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小山 元道*; 山下 享介*; 諸岡 聡; Yang, Z.*; Varanasi, R. S.*; 北條 智彦*; 川崎 卓郎; Harjo, S.
鉄と鋼, 110(3), p.205 - 216, 2024/02
被引用回数：0 パーセンタイル：0.02
deformation experiments with cold-rolled and intercritically annealed Fe-5Mn-0.1C steel were carried out at ambient temperature to characterize the deformation heterogeneity during L
ders band propagation. Deformation band formation, which is a precursor phenomenon of Lders band propagation, occurred even in the macroscopically elastic deformation stage. The deformation bands in the Lders front grew from both the side edges to the center of the specimen. After macroscopic yielding, the thin deformation bands grew via band branching, thickening, multiple band initiation, and their coalescence, the behavior of which was heterogeneous. Thick deformation bands formed irregularly in front of the region where the thin deformation bands were densified. The thin deformation bands were not further densified when the spacing of the bands was below 
10 
m. Instead, the regions between the deformation bands showed a homogeneous plasticity evolution. The growth of the thin deformation bands was discontinuous, which may be due to the presence of ferrite groups in the propagation path of the deformation bands. Based on these observations, a model for discontinuous Lders band propagation has been proposed.
小山 元道*; 山下 享介*; 諸岡 聡; 澤口 孝宏*; Yang, Z.*; 北條 智彦*; 川崎 卓郎; Harjo, S.
鉄と鋼, 110(3), p.197 - 204, 2024/02
被引用回数：0 パーセンタイル：0.02The local plasticity and associated microstructure evolution in Fe-5Mn-0.1C medium-Mn steel (wt.%) were investigated in this study. Specifically, the micro-deformation mechanism during Lders banding was characterized based on multi-scale electron backscatter diffraction measurements and electron channeling contrast imaging. Similar to other medium-Mn steels, the Fe-5Mn-0.1C steel showed discontinuous macroscopic deformation, preferential plastic deformation in austenite, and deformation-induced martensitic transformation during Lders deformation. Hexagonal close-packed martensite was also observed as an intermediate phase. Furthermore, an in-situ neutron diffraction experiment revealed that the pre-existing body- centered cubic phase, which was mainly ferrite, was a minor deformation path, although ferrite was the major constituent phase.
neutron diffraction during cryogenic cooling山下 享介*; Harjo, S.; 川崎 卓郎; 諸岡 聡; Gong, W.; 藤井 英俊*; 友田 陽*
ISIJ International, 64(2), p.192 - 201, 2024/01
被引用回数：0 パーセンタイル：0.02 neutron diffraction measurements were performed on Fe-33Ni-0.004C alloy (33Ni alloy) and Fe-27Ni-0.5C alloy (27Ni-0.5C alloy) during cooling from room temperature to the cryogenic temperature (4 K) to evaluate changes in the lattice constants of austenite and martensite, and changes in the tetragonality of martensite due to thermally induced martensitic transformation. As the martensitic transformation progressed, the lattice constants of austenite in both alloys deviated to smaller values than those predicted considering the thermal shrinkage, accompanied by an increase in the full width at half maximum of austenite. The fresh martensite formed in both alloys had a body-centered tetragonal (BCT) structure, regardless of the carbon content. The tetragonality of martensite decreased with progressive martensitic transformation during cooling in the 33Ni alloy, but was almost constant in the 27Ni-0.5C alloy. This suggests that carbon is necessary to maintain the tetragonality of martensite during cooling. The tetragonality of martensite in the 27Ni-0.5C alloy decreased during room temperature aging because of carbon mobility.
西田 真之*; Harjo, S.; 川崎 卓郎; 山下 享介*; Gong, W.
Quantum Beam Science (Internet), 7(1), p.8_1 - 8_15, 2023/03
In this study, the thermal stress alterations generated in a tungsten fiber reinforced titanium composite (W/Ti composite) were evaluated by the neutron stress measurement method at cryogenic temperatures. The W/Ti composite thermal loads were repeated from room temperature to the cryogenic temperature (10 K), and alterations in thermal residual stress were evaluated using the neutron in situ stress measurement method. In this measurement, the stress alterations in the titanium matrix and the tungsten fibers were measured. This measurement was carried out by TAKUMI (MLF-BL19) of J-PARC, a neutron research facility in the Japan Atomic Agency. The measurement method of TAKUMI is the time-of-flight (TOF) method. Owing to this measurement method, the measurement time was significantly shortened compared to the angle-dispersion type measurement by a diffractometer. As a result of the measurement, large compressive stresses of about 1 GPa were generated in the tungsten fibers, and tensile stresses of about 100 MPa existed in the titanium matrix. The thermal stresses due to the temperature change between room temperature and cryogenic temperature is caused by the difference of thermal expansions between the tungsten fibers and the titanium matrix, and these stress values can be approximated by a simple elastic theory equation.
ders deformation in an Fe-5Mn-0.1C medium-Mn steel小山 元道*; 山下 享介*; 諸岡 聡; 澤口 孝宏*; Yang, Z.*; 北條 智彦*; 川崎 卓郎; Harjo, S.
ISIJ International, 62(10), p.2036 - 2042, 2022/10
被引用回数：11 パーセンタイル：85.65(Metallurgy & Metallurgical Engineering)The local plasticity and associated microstructure evolution in Fe-5Mn-0.1C medium-Mn steel (wt.%) were investigated in this study. Specifically, the micro-deformation mechanism during Lders banding was characterized based on multi-scale electron backscatter diffraction measurements and electron channeling contrast imaging. Similar to other medium-Mn steels, the Fe-5Mn-0.1C steel showed discontinuous macroscopic deformation, preferential plastic deformation in austenite, and deformation-induced martensitic transformation during Lders deformation. Hexagonal close-packed martensite was also observed as an intermediate phase. Furthermore, an in-situ neutron diffraction experiment revealed that the pre-existing body-centered cubic phase, which was mainly ferrite, was a minor deformation path, although ferrite was the major constituent phase.
ders band propagation in an Fe-5Mn-0.1C medium Mn steel clarified through 
scanning electron microscopy小山 元道*; 山下 享介*; 諸岡 聡; Yang, Z.*; Varanasi, R. S.*; 北條 智彦*; 川崎 卓郎; Harjo, S.
ISIJ International, 62(10), p.2043 - 2053, 2022/10
被引用回数：7 パーセンタイル：72.10(Metallurgy & Metallurgical Engineering) deformation experiments with cold-rolled and intercritically annealed Fe-5Mn-0.1C steel were carried out at ambient temperature to characterize the deformation heterogeneity during Lders band propagation. Deformation band formation, which is a precursor phenomenon of Lders band propagation, occurred even in the macroscopically elastic deformation stage. The deformation bands in the Lders front grew from both the side edges to the center of the specimen. After macroscopic yielding, the thin deformation bands grew via band branching, thickening, multiple band initiation, and their coalescence, the behavior of which was heterogeneous. Thick deformation bands formed irregularly in front of the region where the thin deformation bands were densified. The thin deformation bands were not further densified when the spacing of the bands was below 10 m. Instead, the regions between the deformation bands showed a homogeneous plasticity evolution. The growth of the thin deformation bands was discontinuous, which may be due to the presence of ferrite groups in the propagation path of the deformation bands. Based on these observations, a model for discontinuous Lders band propagation has been proposed.
Harjo, S.; Gong, W.; 川崎 卓郎; 諸岡 聡; 山下 享介*
ISIJ International, 62(10), p.1990 - 1999, 2022/10
被引用回数：1 パーセンタイル：14.88(Metallurgy & Metallurgical Engineering)Two mechanisms inconsistent each other, a relaxation of type II internal stress and a presence of mobile dislocation, were previously proposed to describe the low elastic limit of as-quenched lath martensite steels. In this study, neutron diffraction experiments were performed to revisit the deformation behavior of lath martensite steel. The highly dense random arrangement dislocations easily moved at the beginning of deformation, then accumulated, annihilated and changed the arrangement differently depending on the orientation of the packet with respect to the deformation direction. The movement of highly dense random arrangement dislocations played an important role as a mechanism at the beginning of deformation, and can be a true feature of mobile dislocations.
Lee, M.-S.*; 川崎 卓郎; 山下 享介*; Harjo, S.; Hyun, Y.-T.*; Jeong, Y.*; Jun, T.-S.*
Scientific Reports (Internet), 12(1), p.3719_1 - 3719_10, 2022/03
被引用回数：6 パーセンタイル：61.59(Multidisciplinary Sciences)Titanium has a significant potential for the cryogenic industrial fields such as aerospace and liquefied gas storage and transportation due to its excellent low temperature properties. To develop and advance the technologies in cryogenic industries, it is required to fully understand the underlying deformation mechanisms of Ti under the extreme cryogenic environment. Here, we report a study of the lattice behaviour in grain families of Grade 2 CP-Ti during in-situ neutron diffraction test in tension at temperatures of 15-298 K. Combined with the neutron diffraction intensity analysis, EBSD measurements revealed that the twinning activity was more active at lower temperature, and the behaviour was complicated with decreasing temperature.
山下 享介*; 古賀 紀光*; 川崎 卓郎; 諸岡 聡; 友野 翔平*; 梅澤 修*; Harjo, S.
Materials Science & Engineering A, 819, p.141509_1 - 141509_10, 2021/07
被引用回数：21 パーセンタイル：87.23(Nanoscience & Nanotechnology)In-situ neutron diffraction measurements were performed on a cold-rolled copper-iron (Cu-Fe) alloy during tensile tests at 293 K and 150 K. The roles of Cu and Fe on the deformation behavior of alloys were discussed and clarified. The strength and work-hardening rate of the alloy increased with decreasing test temperature. Furthermore, the phase stress of Fe increased considerably with decreasing test temperature; however, the response of this stress to the applied true stress exhibited no dependence on the temperature. The phase stresses of Cu changed only slightly with decreasing test temperature. However, the Cu phase stress response to the applied true stress increased with decreasing test temperature, indicating an increase in the work-hardening rate. The strengthening of Fe and the increase in the work-hardening of Cu contributed to an increase in the strength and work-hardening rate of the Cu-Fe alloy at low temperatures.
山下 享介; 友野 翔平*; 諸岡 聡; Harjo, S.; 川崎 卓郎; 行木 辰弥*; 古賀 紀光*; 梅澤 修*
JPS Conference Proceedings (Internet), 33, p.011064_1 - 011064_6, 2021/03
The tensile deformation and stress partitioning behavior of duplex phase alloys consisting of FCC and BCC at low temperatures were investigated using in-situ neutron diffraction during deformation. Cu-40mass%Fe alloy rolled sheet and JIS SUS329J4L duplex stainless steel were used. Both alloys showed a good balance of strength and elongation at low temperatures. In Cu-40mass%Fe alloy, the BCC phase stress at yield point increased by decreasing test temperature. The FCC phase stress at yield point was almost constant regardless of test temperature. The FCC phase started plastic deformation at a low applied true stress. When the BCC phase yielded, phase stress of FCC increased drastically at beginning, then, it increased to applied true stress with the same rate of BCC phase stress at latter regime. On the other hand, both BCC and FCC phase stresses in SUS329J4L increased by decreasing temperature.
山下 享介; Harjo, S.; 梅澤 修*; 川崎 卓郎
JPS Conference Proceedings (Internet), 33, p.011063_1 - 011063_6, 2021/03
Japanese nails have been applied to various wooden building skeletons in Japanese temples and shrines over a period of one thousand years. Since most of Japanese nails in the ancient day are designated as an important cultural property, their destructive examinations can be hardly done. In order to discuss the material and its manufacturing process of the Japanese nails, we have done some experiments on both ancient and present Japanese nails. In this study, phase, texture and residual stress of the Japanese nails were investigated using neutron diffraction. Two types of Japanese nails were provided; one was an ancient nail obtained from Houryuji-temple; the other was a present nail forged by blacksmith. BCC iron peaks are identified in both. Although the cementite and ferrous oxide peaks are detected in the present nail, no cementite is detected in the ancient nail. The residual stresses of each nail were very low. The ferrite grains of each nail were randomly oriented.
古賀 紀光*; 梅澤 修*; 山本 正之*; 山本 卓*; 山下 享介; 諸岡 聡; 川崎 卓郎; Harjo, S.
Metallurgical and Materials Transactions A, 52(3), p.897 - 901, 2021/03
被引用回数：3 パーセンタイル：23.95(Materials Science, Multidisciplinary)Small ball rebound hardness tests demonstrated characteristic hardening at 700 K in the ultra-low carbon and pearlitic steels. The equilibrium phase diagram of Fe-C binary alloy calculated using Thermo-Calc exhibited dissolving of cementite above 700 K. Moreover, in-situ heating neutron diffraction measurement demonstrated the increase of lattice parameter by dissolving of cementite above 700 K. Therefore, it can be concluded that the characteristic hardening above 700 K can be attributed to the solid solute carbon.
山下 享介; 諸岡 聡; Harjo, S.; 川崎 卓郎; 古賀 紀光*; 梅澤 修*
Scripta Materialia, 177, p.6 - 10, 2020/03
被引用回数：32 パーセンタイル：90.20(Nanoscience & Nanotechnology) neutron diffraction measurements during tensile tests at low temperatures of a low alloy steel containing retained austenite have been performed. Evolutions of phase fractions and phase stresses were analyzed and discussed with the progress of deformation. The role of austenite in the steel during deformation at low temperatures was observed not to directly in the contribution to the strengths but in the improvement of the elongation by transformation of austenite to martensite -and in the increasing of the work-hardening rate by an increase in the phase fraction of martensite and the work hardening of martensite.
諸岡 聡; 川崎 卓郎; Harjo, S.; 山下 享介*; 小山 元道*; 澤口 孝宏*; 芳賀 芳範
no journal, ,
第3世代先進高張力鋼とされるQ&P鋼や5mass%前後のMnを添加した中Mn鋼等は、フェライト,マルテンサイト、及びオーステナイトを利用している。この三相の微視組織では、オーステナイトの存在により、鋼は塑性変形をさらに拡大することができ、オーステナイト自体が塑性変形すると、マルテンサイトに変態し、鋼の全体的な強度が向上する。特に、Millerにより提起された中Mn鋼は、2相域焼鈍し、その温度に保持することで、高温域におけるオーステナイト中にC, Mnを濃化させ、30vol.%以上の多量のオーステナイトを残存させることを可能とした。その結果として、第3世代先進高張力鋼の目標に合致する優れた強度-延性バランスを発揮することができる。これまで、Koyamaらは、5Mn-0.1C鋼において、室温における機械特性と詳細な微視組織観察の結果から変形機構の解明を進めている。一方で、Yamashitaらは、低温における機械特性を評価し、室温(298K)と比較して、降伏強度が非常に高くなることを報告しているが、その原因については言及していない。そこで、本研究では、中性子回折法による低温環境下その場測定を用いて、5Mn-0.1C鋼の低温挙動を観測し、低温環境における特異な力学特性の解明を進めることを目的とする。
小山 元道*; 北條 智彦*; Varanasi, R.*; 山下 享介*; 諸岡 聡; 川崎 卓郎; Harjo, S.
no journal, ,
鉄鋼材料では、リューダース変形のようなマクロ不均一変形から微視組織に依存したミクロ不均一変形まで、様々なスケールでの不均一塑性発達が知られる。特に、近年発展が著しい高強度複相鋼板ではミクロレベルの不均一塑性発達が著しく、これが強くマクロ力学特性に影響している。つまり、マクロ変形および特性を制御するためにはミクロ変形を理解することが不可欠となっている。例えば、高延性高強度を両立する中Mn鋼の不均一塑性発達は、初期組織だけでなく、変態誘起塑性に由来した変形中における結晶構造変化(マルテンサイト変態)が、ミクロ変形挙動を複雑化させている。降伏挙動だけを考える場合でも、フェライトと準安定オーステナイトで構成される微細等軸粒を有する中Mn鋼では、その複相組織およびマルテンサイト変態に由来したミクロ不均一変形だけでなく、これに連動したマクロな不均一変形、すなわちリューダース変形が起こるためにその理解は容易ではない。この複雑性のため、中Mn鋼の降伏挙動は未だ研究が続いている。本講演では、マルチスケールその場観察を通して得られた中Mn鋼のリューダース変形挙動の一端を示す。
諸岡 聡; 山下 享介*; 小山 元道*; Harjo, S.; 菖蒲 敬久
no journal, ,
第3世代先進高張力鋼の目標に合致する優れた強度-延性バランスを発揮させるために開発された中Mn鋼は、冷間圧延加工した後に2相域焼鈍することで、フェライトと残留オーステナイトが混在した1m以下の超微細等軸粒組織を呈し、数%の特異な降伏点伸び(Lders帯の伝播を伴う塑性変形)を生じる。本研究は、中性子及び放射光X線回折法によるその場測定の利点を有効活用して、冷間圧延加工後に2相域焼鈍を施した5Mn-0.1C鋼の引張変形挙動の解明を進める。本手法を用いて、引張変形中のフェライト、残留オーステナイト、加工誘起マルテンサイトの格子ひずみ(応力)変化及び、相分率変化を捉えることで、5Mn-0.1C鋼の引張変形挙動である降伏現象、降伏点伸び、加工硬化を解釈することに成功した。
