研究者詳細 - 髙田　尚記

論文 - 髙田　尚記

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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

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

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

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

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

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

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

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

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

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 招待有り査読有り国際誌

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

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 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

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

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 Open Access

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

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

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

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

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

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 Open Access

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

Effect of heat treatment on solute Si content in Al-12%Si alloy additive-manufactured by laser powder bed fusion 査読有り Open Access

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

Keikinzoku/Journal of Japan Institute of Light Metals 72 巻 ( 5 ) 頁： 178 - 184 2022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：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

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

Observation of compressive deformation behavior of Al-12%Si alloy lattice structures additive-manufactured by laser powder bed fusion using mechanical stress-induced luminescent material 査読有り Open Access

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

Keikinzoku/Journal of Japan Institute of Light Metals 72 巻 ( 5 ) 頁： 246 - 250 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

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 Al5Mg3.5Zn (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 agehardening of these alloys at 300°C. The added Cu element partitioned into not only the T-Al6Mg11Zn11 phase but

DOI： 10.2320/matertrans.MT-L2021021

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

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

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