Surface segregation phenomena of solute elements in Al–Pb and Al–Fe dilute binary alloys

Surface segregation of Pb in Al-0.13–13 at.-ppm Pb foils and Fe in Al-6–140 at.-ppm Fe foils after heat treatment was studied by Rutherford back-scattering spectroscopy (RBS) and transmission electron microscopy (TEM). The degree of segregation (segregated composition/foil composition) was greater than 1500 in the Al–Pb system but is less than 160 in the Al–Fe system. The maximum segregation temperature was 923 K in the Al–Pb system, but was 723 K in the Al–Fe system. Lead segregated not to the aluminum surface but to the oxide film. Iron, however, segregated at the aluminum surface, i.e., at the interface of the oxide film/aluminum matrix.