Harjo, S.; 川崎 卓郎; Gong, W.*; 山下 享介*; 諸岡 聡; 相澤 一也
no journal, ,
TAKUMIは、材料工学や機械工学に関わる材料研究のための飛行時間型中性子回折装置である。機械部品内のひずみ・応力マッピング,構造材料または機能材料の低温から高温までの広い温度範囲の変形下での組織(結晶構造変化,欠陥,内部応力等)変化、製造(加工熱処理)過程での組織(結晶構造変化,欠陥等)変化、及び工学材料の集合組織測定である。最近流行の高エントロピー合金及び日本で開発された新概念のミルフィーユ構造材料に関する研究も行われている。これらの実験を行うために、TAKUMIは様々な試料環境装置を独自に、またはユーザーと一緒に開発した。
山下 享介; 諸岡 聡; 古賀 紀光*; 梅澤 修*
no journal, ,
準安定FCC相(オーステナイト:
)を含む低合金鋼に対し、低温引張変形中その場中性子回折を実施した。その際の応力-ひずみの関係、量の変化、母相
との応力分配挙動および安定性に及ぼす結晶方位の影響をそれぞれ調査した。低温引張試験および中性子回折試験はJ-PARC内の「匠」にて実施した。Rietveld解析には、粉末回折データ解析ソフトウェアであるZ-RietveldおよびMAUDを用いた。低温引張試験後でもは全て変態せず一部が残存していた。293Kでは111-の積分強度比が変形に伴い増加しており、変形に対し安定であった。低温では、111-の積分強度比は塑性変形の開始直後に若干減少するが、その後ほぼ定常となった。これは、温度の低下に伴いの相安定性が低下し、111-も変態するようになるが、他の方位から
111
へと結晶回転することで、変態量と新たに111へと向く量が釣り合うようになることを示唆している。低温域では、111-も変態することで、293Kと比較して変形初期の高い加工硬化に寄与するとともに、変形後期(10%ひずみ以上)でも一部のが残っていることから変態誘起塑性効果により優れた強度-延性バランスを発現したと示唆される。
Harjo, S.; 川崎 卓郎; Gong, W.*; 山下 享介; 諸岡 聡; 原田 剛*; 相澤 一也
no journal, ,
TAKUMI is a time-of-flight neutron diffractometer dedicated for engineering materials sciences. Experiments in TAKUMI vary from internal strain mapping in engineering components, microstructural evolutions during deformations of structural or functional materials at various temperatures, microstructural evolutions during manufacturing (thermo-mechanical) processes, as well as texture analyses of engineering materials. In the presentation, the current status of TAKUMI, its sample environmental devices, the scientific trends in TAKUMI and some research examples will be introduced.
山下 享介; 諸岡 聡; Harjo, S.; 古賀 紀光*; 梅澤 修*
no journal, ,
準安定オーステナイトを含む低合金鋼に対し、134Kから293Kの温度範囲での低温引張変形中その場中性子回折をJ-PARCの「匠」にて実施した。その際の応力-ひずみ応答、オーステナイトの体積率、構成相の相応力および結晶方位の変化を調査した。低温にて低合金鋼は優れた強度-延性バランスを示した。フェライト母相とマルテンサイトの相応力は温度の低下に伴い増加した。一方、オーステナイトの相応力は低温では印加応力に対しほぼ定常となっていた。これはオーステナイトは塑性変形よりもマルテンサイト変態を優先することを示唆している。111方向が引張軸に対し平行なオーステナイト(111-)は室温で最も安定であった。低温では5%ひずみ以下では111-も変態していたが、変形後期(10%ひずみ以上)では積分強度比がほぼ定常となっていた。これは、低温において111-の中で比較的安定性の高いものは均一変形中にマルテンサイト変態しないことを意味している。
