検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年
検索結果: 16 件中 1件目~16件目を表示
  • 1

発表形式

Initialising ...

選択項目を絞り込む

掲載資料名

Initialising ...

発表会議名

Initialising ...

筆頭著者名

Initialising ...

キーワード

Initialising ...

使用言語

Initialising ...

発行年

Initialising ...

開催年

Initialising ...

選択した検索結果をダウンロード

論文

Achieving excellent mechanical properties in type 316 stainless steel by tailoring grain size in homogeneously recovered or recrystallized nanostructures

Liu, M.*; Gong, W.; Zheng, R.*; Li, J.*; Zhang, Z.*; Gao, S.*; Ma, C.*; 辻 伸泰*

Acta Materialia, 226, p.117629_1 - 117629_13, 2022/03

 被引用回数:0 パーセンタイル:0.01(Materials Science, Multidisciplinary)

One hopeful path to realize good comprehensive mechanical properties in metallic materials is to accomplish homogeneous nanocrystalline (NC) or ultrafine grained (UFG) structure with low dislocation density. In this work, high pressure torsion deformation followed by appropriate annealing was performed on 316 stainless steel (SS). For the first time, we successfully obtained NC/UFG 316 SS having uniform microstructures with various average grain sizes ranging from 46 nm to 2.54 $$mu$$m and low dislocation densities. Among the series, an un-precedentedly high yield strength (2.34 GPa) was achieved at the smallest grain size of 46 nm, in which dislocation scarcity induced hardening accounting for 57% of the strength. On the other hand, exceptional strength-ductility synergy with high yield strength (900 MPa) and large uniform elongation (27%) was obtained in the fully recrystallized specimen having the grain size of 0.38 $$mu$$m. The high yield stress and scarcity of dislocation sources in recrystallized UFGs activated stacking faults and deformation twins nucleating from grain boundaries during straining, and their interaction with dislocations allowed for sustainable strain hardening, which also agreed with the plaston concept recently proposed. The multiple deformation modes activated, together with the effective strengthening mechanisms, were responsible for the outstanding comprehensive mechanical performance of the material.

論文

Effect of hydrogen on evolution of deformation microstructure in low-carbon steel with ferrite microstructure

岡田 和歩*; 柴田 曉伸*; Gong, W.; 辻 伸泰*

Acta Materialia, 225, p.117549_1 - 117549_13, 2022/02

 被引用回数:1 パーセンタイル:86.83(Materials Science, Multidisciplinary)

In this study, the deformation microstructure of hydrogen-charged ferritic-pearlitic 2Mn-0.1C steel was characterized using SEM-BSE, SEM-EBSD, TEM, and neutron diffraction. The microscopic mechanism of hydrogen-related quasi-cleavage fracture along the ${011}$ planes was also discussed. It was found that hydrogen increased the relative velocity of screw dislocations to edge dislocations, leading to a tangled dislocation morphology, even at the initial stage of deformation (strain = 0.03). In addition, the density of screw dislocations at the later stage of deformation (strain = 0.20) increased in the presence of hydrogen. Based on the experimental results, it is proposed that a high density of vacancies accumulated along ${011}$ slip planes by jog-dragging of screw dislocations, and coalescence of the accumulated vacancies led to the hydrogen-related quasi-cleavage fracture along the {011} slip planes.

論文

Nature of dynamic ferrite transformation revealed by ${it in-situ}$ neutron diffraction analysis during thermomechanical processing

柴田 曉伸*; 竹田 泰成*; Park, N.*; Zhao, L.*; Harjo, S.; 川崎 卓郎; Gong, W.*; 辻 伸泰*

Scripta Materialia, 165, p.44 - 49, 2019/05

 被引用回数:17 パーセンタイル:84.71(Nanoscience & Nanotechnology)

Nowadays, a new concept of process utilizing dynamic ferrite transformation, which can achieve ultrafine-grained structure with a mean grain size of approximately 1$$mu$$m, has been proposed. This paper reports transformation mode of dynamic ferrite transformation and formation mechanism of ultrafine-grained structure revealed by our novel technique of ${it in-situ}$ neutron diffraction analysis during thermomechanical processing. Dynamic ferrite transformation occurs in a diffusional manner, whose partitioning behavior changes from para- to ortho-equilibrium with the progress of transformation. Moreover, we propose that dynamic recrystallization of dynamically-transformed ferrite is the main mechanism for the formation of ultrafine-grained structure.

論文

In situ neutron diffraction study on microstructure evolution during thermo-mechanical processing of medium manganese steel

中村 良彦*; 柴田 曉伸*; Gong, W.*; Harjo, S.; 川崎 卓郎; 伊東 篤志*; 辻 伸泰*

Proceedings of International Conference on Martensitic Transformations: Chicago, p.155 - 158, 2018/04

The microstructure evolution of medium manganese steel (Fe-5Mn-2Si-0.1C (wt%)) during thermo-mechanical processing in ferrite + austenite two-phase region was investigated by in situ neutron diffraction analysis and microstructure observations. When the specimens were isothermally held at a temperature of 700$$^circ$$C, the fraction of reversely transformed austenite increased gradually with an increase in the isothermal holding time. However, it did not reach the equilibrium fraction of austenite even after isothermal holding for 10 ks. On the other hand, the fraction of reversely transformed austenite increased rapidly after the compressive deformation at a strain rate of 1 s$$^{-1}$$ at 700$$^circ$$C and reached the equilibrium state during subsequent isothermal holding for around 3 ks.

報告書

JMTRのコンクリート構造物,冷却設備及びユーティリティ設備等の健全性調査概要

海老沢 博幸; 花川 裕規; 浅野 典一; 楠 秀彦; 箭内 智博; 佐藤 信一; 宮内 優; 大戸 勤; 木村 正; 川俣 貴則; et al.

JAEA-Technology 2009-030, 165 Pages, 2009/07

JAEA-Technology-2009-030.pdf:69.18MB

2007年度から開始するJMTR原子炉施設の改修工事に先立ち、「継続使用する設備・機器」の健全性調査を実施した。調査範囲は、原子炉建家を筆頭に、排気筒,一次冷却系の塔槽類,カナルエキスパンドジョイント,UCL高架水槽,二次系冷却塔及び配管,非常用発電機等、多岐にわたった。その結果、一部補修を要する部分が確認され補修を行ったが、今後の長期保全計画に沿った保守管理を行うことで、十分な安全確保と長期使用に耐えうることが確認された。原子炉更新課は、以上の健全性調査の結果を踏まえて改修工事を進めている。

口頭

First trial of in situ neutron diffraction experiment with thermo-mechanical simulator at J-PARC

Harjo, S.; 柴田 曉伸*; Park, N.*; 川崎 卓郎; 大石 毅一郎*; 相澤 一也; 辻 伸泰*

no journal, , 

A new sample environmental device for simulating thermo-mechanical processes of materials (thermec-mastor) has been installed in a collaboration between a research group in Kyoto University and BL19 in MLF of J-PARC, within a scheme of Elements Strategy Initiative for Structural Materials supported by Ministry of Education, Culture, Sports, Science and Technology, Japan. This new device is designed to heat the specimens by induction heating and cool them by gas injection. The highest rates for heating and cooling are about 30 K/s. It can also apply compressive deformation with the highest rate of 100 mm/s. The basic design and the commissioning progress of the thermec-mastor will be briefly introduced together with the first neutron diffraction data on steels. At 300 kW accelerator operation, diffraction patterns sliced with the interval time of about 1 s could be used to determine the occurrence of phase transformation during thermo-mechanical processes.

口頭

Dislocation monitoring during deformation and new sample environment device for engineering studies

Harjo, S.; 川崎 卓郎; 友田 陽*; 柴田 曉伸*; 辻 伸泰*; 相澤 一也

no journal, , 

Two topics done at TAKUMI of MLF, J-PARC are introduced. Evolutions of dislocation characteristics during tensile deformation in a lath martensitic steel have been possible to be monitored by applying the convolutional multiple whole profile (CMWP) fitting method, to understand the strengthening behavior of metallic material with extremely high dislocation density induced during the material preparation. This method is possible to be applied to understand the deformation behaviour of bulk nano materials. A new sample environmental device for simulating Thermo-Mechanical Controlling Process of materials (thermec-mastor) has been installed in a collaboration between a research group in Kyoto University and TAKUMI. This new device is designed to heat and cool a specimen rapidly, and to apply compression with a high strain rate. The basic design and the commissioning progress of the thermec-mastor will be briefly introduced together with the first neutron diffraction data on steels.

口頭

J-PARCでの加工熱処理シミュレータを用いたその場中性子回折の予備実験

Harjo, S.; 川崎 卓郎; 相澤 一也; 柴田 曉伸*; 辻 伸泰*

no journal, , 

金属材料の加工熱処理制御プロセスをシミュレートするための新しいサンプル環境装置(thermec-mastor)は、文部科学省の構造材料元素戦略プロジェクト内で、京都大学とMLFのBL19(匠)研究グループ間の共同で開発し匠にインストールされた。本装置は、試験片を誘導加熱により加熱し、ガス注入によって冷却できるように設計されている。加熱と冷却の最高速度は約30K/sで、最高速度が100mm/sの圧縮変形を適用することが可能である。本装置の基本設計及び本装置を用いた鉄鋼材料の加工熱処理制御プロセス中のその場中性子回折実験について紹介する。

口頭

Q&Pプロセスにおける相変態と炭素分配に及ぼすオーフォミングの影響

Gong, W.*; Harjo, S.; 柴田 曉伸*; 友田 陽*; 篠崎 智也*; 辻 伸泰*

no journal, , 

Quenching and partitioning (Q&P) process is an effective approach to control the amount and stability of retained austenite. Our previous study confirmed that carbon partitioning and isothermal transformation simultaneously occurred below martensitic transformation starting (Ms) temperature. In order to deepen the understanding on controlling microstructures through Q&P processes, the effect of ausforming on phase transformation and carbon partitioning during the Q&P process were investigated by the use of in-situ neutron diffraction in the present study.

口頭

Deformation mechanisms of AZ31 alloy at cryogenic temperature investigated by in-situ neutron diffraction

Gong, W.; Harjo, S.; 眞山 剛*; 川崎 卓郎; 相澤 一也; Sun, B.*; 辻 伸泰*

no journal, , 

その場中性子回折による極低温圧縮変形中のAZ31マグネシウム合金の変形挙動と変形メカニズムを調べた。21Kでの応力-ひずみ曲線は、室温よりわずかに高い降伏応力を示したが、破断応力と破断ひずみが大幅に高くなったこと分かった。極低温でのc軸引張双晶の促進とc軸圧縮双晶の抑制が、AZ31合金の引張強さ・破断伸びともに向上させる理由であることが明らかにした。

口頭

Strain hardening behavior of metastable austenitic steel with TRIP effect; Insights from stress and strain partitioning

Mao, W.; Gao, S.*; Gong, W.; Bai, Y.*; Park, M.-H.*; 柴田 曉伸*; 辻 伸泰*

no journal, , 

In this study, strain hardening behavior of Fe-24Ni-0.3C metastable austenitic steel having deformation induced martensitic transformation (DIMT) during deformation was investigated by tensile test with in-situ neutron diffraction, aiming to clarify the mechanism of the enhanced strain hardening caused by the DIMT. The results suggested that the evolution of phase stress of martensite during the deformation plays an important role in the strain hardening. It was found that during deformation the phase stress of martensite firstly increased rapidly from a low value, and then the rate of increase decreased as it approached 1.8 GPa. A dramatic increase in the stress partitioning between austenite and martensite was generated due to the rapid increase of martensite phase stress, which contributed significantly to the increase in the overall strain hardening rate of the material. The analysis of plastic deformation of austenite and martensite reveals that the rapid increase in stress partitioning occurred during the elasto-plastic deformation stage and arose from the occurrence of the plastic strain misfits.

口頭

In-situ neutron diffraction study of deformation behavior of AZ31 alloy at 21K

Gong, W.; Harjo, S.; 眞山 剛*; 川崎 卓郎; 相澤 一也; Sun, B.*; 辻 伸泰*

no journal, , 

We conducted in-situ neutron diffraction experiments to investigate the temperature dependence of deformation mechanisms at 21 K in an AZ31 Mg alloy. The neutron diffraction results demonstrate that the extension twinning was enhanced at cryogenic temperature, which can provide additional capacity for strain accommodation and work hardening. Moreover, the contraction double twinning, as known to be the crack initiation source in Mg alloys, was suppressed at 21 K. The different sensitivity to temperature of various deformation modes is considered to be the reason for the simultaneous increase in strength and ductility of the commercial AZ31 alloy at 21K.

口頭

In-situ neutron diffraction study of cryogenic deformation behavior in AZ31 magnesium alloy

Gong, W.; Harjo, S.; 眞山 剛*; 川崎 卓郎; 相澤 一也; 辻 伸泰*

no journal, , 

Magnesium and its alloys have potential for application in various fields, in which, the applications such as aerospace, storage, and transport of liquid cryogenics, require the materials to withstand high stress at extreme temperature. In present study, we conducted in-situ neutron diffraction experiments to investigate the cryogenic deformation behavior in a commercial extruded AZ31 Mg alloy. The neutron diffraction results demonstrate that the changes in activity of deformation modes are considered to be the reason for the simultaneous increase in strength and ductility of the commercial AZ31 alloy at cryogenic temperature.

口頭

Grain size effect on the strain hardening behavior of Fe-24Ni-0.3C metastable austenitic steel studied by in-situ neutron diffraction

Mao, W.; Gao, S.*; Gong, W.; Park, M. H.*; Bai, Y.*; 柴田 曉伸*; 辻 伸泰*

no journal, , 

Deformation induced martensitic transformation (DIMT) during plastic deformation of metastable austenitic steels plays an important role in enhancing their strain hardening, leading to an outstanding combination of strength and tensile ductility. In this study, Fe-24Ni-0.3C metastable austenitic steel specimens having mean grain sizes ranging from 1.3 micrometer to 35 micrometers were fabricated by cold rolling and subsequent annealing processes. The effect of the grain size on the strain hardening behavior and DIMT in the material was investigated by tensile test at room temperature with in-situ neutron diffraction. Results obtained by the in-situ neutron diffraction showed that the enhanced strain-hardening rate was caused not only by the increase of the volume fraction of martensite but also by the rapid increase of the internal stress within martensite. When the grain size changed within the coarse grained region (35 micrometers to 4 micrometers) the influence of the grain size on the stress partitioning between austenite and martensite was relatively small, thus the work-hardening behavior was mainly determined by the increasing rate of the volume fraction of martensite. However, when the grain size decreased down to ultrafine grain regime (smaller than 2 micrometers), the internal stress in martensite significantly increased, which resulted in the increasing work-hardening rate. The increasing stress in martensite in the ultrafine grained specimens is explained by the enhanced elastic stress associated with the incompatibility between martensite and austenite phases.

口頭

Multi-scale characterization of twinning and detwinning in AZ31 alloy

Gong, W.; Zheng, R.*; Harjo, S.; 川崎 卓郎; 相澤 一也; 辻 伸泰*

no journal, , 

Extension twinning and detwinning play crucial roles in cyclic loading deformation of magnesium (Mg) and its alloys. The occurrences of twining and detwinning are accompanied by the motion of twin boundaries (TBs), and then the interaction between the TBs and lattice defects such as dislocations and various boundaries is the key factor for the mechanical properties. Because of the complex microstructures introduced by cyclic deformation, the work hardening mechanisms associated with twinning and detwinning in Mg alloys are still far from being understood. In the present study, twinning and detwinning behavior of a commercial AZ31 Mg alloy during cyclic compression-tension deformation was evaluated in multi-scale using in-situ neutron diffraction (ND), identical area electron backscatter diffraction (EBSD), and transmission electron microscopy techniques. The relationship between the mechanical responses in cyclic deformation and microstructures was investigated.

口頭

In situ neutron diffraction study on lattice parameter changes of austenite and martensite during transformation in Fe-18Ni alloy

Gong, W.; Harjo, S.; 友田 陽*; 諸岡 聡; 川崎 卓郎; 柴田 曉伸*; 辻 伸泰*

no journal, , 

Austenite to martensite transformation in steels is a volume expansion phase transformation. However, the puzzling results have still been reported that a hydrostatic compressive stress was observed in austenite as opposite to the Eshelby's inclusion theory. In present study, we carried out neutron diffraction experiments having higher penetration ability than above methods to investigate the lattice parameter changes in real time during martensitic transformation. A high-purity Fe-18Ni binary alloy was selected to avoid the chemical contribution from the interstitial element. Several measuring processes were carefully designed and performed by in-situ neutron diffraction. Thermal phase stresses in martensite and austenite phases were separated from those stemmed from the face-centered cubic to body-centered cubic transformation strains and lattice defects. As results, the plastic accommodation is suggested to affect the lattice parameter of austenite and then its phase stress.

16 件中 1件目~16件目を表示
  • 1