Structure, Stability, and Mechanical Properties of Intermetallic Phases


Book Description

The importance of the structural stability of intermetallics with regard to their mechanical properties is illustrated with two case studies. First, the importance of structural and thermal defects for the strength of (weakly ordered) FeAl and (strongly ordered) NiAl is shown. Several inconsistencies and unresolved issues in the present understanding of point defects in FeAl are addressed. Since point defects alone may not explain the mechanical differences between these two materials, the role of dislocations is considered as well. It is shown that the differences in the atomic bonding of FeAl and NiAl, which deter-mine the active slip systems, are likely to influence the compositional dependence of the strength of these two intermetallics. Second, the class of the trialuminides is reviewed with emphasis on Al3Ti. In addition to stabilizing a cubic crystal structure, the ratio of K/G, where K is the bulk modulus and G the shear modulus, needs to be increased in order to achieve extensive plastic deformation at room temperature. It is not clear, at the present time, to what extent macroalloying of trialuminides can achieve this goal, although promising results have been reported for Al3Ti containing relatively high concentrations (14 at. %) of chromium.




Structure and Properties of Intermetallics in Pre-Transitional Low-Stability States


Book Description

This book is dedicated to the fundamental physical aspects of stability, the influence of structural defects on the properties and structural phase transformations of BCC alloys. The authors present patterns that occur in the structural-phase states of functional alloys with low stability or instability under thermal cycling effects. Structural-phase transformations and the physical laws governing the influence of the thermomechanical effect on the properties of alloys are examined to advance development of technological processes for processing functional materials. Features: Studies the correlation between structural phase states and changes in the physico-mechanical properties of intermetallic compounds Explores the influence of thermomechanical cycling on the properties of functional alloys Details low-stability pretransition states in alloys




Intermetallics


Book Description

Derived from the highly acclaimed series Materials Science and Technology, this book covers the properties as well as the present and emerging applications of intermetallics. Mechanical characteristics, microstructure as well as the environmental influence on intermetallics are treated in depth. In addition, the prospects and risks inherent in materials development as well as typical applications of intermetallics are critically assessed. It is the author's aim to provide the basis for understanding the physical mechanisms, which influence the properties of the materials and ultimately their areas of application. Materials covered include: Titanium Aluminides and Related Phases * Nickel Aluminides and Related Phases * Iron Aluminides and Related Phases * Cu-Base Phases * A15 Phases * Laves Phases * Rare-Earth Compound * Beryllides * Silicides Intermetallics is a valuable source of information for researchers and graduate students working in materials science, metallurgy, condensed-matter physics, and engineering.




Intermetallic Compounds


Book Description

Intermetallic compounds are usually brittle with high melting points. Their properties are often found among ceramic and metallic materials. In most cases, their hot corrosion resistance and simultaneously hardness are important. One of the main applications of intermetallic compounds is for superalloy turbine blades in which they show appropriate high-temperature-related properties. This book collects new developments about intermetallic compounds and their recent usages.




Ordered Intermetallics


Book Description

Ordered intermetallics constitute a unique class of metallic materials which may be developed as new-generation materials for structural use at high temperatures in hostile environments. At present, there is a worldwide interest in intermetallics, and extensive efforts have been devoted to intermetallic research and development in the U.S., Japan, European countries, and other nations. As a result, significant advances have been made in all areas of intermetallic research. This NATO Advanced Workshop on ordered intermetallics (1) reviews the recent progress, and (2) assesses the future direction of intermetallic research in the areas of electronic structure and phase stability, deformation and fracture, and high-temperature properties. The book is divided into six parts: (1) Electronic Structure and Phase Stability; (2) Deformation and Dislocation Structures; (3) Ductility and Fracture; (4) Kinetic Processes and Creep Behavior; (5) Research Programs and Highlights; and (6) Assessment of Current Research and Recommendation for Future Work. The first four parts review the recent advances in the three focus areas. The fifth part provides highlights of the intermetallic research under major programs and in different institutes and countries. The last part provides a forum for the discussion of research areas for future studies.




Mechanical Properties of Complex Intermetallics


Book Description

This book will be the last one in a series of 4 books issued yearly as a deliverable of the research school established within the European Network of Excellence CMA (for Complex Metallic Alloys). It is written by reputed experts in the fields of metal physics, surface physics and chemistry, metallurgy and process engineering, combining expertise found inside as well as outside the network. The CMA network focuses on the huge group of largely unknown multinary alloys and compounds formed with crystal structures based on giant unit cells containing clusters, with many tens up to more than thousand atoms per unit cell. In these phases, for many phenomena, the physical length scales are substantially smaller than the unit-cell dimension. Hence, these materials offer unique combinations of properties, which are mutually excluded in conventional materials: metallic electric conductivity combined with low thermal conductivity, combination of good light absorption with high-temperature stability, combination of high metallic hardness with reduced wetting by liquids, electrical and thermal resistance tuneable by composition variation, excellent resistance to corrosion, reduced cold-welding and adhesion, enhanced hydrogen storage capacity and light absorption, etc. The series of books will concentrate on: development of fundamental knowledge with the aim of understanding materials phenomena, technologies associated with the production, transformation and processing of knowledge-based multifunctional materials, surface engineering, support for new materials development and new knowledge-based higher performance materials for macro-scale applications.







Quantum Mechanical Approach to Understanding Micro-Structural and Mechanical Properties of Intermetallics


Book Description

The primary goal of the proposed research was to study and develop alloying concepts for understanding intermetallic alloys as derived from a first principles quantum mechanical approach. Thus, a major part of our effort was to study and determine ductilizing effects of alloying elements in several intermetallic compounds and to work closely with experimental efforts to evaluate the applicability of the theoretical approach to alloy design. Specifically, highly precise all-electron quantum mechanical electronic structure methods were applied to the study of a number of materials problems in order to obtain from first principles information of relevance to alloy stability on the design of structural materials. Using our recently developed state-of-the-art all-electron self-consistent total energy methods which gives precise solutions of the local density equations, fundamental information was sought about the structural and electronic properties of these alloys in order to predict stable and metastable phases and how alloying effects bonding, crystal ordering and crystal symmetry. The first principles approach used here addresses questions of a metallurgical nature, such as phase stability, crystal structure, equilibrium lattice constants and mechanical properties including the effect of atomic relaxation.




Quantum Mechanical Approach to Understanding Structural, Electronic and Mechanical Properties of Intermetallics


Book Description

Our primary goal is to study and develop alloying concepts for understanding intermetallic alloys as derived from a highly precise quantum mechanical approach. Thus, a major part of our effort is to study and determine ductilizing effects and to work closely with experimental efforts to evaluate the applicability of the theoretical approach to alloy design. Specifically we have studied a number of materials problems to obtain first principles information of relevance to alloy stability and design of structural materials. Fundamental information has been obtained about the structural and electronic properties in order to predict stable and metastable phases and how alloying affects bonding, crystal order and crystal symmetry. Our approach addresses questions of a metallurgical nature, such as phase stability, crystal structure, equilibrium lattice constants, and mechanical properties. For the ordered compounds, tailoring the chemistry of these alloys to obtain higher symmetry (and thus more ductile) crystalline phases is extremely important. The research seeks to explore a new capability for modelling materials and their properties on the computer which have not yet been made in practice. (mjm).