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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, a model is developed to predict the precipitation kinetics and strengthening in Al-Cu-Mg alloys during non-isothermal treatments consisting of controlled heating and cooling.
Abstract: A model is developed to predict the precipitation kinetics and strengthening in Al–Cu–Mg alloys during non-isothermal treatments consisting of controlled heating and cooling. The prediction of the precipitation kinetics is based on the Kampmann and Wagner model. The precipitation strengthening by the shearable Cu–Mg co-clusters is modelled on the basis of the modulus strengthening mechanism and the strengthening by the non-shearable S phase precipitates is based on the Orowan looping mechanism. The model predictions are verified by comparing with hardness, transmission electron microscopy and differential scanning calorimetry data on 2024-T351 aluminium alloys. The microstructural development and strength predictions of the model are generally in close agreement with the experimental data.
34 citations
TL;DR: In this paper, an analytical evaluation of the transition temperature from upper to lower bainite in Fe -0·38C − 0·93Cr (wt-%) steel was carried out, based on the model constructed by Takahashi and Bhadeshia.
Abstract: An analytical evaluation of transition temperature from upper to lower bainite in Fe – 0·38C – 0·93Cr (wt-%) steel was carried out. Calculations were based on the model constructed by Takahashi and Bhadeshia, which involves a comparison between the time tθ needed to precipitate cementite within the bainitic ferrite plates with the time tθ required to decarburise supersaturated ferrite plates. It was found that the distribution of lath widths, shown by histograms, of the bainitic ferrite varies with isothermal transformation temperatures and holding times. The transition between upper and lower bainite is found to occur over a narrow range of temperatures (350 – 410°C) and depends on the thickness of bainitic ferrite laths and the volume fraction of precipitated cementite. On comparing t d and tθ it was found that a transition temperature from upper to lower bainite reaction L S of about 350°C could be predicted if the thickness of bainitic ferrite laths is set as w o = 0·1 μm and the volume fracti...
34 citations
TL;DR: There are several theoretical and empirical thermodynamic models which adequately describe the equilibrium properties of carbon in ferrite and in austenite (e.g. as discussed by the authors ), but these models usually contain unknown parameters which have to be deduced by "curvefitting" to experimental thermodynamic data, and this has made it difficult to judge the validity of particular theories, since the curve-fitting procedure always seems to ensure good agreement with the known Fe-C phase diagram.
Abstract: There are several theoretical and empirical thermodynamic models which adequately describe the equilibrium properties of carbon in ferrite and in austenite (e.g. Refs. 1, 2). These models usually contain unknown parameters which have to be deduced by ‘curve-fitting’ to experimental thermodynamic data, and this has made it difficult to judge the validity of particular theories, since the curve-fitting procedure always seems to ensure good agreement with the known Fe–C phase diagram. However, the analysis of reactions occurring under metastable equilibrium conditions (such as the bainite and martensite transformations) requires the extrapolation of the free energy surfaces of austenite and ferrite; it is clearly desirable to base such extrapolations on physically meaningful laws.
34 citations
TL;DR: In this paper, two-dimensional vanadium carbide (V2C) MXene with layer thickness of 50−100nm was fist synthesized by selectively HF-etching the Al layers from V2AlC MAX phase and then introduced into MgH2 to improve the hydrogen sorption performances.
34 citations
TL;DR: In this paper, the effect of temperature on the crystallization kinetics of bulk amorphous selenium and the alloy As 0.005Se0.995 has been studied using differential scanning calorimetry.
Abstract: The effect of temperature on the crystallization kinetics of bulk amorphous selenium and the alloy As0.005Se0.995 has been studied using differential scanning calorimetry. A time-temperature-transformation (TTT) curve has been plotted from isothermal results over the temperature range 320 to 490 K, and shows the presence of two minima for both materials. Using the empirical Avrami expression for solid-state transformations, a number of kinetic parameters has been determined.
34 citations