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Authors: S. Yamashita, T. Yoshitake, N. Akasaka, S. Ukai, S. Ohnuki
1467
Authors: Se Hwan Chi, Gen-Chan Kim, Jun Hwa Hong, Sang Chul Kwon, Jong Hwa Chang
Abstract: The changes in the microhardness and Young’s modulus of the 2 MeV C+ ion–irradiated IG-110 isotropic nuclear graphite were evaluated by a dynamic ultra-microhardness test. Indentation depth and load dependency of the hardness and elastic modulus were observed possibly due to the formation of a range. Both the hardness and Young’s modulus (E) – dpa curves have shown an incubation dose for about ı 0.3 mdpa. After the incubation dose, both the hardness and E showed a rapid increase with the dose. The doses that corresponds to these rapid increases in the hardness and E coincides with the dose that corresponds to the beginning of the irradiationinduced surface distortion, and the loss of the graphite crystallinity (amorphization).
1471
Authors: Zhang Jian Zhou, Chang Chun Ge
Abstract: B4C is a promising candidate for using as plasma-facing material in fusion devices. In this paper, both B4C/Cu coating FGM (Funetionally graded material) and B4C/Cu bulk FGM containing a spectrum of 0-100% compositional distributions of B4C were fabricated by atmosphere plasma spray and ultra-high pressure consolidation respectively. The microstructure of B4C/Cu FGM showed good graded composition distribution. Water quenching and high heat loading experiments using an electron beam were carried out to evaluate the high heat load resistance of B4C/Cu FGMs. The in situ plasma irradiation in a Tokamak facility showed that the B4C/Cu bulk FGM has higher physical sputtering performance than that of B4C/Cu coating FGM.
1475
Authors: Y. Sumino, H. Watanabe, Naoaki Yoshida
Abstract: In order to investigate the effect of stepwise change of irradiation temperature on pure copper, heavy ion irradiations under constant temperature and varying temperature conditions were performed. Specimens were irradiated up to 10dpa. In the temperature region of 473K ~ 673K, one-step temperature variation and periodic temperature variations were performed during irradiation. The resulting microstructures were compared with those induced by the irradiation at the constant temperature of 673K.
1479
Authors: Jin Sung Jang, Yong Bok Lee, Chang Hee Han, Yong Sun Yi, Seong Sik Hwang
Abstract: High Cr alloys were corrosion tested in supercritical water and the oxide scale was analyzed. Commercial grade two steel specimens; 9CrMoVNb steels, one 9CrMoVNbW steel, one 12Cr-MoVNbWCu steel and one 20Cr Fe-based O.D.S (Oxide Dispersion Strengthened) alloy specimen were investigated. Corrosion tests were conducted within non-deaerated pure supercritical water at 627, 550, and 500oC with 25 MPa. Corrosion rate was estimated by the weight change per unit surface area and the oxide layer was analyzed using a grazing incidence X.R.D (x-ray diffractometer), S.E.M (scanning electron microscope) and T.E.M (transmission electron microscope) equipped with an E.D.S (energy dispersive spectroscope). Corrosion rates of the 9Cr steel specimens were observed to follow the parabolic growth rate law, while those of the specimens with a 12 per cent or higher Cr content showed significantly lower rates. Oxide scale on the 9Cr steel specimen after a corrosion test in a supercritical water was found to consist of three distinctive layers. Through the cross-section T.E.M the outermost layer with about a 35 µm thickness after 200 hr at 627 oC was identified to be magnetite type Fe3O4, and about 25 µm thick intermediate layer was a Cr partitioned magnetite type (Fe,Cr)3O4. The outermost layer showed a coarse columnar structure, while the intermediate one revealed an agglomerate of tiny oxide particles (several tens nm in diameter). The innermost layer next to the matrix phase was found to be the internally oxidized zone. Oxygen atoms seemed to have attacked along the grain boundaries and the lath boundaries and formed oxide CrO3 along the boundaries. Also a Cr depleted zone, and consequently a carbide-free zone, was observed along the interface between the internal oxidation zone and the matrix phase.
