scholarly journals Kink pair production and dislocation motion

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
S. P. Fitzgerald
Keyword(s):  
Pair Production ◽  
Dislocation Motion ◽  
Kink Pair

Atomistic Simulation of kinks for 1/2a Screw Dislocation in Ta

2001 ◽  
Vol 677 ◽  
Author(s):  
Guofeng Wang ◽  
Alejandro Strachan ◽  
Tahir ÇaǦin ◽  
Willam A. Goddard
Keyword(s):  
Activation Energy ◽  
Screw Dislocation ◽  
Formation Energy ◽  
Dislocation Motion ◽  
Migration Energy ◽  
Embedded Atom ◽  
Kink Pair ◽  
Double Kink ◽  
Fixed Boundaries ◽  
Quantum Mechanical Computations

We study the structure and formation energy of kinks in 1/2a<111> screw dislocation in metallic Ta Embedded Atom Model Force Field parameterized using quantum mechanical computations. We studied a/3<112> kinks using a simulation cell containing four dislocations in a quadrupole arrangement. We impose periodic boundary conditions in the directions perpendicular to [111] and fixed boundaries in the [111] direction. We find that two, energetically equivalent, core configurations for the 1/2a<111> dislocation lead to 8 distinguishable single kinks and 16 kink pairs. The different mismatches of core configurations along [111] direction cause variations in kink formation energy. The lowest formation energy of a kink pair is determined to be 0.73 eV. The geometric features of such kink pair have been studied with the help of structural analysis of the atomistic model. We also compare the activation energy for dislocation motion via the double kink mechanism with the activation energy for a rigid dislocation motion from a dipole annihilation simulation. We find that the migration energy for dislocation motion via double kink formation is 0.016 eV/b, which is less than the quarter of the migration energy associated with the kink free motion of a straight dislocation, 0.073 eV/b.

The kink-pair nucleation in edge dislocation motion

2009 ◽  
Vol 11 (3) ◽  
pp. 733-739 ◽  
Author(s):  
Song Yu ◽  
Chong-Yu Wang ◽  
Tao Yu
Keyword(s):  
Edge Dislocation ◽  
Dislocation Motion ◽  
Kink Pair

Internal Friction in Plastically Deformed High-Purity NiAl Single Crystals

1998 ◽  
Vol 552 ◽  
Author(s):  
M. Hirscher ◽  
D. Schaible
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
High Purity ◽  
Formation Enthalpy ◽  
Dislocation Motion ◽  
Zone Melting ◽  
Interstitial Impurity ◽  
Impurity Atoms ◽  
Kink Pair ◽  
Friction Measurements

ABSTRACTHigh-purity stoichiometric NiAl single crystals have been prepared by crucible-free inductive zone melting and afterwards well annealed at temperatures below 1200 K. Internal friction measurements of torsionally deformed single crystals show two relaxation maxima at 500 and 800 K which anneal during the measurement. The first maximum can be assigned to the dislocation motion by kinkpair formation and the annealing to pinning of these dislocations by interstitial impurity atoms. The second maximum is attributed to the Snoek-Köster relaxation of dislocations in the presence of mobile interstitial impurity atoms and the annealing to the pinning of dislocations by vacancies. The kink-pair formation enthalpy in NiAl was estimated.

scholarly journals Temperature and Stress Dependence of Screw Dislocation Mobility in Nb-V-Ta Alloys Using Kinetic Monte Carlo Simulations

2021 ◽  
Vol 8 ◽  
Author(s):  
Xinran Zhou ◽  
Jaime Marian
Keyword(s):  
Monte Carlo ◽  
Screw Dislocation ◽  
Kinetic Monte Carlo ◽  
Waiting Times ◽  
Monte Carlo Model ◽  
High Stress ◽  
Dislocation Motion ◽  
Similar Time ◽  
Kink Pair ◽  
Kink Propagation

In this work we present simulations of thermally-activated screw dislocation motion in Nb-Ta-V alloys for two distinct scenarios, one where kink propagation is solely driven by chemical energy changes, i.e., thermodynamic energy differences, and another one where a migration barrier of 1.0 eV is added to such changes. The simulations have been performed using a kinetic Monte Carlo model for screw dislocation kinetics modified for complex lattice-level chemical environments. At low stresses, we find that dislocation motion in the case with no barrier is controlled by long waiting times due to slow nucleation rates and extremely fast kink propagation. Conversely, at high stress, the distribution of sampled time steps for both kink-pair nucleation and kink propagation events are comparable, resulting in continuous motion and faster velocities. In the case of the 1.0-eV kink propagation energy barrier, at low stresses kink motion becomes the rate-limiting step, leading to slow dynamics and large kink lateral pileups, while at high stresses both kink pair nucleation and kink propagation coexist on similar time scales. In the end, dislocation velocities differ by more than four orders of magnitude between both scenarios, emphasizing the need to have accurate calculations of kink energy barriers in the complex chemical environments inherent to these alloys.

scholarly journals Repulsion leads to coupled dislocation motion and extended work hardening in bcc metals

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
K. Srivastava ◽  
D. Weygand ◽  
D. Caillard ◽  
P. Gumbsch
Keyword(s):  
Work Hardening ◽  
Activation Barrier ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Additional Contribution ◽  
High Symmetry ◽  
Screw Dislocations ◽  
Bcc Metals ◽  
Kink Pair ◽  
Extended Work

Abstract Work hardening in bcc single crystals at low homologous temperature shows a strong orientation-dependent hardening for high symmetry loading, which is not captured by classical dislocation density based models. We demonstrate here that the high activation barrier for screw dislocation glide motion in tungsten results in repulsive interactions between screw dislocations, and triggers dislocation motion at applied loading conditions where it is not expected. In situ transmission electron microscopy and atomistically informed discrete dislocation dynamics simulations confirm coupled dislocation motion and vanishing obstacle strength for repulsive screw dislocations, compatible with the kink pair mechanism of dislocation motion in the thermally activated (low temperature) regime. We implement this additional contribution to plastic strain in a modified crystal plasticity framework and show that it can explain the extended work hardening regime observed for [100] oriented tungsten single crystal. This may contribute to better understanding the increase in ductility of highly deformed bcc metals.

Correlation between Activation Volume and Pillar Diameter for Mo and Nb BCC Pillars

2009 ◽  
Vol 1185 ◽  
Author(s):  
Andreas S. Schneider ◽  
Blythe G. Clark ◽  
Carl P. Frick ◽  
Eduard Arzt
Keyword(s):  
Activation Volume ◽  
Dislocation Motion ◽  
Small Scale ◽  
Compression Tests ◽  
Screw Dislocations ◽  
Loading Rates ◽  
Thermally Activated ◽  
Kink Pair ◽  
Pillar Diameter ◽  
Calculated Activation

AbstractCompression tests with varying loading rates were performed on [001] and [235] oriented small-scale bcc Mo and Nb pillars to determine the contribution of thermally activated screw dislocation motion during deformation. Calculated activation volumes were shown to be in the range of 2 - 9 b3 and by further examination were found to decrease with pillar diameter. This suggests that the kink-pair nucleation of screw dislocations is enhanced by surface effects in the micron and submicron range.

Effect of Improved ThO2 Particle Dispersion in Nickel on High-Temperature Strength

1970 ◽  
Vol 28 ◽  
pp. 444-445
Author(s):  
E. R. Kimmel ◽  
H. L. Anthony ◽  
W. Scheithauer
Keyword(s):  
High Temperature ◽  
Metal Matrix ◽  
Oxide Particle ◽  
Oxide Phase ◽  
Dislocation Motion ◽  
Particle Dispersion ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Oxide Particles ◽  
The Stability

The strengthening effect at high temperature produced by a dispersed oxide phase in a metal matrix is seemingly dependent on at least two major contributors: oxide particle size and spatial distribution, and stability of the worked microstructure. These two are strongly interrelated. The stability of the microstructure is produced by polygonization of the worked structure forming low angle cell boundaries which become anchored by the dispersed oxide particles. The effect of the particles on strength is therefore twofold, in that they stabilize the worked microstructure and also hinder dislocation motion during loading.

DISLOCATION MOTION IN VA METALS STUDIED BY INTERNAL FRICTION

1981 ◽  
Vol 42 (C5) ◽  
pp. C5-67-C5-72
Author(s):  
S. Okuda ◽  
H. Mizubayashi ◽  
N. Kuramochi ◽  
S. Amano ◽  
M. Shimada ◽  
...  
Keyword(s):  
Internal Friction ◽  
Dislocation Motion

EVIDENCE OF NONLINEAR DISLOCATION MOTION IN INTERNAL FRICTION EXPERIMENTS

1987 ◽  
Vol 48 (C8) ◽  
pp. C8-113-C8-117
Author(s):  
H.-J. KAUFMANN ◽  
P. P. PAL-VAL ◽  
V. M. CHERNOV ◽  
D. A. KAMAJEV
Keyword(s):  
Internal Friction ◽  
Dislocation Motion
Sign in / Sign up

Export Citation Format

Share Document