On the Effect of Local Grain-Boundary Chemistry on the Macroscopic Mechanical Properties of a High Purity Y2O3-Al2O3-Containing Silicon Nitride Ceramic PDF Download
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Author: R. O. Ritchie
Publisher:
ISBN:
Category :
Languages : en
Pages : 9
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Book Description
The effects of grain-boundary chemistry on the mechanical properties were investigated on high-purity silicon nitride ceramics, specifically involving the role of oxygen. Varying the grain-boundary oxygen content, by control of oxidizing heat treatments and sintering additives, was found to result in a transition in fracture mechanism from transgranular to intergranular fracture, with an associated increase in fracture toughness. This phenomenon is correlated to an oxygen-induced change in grain-boundary chemistry that appears to affect fracture by ''weakening'' the interface, facilitating debonding and crack advance along the boundaries, and consequently toughening by grain bridging. It is concluded that if the oxygen content in the thin grain-boundary films exceeds a lower limit, which is {approx}0.87 equiv% oxygen content, then the interfacial structure and bonding characteristics favor intergranular debonding during crack propagation; otherwise, transgranular fracture ensues.
Author: R. O. Ritchie
Publisher:
ISBN:
Category :
Languages : en
Pages : 9
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Book Description
The effects of grain-boundary chemistry on the mechanical properties were investigated on high-purity silicon nitride ceramics, specifically involving the role of oxygen. Varying the grain-boundary oxygen content, by control of oxidizing heat treatments and sintering additives, was found to result in a transition in fracture mechanism from transgranular to intergranular fracture, with an associated increase in fracture toughness. This phenomenon is correlated to an oxygen-induced change in grain-boundary chemistry that appears to affect fracture by ''weakening'' the interface, facilitating debonding and crack advance along the boundaries, and consequently toughening by grain bridging. It is concluded that if the oxygen content in the thin grain-boundary films exceeds a lower limit, which is {approx}0.87 equiv% oxygen content, then the interfacial structure and bonding characteristics favor intergranular debonding during crack propagation; otherwise, transgranular fracture ensues.
Author: Materials Research Society. Meeting
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 232
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Book Description
The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners. This book, first published in 2005, showcases how electron microscopy is applied to materials problems and to encourage ideas from both the solid-state and biological communities.
Author:
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Category : Physics
Languages : en
Pages : 820
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Category : Ceramics
Languages : en
Pages : 972
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Author:
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Category : Ceramic materials
Languages : en
Pages : 664
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Category : Glass
Languages : en
Pages : 414
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Author: P. E. J. Flewitt
Publisher: Wiley
ISBN: 9780471979517
Category : Technology & Engineering
Languages : en
Pages : 0
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Book Description
Over recent years the understanding of grain boundaries, interphase boundaries and free surfaces has advanced greatly, leading to a clear recognition that these discontinuities make a significant contribution to the physical and mechanical properties of materials from multiphase metals and alloys to electronic materials. Grain Boundaries -Their Microstructure and Chemistry discusses the interrelationship between microstructure and chemistry of the grain boundary, with particular emphasis on the influence of the environment (air, liquid and liquid metal) and composition (bulk and impurity). This highly practical volume presents a brief background to interphase and grain boundaries, before considering in detail grain boundary composition and composition changes, and how grain boundary composition affects material properties. Very recent advances in techniques such as electron energy loss spectroscopy, high-resolution transmission electron microscopy and atom probe, and the facinating new insights into grain boundary, microstructure that they have revealed, are also discussed. Grain Boundaries - Their Microstructure and Chemistry is an indispensable text for design and safety engineers in many industries, including power and aerospace, as well as for materials scientists and engineers in academia and research institutes.
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Category :
Languages : en
Pages :
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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: John B. Wachtman
Publisher: John Wiley & Sons
ISBN: 9780470451502
Category : Technology & Engineering
Languages : en
Pages : 496
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Book Description
A Comprehensive and Self-Contained Treatment of the Theory and Practical Applications of Ceramic Materials When failure occurs in ceramic materials, it is often catastrophic, instantaneous, and total. Now in its Second Edition, this important book arms readers with a thorough and accurate understanding of the causes of these failures and how to design ceramics for failure avoidance. It systematically covers: Stress and strain Types of mechanical behavior Strength of defect-free solids Linear elastic fracture mechanics Measurements of elasticity, strength, and fracture toughness Subcritical crack propagation Toughening mechanisms in ceramics Effects of microstructure on toughness and strength Cyclic fatigue of ceramics Thermal stress and thermal shock in ceramics Fractography Dislocation and plastic deformation in ceramics Creep and superplasticity of ceramics Creep rupture at high temperatures and safe life design Hardness and wear And more While maintaining the first edition's reputation for being an indispensable professional resource, this new edition has been updated with sketches, explanations, figures, tables, summaries, and problem sets to make it more student-friendly as a textbook in undergraduate and graduate courses on the mechanical properties of ceramics.
Author: Gary Steven Was
Publisher:
ISBN:
Category : Crystallography
Languages : en
Pages : 380
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Book Description
Materials Science Forum Vol. 46.
