On the structure of tilt grain boundaries in cubic metals I. Symmetrical tilt boundaries

1983 ◽  
Vol 309 (1506) ◽  
pp. 1-36 ◽  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Hydrostatic Stress ◽  
Stress Fields ◽  
Boundary Structure ◽  
Structural Elements ◽  
Cubic Metals ◽  
Short Period ◽  
Tilt Boundaries ◽  
Symmetrical Tilt

An atomistic study of tilt grain boundary structures in f.c.c. metals has been made. The principal aim of this study is to understand the structure of long-period (‘general’) tilt boundaries. Boundaries for which Σ< 491 were considered, where Σ is the reciprocal density of coincidence sites. The work is presented in three parts. In this paper three series of atomistic studies of symmetrical tilt boundaries in aluminium and copper are reported. One of the main objectives is to determine whether the stress fields of localized grain boundary dislocations exist in boundaries deviated far from any short-period boundary orientations. On the basis of the results of these studies, a new structural classification of grain boundaries is introduced. Certain boundaries are found to be the fundamental structural elements of other boundaries nearby in the misorientation range. Boundaries that consist of contiguous sequences of one type of fundamental structural elements are called favoured; all other boundaries are called non-favoured. Itis found that favoured boundaries are not always associated with the lowest possible values of Σ and that the same boundaries are not necessarily favoured in all metals with the same crystal structure. With use of the pair interactions to calculate the atomic level stress tensor, the hydrostatic stress fields of the boundaries are displayed. In all cases considered the stress fields of distinct, localized intrinsic grain boundary dislocations were found in non-favoured boundaries. The concept of continuity of boundary structure with misorientation is introduced. It is shown that continuity of boundary structure requires unique boundary structures at all misorientations. With use of this concept it is demonstrated how one can predict the atomic structure and stress field of any non-favoured boundary between two known, successive favoured boundaries. It is also found that an isolated discontinuous change in boundary structure between two successive favoured boundaries may exist, depending on their translation states. Some earlier atomistic studies of tilt boundaries in f.c.c. and b.c.c. metals are reinterpreted in the light of this work.

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.

scholarly journals Effect of Grain Boundary Structure on Grain Boundary Diffusivities in the Au/Ag System

1990 ◽  
Vol 209 ◽  
Author(s):  
Qing Ma ◽  
R. W. Balluffi
Keyword(s):  
Thin Film ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Tilt Angle ◽  
Structural Unit ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Unit Model ◽  
Tilt Boundaries ◽  
Accumulation Method

ABSTRACTGrain boundary chemical diffusivities for a series of symmetric [001] tilt boundaries in the Au/Ag system were measured by the surface accumulation method using newly developed thin-film multi-crystal specimens, in which the grain boundaries feeding the accumulation surface were all of the same type. Possible effects due to segregation at the grain boundaries and surfaces were avoided. CSL boundaries of low-Σ ( i.e., 5, 13, 17, 25) and also more general boundaries with tilt angles between the low-Σ orientations were selected. The diffusivities were found to vary monotonically with tilt angle ( i.e., no cusps at low-Σ's were found) in a manner consistent with the Structural Unit model.

Computed Structures of [001] Symmetrical Tilt Boundaries in Covalently Bonded Materials

1985 ◽  
Vol 63 ◽  
Author(s):  
J. T. Wetzel ◽  
A. A. Levi ◽  
D. A. Smith
Keyword(s):  
Grain Boundary ◽  
Silicon Germanium ◽  
Computer Modelling ◽  
Field Potential ◽  
Boundary Structure ◽  
Bonded Materials ◽  
Grain Boundary Structure ◽  
Covalently Bonded ◽  
Tilt Boundaries ◽  
Symmetrical Tilt

ABSTRACTThe dependence of the structure of (210) and (310) symmetrical [001] tilt boundaries in silicon, germanium and diamond on the Keating covalent force field (potential) has been investigated by computer modelling. We have found that the sensitivity of grain boundary structure to variations of the Keating potential depends on the local atomic arrangement at the grain boundary.

