On the Relationship Between Entropy and Enthalpy of Grain Boundary Segregation |
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Authors: | Pavel Lejček Siegfried Hofmann |
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Institution: | (1) Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Praha 8, Czech Republic;(2) Max-Planck-Institut für Metallforschung, Seestraße 92, 70174 Stuttgart, Germany |
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Abstract: | An extensive study of anisotropy of grain boundary segregation in -iron, performed in the last decade, confirmed the existence of a linear relationship between entropy and enthalpy of solute segregation at individual grain boundaries. A thermodynamic analysis of this relationship is performed in the present work. It is shown that this dependence defines a compensation temperature and an entropy-like parameter. The compensation temperature is not necessarily connected with a phase transformation, but it represents exclusively a mean temperature at which all boundaries approach to a mean value of the Gibbs free energy of segregation. The most important consequences of this dependence are outlined: a reversed anisotropy of grain boundary segregation at temperatures above the compensation temperature, and a new method for the prediction of the enthalpy and entropy of solute segregation at individual grain boundaries. |
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Keywords: | grain boundaries segregation anisotropy thermodynamics |
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