Papers by Author: Eiichi Sato

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Authors: Eiichi Sato, H. Morioka, Kazuhiko Kuribayashi, D. Sundararaman
459
Authors: Shinya Kamimura, Koichi Kitazono, Eiichi Sato, Kazuhiko Kuribayashi
Abstract: A new application of superplasticity was proposed in the manufacturing process of metal foams. Preform sheets were manufactured using superplastic 5083 aluminum alloy sheets through accumulative roll-bonding (ARB) process. Microcellular aluminum foam plates with 50% porosity were produced through solid-state foaming under the superplastic condition. The cell shape was oblate spheroid, which is effective to reduce the thermal conductivity. The present aluminum foam plates have a potential as an excellent heat insulator.
3021
Authors: Masayuki Tsukada, Eiichi Sato, Kazuhiko Kuribayashi
Abstract: Fracture behavior under multiaxial stress state of polycrystalline alumina was studied from the view point of an artificial crack propagation and fracture from a natural flaw. The former was studied by mixed-mode fracture toughness tests; asymmetric four-point bending and diametral compression techniques were carried out using precracked and notched specimens. The latter was studied by biaxial fracture tests in compression and torsion loading; multiaxial fracture statistics was applied to the measured fracture envelope. The ratio KIIC/KIC obtained from the biaxial tests was higher than that obtained by the mixed-mode fracture toughness tests. It revealed that the fracture from an artificial flaw does not simulate the fracture from a naturall flaw in polycrystalline ceramics.
1329
Authors: Koichi Kitazono, Eiichi Sato
Abstract: Aluminum foams having extremely low densities offer a large potential for lightweight structural materials. New manufacturing process without expensive aluminum alloy powder has been developed using conventional bulk aluminum alloy sheets. Preform plate containing blowing agent particles is first manufactured through accumulative roll-bonding (ARB) process. By heating the preform plate, closed-cell aluminum foams having various porosity and cell morphology are produced. It was revealed that ARB processing condition is significantly important to produce suitable aluminum foam with high porosity and uniform pore distribution. Present manufacturing process also possesses a potential to apply to many other metal and alloy foams.
433
Authors: Keita Sekiguchi, Hiroshi Masuda, Hirobumi Tobe, Eiichi Sato
Abstract: A new class of superplastic titanium alloy, Ti–4.5Al–2.5Cr–1.2Fe–0.1C–0.3Cu–0.3Ni, was deformed at 1073 K with strain rates of 1×10−4–1×10−1 s−1, and microstructures in the condition between superplastic regions II and III (= 1×102 s−1) were observed using scanning electron microscope and electron back-scattered diffraction. Continuous dynamic recrystallization was observed, resulting in grain refinement both in α and β phases. The grain size decreased significantly in α phase at the early stage of the deformation and in β phase at the later stage. In the recrystallized microstructure, the major sub-boundaries formed perpendicularly to slip directions <11−20> in α phase and parallel to slip planes {110} in β phase, which might be caused by the difference in the symmetry of the crystal structures.
126
Authors: Eiichi Sato, Hiroshi Masuda, Yoshito Sugino, Shigeharu Ukai
Abstract: High-temperature tensile deformation was performed using an oxide-dispersionstrengthened (ODS) ferritic steel,, which has grain structure largely elongated and aligned in one direction, in the perpendicular direction. In the superplastic region II, two-dimensional grain boundary sliding (GBS) was achieved, in which the material did not shrink in the grain-axis direction and grain-boundary steps appeared only in the surface perpendicular to the grain axis. In this condition, a classical grain switching event was observed. Using kernel average misorientation maps drawn with SEM/EBSD, dominant deformation mechanisms and accommodation processes for GBS were examined in the different regions. Cooperative grain boundary sliding, in which only some of grain boundaries slide, was also observed.
43
Authors: Tomoyasu Yamada, Hisamune Tanaka, Eiichi Sato, Itaru Jimbo
Abstract: The primary creep behavior at ambient temperature of typical h.c.p., b.c.c. and f.c.c. metals and alloys of annealed state was surveyed and the deformation mechanism of CP-Ti was discussed through transmission electron microscopy. Only h.c.p. metals and alloys demonstrated significant creep at ambient temperature. Arrays of straight screw dislocations of b=1/2<2110> and <2110> direction were observed in the crept CP-Ti.
577
Authors: M. Valsan, Eiichi Sato, Kazuhiko Kuribayashi
475
Authors: Koichi Kitazono, Eiichi Sato, Kazuhiko Kuribayashi
541
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