摘要:

The ratio (γ2: γ1) of the work of fracture in crystals of sodium chloride containing known dispersions of one micron diameter cavities to that in normal crystals of sodium chloride, has been determined under dynamic conditions of cleavage. The method, based on measurements of the crack-velocity during cleavage, only permitted an order of magnitude calculation for γ2:γ1; nevertheless, the results show that dispersions of cavities with mean separations less than about 30 microns can increase the work of fracture of a crystal by at least two orders of magnitude. This increased work of fracture in the composite crystals can be correlated with the generation of cleavage steps when the crack intersects the cavities.

ISSN:0031-8086    

DOI:10.1080/14786436808223019

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The interface between explosively welded metals frequently exhibits a regular wave-like profile. The circumstances under which such a profile develops are not fully understood, and existing theories fail to predict some of its observed characteristics.

ISSN:0031-8086    

DOI:10.1080/14786436808223020

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Copper single crystals irradiated to a neutron dose of 1·1 × 1018n/cm2(> 1 MeV) have been cycled between constant plastic elongation limits at room temperature. The general cyclic deformation characteristics have been ascertained and some qualitative ideas on the mechanisms of deformation developed. Transmission electron microscopy reveals that channels completely free of irradiation-produced defects are created during the cyclic strain programme. The width and spacing of the channels have been shown to be a function of the number of cycles. An electron microscope shadowgraph technique has also been used to study the exact shape and distribution of surface slip steps and the results are compared to the channel observations.

ISSN:0031-8086    

DOI:10.1080/14786436808223021

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The stress field of the edgemultipole (dipole cluster) in the basal plane is approximated by the superdipole stress field. The stress fields of different dipole (superdipole) arrays are given for anisotropic cadmium crystal. The stress field components into the secondary non-basal slip planes (pyramidal and prismatic) were computed for the same metal. It was shown that the magnitude of this component is comparable with both the value of flow stresses in the secondary systems and the same component of the pile-up stress field.

ISSN:0031-8086    

DOI:10.1080/14786436808223022

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The anisotropy, ferromagnetic resonance linewidth andg-factor of nickel ferrite may be discussed in terms of the distribution of the cations within the lattice. It is shown that the anisotropy constantK1of A-site Ni2+ions is about 6 × 106erg cm−3while the temperature variation of both thisK1, and the resonance linewidth of the nickel ferrite is consistent with an angular dependence of the energy levels of a ground state multiplet for these ions. It is seen that, contrary to previous suggestions, theg-factor is not a simple function of the magnetic moment of the ferrite.

ISSN:0031-8086    

DOI:10.1080/14786436808223023

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Absolute surface and grain boundary energies have been measured on silicon iron as a function of bulk silicon content, oxygen potential of the controlled atmosphere and temperature. At 1410°c, the silicon concentration at the free surface of Fe–3% Si is approximately 13%. A similar silicon enrichment occurs at grain boundaries. By far the most important effect is that of oxygen adsorption, which reduces the surface energy severely, the saturation surface coverage at 1330°c being 0·47 of a monolayer. An oxygen potential greater than that equivalent to pH2O/pH2=10−4develops a (100) secondary recrystallization texture on thin foils, by virtue of the preferential adsorption of oxygen on (100) planes. At pH2O/pH2< 10−4, the foils show a (110) texture. In addition, the temperature coefficient of surface energy which is -0·36 ergs cm−2°c−1for a clean surface, becomes positive and equal to 0·55 ergs cm−2°c−1in the presence of oxygen adsorption. The relevance of the present observations to the secondary recrystallization mechanism is discussed.

ISSN:0031-8086    

DOI:10.1080/14786436808223024

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Experiments are described in which flow stress, electrical resistivity and dislocation density were measured as functions of tensile plastic strain in 99·996% polycrystalline copper extended up to 10%. Dislocation density was measured by the technique of thin film electron microscopy. An apparent anomaly in the results involving dislocation density measurements is interpreted as being due to dislocation loss during thinning. This appears to have increased rapidly with dislocation density above a critical dislocation density.

ISSN:0031-8086    

DOI:10.1080/14786436808223025

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The flow stress distribution below the surface of previously deformed large copper single crystals is obtained when these are sliced into smaller component crystals. It is found that a considerable flow stress gradient extends for a distance of about 2 mm below the surface, measured along the slip direction. Electron microscope studies show that there is an increase in the cell size of dislocation structures near the surface and a decrease in dislocation density.

ISSN:0031-8086    

DOI:10.1080/14786436808223026

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The variation of d.c. size effect with magnetic field has been measured in aluminium single crystal films with thicknesses between 30 and 80 micron and bulk resistance ratio of about 15 000. It is shown that observations on the Mac Donald effect can give Fermi surface dimensions with accuracy of magneto acoustic measurements.

ISSN:0031-8086    

DOI:10.1080/14786436808223027

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The climb of prismatic dislocation loops in dilute aluminium alloys has been investigated as a function of alloying addition by isothermal annealing of thin foils. It was observed that the loops annealed out by shrinking in all the alloys investigated except for aluminium-magnesium where loop growth occurred. It is proposed that the vacancy supersaturation necessary for the observed growth is due to the production of vacancies in the surface regions of the foil as magnesium atoms become absorbed by a growing surface oxide film. This model has been critically examined by investigating the rate of growth as a function of annealing time, annealing temperature and the oxygen pressure of the annealing environment. The results confirm this model of vacancy production and show that in the alloys containing 0·65% magnesium, diffusion of magnesium to the surface regions is the rate-controlling process whereas in the more concentrated alloys (3·3% and 6·6% Mg) surface oxidation is rate controlling.

ISSN:0031-8086    

DOI:10.1080/14786436808223028

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor