A METHOD FOR EVALUATING RADIATION-INDUCED GRAIN-BOUNDARY SEGREGATION USING ION-IRRADIATED MICROCRYSTALLINE STAINLESS ALLOYS

A new method to evaluate radiation-induced segregation (RIS) at internal interfaces is described. In this method bulk damage is produced in microcrystalline stainless alloys by ion irradiation, and grain boundary composition changes are measured using analytical electron microscopy. Material composition is controlled and modified by high-rate sputter-deposition synthesis of stainless alloys from composite targets. Nickel-rich 304 and 316 stainless steels doped with phosphorus and silicon were deposited and a microcrystalline grain size established by subsequent heat treatment. Irradiation damage was produced, and irradiation parameters varied, using nickel-ion bombardment from a tandem accelerator. Microstructural and microchemical changes during irradiation were documented by transmission electron microscopy (TEM) examination of near surface regions and by high-resolution composition measurements across grain boundary regions with a scanning TEM. The combination of high-rate sputtering to deposit microcrystalline alloys of controlled composition and heavy-ion irradiation enabled parametric studies of RIS to be performed in a timely and inexpensive manner.