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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: In this paper, the volume and entropy changes upon melting at (P_c,T_c) assuming the R ln 2 rule (R is the gas constant) for the disordering entropy of melting.
83 citations
TL;DR: In this paper, the surface relief in a diffusional fcc-hcp transformation and its relation to ledge growth is examined. And the same mechanism is applied to increasingly complex cases, such as the relation to structural ledges, fccbcc transformations and finally a general martensite interface.
83 citations
TL;DR: In this paper, it has been shown that a weighted average diffusivity D ¯ can adequately represent the effective diffusion of carbon that is needed for the application of diffusion-controlled growth.
Abstract: The concentration dependence of the diffusivity D of carbon in austenite causes complications in the kinetic analysis of various diffusion-controlled reactions that arise in steels (see, for example, Ref. 1). The existence of substantial carbon concentration gradients at the transformation interfaces involved in such reactions makes it imperative to account for the variation of D with x (where x is the mole fraction of carbon), and it has been demonstrated that, for most purposes, a weighted average diffusivity D ¯ can adequately represent the effective diffusivity of carbon that is needed for the application of the theory of diffusion-controlled growth. Trivedi and Pound first considered this problem in detail, and obtained (1) D ¯ = ∫
83 citations
TL;DR: In this article, it was shown that nuclei develop from sub-grains situated in regions where there is a rapid change of orientation, either due to the original grain-boundaries or to transition bands introduced inside grains by deformation.
Abstract: Recent experimental evidence on the process of nucleation is reviewed. This suggests that nuclei develop from sub-grains situated in regions where there is a rapid change of orientation, either due to the original grain-boundaries or to transition bands introduced inside grains by deformation. Development of large sub-grains capable of growth at grain-boundaries may be stimulated either by a coalescence of sub-grains adjacent to old grain-boundaries, or at grain edges, by a process of re-establishing the equilibrium angles distorted by deformation. Further understanding of nucleation will require investigation both of the nature of the cold-worked state in polycrystalline materials and also of the mobility of general low-angle boundaries (θ less than 15 °).
83 citations
TL;DR: In this paper, a simple analytical model for predicting the maximum PCM operation temperature compatible with a ten-year retention lifetime of the device was proposed, where the average retention lifetime and average size of crystalline particles at crystallization in the PCM cell were analyzed.
Abstract: Phase-change memory (PCM) reliability is affected by the crystallization of the amorphous chalcogenide material. To reduce measurement time, crystallization of the active material, usually a chalcogenide alloy, is generally studied at high temperature (T > 160degC), while data retention is to be predicted for lower temperatures (T > 120degC). Therefore, a physically based procedure to extrapolate crystallization dynamics from high to operation temperatures is required. This paper shows a simple analytical model for predicting the maximum PCM-operation temperature compatible with a ten-year retention lifetime of the device. Experiments are first analyzed to extract the average retention lifetime and average size of crystalline particles at crystallization in the PCM cell; this allowed the extraction of nucleation rate and growth velocity in the Ge2Sb2Te5 phase-change material. The classical theory for crystallization based on nucleation and growth (N/G) is then used to extrapolate lifetime data to relatively low temperatures for reliability assessment. Our study shows that the temperature dependence of retention lifetime may not obey to the Arrhenius law, as a result of non-Arrhenius nucleation. The dependence of reliability on N/G parameters is finally discussed with reference to different crystallization modes in phase-change materials.
83 citations