The Influence of Grain Boundary Inclination on the Structure and Energy of Σ3 Twin Boundaries in Copper

1991 ◽  
Vol 238 ◽  
Author(s):  
Ulrich Wolf ◽  
F. Ernst ◽  
T. Muschik ◽  
M. W. Finnis ◽  
H. F. Fischmeister
Keyword(s):  
Grain Boundary ◽  
Twin Boundary ◽  
Boundary Plane ◽  
Embedded Atom Method ◽  
Twin Boundaries ◽  
Atomic Structures ◽  
Embedded Atom ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Small Angle Boundary

ABSTRACTIn a combined theoretical and experimental study, the energies and structures of Σ3 [011] twin boundaries in Cu were investigated. The atomic structures and the grain boundary energies were calculated using the Embedded Atom Method (EAM). Grain boundary energies of welded Cu bicrystals of the same boundary orientations were also obtained by the thermal grooving technique. The atomic structure of the symmetric {211} incoherent twin boundary (SITB) was investigated by High Resolution Transmission Electron Microscopy (HRTEM). Calculated grain boundary energies γb plotted against the inclination angle Φ of the boundary plane relative to the {111} coherent twin boundary (CTB) plane show a mininmm for the CTB (Φ = 0°) and a second minimum at Φ = 82°. This dependence on the inclination is also confirmed by the measured energies. Common to all calculated boundary structures is a microface 11 ing into CTB and SITB segments with a symmetric orientation of the adjacent crystals. Additionally, strong relaxations occur for the grain boundaries near the second energy minimum. This relaxation can be interpreted as a sequence of stacking faults located almost perpendicular to the mean boundary plane. They are terminated by partial dislocations which form a small angle boundary. The most apparent feature of these structures is a bending of the {111} planes running across the boundary. The structural properties were confirmed by HRTEM.

Structure of a Near-Coincidence Σ9 Tilt Grain Boundary in Aluminum

1989 ◽  
Vol 159 ◽  
Author(s):  
M. J. Mills ◽  
G. J. Thomas ◽  
M. S. Daw ◽  
F. Cosandey
Keyword(s):  
Grain Boundary ◽  
Interface Structure ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Grain Boundary Plane ◽  
Transmission Electron ◽  
Symmetric Structures ◽  
Atomically Flat ◽  
Image Simulations

ABSTRACTA systematic study of the structure of tilt grain boundaries in aluminum has been initiated. High resolution transmission electron microscopy is being used to examine the interface structure of several bicrystals with <110> tilt axes. In this paper, we report the structure determination of a grain boundary close to the Σ9 (221) symmetric orientation. The grain boundary plane, which appears wavy at lower magnification, is actually composed of atomically flat microfacets. Two distinct, symmetric structures with (221) boundary planes have been identified within individual microfacets. These observations have been compared with structures calculated using the Embedded Atom Method. The semi-quantitative comparison between the observed and predicted grain boundary structures is accomplished using multislice image simulations based on the calculated structures. The results of these comparisons and the evaluation of the relative energies of the microfacets are discussed.

Atomistic Simulation of Grain Boundaries of the Twin Limited Structure in Ni3Al

1994 ◽  
Vol 364 ◽  
Author(s):  
Maria-Lynn Turi ◽  
R. Zugic ◽  
B. Szpunar ◽  
U. Erb ◽  
G. Palumbo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Atomistic Simulation ◽  
Boundary Energy ◽  
Boundary Plane ◽  
Embedded Atom Method ◽  
Grain Boundary Energy ◽  
Embedded Atom ◽  
Grain Boundary Plane ◽  
Dynamics Simulations

AbstractEmbedded atom method molecular dynamics simulations of low Σ grain boundaries in Ni3Al are presented. The results show that the grain boundary plane has a larger effect on grain boundary energy than the Σ value, rigid body translations and stoichiometry. Assessment of the energies of Σ3n (n ≥ 1) grain boundaries in Ni3Al for various grain boundary planes indicates that only the Σ3 grain boundary is energetically preferred. The implications of this result for the development of the twin limited structure based on energetic considerations are discussed.

