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Languages : en
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Boron is added to nickel-base superalloys such as Alloy X-750 in order to enhance high temperature strength and ductility so that the alloy may be more easily hot worked[1]. Boron additions also have been shown to ameliorate intergranular hydrogen embrittlement in nickel[2], and to improve the high temperature resistance of Alloy X-750 to aqueous stress corrosion cracking (SCC) in the absence of irradiation[3]. Recent quantum mechanical calculations demonstrate that boron strengthens grain boundaries in pure nickel[4], and may contribute to the observed benefits of boron on workability and fracture resistance of nickel alloys. Alloy X-750 exhibits greater susceptibility to intergranular stress corrosion cracking (IGSCC) when irradiated[5], and it has been proposed that the presence of grain boundary helium and/or lithium is responsible. Arguments have been advanced that helium embrittlement of the grain boundaries is primarily responsible for the greater observed susceptibility to IGSCC in irradiated X-750[1]. Alternatively, it has been proposed that lithium promotes IGSCC either by entering the water at the crack tip and lowering the local pH, or by inducing a restructuring of the grain boundary itself[1]. Direct embrittlement of grain boundaries by lithium also has been investigated by ion bombardment in Nimonic PE16, illustrating that under certain conditions lithium can produce degrees of embrittlement in nickel comparable to that produced by helium[6]. It is important to understand the relative roles of these species in grain boundary embrittlement in nickel alloys so that better predictive abilities and mitigation strategies can be developed. Toward that end, quantum mechanical calculations have been performed to investigate the influence of isolated lithium and helium atoms on the cohesive strength of an ideal grain boundary in pure nickel.
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Category :
Languages : en
Pages :
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Book Description
Boron is added to nickel-base superalloys such as Alloy X-750 in order to enhance high temperature strength and ductility so that the alloy may be more easily hot worked[1]. Boron additions also have been shown to ameliorate intergranular hydrogen embrittlement in nickel[2], and to improve the high temperature resistance of Alloy X-750 to aqueous stress corrosion cracking (SCC) in the absence of irradiation[3]. Recent quantum mechanical calculations demonstrate that boron strengthens grain boundaries in pure nickel[4], and may contribute to the observed benefits of boron on workability and fracture resistance of nickel alloys. Alloy X-750 exhibits greater susceptibility to intergranular stress corrosion cracking (IGSCC) when irradiated[5], and it has been proposed that the presence of grain boundary helium and/or lithium is responsible. Arguments have been advanced that helium embrittlement of the grain boundaries is primarily responsible for the greater observed susceptibility to IGSCC in irradiated X-750[1]. Alternatively, it has been proposed that lithium promotes IGSCC either by entering the water at the crack tip and lowering the local pH, or by inducing a restructuring of the grain boundary itself[1]. Direct embrittlement of grain boundaries by lithium also has been investigated by ion bombardment in Nimonic PE16, illustrating that under certain conditions lithium can produce degrees of embrittlement in nickel comparable to that produced by helium[6]. It is important to understand the relative roles of these species in grain boundary embrittlement in nickel alloys so that better predictive abilities and mitigation strategies can be developed. Toward that end, quantum mechanical calculations have been performed to investigate the influence of isolated lithium and helium atoms on the cohesive strength of an ideal grain boundary in pure nickel.
Author: Mojmír Šob
Publisher: MDPI
ISBN: 3036501347
Category : Science
Languages : en
Pages : 198
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Book Description
This Special Issue of Nanomaterials collects a series of original research articles providing new insight into the application of computational quantum physics and chemistry in research on nanomaterials. It illustrates the extension and diversity of the field and indicates some future directions. It provides the reader with an overall view of the latest prospects in this fast evolving and cross-disciplinary field
Author: Wolfgang Pfeiler
Publisher: John Wiley & Sons
ISBN: 9783527313211
Category : Technology & Engineering
Languages : en
Pages : 1020
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Book Description
Covering the latest research in alloy physics together with the underlying basic principles, this comprehensive book provides a sound understanding of the structural changes in metals and alloys -- ranging from plastic deformation, deformation dynamics and ordering kinetics right up to atom jump processes, first principle calculations and simulation techniques. Alongside fundamental topics, such as crystal defects, phase transformations and statistical thermodynamics, the team of international authors treats such hot areas as nano-size effects, interfaces, and spintronics, as well as technical applications of modern alloys, like data storage and recording, and the possibilities offered by materials design.
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Category : Chemistry
Languages : en
Pages : 2726
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Book Description
Author:
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Category : Materials
Languages : en
Pages : 1290
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Category : Physics
Languages : en
Pages : 516
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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.
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Category : Aeronautics
Languages : en
Pages : 1002
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Book Description
Author: D.M.R. Taplin
Publisher: Elsevier
ISBN: 1483153428
Category : Technology & Engineering
Languages : en
Pages : 873
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Book Description
Advances in Research on the Strength and Fracture of Materials: Volume 1s—An Overview contains the proceedings of the Fourth International Conference on Fracture held at the University of Waterloo, Canada, in June 1977. The papers review the state of the art with respect to fracture in a wide range of materials such as metals and alloys, polymers, ceramics, and composites. This volume is comprised of 40 chapters and opens with a discussion on progress in the development of elementary fracture mechanism maps and their application to metal deformation processes, along with micro-mechanisms of fracture and the fracture toughness of engineering alloys. The next section is devoted to the fracture of large-scale structures such as steel structures, aircraft, cargo containment systems, nuclear reactors, and pressure vessels. Fracture at high temperatures and in sensitive environments is then explored, paying particular attention to creep failure by cavitation under non-steady conditions; the effects of hydrogen and impurities on brittle fracture in steel; and mechanism of embrittlement and brittle fracture in liquid metal environments. The remaining chapters consider the fracture of non-metallic materials as well as developments and concepts in the application of fracture mechanics. This book will be of interest to metallurgists, materials scientists, and structural and mechanical engineers.
Author: Bo Xiao
Publisher: OAE Publishing Inc.
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 17
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Book Description
High entropy alloys (HEAs), as a new class of structural materials, have attracted extensive interest from numerous metallurgical scientists and engineers. Benefiting from their unique microstructural features and outstanding mechanical performance, HEAs have shown significant potential for applications in many engineering fields, even under extreme conditions. In particular, when exposed to hydrogen and/or intermediate-temperature environments, these HEAs inevitably suffer from severe environmental embrittlement (EE) issues, e.g., hydrogen embrittlement (HE) and intermediate-temperature embrittlement (ITE), resulting in serious premature intergranular failure. In this work, we critically review the state-of-the-art advances of EE in previously reported HEA systems. Particular focus is given to novel strategies to enhance the resistance to EE in different HEAs. Two critical embrittlement phenomena, namely, HE and ITE, are highlighted separately. Finally, we provide perspectives on future research directions and opportunities for EE-resistant HEAs.
