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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 44 (2003), No. 7

  • Prospective and Comparative Assessment of the Eco-Compatibility of Materials

    Hans Warlimont

    pp. 1232-1236

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    DOI:10.2320/matertrans.44.1232

    Abstract

    A new and simple concept is proposed for the systematic and quantitative assessment of the technical, economic and ecological aspects of the ecological compatibility of materials and products. This concept can serve for prospective accounting of eco-compatibility in research and development, and for comparisons of alternative technological solutions. It is based on considering six stages of the life cycle and six efficiency parameters for each stage. The ensuing matrix elements can be selected for qualitative or quantitative analysis. The elementary quantitative treatment is based on suitably defined efficiency parameters. This concept alleviates the treatment of a complete life cycle analysis and inventory computation and is particularly useful when a simple and yet concise insight into selected aspects of eco-compatibility of a material or product is required. Economical aspects are introduced regarding minimum energy and material requirements and as a cost difference parameter in comparative treatments. Examples are given to demonstrate the appropriate selection of aspects to be analysed for a particular assessment and to introduce the specific formulation of pertinent efficiency parameters. Thus, the simplicity and transparency of the method and its results is demonstrated.

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  • Analysis of the Current Status of Ecomaterials in Japan

    Kohmei Halada, Katsutoshi Yamada, Kiyoshi Ijima, Yoshihiko Soeno

    pp. 1237-1243

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    DOI:10.2320/matertrans.44.1237

    Abstract

    Ecomaterials were categorized based on their life cycle and eco-efficiency. Taking ecomaterials in their broadest sense, as “materials for the environment”, there are “function materials for environmental protection” and “materials for advanced energy systems”. These materials improve services such as maintaining the living environment, or rendering energy. “Materials of life-cycle design” which are ecomaterials in the strict sense, are characterized by the stages in life-cycle where the focus of reduction of the environmental burden is given to: “materials with a green environmental profile”, “materials of higher material efficiency”, “materials of higher recyclability”, “materials of hazardous substance free”. On the basis of this classification, the present state of Website home pages and commercialized ecomaterial described in the environmental report book of the enterprise was investigated. There were many “materials of higher material efficiency” and “materials of hazardous substance free”, and these were respectively 39%, and 31% of the total. “Materials of green environmental profile” composed 21%, and “materials of higher recyclability” gleamed 5%. The “materials of life-cycle design” are obviously well represented in the market, appealing as they do to the consumer.

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  • Exergy Analysis to Evaluate Integrated Environmental Impacts

    Yoshihiko Soeno, Hiromitsu Ino, Kiiti Siratori, Kohmei Halada

    pp. 1244-1250

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    DOI:10.2320/matertrans.44.1244

    Abstract

    It is essential to evaluate the environmental impacts of materials or products properly for improving the global environment. However the typical method called Life Cycle Assessment (LCA) has many problems. Especially, it is crucial that various kinds of environmental impacts cannot be integrated. We present an attempt to use the exergy concept to integrate them. We classified the different types of exergy and analyzed the impact of the life cycle of beverage containers (aluminum can, PET bottle) and generation of electricity as examples, focusing on chemical and nuclear materials.

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  • Refractory Materials from Waste

    Franz-Georg Simon, Burkart Adamczyk, Gerd Kley

    pp. 1251-1254

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    DOI:10.2320/matertrans.44.1251

    Abstract

    The recycling of refractory materials in the chemical, metallurgical and glass industry has only had minor relevance until now because of the high performance required from these materials (stability against corrosion, inert when coming into contact with the glass melt, etc.). Refractory lifetimes are limited because of corrosion at higher temperatures. The best furnace lifetimes has been achieved with chromium oxide and chromium oxide corund refractories. Waste from the production and use of refractory material is generated in three main forms: as residues from cutting and grinding, as refractories which have limited or no contact with glass melts, and as refractories with infiltration of sublimation residues or condensates. The waste material is classified as hazardous waste due to its chromium content. In this study, arc furnace technology was used for thermal treatment of the waste materials to enable recycling of refractory materials.

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  • Building Materials from Waste

    Karin Weimann, Lutz B. Giese, Günter Mellmann, Franz-Georg Simon

    pp. 1255-1258

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    DOI:10.2320/matertrans.44.1255

    Abstract

    In Germany, about 60 million tons of demolition waste are generated annually. Approximately 70% of the demolition waste is currently recycled. Most recycling applications, for example in roadbed substructures, can be seen as a kind of downcycling. However, there are also some high-level applications for demolition waste. For instance, crushed and sieved concrete demolition waste can be used as concrete aggregate instead of natural materials. Depending on the crushing process, about a third of the broken concrete is currently concrete sand. At present, concrete sand fraction (0–4 mm) is rarely reused as a concrete aggregate. This is due to the fact that some important characteristics of crushed concrete sand are different from those of natural sand. As a result, it does not reach the standards required for aggregates. Concrete containing such aggregate is of lower quality than concrete made of natural aggregate. This paper describes an experimental investigation on the treatment of concrete sand gained from demolition waste by wet processing using a jig whereby the sand is separated by grain size and, more importantly, by density. Concrete produced with concrete sand which has been treated in this manner should have the same quality as concrete prepared with natural aggregate. Recycled sand used as aggregate substitutes natural resources and avoids disposal of waste. It has all the characteristics of an Ecomaterial.

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  • Life Cycle Assessment on Newly Developing Steel Recycling System by using I/O Table

    Kenichi Nakajima, Yohji Uchiyama, Kohmei Halada

    pp. 1259-1261

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    DOI:10.2320/matertrans.44.1259

    Abstract

    According to increase in a waste scrap, a process is noticed in which a waste scraps is consumed for sheet steel production within severe restriction of impurities concentration. In this study, evaluation of the effect on environmental load decline by LCA is applied to this new recycling technology. Target of this study is not for closed loop recycling system like aluminum can for drink but for open loop recycling system in which many industries are concerned. Authors suggest taking the interindustry-relations table for open loop recycling system. Evaluation made in this research is based on it. By setting up I/O boundary, though increase of environmental load is predicted to be high comparing to those which are assumed as non-open recycling system, still there is a sufficient effect for it. As the result of the analysis, curtailment was estimated that energy consumption and CO2 emission are 16.8 GJ per ton waste scrap and 1.2 t per ton waste scrap, respectively.

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  • Environmental Sustainability of Steel Active Corrosion Protection Processes

    Bruno De Benedetti, Gian Luca Baldo, A. Del Carlo, A. Maglioni

    pp. 1262-1265

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    DOI:10.2320/matertrans.44.1262

    Abstract

    The Integrated Product Policy (IPP), one of the most recent initiatives of the European Commission in the field of sustainable products and services development, considers Life Cycle Assessment (LCA) as natural tool to provide environmental product declarations and verified environmental labels. The need of transparency of environmental performance is getting more importance also in the field of corrosion protection technology. First results of a Life Cycle Assessment on a ‘hot-dip zinc galvanising process’ for generic steel products are here reported to present a set of environmental sustainability indicators of that industrial sector and to support the preparation of a document with an environmental declaration. The study has been carried out according to ISO 14040 standard and the system referred to an average process resulting from two Italian medium-size plants (about 12.000 metric tons of galvanised steel per year each). Different frameworks such as poles and pylons for energy transportation have been considered from a cradle-to-grave (eco-profile) point of view, adding up to energy and environmental results also on the basis of the steel product service life within different corrosion scenarios.

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  • Influence of Phosphorus Micro-Segregation on Ferrite Structure in Cast Strips of 0.1 mass% C Steel

    Osamu Umezawa, Koichi Hirata, Kotobu Nagai

    pp. 1266-1270

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    DOI:10.2320/matertrans.44.1266

    Abstract

    Cast strips of 0.1 mass% C steel with or without phosphorus addition have been characterized by electron back-scattering diffraction pattern (EBSP) measurements. Then the formation of globular ferrite structure was discussed. EBSP analysis combined with optical microscopy clearly showed that a globular grain was fitted to be an α-ferrite grain. The EBSP analysis suggested that the retained-δ grain grew predominantly in the γ-grain and formed the globular α-ferrite during cooling. The microtexture in the globular ferrite structure depended highly on the solidification structure. It is important to scatter the primary dendrite growth direction into neighboring areas to develop fine prior-γ and α structures for the cast strip of high-phosphorus steel.

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  • Utilization of Al Scrap for Fabrication of Al(alloy)/Al2O3 Composite Material

    Noboru Yoshikawa, Hideaki Yamaguchi, Gaku Kitahara, Shoji Taniguchi

    pp. 1271-1275

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    DOI:10.2320/matertrans.44.1271

    Abstract

    In status quo, Al scrap melt is diluted with pure Al and adjusted its composition for reuse. We studied a method to utilize Al scrap directly for fabricating composite materials, which can be used for machine elements having resistance to abrasion. The composite material is a product of displacement reaction between molten Al scrap and SiO2. Its microstructure consists of Al2O3 network and Al alloy among them. In this study, Al alloy was prepared which have a composition of Al scrap due to window frame of houses. The synthesized Al scrap are melted and reacted with SiO2 at 1473 K to obtain the composite material. The mechanical properties of this material were compared with Al/Al2O3 and (Al–Fe)/Al2O3 composite materials fabricated using pure Al, and Al–Fe alloy, respectively. It was demonstrated that the composite materials using scrap had a little higher strength and hardness than Al/Al2O3, and they were not broken into pieces upon fracture, as occurred in the case of (Al–10 at%Fe)/Al2O3. Further studies needed for application of this method was discussed. It was pointed out that the reactivity and the property change with compositional fluctuations of the scraps and reduction of the reaction temperature have to be taken into consideration.

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  • Environmentally Benign Fabricating Process of Magnesium Alloy by Cyclical Plastic Working in Solid-State

    Katsuyoshi Kondoh, Tatsuhiko Aizawa

    pp. 1276-1283

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    DOI:10.2320/matertrans.44.1276

    Abstract

    Solid-state processing via cyclically plastic working to output the green compact has been developed to fabricate magnesium alloys with fine microstructures. The relationship between the energy consumption during the plastic working and the characteristics of hot extruded magnesium alloys was evaluated from the viewpoint of the environmentally benign process. The cyclical plastic working marks a significant advance in refining microstructures, such as matrix grain and silicon particles added to synthesize Mg2Si via solid-state reaction with magnesium. For example, the grain size of hot extruded AZ31 alloy is 3–15 μm, which is remarkably smaller than that with 20–80 μm in employing the cold compact without using such a plastic working. As a result of the grain refinement, AZ31 alloys reveal higher UTS of 330–355 MPa than the conventional alloys of 270 MPa. The energy consumption of the cyclical plastic working with 200 cycles is 10 kJg−1 to fabricate the billet consolidated by hot extrusion, when using a high-speed screw-driven press machine. This is less than 10% of the energy consumed by the conventional recycling process in re-melting wasted magnesium alloys (126 kJg−1). This process is highly capable of producing high performance magnesium alloys with a small energy consumption and is environment-friendly.

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  • Corrosion and Mechanical Properties of Recycled 5083 Aluminum Alloy by Solid State Recycling

    Yasumasa Chino, Mamoru Mabuchi, Satoshi Otsuka, Koji Shimojima, Hiroyuki Hosokawa, Yasuo Yamada, Cui’e Wen, Hajime Iwasaki

    pp. 1284-1289

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    DOI:10.2320/matertrans.44.1284

    Abstract

    Corrosion and Mechanical properties of a recycled 5083 aluminum alloy by solid state recycling have been compared with those of a virgin extrusion which was processed from the ingot block. In the solid state recycling, the machined chips were extruded at 723 K with an extrusion ratio of 44:1 in air. As a result of the salt immersion tests, the mass loss of the solid recycled specimen was not less than twice of that of the virgin extruded specimen. The deterioration in corrosion properties for the solid recycled specimen was attributed to the excessive contamination of iron which promoted galvanic corrosion. As a result of tensile tests, the solid recycled specimen exhibited a good combination of high strength and high elongation to failure at room temperature. The excellent mechanical properties for the solid recycled specimen were attributed to the refined microstructure. However, the elongation to failure of the solid recycled specimen at elevated temperatures more than 573 K was lower than that of the virgin extruded specimen. The contamination of oxide particles is likely to be responsible for the lower elongation in the solid recycled specimen.

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  • Fabrication of SUS304 Regularly Cell-Structured Material and Their Mechanical Properties

    Kanyatip Tantikom, Hidetaka Kanahashi, Shigeo Yamamoto, Tatsuhiko Aizawa

    pp. 1290-1294

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    DOI:10.2320/matertrans.44.1290

    Abstract

    The quasi-static flexural and in-plane compressive properties of SUS304 stainless steel with circular close-packed cells are studied. Micro-stainless steel tubes coated with Ni3P were selected for constructing hexagonal close-packed arrays, which are subsequently joined together to form a cellular structure. The fabrication technique developed, involves the diffusion bonding of stacked metal tubes under the compressive stress state during heat treatment. SUS304 cell-structured materials can achieve the high specific flexural stiffness and specific flexural yield strength nearly equal to those for the dense materials. In-plane compressive properties as well as deformation behavior are also observed and discussed in this paper.

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  • Self-Lubrication of Cl-Implanted Titanium Nitride Coating for Dry Metal Forming

    Atsushi Mitsuo, Thananan Akhadejdamrong, Tatsuhiko Aizawa

    pp. 1295-1302

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    DOI:10.2320/matertrans.44.1295

    Abstract

    Various kinds of lubricants are utilized in every aspect of manufacturing for mass production. To prolong the life time of tools or dies, much amount of lubricants must be used for mechanical machining or metal forming, resulting in massive emission of wasted lubricants. Dematerialization in the environmentally benign manufacturing requires less use and less emission of lubricants as possible to significantly reduce the environmental burden. For that purpose, dry machining or dry metal forming becomes a challenging issue to be solved. In the present paper, new tribological coating design is proposed to significantly reduce the wear volume and friction coefficient and to minimize the emission of wastes in wear. Titanium nitride coating has been widely used for protection of dies and tools from severe wear. Due to high friction coefficient and less wear endurance, adhesive wear often takes place against the stainless steel or ductile metallic alloy counter parts. Hence, even using this type of protective coating, lubricants are indispensable to reduce the friction coefficient and to be free from metallic sticking. Self-lubrication mechanism can be imprinted into titanium nitride coating only by chlorine implantation into it. Under the presence of chlorine in the wear track, the plastically deforming intermediate oxide film is in-situ formed to sustain low friction and low wearing mode in the relatively wide range of normal pressure and sliding velocity on the contact surface. Through the feasibility study, total amount of chlorine used for this self-lubrication is found to be negligibly small, but the self-lubrication mechanism is sustained to be working until the initial titanium nitride coating is completely worn out from the substrate.

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  • Plasma Nitriding as an Environmentally Benign Surface Structuring Process

    Tatsuhiko Aizawa, Hideyuki Kuwahara

    pp. 1303-1310

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    DOI:10.2320/matertrans.44.1303

    Abstract

    Nitriding has been utilized for surface treatment of automotive parts as a typical cheap and reliable processing. Recent requirement to reduce the environmental burden, denies usage of cyanides or cyanates and excessive exhaustion of ammonia gases, which are widely used in practice. Among several candidates, the plasma nitriding might be well recommended as an alternative, environmentally benign surface treatment. Typical features among the above three approaches are first introduced in the present paper to demonstrate the usefulness of plasma nitriding. Both the commercial high alloy steel with type of SR34 and the Fe–14Cr binary alloy were used to understand the feasibility of plasma nitriding. Among various surface-treated steel automotive parts, a piston ring was employed to consider the possibility of plasma nitriding for alternative surface treatment method with comparison to the gas nitriding, the chromium wet-plating and the CrN PVD coating. Both the hardness testing and the scuffing load measurement were utilized for mechanical evaluation of the surface-treated samples. In the case of the normal plasma nitriding, the trade-off-balancing is held for the surface hardness vs. scuffing load relationship. Since the gas-nitriding data were plotted on the obtained master curve, the normal plasma nitriding can be a candidate surface treatment to be working instead of the gas nitriding processes in industry. Of much concern is the advanced plasma nitriding with formation of multi-striped microstructure. Although further validation is necessary to demonstrate its effectiveness as a reliable surface treatment for industry, the above normal trade-off-balancing curve can be extended in the direction to enhance the scuffing load or the wear toughness even at the same level of surface hardness. Both the chromium wet plating and the CrN ion-plating data might well be classified with this new trade-off-balancing curve for mechanical design of piston ring. This high qualification in the mechanical performance must be indispensable for the environmentally benign surface treatment.

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  • Effect of Consolidation Process on Tensile Properties of Fe-Cu P/M Alloy from Rapidly Solidified Powder

    Hideki Kakisawa, Kazumi Minagawa, Susumu Takamori, Yoshiaki Osawa, Kohmei Halada

    pp. 1311-1315

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    DOI:10.2320/matertrans.44.1311

    Abstract

    The possibilities for recycling scrap iron utilizing copper impurity as a reinforcement were investigated. For this purpose, Fe–Cu powder was prepared by high-pressure water atomization and consolidated by groove rolling at a warm temperature in order to maintain the powder microstructure. The effect of the rolling reduction rate on the mechanical properties of the consolidated samples was examined in this paper. The powder was successfully consolidated without coarse copper precipitation by the rolling technique, though pores were observed at the primary powder boundaries at the low reduction rates. With the increase of the reduction rate, the powder was more elongated and adhered with other powder, and the pore volume fraction decreased. Strength and elongation in tensile testing were measured, and the Vickers hardness of the consolidated samples was examined. All the properties tested improved by increasing the reduction rate. The tensile properties required a more intensive rolling process to bring about the full performance originated by the maintained powder microstructure than the hardness. Using the determined optimum rolling condition, a high strength material was achieved via the proposed processing, showing the prospect for a new recycling process of scrap iron.

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  • Hybrid Atomization Process Applied to Fine Lead-Free Solder Powder Production

    Kazumi Minagawa, Yunzhong Liu, Hideki Kakisawa, Yoshiaki Osawa, Susumu Takamori, Kohmei Halada

    pp. 1316-1319

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    DOI:10.2320/matertrans.44.1316

    Abstract

    Considerable R&D efforts in last decade have identified several promising lead-free tin alloys for the replacement of lead-containing solders in microelectronic applications. However, it is difficult or uneconomical to produce high-quality solder balls industrially by means of conventional atomization methods. A new powder-making technology, Hybrid Atomization, was recently developed in order to inexpensively produce very fine uniform spherical powders with mean particle sizes of about or less than 10 μm. This new method effectively combines free-fall gas atomization with centrifugal atomization. For example, Sn–9 mass%Zn powders obtained by hybrid atomization show very fine particle size, spherical shapes, narrow particle size distributions, few satellites, and low oxidation. In this paper, the optimized production of lead-free tin solder powder by hybrid atomization was investigated, and the influences of the powder’s main processing parameters were discussed.

  • Hydrothermal Syntheses of Barium Strontium Titanate Thin Films

    Daojiang Gao, Dingquan Xiao, Jian Bi, Ping Yu, Guanglong Yu, Wen Zhang, Jianguo Zhu

    pp. 1320-1323

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    DOI:10.2320/matertrans.44.1320

    Abstract

    Crystallized polycrystalline barium strontium titanate (Ba0.5Sr0.5TiO3) thin films have been synthesized on the titanium metal substrates by an environmentally conscious method of hydrothermal synthesis. The films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning electronic micrographs (SEM) respectively. The XRD analyses show that the as-grown films are a cubic phase containing a little unidentified phase, which would tend to be a pure cubic phase after being annealed at 600°C for 30 minutes; the XPS analyses reveal that the composition of the as grown Ba0.5Sr0.5TiO3 films is agreement with the stoichiometry, and the valences of Ba, Sr, Ti, and O elements of the films are +2, +2, +4, and −2 respectively; the SEM photographs show that the films are condensely synthesized; and the AFM analyses show that the average surface roughness and the root-mean-square (rms) of the film measured are 0.257 μm and 0.323 μm respectively. It is concluded that an environmentally conscious method of hydrothermal synthesis can be used for preparing multi-element oxide thin films.

  • Preparation by Sol-Gel Method and Characterizations of (Bi4-xLax)Ti3O12 Thin Films

    Lin Shen, Dingquan Xiao, Ping Yu, Jianguo Zhu, Daojiang Gao, Guanglong Yu, Wen Zhang

    pp. 1324-1327

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    DOI:10.2320/matertrans.44.1324

    Abstract

    (Bi4−xLax)Ti3O12 (abbreviated as BLT) thin films were prepared by Sol-Gel processing method with the initial materials of bismuth nitrate (Bi(NO3)3·5H2O), lanthanum nitrate (La(NO3)3·6H2O), and tetrabutyl titanate ((C4H9O)4Ti). The X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies were performed for determining the change of the crystal lattice constant, the surface morphology, the chemical composition of the films, and the chemical bonding energy of the ions in the films. It was found that BLT thin films have high c-axis orientation with monoclinlic structure, and the crystal lattice constants of the films are different from those reported in the literature. The a and b values of the lattice remain constant, but the c value reduces with an increasing lanthanum content x. The chemical composition of the films, and chemical bonding energy of bismuth and lanthanum ions in the near surface region are different from those in the inside region of the films. The films are bismuth enriched in the surface region, and the composition in the “bulk” region is agreement with the stoichiometry.

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  • Controlled Nanophase Development in Photocatalytic Titania

    Li Ying, Lim Suo Hon, Tim White, Ray Withers, Liu Bing Hai

    pp. 1328-1332

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    DOI:10.2320/matertrans.44.1328

    Abstract

    Acid catalyzed hydrolysis of titanium butoxide was used to synthesize homogenous titania gels, which were converted to the anatase and rutile polytypes through controlled firing. The mechanism of this phase transformation was investigated by quantitative powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Condensation to titania is a function of annealing time, temperature and atmosphere. In air, calcinations below 600°C favored the formation of anatase, with rutile only appearing at >600°C. However, in situ transformation where titania nanoparticles were treated under vacuum in the TEM required heating at higher temperatures up to 900°C. This is may be due to the formation of surface layers of reduced titanium oxide that passivate and retard the anatase to rutile transformation. Grain growth and specific surface area varied inversely, with especially rapid crystallization observed at and beyond the transformation temperature. Potential photocatalytic activity was identified with ultraviolet-visible (UV-Vis) spectroscopy. A red shift of the absorption edge for nano-titania was observed due to quantum size effects.

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  • Formation of Whiskers at Dislocation Sites of n-Type GaP Surface during Anodic Etching

    Shigeo Sugawara, Kaichi Saito, Kenji Aoki

    pp. 1333-1335

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    DOI:10.2320/matertrans.44.1333

    Abstract

    It was recently found that the electrochemical dissolution of an n-GaP (111) surface proceeded selectively or uniformly in an aqueous KOH solution, depending on an anodic high-voltage above ten volts. In the present study we report the formation of whiskers at dislocation sites of the n-GaP (111) surface that remain undissolved at an anodic voltage of 16 V in the 0.5 kmol·m−3 KOH solution.

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  • Diffusion Analysis across Grain Boundary in Al-3.7 mass%Cu Alloy Using Analytical Electron Microscopy

    Takeshi Fujita, Kenji Kaneko, Zenji Horita

    pp. 1336-1342

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    DOI:10.2320/matertrans.44.1336

    Abstract

    An Al–3.7 mass%Cu alloy was subjected to aging treatment at selected temperatures in the range from 453 to 548 K. Diffusion coefficients of Cu in the alloy were then determined from Cu concentration profiles measured across the grain boundary. A high spatial resolution analytical electron microscope (AEM) capable of forming a 1 nm probe was used to measure the concentration profiles. As the aging temperature is lower, the diffusion coefficients tend to deviate from the values extrapolated from the higher annealing temperatures. It is suggested that this deviation is due to the presence of quenched-in excess vacancies. The concentration profiles were also measured for the boundaries having different misorientation angles. It is shown that the concentration profiles are essentially the same regardless of the misorientation angles and of the boundary characters except for the misorientation angles smaller than a few degrees.

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  • Production of Ultra-Fine Grained Aluminum Alloy using Friction Stir Process

    Yong-Jai Kwon, Ichinori Shigematsu, Naobumi Saito

    pp. 1343-1350

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    DOI:10.2320/matertrans.44.1343

    Abstract

    1050 aluminum alloy with an ultra-fine grain size was produced through friction stir process (FSP). The influence of tool rotation speed on the temperature profile, microstructure and mechanical properties of the friction stir processed zone (FZ) was also experimentally investigated. FSP was carried out with only a single pass at tool rotation speeds ranging from 560 to 1840 min−1 under a constant tool traverse speed of 155 mm·min−1. The maximum temperature of the FZ was lower than the melting point of the workpiece material, although increasing linearly with the tool rotation speed. The cooling rate of the FZ also increased linearly from 341 to 1473°C·min−1 with the tool rotation speed. The FZ had very low dislocation density and was composed of fine equiaxed grains. These fine grains would result from the growth inhibition of dynamically recrystallized grains by the high cooling rate of the FZ. The grain size of the FZ increased with the tool rotation speed. However, it is noteworthy that, for 560 min−1, the grain size decreased to even the submicron level in spite of only the single pass of FPS. The average hardness of the FZ increased significantly for 560 min−1 to about 37% as compared with the unprocessed zone (UZ), although decreasing with the increase in the tool rotation speed. For 560, 980 and 1350 min−1, the tensile test specimens were fractured in the UZ. This result indicates that the tensile strength of the FZ increased more than that of the UZ by the grain refinement through FSP. Hence, it is concluded that FSP is very effective in producing an ultra-fine grained material with excellent mechanical properties. In addition, it is possible to control its grain size resulting in the mechanical properties by varying the maximum temperature with the tool rotation speed.

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  • Band Structure Formation in Peritectic Fe-Co and Fe-Ni Alloys

    Masaki Sumida

    pp. 1351-1358

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    DOI:10.2320/matertrans.44.1351

    Abstract

    In this paper, band structure formation in peritectic Fe–18.0 at%Co and Fe–4.4 at%Ni alloys is reported. Bridgman type directional solidification experiments were performed, and an island band structure was observed in both of these alloys under low velocity solidification conditions. Solid composition profiles along the growth direction in this band region were determined with electron probe measurements. The solute concentration increased during δ growth, and after an abrupt increase for phase change, it decreased during γ growth. It then decreased abruptly for the phase change to δ. Repetition of this process formed bands. Composition profiles calculated by the convection model were compared with these experimental results, suggesting that island bands form by a mechanism similar to that assumed in the model for discrete bands. Furthermore, the nucleation condition in this model was extended. Applying the nucleation constitutional undercooling criterion, a new calculation was developed. The mechanism of band structure formation is discussed in the light of these results.

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  • The Phase Diagram of Mo-H Alloys under High Hydrogen Pressures

    Yuh Fukai, Masaki Mizutani

    pp. 1359-1362

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    DOI:10.2320/matertrans.44.1359

    Abstract

    The phase diagram of the Mo–H system was determined by in situ X-ray diffraction using synchrotron radiation up to 1200°C and the hydrogen pressure to p(H2) = 5.3 GPa. Three phases were found to exist; a bcc phase (α) of low hydrogen concentrations at low hydrogen pressures, and two high-pressure phases, an hcp (ε) phase at lower temperatures and an fcc (γ) phase at higher temperatures, both having a nearly stoichiometeric composition of x = [H]/[Mo] ∼ 1. A gradual lattice contraction observed in the fcc phase indicates the formation of superabundant Mo-atom vacancies (vacancy-hydrogen clusters).

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  • Mechanical Properties and Microstructures of a Thin Plate of Nickel-Free Stainless Steel with Nitrogen Absorption Treatment

    Daisuke Kuroda, Takao Hanawa, Takaaki Hibaru, Syuji Kuroda, Masaki Kobayashi

    pp. 1363-1369

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    DOI:10.2320/matertrans.44.1363

    Abstract

    We have developed a new manufacturing process for nickel-free austenitic stainless steel. In combination with machining and a nitrogen absorption treatment, this process makes it possible to form small precise devices. However, the temperature for the nitrogen absorption, 1473 K, was sufficiently high for grain growth, and coarsening was observed after nitrogen absorption. Therefore, a nitrogen absorption treatment which allows the retention of strength and ductility was performed with a grain refinement process before nitrogen absorption. In this study, we attempted the refinement of grains by thermo-mechanical treatment before nitrogen absorption treatment. The mechanical properties and microstructures of Fe–24Cr and Fe–24Cr–2Mo with fine grains before and after nitrogen absorption treatment were evaluated to understand the effects of grain refinement on nitrogen absorption. The austenintic phase was only obtained from the surface to a 0.1-mm depth in Fe–24Cr and Fe–24Cr–2Mo with nitrogen absorption at 1473 K for 2.7 ks. The balance between strength and elongation in Fe–24Cr and Fe–24Cr–2Mo with nitrogen absorption at 1473 K for 2.7 ks was better than that in conventional austenitic stainless steel. The values of ultimate tensile strength in both alloys with nitrogen absorption increased with the grain refinement process attempted in this study. The balance between strength and elongation in both alloys with nitrogen absorption over 2.7 ks decreased because of grain growth. Therefore, the process described in this study can be used to manufacture small devices with a great deal of precision and parts with a maximum thickness or diameter of 0.2 mm in a short time. Grain refinement in a nickel-free austenitic stainless steel can increase the balance between the strength and elongation.

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  • Thermal Recovery of Dislocations and Nature of Uniform Elongation during High Temperature Deformation of a Mechanically Milled Al-1.1 mol%Mg-1.2 mol%Cu Alloy

    Tadashi Hasegawa, Wakana Uchino, Kenji Okazaki

    pp. 1370-1375

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    DOI:10.2320/matertrans.44.1370

    Abstract

    Tensile deformation was carried out for a mechanically milled Al–1.1 mol%Mg–1.2 mol%Cu alloy at temperatures of 523–823 K and a true strain rate of 1×100 s−1. The largest uniform elongation prior to local necking occurred at an intermediate temperature (748 K). This temperature dependence of the uniform elongation was analyzed from a strain hardening viewpoint in which the balance of the stored dislocations and the thermal recovery of them is responsible for maintaining a high mobile dislocation density that is exclusively temperature-dependent to sustain a large uniform elongation. It was found that thermal activation process of liberating unlocked immobile dislocations from solute atmosphere is responsible for the temperature dependence of thermal recovery of stored dislocations. The same process applies for the deformation parameters such as the re-mobilization probability of immobile dislocations and the mobile dislocation density that were previously obtained from the analysis of stress-strain behavior on a basis of dislocation dynamics. An activation energy of approximately 32 kJ/mol is equivalent to the vacancy migration energy in aluminum minus the binding energy between a vacancy and a solute atom of magnesium or copper.

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  • Ultra Grain Refinement of Commercial Purity Aluminum by a Multi-Stack ARB Process

    Seong-Hee Lee, Hajime Inagaki, Hiroshi Utsunomiya, Yoshihiro Saito, Tetsuo Sakai

    pp. 1376-1381

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    DOI:10.2320/matertrans.44.1376

    Abstract

    Multi-layer stack accumulative roll bonding (ARB) process is proposed and applied to commercial purity aluminum for ultra grain refinement. The six aluminum sheets 0.5 mm thick, 50 mm wide and 400 mm long were degreased and wire-brushed. The sheets were stacked together, and cold-roll-bonded by 50%-reduction rolling. The roll-bonding was followed by four-pass rolling so that the final thickness was 0.5 mm. The sheet was then cut to the six pieces of same length and the same procedure was repeated to the sheets. The ARB process up to six cycles (an equivalent thickness strain of 13.2) was successfully performed. The tensile strength of the ARB processed aluminum increases with the number of ARB cycles, and it reaches a maximum of 287 MPa after the third cycle. The tensile strength is lower by the six-layer stack ARB than that by the conventional two-layer stack ARB. The elongation slightly decreases with the number of the ARB cycles. TEM observation reveals that ultrafine grains begin to develop at the first cycle, and cover most field after the 3rd cycle, and that their aspect ratio decreases with the number of cycles. The grain size of the six-layer stack ARB is larger than that of the two-layer stack ARB. The effects of the number of the layers in stacking are explained by the redundant shear deformation. It is concluded that multi-layer stack ARB is a suitable process for industrial production of ultrafine-grained coils.

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  • Fabrication of Ultrafine Grained Aluminum by Differential Speed Accumulative Roll-Bonding (ARB) Process

    Seong-Hee Lee, Tetsuo Sakai, Dong Hyuk Shin

    pp. 1382-1385

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    DOI:10.2320/matertrans.44.1382

    Abstract

    The differential speed accumulative roll bonding (DSARB) process was attempted to strengthen 1100 aluminum sheet via grain refinement. The roll peripheral speed of one roll was 2.0 m/min and that of another roll was 3.6 m/min. The roll speed ratio was kept at 1.8. The accumulative roll bonding was conducted up to 6 cycles at ambient temperature without lubrication. For comparison, the conventional accumulative roll bonding (CARB) process was conducted with a rolling speed of 3.0 m/min. The grains developed by the DSARB process were more equiaxed than those produced by the CARB. Tensile strength of the DSARB processed sample was higher than that of the CARB processed sample at the same plane strain compressive strain. The elongation was not affected significantly by the number of ARB cycles. The DSARB process was more effective for grain refinement and strengthening than the CARB process.

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  • Platinum Recovery Using Calcium Vapor Treatment

    Toru H. Okabe, Yoshihiro Kayanuma, Sachiko Yamamoto, Masafumi Maeda

    pp. 1386-1393

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    DOI:10.2320/matertrans.44.1386

    Abstract

    To develop an effective process for the recovery of precious metals from scrap, a new platinum (Pt) extraction process using alloy formation by calcium (Ca) vapor and successive leaching with an aqueous solution were investigated. Pure Pt samples were reacted with Ca vapor at constant temperatures ranging between 1073 and 1173 K for three to twelve hours, and Ca–Pt alloy samples were synthesized. The obtained Ca–Pt alloy was then dissolved in aqua regia or in an aqueous HCl solution at room temperature. Platinum was recovered from the leaching solution by conventional (NH4)2PtCl6 precipitation method, and the amount of Pt obtained by each process was analyzed. It was found that more than 90% of the Pt was recovered by this process. After Ca vapor treatment, 100% of the Pt was dissolved when kept in aqua regia for one hour, whereas only 14% of untreated pure platinum was dissolved when kept in aqua regia for four hours. In some experiments, the obtained Ca–Pt alloy samples were oxidized in air for reducing the amount of acid needed for dissolution. Although Pt hardly dissolves in aqueous HCl solution at room temperature, it was found that Ca vapor treatment followed by oxidation is effective in increasing the rate of dissolution in aqueous HCl solution.

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  • In-situ Photoluminescence, Raman, and IR Spectral Study of Porous Silicon during Exposure to Thermoelectrons/H atoms, /H2O and /O3

    Toshimasa Wadayama, Tuyoshi Arigane, Aritada Hatta

    pp. 1394-1399

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    DOI:10.2320/matertrans.44.1394

    Abstract

    Photoluminescence (PL), Raman, and transmission IR spectral measurements of porous silicon (PS) have been carried out during exposure to thermoelectrons and also subsequent exposure to H atoms, H2O and O3. The PL band of as-anodized PS was significantly decreased by the first exposure to thermoelectrons accompanied by the intensity reduction of the IR bands due to hydrogenated Si species (Si–Hx; x=1–3). Upon subsequent exposure to H atoms the PL band intensity was almost recovered but never exceeded its original intensity. This PL recovery was accompanied by re-generation of Si–Hx bonds. In contrast, an overshooting recovery in the PL intensity took place when thermoelectron-treated PS was exposed to H2O or O3. The obtained IR spectra showed that Si–O and/or Si–OH bonds were formed at the PS surface. These results demonstrate that the PL of the PS is quite sensitive to the oxygen-included surface bonds.

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  • A Feasible SIMS Study for Characterizing Ferric Oxyhydroxides Formed on the Iron Surface Using Deuterium

    Shigeru Suzuki, Yohei Takahashi, Yoshio Waseda

    pp. 1400-1404

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    DOI:10.2320/matertrans.44.1400

    Abstract

    Secondary ion mass spectrometry (SIMS) has been applied to hydrogen and deuterium analysis for ferric oxyhydroxides, which is formed by reaction of an iron substrate with water; either H2O or D2O containing a small amount of sodium chloride. Mass spectra of positive and negative ions obtained by SIMS showed that deuterium in ferric oxyhydroxides can be differentiated from hydrogen, although many species of secondary ion peaks are detected. Mass spectra from an iron sample, which firstly reacted with H2O, subsequently dried and finally reacted with D2O, indicated that D2O reaches a reaction front of the iron substrate through ferric oxyhydroxides formed by reaction with H2O. This implies that the ferric oxyhydroxides formed by reaction with H2O are, more or less, porous and thus water penetrates into ferric oxyhydroxides to the substrate. These results also suggest that SIMS analysis using isotopes enable us to characterize a formation process of ferric oxyhydroxides and permeability of foreign ions in the ferric oxyhydroxides.

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  • XPS Study of Corrosion Behavior of Ti-18Nb-4Sn Shape Memory Alloy in a 0.05 mass% HCl Solution

    Asahi Kawashima, Sadao Watanabe, Katsuhiko Asami, Shuji Hanada

    pp. 1405-1411

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    DOI:10.2320/matertrans.44.1405

    Abstract

    The Ti–18Nb–4Sn alloy has been confirmed to possess much higher corrosion resistance compared to the NiTi alloy throughout immersion time up to 604.8 ks in a 0.05 mass% HCl at 310 K open to air. The Ti–18Nb–4Sn alloy shows higher open circuit potential, compared to titanium metal and NiTi alloy. The higher open circuit potential results in an increase in the thickness of the passive film formed on the alloy. The passive film on the Ti–18Nb–4Sn alloy is rich in niobium as well as tin due to preferential dissolution of titanium. The degree of enrichment of niobium and tin in the film increases with an increase in immersion time. On the other hand, the passive film on the NiTi alloy consists exclusively of titanium. The angle-resolved XPS analysis reveals that the outer part of the passive film on the Ti–18Nb–4Sn alloy is rich in niobium and deficient in titanium. Furthermore, the passive film on the Ti–18Nb–4Sn alloy is composed of a double oxyhydroxide containing titanium, niobium and tin cations. It can, therefore, be said that the formation of the thick and homogeneous double oxyhydroxide film whose outer part is rich in niobium seems responsible for the excellent corrosion resistance of the Ti–18Nb–4Sn alloy.

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  • Feasibility of Plasma Nitriding for Effective Surface Treatment of Pure Aluminum

    Patama Visuttipitukul, Tatsuhiko Aizawa, Hideyuki Kuwahara

    pp. 1412-1418

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    DOI:10.2320/matertrans.44.1412

    Abstract

    Cast aluminum with 99.99% purity was successfully plasma nitrided using nitrogen and hydrogen mixed gas. Pre-sputtering was carried out prior to plasma nitriding in order to eliminate surface oxide film. Sputtering and nitriding durations were varied from 3.6 to 18 ks and 72 ks to 252 ks, respectively. The samples were nitrided at 823 and 873 K to observe the effect of nitriding temperature. The nitrided samples were analyzed by GIXD, XPS, and TEM. Through GIXD and XPS results, formation of AlN was distinctly detected as a nitrided surface. Cross-sectional microstructure of nitrided samples showed that AlN was formed with the thickness up to 3–5 μm. AlN formation is controlled by the diffusion process. The thickness of AlN layer was determined by the nitriding time and temperature. Partial degradation of AlN in the vicinity of the free surface occurred due to its reaction with moisture in air. Partial detachment of AlN layer occurred due to the residual thermal stress, which was caused by the difference in thermal expansion coefficient between AlN and substrate of Al.

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  • Influence of Steel Scrap on Microstructure and Mechanical Properties of Spheroidal Graphite Cast Iron

    Sadato Hiratsuka, Hiroshi Horie, Toshinori Kowata, Katsumi Koike, Kazumichi Shimizu

    pp. 1419-1424

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    DOI:10.2320/matertrans.44.1419

    Abstract

    In this research, the spheroidal graphite cast iron melt was produced by using 7 kinds of steel scraps, the shredder scrap, the surface treated steel sheets, the magnetic steel sheets, the high strength steel and others. The influences of the steel scraps on microstructures and mechanical properties were studied. Zinc, chromium, antimony, nickel, aluminum and manganese were contained in the steel scraps respectively. Using the steel scrap of the used car (shredder scrap), zinc is contained in the iron castings. The antimony included in the magnetic steel sheet was found to be a powerful pearlite stabilizer. The tensile strength and the hardness of cast iron increased with the increasing pearlite percent. Also chromium included in the surface treated steel sheet and manganese in the high strength steel increase the pearlite in the matrix of cast iron.

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  • Glass Transition Behavior and Mechanical Properties of Ni-Si-B-Based Glassy Alloys

    Baolong Shen, Akihisa Inoue

    pp. 1425-1428

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    DOI:10.2320/matertrans.44.1425

    Abstract

    The effect of transition metals Nb and Ta on the glass-forming ability of Ni75Si8B17 was examined. New Ni–Si–B–M (M = Nb, Ta) glassy alloys with high Ni contents above 70 at% were found to exhibit a glass transition before crystallization. The glass transition temperature (Tg) increases continuously with increasing Nb or Ta content. The supercooled liquid region (ΔTx(=Tx−Tg)) and reduced glass transition temperature (Tg⁄Tl) are 30 K and 0.59, for (Ni0.75Si0.08B0.17)96Nb4 and 35 K and 0.61, for (Ni0.75Si0.08B0.17)96Ta4, respectively. These two glassy alloys exhibit high fracture strength and good bend ductility. The maximum fracture strength of the Ni–Si–B–Nb and Ni–Si–B–Ta alloys is 2510 and 2730 MPa, respectively. All the samples can be folded through an angle of 180 degrees without fracture. The use of the glassy-type (Ni0.75Si0.08B0.17)96Ta4 alloy enabled us to form a glassy alloy rod with a diameter of 0.5 mm by the copper mold casting method. The combination of the new alloy composition, high glass-forming ability and good mechanical properties of the Ni-based glassy alloys indicates that the new bulk glassy alloy may be used as a new type of engineering material.

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  • Effects of Snout and Support Roll on Transport Phenomena in a Hot Dip Plating Bath

    Jun Kurobe, Manabu Iguchi

    pp. 1429-1437

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    DOI:10.2320/matertrans.44.1429

    Abstract

    The fluid flow phenomena of plating melt, the motions of dross, and the dispersion of melting ingots in a continuous hot dip plating bath were investigated using a transparent cold model vessel with a reduced scale of one-tenth. This model was equipped with a snout and two support rolls. Water was used as a model for the plating melt. The flow pattern in the bath was basically the same as that in the bath without the snout and the support rolls, but re-circulating flows cased by the existence of the snout were observed in the entry region and in the region enclosed with the belt. Water supplied in the snout through the passage above the sink roll was carried by the belt and exhausted into the entry region. Most top dross and bottom dross were carried by the main flow in the entire bath. A part of the top dross floated on the bath surface and a part of the bottom dross accumulated on the bottom of the bath. The dispersion of tracer, being a model for melted ingots, was mainly controlled by the main flow. The mixing time became shorter in the presence of the snout and support rolls than in the absence of them.

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  • Transmission Electron Microscopy of Interfaces in Joints between Pb-Free Solders and Electroless Ni-P

    Naoki Torazawa, Shigeo Arai, Yoshihisa Takase, Katsuhiro Sasaki, Hiroyasu Saka

    pp. 1438-1447

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    DOI:10.2320/matertrans.44.1438

    Abstract

    Microstructures of joints between a Ni–8 mass%P UBM (under bump metallization) and three different Pb-free solders, i.e., Sn–Ag, Sn–Ag–Cu and Sn–Ag–Cu–Bi were studied by transmission electron microscopy. The phases formed near the joint interfaces as well as inside the solders during soldering were identified on the basis of electron diffraction and EDX analysis without ambiguity. In the Ni–P under bump metallization near the interface with the solders, P-denuded Ni–20 mass%P layer was observed, where a high density of columnar voids were formed. Also, in Ni(Cu) SnP intermetallic, which is adjacent to the P-denuded Ni–20 mass%P, a high density of spherical voids were observed. These voids degrade the joint strength. Change of the above microstructures during thermal cycling between 253 K and 453 K was also observed.

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  • A Model of the β-AlFeSi to α-Al(FeMn)Si Transformation in Al-Mg-Si Alloys

    Niels C. W. Kuijpers, Fred J. Vermolen, Kees Vuik, Sybrand van der Zwaag

    pp. 1448-1456

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    DOI:10.2320/matertrans.44.1448

    Abstract

    During the homogenisation process of Al–Mg–Si extrusion alloys, plate-like β-Al5FeSi particles transform to multiple rounded α-Al12(FeMn)3Si particles. The rate of this β to α transformation determines the time which is required to homogenise the aluminium sufficiently for extrusion. In this paper, a finite element approach is presented which model the development of fraction transformed with time, in the beginning of the transformation, as a function of homogenisation temperature, as-cast microstructure and concentration of alloying elements. We treat the β to α transformation mathematically as a Stefan problem, where the concentration and the position of the moving boundaries of the α and β particles are determined. For the boundary conditions of the model thermodynamic calculations are used (Thermo-Calc). The influence of several process parameters on the modelled transformed fraction, such as the temperature and initial thickness of the β plates, are investigated. Finally the model is validated with experimental data.

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  • Mechanochemical Syntheses of Perovskite KMIIF3 with Cubic Structure (MII = Mg, Ca, Mn, Fe, Co, Ni, and Zn)

    Jaeryeong Lee, Heeyoung Shin, Jaechun Lee, Hunsaeng Chung, Qiwu Zhang, Fumio Saito

    pp. 1457-1460

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    DOI:10.2320/matertrans.44.1457

    Abstract

    An equi-molar mixture of potassium fluoride (KF) and one of alkaline-earth or transition metal fluoride MIIF2 (MII = Mg, Ca, Mn, Fe, Co, Ni, and Zn) was ground in air by using a planetary ball mill to investigate mechanochemical (MC) synthesis of fluoroperovskites KMIIF3. Rietveld refinement for the ground mixtures was conducted on the basis of XRD data to inquire into structural properties of the KMIIF3 synthesized mechanochemically. The synthesis reactions proceed with grinding time, and ultimately a single phase of cubic structural KMIIF3 (Pm3m, Z=1) was obtained after grinding for 21.6 ks. The values of unit cell parameter, a, of KMIIF3 synthesized by MC reaction, are slightly larger than those by solid-state reaction at high temperature, and this may be attributed to structural distortions caused by intensive grinding.

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  • Effect of Nodular Graphite on the Deterioration of Vibration Fracture Resistance of Ferritic Cast Iron under an Aqueous Environment

    Yu-Hua Song, Truan-Sheng Lui, Li-Hui Chen, Jenn-Ming Song

    pp. 1461-1468

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    DOI:10.2320/matertrans.44.1461

    Abstract

    An intergranular fracture feature could be observed when ferritic spheroidal graphite cast irons were tested under continuously wet conditions. The maximum depth of intergranular fractures was closely related to the microstructural feature and ambient environment that caused the deterioration in vibration fracture resistance. Experimental evidence has confirmed the overall D-N curves can be generalized into three characteristic regions. Intergranular fractures occurred in the vicinity of the surface; the existence of nodular graphite act as porosity should be considered as a dominant microstructural factor on the initiation of intergranular fractures. On the other hand, intergranular fractures can be prevented resulting in better vibration fracture resistance when a specimen of ferritic SG cast iron is covered with oil film, or if an identical test is performed using the Fe–3Si steel specimen containing no nodular graphite.

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  • Grain Boundary Microstructure-Controlled Superplasticity in Al-Li-Cu-Mg-Zr Alloy

    Shigeaki Kobayashi, Taichi Yoshimura, Sadahiro Tsurekawa, Tadao Watanabe, Jianzhang Cui

    pp. 1469-1479

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    DOI:10.2320/matertrans.44.1469

    Abstract

    Grain boundary microstructure-controlled superplasticity in an Al–Li alloy is discussed on the basis of OIM observations using the specimens with different grain boundary microstructures. The specimens having the homogeneous {110} textured grains with a high frequency of low-angle boundaries showed superplasticity, whereas the specimen having a heterogeneous and randomly oriented grains with a high frequency of random boundaries did not yield superplasticity. Cavities were preferentially formed at the triple junctions where two or three random boundaries interconnected. From those results, the optimum grain boundary microstructure for superplasticity is discussed in connection with the relationship between grain boundary character distribution (GBCD) and triple junction character distribution. The strain rate change tests were carried out during deformation in order to rejuvenate initially introduced optimal grain boundary microstructure. The superplasticity can be improved by the strain rate change test resulting in an increase of the frequency of low angle boundaries at the early work softening stage of deformation.

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  • Erosion Behavior of CA-15 Tempered Martensitic Stainless Steel

    Hwei-Yuan Teng, Cheng-Hsun Hsu, Sheng-Chien Chiu, Dong-Cherng Wen

    pp. 1480-1487

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    DOI:10.2320/matertrans.44.1480

    Abstract

    Martensite stainless steel (MSS) possesses excellent strength and medium corrosion resistance, and is often used in industrial applications, such as for highly stressed parts like turbine blades and pipe materials. However parts are often damaged by flow field particles interact with the materials, in a solid particle erosion (SPE) phenomenon, which may even lead to injuries. In this paper we discuss the effects of the tempering treatment and the erosion incident angle on the CA-15 MSS erosion behavior. The results show that, in single particle erosion tests, the main mechanisms that cause problems are micro-cutting and deformation craters at low and high incident angles, respectively. In repetitive particle erosion tests, grain boundary cracking is one of the main fracture mechanisms. The platelet mechanism also obvious affected at high incident angle erosion. Materials tempered at 573–673 K, tempered martensitic embrittlement (TME) occurred, which caused serious boundary cracking and grain broken-down. The serious erosion damage showed at medium incident angle for this material that result in combine of cutting, deformation crater, and cracking mechanism. The maximum erosion rate of material occurred at an incident angle of π⁄6 and the deepest erosion penetration occurred at an incident angle of π⁄4.

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  • Formation of Nanocrystalline Structure in Steels by Air Blast Shot Peening

    Minoru Umemoto, Yoshikazu Todaka, Koichi Tsuchiya

    pp. 1488-1493

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    DOI:10.2320/matertrans.44.1488

    Abstract

    The formation of nanocrystalline structure (NS) on the surface of bulk steel samples by a particle impact and air blast shot peening techniques was studied. Nanocrystalline layers with several microns thick were successfully fabricated by these methods. The nanocrystalline layers produced in the present study have extremely high hardness and separated from adjacent deformed morphology region with sharp boundaries. By annealing, nanocrystalline layers showed slow grain growth without recrystallization. Those characteristics are similar to those observed in the NS produced by ball milling and a ball drop deformation. It was suggested that to produce NS by deformation a large strain is a necessary condition and a high strain rate and low temperature are favorable conditions.

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  • The Control of Oxidation-Induced Intergranular Embrittlement by Grain Boundary Engineering in Rapidly Solidified Ni-Fe Alloy Ribbons

    Shin-ichi Yamaura, Sadahiro Tsurekawa, Tadao Watanabe

    pp. 1494-1502

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    DOI:10.2320/matertrans.44.1494

    Abstract

    The relation between grain boundary microstructure and oxidation-induced intergranular embrittlement has been investigated in rapidly solidified and subsequently annealed Ni–39 mass%Fe thin ribbons with different grain boundary microstructures. These thin ribbons were heated in air under different tensile stresses to enhance intergranular oxidation. Oxidation-induced embrittlement was then evaluated by three-point bending tests. It was found that the brittleness of oxidized ribbons varied according to the grain boundary microstructure. Fine-grained microstructure was found to be superior to coarse-grained one by suppressing oxidation-induced embrittlement when the type and the frequency of grain boundaries (that is called the Grain Boundary Character Distribution, GBCD) were properly controlled. Moreover, for a given grain size, grain boundary microstructure containing higher frequencies of special boundaries was shown to be advantageous in the control of oxidation-induced intergranular embrittlement. On the basis of these findings, the importance and usefulness of grain boundary engineering for the control of oxidation-induced intergranular embrittlement are discussed.

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  • Development of a Strain Evaluation Technique Using a Micro Focus X-ray Beam

    Takuji Kita, Yasuo Nagano, Hiroshi Kawamoto, Ryouichi Yokoyama

    pp. 1503-1505

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    DOI:10.2320/matertrans.44.1503

    Abstract

    A strain evaluation technique using a micro focus X-ray beam was developed. An electron gun with two electron lenses was used in order to steadily make a fine focus of an electron beam on a copper target. A target current was 24 μA, and an X-ray brightness 162×109 W/m2 was obtained. X-ray beam was condensed to a converging angle 0.09 deg with a convergent unit, and the minimum focus diameter was 60 μm. A Cu-Kα2’s peak can be easily split from a Kα1’s peak, because the converging angle of the X-ray beam is low and an X-ray brightness is high. A charge coupled device camera can be set in order to observe the irradiated area on a sample. A cubic ZrO2–10 mol%Y2O3 single crystal cut along a (001) plane was selected as a sample to ensure a measurement technique. The difference in a Miller index from an integer was less than 0.4%. A lattice parameter of the specimen was 0.51442±0.00002 nm, and the reference value was 0.5144 nm. Strain was loaded to the sample with a four-point bending jig. A strain tensor was analyzed from the difference in the lattice parameters which were calculated using from 15 to 50 planes. Although the some measured values had a more than 100×10−6 difference from the estimated ones, the other measured values were almost same as the estimated ones within experimental error.

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  • © 2003 The Japan Institute of Metals and Materials

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