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Languages : en
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Abstract : Grain boundary segregation is well known to cause significant embrittlement of alloys. But in certain cases, it has also been observed to increase mechanical strength. This project attempts to assess local mechanical behavior of specific grain boundaries with and without segregation in order to understand association between grain boundary chemistry and deformation mechanism utilizing instrumented nanoindentation technique. It is hypothesized that solute segregation strongly affects the grain boundary energy which in turn affects the deformation mechanism processes. This project also utilizes a unique ability provided by the instrumented indentation technique to interrogate local grain boundary strengthening mechanisms proposed by Hall-Petch and Taylor-Ashby using two different indentation geometries. Grain boundary mechanical properties have typically been interpolated from macroscopic mechanical testing on polycrystalline materials, or alternatively, mechanical test procedures carried out on bulk bicrystals. The disadvantages to these types of studies relate to the difficulty in extracting the local response of a particular grain boundary (in the case of polycrystalline materials) or the grain boundary region (in the case of a bicrystal material) from the overall response of the complex interaction between the presence of the grain boundary and the deformation behavior far from the grain boundary. That is, the grain boundary causes a non-local response to the mechanical behavior. This non-local response is particularly evident in bicrystal deformation, where the macroscopic plastic displacement is inconsistent with that observed for single crystal deformation. Moreover, local hardness testing of grain boundary regions in macroscopically deformed materials show that the deformation in the grain boundary region is leads to greater local dislocation density than found in the grain center. This project is designed to use nanoindentation to isolate the mechanical response of the grain boundary as the dependent variable, where indentation geometry, indentation rate, grain boundary misorientation and sample chemistry are the independent experimental variables. It is proposed that this approach can provide insight into long standing hypotheses regarding grain boundary strengthening mechanisms, including the Hall-Petch pile-up theory, grain boundary source theory, grain boundary layer theory and the Ashby-Taylor strain incompatibility theory.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Abstract : Grain boundary segregation is well known to cause significant embrittlement of alloys. But in certain cases, it has also been observed to increase mechanical strength. This project attempts to assess local mechanical behavior of specific grain boundaries with and without segregation in order to understand association between grain boundary chemistry and deformation mechanism utilizing instrumented nanoindentation technique. It is hypothesized that solute segregation strongly affects the grain boundary energy which in turn affects the deformation mechanism processes. This project also utilizes a unique ability provided by the instrumented indentation technique to interrogate local grain boundary strengthening mechanisms proposed by Hall-Petch and Taylor-Ashby using two different indentation geometries. Grain boundary mechanical properties have typically been interpolated from macroscopic mechanical testing on polycrystalline materials, or alternatively, mechanical test procedures carried out on bulk bicrystals. The disadvantages to these types of studies relate to the difficulty in extracting the local response of a particular grain boundary (in the case of polycrystalline materials) or the grain boundary region (in the case of a bicrystal material) from the overall response of the complex interaction between the presence of the grain boundary and the deformation behavior far from the grain boundary. That is, the grain boundary causes a non-local response to the mechanical behavior. This non-local response is particularly evident in bicrystal deformation, where the macroscopic plastic displacement is inconsistent with that observed for single crystal deformation. Moreover, local hardness testing of grain boundary regions in macroscopically deformed materials show that the deformation in the grain boundary region is leads to greater local dislocation density than found in the grain center. This project is designed to use nanoindentation to isolate the mechanical response of the grain boundary as the dependent variable, where indentation geometry, indentation rate, grain boundary misorientation and sample chemistry are the independent experimental variables. It is proposed that this approach can provide insight into long standing hypotheses regarding grain boundary strengthening mechanisms, including the Hall-Petch pile-up theory, grain boundary source theory, grain boundary layer theory and the Ashby-Taylor strain incompatibility theory.
Author: Prasad Pramod Soman
Publisher:
ISBN:
Category : Grain boundaries
Languages : en
Pages : 0
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Book Description
Grain boundary segregation is well known to cause significant embrittlement of alloys. But in certain cases, it has also been observed to increase mechanical strength. This project attempts to assess local mechanical behavior of specific grain boundaries with and without segregation in order to understand association between grain boundary chemistry and deformation mechanism utilizing instrumented nanoindentation technique. It is hypothesized that solute segregation strongly affects the grain boundary energy which in turn affects the deformation mechanism processes. This project also utilizes a unique ability provided by the instrumented indentation technique to interrogate local grain boundary strengthening mechanisms proposed by Hall-Petch and Taylor-Ashby using two different indentation geometries. Grain boundary mechanical properties have typically been interpolated from macroscopic mechanical testing on polycrystalline materials, or alternatively, mechanical test procedures carried out on bulk bicrystals. The disadvantages to these types of studies relate to the difficulty in extracting the local response of a particular grain boundary (in the case of polycrystalline materials) or the grain boundary region (in the case of a bicrystal material) from the overall response of the complex interaction between the presence of the grain boundary and the deformation behavior far from the grain boundary. That is, the grain boundary causes a non-local response to the mechanical behavior. This non-local response is particularly evident in bicrystal deformation, where the macroscopic plastic displacement is inconsistent with that observed for single crystal deformation. Moreover, local hardness testing of grain boundary regions in macroscopically deformed materials show that the deformation in the grain boundary region is leads to greater local dislocation density than found in the grain center. This project is designed to use nanoindentation to isolate the mechanical response of the grain boundary as the dependent variable, where indentation geometry, indentation rate, grain boundary misorientation and sample chemistry are the independent experimental variables. It is proposed that this approach can provide insight into long standing hypotheses regarding grain boundary strengthening mechanisms, including the Hall-Petch pile-up theory, grain boundary source theory, grain boundary layer theory and the Ashby-Taylor strain incompatibility theory.
Author: Ali Argon
Publisher: Oxford University Press on Demand
ISBN: 0198516002
Category : Science
Languages : en
Pages : 425
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Book Description
Technologically important metals and alloys have been strengthened throughout history by empirical means. The scientific bases of the central mechanisms of such forms of strengthening, developed over the past several decades are presented here through mechanistic models and associated experimental results.
Author: Franz Roters
Publisher: John Wiley & Sons
ISBN: 3527642099
Category : Technology & Engineering
Languages : en
Pages : 188
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Book Description
Written by the leading experts in computational materials science, this handy reference concisely reviews the most important aspects of plasticity modeling: constitutive laws, phase transformations, texture methods, continuum approaches and damage mechanisms. As a result, it provides the knowledge needed to avoid failures in critical systems udner mechanical load. With its various application examples to micro- and macrostructure mechanics, this is an invaluable resource for mechanical engineers as well as for researchers wanting to improve on this method and extend its outreach.
Author: S H Whang
Publisher: Elsevier
ISBN: 0857091123
Category : Technology & Engineering
Languages : en
Pages : 840
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Book Description
Tensile strength, fatigue strength and ductility are important properties of nanostructured metallic materials, which make them suitable for use in applications where strength or strength-to-weight ratios are important. Nanostructured metals and alloys reviews the latest technologies used for production of these materials, as well as recent advances in research into their structure and mechanical properties.One of the most important issues facing nanostructured metals and alloys is how to produce them. Part one describes the different methods used to process bulk nanostructured metals and alloys, including chapters on severe plastic deformation, mechanical alloying and electrodeposition among others. Part two concentrates on the microstructure and properties of nanostructured metals, with chapters studying deformation structures such as twins, microstructure of ferrous alloys by equal channel angular processing, and characteristic structures of nanostructured metals prepared by plastic deformation. In part three, the mechanical properties of nanostructured metals and alloys are discussed, with chapters on such topics as strengthening mechanisms, nanostructured metals based on molecular dynamics computer simulations, and surface deformation. Part four focuses on existing and developing applications of nanostructured metals and alloys, covering topics such as nanostructured steel for automotives, steel sheet and nanostructured coatings by spraying.With its distinguished editor and international team of contributors, Nanostructured metals and alloys is a standard reference for manufacturers of metal components, as well as those with an academic research interest in metals and materials with enhanced properties.
