Nucleation of dislocations from [001] bicrystal interfaces in aluminum

Spearot, Douglas E.; Jacob, Karl I.

doi:10.1016/j.actamat.2005.04.012

Cited by 196 publications

(82 citation statements)

References 31 publications

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“…This deformation mechanism was obvious in many simulation works [14][15][16][17][18][19] , and it was also confirmed by in situ transmission electron microscopy (TEM) experiments 20,21 which showed GBs emitting partial dislocations that formed stacking faults and deformation twins in nanocrystalline Al and Cu. However, experiments at a nanoscale can be very time consuming and costly, and TEM requires samples with a thickness comparable to the grain size, which may induce the structure to relax and thus change the GB structure 1 , so they are very difficult to perform.…”

Section: Introductionmentioning

confidence: 76%

Molecular dynamics study on the grain boundary dislocation source in nanocrystalline copper under tensile loading

Zhang

Lü

Pei

et al. 2015

Mater. Res. Express

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Grain boundary (GB) is the interface between different oriented crystals of the same material, and it can have a significant effect on the many properties of materials. When the average or entire range of grain size is reduced to less than 100 nm, the conventional plastic deformation mechanisms dominated by dislocation processes become difficult and GBmediated deformation mechanisms become increasingly important. One of the mechanisms that can play a profound role in the strength and plasticity of metallic polycrystalline materials is the heterogeneous nucleation and emission of dislocations from GB. In this study, we conducted molecular dynamics simulations to study the dislocation nucleation from copper bicrystal with a number of 〈1 10〉 tilt GBs that covered a wide range of misorientation angles (θ).Wewill show from this analysis that the mechanic behavior of GBs and the energy barrier of dislocation nucleation from GBs are closely related to the lattice crystallographic orientation, GBenergy, and the intrinsic GBstructures. An atomistic analysis of the nucleation mechanisms provided details of this nucleation and emission process that can help us to better understand the dislocation source in GB. Abstract: Grain boundary (GB) is the interface between different oriented crystals of the same material, and it can have a significant effect on the many properties of materials. When the average or entire range of grain size is reduced to less than 100 nm, the conventional plastic deformation mechanisms dominated by dislocation processes become difficult and GB mediated deformation mechanisms become increasingly important. One of the mechanisms that can play a profound role in the strength and plasticity of metallic polycrystalline materials is the heterogeneous nucleation and emission of dislocations from GB. In this study, we conducted molecular dynamics simulations to study the dislocation nucleation from copper bicrystal with a number of <1 1 0> tilt GBs that covered a wide range of misorientation angles (θ). We will show from this analysis that the mechanic behavior of GBs and the energy barrier of dislocation nucleation from GBs are closely related to the lattice crystallographic orientation, GB energy, and the intrinsic GB structures. An atomistic analysis of the nucleation mechanisms provided details of this nucleation and emission process that can help us to better understand the dislocation source in GB.

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Section: Introductionmentioning

confidence: 76%

Molecular dynamics study on the grain boundary dislocation source in nanocrystalline copper under tensile loading

Zhang

Lü

Pei

et al. 2015

Mater. Res. Express

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“…Recent MD simulations have revealed that looplike dislocations nucleate from GBs ͑or the leading partial comes from the GB, but the trailing partial on the same plane arises from the stacking fault left behind by the leading partial͒, 21 or from TBs. 22 This scenario for the formation of dislocation loops is somewhat different from that in conventional coarsegrained metals. For the latter materials, dislocation loops often form from Frank-Read sources inside the grains.…”

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confidence: 95%

Dislocations in nanocrystalline grains

2006

Applied Physics Letters

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Dislocation behavior inside the very small grains of nanocrystalline metals has so far eluded high-resolution transmission electron microscopy ͑TEM͒ examinations. We have identified full dislocations using high-resolution TEM, and the different ways they reside in the 20-30 nm Ni grains. The thermally activated propagation of dislocations, their interactions with twin/grain boundaries and dislocation loops, as well as their storage in nanocrystalline grains are demonstrated and discussed.

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“…Since the crystallographically constructed computational cells may not be in equilibrium, pre-loading relaxations are carried out to obtain their free standing configurations. Following this initial equilibration, approximate quasi-static tensile loading in each deformation increment is achieved though successive loading (at a specified rate of 0.005/ps) and equilibration steps (for 3 ps) using a combination of algorithms for NPT (Melchionna et al, 1993;Spearot et al, 2005) and NVE ensembles (Haile, 1997). The loading process results in a longitudinal strain increment of 0.25% (dilatation increment of $0.75%) per deformation increment.…”

Section: Computational Frameworkmentioning

confidence: 99%

Effect of load triaxiality on polymorphic transitions in zinc oxide

Kulkarni

Sarasamak

Wang

et al. 2008

Mechanics Research Communications

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Molecular dynamics (MD) simulations and first-principles calculations are carried out to analyze the stability of both newly discovered and previously known phases of ZnO under loading of various triaxialities. The analysis focuses on a graphite-like phase (HX) and a body-centered-tetragonal phase (BCT-4) that were observed recently in ½0 1 1 0 -and [0 0 0 1]-oriented nanowires respectively under uniaxial tensile loading as well as the natural state of wurtzite (WZ) and the rocksalt (RS) phase which exists under hydrostatic pressure loading. Equilibrium critical stresses for the transformations are obtained. The WZ ! HX transformation is found to be energetically favorable above a critical tensile stress of 10 GPa in ½01 10 nanowires. The BCT-4 phase can be stabilized at tensile stresses above 7 GPa in [0 0 0 1] nanowires. The RS phase is stable at hydrostatic pressures above 8.2 GPa. The identification and characterization of these phase transformations reveal a more extensive polymorphism of ZnO than previously known. A crystalline structure-load triaxiality map is developed to summarize the new understanding.

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Nucleation of dislocations from [001] bicrystal interfaces in aluminum

Cited by 196 publications

References 31 publications

Molecular dynamics study on the grain boundary dislocation source in nanocrystalline copper under tensile loading

Molecular dynamics study on the grain boundary dislocation source in nanocrystalline copper under tensile loading

Dislocations in nanocrystalline grains

Effect of load triaxiality on polymorphic transitions in zinc oxide

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