Stress partitioning between bcc and cementite phases discussed from phase stress and dislocation density in martensite steels

土田 紀之*; 上路 林太郎*; Gong, W.; 川崎 卓郎; Harjo, S.

Scripta Materialia, 222, p.115002_1 - 115002_6, 2023/01

https://doi.org/10.1016/j.scriptamat.2022.115002

The present study investigated the tensile deformation behavior of quenched and tempered martensite steels at various austenitization and tempering temperatures using in situ neutron diffraction experiments. Phase lattice strains in the bcc and cementite () phases and dislocation structures in the bcc phase were analyzed. The phase lattice strain in bcc became almost stagnant after yielding as the tempering temperature increased. The phase lattice strain in increased linearly with an increase in the flow stress, independent of the austenitization and tempering temperatures. The stress partitioning between bcc and was confirmed after the yielding of bcc, which contributed to the work hardening. The phase stresses of bcc and and their stress partitioning improve the mechanical properties of martensite steels, which can be summarized by the systematic changes in phase lattice strain and dislocation properties due to the austenitization and tempering temperatures.

Enhancement of uniform elongation by temperature change during tensile deformation in a 0.2C TRIP steel

土田 紀之*; Harjo, S.

Metals, 11(12), p.2053_1 - 2053_16, 2021/12

https://doi.org/10.3390/met11122053

To improve uniform elongation (U.El) due to the TRIP effect, it is important to control deformation-induced martensitic transformation (DIMT) until the late part of deformation. In the present study, tensile tests with decreasing deformation temperatures were conducted to achieve continuous DIMT up to the late part of deformation. As a result, the U.El was improved by approximately 1.5 times compared with that in the tensile test conducted at 296 K. The enhancement of the U.El in the temperature change test was discussed with the use of neutron diffraction experiments.

中性子回折により検討したTRIP鋼におけるオーステナイトの粒応力とマルテンサイト変態の関係

Harjo, S.; 川崎 卓郎; 土田 紀之*; 諸岡 聡; Gong, W.

鉄と鋼, 107(10), p.887 - 896, 2021/10

https://doi.org/10.2355/tetsutohagane.TETSU-2021-072

In situ neutron diffraction measurements of two low-alloy TRIP steels and a 304-type stainless steel during tensile and creep tests were performed at room temperature. Changes in the diffraction pattern, the peak integrated intensities of austenite () and the peak positions of were analyzed and discussed to understand a relationship between intergranular stress in and the occurrence of martensitic transformation during deformation. From tensile loading, it was found that the susceptibility of martensitic transformation depended on -() grains, in which -(111) grains underwent martensitic transformation at the latest. The -() dependence in the susceptibility of martensitic transformation was found to be controlled by the shear stress levels in -() grains, which were affected by the intergranular stress partitioning during deformation.

総合討論; 環境移行パラメータのデータベース化と生活圏被ばく線量評価への活用

高橋 知之*; 内田 滋夫*; 武田 聖司; 中居 邦浩*

KURNS-EKR-11, p.97 - 102, 2021/03

https://www.rri.kyoto-u.ac.jp/PUB/report/09_kurns/temp/kurns-ekr-011.pdf

農作物や水産物への元素の移行係数等の生活圏環境移行パラメータに対するIAEAのデータベースの取りまとめ状況や、わが国における放射性廃棄物処分の被ばく線量評価におけるデータベースの活用の状況について概説するとともに、将来の具体的な放射性廃棄物処分の地域における被ばく線量評価を想定した場合に対し、今後の生活圏環境移行パラメータのデータベース構築に必要な戦略、整備されるべき観点、課題点等に関して、専門家の意見と総合討論の結果について取りまとめた。

Thickness dependence of spin Peltier effect visualized by thermal imaging technique

大門 俊介*; 内田 健一*; 氏家 奈緒美*; 服部 靖之*; 坪井 嶺*; 齊藤 英治

Applied Physics Express, 13(10), p.103001_1 - 103001_4, 2020/10

https://doi.org/10.35848/1882-0786/abb2b5

Magnon propagation length in a ferrimagnetic insulator yttrium iron garnet (YIG) has been investigated by measuring and analyzing the YIG-thickness dependence of the spin Peltier effect (SPE) in a Pt/YIG junction system. By means of the lock-in thermography technique, we measured the spatial distribution of the SPE-induced temperature modulation in the Pt/YIG system with the gradation, allowing us to obtain the accurate dependence of SPE with high resolution. Based on the dependence of SPE, we verified the applicability of several phenomenological models to estimate the magnon diffusion length in YIG.

Model intercomparison of atmospheric Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

佐藤 陽祐*; 滝川 雅之*; 関山 剛*; 梶野 瑞王*; 寺田 宏明; 永井 晴康; 近藤 裕昭*; 打田 純也*; 五藤 大輔*; Qulo, D.*; et al.

Journal of Geophysical Research; Atmospheres, 123(20), p.11748 - 11765, 2018/10

https://doi.org/10.1029/2018JD029144

福島第一原子力発電所事故により放出されたCsの大気中の挙動を理解するため、大気拡散モデル相互比較が実施され、12モデルが参加した。モデルで考慮される過程に起因するモデル間の差異に焦点を当てた解析を行うため、全モデルで同じ気象場、水平分解能、及び放出源情報が使用された。モデルアンサンブルによる観測された大気中Cs濃度上昇イベントの捕捉率は40%であり、FMSは80を超えた。解析の結果、大気中Cs濃度上昇イベントの再現には気象場が最も重要な要素であり、気象場の再現性が高い場合のモデル間の差異は、沈着及び拡散過程に起因していることが分かった。また、沈着フラックスが小さいモデル及び拡散が強いモデルは高い性能を示したが、拡散が強いモデルは大気中Cs濃度を過大評価する傾向を示した。

Fabrication of neutron optical devices using PBW technique

酒井 卓郎; 飯倉 寛; 山田 尚人*; 佐藤 隆博*; 石井 保行*; 内田 正哉*

QST-M-8; QST Takasaki Annual Report 2016, P. 140, 2018/03

https://repo.qst.go.jp/records/73811

In this work, we report on the application of a UV/EB curable resin, in proton beam writing (PBW) for the fabrication of fine neutron optics devices. The resin is a liquid at room temperature; therefore, it mixes easily with functional materials, such as neutron absorbers. However, 20-30 m thick neutron absorber must be required as the grating materials. So PBW is a promising technique to fabricate the neutron devices. The fabrication process is similar to lithography. The neutron absorber is gadolinium oxide (GdO). Pattern exposures are performed using 3 MeV proton beams approximately 1 m in diameter. The irradiated areas are quickly cured by polymerization. The fabricated gratings were observed using an optical microscope. The microscopic images show that the patterns of the fabricated structures agree well with the original one. In addition, a lateral direction of the sample was observed using the scanning electron microscope (SEM). The thickness of the sample is approximately 35 m. In conclusion, the fabrication of grating structures is successful and the results also proved that the UV/EB curable resin is very promising material for use in PBW micromachining.

Martensite phase stress and the strengthening mechanism in TRIP steel by neutron diffraction

Harjo, S.; 土田 紀之*; 阿部 淳*; Gong, W.*

Scientific Reports (Internet), 7(1), p.15149_1 - 15149_11, 2017/11

AA2017-0453.pdf:3.62MB

https://doi.org/10.1038/s41598-017-15252-5

Two TRIP-aided multiphase steels with different carbon contents were analyzed in situ during tensile deformation by time-of-flight 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 before deformation, where the higher carbon content increased the phase fraction of retained austenite (). However, the changes in the relative fraction of martensitic transformation with respect to the applied strain were found to be similar in both steels since the carbon concentrations in were similar. The stress contribution from martensite was observed increasing during plastic deformation while that from bainitic ferrite hardly changing and that from decreasing.

Room-temperature creep tests under constant load on a TRIP-aided multi-microstructure steel

土田 紀之*; Nagahisa, N.*; Harjo, S.

Materials Science & Engineering A, 700, p.631 - 636, 2017/07

https://doi.org/10.1016/j.msea.2017.06.049

This study investigated room-temperature creep tests using a low-carbon TRIP steel to clarify the TRIP effect on tensile deformation behavior under constant load. Nominal strain and strain rate increased with an increase in applied stress and those were almost stagnated at holding times of about s. The volume fractions of deformation-induced martensite () at a given true strain obtained from constant load creep tests were larger than those from tensile tests. From the in situ neutron diffraction experiments during the constant load creep tests, the phase strain of the austenite () phase in the creep tests was found to be larger than that in the tensile tests at the same applied stress. This means that the phase strain or true stress of the phase in the TRIP steel was associated with the difference in the volume fraction of between the creep and the tensile tests.

STACYにおけるMOX溶解試験残液の安定化処理

小林 冬実; 住谷 正人; 木田 孝; 石仙 順也; 内田 昇二; 神永 城太; 大木 恵一; 深谷 洋行; 曽野 浩樹

JAEA-Technology 2016-025, 42 Pages, 2016/11

JAEA-Technology-2016-025.pdf:17.88MB

日本原子力研究開発機構原子力科学研究所のSTACY施設では、平成12年から15年にかけて、プルトニウム溶液臨界実験に向けたMOX粉末燃料の溶解に関する基礎試験を実施した。溶解試験で生じた硝酸ウラニル溶液と硝酸プルトニウム溶液からなるMOX溶解試験残液を貯蔵設備にて貯蔵するにあたり、溶液の状態から酸化物へ転換する安定化処理が必要である。さらに、臨界安全の観点から、安定化処理後の酸化物に含まれる水分量を管理する必要がある。MOX溶解試験残液を安定化する方法として、溶液中のウランをアンモニアにより、プルトニウムをシュウ酸により沈殿させ、焙焼して酸化物とする方法を選定した。本報告書は、MOX溶解試験残液に含まれるウラン及びプルトニウムの安定化処理に係る検討及び作業の結果をまとめたものである。本報告書で示した手順に基づく実規模での安定化処理の結果、ウランの回収率は95.6%、プルトニウムの回収率は95.0%であった。また、安定化処理後の酸化物を窒素雰囲気下で再焙焼し、速やかにビニールバッグで溶封することで、酸化物の含水率を低く保つとともに水分の再付着を防止した。