Dislocation dipole formation in deformed crystals

Tetelman, A. S.

doi:10.1016/0001-6160(62)90095-0

Cited by 108 publications

(22 citation statements)

References 11 publications

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“…The first mechanism involves double cross-slip (DCS) of screw dislocations gliding on parallel planes. However, the mechanism must not be confused with the one proposed by Tetelman 83 because the formation of an edge dipole between the incoming dislocations is not observed. Instead, the observed mechanism consists simply in a series of cross-slip events taking place on parallel conjugate planes (Fig.…”

Section: Cyclic Deformation Of Psbsmentioning

confidence: 81%

“…This choice is motivated by the large body of evidence that prismatic loops exist in fcc metals and other crystals structures from very early stages of plastic deformation. 83,84,[106][107][108] Compared to FR sources, the distinctive feature of prismatic loops is that they can be glissile on all four sides and, therefore, they may provide a dynamic source for dislocation multiplication. Moreover, being partially or fully glissile, prismatic loops interacting with the sample boundary give rise naturally to the so-called ''singlearm'' sources, which are believed to contribute a significant portion of plastic strain during compression and tension of micro-pillars.…”

Section: Strain Avalanches In Micro-pillar Compressionmentioning

confidence: 99%

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Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Mohamed

Crosby

et al. 2014

JOM

109

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We present a self-contained review of the discrete dislocation dynamics (DDD) method for the numerical investigation of plasticity in crystals, focusing on recent development and implementation progress. The review covers the theoretical foundations of DDD within the framework of incompatible elasticity, its numerical implementation via the nodal method, the extension of the method to finite domains and several implementation details. Applications of the method to current topics in micro-plasticity are presented, including the size effects in nano-indentation, the evolution of the dislocation microstructure in persistent slip bands, and the phenomenon of dislocation avalanches in micro-pillar compression.

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Section: Cyclic Deformation Of Psbsmentioning

confidence: 81%

Section: Strain Avalanches In Micro-pillar Compressionmentioning

confidence: 99%

Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Mohamed

Crosby

et al. 2014

JOM

109

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“…(ii) Secondly, edge dipoles are formed by a mechanism describable by cross slip and pinching‐off proposed by Tetelman 25 for deformed single crystal Fe‐3 wt% Si. Such mechanism facilitated by a long jog produced by cross slip is best illustrated schematically in Figs.…”

Section: Discussionmentioning

confidence: 99%

“… Schematic illustration for a mechanism of edge dipole formation proposed by Tetelman 25 : (a) two dislocations of same b gliding in parallel planes, (b) reorientation of a portion by applied stress leading to two parallel edge segments of opposite u , and (c) Cross slip resulting in joining of two dislocations, pinching‐off jog forms an edge dipole. …”

Section: Discussionmentioning

confidence: 99%

Deformation Microstructure in (001) Single Crystal Strontium Titanate by Vickers Indentation

Yang

2009

Journal of the American Ceramic Society

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Recent interests on the plastic deformation of strontium titanate (SrTiO3) are derived from its unusual ductile‐to‐brittle‐to‐ductile transition (DBDT). The transition is divided into three regimes (A, B, and C) corresponding to the temperature range of 113–1053 K (−160° to 780°C), 1053 to ∼1503 K (780° to ∼1230°C), and ∼1503–1873 K (∼1230° to 1600°C), discovered by Sigle and colleagues in the MPI‐Stuttgart. We report the dislocation substructures in (001) single crystal SrTiO3 deformed by Vickers indentation at room temperature, studied by scanning and transmission electron microscopy. Dislocation dipoles of screw and edge character are observed and confirmed by inside–outside contrast using ±g‐vector by weak‐beam dark field imaging. They are formed by edge trapping, jog dragging, and cross slip pinching‐off. Similar to dipole breaking off in deformed sapphire (α‐Al2O3) at 1200°C and γ‐TiAl intermetallic at room temperature, the dipoles pinch off at one end, and emit a string of loops at trail. Two sets of slip systems {110}〈〉 and {100}〈011〉 are activated under both 100 g and 1 kg load. The suggestion is that plastic deformation has reached the stage II work hardening, which is characterized by multiplication of dislocations through cross slip, interactions between dislocations, and operating of multiple slip systems.

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“…In turn, a jogged dislocation can be formed as a result of either junction formation or cross-slip. A jogged dislocation can turn into a full dipolar-loop following the classical Johnston-Gilman [32] or Tetelman [33] mechanisms, or from collinear reaction, as shown by Loutat and Johnson in [34]. A comprehensive study of the mechanisms of dipolar-loop formation, interactions, and their role in cyclic plasticity is detailed by the authors in Ref.…”

Section: Debris-dislocation Interaction Mechanismsmentioning

confidence: 99%

The origin of strain avalanches in sub-micron plasticity of fcc metals

Crosby

Erel

et al. 2015

Acta Materialia

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Numerous experimental observations have recently demonstrated two aspects of sub-micron plasticity in nano pillars: (1) the statistical nature of the yield strength, and (2) the existence of dynamic temporal oscillations in the hardening regime. The present work is focused on the second aspect, where we study strain avalanches in nickel nano pillars via a series of 3-D dislocation dynamics (DD) simulations. The computer simulations reveal the existence of a key mechanism that explains the origin of oscillations in post-yield plastic flow in fcc metals. Small dipolar-loops easily form through several cross-slip mechanisms, and then act as internal glide dislocation sources. When dislocations exit pillar boundaries, they leave many dipolar-loops behind. At this stage, the pillar is starved from dislocations and an increase in stress is necessary to keep up with the applied strain rate (hardening stage). At some critical stress level, dipolar-loops become effective Frank-Read sources of new glide dislocations that collectively move in a burst mode, producing strain avalanches (softening stage). The time delay between these two states, which is determined by the average dislocation velocity and pillar diameter, leads to plastic strain oscillations and intermittent dislocation avalanches, consistent with experimental observations.

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Dislocation dipole formation in deformed crystals

Cited by 108 publications

References 11 publications

Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Deformation Microstructure in (001) Single Crystal Strontium Titanate by Vickers Indentation

The origin of strain avalanches in sub-micron plasticity of fcc metals

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