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Author: Saryu Jindal Fensin
Publisher:
ISBN: 9781124315690
Category :
Languages : en
Pages :
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Book Description
This thesis reports research involving the development and application of atomistic simulation methods to study the effects of high homologous temperatures on the structural, thermodynamic, kinetic and mechanical properties of grain boundaries in metals. In this work we study two different elemental systems, namely Ni and Cu, and consider a variety of grain boundary structures characterized by different misorientation angles, twist/tilt character and zero-temperature energies. A method to calculate the disjoining potential from molecular dynamics is developed and applied to grain boundaries in Ni. The disjoining potential characterizes the variation in grain-boundary free energy as a function of the width of a premelted interfacial layer. The MD method for the calculation of this property is applied to grain boundaries that display continuous premelting transitions, as well as a boundary characterized by a disordered atomic structure displaying a finite interfacial width at the melting temperature. We also develop analysis methods to characterize the change in the atomic structure of an asymmetric tilt grain boundary in elemental Cu as a function of temperature. This boundary is characterized by a potential-energy surface with multiple minima as a function of the relative translation of the grains parallel to the interface plane. The structure of this boundary is found to display both disordering and roughening with increasing temperature. The mobility was calculated at high homologous temperatures using a method based on the analysis of the random walk of the interface in equilibrium MD simulations. Finally, the temperature dependent response of this grain boundary to shear was investigated. The dynamical behavior of the boundary in response to an applied shear strain was observed to undergo qualitative changes as the temperature was increased above 700 K.A decrease in shear resistance of the grain boundaries as a function of temperature was characterized by a decrease in the critical shear stress, an upper bound for which was estimated to be roughly a factor of five lower at the melting temperature than at zero temperature.
Author: Saryu Jindal Fensin
Publisher:
ISBN: 9781124315690
Category :
Languages : en
Pages :
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Book Description
This thesis reports research involving the development and application of atomistic simulation methods to study the effects of high homologous temperatures on the structural, thermodynamic, kinetic and mechanical properties of grain boundaries in metals. In this work we study two different elemental systems, namely Ni and Cu, and consider a variety of grain boundary structures characterized by different misorientation angles, twist/tilt character and zero-temperature energies. A method to calculate the disjoining potential from molecular dynamics is developed and applied to grain boundaries in Ni. The disjoining potential characterizes the variation in grain-boundary free energy as a function of the width of a premelted interfacial layer. The MD method for the calculation of this property is applied to grain boundaries that display continuous premelting transitions, as well as a boundary characterized by a disordered atomic structure displaying a finite interfacial width at the melting temperature. We also develop analysis methods to characterize the change in the atomic structure of an asymmetric tilt grain boundary in elemental Cu as a function of temperature. This boundary is characterized by a potential-energy surface with multiple minima as a function of the relative translation of the grains parallel to the interface plane. The structure of this boundary is found to display both disordering and roughening with increasing temperature. The mobility was calculated at high homologous temperatures using a method based on the analysis of the random walk of the interface in equilibrium MD simulations. Finally, the temperature dependent response of this grain boundary to shear was investigated. The dynamical behavior of the boundary in response to an applied shear strain was observed to undergo qualitative changes as the temperature was increased above 700 K.A decrease in shear resistance of the grain boundaries as a function of temperature was characterized by a decrease in the critical shear stress, an upper bound for which was estimated to be roughly a factor of five lower at the melting temperature than at zero temperature.
Author: Gunter Gottstein
Publisher: CRC Press
ISBN: 9780849382222
Category : Technology & Engineering
Languages : en
Pages : 454
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Book Description
The behavior of adjacent materials at the boundary where they meet is an essential aspect of creating new engineering materials. Grain Boundary Migration in Metals is an authoritative account of the physics of grain boundary motion, written by two highly respected researchers. They provide a comprehensive overview of current knowledge regarding the migration process and how it affects microstructure evolution, focusing their treatment exclusively on the properties and behavior of grain boundaries with well defined geometry and crystallography. With their emphasis on applications-such as the characterization of microstructure and texture, recrystallization, and grain growth-the authors effectively fill the gap between the physics of grain boundary motion and its engineering practicality. The need for better microstructural design motivates permanent thrust for research in the field, and continued rapid progress appears inevitable. Grain Boundary Migration in Metals provides a solid foundation in the phenomena and serves as a valuable reference for professionals in materials science, solid state physics, and any industry engaged in metals production and the heat treatment of metals and alloys.
