担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

DOI： 10.4028/www.scientific.net/msf.1024.103

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Japan Institute of Metals  

DOI： 10.2320/matertrans.f-m2020825

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掲載種別：研究論文（学術雑誌）  

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. CeO2-based solid solutions in which Pd partially substitutes for Ce attract considerable attention, owing to their high catalytic performances. In this study, the solid solution (Ce1−x Pdx O2−δ) with a high Pd content (x ~ 0.2) was synthesized through co-precipitation under oxidative conditions using molten nitrate, and its structure and thermal decomposition were examined. The characteristics of the solid solution, such as the change in a lattice constant, inhibition of sintering, and ionic states, were examined using X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM−EDS), transmission electron microscopy (TEM)−EDS, and X-ray photoelectron spectroscopy (XPS). The synthesis method proposed in this study appears suitable for the easy preparation of CeO2 solid solutions with a high Pd content.

DOI： 10.3390/catal10060640

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掲載種別：研究論文（学術雑誌）  

© 2019 Elsevier Ltd Pt supported on CeO2 has various applications as a catalyst. Because chemical states of Pt are hugely significant in offering improved catalytic performance, it is necessary to understand structures of Pt on CeO2 at high temperatures. In this study, PtO2 and PtO2–CeO2 powders were prepared by precipitation in molten sodium nitrate, and their thermal decomposition in air was examined by X-ray diffraction. When PtO2 powder is heated at 600 °C, the oxide decomposes into Pt phase which is accompanied by a slight Pt3O4 phase. On the other hand, in a heat treatment of a PtO2–CeO2 powder, the formation of Pt phase is hindered and Pt3O4 phase is formed preferentially. These results suggest that supporting Pt on CeO2 contributes not only to maintenance of fine dispersion at high temperatures, but also to formation of the Pt3O4 phase, which might play an important role in catalytic reactions. Observation with transmission electron microscopy and chemical analysis with X-ray photoelectron spectroscopy were performed on the powders before and after the heat treatment to discuss the formation of Pt3O4 particles on a PtO2–CeO2 solid solution.

DOI： 10.1016/j.jpcs.2019.109097

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.11279/jfes.91.717

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掲載種別：研究論文（学術雑誌）  

© 2019 Elsevier B.V. Microstructure and yield strength at room temperature and 300 °C in Al-5 wt%Y 2 O 3 and Al-5 wt%La 2 O 3 fabricated by mechanical alloying (MA) have been investigated by transmission electron microscopy and compression test. Al-5 wt%Y 2 O 3 and Al-5 wt%La 2 O 3 were fabricated by MA with powders Al, Y 2 O 3 and La 2 O 3 . The alloy powders were consolidated by hot pressing at 550 °C under 400 MPa. Yield strengths in the consolidated Al-5 wt%La 2 O 3 at room temperature and 300 °C were higher than those in the consolidated Al-5 wt%Y 2 O 3 . Vickers microhardness at room temperature in Al-5 wt%La 2 O 3 after the consolidation increased as compared with that before the consolidation. In contrast, Vickers microhardness at room temperature in Al-5 wt%Y 2 O 3 after the consolidation was almost the same as that before the consolidation. X-ray diffraction analyses revealed that in Al-5 wt%La 2 O 3 , an intermetallic compound Al 11 La 3 was formed during the consolidation. Al 11 La 3 was finely dispersed in the matrix after the consolidation. In Al-5 wt%Y 2 O 3 , however, no intermetallic compound was formed after the consolidation. It is noted that higher yield strength in Al-5 wt%La 2 O 3 than Al-5 wt%Y 2 O 3 at room temperature and 300 °C is derived from grain boundary strengthening and dispersion strengthening due to pinning of Al grain growth and retarding of dislocation motion by fine numerous dispersoids. The key factor is the large number density of dispersoids in Al-5 wt%La 2 O 3 , which is due to the in-situ formation of intermetallic precipitates Al 11 La 3 during the consolidation.

DOI： 10.1016/j.msea.2019.01.091

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掲載種別：研究論文（学術雑誌）  

© 2019 The Ceramic Society of Japan. All rights reserved. Calcium phosphates are essential compounds for the sustenance of life, since, for example, many grains that enable to convert food are necessary for use of the fertilizers made of chemically synthesized crystals. We have demonstrated two alternative dry processes for the conversion of hydroxyapatite to tricalcium phosphate by means of thermodynamically controlled heat and electronically generated heat with pulsed laser light. In addition, the conversion efficiency has been quantitatively determined from the Rietveld analysis for powder X-ray diffractionpatterns of the fired and laser-ablated samples. Both conversion processes recycled animals' bones as the source of calcium phosphate, and in the future, this could compensate for the niche area in the absence of wet process for a phosphorus containing sludge through a sewage treatment.

DOI： 10.2109/jcersj2.18190

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掲載種別：研究論文（学術雑誌）  

© 2018 The Mining and Materials Processing Institute of Japan. FeO–Fe2O3–P2O5and BaO–FeO–Fe2O3–P2O5glasses were immersed in ultrapure water at 120C for 24–168 h. The weight loss of ternary barium iron phosphate glasses immersed for 168 h with a value of < 1.0 × 10−9kg mm−2(< 0.03% of initial sample weight) was ten times smaller than that of the binary iron phosphate glass. A reaction layer was formed during immersion tests on the barium iron phosphate glasses. FE-SEM observations indicated the thickness of reaction layer increased with immersion time up to a thickness of 150–230 nm. Weight loss of dissolution samples was suppressed once the reaction layer reached a thickness greater than 150 nm. TEM-EDS analysis with selected-area electron diffraction patterns revealed the reaction layer consisted of 6-line ferrihydrite and non-crystalline phase containing phosphorus with a Fe–O richer and no Ba (< 1 at%) composition, compared to the original glass composition. The dissolution and precipitation process of ionic species with a role of Ba ions for local pH modification is discussed for the formation of the reaction layer.

DOI： 10.2320/matertrans.M-M2017854

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© 2017 Trans Tech Publications, Switzerland. Dynamic recrystallization in Ti-1100 was investigated. Ti-1100 is one of near α titanium alloys and contains Si for improving high temperature mechanical properties. Ti-1100 exhibits martensitic transformation by quenching into iced brine after solid solution treatment. Hereafter specimens subjected to quenching into iced brine and to cooling in air after solid solution treatment are called IBQ specimen and AC specimen, respectively. After tensile test at high temperature, IBQ specimen exhibits morphological change from lath structure to equiaxed structure, but AC specimen does not. It is indicated that dynamic recrystallization occurs during the tensile test of IBQ specimen. Effect of silicide on the dynamic recrystallization was investigated using two specimens: one included more silicide precipitates and the other less. The former specimen shows smaller recrystallized grains than the latter. It is indicated that the specimen including more silicides exhibits smaller recrystallized grains.

DOI： 10.4028/www.scientific.net/MSF.879.1634

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017 The Japan Institute of Metals and Materials. Effects of α phase nucleating at a transition phase and dislocation on mechanical properties in a metastable β titanium alloy, Ti-6.8Mo-4.5Fe-1.5Al(mass%), were investigated. Tensile test and optical, scanning, and transmission electron microscopy were used. Two-step aging promoted the precipitation of a fine α phase in grain interiors because the α phase nucleated at a transition phase of β′. A precipitation-free zone appeared at first, but finally disappeared during aging. A specimen that included the precipitation-free zone showed lower yield strength and larger elongation than it did without the precipitation-free zone. This was because dislocation could easily glide in the precipitation-free zone, which was verified from examination of the intergranular ductile fracture surface. The transition phase of β′ promoted the disappearance of a precipitation-free zone, due to the promotion of α phase precipitation, resulting in enhancement of yield strength and deterioration of elongation. It is likely that the width of PFZ and the crystallographic orientation of β grains determine fracture mode to be intergranular ductile, intergranular brittle or intragranular fractures. Aging after tensile deformation produced α phase precipitation at dislocation. A specific variant of α phase was selected due to a stress field around the dislocation that included a planar slip band. This resulted in the formation of a large colony of the specific α variant, while elongation deteriorated because the large colony probably facilitated crack propagation.

DOI： 10.2320/matertrans.M2016382

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

© 2016 Atomic Energy Society of Japan. All rights reserved. Development of fine grain 316L with small amount of TiC for high radiation-tolerant performance was tried considering the fabrication process of thermo-mechanical treatments. The materials obtained are UFG316L+2.0 mass% TiC with the grain size of 90–270 nm, depending on the final annealing temperature from 700 ℃ to 900 ℃. The materials were examined by transmission electron microscopy observation, X-ray absorption near-edge structure spectroscopy, high voltage electron microscope electron irradiation and stress corrosion cracking by crevice bent beam method in high-temperature water with 8 ppm dissolved oxygen. The test results showed that the material is generally of excellent quality. Especially void swelling induced by the electron irradiation at 400 ℃ is less than 1/10 compared to the commercial SUS316L.

DOI： 10.1080/00223131.2016.1175390

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

© 2015 Elsevier B.V. Structural materials used in radiation environments require radiation tolerance and sufficient mechanical properties in the controlled state. In order to offer SUS316L austenitic stainless steel with the assumed requirements, nanostructured SUS316L with TiC addition of 2% (SUS316L-2TiC) that is capable of exhibiting enhanced tensile ductility and flow strength sufficient for structural applications was fabricated by advanced powder metallurgical methods. The methods include MA (Mechanical Alloying), HIP (Hot Isostatic Pressing), GSMM (Grain boundary Sliding Microstructural Modification) for ductility enhancement, cold rolling at temperatures below M<inf>d</inf> (the temperature where the martensite phase occurs by plastic deformation) for phase transformation from austenite to martensite and heat treatment for reverse transformation from martensite to austenite. It is shown that the developed SUS316L-2TiC exhibits ultrafine grains with sizes of 90-270 nm, accompanied by TiC precipitates with 20-50 nm in grain interior and 70-110 nm at grain boundaries, yield strengths of 1850 to 900 MPa, tensile strengths of 1920 to 1100 MPa and uniform elongations of 0.6-21%, respectively, depending on the heat treatment temperature after rolling at -196 °C.

DOI： 10.1016/j.jnucmat.2015.08.027

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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© 2014 Taylor & Francis. The new welding method known as F-MAG, which has been developed based on the CO2 gas-shielded arc welding method (MAG), increases deposition rate of weld metal. The F-MAG welding method is combined with hot-wire, as has been used in TIG arc- and laser-welding methods. F-MAG is performed using hot-wire which is inserted into the rear part of the weld pool made with the leading electrode. Hot-wire melts by both electrical heating of itself and heat of the weld pool. Multi-layered weld metals were prepared using F-MAG and MAG. Microstructures and mechanical properties of both as-weld and reheated zones in the uppermost layer of the multi-layered weld metals formed with F-MAG and MAG were examined and the effects of hot-wire on microstructures and mechanical properties were analysed. Both the as-weld and reheated zones of the weld metal formed with F-MAG consisted of acicular ferrite (AF), equiaxed ferrite and so on. Both strength and elongation in as-weld and reheated zones formed with F-MAG were superior compared with those formed with MAG. It could be suggested that strength increased by refinement of AF due to increase in the concentration of alloying elements being contained in the hot-wire. Larger elongation of the weld metal in F-MAG compared with that in MAG could be analysed in terms of the Aggregate of AF Laths with nearly Parallel Slip systems between neighboring AF laths (ALPS). The number of AFs contained in an ALPS formed with FMAG is larger than that with MAG, in spite of the sizes of ALPSs formed with MAG and F-MAG being almost same. Deformation occurs over a lot of AFs in the case of finer AF formed with F-MAG through the rotation of the tensile test piece during deformation, resulting in the larger elongation.

DOI： 10.1080/09507116.2014.921065

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2320/jinstmet.J2015040

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

Nanostructured tungsten (W)-based materials offer many advantages for use as plasma facing materials and components exposed to heavy thermal loads combined with irradiation with high-energy neutron and low-energy ion. This paper first presents the recent progress in nanostructured toughened, fine grained, recrystallized W materials. Thermal desorption spectrometry apparatus equipped with an ion gun has been installed in the radiation controlled area in our Center at Tohoku University to systematically investigate the effects of displacement damage due to high-energy neutron irradiation on hydrogen isotope retention in connection with the nano-or micro-structures in W-based materials. In this paper, the effects of high-energy heavy ion irradiation on deuterium retention in W with different microstructures are described as a preliminary work with the prospective view of neutron irradiation effects.

DOI： 10.1088/0031-8949/2014/T159/014032

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Homogeneous precipitation of a fine α phase in the β matrix of Ti alloys is a promising method for obtaining a highly strengthened Ti-based alloy. Isothermal ω particles are known to be the nucleation sites for fine α-phase precipitation, but an understanding of the kinetics of α-phase formation on isothermal ω particles is still lacking. This study aimed to reveal the effect of isothermal ω particles on α-phase precipitation onset time. Two-step isothermal aging of a Ti-20 at.pct Nb alloy after solid solution treatment at 1273 K (1000 C) was carried out. The first step of the aging at 633 K (360 C) involved the formation of isothermal ω particles in the β matrix. This was followed by a second aging step at 673 K, 723 K, and 773 K (400 C, 450 C, and 500 C) for α-phase precipitation. Suppression of α-phase nucleation on the isothermal ω particles occurred at 673 K (400 C), whereas acceleration of α-phase nucleation on the isothermal ω particles was observed at 723 K and 773 K (450 C and 500 C). Thermodynamic stability of the isothermal ω particles and solute partitioning were controlling factors for the α-phase precipitation kinetics. © 2013 The Minerals, Metals & Materials Society and ASM International.

DOI： 10.1007/s11661-013-2092-1

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掲載種別：研究論文（国際会議プロシーディングス）  

Nanostructured tungsten (W)-based materials offer many advantages for use as plasma facing materials and components exposed to heavy thermal loads combined with irradiation with high-energy neutron and low-energy ion. This paper first presents the recent progress in nanostructured toughened, fine grained, recrystallized W materials. Thermal desorption spectrometry apparatus equipped with an ion gun has been installed in the radiation controlled area in our Center at Tohoku University to systematically investigate the effects of displacement damage due to high-energy neutron irradiation on hydrogen isotope retention in connection with the nano- or micro-structures in W-based materials. In this paper, the effects of high-energy heavy ion irradiation on deuterium retention in W with different microstructures are described as a preliminary work with the prospective view of neutron irradiation effects. © 2014 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2014/T159/014032

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

The growth and coarsening of Cu-particles in 18%Cr-1.5%Cu ferritic stainless steels as a function of Nb content was investigated quantitatively. The samples were solution-treated at 1 250°C and then isothermally aged at 700°C for up to 86 400 s. Fine, spherical Cu-particles nucleated and grew during aging. The radius of the Cu particles increased in proportion to the one-third power of the aging time in all the stainless steels. The radius of the Cu particles in the Nb-added stainless steels was always smaller than that in the Nb-free stainless steel. The normalized standard deviation of the size distribution of the Cu particles increased and reached saturation at a certain value during aging. The increase in the standard deviation during aging was delayed by the addition of Nb. The volume fraction of Cu particles increased and reached saturation at a certain value during aging. The addition of niobium delayed the saturation of the volume fraction of the Cu particles. The slow growth of Cu particles in Nb-added stainless steels is thought to be owing to the slow diffusion of Nb atoms from the Cu particles. © 2014 ISIJ.

DOI： 10.2355/isijinternational.54.1697

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掲載種別：研究論文（国際会議プロシーディングス）  

Aggregate of bainite laths with almost parallel slip systems between neighboring bainite laths, hereafter referred to as ALPS, has great effect on the improvement of mechanical properties in steels. Elongation increases remarkably with increasing the number of bainite laths within an ALPS. When a bainite lath begins to deform, the neighboring bainite lath also easily deforms to relax the deformation strain, because of good parallelism between their slip systems. Under the cooperative deformation of bainite laths, the area of interface between neighboring bainite laths increases during deformation. The increase in the area of interface between neighboring bainite laths suppresses localization of dislocations at the interface, that is, dislocation density per unit area of the interface between neighboring bainite laths hardly increases, resulting in the suppression of nucleation of cracks at the interface between neighboring bainite laths. Ductile fracture would occur along the boundary between ALPSs. It could be suggested that larger ALPS and/or ALPS consisting of large number of bainite laths induce larger elongation in steels. On the other hand, it has been reported that tensile strength increases in proportion to inverse of square root of d, the d being the average size of bainite laths [1]. In order to form fine bainite lath, dislocation network instead of inclusion in austenite was utilized as nucleation site for bainite lath. Great barriers to be overcome exist for the improvement of both strength and toughness. An idea for the improvement of both strength and toughness is shown in this study. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/msf.783-786.926

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掲載種別：研究論文（国際会議プロシーディングス）  

Ti-Mo based alloys have been used as biocompatible materials. Recently the positive use of inexpensive alloying elements becomes important to develop low cost Ti alloys. The purpose of the present study was to reveal the effect of Fe addition in Ti-Mo alloy on the microstructure formation and mechanical properties. Ti-(2.0, 3.0)at%Mo-(0.0~2.0)at%Fe alloys were arc-melted. The alloy buttons were hot-rolled into about 2.0 mm thick sheets at 1073-1223 K. Specimens solid-solution-treated at 1273 K in b phase field were quenched into iced brine. X-ray diffractometry was used to identify phases in the specimens. Microstructures were examined by both optical and transmission electron microscopies. Hardness and Young's modulus of the alloys were evaluated. Addition of Fe in Ti-Mo alloys promoted the formation of athermal omega and increased in hardness. As-quenched Ti-3at%Mo alloy exhibited mixture of α' and α" martensites. The Young's modulus of it was 76 GPa. Ti-2at%Mo-1at%Fe alloy, replacement of 1at%Mo (expensive) by 1at%Fe (inexpensive) from Ti-3at%Mo, also exhibited mixture of α' and α" martensites with the Young's modulus of 85 GPa. Hardness of Ti-2at%Mo-1at%Fe alloy, 329Hv, is greater than that of Ti-3at%Mo alloy, 257 Hv. Ti-2at%Mo-1at%Fe is thought to be a candidate material for a low cost bone replacement Ti alloy with low Young's modulus. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/msf.783-786.1280

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掲載種別：研究論文（国際会議プロシーディングス）  

Microstructures and Vickers microhardness in AZ91 magnesium alloys without and with 1mass%Y addition fabricated by casting were investigated. Vickers microhardness increases with adding 1%Y. Microstructure in AZ91 without Y addition was analyzed to contain mainly α-Mg and Mg17Al12 by X-ray diffraction. Microstructural observations with optical, scanning and transmission electron microscopes show that microstructure consists of α-Mg dendrite, non-equilibrium eutectic Mg17Al12 and lamellar Mg17Al12. The non-equilibrium eutectic Mg17Al12 exists between α-Mg dendrites. The lamellar Mg17Al12 forms near the edge of the α-Mg dendrite arm. The lamellar Mg17Al12 has Burgers orientation relationship for α-Mg matrix. It suggests that the lamellar Mg17Al12 precipitates from Al-supersaturated region within α-Mg dendrite. Addition of Y to AZ91 hardly changes dendrite arm spacing, but decreases a size of region, where longitudinal directions of primary dendrite arms are almost parallel or a single dendrite exists. Y-addition increases nucleation site for dendrite, namely makes the unidirectionally-solidified region fine, resulting in increase in hardness. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/msf.783-786.472

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掲載種別：研究論文（国際会議プロシーディングス）  

Effect of pre-treatment before austenitization on mechanical property in a steel has been investigated. Pre-treatment was done at 500°C for 600, 1200 and 1800s before austenitization at 1440°C for 120s. This pre-treatment was performed in order to introduce dislocation network into austenite, which acts as nucleation site for "bainite laths within austenite grain (BWING)". BWING was formed with isothermal holding at 500°C for 10s after austenitization. Micro-Vickers hardness is measured in a steel with and without pre-treatment. The steel with appropriate pre-treatment exhibits high hardness, because large amounts of BWINGs are formed. In the case of cementites in pearlite being coarsened and the distance between cementites becoming large, dislocation network is apt to be introduced into γ. The dislocation network acts as nucleation site for BWING, resulting in the suppression of formation of intergranular bainite. BWINGs strengthen the steel. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/msf.783-786.992

