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Title: Thermal and Radiation-induced Segregation in Model Ni-base Alloys

Abstract

Since Generation IV nuclear energy systems will operate at higher temperatures than current light water reactors, Ni-base alloys are receiving attention as candidate core materials. One aspect of the radiation response of Ni-base alloys to radiation that is not well understood is grain boundary segregation. In this work, three alloys, specifically Ni-18Cr, Ni-18Cr-9Fe, and Ni-18Cr-0.08P were given a series of thermal treatments and quenching to understand the development of thermal non-equilibrium segregation (TNES). Additionally, they were irradiated using 3.2 MeV protons at temperatures from 200 to 500 C to doses up to 1 dpa. Grain boundary segregation was measured with Auger Electron Spectroscopy and Scanning Transmission Electron Microscopy with Energy Dispersive Spectroscopy. Chromium enrichment due to TNES could be caused by interactions between Ni and Cr or by interactions with impurity elements such as B, C, or N. Under irradiation, the addition of iron to Ni-18Cr reduced the grain boundary chromium depletion, while the addition of phosphorous increased the grain boundary chromium depletion.

Authors:
 [1];  [1];  [2];  [3]
  1. University of Wisconsin, Madison
  2. University of Michigan
  3. 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:
1003506
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: TMS Radiation Effects Symposium, San Antonio, TN, USA, 20060313, 20060316
Country of Publication:
United States
Language:
English
Subject:
29 ENERGY PLANNING, POLICY AND ECONOMY; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ALLOYS; AUGER ELECTRON SPECTROSCOPY; CHROMIUM; IRON; IRRADIATION; NUCLEAR ENERGY; PROTONS; QUENCHING; RADIATION EFFECTS; RADIATIONS; SEGREGATION; SPECTROSCOPY; TRANSMISSION ELECTRON MICROSCOPY; Radiation damage; radiation-induced segregation; Auger spectroscopy; analytical electron microscopy

Citation Formats

Allen, Todd R., Tan, Lizhen, Was, Gary, and Kenik, Edward A. Thermal and Radiation-induced Segregation in Model Ni-base Alloys. United States: N. p., 2006. Web.
Allen, Todd R., Tan, Lizhen, Was, Gary, & Kenik, Edward A. Thermal and Radiation-induced Segregation in Model Ni-base Alloys. United States.
Allen, Todd R., Tan, Lizhen, Was, Gary, and Kenik, Edward A. Sun . "Thermal and Radiation-induced Segregation in Model Ni-base Alloys". United States. doi:.
@article{osti_1003506,
title = {Thermal and Radiation-induced Segregation in Model Ni-base Alloys},
author = {Allen, Todd R. and Tan, Lizhen and Was, Gary and Kenik, Edward A},
abstractNote = {Since Generation IV nuclear energy systems will operate at higher temperatures than current light water reactors, Ni-base alloys are receiving attention as candidate core materials. One aspect of the radiation response of Ni-base alloys to radiation that is not well understood is grain boundary segregation. In this work, three alloys, specifically Ni-18Cr, Ni-18Cr-9Fe, and Ni-18Cr-0.08P were given a series of thermal treatments and quenching to understand the development of thermal non-equilibrium segregation (TNES). Additionally, they were irradiated using 3.2 MeV protons at temperatures from 200 to 500 C to doses up to 1 dpa. Grain boundary segregation was measured with Auger Electron Spectroscopy and Scanning Transmission Electron Microscopy with Energy Dispersive Spectroscopy. Chromium enrichment due to TNES could be caused by interactions between Ni and Cr or by interactions with impurity elements such as B, C, or N. Under irradiation, the addition of iron to Ni-18Cr reduced the grain boundary chromium depletion, while the addition of phosphorous increased the grain boundary chromium depletion.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
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  • The effect of pre-irradiation heat treatments on thermal non-equilibrium grain boundary segregation (TNES) and subsequent radiation-induced grain boundary segregation (RIS) is studied in a series of model austenitic stainless steels. The alloys used for this study are based on AISI 316 stainless steel and have the following nominal compositions: Fe-16Cr-13Ni-1.25Mn (base 316), Fe-16Cr-13Ni-1.25Mn-2.0Mo (316 + Mo) and Fe-16Cr-13Ni-1.25Mn-2.0Mo-0.07P (316 + Mo + P). Samples were heat treated at temperatures ranging from 1100 to 1300 C and cooled at 4 different rates (salt brine quench, water quench, air cool and furnace cool) to evaluate the effect of annealing temperature and quenchmore » rate on TNES. The alloys were than processed with the treatment (temperature and cooling rate) that resulted in the maximum Cr enrichment. Alloys with and without the heat treatment to enrich the grain boundaries with Cr were characterized following irradiation to 1 dpa at 400 C with high-energy protons in order to understand the influence of alloying additions and pre-irradiation grain boundary chemistry on irradiation-induced elemental enrichment and depletion profiles. Various mechanistic models will be examined to explain the observed behavior.« less
  • Comparison of radiation-induced segregation (RIS) measurements from austenitic iron- and nickel-base alloys with calculations using the Perks vacancy-driven RIS model have shown that chromium segregates slower and iron segregates faster than expected from high temperature diffusion measurements. The effect is more pronounced in nickel-base alloys. The segregation process is affected by short range ordering forces and the ordering is strongest in nickel-base alloys. Since nickel enriches and chromium depletes in all iron-chromium-nickel alloys under irradiation, a tendency to form nickel-chromium pairs reduces the chromium segregation, especially in nickel-base alloys. In this work, Perks` model is altered to include ordering energies,more » and the calculated RIS is compared to segregation measurements from iron-chromium-nickel alloys irradiated with 3.2 MeV protons. A single set of ordering energies, an attractive potential between nickel and chromium and a repulsive potential between nickel and iron are used for each alloy. Calculations that do not include ordering overpredict the chromium depletion by up to 4 at% in iron-base alloys and 8 at% in nickel-base alloys. Calculations that include the ordering reduce the difference between model predicted and measured chromium concentrations to less than 2 at% for most iron- and nickel-base alloys.« less
  • The effects of 75-keV Ne{sup +} and 300-keV Ni{sup +} bombardment on electron radiation-induced segregation (RIS) in a Ni-9at.% Al alloy were investigated in-situ using the HVEM (high voltage electron microscope) / Tandem accelerator facility at Argonne National Laboratory. The radial component of defect fluxes generated by a highly-focused 900-keV electron beam was used to induce segregation of Al atoms towards the center of the electron irradiated area via the inverse Kirkendall effect. The radial segregation rate was monitored by measuring the increase in the diameter of the Al enriched zone within which {gamma}{sup `}-Ni{sub 3}Al precipitates form during irradiation.more » Both dual electron-ion and pre-implanted ion- electron irradiations were performed in an attempt to separate the contributions of energetic displacement cascades and implanted ions acting as defect trapping sites to RIS suppression. It was found that 75-keV Ne{sup 3} implantation has a retarding effect on RIS.« less
  • In-situ experiments using the HVEM/Tandem accelerator at ANL were performed to determine effects of 400-keV Zr{sup +} and 75-keV Ne{sup +} implantation on electron radiation-induced segregation (RIS) in Ni- 9at.%Al at 550 and 450 C, respectively. Alteration of RIS kinetics by Ne implantation was studied at two different doses. A highly focused 900-keV electron beam, which produces a radial defect flux away from the beam center, was used to induce segregation of Al atoms in the opposite direction via the inverse Kirkendall effect. Within the irradiated zone, Al enrichment drives the formation of {gamma}`- Ni{sub 3}Al precipitates, and the radialmore » segregation rate of Al was monitored by measuring the growth of the precipitate zone.« less
  • Effects of Ne and Sc implantation on radiation-induced segregation (RIS) in Ni-9at.%Al were studied in-situ using the high-voltage electron microscope/Tandem accelerator at ANL. A highly-focused 900- keV electron beam generated radial defect fluxes which, in turn, induced transport of Al atoms toward the center of the electron- irradiated area via the inverse Kirkendall effect. Radial segregation rate of Al atoms was monitored by measuring the diameter of the {gamma}{prime}-Ni{sub 3}Al zone which formed in the Al-enriched area during irradiation. Ne and Sc implantation effects on RIS were investigated at 550 C; Ne effects were also examined at 625 C tomore » determine effect of temperature on ability of Ne to act as defect trapping sites, causing RIS suppression. It was found that the RIS suppression effect of Ne increased with irradiation temperature and that Sc had a small RIS suppression effect which increased with Sc implantation dose. Ne bubbles which formed during implantation are believed to be responsible for its strong suppression effect. 6 figs, 12 refs« less