Computersimulationen des metallografischen Ätzprozesses
Final Report Abstract
The macroscopic physical properties of two- and multiphase materials are governed by two groups of parameters: (a) intrinsic properties of the constituent phases, e.g. crystal structure, electronic structure and (b) geometric parameters: size, shape, and spatial arrangement of the nano-scale particles of the secondary phases. The basic method to establish the latter parameters is the microscopic study of the surface of the material. However, to obtain satisfactory contrast normally some etching procedure is necessary. The surface relief created by etching can subsequently be imaged with satisfactory contrast. Generally optical, atomic force ( AFM ), and high-resolution scanning electron microscopes ( SEM ) are applied. Since the operation of transmission electron microscopes (TEM ) is more involved they are only used if the results obtained by the other microscopes are unsatisfactory. For all micrographs the question arises what are the real dimensions of the particles of the secondary phases: etched nano-scale particles of a secondary phase may appear too large or too small in the micrographs. Presently the metallographic etching process has been investigated by kinetic Monte Carlo simulations. The activation energy for the dissolution of an atom during etching was related to the atomic binding energy in the solid phase concerned and to the number of nearest neighbors of the atom considered. Briefly, the simulations yield: lower limits for the difference in binding energies necessary (i) to reveal the particles and (ii) to avoid over-etching. The results of the simulations are in very good agreement with our actual experimental microscopic observations of nano-scale plate-shaped particles in a two-phase material.
Publications
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Animations of kinetic Monte Carlo simulations of etching processes
Rudolf Reichelt, Eckhard Nembach
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Experimental determination and mathematical description of the shape and size of nanoscale particles in a solid matrix. Conference on the occasion of the 50th anniversary of the Institute of Materials Physics, Schloss Nordkirchen, im August 2009: "Thermodynamics and Transport Kinetics of Nanostructured Materials"
Rudolf Reichelt, Eckhard Nembach
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Modeling and kinetic Monte Carlo simulations of the metallographic etching process of second phase particles. „Philosophical Magazine“
Rudolf Reichelt, Eckhard Nembach
