Updated on 2026/03/05

写真a

 
NAKADA NOBUO
 
Organization
School of Materials and Chemical Technology Professor
Title
Professor
External link

Degree

  • Dr. of Engineering ( Kyushu University )

Research Interests

  • 混粒

  • 構造・機能材料

  • 組織制御

  • ナノ

  • マルテンサイト変態

  • 引張特性

  • 超微細粒鋼

  • 銅

  • 混粒化

  • 強化機構

  • ひずみ測定

  • 高強度・高延性

  • 結晶粒微細化強化

  • Bailey-Hirchの関係

  • ひずみ分配

  • 応力分配

  • 鉄鋼

  • 機械的性質

  • ナノ構造

  • 加工硬化

  • 超細粒

  • 熱間押出

  • 転位密度

  • 二相組織

  • 結晶学

  • 電子線

  • Wilkinson法

  • 中性子線

  • スケールブリッジング

  • マルテンサイト

  • 鉄鋼材料

  • 相変態

  • 超微細粒

Research Areas

  • Nanotechnology/Materials / Structural materials and functional materials

  • Nanotechnology/Materials / Metallic material properties

  • Nanotechnology/Materials / Composite materials and interfaces

  • Nanotechnology/Materials / Material processing and microstructure control

Education

  • Kyushu University

    2002.4 - 2004.3

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    Country： Japan

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  • Kyushu University

    1998.4 - 2002.3

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    Country： Japan

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Research History

  • 東京工業大学／東京科学大学   物質理工学院   教授

    2022.4

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    Country：Japan

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  • Tokyo Institute of Technology   Associate Professor

    2015.4 - 2022.3

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    Country：Japan

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  • Max-Planck-Institut für Eisenforschung GmbH

    2011.9 - 2012.9

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    Country：Germany

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  • Kyushu University   Faculty of Engineering   Assistant Professor

    2004.4 - 2015.3

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    Country：Japan

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Professional Memberships

Papers

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Research Projects

  • Formation model of transformation-induced internal stress in martensitic steels with selective local strain analysis

    Grant number：24K01193  2024.4 - 2028.3

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

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    Grant amount：\18330000 （ Direct Cost: \14100000 、 Indirect Cost：\4230000 ）

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  • Kink Deformation of Ferrous Alloy with Lamellar Structure and Generalization of Mille-feuille Condition

    Grant number：19H05121  2019.4 - 2021.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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    Grant amount：\6890000 （ Direct Cost: \5300000 、 Indirect Cost：\1590000 ）

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  • investigation of a new type of martensitic reversion from ferrite initial structure

    Grant number：18H01729  2018.4 - 2021.3

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

    Nakada Nobuo

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    Grant amount：\17680000 （ Direct Cost: \13600000 、 Indirect Cost：\4080000 ）

    On the basis of an academic question, How microstructure does the austenite have via bcc-fcc reversion, if the initial bcc has no substructure?, the martensitic reversion formed from recrystallized bcc-ferrite was investigated. The analysis in terms of thermodynamics and kinetics found that the martensitic reversion takes place in Fe-16mass%Ni alloy under the continuous heating at 200 degree C/s. In addition, TEM observations proved that transformed microstructure is developed and high-density dislocations are introduced even through the bcc-fcc reversion.

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  • Systematization of academic background in grain refinement strengthening of steel

    Grant number：15H05768  2015.5 - 2020.3

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

    Setsuo Takaki

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    Grant amount：\158080000 （ Direct Cost: \121600000 、 Indirect Cost：\36480000 ）

    Yielding of well-annealed poly crystalline iron occurs by the dislocation emission from grain boundary and the grain refinement strengthening coefficient increases with an increase of the shear stress τ* which is required for the dislocation emission from grain boundary. τ* is small value in pure iron but changeable depending on the kind and amount of alloying elements which have segregated at grain boundary. The results of this study proved that C, N, Ni, Si, Mn and Al make τ* increase although the degree of effect is different, while Cr does not give so large effect to τ*.

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  • Development of Mechanical Properties in Dual Phase Steels by Percolation Control

    Grant number：15K06488  2015.4 - 2018.3

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

    Nakada Nobuo

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    Grant amount：\4940000 （ Direct Cost: \3800000 、 Indirect Cost：\1140000 ）

    For an essential understanding the microstructural factors dominating mechanical properties of metals with duplex microstructure in a meso scale, a change in 0.2% proof stress depending upon hard austenite fraction was investigated in terms of a microstructural connectivity using Fe-Ni austenitic alloy having a duplex microstructure composed of soft and hard austenite. 0.2% proof stress is continuously increased with increasing the fraction of the hard austenite. Especially, it is efficiently increased according to iso-strain condition when the hard austenite fraction exceeds a critical value. The non-linear strengthening tends to have good correlation with a connectivity of the hard austenite, that is, percolation phenomenon. This suggests that when the hard austenite grains are firmly connected to each other, plastic strain is uniformly distributed between soft and hard austenite during deformation, which leads to a significant strengthening in metals with duplex microstructure.

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  • Characterization and application of deformation and dissolution behavior of soft particles during plastic deformation in soft particle dispersion strengthening steel

    Grant number：26289262  2014.4 - 2017.3

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

    Tsuchiyama Toshihiro, HATA Satoshi, MOROOKA Satoshi, MUNETO Shinji, MURAYAMA Mitsuhiro

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    Grant amount：\14300000 （ Direct Cost: \11000000 、 Indirect Cost：\3300000 ）

    Among the dispersion particles used for strengthening steel, Cu particles, which are softer than iron matrix, were investigated in terms of their role in deformation and fracture of ferritic steel. In general, hard dispersion particles such as carbide and nitride induce ductile fracture originated at these particles, and thus, hard particles tend to reduce the ductility of steel although they are effective for strengthening. However, it was revealed that the soft Cu particles increase strength without reducing ductility too much. The superior mechanical property was explained by the mechanism that the soft particles undergo plastic deformation or dissolution in high strain regime during cold working, which leads to relaxation of stress/strain concentration at the particle interfaces. The results obtained indicates an important guideline for further strengthening of steels.

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  • Fabrication of Ultrafine Grained Austenitic Steel by Chemical Stability Controlled Phase Transformations

    Grant number：24560852  2012.4 - 2015.3

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

    NAKADA Nobuo, TANAKA Masaki

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    Grant amount：\5330000 （ Direct Cost: \4100000 、 Indirect Cost：\1230000 ）

    For further strengthening of TWIP steel which is expected as a next generation automotive steel sheet, a new heat treatment to promote precipitation and dissolution of carbide was applied for Fe-Mn-C alloys, leading to grain refinement via phase transformations. As a result, it was confirmed that austenite matrix is unstabilized after (austenite + carbide) two phase austenitization, namely partial solution treatment, and the heat treatment stimulates martensitic transformation in austenitic steel without any cold-deformation. In addition, it was found that reversion mechanism is discontinuously shifted from diffusive type to martensitic one with increasing heating rate in low Mn steels.

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  • Re-examination of alloy designing for grain refinement strengthening in iron and steel

    Grant number：23360310  2011.11 - 2014.3

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

    TAKAKI Setsuo, TSUCHIYAMA Toshihiro, NAKADA Nobuo

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    Grant amount：\3380000 （ Direct Cost: \2600000 、 Indirect Cost：\780000 ）

    In order to create a database for grain refinement strengthening of iron and steel, the following two researches were carried out. (1) the effects of carbon and nitrogen on grain refinement strengthening were investigated and the difference between carbon and nitrogen was discussed in terms of grain boundary segregation. (2) the effect of individual alloy elements on grain refinement strengthening, so-called Hall-Petch coefficient, was evaluated using interstitial free atoms free (IF) steel. As a result, (1) it was confirmed that carbon increases H-P coefficient more effectively than nitrogen due to a high amount of grain boundary segregation, but the tendency is able to be controlled by heat treatment. (2) the change in H-P coefficient depending on Cr, P and Ni could be evaluated individually.

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  • Development of hybrid microstructure observation method at and identical region

    Grant number：23656437  2011 - 2012

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Exploratory Research

    ADACHI Yoshitaka, NAKADA Nobuo, TOMOTA Tomota

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    Grant amount：\3510000 （ Direct Cost: \2700000 、 Indirect Cost：\810000 ）

    Hybrid observation using EBSD-Wilkinson method, Digital Image Correlation(DIC), and neutron diffraction method have been developed to understand hierarchical deformation and fracture mechanism.

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  • The proposal for the next-generation microstructural control technique of steel by using ultra-fine lath austenitic starting structure

    Grant number：22686065  2010 - 2011

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

    NAKADA Nobuo

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    Grant amount：\19240000 （ Direct Cost: \14800000 、 Indirect Cost：\4440000 ）

    For the production of fine-grained structural steel, the microstructural characteristics of lath austenite formed by martensitic reversion and the microstructure transformed from it were investigated. As a result, it was confirmed in a model steel that the lath austenite has fine lath structure containing high-density dislocations. In addition, it was suggested that martensitic reversion takes place even in a low alloyed steel under the specific condition controlled by alloy designing and heat treatment.

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  • Proposal of Hybrid Steel strengthen by multiple-precipitation of carbide and nano Cu particles

    Grant number：18360332  2006 - 2008

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

    TAKAKI Setsuo, TSUCHIYAMA Toshihiro, NAKAD Nobuo

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    Grant amount：\16370000 （ Direct Cost: \16100000 、 Indirect Cost：\270000 ）

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  • パーライト鋼の組織制御および組織と機械的特性の関係解明

    2006

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    Grant type：Competitive

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  • 鉄鋼材料における共析組織の変態機構解明

    2006

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    Grant type：Competitive

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  • 混粒化によるナノ鉄鋼材料の延性改善

    Grant number：17760572  2005 - 2006

    日本学術振興会  科学研究費助成事業  若手研究(B)

    中田 伸生

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    Grant amount：\1400000 （ Direct Cost: \1400000 ）

    鉄鋼材料の機械的性質(強度-延性バランス)向上を目的に、公称粒径10〜100μmのIF鋼の引張り特性に及ぼす混粒組織の影響を調査した。その結果、組織中の粗大な結晶粒が降伏強度よりも低い応力で降伏(ミクロ降伏)しているにもかかわらず、その降伏強度は公称粒径と降伏強度の関係を表すHall-Petchの関係に従うことが明らかとなった。このことは、ミクロ降伏した結晶粒の割合がある一定値に達した時に、材料(試験片)が降伏(マクロ降伏)することを示しており、組織中に存在する粗大な結晶粒は、降伏強度の大きな低下因子と成らないことを意味している。そして、幾何学的な計算の結果、組織中の70〜80vol.%の結晶粒がミクロ降伏した時、マクロ降伏が生じることも予想された。一方、明瞭な挙動を把握することは出来なかったものの、組織の混粒化はマクロ降伏後の加工硬化や延性(伸び)に影響を及ぼすことが確認され、混粒化による機械的性質の向上が十分に期待できると考えられる。実際に、粒径0.3Fm以下の超微細粒組織を有するCuでは、混粒組織になることで強度が若干低下するものの延性が増大し、強度-延性バランスが大幅に改善されるとの報告がなされている(Yinmin Wang, Mingwei Chen, Fenghua Zhou and En Ma ; NATURE VOL419,(2002),p912)。通常の粒径レベルでは生じ得ないこのような顕著な特性変化が生じたことは、混粒化の影響は結晶粒が微細になるほど顕著になることを示唆している。したがって、微細粒領域における組織の混粒化の有効性については、今後さらに広範囲での詳細な再調査を実施し、明らかにされるべき事項であろう。

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  • Cu含有鋼の物性・特性評価に関する研究

    2005

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    Grant type：Competitive

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  • マルテンサイトからオーステナイトへの逆変態

    2005

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    Grant type：Competitive

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  • 結晶粒微細化強化の効率に及ぼす微量元素の影響

    2005

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    Grant type：Competitive

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  • 高窒素鋼の組織制御

    2004

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    Grant type：Competitive

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  • 高合金マルテンサイト鋼の組織制御

    2004

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    Grant type：Competitive

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  • Property Evaluation and Application of Ultrafine Grained Steel

    Grant number：15206077  2003 - 2005

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

    TAKAKI Setsuo, HIGASHIDA Kenji, TSUCHIYAMA Toshihiro, MORIKAWA Tatsuya, NAKASHIMA Koichi, NAKADA Nobuo

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    Grant amount：\50830000 （ Direct Cost: \39100000 、 Indirect Cost：\11730000 ）

    For the purpose of evaluating the properties of submicron fine grained steels and exploring their possibilities of application, this study had been carried out for three years. We had 8 themes for investigating the submicron fine grained steels, but they are classified into three categories : (1)Fabrication and processing technique of submicron fine grained steels, (2)Microstructure analysis, (3)Evaluation of mechanical properties, and (4)Analysis of strengthening mechanism.
    We succeeded to fabricate submicron fine grained steels by adopting powder metallurgy technique (mechanical milling process). In addition, hot excursion method to form rod steel of several cm in diameter was also developed for applying to automobile parts. As for the analysis of the microstructure obtained, the local structure analysis and measurement of the dislocation density were performed by X ray diffractometry for fine selected areas ; the submicron grained structure and the dislocation substructure were carefully observed with TEM ; the orientation distribution and the texture were examined with FE-SEM-EBSP method. The mechanical properties were investigated by means of tensile testing at various temperatures ranging from low temperature of liquid nitrogen to elevated temperature. As a result, it was clarified that the submicron fine grained steels do not cause brittle fracture but ductile fracture even at low temperature, and that they exhibit superplasticity at elevated temperature, leading to the excellent deformability. Besides, we insisted that the combination of the grain refinement strengthening and other strengthening mechanism should be important to realize further strengthening. On the basis of this idea, the effect of combination of grain refinement and nano-Cu precipitation was investigated, and then we found that the yield strength of the steel is sometimes explained by the addition of both strengthening mechanism. However, it was also found the new facts that the ultrafine grained steel never exhibits age hardening and dislocation strengthening; thus we feel that the submicron fine grained steels should be moved to nano-grained material in the next stage.

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