Neutron diffraction study on martensitic transformation under compressive stress in an ordered FePt

福田 隆*; 山口 貴司*; 掛下 知行*; Harjo, S.; 中本 建志*

Journal of Applied Physics, 126(2), p.025107_1 - 025107_6, 2019/07

AA2019-0505.pdf:1.15MB

https://doi.org/10.1063/1.5098960

We have studied the structure change of an ordered FePt (degree of order 0.75) under a compressive stress applied in the [001] direction by neutron diffraction. In the absence of the stress, the alloy exhibits a weak first order martensitic transformation at 90 K from the L1-type cubic structure to the L6-type tetragonal structure. Under the compressive stress of 100 MPa, the first order nature of the thermally-induced martensitic transformation was undetectable in the temperature range of between 70 K and 270 K. The first order nature of the stress-induced martensitic transformation was also undetectable in the stress range of between 6 MPa and 300 MPa when tested at 120 K and higher temperatures. Under these conditions, the lattice parameters change continuously both in the cooling process and in the stress-applying process. A significant stress-induced softening of lattice was observed between 120 K and 265 K but not at 93 K and 295 K.

Research and development of high intensity beam transport to the target facilities at J-PARC

明午 伸一郎; 大井 元貴; 池崎 清美*; 川崎 智之; 木下 秀孝; 圷 敦*; 西川 雅章*; 福田 真平

Proceedings of 12th International Topical Meeting on Nuclear Applications of Accelerators (AccApp '15), p.255 - 260, 2016/00

At the J-PARC, spallation neutron and muon sources has built at placed at the MLF by using 3-GeVproton beam. By the result of post irradiation examination of the mercury target vessel, damage was found on the surface of the vessel due to the pitting erosion caused by the proton beam. Since the pitting erosion is known to be proportional to the 4th power of the beam current density, peak current density should be kept as low as possible so that beam-flattening system by nonlinear beam optics using octupole magnets was developed. For efficiently beam tuning, a tool was developed by using SAD code system. By the result of the beam study, the peak current density at the target can be reduced by 30% with the present nonlinear optics.

Stress and temperature dependence of the structure of the martensite and X-phase in NiMnGa

福田 隆*; 寺井 智之*; 串田 悠彰*; 掛下 知行*; 長壁 豊隆; 加倉井 和久

Philosophical Magazine, 90(14), p.1925 - 1935, 2010/05

https://doi.org/10.1080/14786430903571479

強磁性形状記憶合金NiMnGaの、母相(P相),中間相(I相),マルテンサイト相(M相),未知のX相の間の構造上の関係を明らかにするため、一軸応力下の単結晶中性子回折により、X相の構造の、応力及び温度依存性を調べた。X相の構造は、最低温度領域に広がるM相やX相の低温低応力側に存在するI相と比べて、応力や温度に強く依存することがわかった。X相からM相への転移に関しては、両相の長周期構造におけるサテライトピークが、応力や温度に関係なく大きく変化することがわかった。一方、X相から高温側のP相への転移に関しては、サテライトピークがゆるやかに消滅することがわかった。I相からX相への転移に関しては、応力下ではサテライトピークの位置や強度が劇的に変化するが、ゼロ応力下では、その変化は連続的であった。これらの結果は、NiMnGaの相図に多重臨界点が存在することを示唆している。

Incommensurate structures of intermediate phase and martensite phase in NiMnGa

串田 悠彰*; 福田 康太*; 寺井 智之*; 福田 敬*; 掛下 知行*; 大庭 卓也*; 長壁 豊隆; 加倉井 和久; 加藤 健一*

Journal of Physics; Conference Series, 165, p.012054_1 - 012054_4, 2009/06

https://doi.org/10.1088/1742-6596/165/1/012054

Neutron diffraction measurements using single crystal and powder synchrotron X-ray diffraction measurements revealed that an intermediate (I-) phase and a martensite (M-) phase in NiMnGa have incommensurate modulated structures. The modulation vectors of the I- and M-phases are nearly equal to = 0.341 at 210 K and = 0.427 at 100 K, respectively. Moreover, displacements of Ni, Mn and Ga atoms in both the I- and M-phase are expressed by sinusoidal waves with the same phase and almost the same amplitudes.

Neutron diffraction study on stress-induced X-phase in NiMnGa

串田 悠彰*; 寺井 智之*; 福田 敬*; 掛下 知行*; 長壁 豊隆; 加倉井 和久

Scripta Materialia, 60(4), p.248 - 250, 2009/02

https://doi.org/10.1016/j.scriptamat.2008.10.018

Neutron diffraction profiles of the X-phase in NiMnGa, which is induced by applying a compressive stress, have revealed that two satellite reflections appear at incommensurate positions of [2-0] with = 0.360 and 1.638 at 240 K under a compressive stress of about 30 MPa. The satellite positions of the X-phase are clearly different from those of the martensite and intermediate phases.

Direct observation of field-induced variant transformation in FePt using pulsed magnetic field X-ray diffraction

Ouyang, Z. W.*; 松田 康弘*; 野尻 浩之*; 稲見 俊哉; 大和田 謙二; 坪田 雅己*; 左近 拓男*; 福田 敬*; 掛下 知行*

Journal of Applied Physics, 102(11), p.113917_1 - 113917_6, 2007/12

https://doi.org/10.1063/1.2822278

X-ray diffraction experiments in pulsed magnetic fields were performed to study the giant magnetic-field-induced strain in the martensitic phase of ordered FePt alloy. The field dependence of the arrangement of the variants (crystallographic domains) was observed directly in pulsed magnetic fields for the first time. The variants with the axis perpendicular to the magnetic field are transformed into variants with the axis nearly parallel to the magnetic field. Moreover, we found that the reorientation behaviors are different for different variants with the same crystallographic direction. The results demonstrate the crucial importance of microscopic investigation, such as X-ray diffraction analysis, of the martensitic transition. We also found that the magnetic-field-induced strain associated with the rearrangement of the variants occurs even in a very fast sweeping pulsed field of up to 1.910 T/s at 1 T.

Simulation of fracture behavior of Zircaloy-4 cladding under reactivity initiated accident conditions with a damage mechanics model combined with fuel performance codes FEMAXI7/RANNS

宇田川 豊; 三原 武; 福田 拓司; 杉山 智之; 鈴木 元衛; 永瀬 文久

no journal, , 

In order to investigate the detailed processes of pellet cladding mechanical interaction (PCMI) failure, a continuum damage mechanics model on FEM calculations has been applied to analyses of the RIA simulated NSRR tests with unirradiated and pre-hydrided claddings. The simulation gave reasonable prediction regarding with cladding fracture strain in hoop direction and reproduced the typical fracture behaviour under PCMI loading characterized by ductile shear zone. The effect of temperature gradient in cladding radial direction on cladding fracture strain was found to be at most 10%. The sensitivity analysis with respect to cladding stress biaxiality showed that plane-strain condition is the more severe stress state, leading to smaller fracture strain by at most 20-30%, than the stress state of equal tensions between hoop and axial directions, for unirradiated cladding with 50-100 micron pre-crack.

超高周波誘導炉による廃棄物減容処理システムの開発,9; 実用大型システム設計

青山 佳男; 山口 大美; 榊原 哲朗; 花本 行生; 村田 実*; 佐々木 尚*; 西川 雄*; 谷口 尚司*; 島崎 真一*; Park, J.*; et al.

no journal, , 

超高周波誘導炉による放射性廃棄物減容処理システムの開発を行った。実用規模の試験装置で得られた焼却溶融性能試験結果に基づき、より大きな実用処理炉の挙動をシミュレーションし、それが実現可能であることを評価した。また、安全性・経済性に関しても考察を行った。

超高周波誘導炉による廃棄物減容処理システムの開発,8; 実証試験, 溶融固化体物性評価

青山 佳男; 山口 大美; 榊原 哲朗; 花本 行生; 村田 実*; 佐々木 尚*; 西川 雄*; 谷口 尚司*; 島崎 真一*; Park, J.*; et al.

no journal, , 

超高周波誘導炉による放射性廃棄物減容処理システムの開発を行った。実用規模の試験装置を使用して製作した溶融固化体の密度,均質性などの固化体特性評価と模擬核種の浸出試験を行い、処分廃棄体としての健全性を確認した。また、核種の浸出メカニズムについても考察した。

EDC試験を用いた水素添加RAG被覆管の破損挙動評価

三原 武; 福田 拓司; 宇田川 豊; 杉山 智之; 永瀬 文久

no journal, , 

被覆管外周部に水素化物が集積した高燃焼度PWR燃料被覆管の水素化物リムはRIA時の破損挙動における初期クラック(き裂)の役割を果たしていることが照射済燃料のNSRR実験などにより示されている。水素化物リムより内面側の水素化物がRIA時破損挙動に与える影響を調べるために表面予き裂導入(RAG)被覆管に水素を添加した後EDC(Expansion Due to Compression)試験を実施した。一般には予き裂長さに対する応力拡大係数で被覆管の破損が整理できたことから、内面側の水化物が破損挙動に及ぼす影響は小さいと考えられる。ただし、予き裂先端に径方向成分を持つ水素化物が析出する場合は、応力拡大係数による評価において内面側水素化物の影響を考慮する必要があることがわかった。