scholarly journals Burgers Vectors in Secondary Grain Boundary Dislocation Structures for near S9, S27 and S81 Boundaries

1985 ◽  
Vol 38 (3) ◽  
pp. 449 ◽  
Author(s):  
CT Forwood ◽  
LM Clarebrough
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Micrographs ◽  
Image Matching ◽  
Boundary Dislocation

The Burgers vectors of secondary grain boundary dislocations, forming networks in near ~9, ~27a, ~27b and ~81a grain boundaries in polycrystalline specimens of a Cu +6 at. % Si alloy, have been determined using the technique of image matching, which involves a comparison of experimental and theoretical electron micrographs. In all cases, the Burgers vectors of the secondary grain boundary dislocations were found to be vectors of the DSC lattice corresponding to the appropriate CSL orientation. Further, in most cases, the Burgers vectors were found to be basis DSC vectors.

The Slip Transfer Process Through Grain Boundaries in HCP Ti

1993 ◽  
Vol 319 ◽  
Author(s):  
J. Shirokoff ◽  
I.M. Robertson ◽  
H.K. Birnbaum
Keyword(s):  
Grain Boundary ◽  
Slip System ◽  
Grain Boundaries ◽  
Slip Systems ◽  
Boundary Dislocation ◽  
Burgers Vector ◽  
Slip Transfer ◽  
Transmission Electron ◽  
Fcc Materials

AbstractInformation on the mechanisms of slip transfer across grain boundaries in an HCP α-Ti alloy has been obtained from deformation experiments performed In situ in the transmission electron microscope. Initially, lattice dislocations are accommodated within the grain boundary until a critical local dislocation density is reached. The boundary then responds by activating slip in the adjoining grain on the slip system experiencing the highest local resolved shear stress and producing the residual grain-boundary dislocation with the smallest Burgers vector. Slip on secondary slip systems may be initiated provided they reduce the magnitude of the Burgers vector of, or eliminate, the residual grainboundary dislocation. The selection rules used to predict the slip system activated by the grain boundary are the same as apply in ordered and disordered FCC materials.

Effect of Grain Boundary Ledges on the Flow Stress in Nickel

1977 ◽  
Vol 35 ◽  
pp. 284-285
Author(s):  
Eswarahalli S. Venkatesh ◽  
L.E. Murr
Keyword(s):  
Flow Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Polycrystalline Materials ◽  
Structure And Properties ◽  
Boundary Dislocation ◽  
Dislocation Source ◽  
Type Relation ◽  
Ledge Density ◽  
Boundary Ledge

In a recent paper1 it was shown that grain boundary ledge structure can be changed by appropriate thermomechanical treatments. Grain boundary ledges are sources of dislocations2. Recently the effects of grain boundaries on the mechanical properties in metals and alloys were studied3,4. For a few years now the structure and properties of grain boundaries and their control have been considered as a means of strengthening polycrystalline materials5,6. Li5 has derived a Hall-Petch type relation in terms of grain boundary dislocation source (ledge) density, m, in the form where L is the grain size, σ0 and α are constants, and G ana b have the usual meaning. The influence of grain boundary ledge density, on the flow stress is considered in this paper.In the present work, pure (99.98%) nickel sheet mill rolled (hot) to 0.022 in. thick was used.

Grain boundary dislocation networks in YBa2Cu3O7-δ

1988 ◽  
Vol 46 ◽  
pp. 622-623
Author(s):  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Boundary Dislocation ◽  
Contrast Imaging ◽  
Plane Normal ◽  
Transmission Electron ◽  
Key Characteristics ◽  
Regular Networks ◽  
Beam Diffraction

The crystallography, morphology, and structure of typical grain boundaries in sintered samples of the high temperature superconducting oxide YBa2Cu3O7-δ (123) have been investigated by transmission electron microscopy using two-beam diffraction contrast imaging and selected area diffraction techniques.Since most of the grains present in sintered samples of 123 are plate shaped with the plate normal parallel to the c-axis of the crystal, the grain boundaries can be divided into two classes: (a) those for which the boundary plane normal is nearly parallel to the c-axis of one of the abutting grains (basal-plane-faced boundaries), and (b) those which are not basal-planefaced. Regular networks of grain boundary dislocations have been observed in high-angle grain boundaries of both types. These networks extend the length of the imagable portion (i.e., sufficiently thin) of the boundary without changing their basic geometry. The line contrast produced by the networks shows several of the key characteristics of dislocation images.

Plasticity of grain boundaries

1980 ◽  
Vol 295 (1413) ◽  
pp. 166-167
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Slip Bands ◽  
Grain Boundary Structure ◽  
Polycrystalline Body

Plastic deformation of a polycrystalline body requires the propagation of slip bands from one grain to another. This process may occur by dislocations being forced through boundaries, new dislocations being nucleated in or adjacent to the grain boundary, or pinned dislocations being released. Whichever of these processes dominates, it is necessary for the grain boundary structure to be reshaped, and in previous work (Pond & Smith, 1977; Pond et al . 1977) we have described experimental observations of grain boundary dislocation processes involved in such activity.

scholarly journals Dislocation strain as the mechanism of phonon scattering at grain boundaries

2016 ◽  
Vol 3 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Hyun-Sik Kim ◽  
Stephen D. Kang ◽  
Yinglu Tang ◽  
Riley Hanus ◽  
G. Jeffrey Snyder
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Boundary Dislocation ◽  
Frequency Dependent ◽  
Strain Model ◽  
Model Frequency ◽  
Thermal Conductivities

Thermal conductivities of polycrystalline thermoelectric materials are satisfactorily calculated by replacing the commonly used Casimir model (freqeuncy-independent) with grain boundary dislocation strain model (frequency-dependent) of Klemens. It is demonstrated that the grain boundaries are better described as a collection of dislocations rather than perfectly scattering interfaces.

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