論文 - 徳永 透子
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SiAlONと耐熱合金のろう付け接合 査読あり
徳永透子, 越山将行, 黒川一哉, 大野宗一, 松浦清隆
日本金属学会誌 81 ( 3 ) 143 - 149 2017年
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Fabrication of Carbon Fiber Oriented Al–Based Composites by Hot Extrusion and Evaluation of Their Thermal Conductivity 査読あり
徳永 透子
Materials Transactions 58 ( 6 ) 938 - 944 2017年
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Fabrication of Al-coated Mg alloy sheet and investigation of its mechanical properties 査読あり
T. Tokunaga, M. Ohno, K. Matsuura
Journal of Functionally Graded Materials 30 1 - 4 2016年
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Grain Refinement and Ductility Improvement by Hot Extrusion Using a Heteromorphic Die with Small Holes 査読あり
Kaho Tomita, Toko Tokunaga, Munekazu Ohno, Kiyotaka Matsuura
MATERIALS TRANSACTIONS 57 ( 6 ) 927 - 934 2016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：JAPAN INST METALS
It has been shown using an Al-4.0mass% Cu alloy as a demonstration material that hot extrusion with the use of a specially-designed die leads to grain refinement and improvement in ductility. The specially-designed die is called in this study the heteromorphic die and it consists of two plates and one spacer. One plate is called the strain-giving die and has six small round holes of 5 mm in diameter, while the other plate is called the shape-giving die and has one big rectangular hole of 9 mm x 15 mm. The spacer separates these two plates at a distance of 10 mm and provides a space between them. The Al-Cu alloy billet was hot-extruded through the six small round holes of the strain-giving die to produce six thin round rods, and after filling the space between the two dies, the six rods passed together through the shape-giving die to form a thick rectangular bar or plate. Tensile tests of the plate were conducted at room temperature, and the results were compared with those of the un-extruded billet and the extruded plate produced by conventional hot extrusion method, that uses only the shape-giving die. The elongation values of the three different tensile specimens produced from (1) the un-extruded billet, (2) the plate extruded by the conventional method and (3) the plate extruded with the heteromorphic die were 21, 35 and 57%, respectively. Most significant elongation was found in the sample extruded with the heteromorphic die, which is most probably due to the finest grain structure observed in this sample. It is suggested that the recrystallization is induced by a large strain generated in the heteromorphic die due to the friction on the large contact area between the extruded metal and the die orifice wall of the strain-giving die."
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Al被覆Mg合金薄板材の作製およびその機械的性質の調査 査読あり
徳永透子, 大野宗一, 松浦清隆
Journal of Functionally Graded Materials 30 1 - 4 2016年
掲載種別：研究論文（学術雑誌）
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熱間押出法による炭素繊維配向制御Al基複合材料の作製およびその熱伝導率評価 査読あり
徳永透子, 高橋晃一, 大野宗一, 佐々木克彦, 今西輝光, 松浦清隆
日本金属学会誌 80 ( 10 ) 640 - 645 2016年
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Sensitivity analysis for thickness uniformity of Al coating layer in extrusion of Mg/Al clad bar 査読あり
Toko Tokunaga, Danuta Szeliga, Kiyotaka Matsuura, Munekazu Ohno, Maciej Pietrzyk
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 80 ( 1-4 ) 507 - 513 2015年09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：SPRINGER LONDON LTD
Although Mg alloys possess many attractive properties, the use of Mg alloys has been limited due to their extremely poor corrosion resistance. In the authors' previous study, they have developed a new process for Mg/Al cladding by hot extrusion with a convex die. In the extrusion process, it was found that the thickness uniformity of the Al coating layer can be controlled by changing the die angle. However, the optimal condition of the extrusion and the influences of extrusion parameters on the coating thickness uniformity remain unclear. In this study, therefore, the sensitivity analysis has been performed in order to evaluate the influences of extrusion parameters on the coating thickness uniformity. The sensitivities of the following five parameters were evaluated: (1) initial thickness of the coating material plate, (2) extrusion temperature, (3) ram speed, (4) die angle, and (5) ratio of simulated flow stress to the experimental one for pure Al. In order to perform the sensitivity analysis, the process for Mg/Al cladding was modeled. The results from the extrusion model fairly agree with the experimental results. Thus, it can be said that the present model of Mg/Al cladding process is reliable. From the sensitivity analysis, it was found that the initial thickness of the coating material plate and die angle influence on the uniformity most. The extrusion temperature, ram speed, and flow stress ratio do not have significant influences.
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多穴ダイスを組み合わせた異形ダイスによる熱間押出材の結晶粒微細化と高延性化 査読あり
富田花帆, 徳永透子, 大野宗一, 松浦清隆
日本金属学会誌 79 ( 4 ) 183 - 190 2015年
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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芯のある研究者を目指して
徳永透子
まてりあ 54 ( 12 ) 639 2015年
掲載種別：研究論文（学術雑誌）
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Physical and numerical modelling of backward extrusion of Mg alloy with Al coating 査読あり
Lukasz Madej, Toko Tokunaga, Kiyotaka Matsuura, Munekazu Ohno, Maciej Pietrzyk
CIRP ANNALS-MANUFACTURING TECHNOLOGY 64 ( 1 ) 253 - 256 2015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：ELSEVIER SCIENCE BV
Although Mg alloys possess many attractive properties, their use has been limited due to their poor corrosion resistance. Therefore, in the present paper a process for Al coating on Mg alloys by hot extrusion was investigated. Physical simulations confirmed capabilities of this process and Al coating on a Mg alloy was obtained. Prediction of microstructure evolution and determination of optimal process parameters were the objectives of the present numerical simulations. Cellular automata were used to reach the former goal, while for the latter goal optimization analysis was applied to find the best technological parameters. (C) 2015 CIRP.
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DUCTILITY IMPROVEMENT OF AL ALLOYS BY HETEROMORPHIC DIE EXTRUSION 査読あり
Kiyotaka Matsuura, Toko Tokunaga, Munekazu Ohno, Kaho Tomita
M2D2015: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON MECHANICS AND MATERIALS IN DESIGN 2063 - 2064 2015年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：INEGI-FEUP
It has been shown that hot extrusion with the use of a specially-designed die, which is called a heteromorphic die, leads to improvement in ductility of Al alloys. The heteromorphic die consists of two plates and one spacer. One plate is called a strain-giving die and has six holes of 5 mm in diameter, while the other plate is called a shape-giving die and has one rectangular hole of 9 mmx15 mm in side length. The spacer separates these plates at a distance of 10 mm and gives a space between them. The Al alloy billet was hot-extruded from the strain-giving die into the space between the two dies to produce six thin bars, and all the six bars passed together through the shape-giving die to become a thick rectangular bar. The rectangular bar produced by the present extrusion was tensile-tested at room temperature and the results were compared with those of the un-extruded billet and the bar produced by a conventional hot extrusion using only the shape-giving die. The elongations of the specimens made of the billet, the bar extruded by the conventional method and the one extruded using the present heteromorphic die were 21, 35 and 57 %, respectively. The largest elongation found in the sample extruded using the present heteromorphic die should be due to the fine recrystallized grain structure in that sample. It is suggested that the recrystallization is induced by a large strain generated in the present heteromorphic die due to the friction at the large contact area between the die hole wall and the alloy.
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SPARK PLASMA SINTERING OF alpha- AND beta-SiAlON 査読あり
Kiyotaka Matsuura, Toko Tokunaga
M2D2015: PROCEEDINGS OF THE 6TH INTERNATIONAL CONFERENCE ON MECHANICS AND MATERIALS IN DESIGN 803 - 804 2015年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：INEGI-FEUP
Combustion-synthesized Y-alpha-SiAlON and Ca-alpha-SiAlON powders have been consolidated by Spark Plasma Sintering (SPS) at 1300-1450 degrees C for 10min, and the mechanical properties of the consolidated bulk samples were investigated. XRD analysis revealed that alpha-SiAlON partially transforms into beta-SiAlON during the SPS and a bulk of alpha/beta-SiAlON mixture was obtained. The fraction of beta-SiAlON increases with the increase in sintering temperature and the alpha to beta transformation ratio is high for Y-alpha-SiAlON compared with Ca-alpha-SiAlON. The hardness of the consolidated bulk increases with sintering temperature and after reaching the peak at 1350 degrees C the hardness gradually decreases with temperature in both the cases of Y-alpha-SiAlON and Ca-alpha-SiAlON. The increase in hardness with temperature arises from increase in density of the sintered body, while the decrease in hardness results from grain growth due to high temperatures. The fracture toughness monotonically increases with temperature and does not show a peak for both SiAlONs, although Y-alpha-SiAlON always exhibits higher toughness than Ca-alpha-SiAlON. The higher toughness of the Y-alpha-SiAlON is attributable to its higher fraction of transformed beta-SiAlON, because the elongated shape of beta-SiAlON leads to prevention of crack propagation.
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Superplastic behavior of Al-coated Mg alloy sheet 査読あり
Toko Tokunaga, Kiyotaka Matsuura, Munekazu Ohno
JOURNAL OF ALLOYS AND COMPOUNDS 601 179 - 185 2014年07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 SCIENCE SA
An Al-coated Mg alloy sheet is fabricated by hot forging an Al-coated Mg alloy plate produced by hot extrusion of a Mg alloy billet together with an Al plate. The sheet consists of recrystallized fine grains both in the Mg alloy substrate and Al coating layer. A thin intermetallic compound layer of Al3Mg2 formed at the Al/Mg interface in the hot-extruded plate. The subsequent hot forging reduces the thickness of the intermetallic layer but induces cracks in the intermetallic compound. This sheet exhibits a large tensile elongation of 550% at 573 K and at a strain rate of 1.0 x 10 (3)s (1). Notably, a tensile test of an Al specimen exhibited only 40% elongation, while that of a Mg alloy specimen exhibited 800% elongation. It is suggested that the large elongation of Al as the coating layer on the Mg alloy is attributable to the good bonding of the Al coating layer and the Mg alloy substrate. The cracks in the intermetallic layer disappear during the tensile tests at elevated temperatures and no cracks are observed in the elongated specimens, which indicates growth of the intermetallic and reparation of the cracks occurred during the low strain-rate hot deformation of the Al-coated Mg alloy sheet. (C) 2014 Elsevier B.V. All rights reserved.
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Determination of the flow stress model of AZ80 Mg alloy 査読あり
Toko Tokunaga, Roman Kuziak, Kiyotaka Matsuura
Computer Methods in Materials Science 14 123 - 130 2014年
掲載種別：研究論文（学術雑誌）
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Corrosion resistance and tensile property of Al-coated Mg-Li alloy produced by hot extrusion 査読あり
Kaho Tomita, Kiyotaka Matsuura, Munekazu Ohno, Toko Tokunaga, Ruizhi Wu, Milin Zhang
Key Engineering Materials 641 69 - 80 2014年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：Trans Tech Publications Ltd
Al-coated Mg-Li alloy rods and plates having a homogeneous coating layer of 180μm in thickness have been produced by hot extrusion of Mg-Li alloy billets together with Al disks. The Al-coated Mg-Li alloy exhibits an excellent corrosion resistance in a weight-loss test with a 0.5 mass% HCl aqueous solution, and it has been revealed by a potentiometric corrosion test with a 3 mass% NaCl aqueous solution that the Al-coated Mg-Li alloy has the same electric potential as that of pure Al. Al-coated Mg-Li alloy sheets produced by hot forging of the extruded plates exhibits good elongation of 22 %, 40 % and 130 % at room temperature, 200 °C and 300 °C, respectively.
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Aluminum Coating on Magnesium-Based Alloy by Hot Extrusion and Its Characteristics 査読あり
Toko Tokunaga, Kiyotaka Matsuura, Munekazu Ohno
Mater. Trans. Vol. 53 ( No.6 ) 1034 - 1041 2012年
掲載種別：研究論文（学術雑誌）
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熱間押出法によるマグネシウム合金のアルミニウム被覆とその材質調査 査読あり
徳永透子, 松浦清隆, 大野宗一
日本金属学会誌 75 ( 11 ) 633 - 639 2011年11月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
