研究者詳細 - 髙田　尚記

論文 - 髙田　尚記

分割表示 >> ／全件表示 198 件中 1 - 198 件目

Elucidating dominant flow channel size for capillary performance of open-cell porous wicks 査読有り国際誌

Shen H., Suzuki A., Takata N., Kobashi M.

International Journal of Heat and Mass Transfer 223 巻 2024年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of Heat and Mass Transfer

The capillary pressure (ΔPcap) and permeability (K) of porous wicks, both of which depend on the size of the flow channel, are crucial for the performance of heat transfer devices including loop heat pipes. However, the flow channel in actual porous wicks shrinks at the connective part between adjacent pores called the throat and does not have a constant size. The dominant flow channel size (average size or throat size) for ΔPcap and K remains unclear. To elucidate the dominant flow channel size, porous aluminum with constant pore size and various throat sizes was controllably fabricated by the space holder method using sodium chloride (NaCl) particles. Two types of pore size (simple pore size reflecting the space holder size and connectivity-reflected pore size) were characterized by X-ray computed tomography. The ΔPcap and K were evaluated by capillary rise tests using water. The average simple pore size was almost constant, but the average connectivity-reflected pore size changed depending on the porosity controlled by the amount of the NaCl space holder because the throat was enlarged, and the connectivity was improved by increasing porosity. It was clarified that ΔPcap changed depending on the average connectivity-reflected pore size regardless of the constant simple pore size. In contrast, K was determined by neither the simple nor connectivity-reflected pore sizes and could be dominated by local size around the throat. These results provide an insight into the design of optimal porous structure appropriate for porous wicks applied to heat transfer applications.

DOI： 10.1016/j.ijheatmasstransfer.2024.125217

Scopus

Four-dimensional electrochemical impedance spectroscopy: Role of microstructure on corrosion behaviour of Al-Si alloys additive-manufactured by laser powder bed fusion 査読有り国際誌

Hoshi Y., Miyazawa R., Otani Y., Kim D., Takata N., Kobashi M.

Corrosion Science 232 巻 2024年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Corrosion Science

Four-dimensional (4D) electrochemical impedance spectroscopy was applied to clarify the role of microstructures on the corrosion behaviour of Al-Si alloys additively manufactured by laser powder bed fusion in the immersion of NaCl solution. 3D complex impedance plots, comprising real, imaginary, and time axes, indicate that the impedance increases gradually at initial stage and then does not show apparent time variation. These behaviours, following surface morphology analysis, are strongly related to the remaining fine silicon particles on the surface due to the preferential Al dissolution, which suppress the further dissolution from underlying along with the protective oxide film formation.

DOI： 10.1016/j.corsci.2024.112018

Scopus

Effect of Cr content on thermally activated deformation in single-crystal micropillars of Fe–Cr binary alloys 査読有り国際共著国際誌

Zhu T., Takata N., Kim D., Kobashi M., Yoshino M., Tsukamura M.

Materials Science and Engineering: A 900 巻 2024年5月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

This study identifies the role of solute Cr in the thermal activation process in the plastic deformation of α-(Fe, Cr) ferrite (BCC solid solutions) using micropillar compression tests for micron-sized single-crystals fabricated on various Fe–Cr binary alloys that were solution-treated at 1573 K. Fe–18%Cr single-crystal micropillars with a mean diameter d of ∼2 μm exhibited a relatively higher strain rate sensitivity (m) of 0.12 for the stress required for slip initiation. Larger Fe–18%Cr micropillars (d = 5 μm) exhibited a lower m value of 0.04. The corresponding activation volume of 50 b3 was equivalent to the millimeter-sized pure Fe and Fe–18%Cr alloy specimens (60–70 b3), indicating the prevalence of a general mechanism involving dislocation motion (kink-pair nucleation of screw dislocations). This mechanism controls the thermal activation process of plastic deformation in the Fe–18%Cr alloy, which has sufficient sources for dislocation multiplication. In the Fe–25%Cr and Fe–40%Cr single crystal micropillars, a less pronounced size-dependent m value (0.01–0.03) was determined, almost independent of specimen size. The corresponding activation volumes of large micropillars (74–77 b3) were similar to those of millimeter-sized specimens, which indicates a mild effect of solute Cr atoms on the thermal activation process of dislocation motion in Fe–Cr binary alloys at ambient temperature. Initial dislocations, rather than Cr content in Fe–Cr binary alloys, led to the low changes in size-dependent activation volume of Fe–Cr alloys with higher Cr content. Planar faults (Cr-enriched regions) were observed in Fe–40%Cr alloys, which may become sufficient sources for dislocation nucleation. However, the influence of Cr-enriched regions on dislocation motion remains unclear.

DOI： 10.1016/j.msea.2024.146499

Scopus

Effect of low-temperature annealing on electric resistivity and mechanical anisotropy of Al-Si binary alloy fabricated by laser-powder bed fusion 査読有り国際誌

Konishi Y., Hamasaki Y., Sasaki T., Adachi H., Ishikawa K., Kim D., Takata N., Miyajima Y.

Journal of Alloys and Compounds 982 巻 2024年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Alloys and Compounds

Al-12mass%Si binary alloy was fabricated by laser-powder bed fusion (L-PBF). The effect of low temperature annealing (LTA) less than 573 K on electrical and mechanical properties, microstructure, and residual stress of L-PBF Al-12mass%Si was investigated. Due to LTA, electrical resistivity at 77 K and 293 K changed from 34 nΩm down to 10 nΩm and from 68 nΩm down to 45 nΩm, respectively. The lattice constant of α-Al phase increased around 0.0005 nm by LTA according to X-ray diffraction. The change was associated with the decrease in the concentration of solid-solution Si of around 3.4 mass% by electrical resistivity measurement and 3 mass% by X-ray diffraction, when the annealing temperature was 473 K. Whereas, Vickers hardness increases around 145 HV compared with that for the as-built value of 141 HV, and then, decreases down to 126 HV and saturates. TEM/EDS observations confirmed the precipitation of fine Si within the α-Al phase. The decrease in annealing temperature increases the time to reach the Vickers hardness peak. 0.2% proof stress obtained by compression tests shows anisotropy, which can be attributed to the anisotropy on residual stress, which still exists after LTA.

DOI： 10.1016/j.jallcom.2024.173737

Scopus

Microstructural origins of high strength of Al–Si alloy manufactured by laser powder bed fusion: In-situ synchrotron radiation X-ray diffraction approach 査読有り国際誌

Takata N., Liu M., Hirata M., Suzuki A., Kobashi M., Kato M., Adachi H.

Journal of Materials Science and Technology 178 巻頁： 80 - 89 2024年4月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science and Technology

The microstructural factors contributing to the high strength of additive-manufactured Al–Si alloys using laser-beam powder bed fusion (PBF-LB) were identified by in-situ synchrotron X-ray diffraction in tensile deformation and transmission electron microscopy. PBF-LB and heat treatment were employed to manufacture Al–12%Si binary alloy specimens with different microstructures. At an early stage of deformation prior to macroscopic yielding, stress was dominantly partitioned into the α-Al matrix, rather than the Si phase in all specimens. Highly concentrated Si solute (∼3%) in the α-Al matrix promoted the dynamic precipitation of nanoscale Si phase during loading, thereby increasing the yield strength. After macroscopic yielding, the partitioned stress in the Si phase monotonically increased in the strain-hardening regime with an increase in the dislocation density in the α-Al matrix. At a later stage of strain hardening, the flow curves of the partitioned stress in the Si phase yielded stress relaxation owing to plastic deformation. Therefore, Si-phase particles localized along the cell walls in the cellular-solidified microstructure play a significant role in dislocation obstacles for strain hardening. Compared with the results of the heat-treated specimens with different microstructural factors, the dominant strengthening factors of PBF-LB manufactured Al–Si alloys were discussed.

DOI： 10.1016/j.jmst.2023.08.050

Scopus

CALPHAD-aided design of high-strength Al-Si-Mg alloys for sufficient laser powder bed fusion processability 査読有り国際誌

Otani Y., Saki K., Takata N., Suzuki A., Kobashi M., Kato M.

Journal of Alloys and Compounds 977 巻 2024年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Alloys and Compounds

This study proposes a design concept for an Al-Si-Mg ternary alloy to achieve both high strength and laser-based powder bed fusion (PBF-LB) processability using calculation of phase diagrams (CALPHAD). The thermodynamic calculations using the CALPHAD method evaluated the Al-10Si-4.5Mg (wt%) alloy composition for strengthening by both the Si and Mg2Si phases and high PBF processability by reducing the risk of hot tearing behind the small freezing range of 27 °C and crack susceptibility index (|dT/d(Fs1/2)|) of 77 °C. The PBF-LB Al-10Si-4.5Mg alloy sample (processed by laser power of 128 W and laser scanning velocity of 1000 mm/s) exhibited a fine three-phase microstructure and exceptional hardness of 199 HV. No hot tearing occurred, whereas many cracks preferentially propagated along the melt pool boundaries during the PBF-LB process. The severe lateral cracking resulted in a maximum relative density of 96 % in the Al-10Si-4.5Mg alloy samples. Preferential cracking could be responsible for the localization of the relatively coarse particles of the brittle Mg2Si phase in the cellular microstructures of the melt pool boundaries. Understanding the lateral cracking mechanism can provide new insights into alloy modification using the controlled solidification path to avoid a specific two-phase eutectic reaction (L→α-Al+Mg2Si) to improve the PBF processability. A modified alloy composition of Al-10Si-3Mg (wt%) was assessed using the CALPHAD approach. PBF-LB processing using the modified alloy powder alleviated cracking and improved the maximum relative density to 98 % for the PBF-LB manufactured samples. This result accentuated the validity of the design strategy for Al-Si-Mg ternary alloy utilizing the CALPHAD method.

DOI： 10.1016/j.jallcom.2024.173449

Scopus

Microstructural factors controlling crack resistance of Zn–Al–Mg alloy coatings prepared via hot-dip galvanizing process: Combined approach of in-situ SEM observation with digital image correlation analysis 査読有り国際誌

Kim D., Takata N., Yokoi H., Suzuki A., Kobashi M.

Journal of Materials Research and Technology 29 巻頁： 1535 - 1541 2024年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Research and Technology

To understand the microstructural factors controlling deformability during the forming process, a comprehensive analysis using in-situ scanning electron microscopy (SEM) with digital image correlation (DIC) for hot-dip Zn–6 %Al–3 %Mg alloy coatings on steel sheets in bending deformation was performed. The Zn–Al–Mg alloy coating exhibited two major microstructural constituents: the primary solidified Al (fcc) phase with dendritic morphologies and a fine ternary eutectic (TE) microstructure of the Zn (hcp), Al, and Zn2Mg phases. Major cracks were initiated on the tensile-strained coating surface, where the strain was localized in the TE regions, whereas the softer dendritic Al phases prevented the crack propagation. Microcracks were initiated in the binary eutectic (BE) Zn/Zn2Mg phases (Al-poor region) localized around the dendritic Al phases, whereas they were arrested in the TE region containing fine granular Al phases. The dendritic Al and fine granular Al phases embedded in the TE microstructure contributed to the high crack resistance.

DOI： 10.1016/j.jmrt.2024.01.235

Scopus

Laser-beam powder bed fusion of Al–Fe–Cu alloy to achieve high strength and thermal conductivity 査読有り国際誌

Cheng Y., Miyawaki T., Wang W., Takata N., Suzuki A., Kobashi M., Kato M.

Additive Manufacturing Letters 8 巻 2024年2月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Additive Manufacturing Letters

Laser-beam powder bed fusion (PBF-LB) technique was used to produce an Al–2.5 %Fe–2 %Cu ternary alloy, featuring a two-phase eutectic composition of α-Al/Al23CuFe4 in non-equilibrium solidification, as determined by thermodynamic calculations. The specimen manufactured by PBF-LB exhibited a high tensile strength exceeding 350 MPa and a low thermal conductivity of approximately 140 W m−1 K−1. Subsequent annealing at 300 °C improved the thermal conductivity to 175 W m−1 K−1 without compromising the strength. This improvement was attributable to forming numerous Al23CuFe4 nanoprecipitates, which consumed solute elements. By appropriately managing the factors contributing to strengthening, a superior strength–conductivity balance can be achieved by implementing post-heat treatments.

DOI： 10.1016/j.addlet.2023.100191

Scopus

Controlling the addition of solute Ti in Al-Mg-Zn-Cu-Ni alloy for enhanced high-temperature creep properties 査読有り国際誌

Li R., Kondo M., Suzuki T., Suzuki A., Takata N.

Materials Science and Engineering: A 889 巻 2024年1月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

This study aims to fundamentally understand the effect of 0.1 at% Ti addition (for introducing solute Ti with low diffusivity into the α-Al matrix) on the microstructure and high-temperature mechanical performance of a heat-resistant Al–5Mg–3.5Zn–2Cu–2Ni (at.%) quinary alloy subjected to heat treatments. The precipitation morphologies of the T-Al6Mg11Zn11 phase are systematically characterized in terms of the distribution of solute Ti, which is controlled by a peritectic reaction during solidification. High-temperature strength and creep properties (200 °C/105 MPa) are examined using the Ti-added alloy specimen and compared with the results of Ti-free quinary alloy specimens. In the Ti-added alloy, solute Ti is distributed within the dendritic α-Al phases formed through the peritectic reaction. The precipitation morphologies vary depending on solute Ti contents in the α-Al matrix after isothermal aging at 200 and 300 °C. Numerous fine T-phase precipitates are homogeneously dispersed in the α-Al matrix containing high solute Ti content. Fine precipitation morphologies appear stable even after long-term exposure at 200 °C. Ti addition extends creep rupture life (at 200 °C) without the loss of static high-temperature strength and room-temperature ductility. The improved creep properties could be responsible for the reduction in creep rate by the refined precipitation morphologies in the α-Al matrix containing higher solute Ti contents. Local coarsening of the precipitates occurs owing to the solute Ti during creep (under stress). The mechanism is discussed in terms of the effect of Ti addition on the phase equilibria between the α-Al and other intermetallic phases.

DOI： 10.1016/j.msea.2023.145859

Scopus

Combustion Foaming of Porous (Al,Fe)<inf>3</inf>Ti with L1<inf>2</inf> Ordered Structure 査読有り国際誌

Suzuki A., Fujishiro T., Takata N., Kobashi M.

Materials Transactions 65 巻 ( 4 ) 頁： 414 - 421 2024年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Transactions

The combustion foaming process enables the fabrication of closed-cell porous intermetallics by utilizing the combustion reactions generating a large amount of heat. A closed-cell porous Al3Ti (D022 crystal structure) fabricated by the combustion foaming process has a lightweight, high stiffness, high melting temperature, and good oxidation resistance but exhibits brittleness due to the poor deformability of Al3Ti. It is known that the addition of third elements (X = Cr, Mn, Fe, etc.) changes the crystal structures from D022 to L12, resulting in an improvement in the deformability in the case of dense materials. In the present study, an attempt was made to fabricate the closed-cell porous (Al, Fe)3Ti with an L12-ordered crystal structure through the combustion foaming. The effect of the amount of the exothermic agent, which was added to control the reaction heat of combustion foaming, on the porosity, pore morphology, microstructure, and constituent phases was investigated. The closed-cell porous L12-(Al, Fe)3Ti without any intermediate phases was successfully fabricated when the exothermic agent was added over 5 vol%. The porosity reached the maximum at approximately 80% when the exothermic agent of 10 vol% was added. The TiB2 particles, which were formed by the reactions of the exothermic agent, were aggregated in the porous sample with the exothermic agent of 5 vol% but uniformly dispersed in the porous samples foamed with the exothermic agent over 10 vol%. Based on the results above and the temperature measurements during the combustion foaming, it is important for fabricating highly porous L12-(Al, Fe)3Ti with the uniform microstructure to control the maximum temperature just above the liquidus temperature of (Al, Fe)3Ti. This study provides new insights into the hierarchical control of porous materials with the desired pore structures and cell wall materials.

DOI： 10.2320/matertrans.MT-M2023213

Scopus

Evaluation of reactive wetting kinetics of carbon fibers by molten Al-Ti alloy and its application to the fabrication of Al/carbon fiber composites 査読有り国際誌

Suzuki A., Ishiguro R., Miwa T., Takata N., Kobashi M., Furukawa Y.

Journal of Alloys and Compounds 968 巻 2023年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Alloys and Compounds

Wetting and interfacial reactions between molten Al and carbon fibers (CFs) are crucial for the fabrication of high-thermal conductive Al/CF composites through liquid-state processes including casting. The formation of Al4C3 which has a low thermal conductivity and high reactivity with water needs to be suppressed while improving wettability. The addition of Ti into molten Al forms TiC and contributes to significant improvement in wettability. To control a thin morphology of TiC, the kinetics of reactive wetting need to be clarified. In the present study, the reactive wetting kinetics between molten Al or Al-Ti alloy and pitch-based CF were investigated using the dipping coverage method combined with microstructural observations. The addition of Ti into molten Al drastically accelerated the wetting and reduced the apparent activation barrier for reactive wetting, which was related to the change in the interfacial products from the Al4C3 phase to the TiC phase. The Al4C3 phase grew while eroding the CFs, whereas the TiC phase formed in a thin-layered morphology around CFs and suppressed the diameter reduction of CF. The reduction in the apparent activation barrier and the morphology of carbides indicated a change in the dominant phenomena for reactive wetting from Al4C3 growth to TiC formation (controlled by diffusion in liquid Al). Based on the kinetics evaluations, CF were hybridized with pure Al and Al-Ti alloy through a casting process, and their thermal conductivities were evaluated. The addition of CF into pure Al degraded the thermal conductivity due to the eroded CF and coarsened Al4C3 phase, whereas the addition of CF into Al-Ti alloy enhanced the thermal conductivity. This study provides new insights into reactive wetting phenomena related to the fabrication of high-thermal conductive metal matrix composites.

DOI： 10.1016/j.jallcom.2023.172168

Scopus

Wear properties of aluminum alloys fabricated by laser powder bed fusion 査読有り国際共著国際誌

Gong S., Takata N., Kobashi M., Shin S.E.

Tribology International 187 巻 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Tribology International

The production of an aluminum alloy using the laser powder bed fusion (LPBF) process results in a unique microstructure that differs from that of the same alloy when cast; this microstructure is advantageous for wear resistance. This study compared the wear resistance of Al-12Si and Al-2.5Fe (mass%) binary alloys produced by LPBF process with their cast equivalents, to analyze their suitability for lightweight wear-resistant parts. The wear resistance of the LPBF-produced alloys was significantly improved owing to the increase in hardness induced by the rapid cooling rate of the LPBF process and the dense dispersion of the fine secondary phase. Thus, Al alloys fabricated using LPBF can provide excellent wear resistance and possess the potential for application as industrial materials.

DOI： 10.1016/j.triboint.2023.108769

Scopus

B2-structured Fe<inf>3</inf>Al alloy manufactured by laser powder bed fusion: Processing, microstructure and mechanical performance 査読有り国際共著国際誌

Vilardell A.M., Pelcastre L., Nikas D., Krakhmalev P., Kato M., Takata N., Kobashi M.

Intermetallics 156 巻 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Intermetallics

Prealloyed Fe3Al was successfully manufactured by laser powder bed fusion. The best set of process parameters led to parts with a relative density of 99.5 %, a surface roughness, Sa, of 31.5 ± 5.6 μm and a hardness of 319 ± 14 HV0.1. Its microstructure as well as its mechanical properties at room and high temperatures were analyzed. The results of the chemical composition showed minor variations in aluminum content oscillating between 21 and 28 at.% along the melt pool. Additionally, elongated grains were observed to grow parallel to the building direction, as well as the development of a weak {001} texture along the building direction. The mechanical properties were influenced by the temperature. Compression tests showed a loss in strength with the increase in temperature, from a yield strength of 621 ± 40 MPa at room temperature to 89 ± 20 MPa at 650 °C. Reciprocating sliding wear tests showed that fragmentation of the intermetallic at room temperature occurs, whereas plastic deformation dominated at higher temperatures. For all temperatures, tribochemical wear was also present due to the oxidation of wear debris.

DOI： 10.1016/j.intermet.2023.107849

Scopus

Effect of low-temperature annealing on electrical resistivity and mechanical properties of laser-powder bed fused AlSi10Mg alloy 査読有り国際誌

Miyajima Y., Nakamura Y., Konishi Y., Ishikawa K., Wang W., Takata N.

Materials Science and Engineering: A 871 巻 2023年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

The AlSi10Mg sample was additive-manufactured using laser powder bed fusion (L-PBF), and subsequent low-temperature annealing (LTA) at 413K or 473 K was applied. Vickers hardness tests show the peak at around 160 HV by 473 K annealing and around 145 HV by 413 K annealing. The flow stress of tensile and compression deformations are also affected by LTA, and peak aging condition gives the highest 0.2% proof stress. 0.2% proof stress obtained by tensile tests is around 270 MPa, whereas that obtained by compression tests is between 326 MPa and 386 MPa. Electrical resistivity at 293 K changes from approximately 80 nΩm down to around 60 nΩm, whereas that at 77 K changes from around 40 nΩm down to around 20 nΩm. The estimated concentration of solute Si in the as-built specimen is between 2.5 mass% and 2.9 mass%, corresponding to the previous results using energy-dispersive X-ray spectroscopy. The lattice constant obtained from XRD increased from 0.4043 nm up to 0.4048 nm by LTA. Both electrical resistivity and XRD measurement indicate a decrease in the concentration of solute atoms. Microstructure observations revealed numerous nano-sized precipitates of Si phase with a plate-like or granular morphologies in α-Al grains due to LTA.

DOI： 10.1016/j.msea.2023.144876

Scopus

Design of Al–Fe–Mn alloy for both high-temperature strength and sufficient processability of laser powder bed fusion 査読有り国際誌

Wang W., Takata N., Suzuki A., Kobashi M., Kato M.

Additive Manufacturing 68 巻 2023年4月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Additive Manufacturing

This paper presents a novel design concept for Al alloys with both sufficient laser powder bed fusion (L-PBF) processability and high-temperature mechanical performance using an Al–Fe–Mn ternary alloy with a refined α-Al/Al6M (M = Fe, Mn) two-phase microstructure. The near-eutectic (liquid → α-Al(fcc) + Al6M) composition of Al–2.5Fe–2Mn (mass%) was designed to avoid the formation of coarse primary intermetallics (having a detrimental effect on the PBF processability for densification) based on non-equilibrium liquidus projection thermodynamic calculations. The designed Al–2.5Fe–2Mn alloy powder exhibited sufficient L-PBF processability, and fully dense centimeter-sized samples (relative densities of above 99%) were successfully prepared. The L-PBF Al–2.5Fe–2Mn alloy samples exhibited a significantly refined solidification microstructure consisting of Al6M and α-Al phases in the melt-pool regions. Fe and Mn alloying elements contributed to the formation of nanoscale Al6M-phase particles and a high solid solution concentration in the α-Al matrix. The strength of the L-PBF Al–2.5Fe–2Mn alloy was slightly reduced at higher temperatures, but remained above 240 MPa at an elevated temperature of 300 °C. This superior high-temperature mechanical performance was attributed to the high thermal stability of the refined α-Al/Al6M two-phase microstructure and the formation of nanosized Al6M-phase precipitates.

DOI： 10.1016/j.addma.2023.103524

Scopus

Microstructural origin of anisotropic tensile ductility of Al-Si alloy manufactured by laser powder bed fusion 査読有り国際誌

Otani Y., Takata N., Suzuki A., Kobashi M., Kato M.

Scripta Materialia 226 巻 2023年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scripta Materialia

Aluminum alloys fabricated by laser powder bed fusion (L-PBF) exhibit anisotropic tensile ductility. To identify microstructural origins in melt-pool (MP) structures (formed by the L-PBF process) contributing to the anisotropic ductility, the local strain distribution inside the MP structure in deformation was quantified by a combination of digital image correlation (DIC) strain analysis and in-situ SEM observations of tensile tests. It was found that higher strain was localized in locally coarsened microstructures (softer regions) along melt-pool boundaries (MPBs). The strain localization played a significant role in crack initiation (and propagation) around MPBs, contributing to fracture. The strain localization at MPBs changed depending on the geometrical relation of the MPBs with the loading direction (LD), which was controlled by the LD with respect to the building direction of L-PBF samples. The three-dimensional MPB distribution related to the LD would be responsible for the anisotropic ductility.

DOI： 10.1016/j.scriptamat.2022.115259

Scopus

Austenite Reversion Behavior of Maraging Steel Additive-manufactured by Laser Powder Bed Fusion 査読有り

Takata N., Ito Y., Nishida R., Suzuki A., Kobashi M., Kato M.

Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 109 巻 ( 3 ) 頁： 201 - 214 2023年

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan

This study was set to fundamentally investigate the characteristics of austenite reversion occurring in maraging steels additive-manufactured by laser powder bed fusion (L-PBF). The maraging steel samples manufactured under different L-PBF process conditions (laser power P and scan speed v) were subjected to heat treatments at 550°C for various durations, compared with the results of the austenitized and water-quenched sample with fully martensite structure. The L-PBF manufactured samples exhibited the martensite structure (including localized austenite (γ) phases) containing submicron-sized cellular structures. Enriched alloy elements were detected along the cell boundaries, whereas such cellar structure was not found in the water-quenched sample. The localized alloy elements can be rationalized by the continuous variations in the γ-phase composition in solidification during the L-PBF process. The precipitation of nanoscale intermetallic phases and the following austenitic reversion occurred in all of the experimental samples. The L-PBF manufactured samples exhibited faster kinetics of the precipitation and austenite reversion than the water-quenched sample at elevated temperatures. The kinetics changed depending on the L-PBF process condition. The enriched Ni element (for stabilizing γ phase) localized at cell boundaries would play a role in the nucleation site for the formation of γ phase at 550°C, resulting in the enhanced austenite reversion in the L-PBF manufactured samples. The variation in the reaction kinetics depending on the L-PBF condition would be due to the varied thermal profiles of the manufactured samples by consecutive scanning laser irradiation operated under different P and v values.

DOI： 10.2355/tetsutohagane.TETSU-2022-066

Scopus

Effects of Mn and Cu Additions on Solidification Microstructure and High-Temperature Strength of Cast AlFe Binary Alloy 査読有り国際誌

Okano N., Takata N., Suzuki A., Kobashi M.

Materials Transactions 64 巻 ( 2 ) 頁： 492 - 499 2023年

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Transactions

In order to investigate the effects of Mn and Cu additions on solidification microstructure and high-temperature strength of cast AlFe alloys, we have fabricated various AlFe-based alloys with compositions of Al1%Fe, Al1%Fe1%Mn, Al1%Fe1%Cu, and Al1%Fe1%Cu1%Mn (mol%) solidified at different cooling rates (0.3 K·s11 and 145 K·s11). In the Al1%Fe binary alloy, the coarsened ª-Al13Fe4 phase with a needle-shaped morphology was often observed in the furnace-cooled sample (0.3 K·s11), whereas the cast sample (145 K·s11) exhibited several elongated ¡ phases surrounded by fine ¡/Al6Fe eutectic microstructure. Such a solidification microstructure was observed in the cast Al1%Fe1%Cu alloy, whereas the Al23CuFe4 phase was locally formed in the finally solidified zone in the furnace-cooled sample. In the Al1%Fe1%Mn alloy, the Al6(Fe, Mn) phase was formed regardless of the cooling rate. Finer ¡/Al6(Fe, Mn) two-phase eutectic microstructure was almost entirely occupied in the cast sample. The fine eutectic microstructure was observed in the cast Al1%Fe1%Cu1%Mn alloy as well. Compression tests for cast alloy specimens revealed that the Al1%Fe1%Cu1%Mn alloy exhibited the highest strength level among the studied alloy specimens, indicating the combined addition of Mn and Cu elements could be effective in improving the high-temperature strength of the cast AlFe alloys.

DOI： 10.2320/matertrans.MT-LA2022010

Scopus

Introducing Hatch Spacing into Deposited Energy Density toward Efficient Optimization of Laser Powder Bed Fusion Process Parameters 査読有り

Kunieda M., Suzuki A., Takata N., Kato M., Kobashi M.

Materials Transactions 64 巻 ( 6 ) 頁： 1099 - 1106 2023年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Transactions

The optimization of processing parameters is indispensable for the laser powder bed fusion (L-PBF) process. The deposited energy density (DED) is one of the process indexes for the L-PBF process and has a simplified formula of P v 0.5, where P is the laser power, and v is the scan speed. This parameter describes the change in the relative density and the melt pool morphology with laser power and scan speed well, whereas it does not include the effect of other processing parameters, e.g., hatch spacing (S). In the present study, an attempt was made to incorporate the effect of S into DED. Al12Si (mass%) alloy cube samples were fabricated by L-PBF under various P, v, and S, for evaluating the relative density and the melt pool morphology. The melt pool depth and width of L-PBF-manufactured Al12Si alloy increased linearly with P v 0.5 and did not exhibit a clear correlation with S. Based on the experimental observation, the effect of hatch spacing on DED was estimated to be S 0.5, and a new index of P v 0.5 S 0.5 was proposed. This index described the change in the relative density of the L-PBF-manufactured Al12Si alloy with laser conditions (P, v, and S) well when the thermal conduction mode melting was dominant. This study also indicated the limitation of the applicability of P v 0.5 S 0.5 under the keyhole or transition mode melting.

DOI： 10.2320/matertrans.MT-ME2022002

Scopus

Improved high-temperature creep properties of heat-resistant Al-Mg-Zn-Cu-Ni quinary alloy by adding a trace amount of Ti 査読有り

Kondo M., Suzuki T., Li R., Takata N.

Keikinzoku/Journal of Japan Institute of Light Metals 73 巻 ( 6 ) 頁： 260 - 265 2023年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

The present study investigated the effect of trace titanium (Ti) addition on high-temperature creep properties of a heat-resistant quinary aluminum (Al) alloy, with a composition of Al-5Mg-3.5Zn-2Cu-2Ni (mol%). Both the quinary alloy and Ti-added alloy were solution-treated at 480°C and then aged at 200°C for 10 hours. The creep tests were conducted at 200°C under 105 MPa. The addition of trace Ti element reduced the minimum creep rate and delayed the onset of the tertiary creep stage (creep acceleration), resulting in the extended creep rupture life of the Al-5Mg-3.5Zn-2Cu-2Ni quinary alloy. The creep rupture life of the Ti-added alloy was higher than that of the A7075 alloy but lower than that of the A2618 alloy, whereas the initial creep rate (up to 0.2% in strain) of the Ti-added quinary alloy was lower than that of the A2618 alloy. The superior creep properties were presumably due to the enhanced stability of the fine precipitation morphologies of the T-Al6Mg11Zn11 phase by solute Ti inside the α-Al matrix.

DOI： 10.2464/jilm.73.260

Scopus

Influence of Dislocation Substructure on Size-Dependent Strength of High-Purity Aluminum Single-Crystal Micropillars 査読有り

Takata N., Uesugi S., Zhu T., Takeyasu S., Suzuki A., Kobashi M.

Materials Transactions 64 巻 ( 8 ) 頁： 1952 - 1958 2023年

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Transactions

In order to understand the influence of dislocation substructures on the size-dependent strength (smaller is stronger) of micron-sized metals, we have fabricated single-crystal cylindrical micropillars with various diameters approximately ranging from 1 to 10µm, which were prepared on the surface of the fully annealed sample and the subsequently cold-rolled samples of high-purity aluminum (Al). The annealed micropillars exhibited a size dependence of the resolved shear stress required for slip. The shear stress (¸i) normalized by shear modulus (G) and the specimen diameter (d) normalized by Burgers vector (b) followed the correlation of ¸i/G = 0.33(d/b)10.63. The size-dependent strength was reduced by cold-rolling, resulting in lower power-law exponents (0.2630.31) for the correlation in the cold-rolled specimens. The fine dislocation substructures introduced by the cold-rolling could be associated with the reduced size-dependent strength, which can be rationalized using the stochastic model of the dislocation source length in an assumption of homogenously distributed dislocations existing in the experimental micropillars. The inhomogeneous dislocation substructure with various dislocation cell sizes would contribute to a variation in the measured strength depending on the location, likely due to the probability of exiting the dislocation cell walls (local variation in dislocation density) in the micropillars fabricated on the cold-rolled Al samples. [doi:10.2320/matertrans.MT-L2023004]

DOI： 10.2320/matertrans.MT-L2023004

Scopus

Investigation of dominant contributors to high strength of additively manufactured Al-Fe alloy by using single-crystal micropillar compression tests 査読有り

Choshi A., Zhu T., Takata N., Suzuki A., Kobash M.

Keikinzoku/Journal of Japan Institute of Light Metals 73 巻 ( 11 ) 頁： 523 - 529 2023年

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

In this study, we aim to address the dominant microstructural parameter of the high strength of Al-Fe alloy components additive-manufactured by the laser powder bed fusion (L-PBF) process. This study systematically investigated the compression response of single-crystal micropillars with a fixed diameter of approximately 3 μm prepared on the surfaces of the L-PBF built Al-2.5%Fe binary alloy sample, and the subsequently heat-treated samples (300°C and 500°C), together with the slowly solidified Al-2.5%Fe alloy sample for comparison. The single-crystal micropillars of the L-PBF built sample exhibited a high yield strength of approximately 250 MPa and pronounced strain hardening. The compressed single-crystal specimens exhibited a uniform deformation indicating the activated multi-slip systems. Such a trend was observed in the 300°C heat-treated sample. However, the relatively low yield strength and strain hardening rate were found in single-crystal micropillars of the 500°C heat-treated sample as well as the slowly solidified sample. In the compressed micropillars, a single-slip system was dominantly activated. These results indicated that numerous nano-sized Al 6Fe-phase particles (contained in the specimens of the L-PBF built sample and the 300°C heat-treated sample) could contribute to high yield strength and the enhanced activation of multi-slip systems resulting in the pronounced strain hardening.

DOI： 10.2464/jilm.73.523

Scopus

Design of heat-resistant Al–Mg –Zn–Cu–Ni quinary alloy: Controlling intermetallic phases and mechanical performance at elevated temperature 査読有り国際誌

Li R., Takata N., Suzuki A., Kobashi M.

Materials Science and Engineering: A 857 巻 2022年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

Owing to good formability, wrought Al alloys are used in a wide range of industries, including turbochargers in automobile engines. The development of Al alloys with increased high-temperature strength is necessary to improve the fuel efficiency of engines. In this study, a modified heat-resistant Al–Mg–Zn–Cu–Ni quinary alloy with superior high-temperature strength and creep rupture life at 200 °C (potential temperature in service for compressor radial impellers) was designed. The thermodynamic assessments provided a modified alloy composition of Al–5Mg–3.5Zn–2Cu–2Ni (at %) exhibiting α-Al phase in equilibrium with T-Al6Mg11Zn11 and Al3(Ni, Cu)2 phases at elevated temperatures. The experimental alloy showed granular T and Al3(Ni, Cu)2 phases often located on grain boundaries in the α-Al matrix, although the undissolved Al3Ni phase (formed in solidification) locally remained. Apart from the T phase, the η-Zn2Mg phase containing Cu element preferentially precipitated on grain boundaries. A large number of fine precipitates were dispersed homogeneously in the grain interior after the aging at 200 °C or 300 °C. Compared to the base alloy with a ternary composition of Al–5Mg–3.5Zn (at %) and conventional Al alloys, the designed quinary alloy (pre-aged at 200 °C for 10 h) showed a high strength at elevated temperatures above 200 °C. The creep-rupture life at 200 °C/105 MPa was remarkably extended to 665 h by the addition of Cu and Ni elements into the base ternary alloy. The rupture life was more than ten times longer than one (57 h) of the ternary alloys. The alloy modification based on the thermodynamic calculations provides an effective approach for designing lightweight Al alloys with superior high-temperature strength and creep rupture life.

DOI： 10.1016/j.msea.2022.144055

Scopus

Effect of solute Ni on thermal activation process of plastic deformation in Fe–18Cr single-crystal micropillars 査読有り国際誌

Zhu T., Li H., Takata N., Kobashi M., Yoshino M.

Materials Science and Engineering: A 857 巻 2022年11月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

The aim of the present study was to identify the effect of solute Ni element on the plastic deformation and its thermal activation process of 18Cr ferritic stainless steels. Single-crystal micropillars with different diameters of approximately 2 and 5 μm were fabricated on the surface of Fe–18%Cr–Ni alloy sheets containing different contents of Ni (0–2 mass%). Compression tests were performed on the micropillars at different initial strain rates to investigate the strain rate sensitivity (m) of stress for the slip initiation and the specimen-size dependence of the m value. In micropillars with a small diameter of 2 μm, the Fe–18%Cr binary alloy specimen exhibited a relatively higher strain-rate sensitivity of initial slip stress (m = 0.12), whereas m was reduced to 0.01 by adding 2% Ni. The same trend was observed in micropillars with a larger size of approximately 5 μm. The experimental results were utilized to evaluate the activation volume of plastic deformation. The activation volumes of the Fe–18%Cr alloy and alloy containing 1% Ni followed the specimen-size dependence trend of activation volume in bcc metals; however, the alloy containing 2% Ni exhibited larger activation volumes, suggesting a different thermal activation process presumably due to the significant interaction that occurred between dislocations and solute Ni atoms in bcc solid-solutions.

DOI： 10.1016/j.msea.2022.144076

Scopus

Machine-learning assisted optimization of process parameters for controlling the microstructure in a laser powder bed fused WC/Co cemented carbide 査読有り国際誌

Suzuki A., Shiba Y., Ibe H., Takata N., Kobashi M.

Additive Manufacturing 59 巻 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Additive Manufacturing

A Single laser scan was performed on a sintered WC/Co composite and the process conditions were optimized to realize a WC/Co two-phase microstructure in a WC/Co composite fabricated by laser powder bed fusion (L-PBF). Laser irradiation on the sintered WC/Co composites generated two different microstructural regions. One is composed of WC and Co phases (WC/Co two-phase region), and the other includes W2C and W3Co3C phases (WC decomposition region). In the L-PBF-fabricated WC/Co composites, these two microstructural regions are distributed in a complex manner and their fractions varies depending on the laser parameters. Using a convolutional neural network model that is trained with the micrographs of single-laser-scanned WC/Co composites, the fractions of the two microstructural regions in the WC/Co composites fabricated by the L-PBF under various laser conditions were quantified. Multiple linear regression analyses revealed that the laser power and spot size contribute more than the scan speed, which has been verified by numerical analysis based on the moving heat source model. A support vector machine (SVM) suggested that low laser power and low scan speed are required for suppressing the WC decomposition in the consolidated samples. The WC decomposition has been successfully suppressed in the samples fabricated under SVM-recommended conditions.

DOI： 10.1016/j.addma.2022.103089

Scopus

Controllable tensile performance of additively manufactured Al–Fe alloy 査読有り国際誌

Qi X., Takata N., Suzuki A., Kobashi M., Kato M.

Materials Science and Engineering: A 855 巻 2022年10月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

Achieving both high strength and ductility is challenging in additive manufacturing of Al alloys using the laser powder bed fusion (L-PBF) process by altering the laser conditions to control the microstructural characteristics. The current work focuses on the influence of varying laser energy density (ED), which is adjusted by different sets of laser power (P) and scan speed (v), on the microstructure-tensile property relationships of the L-PBF-fabricated Al–2.5%Fe alloy under varying laser conditions (P = 204–230 W, v = 450–600 mm/s) with a fixed powder layer thickness (t = 30 μm) and hatch distance (h = 30 μm). With increasing ED (= P/v·t·h), a slight increase in the average size of the columnar α-Al grains was found in the experimental samples concurrently with a higher fraction of <001>-oriented grains. Nanosized particles of the Al6Fe phase with an increased tendency to interconnect were observed in the matrix inside the melt pool, and the θ phase formed within the submicron-sized cellular structure along the melt pool boundaries (MPBs). A low tensile ductility, induced by the local microstructural inhomogeneities across MPBs, was found in all specimens tensile-deformed along the building direction, which was characterized by a preference fracture along the MPBs. At higher applied ED, the tensile ductility of the experimental Al–2.5Fe alloy was significantly improved with only a slight decrease in tensile strength. The difference in concentration of Fe across the MPBs in the matrix was also moderately diminished, which is consistent with the reduced local difference in microhardness across the MPBs under higher ED conditions. Therefore, the present results demonstrate that local microstructural inhomogeneities across MPBs can be controlled by the laser conditions, thereby producing both high strength and good ductility in the L-PBF processed Al–Fe alloys.

DOI： 10.1016/j.msea.2022.143893

Scopus

Enhancing the solid-state joinability of A5052 and CFRTP via an additively manufactured micro-structure 査読有り国際誌

Iwata K., Suzuki A., Kim S.G., Takata N., Kobashi M.

Journal of Materials Processing Technology 306 巻 2022年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Processing Technology

An Al alloy (A5052) sheet was joined with a carbon fiber-reinforced thermoplastic (CFRTP) sheet by hot pressing without melting the CFRTP sheet (that is, solid-state joining). A micro-structure was manufactured via laser irradiation of Al-Ti-C powders bedded on the A5052 sheet. The laser irradiation to Al-Ti-C powders generates numerous particle-shaped protrusions additively on the A5052 sheet, which facilitate the infiltration of CFRTP and mechanically interlock with the CFRTP sheet. To determine the optimal conditions for joining A5052 and CFRTP consisting of a polyamide 6 (PA6) matrix, the effects of joining temperature during hot pressing on the interfacial structure and joint strength were investigated. The maximum joint strength was attained at the joining temperature of 210 °C. At lower temperatures, PA6 was not sufficiently softened to infiltrate the micro-structure, resulting in lower joint strengths. At higher temperatures, carbon fibers (CFs) were exposed on the CFRTP surface and inhibited the penetration of PA6 and CFs into the micro-structure, thereby lowering the joint strength. To infiltrate PA6 and CFs into the micro-structure, hot pressing was performed in a gradient temperature field. The proposed process enabled appropriate infiltration of CFs and PA6 into the micro-structure and led to high and stable joint strength. It is expected that using the additively manufactured micro-structure approach proposed herein, the operating windows of various cutting-edge joining processes can be expanded to more moderate and lower energy conditions.

DOI： 10.1016/j.jmatprotec.2022.117629

Scopus

Microstructural Variations in Laser Powder Bed Fused Al-15%Fe Alloy at Intermediate Temperatures 査読有り国際誌

Wang, WY; Takata, N; Suzuki, A; Kobashi, M; Kato, M

MATERIALS 15 巻 ( 13 ) 2022年7月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

The samples of the Al–15Fe (mass%) binary alloy that were additively manufactured by laser powder bed fusion (L-PBF) were exposed to intermediate temperatures (300 and 500◦C), and the thermally induced variations in their microstructural characteristics were investigated. The L-PBF-manufactured sample was found to have a microstructure comprising a stable θ-Al13Fe4 phase localized around melt-pool boundaries and several spherical metastable Al6Fe-phase particles surrounded by a nanoscale α-Al/Al6Fe cellular structure in the melt pools. The morphology of the θ phase remained almost unchanged even after 1000 h of exposure at 300◦C. Moreover, the nanoscale α-Al/Al6Fe cellular structure dissolved in the α-Al matrix; this was followed by the growth (and nucleation) of the spherical Al6Fe-phase particles and the precipitation of the θ phase. Numerous equiaxed grains were formed in the α-Al matrix during the thermal exposure, which led to the formation of a relatively homogenous microstructure. The variations in these microstructural characteristics were more pronounced at the higher investigated temperature of 500◦C.

DOI： 10.3390/ma15134497

Web of Science

Scopus

PubMed

その他リンク： https://www.mdpi.com/1996-1944/15/13/4497

Fast scanning calorimetry study of Al alloy powder for understanding microstructural development in laser powder bed fusion 査読有り国際誌

Naoki Takata, Mulin Liu, Hongmei Li, Asuka Suzuki, Makoto Kobashi

Materials and Design 219 巻 2022年7月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials and Design

We examined the variation in the solidification microstructure of AlSi10Mg alloy powder over a wide range of cooling rates controlled by using the fast scanning calorimetry (FSC) technique. Two exothermic peaks derived from the primary solidification of the α-Al phases and the α-Al/Si eutectic reaction were detected. These exothermic peaks became broader and shifted to lower temperatures at higher cooling rates. Focus ion beam (FIB) milling enables microstructural characterization of AlSi10Mg powder solidified at controlled cooling rates above 102 °C·s−1 in the FSC equipment. The sample solidified at 4 × 104 °C·s−1 exhibited a fine microstructure consisting of a primary α-Al phase surrounded by lamellar-shaped Si phases. The fraction of the Si phase continuously decreased with increasing cooling rate, indicating higher content of solute Si element in the α-Al phase solidified at a higher cooling rate. The secondary dendrite arm spacing (λ) of the primary α-Al phase decreased in the sample solidified at a higher cooling rate (dT/dt). The relation follows a general equation of λ = A (dT/dt)-n (A: 38.4, n: 0.33) in wide range of cooling rate (10-1 ∼ 104 °C·s−1). The results were utilized to discuss the cooling rate of Al alloys during the laser powder bed fusion (L-PBF) process.

DOI： 10.1016/j.matdes.2022.110830

Scopus

その他リンク： https://www.sciencedirect.com/science/article/pii/S026412752200452X

応力発光体を用いた積層造形 Al-12% Si 合金ラティス構造体の圧縮変形挙動の観察査読有り

加藤正樹, 鈴木飛鳥, Matthew Mcmillan, Xiaoyang Liu, 高田尚記, 小橋眞

軽金属 72 巻 ( 5 ) 頁： 246 - 250 2022年5月

レーザ粉末床溶融結合法による Al-12% Si 合金積層造形体の固溶 Si 濃度の熱処理に伴う変化査読有り

高田尚記，劉牧霖，鈴木飛鳥，小橋眞，加藤正樹，岩井駿平，足立大樹

軽金属 72 巻 ( 5 ) 頁： 178 - 184 2022年5月

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

We have investigated microstructural characteristics and solute Si element in the α-Al (fcc) matrix of Al-12%Si binary alloy additive-manufactured by laser powder bed fusion (L-PBF) process in terms of different locations in the melt-pool structure (inside melt-pool or around melt-pool boundaries). Their variations by post heat-treatments at various temperatures were examined. The fraction of Si phase and lattice parameter of α-Al phase were quantified by XRD measurements combined with sample rotation and oscillation systems. In the L-PBF manufactured sample, the columnar α -Al phases contained highly concentrated Si element in solution (above 3 mol%) inside melt-pools, whereas the measured Si content was approximately 2 mol% in the relatively coarsened α-Al phase along melt-pool boundaries. The location dependence of solute Si content would be associated with a continuous change in growth rate of solid phase in solidification by local heating in the L-PBF process. The solute Si content was significantly reduced by heat-treatments and its location dependence appeared less pronounced. The as-manufactured sample exhibited a lower lattice parameter of α-Al phase with concentrated Si in solution in comparison with the heat-treated samples. The fraction of Si phase became higher in the heat-treated samples. These results were rationalized by microstructural change at elevated temperatures.

DOI： 10.2464/jilm.72.178

Scopus

その他リンク： https://www.jstage.jst.go.jp/article/jilm/72/5/72_7205-T08/_article/-char/ja/

レーザ粉末床溶融結合法によるAl-10%Si-0.4%Mg合金積層造形体の特異的な熱伝導率のイメージベース有限要素解析査読有り

鈴木飛鳥, 宮坂達也, 高田尚記, 小橋眞

軽金属 72 巻 ( 5 ) 頁： 164 - 171 2022年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

Laser powder bed fused Al-10Si-0.4Mg (mass%) alloy exhibits low and anisotropic thermal conductivity. To elucidate dominant microstructural features generating the characteristic thermal conductivity, thermal conduction analysis was performed by an image-based finite element method (FEM) using scanning electron microscope (SEM) images. The serial sectioning images of as-fabricated and 300ºC/2 h heat treated Al-10Si-0.4Mg alloys were obtained by focused ion beam SEM (FIB-SEM) and were used for constructing three-dimensional models. The homogenization method was applied to calculate average thermal conductivity of these models. When the thermal conductivity of α-Al phase was set at the thermal conductivity of pure aluminum, calculated thermal conductivity of as-fabricated model was much higher than experimentally measured thermal conductivity of as-fabricated Al-10Si-0.4Mg alloy, indicating that α-Al phase in the as-fabricated Al-10Si-0.4Mg alloy had much lower thermal conductivity than pure aluminum. In addition, the anisotropy of thermal conductivity appeared only in the as-fabricated model in which the α-Al/Si interfacial thermal resistance was taken into account. These results were used for discussing dominant contributors of low and anisotropic thermal conductivity of laser additive manufactured Al-10Si-0.4Mg alloy.

DOI： 10.2464/jilm.72.164

Scopus

その他リンク： https://www.jstage.jst.go.jp/article/jilm/72/5/72_7205-T06/_article/-char/ja/

Negative strain rate sensitivity of yield strength of Al-Si alloy additive-manufactured using laser powder bed fusion 査読有り国際誌

Takata N., Liu M., Suzuki A., Kobashi M., Kato M.

Scripta Materialia 213 巻 2022年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scripta Materialia

This article reports an unexpected finding of the mechanical behavior of Al-12%Si alloy manufactured using the laser powder bed fusion (L-PBF) process. The as-manufactured specimen has a negative strain rate sensitivity of flow stress at an early stage of tensile deformation (below 3% in strain). The post heat-treated specimens exhibited a positive strain-rate sensitivity and none of these specimens exhibited a serrated stress-strain curve, indicating a mechanism different from the Portevin–LeChatelier effect. Transmission electron microscopy revealed the dynamic precipitation of the nano-sized Si-phase inside the supersaturated solid solution of the α-Al matrix in the as-manufactured specimen deformed at ambient temperatures. The dynamically precipitated Si phase interacted with the introduced dislocations, enhancing the flow stress during the early stages of plastic deformation. The dynamic precipitation could contribute to the negative strain-rate sensitivity of the flow stress at an early stage of tensile deformation (including the yield strength).

DOI： 10.1016/j.scriptamat.2022.114635

Scopus

計算状態図を基にした耐熱アルミニウム鍛造合金の設計と組織制御招待有り査読有り

高田尚記, 鈴木飛鳥, 小橋眞

まてりあ 61 巻 ( 4 ) 頁： 195 - 201 2022年4月

High-temperature strength sustained by nano-sized eutectic structure of Al–Fe alloy manufactured by laser powder bed fusion 査読有り国際誌

Wang W., Takata N., Suzuki A., Kobashi M., Kato M.

Materials Science and Engineering: A 838 巻 2022年3月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering: A

This study investigated the high-temperature strength of a hypereutectic Al–Fe binary alloy (Al–15%Fe) additive-manufactured by laser powder bed fusion (L-PBF). The L-PBF Al–15%Fe alloy exhibited superior yield strength to the other existing L-PBF processed alloys due to α-Al/Al6Fe eutectic structure with a nanoscale cellular morphology. The present results demonstrated the feasibility of using L-PBF processed Al–Fe alloys as high-temperature lightweight materials.

DOI： 10.1016/j.msea.2022.142782

Scopus

Influence of Stabilizing Elements on Ductile-Brittle Transition Temperature (DBTT) of 18Cr Ferritic Stainless Steels 査読有り国際誌

Masataka Yoshino, Tetsuya Tagawa, Hongmei Li, Naoki Takata

ISIJ International 62 巻 ( 4 ) 2022年1月

Change in microstructural characteristics of laser powder bed fused Al–Fe binary alloy at elevated temperature 査読有り国際誌

Qi X., Takata N., Suzuki A., Kobashi M., Kato M.

Journal of Materials Science and Technology 97 巻頁： 38 - 53 2022年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science and Technology

The present study addressed the change in the microstructure of Al–2.5 wt% Fe binary alloy produced using laser powder bed fusion (L-PBF) technique by thermal exposure at 300 °C, and the associated mechanical and thermal properties were systematically examined as well. Multi-semi-cylindrical patterns corresponding to melt pools in the microstructure were macroscopically observed for the as-manufactured sample. No change in the melt-pool morphology was observed after thermal exposure for 1000 h. Inside the melt pools, a large number of the nanoscale metastable Al6Fe phase particles were uniformly distributed inside columnar grains of the α-Al matrix containing concentrated solute Fe in supersaturation. The sequential formation and coarsening of stable θ-Al13Fe4 phases were observed upon exposure to a 300 °C environment, but a considerable amount of nano-sized metastable Al6Fe phases remained even after 1000 h. Furthermore, the thermal exposure continuously reduced the concentration of solute Fe atoms in the α-Al matrix. No significant grain growth was found in α-Al matrix after 1000 h owing to the pinning effect of the dispersed fine particles on grain boundary migration. These results demonstrate a sluggish change in microstructural morphologies of the Al–2.5 wt% Fe alloy. The quantified microstructural parameters addressed dominant strengthening contributions by the solid solution of Fe element and Orowan strengthening mechanism by fine Al–Fe intermetallics in the L-PBF-produced alloy. The high strength level was sustained even after being exposed to 300 °C for long periods. The superior balance of mechanical properties and thermal conductivity can be achieved in the experimental alloys by taking advantage of the various microstructural parameters related to the Al–Fe intermetallic phases and α-Al matrix.

DOI： 10.1016/j.jmst.2021.04.038

Scopus

Solidification microstructure and room-temperature fracture toughness of Al-based cast alloys prepared through eutectic reactions in Al-Mg-Zn ternary system 査読有り

Okano N., Aikawa M., Takata N., Suzuki A., Kobashi M.

Keikinzoku/Journal of Japan Institute of Light Metals 72 巻 ( 1 ) 頁： 79 - 87 2022年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

This study was set to examine the fundamentals of solidification microstructure and room-temperature fracture toughness of different eutectic aluminum (Al) alloys strengthened by T-Al6Mg11Zn11 and/or β-Al3Mg2 intermetallic phases. The thermodynamic calculations for an Al-Mg-Zn ternary system assessed three alloy compositions of Al-22.5Mg-23.5Zn, Al-35.5Mg-2Zn and Al-34.5Mg-5Zn (mol%) corresponding to α-Al/T, α-Al/β and α-Al/T/β eutectic compositions, respectively. The designed alloys were prepared by different cast process for changing the cooling rate in solidification. The Al-22.5Mg-23.5Zn and Al-35.5Mg-2Zn alloys exhibited a number of fibrous α phase surrounded by of T-phase and β-phase matrix, respectively. The morphologies of eutectic microstructures were refined by high cooling rate in solidification. The three-phase microstructure of α, T and β phases was often observed in slowly solidified Al-34.5Mg-5Zn alloy, whereas only the α/β two-phase eutectic microstructure was observed in the rapidly solidified alloy sample. The indentation fracture method using Vickers indentation test was applied to measure the room-temperature fracture toughness of the experimental alloys prepared by mold-casting. The α/β two-phase eutectic alloys exhibited a low fracture toughness of 1.1 MPa·m0.5 in comparison with the α/T two-phase eutectic alloy. The lower fracture toughness would be responsible for the brittleness of β-phase matrix in the α/β two-phase eutectic alloys.

DOI： 10.2464/jilm.72.79

Scopus

Meso-structural Control on Metal Surfaces Based on Powder Metallurgy and Its Application to Metal/Polymer Joining 招待有り査読有り

Suzuki A., Takata N., Kobashi M.

Journal of the Society of Powder Technology, Japan 59 巻 ( 10 ) 頁： 511 - 517 2022年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Society of Powder Technology, Japan

This paper introduces meso-scale structure synthesis on metal surfaces through reaction processes from raw metal powders. The mesostructures are applied to metal/polymer anchor joining. The first topic is the synthesis of Fe-based porous structure on Fe substrate through the combustion reaction of the Fe-Ti-B system. The structure could be controlled in view of the phase equilibria at the maximum temperature of the reaction. A Fe/epoxy resin joint via the porous structure exhibits high tensile strength in a direction perpendicular to the joint interface. The second topic is the fabrication of mesostructure protruded on an Al alloy surface by laser scanning on Al-Ti-C powders. The mesostructural morphology is related to the formation of TiC and Al3Ti phases, which can be understood based on the solidification sequence after the laser irradiation. An Al alloy/CFRTP joint via the mesostructure exhibits high joint strength compared with previously reported similar anchor joints.

DOI： 10.4164/sptj.59.511

Scopus

Influence of Stabilizing Elements on Ductile-Brittle Transition Temperature (DBTT) of 18Cr Ferritic Stainless Steels 査読有り国際誌

Yoshino M., Tagawa T., Li H., Takata N.

ISIJ International 62 巻 ( 4 ) 頁： 788 - 798 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ISIJ International

The influence of different stabilizing elements (Nb, Ti and Zr) which are added to stabilize interstitial elements in the ferrite matrix on the ductile-brittle transition temperature (DBTT) of 18Cr ferritic stainless steels was systematically investigated at different temperatures ranging from −25°C to 75°C. Hot-rolled sheets of 18 mass% Cr ferritic stainless steels containing a trace amount (0.1 atomic%) of Nb, Ti or Zr were studied. The added stabilizing elements formed precipitates of carbides/nitrides in all the steels tested in the present study. The particle diameter of the precipitates observed in the Nb-added steel was much smaller than those in the other steels. The measured DBTTs of the Base steel and the Nb-added, Ti-added and Zr-added steels were 39°C, −3°C, 39°C and 11°C, respectively. Although initiation of cleavage cracks in each steel occurred independent of the kind of stabilizing element, the Nb-added steel exhibited a relatively higher Charpy impact value due to ductile plastic deformation following cleavage crack initiation, resulting in a lower DBTT (superior impact toughness). The occurrence of plastic deformation in the Nb-added steel is considered to be due to the fine carbide and/or nitride precipitates which were homogenously distributed in the material. Detailed analyses of the fracture surfaces were also performed for the other steels, and the results were used as a basis for discussing the effects of each stabilizing element on the DBTT of 18Cr ferritic stainless steels in terms of the precipitation morphologies observed in the ferrite matrix.

DOI： 10.2355/isijinternational.ISIJINT-2021-506

Scopus

Design and controlling microstructure of cast-type aluminum eutectic alloys with an allowable service temperature of 300°C 招待有り査読有り

Takata N., Okano N., Aikawa M., Okano T., Suzuki A., Kobashi M.

Keikinzoku/Journal of Japan Institute of Light Metals 72 巻 ( 6 ) 頁： 381 - 387 2022年

Influence of Added Fourth Elements on Precipitation in Heat-Resistant AlMgZn Ternary Alloys 査読有り国際誌

Ishii H., Takagi R., Takata N., Suzuki A., Kobashi M.

Materials Transactions 63 巻 ( 4 ) 頁： 513 - 521 2022年

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Transactions

DOI： 10.2320/matertrans.MT-L2021021

Scopus

その他リンク： https://www.jstage.jst.go.jp/article/matertrans/63/4/63_MT-L2021021/_article/-char/ja/

Aluminum matrix composites reinforced with multi-walled carbon nanotubes and C<inf>60</inf> manufactured by laser powder bed fusion 査読有り国際共著国際誌

Yoo S., Shin S.E., Takata N., Kobashi M.

Journal of Materials Science 2022年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Science

Carbon nano-materials are widely used as reinforcing materials for aluminum-based composites due to their excellent metallurgical properties. This study presents an approach for manufacturing Al/C composites utilizing a high energy ball milling and laser powder bed fusion (LPBF) process. We prepared Al/C60 and Al/MWCNT composites under 25 different conditions to observe their microstructure and mechanical property trends according to laser power and scan speed. The relative density of LPBFed composites increased as the energy density increased due to the oxide layer present on the aluminum surface and the high laser reflectance. It was found that, as the energy density increased, the increase in nanohardness and elastic modulus of the LPBFed composites was due to the high relative density. However, the high laser power condition of 179 W resulted in the softening of materials due to grain coarsening, resulting in a decrease in nanohardness and elastic modulus. Under the same laser conditions, the nanohardness of the LPBFed Al/2 vol.% MWCNT composites was approximately 0.5 GPa higher than that of the LPBFed Al/1 vol.% C60 composites, which is explained by the high relative density and grain refinement strengthening.

DOI： 10.1007/s10853-022-07119-6

Scopus

その他リンク： https://link.springer.com/article/10.1007/s10853-022-07119-6

Influence of added fourth elements on creep properties of heat-resistant Al-Mg-Zn ternary alloys at 200°C 査読有り

Kondo M., Suzuki T., Li R., Takata N.

Keikinzoku/Journal of Japan Institute of Light Metals 72 巻 ( 6 ) 頁： 473 - 481 2022年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

The effect of Cu or Ni addition on creep properties of a heat-resistant aluminum (Al) alloy (with a composition of Al-5Mg-3.5Zn (mol%)) strengthened by precipitates of T-Al6Mg11Zn11 intermetallic phase was investigated. The quaternary alloys with various Cu contents (0.25-3 mol%) or Ni contents (0.5-2 mol%) were solution-treated at 470 °C and then aged at 200°C for 10 hours. The creep tests were conducted using the heat-treated specimens at 200°C under 105 MPa. Both Cu and Ni additions increased the creep rupture time. The 1 mol% Cu added alloy exhibited the longest creep rupture time due to the enhanced precipitation of the refined intragranular phases (T or MgZn2 phases). However, more than 2 mol% Cu addition led to the transition of T phase to S-Al2CuMg phase formed on grain boundaries. The phase transition might have a detrimental effect on creep rupture time. In the Ni-added alloy specimen, the creep rupture time became longest when 1 mol% Ni was added. The added Ni element promoted the formation of the Al3Ni phase on the grain boundaries, resulting in the suppression of connecting cavities formed on grain boundaries in creep deformation.

DOI： 10.2464/JILM.72.473

Scopus

Optimizing Laser Conditions and Controlling Microstructure/Properties of Laser Powder Bed Fused Al-Si Alloys 招待有り査読有り

Suzuki A., Takata N., Kobashi M., Kato M.

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 69 巻 ( 10 ) 頁： 417 - 425 2022年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy

In the laser beam powder bed fusion (PBF-LB) processes, laser parameters need to be customized for fabricating dense components. Al-Si alloys are representative Al alloys used for the PBF-LB processes. The Al-Si alloys fabricated by the PBF-LB processes exhibit characteristic microstructures and mechanical properties, which are affected by the laser parameters. This paper describes the effect of laser conditions on the relative density, microstructure, and mechanical properties of Al-12Si (mass%) alloy fabricated by the PBF-LB process. The first topic is a machine-learning-assisted exploration of laser parameters (laser power and scan speed) for fabricating dense Al-12Si alloy parts. Using a neural network model, the laser condition range for fabricating dense Al-12Si alloy parts is predicted. A methodology for accurately predicting the laser condition range for fabricating dense components is introduced. The second topic is controlling the microstructures and mechanical properties of the dense Al-12Si alloys. Variations in α-Al crystal grain size/orientation, the width of primary α-Al phase, and solute Si content in α-Al matrix with laser conditions are introduced. The changes in mechanical properties with laser conditions and correlation with microstructural features are also described.

DOI： 10.2497/jjspm.69.417

Scopus

Enhancement in strength and ductility of laser powder bed fused Al–12Si alloy by introducing nanoscale precipitates 査読有り国際誌

Liu M., Takata N., Suzuki A., Kobashi M., Kato M.

Additive Manufacturing Letters 1 巻頁： 100008 2021年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Additive Manufacturing Letters

In order to manage both the strength and ductility of Al–Si alloys additively manufactured by laser powder bed fusion (L-PBF), an attempt was made to introduce nanoscale precipitates within the α-Al (fcc) supersaturated solid solution using the L-PBF manufactured Al–12%Si alloy by artificial aging treatments. The aging treatment at 120°C improved both the tensile strength and ductility (total elongation) of the L-PBF manufactured specimen. The simultaneous strength–ductility enhancement is due to the homogeneously distributed nanoscale Si precipitates that enhanced the strain hardening. These results provide new insights for overcoming the strength-ductility trade-off in the L-PBF manufactured Al alloys.

DOI： 10.1016/j.addlet.2021.100008

Scopus

Precipitation morphology and kinetics of T-Al6Mg11Zn11 intermetallic phase in Al–Mg–Zn ternary alloys 査読有り国際誌

Takata N., Takagi R., Li R., Ishii H., Suzuki A., Kobashi M.

Intermetallics 139 巻 2021年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Intermetallics

This study was undertaken to understand the fundamentals of T-Al6Mg11Zn11 intermetallic phase precipitation in heat-resistant Al–Mg–Zn ternary alloys, with the goal of further strength improvements. The thermodynamic assessment involved three alloy compositions, Al–4Mg–4.5Zn, Al–5Mg–3.5Zn, and Al–7Mg–1.5Zn (at%), with the T phase in a fixed fraction (approximately 6–7.5%) in equilibrium with the α-Al phase at 300 °C. The alloy compositions were set on different tie-lines between the α-Al and T phases in the two-phase region, resulting in varied compositions of each phase. In the three experimental alloys aged at 300 °C, the T phase precipitated on the grain boundaries of the α-Al matrix, and granular precipitates were homogeneously dispersed intragranularly. There was no significant difference in the precipitation morphology. It was demonstrated that the lattice parameters of the T and α-Al phases could be controlled based on the alloy composition and applied heat treatments. However, the lattice parameters have no significant effect on the precipitation morphologies of the thermodynamically stable T phase in the Al–Mg–Zn ternary alloys. The Zn-rich Al–4Mg–4.5Zn alloy exhibited a pronounced softening behavior after 10 h of aging due to the enhanced coarsening of precipitates in the α-Al matrix. The thermal instability of the precipitates was responsible for the transformation sequence from the initially formed metastable phases (η-Zn2Mg associated phases) to the stable T phase. These results provided a fundamental insight that alloy strengthening by introducing thermodynamically stable intermetallic phases is essential for sustaining the strength of heat-resistant Al–Mg–Zn ternary alloys after long-term treatment at elevated temperatures.

DOI： 10.1016/j.intermet.2021.107364

Scopus

Control of microstructural characteristics and mechanical properties of AlSi12 alloy by processing conditions of laser powder bed fusion 査読有り国際誌

Suzuki A., Miyasaka T., Takata N., Kobashi M., Kato M.

Additive Manufacturing 48 巻 2021年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Additive Manufacturing

To elucidate the possibility of controlling the microstructure and mechanical properties of Al–Si alloys additive-manufactured by laser powder bed fusion (L–PBF), the relationship among the laser conditions, microstructural characteristics (crystal grain, cellular microstructure, and solute Si in α-Al matrix), and tensile properties of L–PBF manufactured AlSi12 alloy samples was investigated. The crystal grain size and fraction of <001> oriented α-Al crystal grains toward the building direction increased as the laser power became higher and scanning velocity became slower. The width of cellular microstructure (sub–cell size) where the primary α-Al phase was surrounded by α-Al/Si eutectic microstructure increased as the laser power became higher and scanning velocity became slower. The refinement of microstructure was attributed to the solidification under high cooling rate, which was achieved by low laser power and high scanning velocity. The area fraction of Si phase analyzed from FE–SEM images tended to decrease as the laser power became higher and scanning velocity became slower, suggesting the possibility of solute Si concentration in α-Al matrix controlled by laser conditions. The STEM/EDS analysis revealed high concentration of solute Si in the α-Al matrix (above a solubility limit of 1.5 mol% in the Al–Si binary system) of L–PBF manufactured AlSi12 alloy samples and its concentration became higher in the sample manufactured using a higher laser power. The tensile tests of as–built AlSi12 specimens fabricated under various laser conditions were also performed. High strength and high ductility tended to be achieved when high power laser was applied in slow laser scanning velocity. The 0.2% proof stress was relatively higher when the laser scanning velocity was faster. The mechanical properties correlated with crystal grain size and sub–cell size rather than solute Si in the α-Al matrix. These results provide new insights to control mechanical performance of AlSi12 alloy via L–PBF processing parameters.

DOI： 10.1016/j.addma.2021.102383

Scopus

Precipitation Hardening at Elevated Temperatures above 400 degrees C and Subsequent Natural Age Hardening of Commercial Al-Si-Cu Alloy 査読有り国際誌

Li Ruoqi, Takata Naoki, Suzuki Asuka, Kobashi Makoto, Okada Yuji, Furukawa Yuichi

MATERIALS 14 巻 ( 23 ) 2021年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials

The precipitation of intermetallic phases and the associated hardening by artificial aging treatments at elevated temperatures above 400◦ C were systematically investigated in the commer-cially available AC2B alloy with a nominal composition of Al–6Si–3Cu (mass%). The natural age hardening of the artificially aged samples at various temperatures was also examined. A slight increase in hardness (approximately 5 HV) of the AC2B alloy was observed at an elevated temperature of 480◦ C. The hardness change is attributed to the precipitation of metastable phases associated with the α-Al15 (Fe, Mn)3 Si2 phase containing a large amount of impurity elements (Fe and Mn). At a lower temperature of 400◦ C, a slight artificial-age hardening appeared. Subsequently, the hardness decreased moderately. This phenomenon was attributed to the precipitation of stable θ-Al2 Cu and Q-Al4 Cu2 Mg8 Si6 phases and their coarsening after a long duration. The precipitation sequence was rationalized by thermodynamic calculations for the Al–Si–Cu–Fe–Mn–Mg system. The natural age-hardening behavior significantly varied depending on the prior artificial aging temperatures ranging from 400◦ C to 500◦ C. The natural age-hardening was found to strongly depend on the solute contents of Cu and Si in the Al matrix. This study provides fundamental insights into controlling the strength level of commercial Al–Si–Cu cast alloys with impurity elements using the cooling process after solution treatment at elevated temperatures above 400◦ C.

DOI： 10.3390/ma14237155

Web of Science

Scopus

Controlling WC/Co two-phase microstructure of cemented carbides additive-manufactured by laser powder bed fusion: Effect of powder composition and post heat-treatment 査読有り国際誌

Ibe H., Kato Y., Yamada J., Kato M., Suzuki A., Takata N., Kobashi M.

Materials and Design 210 巻 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier Ltd.

In this study, an attempt is made to control the WC-Co two-phase microstructures by laser powder-bed fusion (LPBF) process using cemented carbide powders with different compositions of WC-25Co (mass%) and WC-17Co (mass%) and post heat-treatment at 1380 °C. The as-built cemented carbide samples had different microstructures from those of the cemented carbides fabricated by conventional manufacturing methods. The microstructures of the as-fabricated WC-25Co and WC-17Co cemented carbides were characterized by two types of regions. Region 1 consisted of W2C and W3Co3C phases, including numerous pores and defects. Region 2 consisted of WC and Co phases. Post heat-treatment of the LPBF-built WC-25Co sample at 1380 °C led to the formation of a defect-free WC-Co two-phase microstructure. In contrast, the W3Co3C phase remained in the LPBF-built WC-17Co sample even after heat treatment. The addition of carbon to the WC-17Co powder prevented the formation of the W3Co3C phase in the cemented carbide processed by LPBF and subsequent heat treatments. The addition of carbon to the WC-17Co powder had a slight effect on the hardness of as-fabricated samples, but reduced the hardness of heat-treated samples. The reduced hardness was attributed to the increased volume fractions of the WC and W3Co3C phases.

DOI： 10.1016/j.matdes.2021.110034

Scopus

その他リンク： https://www.sciencedirect.com/science/article/pii/S026412752100589X

Effect of added stabilizing elements on thermal activation process of plastic deformation in 18Cr ferritic stainless steel 査読有り国際誌

Li H., Takata N., Kobashi M., Yoshino M.

Materials Science and Engineering A 824 巻 2021年9月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science and Engineering A

The effects of a trace amount (~0.1 at.%) of added stabilizing elements (Nb, Ti, and Zr) on the tensile properties of 18Cr ferritic stainless steel sheets at strain rates ranging from 10−3–102 s−1 (from ordinary quasi-static deformation to dynamic deformation) were investigated. The additional Ti or Zr elements formed coarse carbide or nitride precipitates, which consumed interstitial solute elements (C and/or N) in the ferrite matrix. In the Nb-added steel, however, only fine NbN precipitates with a few hundred nanometers in size were observed locally, implying a small amount of solute Nb in the ferrite matrix. Ti or Zr additions had only a slight effect on the deformation resistance of 18Cr ferritic steel sheets and strain rate sensitivity (m) of the flow stress, however, the Nb addition increased the deformation resistance and significantly reduced the strain rate sensitivity. The measured activation volume (v*) values of the Ti- and Zr-added steels (62 b3 and 66 b3) were almost equivalent to one of the 18Cr base steel (64 b3). This result suggested that a general thermally activated process for screw dislocation motion is controlled by double-kink nucleation, which is slightly affected by Ti or Zr additions. The high v* value (106 b3) of the Nb-added steel indicated that the thermally activated process of plastic deformation would be associated with the substitutional solute Nb atoms (act as short-range obstacles) interacting with the moving dislocations. These results showed that the Nb element played a distinct role in plastic deformation from the other stabilizing elements of Ti and Zr.

DOI： 10.1016/j.msea.2021.141866

Scopus

Dual plateau stress of C15-type topologically close-packed lattice structures additive-manufactured by laser powder bed fusion 査読有り国際誌

Liu X., Suzuki A., Takata N., Kobashi M., Kato M.

Scripta Materialia 202 巻 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scripta Materialia

Imitating crystal structures offers new avenues to design lattice structures composed of unit cells with nodes (act as atoms) and struts (act as atomic bonds). We found out unique dual plateau regions in the stress–strain curves of lattice structures inspired by topologically close-packed (TCP) structure of C15 Laves phase (AB2-type intermetallic compounds) and manufactured via the laser powder bed fusion. X-ray computed tomography of compressively deformed lattice structures as well as finite element analysis revealed that the existence of two kinds of units with different relative density caused the dual plateau regions. In addition, the C15 lattice structures exhibited a hybrid deformation mode of bending- and stretch-dominated deformations and can absorb high total energy of 5.0 MJ·m−3 in two stress levels.

DOI： 10.1016/j.scriptamat.2021.114003

Scopus

Control of surface micro− structure for Al alloy/polymer joining fabricated by laser process using Al− Ti− C powders: Effect of powder composition 査読有り国際誌

Seung−Gwang Kim, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Journal of Advanced Joining Processes 4 巻頁： 100068 2021年7月

Thermal activation process of plastic deformation in Fe–18Cr single-crystal micropillars with high-density dislocations 査読有り国際誌

Hongmei Li, Tianqi Zhu, Naoki Takata, Makoto Kobashi, Masataka Yoshino

Materials Science and Engineering: A 819 巻 ( 5 ) 頁： 141459 2021年5月

Processability and Optimization of Laser Parameters for Densification of Hypereutectic Al–Fe Binary Alloy Manufactured by Laser Powder Bed Fusion 査読有り国際誌

Wenyuan Wang, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato

crystals 11 巻 ( 3 ) 頁： 320 2021年3月

In‐Situ X‐ray Observations and Microstructural Characterizations for Understanding Combustion Foaming and Reaction Processes to Synthesize Porous Al3Ti Composites from Al–Ti–B4C Powders 査読有り国際誌

Takamasa Inukai, Asuka Suzuki, Naoki Takata, Makoto Kobashi, Yuji Okada, Yuichi Furukawa

Advanced Engineering Materials 頁： 2001284 2021年3月

Managing both high strength and thermal conductivity of a laser powder bed fused Al–2.5 Fe binary alloy: Effect of annealing on microstructure 査読有り国際誌

Xing Qi, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato

Materials Science and Engineering: A 805 巻頁： 140591 2021年2月

Understanding and suppressing shear band formation in strut-based lattice structures manufactured by laser powder bed fusion 査読有り国際誌

Xiaoyang Liu, Takafumi Wada, Asuka Suzuki, Naoki Takata, Makoto Kobashi, Masaki Kato

Materials & Design 199 巻頁： 109416 2021年2月

Joint strength of Fe/epoxy resin hybrid structure via porous Fe/TiB2 composite layer synthesized by in-situ reaction process 査読有り国際誌

Suzuki Asuka, Noritake Kazuki, Takata Naoki, Kobashi Makoto

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 288 巻 2021年2月

Critical resolved shear stress of activated slips measured by micropillar compression tests for single-crystals of Cr-based Laves phases 査読有り国際共著国際誌

Yunlong Xue, Naoki Takata, Hongmei Li, Makoto Kobashi, LiangYuan

Materials Science and Engineering: A 806 巻 ( 4 ) 頁： 140861 2021年1月

Effect of Trace Solute Titanium on Plastic Deformation of α-(Fe, Cr) Single-Crystal Micropillars Fabricated from 18Cr Ferritic Stainless Steel 査読有り国際誌

Hongmei Li, Tianqi Zhu, Naoki Takata, Makoto Kobashi, Masataka Yoshino

Materials Science and Engineering: A 803 巻頁： 140455 2021年1月

Microstructure of Al-2.5 Fe Binary Alloy Fabricated by Laser Powder Bed Fusion 査読有り国際誌

Xing Qi, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato

Materials Science Forum 1016 巻頁： 1175 - 1180 2021年1月

Inhomogeneous Microstructure and its Thermal Stability of AlSi10Mg Lattice Structure Manufactured via Laser Powder Bed Fusion 査読有り国際誌

Mu Lin Liu, Naoki Takata, Asuka Suzuki, Makoto Kobashi

Materials Science Forum 1016 巻頁： 826 - 831 2021年1月

Mechanical behavior of in-situ alloyed Ti6Al4V(ELI)-3 at.% Cu lattice structures manufactured by laser powder bed fusion and designed for implant applications 査読有り国際共著

A.M. Vilardell, A. Takezawa, A. du Plessis, N. Takata, P. Krakhmalev, M. Kobashi, M.Albu, G. Kothleitner, I. Yadroitsava, I. Yadroitsev

Journal of the Mechanical Behavior of Biomedical Materials 113 巻頁： 104130 2021年1月

Influence of added fourth elements on precipitation in heat-resistant Al-Mg-Zn ternary alloys 査読有り

Ishii H., Takagi R., Takata N., Suzuki A., Kobashi M.

Keikinzoku/Journal of Japan Institute of Light Metals 71 巻 ( 7 ) 頁： 275 - 282 2021年

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Keikinzoku/Journal of Japan Institute of Light Metals

In the present study, we investigated the effects of Cu or Ni additions on the precipitation of intermetallic phases in the heat-resistant aluminum alloy with a ternary composition of Al-5Mg-3.5Zn (mol%). The quaternary alloys with 1 mol%Cu or 1 mol%Ni content were solution-treated at 480 °C and subsequently aged at 300 °C for different periods. Both Cu and Ni additions have a slight effect on the age-hardening of these alloys at 300 °C. The added Cu element partitioned into not only T-Al6Mg11Zn11 phase but η-Zn2Mg phase precipitated in the α-Al matrix. The observed Cu enrichment in the precipitates of T phase indicated high stability of T phase in the Al-Mg-Zn-Cu quaternary system, which was different from the results of thermodynamic calculations using the existing database. The added Ni element enhanced the formation of fine Al3Ni phase located at grain boundaries and slightly influenced the precipitation of T phase in grain interior. These results provided new insights to design novel heat-resistant Al alloys using the Al-Mg-Zn-Cu-Ni system.

DOI： 10.2464/jilm.71.275

Scopus

その他リンク： https://www.jstage.jst.go.jp/article/jilm/71/7/71_710701/_article/-char/ja/

Effect of Annealing on Anisotropic Tensile Properties of Al–12%Si Alloy Fabricated by Laser Powder Bed Fusion 査読有り

Mulin Liu, Takafumi Wada, Asuka Suzuki, Naoki Takata, Makoto Kobashi, Masaki Kato

crystals 10 巻頁： 1007 2020年11月

Formation of multiple intermetallic phases in a hypereutectic Al-Fe binary alloy additively manufactured by laser powder bed fusion 査読有り

Wang Wenyuan, Takata Naoki, Suzuki Asuka, Kobashi Makoto, Kato Masaki

INTERMETALLICS 125 巻 2020年10月

Laser powder bed fusion of a near-eutectic Al-Fe binary alloy: Processing and microstructure 招待有り査読有り

Qi Xing, Takata Naoki, Suzuki Asuka, Kobashi Makoto, Kato Masaki

ADDITIVE MANUFACTURING 35 巻頁： 101308 2020年10月

Morphology and mechanical properties of the T-Al6Mg11Zn11 phase in the eutectic microstructure of Al–Zn–Mg ternary alloys 査読有り

Naoki Takata, Taiki Okano, Motonari Aikawa, Asuka Suzuki, Makoto Kobashi, Koji Hagihara

Intermetallics 124 巻頁： 106881 2020年9月

Manufacturing Aluminum/Multiwalled Carbon Nanotube Composites via Laser Powder Bed Fusion 招待有り査読有り国際共著

Lee Eo Ryeong, Shin Se Eun, Takata Naoki, Kobashi Makoto, Kato Masaki

MATERIALS 13 巻 ( 18 ) 頁： 3927 2020年9月

Manufacturing and characterization of in-situ alloyed Ti6Al4V (ELI)-3 at.% Cu by Laser Powder Bed Fusion 査読有り国際共著

M Vilardell, I Yadroitsev, I Yadroitsava, M Albu, N Takata, M Kobashi, P Krakhmalev, D Kouprianoff, G Kothleitner, A du Plessis

Additive Manufacturing 36 巻頁： 101436 2020年7月

Compressive Properties of Al-Si Alloy Lattice Structures with Three Different Unit Cells Fabricated via Laser Powder Bed Fusion 査読有り

Liu Xiaoyang, Sekizawa Keito, Suzuki Asuka, Takata Naoki, Kobashi Makoto, Yamada Tetsuya

MATERIALS 13 巻 ( 13 ) 頁： 2902 2020年7月

超硬合金粉末を用いたレーザ積層造形の微視組織形成過程査読有り

伊部博之, 加藤雄太, 山田純也, 加藤正樹, 鈴木飛鳥, 高田尚記, 小橋眞

粉体および粉末冶金 67 巻 ( 6 ) 頁： 313-319 2020年6月

Effect of Heat Treatment on Gradient Microstructure of AlSi10Mg Lattice Structure Manufactured by Laser Powder Bed Fusion 査読有り

Liu Mulin, Takata Naoki, Suzuki Asuka, Kobashi Makoto

MATERIALS 13 巻 ( 11 ) 頁： 2487 2020年6月

Strain Rate Sensitivity of Flow Stress Measured by Micropillar Compression Test for Single Crystals of 18Cr Ferritic Stainless Steel 査読有り

Zhu Tianqi, Li Hongmei, Takata Naoki, Kobashi Makoto, Yoshin Masataka

ISIJ INTERNATIONAL 60 巻 ( 4 ) 頁： 774 - 781 2020年4月

Adhesion properties of hydroxide flms formed on the Al-Mg-Si aluminum alloy sheets prepared by steam coating process 査読有り

Hongmei Li, Naoki Takata, Makoto Kobashi, Ai Serizawa

Journal of Light Metal Welding 58 巻 ( Supplement ) 頁： 102 - 106 2020年3月

In Situ Scanning Electron Microscopy Observation of Crack Initiation and Propagation in Hydroxide Films Formed by Steam Coating on Aluminum-Alloy Sheets 査読有り

Li Hongmei, Takata Naoki, Kobashi Makoto, Serizawa Ai

MATERIALS 13 巻 ( 5 ) 頁： 1238 2020年3月

Anomalous strengthening by supersaturated solid solutions of selectively laser melted Al–Si-based alloys 査読有り

Naoki Takata, Mulin Liu, Hirohisa Kodaira, Asuka Suzuki, Makoto Kobashi

Additive Manufacturing 33 巻頁： 101152 2020年2月

Influence of Brazing Time on Liquid Migration and Cell Structure of Porous Aluminum 招待有り査読有り

Kurosaki Tomohito, Kobashi Makoto, Takata Naoki, Suzuki Asuka, Minoda Tadashi

MATERIALS TRANSACTIONS 61 巻 ( 2 ) 頁： 368 - 374 2020年2月

Effect of hot-press thermal history on joint strength of A5052/Polyamide-6 hybrid structure via a porous layer 査読有り

Kim Seung-Gwang, Suzuki Asuka, Takata Naoki, Kobashi Makoto

JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 276 巻頁： 116388 2020年2月

Microstructure and compressive properties of porous hybrid materials consisting of ductile Al/Ti and brittle Al3Ti phases fabricated by reaction sintering with space holder 査読有り

Asuka Suzuki, Naoki Kosugi, Naoki Takata, Makoto Kobashi

Materials Science and Engineering: A 776 巻 ( 3 ) 頁： 139000 2020年1月

Development of gradient microstructure in the lattice structure of AlSi10Mg alloy fabricated by selective laser melting 査読有り

Liu Mulin, Takata Naoki, Suzuki Asuka, Kobashi Makoto

JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY 36 巻頁： 106 - 117 2020年1月

Anomalous size-dependent strength in micropillar compression deformation of commercial-purity aluminum single-crystals 査読有り

Naoki Takata, Soichiro Takeyasu, Hongmei Li, Asuka Suzuki, Makoto Kobashi

Materials Science & Engineering A 772 巻 ( 20 ) 頁： 138710 2020年1月

アルミニウム合金粉末のレーザ積層造形に伴う組織形成の理解に向けて招待有り査読有り

高田尚記，生出佳，小林卓哉，鈴木飛鳥，小橋眞

粉体および粉末冶金 66 巻 ( 12 ) 頁： 573-580 2019年12月

Topology optimization and characterization of Ti6A14V ELI cellular lattice structures by laser powder bed fusion for biomedical applications 招待有り査読有り

Vilardell A. M., Takezawa A., du Plessis A., Takata N., Krakhmalev P., Kobashi M., Yadroitsava I., Yadroitsev I.

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 766 巻 2019年10月

レーザ積層造形技術が生み出すアルミニウム合金造形体の特異な組織形成招待有り査読有り

高田尚記，鈴木飛鳥，小橋眞

鋳造工学 91 巻 ( 9 ) 頁： 612-617 2019年9月

Microstructure and cracking behavior of hydroxide films formed on aluminum-alloy sheets prepared by steam coating 査読有り

Li Hongmei, Takata Naoki, Kobashi Makoto, Serizawa Ai

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 764 巻 ( 9 ) 頁： 138247 2019年8月

Effects of Heat Treatments on Compressive Deformation Behaviors of Lattice‐Structured AlSi10Mg Alloy Fabricated by Selective Laser Melting 査読有り

Asuka Suzuki, Keito Sekizawa, Mulin Liu, Naoki Takata, Makoto Kobashi

Advanced Engineering Materials 頁： 1900571 2019年7月

「高機能溶融亜鉛めっき皮膜創成に向けた基礎研究と応用技術」特集号の発刊に寄せて

高田　尚記，貝沼　亮介

鉄と鋼 105 巻 ( 7 ) 頁： 675 2019年7月

Synthesis and structural control of Fe-based porous layer on Fe substratefor joining with resin parts using combustion reaction 査読有り

Asuka Suzuki, Kazuki Noritake, Naoki Takata, Makoto Kobashi

30 巻頁： 2101-2109 2019年7月

Enhanced Interfacial Reaction of Fe-Si Alloy Sheets Hot-Dipped in Zn melt at 460 degrees C 査読有り

Takata Naoki, Hayano Kunihisa, Suzuki Asuka, Kobash Makoto

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN 105 巻 ( 7 ) 頁： 693-700 2019年7月

Formation of Fe2Al5 Phase Layer on Fe-Si Alloy Sheets Hot-Dipped in Zn-0.2Al Alloy Melt 査読有り

Takata Naoki, Hayano Kunihisa, Suzuk Asuka, Kobashi Makoto

TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN 105 巻 ( 7 ) 頁： 701-708 2019年7月

Formation sequence of Fe-Al intermetallic phases at interface between solid Fe and liquid Zn-6Al-3Mg alloy 査読有り

Yokoi Hiroki, Takata Naoki, Suzuki Asuka, Kobashi Makoto

INTERMETALLICS 109 巻頁： 74-84 2019年6月

Design of laser parameters for selectively laser melted maraging steel based on deposited energy density 査読有り

Asuka Suzuki, Ryoya Nishida, Naoki Takata, Makoto Kobashi, Masaki Kato

Additive Manufacturing 28 巻頁： 160-168 2019年5月

Effect of powder blending ratio on porous structure formed by combustion synthesis reaction between Ni and Al together with space holder 査読有り

Yunmao Shu, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Journal of Functionally Graded Materials 33 巻頁： 38-43 2019年5月

Joining of metals and polymers using powder metallurgy with laser irradiation 査読有り

Seung-Gwang Kim, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Journal of Materials Processing Technology 270 巻頁： 1-7 2019年2月

ろう付用Al–Si系合金材を用いたポーラスアルミニウムの接合におけるポーラスアルミニウムの気孔構造変化と液相の挙動査読有り

黒崎　友仁, 小橋　眞, 高田　尚記, 鈴木　飛鳥, 田中　宏樹, 箕田　正

軽金属 69 巻 ( 2 ) 頁： 93-100 2019年2月

Transmission electron microscopic observation of layered double hydroxide films formed on aluminum alloys prepared by steam coating process 査読有り

Takata N.

Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 105 巻 ( 2 ) 頁： 177 - 182 2019年2月

Microstructure and strength of a novel heat-resistant aluminum alloy strengthened by T-Al6Mg11Zn11 phase at elevated temperatures 査読有り

Naoki Takata, Masato Ishihara, Asuka Suzuki, Makoto Kobashi

Materials Science & Engineering A 739 巻頁： 62-70 2019年1月

Fabrication of porous NiAl intermetallic compounds with a hierarchical open-cell structure by combustion synthesis reaction and space holder method 査読有り

Yunmao Shua, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Journal of Materials Processing Technology 264 巻頁： 182-189 2019年1月

Synthesis of porous Al/Al3Ti composite with hierarchical open–cell structure for combining with phase change material 査読有り

Asuka Suzuki, Shohei Miyake, Wataru Naruse, Naoki Takata, Makoto Kobashi

Journal of Alloys and Compounds 770 巻頁： 1100-1111 2019年1月

Microstructure and Mechanical property o f Porous Nickel aluminides Fabricated by Reactive Synthesis with Space Holder Powder 査読有り

Shu Yunmao, Suzuki Asuka, Takata Naoki, Kobashi Makoto

MRS ADVANCES 4 巻 ( 25-26 ) 頁： 1515-1521 2019年

Tensile Properties of a Heat-Resistant Aluminium Alloy Strengthened by T-Al6Mg11Zn11 Intermetallic Phase 査読有り

Nakatsuka Satoshi, Ishihara Masato, Takata Naoki, Suzuki Asuka, Kobashi Makoto

MRS ADVANCES 4 巻 ( 25-26 ) 頁： 1485-1490 2019年

Effect of boron addition on liquid zinc embrittlement of heat affected zone in 490 MPa grade steels

Yamamoto M.

Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 105 巻 ( 7 ) 頁： 742 - 751 2019年

Toward understanding the mechanism behind microstructure development of aluminum alloy powders additively manufactured by selective laser melting 招待有り査読有り

Takata N.

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 66 巻 ( 12 ) 頁： 573 - 580 2019年

Microstructural characterization of cellular AlSi10Mg alloy fabricated by selective laser melting 査読有り

Mulin Liu, Naoki Takata, Asuka Suzuki, Makoto Kobashi

Materials and Design 157 巻頁： 478-491 2018年8月

Crystallographic Features of Microstructure in Maraging Steel Fabricated by Selective Laser Melting

Takata Naoki, Nishida Ryoya, Suzuki Asuka, Kobashi Makoto, Kato Masaki

METALS 8 巻 ( 6 ) 2018年6月

高純度アルミニウム単結晶マイクロピラーの強度に及ぼす試験片寸法及び形状の影響招待有り査読有り

竹安　崇一郎，高田尚記，鈴木　飛鳥，小橋眞

軽金属 68 巻 ( 5 ) 頁： 250-256 2018年5月

Structural design and bonding strength evaluation of Al/epoxy resin joint via interpenetrating phase layer 査読有り

Asuka Suzuki, Yuta Arai, Naoki Takata, Makoto Kobashi

Journal of Materials Processing Technology 262 巻頁： 11-18 2018年5月

Microstructure of intermetallic-reinforced Al-based alloy composites fabricated using eutectic reactions in Al–Mg–Zn ternary system 査読有り

Naoki Takata, Taiki Okano, Asuka Suzuki, Makoto Kobashi

Intermetallics 95 巻頁： 48-58 2018年4月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We designed two types of Al-based alloy composites reinforced by η-Zn2Mg (hexagonal) and T-Al6Mg11Zn11 (cubic) intermetallic phases using monovariant eutectic reactions in the Al–Mg–Zn ternary system and then attempted to fabricate them using solidification. Thermodynamic assessment revealed two alloy compositions of Al–18Mg–36Zn and Al–22.5Mg–23.5Zn (at%) with the α-Al (fcc) phase reinforced with high fractions (>50%) of the η and T phases. Both alloys exhibited fine two-phase eutectic microstructures consisting of α/η and α/T phases, respectively. The morphology of the α-Al phase in the eutectic colonies varied from lamellae to fibers upon changing the neighboring intermetallic phase. These eutectic microstructures exhibit high stability at an elevated temperature of 300 °C. In addition, the size and spacing of the α-Al phase could be controlled by changing the cooling rate during solidification. The fabricated composites exhibited high hardness values exceeding 220 HV, which were much superior to those of conventional Al alloys. The calculated solidification path and component partitioning in the liquid phase during solidification provided insights into the solidification segregation of Zn element in the Al–18Mg–36Zn alloy. The Zn-enriched regions would enhance the local microstructural change at elevated temperatures, which confirmed by the microstructural observations of the alloy exposed at 300 °C

DOI： 10.1016/j.intermet.2018.01.018

Effect of layer thickness on bonding strength of Al/epoxy resin joints via interpenetrating phase layer 査読有り

Asuka Suzuki, Yuta Arai, Naoki Takata, Makoto Kobashi

Journal of Materials Processing Tech. 254 巻頁： 338-345 2018年1月

Size dependence of microstructure of AlSi⁠10Mg alloy fabricated by selective laser melting 招待有り査読有り

Naoki Takata⁠, Hirohisa Kodaira⁠, Asuka Suzuki, Makoto Kobashi

Materials Characterization 頁： in press 2018年

Enhanced Interfacial Reaction of Fe-Si Alloy Sheets Hot-Dipped in Zn Melt at 460 degrees C 査読有り

Takata Naoki, Hayano Kunihisa, Suzuki Asuka, Kobashi Makoto

ISIJ INTERNATIONAL 58 巻 ( 9 ) 頁： 1608-1615 2018年

金属粉末レーザ積層造形法によって作製されたAl-10Si-0.4Mg合金の組織と機械的性質査読有り

高田尚記, 小平寛久, 関沢圭人, 鈴木飛鳥, 小橋眞

軽金属 67 巻 ( 11 ) 頁： 582-588 2017年11月

化学反応を利用したアルミニウム基複合材料の製造方法招待有り査読有り

小橋眞, 高田尚記, 鈴木飛鳥

軽金属 67 巻 ( 11 ) 頁： 571-575 2017年11月

Solid Fe/Liquid Zn Interfacial Reaction of Hot-Dip Galvanized Fe-Si Alloy Sheets 招待有り査読有り

Naoki Takata, Kunihisa Hayano, Asuka Suzuki, Makoto Kobashi

Proceedings of GALVATEC2017 (11th International Conference on Zinc and Zinc Alloy Coated Steel Sheet) 頁： 177-181 2017年11月

Change in microstructure of selectively laser melted AlSi10Mg alloy with heat treatments

Takata Naoki, Kodaira Hirohisa, Sekizawa Keito, Suzuki Asuka, Kobashi Makoto

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 704 巻頁： 218-228 2017年9月

燃焼合成反応を利用した Fe/TiB2 複合材料の合成とポーラス化査読有り

伊藤峻，高田尚記，小橋眞

粉体および粉末冶金 64 巻 ( 6 ) 頁： 288-294 2017年7月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Porous metals show some unique properties, which bulk metals cannot exhibit. Especially, iron-based porous metals are expected to be applied to structural components because of their high strength, high rigidity, low material cost and so on. In this research, we synthesized porous Fe/TiB2 composites by Fe-Ti-B combustion reaction. Iron, titanium and boron powders were blended to synthesize 30 to 60vol%TiB2 particles in Fe matrix after the combustion synthesis reaction. Four kinds of iron powders (powder size: < 53 μm, < 150 μm, 600 μm and 850-1000 μm) were used. The blended powder was heated to induce the combustion synthesis reaction. When < 53 μm and < 150 μm iron powders were used, irregular shaped and open pores were formed. On the other hand, when 600 μm and 850-1000 μm iron powders were used, spherical pores whose sizes and shapes were similar to those of iron powders were formed

DOI： http://doi.org/10.2497/jjspm.64.288

Compressive properties of porous Ti-Al alloys fabricated by reaction synthesis using a space holder powder

Takata Naoki, Uematsu Keisuke, Kobashi Makoto

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 697 巻頁： 66-70 2017年6月

Synthesis of porous Fe/TiB<inf>2</inf> composites by means of combustion synthesis reaction 査読有り

Ito S.

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 64 巻 ( 6 ) 頁： 288 - 294 2017年6月

Porous Ti–Al Intermetallic Based Alloys Fabricated by Pressure-Sintering Elemental Powders with a Space Holder Powder 査読有り

Naoki Takata, Keisuke Uematsu, Makoto Kobashi

MRS Advances 2 巻 ( 26 ) 頁： 1387-1392 2017年1月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

In the present study, we have attempted to produce the porous Ti–Al intermetallic based alloys by pressure-sintering of the elemental powders of Ti and Al through a combustion reaction, with a NaCl space holder to achieve the development of a highly porous structure. The powders of Ti (particle size: <45 μm) and Al (particle size: <45 μm) were mixed to various total compositions of Ti–0-40 Al (at.%), and NaCl (particle size: 300-400 μm) was mixed with the Ti/Al powder to give a highly porous structure. The mixed powder was sintered at 700 oC under a constant pressure of 30 MPa to form cylindrical specimens with a diameter of 20 mm. The soaking of the specimens in pure water allows for the removal of NaCl (with a volume fraction of 60 %) and the formation of the pores to achieve a controlled relative density of 0.4. The present process can produce porous Ti–Al alloys with various compositions. In as-sintered Ti–Al specimens, an inhomogeneous microstructure consisting of Ti particles surrounded by the a Ti–Al alloy layer (various Ti–Al intermetallic phases) was observed. The as-sintered specimens exhibited the brittle behavior under compression, which is independent of their Al content. However, in a Ti–20Al alloy heat-treated at 1300 °C, a nearly Ti3Al single-phase microstructure appeared in the porous specimen. The heat-treated porous Ti–20Al alloy shows both a high plateau-strength level of approximately 100 MPa and a high plateau-end strain over 50%, resulting in a high absorption energy. The present results demonstrate that controlling the microstructure for the formation of the Ti3Al single-phase would be an effective method to achieve high energy absorption capacity of the porous Ti–Al alloy.

DOI： 10.1557/adv.2017.123

Solid Fe/Liquid Zn Interfacial Reaction of Hot-Dip Galvanized Dual-Phase Steels 査読有り

Naoki Takata, Makoto Kobashi, Masao Takeyama

Proceedings of the 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9) 頁： 496-501 2016年8月

Solidification of Bcc/T1/T2 three-phase microstructure in Mo–Nb–Si–B alloys 査読有り

N. Takata, N. Sekido, M. Takeyama, J.H. Perepezko, M. Follett-Figueroa, C. Zhang

Intermetallics 72 巻頁： 1-8 2016年5月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

The three-phase, (Mo,Nb)ss/(Mo,Nb)5Si3/(Mo,Nb)5SiB2, Bcc/T1/T2 microstructures that develop in Mo–Nb–Si–B alloys have been examined in arc cast and directionally solidified samples to identify the phase sequencing during solidification. A Mo-32.6Nb-19.5Si-4.7B (at.%) alloy was directionally solidified using an optical floating zone (OFZ) furnace in a flowing Ar gas atmosphere at a constant growth rate of 10 mm/h. The microstructure of the directionally solidified alloy is characterized by an elongated T2 phase surrounded by bcc and T1 phases with an interwoven morphology From the evaluation of the microstructures in arc cast ingots of several alloys at a constant 32.6 at%Nb composition, the path of the liquidus valleys with decreasing temperature has been determined to intersect at a common point that establishes the solidification reaction as a eutectic. The incorporation of the experimental results into a computational thermodynamic analysis provides insight on the partitioning of components within each phase during solidification

DOI： doi:10.1016/j.intermet.2016.01.001

Mechanical properties of austenitic heat-resistant Fe–20Cr–30Ni–2Nb steel at ambient temperature 査読有り

Naoya Kanno, Kazuhiro Yoshimura, Naoki Takata, Imanuel Tarigan, Masao Takeyama

Materials Science and Engineering A 662 巻頁： 551–563 2016年4月

Nanoindentation study on solid solution softening of Fe-rich Fe2Nb Laves phase by Ni in Fe-Nb-Ni ternary alloys 査読有り

Naoki Takata, Hassan Ghassemi-Armaki, Masao Takeyama, Sharvan Kumar

Intermetallics 70 巻頁： 7-16 2016年3月

Microstructure Control of Dual-Phase Steels through Hot-Dip Al–Mg–Si Alloy Coating Process 査読有り

Naoki Takata, Tadashi Tsukahara, Satoru Kobayashi, Masao Takeyama

ISIJ International 56 巻 ( 2 ) 頁： 319–325 2016年2月

金属間化合物Fe2Al5 相およびFeAl3 相の室温における機械的性質査読有り

塚原　斉史，高田　尚記，小林　覚，竹山　雅夫

鉄と鋼 102 巻 ( 2 ) 頁： 89-95 2016年2月

Crystallography of Fe2Al5 phase at the interface between solid Fe and liquid Al 査読有り

Takata Naoki, Nishimoto Manamu, Kobayashi Satoru, Takeyama Masao

INTERMETALLICS 67 巻頁： 1-11 2015年12月

Growth of Fe2Al5 Phase on Pure Iron Hot-Dipped in Al-Mg-Si Alloy Melt with Fe in Solution 査読有り

Takata Naoki, Nishimoto Manamu, Kobayashi Satoru, Takeyama Masao

ISIJ INTERNATIONAL 55 巻 ( 7 ) 頁： 1454-1459 2015年7月

Tensile Properties of Austentiic Heat Resisntat Steel of Fe-20Cr-30Ni-2Nb at Ambient Temperature 査読有り

Naoki Takata, Naoya Kanno, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 169-172 2015年6月

Stability of Sigma Phase at Elevaed Temperatures in Mn Added Fe-Cr-Ni Austenitic Heat Resistant Steels 査読有り

Yoshiki Kumagai, Naoki Takata, Satoru Kobayashi, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 157-160 2015年6月

Creep of Super Advanced Fe-Cr-Ni-Nb Austenitic Heat Resistant Steels at 1073 K for A-USC Power Plant 査読有り

Shion Mise, Taro Osaka,Takahiro Kimura, Naoki Takata, Satoru Kobayashi, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 165-168 2015年6月

Microstructural Characterization of Gamma Prime Precipitates in Wrought Ni-Based Superalloy Inconel X-750 査読有り

Hiromu Hisazawa, Yoshihiro Terada, Naoki Takata, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 250-253 2015年6月

Effect of Ti Addition on the Formation of Fe2Nb (TCP) and Ni3Nb (GCP) Phases in Fe-20Cr-35Ni-2.5Nb Austenitic Heat Resistant Steel at 1073 K 査読有り

Hongmei Li, Fagang Gao, Naoki Takata, Satoru Kobayashi, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 161-164 2015年6月

In-Situ Tensile Observation at 1073 K in Laves Phase Strengthened Fe-20Cr-30Ni-2Nb Steels 査読有り

Mari Yoshihara, Naoki Takata, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 153-156 2015年6月

3D Observation of Grain Boundary Precipitation of Fe2Nb Laves Phase in a Novel Austenitic Heat Resistant Steel Fe-20Cr-35Ni-2.5Nb 査読有り

Fagang Gao, Naoki Takata, Satoru Kobayashi, Masao Takeyama

Proceedings of The 1st International Conference on Advanced High-Temperature Materials Technology for Sustainable and Reliable Power Engineering (123HiMAT-2015) 頁： 35-38 2015年6月

Ultrafine ferrite formation through cold-rolling and annealing of low-carbon dual-phase steel 査読有り

Yoshitaka Okitsu, Naoki Takata, Nobuhiro Tsuji

Journal of Materials Science & Technology 31 巻頁： 745-754 2015年3月

Crystallography of Bcc/T1/T2 Three-Phase Microstructure in the Directionally Solidified Mo-Nb-Si-B Alloy 査読有り

Naoki Takata, Nobuaki Sekido, Masao Takeyama, John H. Perepezko

Mater. Res. Soc. Symp. Proc. 1760 巻頁： mrsf14-1760-yy03-03 2015年3月

Morphology and formation of Fe-Al intermetallic layers on iron hot-dipped in Al-Mg-Si alloy melt 査読有り

Takata Naoki, Nishimoto Manamu, Kobayashi Satoru, Takeyama Masao

INTERMETALLICS 54 巻頁： 136-142 2014年11月

6111アルミニウム合金のリジング発生に及ぼす加工熱処理の影響とCube方位粒形成過程査読有り

池田賢一，宮田幸昌，吉原隆浩，高田尚記，中島英治

軽金属 64 巻 ( 8 ) 頁： 353-360 2014年8月

Fe-20Cr-30Ni-2Nbオーステナイト系耐熱鋼の水蒸気雰囲気クリープに及ぼす粒界Laves相の効果査読有り

味噌作裕, Imanuel Tarigan, 木村尭弘, 高田尚記, 上田光敏, 丸山俊夫, 竹山雅夫

鉄と鋼 100 巻 ( 9 ) 頁： 1158-1164 2014年

記述言語：日本語掲載種別：研究論文（学術雑誌）

Creep of carbon free Fe-20Cr-30Ni-2Nb (at.%) steels strengthened by Fe2Nb Laves phase on grain boundaries has been examined in air and steam atmospheres at 1073 K/70 MPa. Sufficiently covering grain boundaries by stable Laves phase can reduce the creep rate, resulting in a significant extension of the creep rupture life without a loss of creep ductility in steam atmosphere as well as air. This effect becomes remarkable in higher area fractions of Laves phase on grain boundaries (ρ) than 80%. The creep rupture strain slightly decrease by steam atmosphere, which would be associated with the interglanular oxidation and its related cracks propagation along grain boundaries enhanced by steam atmosphere in the creep acceleration stage. Its effect can be suppressed by covering grain boundaries by Laves phase (increasing ρ). Therefore, Grain Boundary Precipitation Strengthening by stable Laves phase is a key mechanism for use of materials for boiler tubes in the innovative advanced ultra-super critical (A-USC) thermal power plants to be operated above 973 K.

溶融Znめっき鋼板のFe/Zn固液界面反応に及ぼす鋼板組織の影響査読有り

高田尚記, 竹山雅夫

鉄と鋼 100 巻 ( 9 ) 頁： 1172-1179 2014年

記述言語：日本語掲載種別：研究論文（学術雑誌）

We have examined the growth kinetics of Fe-Zn intermetallics layers formed on Fe-1.5Mn (α-Fe single phase) and Fe-3.5Mn-0.1C (γ-Fe+α-Fe two phase) steel sheets dipped in pure Zn melt at 460 ºC. In an early stage of dipping, FeZn13-ζ phase layer is initially formed and its thickness slightly increases with increasing dipping time till about 10 s, and then all Fe-Zn intermetallics layers (ζ, δ1, Γ) grow following a parabolic law. The growth kinetics can be recognized in both steels. This result demonstrates a slight effect of steel microstructure on the formation of Fe-Zn intermetallics layers. The composition analysis revealed a significant Fe dissolution into pure Zn melt in an early stage of dipping. The supersaturated Fe in Zn melt would provide the driving force for the crystallization of ζ phase layer on steel sheets. The continuous layer of ζ phase would control Fe diffusion for the following growth of the other Fe-Zn intermetallics layers.

CREEP OF THE NOVEL AUSTENITIC HEAT RESISTANT STEEL OF FE-20CR-30NI-2NB UNDER STEAM ATMOSPHERE AT 1073 K 査読有り

Yu Misosaku, Imanuel Tarigan, Naoki Takata, Mitsutoshi Ueda, Toshio Maruyama, Masao Takeyama

Advances in Materials Technology for Fossil Power Plants (Proceedings from 8th International Conference, October 22-25, 2013, Waikoloa, Hawaii, USA) 頁： 1352-1362 2013年10月

Plastic deformation of the C14 Laves phase (Fe,Ni)(2)Nb 査読有り

Takata N., Armaki H. Ghassemi, Terada Y., Takeyama M., Kumar K. S.

SCRIPTA MATERIALIA 68 巻 ( 8 ) 頁： 615-618 2013年4月

Effect of Dislocation Sources on Slip in Fe2Nb Laves Phase with Ni in Solution 査読有り

N. Takata, H. Ghassemi Armaki, Y. Terada, M. Takeyama, K. S. Kumar

Mater. Res. Soc. Symp. Proc. 1516 巻頁： 269-274 2012年12月

Dynamic deformation behavior of ultrafine-grained iron produced by ultrahigh strain deformation and annealing 査読有り

Okitsu Yoshitaka, Takata Naoki, Tsuji Nobuhiro

SCRIPTA MATERIALIA 64 巻 ( 9 ) 頁： 896-899 2011年5月

Susceptibility to Hydrogen Embrittlement of IF Steel with Ultrafine-Grained Structure Produced by Accumulative Roll-Bonding Process 査読有り

. Haruna, T. Nakagawa, D. Terada, N. Takata, N. Tsuji

Materials Science Forum 654-656 巻頁： 1235-1238 2010年8月

Analysis of deformation behaviors of ultrafine grained Cu-30%Zn with bimodal grain-size distribution 査読有り

Morimitsu Takatoshi, Takata Naoki, Terada Daisuke, Tsuji Nobuhiro

15TH INTERNATIONAL CONFERENCE ON THE STRENGTH OF MATERIALS (ICSMA-15) 240 巻 2010年

Ultrafine grained copper alloy sheets having both high strength and high electric conductivity 査読有り

Takata Naoki, Lee Seong-Hee, Tsuji Nobuhiro

MATERIALS LETTERS 63 巻 ( 21 ) 頁： 1757-1760 2009年8月

Increasing the ductility of ultrafine-grained copper alloy by introducing fine precipitates 査読有り

Takata Naoki, Ohtake Yusuke, Kita Kazuhisa, Kitagawa Kazuo, Tsuji Nobuhiro

SCRIPTA MATERIALIA 60 巻 ( 7 ) 頁： 590-593 2009年4月

超強加工された純銅の粒界構造査読有り

池田賢一, 山田康介, 高田尚記, 吉田冬樹, 中島英治, 辻伸泰

ふぇらむ : 日本鉄鋼協会会報 = Bulletin of the Iron and Steel Institute of Japan 14 巻 ( 1 ) 頁： . 2009年1月

A new route to fabricate ultrafine-grained structures in carbon steels without severe plastic deformation 査読有り

Okitsu Yoshitaka, Takata Naoki, Tsuji Nobuhiro

SCRIPTA MATERIALIA 60 巻 ( 2 ) 頁： 76-79 2009年1月

Temperature and Strain Rate Dependence of Flow Stress in Severely Deformed Copper by Accumulative Roll Bonding 査読有り

Kunimine Takahiro, Takata Naoki, Tsuji Nobuhiro, Fujii Toshiyuki, Kato Masaharu, Onaka Susumu

MATERIALS TRANSACTIONS 50 巻 ( 1 ) 頁： 64-69 2009年1月

Transmission Electron Microscopy of Fe(2)Nb Laves Phase With C14 Structure in Fe-Nb-Ni Alloys 査読有り

Takata Naoki, Ishikawa Shigehiro, Matsuo Takashi, Takeyama Masao

ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS 1128 巻頁： 475-480 2009年

Fe2Nb Laves相の構造とそのオーステナイト系耐熱鋼の強化相としての役割

高田尚記, 松尾孝, 竹山雅夫

(独)日本学術振興会耐熱金属材料第123委員会研究報告 50 巻 ( 3 ) 頁： 389-400 2009年

遷移金属Laves相の構造と相安定性

石川茂浩, 高田尚記, 松尾孝, 竹山雅夫

(独)日本学術振興会耐熱金属材料第123委員会研究報告 50 巻 ( 3 ) 頁： 347-360 2009年

Structure of Fe2Nb Laves Phase and Its Role as Strengthener in Austenitic Heat Resistance Steels

Naoki Takata, TAKASHI MATSUO, MASAO TAKEYAMA

Report of the 123rd Committee on Heat-Resisting Materials and Alloys, Japan Society for the Promotion of Science 50 巻 ( 3 ) 頁： 389-400 2009年

Structure and Phase Stability of Transition Metal Laves Phase

Shigehiro Ishikawa, Naoki Takata, TAKASHI MATSUO, MASAO TAKEYAMA

Report of the 123rd Committee on Heat-Resisting Materials and Alloys, Japan Society for Promotion of Science 50 巻 ( 3 ) 頁： 347-360 2009年

Mechanical properties of ultrafine grained ferritic steel sheets fabricated by rolling and annealing of duplex microstructure 査読有り

Okitsu Yoshitaka, Takata Naoki, Tsuji Nobuhiro

JOURNAL OF MATERIALS SCIENCE 43 巻 ( 23-24 ) 頁： 7391-7396 2008年12月

Dynamic deformation behavior of ultrafine grained aluminum produced by ARB and subsequent annealing 査読有り

Takata Naoki, Okitsu Yoshitaka, Tsuji Nobuhiro

JOURNAL OF MATERIALS SCIENCE 43 巻 ( 23-24 ) 頁： 7385-7390 2008年12月

学位取得後の2年間招待有り

高田尚記

まてりあ : 日本金属学会会報 47 巻 ( 6 ) 頁： . 2008年6月

AIC法による低温多結晶シリコン薄膜形成挙動の微細構造解析(TFTの材料・デバイス技術・応用及び一般) 査読有り

池田賢一, 廣田健, 藤本健資, 杉本陽平, 高田尚記, 井誠一郎, 中島英治, 中島寛

電子情報通信学会技術研究報告. SDM, シリコン材料・デバイス 108 巻 ( 1 ) 頁： 95-100 2008年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）

アルミニウム誘起結晶化法(AIC法)により形成された多結晶シリコン(Si)薄膜の形成挙動を透過電子顕微鏡(TEM)内その場加熱観察法等の微細構造解析手法により調査した.走査透過電子顕微鏡(STEM)を用いたエネルギー分散型X線分光法(EDS)分析により,400℃で10時間の熱処理でアモルファスSi(a-Si)とAlが完全に層交換することが確認できた.さらに,200℃での熱処理途中段階でのTEM内その場加熱観察ならびにEDS線分析により,SiとAlが各層内に共存することを明らかにできた.これらの結果より,AICによるa-Siの結晶化はSiの非平衡状態でのAlとの固溶を経由して起こると考えられる.

Direct evidence of polycrystalline silicon thin films formation during aluminum induced crystallization by in-situ heating TEM observation 査読有り

Ii Seiichiro, Hirota Takeshi, Fujimoto Kensuke, Sugimoto Youhei, Takata Naoki, Ikeda Ken-ichi, Nakashima Hideharu, Nakashima Hiroshi

MATERIALS TRANSACTIONS 49 巻 ( 4 ) 頁： 723-727 2008年4月

Grain boundary structure of ultrafine grained pure copper fabricated by accumulative roll bonding 査読有り

Ikeda Ken-ichi, Yamada Kousuke, Takata Naoki, Yoshida Fuyuki, Nakashima Hideharu, Tsuji Nobuhiro

MATERIALS TRANSACTIONS 49 巻 ( 1 ) 頁： 24-30 2008年1月

Grain boundary structures of ARB processed aluminum 査読有り

Ii Seiichiro, Hishida Motoki, Takata Naoki, Ikeda Ken-ichi, Nakashima Hideharu, Tsuji Nobuhiro

NANOMATERIALS BY SEVERE PLASTIC DEFORMATION IV, PTS 1 AND 2 584-586 巻頁： 716-721 2008年

その場加熱SEM/EBSD法による純アルミニウム箔の再結晶挙動の解析

池田賢一, 高田尚記, 波多聰

九州大学中央分析センタ-報告 ( 26 ) 頁： 8-14 2008年

Managing Both Strength and Ductility in Ultrafine Grained Steels

Nobuhiro Tsuji, Naoya Kamikawa, Rintaro Ueji, Naoki Takata, Hirohumi Koyama, Daisuke Terada

ISIJ International 48 巻 ( 8 ) 頁： 1114-1121 2008年

Structure and mechanical properties of severely deformed Cu-Cr-Zr alloys produced by accumulative roll-bonding process 査読有り

Kitagawa K., Akita T., Kita K., Gotoh M., Takata N., Tsuji N.

NANOMATERIALS BY SEVERE PLASTIC DEFORMATION IV, PTS 1 AND 2 584-586 巻頁： 791-796 2008年

Grain Boundary Structure of Ultrafine Grained Pure Copper Fabricated by Accumulative Roll Bonding

Ken-ichi Ikeda, Kousuke Yamada, Naoki Takata, Fuyuki Yoshida, Hideharu Nakashima and Nobuhiro Tsuji

Materials Transactions 49 巻 ( 1 ) 頁： 24-30 2008年

Direct Evidence of Polycrystalline Silicon Thin Films Formation during Aluminum Induced Crystallization by In-Situ Heating TEM Observation

Seiichiro Ii, Takeshi Hirota, Kensuke Fujimoto, Youhei Sugimoto, Naoki Takata, Ken-ichi Ikeda, Hideharu Nakashima and Hiroshi Nakashima

Materials Transactions 49 巻 ( 4 ) 頁： 723-727 2008年

Nanostructured bulk copper fabricated by accumulative roll bonding 査読有り

Takata Naoki, Lee Seong-Hee, Lim Cha-Yong, Kim Sang-Shik, Tsuji Nobuhiro

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 7 巻 ( 11 ) 頁： 3985-3989 2007年11月

6000系アルミニウム合金の立方体方位粒形成過程

宮田幸昌, 吉原隆浩, 高田尚記, 池田賢一, 波多聰, 中島英治

大会講演概要 113 巻頁： 45-46 2007年10月

Change in microstructure and texture during annealing of pure copper heavily deformed by accumulative roll bonding 査読有り

Takata Naoki, Yamada Kousuke, Ikeda Ken-ichi, Yoshida Fuyuki, Nakashima Hideharu, Tsuji Nobuhiro

MATERIALS TRANSACTIONS 48 巻 ( 8 ) 頁： 2043-2048 2007年8月

6000系アルミニウム合金における立方体方位粒形成に及ぼす加工熱処理の影響

宮田幸昌, 吉原隆浩, 高田尚記, 池田賢一, 中島英治

大会講演概要 112 巻頁： 199-200 2007年4月

その場加熱EBSP法を用いた純アルミニウム箔の再結晶過程の解析

池田賢一, 高田尚記, 宮田幸昌, 中島英治

大会講演概要 112 巻頁： 63-64 2007年4月

アルミニウム誘起結晶化法による多結晶シリコン薄膜形成挙動のその場加熱観察査読有り

池田賢一, 廣田健, 藤本健資, 杉本陽平, 高田尚記, 井誠一郎, 中島英治, 中島寛

日本金屬學會誌 = Journal of the Japan Institute of Metals 71 巻 ( 2 ) 頁： 158-163 2007年2月

In-situ heating observation for formation behavior of polycrystalline silicon thin films fabricated using aluminum induced crystallization 査読有り

Ikeda Ken-ichi, Hirota Takeshi, Fujimoto Kensuke, Sugimoto Youhei, Takata Naoki, Ii Seiichiro, Nakashima Hideharu, Nakashima Hiroshi

JOURNAL OF THE JAPAN INSTITUTE OF METALS 71 巻 ( 2 ) 頁： 158-163 2007年2月

In-situ EBSP analysis of grain boundary migration during recrystallization in pure aluminum foils 査読有り

Takata Naoki, Ikeda Ken-ichi, Nakashima Hideharu, Tsuji Nobuhiro

Recrystallization and Grain Growth III, Pts 1 and 2 558-559 巻頁： 351-356 2007年

Relation between ridging and texture components in Al-Mg-Si alloy 査読有り

Ikeda Ken-ichi, Yoshihara Takahiro, Takata Naoki, Nakashima Hideharu

RECRYSTALLIZATION AND GRAIN GROWTH III, PTS 1 AND 2 558-559 巻頁： 71-76 2007年

アルミニウム誘起結晶化法による多結晶シリコン薄膜形成挙動のその場加熱観察

池田賢一, 高田尚記, 廣田健, 井誠一郎, 杉本陽平, 中島英治, 中島寛

日本金属学会誌 71 巻 ( 2 ) 頁： 158-163 2007年

ARB法により強ひずみ加工したCu-Cr-Zr合金の組織と機械的特性

大竹祐輔，北川和夫，北和久，高田尚記，辻伸泰，青木庄治

銅と銅合金 46 巻 ( 1 ) 頁： 142-147 2007年

アルミニウム誘起結晶化法による多結晶シリコン形成過程のその場加熱観察

池田賢一, 中島英治, 廣田健, 藤本健資, 杉本陽平, 高田尚記, 井誠一郎, 中島寛

まてりあ : 日本金属学会会報 45 巻 ( 12 ) 頁： . 2006年12月

6111アルミニウム合金のリジング特性と集合組織の関係

池田賢一, 吉原隆浩, 高田尚記, 中島英治

大会講演概要 110 巻頁： 207-208 2006年4月

AIC法により作製された多結晶シリコン薄膜形成過程(薄膜(Si,化合物,有機)機能デバイス・材料・評価技術) 査読有り

池田賢一, 廣田健, 藤本健資, 杉本陽平, 高田尚記, 井誠一郎, 中島英治, 中島寛

電子情報通信学会技術研究報告. OME, 有機エレクトロニクス 106 巻 ( 7 ) 頁： 13-17 2006年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）

Al誘起結晶化法(AIC法)は,低温で多結晶シリコン(Si)薄膜の作製が可能なプロセスとして注目されている.本研究では,種々の膜厚比で蒸着させたAlとアモルファスSi(a-Si)を対象に低温熱処理による結晶化過程について検討した.その結果,多結晶Siは最初に蒸着したAlの膜厚分だけデンドライト状に成長することが明らかになった.本研究の条件では,a-SiとAlを1:1で蒸着させた試料が多結晶Siの膜の形成状態が良好であった.また,TEM内その場加熱観察を行った結果,a-Si中にAlが固溶している様子が観察され,Siは非平衡状態のa-Si/Al固溶体を経由して結晶化することが示唆された.

Annealing behavior and recrystallized texture in ARB processed copper 査読有り

Takata N, Yamada K, Ikeda K, Yoshida F, Nakashima H, Tsuji N

NANOMATERIALS BY SEVERE PLASTIC DEFORMATION 503-504 巻頁： 919-924 2006年

パラジウム<110>対称傾角粒界の原子構造と電子状態査読有り

水口隆, 高田尚記, 池田賢一, 中島英治

日本金屬學會誌 = Journal of the Japan Institute of Metals 69 巻 ( 11 ) 頁： 1010-1015 2005年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）

In this study, the energy and atomic structure of the <110> symmetric tilt boundaries in palladium were calculated using a molecular dynamics (MD) method and the electronic structures of hydrogen in the bulk and at the grain boundaries were calculated using discrete-variational Xα (DV-Xα) molecular orbital cluster calculaion by solving Hartree-Fock-Slater equation. The result of MD simulation revealed that the energy of the <110> symmetric tilt boundary of palladium depended on the misorientation angle and that there were large energy cusps at the misorientation angles which correspond to the {111}Σ3 and {113}Σ11 symmetric tilt boundaries. The atomic structure of all <110> symmetric tilt boundaries could consist of the combination of the {331} Σ19, {111}Σ3 and {113}Σ11 structural units and {110}Σ1 and {001}Σ1 single crystal units. The result of DV-Xα molecular orbital cluster calculation showed that the interstitial hydrogen atoms induced the palladium-hydrogen chemical bond which had a different energy level from the palladium-palladium bond. The component of the palladium-hydrogen bond at the grain boundaries was similar to those in the bulk palladium. It is clarified that electronic structure near the grain boundary is different from that in the perfect crystal.

Low-temperature fabrication of polyerystalline Si thin film using Al-induced crystallization without native Al oxide at amorphous Si/Al interface 査読有り

Sugimoto Y, Takata N, Hirota T, Ikeda K, Yoshida F, Nakashima H, Nakashima H

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44 巻 ( 7A ) 頁： 4770-4775 2005年7月

初めての研究論文執筆を通して招待有り

高田尚記

軽金属 55 巻 ( 4 ) 頁： . 2005年4月

Abnormal Grain Growth of off-Cube Grains in High Purity Aluminum Foils with Cube Texture

Naoki Takata, Fuyuki Yoshida, Ken-ichi Ikeda, Hideharu Nakashima and Hiroshi Abe

Materials Transactions 46 巻 ( 12 ) 頁： 2975-2980 2005年

Atomic and Electronic Structure of <110> Symmetric Tilt Boundaries in Palladium

Naoki Takata, Takashi Mizuguchi, Ken-ichi Ikeda and Hideharu Nakashima

Materials Transactions 45 巻 ( 7 ) 頁： 2099-2105 2004年

Grain boundary structure and its energy of < 110 > symmetric tilt boundary in copper 査読有り

Takata N, Ikeda K, Yoshida F, Nakashima H, Abe H

RECRYSTALLIZATION AND GRAIN GROWTH, PTS 1 AND 2 467-470 巻頁： 807-812 2004年

純銅の<110>対称傾角粒界における粒界エネルギーとその構造

高田尚記, 池田賢一，吉田冬樹，中島英治，阿部弘

日本金属学会誌 68 巻 ( 4 ) 頁： 240-246 2004年

Influence of Purity on the Formation of Cube Texture in Aluminum Foils for Electrolytic Capacitors

Naoki Takata, Ken-ichi Ikeda, Fuyuki Yoshida, Hideharu Nakashima and Hiroshi Abe

Materials Transactions 45 巻 ( 5 ) 頁： 1687-1692 2004年

アルミ誘起結晶化法により作製した多結晶シリコン薄膜の組織

廣田健，高田尚記，池田賢一，吉田冬樹，中島英治，阿部弘，杉本陽平，中島寛

九州大学超高圧電顕室研究報告 ( 28 ) 頁： 59-60 2004年

立方体集合組織を有する高純度アルミニウム箔中に存在する非立方体方位粒の特徴

吉田冬樹, 高田尚記, 池田賢一, 中島英治, 阿部弘

大会講演概要 104 巻頁： 157-158 2003年4月

電解コンデンサ用アルミニウム箔の立方体集合組織形成に及ぼす加工熱処理条件の影響

高田尚記, 池田賢一, 吉田冬樹, 中島英治, 阿部弘

大会講演概要 102 巻頁： 79-80 2002年4月

Influence of partial annealing temperature on cube texture in high purity aluminum foils 査読有り

Ikeda K, Takata N, Yoshida F, Nakashima H, Abe H

ALUMINUM ALLOYS 2002: THEIR PHYSICAL AND MECHANICAL PROPERTIES PTS 1-3 396-4 巻頁： 569-574 2002年

3N と 4N アルミニウム箔の立方体集合組織形成過程

池田賢一, 高田尚記, 吉田冬樹, 中島英治, 阿部弘

大会講演概要 100 巻頁： 317-318 2001年4月

　前のページ - 次のページ　

<髙田 尚記>

論文 - 髙田 尚記

<髙田　尚記>

論文 - 髙田　尚記