摘要:

The nature of ‘grown-in’ dislocations formed in melt spun ribbons of the compound Nb3Al have been studied using transmission electron microscopy. These dislocations have b = ⟨100⟩ and are predominantly screw in character. They are dissociated into two partial dislocations which bound a complex stacking fault according to the reaction

ISSN:0950-0839    

DOI:10.1080/09500839108214667

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The change in energy related to the dissociation of a 1/2 ⟨1l0⟩ screw dislocation into two Shockley partials or of an edge dislocation into the Lomer-Cottrell configuration has been recalculated. It is shown that the exact value, and even the sign, of this change cannot be found using linear isotropic elasticity when the splitting distance is too small.

ISSN:0950-0839    

DOI:10.1080/09500839108214668

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Following principles established in earlier studies of h.c.p. metals we have been able to grow f.c.c. metals with their atomic planes tilted from those of the substrate by a predictable and reproducible angle. In this way copper, gold and platinum have been prepared in the (110) orientation with tuned tilts up to 7°.

ISSN:0950-0839    

DOI:10.1080/09500839108214669

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Surface elastic strain field generated in conical indentation of sintered alumina clay composite was measured to verify the suitability of a superposed combination of Boussinesq and blister stress fields, used previously for analysing the indentation problem. The residual strain measured in the elastic hinterland is used to estimate the blister field strength without any reference to stress relation within that field. The approach may be useful in fracture studies of brittle materials.

ISSN:0950-0839    

DOI:10.1080/09500839108214670

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An atomic structure model for an octagonal quasicrystal is proposed, based on the analysis of the related crystalline β-Mn structure. A salient feature is the occurrence of local 83screw axes. The density and the closest inter-atomic distance are within 5% difference of those of the β-Mn structure. This structural model agrees well with experimental results obtained by electron microscopy and electron diffraction.

ISSN:0950-0839    

DOI:10.1080/09500839108214671

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The Zener model relating stress (σ) to strain (σ) is generalized by applying the fractional calculus. The solution of the resulting fractional initial value problem is given in terms of Fox functions. A comparison with experimental relaxation data demonstrates good agreement with the theoretical predictions, and thus supports the fractional model, which includes as a special case the fractional Maxwell rheological law.

ISSN:0950-0839    

DOI:10.1080/09500839108214672

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The melt-spun Mg39·5Ga16·4A14·1Zn40·0ribbon consists entirely of micrograins of an icosahedral phase (I-phase). The calorimetric and X-ray diffraction studies have shown that the I-phase undergoes an exothermic transformation to an approximant crystalline phase at 630 K on heating at a rate of 20 K min−1. Detailed structural analysis of the crystalline phase has revealed that the phase corresponds to a 3/2–2/1–2/1 rational approximant of I-phase, which has the orthorhombic C-type Bravais lattive with large cell parameters, a = 36·93 ± 0·06 Å, b = 22·83 ± 0·04 Å andc= 22·96 ± 0·04 Å.

ISSN:0950-0839    

DOI:10.1080/09500839108214673

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

An ammonia synthesis catalyst, fabricated by reducing magnetite (Fe3O4) containing small amounts of Al2O3, CaO and K2O, was studied using transmission electron microscopy. It is observed that the Fe3O4crystal grains are transformed into porous or spongy single crystals of body centred cubic iron (α-Fe) extending over large distances (more than l0 μm). Within the original magnetite grain three orientations of the porous α-Fe crystals are observed consistent with a Bain transformation during reduction. The three orientations of the cubic α-Fe crystal grains within the original magnetite crystal grain result from a 45° rotation of the α-Fe crystal unit cell around the three equivalent (100) axes of magnetite.

ISSN:0950-0839    

DOI:10.1080/09500839108214674

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor