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Semisolid casting with ultrasonically melt-treated billets of Al-7mass%Si alloys

China Foundry 2012年第1期9卷 78-83页

作者： yoshiki tsunekawa Masahiro Okumiya Takahiro Motomura Toyota Technological Institute

Abstract： The demand for high performance cast aluminum alloy components is often disturbed by increasing impurity elements, such as iron accumulated from recycled scraps. It is strongly required that coarse plate-like iron compound of β-Al5FeSi turns into harmless form without the need for applying refining additives or expensive virgin ingots. The microstructural modification of Al-7mass%Si alloy billets with different iron contents was examined by applying ultrasonic vibration during the solidification. Ultrasonically melt-treated billets were thixocast right after induction heating up to the semisolid temperature of 583 ℃, the microstructure and tensile properties were evaluated in the thixocast components. Globular primary reAl is required to fill up a thin cavity in thixocasting, so that the microstructural modification by ultrasonic melt-treatment was firstly confirmed in the billets. With ultrasonic melt-treatment in the temperature range of 630 ℃ to 605 ℃, the primary α-AI transforms itself from dendrite into fine globular in morphology. The coarse plate-like β-AIsFeSi compound becomes markedly finer compared with those in non-treated billets. Semisolid soaking up to 583 ℃, does not appreciably affect the size of β-AIsFeSi compounds; however, it affects the solid primary reAl morphology to be more globular, which is convenient for thixocasting. After thixocasting with preheated billets, eutectic silicon plates are extremely refined due to the rapid solidification arising from low casting temperature. The tensile strength of thixocast samples with different iron contents does not change much even at 2mass% of iron, when thixocast with ultrasonically melt-treated billets. However, thixocast AI-7mass%Si-2mass%Fe alloy with non-treated billets exhibits an inferior strength of 80 MPa, compared with 180 MPa with ultrasonically melt-treated billets. The elongation is also improved by about a factor of two in thixocastings with ultrasonically melt-treated billets

关键词： cast Al-Si alloy ultrasonic radiation thixocasting α-Al iron compound

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Improvement in mechanical properties of hypereutectic Al-Si-Cu alloys through sonosolidified slurry

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China Foundry 2014年第4期11卷 396-401页

作者： yoshiki tsunekawa Shinpei Suetsugu Masahiro Okumiya Naoki Nishikawa Yoshikazu Genma Toyota Technological Institute TenpakuNagoya 468-8511Japan Toyota Motor Corporation Toyota 471-8571Japan

For the wider applications,it is necessary to improve the ductility as well as the strength and wear-resistance of hypereutectic AlSi-Cu alloys,which are typical light-weight wear-resistant *** increase in the amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys,but leads to the poor strength and *** is known that dual phase steels composed of hetero-structure have succeeded in bringing contradictory mechanical properties of high strength and ductility *** order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance,ultrasonic irradiation of the molten metal during the solidification,which is called sono-solidification,was carried out from its molten state to just above the eutectic *** sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure,which are,hard primary silicon particles,soft non-equilibrium a-Al phase and the eutectic ***-casting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk *** the rheo-casting with modified sonosolidified slurry held for 45 s at 570 oC,the quantitative optical microscope observation exhibits that the microstructure is composed of 18area%of hard primary silicon particles and 57area%of soft a-Al *** contrast,there exist only 5 area%of primary silicon particles and no a-Al phase in rheo-cast specimen with normally solidified *** the tensile tests of T6 treated rheo-cast specimens with modified sono-solidified slurry exhibit improved strength and 5%of elongation,regardless of having more than 3 times higher amounts of primary silicon particles compared to that of rheo-cast specimen with normally solidified slurry.

关键词： semisolid casting slurry ultrasonic vibration sonosolidification hetero-structure hypereutectic aluminum alloy primary silicon a-Al solid solution

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Microstructure characteristics and tensile property of ultrasonic treated-thixocast A356 alloy

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Transactions of Nonferrous Metals Society of China 2015年第10期25卷 3173-3180页

作者： Waleed KHALIFA Shimaa EL-HADAD yoshiki tsunekawa Department of Mining Petroleum and Metallurgical EngineeringFaculty of EngineeringCairo University Central Metallurgical Research & Development Institute Cairo P.O.Box 87Egypt Toyota Technological Institute 2-12-1 HisakataTempakuNagoya 468-8511Japan

Billets of A356 aluminum alloy were treated using ultrasonic vibrations during *** billets were reheated to the semisolid state at different routes to optimize the *** were,then,thixocast using a die casting *** results showed that the ultrasonic-treated billets exhibited finely distributed α（Al） globules after reheating and *** thixocast ultrasonic-treated billets showed higher ultimate tensile strength and elongation compared with the untreated ***,the thixocast parts showed a tendency to ductile fracture under tension when made from ultrasonic-treated billets,while those made of untreated billets showed brittle fracture with obvious straight *** results revealed the feasibility and competence of ultrasonic melt treatment as a potential route for preparing billets for thixocasting.

关键词： A356 alloy semi-solid forming ultrasonic treatment reheating thixocasting tensile property

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超声熔体处理Al-7%Si合金坯料的半固态铸造

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铸造 2012年第4期61卷 425-430页

作者： yoshiki tsunekawa Masahiro Okumiya Takahiro Motomura 丰田工业大学

由于从循环利用的废料中不断累积增加Fe元素等杂质元素,所以铸造铝合金零部件高性能的要求往往很难实现。要求合金中粗大板条状的含铁化合物β-Al5FeSi在不使用变质剂和昂贵的纯铝锭条件下转变成无害的形貌结构。在凝固过程中通过利用... 详细信息

由于从循环利用的废料中不断累积增加Fe元素等杂质元素,所以铸造铝合金零部件高性能的要求往往很难实现。要求合金中粗大板条状的含铁化合物β-Al5FeSi在不使用变质剂和昂贵的纯铝锭条件下转变成无害的形貌结构。在凝固过程中通过利用超声振动来检测分析其对具有不同铁含量的Al-7%Si合金坯料的显微组织的变质效果。在感应加热至半固态温度583℃后,立即对超声熔体处理的坯料进行触变铸造,然后对触变铸造的铸件进行微观组织和拉伸性能检测分析。在触变铸造时,要求球形的初生α-Al相充填合金组织中的微小孔洞中,以便首先确定在坯料中通过超声熔体处理使合金显微组织产生变质效果。在605~630℃温度范围内进行超声熔体处理时,初生α-Al相从树枝状晶转变为细小的圆球形形貌。与未进行超声熔体处理的坯料相比,坯料超声熔体处理后合金中的粗大板条状β-Al5FeSi化合物相变得明显细小。升至583℃后进行半固态铸造不会明显改变β-Al5FeSi化合物的尺寸大小,可是却会使初生α-Al相的形貌变得更圆整,这有利于触变铸造。经预先加热的坯料进行触变铸造后,由于低的铸造温度,产生了快速凝固效果,使得合金中的共晶硅层片变得特别细小。在对超声熔体处理的坯料进行触变铸造时,具有不同铁含量的触变试样的抗拉强度变化并不大,即使合金含铁量达到2%。然而,用未处理的Al-7%Si-2%Fe合金坯料进行触变铸造时,其强度较差,仅为80 MPa,而用超声熔体处理的同种合金坯料,其抗拉强度达180 MPa。用超声熔体处理的不同含铁量的Al-7%Si合金坯料进行触变铸造时,其伸长率也提高了约一倍,例如触变铸造超声熔体处理的Al-7%Si-0.5%Fe合金坯料时,试样的伸长率为11%,而未进行超声熔体处理的同种合金触变铸造试件,其伸长率只有5%。

关键词：铸造Al-Si合金超声辐射触变铸造 α-Al 含铁化合物

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East Asia Winter Monsoon changes inferred from environmentally sensitive grain-size component records during the last 2300 years in mud area southwest off Cheju Island,ECS

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Science China Earth Sciences 2006年第6期49卷 604-614页

作者： yoshiki Saito Geological Survey of Japan Tsukuba Ibaraki 305-8567 Japan

Environmentally sensitive grain-size component (ESGSC) extracted from grain-size data of a sediment core B2, which were retrieved from mud area southwest off Cheju Island (MACI), East China Sea (ECS), can be used to indicate the variations of East Asia Winter Monsoon (EAWM), with high (low) content/mean-size of ESGCS denote to strong (weak) EAWM. Combined with AMS14C datings core B2 provides a continuous high-resolution record of EAWM changes over the past 2300 years, with an average resolution of 13 years. The results show that the variations of EAWM are con-sistent with temperature changes inferred from historical documents in eastern China over the past 2300 years, from which four climate stages may be identified. In stages before 1900 aBP (50 AD) and 1450―780 aBP (50―1170 AD) the EAWM were comparatively weak, corresponding to warm climate periods in eastern China, respectively. And in stages of 1900―1450 aBP (50―500 AD) and 780―219 aBP (1170―1731 AD) the EAWM were strongly developed, which correspond well to climate changes of two cold periods in eastern China. It is also shown from this study that the stage at 780―219 aBP (1170―1731 AD) was the coldest climate period during the last 2300 years and could be, therefore, related to the Little Ice Age (LIA). Climatic fluctuations appeared obviously in all the four stages, and two climate events of abrupt changes from warm to cold occurred at around 1900 aBP (50 AD) and 780 aBP (1170 AD), of which the latter is probably related to globe-scale changes of atmospheric circulation at that time.

关键词： East China Sea, mud area, environmentally sensitive grain-size component, East Asia Winter Monsoon, Little Ice Age, Late Holocene.

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Mapping urban carbon emissions in relation to local climate zones:Case of the building sector in Bangkok Metropolitan Administration,Thailand

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Energy and Built Environment 2024年第3期5卷 337-347页

作者： Dararat Khamchiangta yoshiki Yamagata Faculty of Architecture Khon Kaen University123Mittraphap HighwayMueang KhonKaen DistrictKhon Kaen40002Thailand Graduate School of System Design and Management Keio UniversityKyousei-kan4-1-1HiyoshiKohoku-kuYokohama223-8526Japan

This study focuses on carbon emissions of the building sector in relation to local climate zone(LCZ)classification,concentrating on two major ***,we estimated carbon emissions in the building sector,which were cal-culated for weekdays and weekends real-time daily energy consumption *** estimations were divided into direct(from petroleum products consumption)and indirect emissions(from electricity consumption).Sec-ond,we examined urban carbon emissions mapping in relation to *** Metropolitan Administration(BMA)was used as the case study and 2016 as the base year for *** results illustrate that indirect emissions in Bangkok can be up to ten times higher than direct *** analysis indicates that LCZ,such as compact high-rise,large low-rise,light industry,and warehouse zones had a relatively higher carbon emission intensity than ***,we identified that the compact high-rise zone has the highest indirect emission intensity,while the light industry and warehouse zone have the greatest direct emission *** results provide insights into the dynamics of carbon emission characteristics in the building sector and the methodology purported here can be used to support low carbon city planning and policymaking in Bangkok.

关键词： Energy consumption Carbon mapping Direct carbon emissions Indirect carbon emissions Local climate zone

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Molecular design and application of luminescent materials composed of group 13 elements with an aggregation-induced emission property

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National Science Review 2021年第6期8卷 80-93页

作者： Shunichiro Ito Masayuki Gon Kazuo Tanaka yoshiki Chujo Department of Polymer Chemistry Graduate School of EngineeringKyoto University

Complexation of π-conjugated ligands by metal or semimetal ions leads to the enhancement of the planarity and rigidity of π-conjugated systems. Boron, especially, has played a central role in the design of luminescent main-group complexes. However, these complexes still suffer the disadvantage of aggregation-caused quenching as well as typical organic fluorophores. It has recently been reported that some types of boron complexes exhibit the aggregation-induced emission(AIE) property. Moreover, AIE behavior from complexes and organometallic compounds composed of the other group 13 elements, such as aluminum and gallium, has emerged in this decade. These observations greatly encourage us to develop advanced functional materials based on the group 13 elements. Indeed, recent research has demonstrated that these classes of materials are potentially versatile scaffolds for constructing chromic luminophores,efficiently emissive π-conjugated polymers and so on. This review mainly describes AIE-active group 13 complexes with four-coordinate structures and their application as photo-functional materials. Proposed mechanisms of the origins of AIE behavior are briefly discussed.

关键词： aggregation-induced emission crystallization-induced emission chromism conjugated polymer group 13

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Semi-3D cultures using Laminin 221 as a coating material for human induced pluripotent stem cells

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Regenerative Biomaterials 2022年第1期9卷 775-793页

作者： yoshiki Nakashima Shinsuke Yoshida Masayoshi Tsukahara Kyoto University Center for iPS Cell Research and Application Foundation(CiRA Foundation) Facility for iPS Cell Therapy(FiT)Kyoto 606-8397Japan

It was previously believed that human induced pluripotent stem cells(hiPSCs)did not show adhesion to the coating material Laminin 221,which is known to have specific affinity for *** this study,we report that human mononuclear cell-derived hiPSCs,established with Sendai virus vector,form peninsular-like colonies rather than embryonic stem cell-like colonies;these peninsular-like colonies can be passaged more than 10 times after ***,initializationdeficient cells with residual Sendai virus vector adhered to the coating material Laminin 511 but not to Laminin ***,the expression of undifferentiated markers tended to be higher in hiPSCs established on Laminin 221 than on Laminin *** Laminin 221,hiPSCs15M66 showed a semi-floating colony *** expression of various markers of cell polarity was significantly lower in hiPSCs cultured on Laminin 221 than in hiPSCs cultured on Laminin ***,201B7 and 15M66 hiPSCs showed 3D cardiomyocyte differentiation on Laminin ***,the coating material Laminin 221 provides semi-floating culture conditions for the establishment,culture and induced differentiation of hiPSCs.

关键词： human induced pluripotent stem cells(hiPSCs) regenerative medicine coating material cardiomyocyte therapeutic cells

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Positive Luminescent Sensor for Aerobic Conditions Based on Polyhedral Oligomeric Silsesquioxane Networks

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Chemical Research in Chinese Universities 2021年第1期37卷 162-165页

作者： Kazumasa SUENAGA Kazuo TANAKA yoshiki CHUJO Department of Polymer Chemistry Graduate School of EngineeringKyoto UniversityKatsuraNishikyo-kuKyoto615-8510Japan

There are numerous numbers of hypoxia-selective luminescent probes based on oxygen quenching of *** show a unique design for luminescent probes to detect hyperoxia utilizing hybrid networks consisting of aggregation-induced emission(AIE)-active dyes and disulfide *** the initial state,emission from the AIE-active dyes is inducible by suppressing energy-consumable intramolecular motions in the hybrid matrices,while the decrease in intensity was detected by releasing molecular motions corresponded to bond scission at the disulfide ***,it was shown that this process selectively proceeds in *** a result,positive luminescent signals were obtained in hyperoxia.

关键词： Polyhedral oligomeric silsesquioxane(POSS) Network polymer Hypoxia Luminescent probe

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Non-Kramers doublet ground state in a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) investigated by ultrasonic measurements

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Chinese Physics B 2024年第6期33卷 405-411页

作者：张化远 Kazuhei Wakiya Mitsuteru Nakamura Masahito Yoshizawa yoshiki Nakanish Graduate School of Science and Engineering Iwate UniversityMorioka 020-8551Japan

We performed ultrasonic measurements on a quaternary cubic compound PrRu_(2)In_(2)Zn_(18) to explore the ground state properties derived from non-Kramers Γ_(3) doublet of Pr^(3+).PrRu_(2)In_(2)Zn_(18) is a quaternary derivative of the ternary compound PrRu_(2)Zn_(20) that exhibits a structural phase transition at T_S=138 *** PrRu_(2)In_(2)Zn_(18),the Zn atoms at the 16c site in PrRu_(2)Zn_(20) are selectively replaced by In atoms.A monotonic increase was observed in the temperature dependence of elastic constants C_L=(C_(11)+2C_(12)+4C_(44))/3 and C_(T)=(C_(11)-C_(12)+C_(44))/3 in the temperature range around T_(S) to which an elastic softening was observed in(C_(11)-C_(12))/2 for PrRu_(2)Zn_(20).The disappearance of the softening indicates that the structural transition in PrRu_(2)Zn_(20) is suppressed by the substitution of Zn ions by In ones with a larger ionic ***,the C_(T) of PrRu_(2)In_(2)Zn_(18) exhibits a precursor Curie-type elastic softening toward low temperatures being responsible for the non-Kramers Γ_(3) ground *** discuss the ground state and the evolution of the elastic properties of the different single-crystal samples of PrRu_(2)In_(2)Zn_(18) grown under different conditions.

关键词： ultrasonic measurements non-Kramers doublet structural phase transition crystalline electric field effect

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