Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Mitsuhara Masatoshi Last modified date:2022.11.09

Associate Professor / Structural Material Science / Department of Advanced Materials Science and Engineering / Faculty of Engineering Sciences

1. Recent Studies on TEM/STEM Tomography.
2. Effects of O and Al Addition on T winning Deformation in Titanium.
3. 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..
4. Dislocation Motion and Microstructure Evolution Deformed during Creep at Room Temperature in Ti-6Al-4V Alloy.
5. Hiroshi Akamine, Masatoshi Mitsuhara, Minoru Nishida, Vahid Samaee, Dominique Schryvers, Genki Tsukamoto, Tomonori Kunieda, Hideki Fujii, Precipitation Behaviors in Ti–2.3 Wt Pct Cu Alloy During Isothermal and Two-Step Aging, Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 10.1007/s11661-021-06265-x, 52, 7, 2760-2772, 2021.07, Time evolution of precipitates related to age-hardening in Ti–2.3 wt pct Cu alloys was investigated by electron microscopy. In isothermal aging at 723 K, the hardness increases continuously owing to precipitation strengthening, whereas in two-step aging where the aging temperature is switched from 673 K to 873 K after 100 hours, the hardness is found to drastically drop after the aging temperature switches. In isothermal aging, metastable and stable precipitates are independently nucleated, whereas characteristic V-shaped clusters of precipitates are observed during the two-step aging. It is revealed by atomic-scale observations that the V-shaped clusters are composed of metastable and stable precipitates and each type of precipitate has a different orientation relationship with the α phase: (10 3 ¯) //(0001) and [0 1 ¯ 0] //[11 2 ¯ 0] for the metastable, and (201)//(1 1 ¯ 03) and [0 1 ¯ 0] //[11 2 ¯ 0] for the stable precipitates, respectively. The drop in hardness during two-step aging can be explained by a synergistic effect of decreased precipitation strengthening and solid solution strengthening. α α α α.
6. Mitsuhiro Matsuda, Yuta Yamada, Yuta Himeno, Kenji Shida, Masatoshi Mitsuhara, Motohide Matsuda, Magnéli Ti4O7 thin film produced by stepwise oxidation of titanium metal foil, Scripta Materialia, 10.1016/j.scriptamat.2021.113829, 198, 2021.06, A 3-μm-thick film of Magnéli Ti O was successfully fabricated on the surface of Ti metal foil by a stepwise oxidation process involving annealing at 973 K in air followed by heating to 1173 K under a low oxygen partial pressure. Transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy showed that the Magnéli Ti O phase consisted of a period of four layers of equiaxial grains several hundreds of nanometers in size. The black Magnéli Ti O thin film formed by our process absorbed light in the visible and near-infrared regions. 4 7 4 7 4 7.
7. 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..
8. 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..
9. Nozomu Adachi, Yasutaka Matsuo, Yoshikazu Todaka, Mikiya Fujimoto, Masahiro Hino, Masatoshi Mitsuhara, Yojiro Oba, Yoshinori Shiihara, Yoshitaka Umeno, Minoru Nishida, Effect of grain boundary on the friction coefficient of pure Fe under the oil lubrication, Tribology International, 10.1016/j.triboint.2020.106781, 155, 2021.03, In this study, the effect of grain boundary on the frictional behavior under the oil-lubricated condition was investigated by varying the grain size (crystallite size) of the pure Fe samples prepared via physical vapor deposition. A high fraction of grain boundary in the sample yielded a low friction coefficient μ in the case of a lubrication oil that formed a chemisorbed film on the surface of the material. Thick absorbed layer formed on the surface was observed only in the sample with high fraction of grain boundary. These results indicate that a disordered structure in the vicinity of grain boundary preferentially forms chemisorbed films and reduces μ by protecting the surface of the material..
10. 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..
11. M. Matsuda, K. Arai, M. Mitsuhara, Y. Yamabe-Mitarai, M. Nishida, Self-accommodation and morphological characteristics of the B33 martensite in Zr–Co–Pd alloys, Journal of Materials Science, 10.1007/s10853-020-05599-y, 56, 9, 5899-5909, 2021.03, Thermoelastic martensitic transformation (MT) plays a vital role in shape memory effects and superelasticity of various alloys. To understand the self-accommodation mechanism of the MT of Zr–Co–Pd alloys, which demonstrate typical MT from B2 to B33 structure, the configuration of the alloy’s martensite variants and their crystallographic relationship were investigated by electron backscatter diffraction, transmission electron microscopy, and high-angle annular dark-field scanning transmission electron microscopy. Results suggest that two habit plane variants (HPVs) bounded by {021} compound twinning are formed around each < 100> axes of the B2 parent phase. It is determined that the minimum self-accommodation unit, to relax the strain energy accompanying MT, is a pair of trapezoid- or triangle-shaped HPVs. No lattice invariant shear exists in the martensite variants with a trapezoid- or triangle-shape. In the latter stage of MT, each HPV pair may contact and impinge on {110} plane of B2 parent phase, which is shear and shuffling plane on MT. The combination of the four variants forms the roof-type morphology. B33 B2 B2.
12. Ryoma Fukuoka, Kazushige Tokuno, Masatoshi Mitsuhara, Kohei Yamakoshi, Shinnosuke Tsuchida, Junji Miyamoto, Masahiro Hagino, Dislocation structures formed inside dislocation channels of rapid-cooled and tensile-deformed aluminum single crystals, Materials Transactions, 10.2320/matertrans.MT-M2020255, 62, 2, 221-228, 2021.02, Dislocation structures inside the cleared dislocation channels in rapid-cooled and tensile-deformed aluminum single crystals were investigated by using transmission electron microscope (TEM). The present study especially focused on the dislocation structures at their early formation stage. In their very beginning stage, arrays of prismatic dislocation loops of the primary slip system were essentially formed elongating along [1- 2 1] direction and each prismatic loop stacked to [1- 0 1]. With the progress of plastic deformation, the number of the prismatic loops composing the array increased and produced tangled structures with dislocations of the primary coplanar slip system. The tangled structures may act as strong obstacles against the following primary dislocations and become a triggering factor for the creation of the cell structure..
13. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Relationship between creep strength and magnetic properties of cobalt-bearing high chromium ferritic steel, ISIJ International, 10.2355/isijinternational.ISIJINT-2020-315, 61, 1, 408-416, 2021.01, In this study, the relationship between changes in the magnetic properties and creep strength with the addition of 3 or 6 mass% Co was investigated for ferritic steel containing 15 mass% Cr. Co addition up to 6 mass% hardly contributed to solid solution strengthening or precipitation strengthening at room temperature. However, in the range of 650 to 750°C, the steel with the larger amount of Co exhibited higher creep strength, which is explained by a reduction in the diffusion rate associated with a change in magnetic properties by Co addition. An increase of the volume magnetization of the steel with increasing Co content in the range from room temperature to about 800°C was confirmed. Comparing the difference in volume magnetization and the ratio of the creep strain rate for steels with different amounts of Co, a clear correlation was found. That is, at the temperature at which the difference in volume magnetization reached a maximum, the peak of the creep strain rate ratio was also 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, the steels exhibit no significant difference in the creep strength. However, at a temperature where one steel loses its ferromagnetism but the other steel retains it, a significant difference in the creep strength is observed..
14. S. Hata, T. Honda, H. Saito, M. Mitsuhara, T. C. Petersen, M. Murayama, Electron tomography: An imaging method for materials deformation dynamics, Current Opinion in Solid State and Materials Science, 10.1016/j.cossms.2020.100850, 24, 4, 2020.08, The combination of in-situ and three-dimensional (3D) in transmission electron microscopy (TEM) is one of the emerging topics of recent advanced electron microscopy research. However, to date, there have been only handful examples of in-situ 3D TEM for material deformation dynamics. In this article, firstly, the authors briefly review technical developments in fast tilt-series dataset acquisition, which is a crucial technique for in-situ electron tomography (ET). Secondly, the authors showcase a recent successful example of in-situ specimen-straining and ET system development and its applications to the deformation dynamics of crystalline materials. The system is designed and developed to explore, in real-time and at sub-microscopic levels, the internal behavior of polycrystalline materials subjected to external stresses, and not specifically targeted for atomic resolution (although it may be possible). Technical challenges toward the in-situ ET observation of 3D dislocation dynamics are discussed for commercial structural crystalline materials, including some of the early studies on in-situ ET imaging and 3D modeling of dislocation dynamics. A short summary of standing technical issues and a proposed guideline for further development in the 3D imaging method for dislocation dynamics are then discussed..
15. 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, The formation process of the kink bands in a directionally solidified, polycrystalline, long-period stacking ordered (LPSO) Mg Zn Y 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. 85 6 9.
16. 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, We investigated the pseudo three-dimensional features of kink bands formed by the compression deformation of a directionally solidified Mg Zn Y 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. 85 6 9.
17. Kazuki TONOTSUKA, Yoshikazu TODAKA, Nozomu ADACHI, Motohiro HORII, Kenichi TODA, Masatoshi MITSUHARA, Masumi IWASAKI, Yoshinori SHIIHARA, Yoshitaka UMENO, Minoru NISHIDA, Hideharu NAKASHIMA, Effect of lattice defects on tribological behavior for high friction coefficient under TCP added PAO lubrication in nanostructured steels, ISIJ International, 10.2355/isijinternational.ISIJINT-2019-707, 60, 6, 1358-1365, 2020.06, The effect of lattice defects on the tribological behavior under tricresyl phosphate (TCP) added poly-α-olefin (PAO) lubrication was investigated in the nanostructured steels produced by heavy plastic deformation processes. In surface-nanostructured SUJ2-bearing steel, tribological behavior with high friction coefficient was observed in ball-on-disk tests when compared to non-deformed steel. In addition, a similar phenomenon was observed in ultra-low carbon (ULC) steel with a high density of lattice defects (grain boundary, dislocation and so on). By increasing the density of lattice defects, a higher friction coefficient was observed. The reason for the tribological behavior with high friction coefficient seems to be that the compound film of Fe-O-P system formed in the ball-on-disk test was worn down..
18. 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, 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..
19. 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, 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..
20. Kazuaki Okada, Koji Obayashi, Yoshikazu Todaka, Nozomu Adachi, Masatoshi Mitsuhara, Friction property under lubrication for case hardening steel subjected to combined thermomechanical treatment with excess vacuum carburizing and subsequent severe plastic deformation and induction hardening, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.TETSU-2019-082, 106, 4, 194-204, 2020.01, Friction property of the case hardening steel subjected to excess vacuum carburizing and subsequent severe plastic deformation and induction hardening was evaluated by the traction test. The purpose of this study is to clarify the effect of fine microstructure on the friction property, focusing on the interaction between the fine microstructure and the lubricating oil additives. The vacuum carburizing treatment is performed at the hyper-eutectoid composition of 1.0 mass% C. Subsequently, the carburized surface was formed the white layer by the surface-nanostructured wearing (SNW) process, and the specimen having the initial microstructure was subjected to induction hardening. The microstructure of the condition with SNW was finer compared to that with SNW-less. According to the traction test, traction coefficient (ì) in the specimen having the fine microstructure on the rolling contact surface decreased. Therefore, it was found that the decrease of ì could be achieved by the application of high-density lattice defects (grain boundaries in this study). After the test, the rolling contact surface of the specimen with fine microstructure became smooth, and the surface showed high reactivity with the lubricating oil additives and formed the compound film of Fe-O-P system having a fine, spherical morphology. The surface roughness was improved by the presence of the wear particles on the surface. Therefore, it was thought that the ì was decreased because the transition to a mild friction condition was caused due to the dispersion of the contact pressure..
21. Mitsuhiro Matsuda, Ryo Matsuoka, Minoru Nishida, Masatoshi Mitsuhara, Microstructural characterization of martensite with long period stacking order structure in Hf-Co-Pd alloy, Materials Transactions, 10.2320/matertrans.MT-MJ2019002, 61, 1, 27-32, 2020.01, Microstructural characterization of martensite with long period stacking order (LPSO) structure in a Hf-Co-Pd alloy was investigated by transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). LPSO structure with six stacking sequences; 6O (orthorhombic) (Space group: Immm), were newly discovered. Based on the electron diffraction experiments, the lattice parameters of LPSO phase were estimated to be a = 0.33 nm, b = 0.45nm and c = 1.53 nm. The formation mechanism of martensite with LPSO structure and the crystallographic orientation relationship between parent B2 phase and 6O martensite are also discussed..
