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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, three different morphologies of pearlite have been formed isothermally at three temperatures in a eutectoid steel and the interlamellar spacings of these morphologies have been measured by scanning and transmission electron microscopy.
45 citations
25 May 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors used a modification of the transformation equation proposed by Li et al. to predict the microstructure and properties of heat-treated steels by incorporating appropriate models for the kinetics of various austenite transformations.
Abstract: Finite element simulations that predict the microstructure and properties of heat-treated steels can be significantly improved by incorporating appropriate models for the kinetics of various austenite transformations. In the present study the austenite decomposition kinetics for a 1045 steel was modeled using a modification of the transformation equation proposed by Li et al. [1]. The kinetics of the continuous cooling transformation were determined directly from an isothermal transformation diagram. To verify the predictions of the model, an end-quench test was used because it produces a wide range of microstructures. The microstructures predicted by the kinetics model for the end-quenched sample were confirmed by quantification of the microstructures observed in the end-quench experiments. Furthermore, the predicted hardness profile was in good agreement with the experimentally measured hardness profile. The kinetics model developed in the present study was compared to the models proposed by Kirkaldy and Venugopalan [2] and the unmodified model by Li. The present model provides a more accurate prediction. A microstructural-based hardness equation from the literature was also evaluated and it predicted hardness values that were above the experimentally measured values. The model we propose predicts the experimental hardness profile more accurately, since it is based on the calculated microstructure and experimental hardness values of martensite, bainite, and ferrite/pearlite.
45 citations
TL;DR: In this article, the thermically induced h.p.c. martensitic phase transformation was studied in Co-32 at.% Ni single crystals by the weak-beam method of transmission electron microscopy (TEM).
Abstract: The thermically induced h.c.p. to f.c.c. martensitic phase transformation was studied in Co-32 at.% Ni single crystals by the weak-beam method of transmission electron microscopy (TEM). In this alloy the mean transformation temperature is at RT and therefore both phases are stable at RT. At the beginning of the transformation new f.c.c. lamellae grow from the thick into the thin region of the specimen. At the front of the lamella a Shockley partial dislocation must lie on every other close-packed plane. The dislocation contrast of the front observed by weak-beam images is similar to that of a single partial dislocation, even when the lamella is up to 50 atom layers thick. The minimum thickness of the lamellae is 6 to 10 close-packed planes; the lamellae grow in thickness by ledges. The lack of long range stress fields and the observation of lamellae of discrete height seem to indicate that at the front of the lamellae all three coplanar Burgers vectors of the partial dislocations are present and ...
45 citations
TL;DR: In this paper, the morphology of acicular ferrite in alloy-steel weld metals has been investigated and the effect of the grain size of prior austenite on acicular Ferrite transformation has also been studied.
Abstract: In this paper, the morphology of acicular ferrite in alloy-steel weld metals has been investigated. The effect of the grain size of prior austenite on acicular ferrite transformation has also been studied. It is found that acicular ferrite can form in reheated weld metals when the austenite grain size is relatively large. On the other hand, classical sheaf-like bainite will form at the same temperature if the austenite grain size is kept small. Further results strongly suggest that acicular ferrite is in fact intragranular bainite rather than intragranular Widmanstatten ferrite.
45 citations
TL;DR: In this article, an analytical solution for the mechanism of nucleation and growth of hydrogen pore in the solidifying A356 aluminum alloy is derived, based on a model of initial transient hydrogen redistribution in the growing dendritic grain.
45 citations