Abstract
Segregation in materials can be broadly divided into two types; equilibrium (ES) and non-equilibrium (NES). In the former1 the segregating species is assumed to have reached a steady-state equilibrium at a particular temperature such that the rate of capture at a sink exactly balances the rate of evaporation from the sink by thermal excitation. Subsequent rapid cooling to room temperature does not significantly alter the segregation profile. A simple concentration step change can be assumed to occur at the matrix-sink interface, with no significant concentration gradients present in the adjacent matrix. With NES, the concentration profile at the boundary is determined by the capture of solute atoms during quenching from an elevated temperature2 and so solute concentration gradients occur in the matrix adjacent to the boundary. The extent of the profiles is determined by the diffusion rates of the migrating species, and these can also be on the scale of inter-planar spacings. Much wider depletion and segregation profiles can also be produced by precipitation reactions at grain boundaries during high temperature anneals. Although point defects and linear defects can trap solute atoms, in this paper we shall consider sinks to be two-dimensional, i.e. grain boundaries, precipitate/matrix interfaces.
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Titchmarsh, J.M., Vatter, I.A. (1989). EDX and EELS Studies of Segregation in STEM. In: Cherns, D. (eds) Evaluation of Advanced Semiconductor Materials by Electron Microscopy. NATO ASI Series, vol 203. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-0527-9_9
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DOI: https://doi.org/10.1007/978-1-4613-0527-9_9
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