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Chong, Y.*; Gholizadeh, R.*; Guo, B.*; Tsuru, Tomohito; Zhao, G.*; Yoshida, Shuhei*; Mitsuhara, Masatoshi*; Godfrey, A.*; Tsuji, Nobuhiro*
Acta Materialia, 257, p.119165_1 - 119165_14, 2023/09
Times Cited Count:5 Percentile:90.07(Materials Science, Multidisciplinary)Metastable titanium alloys possess excellent strain-hardening capability, but suffer from a low yield strength. As a result, numerous attempts have been made to strengthen this important structural material in the last decade. Here, we explore the contributions of grain refinement and interstitial additions in raising the yield strength of a Ti-12Mo (wt.%) metastable titanium alloy. Surprisingly, rather than strengthening the material, grain refinement actually lowers the ultimate tensile strength in this alloy. This unexpected and anomalous behavior is attributed to a significant enhancement in strain-induced martensite phase transformation, where in-situ synchrotron X-ray diffraction analysis reveals, for the first time, that this phase is much softer than the parent phase. Instead, a combination of both oxygen addition and grain refinement is found to realize an unprecedented strength-ductility synergy in a Ti-12Mo-0.3O (wt.%) alloy. The advantageous effect of oxygen solutes in this ternary alloy is twofold. Firstly, solute oxygen largely suppresses strain-induced transformation to the martensite phase, even in a fine-grained microstructure, thus avoiding the softening effect of excessive amounts of martensite. Secondly, oxygen solutes readily segregate to twin boundaries, as revealed by atom probe tomography. This restricts the growth of deformation twins, thereby promoting more extensive twin nucleation, leading to enhanced microstructural refinement. The insights from our work provide a cost-effective rationale for the design of strong yet tough metastable titanium alloys, with significant implications for more widespread use of this high strength-to-weight structural material.
Guo, B.*; Mao, W.; Chong, Y.*; Shibata, Akinobu*; Harjo, S.; Gong, W.; Chen, H.*; Jonas, J. J.*; Tsuji, Nobuhiro*
Acta Materialia, 242, p.118427_1 - 118427_11, 2023/01
Times Cited Count:7 Percentile:72.10(Materials Science, Multidisciplinary)Chong, Y.*; Tsuru, Tomohito; Guo, B.*; Gholizadeh, R.*; Inoue, Koji*; Tsuji, Nobuhiro*
Acta Materialia, 240, p.118356_1 - 118356_15, 2022/11
Times Cited Count:16 Percentile:92.91(Materials Science, Multidisciplinary)In this study, we systematically investigated the influences of nitrogen content and grain size on the tensile properties and deformation behaviors of titanium at room temperature. By high-pressure torsion and annealing, we obtained ultrafine-grained (UFG) Ti-0.3wt.%N alloy with a fully recrystallized microstructure, which combined an unprecedented synergy of ultrahigh yield strength (1.04 GPa) and large uniform elongation (10%). The hardening and strain-hardening mechanisms of Ti-0.3wt.%N alloy were comprehensively studied via deformation substructure observation and first-principles calculations. It is revealed that the contributions of nitrogen to the excellent strength/ductility balance in UFG Ti-0.3wt.%N were twofold. On one hand, nitrogen atoms inside the grains strongly impeded the motion of dislocations on prismatic plane due the shuffling of nitrogen from octahedral to hexahedral site, giving rise to a six-fold increase in the friction stress than pure Ti. Moreover, the greatly reduced stacking fault energy difference between prismatic and pyramidal planes in Ti-0.3wt.%N alloy facilitated an easier activation of dislocations, which contributed to an enhanced strain-hardening rate. On the other hand, some nitrogen atoms segregated near the grain boundaries, a phenomenon discovered in -titanium for the first time. These segregated nitrogen atoms served as an additional contributor to the yield strength of UFG Ti-0.3wt.%N, by raising the barrier against dislocation slip transfer between grains. Our experimental and theoretical calculation work provide insights for the design of affordable high strength titanium without a large sacrifice of ductility, shedding lights on a more widespread use of this high strength to weight material.
Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Health Physics, 121(6), p.613 - 620, 2021/12
Times Cited Count:1 Percentile:15.09(Environmental Sciences)According to the implementing arrangement between JAEA (Japan Atomic Energy Agency) and KAERI (Korea Atomic Energy Research Institute) in the field of the radiation protection and environmental radiation monitoring, the joint measurement has been conducted to assess the radioactive cesium deposition in the ground around the Fukushima Daiichi Nuclear Power Plants (FDNPP). First, mobile gamma-ray spectrometry using backpack survey platform was conducted to assess the distribution of dose rate around specific three survey sites. The carborne survey using gamma-ray spectrometers, as loading inside a vehicle, was successfully conducted to compare measured dose rates in routes from site to site and verify evaluation methods including the attenuation correction.
Kim, B. K.*; Tan, L.*; Sakasegawa, Hideo; Parish, C. M.*; Zhong, W.*; Tanigawa, Hiroyasu*; Kato, Yutai*
Journal of Nuclear Materials, 545, p.152634_1 - 152634_12, 2021/03
Times Cited Count:1 Percentile:15.09(Materials Science, Multidisciplinary)Ji, Y.-Y.*; Ochi, Kotaro; Hong, S. B.*; Nakama, Shigeo; Sanada, Yukihisa; Mikami, Satoshi
Radiation Physics and Chemistry, 179, p.109205_1 - 109205_11, 2021/02
Times Cited Count:7 Percentile:75.12(Chemistry, Physical)In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with several dose rate levels around the Fukushima Daiichi Nuclear Power Plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr(Ce) detectors to assess the radioactive cesium deposition in the ground. The diverse levels of radioactivity of Cs were then distributed to six survey sites from 30 to 3000 kBq m in the measurement period of October 2018. A method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site.
Kim, S. H.*; Hwang, S.; Ahn, J. K.*; Ekawa, Hiroyuki; Hayakawa, Shuhei; Hong, B.*; Hosomi, Kenji; Imai, Kenichi; Kim, M. H.*; Lee, J. Y.*; et al.
Nuclear Instruments and Methods in Physics Research A, 795, p.39 - 44, 2015/09
Times Cited Count:4 Percentile:32.74(Instruments & Instrumentation)Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07
Times Cited Count:29 Percentile:73.10(Astronomy & Astrophysics)We report on the event structure and double helicity asymmetry () of jet production in longitudinally polarized collisions at = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured = -0.0014 0.0037 at the lowest bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various distributions.
Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06
Times Cited Count:184 Percentile:99.42(Physics, Nuclear)Transverse momentum distributions and yields for , and in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as and scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.
Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.
Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04
Times Cited Count:9 Percentile:52.86(Physics, Nuclear)Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.
Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03
Times Cited Count:177 Percentile:98.48(Astronomy & Astrophysics)The PHENIX experiment at RHIC has measured the invariant differential cross section for production of , , and mesons in collisions at = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, and , determining the high and characterizing the low regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
Yang, H. L.*; Kim, Y. S.*; Park, Y. M.*; Bae, Y. S.*; Kim, H. K.*; Kim, K. M.*; Lee, K. S.*; Kim, H. T.*; Bang, E. N.*; Joung, M.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Because the 2010 operation of Korea Superconducting Tokamak Advanced Research (KSTAR) mainly aims to achieve strongly elongated and diverted plasma, all the necessary hardware systems to provide an essential circumstance for the plasma shaping were newly installed and upgraded in 2010. In this paper, general configuration of the upgraded systems described earlier will be outlined. Moreover, several key performances and test results of the systems will be also reported in summary.
Im, H. J.*; Ito, Takahiro*; Kim, H.-D.*; Kimura, Shinichi*; Lee, K. E.*; Hong, J. B.*; Kwon, Y. S.*; Yasui, Akira; Yamagami, Hiroshi
Physical Review Letters, 100(117), p.176402_1 - 176402_4, 2008/05
Times Cited Count:60 Percentile:88.00(Physics, Multidisciplinary)Ce 4-4 resonant angle-resolved photoemission spectroscopy was carried out to study the electronic structure of strongly correlated Ce 4 electrons in a quasi-two-dimensional nonmagnetic heavy-fermion system CeCoGeSi. For the first time, dispersive coherent peaks of an state crossing the Fermi level, the so-called Kondo resonance, are directly observed together with the hybridized conduction band. Moreover, the experimental band dispersion is quantitatively in good agreement with a simple hybridization-band picture based on the periodic Anderson model. The obtained physical quantities, i.e., coherent temperature, Kondo temperature, and mass enhancement, are comparable to the results of thermodynamic measurements. These results manifest an itinerant nature of Ce 4 electrons in heavy-fermion systems and clarify their microscopic hybridization mechanism.
