Updated on 2024/10/01

Information

 

写真a

 
YAMASAKI SHIGETO
 
Organization
Faculty of Engineering Department of Materials Science and Engineering Associate Professor
School of Engineering (Concurrent)
Graduate School of Engineering (Concurrent)
Title
Associate Professor
Contact information
メールアドレス
Tel
0928022949
External link

Degree

  • Dr. Eng.

Research Interests・Research Keywords

  • Research theme: High temperature deformation of metals and alloys

    Keyword: creep, Portevin-LeChatelier Effect

    Research period: 2007.4

Awards

  • 研究奨励賞

    2021.3   日本鉄鋼協会  

  • 日本鉄鋼協会 研究奨励賞

    2021.3   日本鉄鋼協会  

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    日本鉄鋼協会より、鉄鋼及びその関連領域において優れた研究実績を挙げている若手研究・技術者に送られる賞

  • 俵論文賞

    2019.3   日本鉄鋼協会  

  • 日本鉄鋼協会 俵論文賞

    2019.3   日本鉄鋼協会  

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    研究論文(伊藤孝矩, 山﨑重人, 光原昌寿, 中島英治, 西田稔, 米村光治: 「金属間化合物により粒界被覆した多結晶Ni基耐熱合金の微細組織とクリープ特性」, 鉄と鋼, Vol.103, No.7, pp.434-442.)の内容が高く評価されたもの。

  • 金属組織写真賞 第2部門 奨励賞

    2016.3   日本金属学会  

  • 日本金属学会 第66回金属組織写真賞, 奨励賞

    2016.3   日本金属学会  

  • TOP 25 most downloaded articles for Scripta Materialia in the period April to June 2015

    2015.12   Elsevier  

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Papers

  • Relationship between Creep Strength and Magnetic Properties of Cobalt-bearing High Chromium Ferritic Steel Reviewed International journal

    Yamasaki, S., Mitsuhara, M. & Nakashima, H.

    isij international   2021.1

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • コバルト含有高クロムフェライト鋼のクリープ強度と磁気特性の関係 Reviewed

    山﨑重人, 光原昌寿 & 中島英治,

    鉄と鋼   2020.11

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • Evaluation of depth of dislocation visibility in SEM electron channeling contrast imaging in Ti-6Al-4V alloy using serial sectioning method Reviewed International journal

    Yamasaki, S., Deguchi, M., Mitsuhara, M., Nakashima, H., Ota, Y. & Kubushiro, K.

    Microscopy   2020.10

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

  • Kink Formation Process in Long-Period Stacking Ordered Mg-Zn-Y Alloy Reviewed International journal

    Shigeto Yamasaki, Tsubasa Tokuzumi Wansong Li, Masatoshi Mitsuhara, Koji Hagihara, Toshiyuki Fujii, Hideharu Nakashima

    Acta Materialia   195 ( 15 )   25 - 34   2020.8

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1016/j.actamat.2020.04.051

  • 窒素を有効利用した700℃級次世代耐熱フェライト鋼の開発

    山﨑重人、光原昌寿、中島英治

    ふぇらむ   24 ( 8 )   498 - 504   2019.8

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  • Effect of Fe addition on heat-resistant aluminum alloys produced by selective laser melting Reviewed

    Shigeto Yamasaki, Tomo Okuhira, Masatoshi Mitsuhara, Hideharu Nakashima, Jun Kusui, Mitsuru Adachi

    Metals   9 ( 4 )   2019.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.3390/met9040468

  • Development of high-chromium ferritic heat-resistant steels with high nitrogen content Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    isij international   58 ( 6 )   1146 - 1154   2018.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/isijinternational.ISIJINT-2017-758

  • Deformation microstructure and fracture behavior in creep-exposed Alloy 617 Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Materials Transactions   58 ( 3 )   442 - 449   2017.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2320/matertrans.M2016407

  • Evaluation of local creep strain in face-centred cubic heatresistant alloys using electron backscattered diffraction analysis Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Mitsuharu Yonemura

    isij international   57 ( 5 )   851 - 856   2017.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/isijinternational.ISIJINT-2016-712

  • Development of high-chromium ferritic heat-resistant steels with high-nitrogen addition Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan   103 ( 1 )   64 - 72   2017.1

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/tetsutohagane.TETSU-2016-057

  • 3D visualization of dislocation arrangement using scanning electron microscope serial sectioning method Reviewed

    S. Yamasaki, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima

    Scripta Materialia   101   80 - 83   2015.5

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.scriptamat.2015.02.001

  • Low stress creep deformation in high chromium ferritic heat-resistant steel evaluated by helicoid spring creep test method Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima

    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan   100 ( 5 )   688 - 695   2014.5

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/tetsutohagane.100.688

  • Low-stress creep deformation in long-term aged ferritic heat-resistant steel Reviewed

    Shigeto Yamasaki, Masatoshi Mitsuhara, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima

    Materials Transactions   55 ( 5 )   842 - 849   2014.5

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    DOI: 10.2320/matertrans.M2013427

  • Strain Rate Dependence of Slip Persistence in TiZrNbHfTa Investigated with Microcantilever Bending Tests

    Tanaka Masaki, Yamasaki Shigeto, Morikawa Tatsuya

    MATERIALS TRANSACTIONS   65 ( 9 )   1055 - 1060   2024.9   ISSN:13459678 eISSN:13475320

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    Language:English   Publisher:The Japan Institute of Metals and Materials  

    <p>The strain-rate dependence of slip persistence in TiZrNbHfTa was investigated using microcantilever bending tests instead of conventional single-crystal tensile tests. These tests were performed using micrometre-sized cantilevers fabricated within a grain of the polycrystalline material, and the ψ–χ relationship was obtained in detail. Bending tests were conducted in two strain rates to determine the ψ–χ relationship. The results showed that the slip plane macroscopically persisted on the {112} plane in the high-strain-rate test, while in the low-strain-rate test, the apparent slip plane roughly coincided with the plane where the maximum shear stress was applied. Detailed tracing of the slip bands, using atomic force microscopy, on the specimen surface showed that the slip plane was microscopically persisted on the {112} plane in high-strain-rate tests, while in low-strain-rate tests, the slip plane often cross-slipped between the {112} and {110} planes.</p>

    DOI: 10.2320/matertrans.mt-ma2024010

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  • Mapping of Microscopic and Local Stress-Strain Curve Information by Combination of Digital Image Correlation and High-Resolution Electron Backscatter Diffraction Methods

    Yamasaki Shigeto, Matsuo Hirofumi, Morikawa Tatsuya, Tanaka Masaki

    Journal of the Japan Institute of Metals and Materials   88 ( 9 )   216 - 225   2024.9   ISSN:00214876 eISSN:18806880

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    Language:Japanese   Publisher:The Japan Institute of Metals and Materials  

    <p>Microscopic stress-strain curves were obtained by applying stress measurements using the HR-EBSD method and strain measurements using the DIC method to the same field of view in SEM <i>in-situ</i> tensile tests. From the analysis of these microscopic stress-strain curves, yield stress map and work hardening rate map were successfully produced. The relationship between these mechanical property value maps and the microstructure is investigated. The yield stress maps confirm the tendency of the local yield stress to show different values for different grains, but the Schmid factor alone cannot explain the magnitude of the yield stress. When adjacent grains with significantly different Schmid factors deformed cooperatively, the yield stress is found to increase as a result of stress partitioning. Localized regions of extreme work hardening rates were observed in the work hardening rate maps. These regions were located close to grain boundaries with low <i>m</i>′ values where slip transfer was difficult and an interruption of the slip bands was observed. In addition, the rate of increase of GND density with strain was large in these regions. From these results, it can be understood that the extreme work hardening rates are due to increased back stresses caused by the accumulation of dislocations on low <i>m</i>′ grain boundaries.</p>

    DOI: 10.2320/jinstmet.j202404

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  • Plastic anisotropy in yield stress of drawn pearlitic steels

    Takumi Akada, Rintaro Ueji, Masatoshi Mitsuhara, Shigeto Yamasaki, Masaki Tanaka

    Materials Science and Engineering: A   898   2024.4   ISSN:0921-5093 eISSN:1873-4936

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    Plastic anisotropy in the yield stress of pearlitic steels evolved by drawing was studied. The tension and compression tests were performed in parallel and perpendicular directions to the drawing direction. The yield stress in the parallel tension and vertical compression tests increased with the increase in drawing strain. On the other hand, in the parallel compression, the yield stress decreased significantly at the small drawing strain and then increased at the larger strain. The difference between the yield stress at the tension and at the compression did not change largely after the start of the drawing. The observation of microstructure indicated no significant heterogeneity of the deformation microstructure and texture at the different locations in the radial direction of the drawn samples, meaning that the plastic anisotropy was brought by reasons other than the non-uniformity of the deformation condition. The measurement of the distribution of the local misorientation in ferrite suggested the large plastic deformation even at smaller strain by drawing. This result indicates that the residual stress in plastically deformed ferrite brings back stress, which can be the source of the plastic anisotropy.

    DOI: 10.1016/j.msea.2024.146380

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  • Thermoelectric Properties of Ba<sub>8</sub>Cu<i><sub>x</sub></i>Si<i><sub>y</sub></i>Ge<sub>46-<i>x</i>-<i>y</i> </sub> Clathrates Synthesized by the Czochralski Method

    Takagi, K; Matsukawa, Y; Araki, S; Saeki, R; Yamasaki, S; Arita, M; Munetoh, S

    ACS APPLIED ENERGY MATERIALS   7 ( 7 )   2665 - 2670   2024.3   ISSN:2574-0962

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    A type-I clathrate Ba8CuxSiyGe46-x-y ingot consisting of millimeter-sized grains with different crystallographic orientations was synthesized by the Czochralski method. The lower part of the ingot contained more Cu and Ge within the clathrate phase. The electrical resistivities of the top, middle, and bottom of the ingot at 550 °C were 0.78, 1.72, and 1.55 mΩ·cm, respectively. The differences in these values are consistent with the carrier concentration and calculated anisotropic effective mass of the electrons, which are based on the actual chemical composition and crystal orientation, respectively. The resistivity of the top part with few grain boundaries is less than a quarter of that of the hot-pressed sample with a similar composition. Despite the different carrier concentrations, the Seebeck coefficient of all parts had similar values of approximately −120 μV/K at 550 °C. The thermal conductivity at 350 °C was approximately 3.0 W/m·K for top part and 2.5 W/m·K for middle and bottom parts, about 1.5-1.8 times larger than those of previous reported hot-pressed samples. The power factor and dimensionless figure of merit ZT value of the top reached 18.8 μW/cm·K2 and 0.34, respectively. These results indicate that fabrication by the Czochralski method can improve the thermoelectric performance of Ba8CuxSiyGe46-x-y clathrates.

    DOI: 10.1021/acsaem.3c02961

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  • Bridging between Heterogeneous Local Strain Distribution and Macroscopic Stress-strain Curves

    Takahashi Manabu, Ueno Kotaro, Sakaguchi Kenta, Hayashi Kohtaro, Kawata Hiroyuki, Yamasaki Shigeto

    Tetsu-to-Hagane   110 ( 3 )   90 - 100   2024.2   ISSN:00211575 eISSN:18832954

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    Language:Japanese   Publisher:The Iron and Steel Institute of Japan  

    <p>A modified continuum composite model was utilized to analyze the stress–strain behavior of as-quenched steels with a fully martensitic microstructure. The model was employed to express the stress–strain curves obtained by a simple tensile test and those obtained by forward and backward loading using a simple shear test machine. The study confirmed that the model can represent the stress–strain behavior under both forward and backward deformation. In addition, the evolution of local strain distributions during plastic deformation was investigated using a digital image correlation method. The strain distributions and their evolution during deformation were qualitatively represented using this model. The discrepancies between the model calculations and experiments are due to the limitations of the iso-work assumption and the impact of slip deformation on the macroscopic work-hardening behavior of martensitic steels. Highly strain-concentrated regions aligned along the longitudinal direction of the lath and block, known as in-lath-plane slips, may not play an important role in the work-hardening behavior of as-quenched martensitic steels. However, the other slips, namely the out-of-lath slip, may play a significant role in the work hardening of as-quenched martensitic steels.</p>

    DOI: 10.2355/tetsutohagane.tetsu-2023-063

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  • Bridging between Heterogeneous Local Strain Distribution and Macroscopic Stress-strain Curves

    Takahashi Manabu, Ueno Kotaro, Sakaguchi Kenta, Hayashi Kohtaro, Kawata Hiroyuki, Yamasaki Shigeto

    ISIJ International   64 ( 2 )   345 - 353   2024.1   ISSN:09151559 eISSN:13475460

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    Language:English   Publisher:The Iron and Steel Institute of Japan  

    <p>A modified continuum composite model was utilized to analyze the stress–strain behavior of as-quenched steels with a fully martensitic microstructure. The model was employed to express the stress–strain curves obtained by a simple tensile test and those obtained by forward and backward loading using a simple shear test machine. The study confirmed that the model can represent the stress–strain behavior under both forward and backward deformation. In addition, the evolution of local strain distributions during plastic deformation was investigated using a digital image correlation method. The strain distributions and their evolution during deformation were qualitatively represented using this model. The discrepancies between the model calculations and experiments are due to the limitations of the iso-work assumption and the impact of slip deformation on the macroscopic work-hardening behavior of martensitic steels. Highly strain-concentrated regions aligned along the longitudinal direction of the lath and block, known as in-lath-plane slips, may not play an important role in the work-hardening behavior of as-quenched martensitic steels. However, the other slips, namely the out-of-lath slip, may play a significant role in the work hardening of as-quenched martensitic steels.</p>

    DOI: 10.2355/isijinternational.isijint-2023-140

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  • Three-Dimensional Observation of Dislocation Structure by FIB-SEM

    Yamasaki Shigeto

    KENBIKYO   58 ( 3 )   90 - 94   2023.12   ISSN:13490958 eISSN:24342386

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    Language:Japanese   Publisher:The Japanese Society of Microscopy  

    <p>Three-dimensional visualization of dislocations by serial sectioning of SEM-ECCI images was performed on a creep-deformed nickel-based heat-resistant alloy. By performing serial tomograms of ECCI images, a volume of approximately 5 μm × 5 μm × 0.3 μm volume was successfully reconstructed. By incorporating the crystal orientation information obtained by the SEM-EBSD method, we confirmed that the three-dimensional arrangement of dislocations, such as slip planes and cross-slip, is accurately reflected in the three-dimensional volume. Thus, serial sectioning of ECCI images enables us to observe and analyze the bulk dislocation microstructure in three dimensions in the micrometer scale range.</p>

    DOI: 10.11410/kenbikyo.58.3_90

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  • Temperature dependence of deformation and fracture in a beta titanium alloy of Ti-22V-4Al

    Yano Rei, Tanaka Masaki, Yamasaki Shigeto, Morikawa Tatsuya, Tsuru Tomohito

    Journal of Japan Institute of Light Metals   73 ( 10 )   497 - 503   2023.10   ISSN:04515994 eISSN:18808018

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    <p>Impact tests and tensile tests were conducted between 77 K and 450 K in order to elucidate the temperature dependence of absorbed-impact energy, yield stress, effective shear stress, activation volume, and activation enthalpy. The impact-absorbed energy decreased with decreasing test temperature, however, this alloy did not undergo low-temperature embrittlement although it has a bcc structure. Tensile tests showed changes in both the work-hardening rate and the temperature dependence of yield stress at approximately 150 K. This suggests a change in the mechanism behind the plastic deformation at the temperature. The temperature dependence of the activation enthalpy for dislocation glide suggests that the process of climbing over the Peierls potential (kink-pair nucleation) is the dominant mechanism for the dislocation glide from 150 K to 200 K, while the interaction between a dislocation and solute atoms dominantly controls the dislocation glide above 200 K. Superelasticity appears in stress-strain curves tested below 120 K, suggesting that the yielding is governed by transformation-induced plasticity below 120 K. The enhanced toughness at low temperatures in these alloys is discussed from the viewpoint of dislocation shielding theory.</p>

    DOI: 10.2464/jilm.73.497

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  • Acquisition of microscopic and local stress-strain curves by combination of HR-EBSD and DIC methods

    Shigeto Yamasaki, Hirofumi Matsuo, Tatsuya Morikawa, Masaki Tanaka

    Scripta Materialia   235   115603 - 115603   2023.10   ISSN:1359-6462 eISSN:1872-8456

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    Language:Others   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    A method for obtaining microscopic and localized stress-strain curves is proposed by combining strain measurements using the digital image correlation (DIC) method with stress measurements using high-resolution electron backscattered diffraction (HR-EBSD). A dataset containing 11 steps of stress–strain information in a single subset was created by applying georeferencing to DIC strain maps and HR-EBSD stress maps measured in a deformation-interrupted microstructure. This analysis allowed us to obtain local stress-strain curves and strain energy maps of polycrystalline nickel alloys. A comparison of the stress-strain curves obtained from any subset in the map revealed that these curves show extremely diverse shapes depending on the location in the microstructure.

    DOI: 10.1016/j.scriptamat.2023.115603

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  • Micromechanical testing for quantitative characterization of apparent slip system: Extinction of persistence of slip in carbon bearing Fe-3% Si

    Tanaka Masaki, Takenaka Masanori, Yamasaki Shigeto, Morikawa Tatsuya

    Scripta Materialia   232   115473   2023.7   ISSN:13596462

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    The effect of carbon on the persistence of the slip in Fe–3 mass% Si was investigated. We applied micro-sized cantilever bending tests to obtain ψ–χ relationships that enable quantitative analysis of the persistence of the slip. It was demonstrated that the result from decarburized specimens using this method is consistent with those obtained in previous studies from bulk-sized tensile test specimens. This novel method eliminates the difficulty of preparing bulk-sized single-crystal specimens for investigating the persistence of the slip. The persistence of the slip weakened in aged specimens containing 0.016 mass% C and disappeared in quenched specimens with the same carbon content, where wavy slip bands were observed. The reason for these changes in the macroscopically apparent slip plane is explained by the assumption that the frequency of nucleating kink-pair in the competitive {110} planes is a function of the resolved shear stress.

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  • Micromechanical testing for quantitative characterization of apparent slip system: Extinction of persistence of slip in carbon bearing Fe-3% Si

    Masaki Tanaka, Masanori Takenaka, Shigeto Yamasaki, Tatsuya Morikawa

    Scripta Materialia   232   2023.7   ISSN:1359-6462 eISSN:1872-8456

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    The effect of carbon on the persistence of the slip in Fe–3 mass% Si was investigated. We applied micro-sized cantilever bending tests to obtain ψ–χ relationships that enable quantitative analysis of the persistence of the slip. It was demonstrated that the result from decarburized specimens using this method is consistent with those obtained in previous studies from bulk-sized tensile test specimens. This novel method eliminates the difficulty of preparing bulk-sized single-crystal specimens for investigating the persistence of the slip. The persistence of the slip weakened in aged specimens containing 0.016 mass% C and disappeared in quenched specimens with the same carbon content, where wavy slip bands were observed. The reason for these changes in the macroscopically apparent slip plane is explained by the assumption that the frequency of nucleating kink-pair in the competitive {110} planes is a function of the resolved shear stress.

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  • Temperature dependence of the yield stress in TiZrNbHfTa body-centred cubic high-entropy alloy

    Tanaka Masaki, Yamasaki Shigeto, Morikawa Tatsuya

    Materials Science and Engineering A   871   144917   2023.4   ISSN:09215093 eISSN:18734936

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    Body-centred cubic (bcc) high-entropy alloys exhibit high strength. However, their yield behaviour and controlling mechanisms are still ambiguous. In this study, the temperature dependence of the yield stress, effective stress, activation volume, and activation enthalpy in a polycrystalline bcc refractory high-entropy alloy of TiZrNbHfTa were measured by tensile tests at 77–750 K. At temperatures above 650 K, the temperature dependence of the yield stress disappeared, and serration appeared in stress–strain curves. By extrapolating the effective shear stress to 0 K, the Peierls stress was estimated to be 580 MPa. The value was compared with different crystals using the relationship (τ_p)/(μ) and (h)/(b) , where τ_p is the Peierls stress, μ is the shear modulus, h is the distance between the slip planes, and b is the Burgers vector. The (τ_p)/(μ) value in this study was slightly higher than that of other bcc crystals. The activation enthalpy below 260 K corresponds to that of other bcc crystals with high Peierls potentials, suggesting kink-pair nucleation is the controlling mechanism of the dislocation glide in this temperature range. Meanwhile, the activation enthalpy above 260 K deviated from the trendline, indicating the changes in the dislocation glide from the kink-pair nucleation to other one.

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  • Temperature dependence of the yield stress in TiZrNbHfTa body-centred cubic high-entropy alloy

    Masaki Tanaka, Shigeto Yamasaki, Tatsuya Morikawa

    Materials Science and Engineering: A   871   2023.4   ISSN:0921-5093 eISSN:1873-4936

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    Body-centred cubic (bcc) high-entropy alloys exhibit high strength. However, their yield behaviour and controlling mechanisms are still ambiguous. In this study, the temperature dependence of the yield stress, effective stress, activation volume, and activation enthalpy in a polycrystalline bcc refractory high-entropy alloy of TiZrNbHfTa were measured by tensile tests at 77–750 K. At temperatures above 650 K, the temperature dependence of the yield stress disappeared, and serration appeared in stress–strain curves. By extrapolating the effective shear stress to 0 K, the Peierls stress was estimated to be 580 MPa. The value was compared with different crystals using the relationship [Formula presented] and [Formula presented], where τp is the Peierls stress, μ is the shear modulus, h is the distance between the slip planes, and b is the Burgers vector. The [Formula presented] value in this study was slightly higher than that of other bcc crystals. The activation enthalpy below 260 K corresponds to that of other bcc crystals with high Peierls potentials, suggesting kink-pair nucleation is the controlling mechanism of the dislocation glide in this temperature range. Meanwhile, the activation enthalpy above 260 K deviated from the trendline, indicating the changes in the dislocation glide from the kink-pair nucleation to other one.

    DOI: 10.1016/j.msea.2023.144917

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  • Role of disclinations around kink bands on deformation behavior in Mg–Zn–Y alloys with a long-period stacking ordered phase

    Tsubasa Tokuzumi, Masatoshi Mitsuhara, Shigeto Yamasaki, Tomonari Inamura, Toshiyuki Fujii, Hideharu Nakashima

    Acta Materialia   248   2023.4   ISSN:1359-6454 eISSN:1873-2453

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    Mg–Zn–Y alloys that contain an Mg-based long-period stacking ordered (LPSO) phase exhibit excellent mechanical properties because of the kink bands formed by plastic deformation. Such “kink-band strengthening” has attracted significant attention. Herein, we conducted deformation tests on directionally solidified single-phase LPSO Mg85Zn6Y9 alloys to investigate the kink-band strengthening mechanism. High-angular resolution electron backscatter diffraction was performed to detect misorientation between the matrices on either side of the kink bands. The misorientations corresponded to the magnitudes of the Frank vectors of the disclinations around the kink, and closely matched the estimations from geometric analysis, which supported the existence of disclinations. Moreover, the Frank vector of the kink bands increased after shear deformation, which indicates that shear deformation introduced new disclinations around the kinks. Scanning electron microscopy demonstrated that the kinks clearly obstructed basal ⟨a⟩ slip. Furthermore, scanning transmission electron microscopy of a sheared kink band revealed dislocation pile-ups on both sides of the kink/matrix interface, as well as the formation of secondary kinks that stabilized the structure against shear deformation (i.e., self-accommodation) and bend contours caused by elastic stress fields. The results suggest that disclinations behave as long-range obstacles to dislocation motion (e.g., by reducing the increase in kink-band self-energy or by the elastic stress field of disclinations). We believe that this study will play a key role in identifying the factors responsible for kink-band strengthening in LPSO-phase Mg alloys and in understanding the phenomena underlying the strengthening mechanism.

