Papers by Author: Mitsuaki Furui

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Authors: Mitsuaki Furui, Shouyou Sakashita, Shougo Suzuki, Tetsuo Aida, Yuusuke Ishisaka, Masayuki Yamamoto, Masayuki Ohta
Abstract: We have proposed a new extrusion process functionally combined with torsion. Extrusion-torsion simultaneous processing is a very attractive technique for fabricating a rod-shape material with high strength and excellent workability. To improve the hardness, the aging treatment was performed with AZ91D magnesium alloy screw thread-rolled at room temperature using extrusion-torsion simultaneous processing. The distribution of hardness from the tip to center in as thread-rolled screw was modified to uniform distribution by the isothermal aging treatment at 423 K for 460.8 ks. The peak hardness was not depended on the working temperature and rotation speed during extrusion-torsion simultaneous processing. β-Mg17Al12 precipitates are obviously grown in as peak-aged condition comparing with as thread-rolled condition.
Authors: Masahiro Shinsen, Mitsuaki Furui, Susumu Ikeno, Takekazu Nagae
Abstract: In present work, bar samples of pure copper and Cu-Zn alpha single phase alloys setting 20mm in diameter and 150mm in length processed by torsion in the rotation speed to 1rpm every 60° twist angles. Then, deformed samples were researched microstructure and their characteristics. Microstructures of non-deformation samples were isometric, however, deformed samples streaky. Elements of bar drawn 10×10mm mesh were developed parallelogram. It was trend angle of between stretchable direction in microstructures and torsion axis increased more torsion angles. It was coincident with between the angle and deformed direction of microstructures. Shear strain was calculated by twist angle by theoretical formula. Their value corresponded rough with measurement from mesh variation. Pure copper and Cu-Zn alpha phase alloys were similar deformation microstructure, but fracture twist angle in copper was more than Cu-Zn alloys, and it was trend fracture angle had decreased as concentration of Zn increased. This trend was difference of fracture elongation obtained in tensile test.
Authors: Yuhei Ebata, Mitsuaki Furui, Susumu Ikeno, Katsuya Sakakibara, Seiji Saikawa
Abstract: In this study, age-hardening behavior of Mg-Xmass%Al alloys (X=3, 4.5, 6, 7.5 and 9mass%) were investigated by Vickers hardness measurement and optical microscopic observation. Each alloy was solution-treated and then isothermal-aged at 473, 498 and 523K. In the case of aluminum content less than 6mass%, Mg-3mass%Al and Mg-4.5mass%Al alloys, occurred insignificant age hardening. In the case of aluminum content higher than 6mass%, Mg-6mass%Al, Mg-7.5mass%Al and Mg-9mass%Al alloys, occurred remarkable age hardening. For each aging temperature, with heighten aluminum content, increase the value of maximum hardness and shorten time to maximum hardness. Mean hardness of discontinuous precipitation during aging increased with lower aging temperature and higher aluminum content. Furthermore, over-aged microstructure of Mg-Al system alloys differed from aluminum content or aging temperature.
Authors: H. Takano, Mitsuaki Furui, Susumu Ikeno, Tomoyasu Yamaguchi, Seiji Saikawa
Abstract: Our recent studies showed that continuous and cellular precipitates are covered with the whole of crystal grain in age hardable AM60 magnesium alloy cast into permanent molds, which have the average grain size of 75-85μm. Also, continuous precipitation is generated nearby grain boundary in the same alloys cast into sand molds, which have the average grain size of 138-147μm. It’s thought that permanent mold castings have the age hardening behavior of intragranular precipitation participation type that is influenced by continuous precipitates. It’s also thought that sand mold castings have the age hardening behavior of grain boundary participation type that is influenced by cellular precipitates. In this study, AM60 magnesium alloy with larger grain size was used to detect the grain size dependence of microstructure and aging behavior. In the microstructure of as-cast condition, the larger the grain size, it was shown that the none-equilibrium crystallized β phase with eutectic reaction during the solidification between liquidus and solidus temperatures becomes large-size. In the age hardening curves, the peak hardness values become higher with decreasing of grain size.
Authors: Shunsuke Saito, Satoshi Sunada, Mitsuaki Furui, Susumu Ikeno, Seiji Saikawa
Abstract: The corrosion behavior of Mg-6mass%Al alloy with different microstructure conditions was studied by electrochemical method in Na2SO4 and NaCl solutions. A measurement of polarization curves was carried out in order to investigate the fundamental electrochemical characteristics. Electrochemical impedance spectroscopy was carried out to discuss the corrosion characteristics that were obtained from polarization curves. Electrochemical measurements were carried out with as-cast, as solution-treated and two kinds of aged specimens, respectively. For measurement of polarization curves, the apparent difference was exhibited in behavior showing the pitting corrosion by difference of solutions. In all specimens, the corrosion current density which occurred in four kinds of specimens was higher in the NaCl solution than in Na2SO4 solution.
Authors: Shouhei Shimizu, Mitsuaki Furui, Hiroshi Anada
Abstract: It makes use of that excellent nature, high purity aluminum is being used as a function material in the electron, the high technology industry and information. Generally that material is molded as a slab, and processed through such as metal rolling is given after that, and it is being made. It is increase demand that it use for condenser. Condenser capacity is increase by making a (100) oriented cube texture crystal. It is known effective to increase a solid solubility of iron to aluminum that make increase the condenser capacity. Therefore, the cooling rate of Al-10,100 and 1000ppm content Fe was controlled by single roller equipment. Research was done about the relations of the amount of solid solubility of iron to aluminum and the cooling rate. It is result that the amount of solid solubility of iron to aluminum becomes 800ppm at the cooling rate of 2×103 K/s. When the cooling rate rises, the amount of solid solubility increases. The change appears in the separation thing as well because the amount of iron changes by this when the cooling rate is high. When iron is solid solubled in aluminum, it is bigger than the case of solid solubility formed by other general metal elements. Hardness is four times rose more than pure aluminum by solid solubility of iron to aluminum about 800ppm.
Authors: Mitsuaki Furui, Susumu Ikeno, Seiji Saikawa
Abstract: It is well-known that age hardening occurs in Mg-Al system alloys, when the alloy containing aluminum exceeds 6mass%. This precipitation reaction depends on aluminum content and aging temperature. The aging behavior in AZ91 magnesium alloy was investigated and it is the subject of this paper. However, for the Mg-Al system alloys, the influence of aluminum content on aging hardening characteristics has not been researched in detail so far. In this study, continuous and discontinuous precipitations during aging in Mg-Al system alloys cast into sand and iron molds were investigated by means of hardness measurement and microstructure observation with optical microscopy and transmission electron microscopy. Variation of hardness with aging was found to be caused mainly by the discontinuous precipitation along the grain boundaries from the composite rule in hardness. In iron mold castings, It was found that the variation of hardness with aging was found to be caused mainly by the continuous precipitation inside the crystal grain.
Authors: Hiroshi Yamada, Mitsuaki Furui, Susumu Ikeno, Yukio Sanpei, Katsuya Sakakibara, Seiji Saikawa
Abstract: AM60 magnesium alloy castings gave the solution treatment at 688K for 86.4ks. After that, aging treatment was carried out at three temperatures of 473, 498 and 523K. The age hardening curve obtained, hardness of all the specimens in the condition of peak aging was increased by decreasing the aging temperature. In the condition of long aging time, a cellular precipitation grows up from grain boundary to crystal grain. Fine cellular precipitation and intergranular precipitation obviously occurs at the lower aging temperature.
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