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

MATERIALS TRANSACTIONS Vol. 46 (2005), No. 12

  • Waste Input–Output Material Flow Analysis of Metals in the Japanese Economy

    pp. 2550-2553

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    DOI:10.2320/matertrans.46.2550

    This paper develops a theoretical model of material flow analysis (MFA) within the framework of the Waste Input–Output model (WIO) (Nakamura and Kondo). The model is developed based on two fundamental ingredients: yield ratios and the degree of fabrication. In manufacturing process, multiplication of physical inputs by the yield ratios gives the portion that enters physical outputs, with the rest being discarded as process waste without entering outputs. In input–output analysis, the degree of fabrication can be visualized as triangularity of the input coefficients matrix (goods of lower degree of fabrication can enter those of higher fabrication, but the reverse does not hold), which is known to emerge through an appropriate reordering of sectors. Application to the Japanese IO data indicates that the model can provide accurate estimates of the weight as well as the composition of metals (Fe, Cu, Pb, Zn, and Al) used in a passenger car. The model is also used to estimate the major final use categories (household consumption, public consumption, capital investment, inventory investment, and export) of metals.
  • Web-Site Survey of Recent Ecomaterial Developments in Japan

    pp. 2554-2560

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    DOI:10.2320/matertrans.46.2554

    One of the gravest environmental problems facing us today is how to manage materials we use and produce as a result of the industrial development in the 20th century. The concept of ecomaterials was proposed with their full life-cycle taken into consideration in 1991 and has widely developed now. There have been many governmental activities for the creation of sustainable society in Japan such as enactments of environmental laws and regulations. Many Japanese enterprises have been also engaged in a lot of activities for environmental protection. Owing to their endeavour, ecomaterials in Japan have been developed and their number has increased yearly. The research was made on how ecomaterials are currently used in Japan. All the information was obtained from the Web-sites 2004 year version environmental reports of the organizations concerned. In this paper, ecomaterials produced by two hundred and sixty six listed companies on the stock market were researched and classified into six categories. About 3900 ecomaterials were found in the 2004 year version environmental reports of 266 companies researched, whereas the number of ecomaterials researched in the year 2001 was only 1898 in 286 companies and in the year 2003 about 3700 in 281 companies. This means the number of ecomaterials in Japan in the year 2003 nearly doubled compared to that of 2001 and increased further in 2004. It also indicates the realization on the part of Japanese companies of the importance of ecomaterials resulting in the advancement of related research activities. Higher materials efficiency products of user friendly, energy saving and high performance type, which are the results of years of engineering research and development are being promoted as newly improved and efficient products. It seems that the time is approaching when it is necessary to consider as a part of environmental problems the limited availability of natural resources and to promote a sustainable society from a broader perspective.
  • “Ecological Rucksack” of High-Definition TVs

    pp. 2561-2566

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    DOI:10.2320/matertrans.46.2561

    In order to verify the effectiveness of the “Ecological Rucksack” as an indicator on resource utilization for electrical and electronic equipments, the Ecological Rucksack of 36-inch high-definition TVs produced in 1993 and 2003 has been estimated in cooperation with the Wuppertal Institute in Germany. The Ecological Rucksack (abiotic material) of the 1993 product was 19 tons (product mass 91.0 kg) and that of the 2003 product was 7.7 tons (product mass 79.5 kg), therefore, an approximate 11 tons or 60% reduction. The breakdown of the Ecological Rucksack (abiotic material) of the 1993 product indicated that the values associated with the print circuit board mounted inc. electronic components (hereafter called PC board) represented approximately 50% of the total, followed by power consumption during use at 40%. The PC board represented less than 10% of the product mass but occupied approx 50% of the Ecological Rucksack (abiotic material). The smaller and lighter PC boards employed in the later product substantially contributed to the reduction of Ecological Rucksack. As evident in the example of the PC board, the consideration of Ecological Rucksack reveals the hidden material flow and presents a new approach to resource utilization.
    However as for the materials used over the life cycle of a high-definition TV set, the factors obtainable from the MI factors table represented only 25% of the product mass. By applying the MI factors of materials with equivalent properties, the rate of MI factors increased to 99% of the product mass, thereby enabling an estimation of the Ecological Rucksack for a TV set. The estimation made this time around underlined the fact that further examination of the data was required for the PC board, because it would strongly affect the evaluation results for determining the Ecological Rucksack of a high-definition TV set. Further enhancement of the database is therefore required for enabling applications to electric and electronic equipment.
  • Conceptual Design of Super Environment-Conscious Intelligent Composites Incorporated with Life-Cycle Program of Self-Repair and Self-Collapse and Application for Environment-Conscious Interior Planning in Buildings

    pp. 2567-2573

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    DOI:10.2320/matertrans.46.2567

    Super environment-conscious intelligent composite materials incorporated with life-cycle program of self-repair during in service and self-collapse after designed service life are proposed. One example is carbon short-cut fiber reinforced composites (CFRC) incorporated into matrix mortar with numerous two kinds of micro capsules imbedded with two smaller capsules containing nanometer-size reacting particle (calcium oxide (CaO) or cement) and initiating one (highly water-containing resin particle). These double capsules are incorporated during mixing mortar and fiber as chemical admixture, but they are stably dispersed, not breaking during in service of composites. By triggering these double capsules by external electromagnetic wave having two different frequencies, these capsules are broken, and chemical reaction occurs. As the results, self-repair is made to occur in the crack part during in service by the rather mild hydration reaction of cement, and self-collapse after designed service life by the rapid expansive hydration reaction of CaO. These cement composites are intelligent due to the appropriate response to the controlled external electromagnetic trigger, and environment-friendly due to the elongation of service life by self-repair, and the easiness of demolition and recycling by self-collapse. The same concept is also applied to carbon continuous fiber reinforced plastic reinforced concrete (CFRPRC). Other than double microcapsules, glass optical fibers are also imbedded into matrix resin of FRP. By detecting the change of electric resistance of CFRP, we can predict the collapse. By triggering the embedded double capsules, self-repair and self-collapse are made to occur. These pseudo-biological functions of self-repair and self-collapse are also incorporated into base concrete. These CFRPRC are enough to become intelligent and environment-friendly. By using well designed these super environment-conscious intelligent composites, I try to realize environment-conscious interior planning in which non-adhesive, but joint or set-in type interior construction are considered.
  • Dense P/M Component Produced by Solid Freeform Fabrication (SFF)

    pp. 2574-2581

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    DOI:10.2320/matertrans.46.2574

    Using fine metal powders, we were able to fabricate dense P/M (powder metallurgy) products by a three-dimensional inkjet printing system. We used carbonyl nickel powder with a mean particle size of 5 μm as a raw material and examined two binder supply methods: (i) supplying a binder directly from the inkjet head (DB method), and (ii) coating the powder with a water-soluble polymer and then supplying thin polymer-dissolved water from the inkjet head (CB method). The layered green product was sintered in a hydrogen atmosphere at a temperature in the range of 1073–1623 K. Sintered samples fabricated by the CB method had non-uniform microstructure due to agglomeration of the coated powder. In samples made by the DB method, the macroscopic shape was retained after high-temperature sintering at 1623 K, and a high density of over 90% was achieved, which was attributed to uniform powder cohesion in the laminating process.
  • Fabrication of Composite Materials Using Al Scrap and Wasted Glass

    pp. 2582-2585

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    DOI:10.2320/matertrans.46.2582

    Model experiments were performed for fabricating composite materials using Al scrap and waste glasses. Significance of the fabrication using the waste matters was discussed from an environmental point of view. Al alloy having composition of the Al scrap was melted and infiltrated into a soda-lime glass beads’ bed by a vacuum process. Reaction layer was formed at the interface between the glass beads and the molten Al alloy. The layer thickness of 50 microns was obtained after 1 h reaction. The composite materials showed a strong bonding between the filler (the glass particles) and the matrix. Variation of the layer thickness was measured at various conditions of the reaction time and temperature.
    Distribution of the metal elements in the microstructure of the composite material was analyzed with SEM/EDX. It was shown that not only Si but also some elements were removed from the glass to the Al alloy matrix. Behaviors of the other elements were discussed, considering the thermodynamics. Compression test of the composite materials was performed. They fractured in a brittle manner once, however, after the fracture, they were not broken into pieces, but followed by the ductile deformation.
  • Innovative Reuse of Agricultural Wastes as Industrial Raw Materials to Form Magnesium Composites

    pp. 2586-2591

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    DOI:10.2320/matertrans.46.2586

    Innovative reuse process of rice husks (RH), being one of the representative agricultural wastes, has been developed to fabricate magnesium composites by solid-state reaction to form magnesium silicide (Mg2Si) reinforcements, having high hardness and Young’s modulus. From a view point of the biomass energy, rice husks, including about 70 mass% organics, could be effectively used as environmentally benign fuels to supply electric power or biomass ethanol. Considering that the most of the rice husk wastes after absorbing organics is SiO2, the solid-state synthesis of Mg2Si compounds by reaction of SiO2 with magnesium was suggested in this study. First of all, the effect of the acid washing treatment to remove organics of rice husks on the crystallization of amorphous SiO2 was evaluated by TG-DTA and XRD analysis. The carbon content of 0.05% in the wastes was drastically reduced by using acid-washed rice husks, compared to that of non acid-washed ones (0.19%). When employing the wastes with and without the acid washing treatment, the crystallization temperature is about 1273 and 1073 K, respectively. The latter showed the lower crystallization temperature because the reaction of the alkaline contents, such as K, P, and Ca, with SiO2 during heating caused to decrease the SiO2 melting point. Rice husk wastes burned at 1273 K after the acid treatment was mixed with AZ31 magnesium alloy powder to fabricate the magnesium composites including Mg2Si dispersoids. Microscope observation and XRD analysis indicated that the amorphous SiO2 included the wastes was more effective to promote Mg2Si formation.
  • Mechanical Properties of Mg–Al–Ca Alloy Recycled by Solid–State Recycling

    pp. 2592-2595

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    DOI:10.2320/matertrans.46.2592

    Solid-state recycling for runner scraps of Mg–Al–Ca alloy was carried out by extrusion at 673 K and mechanical properties of the recycled Mg alloy were investigated by tensile tests. At room temperature, the recycled specimen showed a good combination of high ultimate tensile strength (348 MPa), high 0.2% proof stress (305 MPa) and large elongation (9%). Additionally, the recycled specimen exhibited superplastic behavior at 573 and 673 K. The excellent mechanical properties of the recycled specimen result most likely from fine dispersion of precipitates which is attained by hot extrusion.
  • High-Speed Twin Roll Casting of Thin Aluminum Alloy Strips Containing Fe Impurities

    pp. 2596-2601

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    DOI:10.2320/matertrans.46.2596

    In this work, the mechanical properties of roll-cast recycled aluminum alloy were investigated. Fe was added to 6111 aluminum alloy to simulate recycled aluminum alloy. The Fe content was varied between 0.14 and 1.02 mass%. A high-speed twin roll caster was used because it exhibits better cooling characteristics than the conventional twin roll casters. The strip was cast at a speed of 60 m/min and the resulting strip microstructure was not columnar, but equiaxed or globular. When the Fe content was 0.4 mass%, the Fe content does not appear to exert any influence on the tension test results after T6 heat treatment, and after a 180-degree bending test no cracks occurred on the outer surface.
  • High-Speed Twin-Roll Strip Casting of Al–Mg–Si Alloys with High Iron Content

    pp. 2602-2608

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    DOI:10.2320/matertrans.46.2602

