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 Atomistic Simulations of Defect Nucleation and Free Volume in Nanocrystalline Materials written by Garritt J. Tucker and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Atomistic simulations are employed in this thesis to investigate defect nucleation and free volume of grain boundaries and nanocrystalline materials. Nanocrystalline materials are of particular interest due to their improved mechanical properties and alternative strain accommodation processes at the nanoscale. These processes, or deformation mechanisms, within nanocrystalline materials are strongly dictated by the larger volume fraction of grain boundaries and interfaces due to smaller average grain sizes. The behavior of grain boundaries within nanocrystalline materials is still largely unknown. One reason is that experimental investigation at this scale is often difficult, time consuming, expensive, or impossible with current resources. Atomistic simulations have shown the potential to probe fundamental behavior at these length scales and provide vital insight into material mechanisms. Therefore, work conducted in this thesis will utilize atomistic simulations to explore structure-property relationships of face-centered-cubic grain boundaries, and investigate the deformation of nanocrystalline copper as a function of average grain size. Volume-averaged kinematic metrics are formulated from continuum mechanics theory to estimate nonlocal deformation fields and probe the nanoscale features unique to strain accommodation mechanisms in nanocrystalline metals. The kinematic metrics are also leveraged to explore the tensile deformation of nanocrystalline copper at 10K. The distribution of different deformation mechanisms is calculated and we are able to partition the role of competing mechanisms in the overall strain of the nanocrystalline structure as a function of grain size. Grain boundaries are observed to be influential in smaller grained structures, while dislocation glide is more influential as grain size increases. Under compression, however, the resolved compressive normal stress on interfaces hinders grain boundary plasticity, leading to a tension-compression asymmetry in the strength of nanocrystalline copper. The mechanisms responsible for the asymmetry are probed with atomistic simulations and the volume-averaged metrics. Finally, the utility of the metrics in capturing nonlocal nanoscale deformation behavior and their potential to inform higher-scaled models is discussed.
Download or read book Nanocrystalline Alloys written by Timothy John Rupert and published by . This book was released on 2011 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline materials have experienced a great deal of attention in recent years, largely due to their impressive array of physical properties. In particular, nanocrystalline mechanical behavior has been of interest, as incredible strengths are predicted when grain size is reduced to the nanometer range. The vast majority of research to this point has focused on quantifying and understanding the grain size-dependence of strength, leading to the discovery of novel, grain boundary-dominated physics that begin to control deformation at extremely fine grain sizes. With the emergence of this detailed understanding of nanocrystalline deformation mechanisms, the opportunity now exists for studies that explore how other structural features affect mechanical properties in order to identify alternative strengthening mechanisms. In this thesis, we seek to extend our current knowledge of nanocrystalline structure-property relationships beyond just grain size, using combinations of structural characterization, mechanical testing, and atomistic simulations. Controlled experiments on Ni-W are first used to show that solid solution addition and the relaxation of nonequilibrium grain boundary state can dramatically affect the strength of nanocrystalline metals. Next, the sliding wear response of nanocrystalline Ni-W is investigated, to show how alloying and grain boundary structural state affect a more complex mechanical property. This type of mechanical loading also provides a strong driving force for structural evolution, which, in this case, is found to be beneficial. Mechanically-driven grain growth and grain boundary relaxation occur near the surface of the Ni-W samples during sliding, leading to a hardening effect that improves wear resistance and results in a deviation from Archard scaling. Finally, molecular dynamics simulations are performed to confirm that mechanical cycling alone can indeed relax grain boundary structure and strengthen nanocrystalline materials. In all of the cases discuss above, our observations can be directly connected to the unique deformation physics of nanocrystalline materials.
Download or read book Understanding Grain Boundary and Stress Concentration Effects on Strengthening Mechanisms in Nanotwinned Metals written by Qiongjiali Fang and published by . This book was released on 2020 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: The superior strength and large tensile plasticity of nanotwinned (nt) face-centered-cubic metals have been explained by different twin size-dependent dislocation mechanisms and their inherent strengthening/softening effects. Grain boundary (GB) plasticity generally induces softening in nanocrystalline metals; however, our current understanding of the role of GBs in plasticity of nt metals remains limited. Contradicting reports exist in literature on how twin size influences stress concentration at GB -- twin boundary (TB) intersections, which facilitates dislocation nucleation. In this thesis, molecular dynamics (MD) simulations and finite element analysis (FEA) were used to study the effects of GB plasticity and stress concentrations, on the mechanical behaviors of four different columnar-grained nt fcc metals. First, the extent of GB plasticity was found to be the same for different TB spacing (TBS). A special GB deformation mechanism, ductile cracking along GB was observed in nt Ni at small TBS, resulting from the higher GB plasticity of nt Ni. In addition, GB plasticity also depends on the strain rate, which contributes to strain rate sensitivity in nt fcc metals. Second, it was found that stress concentration at GB -- TB intersections decreases as TBS decreases in both anisotropic elasticity theory and atomistic simulations, which is contrary to past experimental results. Stress concentration at the intersection of two regions with different TBSs could be estimated simply by geometric average of stress concentrations in adjacent regions with homogeneous CTB distributions, suggesting that the paradox in stress concentration between experiments and our simulation may be related to the uneven TB distribution in experiments. Initial nucleation of twinning partials is predicted to occur at lower strain as TB spacing decreases, when the stress concentrations are smaller, because of a transition from stress-controlled to source-controlled dislocation nucleation. Therefore, this thesis shows that it is necessary to tailor the size and distribution of grains and nanotwins to achieve ideal mechanical properties in columnar-grained nt metals.
