Download or read book Atomistic Studies of Grain Boundaries in Alloys and Compounds Progress Report July 1990 October 1992 written by and published by . This book was released on 1992 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atomistic Studies of Grain Boundaries and Heterophase Interfaces in Alloys and Compounds Final Report July 1987 August 1998 written by and published by . This book was released on 1998 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Atomistic Studies of Grain Boundaries with Segregated Impurities Progress Report July 1 1979 June 30 1980 written by and published by . This book was released on 1980 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Government Reports Annual Index written by and published by . This book was released on 1994 with total page 1190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.

Download or read book Government Reports Announcements Index written by and published by . This book was released on 1993 with total page 1360 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1556 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atomistic Studies of Grain Boundaries with Segregated Impurities Progress Report July 1 1980 June 30 1981 written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this research project is to carry out atomistic studies of grain boundaries with impurities. The emphasis of the investigation is on the effect of segregation upon the structure of grain boundaries and their properties. Since the necessary precursor of any atomistic study is a description of interatomic interactions an empirical scheme for the construction of interatomic potentials was first developed. In this scheme which was summarized in a previous report, the interatomic interactions are described by pair potentials together with a volume dependent term which represents a major contribution to the overall energy of the studied system. A new relaxation method had to be developed that includes the volume dependent term into the calculations which are then carried out at constant pressure rather than at constant volume. Furthermore, this method also includes the possibility of dealing with spatially varying concentration of impurities. It is described in more detail in the report.

Download or read book Progress Report for Period Ending written by University of California, San Francisco. Radiological Laboratory and published by . This book was released on 1962-09 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Interstitial Impurities on the Low temperature Tensile Properties of Tungsten written by Joseph R. Stephens and published by . This book was released on 1964 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study was undertaken to determine the effects of the interstitial impurities oxygen and carbon on the mechanical properties of polycrystalline tungsten and high-purity tungsten single crystals. Results of tensile tests showed that additions of both oxygen and carbon to polycrystalline tungsten produced a marked increase in the ductile to brittle transition temperature. Oxygen and carbon produced a much smaller increase in the transition temperature of the single-crystal specimens compared with equivalent amounts of impurities in the polycrystalline specimens. Addition of oxygen to polycrystalline tungsten lowered both the ultimate tensile strength and the yield strength, but had no measurable effect on the strength properties of single-crystal specimens. Carbon additions to both polycrystalline and single-crystal specimens did not affect the ultimate tensile strength; however, a large increase in the yield strength resulted. The results suggest that oxygen embrittlement in tungsten is caused by grain-boundary segregation, while carbon embrittlement results from an interaction between carbon atoms and dislocations within the tungsten lattice.

Download or read book Midsize Facilities written by National Research Council and published by National Academies Press. This book was released on 2006-04-06 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the instruments now used for materials research are too complex and expensive for individual investigators to own, operate, and maintain them. Consequently, they have become increasingly consolidated into multi-user, small to midsized research facilities, located at many sites around the country. The proliferation of these facilities, however, has drawn calls for a careful assessment of best principles for their operation. With support from the Department of Energy and the National Science Foundation, the NRC carried out a study to characterize and discuss ways to optimize investments in materials research facility infrastructure with attention to midsize facilities. This report provides an assessment of the nature and importance of mid-sized facilities, their capabilities, challenges they face, current investment, and optimizing their effectiveness.

Download or read book Complex Inorganic Solids written by Patrice E. A. Turchi and published by Springer Science & Business Media. This book was released on 2007-12-31 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the key aspects of this volume is to cut across the traditional taxonomy of disciplines in the study of alloys. Hence there has been a deliberate attempt to integrate the different approaches taken towards alloys as a class of materials in different fields, ranging from geology to metallurgical engineering. The emphasis of this book is to highlight commonalities between different fields with respect to how alloys are studied. The topics in this book fall into several themes, which suggest a number of different classification schemes. We have chosen a scheme that classifies the papers in the volume into the categories Microstructural Considerations, Ordering, Kinetics and Diffusion, Magnetic Considerations and Elastic Considerations. The book has juxtaposed apparently disparate approaches to similar physical processes, in the hope of revealing a more dynamic character of the processes under consideration. This monograph will invigorate new kinds of discussion and reveal challenges and new avenues to the description and prediction of properties of materials in the solid state and the conditions that produce them.

Download or read book The Materials Science of Thin Films written by Milton Ohring and published by Academic Press. This book was released on 1992 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: Prepared as a textbook complete with problems after each chapter, specifically intended for classroom use in universities.

Download or read book Nanostructure Science and Technology written by Richard W. Siegel and published by Springer Science & Business Media. This book was released on 1999-09-30 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Timely information on scientific and engineering developments occurring in laboratories around the world provides critical input to maintaining the economic and technological strength of the United States. Moreover, sharing this information quickly with other countries can greatly enhance the productivity of scientists and engineers. These are some of the reasons why the National Science Foundation (NSF) has been involved in funding science and technology assessments comparing the United States and foreign countries since the early 1980s. A substantial number of these studies have been conducted by the World Technology Evaluation Center (WTEC) managed by Loyola College through a cooperative agreement with NSF. The National Science and Technology Council (NSTC), Committee on Technology's Interagency Working Group on NanoScience, Engineering and Technology (CT/IWGN) worked with WTEC to develop the scope of this Nanostucture Science and Technology report in an effort to develop a baseline of understanding for how to strategically make Federal nanoscale R&D investments in the coming years. The purpose of the NSTC/WTEC activity is to assess R&D efforts in other countries in specific areas of technology, to compare these efforts and their results to U. S. research in the same areas, and to identify opportunities for international collaboration in precompetitive research. Many U. S. organizations support substantial data gathering and analysis efforts focusing on nations such as Japan. But often the results of these studies are not widely available. At the same time, government and privately sponsored studies that are in the public domain tend to be "input" studies.

Download or read book The Gaussian Approximation Potential written by Albert Bartók-Pártay and published by Springer Science & Business Media. This book was released on 2010-07-27 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation of materials at the atomistic level is an important tool in studying microscopic structures and processes. The atomic interactions necessary for the simulations are correctly described by Quantum Mechanics, but the size of systems and the length of processes that can be modelled are still limited. The framework of Gaussian Approximation Potentials that is developed in this thesis allows us to generate interatomic potentials automatically, based on quantum mechanical data. The resulting potentials offer several orders of magnitude faster computations, while maintaining quantum mechanical accuracy. The method has already been successfully applied for semiconductors and metals.

Download or read book Atomistic Spin Dynamics written by Olle Eriksson and published by Oxford University Press. This book was released on 2017 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several large experimental facilities that focus on detection and probing magnetization dynamics have been realized in Europe, USA and Japan. This book covers theoretical and practical aspects of the vibrant and emerging research field of magnetization dynamics.

Download or read book NAA SR written by U.S. Atomic Energy Commission and published by . This book was released on 1958 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: