九州大学 研究者情報
論文一覧
山﨑 重人(やまさき しげと) データ更新日:2024.01.11

准教授 /  工学研究院 材料工学部門


原著論文
1. Shigeto Yamasaki, Masaki Tanaka, Tatsuya Morikawa, Yasuaki Watanabe, Mitsuo Yamashita, Sakae Izumi, Evaluation of cleavage fracture behavior of C14 Fe2W laves phase by first principle calculation and crystal orientation analysis, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.TETSU-2021-069, 107, 11, 977-985, 2021.11, Cleavage fracture of C14 Fe2W Laves phase was investigated using crystal orientation measurement with scanning electron microscopy and first-principles calculations. Trace analysis of the orientations of cleavage planes reveals that cleavage fracture occurred at five types of crystal planes of (0001), {1100}, {1120}, {1101} and {1122}, among which the fracture at (0001) is the most preferable. The first-principle calculations of the surface energy for fracture, Young's modulus, and Poisson's ratio showed that the minimum fracture toughness value of 1.62 MPa·m1/2 was obtained at (0001). The tendency that the values of calculated fracture toughness become larger with the higher indexed planes is almost the same as the frequency of the types of cleavage planes in the trace analysis. It is concluded that the fracture toughness of C14 Fe2W Laves phase is controlled by the surface energy for fracture and Young’s modulus..
2. Junji Shimamura, Tatsuya Morikawa, Shigeto Yamasaki, Masaki Tanaka, Sulfide Stress Cracking (SSC) of Low Alloy Linepipe Steels in Low H<sub>2</sub>S Content Sour Environment, ISIJ International, 10.2355/isijinternational.isijint-2022-236, 62, 10, 2095-2106, 2022.10.
3. Shigeto Yamasaki, Tatsuya Morikawa, Masaki Tanaka, Yasuaki Watanabe, Mitsuo Yamashita, Sakae Izumi, Evaluation of Cleavage Fracture Behavior of C14 Fe<sub>2</sub>W Laves Phase by First-principles Calculations and Crystal Orientation Analysis, ISIJ International, 10.2355/isijinternational.isijint-2022-122, 62, 10, 2118-2125, 2022.10.
4. Shigeto Yamasaki, Hirofumi Matsuo, Tatsuya Morikawa, Masaki Tanaka, Acquisition of microscopic and local stress-strain curves by combination of HR-EBSD and DIC methods, Scripta Materialia, 10.1016/j.scriptamat.2023.115603, 235, 115603-115603, 2023.10.
5. 嶋村 純二, 森川 龍哉, 山﨑 重人, 田中 將己, 低合金鋼ラインパイプの低H2S濃度サワー環境下における硫化物応力腐食割れ挙動, 鉄と鋼, https://doi.org/10.2355/tetsutohagane.TETSU-2022-013, 108, 9, 642-655, 2022.09.
6. 安達 充, 奥平 有, 山﨑 重人, 光原 昌寿, 中島 英治, 小岩井 修二, 橋詰 良樹, 村上 勇夫, 寺田 大将, レーザ積層造形法と電子ビーム積層造形法で作製したAC8A アルミニウム合金のミクロ組織と引張特性, 軽金属, https://doi.org/10.2464/jilm.72.206, 72, 5, 206-213, 2022.05.
7. Genki Tsukamoto, Tomonori Kunieda, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Effects of temperature and grain size on active twinning systems in commercially pure titanium, Journal of Alloys and Compounds, 10.1016/j.jallcom.2021.161154, 884, 2021.12, In order to clarify the effects of grain boundary, grain size and deformation temperature on twinning deformation in polycrystalline commercially pure titanium, active twinning systems during compression deformation at temperatures from 25 °C to 800 °C investigated using SEM/EBSD techniques. Four twinning systems were confirmed to operate under compression at 10% strain in a deformation temperature dependent manner: {112̅1} and {112̅2} twins were observed only at relatively low temperatures (e.g. ≦ 400 °C), while, {101̅1} twins were observed at relatively high temperatures (e.g. ≧ 400 °C), and {101̅2} twins formed at every tested temperature (25 °C–800 °C). Our results suggested that the effects of strain concentration at grain boundaries on twinning differ based on the active twinning systems, which are affected by: 1) the difference in the formation temperature ranges between single-crystal and polycrystalline specimens, 2) the ratio of the number of deformation twins touching grain boundaries to the total number of deformation twins, and 3) grain size dependence..
8. Tanaka, M., Okajo, S., Yamasaki, S. & Morikawa, T., Persistent slip observed in TiZrNbHfTa: A body-centered high-entropy cubic alloy, Scripta Materialia, 2021.07.
9. Masaki Tanaka, Shinji Okajo, Shigeto Yamasaki, Tatsuya Morikawa, Persistent slip observed in TiZrNbHfTa: A body-centered high-entropy cubic alloy, Scripta Materialia, 10.1016/j.scriptamat.2021.113895, 200, 2021.07, Slip properties of TiZrNbHfTa were evaluated to obtain ψ–χ relationships, where χ is defined as the angle between the maximum shear stress plane and (1¯01). ψ is defined as the angle between the apparent slip plane and (1¯01). Bending tests were conducted with micrometer-sized cantilevers fabricated from a single grain with a focused ion beam. Slip bands appear to be straight on a micrometer length-scale, as for Fe–Si alloys, which suggests a persistent slip. However, the ψ–χ relationship indicated that ψ is nearly the same as χ, suggesting that there is no persistent slip. Detailed observations with an atomic force microscope confirm that cross-slipping is so frequent at a sub-micrometer length-scale that the slip bands appear to be straight and the maximum shear stress plane is observed on a micrometer length-scale. Here, TiZrNbHfTa shows abnormally frequent cross-slipping, which is a novel characteristic of high-entropy body-centered cubic alloys..
10. Shigeto Yamasaki, Misaki Deguchi, Masatoshi Mitsuhara, Hideharu Nakashima, Yutaro Ota, Keiji Kubushiro, Evaluation of depth of dislocation visibility in SEM electron channeling contrast imaging in Ti-6Al-4V alloy using serial sectioning method, Microscopy, 10.1093/jmicro/dfaa060, 70, 3, 265-277, 2021.06, In this study, we conducted a quantitative evaluation of dislocation density by scanning electron microscopy electron channeling contrast imaging for α grains of a Ti-6Al-4V alloy deformed at room temperature. The depth of visibility of dislocations is experimentally measured as 140 to 160 nm by a serial sectioning observation. This result is compared with the theoretical value and applied to evaluate dislocation density. These factors confirm that the theoretically calculated value of the depth of visibility, at 5 to 6 times the extinction distance, is valid for the hexagonal close-packed Ti alloy..
11. Shigeto Yamasaki, Tomoki Miike, Masatoshi Mitsuhara, Hideharu Nakashima, Ryutaro Akiyoshi, Takahiko Nakamura, Shimpei Kimura, Quantitative analysis of the Portevin–Le Chatelier effect by combining digital image correlation and dead-weight-type tensile test, Materials Science and Engineering A, 10.1016/j.msea.2021.141277, 816, 2021.06, A quantitative evaluation method of a serration deformation behavior by a dead-weight tensile test combined with a strain measurement by a DIC method is proposed. This method applies to binary solid solution aluminum alloys and a ternary cluster strengthened aluminum alloy. In the dead-weight tensile test, the serrated flow was measured as a stress-strain curve with a stepped-shape divided into two stages of a stress rising phase and a strain burst phase. By adopting this tensile test, the serration deformation behavior can be measured with an extremely reproducibility. It was confirmed that an elastic deformation occurs predominantly in the stress rising phase, and this deformation behavior is discussed in relation to the concentration of solid solution elements. Propagation of PLC bands has occurred in the strain burst phase. An activation volume obtained from the strain rate in the PLC bands was in good agreement with a calculated value based on a distribution interval assuming a regular square distribution of solute elements. For the ternary alloy strengthened by clusters, it is also shown that this method can be applied to the qualitative estimation of the change in the residual amount of the solid solution element in the matrix during natural aging..
12. Kawano, Y., Mayama, T., Mitsuhara, M., Yamasaki, S. & Sato, M., Generalized Slip Operation Factor Considering Contribution of Secondary Slip Systems, Materials Today Communications, 2021.03.
13. Yoshiki Kawano, Tsuyoshi Mayama, Masatoshi Mitsuhara, Shigeto Yamasaki, Michihiro Sato, Generalized Slip Operation Factor Considering Contribution of Secondary Slip Systems, Materials Today Communications, 10.1016/j.mtcomm.2021.102041, 26, 2021.03, Slip operation factor (SOF), which considers the effect of mechanical interactions between plastically “soft” and “hard” regions, is a function of the Schmid factor (SF) and critical resolved shear stress (CRSS). It is used as an indicator to efficiently predict the ease of slip operation of metal materials at the grain level. While SOF could predict strain distributions, it was not compliant to the prediction of those for individual slip systems. Additionally, the contribution of secondary slip systems was disregarded in the SOF. In this study, the SOF was first extended to adapt to individual slip systems. This extended and generalized form of the SOF was called SOFS. Next, the contribution of secondary slip systems was considered in SOF, where the modified version of the SOF was called MSOF. Polycrystalline α-Ti models were built from crystal orientation maps obtained by electron back-scattered diffraction (EBSD), and the strain distributions under uniaxial tensile loading were predicted using the SOF, SOFS, and MSOF. The results obtained were compared with those obtained via crystal plasticity finite element (CPFE) analysis. The distributions obtained by the SOFS were similar to slip strain distributions for individual slip systems when single slips were dominant and the deformation was slight. The MSOF also successfully predicted the strain distributions with higher accuracy than that offered by the SOF..
14. Yamasaki, S., Mitsuhara, M. & Nakashima, H., Relationship between Creep Strength and Magnetic Properties of Cobalt-bearing High Chromium Ferritic Steel, isij international, 2021.01.
15. Koichi Suematsu, Wataru Harano, Shigeto Yamasaki, Ken Watanabe, Kengo Shimanoe, One-trillionth level toluene detection using a dual-designed semiconductor gas sensor: Material and sensor-driven designs, ACS Applied Electronic Materials, 10.1021/acsaelm.0c00902, 2, 12, 4122-4126, 2020.12, Lowering the volatile organic compound (VOC) gas detection limit toward the ppt level on a resistive-type semiconductor gas sensor was achieved by combining the material and sensor-driven designs. We fabricated Pd-SnO2 clustered nanoparticles, a material that is highly sensitive to VOC gas, on a microsensor device with a double-pulse-driven mode. This mode was involved in switching the heater-on periods at high-temperature preheating and measurement phases and the rest phase during a heater-off period between preheating and measurement phases. The electrical resistance in synthetic air and the sensor response to toluene increased as preheating temperatures increased because of an increase in the amount of O2− adsorbed on the particle surface. In addition, extending the rest time between the preheating and measurement phases significantly improved the sensor response to toluene. According to the relationship between the sensor response and toluene concentration, we improved the lower detection limit for toluene gas to below 10 ppt, with preheating and measurement temperatures at 400 and 250 °C, respectively, and rest time at 100 s. Therefore, the combination of the material and sensor-driven designs may play a key role in improving the sensor performance..
16. 山﨑重人, 光原昌寿 & 中島英治,, コバルト含有高クロムフェライト鋼のクリープ強度と磁気特性の関係, 鉄と鋼, 2020.11.
17. Suematsu, K., Harano, W., Yamasaki, S., Watanabe, K. & Shimanoe, K., One-trillionth level toluene detection using a dual-designed semiconductor gas sensor: Material and sensor-driven designs, ACS Applied Electronic Materials, 2020.11.
18. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Relationship between Creep Strength and Magnetic Properties of Cobalt-bearing High Chromium Ferritic Steel, TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN, 10.2355/tetsutohagane.TETSU-2020-041, 106, 11, 12-22, 2020.11, In this study, the relation between the change of the magnetic properties and the creep strength with the addition of Co was investigated for ferritic steel containing 15 mass%Cr. Co addition up to 6 mass% hardly contributes to solid solution strengthening and precipitation strengthening at room temperature. However, in the range of 650 degrees C to 750 degrees C, it was confirmed that the addition of Co was effective for the creep strengthening because the steel with a larger amount of Co had higher creep strength. This creep strengthening is explained by a reduction in the diffusion rate associated with a change in magnetic properties by Co addition. The increase of the volume magnetization of the steel with increase of Co amount in the temperature range from room temperature to about 800 degrees C was confirmed. Comparing the difference in volume magnetization and the ratio of creep strain rate for steels with different amounts of Co, a clear correlation was found between the values. That is, at the temperature at which the difference in volume magnetization becomes maximum, the peak of the creep strain rate ratio was observed. This result is explained as follows. In a low temperature region where the magnetization is large or in a high temperature region above the Curie point of both steels, there is no significant difference in the creep strength between them. However, in the temperature where one steel loses the ferromagnetism but the other steel maintains ferromagnetism, a significant difference in the creep strength was observed..
19. Yamasaki, S., Deguchi, M., Mitsuhara, M., Nakashima, H., Ota, Y. & Kubushiro, K., Evaluation of depth of dislocation visibility in SEM electron channeling contrast imaging in Ti-6Al-4V alloy using serial sectioning method, Microscopy, 2020.10.
20. Misaki Deguchi, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Yutaro Ota, Dislocation motion and microstructure evolution deformed during creep at room temperature in Ti-6Al-4V alloy, Keikinzoku/Journal of Japan Institute of Light Metals, 10.2464/JILM.70.405, 70, 8, 405-414, 2020.10, The deformation behavior and microstructure evolution of Ti-6Al-4V alloy under room temperature creep was investigated using mechanical test and scanning electron microscope observation with electron back-scatter diffraction method. The alloys were creep deformed and ruptured under initial stresses of 874 MPa, 889 MPa and 904 MPa at room temperature. The rapid stress change test revealed that creep deformation was controlled by the viscous slip motion of dislocations. The stress exponent was estimated as 59. The strain rate of acceleration creep region calculated by the Norton's law with the high stress exponent was inconsistent with that measured by the experimental creep test. Using the slip trace analysis, it was found that single dislocation slip in basal and prism were mainly activated in the early stage of creep, and multiple slips were often observed as the deformation progresses. Especially, the multiple slip including 1st pyramidal slip believed to be effective for suppressing strain rate acceleration in creep. In addition, the work hardening behavior during creep showed a strain rate dependence, indicating that the lower the strain rate is, the more work hardening occurs..
21. Shigeto Yamasaki, Tsubasa Tokuzumi Wansong Li, Masatoshi Mitsuhara, Koji Hagihara, Toshiyuki Fujii, Hideharu Nakashima, Kink Formation Process in Long-Period Stacking Ordered Mg-Zn-Y Alloy, Acta Materialia, https://doi.org/10.1016/j.actamat.2020.04.051, 195, 15, 25-34, 2020.08.
22. Tsubasa Tokuzumi, Shigeto Yamasaki, Wansong Li, Masatoshi Mitsuhara, Hideharu Nakashima, Morphological and crystallographic features of kink bands in long-period stacking ordered Mg-Zn-Y alloy analyzed by serial sectioning SEM-EBSD observation method, Materialia, https://doi.org/10.1016/j.mtla.2020.100716, 12, 100716, 2020.08.
23. Deguchi, M., Yamasaki, S., Mitsuhara, M., Nakashima, H. & Ota, Y., Ti-6Al-4V 合金における室温クリープ中の転位の運動様式と変形組織の発達過程, 軽金属, 2020.08.
24. Shigeto Yamasaki, Tsubasa Tokuzumi, Wansong Li, Masatoshi Mitsuhara, Koji Hagihara, Toshiyuki Fujii, Hideharu Nakashima, Kink Formation Process in Long-Period Stacking Ordered Mg-Zn-Y Alloy, Acta Materialia, 10.1016/j.actamat.2020.04.051, 195, 25-34, 2020.08, © 2020 Acta Materialia Inc. The formation process of the kink bands in a directionally solidified, polycrystalline, long-period stacking ordered (LPSO) Mg85Zn6Y9 phase during compression deformation was investigated. In-situ compression observations by scanning electron microscopy and electron backscattered diffraction analysis revealed that regions with localized crystal orientation rotation appeared before ridge kinks formed as surface relief. In this paper, it is called as pre-kink The observed pre-kinks were composed of two separate regions rotated in opposite directions to each other and distinguished from one another by the three boundaries. A transmission electron microscopy observation revealed that the boundaries of the pre-kink are sub-boundaries consisting of edge dislocation array, and both its ends are terminated within the matrix. These characteristics match the reported that of regular ridge kink boundaries. In addition, while pre-kinks do not possess the ability of complete reversibility, its boundaries are capable of moving elastically..
25. Tsubasa Tokuzumi, Shigeto Yamasaki, Wansong Li, Masatoshi Mitsuhara, Hideharu Nakashima, Morphological and crystallographic features of kink bands in long-period stacking ordered Mg-Zn-Y alloy analyzed by serial sectioning SEM-EBSD observation method, Materialia, 10.1016/j.mtla.2020.100716, 12, 2020.08, © 2020 Acta Materialia Inc. We investigated the pseudo three-dimensional features of kink bands formed by the compression deformation of a directionally solidified Mg85Zn6Y9 alloy. The kink bands of interest included ridge kinks with clear surface relief and gentle kinks with almost no surface relief. Observation of surface undulation by laser microscopy and electron backscatter diffraction with serial sectioning by mechanical polishing revealed the pseudo three-dimensional morphology and crystal rotation of these kink bands. The features of the observed kink bands are explained by a pseudo three-dimensional arrangement of disclination lines..
26. Wansong Li, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, In situ EBSD study of deformation behavior of primary α phase in a bimodal Ti-6Al-4V alloy during uniaxial tensile tests, Materials Characterization, 10.1016/j.matchar.2020.110282, 163, 2020.05, [URL].
27. Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo, Daisuke Hirakami, Noritaka Horii, Ken Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki, Electron tomography imaging methods with diffraction contrast for materials research
, Microscopy, 10.1093/jmicro/dfaa002, 69, 3, 141-155, 2020.05.
28. Wansong Li, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, In situ EBSD study of deformation behavior of primary α phase in a bimodal Ti-6Al-4V alloy during uniaxial tensile tests, Materials Characterization, 10.1016/j.matchar.2020.110282, 163, 2020.05, © 2020 Elsevier Inc. Uniaxial tension experiments and electron backscatter diffraction were performed on a bimodal Ti-6Al-4V alloy to study in situ the deformation behavior of primary hcp-Ti (αp). It was found that the strain could be accommodated by the activation of slip systems and by grain rotations. The prismatic slip was the primary slip mode of the αp. From the analysis of kernel average misorientation and geometrically necessary dislocation, it was shown that the dislocations mainly distributed in the vicinity of grain and sub-grain boundaries, and part of the dislocations distributed around slip lines. It was the dislocation activities that led to the formation of the low angle grain boundary and its transformation to the high angle grain boundary. It's important that tracking of deformation heterogeneities with significance to performance. By analyzing the rotation angle, average rotation rate, and rotation path of grains, it was shown that grain rotation heterogeneity occurred during the deformation. From the observation of the loading direction, grain rotation paths kept with the texture evolution direction of all αp. The grains activated in the basal slip gradually rotated to the ⟨101¯1⟩ pole and enhanced the intensity of the ⟨101¯1⟩ texture. Meanwhile, the grains activated in prismatic or 1st-order pyramidal slip rotated to the ⟨101¯0⟩ pole and enhanced the intensity of the ⟨101¯0⟩ texture. Grain rotation and texture evolution are related to mechanical properties..
29. Satoshi Hata, Hiromitsu Furukawa, Takashi Gondo, Daisuke Hirakami, Noritaka Horii, Ken Ichi Ikeda, Katsumi Kawamoto, Kosuke Kimura, Syo Matsumura, Masatoshi Mitsuhara, Hiroya Miyazaki, Shinsuke Miyazaki, Mitsu Mitsuhiro Murayama, Hideharu Nakashima, Hikaru Saito, Masashi Sakamoto, Shigeto Yamasaki, Electron tomography imaging methods with diffraction contrast for materials research, Microscopy, 10.1093/jmicro/dfaa002, 69, 3, 141-155, 2020.03, © 2020 The Author(s). Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable the visualization of three-dimensional (3D) microstructures ranging from atomic to micrometer scales using 3D reconstruction techniques based on computed tomography algorithms. This 3D microscopy method is called electron tomography (ET) and has been utilized in the fields of materials science and engineering for more than two decades. Although atomic resolution is one of the current topics in ET research, the development and deployment of intermediate-resolution (non-atomic-resolution) ET imaging methods have garnered considerable attention from researchers. This research trend is probably not irrelevant due to the fact that the spatial resolution and functionality of 3D imaging methods of scanning electron microscopy (SEM) and X-ray microscopy have come to overlap with those of ET. In other words, there may be multiple ways to carry out 3D visualization using different microscopy methods for nanometer-scale objects in materials. From the above standpoint, this review paper aims to (i) describe the current status and issues of intermediate-resolution ET with regard to enhancing the effectiveness of TEM/STEM imaging and (ii) discuss promising applications of state-of-the-art intermediate-resolution ET for materials research with a particular focus on diffraction contrast ET for crystalline microstructures (superlattice domains and dislocations) including a demonstration of in situ dislocation tomography..
30. Yoshiki Kawano, Michihiro Sato, Tsuyoshi Mayama, Masatoshi Mitsuhara, Shigeto Yamasaki, Quantitative evaluation of slip activity in polycrystalline α-titanium considering non-local interactions between crystal grains, International Journal of Plasticity, 10.1016/j.ijplas.2019.12.001, 127, 2020.01, [URL].
31. 山﨑重人、光原昌寿、中島英治, 窒素を有効利用した700℃級次世代耐熱フェライト鋼の開発, ふぇらむ, 24, 8, 498-504, 2019.08.
32. Shigeto Yamasaki, Tomo Okuhira, Masatoshi Mitsuhara, Hideharu Nakashima, Jun Kusui, Mitsuru Adachi, Effect of Fe addition on heat-resistant aluminum alloys produced by selective laser melting, Metals, 10.3390/met9040468, 9, 4, 2019.04, [URL].
33. Shigeto Yamasaki, Tomo Okuhira, Masatoshi Mitsuhara, Hideharu Nakashima, Jun Kusui, Mitsuru Adachi, Effect of Fe addition on heat-resistant aluminum alloys produced by selective laser melting, Metals, 10.3390/met9040468, 9, 4, 2019.04, © 2019 by the authors. Licensee MDPI, Basel, Switzerland. The effect of Fe addition on the high-temperature mechanical properties of heat-resistant aluminum alloys produced by selective laser melting (SLM) was investigated in relation to the alloy microstructures. Fe is generally detrimental to the properties of cast aluminum alloys; however, we found that Fe-containing alloys produced by SLM had improved high-temperature strength and good ductility. Microstructural observations revealed that the increase in the high-temperature strength of the alloys was due to the dispersion of fine rod-shaped Fe-Si-Ni particles unique to the SLM material instead of the cell-like structure of eutectic Si..
34. Yuki Uchida, Sho Nakandakari, Kenji Kawahara, Shigeto Yamasaki, Masatoshi Mitsuhara, Hiroki Ago, Controlled Growth of Large-Area Uniform Multilayer Hexagonal Boron Nitride as an Effective 2D Substrate, ACS nano, 10.1021/acsnano.8b03055, 12, 6, 6236-6244, 2018.06, [URL].
35. Yuki Uchida, Sho Nakandakari, Kenji Kawahara, Shigeto Yamasaki, Masatoshi Mitsuhara, Hiroki Ago, Controlled Growth of Large-Area Uniform Multilayer Hexagonal Boron Nitride as an Effective 2D Substrate, ACS Nano, 10.1021/acsnano.8b03055, 12, 6, 6236-6244, 2018.06, © Copyright 2018 American Chemical Society. Multilayer hexagonal boron nitride (h-BN) is an ideal insulator for two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides, because h-BN screens out influences from surroundings, allowing one to observe intrinsic physical properties of the 2D materials. However, the synthesis of large and uniform multilayer h-BN is still very challenging because it is difficult to control the segregation process of B and N atoms from metal catalysts during chemical vapor deposition (CVD) growth. Here, we demonstrate CVD growth of multilayer h-BN with high uniformity by using the Ni-Fe alloy film and borazine (B3H6N3) as catalyst and precursor, respectively. Combining Ni and Fe metals tunes the solubilities of B and N atoms and, at the same time, allows one to engineer the metal crystallinity, which stimulates the uniform segregation of multilayer h-BN. Furthermore, we demonstrate that triangular WS2 grains grown on the h-BN show photoluminescence stronger than that grown on a bare SiO2 substrate. The PL line width of WS2/h-BN (the minimum and mean widths are 24 and 43 meV, respectively) is much narrower than those of WS2/SiO2 (44 and 67 meV), indicating the effectiveness of our CVD-grown multilayer h-BN as an insulating layer. Large-area, multilayer h-BN realized in this work will provide an excellent platform for developing practical applications of 2D materials..
36. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Development of high-chromium ferritic heat-resistant steels with high nitrogen content, isij international, 10.2355/isijinternational.ISIJINT-2017-758, 58, 6, 1146-1154, 2018.01, [URL].
37. Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Effect of Bi or Sb addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys, Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, 10.2320/jinstmet.J2017025, 81, 11, 502-509, 2017.09, [URL].
38. Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Effect of Bi or Sb addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys, Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, 10.2320/jinstmet.J2017025, 81, 11, 502-509, 2017.09, © 2017 The Japan Institute of Metals and Materials. Global concerns over the environmental impact and health effects of the lead-based solders have led to the development of lead-free solder alloys. Further improvements in the reliability of lead-free solder alloys at high temperatures are required for downsizing of electronic components in vehicles. In this work, tensile and creep tests and microstructure analysis were carried out to determine the effect of Bi or Sb addition on high-temperature deformation behavior in Sn-Cu-Ni solder alloys. The addition of Bi or Sb increased the strength of the Sn-Cu-Ni solder alloys. The stress exponent was estimated to be ≥3, indicating that the high- Temperature deformation was controlled by dislocation creep. Furthermore, in both the alloys, the stress exponent observed in the low stress region was nearly equal to 3 and discontinuously increased to ≥7 in the high stress region. For Sb addition, the solute atmosphere drag mechanism was observed in the low stress region..
39. Motomichi Koyama, Keita Yamanouchi, Qinghua Wang, Shien Ri, Yoshihisa Tanaka, Yasuaki Hamano, Shigeto Yamasaki, Masatoshi Mitsuhara, Masataka Ohkubo, Hiroshi Noguchi, Kaneaki Tsuzaki, Multiscale in situ deformation experiments
A sequential process from strain localization to failure in a laminated Ti-6Al-4V alloy, Materials Characterization, 10.1016/j.matchar.2017.04.010, 128, 217-225, 2017.06, [URL].
40. Motomichi Koyama, Keita Yamanouchi, Qinghua Wang, Shien Ri, Yoshihisa Tanaka, Yasuaki Hamano, Shigeto Yamasaki, Masatoshi Mitsuhara, Masataka Ohkubo, Hiroshi Noguchi, Kaneaki Tsuzaki, Multiscale in situ deformation experiments: A sequential process from strain localization to failure in a laminated Ti-6Al-4V alloy, Materials Characterization, 10.1016/j.matchar.2017.04.010, 128, 217-225, 2017.06, © 2017 Elsevier Inc. The microscopic factors causing tensile failure of an α/β laminated Ti-6Al-4V alloy were investigated through in situ scanning electron microscopy and sampling moiré at an ambient temperature. Specifically, multiscale in situ microscopic observations were conducted to extract the most crucial factor of the failure. Slip localization in the vicinity of an intergranular α-sheet was clarified to be the primary factor that causes failure of the Ti-6Al-4V alloy. In addition, no relationship between interfacial strain localization and macroscopic shear localization at 45 degrees against the tensile direction was observed..
41. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Deformation microstructure and fracture behavior in creep-exposed Alloy 617, Materials Transactions, 10.2320/matertrans.M2016407, 58, 3, 442-449, 2017.01, [URL].
42. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Development of high-chromium ferritic heat-resistant steels with high-nitrogen addition, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.TETSU-2016-057, 103, 1, 64-72, 2017.01, [URL].
43. Masayuki Takano, Keiji Kuroda, Kohei Hase, Shuuto Tanaka, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Effect of Cu and Ni addition on high temperature deformation behavior in Sn-Cu-Ni solder alloys, Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals, 10.2320/jinstmet.J2016069, 81, 7, 337-344, 2017.01, [URL].
44. Takanori Ito, Shigeto Yamasaki, Masatoshi Mitsuhara, Minoru Nishida, Mitsuharu Yonemura, Effect of intergranular carbides on creep strength in nickel-based heat-resistant alloys, Materials Transactions, 10.2320/matertrans.M2016291, 58, 1, 52-58, 2017.01, [URL].
45. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Mitsuharu Yonemura, Evaluation of local creep strain in face-centred cubic heatresistant alloys using electron backscattered diffraction analysis, isij international, 10.2355/isijinternational.ISIJINT-2016-712, 57, 5, 851-856, 2017.01, [URL].
46. Takanori Ito, Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Minoru Nishida, Mitsuharu Yonemura, Microstructure and creep property in polycrystalline Ni-based alloy with intergranular intermetallics, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.TETSU-2016-107, 103, 7, 434-442, 2017.01, [URL].
47. Masatoshi Mitsuhara, Shigeto Yamasaki, Masaki Miake, Hideharu Nakashima, Minoru Nishida, Junichi Kusumoto, Akihiro Kanaya, Creep strengthening by lath boundaries in 9Cr ferritic heat-resistant steel, Philosophical Magazine Letters, 10.1080/09500839.2016.1154200, 96, 2, 76-83, 2016.02, [URL].
48. Masatoshi Mitsuhara, Shigeto Yamasaki, Masaki Miake, Hideharu Nakashima, Minoru Nishida, Junichi Kusumoto, Akihiro Kanaya, Creep strengthening by lath boundaries in 9Cr ferritic heat-resistant steel, Philosophical Magazine Letters, 10.1080/09500839.2016.1154200, 96, 2, 76-83, 2016.02, © 2016 Taylor and Francis. The interactions between dislocations and lath boundaries in Grade 91 steel were observed by an in situ transmission electron microscopy tensile test at 973 K. Dislocations glided slowly and bowed out in a martensite lath interior. The ends of the dislocation were connected to the lath boundaries. In a tempered specimen, the pinning stress caused by the lath boundary was estimated to be >70 MPa with a lath width of 0.4 m. In crept specimens, lath coarsening reduced the pinning effect..
49. S. Yamasaki, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, 3D visualization of dislocation arrangement using scanning electron microscope serial sectioning method, Scripta Materialia, 10.1016/j.scriptamat.2015.02.001, 101, 80-83, 2015.05, [URL].
50. S. Yamasaki, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, 3D visualization of dislocation arrangement using scanning electron microscope serial sectioning method, Scripta Materialia, 10.1016/j.scriptamat.2015.02.001, 101, 80-83, 2015.05, © 2015 Acta Materialia Inc. Published by Elsevier Ltd. We performed the three-dimensional visualization of dislocations through serial sectioning and use of SEM electron channeling contrast (ECC) images for a crept nickel-based alloy. We successfully reconstructed a volume of approximately 7.5 μm3, including dislocation arrangements, by performing calculations based on the continuous tomograms of ECC images. By incorporating the information on crystal orientation obtained by the electron back-scattered diffraction, we verified that the three-dimensional arrangement of dislocations, such as slip plane, was accurately reflected in the three-dimensional volume..
51. Shigeto Yamasaki, Masatoshi Mitsuhara, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low stress creep deformation in high chromium ferritic heat-resistant steel evaluated by helicoid spring creep test method, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.100.688, 100, 5, 688-695, 2014.05, [URL].
52. Shigeto Yamasaki, Masatoshi Mitsuhara, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-stress creep deformation in long-term aged ferritic heat-resistant steel, Materials Transactions, 10.2320/matertrans.M2013427, 55, 5, 842-849, 2014.05, [URL].
53. 小池幸司, 山崎重人, 池田賢一, 波多聰, 中島英治, 純ニッケルの極低ひずみ速度クリープの変形機構の解明, 日本金属学会講演概要(CD-ROM), 153rd, ROMBUNNO.P124, 2013.09.
54. 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治, オーステナイト系耐熱鋼の局所結晶方位解析によるクリープひずみの評価, 材料とプロセス(CD-ROM), 26, 1, ROMBUNNO.258, 2013.03.
55. 光原昌寿, 市瀬祐輔, 市瀬祐輔, 山崎重人, 池田賢一, 波多聰, 中島英治, 長谷川泰士, SEM/EBSD法によるクリープ変形に伴うGr.92鋼溶接継手の組織変化挙動解析, 材料とプロセス(CD-ROM), 25, 2, ROMBUNNO.266, 2012.09.
56. 山崎重人, 池田賢一, 波多聰, 中島英治, フェライト系耐熱鋼の低応力クリープ変形挙動, 日本金属学会講演概要(CD-ROM), 150th, ROMBUNNO.528, 2012.03.
57. 市瀬祐輔, 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治, 長谷川泰士, 局所方位解析法を用いたフェライト系耐熱鋼溶接熱影響部クリープ弱化要因の特定, 日本金属学会講演概要(CD-ROM), 149th, ROMBUNNO.POSUTASESSHON,439, 2011.10.
58. Junjie Shen, Shigeto Yamasaki, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-temperature creep at ultra-low strain rates in pure aluminum studied by a helicoid spring specimen technique, Materials Transactions, 10.2320/matertrans.M2010405, 52, 7, 1381-1387, 2011.07, [URL].
59. Junjie Shen, Shigeto Yamasaki, Ken Ichi Ikeda, Satoshi Hata, Hideharu Nakashima, Low-temperature creep at ultra-low strain rates in pure aluminum studied by a helicoid spring specimen technique, Materials Transactions, 10.2320/matertrans.M2010405, 52, 7, 1381-1387, 2011.07, The creep behavior in pure aluminum has been investigated by helicoid spring creep tests at strain rates, ε̇, lower than 10-10 s-1 and low temperature ranging from 0.32Tm to 0.43T m. It was found that the creep behavior in this region depends strongly on grain sizes and impurity concentrations. For high-purity aluminum (5 N Al) with an average grain size, dg > 1600 μm, nearly the wire diameter of the spring sample, where the role of grain boundary during creep deformation can be negligible, the stress exponent was n ∼ 5 and the activation energy was Qc = 32 kJ/mol. Microstructural observation showed the formation of large dislocation cells (∼10μm) and tangled dislocations at the cell walls. For high-purity aluminum (5N Al) with d g = 24 μm, the stress exponent was n ∼ 1 and the activation energy was Qc = 15kJ/mol. On the other hand, for commercial low-purity aluminum (2 N Al) with dg = 25 μm, the stress exponent was n = 2 and the activation energy was Qc = 25 kJ/mol. Microstructural observations revealed dislocations emitted from grain boundaries, those dislocations interacting with intragranular dislocations and the formation of dislocation cells in the grains. Based on those experimental results, the low-temperature creep mechanisms in pure aluminum at ε̇
60. 光原 昌寿, 原田 絵梨香, 山崎 重人, 池田 賢一, 波多 聰, 中島 英治, 大塚 智史, 皆藤 威二, 酸化物分散強化型9Crフェライト系耐熱鋼の3次元組織と高温強度, 可視化情報学会誌 = Journal of the Visualization Society of Japan, 10.3154/jvs.31.98, 31, 122, 98-103, 2011.07, 高速増殖炉内燃料被覆管の候補材料として研究開発が行われている酸化物分散強化(ODS)型9Crフェライト系耐熱鋼について,内部に生成するイットリア系酸化物の分散状態を電子線トモグラフィーにより3次元的に評価した.酸化物は,高密度な領域と低密度な領域が鋼管の押出し方向と平行になるように積層した分布を持っていた.それぞれの領域で,酸化物による変形への抵抗力を粒径や粒子間距離などから算出すると,700℃において,高密度領域では232~278MPa,低密度領域では154~184MPaであった.さらに,クリープ特性を評価したところ,約140MPaでクリープ変形機構の遷移が認められた.このしきい値は,低密度領域の酸化物による変形の抵抗力におおよそ一致している.すなわち,低密度に酸化物が分散した領域において転位の運動が速く,このことがODS鋼の高温強度や変形機構に強く影響を及ぼしていると示唆された..
61. 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治, コイルばねクリープ試験法による改良9Cr‐1Mo鋼の極低速クリープ挙動評価, 材料とプロセス(CD-ROM), 23, 2, ROMBUNNO.277, 2010.09.
62. 富田成明, 浜島和雄, 山崎重人, 光原昌寿, 池田賢一, 波多聰, 中島英治, Pt系分散強化合金の低応力領域でのクリープ特性の検討, 日本金属学会講演概要, 146th, 365, 2010.03.
63. 山崎重人, 藤本健資, 光原昌寿, 池田賢一, 波多聰, 中島英治, 木村光男, コイルばねクリープ試験法による高Cr鋼の低速クリープ挙動評価, 材料とプロセス(CD-ROM), 22, 2, ROMBUNNO.PS-35, 2009.09.
64. 光原昌寿, 山崎重人, 池田賢一, 波多聰, 中島英治, コイルばねクリープ試験法によるSUS304鋼のクリープ挙動解析, 材料とプロセス(CD-ROM), 21, 2, ROMBUNNO.TO121, 2008.09.

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pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。