摘要:

A crystallographic etching technique has been used to demonstrate that deformation banding is an important deformation mode in copper. In a cold-rolled coarse-grained copper, deformation banding occurs and the different banding geometries divide the grains into a large number of regions with different orientations. Because of the important effect on microstructure, deformation banding is considered to influence the development of deformation texture. In particular, the {110}⟨112⟩ texture component, an important component of the copper-type rolling texture which cannot be explained by existing deformation models, is shown to be formed by deformation banding.

ISSN:0950-0839    

DOI:10.1080/09500839308242410

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this letter we compare the plastic properties of crumpled surfaces, crumpled wires and massive spheres of pastes deformed between parallel platens. All these systems have a spherical shape but different topological dimensions. Power laws are obtained from experiments and the dependence of the critical exponents on topology is examined. A comparison is made with the plastic deformation of solid (metallic) spheres.

ISSN:0950-0839    

DOI:10.1080/09500839308242411

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A model is developed which predicts an ordering of the dislocation multiplication sources in Si1−xGex/Si heteroepitaxial systems. This ordering results in an increased probability for threading dislocations to annihilate. It is shown that, following certain selection rules for dislocation multiplication, an infinite three-dimensional network of misfit dislocations can develop throughout the compositionally graded Si1−xGexlayer. The model is consistent with existing experimental data.

ISSN:0950-0839    

DOI:10.1080/09500839308242412

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Direct observation in a scanning electron microscope of the evolution of the grain-boundary sliding (GBS) process in a Pb-62wt%Sn eutectic alloy during superplastic deformation in shear is reported. The distribution of GBS along the shear surface is found to be inhomogeneous and there is evidence of coupling of the processes of GBS and grain-boundary migration. The rate of GBS increases at small stages of strain (up to about 0·8) and decreases thereafter, indicating that the GBS process is eventually accompanied by strain hardening. The observations are compatible with the dislocation model for GBS.

ISSN:0950-0839    

DOI:10.1080/09500839308242413

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An analogy between the occurrence of intragranular dislocation slip and intergranular (grain-boundary) sliding at different structural levels is discussed. Observation ofin-situsuperplastic tensile deformation in a scanning electron microscope on a Pb-62wt.%Sn eutectic alloy showed that the phenomenon of intergranular sliding on the scale of the entire deformed volume and on the scale of grain groups is similar to the occurrence of intragranular dislocation slip deformation at these microstructural levels.

ISSN:0950-0839    

DOI:10.1080/09500839308242414

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Evidence of a shape-dependent superheating of entrained nanosized Pb particles in a Zn matrix has been presented. It is shown that size dependence and pressure effects cannot explain the observed differences in melting points. The importance of crystallography and morphology at the microlevel at the interphase interface in controlling interfacial melting has been emphasized in order to explain the melting of entrained particles.

ISSN:0950-0839    

DOI:10.1080/09500839308242415

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The steady-state creep behaviour and dislocation configurations generated by the creep of a quasicrystal have been reported for the first time. Volume-diffusion controlled climb of dislocations is the probable rate-controlling mechanism for steady-state creep deformation of an Al65Co20Cu15quasicrystal in the investigated temperature and stress range. Two different configurations of dislocations, namely complex and kinked, were observed. All these dislocations, which consist of both edge and screw segments, have Burgers vectors parallel to the tenfold axis. A complex dislocation configuration arises because of dislocation generation at the kink nodes.

ISSN:0950-0839    

DOI:10.1080/09500839308242416

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Specific heatCp, a.c. and d.c. magnetic susceptibility χ, electrical resistivity ρ and upper critical fieldHc 2measurements were performed in two Zr-Ce alloys with 1·3 and 2·3 at.% Ce, whose superconducting transition temperatureTcand Sommerfeld coefficient γ are enhanced with respect to those of pure Zr. In the case of the 2·3 at.% Ce alloy, for whichTc(= 2·85 K) and γ (= 13·4 mJ K−2mol−1) are almost five times larger than those of Zr, the dHc 2/dTslope is - 3·5 T K−1and ρ(T) shows a Kondo-like maximum at 20 K. ItsCp(T) dependence follows a power law (T3) forT< ½Tc, with a jump atTcof ΔCp≈ 1·1 γTc. The superconducting parameters of this sample, extracted fromCp(T) andHc 2, are in better agreement with the prediction for a p-wave-type superconductor (with an axial symmetry order parameter) rather than with those for a conventional Bardeen-Cooper-Schrieffer system.

ISSN:0950-0839    

DOI:10.1080/09500839308242417

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The grey-white phase interfaces of tin have been studied using high-resolution electron microscopy (HREM). The lattice fringe images revealed the interfacial regions of the transitional atomic arrangement from grey tin (α-phase) into white tin β-phase). The orientation relationship obtained from the lattice fringe image between α- and β-phases is that the (011) plane of grey tin is parallel to the (001) plane of white tin and the [211] direction of grey tin is nearly parallel to the [010] direction of white tin. A model of the α → β transformation mechanism is proposed on the basis of the atomic arrangement observed by HREM. The model indicates that the α → β transformation of tin is accomplished partly by martensitic transformation and partly by atomic motion that is massive in nature.

ISSN:0950-0839    

DOI:10.1080/09500839308242418

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An explanation of the spin gap observed by Bucheret al.in 1993 in the conductivity of YBa2Cu4O8is given, based on the bipolaron theory of these materials.

ISSN:0950-0839    

DOI:10.1080/09500839308242419

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor