Dislocations in Solids – serie

This is the first volume to appear under the joint editorship of J.P. Hirth and F.R.N. Nabarro. While Volume 11 concentrated on the single topic of dislocations and work hardening, the present volume spreads over the whole range of the study of dislocations from the application by Kl�man and his colleagues of homotopy theory to classifying the line and point defects of mesomorphic phases to Chaudhri's account of the experimental observations of dislocations formed around indentations.Chapter 64, by Cai, Bulatove, Chang, Li and Yip, discusses the influence of the structure of the core of a dislocation on its mobility. The power of modern computation allows this topic to be treated from the first principles of electron theory, and with empirical potentials for more complicated problems. Advances in electron microscopy allow these theoretical predictions to be tested.In Chapter 65, Xu analyzes the emission of dislocations from the tip of a crack and its influence on the brittle to ductile transition. Again, the treatment is predominantly theoretical, but it is consistently related to the very practical example of alpha iron.In a dazzling interplay of experiment and abstract mathematics, Kl�man, Lavrentovich and Nastishin analyze the line and point structural defects of the many mesomorphic phases which have become known in recent years.Chapter 67, by Coupeau, Girard and Rabier, is essentially experimental. It shows how the various modern techniques of scanning probe microscopy can be used to study dislocations and their interaction with the free surface.Chapter 68, by Mitchell and Heuer, considers the complex dislocations that can form in ceramic crystals on the basis of observations by transmission electron microscopy and presents mechanistic models for the motion of the dislocations in various temperature regimes.While the underlying aim of the study of dislocations in energetic crystals by Armstrong and Elban in Chapter 69 is to understand the role of dislocations in the process of detonation, it has the wider interest of studying dislocations in molecular crystals which are ``elastically soft, plastically hard, and brittle''.Chaudhri in Chapter 70 discusses the role of dislocations in indentation processes, largely on the basis of the elastic analysis by E.H. Yoffe. The special case of nanoindentations is treated only briefly.

Dislocations are lines of irregularity in the structure of a solid analogous to the bumps in a badly laid carpet. Like these bumps they can be easily moved, and they provide the most important mechanism by which the solid can be deformed. They also have a strong influence on crystal growth and on the electronic properties of semiconductors.�Influence of dislocations on piezoelectric behavior�New mechanisms for hardening in twinned crystals�Bringing theories of martensite transformation into agreement�Atomic scale motion of dislocations in electron microscopy�Dislocation patterns deduced from X-ray diffraction�Role of dislocations in friction�Dislocation motion in quasicrystals

New models for dislocation structure and motion are presented for nanocrystals, nucleation at grain boundaries, shocked crystals, interphase interfaces, quasicrystals, complex structures with non-planar dislocation cores, and colloidal crystals. A review of experimentally established main features of the magnetoplastic effect with their physical interpretation explains many diverse results of this type. The model has many potential applications for forming processes influenced by magnetic fields. Dislocation model for the magnetoplastic effect New mechanism for dislocation nucleation and motion in nanocrystals New models for the dislocation structure of interfaces between crystals with differing crystallographic structure A unified view of dislocations in quasicrystals, with a new model for dislocation motion A general model of dislocation behavior in crystals with non-planar dislocation cores Dislocation properties at high velocities Dislocations in colloidal crystals

Bacon and Osetsky present an atomistic model of dislocation-particle interactions in metal systems, including irradiated materials. This work is important in simulating actual behavior, removing earlier reliance on assumed mechanisms for dislocation motion. New mechanisms for dislocation generation under shock loading are presented by Meyers et al. These models provide a basis for understanding the constitutive behavior of shocked material. Saada and Dirras provide a new perspective on the Hall-Petch relation, with particular emphasis on nanocrystals. Of particular significance, deviations from the traditional stress proportional to the square-root of grain size relation are explained. Robertson et al consider a number of effects of hydrogen on plastic flow and provide a model that provides an explanation of the broad range of properties. Flow stress of metal systems with particle hardening, including radiation effects New model for dislocation kinetics under shock loading Explanation of effects of nanoscale grain size on strength Mechanism of hydrogen embrittlement in metal alloys