Author: Isao Tanaka
Publisher: Springer
ISBN: 9789811677144
Category : Technology & Engineering
Languages : en
Pages : 278
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Book Description
This open access book presents the novel concept of plaston, which accounts for the high ductility or large plastic deformation of emerging high-performance structural materials, including bulk nanostructured metals, hetero-nanostructured materials, metallic glasses, intermetallics, and ceramics.The book describes simulation results of the collective atomic motion associated with plaston, by computational tools such as first-principle methods with predictive performance and large-scale atom-dynamics calculations. Multi-scale analyses with state-of-the art analytical tools nano/micro pillar deformation and nano-indentation experiments are also described. Finally, through collaborative efforts of experimental and computational work, examples of rational design and development of new structural materials are given, based on accurate understanding of deformation and fracture phenomena.This publication provides a valuable contribution to the field of structural materials research.
Author: Yuqing Weng
Publisher: Springer Science & Business Media
ISBN: 3540772308
Category : Technology & Engineering
Languages : en
Pages : 588
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Book Description
This book discusses results of the New Generation Iron and Steel Materials research project funded over the last ten years. It thoroughly describes theoretical achievements in ultra-fine grain steel and its refinement. It also discusses progress in related areas of engineering and technology. The author has been engaged in the research of new generation structural materials for the last twelve years being Chief Scientist of three national research programs in China.
Author: Rozaliya Barabash
Publisher: World Scientific
ISBN: 1908979631
Category : Science
Languages : en
Pages : 478
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Book Description
This book highlights emerging diffraction studies of strain and dislocation gradients with mesoscale resolution, which is currently a focus of research at laboratories around the world. While ensemble-average diffraction techniques are mature, grain and subgrain level measurements needed to understand real materials are just emerging. In order to understand the diffraction signature of different defects, it is necessary to understand the distortions created by the defects and the corresponding changes in the reciprocal space of the non-ideal crystals. Starting with a review of defect classifications based on their displacement fields, this book then provides connections between different dislocation arrangements, including geometrically necessary and statistically stored dislocations, and other common defects and the corresponding changes in the reciprocal space and diffraction patterns. Subsequent chapters provide an overview of microdiffraction techniques developed during the last decade to extract information about strain and dislocation gradients. X-ray microdiffraction is a particularly exciting application compared with alternative probes of local crystalline structure, orientation and defect density, because it is inherently non-destructive and penetrating.
Author: D. Caillard
Publisher: Elsevier
ISBN: 0080542786
Category : Technology & Engineering
Languages : en
Pages : 453
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Book Description
KEY FEATURES: - A unified, fundamental and quantitative resource. The result of 5 years of investigation from researchers around the world - New data from a range of new techniques, including synchrotron radiation X-ray topography provide safer and surer methods of identifying deformation mechanisms - Informing the future direction of research in intermediate and high temperature processes by providing original treatment of dislocation climb DESCRIPTION: Thermally Activated Mechanisms in Crystal Plasticity is a unified, quantitative and fundamental resource for material scientists investigating the strength of metallic materials of various structures at extreme temperatures. Crystal plasticity is usually controlled by a limited number of elementary dislocation mechanisms, even in complex structures. Those which determine dislocation mobility and how it changes under the influence of stress and temperature are of key importance for understanding and predicting the strength of materials. The authors describe in a consistent way a variety of thermally activated microscopic mechanisms of dislocation mobility in a range of crystals. The principles of the mechanisms and equations of dislocation motion are revisited and new ones are proposed. These describe mostly friction forces on dislocations such as the lattice resistance to glide or those due to sessile cores, as well as dislocation cross-slip and climb. They are critically assessed by comparison with the best available experimental results of microstructural characterization, in situ straining experiments under an electron or a synchrotron beam, as well as accurate transient mechanical tests such as stress relaxation experiments. Some recent attempts at atomistic modeling of dislocation cores under stress and temperature are also considered since they offer a complementary description of core transformations and associated energy barriers. In addition to offering guidance and assistance for further experimentation, the book indicates new ways to extend the body of data in particular areas such as lattice resistance to glide.
Author: Anthony C. Fischer-Cripps
Publisher: Springer Science & Business Media
ISBN: 1475759436
Category : Technology & Engineering
Languages : en
Pages : 283
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Book Description
This new edition of Nanoindentation includes a dedicated chapter on thin films, new material on dynamic analysis and creep, accounts of recent research, and three new appendices on nonlinear least squares fitting, frequently asked questions, and specifications for a nanoindentation instrument. Nanoindentation Second Edition is intended for those who are entering the field for the first time and to act as a reference for those already conversant with the technique.