Ioki, Kimihiro; Elio, F.*; Barabash, V.*; Chuyanov, V.*; Rozov, V.*; Wang, X.*; Chen, J.*; Wang, L.*; Lorenzetto, P.*; Peacock, A.*; et al.
Fusion Engineering and Design, 82(15-24), p.1774 - 1780, 2007/10
Times Cited Count:13 Percentile:65.94(Nuclear Science & Technology)In December 2005, the new procurement allocation plan of the ITER components among the seven Parties was prepared. The need to qualify for procurement of the specific components was especially introduced in the document. The main features and milestones of the qualification program are described in "Procurement Plan" for each specific component. Due to the complicated features of FW procurement, the procurement document has to be developed precisely. To guarantee high quality of 1700 FW panels produced by 6 different Parties, a qualification program is essential. The qualification mock-up is 80 mm wide, 240 mm long and 81 mm thick with 3 beryllium tiles 10 mm thick. Heat load tests will be performed on the qualification mock-ups in 2007 in EU and USA facilities. The maximum design heat load on the ITER FW is 0.5 MW/m (steady state) 30,000 shots. Mechanical tests of joints are also required using standardized methods. Only Parties which have satisfied the acceptance criteria of the qualification tests can proceed to the procurement stage of the ITER FW. Semi-prototypes (roughly 1000 mm 200 mm) are also requested before the ITER FW manufacturing.
Kozhevnikov, I. V.*; Voronov, A. S.*; Roshchin, B. S.*; Asadchikov, V. E.*; Mednikov, K. N.*; Pirozhkov, A. S.; Ragozin, E. N.*; Wang, Z.*; Zhong, Z.*; Wang, F.*
Crystallography Reports, 51(6), p.1075 - 1081, 2006/12
Times Cited Count:5 Percentile:48.67(Crystallography)Sukhovitskij, E.*; Chiba, Satoshi; Lee, J.*; Kim, B.*; Hong, S.*
Journal of Nuclear Science and Technology, 40(2), p.69 - 76, 2003/02
Times Cited Count:8 Percentile:49.75(Nuclear Science & Technology)no abstracts in English
Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.*; Homma, Takayuki; Kondo, Shuji; Esirkepov, T. Z.; et al.
no journal, ,
The acceleration method of laser plasma electron acceleration has very strong electric field, however, the acceleration length is veryshort. Hence, the energy gain of electron beams were confined to be approximately 100 MeV. Recently, this problem was solved by using discharge capillary. The feature of plasma was used that high dense plasma has low refractive index. Distributing plasma inside capillary as low dense plasma is in the center of capillary and high dense plasma is in the external side of capillary can make a laser pulse propaget inside capillary with initial focal spot size. Experiments with capillary were performed in China Academy of Engineering Physics (CAEP) and Japan Atomic Energy Agency (JAEA). We obtained the results of 4.4 J laser pulse optical guiding in 4 cm capillary and 0.56 GeV electron production in CAEP in 2006, and 1 J laser pulse optical guiding in 4 cm capillary and electron beams productions.
Ji, Y.-Y.*; Mikami, Satoshi; Hong, B. S.*; Sanada, Yukihisa; Jang, M.*; Ochi, Kotaro; Nakama, Shigeo
no journal, ,
Akiba, Masato; Boccaccini, L. V.*; Cho, S. Y.*; Devidov, V.*; Enoeda, Mikio; Feng, K. M.*; Hong, B. G.*; Kovalenko, V.*; Ying, A.*
no journal, ,
A recent study in the frame of the Test Blanket Working Group aimed to identify general issues connected to solid breeder blanket concept and to assess particular needs related to the development of its different variants. The present paper overviews the results of this study, outlining its outcomes for the implementation of an international co-operation programme and giving guidelines for the identification of a limited number of basic TBM configurations suitable for being tested in ITER.