Download or read book Atomistic simulation of radiation induced amorphization of intermetallic compounds written by Ramaswami Devanathan and published by . This book was released on 1993 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics of Radiation induced Amorphization in Intermetallic Compounds written by and published by . This book was released on 1992 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radiation induced Amorphization of Intermetallic Compounds written by and published by . This book was released on 1991 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present paper, important results of our recent computer simulation of radiation-induced amorphization in the ordered compounds CuTi and Cu4Ti3 are summarized. The energetic, structural, thermodynamic and mechanical responses of these intermetallics during chemical disordering, point-defect production and heating were simulated, using molecular dynamics and embedded-atom potentials. From the atomistic details obtained, the critical role of radiation-induced structural disorder in driving the crystalline-to-amorphous phase transformation is discussed. 25 refs., 4 figs.
Download or read book Dynamics of Radiation induced Amorphization in Intermetallic Compounds written by and published by . This book was released on 1992 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent progress in molecular-dynamics simulations of radiation-induced crystalline-to-amorphous transition in intermetallic compounds and the relationship between amorphization and melting are discussed. By focusing on the mean-square static displacement, which provides a generic measure of energy stored in the lattice in the forms of chemical and topological disorder, a unified description of solid-state amorphization as a disorder-induced, isothermal melting process can be developed within the framework of a generalized Lindemann criterion.
Download or read book Radiation induced Amorphization of Intermetallic Compounds written by and published by . This book was released on 1991 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radiation induced Crystalline to amorphous Transition in Intermetallic Compounds of the Cu Ti Alloy System written by and published by . This book was released on 1992 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent progress in molecular-dynamics studies of radiation-induced crystalline-to-amorphous transition in the ordered intermetallic compounds of the Cu-Ti system is discussed. The effect of irradiation was simulated by the generation of Frenkel pairs, which resulted in both the formation of stable point defects and chemical disorder upon defect recombination. The thermodynamic, structural and mechanical responses of the compounds during irradiation were determined by monitoring changes in the system potential energy, volume expansion, pair correlation function, diffraction patterns, and elastic constants. It was found that the intermetallics Cu4Ti3, CuTi, and CuTi2 could be rendered amorphous by the creation of Frenkel pairs, but Cu4Ti could not, consistent with experimental observations during electron irradiation. However, the simulations showed that Cu4Ti did become amorphous when clusters of Frenkel pairs were introduced, indicating that this compound may be susceptible to amorphization by heavy-ion bombardment. A generalization of the Lindemann criterion was used to develop a thermodynamic description of solid-state amorphization as a disorder- induced melting process.
Download or read book Atomistic Simulation of Radiation induced Amorphization of the B2 Ordered Intermetallic Compound NiTi written by and published by . This book was released on 1990 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Amorphization of the B2 intermetallic compound NiTi under electron irradiation has been investigated using molecular dynamics. The effect of irradiation was simulated using two processes: (1) Ni and Ti atoms were exchanged, resulting in chemical disorder, and (2) Frenkel pairs were introduced, leading to the formation of stable point defects and also chemical disorder upon mutual recombination of interstitials and vacancies. After (approximately)0.4 exchanges per atom, the first process resulted in an energy increase of approximately 0.11 eV/atom and a volume increase of 1.91%. On the other hand, after introducing (approximately)0.5 Frenkel pairs per atom, the second process led to smaller increases of 0.092 eV/atom in energy and 1.43% in volume. The calculated radial distribution functions (RDFs) were essentially identical to each other and to the calculated RDF of a quenched liquid. The structure factor, however, showed that long-range order was still present after atom exchanges, while the introduction of Frenkel pairs resulted in the loss of long-range order. It was concluded that point defects are necessary for amorphization to occur in NiTi, although chemical disorder alone is capable of storing enough energy to make the transition possible. 18 refs., 3 figs.
Download or read book Irradiation induced Amorphization and Elastic Shear Instability in Intermetallic Compounds written by and published by . This book was released on 1989 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previously we reported a substantial ((approximately)50%) decrease in shear modulus prior to amorphization in Kr irradiated Zr3Al, and proposed that amorphization is triggered when the crystalline lattice becomes unstable against shear stress. In the present work, the relation between amorphization and shear elastic instability has been investigated in two additional compounds (FeTi and NiAl) during room temperature irradiation with 1.7-MeV Kr. A shear modulus was measured using Brillouin scattering; structural information was obtained in situ in a high voltage electron microscope interfaced to a tandem accelerator. During irradiation of FeTi, chemical disordering and a large ((approximately)40%) decrease of shear modulus were observed, and an amorphous phase developed subsequently. In contrast, NiAl remained crystalline and chemically ordered during irradiation, and exhibited only a (approximately)10% decrease in shear modulus. Hence, these two results provide further support that a shear instability triggers irradiation-induced amorphization. The shear instability mechanism may also apply to other solid-state amorphization techniques, e.g., hydrogen charging and mechanical deformation. 22 refs., 3 figs.
Download or read book Statics and Dynamics of Alloy Phase Transformations written by Patrice E.A. Turchi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 725 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of phase transformations in substitutional alloys, including order disorder phenomena and structural transformations, plays a crucial role in understanding the physical and mechanical properties of materials, and in designing alloys with desired technologically important characteristics. Indeed, most of the physical properties, including equilibrium properties, transport, magnetic, vibrational as well as mechanical properties of alloys are often controlled by and are highly sensitive to the existence of ordered compounds and to the occurrence of structural transformations. Correspondingly, the alloy designer facing the task of processing new high-performance materials with properties that meet specific industrial applications must answer the following question: What is the crystalline structure and the atomic configuration that an alloy may exhibit at given temperature and concentration? Usually the answer is sought in the phase-diagram of a relevant system that is often determined experimentally and does not provide insight to the underlying mechanisms driving phase stability. Because of the rather tedious and highly risky nature of developing new materials through conventional metallurgical techniques, a great deal of effort has been expended in devising methods for understanding the mechanisms contrOlling phase transformations at the microscopic level. These efforts have been bolstered through the development of fully ab initio, accurate theoretical models, coupled with the advent of new experimental methods and of powerful supercomputer capabilities.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Point Defects on the Amorphization of Metallic Alloys During Ion Implantation NiTi written by and published by . This book was released on 1985 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical model of radiation-induced amorphization of ordered intermetallic compounds is developed. The mechanism is proposed to be the buildup of lattice defects to very high concentrations, which destabilizes the crystalline structure. Because simple point defects do not normally reach such levels during irradiation, a new defect complex containing a vacancy and an interstitial is hypothesized. Crucial properties of the complex are that the interstitial sees a local chemical environment similar to that of an atom in the ordered lattice, that the formation of the complex prevents mutual recombination and that the complex is immobile. The evolution of a disorder based on complexes is not accompanied by like point defect aggregation. The latter leads to the development of a sink microstructure in alloys that do not become amorphous. For electron irradiation, the complexes form by diffusional encounters. For ion irradiation, complexes are also formed directly in cascades. The possibility of direct amorphization in cascades is also included. Calculations for the compound NiTi show reasonable agreement with measured amorphization kinetics.
Download or read book Transformation Processes in Minerals written by Simon A. Redfern and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-12-17 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 39 of Reviews in Mineralogy and Geochemistry about Transformation Processes in Minerals summarises the current state of the art. The selection of transformation processes covered here is by no means comprehensive, but represents a coherent view of some of the most important processes which occur specifically in minerals. Contents: Rigid unit modes in framework structures Strain and elasticity at structural phase transitions in minerals Mesoscopic twin patterns in ferroelastic and co-elastic minerals High-pressure structural phase transitions Order-disorder phase transitions Phase transformations induced by solid solution Magnetic transitions in minerals NMR spectroscopy of phase transitions in minerals Insights into phase transformations from Mössbauer spectroscopy Hard mode spectroscopy of phase transitions Synchrotron studies of phase transformations Radiation-induced amorphization
Download or read book Irradiation Induced Nanostructures written by and published by . This book was released on 1999 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper summarizes the results of the studies of the irradiation-induced formation of nanostructures, where the injected interstitials from the source of irradiation are not major components of the nanophase. This phenomena has been observed by in situ transmission electron microscopy (TEM) in a number of intermetallic compounds and ceramics during high-energy electron or ion irradiations when the ions completely penetrate through the specimen. Beginning with single crystals, electron or ion irradiation in a certain temperature range may result in nanostructures composed of amorphous domains and nanocrystals with either the original composition and crystal structure or new nanophases formed by decomposition of the target material. The phenomenon has also been observed in natural materials which have suffered irradiation from the decay of constituent radioactive elements and in nuclear reactor fuels which have been irradiated by fission neutrons and other fission products. The mechanisms involved in the process of this nanophase formation are discussed in terms of the evolution of displacement cascades, radiation-induced defect accumulation, radiation-induced segregation and phase decomposition, as well as the competition between irradiation-induced amorphization and recrystallization.
Download or read book Materials Interfaces written by D. Wolf and published by Springer Science & Business Media. This book was released on 1992-10-31 with total page 748 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many of the most important properties of materials in high-technology applications are strongly influenced or even controlled by the presence of solid interfaces. In this work, leading international authorities review the broad range of subjects in this field focusing on the atomic level properties of solid interfaces.
Download or read book Materials Modification by High fluence Ion Beams written by Roger Kelly and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Study Institute on Materials Modification by High-Fluence Ion Beams, Viana do Castelo, Portugal, August 24-September 4, 1987
Download or read book Energy Research Abstracts written by and published by . This book was released on 1994 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phase Transformations written by Srikumar Banerjee and published by Elsevier. This book was released on 2010-05-31 with total page 837 pages. Available in PDF, EPUB and Kindle. Book excerpt: The terms phase transitions and phase transformations are often used in an interchangeable manner in the metallurgical literature. In Phase Transformations, transformations driven by pressure changes, radiation and deformation and those occurring in nanoscale multilayers are brought to the fore. Order-disorder transformations, many of which constitute very good examples of continuous transformations, are dealt with in a comprehensive manner. Almost all types of phase transformations and reactions that are commonly encountered in inorganic materials are covered and the underlying thermodynamic, kinetic and crystallographic aspects elucidated. - Shows readers the advancements in the field - due to enhanced computing power and superior experimental capability - Drawing upon the background and the research experience of the authors, bringing together a wealth of experience - Written essentially from a physical metallurgists view point
