scholarly journals Dislocation Topological Evolution and Energy Analysis in Misfit Hardening of Spherical Precipitate by the Parametric Dislocation Dynamics Simulation

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6368
Author(s):  
Haiwei Zheng ◽  
Jianbin Liu ◽  
Shinji Muraishi
Keyword(s):  
Slip Plane ◽  
Dislocation Line ◽  
Strain Curve ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Slip Mechanism ◽  
Topological Evolution ◽  
Spherical Precipitate ◽  
Primary Slip Plane

Interaction of a single dislocation line and a misfit spherical precipitate has been simulated by the Parametric Dislocation Dynamics (PDD) method in this research. The internal stress inside the precipitate is deduced from Eshelby’s inclusion theory, the stress of the dislocation line and outside the precipitate is calculated by Green’s function. The influence of different relative heights of the primary slip plane on dislocation evolution is investigated, while the cross-slip mechanism and annihilation reaction are considered. The simulation results show three kinds of dislocation topological evolution: loop-forming (Orowan loop or prismatic loop), helix-forming, and gradual unpinning. The dislocation nodal force and the velocity vectors are visualized to study dislocation motion tendency. According to the stress–strain curve and the energy curves associated with the dislocation motion, the pinning stress level is strongly influenced by the topological change of dislocation as well as the relative heights of the primary slip plane.

Dislocation Dynamics Simulations of Dislocation-Particle Bypass Mechanisms

2020 ◽  
Vol 985 ◽  
pp. 35-41
Author(s):  
Jianbin Liu ◽  
Shinji Muraishi
Keyword(s):  
Slip Plane ◽  
Dislocation Line ◽  
Simulation Method ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Dislocation Slip ◽  
Relative Height ◽  
Dislocation Interaction ◽  
Slip Planes ◽  
Line Elements

Effect of precipitation strengthening on metal is generally attributed to the dislocation interaction with the precipitate which acts as the barrier to the dislocation motion on the slip plane. In order to achieve better understanding of critical events of dislocation motion and evolution of dislocation microstructure, we have developed numerical simulation method of dislocation-dislocation and dislocation-particle interactions by means of discrete dislocation dynamics at mesoscopic scale. In this work, Green’s function method is utilized for the computation of the stress fields of dislocation and misfitting particle, and the interaction forces acting on the dislocation. We also proposed the efficient algorithm of the connectivity vector for the dislocation line elements, linked-list data structure, to deal with the flexible interaction of dislocation line elements. The geometrical effect of dislocation slip planes on the dislocation bypassing behaviors is tested by changing the relative height of dislocation slip plane against the center plane of spherical particle, where cross slip event is also taken into account for the dislocation motion. Simulation results show a wide variety of topological changes of dislocation during motion on the slip planes around the particle, which results from the stress field of the particle varied with the relative height between the dislocation slip plane and center plane of particle. The full analysis of the mechanisms of dislocation line bypassing misfitting particle has been explained in this study.

Stochastic Dislocation Dynamics under Creep Conditions in Metals

2002 ◽  
Vol 731 ◽  
Author(s):  
Masato Hiratani ◽  
Hussein M. Zbib
Keyword(s):  
Thermal Fluctuation ◽  
Dislocation Motion ◽  
Cross Slip ◽  
Dislocation Dynamics ◽  
Atomistic Simulations ◽  
Thermal Processes ◽  
New Model ◽  
Slip Mechanism ◽  
Fcc Metals ◽  
Thermally Activated

AbstractA stochastic model is proposed to study dislocation dynamics in metallic single crystals. A Langevin type thermal fluctuation is taken into account for the model to maintain thermal equilibrium. This approach works as Brownian motion of segmental dislocations. Additionally, a new model for implementing the cross slip mechanism in FCC metals is developed based on results obtained by atomistic simulations. This new model is capable of simulating realistic thermal processes such as thermally activated dislocation motion during easy glide or cross slip during cold working of metals.

Grain Size Strengthening in Microcrystalline Copper: A Three-Dimensional Dislocation Dynamics Simulation

2009 ◽  
Vol 423 ◽  
pp. 25-32 ◽  
Author(s):  
Christophe de Sansal ◽  
Benoit Devincre ◽  
Ladislas P. Kubin
Keyword(s):  
Plastic Deformation ◽  
Mechanical Response ◽  
Initial Density ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Key Factors ◽  
Slip Mechanism ◽  
Dynamics Simulations ◽  
Dislocation Sources

This article reports on a study of the microstructure and mechanical response of copper polycrystals with grain sizes in the micrometer range. Three-dimensional dislocation dynamics simulations are used for the first time to investigate grain boundary strengthening and the Hall-Petch law. The methodology, which involves constructing a microcrystalline representative volume element with periodic boundary conditions, is briefly presented. Simulation results show that the initial density of dislocation sources and the cross-slip mechanism are two key factors controlling the heterogeneity of plastic deformation within the grains. At yield, the smaller the grains size, the more plastic deformation is heterogeneously distributed between grains and homogeneously distributed inside the grains. A size effect is reproduced and it is shown that the Hall-Petch exponent decreases from the very beginning of plastic flow and may reach a stable value at strains larger than the conventional proof stress.

