A study of the chemical composition of grain boundaries and creep cavity surfaces in a Cu-Sb alloy

Chemical compositions of grain boundaries and creep cavity surfaces in Cu + 0.5 at. pct Sb have been measured quantitatively using Auger Electron Spectroscopy. The grain boundary enrichment ratio for antimony due to segregation was found to be greater than 16. The distribution of antimony on the fracture surface was very homogeneous, with concentrations of about 7 at. pct on the grain boundaries and 9.2 at. pct on the cavity surfaces. The ratio of grain boundary segregation to surface segregation was lower than expected and possible reasons for this discrepancy are discussed. Other impurities (C, S, and O) were more inhomogeneously distributed. Carbon was found mainly on the walls of the cavities and on the grain boundaries while sulfur preferentially concentrated at steps on the cavity surfaces. The distribution of oxygen is closely related to the morphology of the fracture surface. It is concluded that oxygen arises from contamination of intergranular microcracks which extend to the surface of the sample and were exposed to the atmosphere. The highly reproducible Auger spectra clearly indicates that all other impurities were present in the material prior to microanalysis.