22. 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, An indicator to predict the slip operation at the crystal-grain level, namely slip operation factor (SOF), was established as a function of the Schmid factor (SF) and critical resolved shear stress (CRSS). Plastically "soft" and "hard" regions were estimated by the Schmid factor values normalized by the CRSS - the normalized Schmid factor (NSF). The effect of the interaction among the regions was incorporated into SOF. A microstructural map of α-titanium (α-Ti) was obtained by the electron backscatter diffraction patterns. Several spatial distributions of SOF were calculated based on the map by changing the interaction range among the regions. The distributions were compared with those of the strains obtained by the crystal plasticity finite element (CPFE) analysis. Good agreement between the distributions was found near the macroscopic yield point when the interaction range was appropriate, although some significant differences between the distributions were also noticed after the yielding point. The prediction accuracy by SOF was higher than that by SF and NSF. The reasons for the high accuracy revealed by the SOF analysis and the differences between the distributions indicated by the CPFE analysis were also investigated..
23. 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, 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..
24. Kazuki Tonotsuka, Yoshikazu Todaka, Nozomu Adachi, Motohiro Horii, Kenichi Toda, Masatoshi Mitsuhara, Masumi Iwasaki, Yoshinori Shiihara, Yoshitaka Umeno, Minoru Nishida, Hideharu Nakashima, Effect of lattice defects on tribological behavior for high friction coefficient under TCP added PAO lubrication in nanostructured steels, Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan, 10.2355/tetsutohagane.TETSU-2018-043, 105, 2, 160-167, 2019.02, Synopsis: The effect of lattice defects on the tribological behavior for high friction coefficient under tricresyl phosphate (TCP) added poly-α-olefin (PAO) lubrication was investigated in the nanostructured steels produced by heavy plastic deformation processes. In the surface-nanostructured SUJ2 bearing steel, the tribological behavior with high friction coefficient was observed in the ball-on-disk tests in comparison with the non-deformed steel. In addition, the similar phenomenon was observed in the ultra-low carbon (ULC) steel with high-density of lattice defects (grain boundary, dislocation and so on). By increasing the density of lattice defects, higher friction coefficient was shown. The reason of the tribo-logical behavior with high friction coefficient seems that the compound film of Fe-O-P system formed in the ball-on-disk test was worn..
25. Long-period Stacking Ordered Structure of Martensite in Zr-Co Based Alloys.
26. Yoshiki Kawano, Tetsuya Ohashi, Tsuyoshi Mayama, Masatoshi Mitsuhara, Yelm Okuyama, Michihiro Sato, Crystal plasticity analysis of microscopic deformation mechanisms and GN dislocation accumulation depending on vanadium content in ¢ phase of two-phase Ti alloy, Materials Transactions, 10.2320/matertrans.M2019016, 60, 6, 959-968, 2019.01, Inhomogeneous deformation of a single ¡-¢ colony in a Ti6Al4V alloy under uniaxial tensile conditions was numerically simulated using a crystal plasticity finite element (CPFE) method, and we predicted density changes in geometrically necessary dislocations (GNDs) depending on the vanadium concentration in the ¢ phase (V¢). The geometric model for the CPFE analysis was obtained by converting data from electron back-scatter diffraction patterns into data for the geometric model for CPFE analysis, using a data conversion procedure previously developed by the authors. The results of the image-based crystal plasticity analysis indicated that smaller V¢ induced greater stress in the ¡ phase and smaller stress in the ¢ phase close to the ¡-¢ interfaces in the initial stages of deformation because of the elastically softer ¢ phase with lower V¢. This resulted in greater strain gradients and greater GND density close to the interfaces in the initial stages of deformation within the single ¡-¢ colony when the ¢ phase plastically does not deform..
27. Mitsuharu Yonemura, Masatoshi Mitsuhara, Damage mechanism of nickel-based creep-resistant alloys strengthened by the Laves phase at the grain boundary, Philosophical Magazine, 10.1080/14786435.2018.1524161, 98, 36, 3247-3266, 2018.12, This study proposes a design guideline for polycrystal Ni-based model alloys with high ductility and 100-MPa creep rupture strength beyond 800°C and 105h. These alloys are strengthened by both the precipitation of fine γ′ particles inside the grain and the Laves phase at the grain boundary. For investigating the damage mechanism, transformation from the non-equilibrium Laves phase to the σ phase at the grain boundary and formation of the equilibrium needle-like Laves phase inside the grain are promoted by increasing the Fe concentration. The rupture time of Fe-free alloys significantly increases because of the equilibrium Laves phase at the grain boundary owing to a suitable Mo equivalent. In particular, W addition can help achieve high-temperature creep strength. The precipitate-free zone (PFZ) is predominantly formed by prior migration at the grain boundary without precipitation. Creep rupture occurs at the precipitation/matrix interface in the PFZ. Therefore, transformation control from the Laves to the σ phase at the grain boundary suppresses creep degradation. Consequently, a Ni-based alloy with strength >100 MPa and rupture elongation >20% at 800°C and 105h is fabricated using Larson–Miller parameter conversion, and the alloy design guideline’s validity is confirmed..
28. K. Yamamoto, R. Noguchi, M. Mitsuhara, M. Nishida, T. Hara, D. Wang, H. Nakashima, Wide range control of Schottky barrier heights at metal/Ge interfaces with nitrogen-contained amorphous interlayers formed during ZrN sputter deposition, Semiconductor Science and Technology, 10.1088/1361-6641/aae4bd, 33, 11, 2018.10, A ZrN contact on a Ge substrate can alleviate the intrinsic Fermi-level pinning (FLP) position toward conduction band edge, which is induced by an amorphous interlayer (a-IL) containing nitrogen atoms at the interfaces. Since the a-IL could be retained on the Ge surface, we demonstrated a wide range Schottky barrier height (SBH) control for metal/a-IL/Ge contacts. The sputtering power for ZrN affects the SBH, pinning factor (S), and effective charge neutral level. A high S value of 0.26 was achieved, which is comparable to that of metal/Si contacts. A model was proposed for explaining the mechanism of this effective FLP alleviation..
29. Crystal plasticity analysis on microscopic deformation of Ti-6Al-4V alloy depending on the vanadium content in β phase.
30. Shigeto Yamasaki, Masatoshi Mitsuhara, Hideharu Nakashima, Development of High-Chromium Ferritic Heat-Resistant Steels with High Nitrogen Content, ISIJ International, 58, 6, 2018.06.
31. 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, 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 (B
) 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 WS
grains grown on the h-BN show photoluminescence stronger than that grown on a bare SiO
substrate. The PL line width of WS
/h-BN (the minimum and mean widths are 24 and 43 meV, respectively) is much narrower than those of WS
(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..
32. Chengwu wang, Syuhei kurokawa, Toshiro Doi, Julong Yuan, Masatoshi Mitsuhara, Weifeng Yao, Kehua Zhang, SEM, AFM and TEM Studies for Femtosecond Laser Irradiation Effect on 4H-SiC Substrate at Near Threshold Fluence, the ECS Journal of Solid State Science and Technology, 7, 2, 29-34, 2018.02.
33. Mitsuhiro Matsuda, Yoshimasa Shinagawa, Kazuki Takashima, Masatoshi Mitsuhara, Minoru Nishida, Characterization of Antiphase Boundary-Like Structure of B33 Martensite in ZrCoPd Alloy, Materials Transactions, 10.2320/matertrans.M2018146, 59, 10, 1567-1573, 2018.01, The antiphase boundary (APB)-like structure of B33 martensite in a ZrCoPd alloy was investigated by means of conventional transmission electron microscopy and high-Angle annular dark-field scanning transmission electron microscopy. The APB-like structure had atomic shifts along both the c-Axis on the (010)B33 basal plane and the b-Axis on the (001) B33 plane. The displacement vector of the APB-like structure could be expressed as R = (0, 1/4, =)B33 The formation mechanism of the APB-like structure was also elucidated..
34. 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, New ferritic heat-resistant steels with high nitrogen content were prototyped and their microstructures and mechanical properties at high temperature were evaluated. The addition of 0.3 mass% N into ferritic steels was achieved without the formation of blowholes by applying pressurized melting methods under an atmosphere of up to 4.0 MPa. The high-nitrogen ferritic heat-resistant steels contained several kinds of nitrides within the lath martensitic structure. V-rich coarse particles were identified as crystallized MN. Fine VN or Cr
N particles were precipitated on the martensitic grain boundaries such as prior-austenite grain boundary, packet boundary, block boundary and lath boundary depending on the V content. The martensitic structure of the high-nitrogen steels contained a hierarchical microstructure including martensitic laths, blocks, packets, and prior-austenitic grains. These martensitic structures satisfied the Kurdjumov–Sachs relationship as with conventional carbon steel. The creep strengths of the prototyped steels were comparable with those of Gr. 91 steel, albeit lower than those of Gr. 92. Additional precipitates other than nitrides are required for further strengthening of the developed steels..
35. Chengwu Wang, Syuhei Kurokawa, Toshiro Doi, Julong Yuan, Li Fan, Masatoshi Mitsuhara, Huizong Lu, Weifeng Yao, Yu Zhang, Kehua Zhang, SEM, AFM and TEM studies for repeated irradiation effect of femtosecond laser on 4H-SiC surface morphology at near threshold fluence, ECS Journal of Solid State Science and Technology, 10.1149/2.0421712jss, 7, 2, P29-P34, 2018.01, In order to investigate the interaction of femtosecond (fs) laser and hard-to-process semiconductor material 4H-SiC at near-threshold fluence, fs laser was repeatedly irradiated to SiC surface at different scanning velocities and scan times. The evolutions of surface morphologies were observed and discussed according to Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM) and Transmission Electron Microscope (TEM). Discontinuous zones were ablated in SiC surface after laser irradiation at near-threshold fluence 1.1 J/cm2. High spatial frequency rippled structures substantially shorter than the wavelength of incident fs laser were fabricated. The width of the ablated zones increased with lower scanning velocities and more scan times. The mechanism was discussed. Incubation effect occurred in the subsurface of SiC triggered inhomogeneous energy deposition accumulation, which was responsible for the discontinuous ablated zones. Moreover, an amorphous layer with a thickness of about 30 nm was observed in 4H-SiC surface where no ablation was induced after repeated irradiation. This was discussed and explained from the aspects of molecular dynamics simulations of fs laser irradiation to semiconductor materials..
36. Rolling Contact Fatigue Behavior in Surface Nanostructured Steels.
37. 213 The function of β-phase within a lamellar microstructure deforming in Ti-6Al-4V alloy.
38. 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, 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..
39. 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, 2017.05, Creep strain in SUS347HTB austenitic heat-resistant steel and Ni-based heat-resistant alloys was evaluated by electron backscattered diffraction (EBSD). Localized crystallographic misorientations in the crept samples were quantified by using misorientation indicators such as kernel average misorientation and grain reference orientation deviation. In most crept samples, the misorientation indicators increased with creep deformation. However, this trend was not observed for alloys with dense dispersions. We proposed a method to extract and evaluate data only near the grain boundary from the total EBSD data. For Ni-based alloys, the misorientation indicators tended to increase preferentially near grain boundaries. Conversely, there was no substantial difference between the misorientation indicators near grain boundaries and the intergranular region for SUS347HTB. Consequently, although it is necessary to limit the region for evaluating the misorientation indicators according to the dispersion density of the reinforcing phase in the materials, the misorientation indicators, such as kernel average misorientation or grain reference orientation deviation, are useful for evaluating the creep strain in face-centred cubic heat-resistant alloys..
40. 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, 2017.03, The causes of the change in creep rupture ductility with the creep test temperature in Alloy 617 were investigated. The rupture ductility in the creep test was low at 700°C, whereas it was high at 800°C. Although the rupture ductility depended on the creep test temperature, creep fracture occurred due to cavity formation at the grain boundaries under all the creep conditions. In the sample crept at 800°C, subgrains developed with creep deformation. However, the crept sample at 700°C fractured before the subgrain formation. Although the work hardening due to the creep deformation occurred at 700°C, the work hardening in the sample crept at 800°C was small. The deformation of the grains was suppressed by the work hardening and by γ particle dispersion strengthening at 700°C. The difference in the strength in the crystal grains that resulted from the microstructure formed during creep caused the difference in the growth of the cavities..
41. Joshua A. Stuckner, Guo Quan Lu, Masatoshi Mitsuhara, William T. Reynolds, Mitsuhiro Murayama, The Influence of Processing Conditions on the 3-D Interconnected Structure of Nanosilver Paste, IEEE Transactions on Electron Devices, 10.1109/TED.2016.2639363, 64, 2, 494-499, 2017.02, Nanosilver paste is a promising material for power device interconnects. Interconnects are fabricated from nanosilver paste through a sintering process that drives off solvents and dispersants and fuses the silver particles. The integrity of the resulting interconnect is affected by the silver microstructure. This paper explored how sintering temperature, atmosphere, and time influenced microstructure as revealed by transmission electron microscopy and 3-D imaging via dual-beam serial sectioning. Nanosilver paste was sintered in combinations of the following parameters: A sintering atmosphere of air or nitrogen; temperatures of 120 °C or 255 °C; and sintering times of 5, 10, or 30 min. For the 255 °C temperature, oxygen in air facilitated removal of organic solvent and dispersant molecules and led to a microstructure with a coarser ligament network than samples sintered at the same temperature and times in nitrogen. The coarser ligament network was characterized by thick connected ligaments, large connected pores, and few isolated pores; this microstructure has been correlatedwith improved mechanical strength. Details of both 2-D and 3-D ligament network morphology, grain morphology, grain size, and the associated grain boundaries are discussed..
42. Masaru Itakura, Shin ichi Murayama, Masatoshi Mitsuhara, Minoru Nishida, Hiroaki Koga, Masaki Nakano, Hirotoshi Fukunaga, Microstructures of Ta-inserted SmCo5/Fe nanocomposite thick film magnets, Materials Transactions, 10.2320/matertrans.M2017035, 58, 10, 1351-1355, 2017.01, Ta-inserted SmCo5/Fe nanocomposite thick film magnets were synthesized by high-speed pulsed laser deposition followed by pulse annealing. The microstructures of the film magnets were characterized by high-resolution scanning electron microscopy and scanning transmission electron microscopy. The as-deposited thick film possessed a multilayered Sm-Co/Ta/α-Fe/Ta structure with amorphous Sm-Co layers and [110]-oriented crystalline α-Fe layers. After pulse annealing, many fine grains of Laves phase TaCo2 were formed, and then the multilayered structure was converted to a granular nanocomposite thick film magnet composed of fine crystalline grains of Sm(Co, Fe)5, α-(Fe, Co), and TaCo2. The volume fractions and grain sizes of hard magnetic Sm(Co, Fe)5, soft magnetic α-(Fe, Co), and TaCo2 were controlled by the thicknesses of the Ta layer, producing a nanocomposite thick film magnet with good exchange coupling..
43. Fumiya Watanabe, Zeid A. Nima, Takumi Honda, Masatoshi Mitsuhara, Minoru Nishida, Alexandru S. Biris, X-ray photoelectron spectroscopy and transmission electron microscopy analysis of silver-coated gold nanorods designed for bionanotechnology applications, Nanotechnology, 10.1088/1361-6528/28/2/025704, 28, 2, 2017.01, Multicomponent nano-agents were designed and built via a core-shell approach to enhance their surface enhanced Raman scattering (SERS) signals. These nano-agents had 36 nm �12 nm gold nanorod cores coated by 4 nm thick silver shell films and a subsequent thin bifunctional thiolated polyethylene glycol (HS-PEG-COOH) layer. Ambient time-lapsed SERS signal measurements of these functionalized nanorods taken over a two-week period indicated no signal degradation, suggesting that large portions of the silver shells remained in pure metallic form. The morphology of the nanorods was characterized by transmission electron microscopy (TEM) and ultra-high resolution scanning TEM. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were utilized to assess the oxidation states of the silver shells covered by HS-PEG-COOH. The binding energies of Ag 3d XPS spectra yielded very small chemical shifts with oxidation; however, the AES peak shapes gave meaningful information about the extent of oxidation undergone by the nano-agent. While the silver shells without HS-PEG-COOH coatings oxidized significantly, the silver shells with HS-PEG-COOH remained predominantly metallic. In fact, six month-old samples still retained mostly metallic silver shells. These findings further demonstrate the stability and longevity of the nanostructures, indicating their significant potential as plasmonically active agents for highly sensitive detection in various biological systems, including cancer cells, tissues, or even organisms..
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, Creep behaviors and microstructures for two Ni-based heat-resistant alloys with different carbon contents were investigated. The chemical compositions of the alloys were Ni-20Cr-15Co-6Mo-1Ti-2Al-2Nb-0.004 and 0.021C (mass%). The 0.004C and 0.021C alloys are referred to as the low-and high-C alloys, respectively. After solid-solution treatment at 1373 K for 1 h and isothermal annealing at 1023 K for 32 h, fine Ni3Al (γ) particles were formed in the grain interior of both alloys. The average diameter and number density of γ particles were similar in both alloys. M23C6 carbides were formed on grain boundaries after the isothermal annealing. Coverage ratios with the carbides in the high-C alloy were higher than that in the low-C alloys. Creep tests were performed at 1123 K and 130 MPa. The rupture time for the high-C alloy was longer than that for the low-C alloy, though both minimum creep rates were similar. In the high-C alloy, the creep strain was stored uniformly in the grain interior and the formation of a precipitate-free zone during the creep deformation was suppressed. Therefore, intergranular carbides with a high coverage ratio decreased the creep rate in the acceleration region..
45. L. Morsdorf, O. Jeannin, D. Barbier, Masatoshi Mitsuhara, D. Raabe, C. C. Tasan, Multiple mechanisms of lath martensite plasticity, Acta Materialia, 10.1016/j.actamat.2016.09.006, 121, 202-214, 2016.12, The multi-scale complexity of lath martensitic microstructures requires scale-bridging analyses to better understand the deformation mechanisms activated therein. In this study, plasticity in lath martensite is investigated by multi-field mapping of deformation-induced microstructure, topography, and strain evolution at different spatial resolution vs. field-of-view combinations. These investigations reveal site-specific initiation of dislocation activity within laths, as well as significant plastic accommodation in the vicinity of high angle block and packet boundaries. The observation of interface plasticity raises several questions regarding the role of thin inter-lath austenite films. Thus, accompanying transmission electron microscopy and synchrotron x-ray diffraction experiments are carried out to investigate the stability of these films to mechanical loading, and to discuss alternative boundary sliding mechanisms to explain the observed interface strain localization..
46. EBSD‐FEMデータ変換インターフェースの構築とTi‐6Al‐4V合金の結晶塑性解析への適用.
47. Jesbains Kaur, Noriyuki Kuwano, Khairur Rijal Jamaludin, Masatoshi Mitsuhara, Hikaru Saito, Satoshi Hata, Shuhei Suzuki, Hideto Miyake, Kazumasa Hiramatsu, Hiroyuki Fukuyama, Electron microscopy analysis of microstructure of postannealed aluminum nitride template, Applied Physics Express, 10.7567/APEX.9.065502, 9, 6, 2016.06, The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200nm thickness on a sapphire (0001) substrate by metal-organic vapor phase epitaxy. The AlN template was annealed under (N2 + CO) atmosphere at 1500-1650 °C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure..
48. K. Jesbains, N. Kuwano, K. R. Jamaludin, H. Miyake, K. Hiramatsu, S. Suzuki, Masatoshi Mitsuhara, Satoshi Hata, Y. Soejima, Reduction of dislocation density of aluminium nitride buffer layer grown on sapphire substrate, Journal of Mechanical Engineering and Sciences, 10.15282/jmes.10.1.2016.14.0182, 10, 1, 1908-1916, 2016.06, An aluminium nitride (AlN) buffer layer with 200 nm thickness was grown on (0001) sapphire substrate using the metal-organic vapour phase epitaxy (MOVPE) method in a low-pressure furnace, followed by a clean-up treatment of sapphire substrate at 1100°C. Thereafter, the AlN buffer layer was annealed at a high temperature in the range of 1500°C to 1700°C for 2 hours under the atmosphere of N2+CO. The objective of this research is to determine the microstructure changes with different annealing temperatures. Cross-sectional TEM has revealed that, after annealing at 1500°C, two types of defects remained in the AlN buffer layer: inverted cone shape domains and threading dislocations. The former domains were observed in an image taken with diffraction of g=0002, but not in an image with g=1010. The morphology and the diffraction condition for the image contrast strongly, suggesting that the domains are inversion domains. The threading dislocations were invisible in the image taken with the diffraction of g=0002, revealing that they were a-Type dislocations. However, after annealing at 1600oC, the inversion domains coalesced with each other to give a two-layer structure divided by a single inversion domain boundary at the centre of the AlN buffer layer. The density of threading dislocation was roughly estimated to be 5×109 cm-2 after annealing at 1500°C, and to be reduced to 5×108 cm-2 after annealing at 1600°C. These experimental results validate the fact that the annealing temperature around 1600°C is high enough to remove the defects by the diffusion process. Therefore, it was discovered that high temperature annealing is an effective treatment to alter the microstructure of AlN thin films and remove defects by the diffusion process. Annealing at high temperature is recommended to increase the emission efficiency for fabrication of optoelectronic devices..
49. M. Mitsuhara, T. Masuda, M. Nishida, T. Kunieda, H. Fujii, Precipitation Behavior During Aging in alpha Phase Titanium Supersaturated with Cu, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 10.1007/s11661-016-3344-7, 47A, 4, 1544-1553, 2016.04.
50. M. Matsuda, M. Mitsuhara, K. Takashima, M. Nishida, Antiphase Boundary-Like Structure of B19 Martensite in Ti-Ni-Pd Shape Memory Alloy, MATERIALS TRANSACTIONS, 10.2320/matertrans.MB201505, 57, 3, 250-256, 2016.03.
51. M. Mitsuhara, S. Yamasaki, M. Miake, Hideharu Nakashima, M. Nishida, J. Kusumoto, A. 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.
52. Y. Soejima, S. Motomura, M. Mitsuhara, T. Inamura, M. Nishida, In situ scanning electron microscopy study of the thermoelastic martensitic transformation in Ti-Ni shape memory alloy, ACTA MATERIALIA, 10.1016/j.actamat.2015.10.017, 103, 352-360, 2016.01.
53. Hiroshi Akamine, Masatoshi Mitsuhara, Minoru Nishida, Developments of coal-fired power plants
Microscopy study of Fe-Ni based heat-resistant alloy for efficiency improvement, Evergreen, 3, 2, 45-53, 2016.01, Anthropogenic emissions of greenhouse gases are one of the possible reasons for the global warming. Coal consumption is predicted to be increased over several decades due to increasing demands in some countries. In the medium-term energy strategy, coal-fired power plants thus need to be developed. For this purpose, developments of new heat-resistant alloys that can stand severe steam conditions in advanced power plants are essential. A potential alloy was studied, which revealed that hardness of the alloy is related to the distribution of precipitates. The development of the alloy is also vital to make the power plants more economically competitive..
54. Dmitry Tyutyunnikov, Masatoshi Mitsuhara, Christoph T. Koch, Two-dimensional misorientation mapping by rocking dark-field transmission electron microscopy, Ultramicroscopy, 10.1016/j.ultramic.2015.07.003, 159, P1, 26-33, 2015.12, In this paper we introduce an approach for precise orientation mapping of crystalline specimens by means of transmission electron microscopy. We show that local orientation values can be reconstructed from experimental dark-field image data acquired at different specimen tilts and multiple Bragg reflections. By using the suggested method it is also possible to determine the orientation of the tilt axis with respect to the image or diffraction pattern. The method has been implemented to automatically acquire the necessary data and then map crystal orientation for a given region of interest. We have applied this technique to a specimen prepared from a Ni-based super-alloy CMSX-4. The functionality and limitations of our method are discussed and compared to those of other techniques available..
55. 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.
56. Three-Dimensional Observation of Lattice Defects Using Electron Tomography
Three-dimensionalization, i.e., direct representation or fabrication of three-dimensional (3D) objects, is now a key technology in various science and engineering fields. Electron microscopy, a vital nanoscale characterization tool, is no exception, thus various imaging methods have been developed to extend its imaging capabilities from conventional two dimensions to three dimensions. In this article, we focus on electron tomography (ET), which is a typical 3D imaging method using transmission electron microscopy (TEM) or scanning transmission electron microscopy(STEM), and overview the current status and future prospects of ET and an application of ET to 3D imaging of dislocations in crystalline materials as an practical example..
57. Y. Miyajima, S. Komatsu, M. Mitsuhara, S. Hata, Hideharu Nakashima, N. Tsuji, Microstructural change due to isochronal annealing in severely plastic-deformed commercial purity aluminium, PHILOSOPHICAL MAGAZINE, 10.1080/14786435.2015.1021400, 95, 11, 1139-1149, 2015.04.
58. M. Matsuda, F. Tanaka, S. Tsurekawa, K. Takashima, M. Mitsuhara, M. Nishida, Novel long-period stacking-ordered structure of martensite in zirconium-cobalt-palladium alloys, PHILOSOPHICAL MAGAZINE LETTERS, 10.1080/09500839.2014.995739, 95, 1, 21-29, 2015.01.
59. M. Matsuda, S. Nishimura, S. Tsurekawa, K. Takashima, Masatoshi Mitsuhara, Minoru Nishida, Crystallography and morphology of antiphase boundary-like structure induced by martensitic transformation in Ti-Pd-Fe alloy, Journal of Alloys and Compounds, 10.1016/j.jallcom.2014.08.258, 618, 527-532, 2015.01, The antiphase boundary (APB)-like structure of both 9R and B19 martensites in the Ti-Pd-Fe alloy was investigated by means of transmission electron microscopy. Some APB-like structures with curved and wide contrasts along the (0 0 1)9Rbasal plane are observed in 9R martensitic plates. The atomic displacement on the APB-like structure reflects the atomic movement stemming from the microdomains formed as a pre-martensitic transformation. The displacement vector of the APB-like structure in the B19 martensite can be expressed as R = 〈1/3 0 -1/2〉B19. The density of APB-like contrasts increases by the substitution of Fe for Pd in Ti-Pd-Fe alloy..
60. N. Kuwano, Y. Ryu, M. Mitsuhara, C.H. Lin, S. Uchiyama, T. Maruyama, Y. Suzuki, S. Naritsuka, Behavior of defects in a-plane GaN films grown by low-angle-incidence microchannel epitaxy (LAIMCE), Journal of Crystal Growth, Vol.401, 409-413, 2014.07.
61. 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, Vol.55, pp.842-849, 2014.05.
62. Keisuke Yamamoto, Masatoshi Mitsuhara, Keisuke Hiidome, Ryutaro Noguchi, Minoru Nishida, Dong Wang, and Hiroshi Nakashima, Role of an interlayer at a TiN/Ge contact to alleviate the intrinsic Fermi-level pinning position toward the conduction band edge, Applied Physics Letters, Vol.104, pp.132109-1-4, 2014.03.
63. M. Matsuda, R. Yamashita, S. Tsurekawa, K. Takashima, M. Mitsuhara, M. Nishida, Antiphase boundary-like structure of B19′ martensite via R-phase transformation in Ti–Ni–Fe alloy, Journal of Alloys and Compounds, Vol.586, pp.87-93, 2014.02.
64. B. Karbakhsh Ravari, M. Mitsuhara, S. Farjami, M. Nishida , Effect of thermal cycling on multistage martensitic transformation in aged Ti- 50.8 at.% Ni alloy , Materials Transactions, Vol.54, pp.2185-2188, 2013.12.
65. E. Okunishi, T. Kawai, M. Mitsuhara, S. Farjami, M. Itakura, M. Nishida, HAADF-STEM studies of athermal and isothermal ω-phase in β-Zr alloy, Journal of Alloys and Compounds, Vol.577S, pp.S713-S716, 2013.11.
66. H. Akamine, S. Farjami, M. Mitsuhara, M. Nishida, T. Fukuda and T. Kakeshita , Electron Microscopy Study of Preferential Variant Selection in CoPt Alloy Ordered under a Magnetic Field, MATERIALS TRANSACTIONS , Vol.54, pp.1715-1718, 2013.08.
67. Tomonori Tokunaga, Hideo Watanabe, Naoaki Yoshida, Takuya Nagasaka, Ryuta Kasada, Young-Ju Lee, Akihiko Kimura, Masayuki Tokitani, Masatoshi Mitsuhara, Tatsuya Hinoki, Hideharu Nakashima, Suguru Masuzaki, Takeshi Takabatake, Nobuyoshi Kuroki, Koichiro Ezato, Satoshi Suzuki, Masato Akiba, Development of high-grade VPS-tungsten coatings on F82H reduced activation steel, Journal of Nuclear Materials, Vol.442, pp.S287-S291, 2013.01.
68. R. Miyagawa, S. Yang, H. Miyake, K. Hiramatsu, T. Kuwahara, M. Mitsuhara, N. Kuwano, Microstructure of AlN grown on a nucleation layer on a sapphire substrate, Applied Physics Express, Vol.5, p.025501, 2012.01.
69. Jung Ho Kim, Sangjun Oh, Yoon-Uk Heo, Satoshi Hata, Hiroaki Kumakura, Akiyoshi Matsumoto, Masatoshi Mitsuhara, Seyong Choi, Yusuke Shimada, Minoru Maeda, Judith L MacManus-Driscoll, Shi Xue Dou, Microscopic role of carbon on MgB2 wire for critical current density comparable to NbTi, NPG Asia Materials, Vol.4, p.e3, 2012.01.
70. H. Idrissi, S. Turner, M. Mitsuhara, B. Wang, S. Hata , M. Coulombier, JP. Raskin, T. Pardoen, G. Van Tendeloo, D. Schryvers, Point defect clusters and dislocations in FIB irradiated nanocrystalline aluminium films: an electron tomography and aberration-corrected high resolution ADF-STEM study, Microscopy and Microanalysis, Vol.17, pp.983-990, 2011.11.
71. 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、皆籐威二, 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, Vol.31, pp.98-103, 2011.07.
72. S. Hata, H. Miyazaki, S. Miyazaki, M. Mitsuhara, M. Tanaka, K. Kaneko, K. Higashida, K. Ikeda, H. Nakashima, S. Matsumura, J. S. Barnard, J. H. Sharp, P. A. Midgley, High-angle triple-axis specimen holder for three-dimensional diffraction contrast imaging in transmission electron microscopy, Ultramicroscopy, Vol.111, pp.1168-1175, 2011.03.
73. U. D. Kulkarni, S. Hata, T. Nakano, M. Mitsuhara, K. Ikeda, H. Nakashima, Monte Carlo simulation of antiphase boundaries and growth of antiphase domains in Al5Ti3 phase in Al-rich gamma-TiAl intermetallics, Philosophical Magazine, Vol.91, pp.3068-3078, 2011.02.
74. U. D. Kulkarni, S. Hata, M. Mitsuhara, K. Ikeda, Ordering transformations in Ni75Mo15Mn10 alloy, Transactions of The Indian Institute of Metals, Vol.63, pp.819-822, 2010.10.
75. Y. Miyajima, S. Komatsu, M. Mitsuhara, S. Hata, H, Nakashima, N. Tsuji, Change in electrical resistivity of commercial purity aluminium severely plastic deformed, Philosophical Magazine, Vol.90, pp.4475-4488, 2010.09.
76. Y. Miyajima, S. Komatsu, M. Mitsuhara, S. Hata, H, Nakashima, N. Tsuji, Quantification of Internal Dislocation Density Using Scanning Transmission Electron Microscopy
in Ultrafine Grained Pure Aluminum Fabricated by Severe Plastic Deformation, Materials Science and Engineering A, Vol.528, pp.776-779, 2010.09.
77. M. Mitsuhara, S. Hata, K. Ikeda, H. Nakashima, M. Tanaka, K. Higashida, Three-dimensional evaluation of dislocation arrangement
using electron tomography in austenitic steel, Proceedings of the 31st Ris? International Symposium on Materials Science, pp.353-360, 2010.08.
78. H. Matsuo, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, Electron microscopy analysis for crack propagation behavior of alumina, International Journal of Fatigue, 10.1016/j.ijfatigue.2009.06.006, 32, 3, 592-598, 2010.03, In order to clarify crack propagation behavior of alumina (α-Al O ), intergranular and transgranular fractures of alumina were investigated by electron microscopy techniques. For the intergranular fractures cracked grain boundaries were investigated by scanning electron microscopic electron back-scattered diffraction (SEM-EBSD) analysis. It was revealed that the intergranular fracture behavior of polycrystalline alumina with random distribution of crystallographic orientations is independent on grain boundary characters. For the transgranular fractures, fracture surfaces formed in a single-crystalline alumina were observed by electron tomography combined with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high resolution TEM (HR-TEM). Three kinds of fracture surfaces were observed: even fracture surfaces, even fracture surfaces with step-terraces and fracture surfaces composed of the even fracture surface and the curved one. The even fracture surfaces mostly consist of cleavage planes parallel to {1 over(1, ̄) 0 2} and {1 over(1, ̄) 0 4}. On the other hand, the even fracture surfaces with step-terraces consist of the cleavage planes and basal planes (0 0 0 1). For the fracture surfaces composed of the even fracture surface and the curved one, both the even and curved shapes the even parts were formed by the fine cleavage planes and basal planes, whose intervals were inhomogeneous. It was indicated that the fracture surfaces in alumina are composed of the cleavage planes or basal plane at an atomic scale. © 2009 Elsevier Ltd. All rights reserved. 2 3.
79. H. Matsuo, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, Optimal imaging conditions for dislocation tomography using scanning transmission electron microscopy, International Journal of Fatigue, Vol.32, pp.592-598, 2010.01.
80. S. Sadamatsu, M. Tanaka, K. Higashida, K. Kaneko, M. Mitsuhara, S. Hata, M. Honda, Crack tip dislocations observed by combining scanning trasmission electron microscopy and computed tomography, Advanced Materials Research, Vol.89-91, pp.473-478, 2010.01.
81. Y. Yahiro, M. Mitsuhara, K Tokunaga, N. Yoshida, T. Hirai, K, Ezato, S. Suzuki, M .Akiba, H. Nakashima, Characterization of thick plasma spray tungsten coating on ferritic/martensitic steel F82H for high heat flux armor, Journal of Nuclear Materials, Vol.386-388, pp.784-788, 2009.01.
82. K. Yamada, M. Mitsuhara, S. Hata, Y. Miyanaga, R. Teranishi, N. Mori, M. Mukaida, K. Kaneko, Three-dimensional observation of microstructures in Y123 films fabricated by TFA-MOD method, Physica C, Vol.469, pp.1446-1449, 2009.01.
83. M. Tanaka, M. Honda, M. Mitsuhara, S. Hata, K. Kaneko, K. Higashida, Three-dimensional analyses of crack tip dislocations observed by electron tomography, Korean Journal of Microscopy, Korean Journal of Microscopy, Vol.38 Supplement, pp.221-222, 2008.11.
84. M. Mitsuhara, M. Tanaka, K. Ikeda, S. Hata, H. Nakashima, Three-dimensional imaging of dislocations in steel using STEM tomography, Korean Journal of Microscopy, Vol.38 Supplement, pp.223-224, 2008.11.
85. T. Isobe, M. Mitsuhara, K. Ikeda, S. Hata, H. Nakashima, Y. Todaka, M. Umemoto, Electron Microscopy Observation of Pure Copper Deformed by High Pressure Torsion, Proc. International Symposium on Giant Straining Process for Advanced Materials (GSAM-2008), pp.83-84, 2008.11.
86. Masaki Tanaka, Masaki Honda, Masatoshi Mitsuhara, Satoshi Hata, Kenji Kaneko, Kenji Higashida, Three-Dimensional Observation of Dislocations by Electron Tomography in a Silicon Crystal (vol 49, pg 1953, 2008), MATERIALS TRANSACTIONS, 10.2320/matertrans.E2008002, 49, 11, 2753-2753, 2008.11.
87. M. Tanaka, M. Honda, M. Mitsuhara, S. Hata, K. Kaneko, K. Higashida, Three-dimensional observation of dislocations by electron tomography in a silicon crystal, Materials Transactions, Vol.49, pp.1953-1956, 2008.08.
88. M. Tanaka, K. Higashida, K. Kaneko, S. Hata, M. Mitsuhara, Crack tip dislocations revealed by electron tomography in silicon single crystal, Scripta Materialia, Vol.59, pp.901-904, 2008.07.
89. M. Mitsuhara, Y. Yoshida, K. Ikeda, H. Nakashima and T. Wakai, Effects of Addition of V and Nb on Ω in High Cr Ferritic Steels, Materials Science Forum, Vol.561-565, pp.95-98, 2007.11.
90. M. Mitsuhara, Y. Yoshida, K. Ikeda, H. Nakashima and T. Wakai, Mechanism of Creep Strengthening in High Cr Ferritic Heat Resistant Steel added V and Nb, Proc. the 1st International Symposium on Steel Science (IS3-2007), pp.227-230, 2007.05.
91. M. Mitsuhara, Y. Yoshida, K. Ikeda, H. Nakashima and T. Wakai, Effect of Vanadium and Niobium on Creep Strength in 10% Chromium Steel Analyzed by STEM-EDS, Proc. CREEP8, Eighth International Conference on Creep and Fatigue at Elevated Temperatures, CREEP 2007-26746, pp.1-5, 2007.05.
92. Material property of tungsten coated reduced-activation ferritic/martensitic steel.
93. M. Mitsuhara, D. Terada and H. Nakashima, Life Assessment of Heat Resistant Steels using the Omega Method, Proc. FAILURES 2006, pp.287-297, 2006.02.
94. 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.