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論文

Si-addition contributes to overcoming the strength-ductility trade-off in high-entropy alloys

Wei, D.*; Gong, W.; 都留智仁; Lobzenko, I.; Li, X.*; Harjo, S.; 川崎卓郎; Do, H.-S.*; Bae, J. W.*; Wagner, C.*; et al.

International Journal of Plasticity, 159, p.103443_1 - 103443_18, 2022/12

https://doi.org/10.1016/j.ijplas.2022.103443

被引用回数：3 パーセンタイル：80.2(Engineering, Mechanical)

Face-centered cubic single-phase high-entropy alloys (HEAs) containing multi-principal transition metals have attracted significant attention, exhibiting an unprecedented combination of strength and ductility owing to their low stacking fault energy (SFE) and large misfit parameter that creates severe local lattice distortion. Increasing both strength and ductility further is challenging. In the present study, we demonstrate via meticulous experiments that the CoCrFeNi HEA with the addition of the substitutional metalloid Si can retain a single-phase FCC structure while its yield strength (up to 65%), ultimate strength (up to 34%), and ductility (up to 15%) are simultaneously increased, owing to a synthetical effect of the enhanced solid solution strengthening and a reduced SFE. The dislocation behaviors and plastic deformation mechanisms were tuned by the addition of Si, which improves the strain hardening and tensile ductility. The present study provides new strategies for enhancing HEA performance by targeted metalloid additions.

論文

Metalloid substitution elevates simultaneously the strength and ductility of face-centered-cubic high-entropy alloys

Wei, D.*; Wang, L.*; Zhang, Y.*; Gong, W.; 都留智仁; Lobzenko, I.; Jiang, J.*; Harjo, S.; 川崎卓郎; Bae, J. W.*; et al.

Acta Materialia, 225, p.117571_1 - 117571_16, 2022/02

https://doi.org/10.1016/j.actamat.2021.117571

被引用回数：22 パーセンタイル：99.69(Materials Science, Multidisciplinary)

Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have ex-tended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions.

論文

Work hardening behavior of hot-rolled metastable Fe $_{50}$ Co $_{25}$ Ni $_{10}$ Al $_{5}$ Ti $_{5}$ Mo $_{5}$ medium-entropy alloy; In situ neutron diffraction analysis

Kwon, H.*; Harjo, S.; 川崎卓郎; Gong, W.; Jeong, S. G.*; Kim, E. S.*; Sathiyamoorthi, P.*; 加藤秀実*; Kim, H. S.*

Science and Technology of Advanced Materials, 23(1), p.579 - 586, 2022/00

https://doi.org/10.1080/14686996.2022.2122868

Metastability engineering is a strategy to enhance the strength and ductility of alloys via deliberately lowering phase stability and prompting deformation-induced martensitic transformation. In this work, the martensitic transformation and its effect on the mechanical response of a Fe $_{50}$ Co $_{25}$ Ni $_{10}$ Al $_{5}$ Ti $_{5}$ Mo $_{5}$ medium-entropy alloy (MEA) were studied by in situ neutron diffraction under tensile loading. This work shows how great a role FCC to BCC martensitic transformation can play in enhancing the mechanical properties of ferrous MEAs.

論文

Suppressed lattice disorder for large emission enhancement and structural robustness in hybrid lead iodide perovskite discovered by high-pressure isotope effect

Kong, L.*; Gong, J.*; Hu, Q.*; Capitani, F.*; Celeste, A.*; 服部高典; 佐野亜沙美; Li, N.*; Yang, W.*; Liu, G.*; et al.

Advanced Functional Materials, 31(9), p.2009131_1 - 2009131_12, 2021/02

https://doi.org/10.1002/adfm.202009131

被引用回数：17 パーセンタイル：81.17(Chemistry, Multidisciplinary)

有機-無機ハロゲン化物ペロブスカイトは非常に柔らかいために、圧力などの外部刺激により格子定数を容易に変化させることができ、有用な光電特性を引き出すのに有効である。一方でこの特性は、多少の加圧でも、格子を歪ませてしまい、光と物質の相互作用を弱め、それによる性能の低下を引き起こす。そこで本研究では、代表的な物質であるヨウ化メチルアンモニウム鉛に対して圧力効果および同位体効果を調べ、それらが格子歪を抑制することが分かった。このことは、それらが、これまで得られなかったような光学的,機械的特性を持つ物質を得る手段として有効であることを示している。

論文

Quantifying internal strains, stresses, and dislocation density in additively manufactured AlSi10Mg during loading-unloading-reloading deformation

Zhang, X. X.*; Andr, H.*; Harjo, S.; Gong, W.*; 川崎卓郎; Lutz, A.*; Lahres, M.*

Materials & Design, 198, p.109339_1 - 109339_9, 2021/01

https://doi.org/10.1016/j.matdes.2020.109339

被引用回数：29 パーセンタイル：96.59(Materials Science, Multidisciplinary)

Here, in-situ neutron diffraction is employed to explore the residual strains, stresses, and dislocation density in the LPBF AlSi10Mg during loading-unloading-reloading deformation. It is found that the maximum residual stresses of the Al and Si phases in the loading direction reach up to about -115 (compressive) and 832 (tensile) MPa, respectively. A notable dislocation annihilation phenomenon is observed in the Al matrix: the dislocation density decreases significantly during unloading stages, and the amplitude of this reduction increases after experiencing a larger plastic deformation. At the macroscale, this dislocation annihilation phenomenon is associated with the reverse strain after unloading. At the microscale, the annihilation phenomenon is driven by the compressive residual stress in the Al matrix. Meanwhile, the annihilation of screw dislocations during unloading stages contributes to the reduction in total dislocation density.

論文

Odd and even modes of neutron spin resonance in the bilayer iron-based superconductor CaKFe $_{4}$ As $_{4}$

Xie, T.*; Wei, Y.*; Gong, D.*; Fennell, T.*; Stuhr, U.*; 梶本亮一; 池内和彦*; Li, S.*; Hu, J.*; Luo, H.*

Physical Review Letters, 120(26), p.267003_1 - 267003_7, 2018/06

https://doi.org/10.1103/PhysRevLett.120.267003

被引用回数：28 パーセンタイル：86.36(Physics, Multidisciplinary)

We report an inelastic neutron scattering study on the spin resonance in the bilayer iron-based superconductor CaKFeAs. In contrast to its quasi-two-dimensional electron structure, three strongly -dependent modes of spin resonance are found below = 35 K. The mode energies are below and linearly scale with the total superconducting gaps summed on the nesting hole and electron pockets, essentially in agreement with the results in cuprate and heavy fermion superconductors. This observation supports the sign-reversed Cooper-pairing mechanism under multiple pairing channels and resolves the long-standing puzzles concerning the broadening and dispersive spin resonance peak in iron pnictides. More importantly, the triple resonant modes can be classified into odd and even symmetries with respect to the distance of Fe-Fe planes within the Fe-As bilayer unit. Thus, our results closely resemble those in the bilayer cuprates with nondegenerate spin excitations, suggesting that these two high- superconducting families share a common nature.

論文

Uniaxial pressure effect on the magnetic ordered moment and transition temperatures in BaFe $_{2-x}$ T $_{x}$ As $_{2}$ ( = Co,Ni)

Tam, D. M.*; Song, Y.*; Man, H.*; Cheung, S. C.*; Yin, Z.*; Lu, X.*; Wang, W.*; Frandsen, B. A.*; Liu, L.*; Gong, Z.*; et al.

Physical Review B, 95(6), p.060505_1 - 060505_6, 2017/02

https://doi.org/10.1103/PhysRevB.95.060505

被引用回数：22 パーセンタイル：74.52(Materials Science, Multidisciplinary)

We use neutron diffraction and muon spin relaxation to study the effect of in-plane uniaxial pressure on the antiferromagnetic (AF) orthorhombic phase in BaFe $_{2-x}$ T $_{x}$ As $_{2}$ and its Co- and Ni-substituted members near optimal superconductivity. In the low-temperature AF ordered state, uniaxial pressure necessary to detwin the orthorhombic crystals also increases the magnetic ordered moment, reaching an 11% increase under 40 MPa for BaFe $_{1.9}$ Co $_{0.1}$ As, and a 15% increase for BaFe $_{1.915}$ Ni $_{0.085}$ As. We also observe an increase of the AF ordering temperature () of about 0.25 K/MPa in all compounds, consistent with density functional theory calculations that reveal better Fermi surface nesting for itinerant electrons under uniaxial pressure. The doping dependence of the magnetic ordered moment is captured by combining dynamical mean field theory with density functional theory, suggesting that the pressure-induced moment increase near optimal superconductivity is closely related to quantum fluctuations and the nearby electronic nematic phase.

論文

Overview of plasma-material interaction experiments on EAST employing MAPES

Ding, F.*; Luo, G.-N.*; Pitts, R.*; Litnovsky, A.*; Gong, X.*; Ding, R.*; Mao, H.*; Zhou, H.*; Wampler, W. R.*; Stangeby, P. C.*; et al.

Journal of Nuclear Materials, 455(1-3), p.710 - 716, 2014/12

https://doi.org/10.1016/j.jnucmat.2014.09.017

被引用回数：24 パーセンタイル：89.39(Materials Science, Multidisciplinary)

A movable material probe system (Material and Plasma Evaluation System: MAPES) with an independent pumping system and a sample exchange chamber has been developed and installed on a horizontal port of the EAST tokamak for studies of plasma material interaction (PMI). In the 2012 experimental campaign, deposition and erosion were studied for three samples: mock-up of the outer first wall panels (FWPs) in ITER, castellated tungsten, and molybdenum mirrors. The FWPs with carbon deposition layer were exposed to helium plasmas. The maximum erosion rate of the carbon was valuated to be 8 nm/s. The castellated tungsten with rectangular cells and roof-like shaped cells was exposed to deuterium plasmas to compare amount of deposits on the gap surface. The amount of carbon and boron impurities on the gap surface of the roof-like shaped cells were reduced to less than 30% compared with that of the rectangular cells. The molybdenum mirrors of which protective ducts are installed in front were exposed to deuterium plasmas in order to investigate effects of length of the ducts. It was found that the reflectivity of the mirrors with 60 mm-long protective ducts is kept the initial reflectivity.

論文

Event structure and double helicity asymmetry in jet production from polarized collisions at = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

https://doi.org/10.1103/PhysRevD.84.012006

被引用回数：26 パーセンタイル：70.48(Astronomy & Astrophysics)

重心エネルギー200GeVでの縦偏極陽子陽子衝突からのジェット生成のイベント構造と二重非対称( $A_{LL}$ )について報告する。光子と荷電粒子がPHENIX実験で測定され、イベント構造がPHYTIAイベント生成コードの結果と比較された。再構成されたジェットの生成率は2次までの摂動QCDの計算で十分再現される。測定された $A_{LL}$ は、一番低い横運動量で-0.00140.0037、一番高い横運動量で-0.01810.0282であった。この $A_{LL}$ の結果を幾つかのの分布を仮定した理論予想と比較する。

論文

Identified charged hadron production in collisions at = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; 秋葉康之*; Al-Bataineh, H.*; Alexander, J.*; 青木和也*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903

被引用回数：169 パーセンタイル：99.44(Physics, Nuclear)

200GeVと62.4GeVでの陽子陽子の中心衝突からのの横運動量分布及び収量をRHICのPHENIX実験によって測定した。それぞれエネルギーでの逆スロープパラメーター、平均横運動量及び単位rapidityあたりの収量を求め、異なるエネルギーでの他の測定結果と比較する。またやスケーリングのようなスケーリングについて示して陽子陽子衝突における粒子生成メカニズムについて議論する。さらに測定したスペクトルを二次の摂動QCDの計算と比較する。

論文

Azimuthal correlations of electrons from heavy-flavor decay with hadrons in and Au+Au collisions at $sqrt{s_{NN}}$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; 秋葉康之*; Al-Bataineh, H.*; Alexander, J.*; 青木和也*; Aphecetche, L.*; Aramaki, Y.*; et al.

Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04

https://doi.org/10.1103/PhysRevC.83.044912

被引用回数：8 パーセンタイル：51.17(Physics, Nuclear)

重いフレーバーのメソンの崩壊からの電子の測定は、このメソンの収量が金金衝突では陽子陽子に比べて抑制されていることを示している。われわれはこの研究をさらに進めて二つの粒子の相関、つまり重いフレーバーメソンの崩壊からの電子と、もう一つの重いフレーバーメソンあるいはジェットの破片からの荷電ハドロン、の相関を調べた。この測定は重いクォークとクォークグルオン物質の相互作用についてのより詳しい情報を与えるものである。われわれは特に金金衝突では陽子陽子に比べて反対側のジェットの形と収量が変化していることを見いだした。

論文

Measurement of neutral mesons in + collisions at = 200 GeV and scaling properties of hadron production

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03

https://doi.org/10.1103/PhysRevD.83.052004

被引用回数：161 パーセンタイル：98.47(Astronomy & Astrophysics)

RHIC-PHENIX実験で重心エネルギー200GeVの陽子陽子衝突からの, , と中間子生成の微分断面積を測定した。これらハドロンの横運動量分布のスペクトルの形はたった二つのパラメーター、、のTsallis分布関数でよく記述できる。これらのパラメーターはそれぞれ高い横運動量と低い横運動量の領域のスペクトルを決めている。これらの分布をフィットして得られた積分された不変断面積はこれまで測定されたデータ及び統計モデルの予言と一致している。

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中性子超小角散乱法によるアクチンコンプレックス形成過程の追跡

増井友美; 小泉智; 橋本竹治; 岩瀬裕希; 敷中一洋*; Kwon, H.*; 角五彰*; Gong, J.*

no journal, ,

アクチン分子は生体内に最も豊富に存在する球状タンパク質であり、生体内のアクチン結合タンパク質とともにコンプレックスを形成することで高次構造を形成し、細胞運動を担うことが知られている。このため、細胞運動を理解するためにアクチン分子が形成するコンプレックスの構造の研究は精力的に進められ、蛍光標識したアクチン分子を用いて蛍光顕微鏡観測を中心に研究が進められている。生体内のアクチン濃度は高いが、蛍光顕微鏡観測では高アクチン濃度では背景光が蛍光ノイズとなるため高濃度での振る舞いに関しては不明な点が多いのが現状である。本研究では、中性子超小角散乱法を利用することで、顕微鏡実験より高濃度での実験を実現し、アクチンコンプレックスの構造を追跡した。その結果、顕微鏡実験の濃度ではコンプレックスを形成しない条件下でも、アクチン濃度を高くすることによりコンプレックスを形成することを明らかにした。

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