    DOI: 10.1016/j.actamat.2023.118785

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  • Tensile Deformation Behaviors of Pure Ti with Different Grain Sizes under Wide-Range of Strain Rate

    Misaki Deguchi, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Genki Tsukamoto, Tomonori Kunieda

    Materials   16 ( 2 )   2023.1   ISSN:1996-1944 eISSN:1996-1944

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    In this study, pure titanium equivalent to Grade 1 was subjected to tensile tests at strain rates ranging from 10−6 to 100 s−1 to investigate the relationship between its mechanical properties and its twinning and slip. Deformation properties and microstructures of samples having average grain sizes of 210 μm (Ti-210), 30 μm (Ti-30), and 5 μm (Ti-5) were evaluated. With increasing strain rates, the 0.2% proof stress and ultimate tensile strength increased for all samples; the fracture strain increased for Ti-210, decreased for Ti-5, and changed negligibly for Ti-30. Comparing high (100 s−1) and low (10−6 s−1) strain rates, twinning occurred more frequently in Ti-30 and Ti-210 at high strain rates, but the frequency did not change in Ti-5. The frequency of 1st order pyramidal slip tended to be higher in Ti-30 and Ti-5 at low strain rates. The higher ductility exhibited by Ti-210 at high strain rates was attributed to the high frequency of twinning. In contrast, the higher ductility of Ti-5 at low strain rates was attributed to the activity of the 1st order pyramidal slip.

    DOI: 10.3390/ma16020529

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  • Creep Deformation Behavior and Microstructure of Laves-strengthened Ferritic Heat-resistant Steels Containing Nitrogen or Carbon

    Yamasaki Shigeto, Mitsuhara Masatoshi, Nakashima Hideharu, Kimura Kazuhiro

    Tetsu-to-Hagane   109 ( 3 )   167 - 178   2023   ISSN:00211575 eISSN:18832954

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    <p>The creep deformation behavior and microstructure of a N-containing steel expected to exhibit high creep strength and excellent oxidation resistance were investigated. Even for steel with a high W content, it was possible to form a martensitic microstructure by adding a sufficient amount of N. Comparison of the microstructures of the N-containing steel and a C-containing steel confirmed that the two steels have the same crystal orientation relationship. The N-containing steel precipitated with the Laves phase as a strengthening phase displayed a higher creep strength than conventional steel under relatively high stress. However, the superiority of the creep strength of the N-containing steel relative to the conventional steel decreased under low stress. The stress exponent of the N-containing steel was different from those of the C-containing steel and the conventional steel. This deference considered to be ascribed to the difference of variation behavior of dislocation density during creep deformation.</p>

    DOI: 10.2355/tetsutohagane.tetsu-2022-065

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  • Microstructural Size Effect on Strain-Hardening of As-quenched Low Alloyed Martensitic Steels

    Takahashi M., Sakaguchi K., Kawata H., Hayashi K., Yamasaki S.

    28th IFHTSE 2023 Congress   2023   ISBN:9781713889533

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    Quenched martensitic steels are known to show the characteristic feature of stress-strain relations, with extremely low elastic limits and very large work-hardening. The continuum composite approach is one way to express this characteristic feature of stress-strain curves. Although the overall stress-strain curves, as a function of alloy chemistries of steels, were well represented by this approach, the relationship between the macroscopic deformation behaviors and microstructural information is yet to be clarified. A high-spatial-resolution digital image correlation analysis was conducted to demonstrate the possible unit size corresponding to the microstructure. The continuum composite approach model was also modified to consider the size effect of the microstructure on the stress-strain curves of the as-quenched martensitic steels. Strain concentrations were observed at various boundaries, including lath boundaries, and the characteristic microstructural size was also predicted by the present model, which is smaller than the reported spacing between adjacent strain-concentrated regions.

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  • Microstructural Size Effect on Strain-Hardening of As-Quenched Low-Alloyed Martensitic Steels

    Sakaguchi Kenta, Yamasaki Shigeto, Kawata Hiroyuki, Hayashi Kohtaro, Takahashi Manabu

    ISIJ International   62 ( 10 )   2008 - 2015   2022.10   ISSN:09151559 eISSN:13475460

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    <p>Quenched martensitic steels are known to show the characteristic feature of stress–strain relations, with extremely low elastic limits and very large work-hardening. The continuum composite approach is one way to express this characteristic feature of stress–strain curves. Although the overall stress–strain curves, as a function of alloy chemistries of steels, were well represented by this approach, the relationship between the macroscopic deformation behaviors and microstructural information is yet to be clarified. A high-spatial-resolution digital image correlation analysis was conducted to demonstrate the possible unit size corresponding to the microstructure. The continuum composite approach model was also modified to consider the size effect of the microstructure on the stress–strain curves of the as-quenched martensitic steels. Strain concentrations were observed at various boundaries, including lath boundaries, and the characteristic microstructural size was also predicted by the present model, which is smaller than the reported spacing between adjacent strain-concentrated regions.</p>

    DOI: 10.2355/isijinternational.isijint-2022-114

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  • Sulfide Stress Cracking (SSC) of Low Alloy Linepipe Steels in Low H2S Content Sour Environment

    Junji Shimamura, Tatsuya Morikawa, Shigeto Yamasaki, Masaki Tanaka

    ISIJ International   62 ( 10 )   2095 - 2106   2022.10   ISSN:09151559 eISSN:13475460

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    <p>Resistance to Sulfide Stress Cracking (SSC) caused by local hard zones of pipe inner surface has been required in low alloy linepipe steel. In this study, using two samples with different surface hardness, the detailed SSC initiation behavior was clarified by four-point bend (4PB) SSC tests in which immersion time and applied stress were changed in a sour environment containing 0.15 bar hydrogen sulfide (H<sub>2</sub>S) gas. SSC cracks occurred when the applied stress was higher than 90% actual yield strength (AYS) in higher surface hardness samples over 270 HV0.1. From the fracture surface observation of SSC crack sample, it was found that the mechanism gradually shifted from active path corrosion (APC) to hydrogen embrittlement (HE), and that the influence of APC mechanism remained partially in the process of SSC initiation at the tip of corrosion pit or groove. The polarization measurement in the 4PB SSC test showed that the anodic and cathodic reactions (especially cathodic reactions) were activated when the applied stress was 90% AYS or higher. The FEM coupled analysis simulating the stress and strain concentration at the bottom tip of the corrosion groove and the hydrogen diffusion and accumulation was carried out. The principal stress in the tensile direction showed the maximum value at 0.04–0.06 mm away from the tip of the corrosion groove, and the hydrogen accumulation became the maximum. It was analytically found that the SSC crack initiated and propagated with HE mechanism dominated type when the threshold value of about 0.82 ppm is exceeded.</p>

    DOI: 10.2355/isijinternational.isijint-2022-236

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  • Evaluation of Cleavage Fracture Behavior of C14 Fe2W Laves Phase by First-principles Calculations and Crystal Orientation Analysis

    Shigeto Yamasaki, Tatsuya Morikawa, Masaki Tanaka, Yasuaki Watanabe, Mitsuo Yamashita, Sakae Izumi

    ISIJ International   62 ( 10 )   2118 - 2125   2022.10   ISSN:09151559 eISSN:13475460

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    <p>In this study, the cleavage fracture of the C14 Fe<sub>2</sub>W Laves phase was investigated by first-principles calculations and crystal orientation analysis using scanning electron microscopy. Trace analysis of the orientations of cleavage planes revealed that cleavage fracture occurred in five types of crystal planes: (0001), {1<span style="text-decoration: overline;">1</span>00}, {11<span style="text-decoration: overline;">2</span>0}, {1<span style="text-decoration: overline;">1</span>01}, and {11<span style="text-decoration: overline;">2</span>2}. Among these fractures, the fracture at (0001) is the most preferable. From, the first-principle calculations of the surface energy for fracture, Young’s modulus, and Poisson’s ratio, the minimum fracture toughness value of 1.62 MPa·m<sup>1/2</sup> was obtained at (0001). The tendency of the calculated fracture toughness to become larger with high indexed planes is almost the same as the frequency of the types of cleavage planes in the trace analysis. It was concluded that the fracture toughness of the C14 Fe<sub>2</sub>W Laves phase is controlled by the surface energy for fracture and Young’s modulus.</p>

    DOI: 10.2355/isijinternational.isijint-2022-122

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  • Microstructural Observation and Wrought Processing Optimization for Kinking in LPSO Type Mg Alloy

    Mitsuhara Masatoshi, Yamasaki Shigeto, Ando Daisuke

    Materia Japan   61 ( 9 )   543 - 549   2022.9   ISSN:13402625 eISSN:18845843

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    DOI: 10.2320/materia.61.543

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  • 低合金鋼ラインパイプの低H2S濃度サワー環境下における硫化物応力腐食割れ挙動 Reviewed

    嶋村 純二, 森川 龍哉, 山﨑 重人, 田中 將己

    鉄と鋼   108 ( 9 )   642 - 655   2022.9

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    DOI: https://doi.org/10.2355/tetsutohagane.TETSU-2022-013

  • Microstructure and tensile strength of AC8A aluminum alloy fabricated by laser-based powder bed fusion and electron-based powder bed fusion

    Adachi Mitsuru, Okuhira Tomo, Yamasaki Shigeto, Mitsuhara Masatoshi, Nakashima Hideharu, Koiwai Shuji, Hashizume Yoshiki, Murakami Isao, Terada Daisuke

    Journal of Japan Institute of Light Metals   72 ( 5 )   206 - 213   2022.5   ISSN:04515994 eISSN:18808018

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    <p>The mechanical properties of JISAC8A alloys (Al-12%Si-1%Mg-1%Ni-1%Cu alloy) fabricated by laser-based powder bed fusion (LB) or electron-based powder bed fusion (EB) or gravity casting (CAST) were studied by means of tensile tests at room temperature and 300°C. These alloys were under two types of heat-treatment sequences. One was a T6 treatment, which was corresponding to the heat treatment at 500°C for 2h and 170°C for 4 h, followed by the annealing at 300°C for 10 h. Another was directly annealed at 300°C for 10 h after the fabrication. In the annealed specimens without T6 treatment, the LB alloy showed the highest strength and best elongation at room temperature and 300°C, because eutectic Si particles and Al-Ni-Cu-Fe compounds formed very fine network structure in Al matrix. In the annealed specimens with T6 treatment, the tensile strength at room temperature did not depend on the fabrication methods but the LB alloy showed the best elongation because of finer and isotropic shape of secondary phase particles. The annealed CAST alloy showed the highest strength at 300°C, and the annealed LB alloy showed the lowest strength at 300°C.</p>

    DOI: 10.2464/jilm.72.206

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  • レーザ積層造形法と電子ビーム積層造形法で作製したAC8A アルミニウム合金のミクロ組織と引張特性 Reviewed

    安達 充, 奥平 有, 山﨑 重人, 光原 昌寿, 中島 英治, 小岩井 修二, 橋詰 良樹, 村上 勇夫, 寺田 大将

    軽金属   72 ( 5 )   206 - 213   2022.5

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    DOI: https://doi.org/10.2464/jilm.72.206

  • Sulfide Stress Cracking (SSC) of Low Alloy Linepipe Steels in Low H<sub>2</sub>S Content Sour Environment

    Shimamura Junji, Morikawa Tatsuya, Yamasaki Shigeto, Tanaka Masaki

    Tetsu-to-Hagane   108 ( 9 )   642 - 655   2022   ISSN:00211575 eISSN:18832954

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    <p>Resistance to Sulfide Stress Cracking (SSC) caused by local hard zones of pipe inner surface has been required in low alloy linepipe steel. In this study, using two samples with different surface hardness, the detailed SSC initiation behavior was clarified by four-point bend (4PB) SSC tests in which immersion time and applied stress were changed in a sour environment containing 0.15 bar hydrogen sulfide (H<sub>2</sub>S) gas. SSC cracks occurred when the applied stress was higher than 90% actual yield strength (AYS) in higher surface hardness samples over 270 HV0.1. From the fracture surface observation of SSC crack sample, it was found that the mechanism gradually shifted from active path corrosion (APC) to hydrogen embrittlement (HE), and that the influence of APC mechanism remained partially in the process of SSC initiation at the tip of corrosion pit or groove. The polarization measurement in the 4PB SSC test showed that the anodic and cathodic reactions (especially cathodic reactions) were activated when the applied stress was 90% AYS or higher. The FEM coupled analysis simulating the stress and strain concentration at the bottom tip of the corrosion groove and the hydrogen diffusion and accumulation was carried out. The principal stress in the tensile direction showed the maximum value at 0.04-0.06 mm away from the tip of the corrosion groove, and the hydrogen accumulation became the maximum. It was analytically found that the SSC crack initiated and propagated with HE mechanism dominated type when the threshold value of about 0.82 ppm is exceeded.</p>

    DOI: 10.2355/tetsutohagane.tetsu-2022-013

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  • Effects of temperature and grain size on active twinning systems in commercially pure titanium

    Genki Tsukamoto, Tomonori Kunieda, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Journal of Alloys and Compounds   884   2021.12

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    In order to clarify the effects of grain boundary, grain size and deformation temperature on twinning deformation in polycrystalline commercially pure titanium, active twinning systems during compression deformation at temperatures from 25 °C to 800 °C investigated using SEM/EBSD techniques. Four twinning systems were confirmed to operate under compression at 10% strain in a deformation temperature dependent manner: {112̅1} and {112̅2} twins were observed only at relatively low temperatures (e.g. ≦ 400 °C), while, {101̅1} twins were observed at relatively high temperatures (e.g. ≧ 400 °C), and {101̅2} twins formed at every tested temperature (25 °C–800 °C). Our results suggested that the effects of strain concentration at grain boundaries on twinning differ based on the active twinning systems, which are affected by: 1) the difference in the formation temperature ranges between single-crystal and polycrystalline specimens, 2) the ratio of the number of deformation twins touching grain boundaries to the total number of deformation twins, and 3) grain size dependence.

    DOI: 10.1016/j.jallcom.2021.161154

  • Evaluation of cleavage fracture behavior of C14 Fe<inf>2</inf>W laves phase by first principle calculation and crystal orientation analysis

    Shigeto Yamasaki, Masaki Tanaka, Tatsuya Morikawa, Yasuaki Watanabe, Mitsuo Yamashita, Sakae Izumi

    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan   107 ( 11 )   977 - 985   2021.11

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    Cleavage fracture of C14 Fe2W Laves phase was investigated using crystal orientation measurement with scanning electron microscopy and first-principles calculations. Trace analysis of the orientations of cleavage planes reveals that cleavage fracture occurred at five types of crystal planes of (0001), {1100}, {1120}, {1101} and {1122}, among which the fracture at (0001) is the most preferable. The first-principle calculations of the surface energy for fracture, Young's modulus, and Poisson's ratio showed that the minimum fracture toughness value of 1.62 MPa·m1/2 was obtained at (0001). The tendency that the values of calculated fracture toughness become larger with the higher indexed planes is almost the same as the frequency of the types of cleavage planes in the trace analysis. It is concluded that the fracture toughness of C14 Fe2W Laves phase is controlled by the surface energy for fracture and Young’s modulus.

    DOI: 10.2355/tetsutohagane.TETSU-2021-069

  • Persistent slip observed in TiZrNbHfTa: A body-centered high-entropy cubic alloy Reviewed International journal

    Tanaka, M., Okajo, S., Yamasaki, S. & Morikawa, T.

    Scripta Materialia   2021.7

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  • Persistent slip observed in TiZrNbHfTa: A body-centered high-entropy cubic alloy

    Masaki Tanaka, Shinji Okajo, Shigeto Yamasaki, Tatsuya Morikawa

    Scripta Materialia   200   2021.7

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    Slip properties of TiZrNbHfTa were evaluated to obtain ψ–χ relationships, where χ is defined as the angle between the maximum shear stress plane and (1¯01). ψ is defined as the angle between the apparent slip plane and (1¯01). Bending tests were conducted with micrometer-sized cantilevers fabricated from a single grain with a focused ion beam. Slip bands appear to be straight on a micrometer length-scale, as for Fe–Si alloys, which suggests a persistent slip. However, the ψ–χ relationship indicated that ψ is nearly the same as χ, suggesting that there is no persistent slip. Detailed observations with an atomic force microscope confirm that cross-slipping is so frequent at a sub-micrometer length-scale that the slip bands appear to be straight and the maximum shear stress plane is observed on a micrometer length-scale. Here, TiZrNbHfTa shows abnormally frequent cross-slipping, which is a novel characteristic of high-entropy body-centered cubic alloys.

    DOI: 10.1016/j.scriptamat.2021.113895

  • Evaluation of depth of dislocation visibility in SEM electron channeling contrast imaging in Ti-6Al-4V alloy using serial sectioning method

    Shigeto Yamasaki, Misaki Deguchi, Masatoshi Mitsuhara, Hideharu Nakashima, Yutaro Ota, Keiji Kubushiro

    Microscopy   70 ( 3 )   265 - 277   2021.6

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    In this study, we conducted a quantitative evaluation of dislocation density by scanning electron microscopy electron channeling contrast imaging for α grains of a Ti-6Al-4V alloy deformed at room temperature. The depth of visibility of dislocations is experimentally measured as 140 to 160 nm by a serial sectioning observation. This result is compared with the theoretical value and applied to evaluate dislocation density. These factors confirm that the theoretically calculated value of the depth of visibility, at 5 to 6 times the extinction distance, is valid for the hexagonal close-packed Ti alloy.

    DOI: 10.1093/jmicro/dfaa060

  • Quantitative analysis of the Portevin–Le Chatelier effect by combining digital image correlation and dead-weight-type tensile test

    Shigeto Yamasaki, Tomoki Miike, Masatoshi Mitsuhara, Hideharu Nakashima, Ryutaro Akiyoshi, Takahiko Nakamura, Shimpei Kimura

    Materials Science and Engineering A   816   2021.6

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    A quantitative evaluation method of a serration deformation behavior by a dead-weight tensile test combined with a strain measurement by a DIC method is proposed. This method applies to binary solid solution aluminum alloys and a ternary cluster strengthened aluminum alloy. In the dead-weight tensile test, the serrated flow was measured as a stress-strain curve with a stepped-shape divided into two stages of a stress rising phase and a strain burst phase. By adopting this tensile test, the serration deformation behavior can be measured with an extremely reproducibility. It was confirmed that an elastic deformation occurs predominantly in the stress rising phase, and this deformation behavior is discussed in relation to the concentration of solid solution elements. Propagation of PLC bands has occurred in the strain burst phase. An activation volume obtained from the strain rate in the PLC bands was in good agreement with a calculated value based on a distribution interval assuming a regular square distribution of solute elements. For the ternary alloy strengthened by clusters, it is also shown that this method can be applied to the qualitative estimation of the change in the residual amount of the solid solution element in the matrix during natural aging.

    DOI: 10.1016/j.msea.2021.141277

  • Generalized Slip Operation Factor Considering Contribution of Secondary Slip Systems Reviewed International journal

    Kawano, Y., Mayama, T., Mitsuhara, M., Yamasaki, S. & Sato, M.

    Materials Today Communications   2021.3

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  • Generalized Slip Operation Factor Considering Contribution of Secondary Slip Systems

    Yoshiki Kawano, Tsuyoshi Mayama, Masatoshi Mitsuhara, Shigeto Yamasaki, Michihiro Sato

    Materials Today Communications   26   2021.3

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    Slip operation factor (SOF), which considers the effect of mechanical interactions between plastically “soft” and “hard” regions, is a function of the Schmid factor (SF) and critical resolved shear stress (CRSS). It is used as an indicator to efficiently predict the ease of slip operation of metal materials at the grain level. While SOF could predict strain distributions, it was not compliant to the prediction of those for individual slip systems. Additionally, the contribution of secondary slip systems was disregarded in the SOF. In this study, the SOF was first extended to adapt to individual slip systems. This extended and generalized form of the SOF was called SOFS. Next, the contribution of secondary slip systems was considered in SOF, where the modified version of the SOF was called MSOF. Polycrystalline α-Ti models were built from crystal orientation maps obtained by electron back-scattered diffraction (EBSD), and the strain distributions under uniaxial tensile loading were predicted using the SOF, SOFS, and MSOF. The results obtained were compared with those obtained via crystal plasticity finite element (CPFE) analysis. The distributions obtained by the SOFS were similar to slip strain distributions for individual slip systems when single slips were dominant and the deformation was slight. The MSOF also successfully predicted the strain distributions with higher accuracy than that offered by the SOF.

    DOI: 10.1016/j.mtcomm.2021.102041

  • One-trillionth level toluene detection using a dual-designed semiconductor gas sensor: Material and sensor-driven designs

    Koichi Suematsu, Wataru Harano, Shigeto Yamasaki, Ken Watanabe, Kengo Shimanoe

    ACS Applied Electronic Materials   2 ( 12 )   4122 - 4126   2020.12

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    Lowering the volatile organic compound (VOC) gas detection limit toward the ppt level on a resistive-type semiconductor gas sensor was achieved by combining the material and sensor-driven designs. We fabricated Pd-SnO2 clustered nanoparticles, a material that is highly sensitive to VOC gas, on a microsensor device with a double-pulse-driven mode. This mode was involved in switching the heater-on periods at high-temperature preheating and measurement phases and the rest phase during a heater-off period between preheating and measurement phases. The electrical resistance in synthetic air and the sensor response to toluene increased as preheating temperatures increased because of an increase in the amount of O2− adsorbed on the particle surface. In addition, extending the rest time between the preheating and measurement phases significantly improved the sensor response to toluene. According to the relationship between the sensor response and toluene concentration, we improved the lower detection limit for toluene gas to below 10 ppt, with preheating and measurement temperatures at 400 and 250 °C, respectively, and rest time at 100 s. Therefore, the combination of the material and sensor-driven designs may play a key role in improving the sensor performance.

