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The theory of transformations in metals and alloys

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 proposed an alternative mechanism for defect formation based on the facetted shape of nuclei and errors in stacking of {111} planes which occur during deposition on the facets.
Abstract: In the growth of thin films of compound semiconductors on (001) silicon substrates by vapor deposition techniques, it is usual to employ a two-step process. In this method, an initial (buffer) layer is first grown at a relatively low temperature; once a continuous film has formed on the substrate, its temperature is raised for the subsequent bulk growth. Carrying out the growth in a one-step process by heating the substrate to the final temperature before allowing the gases into the CVD reactor usually results in a polycrystalline aggregate. In this paper, classical nucleation and growth mechanisms are used to explain-the reasons for the different morphology of the one-step and two-step growth films. The heteroepitaxial films on (001) silicon often contain a high density of stacking faults and twins. The occurrence of these planar defects is usually attributed to stresses that arise from lattice mismatch and/or thermal mismatch (differences in coefficients of thermal expansion) between the substrate and the epilayer. It is argued that, in fact, mismatch stresses play a minor role in the generation of planar defects. Instead, an alternative mechanism for their formation is proposed which is based on the facetted shape of nuclei and errors in stacking of {111} planes which occur during deposition on the facets. Conventional and high resolution transmission electron microscopy have been used to investigate three systems grown by CVD or MOCVD: SiC/Si, GaAs/Si and GaP/Si. These systems have different lattice and thermal mismatches, and the results support the proposed model for the formation of defects.

46 citations

Journal ArticleDOI
TL;DR: In this article, a generalized two-dimensional diffusion model was developed which consists of an array of boundaries coupled to the free surface and to the substrate lattice, making use of three nonlinear partial differential equations which describe lattice and grain boundary, and surface diffusion.
Abstract: A generalized two‐dimensional diffusion model has been developed which consists of an array of boundaries coupled to the free surface and to the substrate lattice. The model makes use of three nonlinear partial differential equations which describe lattice, grain boundary, and surface diffusion. This two‐dimensional model has been programmed for the IBM 360 computer using a finite‐difference solution to give concentrations as a function of time. An x‐ray intensity simulation program is developed to give integrated diffracted intensity for a given concentration distribution. This simulated intensity is compared with experimental intensity. Data are presented from a sample containing 8 μ of Ni on a (111)‐oriented Cu crystal diffused for various times at 900°C and a similar sample with 6.5 μ of Ni diffused at 600°C. The simulations are in good agreement with experimental intensity bands. Activation energies and frequency factors are given for volume and grain boundary diffusion which are in good agreement wi...

46 citations

Journal ArticleDOI
TL;DR: In this paper, a non-standard heat-treating process has been successfully applied for improving the mechanical properties of low carbon Fe 0.12% C-0.5% Mn steels, where the process consists of alternate thermal cycling in the γ range and two phase (α + γ ) range with intermediate quenching so as to produce a microduplex fine grained mixture of martensite and proeutectoid ferrite.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanism and the kinetics of the replacement of aragonite by apatite by using a cuttlebone as a starting material and reacting it with di-ammonium hydrogen phosphate solution.

45 citations

Journal ArticleDOI
TL;DR: In this paper, the thermal stability and quantification of different transformation processes involved in the overall crystallization of the Fe50Cr15Mo14C15B6 amorphous alloy were investigated by several characterization techniques.

45 citations