Download or read book Influence of Grain Misorientation on Grain Growth in Nanocrystalline Metals written by Justin Glen Brons and published by . This book was released on 2013 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that the grain size of a material controls its properties, including mechanical strength, electrical conduction, and corrosion resistance. Typically, a fine grain size is desirable, since it allows for these properties to be increased. Nanocrystalline materials have been engineered in order to maximize the benefits associated with this fine grain size. Unfortunately, the high density of grain boundaries for a given volume of the material leads to an increase in the excess energy that is associated with grain boundaries. This excess energy can act as a driving force for grain growth, which causes these nanocrystalline structures to be unstable, with this grain growth often times being detrimental to the material properties. This research investigated the influence of grain boundary mobility and the applied driving force on grain growth in nanocrystalline metal films by focusing on the role grain boundary misorientation plays in regulating grain growth. The was be accomplished by completing two types of studies: (i) Annealing sputter-deposited thin films to study mobility in a case where the driving force is assumed to be dominated by grain boundary curvature and (ii) Mechanically indenting thin films with different microstructural features while submerged in liquid nitrogen. In terms of the latter study, the mobility was expected to be extremely low due to the cryogenic temperatures. Both sets of films were then characterized using precession-enhanced diffraction-based orientation analysis in the transmission electron microscope to quantify the evolution in grain size, grain morphology, and in the grain-to-grain misorientation.

Download or read book Grain Boundary Influence on Radiation Induced Defect Evolution in Nanocrystalline Metals written by James Nathaniel (II) and published by . This book was released on 2019 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of materials that can better withstand the operating environment within nuclear reactors is of critical importance for the longevity of existing and the robustness of future nuclear energy systems. It is conjectured that nanocrystalline materials should exhibit significant reductions in radiation damage, however despite extensive studies, fundamental questions remain regarding defect evolution and migration to grain boundaries. Specifically, the role of grain size and grain boundary properties must be understood to develop insights into how to create new material microstructures that have enhanced radiation tolerance. The work presented makes use of in situ and ex situ experimental approaches to examine the role of grain size and grain boundary character in response to radiation damage in model FCC metals. Heavy ion irradiation experiments were carried out on metal foils under varying experimental conditions followed by post-irradiation analysis of grains ranging from 10 nm to 200 nm in size. Transmission electron microscopy (TEM) and related techniques were used to evaluate defect densities (dislocations and cavities) and defect cluster size as a function of grain size and grain boundary misorientation. Phenomena related to grain boundary response to damage absorption and sink efficiency are examined as well. The goal of this work is to contribute to building a fundamental framework for microstructural design to fabricate more radiation tolerant materials.

Download or read book Grain Rotation as a Mechanism of Grain Growth in Nanocrystalline Materials written by and published by . This book was released on 2002 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain-boundary (GB) properties in a polycrystalline system are generally anisotropic; in particular, both the GB energy and mobility depend on the GB misorientation. Moreover, in nanocrystalline materials, in which the grain size is less than 100 nm, grain rotations leading to the coalescence of neighboring grains via elimination of the common GB between them may provide a new mechanism for grain growth. Here they investigate the combined effect of curvature-driven GB migration and grain-rotation grain-coalescence on the kinetics, topology and morphology of grain growth. A stochastic velocity-Monte-Carlo algorithm based on a variational formulation for the dissipated power is implemented. The presence of both growth mechanisms introduces a physical length scale R{sub c} into the system, enabling the growth process to be characterized by two regimes. If the average grain size is smaller than R{sub c}, grain growth is dominated by the grain-rotation-coalescence mechanism. By contrast, if the average grain size is greater than R{sub c}, growth is dominated by curvature-driven GB migration. The values of the growth exponents, different for the two growth regimes and different from a system with isotropic GB properties, are rationalized in terms of the detailed growth mechanism and the continuous change of the fraction of low-angle GBs in the system. An extended von Neumann-Mullins relation based on averaged GB properties is proposed and verified.

Download or read book Recrystallization and Grain Growth in Metals written by P. Cotterill and published by John Wiley & Sons. This book was released on 1976 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transmission Electron Microscopy written by C. Barry Carter and published by Springer. This book was released on 2016-08-24 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text is a companion volume to Transmission Electron Microscopy: A Textbook for Materials Science by Williams and Carter. The aim is to extend the discussion of certain topics that are either rapidly changing at this time or that would benefit from more detailed discussion than space allowed in the primary text. World-renowned researchers have contributed chapters in their area of expertise, and the editors have carefully prepared these chapters to provide a uniform tone and treatment for this exciting material. The book features an unparalleled collection of color figures showcasing the quality and variety of chemical data that can be obtained from today’s instruments, as well as key pitfalls to avoid. As with the previous TEM text, each chapter contains two sets of questions, one for self assessment and a second more suitable for homework assignments. Throughout the book, the style follows that of Williams & Carter even when the subject matter becomes challenging—the aim is always to make the topic understandable by first-year graduate students and others who are working in the field of Materials Science Topics covered include sources, in-situ experiments, electron diffraction, Digital Micrograph, waves and holography, focal-series reconstruction and direct methods, STEM and tomography, energy-filtered TEM (EFTEM) imaging, and spectrum imaging. The range and depth of material makes this companion volume essential reading for the budding microscopist and a key reference for practicing researchers using these and related techniques.

