The Experts below are selected from a list of 504 Experts worldwide ranked by ideXlab platform
Ke Yang - One of the best experts on this subject based on the ideXlab platform.
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Lath Boundary thin-film martensite in acicular ferrite ultralow carbon pipeline steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Ming-chun Zhao, Toshihiro Hanamura, Hai Qiu, Ke YangAbstract:Modern pipeline technology for the production of oil and gas pipeline steels is aiming at achieving high strength and toughness. An experimental acicular ferrite (AF) ultralow carbon pipeline steel was investigated to correlate the microstructural characteristic of the steel to its strength and toughness behavior at the present work. The experimental result indicated that the AF ultralow carbon pipeline steel can well satisfy the high strength and toughness requirement. By comparing with the AF conventional carbon pipeline steel, the AF ultralow carbon pipeline steel possesses much higher additional toughness. In addition to having the conventional microstructural characteristics of the AF microstructure, the AF ultralow carbon pipeline steels were observed to present a layer of thin martensite film at the Lath boundaries of the AF microstructure. Increasing in toughness of the AF ultralow carbon pipeline steel was analyzed to be related to the Lath Boundary thin films as well as its microstructural characteristics.
Ming-chun Zhao - One of the best experts on this subject based on the ideXlab platform.
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Lath Boundary thin-film martensite in acicular ferrite ultralow carbon pipeline steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Ming-chun Zhao, Toshihiro Hanamura, Hai Qiu, Ke YangAbstract:Modern pipeline technology for the production of oil and gas pipeline steels is aiming at achieving high strength and toughness. An experimental acicular ferrite (AF) ultralow carbon pipeline steel was investigated to correlate the microstructural characteristic of the steel to its strength and toughness behavior at the present work. The experimental result indicated that the AF ultralow carbon pipeline steel can well satisfy the high strength and toughness requirement. By comparing with the AF conventional carbon pipeline steel, the AF ultralow carbon pipeline steel possesses much higher additional toughness. In addition to having the conventional microstructural characteristics of the AF microstructure, the AF ultralow carbon pipeline steels were observed to present a layer of thin martensite film at the Lath boundaries of the AF microstructure. Increasing in toughness of the AF ultralow carbon pipeline steel was analyzed to be related to the Lath Boundary thin films as well as its microstructural characteristics.
M X Huang - One of the best experts on this subject based on the ideXlab platform.
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an approach to define the effective Lath size controlling yield strength of bainite
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Olivier Bouaziz, Carla Oberbillig, M X HuangAbstract:Abstract A fully bainitic microstructure with negligible carbide precipitation is obtained in two ultra-low carbon steels. The size and misorientation of bainite Laths are analysed by Electron Back Scattering Diffraction (EBSD). It is found that the yield stress of bainite is proportional to the inverse Lath size defined with low Boundary misorientation (2–7°). This can be explained by a theory predicting the flow stress of deformed metals, assuming that both Lath Boundary and dislocation cell Boundary have similar capability of being dislocation obstacles.
Shushi Ikeda - One of the best experts on this subject based on the ideXlab platform.
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effects of aluminum on delayed fracture properties of ultra high strength low alloy trip aided steels
Isij International, 2008Co-Authors: Tomohiko Hojo, Kohichi Sugimoto, Youichi Mukai, Shushi IkedaAbstract:To improve the delayed fracture strength of ultra high-strength low alloy TRIP-aided steels with bainitic ferrite matrix (TBF steels), the effects of aluminum content on hydrogen absorption behavior and delayed fracture properties of 0.2%C–0.2–1.5%Si–1.5%Mn TBF steel were investigated. When aluminum was added to the TBF steel, the diffusible hydrogen increased. It was expected that the hydrogen was charged not only in retained austenite films but also on Lath Boundary. Delayed fracture strength of TBF steels containing aluminum were significantly increased, compared with conventional TBF steel. This was mainly caused by (1) suppression of the stress-assisted martensite transformation resulting from the stabilized or carbon-enriched retained austenite, (2) hydrogen trapping to refined interLath retained austenite films and Lath Boundary, and (3) relaxation of localized stress concentration by TRIP effect of the retained austenite.
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effects of aluminum on delayed fracture properties of ultra high strength low alloy trip aided steels
Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2007Co-Authors: Tomohiko Hojo, Kohichi Sugimoto, Youichi Mukai, Shushi IkedaAbstract:To improve the delayed fracture strength of ultra high-strength low alloy TRIP-aided steels with bainitic ferrite matrix (TBF steels), the effects of aluminum content on hydrogen absorption behavior and delayed fracture properties of 0.2%C-0.5∼1.5%Si-1.5%Mn TBF steel were investigated. When aluminum was added to the TBF steel, the diffusible hydrogen increased. It was expected that the hydrogen was charged not only in retained austenite films but also on Lath Boundary. Delayed fracture strength of aluminum bearing TBF steels was significantly increased, compared with conventional TBF steel. This was mainly caused by (1) suppression of the stress-assisted martensite transformation resulting from the stabilized or carbon-enriched retained austenite, (2) hydrogen trapping to refined interLath retained austenite films and Lath Boundary, and (3) relaxation of localized stress concentration by TRIP effect of the retained austenite.
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ductility and formability of newly developed high strength low alloy trip aided sheet steels with annealed martensite matrix
Isij International, 2002Co-Authors: Kohichi Sugimoto, Akinobu Kanda, Ryo Kikuchi, Shunichi Hashimoto, Takahiro Kashima, Shushi IkedaAbstract:Formable high-strength low-alloy TRIP-aided sheet steels with annealed martensite matrix or "TRIP-aided annealed martensitic steel" were developed for automotive applications. The steels possessed a large amount of plate-like retained austenite along annealed martensite Lath Boundary, whose stability against the strain-induced transformation was higher than that of the conventional "TRIP-aided dual-phase steel" with polygonal ferrite matrix. In a tensile strength range between 600 and 1000 MPa, the TRIP-aided annealed martensite steels exhibited a superior large elongation and reduction of area. In addition, they possessed the same excellent stretch-flangeability and bendability as "TRIP-aided bainitic steel" with bainitic ferrite matrix. These properties were discussed by matrix structure, a strength ratio of second phase to matrix, retained austenite stability, internal stress and so on.
Kohichi Sugimoto - One of the best experts on this subject based on the ideXlab platform.
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effects of aluminum on delayed fracture properties of ultra high strength low alloy trip aided steels
Isij International, 2008Co-Authors: Tomohiko Hojo, Kohichi Sugimoto, Youichi Mukai, Shushi IkedaAbstract:To improve the delayed fracture strength of ultra high-strength low alloy TRIP-aided steels with bainitic ferrite matrix (TBF steels), the effects of aluminum content on hydrogen absorption behavior and delayed fracture properties of 0.2%C–0.2–1.5%Si–1.5%Mn TBF steel were investigated. When aluminum was added to the TBF steel, the diffusible hydrogen increased. It was expected that the hydrogen was charged not only in retained austenite films but also on Lath Boundary. Delayed fracture strength of TBF steels containing aluminum were significantly increased, compared with conventional TBF steel. This was mainly caused by (1) suppression of the stress-assisted martensite transformation resulting from the stabilized or carbon-enriched retained austenite, (2) hydrogen trapping to refined interLath retained austenite films and Lath Boundary, and (3) relaxation of localized stress concentration by TRIP effect of the retained austenite.
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effects of aluminum on delayed fracture properties of ultra high strength low alloy trip aided steels
Tetsu To Hagane-journal of The Iron and Steel Institute of Japan, 2007Co-Authors: Tomohiko Hojo, Kohichi Sugimoto, Youichi Mukai, Shushi IkedaAbstract:To improve the delayed fracture strength of ultra high-strength low alloy TRIP-aided steels with bainitic ferrite matrix (TBF steels), the effects of aluminum content on hydrogen absorption behavior and delayed fracture properties of 0.2%C-0.5∼1.5%Si-1.5%Mn TBF steel were investigated. When aluminum was added to the TBF steel, the diffusible hydrogen increased. It was expected that the hydrogen was charged not only in retained austenite films but also on Lath Boundary. Delayed fracture strength of aluminum bearing TBF steels was significantly increased, compared with conventional TBF steel. This was mainly caused by (1) suppression of the stress-assisted martensite transformation resulting from the stabilized or carbon-enriched retained austenite, (2) hydrogen trapping to refined interLath retained austenite films and Lath Boundary, and (3) relaxation of localized stress concentration by TRIP effect of the retained austenite.
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ductility and formability of newly developed high strength low alloy trip aided sheet steels with annealed martensite matrix
Isij International, 2002Co-Authors: Kohichi Sugimoto, Akinobu Kanda, Ryo Kikuchi, Shunichi Hashimoto, Takahiro Kashima, Shushi IkedaAbstract:Formable high-strength low-alloy TRIP-aided sheet steels with annealed martensite matrix or "TRIP-aided annealed martensitic steel" were developed for automotive applications. The steels possessed a large amount of plate-like retained austenite along annealed martensite Lath Boundary, whose stability against the strain-induced transformation was higher than that of the conventional "TRIP-aided dual-phase steel" with polygonal ferrite matrix. In a tensile strength range between 600 and 1000 MPa, the TRIP-aided annealed martensite steels exhibited a superior large elongation and reduction of area. In addition, they possessed the same excellent stretch-flangeability and bendability as "TRIP-aided bainitic steel" with bainitic ferrite matrix. These properties were discussed by matrix structure, a strength ratio of second phase to matrix, retained austenite stability, internal stress and so on.
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retained austenite characteristics and stretch flangeability of high strength low alloy trip type bainitic sheet steels
Isij International, 2002Co-Authors: Kohichi Sugimoto, Kiyotaka Nakano, Sungmoo Song, Takahiro KashimaAbstract:Retained austenite characteristics and stretch-flangeability in low alloy TRIP type bainitic sheet steels with different silicon and manganese contents were investigated for automotive applications. As increasing silicon and manganese contents, an initial volume fraction of retained austenite film along bainitic ferrite Lath Boundary was increased in accompany with a decrease in the carbon concentration. An excellent stretch-flangeability was completed in the steels containing a small amount of stable retained austenites (i.e., volume fraction of 2-4 vol% and carbon concentration of more than 1.0 mass%). This was caused by small surface damage on hole-punching and effective strain-induced transformation plasticity of untransformed retained austenite on hole-expanding. When austempered at temperatures less than M s of the steel after intercritical annealing, further superior stretch-flangeability was achieved due to absence of initial blocky martensite, resulting from developments of long shear section and severe plastic flow and difficult void-initiation on hole-punching.
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effects of second phase morphology on retained austenite morphology and tensile properties in a trip aided dual phase steel sheet
Isij International, 1993Co-Authors: Kohichi Sugimoto, Masahiro Misu, Mitsuyuki Kobayashi, Hidenori ShirasawaAbstract:The relationship between second phase morphology and retained austenite morphology and the influences of these two kinds of morphology on tensile properties of a 0.17C-1.41Si-2.00Mn (mass%) TRIP-aided dual-phase steel have been investigated in a temperature range between 20 and 400°C.A large amount of fine retained austenite was obtained when the second phase morphology was "a network structure" or "an isolated fine and acicular one." The retained austenite particles were nearly isolated in the ferrite matrix away from bainite islands and were moderately stable. On the other hand, "an isolated coarse structure" of second phase resulted in a small amount of more stable retained austenite film along bainite Lath Boundary.The influence of second phase morphology on the flow curve significantly differed from that of a conventional ferrite-martensite dual-phase steel. Isolated retained austenite particles lowered the flow stress, and resultantly reduced the effects of second phase morphology (i.e., network effect or fine grain size effect) on flow stress. However, the isolated retained austenite particles enhanced effectively the ductility, particularly at 50-100°C, due to the moderate strain induced transformation. On the other hand, retained austenite films along bainite Lath Boundary scarcely influenced on tensile properties of the steel. These results were discussed on the basis of a continum theory.
