Radiation hardening mechanism in Fe--C--Mn type alloys

Radiation damage in Fe-C-Mn type alloys, chosen as a first approximation to low-carbon pressure vessel steels, was studied after irradiation at two temperature regions [80 to 100 C (176 to 212 F) and 160 to 180 C (320 to 356 F)]. Effect of saturation and "oversaturation" (expressed by softening) on yield strength was confirmed. This effect depends on alloy structure and content of both alloy elements-carbon in the form of pearlite substantially increases the tendency to "oversaturation," while manganese shifts the saturation dose to higher values. For pure iron a saturation dose equal to about 4 × 1019 n/cm2 (En > 1 MeV) was found. At the same time the presence of carbon results in the suppression of yield strength increase during irradiation, while manganese enhances this yield strength increase if more than approximately 0.5 weight percent manganese is present. On the basis of the analysis of individual parameter changes in the model of radiation hardening in Fe-C-Mn type alloys, an explanation is proposed of the influence of neutron dose at irradiation temperatures of 80 to 100 C (176 to 212 F) on the change in the tensile stress-strain curve, as well as the influence of carbon and manganese on the saturation and oversaturation effect.