Papers - HAGIHARA Koji
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Operative slip systems and anomalous strengthening in Ni3Nb single crystals with the D0a structure Reviewed
Y. Umakoshi, K. Hagihara, T. Nakano
Intermetallics 9 ( 10-11 ) 955 - 961 2001.10
Language：English Publishing type：Research paper (scientific journal)
The plastic deformation behavior of Ni3Nb single crystals was examined in tension and compression to determine the operative slip and twinning systems, and to explore the anomalous strengthening behavior. A strong temperature dependence of the CRSS for both the slip and twinning systems was observed, which was dependent on the sample orientation. Anomalous flow behavior was also observed in Ni3Nb crystals deformed by (010)[100] and (001)[100] slip. The anomalous strengthening mechanism is discussed on the basis of both the anisotropy of APB energy and the formation of dragging atmosphere around moving dislocations. © 2001 Elsevier Science Ltd. All rights reserved.
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Cyclic deformation behavior of Ni3Nb single crystals deforming by slip on (010)[100] Reviewed
K. Hagihara, T. Nakano, Y. Umakoshi
Intermetallics 9 239 - 244 2001.08
Publishing type：Research paper (scientific journal)
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Plastic deformation behaviour of Ni-based intermetallics single crystals for high-temperature heat-resistance
HAGIHARA Koji, NAKANO Takayoshi, UMAKOSHI Yukichi
27 ( 4 ) (22) 2001.07
Language：Japanese Publishing type：Research paper (scientific journal)
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Deformation twins in Ni3Nb single crystals with DOa structure Reviewed
K. Hagihara, T. Nakano, Y. Umakoshi
Mat. Res. Soc. Sympo. Proc 646 N5.23.1 2001.03
Language：English Publishing type：Research paper (international conference proceedings)
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Cyclic deformation behavior of Ni3Nb single crystals deforming by slip on (010)[100]
K Hagihara, T Nakano, Y Umakoshi
INTERMETALLICS 9 ( 3 ) 239 - 244 2001.03
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD
Cyclic deformation behavior in Ni3Nb single crystals deforming by slip on (010)[100] was investigated. Fatigue tests were performed in a symmetrical push/pull mode at a fixed total strain amplitude (Delta epsilon) from +/-0.06 to +/-0.30% at ambient temperature. The cyclic hardening behavior varied below and above Delta epsilon = +/-0.15%. In the low strain amplitude group. the maximum stress amplitude reached a saturated value after initial strong hardening. while the cyclic hardening behavior in the high strain amplitude group were divided into three stages including the initial strong hardening. This initial strong hardening is related to the exhaustion hardening caused by the Kear-Wilsdorf locking. The hardening mechanism in each stage is discussed focusing on the cyclic stress-strain behavior, slip trace morphology and dislocation structure, (C) 2001 Elsevier Science Ltd. All rights reserved.
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Deformation Substructure in Ni_3Nb Single Crystals with the D0_a Struntre
HAGIHARA Kouji, NAKANO Takayoshi, UMAKOSHI Yukichi
Materia Japan 39 ( 12 ) 996 - 996 2000.12
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japan Institute of Metals and Materials
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Plastic deformation behaviour and operative slip systems in Ni3Nb single crystals Reviewed
K. Hagihara, T. Nakano, Y. Umakoshi
Acta Materialia 48 1469 - 1480 2000.05
Publishing type：Research paper (scientific journal)
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Plastic deformation behaviour and operative slip systems in Ni3Nb single crystals
K Hagihara, T Nakano, Y Umakoshi
ACTA MATERIALIA 48 ( 7 ) 1469 - 1480 2000.04
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
Temperature and orientation dependence of yield stress and operative slip system in Ni3Nb single crystals were examined. Four slip systems of (010)[100], (001)[100], {201}[10 (2) over bar] and (010)[001] and three twinning systems of {011}[0 (1) over bar 1], {211}[<(10)over bar> 7 13] and {012}[0 (2) over bar 1] were activated depending on the crystal orientation and tested temperature. Anomalous strengthening was observed for some orientations where (010)[100] or {201}[10 (2) over bar] slip was operative. A remarkable increase in the critical resolved shear stress (CRSS) for the (010)[100] slip occurred over a wide temperature range from -196 to 800 degrees C. The CRSS did not satisfy Schmid's law and the strain rate sensitivity of flow stress at a small plastic strain was negligible between room temperature and 700 degrees C where an anomalous stress increase occurred. The anomalous strengthening mechanism in Ni3Nb crystals deformed by [100] dislocations was discussed on the basis of anisotropy of APE energy on (010) and (001) in analogy with that in Ni3Al with the L1(2) structure. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.
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Strength and deformation mechanism of C40-based single crystal and polycrystalline silicides Reviewed
Y. Umakoshi, T. Nakano, K. Kishimoto, D. Furuta, K. Hagihara, M. Azuma
Materials Science and Engineering A 261 113 - 121 1999.10
Publishing type：Research paper (scientific journal)
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Plastic Deformation Behavior of Ni3Nb Single Crystals Reviewed
Koji Hagihara, Takayoshi Nakano, Yukichi Umakoshi
Proceedings of MRS Symposium 552 KK10.7.1 1999.09
Language：English Publishing type：Research paper (international conference proceedings)
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Plastic deformation behaviour of Ni<sub>3</sub>Nb single crystals
Koji Hagihara
MRS Sympo. Proc. : High temperature Ordered Intermetallics Alloys . 552 KK10.7.1 1999
Publishing type：Research paper (scientific journal)
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Mechanical properties of C40-based ternary Mo(Si,Al)2 and quaternary (Mo,Zr)(Si,Al)2 silicides Reviewed
K. Hagihara, T. Nakano, Y. Umakoshi
Scripta Materialia 38 471 - 476 1998.10
Publishing type：Research paper (scientific journal)
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Mechanical properties of C40-based ternary Mo(Si,Al)(2) and quaternary (Mo,Zr)(Si,Al)(2) silicides
K Hagihara, T Nakano, Y Umakoshi
SCRIPTA MATERIALIA 38 ( 3 ) 471 - 476 1998.01
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
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Stress anomaly in Al-rich Ti-Al single crystals deformed by the motion of 1/2〈110] ordinary dislocations Reviewed
T. Nakano, K. Hagihara, T. Seno, N. Sumida, M. Yamamoto, Y. Umakoshi
Philosophical Magazine Letters 78 ( 5 ) 385 - 391 1998
Language：English Publishing type：Research paper (scientific journal)
The microstructure and plastic deformation behaviour of Al-rich Ti-Al single crystals containing 54.7 and 58.0at.%Al have been examined, focusing on the effect of chemical ordering of a Al5Ti3superstructure on anomalous strengthening. Fine precipitates with the Al5Ti3 superstructure were developed in the L10matrix of the Ti-58.0 at. % Al alloy. The size and volume fraction of the precipitates varied depending on temperature. An anomalous increase in the yield stress of the two alloys appeared at around 800°C. This strengthening mechanism is discussed on the basis of the difference in antiphase-b oundary energies on (111), (110) and (001) planes in the Al5Ti3phase. © 1998 Taylor &
Francis Ltd.
