Surface segregation in a Ni-1 at% Pd alloy

The surface composition of a Ni-1 at% Pd alloy has been determined by Auger electron spectroscopy after equilibration of the alloy at several temperatures in the range 550 to 800°C. Moderate segregation of Pd to the surface of the alloy has been observed, with concentrations of up to ~～30 at% being detected at the surface after equilibration at 550°C. The heat of segregation (or adsorption) of Pd has been found to agree reasonably well with the predictions of a previously developed unified model of surface segregation in alloys. The kinetics of Pd segregation to the surface have also been measured between 500 and 700°C. Analysis of the kinetic data yields apparent diffusivities of Pd through the alloy that are suggestive of a dominant grain boundary transport mechanism.