|About this Abstract
||2018 TMS Annual Meeting & Exhibition
||Accelerated Materials Evaluation for Nuclear Application Utilizing Test Reactors, Ion Beam Facilities and Integrated Modeling
||The Structure and Composition of Mn-Ni-Si Precipitates in an Irradiated High-Ni RPV Steel Following Aging at 425°C for 57 Weeks
||Soupitak Pal, Peter Wells, G Robert Odette
|On-Site Speaker (Planned)
Long-term aging (425°C/57 weeks) of an irradiated high Ni (1.6%) RPV steel is carried out to examine the thermal stability of Mn-Ni-Si precipitates to determine if they are caused by radiation-induced segregation or accelerated by radiation-enhanced diffusion. The average diameter of the annealed precipitates is ≈ 5nm, with a corresponding volume fraction of ≈ 0.1%. Precipitate characterization by conventional diffraction and HRTEM methods is difficult due to their small size, low volume fraction and the high matrix background dislocation density. Thus convergent beam nanoprobe diffraction, which is capable of obtaining information from such small features, was used, in conjunction with EDS and APT, to characterize the precipitate structure and composition. While convergent beam nanoprobe diffraction cannot measure d-spacings, the pattern of extra spots indicates that the aged precipitates are likely a near stoichiometric Mn<SUB>3</SUB>Ni<SUB>3</SUB>Si<SUB>2</SUB>−Γ<SUB>1</SUB> phase, with a hexagonal structure and a space group symmetry P63/mmc.
||Planned: Supplemental Proceedings volume