On ‘interface-plane scheme’ and symmetric grain boundaries

2012 ◽  
Vol 227 (4) ◽  
pp. 199-206 ◽  
Author(s):  
Adam Morawiec
Keyword(s):  
Grain Boundaries ◽  
Interface Plane ◽  
Plane Scheme

Links Between the Interface Plane Scheme and Grain Boundary Properties

1996 ◽  
Vol 458 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Knowledge Base ◽  
Boundary Plane ◽  
Interface Plane ◽  
Experimental Knowledge ◽  
High Occurrence ◽  
Boundary Properties ◽  
Plane Scheme

ABSTRACTThis paper describes the current experimental knowledge base concerning the geometry and property relationships at the gram boundary plane. In order to analyse the data the interface-plane scheme is used, and its application is described here. The most important points to emerge from the data are that particular boundary properties - energy, mobility, segregation, precipitation and cracking - correlate with boundary plane types. Recent data illustrating the high occurrence of asymmetrical tilt grain boundaries and importance of low-index grain boundary planes are discussed in more detail.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

The (111)/(100) interface in cubic materials

1994 ◽  
Vol 52 ◽  
pp. 522-523
Author(s):  
Sundar Ramamurthy ◽  
C. Barry Carter
Keyword(s):  
Grain Boundaries ◽  
Coincident Site Lattice ◽  
Interface Plane ◽  
Polycrystalline Thin Films ◽  
Cubic Materials ◽  
Wide Range ◽  
Low Energies ◽  
Cubic System ◽  
The Stability ◽  
Microscopy Techniques

Descriptions of crystalline interfaces have concentrated on grain boundaries using the framework of the coincident-site-lattice (CSL) model. Within this framework, an interface-plane scheme can be formulated to describe all types of crystalline interfaces, homophase or heterophase. Low Σ values, the inverse density of CSL sites, are associated with boundaries with low energies. However, stable interfaces that cannot be described by such models are often found experimentally in thin-film, semi-bulk and bulk forms. The stability of such interfaces thus depends on factors other than the geometry of the interface.Crystallography of the (111)/(100) interface in the cubic system has been studied extensively in a wide range of materials using different electron-microscopy techniques. Recently, this interface has spurred interest in the growth of tri-crystal microstructures to study junctions in polycrystalline thin films where three identical grain boundaries meet along a line. In this paper we review the (111)/(100) interface showing different examples from our recent work.

scholarly journals Hydrogen behaviour at twist {110} grain boundaries in α -Fe

2017 ◽  
Vol 375 (2098) ◽  
pp. 20160402 ◽  
Author(s):  
Eunan J. McEniry ◽  
Tilmann Hickel ◽  
Jörg Neugebauer
Keyword(s):  
Grain Boundaries ◽  
Coincidence Site Lattice ◽  
Critical Role ◽  
Tight Binding ◽  
Structural Defects ◽  
Interface Plane ◽  
Extended Defects ◽  
Binding Model ◽  
Σ3 Boundary

The behaviour of hydrogen at structural defects such as grain boundaries plays a critical role in the phenomenon of hydrogen embrittlement. However, characterization of the energetics and diffusion of hydrogen in the vicinity of such extended defects using conventional ab initio techniques is challenging due to the relatively large system sizes required when dealing with realistic grain boundary geometries. In order to be able to access the required system sizes, as well as high-throughput testing of a large number of configurations, while remaining within a quantum-mechanical framework, an environmental tight-binding model for the iron–hydrogen system has been developed. The resulting model is applied to study the behaviour of hydrogen at a class of low-energy {110}-terminated twist grain boundaries in α -Fe. We find that, for particular Σ values within the coincidence site lattice description, the atomic geometry at the interface plane provides extremely favourable trap sites for H, which also possess high escape barriers for diffusion. By contrast, via simulated tensile testing, weakly trapped hydrogen at the interface plane of the bulk-like Σ3 boundary acts as a ‘glue’ for the boundary, increasing both the energetic barrier and the elongation to rupture. This article is part of the themed issue ‘The challenges of hydrogen and metals’.

scholarly journals Application of Microtexture Measurements in the SEM to Grain Boundary Parameters

