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Harjo, S.; 川崎 卓郎; 友田 陽*; Gong, W.
Materials Science Forum, 905, p.46 - 51, 2017/08
To understand the strengthening mechanism of a metallic material with high dislocation density, the plastic deformation behavior of lath martensite was studied by means of in situ neutron diffraction measurements during tensile deformations using a 22SiMn2TiB steel and a Fe-18Ni alloy. The characteristics of dislocation were analyzed and were discussed with the relation of stress-strain curves. The dislocation densities induced by martensitic transformation during heat-treatment in both materials were found to be originally as high as 10
m
order, and subsequently to increase slightly by the tensile deformation. The parameter M value which displays the dislocation arrangement dropped drastically at the beginning of plastic deformation in both materials, indicating that the random arrangement became more like a dipole arrangement.
友田 陽*; 佐藤 成男*; Harjo, S.; 徐 平光; Gong, W.; 川崎 卓郎
no journal, ,
Heterogeneous deformation behavior in a polycrystalline steel has been characterized using SEM/EBSD and neutron diffraction measurements which provide complemental insights combining microscopic details and their global averages. Type 1 (macroscopic), 2 (intergranular) and 3 (grain interior) stresses are overlapped to generate during plastic deformation accompanying substructure evolution. Upon annealing of a plastically deformed steel, the residual stresses are relived and dislocation density decreases resulting in recovery and recrystallization. To understand these phenomena quantitatively, in situ monitoring of dislocations has strongly been desired. SUS310 stainless steel was deformed in tension at room temperature followed by annealing under in situ neutron diffraction using an engineering neutron diffractometer, TAKUMI, at MLF/J-PARC. The obtained time sliced diffraction profiles were analyzed using the CMWP fitting method. As results, dislocation density was found to increase with tensile plastic deformation and decrease upon annealing. Changes in dislocation densities in individual 
hkl
family grains were different from each other in the axial direction but nearly identical in the radial direction.
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.
鈴木 裕士; 楠 浩一*; 兼松 学*
no journal, ,
近年、鉄筋コンクリート建築物といった建築・土木構造物においては、都市地震災害によるリスクを最小限に抑えるために、高い耐震性能が求められている。鉄筋コンクリート構造においては、コンクリートと鉄筋の付着抵抗が、鉄筋コンクリートの性能を議論するうえで非常に重要なパラメータの一つであり、コンクリートに埋設された鉄筋のひずみ分布を測定することで評価されてきた。本研究では、そのひずみ分布測定に飛行時間中性子回折法を応用した。その結果、埋設された鉄筋の三次元変形挙動を正確に評価することができ、さらに、コンクリートひび割れ周りの鉄筋のひずみ分布や腐食鉄筋周りのひずみ分布から付着劣化を評価することにも成功した。中性子回折法は、鉄筋コンクリートの構造力学研究における新しいひずみ測定技術として期待される。
鈴木 裕士; 兼松 学*; Bae, S.*; 城 鮎美; 菖蒲 敬久
no journal, ,
圧縮負荷におけるポートランドセメント硬化体(PC硬化体)のカルシウムシリケート化合物(CSH)のナノ構造の変形挙動を、シンクロトロン放射光により測定した原子対相関関数(PDF)により評価することに成功した。PC硬化体のPDFは、CSH粒子のサイズに一致する2.0nm以下の短距離構造に特異な変形挙動を示した。一方で、それ以上の長距離構造では、ブラッグ回折のピークシフトから得られた水酸化カルシウム相(CH)の変形挙動にほぼ一致した。CSHの圧縮変形挙動は粒状材料の変形挙動に類似しており、CSH粒子間のすべりと密度の変化に起因した3つの変形段階に分けることができた。このように、PDFを応用することにより、PC硬化体のCSHナノ構造の変形機構を理解できる可能性のあることを示した。