    DOI: 10.1021/acsaelm.0c00902

  • Relationship between Creep Strength and Magnetic Properties of Cobalt-bearing High Chromium Ferritic Steel

    Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN   106 ( 11 )   12 - 22   2020.11

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    In this study, the relation between the change of the magnetic properties and the creep strength with the addition of Co was investigated for ferritic steel containing 15 mass%Cr. Co addition up to 6 mass% hardly contributes to solid solution strengthening and precipitation strengthening at room temperature. However, in the range of 650 degrees C to 750 degrees C, it was confirmed that the addition of Co was effective for the creep strengthening because the steel with a larger amount of Co had higher creep strength. This creep strengthening is explained by a reduction in the diffusion rate associated with a change in magnetic properties by Co addition. The increase of the volume magnetization of the steel with increase of Co amount in the temperature range from room temperature to about 800 degrees C was confirmed. Comparing the difference in volume magnetization and the ratio of creep strain rate for steels with different amounts of Co, a clear correlation was found between the values. That is, at the temperature at which the difference in volume magnetization becomes maximum, the peak of the creep strain rate ratio was observed. This result is explained as follows. In a low temperature region where the magnetization is large or in a high temperature region above the Curie point of both steels, there is no significant difference in the creep strength between them. However, in the temperature where one steel loses the ferromagnetism but the other steel maintains ferromagnetism, a significant difference in the creep strength was observed.

    DOI: 10.2355/tetsutohagane.TETSU-2020-041

  • One-trillionth level toluene detection using a dual-designed semiconductor gas sensor: Material and sensor-driven designs Reviewed International journal

    Suematsu, K., Harano, W., Yamasaki, S., Watanabe, K. & Shimanoe, K.

    ACS Applied Electronic Materials   2020.11

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  • Dislocation motion and microstructure evolution deformed during creep at room temperature in Ti-6Al-4V alloy

    Misaki Deguchi, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Yutaro Ota

    Keikinzoku/Journal of Japan Institute of Light Metals   70 ( 8 )   405 - 414   2020.10

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    The deformation behavior and microstructure evolution of Ti-6Al-4V alloy under room temperature creep was investigated using mechanical test and scanning electron microscope observation with electron back-scatter diffraction method. The alloys were creep deformed and ruptured under initial stresses of 874 MPa, 889 MPa and 904 MPa at room temperature. The rapid stress change test revealed that creep deformation was controlled by the viscous slip motion of dislocations. The stress exponent was estimated as 59. The strain rate of acceleration creep region calculated by the Norton's law with the high stress exponent was inconsistent with that measured by the experimental creep test. Using the slip trace analysis, it was found that single dislocation slip in basal and prism were mainly activated in the early stage of creep, and multiple slips were often observed as the deformation progresses. Especially, the multiple slip including 1st pyramidal slip believed to be effective for suppressing strain rate acceleration in creep. In addition, the work hardening behavior during creep showed a strain rate dependence, indicating that the lower the strain rate is, the more work hardening occurs.

    DOI: 10.2464/JILM.70.405

  • Morphological and crystallographic features of kink bands in long-period stacking ordered Mg-Zn-Y alloy analyzed by serial sectioning SEM-EBSD observation method Reviewed International journal

    Tsubasa Tokuzumi, Shigeto Yamasaki, Wansong Li, Masatoshi Mitsuhara, Hideharu Nakashima

    Materialia   12   100716   2020.8

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    DOI: https://doi.org/10.1016/j.mtla.2020.100716

  • Morphological and crystallographic features of kink bands in long-period stacking ordered Mg-Zn-Y alloy analyzed by serial sectioning SEM-EBSD observation method

    Tsubasa Tokuzumi, Shigeto Yamasaki, Wansong Li, Masatoshi Mitsuhara, Hideharu Nakashima

    Materialia   12   2020.8

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    © 2020 Acta Materialia Inc. We investigated the pseudo three-dimensional features of kink bands formed by the compression deformation of a directionally solidified Mg85Zn6Y9 alloy. The kink bands of interest included ridge kinks with clear surface relief and gentle kinks with almost no surface relief. Observation of surface undulation by laser microscopy and electron backscatter diffraction with serial sectioning by mechanical polishing revealed the pseudo three-dimensional morphology and crystal rotation of these kink bands. The features of the observed kink bands are explained by a pseudo three-dimensional arrangement of disclination lines.

    DOI: 10.1016/j.mtla.2020.100716

  • Kink Formation Process in Long-Period Stacking Ordered Mg-Zn-Y Alloy

    Shigeto Yamasaki, Tsubasa Tokuzumi, Wansong Li, Masatoshi Mitsuhara, Koji Hagihara, Toshiyuki Fujii, Hideharu Nakashima

    Acta Materialia   195   25 - 34   2020.8

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    © 2020 Acta Materialia Inc. The formation process of the kink bands in a directionally solidified, polycrystalline, long-period stacking ordered (LPSO) Mg85Zn6Y9 phase during compression deformation was investigated. In-situ compression observations by scanning electron microscopy and electron backscattered diffraction analysis revealed that regions with localized crystal orientation rotation appeared before ridge kinks formed as surface relief. In this paper, it is called as pre-kink The observed pre-kinks were composed of two separate regions rotated in opposite directions to each other and distinguished from one another by the three boundaries. A transmission electron microscopy observation revealed that the boundaries of the pre-kink are sub-boundaries consisting of edge dislocation array, and both its ends are terminated within the matrix. These characteristics match the reported that of regular ridge kink boundaries. In addition, while pre-kinks do not possess the ability of complete reversibility, its boundaries are capable of moving elastically.

    DOI: 10.1016/j.actamat.2020.04.051

  • Ti-6Al-4V 合金における室温クリープ中の転位の運動様式と変形組織の発達過程 Reviewed

    Deguchi, M., Yamasaki, S., Mitsuhara, M., Nakashima, H. & Ota, Y.

    軽金属   2020.8

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  • In situ EBSD study of deformation behavior of primary α phase in a bimodal Ti-6Al-4V alloy during uniaxial tensile tests Reviewed

    Wansong Li, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Materials Characterization   163   2020.5

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    DOI: 10.1016/j.matchar.2020.110282

  • In situ EBSD study of deformation behavior of primary α phase in a bimodal Ti-6Al-4V alloy during uniaxial tensile tests

    Wansong Li, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Materials Characterization   163   2020.5

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    © 2020 Elsevier Inc. Uniaxial tension experiments and electron backscatter diffraction were performed on a bimodal Ti-6Al-4V alloy to study in situ the deformation behavior of primary hcp-Ti (αp). It was found that the strain could be accommodated by the activation of slip systems and by grain rotations. The prismatic slip was the primary slip mode of the αp. From the analysis of kernel average misorientation and geometrically necessary dislocation, it was shown that the dislocations mainly distributed in the vicinity of grain and sub-grain boundaries, and part of the dislocations distributed around slip lines. It was the dislocation activities that led to the formation of the low angle grain boundary and its transformation to the high angle grain boundary. It's important that tracking of deformation heterogeneities with significance to performance. By analyzing the rotation angle, average rotation rate, and rotation path of grains, it was shown that grain rotation heterogeneity occurred during the deformation. From the observation of the loading direction, grain rotation paths kept with the texture evolution direction of all αp. The grains activated in the basal slip gradually rotated to the ⟨101¯1⟩ pole and enhanced the intensity of the ⟨101¯1⟩ texture. Meanwhile, the grains activated in prismatic or 1st-order pyramidal slip rotated to the ⟨101¯0⟩ pole and enhanced the intensity of the ⟨101¯0⟩ texture. Grain rotation and texture evolution are related to mechanical properties.

    DOI: 10.1016/j.matchar.2020.110282

  • Electron tomography imaging methods with diffraction contrast for materials research Invited Reviewed International journal

    Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo, Daisuke Hirakami, Noritaka Horii, Ken Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki

    Microscopy   69 ( 3 )   141 - 155   2020.5

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    DOI: 10.1093/jmicro/dfaa002

  • Electron tomography imaging methods with diffraction contrast for materials research Invited Reviewed International journal

    Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo, Daisuke Hirakami, Noritaka Horii, Ken Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki

    Microscopy   69 ( 3 )   141 - 155   2020.3

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    © 2020 The Author(s). Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable the visualization of three-dimensional (3D) microstructures ranging from atomic to micrometer scales using 3D reconstruction techniques based on computed tomography algorithms. This 3D microscopy method is called electron tomography (ET) and has been utilized in the fields of materials science and engineering for more than two decades. Although atomic resolution is one of the current topics in ET research, the development and deployment of intermediate-resolution (non-atomic-resolution) ET imaging methods have garnered considerable attention from researchers. This research trend is probably not irrelevant due to the fact that the spatial resolution and functionality of 3D imaging methods of scanning electron microscopy (SEM) and X-ray microscopy have come to overlap with those of ET. In other words, there may be multiple ways to carry out 3D visualization using different microscopy methods for nanometer-scale objects in materials. From the above standpoint, this review paper aims to (i) describe the current status and issues of intermediate-resolution ET with regard to enhancing the effectiveness of TEM/STEM imaging and (ii) discuss promising applications of state-of-the-art intermediate-resolution ET for materials research with a particular focus on diffraction contrast ET for crystalline microstructures (superlattice domains and dislocations) including a demonstration of in situ dislocation tomography.

    DOI: 10.1093/jmicro/dfaa002

  • Quantitative evaluation of slip activity in polycrystalline α-titanium considering non-local interactions between crystal grains Reviewed

    Yoshiki Kawano, Michihiro Sato, Tsuyoshi Mayama, Masatoshi Mitsuhara, Shigeto Yamasaki

    International Journal of Plasticity   127   2020.1

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    DOI: 10.1016/j.ijplas.2019.12.001

  • Effect of Fe addition on heat-resistant aluminum alloys produced by selective laser melting

    Shigeto Yamasaki, Tomo Okuhira, Masatoshi Mitsuhara, Hideharu Nakashima, Jun Kusui, Mitsuru Adachi

    Metals   9 ( 4 )   2019.4

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    © 2019 by the authors. Licensee MDPI, Basel, Switzerland. The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that Fe-containing alloys produced by SLM had improved high-temperature strength and good ductility. Microstructural observations revealed that the increase in the high-temperature strength of the alloys was due to the dispersion of fine rod-shaped Fe-Si-Ni particles unique to the SLM material instead of the cell-like structure of eutectic Si.

    DOI: 10.3390/met9040468

  • Controlled Growth of Large-Area Uniform Multilayer Hexagonal Boron Nitride as an Effective 2D Substrate Reviewed

    Yuki Uchida, Sho Nakandakari, Kenji Kawahara, Shigeto Yamasaki, Masatoshi Mitsuhara, Hiroki Ago

    ACS Nano   12 ( 6 )   6236 - 6244   2018.6

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    © Copyright 2018 American Chemical Society. Multilayer hexagonal boron nitride (h-BN) is an ideal insulator for two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, because h-BN screens out influences from surroundings, allowing one to observe intrinsic physical properties of the 2D materials. However, the synthesis of large and uniform multilayer h-BN is still very challenging because it is difficult to control the segregation process of B and N atoms from metal catalysts during chemical vapor deposition (CVD) growth. Here, we demonstrate CVD growth of multilayer h-BN with high uniformity by using the Ni-Fe alloy film and borazine (B3H6N3) as catalyst and precursor, respectively. Combining Ni and Fe metals tunes the solubilities of B and N atoms and, at the same time, allows one to engineer the metal crystallinity, which stimulates the uniform segregation of multilayer h-BN. Furthermore, we demonstrate that triangular WS2 grains grown on the h-BN show photoluminescence stronger than that grown on a bare SiO2 substrate. The PL line width of WS2/h-BN (the minimum and mean widths are 24 and 43 meV, respectively) is much narrower than those of WS2/SiO2 (44 and 67 meV), indicating the effectiveness of our CVD-grown multilayer h-BN as an insulating layer. Large-area, multilayer h-BN realized in this work will provide an excellent platform for developing practical applications of 2D materials.

