Fractal character of slip lines of Cd single crystals

1985 ◽  
Vol 35 (8) ◽  
pp. 897-900 ◽  
Author(s):  
B. Sprušil ◽  
F. Hnilica
Keyword(s):  
Single Crystals ◽  
Slip Lines ◽  
Fractal Character

THE NATURE AND FORMATION OF BANDS OF DEFORMATION IN SINGLE CRYSTALS OF α-PHASE COPPER–ALUMINIUM ALLOYS

1967 ◽  
Vol 45 (2) ◽  
pp. 453-479 ◽  
Author(s):  
J. W. Mitchell ◽  
J. C. Chevrier ◽  
B. J. Hockey ◽  
J. P. Monaghan Jr.
Keyword(s):  
Surface Topography ◽  
Single Crystals ◽  
Aluminium Alloys ◽  
Optical Microscope ◽  
Step Height ◽  
Interference Microscopy ◽  
Slip Lines ◽  
Α Phase ◽  
Transmission Electron ◽  
Characteristic Features

The mechanism of the deformation in tension of [321] axis square-sectioned single crystals of α-phase copper–aluminium alloys with [Formula: see text] and [Formula: see text] surfaces has been studied. Extensive use has been made of interference microscopy and carbon replicas for the determination of the surface topography of the bands of deformation. It has been shown that, in addition to the discrete slip lines which are seen with the optical microscope and in replicas, there is a background of plastic deformation on a much finer scale which is not resolved. The integrated step height across bands of deformation corresponding with this fine slip can be measured on the interferograms. The integrated step height between corresponding points on the opposite [Formula: see text] surfaces was found to be equal. The studies of surface topography were supplemented by work on the nature of the distributions of dislocations within the crystals by etching and transmission electron microscopy. It was found that the dislocations are largely present as interleaved pileups of parallel positive and parallel negative dislocations in near-edge orientations and as closely spaced multipolar distributions. Large pileups of several hundred dislocations have been observed and correlated with surface slip lines. They appear to be introduced as avalanches from surface sources. Characteristic features of this previously unrecognized type of band of deformation have been established and the mechanism proposed for the formation of the bands recalls many of the features of the dynamical model for the multiplication of dislocations discussed by Frank in 1947. The background on which the slip lines are superimposed appears to be due to the limited activation by the shear stress within the band of deformation of a uniform distribution of sources.

Slip Lines in Deformed Zinc Single Crystals

1964 ◽  
Vol 6 (2) ◽  
pp. K69-K72 ◽  
Author(s):  
P. Kratochvíl ◽  
M. Boček
Keyword(s):  
Single Crystals ◽  
Slip Lines

scholarly journals Slip in Single Crystals of Ice

1968 ◽  
Vol 7 (51) ◽  
pp. 479-491 ◽  
Author(s):  
C. J. Readings ◽  
J. T. Bartlett
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Slip Band ◽  
Basal Plane ◽  
Pure Water ◽  
Cross Slip ◽  
Average Thickness ◽  
Bridgman Technique ◽  
Slip Lines ◽  
The Relationship

AbstractRectangular specimens of ice (c.5 cm × 2 cm × 0.5 cm) were cut from large single crystals (c, 10 cm × 5 cm2) grown from pure water by a modified Bridgman technique. When these specimens were deformed under controlled conditions, slip lines which were predominantly parallel to the basal plane became visible. In some cases short. perpendicular segments were also seen which can be interpreted as evidence for cross-slip in ice. Measurements of slip-band spacings were made on silvered “formvar” replicas of some deformed crystals. These measurements showed that “coarse” slip occurred when the resolved shear stress on the basal plane.σ, was greater than about 0.2 bars, and that the average thickness of the slip lamellae,d(cm) was approximately given by Wakahama’s relationship. (σ−0.2)d= 0.45 × 10−3. At lower stresses “fine” slip occurred, and the relationship between the average thickness of the lamellae and the resolved shear stress was more adequately described by Taylor’s formula,σd= 7.2 × 10−5. It is. however, possible that both coarse and fine slip occurred at higher stresses, but that the fine slip was then below the limit of resolution.

scholarly journals Slip in Single Crystals of Ice

1968 ◽  
Vol 7 (51) ◽  
pp. 479-491
Author(s):  
C. J. Readings ◽  
J. T. Bartlett
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Slip Band ◽  
Basal Plane ◽  
Pure Water ◽  
Cross Slip ◽  
Average Thickness ◽  
Bridgman Technique ◽  
Slip Lines ◽  
The Relationship

AbstractRectangular specimens of ice (c. 5 cm × 2 cm × 0.5 cm) were cut from large single crystals (c, 10 cm × 5 cm2) grown from pure water by a modified Bridgman technique. When these specimens were deformed under controlled conditions, slip lines which were predominantly parallel to the basal plane became visible. In some cases short. perpendicular segments were also seen which can be interpreted as evidence for cross-slip in ice. Measurements of slip-band spacings were made on silvered “formvar” replicas of some deformed crystals. These measurements showed that “coarse” slip occurred when the resolved shear stress on the basal plane. σ, was greater than about 0.2 bars, and that the average thickness of the slip lamellae, d (cm) was approximately given by Wakahama’s relationship. (σ−0.2) d = 0.45 × 10−3. At lower stresses “fine” slip occurred, and the relationship between the average thickness of the lamellae and the resolved shear stress was more adequately described by Taylor’s formula, σd = 7.2 × 10−5. It is. however, possible that both coarse and fine slip occurred at higher stresses, but that the fine slip was then below the limit of resolution.

The Microstructure of Shock-Synthesized Diamond

1967 ◽  
Vol 25 ◽  
pp. 324-325
Author(s):  
Lucien F. Trueb
Keyword(s):  
Single Crystals ◽  
Preferred Orientation ◽  
High Magnification ◽  
Texture Pattern ◽  
Shock Process ◽  
New Type ◽  
Diffraction Diagram

A new type of synthetic industrial diamond formed by an explosive shock process has been recently developed by the Du Pont Company. This material consists of a mixture of two basically different forms, as shown in Figure 1: relatively flat and compact aggregates of acicular crystallites, and single crystals in the form of irregular polyhedra with straight edges.Figure 2 is a high magnification micrograph typical for the fibrous aggregates; it shows that they are composed of bundles of crystallites 0.05-0.3 μ long and 0.02 μ. wide. The selected area diffraction diagram (insert in Figure 2) consists of a weak polycrystalline ring pattern and a strong texture pattern with arc reflections. The latter results from crystals having preferred orientation, which shows that in a given particle most fibrils have a similar orientation.

A New Defect in Polyethylene Single Crystals

1973 ◽  
Vol 31 ◽  
pp. 70-71
Author(s):  
E. L. Thomas ◽  
S. L. Sass
Keyword(s):  
Single Crystals ◽  
Screw Dislocation ◽  
Small Distance ◽  
Dipole Model ◽  
Dislocation Dipole ◽  
Chain Folding ◽  
Black And White ◽  
Polymer Crystal ◽  
Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

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