Author:
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ISBN:
Category :
Languages : en
Pages :
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An attempt is made to distinguish those fundamental aspects of grain boundaries which should be relevant to the problem of the time dependent fracture of high temperature structural materials. These include the basic phenomena which are thought to be associated with cavitation and cracking at grain boundaries during service and with the more general microstructural changes which occur during both processing and service. A very brief discussion of the current state of knowledge of these fundamentals is given.
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Category : Aeronautics
Languages : en
Pages : 702
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Book Description
Author: Pavel Lejcek
Publisher: Springer Science & Business Media
ISBN: 3642125050
Category : Technology & Engineering
Languages : en
Pages : 249
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Book Description
Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.
Author: Thomas Tsakalakos
Publisher: Springer Science & Business Media
ISBN: 9400710194
Category : Technology & Engineering
Languages : en
Pages : 694
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Book Description
The Advanced Study Institute on Synthesis, Functional Properties and Applications of Nanostructures, held at the Knossos Royal Village, Heraklion, Crete, Greece, July 26, 2002 - August 4, 2002, successfully reviewed the state-of-the-art of nanostructures and nanotechnology. It was concluded that Nanotechnology is widely agreed to be the research focus that will lead to the next generation of breakthroughs in science and engineering. There are three cornerstones to the expectation that Nanotechnology will yield revolutionary advances in understanding and application: • Breakthroughs in properties that arise from materials fabricated from the nanoscale. • Synergistic behavior that arise from the combination of disparate types of materials (soft vs. hard, organic vs. inorganic, chemical vs. biological vs. solid state) at the nanoscale. • Exploitation of natural (e.g. chemical and biological) assembly mechanisms that can accomplish structural control at the nanoscale. It is expected that this will lead to paradigms for assembling bio-inspired functional systems that accomplish desirable properties that are either unavailable or prohibitively expensive using top-down approaches.
Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 754
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Book Description
Author: Geoffrey Allan Chadwick
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 422
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Book Description
Author: J. F. Nye
Publisher: Oxford University Press
ISBN: 9780198511656
Category : Mathematics
Languages : en
Pages : 356
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Book Description
First published in 1957, this classic study has been reissued in a paperback version that includes an additional chapter bringing the material up to date. The author formulates the physical properties of crystals systematically in tensor notation, presenting tensor properties in terms of their common mathematical basis and the thermodynamic relations between them. The mathematical groundwork is laid in a discussion of tensors of the first and second ranks. Tensors of higher ranks and matrix methods are then introduced as natural developments of the theory. A similar pattern is followed in discussing thermodynamic and optical aspects.
Author: Tianyi Chen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Our study is focused on the behavior of grain boundaries in uranium dioxide system under irradiation conditions. The research can be seen as two parts: the study of interaction of the grain boundary and the damage cascade, and the calculation of Kapitza resistance of grain boundaries. The connection between these two parts lies in that damage cascades bring in changes in the structure and other properties of grain boundaries, and inevitably the Kapitza resistance of the grain boundary changes as well. For the first part, we studied interactions of grain boundaries and damage cascades in uranium dioxide system by simulating two types of bombardments: one direct bombardment into a grain boundary leading to ballistic-collision-mediated interface mixing; the other bombardment is in the close vicinity of a grain boundary causing interface biased defect migration. We found that more defects are trapped by the grain boundary followed by the first type of bombardment, resulting in enhanced grain boundary energy. By comparing with the second type of bombardment, we are able to reveal the mechanisms of the interaction between defects and grain boundaries. For the second part, we employed the non-equilibrium molecular dynamics method to calculate the Kapitza resistance of different coincident site lattice boundaries with or without defects loaded, and later we found that a universal positive correlation between the Kapitza resistance and the grain boundary energy can be well established, regardless of the cause of boundary energy changes. Our study provides a deeper understanding of the Kapitza resistance of the grain boundary and its evolutions under irradiation, which benefits multi-scale modeling of uranium dioxide thermal properties under extreme radiation conditions as well as experimental studies of fuel material thermal properties. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151387
