Download or read book Fatigue Induced Abnormal Grain Growth in Nanocrystalline Metals written by and published by . This book was released on 2015 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue induced Abnormal Grain Growth in Nanocrystalline Metals written by and published by . This book was released on 2015 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fatigue Stress Concentration and Notch Sensitivity in Nanocrystalline Metals written by and published by . This book was released on 2016 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies have shown the potential for nanocrystalline metals to possess excellent fatigue resistance compared to their coarse-grained counterparts. Although the mechanical properties of nanocrystalline metals are believed to be particularly susceptible to material defects, a systematic study of the effects of geometric discontinuities on their fatigue performance has not yet been performed. In the present work, nanocrystalline Ni-40 wt%Fe containing both intrinsic and extrinsic defects were tested in tension-tension fatigue. The defects were found to dramatically reduce the fatigue resistance, which was attributed to the relatively high notch sensitivity in the nanocrystalline material. Microstructural analysis within the crack-initiation zones underneath the defects revealed cyclically-induced abnormal grain growth (AGG) as a predominant deformation and crack initiation mechanism during high-cycle fatigue. Furthermore, the onset of AGG and the ensuing fracture is likely accelerated by the stress concentrations, resulting in the reduced fatigue resistance compared to the relatively defect-free counterparts.

Download or read book Fatigue and Fracture of Nanostructured Materials written by Pasquale Cavaliere and published by Springer Nature. This book was released on 2020-10-27 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the main approaches for production and synthesis of nanostructured metals and alloys, taking into account the fatigue behavior of materials in additive manufactured components. Depending on the material type, form, and application, a deep discussion of fatigue properties and crack behavior is also provided. Pure nanostructured metals, complex alloys and composites are further considered. Prof. Cavaliere’s examination is supported by the most up-to-date understanding from the scientific literature along with a thorough presentation of theory. Bringing together the widest range of perspective on its topic, the book is ideal for materials researchers, professional engineers in industry, and students interested in nanostructured materials, fracture/fatigue mechanics, and additive manufacturing. Describes in detail the relevance of nanostructures in additive manufacturing technologies; Includes sufficient breadth and depth on theoretical modelling of fatigue and crack behavior for use in the classroom; Identifies many open questions regarding different theories through experimental finding; Contextualizes the latest scientific results for readers in industry.

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 Mechanical Properties and Radiation Tolerance of Ultrafine Grained and Nanocrystalline Metals written by Cheng Sun and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Austenitic stainless steels are commonly used in nuclear reactors and have been considered as potential structural materials in fusion reactors due to their excellent corrosion resistance, good creep and fatigue resistance at elevated temperatures, but their relatively low yield strength and poor radiation tolerance hinder their applications in high dose radiation environments. High angle grain boundaries have long been postulated as sinks for radiation-induced defects, such as bubbles, voids, and dislocation loops. Here we provide experimental evidence that high angle grain boundaries can effectively remove radiation-induced defects. The equal channel angular pressing (ECAP) technique was used to produce ultrafine grained Fe-Cr-Ni alloy. Mechanical properties of the alloy were studied at elevated temperature by tensile tests and in situ neutron scattering measurements. Enhanced dynamic recovery process at elevated temperature due to dislocation climb lowers the strain hardening rate and ductility of ultrafine grained Fe-Cr-Ni alloy. Thermal stability of the ultrafine grained Fe-Cr-Ni alloy was examined by ex situ annealing and in situ heating within a transmission electron microscope. Abnormal grain growth at 827 K (600°C) is attributed to deformation-induced martensite, located at the triple junctions of grains. Helium ion irradiation studies on Fe-Cr-Ni alloy show that the density of He bubbles, dislocation loops, as well as irradiation hardening are reduced by grain refinement. In addition, we provide direct evidence, via in situ Kr ion irradiation within a transmission electron microscope, that high angle grain boundaries in nanocrystalline Ni can effectively absorb irradiation-induced dislocation loops and segments. The density and size of dislocation loops in irradiated nanocrystalline Ni were merely half of those in irradiated coarse grained Ni. The results imply that irradiation tolerance in bulk metals can be effectively enhanced by microstructure refinement. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149516

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 ABNORMAL GRAIN GROWTH IN NICKEL BASE HEAT RESISTENT ALLOYS written by R.F. DECKER, A.I. RUSH, A.G. DANO, J.W. FREEMAN and published by . This book was released on 1956 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Fatigue Behavior and Encrustation Characteristics of Nanocrystalline Metals written by Li-Chung Lai and published by . This book was released on 2009 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: The nanocrstalline (NC) metals have been reported to have high mechanical performance owing to it's small grain interior and a large volume fraction of grain boundary (GB) atoms. Small grain leads to the forbidden dislocation activities in grain interior while GB activities become dominant due to a higher volume fraction of GB atoms. Regarding the fatigue response to nanocrstalline metals, it has been reported that decreasing grain led to both significantly improvement on the fatigue-endurance limit and deleterious effect on the resistance to subcritical fatigue crack propagation. The increases endurance limit has been attributed to the greater resistance to fatigue crack initiation at near-surface regions. On the other hand, the less resistance to fatigue crack growth were resulted from less tortuous fatigue crack profiles supported by the deflection/closure theory. However, it has never been studied the influence of proceeding and pre-existing defects on the fatigue performance considering the difference response of NC structure from than coarse grain (CG) structure. In the present work, the influence of electrical discharge machining (EDM) and surface defects on the fatigue behavior of both conventional cold-rolled CG and electro-deposited (ED) NC Ni were investigated. The experimental results revealed considerable influence by EDM on the fatigue strength of NC Ni, while it has little or no affect on that for CG Ni. Specifically, EDM led to a 50 to 75% reduction in fatigue strength for NC Ni despite a relatively small depth of EDM affected material (~1% of width). Rationale for this effect can be attributed to grain growth, microcracks, and higher sulfur content at the GBs in the EDM affected zone. In addition, the pre-existing surface defects that appear to be due to impurity segregation near the electro-deposition substrate significantly reduced the fatigue resistance of ED NC Ni. In order to understand the fatigued behavior in NC Ni, crack tip grain structures were investigated using transmission electron microscope (TEM). Crack tip grain growth was observed at early state of crack propagation with low stress intensity factor (K ~ 6 MPa m 1/2). As K increased, the size of grain growth zone increased exponentially in width a crack propagation behavior transmitted from interganular to transgranular. It appears that this transmission is associated with grain growth. The coalesced grains due to grain rotation/GB diffusion created larger paths for more extended dislocation movement. Dislocation activities become less forbidden and the dislocation-slip mechanism can be dominant leading to a more plastically transgranular fracture. In addition to fatigue study of ED NC Ni, encrustation on ED NC Ti was investigated. The use of materials for medical applications in the urinary tract is hampered by the formation of calcium-based crystalline deposits, generally referred to as encrustation, that act as precursors to urinary stones. Anecdotal evidence suggests that titanium can possess encrustation-resistant properties in vivo and may be useful in urologic applications. To test the utility of coating surfaces with nanotructured titanium, several forms of materials were submersed in artificial urine with saturating concentrations of calcium for a period of 14 days. The specimens were then analyzed using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) to determine the extent of encrustation on the surface of the various samples. Our observations indicate that nanostructured titanium offers superior resistance to encrustation when compared to polyurethane, polyvinyl chloride or conventional coarser grained titanium. Further studies investigating the use of nanostructured titanium in urologic applications are warranted.

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 Abnormal grain growth in metals written by James Dennis and published by . This book was released on 2008 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 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 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 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.