QUANTITATIVE PREDICTION OF SURFACE SEGREGATION

An assessment has been made of the 32 available equilibrium measurements for surface segregation in substitutional pure binary alloy systems. These measurements have been analyzed in relation to the various terms proposed for the free energy of segregation. Three terms have been selected, the surface energies of the constituents, their enthalpy of mixing and a term related to the release of strain energy on segregation. A least squares fitting of the measurements to the three terms shows that some of the current theories are valid but that the importance of each term may not have been correctly emphasized. The assessment leads to a simple predictive relationship, valid for both dilute and concentrated alloy systems, which correlates with the experimental results over the range of free energies of segregation from -80 to 20 kJ/mol, with a standard deviation of less than 9 kJ/mol. © 1979.