Property Changes Resulting from Impurity-Defect Interactions in Iron and Pressure Vessel Steel Alloys

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Abstract
The effects of 0.3 atomic percent copper, vanadium, nickel, and phosphorus and 0.1 atomic percent carbon addition on the irradiation response of pure iron have been investigated to clarify the role of copper and phosphorus in embrittlement of pressure vessel steels. Compression tests and transmission electron microscopy (TEM) analysis of the aforementioned alloys and selected heats of pressure vessel steel and weldment have been examined after irradiation to fluences of 2.5 × 1019 and 4.5 × 1020 n/cm2 > 1 MeV at 290 C (550 F). Copper is found to influence the properties by promoting nucleation of defect aggregates, probably vacancy loops, at low fluences, thus increasing the radiation strengthening and shifting the transition temperature upward. Small voids were observed in the 0.3Ni, 0.3Cu, and 0.1C alloys and in pure iron but not in 0.3V or 0.3P alloys.