Abstract
The equilibrium surface composition of a Cu-0.83 at. % Ag alloy has been studied over the range from 600°–400°C. Above 450°C the alloy consists of a single phase, whereas below that temperature the material separates into copper-rich and silver-rich phases. The kinetics of equilibration appear to be controlled by grain boundary diffusion, leading to more rapid equilibration than expected on the basis of lattice diffusion-controlled kinetics. In the single-phase regime, silver segregates to the surface with an average enthalpy of segregation of −24 kJ/mol and an entropy of segregation of 0.94 J/mol K, and displays a trend of increasing equilibrium silver surface concentration with decreasing temperature. Theoretical estimates of the enthalpy of segregation yield the somewhat more negative values of −60 and −47 kJ/mol, respectively. In the two-phase regime, the surface continues to be enriched in silver, but the silver surface concentration decreases with decreasing temperature as a result of the rapidly decreasing equilibrium solubility of silver in copper.
Publisher
Springer Science and Business Media LLC
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Cited by
28 articles.
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