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Characterization of phosphorus segregation in neutron-irradiated pressure vessel steels by atom probe field ion microscopy

Conference ·
OSTI ID:39118
An atom probe field ion microscopy characterization of A533B and Russian VVER 440 and 1000 pressure vessel steels has been performed to determine the phosphorus coverage of grain and lath boundaries. Field ion micrographs of grain and lath boundaries have revealed that they are decorated with a semi-continuous film of discrete brightly-imaging precipitates that were identified as molybdenum carbonitride precipitates. In addition, extremely high phosphorus levels were measured at the boundaries. The phosphorus segregation was found to be confined to an extremely narrow region indicative of monolayer-type segregation. The phosphorus coverages determined from the atom probe results of the unirradiated materials were in excellent agreement with predictions based on McLean`s equilibrium model of grain boundary segregation. The boundary phosphorus coverage of a neutron-irradiated weld material was significantly higher than that observed in the unirradiated material.
Research Organization:
Oak Ridge National Lab., TN (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States); Nuclear Regulatory Commission, Washington, DC (United States)
DOE Contract Number:
AC05-84OR21400
OSTI ID:
39118
Report Number(s):
CONF-941144--109; ON: DE95009129
Country of Publication:
United States
Language:
English