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The theory of transformations in metals and alloys
01 Jan 1965-
TL;DR: In this paper, the authors present a general introduction to the theory of transformation kinetics of real metals, including the formation and evolution of martensitic transformations, as well as a theory of dislocations.
Abstract: Part I General introduction. Formal geometry of crystal lattices. The theory of reaction rates. The thermodynamics of irreversable processes. The structure of real metals. Solids solutions. The theory of dislocations. Polycrystalline aggregates. Diffusion in the solid state. The classical theory of nucleation. Theory of thermally activated growth. Formal theory of transformation kinetics. Part II Growth from the vapour phase. Solidification and melting. Polymorphic Changes. Precipitation from supersaturated solid solution. Eutectoidal transformations. Order-disorder transformations. Recovery recrystalisation and grain growth. Deformation twinning. Characteristics of martensic transformations. Crystallography of martensitic transformations. Kinetics of martensitic transformations. Rapid solidification. Bainite steels. Shape memory alloys.
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TL;DR: Optimize the procedures for solar cells based on lead bromide perovskite, resulting in 5.4% efficiency and Voc of 1.24 V, improving the performance in this class of devices.
Abstract: Hybrid organic/lead halide perovskites are promising materials for solar cell fabrication, resulting in efficiencies up to 18%. The most commonly studied perovskites are CH3NH3PbI3 and CH3NH3PbI3–xClx where x is small. Importantly, in the latter system, the presence of chloride ion source in the starting solutions used for the perovskite deposition results in a strong increase in the overall charge diffusion length. In this work we investigate the crystallization parameters relevant to fabrication of perovskite materials based on CH3NH3PbI3 and CH3NH3PbBr3. We find that the addition of PbCl2 to the solutions used in the perovskite synthesis has a remarkable effect on the end product, because PbCl2 nanocrystals are present during the fabrication process, acting as heterogeneous nucleation sites for the formation of perovskite crystals in solution. We base this conclusion on SEM studies, synthesis of perovskite single crystals, and on cryo-TEM imaging of the frozen mother liquid. Our studies also included t...
391 citations
TL;DR: In this article, the compatibility of the field equations and jump conditions of the one-dimensional theory of elastic bars with two additional constitutive requirements: a kinetic relation controlling the rate at which the phase transition takes place and a nucleation criterion for the initiation of phase transition.
Abstract: This paper treats the dynamics of phase transformations in elastic bars The specific issue studied is the compatibility of the field equations and jump conditions of the one-dimensional theory of such bars with two additional constitutive requirements: a kinetic relation controlling the rate at which the phase transition takes place and a nucleation criterion for the initiation of the phase transition A special elastic material with a piecewise-linear, non-monotonic stress-strain relation is considered, and the Riemann problem for this material is analyzed For a large class of initial data, it is found that the kinetic relation and the nucleation criterion together single out a unique solution to this problem from among the infinitely many solutions that satisfy the entropy jump condition at all strain discontinuities
390 citations
TL;DR: In this article, a plethora of relevant experimental results on internal homogeneous crystal nucleation in silicate glasses obtained in the last four decades, and their analyses in the framework of the classical nucleation theory (CNT) are outlined.
Abstract: We review a plethora of relevant experimental results on internal homogeneous crystal nucleation in silicate glasses obtained in the last four decades, and their analyses in the framework of the classical nucleation theory (CNT). The basic assumptions and equations of CNT are outlined. Particular attention is devoted to the analysis of the properties of the critical nuclei, which, to a large extent, govern nucleation kinetics. The main methods employed to measure nucleation rates are described and the possible errors in the determination of the crystal number density (and, correspondingly, in nucleation rates) are discussed. The basic regularities of both time and temperature dependencies of nucleation rates are illustrated by numerous experimental data. Experimental evidence for a correlation between maximum nucleation rates and reduced glass transition temperatures is presented and theoretically justified. Special attention is given to serious problems that arise in the quantitative description of nucleation rates when using the CNT, for instance: the dramatic discrepancy between calculated and measured nucleation rates; the high value of the crystal nuclei/melt surface energy, σcm, if compared to the expected value estimated via Stefan’s rule; the increase of σcm with increasing temperature; and the discrepancies between the values of the surface energy and the time-lag for nucleation when independently estimated from nucleation and growth kinetics. The analysis of the above mentioned problems leads to the following conclusion: in contrast to Gibbs’ description of heterogeneous systems underlying CNT, the bulk thermodynamic properties of the critical nuclei generally differ from those of the corresponding macro-phase resulting simultaneously in significant differences of the surface properties as compared with the respective parameters of the planar interfaces. In particular, direct experimental evidence is presented for compositional changes of the crystal nuclei during formation of the critical nuclei and their growth from critical to macro-sizes. In addition, detailed examinations of crystal nucleation and growth kinetics show a decrease of both the thermodynamic driving force for nucleation and of the critical nuclei/liquid interfacial energy, as compared with the respective properties of the macro-phase. However, despite significant progress in understanding crystal nucleation in glasses in the past four decades, many problems still exist and this is likely to remain a highly interesting subject for both fundamental and applied research for a long time.
378 citations
TL;DR: In this paper, the authors reviewed new perspectives on the phase field approach in modeling deformation and fracture at the fundamental defect level, including the ability to predict fundamental properties of individual defects such as size, formation energy, saddle point configuration and activation energy of defect nuclei, and the micromechanisms of their mutual interactions.
375 citations
TL;DR: In this paper, a common basis of reaction-rate theories is discussed for isothermal and non-isothermal transformations, and compatible recipes have been obtained for the extraction of kinetic parameters from isothermally and nonsmooth conducted experiments, which can also be applied to heterogeneous reactions, and that these methods constitute (only) a special case of the general analysis proposed.
Abstract: A common basis of reaction-rate theories is discussed for isothermal and non-isothermal transformations As a result compatible recipes have been obtained for the extraction of kinetic parameters from isothermally and non-isothermally conducted experiments It follows that so-called Kissinger-like methods for non-isothermal kinetic analysis, originally derived for homogeneous reactions, can also be applied to heterogeneous reactions, and that these methods constitute (only) a special case of the general analysis proposed The recipes presented are illustrated by a series of examples taken from recent research on solid-state transformations; among other things, isothermal and non-isothermal analyses of the same transformation are compared and use of the notion of “effective activation energy”, that varies during the course of an overall transformation, is discussed
372 citations