摘要:

The Burgers vectors and geometry of unusual hexagonal dislocation networks in β-brass have been studied by electron microscopy. The results establish conclusively the presence of unresolved superlattice dislocations for which the Burgers vectors are effectively ⟨111⟩ and they further highlight effects of elastic anisotropy on the orientation instability of dislocations and on the nature of dislocation images.

ISSN:0031-8086    

DOI:10.1080/14786436808226166

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Changes in moiré fringe patterns due to dynamical electron diffraction effects have been observed in electron micrographs of epitaxial deposits of silver on molybdenite. These changes occur in regions of the specimen where the film is curved, i.e. in the vicinity of bend contours. The most easily detected change due to diffraction effects is a deviation of the moiré fringes as they obliquely cross a Bragg fringe. The measurable parameters of these deviated regions are in good quantitative agreement with theoretical predictions based on the column approximation for the two-beam case.

ISSN:0031-8086    

DOI:10.1080/14786436808226167

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The movement of a flexible dislocation line through a random array of circular dislocation loops has been studied, using a digital computer, on the basis of the line tension approximation. The dislocation moves on a {111} plane of a face-centred cubic crystal and interacts with {110} prismatic loops by the formation of short junction reactions at the points of intersection. The critical stress required to propagate the dislocation through the loops is μb/1·75L, whereLis the average spacing of the reactive loops cutting the glide plane (one-third of all the loops are reactive). This result is independent of the radius and sense of the loops and the edge-screw character of the glide dislocation. It is slightly increased when the loops are distributed more uniformly, in disagreement with the factor two reduction predicted by Westmacottet al: (1966).

ISSN:0031-8086    

DOI:10.1080/14786436808226168

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

An electron microscopic investigation is described of the effect of high temperature annealing on deformed copper single crystals containing dispersed second phases of either cobalt or silica. Sections of selected orientation cut from the deformed crystals were annealed at 700°C. It was found that specimens deformed into Stage I recovered to the low dislocation densities present before deformation, whereas the crystals deformed to Stage II recovered to form structures consisting of sheets of dislocation networks on the primary slip planes. Several of the basic networks were analysed, and their formation and distribution are discussed in terms of a modification of the deformation structures.

ISSN:0031-8086    

DOI:10.1080/14786436808226169

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Transverse sound waves, in the frequency range 50 to 90 Mc/s, have been propagated through single crystal samples of potassium at 4°K, and the magnetoacoustic effects observed with the magnetic field applied in directions perpendicular (up to 35 kG) and parallel (up to 60 kG) to the propagation direction. For the perpendicular field case, good agreement with the free-electron model was obtained. For propagation along the field, the attenuation and rotation of polarization of linearly polarized waves propagating along [100] were measured, and observations were also made on a [110] oriented crystal. Within experimental error, the evidence agrees with the free-electron model, phonon–helicon interaction effects having been taken fully into account, and there is no definite support for the spin density wave model for the ground state of potassium.

ISSN:0031-8086    

DOI:10.1080/14786436808226170

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

This note points out that, as a consequence of the distinction in solids between surface tension γ and surface energy [sgrave], a strain field generally exists around gas bubbles even in thermodynamic equilibrium. The existence of this strain field leads to a small attraction between bubbles but in typical practical situations this is only significant for bubble migration when they are close together compared to their radii.

ISSN:0031-8086    

DOI:10.1080/14786436808226171

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

It is shown that recent calculations on crack size indicate an inadequacy in the usual crack nucleation condition.

ISSN:0031-8086    

DOI:10.1080/14786436808226172

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

For axial crystals there are only two independent non-zero Grüneisen functions, γ1= γ2and γ3—even for those axial crystals which have non-zero elastic constantscΛμfor Λ = 1, 2, 3 and μ = 4, 5, 6. The results γ1= γ2and γ4= γ5= γ6= 0 follow from the symmetry in the same way as the corresponding results for the thermal expansion coefficients. The expressions for γ1and γ3given by Barron and Munn (1967) are valid for all axial crystals.

ISSN:0031-8086    

DOI:10.1080/14786436808226173

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Atomic Spectra. By W. R. Hindmarsh. (Pergamon Press, 1967.) [Pp. ix + 365.] Price: hard cover £2 5s. 0d., soft cover £1 15s. 0d.

ISSN:0031-8086    

DOI:10.1080/14786436808226174

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor