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Diffusion is an omnipresent but important phenomenon in a wide variety of disciplines and applications in physical, chemical, biological, geologic, materials science and engineering processes. While diffusion-controlled phase transformations involve in a variety of materials processes, ranging from solidification to different solid-state transformations. Modeling of diffusion and diffusion-controlled phase transformations in alloys has been of long-standing fundamental interests because advance modeling can help to improve the understanding of complex materials processes. Moreover, as the recent boost in Integrated Computational Materials Engineering (ICME) and Materials Genome Initiative (MGI) projects, additional emphasis on the necessity and urgency of the quantitative modeling of diffusion and diffusion-controlled phase transformations in alloys has been laying, which can provide useful information for accelerating the novel alloys design. Consequently, the purpose of this book, entitled Modeling of Diffusion and Diffusion-Controlled Phase Transformations in Alloys is to provide a collection of the commonly used computational approaches for modeling diffusion and diffusion-controlled phase transformations, as well as their current status, recent developments, future trends and applications in different alloys.
Diffusion-controlled processes still remain the most important and interesting phenomena in materials science. Among the problems which are currently to the fore, are the synergy of diffusion and morphological evolution, the initial stages of solid-state reactions, the analysis of nano- materials and related phenomena, thermo- and electromigration, and the reliability of solder joints and interconnects in microelectronic devices. A number of challenging problems still remain within the “classical” areas of nucleation, reactive- and inter-diffusion, phase growth in multicomponent and binary systems, and decomposition and ripening. Volume is indexed by Thomson Reuters CPCI-S (WoS)
Diffusion is an omnipresent, but the important phenomenon in a wide variety of disciplines and applications in physical, chemical, biological, geologic, materials science and engineering processes. While diffusion-controlled phase transformations involve in a variety of materials processes, ranging from solidification to different solid-state transformations. Modeling of diffusion and diffusion-controlled phase transformations in alloys has been of long-standing fundamental interests because advance modeling can help to improve the understanding of complex materials processes. Moreover, as the recent boost in Integrated Computational Materials Engineering (ICME) and Materials Genome Initiative (MGI) projects, additional emphasis on the necessity and urgency of the quantitative modeling of diffusion and diffusion-controlled phase transformations in alloys has been laying, which can provide useful information for accelerating the novel alloys design. Consequently, the purpose of this book, entitled "Modeling of Diffusion and Diffusion-Controlled Phase Transformations in Alloys" is to provide a collection of the commonly used computational approaches for modeling diffusion and diffusion-controlled phase transformations, as well as their current status, recent developments, future trends and applications in different alloys.
Dissertation consists of multiple works. The first part is devoted to self-diffusion along dislocation cores in aluminum followed by the development of embedded atom method potentials for Co, NiAl, CoAl and CoNi systems. The last part focuses on martensitic phase transformation (MPT) in NixAl1-x and AlxCoyNi1-x-y alloys. New calculation methods were developed to predict diffusion coefficients in metal as functions of temperature. Self-diffusion along screw and edge dislocations in aluminum was studied by molecular dynamic (MD) simulations. Three types of simulations were performed with and without (intrinsic) pre-existing vacancies and interstitials in the dislocation core. We found that the diffusion along the screw dislocation was dominated by the intrinsic mechanism, whereas the diffusion along the edge dislocation was dominated by the vacancy mechanism. The diffusion along the screw dislocation was found to be significantly faster than the diffusion along the edge dislocation, and the both diffusivities were in reasonable agreement with experimental data. The intrinsic diffusion mechanism can be associated with the formation of dynamic Frenkel pairs, possibly activated by thermal jogs and/or kinks. The simulations show that at high temperatures the dislocation core becomes an effective source/sink of point defects and the effect of pre-existing defects on the core diffusivity diminishes. First and the foremost ingredient needed in all atomistic computer simulations is the description of interaction between atoms. Interatomic potentials for Co, NiAl, CoAl and CoNi systems were developed within the Embedded Atom Method (EAM) formalism. The binary potentials were based on previously developed accurate potentials for pure Ni and pure Al and pure Co developed in this work. The binaries constitute a version of EAM potential of AlCoNi ternary system. The NiAl potential accurately reproduces a variety of physical properties of the B2-NiAl and L12-Ni3Al phases. The potential is expected to be especially suitable for simulations of hetero-phase interfaces and mechanical behavior of NiAl alloys. Apart from properties of the HCP Co, the new Co potential is accurate enough to reproduce several properties of the FCC Co which were not included in the potential fit. It shows good transferability property. The CoAl potential was fitted to the properties of B2-CoAl phase as in the NiAl fitting where as the NiCo potential was fitted to the ab initio formation energies of some imaginary phases and structures. Effect of chemical composition and uniaxial mechanical stresses was studied on the martensitic phase transformation in B2 type Ni-rich NiAl and AlCoNi alloys. The martensitic phase has a tetragonal crystal structure and can contain multiple twins arranged in domains and plates. The twinned martensites were always formed under the uniaxial compression where as the single variant martensites were the results of the uniaxial tension. The transformation was reversible and characterized by a significant temperature hysteresis. The magnitude of the hysteresis depends on the chemical composition and stress.
The CALPHAD approach is applied to kinetic studies of phase transformations and aging of prototypes of Ni-Cr-Mo-based alloys selected for waste disposal canisters in the Yucca Mountain Project (YMP). Based on a previous study on alloy stability for several candidate alloys, the thermodynamic driving forces together with a newly developed mobility database have been used to analyze diffusion-controlled transformations in these Ni-based alloys. Results on precipitation of the Ni2Cr-ordered phase in Ni-Cr and Ni-Cr-Mo alloys, and of the complex P- and [delta]-phases in a surrogate of Alloy 22 are presented, and the output from the modeling are compared with experimental data on aging.
Expanded and revised to cover developments in the field over the past 17 years, and now reprinted to correct errors in the prior printing, Phase Transformation in Metals and Alloys, Third Edition provides information and examples that better illustrate the engineering relevance of this topic. It supplies a comprehensive overview of specific types o
In the decade since the first edition of this popular text was published, the metallurgical field has undergone rapid developments in many sectors. Nonetheless, the underlying principles governing these developments remain the same. A textbook that presents these advances within the context of the fundamentals is greatly needed by instructors in the field Phase Transformations in Metals and Alloys, Second Edition maintains the simplicity that undergraduate instructors and students have come to appreciate while updating and expanding coverage of recently developed methods and materials. The book is effectively divided into two parts. The beginning chapters contain the background material necessary for understanding phase transformations - thermodynamics, kinetics, diffusion theory and the structure and properties of interfaces. The following chapters deal with specific transformations - solidification, diffusional transformation in solids and diffusionless transformation. Case studies of engineering alloys are incorporated to provide a link between theory and practice. New additions include an extended list of further reading at the end of each chapter and a section containing complete solutions to all exercises in the book Designed for final year undergraduate and postgraduate students of metallurgy, materials science, or engineering materials, this is an ideal textbook for both students and instructors.
Given that the basic purpose of all research in materials science and technology is to tailor the properties of materials to suit specific applications, phase transformations are the natural key to the fine-tuning of the structural, mechanical and corrosion properties. A basic understanding of the kinetics and mechanisms of phase transformation is therefore of vital importance. Apart from a few cases involving crystallographic martensitic transformations, all phase transformations are mediated by diffusion. Thus, proper control and understanding of the process of diffusion during nucleation, growth, oxidation, sintering, etc are essential for optimising the properties of materials to meet specific needs.
Developed by the late metallurgy professor and master experimentalist Hubert I. Aaronson, this collection of lecture notes details the fundamental principles of phase transformations in metals and alloys upon which steel and other metals industries are based. Mechanisms of Diffusional Phase Transformations in Metals and Alloys is devoted to solid-s