1483
Authors: Tamaz Eterashvili, T. Dzigrashvili, M. Vardosanidze
Abstract: The structure of austenitic steel before and after 25% of total number of cycles of low cycle fatigue tests conducted at room temperature is studied using TEM. It is shown that the cyclic deformation of the steel proceeds heterogeneously. The microstructure of the steel is investigated in the area between the deformed and undistorted parts of the samples. The crystallography of the observed twins and the slip bands is specified. The value of local plastic deformation within a micro area of a grain is measured, and the influence of microstructure on crack initiation is discussed.
1487
Authors: H. Watanabe, M. Nagamine, K. Yamasaki, Naoaki Yoshida, Nam-Jin Heo, Takuya Nagasaka, Takeo Muroga
Abstract: Laser welded high purity V-4Cr-4Ti alloy (NIFS-HEAT2), fabricated by National Institute for Fusion Science (NIFS), was used for this study. Copper ion irradiation was carried out with the tandem accelerator at Kyushu University. The TEM samples were sliced from the welded materials and irradiated at 573 and 873K up to the dose of 12 dpa. The microstructure before irradiation showed that relatively large precipitates, which were commonly observed in NIFS-HEAT2, disappeared in the center of the weld metal. After the ion irradiation, fine titanium oxides with {100} habit planes were detected even at the dose of 0.75 dpa. However, less number density of these oxides were observed in the base metal after the same irradiation conditions. This means that the behaviors of oxygen atoms, which dissolved from the large precipitates during the laser welding, is essential to the microstructural evolution of welded V-4Cr-4Ti alloys.
1491
Authors: C.H. Wu
Abstract: In the framework of the European Fusion Research Program, a great effort has been made to develop an innovative carbon-based ceramic material to meet all of all operational requirements. After a decade of research and development, It is succeeded to develop an advanced material: namely, a 3D CFC, contains about 8-10 at% of Silicon with porosity is about 3-5% . This advanced ceramic material possess very high thermal conductivity, dimensional stability under the neutron irradiation, lower chemical erosion (longer life time), lower tritium retention and lower reactivity with water and oxygen (safety concern) . This innovative ceramic materials seems very promising for application in the high temperature, neutron and hydrogen environment. A detailed discussion on development , properties and application of material is presented.
1497
Authors: Koichi Matsuda, Yoshimi Watanabe, Kazuhisa Yamagiwa, Yasuyoshi Fukui
Abstract: Near net shape forming of Al-Al3Fe functionally graded materials (FGMs) have been studied. FGM billets fabricated by a centrifugal method were extruded under the condition of a mixture of molten Al eutectic and solid Al3Fe particles. Both distribution and profile of Al3Fe particles were characterized by and the variation of volume fraction of Al3Fe particles was observed. Shore hardness of the Al matrix was also measured to evaluate the strength of the FGM before and after the semi-solid forming associated with the character of distributed Al3Fe particles. It was confirmed that Shore hardness increased with increasing the volume fraction of Al3Fe particles and after the semi-solid forming than before. This was due to the fact that Al3Fe particles after the semi-solid forming became fine by shear stress introduced by liquid Al flow.
1503
Authors: S.Y. Park, Moon Chul Kim, Heung Sub Song, Chan Gyung Park
Abstract: Fabrication of two different types of functionally graded tungsten carbide cobalt (WC-Co) coatings has been tried by using detonation gun to enhance both the hardness in the surface region and the toughness of the coating. Five layers with a continuous compositional change of 75 to 92 wt.% of WC were sprayed to obtain ‘layer-structured gradient’ coatings. Each layer was controlled to have both minimum porosity and minimum phase decomposition of WC. New types of ‘continuously graded’ coatings were also fabricated to eliminate any obvious interfaces between layers by the ‘shot control method’ of detonation gun spraying. The wear resistance of these coatings was measured and compared to that of conventional WC-Co coatings by using dry sand abrasion tests under the condition of 20kg load and 200rpm rotating wheel. Present functionally graded coatings revealed more improved wear resistance than that of conventional coatings.
1507

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