The Study of Defects in Metals Using High Resolution Transmission Electron Microscopy and Atomistic Calculations

1990 ◽  
Vol 183 ◽  
Author(s):  
M. J. Mills ◽  
M. S. Daw
Keyword(s):  
Grain Boundary ◽  
Good Description ◽  
Dislocation Core ◽  
Thin Foil ◽  
Core Structure ◽  
Embedded Atom ◽  
Pair Potentials ◽  
Transmission Electron ◽  
Atomistic Calculations ◽  
Stringent Test

AbstractThe coupling of HRTEM with atomistic calculations is described for the study of grain boundaries and dislocations in aluminum. HRTEM images of the Σ9 (221) [110] grain boundary are compared with molecular statics calculations using both the Embedded Atom Method (EAM) and two pair potentials. Comparison between observed and simulated images are shown to serve as a stringent test of the theoretical methods. Atomistic calculations can in turn provide threedimensional information about the defect structure. Using the EAM, it is also possible to account for the effects of thin foil geometries on the minimim energy configuration of defects. While these effects are found to be minimal for grain boundary structures, the influence of the thin-foil geometries on the core structure of the 60° dislocation in aluminum is discussed. These comparisons indicate that the EAM function provides a good description of grain boundary structures, but fails to reproduce the observed dislocation core structure due to a low predicted value of the intrinsic stacking fault energy (SFE) on the (111). In contrast, the pair potentials used in this study provide reasonable SFE values, but appear to be less accurate for the prediction of the Σ9 (221) [110] grain boundary structures.

Mechanism of Stress-Driven Grain Boundary Migration in Nanotwinned Materials

2018 ◽  
Vol 55 (1) ◽  
pp. 21-25 ◽  
Author(s):  
N.V. Skiba
Keyword(s):  
Theoretical Model ◽  
Grain Boundary ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Grain Boundary Migration ◽  
High Angle ◽  
Twin Boundaries ◽  
Critical Stresses ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Abstract Stress-driven grain boundary (GB) migration in ultrafine-grained materials with nanotwinned structure is theoretically described. In the framework of the theoretical model, the stress-driven high-angle GB migration is accompanied by migration of twin boundaries which adjoin this GB. Energetic characteristics and critical stresses of the GB migration accompanied by the twin boundary migration are calculated.

DFT study of hydrogen and helium defects at the (112̄1) twin boundary in hcp scandium

2017 ◽  
Vol 31 (11) ◽  
pp. 1750080
Author(s):  
Kaimin Fan ◽  
Jing Tang ◽  
Li Yang ◽  
Yongqing Hu ◽  
Qingqiang Sun ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Twin Boundary ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Boundary Energy ◽  
Boundary Plane ◽  
Octahedral Interstice ◽  
Tetrahedral Interstice ◽  
Densities Of States ◽  
Formation Energies

We have investigated the grain boundary energy of ([Formula: see text]) twin boundaries, the formation energies of hydrogen (H) and helium (He) defects in tetrahedral (T) and octahedral (O) interstitial sites at the ([Formula: see text]) twin boundary in hcp scandium (Sc) by first-principles calculations based on density functional theory. It is found that the formation energies of the tetrahedral and octahedral interstices H, and tetrahedral interstice He increase significantly towards the ([Formula: see text]) twin boundary plane, while the formation energy of the octahedral interstice He atom near the ([Formula: see text]) twin boundary plane decreases. To analyze these results, we present the electronic densities of states (DOSs) of H, He and their nearest-neighbor Sc (NN-Sc) atoms in several tetrahedral and octahedral configurations. We have also calculated the formation energies of He-vacancy clusters (He[Formula: see text]V) in the Sc grain boundary, which indicates the stabilities of He[Formula: see text]V clusters depend on the variations of the relaxed vacancy volume near the ([Formula: see text]) twin boundary plane.

The Morphology of Grain Boundary Interactions with Twins in YBa2Cu3O7−δ

1993 ◽  
Vol 319 ◽  
Author(s):  
Jenn-Yue Wang ◽  
A. H. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Twin Boundary ◽  
Interfacial Energy ◽  
Coincidence Site Lattice ◽  
The Other ◽  
Twin Boundaries ◽  
Site Lattice ◽  
Dislocation Arrays

AbstractVarious morphologies are observed where twins meet grain boundaries in YBa2Cu3O7−δ. Twins may be “correlated” at the boundary (i.e. twin boundaries from one grain may meet a twin boundary from the other grain in a quadruple junction) and the twins may be narrowed or “constricted” at the boundary. These effects are determined by the interfacial energy. We estimate the energy of the various interfaces by determining the dislocation arrays they contain, using the constrained coincidence site lattice (CCSL) model and Bollmann's O2-lattice formalism. Our approach indicates that there are significant changes in the energy of the interfaces and is thus able to explain the variety of observed morphologies.

An Experimental and Computational Study of the Elastic-Plastic Transition in Thin Films

2001 ◽  
Vol 673 ◽  
Author(s):  
Erica T. Lilleodden ◽  
Jonathan A. Zimmerman ◽  
Stephen M. Foiles ◽  
William D. Nix
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Computational Study ◽  
Strong Dependence ◽  
Embedded Atom Method ◽  
Shear Stresses ◽  
Gradient Plasticity ◽  
Embedded Atom ◽  
Low Dislocation Density ◽  
Dislocation Sources

ABSTRACTNanoindentation studies of thin metal films have provided insight into the mechanisms of plasticity in small volumes, showing a strong dependence on the film thickness and grain size. It has been previously shown that an increased dislocation density can be manifested as an increase in the hardness or flow resistance of a material, as described by the Taylor relation [1]. However, when the indentation is confined to very small displacements, the observation can be quite the opposite; an elevated dislocation density can provide an easy mechanism for plasticity at relatively small loads, as contrasted with observations of near-theoretical shear stresses required to initiate dislocation activity in low-dislocation density materials. Experimental observations of the evolution of hardness with displacement show initially soft behavior in small-grained films and initially hard behavior in large-grained films. Furthermore, the small-grained films show immediate hardening, while the large grained films show the ‘softening’ indentation size effect (ISE) associated with strain gradient plasticity. Rationale for such behavior has been based on the availability of dislocation sources at the grain boundary for initiating plasticity. Embedded atom method (EAM) simulations of the initial stages of indentation substantiate this theory; the indentation response varies as expected when the proximity of the indenter to a Σ79 grain boundary is varied.

Structure and Dissociation of 15° Tilt Boundaries in Germanium

1983 ◽  
Vol 25 ◽  
Author(s):  
W. Skrotzki ◽  
H. Wendt ◽  
C. B. Carter ◽  
D. L. Kohlstedt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundary ◽  
Czochralski Method ◽  
Boundary Plane ◽  
First Order ◽  
Grain Boundary Plane ◽  
Transmission Electron ◽  
Theoretical Predictions ◽  
Tilt Boundaries

ABSTRACTThe structure and dissociation of grain boundaries in Ge bicrystals, grown by the Czochralski method, have been analyzed by visible light and transmission electron microscopy. The seed crystals were oriented to yield either a symmetric or an asymmetric grain boundary plane with a 15° rotation about a common <110> direction. The asymmetric boundary, with a {111} boundary plane, dissociated along most of its length into a first order twin boundary (Σ 3) and a symmetric 55° grain boundary (Σ 41c). The symmetric 15° boundary is composed of an array of Lomer dislocations. Contrary to theoretical predictions, this boundary is stable.

Twin Boundaries and Stacking Faults in Monazite (Monoclinic LaPO4)

2004 ◽  
Vol 819 ◽  
Author(s):  
Randall S. Hay
Keyword(s):  
Room Temperature ◽  
Deformation Twin ◽  
Stacking Faults ◽  
Temperature Deformation ◽  
Formation Mechanisms ◽  
Twin Boundaries ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Fault Migration ◽  
Lattice Formation

AbstractMonazite (LaPO4) was indented at room temperature. Deformation twin boundaries and stacking faults were characterized by high resolution transmission electron microscopy. Kinked deformation twins were also characterized and analyzed. Three types of stacking faults associated with climb-dissociated partial dislocations were observed. Two were found on twin boundaries, and a third in the lattice. Formation mechanisms are discussed. The superimposition of stacking faults along twin boundaries during deformation twinning and the glide of climb-dissociated partial dislocations allowed by stacking fault migration are discussed. The possible relationship between the formation mechanisms for these defects and the low- temperature recrystallization and self-annealing of defects in monazite is considered.

Preferred inclinations of grain boundaries in epitaxially grown bicrystalline thin films of gold

1978 ◽  
Vol 36 (1) ◽  
pp. 434-435
Author(s):  
F. Cosandey ◽  
Y. Komem ◽  
C. L. Bauer
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Energy ◽  
Boundary Plane ◽  
Boundary Structure ◽  
Structural Elements ◽  
Grain Boundary Energy ◽  
Transmission Electron ◽  
A New Technique ◽  
Misorientation Of Grains

Energy and concomitant structure of grain boundaries are related to inclination of the boundary plane as well as misorientation of grains defining the boundary. Although increasing information is becoming available on variation of grain boundary energy with misorientation, still relatively little is known about variation of grain boundary energy with inclination. The purpose of this research is to examine preferred inclinations of preselected grain boundaries in gold by transmission electron microscopy (TEM) in order to identify principal structural elements and to relate these elements to the energy of special grain boundary configurations.Grain boundaries examined in this research are produced by a new technique involving vapor deposition of gold on common (001) surfaces of bicrystalline substrates of NaCl, characterized by preselected rotation about a common [001] axis, and subsequent epitaxial growth to form a bicrystalline thin film. These films are then removed from their substrates and examined by TEM. The principal advantage of this technique is that the grain boundary is formed during the deposition and growth process, thus resulting in a more perfect boundary structure while eliminating necessity of a separate bonding operation.

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