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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
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 L
ders 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.
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
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.
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
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：5 パーセンタイル：64.46(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：2 パーセンタイル：32.54(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：0 パーセンタイル：0(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：66.14(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：83.73(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：25.78(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：31 パーセンタイル：90.48(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.
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。
山下 享介; Harjo, S.; 川崎 卓郎; 諸岡 聡; Wu, G.*
no journal, ,
Fe-33Ni-0.004C合金およびFe-27Ni-0.5C合金に対して298 Kから4 Kまでの温度域にてその場中性子回折試験を行い、冷却中に生じるマルテンサイト(M)の格子定数や軸比の変化から炭素含有量の違いによるマルテンサイト変態挙動や自己焼戻し挙動の相違を調査した。Fe-33Ni-0.004C合金では、180 KでMが確認され、BCT構造に起因する非対称なピークが現れていた。170Kより低温ではMのピークはより対称的になっており、Mの軸比は低下していた。一方、Fe-27Ni-0.5C合金では、190KにてBCT構造特有のa軸とc軸に対応したピークが分離したピークプロファイルが得られたが、Fe-33Ni-0.004C合金で生じた温度の低下に伴う顕著な軸比の低下は見られなかった。4Kまで冷却した後に298Kで保持すると、Fe-27Ni-0.5C合金は顕著な軸比の減少を示した。Fe-33Ni-0.004C合金では、このような軸比の低下はほぼ生じておらず、298 Kでは炭素の拡散による自己焼戻しが生じたと示唆される。いずれの合金においても生成するMはBCT構造であり、炭素含有量の違いは自己焼戻し挙動に影響し、軸比の変化挙動の相違をもたらすと考えられる。
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。
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.
Harjo, S.; 川崎 卓郎; Gong, W.*; 山下 享介; 諸岡 聡; 鈴木 裕士; 相澤 一也
no journal, ,
TAKUMI is a time-of-flight neutron diffractometer dedicated for engineering materials sciences, which was installed at beamline 19 in Materials and Life Science Experimental Facility of J-PARC. Careful analysis of the Bragg peaks in a neutron diffraction pattern can reveal important structural details of a sample material such as internal stresses, phase conditions, dislocations, texture etc. 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; Harjo, S.; 川崎 卓郎; 諸岡 聡; Gong, W.*
no journal, ,
本研究は、マルテンサイト(M)変態に伴う塑性緩和が生じないとされる薄板状Mを生成するFe-31Ni-10Co-3Ti合金に対して冷却中その場中性子回折測定を実施し、オーステナイト(A)の格子定数の変化とM変態挙動について調査した。また得られた結果についてFe-Ni-C合金の結果と比較した。冷却中その場中性子回折測定はJ-PARC-MLF内の工学材料回折装置「匠」にて実施した。冷凍機を用いて冷却中では290Kから4Kまで10Kごとに、その後の4Kから290Kまでの昇温中では50Kごとに15min間保持し、その際の回折パターンを得た。Mの回折パターンは100Kで確認され、その構造はBCT構造であった。温度の低下に伴い、Mの相分率は増大し、30Kで変態は停滞していた。昇温後のMの相分率は21%であった。Aの格子定数は温度の低下に伴い減少したが、M変態の開始後からM変態が完了する30Kまでの温度域では、熱収縮から予測される格子定数よりも小さな値を示した。この傾向はFe-Ni-C合金でも同様であり、M変態が生じることでAに圧縮の内部応力が生じていることを示唆している。このときFe-31Ni-10Co-3Ti合金ではinvar効果も生じていた。Mの格子定数の変化はa軸とc軸で異なっていたことから、a軸とc軸で熱収縮および熱膨張の挙動が異なることが示唆された。
諸岡 聡; 山下 享介; Harjo, S.; 土山 聡宏*
no journal, ,
現代の自動車設計は、車両の軽量化、燃料効率の向上、乗客の安全性の向上を考慮したうえで、新しい高強度鋼(AHSS)の開発が必要とされており、中Mn鋼はAHSSの第3世代に望まれる特性目標を達成するために提案された鋼種の1つである。土山らは、5.0Mn鋼にQP熱処理を施すことで、フェライトをマルテンサイトに置き換えることによって連続降伏を促進し、強度と延性のバランスを向上させることを提案している。しかしながら、マルテンサイトの導入は、(+)二相域焼鈍中のオーステナイトの不完全な安定化によってのみ可能であり、C及びMn分配が不十分な未変態オーステナイトの形成に繋がることも懸念される。そのため、中Mn鋼を構成する結晶相の変形挙動を詳細に理解する必要がある。本研究は、中性子回折法によるその場測定を用いて、5.0Mn鋼の変形挙動を調査することを目的とする。本実験はJ-PARC MLFに設置されたTAKUMI(BL19)を使用して、中性子回折法による引張変形中その場測定を実施した。引張変形による任意時間の回折パターンの変化に対して、格子面間隔・積分強度の情報を評価することで、マルテンサイトの導入による元素分配が不十分な未変態オーステナイトの変形挙動を観測することに成功した。
