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Characterization Of Dislocation Core Structures In Bcc Metals
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Book Synopsis Characterization of Dislocation Core Structures in BCC Metals by :
Download or read book Characterization of Dislocation Core Structures in BCC Metals written by and published by . This book was released on 2004 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The scientific aim of this study was to use state-of-the-art TEM techniques to experimentally describe dislocation core structures in bcc metals through experimental characterization of screw dislocations in single-crystalline Mo. Methods were developed for deriving localized electron structure data from electron energy loss spectra (EELS) taken from perfect lattice regions and along dislocations and low angle boundaries in ordered NiAl. Significant changes in the fine structure of the NiL edge were associated with 001 dislocations in NiAl and comparisons with first-principles were used to characterize localized electronic structure and bonding in the vicinity of this dislocation. However, difficulties associated with the position of the energy edges for Mo precluded application of this technique to the study of 1/2111 screw dislocations in single-crystalline Mo. For this reason, the majority of this study focused on: direct HREM observations of the atomic columns surrounding 1/2111 screw dislocations in Mo, characterization of the displacement fields associated with these dislocations, mitigation of experimental noise, and comparison of the experimental observations with theoretically predicted dislocation structures.
Book Synopsis Experimental Determination of Dislocation Core Structures by HRTEM by :
Download or read book Experimental Determination of Dislocation Core Structures by HRTEM written by and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overarching scientific goal of this study is to use state-of-the-art TEM techniques to experimentally characterize dislocation core structures in metals and alloys at the atomic scale. The past year has involved the culmination of efforts on intermetallic alloys and pure fcc metals and the development of new techniques for the study of bcc metals and alloys. Our work on (Ni, Fe)3 Ge indicated that changes in mechanical behavior associated with Fe additions are related to variations in dislocation core geometry and its effect on dislocation mobility. These findings have both motivated and been found to be in agreement with first principles based calculations of dislocation core structures in these alloys. In a related study, our weak-beam TEM and HREM experimental observations of dislocation core structures in fcc gold and iridium have been shown to be in excellent agreement with theoretical predictions for these metals. More recent efforts have focused on developing the techniques for characterizing dislocation core structures in bcc metals. Direct HREM observations of dislocation cores and the derivation of localized electron structure data from electron energy loss spectra (EELS) measurements are long term goals, and preliminary steps toward these challenging tasks are underway.
Book Synopsis Hierarchical Characterization of Deformation Heterogeneities InBCC Crystals by : J. W. Morris
Download or read book Hierarchical Characterization of Deformation Heterogeneities InBCC Crystals written by J. W. Morris and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Deformation behavior of body-centered cubic (BCC) metals is being investigated by white beam x-ray microdiffraction to characterize the dislocation structure that results from uniaxial compression experiments. The measurements were performed on molybdenum single crystals and a tantalum bicrystal as part of a hierarchical characterization effort. Results show heterogeneities in the deformed structure and misorientation maps consistent with results obtained from Orientation Imaging Microscopy (OIM). Additionally, the technique allows for the determination of the active glide systems as well as of the dislocation densities in function of the position in the sample.
Book Synopsis Dislocation Dynamics and Plasticity by : Taira Suzuki
Download or read book Dislocation Dynamics and Plasticity written by Taira Suzuki and published by Springer Science & Business Media. This book was released on 2013-03-07 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the 1950s the direct observation of dislocations became possible, stimulat ing the interest of many research workers in the dynamics of dislocations. This led to major contributions to the understanding of the plasticity of various crys talline materials. During this time the study of metals and alloys of fcc and hcp structures developed remarkably. In particular, the discovery of the so-called in ertial effect caused by the electron and phonon frictional forces greatly influenced the quantitative understanding of the strength of these metallic materials. Statis tical studies of dislocations moving through random arrays of point obstacles played an important role in the above advances. These topics are described in Chaps. 2-4. Metals and alloys with bcc structure have large Peierls forces compared to those with fcc structure. The reasons for the delay in studying substances with bcc structure were mostly difficulties connected with the purification techniques and with microscopic studies of the dislocation core. In the 1970s, these difficulties were largely overcome by developments in experimental techniques and computer physics. Studies of dislocations in ionic and covalent bonding materials with large Peierls forces provided infonnation about the core structures of dislocations and their electronic interactions with charged particles. These are the main subjects in Chaps. 5-7.
Download or read book Dislocations in Solids written by and published by Elsevier. This book was released on 2009-08-28 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: New materials addressed for the first time include the chapters on minerals by Barber et al and the chapter on dislocations in colloidal crystals by Schall and Spaepen. Moriarty et al extend the first principles calculations of kink configurations in bcc metals to high pressures, including the use of flexible boundary conditions to model dilatational effects. Rabier et al clarify the issue of glide-shuffle slip systems in diamond cubic and related III-V compounds. Metadislocations, discussed by Feuerbacher and Heggen, represent a new type of defect in multicomponent metal compounds and alloys. Kink mechanisms for dislocation motion at high pressure in bcc metals Dislocation core structures identified in silicon at high stress Metadislocations, a new type of defect, identified and described Extension of dislocation concepts to complex minerals First observations of dislocations in colloidal crystals
Book Synopsis Understanding Materials by : Colin Humphreys
Download or read book Understanding Materials written by Colin Humphreys and published by CRC Press. This book was released on 2020-01-29 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a very special book for two reasons. First, it is a tribute to Professor Sir Peter Hirsch from his students, colleagues and friends. Second, it is a collection of specially written review articles by world-class scientists that take the readers from the origins of modem materials science through to the cutting edge of the subject in the twenty- first century. The book will be a valuable resource for all researchers in materials science, particularly those specialising in electron microscopy and diffraction, and in the mechanical properties of materials. The front and back covers of this book are coloured images of historic electron micrographs depicting the first observation in the world of moving dislocations. The pictures were taken by Mike Whelan, then a research student of Peter Hirsch. The image on the front cover is before some dislocations have moved, and the back cover image is after the movement. See if you can spot the difference! This book had its genesis in a symposium organised by Mike Goringe, John Hutchison and myself to mark the retirement of Peter Hirsch from the Isaac Wolfson Chair of Metallurgy at Oxford. This symposium brought together a large number of Peter's former students and colleagues. Some of the most distinguished of these have now written the chapters in this book. The opening chapter, by Professor Ugo Valdre, provides a fascinating biographical sketch of Peter Hirsch from his early career in Cambridge to his retirement in Oxford. It contains many illuminating insights into the personality of Peter, both as a scientist and as a man. The next two chapters focus on the development of electron microscopy and diffraction. Professor Mike Whelan gives an eye-witness account of the seminal early work of Peter and his colleagues at Cambridge on the first observation of dislocations and their movements, using trans-mission electron microscopy. Professor Archie Howie extends this account to the present day, describing nanometer-scale resolution in scanning electron microscopes and atomic scale resolution in the scanning tunnelling microscope.
Book Synopsis Fundamental Aspects of Dislocation Interactions by : G. Kostorz
Download or read book Fundamental Aspects of Dislocation Interactions written by G. Kostorz and published by Elsevier. This book was released on 2013-09-03 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III covers the papers presented at a European Research Conference on Plasticity of Materials-Fundamental Aspects of Dislocation Interactions: Low-Energy Dislocation Structures III, held on August 30-September 4, 1992 in Ascona, Switzerland. The book focuses on the processes, technologies, reactions, transformations, and approaches involved in dislocation interactions. The selection first offers information on work softening and Hall-Petch hardening in extruded mechanically alloyed alloys and dynamic origin of dislocation structures in deformed solids. Discussions focus on stress-strain behavior in relation to composition, structure, and annealing; comparison of stress-strain curves with work softening theory; sweeping and trapping mechanism; and model of dipolar wall structure formation. The text then ponders on plastic instabilities and their relation to fracture and dislocation and kink dynamics in f.c.c. metals studied by mechanical spectroscopy. The book takes a look at misfit dislocation generation mechanisms in heterostructures and evolution of dislocation structure on the interfaces associated with diffusionless phase transitions. Discussions focus on dislocation representation of a wall of elastic domains; equation of equilibrium of an elastic domain; transformation of dislocations; and theoretical and experimental background. The selection is a valuable reference for readers interested in dislocation interactions.
Book Synopsis Microstructural Characterization of Dislocation Networks During Harper-Dorn Creep of Fcc, Bcc, and Hcp Metals and Alloys by :
Download or read book Microstructural Characterization of Dislocation Networks During Harper-Dorn Creep of Fcc, Bcc, and Hcp Metals and Alloys written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Harper-Dorn (H-D) creep is observed in metals and geological materials exposed to very low stresses at temperatures close to the melting point. It is one of several types of creep processes wherein the steady-state strain rate is proportional to the applied stress, Nabarro-Herring creep and Coble creep being two other important processes. H-D creep can be somewhat insidious because the creep rates are much larger than those expected for Nabarro-Herring or Coble creep. Since the working conditions of structural components of power plants and propulsion systems, as well as the motion of the earth's mantle all involve very low stresses, an understanding of the factors controlling H-D creep is critical in preventing failures associated with those higher-than-expected creep rates. The purpose of this investigation was to obtain missing microstructural information on the evolution of the dislocation structures during static annealing of materials with fcc, bcc and hcp structure and use obtained results to test predictive capabilities of the dislocation network theory of H-D creep. In our view the evolutionary processes during static annealing and during Harper-Dorn creep are intimately related. The materials used in this study were fcc aluminum, hcp zinc and bcc tin. All characterizations of dislocation structures, densities and dislocation link length distributions were carried