Download or read book Molecular Dynamics Simulation of Nanostructured Materials written by Snehanshu Pal and published by CRC Press. This book was released on 2020-05-15 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molecular dynamics simulation is a significant technique to gain insight into the mechanical behavior of nanostructured (NS) materials and associated underlying deformation mechanisms at the atomic scale. The purpose of this book is to detect and correlate critically current achievements and properly assess the state of the art in the mechanical behavior study of NS material in the perspective of the atomic scale simulation of the deformation process. More precisely, the book aims to provide representative examples of mechanical behavior studies carried out using molecular dynamics simulations, which provide contributory research findings toward progress in the field of NS material technology.
Download or read book Atomistic Modeling of Materials Failure written by Markus J. Buehler and published by Springer Science & Business Media. This book was released on 2008-08-07 with total page 547 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an introduction to molecular and atomistic modeling techniques applied to fracture and deformation of solids, focusing on a variety of brittle, ductile, geometrically confined and biological materials. The overview includes computational methods and techniques operating at the atomic scale, and describes how these techniques can be used to model cracks and other deformation mechanisms. The book aims to make new molecular modeling techniques available to a wider community.
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 Nanomaterials written by K.T. Ramesh and published by Springer Science & Business Media. This book was released on 2009-06-12 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book grew out of my desire to understand the mechanics of nanomaterials, and to be able to rationalize in my own mind the variety of topics on which the people around me were doing research at the time. The ?eld of nanomaterials has been growing rapidly since the early 1990s. I- tially, the ?eld was populated mostly by researchers working in the ?elds of synt- sis and processing. These scientists were able to make new materials much faster than the rest of us could develop ways of looking at them (or understanding them). However, a con?uence of interests and capabilities in the 1990s led to the exp- sive growth of papers in the characterization and modeling parts of the ?eld. That con?uence came from three primary directions: the rapid growth in our ability to make nanomaterials, a relatively newfound ability to characterize the nanomate- als at the appropriate length and time scales, and the rapid growth in our ability to model nanomaterials at atomistic and molecular scales. Simultaneously, the commercial potential of nanotechnology has become app- ent to most high-technology industries, as well as to some industries that are tra- tionally not viewed as high-technology (such as textiles). Much of the rapid growth came through the inventions of physicists and chemists who were able to develop nanotechnology products (nanomaterials) through a dizzying array of routes, and who began to interface directly with biological entities at the nanometer scale. That growth continues unabated.
Download or read book Handbook of Nanomaterials Properties written by Bharat Bhushan and published by Springer Science & Business Media. This book was released on 2014-03-13 with total page 1467 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanomaterials attract tremendous attention in recent researches. Although extensive research has been done in this field it still lacks a comprehensive reference work that presents data on properties of different Nanomaterials. This Handbook of Nanomaterials Properties will be the first single reference work that brings together the various properties with wide breadth and scope.
Download or read book Deformation Based Processing of Materials written by Heng Li and published by Elsevier. This book was released on 2019-03-11 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Deformation Based Processing of Materials: Behavior, Performance, Modeling and Control focuses on deformation based process behaviors and process performance in terms of the quality of the needed shape, geometries, and the requested properties of the deformed products. In addition, modelling and simulation is covered to create an in-depth and epistemological understanding of the process. Other topics discussed include ways to efficiently reduce or avoid defects and effectively improve the quality of deformed parts. The book is ideal as a technical document, but also serves as scientific literature for engineers, scientists, academics, research students and management professionals involved in deformation based materials processing.
