摘要:

Measurements of optical reflectivity have been used to investigate diffusion and intermetallic compound formation in thin-film diffusion couples of silver–aluminium. The couples were prepared by vacuum deposition of the two metals in succession on glass substrates. The specimens were annealed at temperatures up to 240°C and reflectivity measurements were made at both the free surface and the substrate side. An intermediate zone of Ag2Al was formed by diffusion and a marked change in reflectivity occurred as this compound approached the surface. Electron diffraction was used to confirm the presence of this compound.

ISSN:0031-8086    

DOI:10.1080/14786436808223171

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The mist zone, the arc of stippled surface surrounding the mirror-smooth area at the origin of fracture, was examined in detail using an optical microscope and progressive etching.

ISSN:0031-8086    

DOI:10.1080/14786436808223172

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Single crystals of natural magnetite have been subjected to extended elastic deformation. The irreversible magnetic effects investigated were the acquisition of remanence and reduction of saturation remanence by compression in a null or directed magnetic field. The magnitude of the remanent moment is dependent on a complementary combination of the extent of deformation and magnitude of the field. The strain-induced moment is much larger than the isothermal remanence acquired in the deformation field, and has a significantly greater relative stability. The transitory effects of interest under the influence of applied stress were increase of saturation remanence and changes in microscopic coercivity spectrum. A structure-dependent model has been developed to interpret the behaviour. The magnetomechanical effects may be associated with the response of a multidomain configuration to changes induced in the internal mechanical microstructure. These changes are caused by the stress, and are attributed to the movement of mobile defects such as dislocations.

ISSN:0031-8086    

DOI:10.1080/14786436808223173

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Electrical conductivity measurements were employed to investigate the kinetics of copper precipitation out of supersaturated silicon between 30°C and 70°C. The kinetics were observed to follow a (time)nrate equation wheren=0·687 ± 0·043. An activation energy of 1·10 ± 0·05 ev was found for the process. The results are discussed with reference to current theories of precipitation at dislocations. It was concluded that the reaction is not diffusion controlled, and a transient rate limitation theory was employed to describe the results qualitatively.

ISSN:0031-8086    

DOI:10.1080/14786436808223174

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The structures of the III–V and II–VI compounds are discussed with respect to the effective charges on the ions. It is shown that as the effective charge on the Group III or Group II ion increases, the stable structure changes from the sphalerite to the wurtzite structure.

ISSN:0031-8086    

DOI:10.1080/14786436808223175

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A study has been made of the influence of impurities on the environment-sensitive mobility of near-surface edge dislocations introduced by a diamond indenter into freshly cleaved MgO surfaces. The environments used were solutions of DMF or DMSO in H2O, and DMF in DMSO. It was found that the extent of edge dislocation motion resulting from the application of a fixed indenter load for a given time varied in a rather complicated manner with composition of the environment. The characteristic features of this variation for DMSO–DMF environments were reproduced by all three types of MgO used, but the relative positions of the maxima and minima were dependent on the concentration and state of ionization of the impurities. Though the observations cannot be interpreted in detail, they appear consistent with a mechanism for Rebinder effects in ionic crystals proposed earlier by the authors.

ISSN:0031-8086    

DOI:10.1080/14786436808223176

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Polyethylene terephthalate sheet which had been oriented by drawing was subsequently deformed in tension where the primary variable was the angle between the stress and the initial drawing direction. The beginning of yielding was marked by the formation of a narrow deformation band which had the following important characteristics: (1) the shear strain in the band was about 200%, (2) the direction of the band was nearly but definitely not parallel to the initial drawing direction and (3) the direction of optical extinction under crossed polarizers rotated from the initial drawing direction toward the axis of stress.

ISSN:0031-8086    

DOI:10.1080/14786436808223177

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The massive phase transformation which occurs in Cu–Ga alloys on quenching from the high temperature β-phase has been studied using the technique of electron microscopy. The transformed alloys consist of a fine lamellar structure of h.c.p. or h.c.p. plus f.c.c. phases. The lamellae are twisted with respect to one another along the close-packed planes and are grouped together into packets or blocks which are joined by sub-grain boundaries that are similarly twisted.

ISSN:0031-8086    

DOI:10.1080/14786436808223178

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The temperature and strain rate dependence of the flow stress of ordered and disordered polycrystalline Cu3Au was investigated in the range 20°–420°K. A thermally activated deformation mechanism was observed at temperatures less than ∼100°K and ∼340°K for the ordered and disordered material respectively. For ordered Cu3Au, the experimental data were shown to correlate well with the requirements of the Peierls mechanism over the entire thermally activated region; for the disordered material, good agreement was only obtained at temperatures less than ∼120°K, and it appeared that deformation was by the intersection mechanism in the temperature range ∼220°–340°K.

ISSN:0031-8086    

DOI:10.1080/14786436808223179

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A theoretical model, which considers the contribution to sputtering both from random ejections of surface atoms and from collision sequences initiated at different depths, provides a better understanding of the mechanism of sputtering from close-packed crystal directions, in particular for high energy sputtering. The model is based on a (1/E2) energy spectrum in the collision cascade, and also allows for thermal vibrations.

ISSN:0031-8086    

DOI:10.1080/14786436808223180

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor