Updated on 2025/04/16

Information

 

写真a

 
KAWAHARA YASUHITO
 
Organization
Faculty of Engineering Department of Materials Science and Engineering Assistant Professor
School of Engineering （Concurrent）
Title
Assistant Professor
Contact information
メールアドレス
Tel
0928022969
Profile
金属材料特性と微細構造の間には密接な相関があることから、微細構造の詳細な理解に基づく材料組織制御が重要である。特に近年、金属材料において、組織設計が原子スケールにまで及んでいることを鑑みると、金属材料に添加された合金元素の存在状態や、金属材料中に発現した結晶欠陥構造を原子スケールで理解し、金属材料特性と相関づけることが必要不可欠であると考えられる。そこで私は、透過型電子顕微鏡（TEM）を用いることにより、TEM内その場引張・加熱観察や原子分解能TEM観察などを行うことで、金属材料における微細構造を原子スケールで理解し、かつ金属材料の加工熱処理に伴う微細構造の変化を追随することで、未解明であった金属材料特性の起源の解明に取り組んでいる。
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Research Areas

  • Nanotechnology/Materials / Metallic material properties

  • Nanotechnology/Materials / Inorganic materials and properties

  • Nanotechnology/Materials / Structural materials and functional materials

Degree

  • Ph.D

Research History

  • Kyushu University Faculty of Engineering Assistant Professor 

    2024.4 - Present

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  • Japan Society for the Promotion of Science 特別研究員（PD）  

    2023.10 - 2024.3

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  • Japan Society for the Promotion of Science 特別研究員（DC1）  

    2021.4 - 2023.9

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Education

  • Kyushu University   Faculty of Engineering   材料工学専攻

    2021.4 - 2023.9

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Research Interests・Research Keywords

  • Research theme： 金属材料

    Keyword： 金属材料

    Research period： 2024

  • Research theme： 透過型電子顕微鏡

    Keyword： 透過型電子顕微鏡

    Research period： 2024

  • Research theme： 転位

    Keyword： 転位

    Research period： 2024

  • Research theme： 析出

    Keyword： 析出

    Research period： 2024

  • Research theme： クラスタ―

    Keyword： クラスタ―

    Research period： 2024

  • Research theme： Nano-structural characterization of metallic materials by 4D-STEM

    Keyword： low-carbon steel, austenitic stainless steel, aluminum alloy, cluster, dislocation, scanning transmission electron microscopy, 4D-STEM

    Research period： 2022.9

  • Research theme： The interaction between clusters and dislocations in metallic materials

    Keyword： low-carbon steel, austenitic stainless steel, aluminum alloy, cluster, dislocation, transmission electron microscopy

    Research period： 2021.4

Awards

  • The Awards for Excellent Academic Research

    2023.9   Kyushu University  

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  • ICAS2022 Poster Award

    2022.5   ICAS2022  

  • ICAS2022 Poster Award

    2022.5   ICAS2022  

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  • エネルギーウィーク2022 奨励賞

    2022.1   エネルギーウィーク2022  

  • エネルギーウィーク2022 奨励賞

    2022.1   エネルギーウィーク2022  

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  • 優秀口頭発表賞（第64回シンポジウム）

    2021.11   日本顕微鏡学会  

  • Paper Award Kyushu MMIJ（2021年度講演大会）

    2021.5   資源・素材学会九州支部  

  • 努力賞（第180回春季大会）

    2021.3   日本鉄鋼協会  

  • エネルギーウィーク2021 銅賞

    2021.1   エネルギーウィーク2021  

  • Paper Award Kyushu MMIJ（2020年度講演大会）

    2020.5   資源・素材学会九州支部  

  • ポスター優秀発表賞（2019年度講演大会）

    2019.12   日本顕微鏡学会九州支部  

  • Outstanding Student Award Kyushu MMIJ

    2019.3   資源・素材学会九州支部  

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Papers

  • Cu distribution in intermetallic phases in extruded Al-Mg-Si-Cu alloys

    Yasuhito Kawahara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyset, Randi Holmestad, Kenji Kaneko

    Journal of Alloys and Compounds   1012   2025.1   （ ISSN:0925-8388 eISSN:1873-4669 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Journal of Alloys and Compounds  

    Primary Fe-containing intermetallic phases are formed in Al-Mg-Si-Cu alloys during industrial processes, which can change Cu distribution as well as the strength of the alloys. However, there is no literature which correlates the Cu distribution with microstructures of the intermetallic phases. In this study, we carried out microscopic analysis to characterize the Cu distributions in extruded Al-Mg-Si-Cu alloys with the focus on primary Fe-containing intermetallic phases. The primary α-phase was confirmed as the primary particle in the alloys, typically elongated along the extrusion direction. Cu was found to be enriched in αsc-phases formed in the Si-rich Al-Mg-Si-Cu alloy, while being depleted in αbcc-phases in the Mg-rich alloy variant. FactSage calculations suggested that αsc-phase was more stable in Si-rich variants than in Mg-rich variants, slightly influenced by Cu content. These results suggest that it is effective to maintain more Cu atoms in solid solution by increasing Mg/Si ratio to optimize the α-phase as the αbcc-phase.

    DOI： 10.1016/j.jallcom.2025.178472

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  • Combined effect of interstitial-substitutional elements on dislocation dynamics in nitrogen-added austenitic stainless steels

    Yasuhito Kawahara, Shunya Kobatake, Kenji Kaneko, Taisuke Sasaki, Tadakatsu Ohkubo, Chikako Takushima, Jun Ichi Hamada

    Scientific Reports   14 ( 1 )   4360   2024.12   （ ISSN:2045-2322 eISSN:2045-2322 ）

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    Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Scientific Reports  

    Combined addition of interstitial-substitutional elements has been acknowledged to contribute to the increase in the strengths of steels. For further improvements in mechanical properties, their atomic-scale interaction mechanisms with dislocations are required to be examined. In this study, both high-resolution transmission electron microscopy and atom-probe tomography were used to correlate interstitial-substitutional elements with dislocation characteristics in austenitic stainless steels. Three types of dislocation core structures are identified and associated with their strain fields as well as N and Cr atoms in the N-added steels. It is revealed that N atoms interact elastically with the dislocations, followed by the segregation of Cr atoms via the chemical interaction between N and Cr atoms. This insight significantly improves the understanding of the multiple alloying mechanism in metallic materials such as interstitial alloys and high-entropy alloys.

    DOI： 10.1038/s41598-024-54852-w

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  • Chirality in Singlet Fission: Controlling Singlet Fission in Aqueous Nanoparticles of Tetracenedicarboxylic Acid Ion Pairs

    Ilias Papadopoulos, Joseph Ka‐Ho Hui, Masa‐aki Morikawa, Yasuhito Kawahara, Kenji Kaneko, Kiyoshi Miyata, Ken Onda, Nobuo Kimizuka

    Advanced Science   11 ( 39 )   e2405864   2024.8   （ eISSN:2198-3844 ）

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Advanced Science  

    The singlet fission characteristics of aqueous nanoparticles, self-assembled from ion pairs of tetracene dicarboxylic acid and various amines with or without chirality, are thoroughly investigated. The structure of the ammonium molecule, the counterion, is found to play a decisive role in determining the molecular orientation of the ion pairs and its regularity, spectroscopic properties, the strength of the intermolecular coupling between the tetracene chromophores, and the consequent singlet fission process. Using chiral amines has led to the formation of crystalline nanosheets and efficient singlet fission with a triplet quantum yield as high as 133% ±20% and a rate constant of 6.99 × 109 s−1. The chiral ion pairs also provide a separation channel to free triplets with yields as high as 33% ±10%. In contrast, nanoparticles with achiral counterions do not show singlet fission, which gave low or high fluorescence quantum yields depending on the size of the counterions. The racemic ion pair produces a correlated triplet pair intermediate by singlet fission, but no decorrelation into two free triplets is observed, as triplet-triplet annihilation dominates. The introduction of chirality enables higher control over orientation and singlet fission in self-assembled chromophores. It provides new design guidelines for singlet fission materials.

    DOI： 10.1002/advs.202405864

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  • Formation of core-shell structured carbides via interphase precipitations in V-Nb microalloyed steels

    Yasuhito Kawahara, Asaka Tokuhisa, Takuya Maeda, Hiroyuki Shirahata, Ryuji Uemori, Kenji Kaneko

    Scripta Materialia   249   2024.8   （ ISSN:1359-6462 eISSN:1872-8456 ）

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    Publishing type：Research paper (scientific journal)   Publisher：Scripta Materialia  

    It is one of the most effective methods to manipulate the atomic-scale structures of carbides formed by interphase precipitation to enhance the strengths of the microalloyed steel. In this study, conventional TEM, STEM-EDS, and HR-STEM were carried out to understand the origin of fine carbide precipitation in V-Nb multiple microalloyed ferritic steels. TEM characterizations showed that the multiple additions of V and Nb resulted in B1 structured alloy carbides with (V,Nb)C-cores and VC-shells, resulting in denser carbide precipitation compared to single additions of these elements. Thermo-Calc calculations and TEM results suggest that the precipitation kinetics of the (V,Nb)C-cores depends on the balance between its driving force and the misfit strain with the surrounding matrix, while that of the VC-shells is achieved by aging precipitation.

    DOI： 10.1016/j.scriptamat.2024.116169

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  • Influence of Nitrogen Content and Deformation Temperatures on Dislocation Structures in Austenitic Stainless Steels

    Yabuki Soh, Kawahara Yasuhito, Kobatake Shunya, Takushima Chikako, Hamada Jun-ichi, Kaneko Kenji

    Tetsu-to-Hagane   110 ( 10 )   779 - 787   2024.8   （ ISSN:00211575 eISSN:18832954 ）

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    Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

    <p>Nitrogen-added austenitic stainless steels exhibit excellent work-hardenability due to planar slips of dislocations. Two mechanisms of the planar slip have been proposed so far: glide plane softening mechanism and stacking-fault energy (SFE) reduction mechanism, which are thought to be dependent on nitrogen content and deformation temperature. In this study, conventional TEM, STEM-EDS and HR-STEM characterizations were carried out to clarify the influences of deformation temperature and nitrogen content on the dislocation characteristics of austenitic stainless steels. In the case of the nitrogen-added steel, the dislocation configurations became planar at a high temperature, 973 K. HR-STEM analysis revealed that SFE decreased with N addition and increased with temperature increase. Weak-beam TEM and HR-STEM analyses revealed that the planar dislocations were composed of 60° mixed-dislocations and SFs at room temperature, and edge-dislocation and SFs at 973 K. These results suggested that the edge components of defects interacted elastically with N and N-Cr pairs and contributed to the origin of the planar slips.</p>

    DOI： 10.2355/tetsutohagane.tetsu-2024-054

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  • Combined effect of interstitial-substitutional elements on dislocation dynamics in nitrogen-added austenitic stainless steels

    Kawahara Yasuhito, Kobatake Shunya, Kaneko Kenji, Sasaki Taisuke, Ohkubo Tadakatsu, Takushima Chikako, Hamada Jun-ichi

    scientific reports   14   4360   2024.2   （ eISSN:20452322 ）

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    Language：English   Publisher：Springer  

    Combined addition of interstitial-substitutional elements has been acknowledged to contribute to the increase in the strengths of steels. For further improvements in mechanical properties, their atomic-scale interaction mechanisms with dislocations are required to be examined. In this study, both high-resolution transmission electron microscopy and atom-probe tomography were used to correlate interstitial-substitutional elements with dislocation characteristics in austenitic stainless steels. Three types of dislocation core structures are identified and associated with their strain fields as well as N and Cr atoms in the N-added steels. It is revealed that N atoms interact elastically with the dislocations, followed by the segregation of Cr atoms via the chemical interaction between N and Cr atoms. This insight significantly improves the understanding of the multiple alloying mechanism in metallic materials such as interstitial alloys and high-entropy alloys.

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  • Lessons Through Electron Microscopy Experiment

    Kawahara Yasuhito

    Materia Japan   63 ( 1 )   69 - 69   2024.1   （ ISSN:13402625 eISSN:18845843 ）

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

    DOI： 10.2320/materia.63.69

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  • Characterization of the precipitation sequence of transition carbides from carbon clusters by transmission electron microscopy

    Kawahara Yasuhito, Takahashi Jun, Sawada Hideaki, Kaneko Kenji

    Proceedings of International Symposia on Steel Science   2024 ( 0 )   88 - 95   2024   （ eISSN:27596621 ）

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

    <p>The structures of carbon clusters and carbides in a low-carbon ferritic steel were investigated at atomic-scale by annular dark-field scanning transmission electron microscopy. In the low-carbon ferritic steel aged at 473 K for 1 h, some homogeneously dispersed ε-carbides were formed within the matrix as closely spaced granules aligned to <001> of the ferrite matrix, and others were heterogeneously formed on AlN precipitates. The ε-carbides formed on AlN precipitates were coexisted with carbon clusters with c/a ratio of 1.1, possibly formed via Zener-ordering. In-situ heating experiments showed that ε-carbides acted as precursors for θ-carbides via dissolution of ε-carbides. The microstructural evidence showed that the precipitation sequence of the low-carbon ferritic steels aged at 473 K is proposed as: supersaturated solid-solution → carbon clusters → ε-carbides → θ-carbides, suggesting that Zener-ordering should be the most fundamental step for the carbide precipitation sequence.</p>

    DOI： 10.2355/isijisss.2024.0_88

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  • Characterization of the precipitation sequence of transition carbides from carbon clusters by transmission electron microscopy

    KAWAHARA Yasuhito, TAKAHASHI Jun, SAWADA Hideaki, KANEKO Kenji

    Proceedings Book. International Symposium on Steel Science   7th   2024   （ ISSN:2759-6621 ）

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  • Nucleation and Phase Development of Precipitates in Age-hardenable Aluminium Alloys Studied by 4D-STEM

    Randi Holmestad, Elisabeth Thronsen, Yasuhito Kawahara, Tina Bergh, Jørgen A. Sørhaug, Christoph M. Hell, Ruben Bjørge, Emil F. Christiansen, Kenji Kaneko, Calin D. Marioara

    Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada   29 ( 1 )   305 - 306   2023.7   （ ISSN:1431-9276 eISSN:1435-8115 ）

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    Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada  

    DOI： 10.1093/micmic/ozad067.141

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  • Transition from carbon clusters to ε, θ-carbides in a quenched and aged low-carbon ferritic steel

    Yasuhito Kawahara, Kenji Kaneko, Hideaki Sawada, Jun Takahashi

    Acta Materialia   252   2023.6   （ ISSN:1359-6454 eISSN:1873-2453 ）

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    Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Acta Materialia  

    Carbon redistribution is one of the fundamental issues in quenched and aged carbon steels, which results in carbon clustering and carbide precipitation. Carbon clusters and carbides act as obstacles for dislocations, which have been known closely correlated with strengths of steels. In this study, conventional TEM, atomically-resolved TEM and In-situ heating TEM observations were carried out to understand carbon redistribution in a low-carbon ferritic steel aged at 473 K. Some ε-carbides were uniformly precipitated in the matrix, and the others were heterogeneously precipitated along dislocations. These ε-carbides were coexisted with carbon clusters with c/a ratio of 1.1, assumed to be the formation of Zener-ordered Fe8C. Moreover, θ-carbides were found precipitated from ε-carbides via dissolution of ε-carbides, confirmed by In-situ heating TEM experiments. These results suggested that Zener ordering should be the fundamental step for the following carbide precipitation sequences in the steel aged at 473 K.

    DOI： 10.1016/j.actamat.2023.118919

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  • Characterization of age hardening mechanism of low-temperature aged low-carbon steel by transmission electron microscopy

    Yasuhito Kawahara, Takuya Maeda, Keisuke Kinoshita, Jun Takahashi, Hideaki Sawada, Ryo Teranishi, Kenji Kaneko

    Materials Characterization   183   2022.1   （ ISSN:1044-5803 eISSN:1873-4189 ）

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    Language：Others   Publishing type：Research paper (scientific journal)   Publisher：Materials Characterization  

    Low-temperature aging treatment at 323 K results in the dramatical increase in hardness in low-carbon ferritic steels quenched from 983 K, possibly caused by carbon clusters and/or fine ε-carbides. In this study, transmission electron microscopy (TEM) analysis was carried out to characterize the change of the microstructure during the low-temperature aging treatment. Until the early stage of the peak hardness, the carbon clusters were formed homogeneously with zig-zag structures. At the latter stage of the peak hardness, it was found that the ε-carbides were partially precipitated within the carbon clusters, which suggested that the carbon clusters might have acted as the precursors of ε-carbides. In-situ tensile TEM observations showed that dislocation motions were free-glide type, and carbon clusters and fine-carbides interacted with dislocations via cutting-type. Dislocation interaction force was also evaluated, which suggested that the lattice misfit played as important role of the interaction mechanism.

    DOI： 10.1016/j.matchar.2021.111579

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  • Formation of core-shell type structure in Duplex Martensitic Steel

    Kenji Kaneko, Takuya Maeda, Yasuhito Kawahara, Kazuhiro Ichino, Takuro Masumura, Toshihiro Tsuchiyama, Hiroyuki Shirahata, Ryuji Uemori

    Scripta Materialia   193   112 - 116   2021.3

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    Microstructures of both as-quenched and intercritical-annealed medium-Mn steel were investigated by transmission electron microscopy to acquire a better understanding of γ–ɛ and γ–α′ martensitic transformations. The orientation relationships among each phases were determined as (1¯10)α′//(0001)ε,[111]α′//[112¯0]ε for the case of as-quenched sample, and (1¯10)α′//(1¯11)γ//(0001)ε,[111]α′//[110]γ//[112¯0]ε for the case of intercritical-annealed sample, respectively. In addition, the presences of core-shell type microstructures with the gradient of Mn concentration were confirmed with ɛ–martensite being surrounded by retained γ. Mn concentration of each phase was found dependent on the growth of reversed γ controlled by Mn diffusion during intercritical annealing. It was strongly suggested that the gradient of Mn concentration occurred during intercritical annealing affected the phase stability, which resulted in the formation of ε/γ core-shell microstructures.

    DOI： 10.1016/j.scriptamat.2020.10.044

  • Effect of nitrogen addition on the stacking-fault energies in Si-added austenitic stainless steel

    Yasuhito Kawahara, Ryo Teranishi, Chikako Takushima, Jun Ichi Hamada, Kenji Kaneko

    ISIJ International   61 ( 3 )   1029 - 1036   2021.3

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    Austenitic stainless steels have superior room temperature and high temperature strengths, strongly influenced by stacking-faults in the steel microstructure. Nitrogen addition makes substantial contribution to room temperature and high temperature strengths, so it is essential to consider the effect of nitrogen on the stacking-fault energies (SFE) to understand strength mechanism of the steel and to enhance the strength. In this study, SFE were measured by weak-beam TEM method, and deformation mechanisms of nitrogen-added austenitic stainless steels at room temperature and at high temperature (1 173 K) were discussed in terms of SFE in Si-added austenitic stainless steel (Fe-19 wt&#37;Cr-13 wt&#37;Ni-0.05 wt&#37;C-3 wt&#37;Si-x wt&#37;N). Nitrogen addition resulted in the decrease of SFE, which changed dislocation structures at room temperature and at 1 173 K. At room temperature, nitrogen addition resulted in dislocation localization, and at 1 173 K, all samples formed the sub-grain structure, caused by the dislocation recovery. It was revealed that the increase of nitrogen content resulted in the increase of the dislocation density in the sub-boundary, which indicates that the decrease of SFE contributes to the high temperature strength.

    DOI： 10.2355/ISIJINTERNATIONAL.ISIJINT-2020-609

  • Plan-view characterization of intergranular precipitates on grain boundaries by combination of FIB lift out method and TEM analyses: A case study in austenitic stainless steel

    Kousei Sato, Kenji Kaneko, Toru Hara, Yasuhito Kawahara, Jun ichi Hamada, Chikako Takushima, Ryo Teranishi

    Micron   138   2020.11

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    A new characterization method is proposed to study intergranular precipitates of polycrystalline material in the planar manner. A dual beam focused ion beam (FIB) - scanning electron microscopy (SEM) was applied to fabricate thin FIB lamella with a grain boundary parallel to the lamella to investigate for transmission electron microscopy (TEM). Distributions, microstructures and compositions of intergranular precipitates of austenitic stainless steel were then examined by TEM, scanning transmission electron microscopy (STEM), and energy dispersive X-ray spectroscopy (EDS). This plan-view microstructural characterization methods would play important roles in the case of materials where the intergranular precipitates play key roles for their physical and chemical properties.

    DOI： 10.1016/j.micron.2020.102927

  • An answer to the carbon cluster in low-temperature aged ferritic low-carbon steel

    Takuya Maeda, Yasuhito Kawahara, Keisuke Kinoshita, Hideaki Sawada, Jun Takahashi, Ryo Teranishi, Kenji Kaneko

    Materials Characterization   159   2020.1

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    The morphology and crystal structure of the carbon cluster in a low-temperature aged low-carbon ferritic steel were clarified by performing conventional and in-situ TEM, and atomically-resolved ADF-STEM observation. The carbon cluster grow parallel to <001> direction of the matrix, whose morphology was presumed to be either disk or plate. Lattice constant of the carbon cluster was measured by peak fitting of atomic columns observed by ADF-STEM. The result clarified that the structure of the carbon cluster was martensite-like body-centered tetragonal (bct) structure. This martensite-like bct structure suggested that the carbon cluster was supersaturated with carbon atoms occupying specific octahedral sites.

    DOI： 10.1016/j.matchar.2019.110006

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Presentations

  • 薄膜プロセスを用いたBa8CuxSi46-x発電材料における組成傾斜領域の微細構造解析

    中島康雄, 河原康仁, 宗藤伸治, 寺西亮

    2024年度日本金属学会, 日本鉄鋼協会, 軽金属学会 九州支部共催  2024.6 

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    Event date： 2024.6

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  • V及びNb複合添加鋼におけるコアシェル型合金炭化物の相界面析出現象

    河原 康仁, 徳久 朝佳, 鈴木 良河, 金子 賢治, 植森 龍治, 前田 拓也, 中村 修一

    日本鉄鋼協会第187回春季講演大会  2024.3 

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    V及びNb複合添加鋼におけるコアシェル型合金炭化物の相界面析出現象

  • 2D and 4D high-resolution scanning transmission microscopy of GP-zones in the 6xxx system

    Christoph Martin Hell, Yasuhito Kawahara, Jonas Frafjord, Ruben Bjørge, Kenji Kaneko, Randi Holmestad

    IMC20  2023.9 

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    2D and 4D high-resolution scanning transmission microscopy of GP-zones in the 6xxx system

  • Al-Mg-Si合金におけるクラスターの原子構造に及ぼすCu添加の影響

    河原康仁, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, 金子賢治

    日本顕微鏡学会第79回学術講演会  2023.6 

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  • Atomic-scale study of GP-zones in Al-Mg-Si-Cu alloys by four-dimensional scanning transmission electron microscopy

    Yasuhito Kawahara, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, Kenji Kaneko

    IMC20 Satellite Symposium  2023.9 

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    Atomic-scale study of GP-zones in Al-Mg-Si-Cu alloys by four-dimensional scanning transmission electron microscopy

  • Atomically resolved STEM and 3DAP analysis of the dislocation dragging mechanisms in nitrogen-added Fe-Cr-Ni austenitic stainless steels

    Yasuhito Kawahara, Shunya Kobatake, Chikako Takushima, Jun-ichi Hamada, Taisuke Sasaki, Tadakatsu Ohkubo, Kenji Kaneko

    IMC20  2023.9 

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    Atomically resolved STEM and 3DAP analysis of the dislocation dragging mechanisms in nitrogen-added Fe-Cr-Ni austenitic stainless steels

  • Dislocation analyses in Nitrogen-added Austenitic Stainless Steels

    Soh Yabuki, Yasuhito Kawahara, Chikako Takushima, Junichi Hamada, Kenji Kaneko

    IMC20 Satellite Symposium  2023.9 

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    Dislocation analyses in Nitrogen-added Austenitic Stainless Steels

  • Influence of Cu addition on the atomic structure of early-stage precipitates in 6XXX alloys

    Yasuhito Kawahara, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, Kenji Kaneko

    INTPART Workshop  2023.4 

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    Influence of Cu addition on the atomic structure of early-stage precipitates in 6XXX alloys

  • Nucleation and Phase Development of Precipitates in age-hardenable Aluminium Alloys studied by 4DSTEM Invited

    Randi Holmestad, Elisabeth Thronsen, Yasuhito Kawahara, Tina Bergh, Jørgen A, Sørhaug, Christoph M. Hell, Ruben Bjørge, Kenji Kaneko, Calin Marioara

    M&M 2023  2023.7 

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    Nucleation and Phase Development of Precipitates in age-hardenable Aluminium Alloys studied by 4DSTEM

  • オーステナイト系ステンレス鋼におけるN-Crクラスターと転位の相互作用

    河原康仁, 小畠駿哉, 多久島睦子, 濱田純一, 金子賢治

    2023年度日本鉄鋼協会 材料の組織と特性部会 若手金属材料研究者の交流(若手)フォーラム  2023.6 

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  • Al-Mg-Si合金の析出過程に及ぼすCu添加の影響

    河原康仁, 吉川有太, 金子賢治

    日本顕微鏡学会第78回学術講演会  2022.5 

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  • Influence of nitrogen addition on the temperature dependences of hardening mechanisms in austenitic stainless steels

    Yasuhito Kawahara, Shunya Kobatake, Chikako Takushima, Jun-ichi Hamada, Kenji Kaneko

    ICAS2022  2022.5 

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    Influence of nitrogen addition on the temperature dependences of hardening mechanisms in austenitic stainless steels

  • Influences of Cu addition on precipitation hardening mechanisms in Al-Mg-Si alloys

    Yasuhito Kawahara, Yuta Kikkawa, Kenji Kaneko

    ICAA18  2022.9 

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    Influences of Cu addition on precipitation hardening mechanisms in Al-Mg-Si alloys

  • 鉄鋼材料における炭素クラスターを介した炭化物の析出機構の直接観察

    河原康仁, 高橋淳, 澤田英明, 金子賢治

    九州大学エネルギーウィーク2022  2022.1 

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  • Al-Mg-Si合金の析出強化に及ぼすCu添加の影響

    河原康仁, 寺西亮, 金子賢治, 宍戸久郎

    日本顕微鏡学会第64回シンポジウム  2021.11 

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  • その場引張TEM法によるAl-Mg-Si合金の析出強化の定量評価

    河原康仁, 佐藤幸生, 寺西亮, 宍戸久郎, 金子賢治

    日本金属学会第169回講演大会  2021.9 

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  • その場引張TEM法によるCクラスターと転位の相互作用の解明

    河原康仁, 佐藤幸生, 寺西亮, 金子賢治, 高橋淳, 澤田英明

    日本鉄鋼協会第180回春季講演大会  2021.3 

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  • その場引張TEM観察によるAl-Mg-Si系合金の析出強化に及ぼすCu添加の影響の解明

    河原康仁, 佐藤幸生, 寺西亮, 宍戸久郎, 金子賢治

    九州大学エネルギーウィーク2021  2021.1 

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  • 低炭素鋼における炭素クラスターを介した炭化物の析出機構の解明

    河原康仁, 佐藤幸生, 寺西亮, 金子賢治, 高橋淳, 澤田英明

    日本顕微鏡学会第77回学術講演会  2021.6 

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  • 透過電子顕微鏡法を用いた炭素鋼におけるCクラスターと転位の相互作用の解明

    河原康仁, 佐藤幸生, 寺西亮, 金子賢治, 木下恵介, 高橋淳, 澤田英明

    2020年度資源・素材学会九州支部「若手研究者および技術者の研究発表会」  2021.5 

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  • 低炭素鋼におけるCクラスターの高分解能TEM観察による原子構造解析

    河原康仁, 佐藤幸生, 寺西亮, 木下恵介, 高橋淳, 澤田英明, 金子賢治

    2020年度資源・素材学会九州支部「若手研究者および技術者の研究発表会」  2020.5 

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  • 低炭素鋼におけるCクラスターと転位の相互作用の解明

    河原康仁, 佐藤幸生, 寺西亮, 木下恵介, 高橋淳, 澤田英明, 金子賢治

    2020年度日本鉄鋼協会春季大会  2020.3 

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  • 炭素クラスターと転位の相互作用のその場および静的解析

    河原康仁, 金子賢治, 木下惠介, 澤田英明, 高橋淳

    日本顕微鏡学会第63回シンポジウム「顕微鏡オンラインフォーラム2020」  2020.11 

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  • SUSXM15J1における積層欠陥の観察

    河原康仁, 佐藤幸生, 寺西亮, 多久島睦子, 松橋透, 金子賢治

    2019年度日本金属学会, 日本鉄鋼協会, 軽金属学会 九州支部共催  2019.6 

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  • オーステナイト系ステンレス鋼における積層欠陥エネルギーへの窒素添加の影響

    河原康仁, 佐藤幸生, 寺西亮, 多久島睦子, 溝口太一郎, 金子賢治

    2019年度日本顕微鏡学会九州支部会  2019.12 

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  • 窒素添加オーステナイト系ステンレス鋼における積層欠陥エネルギーの測定

    河原康仁, 佐藤幸生, 寺西亮, 多久島睦子, 松橋透, 金子賢治

    2019年度資源・素材学会九州支部「若手研究者および技術者の研究発表会」  2019.5 

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  • 鉄鋼材料における炭素クラスターを介した炭化物の析出機構の直接観察

    河原康仁, 高橋淳, 澤田英明, 金子賢治

    九州大学エネルギーウィーク2022  2022.1 

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  • 窒素添加オーステナイト系ステンレス鋼における時効処理が粒内析出物に及ぼす影響

    原子大輝, 河原康仁, 多久島睦子, 濱田純一, 金子賢治

    2024年度日本金属学会, 日本鉄鋼協会, 軽金属学会 九州支部共催  2024.6 

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  • オーステナイト系ステンレス鋼におけるN-Crクラスターと転位の相互作用

    河原康仁, 小畠駿哉, 多久島睦子, 濱田純一, 金子賢治

    2023年度日本鉄鋼協会 材料の組織と特性部会 若手金属材料研究者の交流(若手)フォーラム  2023.6 

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  • V及びNb複合添加鋼におけるコアシェル型合金炭化物の相界面析出現象

    河原 康仁, 徳久 朝佳, 鈴木 良河, 金子 賢治, 植森 龍治, 前田 拓也, 中村 修一

    日本鉄鋼協会第187回春季講演大会  2024.3 

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  • Nucleation and Phase Development of Precipitates in age-hardenable Aluminium Alloys studied by 4DSTEM Invited

    Randi Holmestad, Elisabeth Thronsen, Yasuhito Kawahara, Tina Bergh, Jørgen A, Sørhaug, Christoph M. Hell, Ruben Bjørge, Kenji Kaneko, Calin Marioara

    M&M 2023  2023.7 

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  • Mg過剰型Al-Mg-Si合⾦における時効硬化に及ぼすCu添加の影響

    田中優大, 河原康仁, 金子賢治

    2024年度日本金属学会, 日本鉄鋼協会, 軽金属学会 九州支部共催  2024.6 

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  • Influences of Cu addition on precipitation hardening mechanisms in Al-Mg-Si alloys

    Yasuhito Kawahara, Yuta Kikkawa, Kenji Kaneko

    ICAA18  2022.9 

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  • Influence of nitrogen addition on the temperature dependences of hardening mechanisms in austenitic stainless steels

    Yasuhito Kawahara, Shunya Kobatake, Chikako Takushima, Jun-ichi Hamada, Kenji Kaneko

    ICAS2022  2022.5 

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  • Influence of Cu addition on the atomic structure of early-stage precipitates in 6XXX alloys

    Yasuhito Kawahara, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, Kenji Kaneko

    INTPART Workshop  2023.4 

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  • Dislocation analyses in Nitrogen-added Austenitic Stainless Steels

    Soh Yabuki, Yasuhito Kawahara, Chikako Takushima, Junichi Hamada, Kenji Kaneko

    IMC20 Satellite Symposium  2023.9 

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  • Atomically resolved STEM and 3DAP analysis of the dislocation dragging mechanisms in nitrogen-added Fe-Cr-Ni austenitic stainless steels

    Yasuhito Kawahara, Shunya Kobatake, Chikako Takushima, Jun-ichi Hamada, Taisuke Sasaki, Tadakatsu Ohkubo, Kenji Kaneko

    IMC20  2023.9 

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  • Atomic-scale study of GP-zones in Al-Mg-Si-Cu alloys by four-dimensional scanning transmission electron microscopy

    Yasuhito Kawahara, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, Kenji Kaneko

    IMC20 Satellite Symposium  2023.9 

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  • Al-Mg-Si合金の析出過程に及ぼすCu添加の影響

    河原康仁, 吉川有太, 金子賢治

    日本顕微鏡学会第78回学術講演会  2022.5 

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  • Al-Mg-Si合金におけるクラスターの原子構造に及ぼすCu添加の影響

    河原康仁, Christoph Martin Hell, Calin Daniel Marioara, Elisabeth Savitri Thrane, Eva Anne Mørtsell, Jostein Røyse, Randi Holmestad, 金子賢治

    日本顕微鏡学会第79回学術講演会  2023.6 

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  • 2D and 4D high-resolution scanning transmission microscopy of GP-zones in the 6xxx system

    Christoph Martin Hell, Yasuhito Kawahara, Jonas Frafjord, Ruben Bjørge, Kenji Kaneko, Randi Holmestad

    IMC20  2023.9 

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  • Characterization of the precipitation sequence of transition carbides from carbon clusters by transmission electron microscopy Invited

    Yasuhito Kawahara, Kenji Kaneko, Jun Takahashi, Hideaki Sawada

    The 7th International Symposium on Steel Science - ISSS 2024  2024.11 

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  • Fe-N二元系オーステナイトにおける 変形組織の微細構造解析

    河原康仁, 増村拓朗, 土山聡宏, 古谷野有

    日本鉄鋼協会第189回講演大会  2025.3 

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  • Atomic-scale characterization of L-phase in Mg-rich Al-Mg-Si-Cu alloys

    田中優大, 河原康仁, 金子賢治

    日本金属学会2024年秋期(第175回)講演大会  2024.9 

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  • 時効処理を施した窒素添加オーステナイト系ステンレス鋼における析出物と硬度の関係

    原子大輝, 河原康仁

    日本鉄鋼協会第189回講演大会  2025.3 

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  • 窒素添加オーステナイト系ステンレス鋼 におけるN-Cr対と転位の相互作用

    河原康仁, 金子賢治, 佐々木泰祐, 大久保忠勝, 多久島睦子, 濱田純一

    第188回日本鉄鋼協会  2024.9 

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  • 窒素添加量及び変形温度の異なる オーステナイト系ステンレス鋼における転位組織の解析

    原子大輝, 矢吹創, 河原康仁, 金子賢治, 多久島睦子, 濱田純一

    日本鉄鋼協会第188回講演大会  2024.9 

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  • 薄膜プロセスにより組成傾斜させた Ba8CuxSi46-x発電材料の微細構造解析

    中島康雄, 河原康仁, 宗藤伸治, 寺西亮

    第33回新構造・機能制御と傾斜機能材料シンポジウム(FGMs-2024 in愛媛）  2024.12 

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MISC

  • 電子顕微鏡での研究を通じて

    河原 康仁

    まてりあ   2024.1

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    Lessons Through Electron Microscopy Experiment

    DOI： 10.2320/materia.63.69

  • Mg過剰型Al-Mg-Si-Cu合金中に析出したL相の原子スケール解析

    田中優大, 河原康仁, 金子賢治

    日本金属学会講演大会(Web)   175th   2024

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  • Mg過剰型Al-Mg-Si合金における時効硬化に及ぼすCu添加の影響

    田中優大, 河原康仁, 金子賢治

    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合同学術講演大会講演概要集   2024   2024

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  • Interfacial precipitation of core-shell structured carbides in V-Nb multiple micro-alloyed steels

    河原康仁, 徳久朝佳, 鈴木良河, 金子賢治, 植森龍治, 前田拓也, 中村修一

    材料とプロセス(CD-ROM)   37 ( 1 )   2024   （ ISSN:1882-8922 ）

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  • The interaction between N-Cr pairs and dislocations in nitrogen-added austenitic stainless steels

    河原康仁, 金子賢治, 佐々木泰祐, 大久保忠勝, 多久島睦子, 濱田純一

    材料とプロセス(CD-ROM)   37 ( 2 )   2024   （ ISSN:1882-8922 ）

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  • 窒素添加オーステナイト系ステンレス鋼における時効処理が粒内析出物に及ぼす影響

    原子大輝, 河原康仁, 金子賢治, 多久島睦子, 濱田純一

    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合同学術講演大会講演概要集   2024   2024

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  • Characterization of dislocation structures in austenitic stainless steels with different nitrogen content and deformation temperatures

    原子大輝, 矢吹創, 河原康仁, 金子賢治, 多久島睦子, 濱田純一

    材料とプロセス(CD-ROM)   37 ( 2 )   2024   （ ISSN:1882-8922 ）

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  • 薄膜プロセスを用いたBa<sub>8</sub>Cu<sub>x</sub>Si<sub>46-x</sub>発電材料における組成傾斜領域の微細構造解析

    中島康雄, 河原康仁, 宗藤伸治, 寺西亮

    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合同学術講演大会講演概要集   2024   2024

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  • 国際的な交流を進めるうえでの学び

    河原康仁

    軽金属   2023.4

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  • 国際的な交流を進めるうえでの学び

    河原康仁

    軽金属   73 ( 4 )   190 - 190   2023.4

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  • Al-Mg-Si合金の析出強化機構へのCu添加量の影響

    吉川有太, 河原康仁, 佐藤幸生, 金子賢治

    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合同学術講演大会講演概要集   2022   2022

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Professional Memberships

  • 日本金属学会

  • 日本鉄鋼協会

  • 日本顕微鏡学会

  • 日本顕微鏡学会

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  • 日本鉄鋼協会

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  • 日本金属学会

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Committee Memberships

  • 一般社団法人 日本鉄鋼協会 「材料の組織と特性部会」若手フォーラム   大学委員  

    2024.4 - Present   

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  • 一般社団法人 日本鉄鋼協会 「材料の組織と特性部会」若手フォーラム   博士委員  

    2023.4 - 2024.3   

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    Committee type：Academic society

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Research Projects

  • Elucidation of the mechanism for Portevin-Le Chatelier by in-situ TEM observation and exploration of solid-solution strengthening principle

    Grant number：24KK0101  2024.9 - 2028.3

    Grants-in-Aid for Scientific Research  Fund for the Promotion of Joint International Research (International Collaborative Research)

    高木 秀有, 金子 賢治, 大村 孝仁, 河原 康仁

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    Grant type：Scientific research funding

    本研究では，転位と固溶元素のクラスタとの相互作用で生じる応力-歪み線図上でみられるセレーション（PLC）の発現メカニズムを解明する．これを実現するために，透過電子顕微鏡（TEM）を用いた最先端の組織観察技術を有するLawrence Berkeley National Laboratory（LBNL）と，広範囲の固溶元素のクラスタを特定する新規解析技術を共同開発する．これら技術を融合させた高分解能TEM観察によってPLC発現メカニズムを解明することで，これまでに実験，理論および計算機実験で検討されてきた材料の強化法の一つである固溶強化の原理を顕わにする．

    CiNii Research

  • Characterization of the interaction mechanism between carbon cluster and dislocation in steel

    Grant number：22KJ2381  2022 - 2023

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for JSPS Fellows

    河原 康仁

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    Authorship：Principal investigator  Grant type：Scientific research funding

    鉄鋼材料を50度で時効処理することで生じる炭素クラスターは、優れた強化能を有する可能性が指摘されている。これまでの研究で、その場引張TEM法を適用することで、転位が炭素クラスターに対して大きく張り出す様子を直接観察することに成功し、炭素クラスターが高強度化に直接寄与することを実証するに至った。また、炭素クラスターを介して、ε炭化物が析出する様子が観察され、炭素クラスターがε炭化物の分散状態を左右することが判明した。
    そこで本研究では、炭素クラスターを活用した高強度化を推進するべく、炭素クラスターの結晶構造を明らかにすることで、炭素クラスターの形成機構の起源を探ることを目的としている。

    CiNii Research

Educational Activities

  • ・材料工学実験第一（2024年度〜）
    ・所属研究室における学部生や大学院生向け研究指導

Class subject

  • 材料工学実験第一

    2024.4 - 2024.6   Spring quarter