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Fabrication of Al-Coated Mg-Li Alloy Sheet and Investigation of Its Properties

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Acta Metallurgica Sinica(English Letters) 2019年第2期32卷 169-177页

作者： Tian-Long Zhang Toko Tokunaga Munekazu Ohno Mi-Lin Zhang kiyotaka matsuura Graduate School of Engineering Hokkaido University Faculty of Engineering Hokkaido University College of Materials Science and Chemical Engineering Harbin Engineering University

An Al-coated Mg-8 mass% Li alloy rectangular bar was fabricated by hot extrusion, and then, it was hot-rolled into a thin sheet. The Al coating was uniform in thickness and had good bonding with the substrate during all the processing. This Alcoated Mg–Li alloy exhibited a good corrosion resistance in a 0.5 mass% HCl aqueous solution. No intermetallic compound was observed at the Al/Mg–Li interface after the extrusion and the rolling. The Al-coated Mg–Li alloy sheet exhibited an elongation to fracture of 35% at room temperature at a strain rate of 0.001 s(-1)without any debonding between the coating and the substrate. When tensile tested at 573 K at 0.001 s(-1)in the air, the Al coating remained undamaged even until an elongation of about 150%. Further elongation generated cracks on the coating and the specimen fractured at an elongation of about 200%. In an Ar atmosphere, the specimen exhibited a fracture elongation of over 400% under the same conditions at 573 K at 0.001 s(-1), although a large number of cracks generated on the Al coating.

关键词： Mg–Li alloy Composite material Coating Mechanical properties Superplasticity

A Role of Vaporization of Metal Oxide in Formation of SiO2 Scale on Metal Disilicides

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A Role of Vaporization of Metal Oxide in Formation of SiO2 S...

Controlling of Abnormal Austenite Grain Growth in Banded Ferrite/Pearlite Steel by Cold Deformation

The Fourth International Conference on Physical and Numerical Simulation of Materials (ICPNS’2004)

作者： Kazuya Kurokawa Kenichi Ohsasa kiyotaka matsuura Center for Advance Research of Energy Conversion Materials Hokkaido University Kita 13 Nishi 8 Kita-ku Sapporo 060-8628 Japan. Division of Molecular Chemistry Graduate School of Engineering Hokkaido University Kita 13 Nishi 8 Kita-ku Sapporo 060-8628. Japan. Materials Science and Engineering Graduate School of Engineering Hokkaido University Kita 13 Nishi 8 Kita-ku. Sapporo 060-8628 Japan.

It is well known that some metal disilicides, for example MoSi2 and WSi2, show excellent oxidation resistance at high temperatures. Therefore, these disilicides are being considered as promising materials for applications in oxidizing environments at ultra-high *** excellent oxidation resistance of the disilicides is due to the formation of a protective SiO2 scale. When a metal oxide formed as an oxidation product possesses a high vapor pressure, the vaporization often plays an important role in the formation of a protective SiO2 scale. That is to say, as a consequent of simultaneous formation of metal and silicon oxides at an early stage of oxidation and subsequent evaporation of the metal oxide, only SiO2 may remain on the disilicide substrate. The vapor pressures of MoO3, V2O5, WO3, and Re2O7 are very high, and the high vapor pressure must be advantageous for forming a SiO2 *** the present study, oxidation tests of some disilicides, MoSi2, WSi2, VSi2, and ReSi1.75, were carried out in air at temperatures ranging from 773 to 1773 K. Based on the results, a relationship between vapor pressure of metal oxide and formation of SiO2 scale was clarified. Namely, when the vapor pressure of metal oxide reaches 10 Pa, a SiO2 scale forms on the disilicides. The vapor pressure of 10 Pa corresponds to about 473 K in Re2O7, 1073 K in MoO3. 1173 K in V2O5. and 1673 K in WO3.

关键词： Metal oxide SiO2 Vaporization

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Controlling of Abnormal Austenite Grain Growth in Banded Fer...

“第十届中国钢铁年会”暨“第六届宝钢学术年会”

作者： Xianguang Zhang kiyotaka matsuura Munekazu Ohno Goro Miyamoto Tadashi Furuhara Hokkaido University Institute for Materials Research Tohoku University Division of Materials Science and Engineering Faculty of EngineeringHokkaido University

Inhibition of austenite grain growth above the eutectoid temperature in steels is of great importance in the steel production processes. The occurrence of abnormal grain growth of austenite during heating process in steels is a serious problem because the mechanical properties of steels are degraded due to duplex distribution or extremely coarse austenite grain structures caused by the abnormal grain growth. In the authors’ recent work, it was found that the grain-coarsening temperature, Tc,（the temperature above which abnormal grain growth occurs） is much lower in a ferrite/pearlite（F/P） banded 0.2 pct carbon steel than in a non-banded steel although annealing at high temperatures is needed to eliminate the F/P banded structure. Instead, in this study we focus on the effects of cold deformation on the abnormal grain growth of austenite. Here it is shown that the abnormal grain growth that occurred in the F/P banded steel at low temperatures compared with non-banded steel can be completely inhibited by applying cold deformation before austenitizing. These should be attributed to the uniform distribution of AlN precipitates caused by the cold deformation. This provides a guideline for the industry to control the abnormal austenite grain growth effectively.

关键词： austenite banded structure abnormal grain growth cold deformation precipitate

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亚包晶钢中奥氏体组织的特征及形成机理

水钢科技 2016年第1期 53-62页

作者： i Munekazu OHNO Shingo TSUCHIYA kiyotaka matsuura 刘立德高长益张东升叶雅妮赵光凤日本北海道大学日本普利司通公司首钢水钢技术中心贵州六盘水553028

我们采用快速定向凝固方法研究了亚包晶钢奥氏体组织的形成过程．试验的冷却条件与实际连铸过程铸坯表面的冷却条件相近。在本研究所使用的亚包晶钢中．可观察到粗大的柱状奥氏体晶粒组织。试验表明，粗大的柱状奥氏体晶粒来自于8相中... 详细信息

我们采用快速定向凝固方法研究了亚包晶钢奥氏体组织的形成过程．试验的冷却条件与实际连铸过程铸坯表面的冷却条件相近。在本研究所使用的亚包晶钢中．可观察到粗大的柱状奥氏体晶粒组织。试验表明，粗大的柱状奥氏体晶粒来自于8相中细小的柱状奥氏体晶粒的不连续生长。在晶粒生长过程中，8相争残余液相是抑制相。总结了在碳含量为0．05％-0．45％的碳钢中，在快速定向凝固过程中。奥氏体组织的特征和形成机理。

关键词：奥氏体组织亚包晶钢凝固铸造晶粒生长

高V、N微合金钢动态CCT曲线及纳米碳氮化物析出冷速敏感性

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稀有金属材料与工程 2024年第4期53卷 1065-1074页

作者：石鹏张献光舒春阳齐江华郭晃勋陈佳俊闫建昊松浦清隆裴逸武北京科技大学冶金与生态工程学院北京100083 湖南华菱涟源钢铁有限公司涟钢技术中心湖南娄底417000 北海道大学工学院材料科学与工程系日本札幌060-8628

为实现对高V、N微合金钢轧制-冷却工艺过程中组织、析出相的精准控制,利用Gleeble-1500D热模拟实验机研究了轧后不同冷速下实验钢的热膨胀曲线、相变规律、过冷奥氏体动态连续冷却转变曲线(动态CCT曲线),并着重研究了微观组织演变行为... 详细信息

为实现对高V、N微合金钢轧制-冷却工艺过程中组织、析出相的精准控制,利用Gleeble-1500D热模拟实验机研究了轧后不同冷速下实验钢的热膨胀曲线、相变规律、过冷奥氏体动态连续冷却转变曲线(动态CCT曲线),并着重研究了微观组织演变行为、显微硬度和纳米碳氮化物析出行为对冷却速率的敏感性。结果表明:冷却速率低于3℃/s时,实验钢显微组织由铁素体和珠光体组成;当冷却速率位于3℃/s时,发生贝氏体相变,基体组织由铁素体、珠光体和贝氏体组成;冷却速率为8℃/s时,珠光体组织消失,马氏体组织开始出现,基体组织由沿晶铁素体、贝氏体和马氏体组成;当冷却速率达到20℃/s时,基体组织中马氏体占主,并由少量先共析铁素体和贝氏体组成。此外,冷却速率对纳米碳氮化物的析出行为也具有显著影响,冷速处于1℃/s以内时,多边形铁素体中纳米析出相直径和数密度具有较强的冷却速率敏感性,纳米析出相直径随冷速提升显著降低,数密度随冷速提升而提高;冷速由1℃/s增加至3℃/s时,纳米析出相直径进一步降低,而数密度趋于稳定;当冷速继续增至5℃/s时,纳米析出相直径保持稳定,数密度呈现下降趋势。研究还发现,贝氏体组织中纳米析出相较少,贝氏体不利于纳米相析出。基于上述组织演变与析出规律的研究,工业化试制出了屈服强度700 MPa以上、满足抗震要求的高V、N微合金钢。

关键词：高V、N钢冷却速率动态CCT曲线相变规律纳米析出相

Rate-, state-, and pressure-dependent friction model based on the elastoplastic theory

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Friction 2020年第4期8卷 768-783页

作者： Shingo OZAKI Takeru matsuura Satoru MAEGAWA Division of System Research Yokohama National UniversityTokiwadai 79-5Hodogaya-kuYokohama 240-8501Japan Department of Electrical and Mechanical Engineering Nagoya Institute of TechnologyGokiso-choShowa-kuNagoya 466-8555Japan

Adhesion is one of essences with respect to rubber friction because the magnitude of the friction force is closely related to the magnitude of adhesion on a real contact area. However, the real contact area during sliding depends on the state and history of the contact surface. Therefore, the friction force occasionally exhibits rate-, state-, and pressure dependency. In this study, to rationally describe friction and simulate boundary value problems, a rate-, state-, and pressure-dependent friction model based on the elastoplastic theory was formulated. First, the evolution law for the friction coefficient was prescribed. Next, a nonlinear sliding surface (frictional criterion) was adopted, and several other evolution laws for internal state variables were prescribed. Subsequently, the typical response characteristics of the proposed friction model were demonstrated, and its validity was verified by comparing the obtained results with those of experiments conducted considering the contact surface between a rough rubber hemisphere and smooth acrylic plate.

关键词： adhesion friction model elastoplastic theory contact surface stick-slip

Phase Equilibrium for the CaO-SiO_2-FeO-P_2O_5 System at 1673K for Dephosphorization With Multi Phase Flux

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Journal of Iron and Steel Research International 2011年第S2期18卷 84-86页

作者： Hiroyuki matsuura Fumitaka TSUKIHASHI Graduate School of Frontier Sciences The University of Tokyo Kashiwa Chiba 277-8561 Japan

Development of the efficient hot metal dephosphorization processes during steelmaking process is one of the most essential topics for the production of high grade clean steels. Since the formation of solid solution composed of tricalcium phosphate and dicalcium silicate could obtain a considerable mass transfer of phosphorus from liquid slag into solid phase during hot metal dephosphorization, itcould obviously sustain a high phosphatecapacityof theliquid slag without huge consumption of lime or addition of fluxes, such as fluorite. The above outlines are the main idea of multi phase flux dephosphorization. For the last few decades, many studies have been done towards the scientific principles and the commercial utilization of this technique. However, the reaction mechanism by using multi phase fluxes remains unclear even by now due tolack of evidence. Based on those previous works, providing a reliable and available phase diagram for the fundamental understanding of the reaction mechanism of multi phase flux dephosphorization has become the main purpose of present research. As well known, the CaO-SiO2-FeO-P2O5 slag is the main component of current steelmaking process. Hence the CaO-SiO2-FeO-P2O5 system at equilibrium has been studied at 1673K with low oxygen partial pressure. The solid phase coexisting with liquid flux is approved to be the solid solution composed of CaO, SiO2 and P2O5. Phosphorus distributes mainly in solid solution rather than liquid phase.

关键词： steelmaking dephosphorization multi phase flux thermodynamics phase diagram

Selective synthesis of carbon monoxide via formates in reverse water–gas shift reaction over alumina-supported gold catalyst

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Journal of Energy Chemistry 2016年第2期25卷 304-308页

作者： Nobuhiro Ishito Kenji Hara kiyotaka Nakajima Atsushi Fukuoka Institute for Catalysis Hokkaido University Graduate School of Chemical Sciences and Engineering Hokkaido University School of Engineering Tokyo University of Technology

Thermal decomposition of formic acid on SiO2, CeO2 and γ-Al2O3 was studied as an elementary step of reverse water–gas shit reaction（RWGS） over supported Au catalysts. γ-Al2O3 showed the highest CO selectivity among the tested oxides in the decomposition of formic acid. Infrared spectroscopy showed the formation of four formate species on γ-Al2O3： three η~1-type and one μ~2-type species, and these formates decomposed to CO at 473 K or higher. Au-loaded γ-Al2O3 samples were prepared by a depositionprecipitation method and used as catalysts for RWGS. The supported Au catalyst gave CO with high selectivity over 99% from CO2 and H2, which is attributed to the formation of formates on Au and subsequent decomposition to CO on γ-Al2O3.

关键词： Reverse water–gas shift reaction Carbon dioxide Hydrogen Formate Carbon monoxide Alumina Gold

Preparation and incubation conditions affect the DNA integrity of ejaculated human spermatozoa

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Asian Journal of Andrology 2010年第5期12卷 753-759页

作者： Rieko matsuura Takumi Takeuchi Atsumi Yoshida The Reproduction Center Kiba Park Clinic Tokyo 135-0042 Japan

Appropriate semen processing and assessment are critical for successful infertility treatment. We investigated whether laboratory procedures including semen preparation and incubation affect sperm DNA integrity. A total of 153 infertile men were involved. Conventional semen parameters and sperm chromatin structure assay （SCSA） parameters, that is, DNA fragmentation index （%DFI） and high DNA stainability （%HDS）, were assessed on the flesh ejaculated semen samples, which were treated and incubated under different conditions. Negative correlations were identified between the %DFI and sperm concentration, motility, progressive motility and morphology. A lower percentage of DFI was detected in spermatozoa when density gradient centrifugation （DGC） was followed by swimup treatment in comparison with DGC alone （P 〈 0.01）. Although the %DFI increased in a time-dependent manner with incubation both at room temperature （RT） and at 37℃ in air, the %DFI after 24 h at RT was significantly lower than that at 37℃ （P 〈 0.05）. Incubation with 5% CO2 was effective in maintaining sperm motility （P 〈 0.01）; however, it induced further elevation of %DFI （P 〈 0.001）. Thus, sperm DNA damage was associated with longer incubation periods. Interestingly, common culture conditions, such as maintaining pH and temperature, compromised the sperm DNA integrity.

关键词： density gradient centrifugation DNA damage male infertility sperm chromatin structure assay spermatozoa