    DOI: 10.1021/acsnano.8b03055

  • Controlled Growth of Large-Area Uniform Multilayer Hexagonal Boron Nitride as an Effective 2D Substrate Reviewed

    Yuki Uchida, Sho Nakandakari, Kenji Kawahara, Shigeto Yamasaki, Masatoshi Mitsuhara, Hiroki Ago

    ACS nano   12 ( 6 )   6236 - 6244   2018.6

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    DOI: 10.1021/acsnano.8b03055

  • Effect of Bi or Sb addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys Reviewed

    Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals   81 ( 11 )   502 - 509   2017.9

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    DOI: 10.2320/jinstmet.J2017025

  • Effect of Bi or Sb addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys Reviewed

    Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals   81 ( 11 )   502 - 509   2017.9

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    © 2017 The Japan Institute of Metals and Materials. Global concerns over the environmental impact and health effects of the lead-based solders have led to the development of lead-free solder alloys. Further improvements in the reliability of lead-free solder alloys at high temperatures are required for downsizing of electronic components in vehicles. In this work, tensile and creep tests and microstructure analysis were carried out to determine the effect of Bi or Sb addition on high-temperature deformation behavior in Sn-Cu-Ni solder alloys. The addition of Bi or Sb increased the strength of the Sn-Cu-Ni solder alloys. The stress exponent was estimated to be ≥3, indicating that the high- Temperature deformation was controlled by dislocation creep. Furthermore, in both the alloys, the stress exponent observed in the low stress region was nearly equal to 3 and discontinuously increased to ≥7 in the high stress region. For Sb addition, the solute atmosphere drag mechanism was observed in the low stress region.

    DOI: 10.2320/jinstmet.J2017025

  • Multiscale in situ deformation experiments A sequential process from strain localization to failure in a laminated Ti-6Al-4V alloy Reviewed

    Motomichi Koyama, Keita Yamanouchi, Qinghua Wang, Shien Ri, Yoshihisa Tanaka, Yasuaki Hamano, Shigeto Yamasaki, Masatoshi Mitsuhara, Masataka Ohkubo, Hiroshi Noguchi, Kaneaki Tsuzaki

    Materials Characterization   128   217 - 225   2017.6

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    DOI: 10.1016/j.matchar.2017.04.010

  • Multiscale in situ deformation experiments: A sequential process from strain localization to failure in a laminated Ti-6Al-4V alloy Reviewed

    Motomichi Koyama, Keita Yamanouchi, Qinghua Wang, Shien Ri, Yoshihisa Tanaka, Yasuaki Hamano, Shigeto Yamasaki, Masatoshi Mitsuhara, Masataka Ohkubo, Hiroshi Noguchi, Kaneaki Tsuzaki

    Materials Characterization   128   217 - 225   2017.6

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    © 2017 Elsevier Inc. The microscopic factors causing tensile failure of an α/β laminated Ti-6Al-4V alloy were investigated through in situ scanning electron microscopy and sampling moiré at an ambient temperature. Specifically, multiscale in situ microscopic observations were conducted to extract the most crucial factor of the failure. Slip localization in the vicinity of an intergranular α-sheet was clarified to be the primary factor that causes failure of the Ti-6Al-4V alloy. In addition, no relationship between interfacial strain localization and macroscopic shear localization at 45 degrees against the tensile direction was observed.

    DOI: 10.1016/j.matchar.2017.04.010

  • Effect of Cu and Ni addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys Reviewed

    Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima

    Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals   81 ( 7 )   337 - 344   2017.1

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    DOI: 10.2320/jinstmet.J2016069

  • Microstructure and creep property in polycrystalline Ni-based alloy with intergranular intermetallics Reviewed

    Takanori Ito, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Minoru Nishida, Mitsuharu Yonemura

    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan   103 ( 7 )   434 - 442   2017.1

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    DOI: 10.2355/tetsutohagane.TETSU-2016-107

  • Effect of intergranular carbides on creep strength in nickel-based heat-resistant alloys Reviewed

    Takanori Ito, Shigeto Yamasaki, Masatoshi Mitsuhara, Minoru Nishida, Mitsuharu Yonemura

    Materials Transactions   58 ( 1 )   52 - 58   2017.1

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    DOI: 10.2320/matertrans.M2016291

  • Creep strengthening by lath boundaries in 9Cr ferritic heat-resistant steel Reviewed

    Masatoshi Mitsuhara, Shigeto Yamasaki, Masaki Miake, Hideharu Nakashima, Minoru Nishida, Junichi Kusumoto, Akihiro Kanaya

    Philosophical Magazine Letters   96 ( 2 )   76 - 83   2016.2

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    DOI: 10.1080/09500839.2016.1154200

  • Creep strengthening by lath boundaries in 9Cr ferritic heat-resistant steel Reviewed

    Masatoshi Mitsuhara, Shigeto Yamasaki, Masaki Miake, Hideharu Nakashima, Minoru Nishida, Junichi Kusumoto, Akihiro Kanaya

    Philosophical Magazine Letters   96 ( 2 )   76 - 83   2016.2

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    © 2016 Taylor and Francis. The interactions between dislocations and lath boundaries in Grade 91 steel were observed by an in situ transmission electron microscopy tensile test at 973 K. Dislocations glided slowly and bowed out in a martensite lath interior. The ends of the dislocation were connected to the lath boundaries. In a tempered specimen, the pinning stress caused by the lath boundary was estimated to be >70 MPa with a lath width of 0.4 m. In crept specimens, lath coarsening reduced the pinning effect.

    DOI: 10.1080/09500839.2016.1154200

  • 3D visualization of dislocation arrangement using scanning electron microscope serial sectioning method Reviewed

    S. Yamasaki, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima

    Scripta Materialia   101   80 - 83   2015.5

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    © 2015 Acta Materialia Inc. Published by Elsevier Ltd. We performed the three-dimensional visualization of dislocations through serial sectioning and use of SEM electron channeling contrast (ECC) images for a crept nickel-based alloy. We successfully reconstructed a volume of approximately 7.5 μm3, including dislocation arrangements, by performing calculations based on the continuous tomograms of ECC images. By incorporating the information on crystal orientation obtained by the electron back-scattered diffraction, we verified that the three-dimensional arrangement of dislocations, such as slip plane, was accurately reflected in the three-dimensional volume.

    DOI: 10.1016/j.scriptamat.2015.02.001

  • 純ニッケルの極低ひずみ速度クリープの変形機構の解明

    小池幸司, 山崎重人, 池田賢一, 波多聰, 中島英治

    日本金属学会講演概要(CD-ROM)   153rd   ROMBUNNO.P124   2013.9

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    純ニッケルの極低ひずみ速度クリープの変形機構の解明

  • オーステナイト系耐熱鋼の局所結晶方位解析によるクリープひずみの評価

    山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治

    材料とプロセス(CD-ROM)   26 ( 1 )   ROMBUNNO.258   2013.3

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    オーステナイト系耐熱鋼の局所結晶方位解析によるクリープひずみの評価

  • SEM/EBSD法によるクリープ変形に伴うGr.92鋼溶接継手の組織変化挙動解析

    光原昌寿, 市瀬祐輔, 市瀬祐輔, 山崎重人, 池田賢一, 波多聰, 中島英治, 長谷川泰士

    材料とプロセス(CD-ROM)   25 ( 2 )   ROMBUNNO.266   2012.9

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    SEM/EBSD法によるクリープ変形に伴うGr.92鋼溶接継手の組織変化挙動解析

  • フェライト系耐熱鋼の低応力クリープ変形挙動

    山崎重人, 池田賢一, 波多聰, 中島英治

    日本金属学会講演概要(CD-ROM)   150th   ROMBUNNO.528   2012.3

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    フェライト系耐熱鋼の低応力クリープ変形挙動

  • 局所方位解析法を用いたフェライト系耐熱鋼溶接熱影響部クリープ弱化要因の特定

    市瀬祐輔, 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治, 長谷川泰士

    日本金属学会講演概要(CD-ROM)   149th   ROMBUNNO.POSUTASESSHON,439   2011.10

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    局所方位解析法を用いたフェライト系耐熱鋼溶接熱影響部クリープ弱化要因の特定

  • Low-temperature creep at ultra-low strain rates in pure aluminum studied by a helicoid spring specimen technique Reviewed

    Junjie Shen, Shigeto Yamasaki, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima

    Materials Transactions   52 ( 7 )   1381 - 1387   2011.7

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    DOI: 10.2320/matertrans.M2010405

  • 酸化物分散強化型9Crフェライト系耐熱鋼の3次元組織と高温強度

    光原 昌寿, 原田 絵梨香, 山崎 重人, 池田 賢一, 波多 聰, 中島 英治, 大塚 智史, 皆藤 威二

    可視化情報学会誌 = Journal of the Visualization Society of Japan   31 ( 122 )   98 - 103   2011.7

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    Three-dimensional Microstructure and High Temperature Strength in ODS 9Cr Ferritic Heat Resistant Steels
    Oxide-dispersion-strengthened (ODS) 9Cr ferritic heat resistant steel is a leading candidate for a cladding material used in advanced fast reactor fuels because of its superior radiation resistance and high-temperature strength. In this study, distribution of oxides, which is presumed to be a dominant factor of the high-temperature strength, has been evaluated by three-dimensional (3D) observations using electron tomography. The oxide distribution was classified into two regions, whose number densities were high or low. Dislocation pinning forces caused by the oxides were estimated from the 3D data in each region. A good coincidence was recognized between the force in the low-density region and a threshold stress at which the creep deformation mechanism changes. Therefore, the high temperature deformation behavior of ODS steels is influenced by dislocation motions in the low-density regions of oxides.

    DOI: 10.3154/jvs.31.98

  • Low-temperature creep at ultra-low strain rates in pure aluminum studied by a helicoid spring specimen technique Reviewed

    Junjie Shen, Shigeto Yamasaki, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima

    Materials Transactions   52 ( 7 )   1381 - 1387   2011.7

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    The creep behavior in pure aluminum has been investigated by helicoid spring creep tests at strain rates, ε̇, lower than 10-10 s-1 and low temperature ranging from 0.32Tm to 0.43T m. It was found that the creep behavior in this region depends strongly on grain sizes and impurity concentrations. For high-purity aluminum (5 N Al) with an average grain size, dg > 1600 μm, nearly the wire diameter of the spring sample, where the role of grain boundary during creep deformation can be negligible, the stress exponent was n ∼ 5 and the activation energy was Qc = 32 kJ/mol. Microstructural observation showed the formation of large dislocation cells (∼10μm) and tangled dislocations at the cell walls. For high-purity aluminum (5N Al) with d g = 24 μm, the stress exponent was n ∼ 1 and the activation energy was Qc = 15kJ/mol. On the other hand, for commercial low-purity aluminum (2 N Al) with dg = 25 μm, the stress exponent was n = 2 and the activation energy was Qc = 25 kJ/mol. Microstructural observations revealed dislocations emitted from grain boundaries, those dislocations interacting with intragranular dislocations and the formation of dislocation cells in the grains. Based on those experimental results, the low-temperature creep mechanisms in pure aluminum at ε̇ < 10-10 s-l have been discussed. © 2011 The Japan Institute of Metals.

    DOI: 10.2320/matertrans.M2010405

  • コイルばねクリープ試験法による改良9Cr‐1Mo鋼の極低速クリープ挙動評価

    山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治

    材料とプロセス(CD-ROM)   23 ( 2 )   ROMBUNNO.277   2010.9

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    コイルばねクリープ試験法による改良9Cr‐1Mo鋼の極低速クリープ挙動評価

  • Pt系分散強化合金の低応力領域でのクリープ特性の検討

    富田成明, 浜島和雄, 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治

    日本金属学会講演概要   146th   365   2010.3

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    Pt系分散強化合金の低応力領域でのクリープ特性の検討

  • コイルばねクリープ試験法による高Cr鋼の低速クリープ挙動評価

    山崎重人, 藤本健資, 光原昌寿, 池田賢一, 波多聰, 中島英治, 木村光男

    材料とプロセス(CD-ROM)   22 ( 2 )   ROMBUNNO.PS-35   2009.9

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    コイルばねクリープ試験法による高Cr鋼の低速クリープ挙動評価

  • コイルばねクリープ試験法によるSUS304鋼のクリープ挙動解析

    光原昌寿, 山崎重人, 池田賢一, 波多聰, 中島英治

    材料とプロセス(CD-ROM)   21 ( 2 )   ROMBUNNO.TO121   2008.9

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    コイルばねクリープ試験法によるSUS304鋼のクリープ挙動解析

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Presentations

  • 加速クリープに関するレビュー ~加速クリープに関する現状の理解と問題点~

    山﨑重人

    日本鉄鋼協会「高温材料の高強度化」研究会 第6回研究会  2021.4 

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    Event date: 2021.5

    Language:Japanese  

    Country:Japan  

  • ミルフィーユ構造Mg系合金に生じるキンクバンドの特徴

    山﨑重人

    日本鉄鋼協会 材料の組織と特性部会 若手フォーラム 第3 回研究会  2020.11 

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    Event date: 2021.5

    Language:Japanese  

    Country:Japan  

  • 長周期積層構造 Mg-Zn-Y 合金におけるキンク形成過程

    山﨑重人, 徳澄翼, 光原昌寿, 中島英治, 田中將己

    第62回日本顕微鏡学会九州支部学術講演会  2020.11 

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    Event date: 2021.5

    Language:Japanese  

    Country:Japan  

  • コバルト添加フェライト系耐熱鋼のクリープ強度と磁気特性の関係

    山﨑重人

    日本鉄鋼協会 第181回春季講演大会  2021.3 

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    Event date: 2021.5

    Language:Japanese  

    Country:Japan  

  • フェライト系耐熱鋼の磁気変態点変化がクリープ変形に及ぼす影響

    藤野翔太, 山﨑重人, 光原昌寿, 中島英治

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 令和元年度 合同学術講演大会  2019.6 

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    Venue:熊本県民交流館パレア  

  • In-situ EBSD characterization of deformation behavior of primary alpha phase in Ti-6Al-4V International conference

    W. Li, S. Yamasaki, M. Mitsuhara, H. Nakashima

    The 14th World Conference on Titanium  2019.6 

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    Venue:Nantes, France  

  • 耐熱合金の高温変形 Invited

    山﨑重人

    駒場材料学セミナー  2019.8 

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    Venue:東京大学 駒場キャンパス  

  • 定負荷速度引張試験で測定したアルミニウム合金のセレーション変形

    山﨑重人, 三池友樹, 光原昌寿, 中島英治, 秋吉竜太郎, 木村申平

    高温変形の組織ダイナミクス研究会「2019年度 夏の学校」  2019.9 

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    Venue:石川県青少年総合研修センター  

  • フェライト系耐熱鋼の実用ひずみ速度域でのクリープ変形

    山﨑重人, 光原昌寿, 中島英治

    日本鉄鋼協会  2019.9 

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    Venue:岡山大学  

  • Creep behavior of ferritic heat resistant steel added with nitrogen International conference

    S. Yamasaki, M. Mitsuhara and H. Nakashima

    Joint EPRI-123HiMAT International Conference on Advances in High Temperature Materials  2019.10 

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    Venue:Nagasaki Brick Hall  

  • クリープ試験の改良と応用 Invited

    山﨑重人, 光原昌寿, 中島英治

    日本鉄鋼協会「高温材料の高強度化」研究会  2019.11 

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    Venue:レクトーレ箱根強羅  

  • LPSO単相多結晶Mg-Zn-Y合金におけるキンク形成過程

    山﨑重人, 徳澄翼, 光原昌寿, 中島英治, 萩原幸司, 藤居俊之

    軽金属学会 第137回秋期講演大会  2019.11 

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    Venue:東京農工大学 小金井キャンパス  

  • Ti-6Al-4V合金の室温クリープ変形挙動の評価

    出口岬,山﨑重人,光原昌寿, 中島英治, 大田祐太朗

    軽金属学会 第137回秋期講演大会  2019.11 

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    Venue:東京農工大学 小金井キャンパス  

  • Growth behavior of M23C6 carbides in high-Cr ferritic heat-resistant steels International conference

    M. Mitsuhara, S. Yamasaki, R. Arakane, R. Takao, H. Nakashima

    Joint EPRI-123HiMAT International Conference on Advances in High Temperature Materials  2019.10 

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    Venue:Nagasaki Brick Hall  

  • Microscopic observation of formation process of kink bands in Mg-Zn-Y alloy with LPSO phase Invited International conference

    Masatoshi Mitsuhara, Shigeto Yamasaki, Hideharu Nakashima, Koji Hagihara, Toshiyuki Fujii

    Mini-symposium: ”Elastic defects and structures. Modeling and experiments”  2019.8 

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    Venue:Kyushu University  

  • αTiにおけるすべり系活動への結晶粒間相互作用の影響とその範囲

    河野義樹、眞山剛、光原昌寿、山﨑重人、佐藤満弘

    日本金属学会2019年秋期(第165回)講演大会  2019.9 

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    Venue:岡山大学  

  • LPSO単相Mg-Zn-Y合金におけるキンク変形の前駆現象

    光原昌寿、山﨑重人、惣島雅樹、中島英治、萩原幸司、藤居俊之

    日本金属学会2019年秋期(第165回)講演大会  2019.9 

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    Venue:岡山大学  

  • デジタル画像相関法による純鉛の局所クリープ変形挙動解析

    奥村啓太, 山﨑重人, 光原昌寿, 中島英治

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 令和元年度 合同学術講演大会  2019.6 

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    Venue:熊本県民交流館パレア  

  • 定負荷速度引張試験により測定した2元系アルミニウム固溶体合金のセレーション挙動

    古賀鈴, 山﨑重人, 光原昌寿, 中島英治, 秋吉竜太郎, 徳田健二, 有賀康博

    軽金属学会 第134 回春期大会  2018.5 

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    Venue:熊本大学  

  • 耐熱合金のクリープ変形の測定と定量的組織観察

    山﨑重人

    日本金属学会 第1回若手研究グループ研究会「多様な先端観察・測定法を用いた組織の定量と力学特性解析への適用」  2018.4 

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    Venue:弘前大学  

  • レーザー積層法により作製した耐熱アルミニウム合金への遷移元素添加

    奥平有, 山﨑重人,光原昌寿,中島英治,西田稔, 楠井潤, 安達充

    日本金属学会 春期(第162回)講演大会  2018.3 

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    Venue:千葉工業大学  

  • 電子ビーム積層法およびレーザー積層法により作製したAC8A合金の高温強度特性

    奥平有, 山﨑重人,光原昌寿,中島英治,西田稔, 楠井潤, 安達充

    日本金属学会 春期(第162回)講演大会  2018.3 

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    Venue:千葉工業大学  

  • Relationship between Creep Deformation and Microstructure of Heat-Resistant Alloys Invited International conference

    S. Yamasaki

    MJIIT MICROSCOPY LABORATORY WORKSHOP SERIES-2  2018.3 

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    Venue:マレーシア工科大学   Country:Malaysia  

  • 長時間時効した“Hastelloy X”合金の組織とクリープ変形挙動(第二報)

    山﨑重人, 光原昌寿, 中島英治, 齊藤大蔵, 吉岡洋明

    平成29年度 3月期 耐熱金属材料第123委員会  2018.3 

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    Venue:東京工業大学  

  • マイクロシェブロンノッチ曲げ試験法とSEM/FIBトモグラフィーを組み合わせた亀裂進展経路の3次元解析

    吉田歩夢, 本田佳暉, 山﨑重人, 光原昌寿, 中島英治, 後藤裕明, 津田圭一

    第59回 日本顕微鏡学会 九州支部集会・学術講演会  2017.12 

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    Venue:ニューウェルシティ宮崎  

  • 窒素添加マルテンサイト耐熱鋼のクリープ変形挙動

    山﨑重人, 當山守人, 堀翔太郎, 光原昌寿, 中島英治

    高温変形の組織ダイナミクス研究会「平成29年度夏の学校」  2017.9 

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    Venue:サンヒルズ三河湾  

  • 多結晶Ni基耐熱合金のクリープ変形中に生じる転位とγ'析出物の相互作用

    百武優佑, 山﨑重人, 光原昌寿, 中島英治

    高温変形の組織ダイナミクス研究会「平成29年度夏の学校」  2017.9 

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    Venue:サンヒルズ三河湾  

  • 定負荷速度引張試験により測定したAl合金とNi合金のセレーション挙動

    古賀鈴, 山﨑重人, 光原昌寿, 中島英治, 秋吉竜太郎, 高木康夫 徳田健二

    高温変形の組織ダイナミクス研究会「平成29年度夏の学校」  2017.9 

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    Venue:サンヒルズ三河湾  

  • WC-Co 超硬合金の残留応力解析

    本田佳暉, 山﨑重人, 光原昌寿, 中島英治, 後藤裕明, 津田圭一

    日本金属学会 秋期(第161回)講演大会  2017.9 

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    Venue:北海道大学  

  • Al 添加α-Ti 合金における双晶界面の高分解能観察

    徳永隼人, 山﨑重人, 光原昌寿, 中島英治, 塚本元気, 國枝知徳

    日本金属学会 秋期(第161回)講演大会  2017.9 

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    Venue:北海道大学  

  • 金属積層工法を用いたAC8A アルミニウム合金の高温強度特性

    奥平有, 山﨑重人, 光原昌寿, 中島英治, 西田稔, 安達充, 栗田健也, 永田佳彦, 小岩井修二

    日本金属学会 秋期(第161回)講演大会  2017.9 

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    Venue:北海道大学  

  • Laves相により強化されたフェライト単相耐熱鋼のクリープ変形挙動と微細組織

    堀翔太郎, 山﨑重人, 光原昌寿, 中島英治, 木村一弘

    日本鉄鋼協会 第174 回秋季講演大会  2017.9 

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    Venue:北海道大学  

  • Development of new ferritic heat-resistant steel with high nitrogen and tungsten addition International conference

    S. Yamasaki, M. Mitsuhara and H. Nakashima

    IU-MRS (International union of Materials Research Society) 2017  2017.8 

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    Venue:京都大学   Country:Japan  

