Atomistic Studies of Grain Boundaries in Disordered and Ordered Binary Alloys PDF Download
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Author: Min Yan
Publisher:
ISBN:
Category :
Languages : en
Pages : 510
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Book Description
Author: Min Yan
Publisher:
ISBN:
Category :
Languages : en
Pages : 510
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Book Description
Atomic structure and atomic level properties of grain boundaries in binary alloys have been studied theoretically. Both ordered and disordered alloys were investigated with the aim responsible for the physical and mechanical properties differing from pure metals. An integral part is atomic interactions. The first are the many-body potentials akin to the embedded atom method. The most important potentials for Cu-Bi which combined empirical data and ab initio electronic structure calculations to construct reliable potentials. LMTO based tight-binding method were developed fully for pure metals with future application alloys. Structural studies were carried out for disordered Cu-Bi and ordered Ni3Al and Cu3Au alloys. In the former case the investigation was linked with HREM, and result is solution of structure of? = 3 (111)/(11{bar 1}) facets containing Bi formed during segregation from originally curved boundaries. In the latter case, effect of ordering strength and stoichiometry deviations the boundary structure was investigated. The most interesting finding is a very different behavior of Ni rich and Al rich Ni3Al which may explain why only Ni rich compounds can be ductilized by boron. In both cases the surplus element segregates to the boundaries.
Author:
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Category :
Languages : en
Pages : 13
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In this research project we carry out theoretical, computer modeling, studies of the atomic structure of grain boundaries in binary alloys. Both ordered and disordered alloys are investigated. The goal is to analyze those structural, chemical and electronic features that distinguish alloys from pure metals and are responsible for remarkably different intergranular fracture behavior of alloys when compared with pure metals. The most important phenomenon is, of course, segregation and related structural changes in the boundary region. When studying segregation phenomena copper-bismuth is a very suitable model system since bismuth segregation occurs readily, leads to boundary faceting and thus to remarkable changes in the boundary structure, as well as to a very strong embrittlement. Our recent research concentrated on the investigation of the structure of? = 3 (111)/(11{bar 1}) facets formed during segregation from boundaries which were originally curved.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 34
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Book Description
Atomic structure and atomic level properties of grain boundaries in binary alloys have been studied theoretically. Both ordered and disordered alloys were investigated with the aim responsible for the physical and mechanical properties differing from pure metals. An integral part is atomic interactions. The first are the many-body potentials akin to the embedded atom method. The most important potentials for Cu-Bi which combined empirical data and ab initio electronic structure calculations to construct reliable potentials. LMTO based tight-binding method were developed fully for pure metals with future application alloys. Structural studies were carried out for disordered Cu-Bi and ordered Ni3Al and Cu3Au alloys. In the former case the investigation was linked with HREM, and result is solution of structure of [Sigma] = 3 (111)/(11{bar 1}) facets containing Bi formed during segregation from originally curved boundaries. In the latter case, effect of ordering strength and stoichiometry deviations the boundary structure was investigated. The most interesting finding is a very different behavior of Ni rich and Al rich Ni3Al which may explain why only Ni rich compounds can be ductilized by boron. In both cases the surplus element segregates to the boundaries.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Book Description
The overarching goal of the research supported by this grant was investigation of the structure and properties of interfaces in multicomponent systems by atomistic modeling. Initially, the research was devoted to studies of segregation to grain boundaries in binary disordered alloys. The next step was then studies of the structure and properties of grain boundaries in ordered compounds, specifically Ni3Al and NiAl, and grain boundary segregation in these compounds in the case of off-stoichiometry. Finally, the structure of Nb/sapphire interfaces, in particular the core configurations of the misfit dislocations, was studied.
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Category : Power resources
Languages : en
Pages : 486
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Category : Aeronautics
Languages : en
Pages : 602
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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: Hongying Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 534
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Category : Dissertations, Academic
Languages : en
Pages : 826
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Author:
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Category :
Languages : en
Pages :
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The necessary precursor for any atomistic studies is a description of interatomic forces. Since no satisfactory description of interatomic forces in binary alloys could be found, the first stage of the research was devoted to this problem. The energy of the lattice was written as a sum of pair interactions and of a density dependent term. For pure metals the parameters in both the pair potential and the density dependent term were determined so as to fit the cohesive energy and elastic constants, and satisfy the condition of equilibrium for the experimentally known lattice parameter. The potentials and density dependent terms for pure metals were then used in constructing the corresponding description of interatomic interactions in alloys, using a modified method. The principle modifications are use of density dependent terms and fitting of the enthalpy of mixing. These procedures are described in detail. The grain boundary studies were started for the systems Cu-Ag, Cu-Bi and Au-Ag. However, since the density dependent part of the energy must now be taken into account explicitly a substantial modification of existing computer programs for grain boundary calculations is needed. This is at present in progress and thus only the directions of this work are reported. A limited effort was also devoted to the development of a theory of intergranular fracture in embrittled materials. The main purpose is to establish a relationship between the cohesive energy and the plastic work which would enable us to use the recently developed technique of measuring the local stress of fracture for direct studies of intergranular cohesion.
