that the observed embrittlement in metallic nanowires is governed by the hydrogen-induced suppression of dislocation nucleation at the free surface of NWs.

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“…Recent experiments in steels suggest that, in the presence of H, nanovoids are formed along GBs and that coalescence of these nanovoids could lead to embrittlement fracture along grain boundaries [27]. Mechanisms for this behavior remain to be uncovered, however [28,29].…”

mentioning

confidence: 99%

Atomistic study of hydrogen embrittlement of grain boundaries in nickel: II. Decohesion

Tehranchi

2017

Modelling Simul. Mater. Sci. Eng.

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Abstract. Atomistic simulations of bicrystal samples containing a grain boundary are used to examine the effect of hydrogen atoms on the nucleation of intergranular cracks in Ni. Specifically, the theoretical strength is obtained by rigid separation of the two crystals above and below the GB and the yield strength (point of dislocation emission) is obtained by standard tension testing normal to the GB. These strengths are computed in pure Ni and Ni with H segregated to the grain boundaries under conditions typical of H embrittlement in Ni, and in highly-H-saturated states. In all GBs studied here, the theoretical strengthσ is not significantly reduced by the presence of the hydrogen atoms. Similarly, with the exception of the NiΣ27(115) 110 boundary, the yield strength σy is not significantly altered by the presence of segregated H atoms. In all cases, the theoretical strengths are ∼25 GPa and the yield strengths are ∼10 GPa, so that (i) the theoretical strength is always well above the yield strength, with or without H, and (ii) both strengths are far above the bulk plastic flow stress, σ B y of Ni and Ni alloys. Complementing recent work showing that H does not change the ability of GB cracks to emit dislocations and blunt, the present work indicates that hydrogen atoms segregated to the GB have little effect on lowering the GB strength and so do not significantly facilitate nucleation of intergranular cracks.

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Hydrogen–vacancy–dislocation interactions inα-Fe

Cited by 31 publications

References 34 publications

A phase field formulation for hydrogen assisted cracking

A phase field formulation for hydrogen assisted cracking

Hydrogen embrittlement in metallic nanowires

Atomistic study of hydrogen embrittlement of grain boundaries in nickel: II. Decohesion

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