    Thin strips of the 6063 aluminum alloy and the alloys with increased nominal Fe contents (0.7–6 mass%Fe) were fabricated directly from the molten alloys using a vertical-type high speed twin-roll strip caster equipped with a pair of water-cooled pure copper rolls. The estimated cooling rates from the DAS measurement were about 4500 and 100°C/s at the near the surface region and the mid-thickness region of the strip respectively. Refinement of Al–Fe–Si intermetallic compound particles was also successfully achieved, however, segregated coarse particles were also observed at the mid-thickness region. The cast strips were cold-rolled and heat-treated to form 0.5 mm-thick thin sheets. They were either naturally aged at room temperature (T4) or artificially aged (T6), and then subjected to bending, tensile and hardness tests. No detrimental effect of Fe was appeared concerning the bendability even in the alloy containing 3 mass%Fe. No cracking took place even in the 180° bending (hemming) test. The reduction of age-hardenability was evident for the alloy with 1 mass%Fe and more. The alloy sheet containing 0.7 mass%Fe exhibited not only a good bendability in the T4 condition but also the larger proof stress and UTS than those of the master alloy in the T6 condition. This means that the capacity of Fe impurity in a 6063 alloy (0.35 mass% according to JIS) can be doubled by using the present roll caster. Strip casting at a high cooling rate using the present roll caster is considered to be a promising method for reducing the detrimental effect of impurity iron from the scrap melt.
  • Microstructural Refinement of Hyper-Eutectic Al–Si–Fe–Mn Cast Alloys to Produce a Recyclable Wrought Material

    pp. 2609-2615

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    DOI:10.2320/matertrans.46.2609

    Although the cascade of material flow is presently suitable for the aluminum recycling, a better utilization of secondary alloys is required. In order to establish an upgradeable recycling design for developing wrought products from secondary aluminum alloys, a fine distribution of the primary phases in hyper-eutectic Al–Si–Fe–Mn cast materials has been achieved. Two novel processes were adopted. One was repeated thermomechanical treatment (RTMT), which involves a repetition of a multi-step cold-working followed by heat treatment. The other was rapid solidification by high-speed twin-roll casting to develop a fine solidification structure in a thin sheet. By applying these processes, refined microstructures were successfully obtained. Microstructural refinement by RTMT resulted in the avoidance of early fracture that was detected in the cast material by a tensile test. The RTMT imparted good ductility; therefore, it was possible to allow greater flexibility in the cold working of Al–Si–Fe–Mn cast materials.
  • Mechanical Properties of Thermomechanical Treated Hyper-Eutectic Al–Si–(Fe,Mn,Cu) Materials

    pp. 2616-2623

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    DOI:10.2320/matertrans.46.2616

    Tensile and high-cycle fatigue behavior of thermomechanical treated hyper-eutectic Al–Si–(Fe,Mn,Cu) materials were studied. Through the repeated thermomechanical treatment (RTMT) which is a repeat of the multi steps cold-working followed by heat treatment, Si crystals and/or intermetallic compounds were broken into some fragments and dispersed in the aluminum matrix. Fine dispersion of the second phase particles exhibited good ductility, since early fracture was overcome. A few large Si crystals or aggregates of compounds, however, gave an origin of fatigue crack generation. Since microcrack linkage generates a larger fetal crack, not only refinement but also random distribution of second particles may be required to improve fatigue strength at and below room temperature. At higher temperature, on the other hand, dynamic recovery may cause apparent strain rate dependence on flow curves.
  • Fabrication of Porous Aluminum by Spacer Method Consisting of Spark Plasma Sintering and Sodium Chloride Dissolution

    pp. 2624-2628

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    DOI:10.2320/matertrans.46.2624

    Porous aluminum with a porosity of 78% and pore size of 850–1000 μm was fabricated under various sintering pressure, sintering time and raw Al powder size conditions by the spacer method consisting of spark plasma sintering (SPS) and sodium chloride (NaCl) dissolution. The effects of the fabrication conditions on compressive properties of the porous Al were investigated. The sintering pressure of 20 MPa and sintering time of 10 min were needed to fabricate robust porous Al under the sintering temperature of 843 K and raw Al powder size of 3 μm. Also, the porous Al specimen fabricated from Al powder of 300 μm exhibited much lower flow stress than those fabricated from Al powder of 3 and 20 μm when employing the temperature of 843 K, the pressure of 20 MPa and the duration time of 10 min. This indicates that the raw Al powder size is needed to be much smaller than the spacer size. This is because the Al particle cannot touch with adjacent Al particles when the Al powder size is comparable to the spacer size.
  • Evaluation of Nanoporous Aluminum Silicate Including Active Oxygen Species

    pp. 2629-2632

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    DOI:10.2320/matertrans.46.2629

    The catalytic activities of propylene oxidation on different aluminum silicates with the mayenite structure [Ca12Al14−xSixO33+0.5x (x=0,4)] formed at 500, 800 and 1000°C were investigated. The aluminum silicates were prepared by the hydrothermal and solid-state reactions of a stoichiometric mixture of calcium oxide, alumina sol and silica. The XRD results of the aluminum silicates obtained by the solid-state reaction showed that the peak intensities of the mayenite phases became larger as the calcination temperature increased. The aluminum silicates included two kinds of active oxygen species (O22−, O2) related to Raman shifts around 887 and 1092 cm−1, respectively. As a result, the aluminum silicates exhibited oxidation activities based on the easily reducible active oxygen species. Notably, the Ca12Al10Si4O35 calcined at 1000°C without the hydrothermal treatment showed the highest activity of all catalysts, indicating that the crystal structures play an important role in determining the catalytic activity.
  • Energy Absorption and Crushing Behaviour of Foam-Filled Aluminium Tubes

    pp. 2633-2636

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    DOI:10.2320/matertrans.46.2633

    The crushing behaviour and energy absorption of foam filled aluminium tubular structures were investigated using the quasi-static compressive tests. The crushing behaviour of the tubular structures changed due to foam filling. The energy absorption of the foam filled tubular structures was improved significantly. Foam filling caused an interaction effect between the tube and the foam during progressive crushing, leading to an increase in the mean crushing load compared to that of the foam or tube itself. This interaction effect might be affected by several parameters such as the density of the foam, the properties of both the foam material and tube material, and the thickness and outer diameter of the tube. In particular, the interaction effect essentially depended on the ratio of the mean crushing force of the foam to that of the tube.
  • Deformation Characteristics at Elevated Temperature in Recycled 5083 Aluminum Alloy by Solid State Recycling

    pp. 2637-2640

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    DOI:10.2320/matertrans.46.2637

    Deformation mechanism of the recycled aluminum alloy by solid state recycling at elevated temperature was investigated. Elongation of the recycled specimen did not decrease when deformation mechanism was other than grain boundary sliding. Harmful effect of contaminations is negligible when deformation mechanism is related to dislocation activity in grains.
  • Application of Nd:YAG Laser to Aluminum Alloy Sorting

    pp. 2641-2646

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    DOI:10.2320/matertrans.46.2641

    It is important to develop an effective sorting system of aluminum to reduce the cascade recycling of aluminum scraps by instead returning the scraps to wrought aluminum. A feasibility study has been conducted to develop a new sorting process of aluminum scraps. In this study, irradiation of an aluminum surface by pulsed Nd:YAG laser and an automatic sorting method by a pattern-matching method were tested to identify the alloy number of aluminum scraps. For sorting test samples, seven aluminum alloys (1050, 2024, 3003, 4343, 5052, 6063, 7075) were selected from seven wrought aluminum alloy series. The surface of the aluminum irradiated and melted by a YAG laser beam. The surface morphology, including the molten area, brightness profile and change in color, was observed after irradiation. There was a difference in the surface morphology among the aluminum alloys after irradiation. The effect of laser irradiation conditions such as the defocus distance, input energy and laser irradiation angle on the surface morphology after irradiation was investigated to establish the appropriate conditions of laser irradiation for sorting aluminum alloys. It was clear that the surface morphology of aluminum seems to depend on physical properties such as thermal conductivity and liquidus temperature. Therefore, it seems possible to establish an automated aluminum sorting method by using the pattern matching method on irradiated aluminum samples.
  • Near-Net-Shape Fabrication of Porous Alumina-Spinel Castings

    pp. 2647-2650

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    DOI:10.2320/matertrans.46.2647

    The dispersion and fluidity of aqueous platelet γ-alumina slurries were enhanced by addition of ammonium polyacrylate (PAA) as a dispersant at pH 10. Magnesia powder was mixed with the slurries using a planetary mixer for 150 s after ball milling of the slurries for 24 h. Magnesia was eluted gradually into the aqueous media by formation of a chelate with PAA. The slurries were solidified by PAA deficiency because of reduction of the electrostatic repulsive force between the alumina particles. The degree of shrinkage of the green body on drying was very small, and this was therefore regarded as a near-net-shaping process. A porosity of about 60% and strength of 45 MPa were obtained in bodies fired at 1300°C and the mean pore diameter was 0.6 μm.
  • Seeding on the Synthesis of MCM-22 (MWW) Zeolite by Dry-Gel Conversion Method and its Catalytic Properties on the Skeleton Isomerization and the Cracking of Hexane

    pp. 2651-2658

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    DOI:10.2320/matertrans.46.2651

    The effects of seeding on synthesis of MCM-22 (MWW) have been studied by the dry gel conversion (DGC) method. Highly reproducible crystalline MWW zeolite could be obtained by DGC method, using seeds of calcined sodium MWW with SiO2/Al2O3=31. Crystallization of MWW phase was completed in the presence of seeds (2 mass% against SiO2) at 150°C within two days. The small amount of seed (0.25 mass% against SiO2) was sufficient for the required phase formation of MWW. The MWW with SiO2/Al2O3 ratio from 35 to 66 was obtained as pure phase; however, the crystallinity of MWW decreased with further increase in the ratio: products were contaminated with impurities.
    The catalytic properties of MWW were examined in the skeleton isomerization and the cracking of hexane, and compared to zeolites such as BEA, MFI, and MOR. The catalytic activities were in the order: MFI>BEA>MWW>>MOR; however, the selectivity for the isomerization were in the order: BEA>MWW>MFI. These catalytic properties were due to the differences of structures and acid strength of zeolites.
  • Zincoaluminophosphate Molecular Sieves with AFI and ATS Topologies: Synthesis by Dry-Gel Conversion Methods and Their Catalytic Properties in the Isopropylation of Biphenyl

    pp. 2659-2667

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    DOI:10.2320/matertrans.46.2659

    Zincoaluminophosphates, ZnAPO-5 and ZnAPO-36 with AFI and ATS topologies, were successfully synthesized by dry-gel conversion (DGC) method: vapor-phase transport (VPT) and steam-assisted conversion (SAC) methods. ZnAPO-5 was synthesized successfully at 175°C by VPT and SAC methods using Et3N as structure directing agent (SDA). ZnAPO-36 was also obtained by VPT and SAC methods using Pr3N as SDA. The heating protocol was a key factor for the crystallization in the synthesis of ZnAPO-36: the best result was obtained by heating at 140°C for 1 d after aging of the gel at 105°C for 2 d. Calcination procedure is important to get microporous molecular sieves. ZnAPO-5 by VPT method calcined at 550°C gave clear XRD with high microporosity. Highly microporous ZnAPO-36 by VPT method was obtained by careful calcination. Characterization of these zincoaluminophosphates was performed by XRD, NH3-TPD, TG, SEM, N2 adsorption, and ICP analysis. ZnAPO-5 and ZnAPO-36 have the Brønsted acidic characters by the substitution of a part of aluminum with zinc.
    The isopropylation of biphenyl (BP) over these molecular sieves gave different level of the selectivities for 4,4′-DIPB: 60–75% for ZnAPO-5 and 35–45% for ZnAPO-36: these selectivities are in the similar level to corresponding magnesioaluminophosphates corresponding magnesioaluminophosphates. These differences of ZnAPO-5 and ZnAPO-36 in the selectivity are due to the pore structure: ZnAPO-5 has one-dimensional straight channel; however, ZnAPO-36 has one-dimensional channel with side pocket. The steric restriction by ZnAPO-5 effectively controls the transition state to differentiate the slim isomers from others; however, pores of ZnAPO-36 cannot differentiate effectively the isomers because of their side pockets.
  • Synthesis of Poly(Methylacrylate-b-ε-Caprolactone) and Application to Compatibilizer for Poly(L-Lactide)/Poly(ε-Caprolactone) Blend System

    pp. 2668-2672

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    DOI:10.2320/matertrans.46.2668

    Poly(L-lactic acid) (PLLA) was blended with poly(ε-caprolactone) (PCL) using a single-screw extruder in order to modify poor characteristic of these polymers. When the polymer was blended, the block copolymer that is synthesized by methyl acrylate (MA) and ε-caprolactone (ε-CL) via an atom transfer radical polymerization was used as a novel compatibilizer. The structure of the synthesized compatibilizer is determined by 1H or 13C NMR. From this result, it was found that the ring-opening polymerization of the ε-CL was taken place in the hydroxyl end group of MA. Moreover, the morphologies of the PLLA/PCL solvent-cast blend films were observed by the optical microscope and SEM. From the optical microscopic observation, the morphologies of the solvent-cast blend films with the synthesized compatibilizer were more homogeneous than that of the solvent-cast blend films without the compatibilizer. It was confirmed that the phase structure of the solvent-cast blend films with the compatibilizer was more stable than that of solvent-cast blend films without the compatibilizer.
  • Gas Adsorption Properties of Woodceramics

    pp. 2673-2678

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    DOI:10.2320/matertrans.46.2673

    Gas adsorption properties of woodceramics prepared from cedar (Cryptomeria japonica, abbreviated as CE), apple waste (AP), and chicken waste (CH) were studied. Depending on the starting material, woodceramics differed in physisorption properties as evaluated by specific surface area (SSA) obtained by BET (Brunauer–Emmett–Teller) method, in pore structure and size, and in chemical adsorption properties for perfumery substances. CH and AP yielded lower SSA as compared with CE, however, they showed higher gas selectivity for oxygen vs nitrogen gas molecules. The adsorption ability of CE on perfumery essential oil components was evaluated for the first time using the rapid measuring method for VOCs; i.e., the adsorption capacity of cedar-based woodceramics for perfumery materials (essential oil extracts: carvone, pulegone, geraniol, citronellol, menthone, nerol, and citral) was examined. CE showed particularly strong affinity with geraniol and citral, in which more than 99.9% of the compounds were adsorbed. About 99.7–99.8% of pulegone and menthone, 99.0% of nerol, 97.9% of carvone, and 94.0% of citronellol were adsorbed by CE. The adsorption affinity was also influenced by the particle size; particles coarser than 4.0 mm in size showed stronger adsorption.
  • Woodceramic Heating Elements for Low Temperature Heating

    pp. 2679-2684

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    DOI:10.2320/matertrans.46.2679

    Woodceramics are carbon–carbon composites produced by impregnating plant-origin lignocellulosic materials with phenolic resin and by carbonizing the resulting precursor at temperatures higher than 650°C. Since the electric resistance of the woodceramics changes as a function of the carbonizing temperature, heating elements for use in biological incubator systems can be prepared by controlling the electric resistance to obtain optimal Joule heat. Woodceramic heating blocks carbonized at temperatures lower than 800°C were found preferable from the viewpoint of lower water absorptivity. Then, woodceramic test specimens (310×52×18 mm3) were produced from medium density fiberboard (MDF) at carbonizing temperatures of 650, 700, 750, and 800°C (which are simply denoted as 650, 700, 750, and 800, respectively). The electric resistance of the test specimens 650, 700, 750, and 800 at applied voltage of 10 V was 50, 10, 8, and 4 Ω, respectively. Thus, single test piece of 650, 3 serially connected 700, 7 serially connected 750, and 10 serially connected 800 were used to obtain the temperature profile. Temperature rise of each test specimen was measured under applied voltages of 10, 20, 30, and 40 V. For 650, fair temperature stability was obtained at 22°C (10 V) and 27–31°C (20 V). The advantages of the woodceramic heaters as compared with the conventional ceramic heaters are: (1) quick rise in temperature; (2) high stability at designated temperature; (3) lower power consumption; and (4) free of air convection (heats the sample directly and homogeneously).
  • Surface Structure of Woodceramics Manufactured from Cedar

    pp. 2685-2689

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    DOI:10.2320/matertrans.46.2685

    Systematic morphological observations and surface analyses were completed in order to clarify the surface structure of “woodceramics”, i.e., carbon-carbon composite materials consisting of plant-originated carbon reinforced by carbon generated from phenol resin. The woodceramics manufactured from cedar sawdust at various temperatures (650°, 700°, 800°, 1000° and 1200°C) in a nitrogen atmosphere were examined. The microstructure was not affected by the manufacturing temperatures; bundles of the micro-tubes of the original plant (cedar) were preserved. The nanostructure was also unaffected by the manufacturing temperatures except for the one manufactured at the highest temperature (1200°C). Fine needles (fibers) on the surface of the 1000°C-prepared specimen were incorporated into the substrate for the 1200°C-prepared specimen. The oxygen/carbon atomic ratio (0.14) determined by XPS was approximately constant for all specimens manufactured at various temperatures. This value agreed with that of the bulk composition (0.12) except for the one (0.07) manufactured at the highest temperature (1200°C). The binding energy of C1s (284.1 eV) was attributed to elementary carbon. The binding energies of C1s and O1s (532.4 eV) were unchanged by the manufacturing at different temperatures. The specimens manufactured at low temperatures (650°, 700° and 750°C) showed high hydrogen/oxygen atomic ratios (2.6, 2.0 and 1.9, respectively) while those manufactured at high temperatures (1000° and 1200°C) had the lower values (1.3 and 1.4, respectively). The X-ray diffraction analysis indicated an amorphous phase with weak hallos at 23.7° and 43.1° (d-spacing; 0.375 and 0.210 nm, respectively). The weak peaks at 30.41°, 35.30° and 50.84° (d-spacings; 0.2937, 0.2541 and 0.1795 nm, respectively) that appeared eventually were attributed to a minute amount of impurities.
  • Carrier-Concentration-Dependent Transport and Thermoelectric Properties of PbTe Doped with Sb2Te3

    pp. 2690-2693

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    DOI:10.2320/matertrans.46.2690

    The conversion of heat to electricity by thermoelectric (TE) devices may play a key role in the future for energy production and utilization. Lead telluride (PbTe) is one of the best TE materials used for TE generator in the medium temperature. In this report, the transport and TE properties of PbTe doped with antimony telluride (Sb2Te3), which has been used to optimize the carrier concentration for improved TE performance, have been studied. The scattering factor is estimated from the temperature-dependent Hall mobility and the results indicate that the scattering mechanism is changed from an ionized impurity scattering to the interaction between an acoustical and an optical phonon scattering as carrier concentration decreases and the temperature increases. The thermal conductivities for all the samples exhibit linearly dependence with reciprocal temperature and the slope increases with the carrier concentration increasing. The effective maximum power Pmax for PbTe samples increases with an increase of carrier concentration when the temperature gradient is over 400 K and is comparable to the functional gradient materials with the same carrier concentration. This result indicates that high TE performance has been achieved in PbTe with Sb2Te3 as dopants.
  • Photocatalytic Decomposition of Acetaldehyde over Rubidium Bismuth Niobates under Visible Light Irradiation

    pp. 2694-2698

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    DOI:10.2320/matertrans.46.2694

    Two types of rubidium bismuth niobate, RbBi2Nb5O16 and RbBiNb2O7, were prepared by a conventional solid state reaction method and characterized by X-ray diffraction analysis, UV–vis spectroscopy and SEM. These oxides can absorb up to approximately 420–440 nm wavelength of visible light. The photocatalytic activity of the two niobates in decomposing gaseous acetaldehyde, an indoor pollutant, was evaluated under visible light irradiation. The results indicated that RbBi2Nb5O16 showed a higher photocatalytic activity than RbBiNb2O7, in accordance with their different absorption properties. Moreover, RbBi2Nb5O16 deposited with 1 mass%–Pd on the surface exhibited approximately three times better photocatalytic activity than the bare material.
  • Substitution Effects of the Trivalent Cations M3+ on the Photophysical and Photocatalytic Properties of In12NiM2Ti10O42 (M = Al, Cr, Ga)

    pp. 2699-2703

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    DOI:10.2320/matertrans.46.2699

    A new series of visible-light-driven photocatalysts In12NiM2Ti10O42 (M = Al, Cr, Ga) with a pyrochlore-related layered structure were synthesized by the conventional solid-state reaction method. The substitution effects of trivalent cations M3+ on the electronic structure, photophysical and photocatalytic properties were investigated. It was found that although the three materials were all crystallized in a monoclinic symmetry with the same space group P21/a, their photocatalytic activities of H2 evolution were quite different. In comparison with In12NiAl2Ti10O42 and In12NiGa2Ti10O42, In12NiCr2Ti10O42 showed the narrowest band gap and highest activity, which could be ascribed to the formation of broadly dispersed continuous conduction and valence bands due to the involvement of partially filled Cr 3d orbitals in addition to Ni 3d orbitals. The present study suggests a promising method for developing visible-light-driven photocatalysts with tailored properties via transition-metal(s)-mediated band structure engineering.
  • Evaluation of a New Hydrogen Generating System: Ni-Rich Magnesium Alloy Catalyzed by Platinum Wire in Sodium Chloride Solution

    pp. 2704-2708

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    DOI:10.2320/matertrans.46.2704

    Fuel cells are often seen as a long-term solution to environmental problems such as CO2 emission associated with transportation. To ensure long-term sustainability and the supply of fuel, new renewable of hydrogen (H2) generator have to be introduced. In this study, Ni-rich AZ91D magnesium alloy ingot, which was considered as waste material, was used as a H2 generator in sodium chloride (NaCl) solution with catalyst. The chemical reaction Mg+H2O→H2+Mg(OH)2 occurred in NaCl aqueous solution. The H2 evolution rate depended on the solution’s temperature (25 or 70°C), length of catalyst (0.9 or 1.8 m) and the concentration of NaCl solution (5 or 10 mass%). The H2 evolution rate increased with increasing the solution’s temperature. The catalyst (Pt wire) could significantly improve the H2 generation rate. In addition, the by-product of this method is Mg(OH)2, a non-toxic chemical compound which is usually used as flame retardant.
  • Ammonia Decomposition Catalyst with Resistance to Coexisting Sulfur Compounds

    pp. 2709-2712

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    DOI:10.2320/matertrans.46.2709

