Heavy-ion cascade effects on radiation-induced segregation kinetics in Cu-1%Au alloys

Various dual ion irradiations were conducted to investigate the effect of heavy-ion cascades on the fluxes of freely migrating defects which drive radiation-induced segregation (RIS) in Cu-1at.%Au alloys. In situ Rutherford backscattering spectroscopy (RBS) was used to measure the RIS suppression effect of heavy-ion bombardment (with 300-keV Al+, 800-keV Cu+, and 1.2-MeV Ag+) on 1.5-MeV He+-RIS of Au in the near-surface region of the alloy during concurrent He+ and heavy-ion irradiations at 400 deg. C. Results demonstrated that the suppression of He+-RIS correlated well with the cascade volume produced by concurrent Al+, Cu+, and Ag+ irradiation per second and was independent of the weighted average primary recoil energy. Model calculations of the kinetics of RIS during dual beam irradiation were also performed and compared with the measurements. Information regarding the energetics of freely migrating point defects and their relative production efficiencies was obtained from systematic fitting. Using the values previously reported for the energies of formation and migration for vacancies and interstitials in Cu, the binding and migration energies of Au-interstitial and Au-vacancy complexes in the alloy were found to be -0.14, 0.15, and 0.03 and 0.76 eV, respectively. The respective derived efficiencies of freely migrating defect production by energetic He+, Al+, Cu+, and Ag+ ions were 0.25, 0.12, 0.09, and 0.08