Faculty Profiles - KOBASHI, Makoto

Papers - KOBASHI, Makoto

Division display 21 - 40 of about 305 ／ All the affair displays >>

Managing both high strength and thermal conductivity of a laser powder bed fused Al-2.5Fe binary alloy: Effect of annealing on microstructure Reviewed

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

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING Vol. 805 page： 140591 2021.2

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

The microstructure of Al-2.5Fe (wt%) binary alloy samples additively manufactured by laser powder bed fusion (L-PBF) was systematically characterized, and its change due to subsequent annealing at 300 degrees C and 500 degrees C was examined. The as-fabricated samples featured homogeneous distribution of numerous fine particles of the metastable Al6Fe phase in the solidification microstructure where melt pools formed, and a relatively coarsened cellular structure was observed around the boundaries between the melt pools formed at different locations (melt pool boundaries). After the annealing at 300 degrees C, a slight growth of the nano-sized Al6Fe phase occurred, and coarsened plate-like.-Al13Fe4 phases were locally formed in the cellular structure at melt pool boundaries. Annealing at 500 degrees C induced a pronounced transformation of the metastable Al6Fe phase to the stable.-Al13Fe4 phase in the microstructure where melt pools formed, although no significant change in the microstructure of the a-Al matrix was detected. The thermal conductivity and tensile properties of as-fabricated and subsequently annealed specimens were measured. The as-fabricated specimens exhibited a high tensile strength of similar to 320 MPa and a thermal conductivity of similar to 150 W m(-1) K-1. Annealing at 300 degrees C improved the thermal conductivity to similar to 185 W m(-1) K-1 without a loss of tensile strength, whereas annealing at 500 degrees C significantly decreased the tensile strength. These results are utilized to discuss a balance between mechanical properties and thermal conductivity, which provided novel insights for managing both high strength and thermal conductivity of L-PBFbuilt Al-Fe binary alloys by controlling microstructure.

DOI： 10.1016/j.msea.2020.140591

Web of Science

researchmap

Understanding and suppressing shear band formation in strut-based lattice structures manufactured by laser powder bed fusion

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

MATERIALS & DESIGN Vol. 199 2021.2

Understanding and suppressing shear band formation in strut-based lattice structures manufactured by laser powder bed fusion

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

MATERIALS & DESIGN Vol. 199 2021.2

Fabrication of Metal Matrix Composite Containing Manganese Nitride Showing Giant Negative Thermal Expansion by Compressive Torsion Processing Reviewed

Koshi Takenaka, Kentaro Otsuka, Yoshihiko Okamoto, Yuji Kume, Makoto Kobashi

MATERIALS TRANSACTIONS Vol. 62 ( 5 ) page： 590 - 595 2021

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS & MATERIALS

Antiperovskite manganese nitride Mn3.1Zn0.5Sn0.4N was composited with Al by compressive torsion processing (CTP). This class of nitrides is anticipated for use as a thermal-expansion compensator because of giant negative thermal expansion (NTE). It is difficult to form a composite with molten metal that causes a chemical reaction. To date, only limited success has been achieved. Composites formed by CTP at 573K exhibit lower thermal expansion and electrical resistivity than those produced by electric-current sintering. That achievement is attributable to suppressed chemical erosion of the filler by treatment at a lower temperature while the strong mechanical energy strengthens the interface between the filler and the matrix and reduces pores in the material. Compressive torsion processing is a promising method for forming metal matrix composites containing giant NTE fillers.

DOI： 10.2320/matertrans.MT-M2020363

Web of Science

researchmap

Induction-activated self-propagating, high-temperature synthesis of nickel aluminide

Shekari M., Adeli M., Khobzi A., Kobashi M., Kanetake N.

ADVANCED POWDER TECHNOLOGY Vol. 28 ( 11 ) page： 2974 - 2979 2017.11

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 Vol. 704 page： 218 - 228 2017.9

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 Vol. 697 page： 66 - 70 2017.6

Pressure-less melt infiltration characteristics of Mg melt into Ti powder preforms with various pore structures: Toward the application to the binder jetting additive manufacturing

Zhuoyu Li, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Journal of Materials Processing Technology Vol. 331 page： 118509 - 118509 2024.10

Enhancing Capillary Pressure of Porous Aluminum Wicks by Controlling Bi-Porous Structure Using Different-Sized NaCl Space Holders

Hongfei Shen, Asuka Suzuki, Naoki Takata, Makoto Kobashi

Materials Vol. 17 ( 19 ) page： 4729 - 4729 2024.10

Publishing type：Research paper (scientific journal) Publisher：MDPI AG

Capillary pressure and permeability of porous media are important for heat transfer devices, including loop heat pipes. In general, smaller pore sizes enhance capillary pressure but decrease permeability. Introducing a bi-porous structure is promising for solving this trade-off relation. In this study, the bi-porous aluminum was fabricated by the space holder method using two different-sized NaCl particles (approximately 400 and 40 μm). The capillary pressure and permeability of the bi-porous Al were evaluated and compared with those of mono-porous Al fabricated by the space holder method. Increasing the porosity of the mono-porous Al improved the permeability but reduced the capillary pressure because of better-connected pores and increased effective pore size. The fraction of large and small pores in the bi-porous Al was successfully controlled under a constant porosity of 70%. The capillary pressure of the bi-porous Al with 40% large and 30% small pores was higher than the mono-porous Al with 70% porosity without sacrificing the permeability. However, the bi-porous Al with other fractions of large and small pores did not exhibit properties superior to the mono-porous Al. Thus, accurately controlling the fractions of large and small pores is required to enhance the capillary performance by introducing the bi-porous structure.

DOI： 10.3390/ma17194729

Web of Science

PubMed

researchmap

Variation in microstructural features of melt-pool structure in laser powder bed fused Al–Fe–Cu alloy at elevated temperatures

Yue Cheng, Takanobu Miyawaki, Wenyuan Wang, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato

Journal of Materials Research and Technology Vol. 32 page： 4048 - 4058 2024.9

Thermal stability of refined Al<inf>6</inf>(Fe, Mn) phase formed in laser powder bed fusion process

Wenyuan Wang, Yifan Xu, Misaki Deguchi, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato, Masatoshi Mitsuhara, Hideharu Nakashima

Journal of Alloys and Compounds Vol. 992 2024.7

Publishing type：Research paper (scientific journal)

The addition of Mn in Al–Fe alloys stabilizes the Al6Fe metastable phase (orthorhombic structure, oC28) owing to the partial occupation of Fe sublattice sites by Mn atoms (formation of Al6(Fe, Mn) phase), thereby achieving superior high-temperature strength of Al–Fe–Mn ternary alloys that are manufactured via laser powder bed fusion (L-PBF) process. This study aimed to fundamentally understand the thermal stability of the refined Al6(Fe, Mn) phase formed in the L-PBF fabricated Al–2.5%Fe–2%Mn alloy in terms of a thermodynamic approach and the kinetics of morphological changes in the Al6(Fe, Mn) phase at elevated temperatures ranging from 200 to 500 ℃. The L-PBF processed samples showed a high hardness of approximately 125 HV due to the formation of numerous dispersoids of the Al6(Fe, Mn) phase with sizes of several tens of nanometers in the α-Al matrix containing concentrated solute elements of Fe and Mn. The hardness and microstructure were almost unchanged even after exposure to a high temperature of 200 ℃ for an extended period of 1000 h. Upon exposure to 300 ℃, nucleation and growth of the Al6(Fe, Mn) phase occurred locally, particularly at grain boundaries in the α-Al matrix. Such a local growth contributed to a reduction in hardness upon thermal exposure. Simultaneously, numerous nanoscale precipitates were formed in the α-Al matrix, resulting in a suppressed reduction in hardness. Contrary to the result of the thermodynamic calculations, the θ-Al13Fe4 phase was scarcely found even after long-term exposure to 500 ℃. The θ-phase formation was accompanied by the dissolution of the refined Al6Fe metastable phase for strengthening, which significantly reduced the hardness during thermal exposure. The suppressed θ-phase formation could be associated with the thermodynamically stable Al6(Fe, Mn) phase developed during the L-PBF process, which predominantly contributed to the high microstructural stability of the L-PBF fabricated Al–Fe–Mn alloy at elevated temperatures.

DOI： 10.1016/j.jallcom.2024.174593

Web of Science

Scopus

researchmap

Elucidating dominant flow channel size for capillary performance of open-cell porous wicks Reviewed

Hongfei Shen, Asuka Suzuki, Naoki Takata, Makoto Kobashi

International Journal of Heat and Mass Transfer Vol. 223 page： 125217 - 125217 2024.5

Four-dimensional electrochemical impedance spectroscopy: Role of microstructure on corrosion behaviour of Al-Si alloys additive-manufactured by laser powder bed fusion Reviewed

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

CORROSION SCIENCE Vol. 232 2024.5

Effect of Cr content on thermally activated deformation in single-crystal micropillars of Fe-Cr binary alloys Reviewed

Zhu, TQ; Takata, N; Kim, D; Kobashi, M; Yoshino, M; Tsukamura, M

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING Vol. 900 2024.5

In-Situ SEM Observation and DIC Strain Analysis for Deformation and Cracking of Hot-Dip ZnMgAl Alloy Coating Reviewed

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

CORROSION SCIENCE AND TECHNOLOGY-KOREA Vol. 23 ( 2 ) page： 113 - 120 2024.4

Microstructural origins of high strength of Al–Si alloy manufactured by laser powder bed fusion: In-situ synchrotron radiation X-ray diffraction approach Reviewed

Naoki Takata, Mulin Liu, Masahiro Hirata, Asuka Suzuki, Makoto Kobashi, Masaki Kato, Hiroki Adachi

Journal of Materials Science and Technology Vol. 178 page： 80 - 89 2024.4

Language：English Publishing type：Research paper (scientific journal)

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

Web of Science

Scopus

researchmap

CALPHAD-aided design of high-strength Al-Si-Mg alloys for sufficient laser powder bed fusion processability Reviewed

Yuki Otani, Keito Saki, Naoki Takata, Asuka Suzuki, Makoto Kobashi, Masaki Kato

Journal of Alloys and Compounds Vol. 977 page： 173449 - 173449 2024.3

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 Reviewed

Dasom Kim, Naoki Takata, Hiroki Yokoi, Asuka Suzuki, Makoto Kobashi

Journal of Materials Research and Technology Vol. 29 page： 1535 - 1541 2024.3

Laser-beam powder bed fusion of Al-Fe-Cu alloy to achieve high strength and thermal conductivity Reviewed

Cheng, Y; Miyawaki, T; Wang, WY; Takata, N; Suzuki, A; Kobashi, M; Kato, M

ADDITIVE MANUFACTURING LETTERS Vol. 8 page： 100191 2024.2

Al-Si 合金中のSi 含有量による炭素繊維／溶湯界面の化合物制御 Reviewed

古川雄一, 冨田高嗣, 三輪拓海, 鈴木飛鳥, 高田尚記, 小橋眞

鋳造工学 page： 68 - 72 2024.2

　 PREV - NEXT 　

<KOBASHI, Makoto>

Papers - KOBASHI, Makoto