摘要:

The structure of dislocations produced by uniaxial compression along the [321] direction of InP single crystals was studied by conventional and high-resolution transmission electron microscopy. The dominating dislocation configuration was found to be the edge dipole belonging to the primary slip system. Nearly all dislocations were dissociated into partial dislocations which could be observed by the weak-beam technique. For the first time, high-resolution lattice-fringe images of edge dipoles in the ⟨112⟩ orientation were obtained. The arrangement of the two dipole dislocations agrees with the theory of linear elasticity.

ISSN:0950-0839    

DOI:10.1080/09500839208207524

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Antiphase boundaries (APBs) may lead to stress homogenization through dislocation/APB interactions and reduce the tendency for intergranular failure in ordered intermetallics. It is shown for ordered iron aluminides that these interactions are influenced by the APB energy. The interactions are maximized at intermediate (≃32 at.%) Al-contents. A high APB energy inhibits the formation of mechanical as well as thermal APBs and contributes to intergranular failure observed at high (40 at.% or more) Al-contents.

ISSN:0950-0839    

DOI:10.1080/09500839208207525

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The possibility of measuring the ‘true’ grain boundary (gb) diffusion coefficient in the so-called C kinetic regime is demonstrated for self-diffusion of silver. Although the criteria for the C-type diffusion have sometimes been experimentally established, we point out the existence of a transitional region in which the classical analysis of gb diffusion profiles (assuming either B- or C-type conditions) is wrong. In this region an alternative method, initially proposed by one of us, is tested. It allows the determination of both the true gb double products and the true gb diffusion coefficients from the experimental profiles. The ratio of these values gives the thickness δ of the gb, and the values obtained justify the usual assumption δ=0·5 nm.

ISSN:0950-0839    

DOI:10.1080/09500839208207526

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Computer simulations of domain coarsening have given excellent agreement with patterns observed experimentally in grain-boundary networks. In contrast, the statistical distribution functions predicted by scaling theories do not agree well with these. We identify the cause of the failure to be a size correlation effect that is a consequence of the topological connectivity of the network. The scaling analysis is accordingly modified and leads to much better agreement with the observations.

ISSN:0950-0839    

DOI:10.1080/09500839208207527

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A single grain of the icosahedral Al—Pd—Mn phase has been extracted from an ingot, slowly cooled from the melt by the Bridgman technique. It has an approximate size of 1·5 cm × 0·5 cm × 0·5 cm and has been fully characterized by various techniques to be of perfect icosahedral symmetry.

ISSN:0950-0839    

DOI:10.1080/09500839208207528

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Enlarged channels in the c direction of α-quartz arising from edge dislocations have been shown to give rise to easy diffusion paths for oxygen-containing molecules. It is demonstrated here that much closer agreement with diffusion experiments in fused silica is obtained for channels in basal dislocations, which could be equally typical of channels in amorphous silica.

ISSN:0950-0839    

DOI:10.1080/09500839208207529

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Helical dislocations composed of very straight ⟨110⟩ line segments (helical shape due to climb from original screw orientation) have been observed by transmission electron microscopy in a region of diamond where growth had occurred on non-faceted, near-{100}-orientation surfaces. Of the six ⟨110⟩ segments forming each helix turn, the two that are pure edge segments normal to the helix axial Burgers vector are about ten times longer than the other segments, thereby producing strong flattening of the helix in the cube plane containing the helix axis. One of 30 such helices counted in a thinned specimen area of 3 × 104μm2was studied in detail. Its major and minor diameters were 5 and 0·6 μm respectively. The helix axis was marked by a line of vesicles, diameters from about 20 to about 130 nm, producing matrix strain contrast attributed to fluid under pressure within the vesicles. Diffraction contrast analysis showed the helix to be of interstitial character, and the vacancy volume emitted to form the helix was found to equal that of vesicles in the same axial length.

ISSN:0950-0839    

DOI:10.1080/09500839208207530

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Cr—C coatings made by physical vapour deposition techniques have been observed by transmission electron microscopy and X-ray diffraction. At a carbon concentration of 40 at.%, the grains are well defined. Their structures consist of very small ordered areas embedded in a vitreous matrix. This structure does not correspond to stable chromium carbides (Cr23C6, Cr7C3or Cr3C2); in fact, this new metastable microstructure has an incommensurate structure related to that of Cr3C2.

ISSN:0950-0839    

DOI:10.1080/09500839208207531

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor