TY - JOUR
T1 - Helium effects on tensile properties of powder metallurgical-processed tungsten for fusion reactor applications
AU - Hasegawa, Akira
AU - Sato, Yusuke
AU - Hattori, Takaya
AU - Kanamaru, Ryota
AU - Du, Luo
AU - Miyazawa, Takeshi
AU - Nogami, Shuhei
N1 - Funding Information:
The authors are grateful to the staff of the Cyclotron and Radioisotope Center (CYRIC) of Tohoku University for allowing the use of their cyclotron accelerator for collaboration research. We would also like to thank the staff of the radioisotope laboratory of the Faculty of Engineering of Tohoku University, and the staff of the hot laboratory of the International Research Center for Nuclear Materials Science, Institute for Material Research of Tohoku University. This study was financially supported by JSPS KAKENHI (Grant Number 17H01364). In addition, this study was performed with the support and under the auspices of the National Institute for Fusion Science (NIFS) Collaboration Research program (NIFS 11K0BF019). We would like to thank Editage (www.editage.com) for English language editing.
Funding Information:
The authors are grateful to the staff of the Cyclotron and Radioisotope Center (CYRIC) of Tohoku University for allowing the use of their cyclotron accelerator for collaboration research. We would also like to thank the staff of the radioisotope laboratory of the Faculty of Engineering of Tohoku University, and the staff of the hot laboratory of the International Research Center for Nuclear Materials Science, Institute for Material Research of Tohoku University. This study was financially supported by JSPS KAKENHI (Grant Number 17H01364). In addition, this study was performed with the support and under the auspices of the National Institute for Fusion Science (NIFS) Collaboration Research program (NIFS 11K0BF019).
Publisher Copyright:
© 2021 The Author(s)
PY - 2021/12
Y1 - 2021/12
N2 - Powder metallurgical processing of Tungsten (W) followed by thermomechanical treatment, including rolling and stress relief (SR) heat treatment, is a candidate fabrication process for W materials for fusion applications. Helium (He) is insoluble in almost all metals, and grain boundary embrittlement occurs on the accumulation of He on their grain boundaries. In this study, the effects of He concentration, test temperature, and strain rate on the mechanical properties of SR-W were investigated using tensile tests. The He effects were studied by the uniform implantation of high-energy He-ions into specimens by cyclotron accelerator irradiation and by tensile tests from 300 °C to 1300 °C. The examined He concentration was below 20 appm. Vickers hardness tests on an isochronal annealed specimen up to 1500 °C showed that the threshold concentration of He for suppressing the recovery and recrystallization of the microstructure of SR-W by annealing was between 2 and 20 appm. The tensile test showed a slight increase in the ultimate tensile strength (UTS) at He concentrations up to 20 appm; however, no clear effect on the elongation or fracture mode was observed. The results of the tensile test conducted at 1300 °C on a 20-appm He-implanted specimen showed that its softening and ductility by recrystallization were suppressed; however, there was no observation of grain boundary embrittlement by He implantation. The results suggest that the mechanism of the mechanical response of He-implanted SR-W was He suppression of the recovery and recrystallization of the layered structure unique to SR-W up to 1500 °C. Moreover, at the level of He concentration introduced by nuclear transmutation in the divertor of a fusion reactor without displacement damage, no severe effect occurred to promote the embrittlement of SR-W.
AB - Powder metallurgical processing of Tungsten (W) followed by thermomechanical treatment, including rolling and stress relief (SR) heat treatment, is a candidate fabrication process for W materials for fusion applications. Helium (He) is insoluble in almost all metals, and grain boundary embrittlement occurs on the accumulation of He on their grain boundaries. In this study, the effects of He concentration, test temperature, and strain rate on the mechanical properties of SR-W were investigated using tensile tests. The He effects were studied by the uniform implantation of high-energy He-ions into specimens by cyclotron accelerator irradiation and by tensile tests from 300 °C to 1300 °C. The examined He concentration was below 20 appm. Vickers hardness tests on an isochronal annealed specimen up to 1500 °C showed that the threshold concentration of He for suppressing the recovery and recrystallization of the microstructure of SR-W by annealing was between 2 and 20 appm. The tensile test showed a slight increase in the ultimate tensile strength (UTS) at He concentrations up to 20 appm; however, no clear effect on the elongation or fracture mode was observed. The results of the tensile test conducted at 1300 °C on a 20-appm He-implanted specimen showed that its softening and ductility by recrystallization were suppressed; however, there was no observation of grain boundary embrittlement by He implantation. The results suggest that the mechanism of the mechanical response of He-implanted SR-W was He suppression of the recovery and recrystallization of the layered structure unique to SR-W up to 1500 °C. Moreover, at the level of He concentration introduced by nuclear transmutation in the divertor of a fusion reactor without displacement damage, no severe effect occurred to promote the embrittlement of SR-W.
KW - Embrittlement
KW - Mechanical properties
KW - Recovery and recrystallization
KW - Stress relief treatment
KW - Transmutation effects
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U2 - 10.1016/j.nme.2021.101076
DO - 10.1016/j.nme.2021.101076
M3 - Article
AN - SCOPUS:85122838048
SN - 2352-1791
VL - 29
JO - Nuclear Materials and Energy
JF - Nuclear Materials and Energy
M1 - 101076
ER -