摘要:

An aluminium-2% magnesium alloy solidified to a pronounced sub-structure shows, when tested in tension, at approximately 300°C an abrupt change in the mode of plastic deformation. Above this ‘transition’ temperature, where the flow stress maintains a steady value up to high strains, restoration is suggested to occur by means of a ‘stress-induced’ knitting process combined with dislocation annihilation, when vacancies created in the process are rapidly destroyed at high temperatures. The structure remains all the time polygonal, consisting of cells separated by two-dimensional dislocation networks which have a remarkable regularity.

ISSN:0031-8086    

DOI:10.1080/14786436808218185

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A recent calculation of the explicit temperature dependence of the quasiharmonic second-order elastic constants of the f.c.c. lattice with arbitrary nearest-neighbour central forces is used to calculate the bulk modulus, polycrystalline shear modulus and the polycrystalline longitudinal wave velocity for argon. The numerical calculations are based on a Mie-Lennard-Jones (12–6) potential and cover the range 0<T ≲ 60°K. There is reasonable agreement with available experimental data. At the highest temperatures comparison of the theoretical and experimental bulk modulus suggests that higher order anharmonic effects may be important for solid argon.

ISSN:0031-8086    

DOI:10.1080/14786436808218186

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Direct observations of the energy loss spectra from phase precipitates in Al + 4 wt. % Cu alloy have been made by means of combined electron microscopy and energy analysis in order to examine the difficulties involved in using this technique for qualitative microanalysis of precipitated phases. It is concluded that a microanalysis will be completely reliable if the peaks in the characteristic energy loss spectra (0 to 50 ev) from matrix and precipitate are reasonably well defined and well separated. If this is not so, then the precipitate must extend from the top to the bottom surface of the electron microscope specimen before any reliable information can be obtained. As far as the extension of the technique to the study of segregation effects is concerned, it is concluded that the boundaries at which such effects are expected must be aligned parallel to the incident electron beam.

ISSN:0031-8086    

DOI:10.1080/14786436808218187

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Effects related to the terms αi j kHiEjEkand βi j kEiHjHkin the Gibbs function are discussed, especially in relation to the measurement by O'Dell, of a magneto-electric effect induced by an electric field. It is pointed out that it would be interesting to establish (H, T) phase diagrams.

ISSN:0031-8086    

DOI:10.1080/14786436808218188

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A theoretical analysis has been made with respect to the low angle tilt boundary configurations in superlattices and applied specifically to the FeCo alloy. It is found that for small tilt angles the wall may consist of superlattice dislocations extended either along the slip plane or perpendicular to it depending on the anti-phase boundary energy variation with orientation. As the angle of misfit increases, the wall composed of vertically extended dislocations is favoured in all cases, the extension being equal to one-half the spacing between superlattice dislocations. The boundary is thus effectively disordered.

ISSN:0031-8086    

DOI:10.1080/14786436808218189

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Possible forms of contrast to be expected in field-ion micrographs from specimens containing perfect dislocation loops and dislocation dipoles are discussed in terms of an extension of the type of contrast seen from single isolated dislocations. These predictions are related to the actual contrast seen in field-ion micrographs of these defects. Further, the occurrence of these defects is correlated with the history of the specimens. The paper shows that while the amount of new information that can be obtained on dislocations in general by field-ion microscopy is strictly limited, the technique has distinct utility in studies of small dislocation loops.

ISSN:0031-8086    

DOI:10.1080/14786436808218190

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The deformed structure of quench-hardened gold was examined with transmission electron microscopy. It was found that plastic deformation takes place in confined regions, thereby forming the slip channels which are free of tetrahedral stacking faults. From the observation it was concluded that dislocations have contact interactions with the tetrahedral stacking faults. Small sized defects were often seen where dislocation activity had taken place. From an analysis of the distribution of the defects it was shown that these small defects are products of the reaction between moving dislocations and tetrahedral stacking faults.

ISSN:0031-8086    

DOI:10.1080/14786436808218191

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The diffusion thermopowers of Cu and Ag alloyed with B group metals are shown to be separable into two terms, one proportional to the resistivity and the other associated with a rigid band structure for the alloys. A simple theoretical approach also predicts the separation of terms. The Nordheim-Gorter relation is discussed and the analysis indicates no [200] Brillouin zone contact for any of the alloys.

ISSN:0031-8086    

DOI:10.1080/14786436808218192

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The intensity of x-rays generated in an attack-polished bulk specimen under given electron bombardment conditions has been shown to depend on the crystal orientation. It has been found that the intensity can be changed by about 1·5% by changing the angle of incidence of the electron beam.

ISSN:0031-8086    

DOI:10.1080/14786436808218193

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A remarkably reversible slip-unslip process has been observed on low strain amplitude fatigue hardened copper single crystals. Slip lines formed on an electropolished surface in one half cycle almost vanish on the subsequentreverse half-cycle, then reappear on the next forward stroke. This process has been observed at least 300 μ below the original surface shortly after saturation. The dislocation structure was composed of dense dipole-monopole mats elongated on the primary slip plane and it is suggested that the reversibility results from interactions between these mats and their surrounding elastic matrix.

ISSN:0031-8086    

DOI:10.1080/14786436808218194

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor