Faculty Profiles - TAKEMOTO Yoshito

Papers - TAKEMOTO Yoshito

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DEFORMATION-INDUCED TRANSFORMATION OF OMEGA-PHASE IN AGED TI-14 MASS-PERCENT-MO ALLOY Reviewed

Y TAKEMOTO, M HIDA, A SAKAKIBARA

JOURNAL OF THE JAPAN INSTITUTE OF METALS 59 ( 8 ) 780 - 787 1995

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS

Ti-14 mass%Mo alloys aged for 1x10(6) s at 623 K were deformed by means of a tensile test at 300, 523, 623 and 723 K in Ar atmosphere or of rolling at room temperature in order to investigate the brittle fracture mechanism related to the omega phase. These deformed specimens were observed by optical and transmission electron microscopy. Both deformed structures consisted of many band-like products. In the products, very few omega particles could be found. Instead, zones having a structure different from omega, beta and alpha phases existed. It was found that these zones possessed a body centered triclinic structure, which was newly named beta '' on account of the structural similarity to the beta phase. The beta '' was transformed from omega by deformation. In the transformation process to beta '', one omega variant changed into two types of beta ''; one was closely related to the beta matrix, and the other had a {112}[111] twin relation to the former. It is suggested that the band products act as a path of crack propagation prior to the brittle fracture in the aged Ti-Mo alloy.

DOI： 10.2320/jinstmet1952.59.8_780

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STRUCTURAL STABILITY AND MECHANOCHEMICAL ACTIVITY OF TITANIUM NITRIDE PREPARED BY MECHANICAL ALLOYING Reviewed

WY LIM, M HIDA, A SAKAKIBARA, Y TAKEMOTO, S YOKOMIZO

JOURNAL OF MATERIALS SCIENCE 28 ( 13 ) 3463 - 3466 1993.7

Language：English Publishing type：Research paper (scientific journal) Publisher：CHAPMAN HALL LTD

Pure titanium nitride (TiN) was synthesized by mechanical alloying (MA). In order to prevent the contamination from the MA vial and atmospheric gas, the MA steel vial was replaced with a titanium vial and atmospheric gas was deoxidized using sponge titanium heated to 623 K. The mechanochemical activity during MA was estimated from the gas purification temperature. The investigation of thermal and pressure stability by thermal treatment and hot isostatic pressing (HIP) revealed that titanium nitride, TiN, was stable on heating to 1173 K under a vacuum, but became unstable under a high pressure, 100 M Pa.

DOI： 10.1007/BF01159823

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Mechanism of ω→α Transformation in β-Ti Alloy Reviewed

J. Japan Inst. Metals 57 ( 3 ) 261 - 267 1993

STRUCTURAL RELAXATION OF INTERFACE OF (332) (113) TWIN IN BETA-TI ALLOY Reviewed

Y TAKEMOTO, M HIDA, A SAKAKIBARA

JOURNAL OF THE JAPAN INSTITUTE OF METALS 57 ( 12 ) 1471 - 1472 1993

THE DSC AND EXAFS STUDIES OF MECHANICAL AGITATION EFFECTS ON THE LOCAL-STRUCTURE OF SPLAT-COOLED AMORPHOUS NI75SI8B17 ALLOY Reviewed

M HIDA, Y TAKEMOTO, A SAKAKIBARA, H MAEDA

JOURNAL OF NON-CRYSTALLINE SOLIDS 144 ( 2-3 ) 196 - 202 1992.7

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Effects of mechanical agitation, extreme cold working, on the structural changes of splat-cooled amorphous alloy were investigated by the differential scanning calorimetry (DSC) and extended X-rav absorption fine structure (EXAFS) methods. The amorphous alloy composed of both matrix and Ni-enriched clusters did not have a detectable endothermic reaction. Since an amorphous alloy agitated by filing did have an endothermic reaction related to a decrease of glass transition temperature as measured by DSC. mechanical agitation has an effect on the structural relaxation and is interpreted with a proposed hierarchy diagram. The filed amorphous phase was changed by milling for 20 h into a chemically homogeneous amorphous state. Further. by milling for 100 h it eventually changed to an amorphous state such as a supercooled liquid matrix with small mean bond distance. Its glass transition temperature, T(g), was decreased to near room temperature. In this state, molecular clusters with large bond distance were separated as a precursor of metastable phase from the supercooled liquid.

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Ti Fiber-Reinforced and Ti Sheet-Enveloped Cast Mg Composite Reviewed

Moritaka Hida, Akira Sakakibara, Yoshito Takemoto, Hiroyuki Okada, Seiji Koga

journal of the japan society of powder and powder metallurgy 39 ( 6 ) 464 - 467 1992

DUCTILITY IMPROVEMENT OF TI-MO ALLOY DUE TO TITANIZING Reviewed

Y TAKEMOTO, M HIDA, A SAKAKIBARA, N NISHIDA

JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 ( 5 ) 524 - 530 1992

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS

Diffusion heat-treated Ti-20 mass % Mo (DHT) alloys were prepared by titanizing to improve the ductility, and tested in tension. The DHT alloy had a diffusion layer about 120-mu-m in thickness. The quenched DHT alloy was deformed by twinning in the surface layer and by slip in the interior. Many cracks were generated over the surface of the aged specimen during testing, but the propagation of these cracks were prevented at the interface between the titanized surface layer and the interior. Both the quenched and the aged DHT alloys were elongated well in comparison with non DHT alloys. The formation of diffusion layer in DHT alloy caused a mismatch of deformation modes between the surface layer and the interior.
It was observed using HR-TEM that the growth of omega-particles were remarkably retarded in the interior of aged DHT alloy, and the center of the omega-particle was reversely transformed to beta-phase. It was also found that an unusual fcc phase was formed by the stress induced stacking faults at the interface.

DOI： 10.2320/jinstmet1952.56.5_524

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SOLUTE ENRICHMENT IN THE OMEGA PHASE IN TI-14MO Reviewed

Y TAKEMOTO, M HIDA

SCRIPTA METALLURGICA ET MATERIALIA 25 ( 2 ) 299 - 302 1991.2

EXAFS AND DIFFRACTION STUDIES OF ATHERMAL AGITATION EFFECTS ON THE LOCAL-STRUCTURE OF AMORPHOUS NI75SI8B17 ALLOY Reviewed

M HIDA, H MAEDA, K KANI, H MORI, A SAKAKIBARA, Y TAKEMOTO

JOURNAL OF NON-CRYSTALLINE SOLIDS 117 ( 118 ) 144 - 147 1990.2

Mechanically Alloyed Ti-Mo Solid Solution and Its Microstructure Reviewed

Woo-Yeong Lim, Moritaka Hida, Akira Sakakibara, Yoshito Takemoto, Hironobu Meada, Eiichi Sukedai

J. Japan Society of Powder and Powder Metallurgy 37 ( 5 ) 636 - 639 1990

Language：Japanese Publisher：Japan Society of Powder and Powder Metallurgy

Mixture of Ti and Mo powders was mechanically alloyed to obtain β-type Ti-20mass-%Mo alloy. The mechanism of mechanical alloying(MA) of Ti-20mass%Mo and microstructure of its product were investigated by X-ray diffraction, XAFS and TEM. X-ray diffraction profile showed that complete alloying was attained by the 36ks-MA, but incompleteness was revealed by the analysis of XAFS. According to the result of XAFS, 144ks-MA was needed to accomplish alloying. The radial structural parameters of j-th shell, R _j, N _j and σ _j are obtained by curve fitting method on a two-shell, double Mo-Mo and Mo-Ti pairs. Nearest neighbor bond length(R _j) decreased with the time of MA. From the observation of TEM, it was revealed that mechanically alloyed particle was composed of small domains with different lattice images in direction, like subgrains. Deformation of the lattice image was also recognized for the MA specimen.

DOI： 10.2497/jjspm.37.636

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Other Link： https://jlc.jst.go.jp/DN/JALC/00003555705?from=CiNii

CHANGE OF DEFORMATION MODE CAUSED BY AGING OF TI-14 MASS-PERCENT MO ALLOY SINGLE-CRYSTALS AND EMBRITTLEMENT MECHANISM DUE TO THE OMEGA-PHASE Reviewed

Y TAKEMOTO, M HIDA, E SUKEDAI, A SAKAKIBARA

JOURNAL OF THE JAPAN INSTITUTE OF METALS 53 ( 10 ) 1004 - 1012 1989.10

INFLUENCES OF ENVIRONMENT IN HEAT-TREATMENT AND PRE-AGING AT ROOM-TEMPERATURE ON AGE-HARDENING OF TI-MO ALLOYS Reviewed

M HIDA, E SUKEDAI, Y TAKEMOTO

MATERIALS TRANSACTIONS JIM 30 ( 2 ) 102 - 106 1989.2

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