Testing of time-of-flight neutron diffraction imaging using a high-resolution scintillator detector with wavelength-shifting fibers

川崎 卓郎; 中村 龍也; Gong, W.*; 及川 健一

Physica B; Condensed Matter, 551, p.460 - 463, 2018/12

https://doi.org/10.1016/j.physb.2018.01.067

Neutron diffraction is widely used for the investigation of lattice strain, texture and phase transformation in bulk materials. Although the distributions of these characteristics can be obtained by scanning the sample, the spatial resolution of the measurement is limited. Recently, Bragg-edge imaging technique is developed and adopted for the evaluations of lattice strain, crystal orientation and phase distributions in polycrystalline engineering materials such as steel. On the other hand, neutron diffraction imaging has a potential to be another technique for such purpose. Diffraction imaging at a pulsed neutron source requires a counting type two-dimensional position sensitive detector with high spatial resolution. We developed prototype imaging detector with wavelength-shifting fiber (WLSF) readout, and tried to observe sub grains in the b-Sn single crystal and grain distribution in the coarse-grained steel plate at NOBORU (BL10) of J-PARC MLF.

Deformation of CoCrFeNi high entropy alloy at large strain

Wang, B.*; He, H.*; Naeem, M.*; Lan, S.*; Harjo, S.; 川崎 卓郎; Nie, Y.*; Wang, X.-L.*; 他7名*

Scripta Materialia, 155, p.54 - 57, 2018/10

https://doi.org/10.1016/j.scriptamat.2018.06.013

The deformation behavior of an equi-atomic face-centered-cubic CoCrFeNi high entropy alloy was investigated by in-situ neutron diffraction under tensile loading up to 40% applied strain. A three-stage deformation behavior was fully captured by lattice strain and texture evolution. In spite of the chemical complexity, the deformation in CoCrFeNi is dominated by dislocation activities. Analysis of diffraction and microscopy data shows that the deformation progresses from dislocation slip to severe entanglement, where a sharp increase in dislocation density was observed. The neutron diffraction data, corroborated by transmission electron microscopy analysis, provided microscopic insights of the previously reported three-stage hardening behavior.

中性子回折法による曲げとせん断を受けた鉄筋コンクリートの付着応力度の非破壊評価

鈴木 裕士; 楠 浩一*; 佐竹 高祐*; 兼松 学*; 小山 拓*; 丹羽 章暢*; 椛山 健二*; 向井 智久*; 川崎 卓郎; Harjo, S.

非破壊検査, 67(4), p.180 - 186, 2018/04

https://doi.org/10.11396/jjsndi.67.180

本研究では、中性子回折法により二次元的に配筋した主筋およびせん断補強筋の応力分布を測定することにより、曲げモーメントを負荷した鉄筋コンクリート梁試験体の付着挙動を評価した。その結果、周囲のコンクリートによる主筋横方向の変形拘束が無視できるほどに小さいという前提に基づき、試験体を回転することなく、曲げ付着挙動の評価の鍵となる主筋の付着応力度分布の変化、およびせん断補強筋の軸応力変化の定量評価に成功した。ひずみゲージ法により測定されたコンクリートの巨視的な変形挙動との比較により,載荷に伴う曲げひび割れの発生と、それに続くせん断ひび割れの発生が、その周辺における付着劣化の原因となり、それに伴い主筋軸応力分布が変化することを確認した。本研究により、中性子応力測定技術は、鉄筋コンクリート梁の曲げ付着挙動の評価にも有効な手段であることを確認した。

Effect of hydrogenation conditions on the microstructure and mechanical properties of zirconium hydride

牟田 浩明*; 西金 遼二*; 安藤 祐介*; 松永 純治*; 坂本 寛*; Harjo, S.; 川崎 卓郎; 大石 佑治*; 黒崎 健*; 山中 伸介*

Journal of Nuclear Materials, 500, p.145 - 152, 2018/03

https://doi.org/10.1016/j.jnucmat.2017.12.027

Precipitation of brittle zirconium hydrides deteriorate the fracture toughness of the fuel cladding tubes of light water reactor. In the present study, to elucidate relationship between mechanical properties and microstructure, two -phase zirconium hydrides and one -phase zirconium hydride were carefully fabricated considering volume changes at the metal-to-hydride transformation. The -hydride that was fabricated from -zirconium exhibits numerous inner cracks due to the large volume change. Analyses of the neutron diffraction pattern and electron backscatter diffraction (EBSD) data show that the sample displays significant stacking faults in the plane and in the pseudo-layered microstructure. On the other hand, the -hydride sample fabricated from -zirconium at a higher temperature displays equiaxed grains and no cracks.

Changes of dislocation density and dislocation arrangement during tensile deformation in lath martensitic steels

Harjo, S.; 川崎 卓郎; 諸岡 聡

Advanced Experimental Mechanics, 2, p.112 - 117, 2017/10

https://doi.org/10.11395/aem.2.0_112

To understand strengthening mechanism in lath martensitic steels, in situ neutron diffractions during tensile deformation for 22SiMn2TiB steel and Fe-18Ni alloy were performed using TAKUMI of J-PARC. Profile analyses were performed using Convolutional Multiple Whole Profile (CMWP) fitting and Williamson-Hall (W-H) methods. As results, the dislocation densities as high as 10 m in the as-quenched states of both steels were determined hardly to change or slightly increase by the CMWP method. The reliability of the dislocation density obtained from the W-H method was low, because the whole profile was not considered for the analysis. In the former method, the values of parameter M related to dislocations arrangement was found to decrease rapidly for both steels at the beginning of plastic deformation. Hence, high work hardening in the lath martensitic steels was considered due to the dislocations rearrangements with plastic deformation.

Work hardening, dislocation structure, and load partitioning in lath-martensite determined by neutron diffraction line profile analysis

Harjo, S.; 川崎 卓郎; 友田 陽*; Gong, W.*; 相澤 一也; Tichy, G.*; Shi, Z.*; Ungar, T.*

Metallurgical and Materials Transactions A, 48(9), p.4080 - 4092, 2017/09

AA2017-0020.pdf:3.33MB

https://doi.org/10.1007/s11661-017-4172-0

neutron diffraction during tensile deformation of lath martensite steel containing 0.22 mass% of carbon, is performed using TAKUMI of J-PARC. The diffraction peaks at plastically deformed states exhibit asymmetries as the reflection of redistributions of the stress and dislocation densities/arrangements in lath-packets where the dislocation glides are favorable (soft packet) and unfavorable (hard packet). The dislocation density is as high as 10 m at the as-quenched state, and then during tensile straining, the load and the dislocation density become different between the two lath-packets. The dislocation character and arrangement vary also in the hard packet, but hardly change in the soft packet. The hard packet plays an important role in the high work hardening in martensite, which could be understood by taking into account not only the increase of the dislocation density but also the change in dislocation arrangement.

Quantitative evaluation of texture and dislocations during annealing after hot deformation in austenitic steel using neutron diffraction

友田 陽*; 佐藤 成男*; Uchida, M.*; 徐 平光; Harjo, S.; Gong, W.; 川崎 卓郎

Materials Science Forum, 905, p.25 - 30, 2017/08

https://doi.org/10.4028/www.scientific.net/MSF.905.25

Microstructural change during hot compressive deformation at 700 C followed by isothermal annealing for a Fe-32Ni austnitic alloy was monitored using neutron diffraction. The evolution of deformation texture with 40% compression and its change to recrystallization texture during isothermal annealing were presented by inverse pole figures for the axial and radial directions. The change in dislocation density was tracked using the convolutional muli-profile whole profile fitting method. To obtain the fitting results with good statistics, at least 60 s time-slicing for the event-mode recorded data was needed. The average dislocation density in 60 s after hot compression was determined to be 2.8 10 m that decreased with increasing of annealing time.

In-situ residual stress analysis during thermal cycle of a dissimilar weld joint using neutron diffraction and IEFEM

秋田 貢一; 柴原 正和*; 生島 一樹*; 西川 聡*; 古川 敬*; 鈴木 裕士; Harjo, S.; 川崎 卓郎; Vladimir, L.*

溶接学会論文集(インターネット), 35(2), p.112s - 116s, 2017/06

Residual stresses near the weld metal of the joints before and after a thermal cycle were measured using a reactor based neutron diffraction technique in room temperature. In-situ residual stress measurements were performed on the plate type sample using a pulsed neutron diffraction technique under thermal cycles. Residual stress behaviors of the samples were examined also by the idealized explicit FEM (IEFEM), which agreed well with the experimental results of the residual stress behaviors during thermal cycles. Thermal stresses were induced near the weld metal by the difference of the linear expansion coefficients of the dissimilar base metals. Since the thermal stress exceeded the yield stress of the material during the first heating process, the residual stresses near the weld metal were redistributed and a part of the residual stress was relaxed.

A Comparative study of the crystallite size and the dislocation density of bent steel plates using Bragg-edge transmission imaging, TOF neutron diffraction and EBSD

及川 健一; Su, Y.; 友田 陽*; 川崎 卓郎; 篠原 武尚; 甲斐 哲也; 廣井 孝介; Zhang, S.*; Parker, J. D.*; 佐藤 博隆*; et al.

Physics Procedia, 88, p.34 - 41, 2017/00

https://doi.org/10.1016/j.phpro.2017.06.004

TOFブラッグエッジ透過イメージング法を用い、塑性変形させた曲げ鉄鋼試料の微細構造を解析し、得られた結果を中性子回折法及びEBSD法により比較検証を行った。その結果、テキスチャ等は非常に良い一致を示したが、結晶子サイズを中性子回折法による消衰効果から見積もることはうまく行かなかった。そこで、回折プロファイルのブロードニング幅解析から結晶子サイズを求めることを試み、またEBSD法から結晶歪みの解析結果も合わせて再検討を行った。

Line profile analyses of a martensitic steel during continuous and stepwise tensile deformations

川崎 卓郎; Harjo, S.; Gong, W.; 相澤 一也

Journal of Physics; Conference Series, 746(1), p.012044_1 - 012044_6, 2016/10

https://doi.org/10.1088/1742-6596/746/1/012044

The microstructure of the metallic material is widely investigated in order to understand mechanical properties of the material by line profile analysis for X-ray and neutron diffraction data. Neutron diffraction has an advantage for obtaining averaged information of the microstructure inside the bulky material owing to its high transmittance. Further, the variation of the microstructure in the material during mechanical process is able to be observed by in-situ measurements. The Convolutional Multiple Whole Profile (CMWP) fitting method is a state of the art technique for line profile analysis. The dislocation characteristics are evaluated from the shape of the peak profile including the tail by this technique. In this study, the dislocation characteristics in martensitic steels during tensile deformation were studied by in-situ neutron diffraction measurement using the Engineering Materials Diffractometer TAKUMI at J-PARC through line profile analysis using the CMWP fitting method.