Principal preferred orientation evaluation of steel materials using time-of-flight neutron diffraction

徐 平光; Zhang, S.-Y.*; Harjo, S.; Vogel, S. C.*; 友田 陽*

Quantum Beam Science (Internet), 8(1), p.7_1 - 7_13, 2024/01

https://doi.org/10.3390/qubs8010007

Comprehensive information about the microstructure and crystal structure evolution during the preparation/production processes of various materials is in great demand in order to precisely control the microstructure morphology and the preferred orientation characteristics for the excellent strength-ductility-toughness balance of advanced engineering materials. isothermal annealing experiments of cold rolled 17Ni-0.2C (mass %) martensitic steel sheets were carried out by using the TAKUMI and ENGIN-X time-of-flight neutron diffractometers, respectively. The inverse pole figures based on full-profile refinement were extracted to roughly evaluate the preferred orientation features along three principal sample directions of investigated steel sheets using the General Structure Analysis System (GSAS) software with built-in generalized spherical harmonic functions. The consistent rolling direction (RD) inverse pole figures from TAKUMI and ENGIN-X have confirmed that the time-of-flight neutron diffraction has high repeatability and statistical reliability, revealing that the principal preferred orientation evaluation of steel materials is available through 90 TD ND (transverse direction normal direction) rotation of the investigated specimen on the sample stage during two neutron diffraction experiments. Moreover, these RD, TD and ND inverse pole figures before and after in situ experiments were compared with the corresponding inverse pole figures recalculated respectively from the MUSASI-L complete pole figure measurement and the HIPPO in situ microstructure evaluation. The similar orientation distribution characteristics suggested that the principal preferred orientation evaluation method can be applied to in situ microstructure evolution of bulk orthorhombic materials and spatially resolved principal preferred orientation mappings of large engineering structure parts.

Fatigue crack non-propagation behavior of a gradient steel structure from induction hardened railway axles

Zhang, H.*; Wu, S. C.*; Ao, N.*; Zhang, J. W.*; Li, H.*; Zhou, L.*; 徐 平光; Su, Y. H.

International Journal of Fatigue, 166, p.107296_1 - 107296_11, 2023/01

https://doi.org/10.1016/j.ijfatigue.2022.107296

Abnormal damages in railway axles can lead to a significant hazard to running safety and reliability. To this end, a surface treatment was selected to effectively inhibit fatigue crack initiation and growth. In this study, a single edge notch bending fatigue test campaign with artificial notches was conducted to elucidate the fatigue crack non-propagation behavior in railway S38C axles subjected to an induction hardening process. The fatigue cracking behavior in the gradient structure was revealed by optical microscopy, electron backscatter diffraction, and fractography. The microhardness distribution was measured using a Vickers tester. The obtained results show that the microhardness of the strengthening layer is nearly triple that of the matrix. Owing to the gradient microstructures and hardness, as well as compressive residual stress, the fatigue long crack propagates faster once it passes through the hardened zone (approximately 2.0 mm in the radial depth). Thereafter, local retarding (including deflection, branching, and blunting) of the long crack occurs because of the relatively coarse ferrite and pearlite in the transition region and matrix. Totally, this fatigue cracking resistance is reasonably believed to be due to the gradient microstructure and residual stress. These findings help to tailor a suitable detection strategy for maximum defects or cracks in railway axles.

Effects of residual stress and plastic strain on hydrogen embrittlement of a stretch-formed TRIP-aided martensitic steel sheet

北條 智彦*; 秋山 英二*; 齋藤 寛之*; 城 鮎美*; 安田 良*; 菖蒲 敬久; 衣笠 潤一郎*; 湯瀬 文雄*

Corrosion Science, 177, p.108957_1 - 108957_9, 2020/12

https://doi.org/10.1016/j.corsci.2020.108957

変態誘起塑性マルテンサイト鋼の半球延伸成形試験片の水素助長割れを調査した。水素の伝搬により、鋼板に形成された球体のすそにき裂が生じ、き裂は半径方向に沿って球体の中腹から平面に向かって伝播した。残留オーステナイトの応力,塑性ひずみ,体積分率の分布を、SPring-8でのシンクロトロンX線放射を利用したエネルギー分散型X線回折法を使用して分析した。測定された引張応力が最も高い領域でき裂の発生が起こったことは重要である。加えて塑性ひずみと結果として生じるマルテンサイト変態の影響も示唆された。

Real time observation of martensite transformation for a 0.4C low alloyed steel by neutron diffraction

Wang, Y.*; 友田 陽*; 大村 孝仁*; 諸岡 聡; Gong, W.*; Harjo, S.

Acta Materialia, 184, p.30 - 40, 2020/02

https://doi.org/10.1016/j.actamat.2019.11.051

A high-intensity and high-resolution neutron diffractometer with a thermomechanically controlled processing simulator was employed in-situ to investigate martensite transformation behavior with and without ausforming for a medium-carbon low-alloy steel. Serial neutron diffraction profiles have revealed that the transformation behavior could be successfully monitored during quenching with and without the ausforming process. The lattice parameter and the full width at half maximum of austenite peaks significantly decreases and increases upon martensite transformation, respectively. After ausforming, the data reveal that lattice parameters are larger in austenite whereas smaller in martensite compared with those in the non-ausformed case, which is ascribed to the introduced dislocations. The cutting-edge operant quantitative measurements with neutron diffraction for steel production is demonstrated.

The Present state of manufacturing LWR pressure vessels in Japan, 1; Heavy section RPV steels

長谷川 正義*; 川崎 正之; 藤村 理人

JAERI-M 5809, 39 Pages, 1974/07

JAERI-M-5809.pdf:1.56MB

日本における原子炉圧力容器鋼材は、原子炉の要求する品質を有している。本論文では、最近の超厚板の製造の現状をまとめたものである。本報告書は1974年10月にIAEAのワーキング・グループで紹介される。

原子炉用鉄鋼材料の照射効果

川崎 正之; 藤村 理人

日本金属学会会報, 4(2), p.77 - 89, 1965/00

https://doi.org/10.2320/materia1962.4.77

原子炉における鉄鋼材料の主な用途は圧力容器、ダクト、熟交換器などのいわゆる高温高圧構造系である。これらの構造系は原子炉の安全性について最も重要な役割を果す部材であるので、品質の高い鉄鋼材料が使用され、それらの溶接部も主として無欠陥の溶接が要求されることが多い。また、鉄鋼材料の種類も各種の鋼種が使用され、炭素鋼、低合金鋼、ステンレス鋼、ステンレス・クラッド鋼などを多量使用する。これらの圧力容器および配管系は、設計、工作技術上の難点をかかえている上に、原子炉寿命中に速中性子照射を10~10n/cm程度うけていわゆる照射脆化を生ずる。鉄鋼材料の照射脱化の程度は10n/cmの速中性子照射量を超えると加速度的に脆性破壊遷移温度の上昇を示すので、原子炉の安全上重要な問題点となっている。

In-situ measurement of internal strain distribution in laser welding materials under high temperature and tensile stress using synchrotron radiation

菖蒲 敬久; 城 鮎美; 村松 壽晴; 山田 知典; 永沼 正行; 小澤 隆之

no journal, , 

本講演では、レーザーにより重合せ溶接した鉄鋼材料(厚さ2mm+5mm、幅6mm)に対して、使用環境下である高温、および上下の板を反対方向に引張った負荷状態における内部ひずみ分布を、高エネルギー放射光X線を利用した非破壊測定、および有限要素法によるシミュレーションを行ったのでその結果を紹介する。引張負荷中で界面近傍に引張、圧縮ひずみが観測され、有限要素と一致した結果が得られた。一方、同時期に作成した試験片では界面近傍に引張、圧縮ひずみがあまり出現しない結果が得られ、この2つの違いが内部欠陥によるものであることを推察している。

Monitoring martensitic transformation during tensile test in TRIP steels using neutron diffraction

Harjo, S.; 土田 紀之*

no journal, , 

TRIP-aided multiphase steels with different carbon contents were analyzed in situ during tensile deformation by TOF neutron diffraction to clarify the deformation induced martensitic transformation behavior and its role on the strengthening mechanism. The difference in the carbon content affected mainly the difference in the phase fractions, where the higher carbon content increased the fraction of retained austenite (). However, changes in the relative fraction of martensitic transformation during deformation were found to be similar in both steels. The relative fraction of martensitic transformation increased with increasing of phase stress. The martensite phase stress was much larger than that of or bainitic ferrite since the martensite was generated at the beginning of plastic deformation. The stress contribution from martensite increased during plastic deformation while that from bainitic ferrite hardly changed and that from decreased.

放射光を用いた高温実環境下における材料強度評価

菖蒲 敬久

no journal, , 

本講演では、実環境を想定した測定として、レーザーにより重合せ溶接した鉄鋼材料(厚さ2mm+5mm、幅6mm)に対して、使用環境下である高温、および上下の板を反対方向に引張った負荷状態における内部ひずみ分布を、高エネルギー放射光X線による非破壊測定、及び有限要素法によるシミュレーションを行ったのでその結果を紹介する。

淡水環境で電気微生物腐食を引き起こすメタン菌の分離と解析

平野 伸一*; 若井 暁*; 上野 文義; 岡本 章玄*

no journal, , 

嫌気条件下の金属鉄の微生物腐食に関して、鉄から直接電子を引き抜くことでカソード反応を促進し顕著な腐食を引き起こす電気微生物腐食(EMIC)が報告された。これまでに、海水環境下からEMIC能を持つ硫酸還元菌、メタン菌が分離され研究が進められているが、淡水環境でのEMICの知見は非常に限られており、EMIC能を持つ微生物の腐食リスクへの関与は不明である。本研究では淡水環境である河川、地下水を対象としてEMIC能をもつ微生物を探索し、その腐食能を評価することを目的とした。その結果、淡水環境でEMIC能を有するメタン菌を初めて見出し、炭素鋼の腐食速度は0.36mm/yと海洋由来のメタン菌と同等の高い腐食活性を示した。