Nucleation and amorphization of radiation-produced phases in a modified austenitic stainless steel during Ni-ion irradiation

The nucleation and amorphization of radiation-induced (G) and radiation-enhanced (eta) phases in a silicon- and titanium-modified austenitic stainless steel have been studied under nickel-ion irradiation. These silicon- and nickel-enriched phases form under high-temperature (950 K) irradiation as the result of radiation-induced segregation to radiation-produced interstitial dislocation loops. Availability of carbon promotes the formation of eta phase relative to G phase. Under lower temperature (450 K) irradiation, G and eta phases are amorphized without significant change in composition of metallic elements. Two carbide phases (MC, M23C6) remain crystalline for the same irradiation conditions. The amorphization of the silicides may result from (1) radiation damage increasing their free energy above that of the amorphous state or (2) direct formation of the amorphous phase in the damage cascade