DOSE DEPENDENCE OF RADIATION-INDUCED SEGREGATION IN NI-1 AT PERCENT-SI

Measurements have been made of alloy composition as a function of depth from the external surface in Ni-1 at% Si specimens after irradiation with 3-MeV 58Ni+ ions to several different doses at nominal temperatures of 525 and 600°C. Very rapid segregation of Si toward the external surface occurred during irradiation. Surface concentrations of Si in excess of the 10 at% solubility limit were found at both irradiation temperatures after a dose of only ~0.05 dpa. The rate of segregation decreased markedly in the dose range from ~1-10 dpa. Qualitative agreement was found between the experimental observations and calculations made using a modified Johnson-Lam segregation model. The present investigation suggests that radiation-induced segregation may significantly alter the mechanical behavior of irradiated alloys long before the onset of void swelling. © 1979.