SEDL / STP / STP1046V2-EB / STP49446S

Fine-Scale Microstructural Characterization of Pressure Vessel Steels and Related Materials Using APFIM

Miller, Michael K.
Research staff, Oak Ridge National Laboratory, Oak Ridge, TN

Burke, Mary Grace
Senior research scientist, Westinghouse R&D Center, Pittsburgh, PA

Pages: 20    Published: Jan 1990

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Abstract

Atom probe field-ion microscopy has been used to characterize the ultrafine microstructure of neutron-irradiated A302B and A212B pressure vessel steels, A533B submerged arc welds, and several model Fe-Cu alloys. The atomic spatial resolution of this technique permits a complete microstructural and chemical description of the ultrafine features that control the mechanical properties to be made. A variety of ultrafine features, including roughly spherical and disc-shaped copper precipitates and clusters, copper atmospheres, copper phosphides, phosphorus clusters, spherical and rod-shaped molybdenum carbides, molybdenum phosphides, disc-shaped molybdenum nitrides, and iron nitride precipitates, were observed in these materials. The presence of these features was found to be material dependent. The atom probe also revealed a complex pattern of segregation and precipitation at grain boundaries and segregation to precipitate-ferrite interfaces.