摘要:

AbstractEs sind Strukturmodelle für Korngrenzen in reinen Metallen, in Legierungen und für Phasengrenzen zwischen zwei Kristallen unterschiedlicher Elemente bekannt. Geometrische und energetische Vorstellungen dazu werden diskutiert. Mit einer energetischen Methode wird versucht, die Struktur von Korngrenzen zu bestimmen. Die Ergebnisse der theoretischen Arbeiten sind geeignet, die Deutung experimenteller Ergebnisse an orientierten Bikristallen zu fördern. Die direkte Untersuchung des Korngrenzeneinflusses auf die Eigenschaften von Vielkristallen bleibt aber eine Notwendigke

ISSN:0023-4753    

DOI:10.1002/crat.19790140302

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

ISSN:0023-4753    

DOI:10.1002/crat.19790140303

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe basic physical problems of the geometric models and structural models of grain boundaries based on computer simulations are considered. By comparing the approximations made in these models with the general solution of the problem based on the theory of metallic cohesion, we are led to conclude thatigeometric grain boundary models (coincidence models) may be used to derive certain geometric features of a boundary (e.g. the boundary periodicity). However, due to the fact that interatomic forces are neglected, it seems not possible to deduce the actual atomic structure and properties of grain boundaries on the basis of these models.iiDislocation models of grain boundaries seem to be of physical significance only for low energy boundaries. In all other boundaries, misfit dislocation are theoretically and experimentally found to be delocalized in the sense that their core is smeared out in the plane of the boundary.iiiStructural boundary models deduced by computing the minimum energy atomic configuration using pairwise interatomic potential functions seem to represent a reasonable approximation of the actual atomic structure.ivThe experimental and theoretical evidence presented indicates that grain boundary properties can, in general, not be derived from computer models, as these properties depend partially on electronic effects.vFurther developments of the physical understanding of grain boundaries seems to require the incorporation of electronic effects in the theory of interfaces.

ISSN:0023-4753    

DOI:10.1002/crat.19790140304

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractDie Wasserstoffdiffusion in Ein‐ und Polykristallen von Nickel wurde mit dem Ziel untersucht, den Einfluß der Korngrenzen zu ermitteln. Es wird gefunden, daß die geringen Unterschiede in den Diffusionskoeffizienten sich nicht eindeutig auf die Unterschiede zwischen den polykristallinen Materialien und den Einkristallen zurückführen lassen. Die Korngrenzen beeinflussen den Mechanismus der Diffusion nicht wesen

ISSN:0023-4753    

DOI:10.1002/crat.19790140305

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractOptical studies have been made of the microstructures on the natural {100} and {111} faces of natural fluorite crystals. The protrudance of triangular elevations, growth pyramids, and natural etch pits have been observed on a large number of crystals. It is suggested that fluorite crystals grown by two‐dimensional spreading and piling of growth layers parallel to {100} faces. The natural etch pits on {100} and {111} faces suggest that they have been produced as a result of a dissolution process in nature. The natural faces have been etched in the laboratory and it is established that the pits indicate the existence of linear defects in the crystals. The implications are discusse

ISSN:0023-4753    

DOI:10.1002/crat.19790140306

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

ISSN:0023-4753    

DOI:10.1002/crat.19790140307

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractThe effect of temperature (20–100°C) and concentration of H2SO4etching solutions on the etching behaviour of {111} faces of calcium fluoride crystals is investigated. Whisker growth of calcium sulphate is observed. Temperature of the etchant also has an effect on their formation. The kinetics of dissolution at the sites of dislocations and general dissolution have been studied. Studies on induction period and its dependence on the concentration of the acid and temperature are also described. It is observed that: (i) at low and high acid concentrations, the dissolution is diffusion controlled while it is predominantly reaction‐rate controlled in the intermediate concentration range and (ii) the growth rate of calcium sulphate whiskers decreases with time and their induction period decreases with increase in the temperature of the solution. The implications are discu

ISSN:0023-4753    

DOI:10.1002/crat.19790140308

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractIn weathering crusts, sedimentary rocks and zones of hydrothermal transformation frequently mixed‐layer illite‐montmorillonite will occur. Based upon new experimental transformations of montmorillonite and beidellite under hydrothermal conditions in the presence of potassium chloride it is shown that mixed‐layer illite‐montmorillonite, with decreasing expandable proportion, occurs in the form of transitional stages of the montmorillonite → illite transformation. Besides the increase of reaction temperature or potassium concentration, it is first of all an increased charge of the (Si, Al)O4tetrahedral layers of the dioctahedral smectites that contribute considerably to accelerating the formation of illite‐montmorillonite mixed‐layers, lowering their expandable proportion and converting these mixed lay

ISSN:0023-4753    

DOI:10.1002/crat.19790140309

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

ISSN:0023-4753    

DOI:10.1002/crat.19790140310

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY

摘要:

AbstractEs wird über Texturuntersuchungen an Co‐legierten weichmagnetischen Fe‐Ni‐Basislegierungen, die einer kombinierten mechanisch‐thermischen Behandlung unterzogen worden waren, berichtet. Während für die binären Systeme NiFe und NiCo die Ausbildung einer scharfen Würfeltextur seit längerem bekannt ist, wurde eine solche für ternäre NiFeCo‐Legierungen bisher als nicht möglich und Co als ein die Würfellagebildung behinderndes Element angesehen. Wie jedoch die Ergebnisse zeigen, läßt sich auch an ternären Legierungen mit Ni‐Gehalten von 45 bis 50% und Co‐Anteilen bis zu etwa 25% eine scharf ausgeprägte Würfellag

ISSN:0023-4753    

DOI:10.1002/crat.19790140311

出版商:WILEY‐VCH Verlag    

年代:1979

数据来源: WILEY