摘要:

The cathodoluminescence mode in the scanning electron microscope has been used to image bands of dislocations in zinc oxide. It has been shown that dislocations lying on pyramidal, {1012}, planes are generated beneath indentations on {0001} surfaces. Basal plane dislocations lying parallel to the surface are also observed. Indentations on {1100} prismatic surfaces result in slip on {0001} and {0110} planes.

ISSN:0950-0839    

DOI:10.1080/09500839008206484

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Selection rules are derived for delimiting boundaries in the structural unit model of high-angle grain boundary structure. The rules arise from the condition that the structural units fit compatibly together in the boundary plane. Rules are given for pure twist, pure tilt and mixed tilt and twist trajectories in the five-dimensional macroscopic parameter space of grain boundaries. The application of the rules to a series of simulated mixed tilt and twist boundaries is described.

ISSN:0950-0839    

DOI:10.1080/09500839008206485

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Titanium aluminides with a TiAl/Ti3Al two-phase microstructure exhibit mechanical properties which are superior to those for either single-phase TiAl or Ti3Al. The TiAl lamella in the two-phase microstructures show differently oriented TiAl regions which are frequently observed to coexist within the same TiAl lamella. The atomic arrangements of these regions are similar to antiphase domains/{011} twins of TiAl. However, the mechanism by which these regions are formed cannot be derived from the TiAl phase alone. This study suggests that, for two-phase titanium aluminides, Ti3Al has a strong influence on the development of the TiAl microstructure.

ISSN:0950-0839    

DOI:10.1080/09500839008206486

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Electron-beam-induced solid-phase epitaxy (SPE) has been obtained on cross-sections of implanted Si layers, byin situirradiation in the electron microscope, with electrons of energies of 200, 250 and 300 keV, at both room and liquid-nitrogen temperature. The, absence of a transition from SPE to layer-by-layer amorphization (which is observed during ion-beam irradiation on decreasing the temperature below a certain critical value) and the athemal nature of the electron-induced crystallization process below room temperature, indicate that, although elastic displacement is the basic mechanism of both processes, the models which describe ion-beam-induced epitaxy in the temperature range 200≤T≤400°C cannot be extrapolated to explain the results of electron irradiation below room temperature.

ISSN:0950-0839    

DOI:10.1080/09500839008206487

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

X-ray powder diffraction spectra have been measured for melt-spun Al-Si–Mn, Al-Cu–Fe and Al-Li–Cu and Bridgman-grown Al-Li-Cu quasicrystals to investigate the phason strain frozen during the solidification process. For the melt-spun samples, most of the peaks have a shoulder or a tail which is attributed to the anisotropic linear phason strain. The peak shapes for the three melt-spun samples are essentially the same, which indicate that the same type of linear phason is quenched in these samples. In contrast, symmetric peak shapes without shoulders nor tails are seen for the Bridgman-grown Al-Li–Cu, indicating that it contains little linear phason strain.

ISSN:0950-0839    

DOI:10.1080/09500839008206488

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An icosahedral phase is found to precipitate from the ferrite phase of a duplex ferritic-austenitic stainless steel after ageing for > 1000 h at 500°C and to exhibit the following orientation relationships with the ferrite matrix: i5//[110]α, i3//[111]α, i2//[112]α. A brief discussion concerning the experimental results is presented.

ISSN:0950-0839    

DOI:10.1080/09500839008206489

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Diffraction contrast images of a line defect, and splitting and shifting of the higher-order Laue-zone lines induced by the strain field of the line defect, have been observed in the Al76Si4Mn20quasicrystalline icosahedral phase. This phenomenon suggests that convergent-beam electron diffraction can be used to study such defects not only in crystals but also in quasicrystals.

ISSN:0950-0839    

DOI:10.1080/09500839008206490

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The electron diffraction contrast of dislocations in icosahedral Al65Cu20Fe15quasicrystals has been analysed. The displacements in the translational degree of freedom were characterized by a Burgers vector parallel to a twofold quasicrystal axis. Evidence of displacements in the phason degree of freedom was obtained by high-resolution electron microscopy.

ISSN:0950-0839    

DOI:10.1080/09500839008206491

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Structural ordering in annealed anodic oxide films on aluminium has been investigated by microdiffraction. Microdiffraction, allied with the specimen preparation technique of ultramicrotomy, enables the diffraction patterns to be extracted from exceedingly small volumes, about 103nm3, of film material. From this approach, it has been found for the first time that relatively low-temperature annealing of the amorphous anodic oxide films on aluminium results in the development of microcrystalline regions which are too fine to be detected by the conventional X-ray or electron diffraction. The effect of structural ordering on the ionic conductivity in the annealed anodic oxide is also considered.

ISSN:0950-0839    

DOI:10.1080/09500839008206492

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Finnis–Sinclair potentials are developed for computer simulations in which van der Waals type interactions between well separated atomic clusters are as important as the description of metallic bonding at short range. The potentials always favour f.c.c. and h.c.p. structures over the b.c.c. structure. They display convenient scaling properties for both length and energy, and a number of properties of the perfect crystal may be derived analytically.

ISSN:0950-0839    

DOI:10.1080/09500839008206493

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor