Interaction Between Lattice Dislocations and Grain Boundaries In Ordered Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
B.J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.W. Schapink
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Shockley Partial Dislocation ◽  
Screw Dislocations ◽  
Applied Shear Stress ◽  
Tilt Boundaries

ABSTRACTThe interaction of 1/2<1 1 0> screw dislocations with symmetric [1 1 0] tilt boundaries was investigated by atomistic simulations using many-body potentials representing ordered compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the interaction in ordered compounds shows similarities to the interaction in fcc.

Atomistic Simulations of [001] Symmetric Tilt Boundaries in Ni3Al

1986 ◽  
Vol 81 ◽  
Author(s):  
S. P. Chen ◽  
A. F. Voter ◽  
D. J. Srolovitz
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Simulation Study ◽  
Atomistic Simulation ◽  
Atomistic Simulations ◽  
Boundary Composition ◽  
Symmetric Tilt ◽  
Tilt Boundaries ◽  
Cohesive Energies

AbstractWe report a systematic atomistic simulation study of [001] symmetric tilt grain boundaries (GB) in Ni3Al, Ni, and Al. We found that the grain boundary energies and cohesive energies of Ni3Al and pure fcc Ni are approximately thesame. Grain boundary energies aid cohesive energies in Ni3Al depends stronglyon the grain boundary composition. The Al-rich boundaries have highest grain boundary energies and lowest cohesive energies. This offers an explanation for the stoichiometric effect on the boron ductilization

Atomic Structure Calculations of the Interaction between Lattice Dislocations and Grain Boundaries

1990 ◽  
Vol 193 ◽  
Author(s):  
B. J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F. W. Schapink
Keyword(s):  
Grain Boundaries ◽  
Atomic Structure ◽  
Many Body ◽  
Screw Dislocations ◽  
Symmetric Tilt ◽  
Ordered Alloys ◽  
Atomistic Calculations ◽  
Tilt Boundaries ◽  
Atomic Structure Calculations ◽  
Structure Calculations

ABSTRACTThe interaction between screw dislocations and [1 1 0] symmetric tilt boundaries is investigated by atomistic calculations. In order to study the differences between fcc and ordered alloys and to study the effect of increasing ordering tendency, many-body potentials representing Cu, Cu3Au and Ni3Al were used. For the ordered alloys, the different possible ordering configurations of the boundaries that were studied are discussed.

Interaction between Lattice Dislocations and Grain Boundaries in Ordered Compounds: Theory and Experiment

1990 ◽  
Vol 186 ◽  
Author(s):  
B. J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.D. Tichelaar ◽  
F.W. Schapink
Keyword(s):  
Atomistic Simulation ◽  
Coherent Twin Boundary ◽  
Many Body ◽  
Screw Dislocations ◽  
Transmission Electron ◽  
Applied Shear Stress ◽  
Tilt Boundaries ◽  
In Situ Observations ◽  
Theory And Experiment

AbstractThe interaction between a screw dislocation and symmetric [1 1 0] tilt boundaries under the influence of an applied shear stress was investigated by atomistic simulation. Many-body potentials representing Cu and Ni3Al were used for the description of the interatomic forces. A comparison will be made with in-situ observations in a transmission electron microscope of the interaction of screw dislocations with a coherent twin boundary.

Freeze-fracture TEM of the helical smectic A* phase

1992 ◽  
Vol 50 (1) ◽  
pp. 278-279
Author(s):  
K.J. Ihn ◽  
R. Pindak ◽  
J. A. N. Zasadzinski
Keyword(s):  
Liquid Crystal ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Freeze Fracture ◽  
Smectic Phase ◽  
Layer Spacing ◽  
Screw Dislocations ◽  
Smectic A ◽  
Smectic Phases ◽  
Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

DISSOCIATED DISLOCATIONS AND THE SCHMID LAW OF RESOLVED SHEAR STRESS IN b.c.c. METALS

1967 ◽  
Vol 45 (2) ◽  
pp. 939-943 ◽  
Author(s):  
F. R. N. Nabarro ◽  
T. R. Duncan
Keyword(s):  
Shear Stress ◽  
Partial Dislocation ◽  
Shear Stresses ◽  
Screw Dislocations ◽  
The Core

The dissociation of screw dislocations on [Formula: see text] planes in a b.c.c. metal can lead to unequal shear stresses for glide in opposite directions, while dissociation on [Formula: see text] planes cannot. Glide will occur in the former configuration only if the radius of the core of a partial dislocation exceeds [Formula: see text] of the radius of a symmetrically dissociated dislocation. If this condition is not satisfied, one partial dislocation runs to infinity before the remaining two coalesce.

Dislocation—like Defects in an Amorphous Lennard—jones Solid

1986 ◽  
Vol 82 ◽  
Author(s):  
L. T. Shi ◽  
P. Chaudhari
Keyword(s):  
Computer Simulation ◽  
Shear Stress ◽  
Screw Dislocations ◽  
Lennard Jones ◽  
Simulation Techniques ◽  
Applied Shear Stress ◽  
Computer Simulation Techniques

ABSTRACTIt has been found, using computer simulation techniques, that both edge and screw dislocations can be stably introduced into an amorphous Lennard-Jones solid, and can be moved through the model under an applied shear stress.

The Structure of Dislocations in Low-Angle Grain Boundaries in the Diamond Cubic Lattice

1981 ◽  
Vol 5 ◽  
Author(s):  
C.B. Carter
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Burgers Vector ◽  
Cubic Lattice ◽  
Partial Dislocations ◽  
Tilt Boundaries ◽  
P Type ◽  
Twist Boundaries

ABSTRACTDislocations in low-angle tilt boundaries exhibit a wide variety of Burgers vector including a/2<112> a<001> and a<111>. The dislocations are usually dissociated: Shohkley, stair-rod and Frank partial dislocations may each be formed together with associated intrinsic and extrinsic stackingfaults. Dislocations in low-angle {111} twist boundaries are usually assumed to dissociated by a glide mechanism to give two types of extended nodes, known as P–type and K–type, which contain intrinsic and extrinsic stacking-faults respectively. It is shown that dissociation by climb actually occurs for both types of grain boundary.

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