Download or read book Recrystallization and Grain Growth III written by Suk Joong L. Kang and published by Trans Tech Publications Ltd. This book was released on 2007-10-15 with total page 1544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recrystallization and grain-growth, together with phase transformations, are the fundamental processes of microstructural evolution which occur during the thermomechanical treatment of engineering materials. Volume is indexed by Thomson Reuters CPCI-S (WoS).

Download or read book Grain Growth in Polycrystalline Materials II written by Hideo Yoshinaga and published by . This book was released on 1996 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain Growth is one of the most fundamental microstructural changes, and occurs in all types of polycrystalline material. It is of major scientific interest, and of great importance in a wide range of industrial applications. This volume presents the most recent contributions to the research effort on the experimental study, theory and simulation of grain growth. Currently available experimental data are compared with recent theoretical results, and the most promising areas for future research are identified. Applications of the new findings to industrial experiences and problems are presented. The principal topics covered are normal and abnormal grain growth, texture, drag effects, topological aspects, grain size-effects, and boundary structure, mobility and interaction with particles and impurity atoms.

Download or read book Understanding the Mechanistic Role of Grain Boundaries on the Strength and Deformation of Nanocrystalline Metals Using Atomistic Simulations written by Satish Rajaram and published by . This book was released on 2019 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline (NC) materials, defined structurally by having average grain sizes less than 100nm, exhibit a number of enhanced mechanical properties such as ultrahigh strength, improved wear resistance and greater resistance to fatigue crack initiation compared to coarser grained polycrystalline (PC) materials. NC materials exhibit these improved properties, in part, due to the increased grain boundary (GB) volume fraction. NC materials strength increases with decreasing grain size, known as the Hall-Petch (HP) effect often resulting in a peak strength between 10-20nm. Studies have shown that NC materials strength decreases due to the shift from dislocation-dominant to GB-dominant deformation mechanisms in the plastic flow regime as average grain size decreases below 10-20nm. While the potential improved properties are of interest, the application of NC materials are hindered due to microstructural instability i.e., grain growth to reduce the total energy of the system, thus degrading desired mechanical properties. Numerous studies have looked at avenues to stabilize NC microstructure, namely through thermodynamics and kinetics, alloying has been one significant strategy used to stabilize NC materials. As these processes are used to stabilize NC microstructures to thermally-induce grain growth, they add additional uncertainty as the deformation and GB behavior of pure NC materials are still not fully understood. Experimental work on NC materials is difficult due to the length scale being investigated as it is difficult to manufacture and can be time consuming to analyze with current technology. Atomistic simulations have shown the potential to investigate fundamental behavior at the nanoscale and provide important insight in the mechanisms that drive the mechanical behavior of NC materials. This thesis will use atomistic simulations to study the structure-property relationship of face-centered-cubic (fcc) metals by focusing on GBs to investigate the strength of NC nickel. During the course of this thesis, four aspects that govern NC behavior will be studied, yielding, plasticity, thermal effects, and GB disorder to elucidate deeper insight into the underlying deformation mechanisms that control the strength of FCC NC metals i.e., flow stress, in the grain size regime 6 to 20nm.

Download or read book Influences of Stress driven Grain Boundary Motion on Microstructural Evolution in Nanocrystalline Metals written by Mohammad Aramfard and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline (NC) metals with averaged grain size smaller than 100 nm have shown promising mechanical properties such as higher hardness and toughness than conventional coarse-grained metals. Unlike conventional metals in which the deformation is controlled by dislocation activities, the microstructural evolution in NC metals is mainly dominated by grain rotation and stress-driven grain boundary motion (SDGBM) due to the high density of grain boundaries (GBs). SDGBM is thus among the most studied modes of microstructural evolution in NC materials with particular interests on their fundamental atomistic mechanisms. In the first part of this thesis, molecular dynamics simulations were used to investigate the influences of Triple Junctions (TJs) on SDGBM of symmetric tilt GBs in copper by considering a honeycomb NC model. TJs exhibited asymmetric pinning effects to the GB migration and the constraints by the TJs and neighboring grains led to remarkable non-linear GB motion in directions both parallel and normal to the applied shear. Based on these findings, a generalized model for SDGBM in NC Cu was proposed. In the second part, the interaction of SDGBM with crack, voids and precipitates was investigated. It was found that depending on the GB structure, material type and temperature, there is a competition between different atomistic mechanisms such as crack healing, recrystallization and GB decohesion. It is hoped that the findings of this work could clarify the micro-mechanisms of various experimental phenomena such as grain refinement in metals during severe plastic deformation, which can be used to design optimized route of making stabilized bulk NC metals.

Download or read book Quantification of Grain Boundary Mediated Plasticity Mechanisms in Nanocrystalline Metals written by Jason F. Panzarino and published by . This book was released on 2016 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline metals have been a topic of great discussion over recent years due to their exceptional strengths and novel grain boundary-mediated deformation mechanisms. Their microstructures are known to evolve through dynamic processes such as grain boundary migration and grain rotation, but how the collective interaction of these mechanisms alter the microstructure on a larger scale is not completely understood. In this thesis, we present coupled atomistic modeling and experimental tasks that aim to understand how the grain structure, grain boundaries, and associated grain boundary network change during nanocrystalline plasticity. Due to the complex three-dimensional nature of these mechanisms and the limited spatial and temporal resolution of current in-situ experimental techniques, we turn to atomistic modeling to help understand the dynamics by which these mechanisms unfold. In order to provide a quantitative analysis of this behavior, we develop a tool which fully characterizes nanocrystalline microstructures in atomistic models and subsequently tracks their evolution during molecular dynamics simulations. We then use this algorithm to quantitatively track grain structure and boundary network evolution in plastically deformed nanocrystalline Al, finding that higher testing temperature and smaller average grain size results in increased evolution of grain structure with evidence of larger scale changes to the grain boundary network also taking place. This prompts us to extend our analysis technique to include full characterization of grain boundary networks and rigorous topographical feature identification. We then employ this tool on simulations of Al subject to monotonic tension, cycling loading, and simple annealing, and find that each case results in different evolution of the grain boundary network. Finally, our computational work is complemented synergistically by experimental analyses which track surface microstructure evolution during sliding wear of nanocrystalline Ni-W thin films. These experiments track the development of a surface grain growth layer which evolves through grain boundary mediated plasticity and we are able to make direct connections between this evolution and that which was observed in our simulation work. All of the findings of this thesis are a direct result of the dynamic and collective nature by which nanocrystalline materials deform.

Download or read book Grain growth in nanocrystalline metals written by Robert Gralla and published by . This book was released on 2010 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Grain Boundary Segregation in Metals written by Pavel Lejcek and published by Springer Science & Business Media. This book was released on 2010-07-20 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Grain Growth in Polycrystalline Materials written by G. Abbruzzese and published by . This book was released on 1992 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: The volumes present investigations on grain growth phenomena and their observation in various materials: metals and alloys, ceramics, sintered materials, thin films, etc.; normal and abnormal grain growth including twinning, texture, particle and other drag effects as well as analysis of topological aspects and grain size and grain orientation correlations; grain boundary structure, mobility and interaction with particles and impurity atoms. Experimental methods applicable to measurements of grain size, orientation of individual grains, etc.

Download or read book Grain Growth in Nanocrystalline Metals and Alloys written by and published by . This book was released on 2013 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Grain Boundary Character written by Tomasz Tański and published by BoD – Books on Demand. This book was released on 2017-01-11 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains eight chapters with original and innovative research studies in the field of grain boundaries. The results presented in the chapters of this book are very interesting and inspiring. This book will be very valuable to all researchers who are interested in the influence of grain boundaries on the structure and different kinds of properties of engineering materials. This book is also addressed to students and professional engineers working in the industry as well as to specialists who pay attention to all aspects related to grain boundaries and their impact on the various properties of innovative materials. The chapters of this book were developed by respected and well-known researchers from different countries.

Download or read book Science at the Interface written by and published by . This book was released on 2009 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interfaces are a critical determinant of the full range of materials properties, especially at the nanoscale. Computational and experimental methods developed a comprehensive understanding of nanograin evolution based on a fundamental understanding of internal interfaces in nanocrystalline nickel. It has recently been shown that nanocrystals with a bi-modal grain-size distribution possess a unique combination of high-strength, ductility and wear-resistance. We performed a combined experimental and theoretical investigation of the structure and motion of internal interfaces in nanograined metal and the resulting grain evolution. The properties of grain boundaries are computed for an unprecedented range of boundaries. The presence of roughening transitions in grain boundaries is explored and related to dramatic changes in boundary mobility. Experimental observations show that abnormal grain growth in nanograined materials is unlike conventional scale material in both the level of defects and the formation of unfavored phases. Molecular dynamics simulations address the origins of some of these phenomena.

Download or read book Grain Size Control written by T. Gladman and published by CRC Press. This book was released on 2020-11-25 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Grain Size Control provides an excellent account of the understanding of many matters concerning grains, grain structure, and grain growth in controlling the grain size of polycrystalline metals. It considers the application of the principles of grain growth.