Shock response of nanotwinned copper from large-scale molecular dynamics simulations

Yuan, Fuping; Wu, Xiaolei

doi:10.1103/physrevb.86.134108

Cited by 37 publications

(21 citation statements)

References 52 publications

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“…Because of a shift in the dominant deformation mechanisms from dislocationmediated plasticity to GB-associated plasticity, the strength/hardness of metals has been found to increase first with decreasing grain size down to a critical grain size (10-20 nm), and then decrease with further grain refinement [1,2,[9][10][11][12][13][14][15]. Moreover, a similar trend for twinboundary spacing (TBS) effect on the strength of nanotwinned (NT) metals was also found due to a transition of deformation mechanisms [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 60%

Smaller critical size and enhanced strength by nano-laminated structure in nickel

Wang

Yuan

2015

Computational Materials Science

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a b s t r a c tBecause of a shift in the dominant deformation mechanisms, the strength/hardness of metals increases with decreasing grain size down to a critical value, then decreases with further grain refinement. Here, laminated structure with low-angle grain boundaries was found to have smaller critical size and enhanced strength when compared to the equiaxed grain structure, through a series of large-scale molecular dynamics simulations. Then, the corresponding atomistic mechanisms were investigated by checking and comparing the rotations of grains and equivalent strain partitioning in grain boundary atoms. In laminated structure, grain boundary activies were found to be promoted with decreasing lamellar thickness. More importantly, when compared to the equiaxed grain structure at the same length scale (lamellar thickness/grain size), grain boundary activities were found to be inhibited by the laminated structure, which is the main reason for the enhanced strength and the smaller critical size. Besides grain boundary activities, formation of extended dislocations, formation of deformation twins, partial dislocations interacting with formed TBs, partial dislocation blocking by and even transmission through low-angle grain boundaries were also found to play important roles in plastic deformation of nano-laminated structure. The current findings should provide insights for designing stronger and more stable nanostructured metals.Ó 2015 Published by Elsevier B.V.

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Section: Introductionmentioning

confidence: 60%

Smaller critical size and enhanced strength by nano-laminated structure in nickel

Wang

Yuan

2015

Computational Materials Science

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“…In contrast to conventional strengthening strategies using hard foreign phases or structures, NT grain strengthening metals are single-phased and do not contain any phase boundaries, which are usually the sites for crack nucleation, resulting in superior strength-ductility synergy. The enhanced strength-ductility synergy is due to the fact that TBs are not only effective in blocking dislocation motion, but also can act as slip planes to accommodate dislocations [7,8,[16][17][18][19][20]. However, the deformation and the interplaying mechanisms between the larger twin-free grains and smaller bundles of nanotwins in this hierarchical structure still remain unclear.…”

Section: Introductionmentioning

confidence: 99%

“…Such expectation has been realized through the emergence of several strategies in recent decades, such as, solid solution alloying, nanoprecipitate dispersion, transformation and twining-induced plasticity, engineering coherent twin boundaries (TBs) at the nanoscale, bimodal grain size distribution and gradient grained structure [1][2][3][4][5][6][7][8][9][10][11]. Recently, using low-temperature and high-rate severe plastic deformation and subsequent intercritical annealing, a novel strategy for strengthening austenitic steels or copper was introduced [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Tensile deformation mechanisms of the hierarchical structure consisting of both twin-free grains and nanotwinned grains

Yuan

Chen

2014

Philosophical Magazine Letters

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A series of large-scale molecular dynamics simulations have been performed to investigate the tensile properties and atomistic deformation mechanisms for the nanostructured Cu with three typical microstructures: the hierarchical structure consisting of both twin-free grains (d = 70 nm) and grains with bundles of smaller nanotwins (d = 70 nm, λ = 10 nm), the fully nanograined structure and the fully nanotwinned structure. The average flow stress of the hierarchically structure is found to be higher than that calculated by rule of mixture. As compared with that of fully nanograined structure, the strength for the twin-free grains in the hierarchical structure is promoted and gives extra hardening due to the increased dislocation density and dislocation behaviours. It is also found that the nanotwin bundles are more deformable than the twin-free grains in the hierarchical structure according to the deviatoric strain invariant contour. This indicates that the fully nanograined structure cannot only be strengthened to a higher level, but also obtain better ductility by embedded with stronger bundles of smaller nanotwins. Thus, a superior strength-ductility synergy could be obtained in this kind of hierarchical structures, and this novel strategy has also been implemented in bulk austenitic steels or copper by recent experiments.

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“…16,18 Molecular dynamics (MD) simulations have proven to be particularly useful for modeling shock response and providing valuable physical insights and atomic-level deformation mechanisms for experimental results conducted at extreme conditions. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Previous MD studies on the shock response of nanostructured metals were mostly limited on twin-free nanocrystalline (NC) metals. [21][22][23][24][25][26][28][29][30][31][32][33][34] Unlike single crystal, the mechanical properties and microstructure evolutions in the NC metals under shock loading are expected to be affected by the presence of a large volume fraction of grain boundaries (GBs).…”

Section: Introductionmentioning

confidence: 99%

Twin boundary spacing effects on shock response and spall behaviors of hierarchically nanotwinned fcc metals

Yuan¹,

Chen²,

Jiang³

et al. 2014

Journal of Applied Physics

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Atomistic deformation mechanisms of hierarchically nano-twinned (NT) Ag under shock conditions have been investigated using a series of large-scale molecular dynamics simulations. For the same grain size d and the same spacing of primary twins λ1, the average flow stress behind the shock front in hierarchically NT Ag first increases with decreasing spacing of secondary twins λ2, achieving a maximum at a critical λ2, and then drops as λ2 decreases further. Above the critical λ2, the deformation mechanisms are dominated by three type strengthening mechanisms: (a) partial dislocations emitted from grain boundaries (GBs) travel across other boundaries; (b) partial dislocations emitted from twin boundaries (TBs) travel across other TBs; (c) formation of tertiary twins. Below the critical λ2, the deformation mechanism are dominated by two softening mechanisms: (a) detwinning of secondary twins; (b) formation of new grains by cross slip of partial dislocations. Moreover, the twin-free nanocrystalline (NC) Ag is found to have lower average flow stress behind the shock front than those of all hierarchically NT Ag samples except the one with the smallest λ2 of 0.71 nm. No apparent correlation between the spall strength and λ2 is observed in hierarchically NT Ag, since voids always nucleate at both GBs and boundaries of the primary twins. However, twin-free NC Ag is found to have higher spall strength than hierarchically NT Ag. Voids can only nucleate from GBs for twin-free NC Ag, therefore, twin-free NC Ag has less nucleation sources along the shock direction when compared to hierarchically NT Ag, which requiring higher tensile stress to create spallation. These findings should contribute to the understandings of deformation mechanisms of hierarchically NT fcc metals under extreme deformation conditions.

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Shock response of nanotwinned copper from large-scale molecular dynamics simulations

Cited by 37 publications

References 52 publications

Smaller critical size and enhanced strength by nano-laminated structure in nickel

Smaller critical size and enhanced strength by nano-laminated structure in nickel

Tensile deformation mechanisms of the hierarchical structure consisting of both twin-free grains and nanotwinned grains

Twin boundary spacing effects on shock response and spall behaviors of hierarchically nanotwinned fcc metals

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