The Interaction of Twin Boundaries with Grain Boundaries in YBa2Cu3O7-δ

1994 ◽  
Vol 357 ◽  
Author(s):  
Jenn-Yue Wang ◽  
Alexander H. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Small Angle ◽  
Driving Force ◽  
The Other ◽  
Twin Boundaries ◽  
Domain Structures ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
System Energy

AbstractTwins in YBa2Cu3O7-δ may be “correlated” at [001] tilt grain boundaries (i.e. twin boundaries from one grain may meet twin boundaries from the other grain in quadruple junctions) and the twins may also be narrowed or “constricted” at the boundary. These effects are more pronounced in the regime of small angle grain boundaries. Based on TEM observations, a tentative threshold misorientation angle of approximately 15° is identified, below which there is a significant driving force reducing the system energy by correlation. The energies of various grain boundary domain structures associated with the twins were estimated on the basis of the dislocations they contain. Success has been obtained in explaining twin correlation in symmetrical tilt boundaries.

On the structure of tilt grain boundaries in cubic metals. III. Generalizations of the structural study and implications for the properties of grain boundaries

1983 ◽  
Vol 309 (1506) ◽  
pp. 55-68 ◽  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Sliding ◽  
Grain Boundary Diffusion ◽  
Boundary Structure ◽  
Necessary Condition ◽  
Reference Structure ◽  
Tilt Boundaries ◽  
Basis Vectors

The results of atomistic calculations of long-period tilt boundaries, which were reported in the preceding parts I and II, are generalized and represented concisely by using two-dimensional lattices, called decomposition lattices. The basis vectors of a decomposition lattice characterize the two fundamental structural elements composing all boundaries in a continuous series of boundary structures. Conversely, the governing condition on the basis vectors is that the boundary structure can change continuously throughout the misorientation range between the boundaries represented by the basis vectors. On assuming that no discontinuous changes in boundary structure occur at non-favoured boundary orientations, and that all boundaries considered are stable with respect to faceting, the governing condition may be used to deduce selection rules for adjacent favoured boundaries and the existence of other favoured boundaries in the misorientation range between two given favoured boundaries. The necessary condition for a discontinuous change in boundary structure to be possible at a non-favoured boundary orientation is formulated. Various aspects of intrinsic and extrinsic grain boundary dislocations (g.b.ds) are treated. It is first shown that the observation of intrinsic g.b.d. networks in the transmission electron microscope does not necessarily imply that the reference structure, preserved by those g.b.ds, is a favoured boundary. Secondly, it is argued that extrinsic g.b.ds provide imperfect steps with Burgers vector components parallel to the boundary that do not exist in equilibrium high-angle tilt boundaries. Finally, an explanation of the physical basis of plane matching dislocations is proposed. A general classification of grain boundary properties is introduced that is based on the results of this investigation of grain boundary structure. It is argued that only properties, such as grain boundary diffusion, that depend exclusively on the atomic structure of the boundary core may be used to detect favoured boundaries. Favoured boundaries exist at those misorientations where such a property is continuous but its first derivative, with respect to misorientation, is not. Grain boundary diffusion, the energy against misorientation relation and grain boundary sliding and migration are then discussed.

On the structure of tilt grain boundaries in cubic metals II. Asymmetrical tilt boundaries

1983 ◽  
Vol 309 (1506) ◽  
pp. 37-54 ◽  
Keyword(s):  
Tilt Boundary ◽  
Boundary Structure ◽  
Reference Structure ◽  
High Angle ◽  
Cubic Metals ◽  
Long Period ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
Atomistic Study

The results of the study of symmetrical tilt boundaries, reported in the preceding part I, are generalized to asymmetrical tilt boundaries. A classification of tilt boundaries in cubic crystals is developed that reveals which boundaries to choose in order to study equilibrium faceting or intrinsic grain boundary dislocations (g.b.ds) accommodating a misorientation. Two series of atomistic studies of asymmetrical tilt boundary structures are presented based on this classification. The first is a study of long-period (27 ^ 97) [110] asymmetrical tilt boundaries in aluminium. The aims of this study are to investigate whether these boundaries are composed of fundamental structural elements, in the same way as was found in part I for symmetrical tilt boundaries, and to see if localized, distinct stress fields of edge g.b.ds exist throughout the misorientation range. With use of the results of this study, and the principle of continuity of boundary structure enunciated in part I, the boundary unit representation of a 27 — 1193 asymmetrical tilt boundary is derived as an example. It is generally found that the Burgers vectors of intrinsic secondary g.b.ds in tilt boundaries, based on favoured boundary reference structures, are non-primitive d.s.c. vectors. The reason for this is given and a simple formula is presented to derive the Burgers vectors of such dislocations for any favoured tilt boundary reference structure. It is pointed out that, in general, very low angle {0 < 1° say) tilt boundaries cannot be described in terms of units from high angle tilt boundaries, and the transition from the low angle to high angle regimes is discussed. The second atomistic study is an investigation of equilibrium faceting of long-period 27 — 3 [110] tilt boundaries with use of an empirical potential for copper. The limi tations of computer simulation methods using periodic border conditions to study faceting are stated. It is shown, however, that the constraints imposed by the use oi periodic border conditions may be used in a positive sense to carry out the Wultt construction, and thereby deduce equilibrium faceting behaviour.

ELECTRON MICROSCOPE STUDIES OF GRAIN BOUNDARY STRUCTURE IN CUBIC METALS

1975 ◽  
Vol 36 (C4) ◽  
pp. C4-17-C4-22 ◽  
Author(s):  
R. W. BALLUFFI ◽  
P. J. GOODHEW ◽  
T. Y. TAN ◽  
W. R. WAGNER
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Boundary Structure ◽  
Cubic Metals ◽  
Grain Boundary Structure

Microstructures of a-axis oriented YBCO films made by hybrid plasma sputtering

1995 ◽  
Vol 10 (4) ◽  
pp. 803-809 ◽  
Author(s):  
W. Ito ◽  
A. Oishi ◽  
S. Mahajan ◽  
Y. Yoshida ◽  
T. Morishita
Keyword(s):  
Electron Microscopy ◽  
Grain Boundary ◽  
Anisotropic Growth ◽  
Plan View ◽  
Plasma Sputtering ◽  
Transmission Electron ◽  
Hybrid Plasma ◽  
Tilt Boundaries ◽  
Symmetrical Tilt ◽  
Twist Boundaries

Microstructures of a-axis oriented YBa2Cu3O7−x films made by newly developed de 100 MHz hybrid plasma sputtering were investigated using transmission electron microscopy (TEM). The films deposited on (110) NdGaO3 and (100) SrTiO3 substrates were found to grow in a perfect epitaxial fashion and with clear interface. The plan view of the TEM image showed that both films were comprised of two kinds of grains having the c axis aligning along two perpendicular directions in the plane with equal probability. The structures of the grain boundary, however, were found to be very different for the two films from the plan views. The film on NdGaO3 showed a lot of twist boundaries, while the film on SrTiO3 consisted of many symmetrical tilt boundaries and basal-plane-faced tilt boundaries. The type of grain boundary is determined by the anisotropic growth rates of the film between c direction and a-b direction.

Structural and Mechanical Properties of Nanophase Ni: A Molecular-Dynamics Study of the Influence of Grain-Boundary Structure on Elastic and Plastic Behavior

1997 ◽  
Vol 492 ◽  
Author(s):  
H. Van Swygenhoven ◽  
M. Spaczér ◽  
A. Caro
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Diffusion Mechanism ◽  
Distribution Functions ◽  
Boundary Structure ◽  
Plastic Behavior ◽  
Self Diffusion ◽  
Common Neighbour ◽  
Grain Boundary Structure

ABSTRACTMolecular dynamics computer simulations of high load plastic deformation at temperatures up to 500K of Ni nanophase samples with mean grain size of 5 nm are reported. Two types of samples are considered: a polycrystal nucleated from different seeds, each having random location and random orientation, representing a sample with mainly high angle grain boundaries, and polycrystals with seeds located at the same places as before, but with a limited missorientation representing samples with mainly low angle grain boundaries. The structure of the grain boundaries is studied by means of pair distribution functions, coordination number, atom energetics, and common neighbour analysis. Plastic behaviour is interpreted in terms of grain-boundary viscosity, controlled by a self diffusion mechanism at the disordered interface activated by thermal energy and stress.

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.

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