Residual Elements and Irradiation Embrittlement.
NAVAL RESEARCH LAB WASHINGTON D C
Pagination or Media Count:
Past work on the role of residual elements particularly copper and phosphorus in the enhanced irradiation embrittlement observed in pressure-vessel steels irradiated at 550F 288C is reviewed. Only three mechanisms for explaining the embrittlement are plausible--temper embrittlement, irradiation-enhanced diffusion to an interface, and enhanced nucleation of defect aggregates which produce hardening and embrittlement. Experiments employing scanning microscopy and Auger spectroscopy show that the embrittlement is not produced by segregation of copper or phosphorus at an interface. Microhardness recovery experiments indicate that the embrittlement in copper-containing alloys is accompanied by greater irradiation hardening. Transmission electron micrographs of special iron alloys doped with 0.3 at- copper show a microstructure indicative of a higher concentration of defect aggregates than pure iron irradiated under the same conditions. These aggregates are believed to be vacancy in nature because vacancies are mobile during irradiation at 550F 288C and because no correlation between embrittlement and copper or phosphorus content are noted after irradiation at temperatures where vacancies are not mobile. Author
- Metallurgy and Metallography
- Fission Reactor Materials