Evolution of spherical nanovoids within copper polycrystals during plastic straining: Atomistic investigation

Peng, Jing; Yuan, Lin; Shivpuri, Rajiv; Zhang, Yuqi; Shan, Debin; Guo, Bin

doi:10.1016/j.ijplas.2017.09.016

Cited by 34 publications

(9 citation statements)

References 42 publications

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“…The origin of the formation of nanovoids and pores therefore appears to be closely linked to microstructural features and the presence of strain in the as-deposited films, as well as under operation. Several reports have detailed the formation of voids due to plastic deformation, i.e., in the absence of hydrogen [58][59][60][61] . It is important to consider that palladium undergoes significant chemical expansion due to dissolution of hydrogen, with additional contributions from vacancy clusters.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen Induced Vacancy Clustering and Void Formation Mechanisms at Grain Boundaries in Palladium

et al. 2020

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Hydrogen has a significant impact on the formation of vacancies, clusters and voids in palladium and other metals. The formation of vacancy-hydrogen complexes in bulk Pd and at 3 and 5 grain boundaries was investigated using first-principles calculations and thermodynamic models. Equilibrium vacancy and cluster concentrations were evaluated as a function of temperature and hydrogen partial pressure based on the Gibbs energy of formation including vibrational and configurational entropies. Vacancies were found to be significantly stabilized by association with interstitial hydrogen, leading to enhanced concentrations by several orders of magnitude. Vacancy clusters were further stabilized at grain boundaries, with equilibrium concentrations reaching site saturation for clusters comprising up to three vacancies. Nanovoids were investigated based on Wulff constructions from calculated surface energies of the (0 0 1) and (1 1 1) terminations as a function of temperature and coverage of hydrogen adsorbates. The most stable termination changed from (1 1 1) in vacuum to (0 0 1) in H 2 , and the surface energies were lowered due to hydrogen adsorbates. Consequently, voids were also stabilized in the presence of hydrogen. Coalescing of vacancies into nanovoids was found to be thermodynamically unfavorable due to the loss of configurational entropy. It was therefore concluded that enhanced concentrations of vacancies and clusters does not directly cause the formation of voids. The formation of voids in Pd-based membranes was discussed in terms of microstructural characteristics, and strain due to chemical expansion and plastic deformation.

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Section: Discussionmentioning

confidence: 99%

Hydrogen Induced Vacancy Clustering and Void Formation Mechanisms at Grain Boundaries in Palladium

et al. 2020

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“…As shown in Figure a, the full‐field CP simulations successfully capture the weakening effect of free surfaces on the flow stress, and the size effects on the fracture of the coarse‐grained (CG) and fine‐grained (FG) foils were analyzed in terms of the simulated grain‐level plastic heterogeneities. Meanwhile, some other simulation methods for the nanoscale deformation, including molecular dynamics (MD), [ 66,67 ] dislocation dynamics (DD), [ 68 ] atomic simulation (AS), [ 69 ] etc., have been used to explain the size‐effect mechanism at the nanoscale. For example, Xu et al [ 70 ] investigated the effects of the orientation, size, and dislocation confinement on the materials behavior in Al nanopillars by MD simulation, which confirmed whether the dislocation‐starvation state can be achieved as shown in Figure 3b.…”

Section: Basic Variants Of Micro/nanoformingmentioning

confidence: 99%

A Review on Micro/Nanoforming to Fabricate 3D Metallic Structures

Wang

et al. 2020

Advanced Materials

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With the rapid development of micro‐electromechanical systems (MEMS), micro/nanoscale fabrication of 3D metallic structures with complex structures and multifunctions is becoming more and more important due to the recent trend of product miniaturization. As a promising micromanufacturing approach based on plastic deformation, micro/nanoforming shows the attractive advantages of high productivity, low cost, near‐net‐shape, and excellent mechanical properties, compared with other non‐silicon‐based micromanufacturing technologies. However, micro/nanoforming is far less established due to the so‐called size effects in terms of materials models, process laws, tooling design, etc. The understanding of basic issues on micro/nanoforming is not yet mature, and it is currently a topic of rigorous investigation. Here, a systematic review on the micro/nanoforming processes of 3D structures with multifunctional properties is presented, wherein also a critical examination of the interplay between relevant length scales and size effects affecting the structural integrity of micro/mesoscale metallic systems is also provided. Finally, the challenges of micro/nanoscale fabrication are proposed, including the development trends of new micro/nanoforming processes, multiple field coupling effects, and theoretical modeling at the trans‐scale.

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“…Understanding the micro-mechanisms and kinetics of the above processes is critical to predicting damage evolution in a given microstructure, as well as establishing guidelines for the design of damage-resistant microstructures. As a result, many efforts have been devoted to understanding damage nucleation and evolution under such loading conditions [1,2]. For example.…”

Section: Introductionmentioning

confidence: 99%

The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

2021

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A void coalescence term was proposed as an addition to the original void nucleation and growth (NAG) model to accurately describe void evolution under dynamic loading. The new model, termed as modified void nucleation and growth model (MNAG model), incorporated analytic equations to explicitly account for the evolution of the void number density and the void volume fraction (damage) during void nucleation, growth, as well as the coalescence stage. The parameters in the MNAG model were fitted to molecular dynamics (MD) shock data for single-crystal and nanocrystalline Ta, and the corresponding nucleation, growth, and coalescence rates were extracted. The results suggested that void nucleation, growth, and coalescence rates were dependent on the orientation as well as grain size. Compared to other models, such as NAG, Cocks–Ashby, Tepla, and Tonks, which were only able to reproduce early or later stage damage evolution, the MNAG model was able to reproduce all stages associated with nucleation, growth, and coalescence. The MNAG model could provide the basis for hydrodynamic simulations to improve the fidelity of the damage nucleation and evolution in 3-D microstructures.

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Evolution of spherical nanovoids within copper polycrystals during plastic straining: Atomistic investigation

Cited by 34 publications

References 42 publications

Hydrogen Induced Vacancy Clustering and Void Formation Mechanisms at Grain Boundaries in Palladium

Hydrogen Induced Vacancy Clustering and Void Formation Mechanisms at Grain Boundaries in Palladium

A Review on Micro/Nanoforming to Fabricate 3D Metallic Structures

The Modified Void Nucleation and Growth Model (MNAG) for Damage Evolution in BCC Ta

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