    A cheap and disposal catalyst will be required for the decomposition of ammonia in the presence of sulfur compounds. The possibility of iron ore and red mud as the ammonia decomposition catalyst was investigated using pure or diluted ammonia containing hydrogen sulfide as a reactant. Among the catalysts tested, red mud had the highest catalytic activity for the ammonia decomposition in the presence of hydrogen sulfide. On the other hand, a relatively low conversion of ammonia was observed using a nickel-based commercial catalyst for the ammonia decomposition. The deactivation behavior of an iron ore catalyst caused by sulfur poisoning depended on the pretreatment atmosphere before the reaction; namely, the deactivation was observed for the H2 pretreatment, while the high level of ammonia conversion remained constant for the CO pretreatment. From the X-ray diffraction pattern of the catalysts, the used iron ore catalyst pretreated in the CO atmosphere included FeCx, which was also included in the red mud that was active for the ammonia decomposition. FeCx may be responsible to the sulfur poisoning resistance.
  • LCA of Manufacturing Lead-Free Copper Alloys

    pp. 2713-2718

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    DOI:10.2320/matertrans.46.2713

    To promote the recycling of copper alloy scrap, we developed a new technique for removing Pb from copper alloy scrap containing 2–6 mass% Pb. However, we must evaluate quantitatively the level of environmental impact reduction that can be obtained using this new technology. In this study, a manufacturing system that produces Pb-free copper alloy products using copper alloy scrap was assessed by means of life cycle assessment (LCA). The superiority of the new manufacturing system that uses Pb-free copper alloy scrap over the conventional one that uses virgin materials was investigated from the viewpoint of environmental impact. LCA software (JEMAI-LCA) was used to assess environmental impacts such as global warming, acidification, energy consumption and resource consumption. We assessed the raw material acquisition and casting process of Pb-free copper alloy products. The subsequent processes such as machining, assembling, transportation, use and recycling/waste processing are not taken into account in the environmental impact assessment. The results show that the conversion of the conventional system that uses virgin materials into the new one that uses Pb-free copper alloy scrap decreases the environmental impact, significantly. This is attributed to the nonutilization of virgin materials and the decrease in energy consumption during the casting process.
  • Removal of Lead from Copper Alloy Scraps by Compound-Separation Method

    pp. 2719-2724

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    DOI:10.2320/matertrans.46.2719

    Recently, the global scale environmental problem has become a critical issue. In metallic material, not only the cost reduction and improvement of mechanical properties but also the decrease in environmental load is required. In copper alloys, several mass% Pb was added to improve the machinability. However, due to the adverse toxicity of Pb that is harmful to the health, a new regulation to limit the amount of Pb permitted in drinking water supplies has been enforced. A huge amount of copper alloy scraps containing Pb will become industrial waste because the scrap will not be available as the raw materials.
    We developed a new technique for removing Pb from copper alloy scraps in order to promote recycle of copper alloy scraps containing Pb. Pb was removed from brass and bronze using compound-separation method.
    Copper alloys containing 2–6 mass% Pb were molten using a high-frequency induction furnace under nitrogen atmosphere. Ca–Si compound and NaF were added into the molten copper alloys to form large particles of a Pb compound. The large particles of the Pb compound were skimmed off from the molten copper alloys. Liquid metal extractions and castings were characterized by electron probe microanalyser (EPMA) and fluorescence X-ray (XRF) analysis.
    The results show that high percentage (83% in brass and 82% in bronze) of Pb removal can be achieved. Therefore Pb-free copper alloys can be produced from copper alloy scraps, resulting in the solution of environmental problems.
  • Influence of an Immersion Gold Plating Layer on Reliability of a Lead-Free Solder Joint

    pp. 2725-2729

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    DOI:10.2320/matertrans.46.2725

    Electroless Ni/Au plating is often performed on a surface of a Cu pad to improve the wettability of lead-free solders on such a pad. Generally, electroless Au plating is performed by an immersion plating method. Since a substitution reaction of Ni and Au occurs selectively on the surface of a Ni layer in immersion plating, the Au layer does not uniformly form on the Ni layer and microvoids or microcracks easily form at the Ni/Au interface. Such defects induce void formation at the joint interface in soldering, and consequently degrade the reliability of the lead-free solder joint. In this study, the influences of immersion plating time on microvoid formation at the joint interface and the reliability of a solder ball joint with a Sn–3 mass%Ag–0.5 mass%Cu lead-free solder were investigated.
  • Comparison of Lead-Free Solder Joints Made by Immersion Gold Plating with Those Produced by Autocatalytic Electroless Gold Plating

    pp. 2730-2736

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    DOI:10.2320/matertrans.46.2730

    Electroless Ni/Au plating is presently in use with high-density Jisso technology in the manufacture of electrical appliances. Electroless Ni/Au plating is said to be less satisfactory than conventional electrolytic plating with respect to the quality of solder joints and lead-free solder in particular. The reason for this is considered the P-rich layer which forms at the interface of solder bulk and Ni layer but this has yet to be fully confirmed.
    Solder joints made by electroless Ni/Au plating and Sn–3 mass%Ag–0.5 mass%Cu lead-free solder balls were examined here for reliability assessment under high temperature storage, using an electroless Ni/Au layer made by autocatalytical deposition and another made by immersion Au plating. Interfacial structure and solder pull strength data for the two layers were compared as basis for this assessment and confirm if solder joints made by electrolytic plating is actually superior.
    At the interface of both layers, cavity formation was found to have occurred by Ni corrosion during Au plating and the number of which appeared to be a factor determining solder joint reliability. Electrolytic Au plating not accompanied by Ni corrosion should provide solder joints with reliability exceeding that by electroless Au plating.
  • Reliability of Solder Joint with Sn–Ag–Cu–Ni–Ge Lead-Free Alloy under Heat Exposure Conditions

    pp. 2737-2744

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    DOI:10.2320/matertrans.46.2737

    The reliability of a solder ball joint with a Sn–Ag–Cu–Ni–Ge lead-free alloy, which is expected to be an advanced lead-free solder, was investigated under heat exposure conditions. Solder ball joints with a eutectic Sn–Ag alloy and a ternary Sn–Ag–Cu alloy were also prepared to compare with that of the Sn–Ag–Cu–Ni–Ge alloy. Microstructual observations of the cross sections of the solder ball joints were conducted to investigate microstructural evolutions in the solders and the growth kinetics of reaction layers formed at joint interfaces. The influence of heat exposure treatment on joint strength was investigated by ball shear test. Moreover, the influence of surface treatment of a Cu pad on the reliability of the solder joint was also investigated.
  • Viscosity Measurements of Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 Supercooled Liquid Alloys by Using a Penetration Viscometer

    pp. 2746-2750

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    DOI:10.2320/matertrans.46.2746

    Viscosity of Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 supercooled liquid alloys having bulk metallic glass forming ability has been measured by using a penetration viscometer with a cylindrical probe under high speed heating conditions at heating rates between 20 and 400°C/min in the temperature range from the glass transition temperatures (Tg) up to above the crystallization temperatures. The viscosity of these alloys decreased with increasing the heating rate and tended to saturate at the heating rate of 200°C/min and above. Their viscosity could be well represented by the Arrhenius relation. The activation energies for viscous flow for Zr55Cu30Al10Ni5 and Pd40Cu30Ni10P20 supercooled liquid alloys were about 350 and 250 kJ/mol, respectively. The viscosity was also fitted by a Vogel–Fulcher–Tammann (VFT) relationship over the entire temperature range.
  • Compositional Dependent Amorphization in Zr Alloy Films by Means of Ni-Implantation

    pp. 2751-2754

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    DOI:10.2320/matertrans.46.2751

    Ni-implantation has been conducted for sputter deposited Zr alloy films to investigate compositional dependent amorphization behavior in proportion to Ni in Zr alloys. As-deposited Zr and Zr–Cu with thickness of 200 nm shows columnar hcp-Zr and nano-crystalline hcp-Zr(Cu), respectively. Implantation of 150 keV Ni+ with the amount of 1×1017 ions/cm2 induces amorphization of Zr and Zr(Cu) with 100 nm in thick. Critical amorphization concentration of penetrated Ni decreases for Ni-implanted Zr–Cu film to be 10 at%Ni as comparison with that of 20 at%Ni for Zr film. The displacement collision effect has been examined by penetration of 300 keV-Ni+. As increasing the beam energy, penetration depth increases to yield equi-axed crystalline surface and inside amorphization, which corresponding to compositional gradient of penetrated Ni. This compositional dependent amorphization via ion implantation implies that induced amorphization is attributed to chemical reaction between penetrated Ni with constituents.
  • Evolution of Mechanical Properties of Cast Zr50Cu40Al10 Glassy Alloys by Structural Relaxation

    pp. 2755-2761

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    DOI:10.2320/matertrans.46.2755

    The volume of a quenched glassy alloy is a variable of cooling rates during the amorphization. Hence a change in the volume caused by the structural relaxation can be regarded as a degree of amorphousness. The density of Zr50Cu40Al10 bulk glassy alloys (BGAs) increases linearly with the annealing temperature below the glass-transition temperature (Tg). With increasing the annealing temperature, the tensile strength and Vickers hardness show constant values, whereas the Young’s moduli and Charpy impact values become larger and smaller, respectively. Especially, Charpy impact values of Zr–Cu–Al BGAs have a linear relationship with the relative value of excessive free volume, which correspond to the volume-change ratio caused by the full structural relaxation.
  • Nucleation and Growth in Undercooled Melts of Bulk-Metallic-Glass Forming Zr60Ni25Al15 Alloy

    pp. 2762-2767

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    DOI:10.2320/matertrans.46.2762

    A levitation method using alternating and static magnetic fields was used to measure nucleation and growth of the crystalline phases in melts of the bulk-metallic-glass forming Zr60Ni25Al15 alloy. For comparison, Zr66.7Ni33.3 and Zr66.5Ni33.2Al0.3 were also examined. Nucleation undercooling in the bulk-metallic-glass forming Zr60Ni25Al15 alloy did not depend on the cooling rate (<102 K/s), and the maximum undercooling observed was approximately 200 K. Recalescence was not observed in the cooling curves of the Zr60Ni25Al15 and the Zr66.5Ni33.2Al0.3 alloys. The growth velocity of the crystalline phase in the Zr60Ni25Al15 alloy was of the order of 10−4 m/s even at a undercooling of 100 K. In contrast, clear recalescence was always observed in the Zr66.7Ni33.3 alloy. The results showed that the addition of Al into the Zr–Ni alloy significantly reduced growth velocity of the crystalline phases. The extremely low growth rate in the Zr–Ni–Al system can contribute to the high glass forming ability.
  • Friction Welding of Zr55Al10Ni5Cu30 Bulk Metallic Glasses

    pp. 2768-2772

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    DOI:10.2320/matertrans.46.2768

    The friction welding of Zr55Al10Ni5Cu30 bulk metallic glasses (BMG) has been tried. An apparatus for the friction welding of BMGs adopting a pneumatic cylinder and gripper based on a conventional lathe, and a welding process which provides a sufficient cooling rate after welding were devised. Friction time and friction pressure were chosen as the control parameters in the friction welding process. Their influences on the shape and volume of the protrusion formed from the welded interface were investigated. In addition, the temperature distribution around the interface during friction welding was measured using an infrared thermal imager. In order to characterize the friction welded interface, X-ray diffraction (XRD) and micrographic observation of welded sections were carried out. A successful joining of Zr55Al10Ni5Cu30 alloy was accomplished through the precise control of friction time and friction pressure. The condition whether crystallization occurred or not during friction welding could be classified depending upon the volume of the protrusion formed at the welded interface which is also related to the thickness of the protrusion formed at the root part of the welded interface.
  • Bulk Glassy Fe–Mo–Ga–P–C–B–Si Alloys with High Glass-Forming Ability and Good Soft Magnetic Properties

    pp. 2773-2776

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    DOI:10.2320/matertrans.46.2773

    The effect of Mo and Si additions on the glass-forming ability (GFA) of Fe77−xMoxGa3P10C4B4Si2 alloys was investigated. The addition of 2 at%Mo combined with 2 at%Si was found to be effective for the extension of the supercooled liquid region (ΔTx) defined by the difference between glass transition temperature (Tg) and crystallization temperature (Tx). The ΔTx value is 33 K for the Fe77Ga3P12C4B4 alloy, and increases to 60 K for the Fe75Mo2Ga3P10C4B4Si2 glassy alloy. In addition, this glassy alloy exhibits a high reduced glass transition temperature (TgTl) of 0.6. The large ΔTx and high TgTl enabled us to prepare the Fe75Mo2Ga3P10C4B4Si2 bulk glassy alloy successfully with a diameter of 2 mm and high saturation magnetization (Is) of 1.27 T. The Fe75Mo2Ga3P10C4B4Si2 glassy alloy also exhibits good soft magnetic properties, i.e., high effective permeability at 1 kHz of 1.1×104 and low coercive force of 5 A/m.
  • Formation and Mechanical Properties of Porous Pd–Pt–Cu–P Bulk Glassy Alloys

    pp. 2777-2780

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    DOI:10.2320/matertrans.46.2777

    Porous Pd35Pt15Cu30P20 bulk glassy alloy rods were prepared by holding the alloy melts under 1 MPa hydrogen atmosphere, followed by water quenching in reduced hydrogen pressures of 0.9 or 0.1 MPa. The volume fraction and size of pores were controlled by hydrogen pressure of the atmosphere. No crystalline phase was observed over the whole pore wall regions. The porous alloys show slightly decreased thermal stability as compared with the pore-free one, but still keep a large supercooled liquid region. The porous alloy rods exhibited significant plastic elongations in compression while the pore-free rod fractured instantly after the elastic strain limit. The high plasticity of the porous alloys is presumed to originate from the generation of a high density of shear-bands resulting from the effect of stress concentration around the pores.
  • Local Atomic Structures of Amorphous Fe80B20 and Fe70Nb10B20 Alloys Studied by Electron Diffraction

    pp. 2781-2784

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    DOI:10.2320/matertrans.46.2781

    Effect of Nb addition on the stabilization of amorphous Fe80B20 alloy was studied by electron diffraction structure analysis with the help of computer simulation. Atomic structure models with dense-random-packing 5000 atoms were constructed to reproduce interference functions obtained experimentally for the amorphous Fe80B20 and Fe70Nb10B20 alloys. In the structure models so obtained, prism-type local atomic arrangements dominated around B atoms in both the alloys, while deformed-bcc and icosahedral-like clusters were frequently found around Fe atoms. The icosahedral-like clusters and short Fe–Fe bondings were more frequently found in Fe70Nb10B20. The difference of glass forming abilities of these alloys is discussed in relation to the local structural differences.
  • Comparative Study on Glassy Phase Stabilities of Zr–Co–Al and Zr–Ni–Al Metallic Glasses

    pp. 2785-2790

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    DOI:10.2320/matertrans.46.2785

    The phase stabilities of Zr–Co–Al and Zr–Ni–Al metallic glasses have been investigated by the thermal analysis and compared with each other. It is found that the largest ΔTx, TgTl and γ parameters of the former are larger than those of the latter, indicating that the former have higher glassy phase stability than the latter. It is also found that the optimum compositions of the former are Zr-poorer and Al-richer than those of the latter and that their transition metal compositions are almost the same. Since Co and Ni have almost the same atomic radius and mixing enthalpy against Zr which are factors correlated with the glassy phase stability, this composition difference may be attributable to another factor, i.e. their difference of the electronic contribution due to the different electronic structure around the Fermi level.
  • Free-Energy Analysis of the Zr–Ni–Al Bulk Metallic Glass from the Local Atomic Arrangements of the Relevant Crystals

    pp. 2791-2798

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    DOI:10.2320/matertrans.46.2791

    Free-energy of Zr–Ni–Al bulk metallic glass (BMG) was estimated by making full use of coordination clusters in the relevant crystals. The clusters in the BMG were determined by using the BMG’s experimentally determined radial distribution functions. and the electronic structure of the identified clusters was calculated by the DVXα cluster calculation. The local atomic arrangements in the Zr–Ni–Al BMG are found to be characterized by the prism clusters with Zr or Ni atom in their center and the Kasper polyhedrons about Al atoms. It was conclude, as a consequence of the present analysis, that the Zr–Ni–Al BMG are stabilized by the low internal-energy of the constituent local atomic clusters assisted by the large entropy caused by the freedom in the bond-direction between the prism clusters and the Kasper polyhedrons.
  • High-Energy X-ray Diffraction Study of Liquid Structure of Metallic Glass-Forming Zr70Cu30 Alloy

    pp. 2799-2802

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    DOI:10.2320/matertrans.46.2799

    High-energy X-ray diffraction experiments were performed for a metallic glass-forming Zr70Cu30 alloy in the liquid state at a high temperature. Conical nozzle levitation was applied as a containerless method of obtaining accurate structure information of a highly reactive melt. The total structure factor obtained for the liquid alloy above its melting point shows a particular shoulder on the second peak, which is probably an indication of local icosahedral short-range ordering typically observed in deeply undercooled liquids. This implies that short-range ordered clusters already exist even in the equilibrium liquid state of Zr-based metallic glass-forming alloys.
  • Incident Photon-Energy Dependence of the Electronic Density of States in Pd42.5Ni7.5Cu30P20 Metallic Glass

    pp. 2803-2806

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    DOI:10.2320/matertrans.46.2803

    Incident photon-energy dependence of photoemission spectra of Pd42.5Ni7.5Cu30P20 metallic glass was measured using a synchrotron radiation facility. Compared to the elemental Pd, Ni, or Cu metal, the electronic density of states of this extremely good glass-former is highly suppressed at the Fermi energy, which indicates the existence of covalent bonds in this metallic mixture. From the incident photon-energy dependence of the spectra, partial density of states of the Pd, Ni, and Cu elements can be estimated, which suggests the selective formation of Pd–P bonds using the Pd 4d states.
  • Undercooling Behavior and Critical Cooling Rate of Pd–Pt–Cu–P Alloy

    pp. 2807-2810

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    DOI:10.2320/matertrans.46.2807

    In order to realize biomedical applications of bulk glassy alloys, we have developed new Pd-based glassy alloys with Ni-free composition in Pd–Pt–Cu–P system and it is revealed that the highest glass-forming ability is obtained at a composition of Pd35Pt15Cu30P20. In addition, the alloy can be formed into bulk glassy rods with diameters of up to at least 30 mm by fluxed water quenching. In order to clarify the critical cooling rate for glass-formation, undercooling behavior and crystal growth rate are also discussed. Crystallization of the alloy under continuous cooling is mainly dominated by surface nucleation. Apparent crystal growth rate of the alloy at 0.73 Tm is evaluated to be 5.2×10−6 m·s−1 and this value is four orders of magnitude higher than that of previous Pd40Cu30Ni10P20 at the same degree of undercooling.
  • Kinetics of Glass Transition Simulated by Path Probability Method

    pp. 2811-2816

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    DOI:10.2320/matertrans.46.2811

    Kinetics of glass transition is simulated within the Path Probability Method (PPM) which is the natural extension of the Cluster Variation Method (CVM) to time domain. Temperature dependences of order parameter during continuous cooling are calculated as a function of cooling rate. When the temperature dependence of viscosity is introduced in the mobility term in the PPM, the order parameter is frozen as approaching the ideal glass transition temperature. Furthermore, a preliminary calculation which incorporates the cooling rate dependence into the viscosity reproduces the experimental tendency of the glass transition temperature. Together with the previous studies of thermodynamic frameworks of glass transition based on the CVM, it is confirmed that the combination of the CVM and PPM provides a unique theoretical tool to study glass transition in a consistent manner covering thermodynamics and kinetics.
  • Classification of Bulk Metallic Glasses by Atomic Size Difference, Heat of Mixing and Period of Constituent Elements and Its Application to Characterization of the Main Alloying Element

    pp. 2817-2829

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    DOI:10.2320/matertrans.46.2817

    Bulk metallic glasses (BMGs) have been classified according to the atomic size difference, heat of mixing (ΔHmix) and period of the constituent elements in the periodic table. The BMGs discovered to date are classified into seven groups on the basis of a previous result by Inoue. The seven groups are as follows: (G-I) ETM/Ln-LTM/BM-Al/Ga, (G-II) ETM/Ln-LTM/BM-Metalloid, (G-III) Al/Ga-LTM/BM-Metalloid, (G-IV) IIA-ETM/Ln-LTM/BM, (G-V) LTM/BM-Metalloid, (G-VI) ETM/Ln-LTM/BM and (G-VII) IIA-LTM/BM, where ETM, Ln, LTM, BM and IIA refer to early transition, lanthanide, late transition, group IIIB–IVB and group IIA-group metals, respectively. The main alloying element of ternary G-I, G-V and G-VII, ternary G-II and G-IV, and ternary G-VI BMGs is the largest, intermediate and smallest atomic radius compared to the other alloying elements, respectively. The main alloying element of ternary BMGs belonging to G-I, G-V, G-VI and G-VII is an element in the atomic pair with the largest and negative value of ΔHmix (ΔHL.N.mix), while the main element of ternary BMGs belonging to G-II and G-IV is independent of the atomic pair with ΔHL.N.mix. The characteristics of the main element derived for the ternary BMGs are directly applicable to multicomponent BMGs belonging to G-I, G-II, G-IV (Mg-based BMGs), G-V and G-VII. The main element can be the larger-sized element in the atomic pair with ΔHL.N.mix or in the same group as the other elements for multicomponent BMGs belonging to G-III, G-IV (Be-containing Zr-based BMG) and G-VI. The main element of BMGs belonging to G-VI tends to change from the element with the smallest atomic radius in a ternary system to an element with a relatively large atomic size in a multicomponent system. The change is due to an increase in glass-forming ability through multicomponent alloying of BMGs belonging to G-VI. The results of the classification of BMGs obtained in the present study are important for further development of BMGs, with the results providing a road map for the development of new BMG compositions.
  • Structural Relaxation in Supercooled Liquids

    pp. 2830-2837

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    DOI:10.2320/matertrans.46.2830

    Relaxation behavior of structural change at the atomic cluster level in supercooled liquids during isothermal annealing processes is investigated for a model alloy system by using molecular dynamics simulations. The simulation results show that the number density of icosahedral clusters increases with the annealing time. Moreover, the number density of icosahedral clusters, the structural relaxation time, and the atomic diffusivity strongly correlate with the packing density of the supercooled liquids for many kinds of systems of alloying components with a variety of atomic size ratios and heats of mixing. This suggests that the packing density would be a good probe to estimate the stability of supercooled liquid phases and the glass-forming ability of the system.
  • Thermodynamic Modeling of the Undercooled Liquid in the Ni–Zr System

    pp. 2838-2843

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    DOI:10.2320/matertrans.46.2838

    Using thermodynamic data obtained over a wide range of temperatures, a thermodynamic assessment of the Ni–Zr system was carried out. The associated solution model was applied to describe the short range ordering in the liquid, and the glass transition was treated as a second order transition, using the Hillert–Jarl functions. The driving force of crystallization, and the time–temperature–transformation (TTT) curves were estimated from the optimized parameter set, and compared with experimental data and the results of previous thermodynamic assessments. Taking into account the low temperature thermodynamic data, the calculated driving force was found to have decreased compared to the previous assessments. Consequently, the nose of the TTT curve was shifted to higher times.
  • Thermal Stability and Magnetic Properties of Fe–Nd–Al Amorphous Alloys

    pp. 2844-2847

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    DOI:10.2320/matertrans.46.2844

    Iron-rich Fe50Nd50−xAlx (x=5, 10, 15, 20 at%) alloys were produced by copper mold casting and melt-spinning in order to examine the formation of amorphous alloys. The bulk amorphous cylinders with diameters up to 1.5 mm have been obtained for the Fe50Nd35Al15 alloy. The crystallization temperature (Tx) and melting temperature (Tm) of the alloy are 774 and 880 K, respectively. Accordingly, the temperature interval of Tm and Tx, ΔTm (=TmTx), is calculated to be 106 K, and the reduced crystallization temperature (TxTm) is 0.88. The small ΔTm and high TxTm values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Fe–Nd–Al alloy. The bulk amorphous cylinder exhibits semi-hard magnetic properties at room temperature, i.e., 0.117 T for remanence and 50 kA/m for intrinsic coercive field for Fe50Nd35Al15 alloy with a diameter of 1.5 mm. Moreover, soft to hard magnetic transition between the ribbon and bulk specimens was observed in the Fe-rich Fe–Nd–Al alloys. The semi-hard magnetic properties for the Fe-rich Fe–Nd–Al amorphous alloys with high amorphous-forming ability are promising for future progress as a new type of Fe-based magnetic material.
  • Effects of Atomic Deviatoric Distortion on Local Glass Transition of Metallic Glasses

    pp. 2848-2855

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    DOI:10.2320/matertrans.46.2848

    The dependence of the glass transition on the local volumetric strain of each atom has been shown by Egami and others. The atomistic strain defined by the deformation tensor of the Voronoi polyhedra exhibits a different tendency from that of the total strain of the whole system. Even below the glass transition temperature, some percent of the atoms have strains that are already over the critical strain predicted by theory. In addition, the atomic deviatoric distortion has a non-zero value, while the total deviatoric distortion remains zero at the glass transition in the heat cycle. In this paper, the strain states at the glass transition, such as the volumetric strain and deviatoric distortion, are investigated for Cu and Zr based amorphous metals with three different compositions. We found that the local glass transition depends on the deviatoric distortion of atoms and, in these cases, starts at 600 K, a lower temperature, than that of the global glass transition at 1100 K.
  • Cutting Characteristics of Bulk Metallic Glass

    pp. 2856-2863

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    DOI:10.2320/matertrans.46.2856

    The establishment of appropriate machining techniques for bulk metallic glasses (BMGs), which exhibit excellent mechanical, physical and chemical properties, is required to apply the BMGs. In this report, the cutting characteristics of BMGs were examined by turning with different tool materials, nose radii (Rn) and cutting speeds (V). Round bars of Zr65Cu15Ni10Al10 and Pd40Cu30Ni10P20 at% BMGs were used as the workpieces. In order to compare the cuttability of the BMGs with that of crystalline alloys, steel (JIS SGD-400D) and free-cutting brass (JIS C3604) were used. The principal cutting force (FH) and surface roughness (Ra) of the machined surfaces were measured. X-ray diffraction patterns were also obtained from the machined surfaces. The value of Ra in the BMGs exhibit the upper end of precise finishing level (i.e., Ra=0.2 μm), and was remarkably lower compared with the steel and a little lower compared with the free-cutting brass in spite of the value of V. The value became smaller with increasing values of Rn, exhibiting a very low value of 0.08 μm for an Rn value of 1.2 mm. The values of FH in both BMGs did not show a clear difference and were half that of the steel for a V value less than 40 m/min, even though the tensile strength of the BMGs was twice as large as the steel. The chip of the BMGs showed an ideal flow type with very short and regular intervals, formed by planar slip, and revealed very homogeneous, flat and featureless back surfaces. From these observations of chips, it is presumed that the reason for the excellent cuttability of BMGs is due to a slipping-off mechanism at planes of very short intervals decided only by the maximum shear stress and non-built-up edges caused by a low glass transition temperature.
  • Effect of Microstructural Change on High-Temperature Deformation in Pre-Annealed Zr65Al10Ni10Cu15 Bulk Metallic Glass

    pp. 2864-2869

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    DOI:10.2320/matertrans.46.2864

    The effect of the microstructural change on the high-temperature tensile deformation behavior in the supercooled liquid region is investigated in the pre-annealed Zr65Al10Ni10Cu15 bulk metallic glass. The microstructure before the tensile test on the specimen annealed at 673 K for 1.8 ks shows that a small amount of icosahedral phase precipitates and a large amount of amorphous phase still remains. On the contrary, the specimen annealed at 673 K for 2.7 ks shows that a large amount of icosahedral phase precipitates and the presence of amorphous phase is hardly noticeable. From the fact that flow stress of the specimen annealed at 673 K for 2.7 ks increases in comparison with that of as-received specimen as well as the specimen annealed at 673 K for 1.8 ks in the tensile test, it seems that the deformation behavior in the tension tests is greatly influenced by the difference in the degree of the precipitation of icosahedral phase. Since the m value is about 0.5 and many grain boundaries of icosahedral phase are formed in the specimen annealed at 673 K for 2.7 ks, the interaction between the icosahedral phase particles must be the cause of increase in initial stress. Accordingly, the microstructure of the gage section after tensile test in the specimen annealed at 673 K for 1.8 ks shows that the large amount of icosahedaral phase precipitates in the amorphous matrix. The strain hardening must be caused by the interaction between the icosahedral phase particles whose precipitation and growth are enhanced by deformation.
  • Characteristics of Shear Bands and Fracture Surfaces of Zr65Al7.5Ni10Pd17.5 Bulk Metallic Glass

    pp. 2870-2874

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    DOI:10.2320/matertrans.46.2870

    In this work, the characteristics of shear bands and fracture surfaces of Zr65Al7.5Ni10Pd17.5 bulk metallic glass fractured by a tensile test was investigated. Zr65Al7.5Ni10Pd17.5 bulk metallic glass shows a yield stress of approximately 1.3 GPa, a fracture stress of approximately 1.5 GPa and a tensile plastic strain of 0.1–0.2% irrespective of the applied strain. Wavy, meandering shear bands were observed in the relatively wide area of specimen surfaces around the point of failure, and typical vein patterns were observed on the fracture surfaces. Shear bands and fracture surfaces were further examined by confocal microscopy to obtain more precise information on their roughness. On the other hand, evidence of viscous flow due to crack propagation was also obtained around the edge at the point of failure on specimen surfaces by confocal microscopy. The deformability of Zr65Al7.5Ni10Pd17.5 bulk metallic glass is discussed on the basis of the obtained results.
  • Molecular Dynamics Simulation on Anelasticity under Tensile and Shearing Stresses in Single Component Amorphous Metal

    pp. 2875-2879

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    DOI:10.2320/matertrans.46.2875

    In this study, the nanoscopic deformation behavior in single amorphous during loading-unloading process under tensile and shearing stresses were analyzed by the molecular dynamics method and were compared with the earlier experimental results where an anelastic behavior was not shown in tensile stress but in shearing stress. In this study a clear anelastic deformation was shown in the shearing stress. However, it didn’t occur in the tensile stress. This corresponds to the earlier experimental result. When an abrupt strain increase in the stress–strain curve was exhibited, the potential energy and atomic volume has been increased suddenly. This result indicates that the anelastic response of the amorphous metal in the shearing stress was generated by local phase transformation.
  • Primary Crystallization of an Al88Gd6Er2Ni4 Metallic Glass

    pp. 2880-2885

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    DOI:10.2320/matertrans.46.2880

    Although pre-crystallization phase separation was reported in the Al88Gd6Er2Ni4 amorphous alloy, this work has found no evidence for it. Surface crystallization was found to occur prior to the major crystallization of α-Al nanocrystals, which caused uneven foil thickness in transmission electron microscopy (TEM) specimens prepared by electro-polishing, resulting in artificial phase separation like contrast in TEM image. Partially crystallized samples were composed of α-Al nanocrystals with little solute content and an amorphous matrix. No solute enrichment was found at the interface between α-Al and the amorphous matrix, which acts as the heterogeneous nucleation sites for further formation of α-Al crystal, resulting in interconnected nanograin microstructure.
  • Relaxation and Crystallization Behavior of the Zr50Cu40Al10 Metallic Glass

    pp. 2886-2892

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    DOI:10.2320/matertrans.46.2886

    We examined relaxation and crystallization behavior of the ternary Zr50Cu40Al10 metallic glass by using positron annihilation and transmission electron microscopy (TEM). Observed changes in positron annihilation lifetime of the alloy annealed isothermally at 673 K, which is below the glass transition temperature, correlate well with observed density changes; while coincidence Doppler broadening (CDB) spectra exhibit no significant change. These observations demonstrate that free volume decreases without a rearrangement of atoms during structural relaxation. On the other hand, CDB spectrum has exhibited considerable changes when the same alloy was annealed at 773 K. TEM observations suggested that crystallization occurs via growth of spherulites of several hundred nm in diameter, which themselves are composed of radially grown grains. Chemical analysis revealed that Cu atoms are partitioned out during the growth of the spherulites. Diffraction study indicated that the unit cell of the crystalline phase belong to an orthorhombic system with a=0.892, b=0.550, and c=1.060 nm; while remaining inter-spherulite regions are found to crystallize into an fcc phase with a=1.28 nm, which is probably isostructural to the τ3 phase.
  • Effect of Al on Local Structures of Zr–Ni and Zr–Cu Metallic Glasses

    pp. 2893-2897

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    DOI:10.2320/matertrans.46.2893

    In order to investigate the role of Al on the thermal stability of supercooled liquid state, the local structures of Zr70M30 and Zr70M20Al10 (M=Ni, Cu) metallic glasses have been studied by the X-ray diffraction and EXAFS measurements. It is found that the different effect of Al substitution on the local structures around Cu and Ni elements is exhibited. No characteristic change is observed in the local structure in the Zr–Cu metallic glass by Al substitution, whereas a drastic change in the environment around Ni atom can be confirmed in the Zr–Ni metallic glass. That is, the coordination number of Zr around Ni decreases significantly by substitution of Al in the Zr–Ni metallic glass. This would be caused by the preferential correlation between Al and Zr. This result suggests that Al plays a dominant role on the formation of novel local structure with a decomposition of the tetragonal Zr2Ni-like local environment in the Zr–Ni binary alloy. We conclude that the novel local structure contributes to the stability of the supercooled liquid state in the Zr–Al–Ni metallic glass.
  • Transformation to Nanocrystallites in Amorphous Alloys Induced by Resonant Electropulsing

    pp. 2898-2907

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    DOI:10.2320/matertrans.46.2898

    The electropulsing-induced low temperature crystallization (e-LTC) of marginal amorphous (a-) alloys, a-Cu50Ti50 and a-Pd80Si20, and a bulk amorphous alloy, a-Zr60Cu30Al10, was investigated by electropulsing at room temperature (RT) and in liquid nitrogen (LN2). Electropulsing was made by means of discharge of a condenser which is characterized by the initial current density, id0, and the decay time, τ, where the frequency of the principal constituent Fourier component of the electropulsing is 1⁄2πτ. The range of id0 was between 108 and 1010 A/m2 and that of τ was between 0.1 and 20 ms. For all the amorphous alloys, the e-LTC took place during single electropulsing with id0 beyond the threshold current density, id0,c, where id0,c was a function of τ. The maximum specimen temperature during the e-LTC was, e.g., 200 K for electropulsing in LN2, indicating that the e-LTC is associated with an athermal process, the resonant collective motion of the relatively high density region here. The dependence of id0,c on τ found for electropulsing in LN2 showed good agreement with that observed at RT, indicating that the density fluctuation responsible for the e-LTC was that frozen at the glass transition temperature. The transmission electron microscopy observation revealed that crystallites formed by the e-LTC showed crystallographic alignment with each other, suggesting that the transformation of the relatively high density regions to a crystalline phase took place. The underlying mechanism of the e-LTC was discussed.
  • Relationship between Deformation and Crystallization in Zr60Al15Ni25 and Zr65Al7.5Cu27.5 Metallic Glass

    pp. 2908-2914

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    DOI:10.2320/matertrans.46.2908

    Deformation behavior of a supercooled liquid region in melt-spun Zr60Al15Ni25 and Zr65Al7.5Cu27.5 metallic glass was investigated. The viscous flow behavior is very sensitive to the strain rate and the size of crystalline precipitates, which can be classified into 4 types based on shape of the stress–strain curve: stress overshoot mode, stable viscous flow mode with constant flow stress, strain hardening mode and strain softening mode. The strain hardening and strain softening are due to the crystalline phase distribution in supercooled liquid. The strain hardening mode was observed in Zr60Al15Ni25, while Zr65Al7.5Cu27.5 deformed with strain softening mode rather than strain hardening mode. Tensile deformation enhanced thermal crystallization in a supercooled liquid region was observed in Zu60Al15Ni25.
  • Is There a Link between Melt Fragility and Elastic Properties of Metallic Glasses?

    pp. 2915-2919

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    DOI:10.2320/matertrans.46.2915

    The concepts of melt strength or fragility, borrowed from the description of inorganic and molecular glasses, has become popular also for metallic alloys: the kinetic fragility is described by the viscous behaviour of the liquid and the thermodynamic fragility by the entropy loss on undercooling. Using the data presently available on viscosity and introducing a new index, the reduced span of the glass transition range, it is shown that kinetic data comply reasonably well to the general trend of the strong-fragile classification. On the other hand, there are discrepancies for the thermodynamic fragility of metallic glass formers with respect to conventional ones. A recent report in Nature (Novikov and Sokolov, October 2004) has suggested a correlation between melt strength/fragility and the elastic moduli of the glassy material (namely the ratio of the bulk to shear modulus). This is checked for metallic glasses which were not discussed by the Authors of the Nature paper, next to inorganic and organic glasses. It is shown that considering a larger material basis and extending the number of property values in the data base, the correlation becomes rather poor. There is, however, the possibility of distinguishing among each class of glasses, e.g. inorganic, organic, metal–metal and metal–metalloid.
  • Thermodynamic Analysis of the Phase Equilibria of the Nb–Ni–Ti System

    pp. 2920-2930

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    DOI:10.2320/matertrans.46.2920

    A thermodynamic analysis of the Nb–Ni–Ti system has been performed following the CALPHAD technique. To enable the thermodynamic description of the binary systems, the results from a previous evaluation were adopted for the Nb–Ni, Nb–Ti, and Ni–Ti systems. However, a slight modification of the parameters was applied to the bcc and Nb6Ni7 phases in the Nb–Ni system, when considering the ternary phase equilibria. The phase boundaries of the Nb–Ni–Ti ternary system at a constant 28 mol%Ni and 60 mol%Ni were determined experimentally by differential scanning calorimetry. A thermodynamic assessment of the ternary system was performed based on the experimental information as well as the reported phase boundaries of the isothermal sections of the Nb–Ni–Ti system at 700, 800, and 900°C. Our calculations reveal that this system includes 15 types of ternary invariant reactions. The ternary eutectic temperature was between 901.6 and 1063.7°C.
  • Evaluation of the Glass-Forming Ability of Zr–Ti–Be Ternary Alloys Using the CALPHAD-Type Approach

    pp. 2931-2939

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    DOI:10.2320/matertrans.46.2931

    The glass-forming ability of Zr–Ti–Be ternary alloys has been evaluated by coupling the Davies–Uhlmann kinetic formulations with the CALPHAD approach. In the computations, time-temperature-transformation (TTT) curves were obtained, which are a measure of the time necessary for the formation of detectable amounts of a crystalline phase from a supercooled liquid as a function of temperature. The critical cooling rates were calculated from the TTT curves, and these enabled us to evaluate the glass-forming ability of this ternary alloy. The driving force for the crystallization of the crystalline phases was derived from the Gibbs energy functions of each phase, where thermodynamic calculations were carried out using a simple ternary extrapolation of the binary data sets with no solubility of the third element in the binary phases except for the liquid, hcp, and bcc phases. The evaluated glass-forming compositional range was in good agreement with experimental data from the Be-rich side. However, the calculated critical cooling rates for some alloys were too low. The validity of the ideal mixing of the metastable ZrBe(B2) and TiBe(B2) phases, and the possibility of the formation of the ternary B2 phase are also discussed from an ab initio energetic point of view, and the critical cooling rates were recalculated assuming an ideal mixing of the metastable ZrBe(B2) and TiBe(B2) phases. The results show that the magnitude of the calculated values achieved was reasonable.
  • Magnetic Properties of Pr–Fe–Al Alloys Produced by the Metallic Mold Casting Method

    pp. 2940-2944

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    DOI:10.2320/matertrans.46.2940

    The structures and magnetic properties of Pr–Fe–Al alloys produced by the metallic mold casting method were investigated. The Pr–Fe–Al alloy consisted of the amorphous phase together with the non-ferromagnetic Pr phase. Magnetic measurements confirmed that the origin of coercivity in the alloys was the amorphous phase. It was found that the Curie temperature and coercivity of the alloys were strongly dependent on the composition of the amorphous phase.
  • Effect of Minor Au Addition on Glass-Forming Ability and Mechanical Properties of Pd–Cu–Au–Si–P Alloys

    pp. 2945-2948

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    DOI:10.2320/matertrans.46.2945

    The glass-forming ability (GFA), thermal stability and mechanical properties of bulk glassy Pd79Cu6−xAuxSi10P5 (x=0–6 at%) alloys were studied. The results revealed that the minor substitution of Au for Cu strongly affects the thermal stability and GFA of Pd–Cu–Au–Si–P alloys. The alloy in which 2 at% Au was added to substitute Cu (Pd79Cu4Au2Si10P5) exhibits the broadest supercooled liquid region (ΔTx=80 K) and possesses the highest GFA among the alloys investigated. The critical diameter for glass formation of this alloy reaches ∼7 mm by copper mold casting. The GFA is dramatically reduced when the Au content is more than 5 at%, beyond which no bulk glasses could be formed. The Young’s modulus, yield strength and maximum compressive strength of the best glass former (Pd79Cu4Au2Si10P5) are 87 GPa, 1525 MPa and 1660 MPa, respectively, with a compressive plastic strain over 13%.
  • Glass-Forming Ability and Mechanical Properties of Sm-Doped Fe–Cr–Mo–C–B Glassy Alloys

    pp. 2949-2953

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    DOI:10.2320/matertrans.46.2949

    Glass-forming ability and mechanical properties of Fe43Cr16Mo16C15B10xSmx alloy were systematically studied in terms of the effect of substitution of rare-earth element Sm for the metalloid element B from 0 to 6 at%. It was found that the thermal stability and glass-forming ability of studied alloys were greatly enhanced by the replacement of B with Sm. With merely 1 at%Sm addition, the supercooled liquid region was extended from 66 to 88 K, and the diameter of the cast rod with fully glassy state increased from 1.5 to 4 mm. When the Sm content is in the range of 2 to 4 at%, the critical diameter for glass formation further increased up to 5 mm. The mechanical properties were also greatly improved by the Sm additions. The Young’s modulus and compressive strength increase respectively from 140 GPa and 2400 MPa for the Fe43Cr16Mo16C15B10 alloy to 189 GPa and 3400 MPa for the Fe43Cr16Mo16C15B8Sm2 alloy. However, no improvement in plasticity was observed in the Sm-added glassy alloys. Similar to the Sm-free glassy alloys, the Sm-doped glassy alloys deformed inhomogeneously and failed in a brittle manner. The mechanism for the improved GFA by the addition of Sm is discussed.
  • Mechanical Behavior of Zr65Al10Ni10Cu15 and Zr52.5Al10Ni10Cu15Be12.5 Bulk Metallic Glasses

    pp. 2954-2958

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    DOI:10.2320/matertrans.46.2954

    The thermal stability and the mechanical behavior of Zr65Al10Ni10Cu15 and Zr52.5Al10Ni10Cu15Be12.5 bulk metallic glasses (BMGs) were investigated by differential scanning calorimetry, uniaxial compressive test, ultrasonic method, and nanoindentation. The substitution of Zr by Be significantly improved the thermal stability of the amorphous phase, exhibited by a wide supercooled liquid region of 116 K. The Be containing BMG exhibited a compressive strength of 1780 MPa, and in particular a high plastic strain of about 6%. The simultaneous operation of multiple shear bands during plastic deformation in Zr52.5Al10Ni10Cu15Be12.5 BMG is proved by the less pronounced serrated flow during the loading process in the compression and nanoindentation, as well as the fracture surface morphologies. A high Debye temperature derived from the ultrasonic measurements indicates a condensed atomic arrangement in the Be containing BMG, and may responsible for the high thermal stability.
  • Indentation Creep Behavior in Ce-Based Bulk Metallic Glasses at Room Temperature

    pp. 2959-2962

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    DOI:10.2320/matertrans.46.2959

    The room temperature creep behaviors of Ce-based bulk metallic glasses were examined by the use of nanoindentation. The creep rate and creep rate sensitivity of Ce-based BMGs were derived from indentation creep curves. The low creep rate sensitivity of Ce-based BMGs indicates that the room temperature creep is dominated by localized shear flow. The experimental creep curves can be described by a generalized Kelvin model. Furthermore, the creep retardation spectrum is calculated for the Ce-based metallic glasses. The results showed that creep retardation spectrum consists of two relatively separated peaks with the well defined characteristic relaxation times.
  • Synthesis of Ti-Based Bulk Metallic Glass Composites Containing WC Particles

    pp. 2963-2967

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    DOI:10.2320/matertrans.46.2963

    The preparation of Ti50Cu28Ni15Sn7 metallic glass composite powders was accomplished by mechanical alloying of pure Ti, Cu, Ni, Sn and WC for 18 ks. In the ball-milled composites, initial WC particles were homogeneously dispersed in the Ti-based alloy glassy matrix. The metallic glass composite powders exhibited a large supercooled liquid region just below the crystallization temperature. The presence of WC nanoparticles did not change the glass formation ability of amorphous Ti50Cu28Ni15Sn7 powders. The as-milled Ti50Cu28Ni15Sn7 and composite powders were consolidated by vacuum hot pressing into compact discs with a diameter and thickness of 10 and 4 mm, respectively. Microstructural analysis showed that the bulk metallic glass composite contained submicron WC particles homogeneously embedded in a highly dense nanocrystalline/amorphous matrix. Incorporation of WC into consolidated composite compacts resulted in a significant increase in hardness.
  • Effect of Trace Additions of Ag on Precipitation in Al–Mg Alloys

    pp. 2968-2974

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    DOI:10.2320/matertrans.46.2968

