Radiation-Induced Segregation in Cu-Au Alloys

Radiation-induced segregation in a Cu-lat.% Au alloy was investigated using in-situ Rutherford backscattering spectrometry. Irradiation with 1.8-MeV helium produced nonequilibrium gold atom depletion in the near surface region. The amount of segregation was measured as a function of dose, dose rate, and temperature. Segregation was observed in the temperature range between about 300 and 500°C. For a calculated dose rate of 3.9 × 10⁻⁵ dpa/s, the radiation-induced segregation rate peaked near 400°C. Theoretical analysis based on the Johnson-Lam model predicted that the amount of segregation would be directly proportional to dose at the early stage of irradiation, would deviate from linearity with a continuously decreasing slope at intermediate doses, and finally approach a constant value after high doses. The analysis also predicted that the segregation rate would vary as the −¼th power of the dose rate at constant dose in the low temperature region. These predictions were all verified experimentally. A procedure for extracting relative defect production efficiencies from similar measurements is discussed.