TY - JOUR
T1 - Phase stability and microstructural evolution in neutron-irradiated ferritic-martensitic steel HT9
AU - Yan, Huan
AU - Liu, Xiang
AU - He, Lingfeng
AU - Stubbins, James
N1 - Funding Information:
This work was funded in part by the U.S. Department of Energy office of Nuclear Energy's Nuclear Energy University Program (NEUP) under Contract No. DOE INL 00127139. The neutron irradiation experiments at the Advanced Test Reactor (ATR) were supported by Nuclear Science User Facilities (NSUF) award 08-92. The post-irradiation experiments were conducted at the Microscopy and Characterization Suite (MaCS), Center for Advanced Energy Studies (NSUF access only project 15-8312) and were supported by the U.S. Department of Energy, Office of Nuclear Energy under DOE Idaho Operations Office Contract DE-AC07-051D14517 as part of a Nuclear Science User Facilities experiment. The authors would like to acknowledge the training and support from MaCS staff Yaqiao Wu, Jatuporn Burns, Megha Dubey, and Joanna Taylor.
Publisher Copyright:
© 2021
PY - 2021/12/15
Y1 - 2021/12/15
N2 - Ferritic Martensitic (F/M) steel HT9 specimens were irradiated in the Advanced Test Reactor up to 4.16 dpa in three temperature ranges (roughly from 300 to 600 °C). The post-irradiation microstructure, including dislocation structure, precipitation and radiation-induced segregation (RIS) was characterized using analytical scanning / transmission electron microscopy (S/TEM), and atom probe tomography (APT). Irradiation hardening was measured using nanoindentation. The results reveal a distinctive pattern of dislocation and precipitate evolution at high temperature, around 600 °C, where various defects and precipitates formed in the low dose regime followed by a recovering process with increasing dose. Dislocation loops formed in all temperature ranges, and the growth of dislocation loops is unconstrained above certain critical temperature, contributing to the increasing dislocation density even prior to doses of 0.5 dpa at 600 °C. Ni/Mn/Si clusters were identified in all temperature ranges and the compositions of these clusters converged to G phase stoichiometrically. Significant coarsening of G phase particles was observed at 600 °C, accompanied by the formation of G phase on grain boundaries. α’ precipitates were only found in the medium and low temperature ranges (below 500 °C). The number density and volume fraction were higher in the low temperature specimens, while larger particles were observed in the medium temperature range. RIS of Cr, Ni, Mn, Si, P was identified at dislocation lines, grain boundaries and phase boundaries, and the temperature dependence is consistent with previous studies. The RIS of Cr to the existing VN particles was confirmed by APT and may accelerate the transition of VN to Cr-rich nitrides. The irradiation hardening contribution from dislocation loops, dislocation lines, G phase and α’ phase was parsed based on a linear dispersed barrier hardening model. The results suggest that most irradiation hardening at high temperature is due to increasing dislocation density with dose.
AB - Ferritic Martensitic (F/M) steel HT9 specimens were irradiated in the Advanced Test Reactor up to 4.16 dpa in three temperature ranges (roughly from 300 to 600 °C). The post-irradiation microstructure, including dislocation structure, precipitation and radiation-induced segregation (RIS) was characterized using analytical scanning / transmission electron microscopy (S/TEM), and atom probe tomography (APT). Irradiation hardening was measured using nanoindentation. The results reveal a distinctive pattern of dislocation and precipitate evolution at high temperature, around 600 °C, where various defects and precipitates formed in the low dose regime followed by a recovering process with increasing dose. Dislocation loops formed in all temperature ranges, and the growth of dislocation loops is unconstrained above certain critical temperature, contributing to the increasing dislocation density even prior to doses of 0.5 dpa at 600 °C. Ni/Mn/Si clusters were identified in all temperature ranges and the compositions of these clusters converged to G phase stoichiometrically. Significant coarsening of G phase particles was observed at 600 °C, accompanied by the formation of G phase on grain boundaries. α’ precipitates were only found in the medium and low temperature ranges (below 500 °C). The number density and volume fraction were higher in the low temperature specimens, while larger particles were observed in the medium temperature range. RIS of Cr, Ni, Mn, Si, P was identified at dislocation lines, grain boundaries and phase boundaries, and the temperature dependence is consistent with previous studies. The RIS of Cr to the existing VN particles was confirmed by APT and may accelerate the transition of VN to Cr-rich nitrides. The irradiation hardening contribution from dislocation loops, dislocation lines, G phase and α’ phase was parsed based on a linear dispersed barrier hardening model. The results suggest that most irradiation hardening at high temperature is due to increasing dislocation density with dose.
KW - Dislocation loop
KW - F/M steel
KW - HT9
KW - Irradiation hardening
KW - Neutron irradiation
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U2 - 10.1016/j.jnucmat.2021.153252
DO - 10.1016/j.jnucmat.2021.153252
M3 - Article
AN - SCOPUS:85113530323
SN - 0022-3115
VL - 557
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
M1 - 153252
ER -