Book•
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 authors used TEM and DSC to evaluate the thermal stability of fully amorphous melt-spun Ti-25.0 and Ti-50.0%Ni alloys.
42 citations
TL;DR: In this article, the authors applied the topological theory of line defects based on symmetry theory to the particular case of twinning dislocations in hexagonal-close-packed (hop) metals.
Abstract: The crystallographic analysis of line defects in interfaces is discussed and applied to the particular case of twinning dislocations in hexagonal-close-packed (hop) metals, which have been studied here by atomistic simulation. Two crystallographic approaches are used; first, the concept of bicrystal structure maps is developed for the case of interfaces between crystals having multiple-atom bases, and second, the topological theory of line defects based on symmetry theory is used. On the basis of the atomistic calculations, some general conclusions concerning the relative contribution to the total energy of dislocations made by their elastic fields and core structures are presented.
42 citations
TL;DR: In this paper, a modified version of the Avrami model was developed for complex lipid crystallization kinetics, which produces excellent fits to experimental data and allows the prediction of physically meaningful parameters, such as changes in nucleation rate and type, growth rate, morphology and dimensionality.
Abstract: The Avrami model was developed to model the kinetics of crystallization and growth of a simple metal system. The original assumptions of the model do not apply for high-volume-fraction crystallizing lipids, although it is incorrectly and frequently applied. A modified form of the Avrami model, wellsuited to complex lipid crystallization kinetics, is developed. It produces excellent fits to experimental data and allows the prediction of physically meaningful parameters, such as changes in nucleation rate and type, growth rate, morphology, and dimensionality. Morphological changes highlighted by time-resolved temperature-controlled polarized light microscopy support its application to crystallizing lipids. The kinetics of crystallization for six separate lipid samples were monitored by pulsed NMR, and fits were performed using the classical and modified Avrami model. In all cases, the modified model provided superior fits to the data compared with that of the classical model. The modified model supports the theory that lipids crystallize and grow into networks via very specific growth modes. Furthermore, the case is made that it is useful for interpreting crystallization kinetics of other systems such as polymer melts, which have nonconstant growth rates, dimensionalities, and nucleation conditions, and whose growth become diffusion-limited within specific regimes.
42 citations
TL;DR: In this paper, an analytical model was developed to describe the deposition process, and the stress distribution within the ZrO 2 coating and iron substrate was derived from the thermal history by a finite element method.
Abstract: An analytical model was developed to describe the deposition process. Assuming the plane solid-liquid interface to move with the solidification rate calculated by this deposition model, the thermal history was also calculated by a finite difference method. The solidification rate changes periodically, causing a temperature fluctuation in the coating layer and substrate during deposition. As the liquid remains discontinuosly at the coating surface, interlamellar layers, such as oxide or glass layers, form discontinuosly. These phenomena can be confirmed in the Ni17Cr4Si3B deposit. Using the stress model proposed in this study, the stress distribution within the ZrO 2 coating and iron substrate was derived from the thermal history by a finite element method. The shape of the predicted residual stress distribution was in good agreement with that measured by X-ray diffraction in the PSZ coating. The differences between the theoretical predictions and experimental results are discussed.
42 citations
Journal Article•
TL;DR: In this article, the second-order Johnson-Mehl equation was used to model the formation of pyrite in the marcasite matrix. But the authors only used infrared spectroscopy.
Abstract: Ansrn-lcr The kinetics of the solid-state transformation of marcasite to pyrite have been investigated using infrared spectroscopy. Kinetic analysis using the Johnson-Mehl or AvramiErofe'ev equation is based on measurements of infrared absorption intensity made on marcasite samples heated in the temperature range of 698-735 K. From the Arrhenius equation, an activation energy of 253 + 8 kJlmol and frequency factor of 4.6 x l0r5/min is calculated for the conversion from marcasite to pyrite. The transformation is modeled by a second-order Johnson-Mehl equation suggesting a nucleation and growth model for the formation of pyrite in the marcasite matrix. INrnooucrroN Pyrite and marcasite are naturally occurring phases in the Fe-S system, dimorphs of composition FeSr. The pyrite crystal structure is cubic (space group Pd3), with the octahedrally coordinated Fe atoms at the corners and face centers of the cube unit cell. Disulfide pairs lie at the center ofthe cube and at the midpoints ofthe cube edges and are oriented such that their axes are parallel to four nonintersecting body diagonals ofthe cubic lattice. Each S atom is tetrahedrally coordinated to three Fe atoms and one S atom. Marcasite has an orthorhombic unit cell (space group Pnnm) and, like pyrite, has Fe atoms in octahedral coordination with S, and S atoms tetrahedrally coordinated to three Fe atoms and one S atom. The difference between the marcasite and pyrite structures is found in the linking of the Fe-centered octahedra. In the marcasite structure, these octahedra share two edges in planes normal to (001); in pyrite, the octahedra are linked at corners (Vaughan and Craig, 1978). The pyrite structure can be obtained
42 citations