Natsuko Sugiura
Nippon Steel
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Featured researches published by Natsuko Sugiura.
Materials Science Forum | 2010
Hiroyuki Kawata; Kunio Hayashi; Natsuko Sugiura; Naoki Yoshinaga; Manabu Takahashi
Lath-shaped upper bainite structures play a very important role in many high-strength steels (HSSs) and ultra high-strength steels (UHSSs). Although bainite transformation is strongly affected by the initial structure, the effect of the second phase in a multi-phase structure is yet to be clearly understood. It is significant for the advancement of UHSS to study this effect. The aim of this study is to clarify the effect of martensite, which forms before bainite, in Fe-0.2C-8Ni alloy. The bainite transformation from an austenite and martensite dual-phase structure is faster than that from single-phase austenite and the nucleation of bainitic ferrite laths are accelerated around martensite. This effect of martensite on bainite kinetics is equivalent to that of polygonal ferrite when their volume fractions are almost the same. This suggests that the boundary between martensite and austenite is a prior nucleation site of bainitic ferrite. Martensite also affects the crystallographic features of bainite. The orientations of bainitic ferrite laths tend to belong to the same block with martensite adjacent. This tendency intensifies with an increase of the transformation temperature of bainite, resulting in the formation of huge blocks consisting of bainitic ferrite and martensite laths at high temperatures (693K and 723K). In contrast, at a low temperature (643K), bainitic ferrite laths belong to same packet as martensite and have several orientations. This change of crystallographic features with transformation temperature can explain with the driving force of the nucleation of bainitic ferrite.
Materials Science Forum | 2011
Natsuko Sugiura; Naoki Yoshinaga
Electro-deposited pure iron has a quite sharp and isotropic <111>//ND fiber texture and a needle-shaped grain elongated in ND. This pure iron shows an r-value exceeding 7, which is difficult to explain from the texture alone. In this study the deformation behavior of electro-deposited pure iron was investigated to reveal the mechanism behind the extremely high r-value. The post-deformation surface slip lines indicated that the particular <110> plane slips, which are perpendicular to ND, exclusively act in the specimen. The tensile deformation caused by this slip system does not require any decrease in thickness, hence the extraordinary high r-value is mainly attributable to this limitation of the active slip system. Presumably, the needle-shaped microstructure affected the limitation of the slip system.
Materials Science Forum | 2014
Naoki Yoshinaga; D Vanderschueren; Leo Kestens; Kohsaku Ushioda; Natsuko Sugiura
The cold rolling and annealing texture formation has been investigated in electro deposited pure iron which has an extremely sharp and isotropic <111>//ND fiber. Regardless of cold rolling reduction, {111}<112> intensified texture is formed after cold rolling. Similar texture remains after recrystallization in 65% cold rolled material while {111}<110> type texture forms in 80% and 90% cold rolled ones. The recrystallized grains at the stage of 5% recrystallization have {111}<112> orientation in 65% cold rolled sheet, whereas {111}<110> is observed in 80% cold rolled one. From this aspect, it is considered that the nucleation orientation plays an important role in the recrystallization texture formation. In the meanwhile, the growth of the recrystallized nuclei is also supposed to affect the recrystallization texture formation. The nuclei with {111}<112> orientation in lightly cold rolled sheet are easier to consume the deformed matrix than they do in heavily cold rolled sheets because their frequency to encounter a deformed grain with nearly the same orientation is much smaller in lightly cold rolled specimen, which can result in a large mobility for growth. Cross cold rolling makes cold rolling texture rather homogeneous <111>//ND fiber, which gives rise to an almost homogeneous <111>//ND fiber after annealing.
Advanced Materials Research | 2014
Natsuko Sugiura; Naoki Yoshinaga
Electro-deposited pure iron has a very sharp and isotropic <111>//ND fiber texture and a needle shaped grain elongated in the ND. This pure iron exhibits an r-value of over 7, and it is difficult to explain such a high r-value only from the texture. Specific {110} plane slips, which are perpendicular to the sheet surface, exclusively act in this material and this limitation of the active slip system is the main mechanism behind the extraordinarily high r-value. Thus, tensile deformation by this slip system doesn’t require a decrease in thickness. In this study, the mechanism of this slip system limitation is investigated. Because both the {110} slip plane and grain boundary are perpendicular to the sheet surface, the slip plane can easily connect with adjacent grains. This good continuity of slip plane with adjacent grain may have an influence on the choice of slip system.
Archive | 2001
Natsuko Sugiura; Naoki Yoshinaga; Manabu Takahashi; Tohru Yoshida
Archive | 2002
Tatsuo Yokoi; Teruki Hayashida; Natsuko Sugiura; Takaaki Nakamura; Takehiro Nakamoto
Archive | 2001
Naoki Yoshinaga; Nobuhiro Fujita; Manabu Takahashi; Yasuhiro Shinohara; Tohru Yoshida; Natsuko Sugiura
Archive | 2001
Natsuko Sugiura; Manabu Takahashi; Naoki Yoshinaga; 直樹 吉永; 夏子 杉浦; 学 高橋
Isij International | 2010
Toshio Ogawa; Naoki Maruyama; Natsuko Sugiura; Naoki Yoshinaga
Archive | 2005
Natsuko Sugiura; Naoki Yoshinaga; Shunji Hiwatashi; Manabu Takahashi; Koji Hanya; Nobuyoshi Uno; Ryoichi Kanno; Akihiro Miyasaka; Takehide Senuma