摘要:

The temperature dependence of ⟨111⟩ tilt grain boundaries with angles of misorientation of 38·2° and 40·5° was investigated in bicrystals of both pure (99·999%) Al and the same Al doped with 10ppmGa in the temperature regime between 400 and 580°C. The grain boundary mobility for the investigated grain boundaries over the entire investigated temperature range is enhanced by minor additions of Ga. Both the activation enthalpy and the pre-exponential factor are affected by Ga doping. The orientation dependence of grain boundary mobility is strongly reduced but not completely removed. The drastic rise in grain boundary mobility by the addition of Ga to pure Al is interpreted as a consequence of a change in the boundary structure and the mechanism of boundary migration owing to a pre-wetting phase transition and formation of a liquid (or quasiliquid) Ga-rich layer on the grain boundary.

ISSN:0950-0839    

DOI:10.1080/09500839508242475

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The first stages of cellular precipitation development and cell formation at interphase boundaries have been investigated in aCu-9 wt% Sb alloy. From optical microscopy observations of the early stages of cellular precipitation it seems that the Tu and Turnbull mechanism controls the reaction initiation. It is demonstrated that discontinuous precipitation with the same morphology and interlamellar spacing can be initiated at interphase boundaries between the matrix and the eutectoid phases, as well as at grain boundaries.

ISSN:0950-0839    

DOI:10.1080/09500839508242476

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Al‒Pd‒Mn single-quasicrystals have been plastically deformed at temperatures between 730 and 800°C up to different strain values and analysed in the transmission electron microscope. Dislocations were created during deformation. The dislocation density ranged between 1·7 × 107cm−2in undeformed samples and 7·8 × 108cm−2in material deformed at 732°C. Six-dimensional dislocation Burgers vectors were determined employing the convergent-beam electron diffraction technique. 87% of these Burgers vectors were oriented parallel to twofold directions in three-dimensional physical space. Their moduli were 0·113, 0·183 and 0·296nm. The ratio of the phason to the phonon component of the Burgers vectors was found to increase with increasing strain. A variety of slip systems was observed. In most cases the respective slip plane normals were parallel to fivefold and threefold directions.

ISSN:0950-0839    

DOI:10.1080/09500839508242477

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A processing technique is developed to fabricate single-crystal yttria-stabilized zirconia (YSZ) on amorphous SiO2on (100) single-crystal Si. The YSZ layer shows high crystallinity with an ion beam channelling minimum of 11 % from Rutherford backscattering. Even though there is a thick intervening amorphous SiO2layer between the Si and the YSZ, the single-crystal YSZ layer is aligned with the crystal Si. The tilt and rotation variations are 0·64° and 1·11° respectively, based on X-ray diffraction Ω-rocking curves on [100] and π scans on [202] of YSZ films. The epitaxial nature of the YSZ on the thick SiO2layer (from 10 to 100 nm) is further confirmed by high-resolution cross-sectional transmission electron microscopy analysis. This processing and the resulting multilayer structure might provide a new option for fabricating innovative microelectronic devices.

ISSN:0950-0839    

DOI:10.1080/09500839508242478

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The core structure and the character of a dislocations on prism planes have been studied for room-temperature-deformed polycrystalline Ti3Al using a combination of experimental and computational techniques of transmission electron microscopy. A comparison of experimental and computer-simulated weak-beam images of prism plane a dislocations in Ti3Al indicates that the image peak separation observed experimentally in typical weak-beam images significantly overestimates the actual superpartial dislocation separation. The image simulations further infer that a recently reported four-peak weak-beam image is inconsistent with a fourfold dissociation of a single superdislocation.

ISSN:0950-0839    

DOI:10.1080/09500839508242479

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

By extending the Stroh sextic formalism to a ten-dimensional formalism, it is shown that the Green function for an elliptic hole or rigid inclusion in an anisotropic elastic medium can be modified easily for an anisotropic medium with piezoelectric, piezomagnetic and magnetoelectric coupling.

ISSN:0950-0839    

DOI:10.1080/09500839508242480

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It is argued that the nanometric dispersion of Bi in a Zn matrix is an ideal model system for heterogeneous nucleation experiments. The classical theory of heterogeneous nucleation with a hemispherical cap model is applied to analyse the nucleation data. It is shown that, unlike the results of earlier experiments, the derived site density for catalytic nucleation and contact angle are realistic and strongly suggest the validity of the classical theory. The surface energy between the 0001 plane of Zn and the 10ł2 plane of Bi, which constitute the epitaxial nucleation interface, is estimated to be 39 mJ m−2.

ISSN:0950-0839    

DOI:10.1080/09500839508242481

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this letter we study the crumpled state observed in metallic closed surfaces submitted to a rapid variation in temperature. Scaling laws for the crumpled volume and the average size are obtained and critical exponents are found. The results are compared with those obtained for crumpled structures at equilibrium.

ISSN:0950-0839    

DOI:10.1080/09500839508242482

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The difference between the heat capacities of chemically disordered and Ll2-ordered Cu3Au was measured by calorimetry from 70 to 300 K. By comparing these measured results with a harmonic heat capacity calculated with a Born-von Kámán model, we estimate the difference in vibrational entropy between disordered and ordered Cu3Au to be (0·14 ± 0·05)kBatom−1at high temperatures. The smaller vibrational entropy of the ordered alloy originates from features of its optical modes, features which seem related to the different sizes of Cu and Au atoms.

ISSN:0950-0839    

DOI:10.1080/09500839508242483

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new vertex-based model of two-dimensional grain growth is presented. The motion of each vertex is determined by the curvature-driven motions of the adjacent boundaries. Boundary curvatures are approximated by a geometrical construction that is fully specified by the locations of the three neighbouring vertices. Simulations based on this model exhibit parabolic growth kinetics for the grain aggregate, and the Mullins-von Neumann growth law is obtained for individual grains.

ISSN:0950-0839    

DOI:10.1080/09500839508242484

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor