File Name: self diffusion and impurity diffusion in pure metals .zip
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Self-diffusion in the hexagonal structure of Zirconium and Hafnium. Computer simulation studies. Paz , C. Self-diffusion by vacancy mechanism is studied in two metals of hexagonal close packed structure, namely Hafnium and Zirconium. Computer simulation techniques are used together with many-body potentials of the embedded atom type. Defect properties are calculated at 0 K by molecular static while molecular dynamic is used to explore a wide temperature range. Keywords: self-diffusion, computer simulation, transition metals.
The diffusion of silver and gold tracers in silver-gold in crystals of 0, 8, 17, 35, 50, 66, 83, 94 and at. It is shown that the limiting error in such measurement is due to temperature uncertainty rather than to the sectioning process. The activation energies obtained do not vary in proportion to the melting point or heat of fusion, and the deviations cannot be rectified in terms of lattice parameter arguments. The activation energies in the pure metals are better accounted for by the theory of Turnbull and Hoffman than by that of Swalin. From the change in frequency factor with composition it is deduced that the activation entropy of migration of a vacancy decreases linearly with composition by 1.
Specifically, vacancy-mediated volume diffusion in pure elements and alloys with dilute concentration of impurities is studied. A novel procedure is discovered for predicting diffusion coefficients that overcomes the shortcomings of the well-known transition state theory, by Vineyard. Alongside, the procedure is straightforward in its application within the conventional harmonic approximation, from the results of static first-principles calculations.
Diffusion in metals is an important phenomenon, which has many applications, for example in all kinds of steel and aluminum production, and in alloy formation technical applications e. In this book the data on diffusion in metals are shown, both in graphs and in equations. Reliable data on diffusion in metals are required by researchers who try to make sense of results from all kinds of metallurgical experiments, and they are equally needed by theorists and computer modelers. The previous compilation dates from , and measurements relying on the electron microprobe and the recent Rutherford backscattering technique were hardly taken into account there.
This textbook provides an introduction to changes that occur in solids such as ceramics, mainly at high temperatures, which are diffusion controlled, as well as presenting research data. Such changes are related to the kinetics of various reactions such as precipitation, oxidation and phase transformations, but are also related to some mechanical changes, such as creep. The book is composed of two parts, beginning with a look at the basics of diffusion according to Fick's Laws. In the second part, the author discusses diffusion in several technologically important ceramics. Of these, three refer to oxide ceramics alumina, magnesia and zirconia.
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