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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 article, the conditions for the initiation of solid grains on nucleant areas of defined size are analyzed, and it is concluded that for potent nucleants, initiating grains at small undercooling, athermal nucleation dominates.
102 citations
TL;DR: In this article, the microstructure of Zn-5 wt% Al polycrystals was studied in the temperature range 250-375 °C, and the fraction of wetted grain boundaries increased with increasing temperature and was independent of annealing time.
102 citations
TL;DR: In this paper, the authors extended the kinetic treatment of glass formation by the introduction of continuous cooling (CT) curves to estimate the cooling rates required to form glasses of various materials.
Abstract: The kinetic treatment of glass formation is extended by the introduction of continuous cooling (CT) curves to estimate the cooling rates required to form glasses of various materials. The CT curves may be constructed from isothermal time-temperature-transformation curves following the approach originally suggested by Grange and Kiefer. The modified analysis is used to evaluate the effects of nucleating heterogeneities on glass formation. It is found that for the concentrations of such heterogeneities found in most liquids, those characterized by contact angles greater than about 100° have a negligible effect on the cooling rate required to form glasses. Heterogeneities with smaller contact angles, can, however, have a significant effect on glass formation, with the critical cooling rate increasing with decreasing contact angle. The effects on glass formation of changes in the contact angle of nucleating heterogeneities are also compared with the effects of changes in the thermodynamic barrier to nucleation (in the crystal-liquid surface energy).
102 citations
TL;DR: In this article, it is suggested that the high boundary mobility associated with misorentations > 10−18° is the origin of pre-existing grain boundaries and transition bands acting as principal sites for nucleation.
Abstract: The phenomenon of nucleation of new grains during annealing of deformed metals is discussed with respect to various aspects of the deformed state, including the stored energy of cold work and various microstructural features. Attention is drawn to those regions of the deformed metal where there is a rapid change of orientation, such as pre-existing grain boundaries and deformation (transition) bands. The currently accepted theory of nucleation, the growth of favoured sub grains, is discussed in the light of the known low mobility of low-angle sub-boundaries. It is suggested that the high boundary mobility associated with misorentations > 10–18° is the origin of pre-existing grain boundaries and transition bands acting as principal sites for nucleation. Recent evidence concerning the initial growth of subgrain ‘nuclei’ is described and it is suggested that subgrain coalescence may often play a crucial role in this process. Subgrain coalscence appears to occur preferentially in those regions of lat...
102 citations
TL;DR: In this article, a new method of kinetic analysis that allows the combined analysis of data obtained under different experimental conditions, i.e. heating pathway, is presented for the crystallization of non-crystalline solids.
Abstract: A new method of kinetic analysis that allows the combined analysis of data obtained under different experimental conditions, i.e. heating pathway, is presented for the crystallization of non-crystalline solids. The method consists of a two-stage procedure. Firstly, an optimization procedure is applied for the determination of the Johnson, Mehl and Avrami (JMA). This optimization procedure is based on the linearization of the rate equation throw a logarithmic transformation; where the correlation coefficient function is the objective function, and the JMA order is the adjustable parameter. The JMA order obtained from this optimization procedure allows one to determine in a second stage the other kinetic parameters, i.e. activation energy and pre-exponential Arrhenius factor. The method proposed here allows one to analyze in a combined way data obtained under any heating profile, because no assumptions are made on the heating profile for the derivation of the rate equation. The method is tested with computed and experimental curves obtained under different heating conditions. The crystallization kinetics of (GeS2)0.3(Sb2S3)0.7 glass are studied from the combined analysis of several curves.
101 citations