  • 長時間時効したHastelloy X合金の組織とクリープ変形挙動

    山﨑重人, 光原昌寿, 中島英治, 齊藤大蔵, 吉岡洋明

    平成29年度 7月期 耐熱金属材料第123委員会  2017.7 

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    Venue:東京工業大学  

  • 窒素含有マルテンサイト鋼のクリープ変形挙動

    山﨑重人、今村祐輔、光原昌寿、中島英治

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 平成29年度 合同学術講演大会  2017.6 

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    Venue:熊本大学  

  • チタンの双晶発生に及ぼす固溶元素の影響

    徳永隼人, 山﨑重人, 光原昌寿, 中島英治, 塚本元気, 國枝知徳

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 平成29年度 合同学術講演大会  2017.6 

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    Venue:熊本大学  

  • HPT加工をした純鉄の摩擦特性と微細組織

    岩﨑眞澄, 山﨑重人, 光原昌寿, 中島英治, 西田稔, 堀井基弘, 戸高義一

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 平成29年度 合同学術講演大会  2017.6 

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    Venue:熊本大学  

  • ラスマルテンサイト鋼のクリープ変形挙動に及ぼす転位密度の影響

    當山守人, 山﨑重人, 光原昌寿, 中島英治

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 平成30年度 合同学術講演大会  2018.6 

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    Venue:北九州国際会議場  

  • 高ひずみ分解能単軸クリープ試験による極低ひずみ速度変形挙動の評価

    加藤 由輝, 山﨑重人, 光原昌寿, 中島英治

    日本金属学会九州支部 日本鉄鋼協会九州支部 軽金属学会九州支部 共催 平成30年度 合同学術講演大会  2018.6 

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    Venue:北九州国際会議場  

  • Creep Deformation and Strengthening Mechanism in Newly Developed Ni-20Cr-15Co-1Ti-2Al-8W Polycrystalline HeatResistant Alloy Invited International conference

    M. Mitsuhara, T. Ito, S. Yamasaki, H. Nakashima, M. Nishida, M. Yonemura

    18th International Conference on the Strength of Materials  2018.6 

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    Venue:オハイオ州立大  

  • 耐熱合金の微細組織の観察・測定と評価

    山﨑重人

    IHI Materials Forum 2018  2018.8 

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    Venue:IHI 横浜事業所  

  • フェライト系耐熱鋼のクリープ強度に及ぼす W と Co 添加の影響

    山﨑重人, 光原昌寿, 中島英治

    高温変形の組織ダイナミクス研究会「平成 30 年度 夏の学校」  2018.9 

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    Venue:ホテル春慶屋  

  • 2 元系アルミニウム固溶体合金のセレーシ ョン挙動

    古賀鈴, 山﨑重人, 光原昌寿, 中島英治, 秋吉竜太郎, 木村申平

    高温変形の組織ダイナミクス研究会「平成 30 年度 夏の学校」  2018.9 

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    Venue:ホテル春慶屋  

  • 金属表面に形成する潤滑油膜に対する結晶方位と結晶粒径の影響

    岩﨑眞澄, 山﨑重人, 光原昌寿, 中島英治, 西田稔, 殿塚一希

    日本鉄鋼協会 第176回秋季講演大会  2018.9 

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    Venue:東北大学  

  • 焼きならし処理のみを施したGr.91鋼における静的時効中のM23C6炭化物成長挙動

    荒金遼河, 山﨑重人, 光原昌寿, 中島英治, 澤田浩太, 木村一弘

    日本鉄鋼協会 第176回秋季講演大会  2018.9 

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    Venue:東北大学  

  • 高Crフェライト系耐熱鋼溶接熱影響部再現組織への前焼き戻し処理の影響

    佐々木王城, 山﨑重人, 光原昌寿, 中島英治, 澤田浩太,久布白圭司

    日本鉄鋼協会 第176回秋季講演大会  2018.9 

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    Venue:東北大学  

  • ラスマルテンサイト鋼のクリープ変形挙動に与える転位密度の影響

    當山守人, 山﨑重人, 光原昌寿, 中島英治

    日本鉄鋼協会 第176回秋季講演大会  2018.9 

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    Venue:東北大学  

  • 高温変形の未踏領域 ~及川洪先生「単相金属・合金の高温クリープ挙動: その理解と問題点」のレビューに基づいて~

    山﨑重人

    鉄鋼協会「高温材料の高強度化」研究会 第2回研究会  2018.10 

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    Venue:淡路 ゆうなぎ荘  

  • Al-Mg-Si合金とAl-Mg-Zn合金のセレーション挙動

    三池友樹, 山﨑重人, 光原昌寿, 中島英治

    軽金属学会 第136回春期大会  2019.5 

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    Venue:富山国際会議場  

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MISC

  • レーザ積層造形法と電子ビーム積層造形法で作製したAC8Aアルミニウム合金のミクロ組織と引張特性—Microstructure and tensile strength of AC8A aluminum alloy fabricated by laser-based powder bed fusion and electron-based powder bed fusion—特集 軽金属材料の三次元造形技術

    安達 充, 奥平 有, 山﨑 重人, 光原 昌寿, 中島 英治, 小岩井 修二, 橋詰 良樹, 村上 勇夫, 寺田 大将

    軽金属   2022.5

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    Language:Japanese  

  • Ti-6Al-4V合金における室温クリープ中の転位の運動様式と変形組織の発達過程

    出口 岬, 山﨑 重人, 光原 昌寿, 中島 英治, 大田 祐太朗

    チタン = Titanium Japan   2021.10

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    Dislocation Motion and Microstructure Evolution Deformed during Creep at Room Temperature in Ti-6Al-4V Alloy

Industrial property rights

Patent   Number of applications: 2   Number of registrations: 0
Utility model   Number of applications: 0   Number of registrations: 0
Design   Number of applications: 0   Number of registrations: 0
Trademark   Number of applications: 0   Number of registrations: 0

Professional Memberships

  • The Iron and Steel Institute of Japan

  • The Japan Institute of Metals and Materials

  • The Japan Institute of Light Metals

  • THE JAPAN INSTITUTE OF METALS AND MATERIALS

  • THE IRON AND STEEL INSTITUTE OF JAPAN

  • THE JAPAN INSTITUTE OF LIGHT METALS

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Academic Activities

  • 2023-2024年度講演大会委員

    日本金属学会  ( Japan ) 2023.5

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    Type:Competition, symposium, etc. 

  • Screening of academic papers

    Role(s): Peer review

    2022

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

    Number of peer-reviewed articles in Japanese journals:3

  • ISIJ international International contribution

    2021.6 - 2025.3

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    Type:Academic society, research group, etc. 

  • 鉄と鋼

    2021.6 - 2025.2

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    Type:Academic society, research group, etc. 

  • 座長

    軽金属学会 第140回春期大会  ( Japan ) 2021.5

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    Type:Competition, symposium, etc. 

  • Screening of academic papers

    Role(s): Peer review

    2021

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:6

    Number of peer-reviewed articles in Japanese journals:2

  • Screening of academic papers

    Role(s): Peer review

    2020

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:4

  • Screening of academic papers

    Role(s): Peer review

    2019

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:3

  • 座長

    日本金属学会 春期(第162回)講演大会  ( Japan ) 2018.3

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    Type:Competition, symposium, etc. 

  • Screening of academic papers

    Role(s): Peer review

    2018

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    Type:Peer review 

    Number of peer-reviewed articles in foreign language journals:2

    Number of peer-reviewed articles in Japanese journals:1

    Proceedings of International Conference Number of peer-reviewed papers:0

    Proceedings of domestic conference Number of peer-reviewed papers:0

  • 座長 International contribution

    IU-MRS (International union of Materials Research Society) 2017  ( Japan ) 2017.8

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Research Projects

  • マルテンサイト鋼の実用環境におけるクリープ変形機構の解明

    2023 - 2024

    日本鉄鋼協会 鉄鋼研究振興助成

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    Authorship:Principal investigator  Grant type:Contract research

  • 微小片持ちはり試験片を用いた転位間相互作用の測定

    Grant number:22H01813  2022 - 2024

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant type:Scientific research funding

  • 菊池バンド幅解析と画像相関法を併用した任意のミクロ領域からの応力-ひずみ曲線取得

    2021 - 2022

    日本金属学会フロンティア研究助成

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    Authorship:Principal investigator  Grant type:Contract research

  • 第2回日本金属学会フロンティア研究助成

    2021

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    Grant type:Donation

  • 磁気変態に伴う拡散速度変化に着目した耐熱鋼の新しいクリープ強化概念の確立

    Grant number:19K15277  2019 - 2020

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant type:Scientific research funding

  • 磁気変態に伴う拡散速度変化に着目した耐熱鋼の新しいクリープ強化概念の確立

    Grant number:19K15277  2019 - 2020

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Early-Career Scientists

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    Authorship:Principal investigator  Grant type:Scientific research funding

  • Ti合金の室温クリープに関する研究

    2018.5 - 2020.3

    Joint research

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    Authorship:Principal investigator  Grant type:Other funds from industry-academia collaboration

  • 高温における亜粒界強化機構の解明

    Grant number:18H01739  2018 - 2020

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Authorship:Coinvestigator(s)  Grant type:Scientific research funding

  • 高温における亜粒界強化機構の解明

    Grant number:18H01739  2018 - 2020

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant type:Scientific research funding

  • アルミニウム合金のしきい応力以下での極低速クリープ変形機構

    2018 - 2019

    平成30年度アルミニウム研究助成事業

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    Authorship:Principal investigator  Grant type:Contract research

  • 分散強化鋼の分散状態の不均一性がしきい応力に及ぼす影響

    2017.6 - 2018.3

    Joint research

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    Authorship:Principal investigator  Grant type:Other funds from industry-academia collaboration

  • ECCI法によるHCP材料の転位観察

    2017.6 - 2018.3

    Joint research

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    Authorship:Principal investigator  Grant type:Other funds from industry-academia collaboration

  • 多結晶金属中の転位組織の不均一性とその力学特性への影響

    Grant number:17H06933  2017 - 2018

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (C)

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    Grant type:Scientific research funding

  • 多結晶金属中の転位組織の不均一性とその力学特性への影響

    Grant number:17H06933  2017 - 2018

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (Start-up)

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    Authorship:Principal investigator  Grant type:Scientific research funding

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Educational Activities

  • 工学府材料工学専攻および工学部材料工学科における下記担当授業科目の担当ならびに所属研究室での研究指導を行っている。

Class subject

  • 結晶化学

    2023.12 - 2024.2   Winter quarter

  • 自動車用金属材料学

    2023.12 - 2024.2   Winter quarter

  • 結晶塑性学

    2023.12 - 2024.2   Winter quarter

  • 耐熱材料工学

    2023.12 - 2024.2   Winter quarter

  • 回折結晶学

    2023.12 - 2024.2   Winter quarter

  • 高温材料強度学第一

    2023.10 - 2023.12   Fall quarter

  • 無機材料解析学

    2023.10 - 2023.12   Fall quarter

  • 無機材料解析学

    2023.10 - 2023.12   Fall quarter

  • 高温材料強度学

    2023.10 - 2023.12   Fall quarter

  • 自動車用金属材料学

    2022.12 - 2023.2   Winter quarter

  • 高温材料強度学第二

    2022.12 - 2023.2   Winter quarter

  • 耐熱材料工学

    2022.12 - 2023.2   Winter quarter

  • 結晶塑性学

    2022.12 - 2023.2   Winter quarter

  • 非鉄材料工学

    2022.10 - 2023.3   Second semester

  • 結晶塑性学

    2021.12 - 2022.2   Winter quarter

  • 高温材料強度学第二

    2021.10 - 2021.12   Fall quarter

  • 非鉄構造材料工学

    2021.10 - 2021.12   Fall quarter

  • 非鉄材料工学

    2021.10 - 2021.12   Fall quarter

  • 物質プロセス工学演習第二C

    2021.4 - 2022.3   Full year

  • 結晶塑性学

    2021.4 - 2021.9   First semester

  • 物質プロセス工学演習第二C

    2020.4 - 2021.3   Full year

  • 物質科学情報集約演習

    2020.4 - 2021.3   Full year

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Other educational activity and Special note

  • 2021  Class Teacher  学部

  • 2021  Special Affairs  九州大学未来創成科学者育成プロジェクト

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    九州大学未来創成科学者育成プロジェクト