Download or read book Introduction to Nanoscience and Nanotechnology written by Gabor L. Hornyak and published by CRC Press. This book was released on 2008-12-22 with total page 1791 pages. Available in PDF, EPUB and Kindle. Book excerpt: The maturation of nanotechnology has revealed it to be a unique and distinct discipline rather than a specialization within a larger field. Its textbook cannot afford to be a chemistry, physics, or engineering text focused on nano. It must be an integrated, multidisciplinary, and specifically nano textbook. The archetype of the modern nano textbook
Download or read book Crystal Plasticity at Micro and Nano scale Dimensions written by Ronald W. Armstrong and published by MDPI. This book was released on 2021-08-31 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present collection of articles focuses on the mechanical strength properties at micro- and nanoscale dimensions of body-centered cubic, face-centered cubic and hexagonal close-packed crystal structures. The advent of micro-pillar test specimens is shown to provide a new dimensional scale for the investigation of crystal deformation properties. The ultra-small dimensional scale at which these properties are measured is shown to approach the atomic-scale level at which model dislocation mechanics descriptions of crystal slip and deformation twinning behaviors are proposed to be operative, including the achievement of atomic force microscopic measurements of dislocation pile-up interactions with crystal grain boundaries or with hard surface coatings. A special advantage of engineering designs made at such small crystal and polycrystalline dimensions is the achievement of an approximate order-of-magnitude increase in mechanical strength levels. Reasonable extrapolation of macro-scale continuum mechanics descriptions of crystal strength properties at micro- to nano-indentation hardness measurements are demonstrated, in addition to reports on persistent slip band observations and fatigue cracking behaviors. High-entropy alloy, superalloy and energetic crystal properties are reported along with descriptions of deformation rate sensitivities, grain boundary structures, nano-cutting, void nucleation/growth micromechanics and micro-composite electrical properties.
Download or read book Proceedings of the 1st World Congress on Integrated Computational Materials Engineering ICME written by The Minerals, Metals & Materials Society (TMS) and published by John Wiley & Sons. This book was released on 2011-06-15 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: In its most advanced form, Integrated Computational Materials Engineering (ICME) holistically integrates manufacturing simulation, advanced materials models and component performance analysis. This volume contains thirty-five papers presented at the 1st World Congress on Integrated Computational Materials Engineering. Modeling processing-microstructure relationships, modeling microstructure-property relationships, and the role of ICME in graduate and undergraduate education are discussed. Ideal as a primary text for engineering students, this book motivates a wider understanding of the advantages and limitations offered by the various computational (and coordinated experimental) tools of this field.
Download or read book Superplasticity in Advanced Materials ICSAM 2003 written by Richard Todd and published by Trans Tech Publications Ltd. This book was released on 2004-02-15 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume is indexed by Thomson Reuters CPCI-S (WoS). Superplastic forming (SPF) has come a long way from its relatively recent history of being of interest only to the aerospace and aeronautical industries, and has made rapid inroads into applications in the automotive, rail, architectural, sports, dental and entertainment sectors.
Download or read book Severe Plastic Deformation written by Burhanettin Altan and published by Nova Publishers. This book was released on 2006 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been already well established that the nanostructured materials (materials with a grain size of 100mm or less) is the future materials. Nanostructured materials possess properties superior to those of conventional, coarse grained materials. Hence designing potentially cost efficient and environmentally friendly products with better performance is a possibility. Among others, nanostructured materials exhibit increased strength, hardness and ductility and provide an opportunity for superplastic forming. When all the procedures in use for the production of nanostructured materials are examined, only severe plastic deformation (SPD) processes exhibit a potential for producing relatively large samples suitable for industrial applications. In this monograph, the state-of-the-art on severe plastic deformation methods is presented in one volume. The monograph is organised into eight chapters, each of which contains papers on different aspect of severe plastic deformation methods prepared by the experts in this field. The topics covered in the monograph are structure formation, phase transformation, superplasticity, mechanical properties of nanostructured materials, electronic and magnetic properties of nanostructured materials, deformation analysis, novel SPD methods, commercialisation of ECAE method.
Download or read book Principles of Inorganic Materials Design written by John N. Lalena and published by John Wiley & Sons. This book was released on 2020-04-10 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn the fundamentals of materials design with this all-inclusive approach to the basics in the field Study of materials science is an important aspect of curricula at universities worldwide. This text is designed to serve students at a fundamental level, positioning materials design as an essential aspect of the study of electronics, medicine, and energy storage. Now in its 3rd edition, Principles of Inorganic Materials Design is an introduction to relevant topics including inorganic materials structure/property relations and material behaviors. The new edition now includes chapters on computational materials science, intermetallic compounds, and covalent compounds. The text is meant to aid students in their studies by providing additional tools to study the key concepts and understand recent developments in materials research. In addition to the many topics covered, the textbook includes: • Accessible learning tools to help students better understand key concepts • Updated content including case studies and new information on computational materials science • Practical end-of-chapter exercises to assist students with the learning of the material • Short biographies introducing pioneers in the field of inorganic materials science For undergraduates just learning the material or professionals looking to brush up on their knowledge of current materials design information, this text covers a wide range of concepts, research, and topics to help round out their education. The foreword to the first edition was written by the 2019 Chemistry Nobel laureate Prof. John B. Goodenough.
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.