1993 ◽  
Vol 20 (1-4) ◽  
pp. 231-242 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Data Collection ◽  
Grain Boundary ◽  
Electron Back Scatter Diffraction ◽  
Boundary Plane ◽  
Geometrical Parameters ◽  
Interface Plane ◽  
Boundary Misorientation ◽  
Grain Boundary Plane ◽  
Grain Boundary Misorientation ◽  
Plane Scheme

This paper discusses how microtexture data, i.e. individual orientations which are measured on a grain and environmentally specific basis, are applied to grain boundary geometrical parameters. Three main areas are addressed: the “interface-plane” scheme for specifying the five degress of freedom of a boundary, comparisons of experimental techniques for data collection, and representation of grain boundary misorientations in Rodrigues-Frank space. Particular attention is paid to electron back-scatter diffraction as a method of probing grain boundary misorientation and the crystallographic orientation of the grain boundary plane.

The Interaction Between Dislocations and Lamellar Grain Boundaries in Pst γ Tiai

1993 ◽  
Vol 319 ◽  
Author(s):  
S. Rao ◽  
C. Woodward ◽  
P.M. Hazzledine
Keyword(s):  
Grain Boundaries ◽  
Soft Mode ◽  
Dislocation Core ◽  
Dislocation Motion ◽  
Core Structure ◽  
Interface Plane ◽  
Atomic Step ◽  
Screw Dislocations ◽  
Dislocation Glide ◽  
Eam Potential

AbstractIn lamellar TiAl the flat-plate geometry of the grains, the barriers to deformation across the grain boundaries and the coherency stresses all contribute to a marked anisotropy in the yield and fracture stresses of the material. Both yield and fracture occur at low stresses when the deformation is within the lamellae (soft mode) and they occur at high stresses when the deformation crosses the lamellae (hard mode). The anisotropy is enhanced by a new effect which can soften the soft mode and harden the hard mode: the geometry of the lamellar boundary produces degeneracies in the planar fault energies at the interfaces which enhance the mobilities of dislocations on these interfaces. These degeneracies modify the core structure of dislocations on or near the interfaces, consequently soft mode dislocations can dissociate widely and move more easily when their glide plane is contained in the interface. Hard mode dislocations can substantially reduce their core energies when intersecting a γ/γ interface, and subsequently become immobilized, by cross slipping on to the interface plane. This paper presents a discussion of the geometry and relative energies of the γ/γ interfaces using elements of Bollman O-lattice theory. In order to investigate the influence of the interfaces on dislocation core structure we have fit an empirical Embedded Atom Method (EAM) potential to the structural and elastic properties of bulk L10 TiAl. The mobility and core structure of the twinning dislocation at the 180° interface and the perfect, 1/2<110] screw dislocation at the 60° and 120° interfaces were calculated using molecular statics within the EAM. We have also studied the influence of one and two atomic step ledges on dislocation mobility in the 120° interface. We find in general that dislocations are more glissile on the γ/γ interfaces, as compared to bulk TiAl and that ledges are weak barriers to dislocation glide. The interfaces themselves are strong barriers to dislocation motion in the hard mode. We find that the 1/2<110] screw dislocations gliding on conjugate {111} planes are trapped at these interfaces, as a result of lower core energies for screw dislocations lying in the interface.

Diffraction effects from interfaces

1987 ◽  
Vol 45 ◽  
pp. 38-41
Author(s):  
J. M. Vitek
Keyword(s):  
Grain Boundaries ◽  
Theoretical Work ◽  
Real Space ◽  
Periodic Array ◽  
Interface Plane ◽  
Fine Scale ◽  
Structural Distortions ◽  
New Information ◽  
Electron Microscopes ◽  
Diffraction Effects

The ability of electron microscopes to examine the structure and composition of materials on a very fine scale has paved the way for a renewed interest in examining the structure at interfaces and grain boundaries. Complemented by theoretical work on the structure of interfaces, much new information has become available. Among the various techniques available for studying the structure at interfaces, diffraction experiments have proved to be very useful. It has been shown, for example, that a periodic array of defects exists within the plane of the interface, leading to extra reflections in the plane of the interface. More recently, the diffraction behavior in the direction perpendicular to the interface plane has been examined. By considering diffraction effects in this direction only (to be referred to as the z direction in real space and the L direction in reciprocal space), information can be derived on the structural distortions in this direction near the interface without interference from any arrays of defects within the interface plane.

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

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