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Title: Embrittlement of RPV steels; An atom probe tomography perspective

Abstract

Atom probe tomography has played a key role in the understanding of the embrittlement of neutron irradiated reactor pressure vessel steels through the atomic level characterization of the microstructure. Atom probe tomography has been used to demonstrate the importance of the post weld stress relief treatment in reducing the matrix copper content in high copper alloys, the formation of {approx}-nm-diameter copper-, nickel-, manganese- and silicon-enriched precipitates during neutron irradiation in copper containing RPV steels, and the coarsening of these precipitates during post irradiation heat treatments. Atom probe tomography has been used to detect {approx}2-nm-diameter nickel-, silicon- and manganese-enriched clusters in neutron irradiated low copper and copper free alloys. Atom probe tomography has also been used to quantify solute segregation to, and precipitation on, dislocations and grain boundaries.

Authors:
 [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931714
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 371
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMS; COPPER; COPPER ALLOYS; EMBRITTLEMENT; GRAIN BOUNDARIES; HEAT TREATMENTS; PRESSURE VESSELS; PROBES; STEELS; TOMOGRAPHY

Citation Formats

Miller, Michael K, and Russell, Kaye F. Embrittlement of RPV steels; An atom probe tomography perspective. United States: N. p., 2007. Web. doi:10.1016/j.jnucmat.2007.05.003.
Miller, Michael K, & Russell, Kaye F. Embrittlement of RPV steels; An atom probe tomography perspective. United States. doi:10.1016/j.jnucmat.2007.05.003.
Miller, Michael K, and Russell, Kaye F. Mon . "Embrittlement of RPV steels; An atom probe tomography perspective". United States. doi:10.1016/j.jnucmat.2007.05.003.
@article{osti_931714,
title = {Embrittlement of RPV steels; An atom probe tomography perspective},
author = {Miller, Michael K and Russell, Kaye F},
abstractNote = {Atom probe tomography has played a key role in the understanding of the embrittlement of neutron irradiated reactor pressure vessel steels through the atomic level characterization of the microstructure. Atom probe tomography has been used to demonstrate the importance of the post weld stress relief treatment in reducing the matrix copper content in high copper alloys, the formation of {approx}-nm-diameter copper-, nickel-, manganese- and silicon-enriched precipitates during neutron irradiation in copper containing RPV steels, and the coarsening of these precipitates during post irradiation heat treatments. Atom probe tomography has been used to detect {approx}2-nm-diameter nickel-, silicon- and manganese-enriched clusters in neutron irradiated low copper and copper free alloys. Atom probe tomography has also been used to quantify solute segregation to, and precipitation on, dislocations and grain boundaries.},
doi = {10.1016/j.jnucmat.2007.05.003},
journal = {Journal of Nuclear Materials},
number = ,
volume = 371,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The University of California Santa Barbara-2 RPV Steel Irradiation experiment was awarded in 2010 by the Nuclear Science User Facility (formerly ATR NSUF) through a competitive peer review proposal process. The experiment involved irradiation of nearly 1300 samples distributed over 13 capsules. The major objective of this experiment was to better understand embrittlement behavior of reactor pressure steels at doses beyond which available data exists yet may be achieved if reactor operating licenses are extended beyond 60 years. The experiment was instrumented during irradiation and active temperature control was used to maintain the temperature at the design temperature. Six samplesmore » were selected from a large matrix of materials to perform atom probe tomography (APT) to look at formation of high dose phases. The nature and formation behavior of these phases is discussed.« less
  • A review of the contributions of the atom probe field-ion microscopy (APFIM) technique to the microstructural characterization of pressure vessel steels and to the understanding of the embrittlement of these materials during neutron irradiation is presented. Atom probe studies have revealed that the microstructure contains a variety of ultrafine clusters and precipitates some of which are only formed during neutron irradiation. Furthermore, there is a complex pattern of segregation of various solutes (including phosphorus, nickel, manganese, or molybdenum) to grain boundaries in some pressure vessel materials, and there may also be additional intergranular precipitation in these materials.
  • Here, three-dimensional chemical imaging of Fe–Cr alloys showing Fe-rich (α)/Cr-rich (α') phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe–Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100–10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni–Mn–Si–Cu-rich G-phase precipitates form at the α/α' interfaces in both alloys. For the 2101more » alloy, Cu clusters act to form a nucleus, around which a Ni–Mn–Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core–shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby–Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30–36).« less