Dislocation-Stacking Fault Tetrahedron Interactions in Cu

2002 ◽  
Vol 124 (3) ◽  
pp. 329-334 ◽  
Author(s):  
B. D. Wirth ◽  
V. V. Bulatov ◽  
T. Diaz de la Rubia
Keyword(s):  
Edge Dislocation ◽  
Interatomic Potential ◽  
High Energy ◽  
Dislocation Motion ◽  
Shear Localization ◽  
Stacking Fault ◽  
Dynamics Simulation ◽  
High Energy Particle ◽  
Face Centered Cubic ◽  
Stacking Fault Tetrahedra

In copper and other face centered cubic metals, high-energy particle irradiation produces hardening and shear localization. Post-irradiation microstructural examination in Cu reveals that irradiation has produced a high number density of nanometer sized stacking fault tetrahedra. The resultant irradiation hardening and shear localization is commonly attributed to the interaction between stacking fault tetrahedra and mobile dislocations, although the mechanism of this interaction is unknown. In this work, we present results from a molecular dynamics simulation study to characterize the motion and velocity of edge dislocations at high strain rate and the interaction and fate of the moving edge dislocation with stacking fault tetrahedra in Cu using an EAM interatomic potential. The results show that a perfect SFT acts as a hard obstacle for dislocation motion and, although the SFT is sheared by the dislocation passage, it remains largely intact. However, our simulations show that an overlapping, truncated SFT is absorbed by the passage of an edge dislocation, resulting in dislocation climb and the formation of a pair of less mobile super-jogs on the dislocation.

Dislocation Dynamics in Icosahedral Al-Pd-Mn Single Quasicrystals

2000 ◽  
Vol 643 ◽  
Author(s):  
Ulrich Messerschmidt ◽  
Martin Bartsch ◽  
Bert Geyer ◽  
Lars Ledig ◽  
Michael Feuerbacher ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Stress Exponent ◽  
High Voltage ◽  
Dislocation Dynamics ◽  
Slip Mechanism ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Slip Planes ◽  
Slip Traces

AbstractThe paper reviews results from in situ straining experiments on Al-Pd-Mn single quasicrystals in a high-voltage electron microscope. Slip planes were determined from the orientation and width of slip traces. Dislocations are generated by a specific cross slip mechanism. On some slip traces, dislocations move at two distinctly different velocities. A stress exponent was determined on a single dislocation by observing its displacement under decreasing load. The in situexperiments reveal the behaviour of individual dislocations in a temperature range where the deformation of bulk specimens is strongly affected by recovery.

scholarly journals 2 Dimensional Dislocation Dynamics – A New Technique for the Simulation of Deformation Microtextures

1997 ◽  
Vol 28 (3-4) ◽  
pp. 167-179
Author(s):  
F. Roters ◽  
D. Raabe
Keyword(s):  
Cold Deformation ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
New Technique ◽  
Linear Elastic ◽  
Straight Line ◽  
Simulation Step ◽  
Local Stresses ◽  
A New Technique ◽  
Edge Dislocations

A new technique for the simulation of microtexture evolution during cold deformation which is based on 2 dimensional (2D) dislocation dynamics is presented. In the simulation all involved dislocations are regarded as infinite straight line detects which are embedded in an otherwise isotropic linear elastic medium. As the model is 2D only edge dislocations are considered.In the first simulation step the net local stresses are derived and used to calculate the resulting dislocation motion. Dislocation multiplication, annihilation and reactions are taken into account. Thermal activation is included. In the second step the local misorientations arising from the dislocation distribution are calculated.This method shows in microscopic detail how misorientations are generated and distributed within grains during plastic deformation.

A New Dislocation-Dynamics Model and Its Application in Thin Film-Substrate Systems

2005 ◽  
Vol 875 ◽  
Author(s):  
E.H. Tan ◽  
L.Z. Sun
Keyword(s):  
Thin Films ◽  
Mechanical Performance ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Dislocation Segment ◽  
Dislocation Loops ◽  
Dynamics Model ◽  
Proposed Model ◽  
Simulation Results ◽  
Film Substrate

AbstractBased on the physical background, a new dislocation dynamics model fully incorporating the interaction among differential dislocation segments is developed to simulate 3D dislocation motion in crystals. As the numerical simulation results demonstrate, this new model completely solves the long-standing problem that simulation results are heavily dependent on dislocation-segment lengths in the classical dislocation dynamics theory. The proposed model is applied to simulate the effect of dislocations on the mechanical performance of thin films. The interactions among the dislocation loops, free surface and interfaces are rigorously computed by a decomposition method. This framework can be used to simulate how a surface loop evolves into two threading dislocations and to determine the critical thickness of thin films. Furthermore, the relationship between the film thickness and yield strength is established and compared with the conventional Hall-Petch relation.

Electric features of dislocations and electric force between dislocations

2020 ◽  
pp. 108128652096564
Author(s):  
Yuanjie Huang
Keyword(s):  
Electric Field ◽  
Dielectric Materials ◽  
Dislocation Motion ◽  
Vital Role ◽  
Dislocation Dynamics ◽  
Electric Force ◽  
Fundamental Knowledge ◽  
Large Dielectric Constant ◽  
Net Charges ◽  
First Time

Dislocations and dislocation dynamics are the cores of material plasticity. In this work, the electric features of dislocations were investigated theoretically. An intrinsic electric field around a single dislocation was revealed. In addition to the well-known Peach–Koehler force, it was established that an important intrinsic electric force exists between dislocations, which is uncovered here for the first time and has been neglected since the discovery of dislocations. The electric forces may be large and sometimes could exceed the Peach–Koehler force for metals and some dielectric materials with large dielectric constant. Therefore, the electric force is anticipated to play a vital role in dislocation dynamics and material plasticity. Moreover, an external electric field could exert an electric force on dislocations and a threshold electric field was subsequently discovered above which this force enables dislocations to glide. Interestingly, it was found that some dislocations move in one direction, but others move in reverse in an identical electric field, which is in agreement with experimental observations. Despite dislocation motion under an electric field, to one’s surprise, both edge and screw dislocations do not carry net charges by themselves, which may tackle the long-standing puzzle on the charges of dislocations. These findings may supply people with new fundamental knowledge on dislocations as well as dislocation dynamics, and may assist people in understanding related phenomena.

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