out using the etch pit method. To obtain quantitative information on the evolution of the dislocation networks during annealing the pure fcc aluminum samples were pre-deformed by creep at 913 and 620 K and then annealed. The higher deformation temperature was selected to generate starting dislocation networks similar to those forming during Harper-Dorn creep and the lower, to obtain higher dislocation densities suitable for reliable estimates of the parameters of the network growth law. The measured experimental link length distribution were, after scaling, (1) the same for all annealing temperatures, (2) time invariant and (3) identical to the distributions obtained previously for Harper-Dorn creep. This has never been shown before and confirms our theoretical expectations that evolution of the dislocation networks during annealing and H-D creep is governed by the same growth law. Obtained results were also used to predict H-D steady creep rates from annealing kinetics data using equations of the dislocation network theory. For the three considered stresses the theory predicts systematically smaller creep rates by the average factor of 4.5. Considering that the creep rates have been predicted from the annealing data alone and without any adjustable parameters, this results shout be considered as outstanding. In case of hcp zinc the samples were pre-deformed in compression at constant stress of 4 MPa at temperature of 573 K and subsequently annealed at the same temperature. During annealing samples readily recrystallized, but it was possible to obtain information on the link length distributions from several unrecrystallized grains. The results showed that the scaled link length distributions were time invariant and similar to those of the aluminum. The annealing studies on bcc tin were also curtailed by the concurrent recrystallization. It was only possible to obtain link length distribution for samples deformed in compression at constant load of 2 MPa at 423 K after unloading. The link length distribution was also in this case similar to that of the aluminum and zinc. These results suggest that the scaled link length distribution is universal and the same for the three considered crystal structures. This supports theoretical findings of these studies that appropriately scaled dislocation link length distribution should both universal and time invariant. We have also investigated the possibility of using alternative methods of estimating local dislocation densities from etch pits which could give more precise estimates of the dislocation link-lengths. The two most promising method are based on the use of Voronoi diagrams and uniform 3-connected nets. Both methods require further testing before they can be used in confidence in the analysis of the etch pit results.
Book Synopsis HREM Examination of Core Structures of Dislocations in B2 Intermetallic Compound Co-Al by : Yu Zhang
Download or read book HREM Examination of Core Structures of Dislocations in B2 Intermetallic Compound Co-Al written by Yu Zhang and published by . This book was released on 1995 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dislocations in Solids written by and published by Elsevier. This book was released on 2004-08-05 with total page 603 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 Kléman 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, Kléman, 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.
Book Synopsis Purification Process and Characterization of Ultra High Purity Metals by : Yoshio Waseda
Download or read book Purification Process and Characterization of Ultra High Purity Metals written by Yoshio Waseda and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book starts with an extended introductory treatise on the fundamentals before moving on to a detailed description of the new methods of purification of transition metals and rare earth metals.
Book Synopsis Dislocation Structures in Single Crystal Tungsten and Tungsten Alloys by : Joseph R. Stephens
Download or read book Dislocation Structures in Single Crystal Tungsten and Tungsten Alloys written by Joseph R. Stephens and published by . This book was released on 1969 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Internal Friction in Metallic Materials by : Mikhail S. Blanter
Download or read book Internal Friction in Metallic Materials written by Mikhail S. Blanter and published by Springer Science & Business Media. This book was released on 2007-05-17 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a unique collection of experimental data in the field of internal friction, anelastic relaxation, and damping properties of metallic materials. It reviews virtually all anelastic relaxation phenomena ever published. The reader is also supplied with explanations of the basic physical mechanisms of internal friction, a summary of typical effects for different groups of metals, and more than 2000 references to original papers.
Book Synopsis Stochastic Studies of Dislocation Mobility in BCC Alloys by : Chaitanya Suresh Deo
Download or read book Stochastic Studies of Dislocation Mobility in BCC Alloys written by Chaitanya Suresh Deo and published by . This book was released on 2003 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Defects and Diffusion in Metals, 2003 by : David J. Fisher
Download or read book Defects and Diffusion in Metals, 2003 written by David J. Fisher and published by Trans Tech Publications Ltd. This book was released on 2003-12-12 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: This sixth volume in the series covering the latest results in the field includes abstracts of papers which appeared between the publication of Annual Retrospective V (Volumes 213-215) and the end of October 2003.
Book Synopsis Heterostructured Materials by : Xiaolei Wu
Download or read book Heterostructured Materials written by Xiaolei Wu and published by CRC Press. This book was released on 2021-11-24 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heterostructured (HS) materials represent an emerging class of materials that are expected to become a major research field for the communities of materials, mechanics, and physics in the next couple of decades. One of the biggest advantages of HS materials is that they can be produced by large-scale industrial facilities and technologies and therefore can be commercialized without the scaling up and high-cost barriers that are often encountered by other advanced materials. This book collects recent papers on the progress in the field of HS materials, especially their fundamental physics. The papers are arranged in a sequence of chapters that will help new researchers entering the field to have a quick and comprehensive understanding of HS materials, including the fundamentals and recent progress in their processing, characterization, and properties.
