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

This book presents the results of research on the regularities during thermocyclic impact on changes in structural-phase states of functional alloys with low-stability or instability in the area of structural-phase transformations. Without clarification of the physical regularities of the influence of thermomechanical impact on the properties of alloys, it is impossible to develop technological processes of processing functional materials; therefore, the book widely uses the results of many years of research by the authors of the book. It is known that critical temperatures and stresses for martensitic transformation, for example, B 2↔︎ B 19′, in NiTi are very sensitive to cycling. The study of structural-phase states, corresponding to changes in physical-mechanical properties of intermetallics in the area of transformations, is a necessary aspect of understanding the nature of the influence of thermomechanical cycling on the properties of functional alloys. This book is dedicated to the fundamental physical aspects of stability, the influence of structural defects on properties and structural-phase transformations of FCC alloys. This book is useful for a wide range of specialists—scientific researchers and engineers, working in the field of materials science and physics of condensed systems, as well as teachers, postgraduates and students, specializing in the field of materials science.

The fascinating world of intermetallics is largely unexplored. There are many exciting physical properties and important technological applications of intermetallics, from magnetism to superconductivity. The main focus of this book is on the statistics, topology and geometry of crystal structures and structure types of intermetallic phases. The underlying physics, in particular chemical bonding, is discussed whenever it helps understand the stability of structures and the origin of their physical properties. The authors' approach, based on the statistical analysis of more than twenty thousand intermetallic compounds in the data base Pearson's Crystal Data, uncovers important structural relationships and illustrates the relative simplicity of most of the general structural building principles. It also shows that a large variety of actual structures can be related to a rather small number of aristotypes. The text aims to be readable and beneficial in one way or another to everyone interested in intermetallic phases, from graduate students to experts in solid state chemistry and physics, and materials science. For that purpose it avoids the use of enigmatic abstract terminology for the classification of structures. Instead, it focuses on the statistical analysis of crystal structures and structure types in order to draw together a larger overview of intermetallics, and indicate the gaps in it - areas still to be explored, and potential sources of worthwhile research. The text should be read as a reference guide to the incredibly rich world of intermetallic phases.

Intermetallic science is closely related to physics, chemistry, metallurgy, materials science & technology, and engineering. This book emphasizes the chemical aspects of this science, and therefore the mutual reactivity of metals and the characteristics of intermetallic compounds. Topics included are: • Phase diagrams of alloy systems. Many intermetallic systems form several compounds, generally not obeying common simple stoichiometric rules, which are often homogeneous in a certain range of compositions. The stability and extension of these phases are conveniently presented through phase diagrams. • Selected aspects of intermetallics structural chemistry, with emphasis on the solid state. The general structural characteristics of intermetallic phases are considered, with attention to nomenclature and to alternative and complementary methods of presenting crystal-chemical data. A brief account is given of derivative and degenerate structures, modular aspects of crystal structures, and of a few special groups of alloys such as quasicrystals and amorphous alloys. A number of selected structural prototypes with typical features, their possible grouping in structural “families and their distribution among different types of alloys are provided. • Intermetallic reactivity trends in the Periodic Table. Attention is given to a few selected elemental parameters such as electron configuration and valence electron number and to their changes along the Table, which act as reference factors of the intermetallic behaviour. As an example, the relationships are considered between crystal structure and the number of valence electrons per atom (or per formula) in various classes of compounds or solid solution phases. • Alloying behaviour systematics of intermetallic systems with a description of the intermetallic reactivity of each element, or group of elements, in the order of their position in the Periodic Table. For each pair of metallic elements, their capability to form intermediate phases is summarised by maps and schemes. • A description of small scale preparation methods of intermetallics. A number of interesting and significant peculiarities are, e.g., those related to their high melting points, insolubility in common solvents, etc. · Systematic treatment of alloying behaviour · Wide overview of intermetallic chemistry · Illustrated, with many examples

Complex metal alloys (CMAs) comprise a huge group of largely unknown alloys and compounds, where many phases are formed with crystal structures based on giant unit cells containing atom clusters, ranging from tens of 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 exclusive in conventional materials, such as metallic electric conductivity combined with low thermal conductivity, good light absorption with high-temperature stability, high metallic hardness with reduced wetting by liquids, etc.This book is the second of a series of books issued yearly as a deliverable to the European Community of the School established within the European Network of Excellence CMA. Written by reputed experts in the fields of metal physics, surface physics, surface chemistry, metallurgy, and process engineering, this book brings together expertise found inside as well as outside the network to provide a comprehensive overview of the current state of knowledge in CMAs.

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.