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掲載種別：研究論文（国際会議プロシーディングス）  

Effect of pre-treatments before austenitization on mechanical properties in steels has been investigated. Pre-treatments are cold rolling and isothermal holding below A1 before austenitization. Pre-treatments were performed in order to introduce dislocation network in austenite (γ), which acts as nucleation site for "bainite laths within γ grain (BWING)". During the pre-treatment of isothermal holding below A1, carbon segregation and/or carbide formation might occur at grain boundary of ferrite (α). Thin γ layer might be formed around the region where carbon segregation and/or carbide formation occurred in the beginning of austenitization. Transformation strain due to α → γ would be effectively relaxed by the deformation of thin γ film, because α had been already hardened by the cold rolling. Dislocations might be introduced dominantly into the thin γ film, and stable dislocation network even in the high temperature region of γ might be formed. BWING nucleates around the dislocation network to relax the strain field around dislocation network. BWING would nucleate also at (BWING/γ) interface cooperatively to relax the strain around the interface, resulting in the formation of "aggregate of bainite laths with nearly parallel slip systems between neighboring bainite laths (ALPS)". Larger ALPS containing a lot of BWINGs might be formed in the pre-treated steel, and improves tensile strength and toughness. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/msf.783-786.932

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE SA  

To better understand the fatigue and tensile properties of SPCC steels welded by metal inert gas welding, the mechanical properties of the welded component in several localized regions, e.g., weld metal, heat affected zone (HAZ) and base metal, were investigated. The tensile and fatigue properties of the weld metals were high compared to the other areas (base metal and HAZ) due to the precipitated Ti containing oxide inclusions in acicular ferrite (bainite). Two typical microstructures were mainly observed in the heat affected zones (HAZ): (i) bainite in a ferrite matrix (HAZ-B) and (ii) a ferrite phase with low internal stress (HAZ-A). The hardness of HAZ-B was higher than HAZ-A because of the partially formed bainite structure and precipitated Ti containing oxide inclusions. The mechanical properties of the weld sample were further investigated using test specimens that included all regions, i.e., weld metal, HAZ and base metal (BHW). The tensile and fatigue properties of the BHW sample were found to be lower than those in all other regions, which was influenced by the high internal stress. The mechanical properties were analyzed using microstructural and crystal characteristics, as examined by TEM and EBSD analysis. In addition, the fatigue strength can be precisely evaluated using a modified Goodman diagram. © 2012 Elsevier B.V.

DOI： 10.1016/j.msea.2012.10.008

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掲載種別：研究論文（国際会議プロシーディングス）  

Thin film of pure Sn is prepared through electroplating Sn on stainless steel and peeling the thin Sn electrodeposit from the stainless steel. Fine Au particles, which are greatly smaller than size of Sn grain, were deposited on Sn-film in vacuum. Both-Sn films with and without the deposition of Au particles were clamped with acrylic resin plates. It was clarified that formation of Au-Sn compounds on surface of Sn-film suppressed formation of whisker. Our idea for the mechanism of whisker formation was confirmed based on the above and former results [1-3]. Conclusion is that aggregation of both edge- and screw-dislocations in small region induces the nucleation and growth of whisker. Suppression of whisker formation could be done through avoiding the aggregation of both edge- and screw-dislocations in small region by forming fine Au-Sn compounds on the surface of Sn-film.

DOI： 10.1007/978-3-319-48764-9_256

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Iron and Steel Institute of Japan  

New welding method (F-MAG) based on CO&lt;sub&gt;2&lt;/sub&gt; gas-shielded arc welding method (MAG) was developed to increase deposition rate of weld metal. In F-MAG, filler wire (hot-wire) heated using direct-current was put into rear part of weld-pool formed with main electrode used in MAG.&lt;br&gt;Multi-layered weld metals were prepared using both F-MAG and MAG. Microstructures of both as-weld and reheated zones in uppermost layer of the multi-layered weld metals were examined and the effects of microstructures on mechanical properties were analyzed. Both the as-weld and reheated zones of weld metal formed with F-MAG consisted of acicular ferrite (AF) and/or equiaxed ferrite and so on. Both strength and elongation in as-weld and reheated zones formed with F-MAG were superior compared with those formed with MAG. It could be suggested that strength increased by refinement of AF due to increase in the concentration of alloy elements being contained in hot-wire. Larger elongation of weld metal in F-MAG compared with that in MAG could be analyzed in terms of the aggregate of AFs with almost parallel slip systems between neighboring AFs, hereafter referred as to ALPS. The number of AFs contained in an ALPS formed in weld metal formed with F-MAG is larger than that with MAG, in spite of the sizes of ALPSs in weld metals formed with MAG and F-MAG being almost same between them. Deformation occurs over a lot of AFs in the case of finer AF through the rotation of tensile test piece during deformation.

DOI： 10.2355/tetsutohagane.99.468

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN INST METALS  

Mitigation of embrittlement caused by recrystallization and radiation is the key issue of tungsten (W based materials for use in the advanced nuclear system such as fusion reactor applications. In this paper, our nanostructured W materials development performed so far to solve the key issue is reviewed, including new original data. Firstly, the basic concept of mitigation of the embrittlement is shown. The approach to the concept has yielded ultra-fine grained, recrystallized (UFGR) W(0.251.5) mass%TiC compacts containing fine TiC dispersoids (precipitates). The UFGR W(0.251.5)% TiC exhibits favorable as well as unfavorable features from the viewpoints of microstructures and various thermo-mechanical properties including the response to neutron and ion irradiations. Most of the unfavorable features stem from insufficient strengthening of weak random grain boundaries (GBs) in the recrystallized state. The focal point on this study is, therefore, to develop a new microstructural modification method to significantly strengthen the random GBs. The method is designated as GSMM (GB Sliding-based Microstructural Modification and has lead to the birth of toughened, fine-grained W1.1% TiC in the recrystallized state (TFGR W1.1TiC). The TFGRW1.1TiC exhibits much improved thermo-mechanical properties. The applicability of TFGRW1.1TiC to the divertor in ITER is discussed. © 2013 The Japan Institute of Metals.

DOI： 10.2320/matertrans.MG201209

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掲載種別：研究論文（国際会議プロシーディングス）  

In order to improve mechanical property, effects of B on microstructure and mechanical property in as-weld metals containing 2-28 wt. ppm B were examined. In B rich as-weld metal, high density of fine acicular ferrite (AF) nucleated within austenite (γ) grain, but in B-poor asweld metal, ferrite precipitated at γ grain boundaries dominantly, resulting in suppressing formation of AF. The strength in B rich as-weld metal increased with increasing the formation of AF, but elongation scarcely increased. In transmission electron micrographs, precipitates were recognized except inclusion of (Ti, Mn) - oxides in B rich as-weld metal. It could be suggested that the formation of peculiar precipitation as well as the inclusion control the mechanical properties.

