TY - JOUR
T1 - Contribution of irradiation-induced defects to hardening of a lowcopper reactor pressure vessel steel
AU - Shimodaira, Masaki
AU - Toyama, Takeshi
AU - Yoshida, Kenta
AU - Inoue, Koji
AU - Ebisawa, Naoki
AU - Tomura, Keiko
AU - Yoshiie, Toshimasa
AU - Konstantinovic, Milan
AU - Gérard, Robert
AU - Nagai, Yasuyoshi
N1 - Score=10
PY - 2018/6/14
Y1 - 2018/6/14
N2 - We investigated the fluence dependence of irradiation-induced solute cluster, dislocation loop, and very
small defect to reveal the hardening mechanism in surveillance test specimens from a reactor pressure
vessel steel with low-Cu content (0.04 wt%) using atom probe tomography (APT), weak-beam scanning
transmission electron microscopy (WB-STEM), and positron annihilation spectroscopy. A high number
density (>1023m3) of solute clusters mainly composed of Ni, Mn, and Si atoms were found in highly
neutron irradiated specimens (~1024 neutrons m2 (E > 1 MeV)) by APT. These solute clusters were one of
the main sources of hardening as reported previously. On the other hand, it was also revealed that
dislocation loops were formed with a number density of ~1022m3 in the high-fluence specimens by
WB-STEM. The estimated hardening due to dislocation loops was more than half of the actual hardening,
showing that dislocation loops are also main source of irradiation hardening at high neutron fluence with
the solid experimental evidences. Regarding specimens subjected to a low neutron fluence (~1023
neutrons m2), very small defects, not detected by either WB-STEM or APT, were formed by positron
annihilation spectroscopy. This result suggested that, at a low neutron fluence, the defects were the
initial hardening source and they may grow the dislocation loops observed by WB-STEM at high fluence
range
AB - We investigated the fluence dependence of irradiation-induced solute cluster, dislocation loop, and very
small defect to reveal the hardening mechanism in surveillance test specimens from a reactor pressure
vessel steel with low-Cu content (0.04 wt%) using atom probe tomography (APT), weak-beam scanning
transmission electron microscopy (WB-STEM), and positron annihilation spectroscopy. A high number
density (>1023m3) of solute clusters mainly composed of Ni, Mn, and Si atoms were found in highly
neutron irradiated specimens (~1024 neutrons m2 (E > 1 MeV)) by APT. These solute clusters were one of
the main sources of hardening as reported previously. On the other hand, it was also revealed that
dislocation loops were formed with a number density of ~1022m3 in the high-fluence specimens by
WB-STEM. The estimated hardening due to dislocation loops was more than half of the actual hardening,
showing that dislocation loops are also main source of irradiation hardening at high neutron fluence with
the solid experimental evidences. Regarding specimens subjected to a low neutron fluence (~1023
neutrons m2), very small defects, not detected by either WB-STEM or APT, were formed by positron
annihilation spectroscopy. This result suggested that, at a low neutron fluence, the defects were the
initial hardening source and they may grow the dislocation loops observed by WB-STEM at high fluence
range
KW - STEM
KW - Atom probe tomography (APT)
KW - Positron annihilation spectroscopy
KW - Reactor pressure vessel steels
KW - Dislocation loop
UR - http://ecm.sckcen.be/OTCS/llisapi.dll/open/35063085
U2 - 10.1016/j.actamat.2018.06.015
DO - 10.1016/j.actamat.2018.06.015
M3 - Article
SN - 1359-6454
VL - 155
SP - 402
EP - 409
JO - Acta Materialia
JF - Acta Materialia
ER -