DOI： 10.1002/9781118792148.ch302

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掲載種別：研究論文（国際会議プロシーディングス）  

The new welding method called as F-MAG, which has been developed based on CO2 gas-shielded arc welding method (CO2 welding) increase deposition rate of weld metal. Microstructures of both as-weld- and reheated-zones in uppermost layer of the multi-layered weld metals were examined and the effects of microstructures on mechanical properties were analyzed. The both zones in weld metal formed with F-MAG consist of acicular ferrite (AF) mainly. Both strength and elongation in both zones formed with F-MAG are superior compared with those with CO2 welding. It can be suggested that strength increases by refinement of AF due to increase in the concentration of alloy elements being contained in hot-wire. Larger elongation in F-MAG could be analyzed in terms of the number of AFs contained in almost same sizes of ALPS. Deformation inherits over a lot of finer AFs, namely, larger fraction of ALPS deforms compared with the case of larger size of AFs by internal stresses around deformed AFs.

DOI： 10.1002/9781118792148.ch276

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Effect of dislocation behavior on formation of whisker in pure Sn has been investigated. Slip system in β-Sn was determined; slip plane is {2 1̄ 1̄) , and Burgers vector b is < 01 1̄] . The magnitude of Burgers vector is larger than the smallest interatomic spacing in β-Sn. This means that there is broad space under the extra half plane of edge dislocation. It sould be noted that pipe diffusion along the edge dislocation is enhanced in β-Sn, resulting in easy supply of Sn atoms at the root of Sn whisker [1, 2]. Si-bearing particles, which precipitate on surface of bulk Sn by heat-treatment in quartz tube, suppress the accumulation of both edge and screw dislocations to same area. It is greatly effective for the suppression of the nucleation of Sn whisker. © 2012 Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/MSF.706-709.751

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Formation of hydroxyapatite (HAp) in simulated body fluid (SBF) on heated nacre has been examined. Nacre is known as composite layer of aragonite platelets and organic materials. Nacre was obtained from the shell of Akoya pearl oyster after removing its prismatic layer. The nacre was heated up to 300°C in air and then soaked in SBF. Nacre heated at 300°C lost iridescent color and became brittle, implying that organic materials which plays a role as glue between aragonite platelets mostly disappeared by heating at 300°C. Formation of HAp particles on nacre in SBF was easier than that on pure Ti. Maximum formation rate of HAp particles was obtained on the nacre heated at 200°C. The amount of HAp particles formed on the nacre heated at 300°C is the smallest. The organic materials in nacre play a critical role for HAp formation on nacre in SBF. © 2012 Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/MSF.706-709.526

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP PUBLISHING LTD  

In this work, the focus is on the thermal shock analysis of fine- and ultra-fine-grained tungsten-based materials doped with 0.5-1.1 wt% TiC that showed in previous studies improved ductility at low temperatures and also performed well when exposed to neutrons and ions (H/He). Herein, the resistance of the material to crack formation is evaluated by applying edge-localized mode-like loads (n = 100) with an energy density of 1 MJ m(-2) at various temperatures up to 150 degrees C by means of an electron beam facility. The results indicate that the cracking threshold is significantly reduced even down to room temperature when the oxygen content is reduced and the combination of grain size, TiC particle size and distribution of TiC-particles to almost each grain boundary reaches its optimum. This is achieved by a post-manufacturing treatment of the material at 1650 degrees C using the material's superplasticity caused by grain boundary sliding at this temperature, which changes the material's microstructure from ultra-fine grains surrounded by weak grain boundaries to fine grains with significantly strengthened grain boundaries.

DOI： 10.1088/0031-8949/2011/T145/014060

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE SA  

Nanostructured vanadium (V) alloys are expected to exhibit high performance under neutron irradiation environments. However, their ultra-fine or refined grains cause significant decrease in flow stress at high temperatures due to grain boundary sliding (GBS), which is the major concern for their high-temperature structural applications such as future fusion reactors. The contribution of GBS to plastic deformation is known to depend strongly on grain size (GS) and may give more significant influence on long-time creep test results than on short-time tensile test results. In order to improve the creep resistance through elucidation of the effect of GS on the uniaxial creep behavior of nanostructured V alloys, a solution and dispersion hardened V alloy, V-1.4Y-7W-9Mo-0.7TiC (in wt%), with GSs from 0.58 to 2.16μm was developed by mechanical alloying and HIP processes, followed by annealing at 1473-1773K, and creep tested at 1073K and 250MPa in vacuum. It is shown that the creep resistance of V-1.4Y-7W-9Mo-0.7TiC increases monotonically with GS: The creep life for the alloy with 2.16μm in GS is as long as 114h, which is longer by factors of 2-30 than those for the other finer grained alloys and by two orders than that for coarse-grained V-4Cr-4Ti (Nifs heat2, GS: 17.8μm) that is a primary candidate material for fusion reactor structural applications. The minimum (steady state) creep rate decreases with increasing GS as ε s∝(1/ℓ) 3, where ε s is the steady state creep rate and ℓ is the grain diameter. The observed superior creep resistance of V-1.4Y-7W-9Mo-0.7TiC is discussed in terms of GS effects on dislocation glide/climb, GBS, and strain hardening capability enhanced by solution and dispersion hardening. © 2011 Elsevier B.V.

DOI： 10.1016/j.msea.2011.06.033

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Creep resistance is the major concern of vanadium and its alloys for fusion reactor structural applications. In order to elucidate the effects of grain size on the creep behavior of solution and dispersion strengthened vanadium alloys, V-1.6Y-8W-0.8TiC specimens with fine grain sizes from 0.58 to 1.45 μm were prepared by mechanical alloying and HIP without any plastic working and tested at 1073 K and 250 MPa in vacuum. It is shown that the creep resistance of V-1.6Y-8W-0.8TiC depends strongly on grain size and increases with increasing grain size: The creep life for the grain size of 1.45 μm is almost one order longer than that of 0.58 μm, and about two orders longer than that of V-4Cr-4Ti (NIFS-Heat 2) although the grain size of V-4Cr-4Ti is as large as 17.8 μm. The observed creep behavior is discussed in terms of grain size effects on dislocation glide and grain boundary sliding. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2010.12.105

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Microstructure formation in V-1.6Y during neutron irradiation at 800 °C was examined with transmission electron microscopy. Faulted vacancy loops were observed in the coarse grains several micrometers in diameter without dispersed Y2O3 particles. The habit plane of the faulted vacancy loop is close to {1 1 6}. Formation of faulted vacancy loops in the vanadium matrix could be induced by oxygen picked up from the environment during irradiation. Denuded zone of faulted vacancy loops was observed around both helical dislocations and grain boundaries. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2011.01.068

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Effects of plastic working and the mechanical-alloying atmosphere on microstructures of ultra-fine-grained, particle-dispersed W-1.1%TiC compacts, which were developed by powder metallurgical methods, have been investigated by transmission electron microscopy. Plastic working increases the density of the compacts by the reduction of number density of Ar bubbles and pores. Plastic working (PW) enhances the precipitation of TiC at weak grain boundaries of W grains. The precipitated TiC dispersoids have a Kurdjumov-Sachs orientation relationship with the W matrix, thereby significantly strengthening weak grain boundaries of W grains. Such strengthening of weak grain boundaries has not been achieved by hot isostatic pressing irrespective of its temperature. The significant improvement in fracture strength and ductility by PW is primarily due to the strengthening of weak grain boundaries and secondarily due to the decrease in Ar bubbles and pores at grain boundaries. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2010.12.117

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

Effects of additions of CeO2 and La2O3 on microstructure and mechanical properties of B4C fabricated under and without hot press have been investigated. Vickers hardness and fracture strength are increased by hot press due to the reduction of porosity because the sintering rate is enhanced. Hardness is increased by the reduction of porosity because crack probably occurs when the hardness is measured due to pore as an initiation point of crack. Hardness increases with increasing additions of CeO2 and La2O3 because porosity decreases due to the formation of CeB6 and LaB6 on the grain boundary of B4C, respectively. The borides are formed through reaction between solid phases, which might induce coherent boundary between boride and B 4C. Such coherency also contributes to strengthening the grain boundary of B4C. The addition of CeO2 enhances the sintering rate more than that of La2O3, resulting in higher hardness of B4C-CeO2 than that of B 4C-La2O3. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2011.01.072

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

B4C-CeO2 composite ceramics with various concentrations of CeO2 were fabricated by hot press. The effects of CeO2 on the microstructures and mechanical properties of the B 4C-CeO2 ceramics have been investigated. During hot press, CeB6 was formed by the reaction between CeO2 and B 4C. The B4C-CeO2 ceramics had higher levels of density, fracture toughness, flexural strength and Vickers hardness than those in monolithic B4C. The microstructures of the B4C-CeO 2 ceramics were observed and analyzed by transmission electron microscopy. In-situ synthesized CeB6 indicated whisker-like shape and grew along the interface with B4C, and different boron carbides with different content of C existed at/around the interface of CeB6 with B4C in the composite ceramics. It made mechanical properties greatly improved. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2010.12.093

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掲載種別：研究論文（国際会議プロシーディングス）  

In this work, the focus is on the thermal shock analysis of fine- and ultra-fine-grained tungsten-based materials doped with 0.5-1.1 wt% TiC that showed in previous studies improved ductility at low temperatures and also performed well when exposed to neutrons and ions (H/He). Herein, the resistance of the material to crack formation is evaluated by applying edge-localized mode-like loads (n=100) with an energy density of 1 MJ m -2 at various temperatures up to 150°C by means of an electron beam facility. The results indicate that the cracking threshold is significantly reduced even down to room temperature when the oxygen content is reduced and the combination of grain size, TiC particle size and distribution of TiC-particles to almost each grain boundary reaches its optimum. This is achieved by a post-manufacturing treatment of the material at 1650°C using the material's superplasticity caused by grain boundary sliding at this temperature, which changes the material's microstructure from ultra-fine grains surrounded by weak grain boundaries to fine grains with significantly strengthened grain boundaries. © 2011 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2011/T145/014060

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Ultra-fine grained (UFG) W-TiC compacts fabricated by powder metallurgical methods utilizing mechanical alloying (MA) are very promising for use in irradiation environments. However, the assurance of room-temperature ductility and enhancement in surface resistances to low-energy hydrogen irradiation are unsettled issues. As an approach to solution to these, microstructural modification by hot plastic working has been applied to UFG W-TiC processed by MA in a purified Ar or H2 atmosphere and hot isostatic pressing (HIP). Hot plastically worked compacts have been subjected to 3-point bend tests at room temperature and TEM microstructural examinations. It is found that the microstructural modification allows us to convert UFG W-1.1%TiC to compacts exhibiting a very high fracture strength and appreciable ductility at room temperature. The compacts of W-1.1%TiC/Ar (MA atmosphere: Ar) and W-1.1%TiC/H2 (MA atmosphere: H2) exhibit re-crystallized structures with approximately 0.5 and 1.5 μm in grain size, respectively. It is shown that the enhancement of fracture resistance by microstructural modifications is attributed to significant strengthening of weak grain boundaries in the re-crystallized state. As a result the modified compacts exhibit superior surface resistance to low-energy deuteron irradiation. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2009.10.015

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Precipitation behavior of a metastable beta Ti alloy, Ti-6.8Mo-4 5Fc- I 5A1(masss%), during two-step aging has been investigated Supersaturated beta phase after solution treatment decomposes into beta+omega phases during the first aging at 300 degrees C for 2ks beta' phase is observed during the second aging at 500 degrees C for 50s. It is suggested that reverse transformation of the omega phase to beta phase during the second aging at 500 degrees C for 50s gives rise to solute-lean and rich regions in the beta phase, and that beta' phase is formed in the solute-rich region beta' phase being coherent with beta phase has larger lattice parameter than beta phase. beta phase acts as nucleation site for alpha phase, and accelerates the nucleation of alpha phase.

DOI： 10.4028/www.scientific.net/MSF.638-642.461

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Ultra-fine grained (UFG) W-TiC consolidates are very promising for use as divertors in fusion reactors, however, the assurance of room-temperature ductility of UFG W-TiC remains unsettled. The assurance requires a sufficient degree of plastic working for the consolidates and thus overcoming of poor plastic workability in UFG W-TiC by applying superplasticity. Therefore, the magnitudes of elongation to fracture and flow stress which are important measures for plastic working were examined for UFG W-(0-1.5)%TiC (in wt%) at 1673-1973 K where superplasticity occurs without appreciable grain growth. It is shown that the elongation and flow stress are strongly dependent on TiC addition and atmosphere (Ar, H2) during mechanical alloying (MA). As the TiC addition increases, the elongation significantly increases without appreciable increase in the flow stress level. W-TiC fabricated with MA in H2 exhibits larger elongation and larger strain rate sensitivity of flow stress than W-TiC with MA in Ar. These results were applied to perform plastic working and the room-temperature bend test results for plastic worked W-1.0%TiC are shown. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2008.12.181

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掲載種別：研究論文（国際会議プロシーディングス）  

Microstructural evolution in a low cost beta titanium alloy, Ti-6.8Mo-4.5Fe-l.5Al, has been investigated especially in view of the initial microstructure before phase precipitation. During aging at 673 K., isothermal α phase is initially formed, and then a phase is formed at the isothermal ω phase which is a nucleation site. A large number density of athcrmal co phase, which is formed by quenching alter solution treatment at 1123 K, likely have an cffcct to accelerate a phase nucleation during aging at 773 K. compared with a specimen not quenched after the solution treatment. In a two-step aging, i.e., the solution treatment →573K for 2 ks-→773 K, the first aging yields formation of isothermal ω phase, and the sccond aging for a short time yields formation of phase and that for a further time yields formation of αphase. Acceleration of α phase formation in the two-step aging is attributable to the fact that β phase is a nucleation site for α phase. The formation β phase occurs in the β stabilizers enriched β phase due to compositional partitioning from ω phase.

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Finer intragranular bainite in steel welds has been known to be effective to improve strength and toughness greatly. The clTect of the starting temperature (B<inf>s</inf>) and the starting time (t<inf>s</inf>) of the nucleation of intragranular bainite on the formation and configuration of intragranular bainite arc examined by controlling the chemical compositions of Ni and B. It could be found that high concentration of Ni and low concentration of B induced high volume fraction of fine intragranular bainite. The results arc analyzed in terms of the BS and the t<inf>s</inf>.

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It is well known that formation of intragranular bainite (IGB) improves toughness of steels. The inclusions of oxide, sulfide, nitride, their complexes and so on act as nucleation sites for IGB. However, the inclusions act as the nucleation site for cleavage. Therefore, instead of inclusions, the stress field around small-angle dislocation boundary (SADB) has been examined whether it is effective or uot for the nucleation of IGB. It was confirmed that SADB acts effectively as nucleation sites for IGB, resulting in both the formation of finer IGB and the improvement of toughness.

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掲載種別：研究論文（国際会議プロシーディングス）  

Microstnicturc formation during cooling from p phase in Ti-{15, 20) Nb-(0, 10, 20) Zr (ai%) alloys have been examined to reveal the effects of cooling rate and Zr addition on the microstructure formation. Specimens solution-treated at 1000°C in (5 phase field were qucnchcd in iccd brine (IBQ) or cooled in air (AC). Decrease of the cooling rate from IBQ to AC results in suppression of α phase formation in Ti-15Nb-(0, 10) Zr and Ti-20Nb alloys. Isothermal to phase formation in the AC specimens suppresses the formation of ω phase. Addition of 20at%Zr into Ti-(15, 20) Nb alloys suppresses formation of α phase in the IBQ specimens. Both cooling rate and Zr addition affect the competitive formation process of α and ω phases in Ti-(15, 20) Nb alloys during cooling front 1000°C.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Microstructure evolutions and hardness variation during aging in metastable beta titanium alloy TIMETAL (R) LCB have been examined. In as-quenched specimen after solution treatment, athermal omega phase formed. Isothermal omega phase formed during aging at 623 K, and alpha phase formed after precipitation of isothermal to phase during aging at 673 and 773 K. Alpha phase nucleated at isothermal omega phase, and had the orientation relationship with beta and omega, (111)(beta)//(0001)(omega)//(11 (2) over bar0)(alpha) and [10 (1) over bar](beta)[11 (2) over bar0](omega)//[0001](alpha). During aging at 873 K, alpha phase formed without isothermal omega phase. Hardness increased with increasing aging time and decreasing aging temperature, partly because number density of isothermal omega or alpha precipitates increased with increasing aging time and decreasing aging temperature.

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（全国大会，その他学術会議）  

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

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記述言語：日本語   出版者・発行元：JAPAN WELDING SOCIETY  

The new welding method called as F-MAG, which has been developed based on CO 2 gas-shielded arc welding method (MAG) increase deposition rate of weld metal. F-MAG welding method is combined with hot-wire, as having been used in TIG arc- and laser-welding methods. F-MAG is performed using hot-wire which is inserted into the rear part of weld pool made with leading electrode. Hot-wire melts by both electrical heating of itself and heat of weld pool. Multi-layered weld metals were prepared using F-MAG and MAG. Microstructures and mechanical properties of both as-weld and reheated zones in uppermost layer of the multi-layered weld metals formed with F-MAG and MAG were examined and the effects of hot-wire on microstructures and mechanical properties were analyzed. Both the as-weld and reheated zones of weld metal formed with F-MAG consisted of acicular ferrite (AF), equiaxed ferrite and so on. Both strength and elongation in as-weld and reheated zones formed with F-MAG were superior compared with those formed with MAG. It could be suggested that strength increased by refinement of AF due to increase in the concentration of alloying elements being contained in hot-wire. Larger elongation of weld metal in F-MAG compared with that in MAG could be analyzed in terms of the Aggregate of acicular ferrite Laths with nearly Parallel Slip systems between neighboring acicular ferrite laths (ALPS). The number of AFs contained in an ALPS formed with F-MAG is larger than that with MAG, in spite of the sizes of ALPSs formed with MAG and F-MAG being almost same. Deformation occurs over a lot of AFs in the case of finer AF formed with F-MAG through the rotation of tensile test piece during deformation, resulting in the larger elongation.

DOI： 10.2207/qjjws.31.104

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Effects of additions of CeO2 and La2O3 on microstructure and mechanical properties of B4C fabricated under and without hot press have been investigated. Vickers hardness and fracture strength are increased by hot press due to the reduction of porosity because the sintering rate is enhanced. Hardness is increased by the reduction of porosity because crack probably occurs when the hardness is measured due to pore as an initiation point of crack. Hardness increases with increasing additions of CeO2 and La2O3 because porosity decreases due to the formation of CeB6 and LaB6 on the grain boundary of B4C, respectively. The borides are formed through reaction between solid phases, which might induce coherent boundary between boride and B4C. Such coherency also contributes to strengthening the grain boundary of B4C. The addition of CeO2 enhances the sintering rate more than that of La2O3, resulting in higher hardness of B4C-CeO2 than that of B4C-La2O3. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2011.01.072

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記述言語：日本語   出版者・発行元：レーザ加工学会  

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Formations of Cu-rich precipitate in 18%Cr-1.5%Cu stainless steels without and with 0.5%Nb have been examined mainly using transmission electron microscopy. The specimens solution-treated at 1250°C were isothermally transformed at various temperatures between 500 and 850°C. Fine spherical Cu-rich solute zones were nucleated in the steels in the beginning of aging. These Cu-rich zones exhibited bcc structure and then transformed into 9R structure with twins during aging. The spherical 9R-Cu particles changed into rod-shaped fcc-Cu particles after prolonged aging. Laves phase of Fe 2Nb type started to form in the Nb-added steel almost after finishing nucleation and growth of Cu particles. Addition of Nb in the steel delayed the nucleation of the Cu-rich zones due to slow diffusion of Nb atoms in ferrite. © 2011 ISIJ.

DOI： 10.2355/isijinternational.51.657

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記述言語：英語   出版者・発行元：IRON STEEL INST JAPAN KEIDANREN KAIKAN  

Bainite lath nucleated WithIN Grain (BWING) has been clarified to be greatly effective for the increase in both strength and toughness. The nucleation of BWING has been enhanced by the introduction of inclusion into austenite, which would act as nucleation site for BWING. However, the inclusion itself would be brittle and at the interface between inclusion and matrix, high density of dislocations are apt to be accumulated under deformation, inducing cleavage at the interface. As density of inclusion increases, steel would be strengthened, but brittle. Therefore, the introduction of dislocation network, that is, Small-Angle Dislocation Network (SADN) into austenite is tried in the present work. SADN would be stable in the high temperature region such as in austenite, because pinned dislocation existed in SADN would prevent the bow-out of dislocations through absorbing point defects. The formation of SADN in austenite, which act as nucleation site for BWING, was clarified experimentally. The bainite lath neighbor to the nucleated one might be formed under relaxing the stress field around the nucleated one and/or inclusion. It was analyzed that the average size of Aggregates of bainite Laths having nearly Parallel Slip systems between neighboring bainite laths (ALPS) corresponds to that of dimples on fracture surface. The process for ductile fracture is offered based on the crystallographic analysis using transmission electron microscopy. © 2011 ISIJ.

DOI： 10.2355/isijinternational.51.274

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記述言語：日本語   出版者・発行元：一般社団法人 日本原子力学会  

核破砕中性子源ターゲットして利用されているタングステンは、再結晶脆化が大きな課題である。本研究では、これまで至難と考えられてきた再結晶脆化を克服するために、再結晶・粒成長過程で導入される極めて弱い粒界の強化及び残留気孔の除去を再結晶組織で初めて実現することにより、再結晶・粒成長状態において靭性に優れるナノ組織W-1%TiC材料を開発したので、その成果を報告する。

DOI： 10.11561/aesj.2010s.0.414.0

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A model for the nucleation and growth processes of Sn whisker is offered. High density of localized screw dislocations by deformation form the dense spiral steps of atomic scale on Sn surface. The spiral steps would induce the nucleation of Sn whisker. Edge dislocations localized at the same region where the dense screw dislocations exist supply Sn atoms to Sn whisker through pipe diffusion. Both screw and edge dislocations would bend along almost one direction, namely, to relax the external shear stress. The image force also helps to bend the dislocations perpendicular to the whisker side-surface. The bending of dislocations at root of whisker leads the bend of whisker. The pipe diffusion of Sn atoms through edge dislocations from bulk Sn toward whisker is suppressed at the bent part of edge dislocation, resulting in release of Sn atoms inside whisker and leading to the growth of whisker near its root. © (2010) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/MSF.638-642.2688

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記述言語：英語   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Precipitation behavior of a metastable beta Ti alloy, Ti-6.8Mo-4 5Fc- I 5A1(masss%), during two-step aging has been investigated Supersaturated beta phase after solution treatment decomposes into beta+omega phases during the first aging at 300 degrees C for 2ks beta' phase is observed during the second aging at 500 degrees C for 50s. It is suggested that reverse transformation of the omega phase to beta phase during the second aging at 500 degrees C for 50s gives rise to solute-lean and rich regions in the beta phase, and that beta' phase is formed in the solute-rich region beta' phase being coherent with beta phase has larger lattice parameter than beta phase. beta phase acts as nucleation site for alpha phase, and accelerates the nucleation of alpha phase.

DOI： 10.4028/www.scientific.net/MSF.638-642.461

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記述言語：英語   出版者・発行元：TRANS TECH PUBLICATIONS LTD  

Isothermal phase transformation in Ti-15Nb-10Zr (at%) alloys has been examined by mainly means of transmission electron microscopy. Specimens solution-treated at 1000°C in β phase field were directly held at temperatures between 350 and 450°C for 1.8-86.4ks, which are called "DH (direct holding)-specimen". On the other hand, some specimens solution-treated at 1000° C were quenched into iced brine and then aged at temperatures between 350 and 450°C, which are called "QA(quench and aging)-specimen". In the DH-specimen held at 400°C ω phase formed in â matrix. Microstructure evolution of QA-specimen aged at 400°C, on the other hand, is as follows. ω phase formed in β matrix after aging for 1.8ks and further aging led to growth of ω phase. After prolonged aging, α phase started to form in β matrix. These experimental results indicate that process of the quenching and reheating promotes the formation of ω phase. Specimen quenched into iced brine after solution treatment exhibited α'' phase formation. The α'' phase in the quenched specimen would transform into β phase during reheating to the aging temperature. Reversion process of α'' → β phase could promote the formation of w phase in β. Microstructure formation in the DH- and QA-specimens at 350 and 450°C will also be explained. © (2010) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/MSF.638-642.582

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DOI： 10.4028/www.scientific.net/MSF.638-642.461

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DOI： 10.14853/pcersj.2009F.0.3B13.0

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

In order to improve the high temperature strength of fine-grained and particle-dispersed V alloys, V-1.6Y-8.5W-0.08C and V-1.6Y-8.5W-0.15C (wt%) were fabricated by mechanical alloying and hot isostatic pressing, followed by annealing at 1000 and 1200 °C for 3.6 ks. Dispersoids of Y2O3, V2C, WC and W2C are detected by X-ray diffraction in the 1000 and 1200 °C-annealed specimens. Tungsten dissolves in the V matrix after annealing at 1200 °C. Tensile tests were performed at temperatures from 800 to 1100 °C at initial strain rates from 1.0 × 10-4 to 1.0 × 10-2 s-1. The yield stress at 900 °C of 1200 °C-annealed V-1.6Y-8.5W-0.15C is approximately 2 times as high as that of V-4Cr-4Ti, due to combination of solution hardening by W and dispersion hardening by the dispersoids. The obtained stress exponent of plastic strain rate and activation energy for deformation suggest that the deformation of V-1.6Y-8.5W-0.08C and V-1.6Y-8.5W-0.15C is controlled by solute atmosphere dragging. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2008.12.187

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記述言語：英語   出版者・発行元：ELSEVIER SCIENCE BV  

Alloying process of vanadium-yttrium powders using mechanical alloying (MA) method was studied. Vanadium powder was compressed after 10 h MA, while yttrium powder was comminuted into small particles. Although yttrium powder was broken into small particles, yttrium scarcely dissolves into vanadium powder. Alloying of yttrium started after 20 h MA and finished after 40 h MA. Molybdenum particle, which came from milling vessels and balls, mixed into vanadium powder after 40 h MA and molybdenum started to dissolve into vanadium powder after 60 h MA. After 80 h MA, Y2O3 particles formed in vanadium powder. Oxygen required for the formation of Y2O3 particles was probably discharged from the vessel wall and balls after flaking of those surface layers. Since prolonged MA caused powder contamination, optimum MA time for making V-1.7Y alloy was 40 h. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2008.12.183

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A model for the nucleation and growth processes of Sn whisker is offered. High density of localized screw dislocations by deformation form the dense spiral steps of atomic scale on Sn surface. The spiral steps would induce the nucleation of Sn whisker. Edge dislocations localized at the same region where dense screw dislocations exist supply Sn atoms to the Sn whisker through pipe diffusion. Both screw and edge dislocations would bend along almost one direction, namely, to relax the external shear stress. The image force also helps to bend the dislocations perpendicular to the whisker side-surface. The bending of dislocations at root of whisker leads the bend of whisker. The pipe diffusion of Sn atoms through edge dislocations from bulk Sn toward whisker is suppressed at the bent part of edge dislocation, resulting in release of Sn atoms inside whisker and leading to the growth of whisker near its root. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/165/1/012089

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