    Effect of Ag additions on the precipitate microstructures of the Al–10Mg alloys has been investigated using transmission electron microscopy (TEM) and electron diffraction.
    In the Al–10Mg alloy aged at 240°C, age-hardening response is attributable initially to an array of coarse-scale, sparsely distributed rod-like and/or plate-like β′ precipitate (particles). At the maximum hardness, the microstructure contained an increased volume fraction of coarse-scale β′ and β precipitate particles. In a well over-aged condition, the microstructure exhibited very coarse-scale β precipitate particles. However, in the Al–10Mg–0.5Ag alloy aged at 240°C, fine-scale and uniformly distributed icosahedral quasicrystalline precipitates were observed in the early stages of ageing, and it was to be replaced by the metastable crystalline T phase after the alloy is aged for 2 h at 240°C. The T phase formed as faceted rods parallel to ⟨110⟩α directions appeared to be the primary strengthening constitute exhibiting maximum hardness. The globular β precipitate particles were observed to be replaced by the metastable rod-like T precipitate particles after the alloy was aged 72 h at 240°C, and the β phase is confirmed to be the equilibrium constitute phase in the over-aged ternary Al–10Mg–0.5Ag alloy.
  • Abnormal Grain Growth of Off-Cube Grains in High Purity Aluminum Foils with Cube Texture

    pp. 2975-2980

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    DOI:10.2320/matertrans.46.2975

    In present study, abnormally coarsened grains in high purity aluminum foils with cube texture ({100}⟨001⟩) after a final annealing was investigated using SEM/EBSP method. Most of abnormally coarsened grains had Goss ({110}⟨001⟩) or S ({123}⟨634⟩) orientations. The coarsened grains with Goss and S-orientations were surrounded by Σ5 and Σ7 coincidence boundaries, respectively. This result clarified that these coincidence boundaries would enhance the abnormal grain growth of Goss and S oriented grains. Grain boundary energy of sub-boundaries between cube-oriented grains provided the driving force for the abnormal grain growth. The distribution of Goss oriented grains in the partially annealed foils was characterized by SEM/EBSP method. This characterization revealed that many Goss-oriented grains were distributed in the transition band on the central layer of the sheets.
  • Isochronal Annealing Behavior of Magnesium Alloy AZ31 after Hot Deformation

    pp. 2981-2987

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    DOI:10.2320/matertrans.46.2981

    Annealing behaviors of hot-deformed magnesium alloy AZ31 were studied at temperatures of 373 to 673 K by optical and SEM/EBSD metallographic observation. The hot-deformed alloy had fine-grained structures developed by grain fragmentation due to continuous dynamic recrystallization (cDRX). Temperature dependence of the average grain size (D) is categorized into three temperature regions, i.e. (a) an incubation period for grain growth at <450 K, (b) rapid grain coarsening at 473–523 K, and (c) normal grain growth at T>550 K. The number of fine grains per unit area, however, is reduced remarkably even in region (a). These lead to grain coarsening taking place continuously in the whole temperature regions. In contrast, the deformation texture scarcely changes even after full annealing at high temperatures. It is concluded that the annealing processes operating in hot-deformed magnesium alloy with cDRXed grain structures can be mainly controlled by grain coarsening accompanied with no texture change, that is continuous static recrystallization (cSRX).
  • Microstructure Evolution in the Phase Separation of the Ni3Al0.40V0.60 Alloy

    pp. 2988-2996

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    DOI:10.2320/matertrans.46.2988

    It has been found that phase separation, i.e., D022 precipitation in the supersaturated L12 matrix to form the L12+D022 equilibrium state, stagnates in the Ni3Al0.52V0.48 alloy under a certain thermodynamic condition. This stagnation originates from the suppression of the long-range vanadium diffusion in the L12 matrix, so-called diffusion blocking. Because diffusion blocking is inherent to the L12 structure, its occurrence depends largely on the morphological features of the L12 matrix. In this study, the microstructure evolution during the phase separation of the Ni3Al0.40V0.60 alloy was examined from the viewpoint of the relation between the variation in the initial microstructure and the appearance of the effect of diffusion blocking. Our results showed that cuboidal domains of about 30 nm on a side formed in the initial L12 matrix and that the D022 regions appeared at the domain boundaries. The microstructure evolution of the alloy was found to proceed via the rearrangement, combination, and growth of these D022 regions, accompanying vanadium migration of about 20 nm in the L12 matrix. The requisite migration length was determined by the size and density of the initial D022 regions, which depend on the size of the L12 cuboidal domains. A shorter migration length than that in the case of the Ni3Al0.52V0.48 alloy was presumed to be advantageous to concealing the effect of diffusion blocking. On that basis, it was concluded that the occurrence of the phase separation in the Ni3Al0.40V0.60 alloy was attributed to the reduction in the size of the cuboidal domains in the initial L12 matrix.
  • Constitutive Relation of Casting Aluminum Alloy A101 Involving Void Evolution

    pp. 2997-3000

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    DOI:10.2320/matertrans.46.2997

    Casting aluminum alloys are highly heterogeneous materials with different types of voids that govern the mechanical behavior of the material. In this paper, based on the analysis of a cylindrical void model and the assumption of matrix incompressibility, the void evolution of a casting aluminum alloy is derived. Through the analysis of the micro-velocity and the strain fields of the cylindrical void model, an endochronic constitutive equation involving void evolution is obtained for cast aluminum alloys. The corresponding finite element procedure is developed and applied to the analysis of the mechanical behavior and the porosity of casting aluminum alloy A101. The computed results show satisfactory agreement with experimental data.
  • Elastic Deformation Behavior of Multi-Functional Ti–Nb–Ta–Zr–O Alloys

    pp. 3001-3007

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    DOI:10.2320/matertrans.46.3001

    We investigated the effect of cold working on the elastic properties of a newly developed multi-functional β titanium alloy, GUM METAL, using in-situ XRD and EBSP analysis. Mechanical and physical properties are changed dramatically by cold working. The alloy has a low elastic modulus (40 GPa), high strength (more than 1100 MPa), high elastic deformability (2.5%) and super-plastic like deformability at room temperature without work hardening. The elastic behavior of the cold worked specimen shows non-linearity, with the gradient of the stress–strain curve in the elastic region continuously decreasing with a stress increase. In-situ XRD measurements during tensile loading show that all β peaks shift monotonically to higher 2θ angles with increasing tensile strain up to 2.7%. This result suggests that the elastic behavior in the alloy is not accompanied by phase transformations, such as stress-induced α″. Additionally, EBSP analysis reveals that the deformation mode in the alloy does not relate to {112}⟨111⟩ or {332}⟨113⟩ twinning. The microstructure of the alloy during deformation is characterized by localized distorted regions ranging in size from several tens of micrometers to submicrometers, with elastic strain located hierarchically in the alloy. It is likely that this microstructure is attributable to its elastic anomaly, which arises at this specific alloy composition of the multifunctional alloy. The above elastic anomaly in the alloy seems to contribute to the development of the unique microstructure during plastic deformation, as well as to its macroscopic elastic behavior.
  • Unusual Wetting of Liquid Metals on Iron Substrate with Oxidized Surface in Reduced Atmosphere

    pp. 3008-3014

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    DOI:10.2320/matertrans.46.3008

    The authors found that a liquid Cu droplet wetted and spread very widely on a solid substrate of Fe in a reduced atmosphere after the surface oxidation of the substrate. The mechanism of the unusual wetting behavior was investigated by using surface-oxidized Fe substrate with liquid Cu, Ag, Sn, and In. It was found that under a reduced atmosphere condition, fine pores were formed at the surface of the substrate which had been oxidized, and that the pores were connected to each other continuously over the whole surface. The liquid metals penetrate into these pores by capillary force to cause the unusual wetting behavior.
  • Characterization of Surface Oxide Film Formed on Ti–8Fe–8Ta–4Zr

    pp. 3015-3019

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    DOI:10.2320/matertrans.46.3015

    We have already developed a novel β-type titanium alloy, Ti–8Fe–8Ta–4Zr, for biomedical applications. Ti–8Fe–8Ta–4Zr showed higher strength than conventional biomedical titanium alloys, such as Ti–6Al–4V ELI, Ti–6Al–7Nb, and Ti–13Nb–13Zr. In addition, the alloy also showed higher corrosion resistance than cp-Ti and Ti–6Al–4V ELI in Hanks’ solution. In particular, the breakdown potential of the alloy (the pitting potential) was over 3.5 V vs. SCE (saturated calomel electrode) and much higher than those of cp-Ti and Ti–6Al–4V ELI. A slightly active region was observed at about 1.7 V vs. SCE that may be related to the high breakdown potential.
    In this study, the surface oxide films on Ti–8Fe–8Ta–4Zr after anodic polarization at 1 and 3 V in Hanks’ solution were characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy to elucidate the high corrosion resistance mechanism of the alloy in Hanks’ solution. In addition, the surface oxide film on the alloy before anodic polarization was also characterized for comparison.
    The surface oxide film on Ti–8Fe–8Ta–4Zr is grown with anodic polarization. Calcium phosphate is formed on the alloy after polarization. The corrosion resistance of the alloy after polarization at a potential above 1.7 V is improved by the concentration of iron and titanium in the surface oxide film. A titanium hyper-oxidized layer with a low iron concentration is observed within the surface oxide film. This layer is generated with polarization and worked as a corrosion-protective layer. The slight active region on the polarization curve may be caused by the dissolution of iron and titanium.
  • Thin Film Characteristics of Sn–3.5Ag–(2.0Cu) Alloy

    pp. 3020-3025

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    DOI:10.2320/matertrans.46.3020

    Sn–Ag–Cu lead-free solders have recently been applied generally in electrical packaging, but a discoloring of the solders often occurs at the injection-ball or the reflow processes. This study investigates the solidification surface characteristics of both the Sn–3.5Ag alloy and the Sn–3.5Ag–2.0Cu alloy to discuss and clarify the differences in composition between the surface and the thin film of subsurface. The results indicate that the solidification surface films of the Sn–3.5Ag–(2.0Cu) are mostly composed of SnO phase and SnO2 phase. The concentration of Sn4+ is higher than that of Sn2+ on the film. And the binding energy of O atoms increases at sites near the solidification surface. On the solidification surface thin film, the Ag content of the Sn–3.5Ag–2.0Cu specimen is higher than the Sn–3.5Ag specimen. In addition, there is few Cu on the solidification surface film of the Sn–3.5Ag–2.0Cu specimen, and adding Cu into Sn–3.5Ag alloy not only can repress the growth of the SnOx phase but also reducing the degree of discoloring.
  • Formation of Manganese Dioxide Coating with Catalytic Activity on Thick Boehmite Film by Hydrothermal Method

    pp. 3026-3029

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    DOI:10.2320/matertrans.46.3026

    Aluminum has excellent workability and surface finishing, but it corrodes easily and has low hardness. Therefore, in this study, an excellent high corrosion resistance oxide film was prepared by hydrothermal treatment on aluminum in the primary treatment. In the secondary treatment, MnO2 was immobilized on high corrosion resistance oxide film by hydrothermal treatment.
    Aluminum was treated by hydrothermal treatment for 30 min under 483 K (2.0 MPa) conditions in a 0.04 kmol/m3 aluminum nitrate aqueous solution. Adding aluminum nitrate to prepared thick boehmite film (20 μm) by formed globules in the primary treatment, and it possessed a wide surface area. The primary processing film was treated for 30 min under 453–483 K (1.0–2.0 MPa) conditions in a potassium permanganate aqueous solution by hydrothermal treatment, and nanoorder MnO2 (30 nm) was immobilized onto the boehmite film. MnO2-boehmite film with wide surface area and high oxidation activity was prepared.
  • Phase Relations, Activities and Minor Elements Distribution in Fe–Pb–As and Fe–Pb–Sb Systems Saturated with Carbon at 1473 K

    pp. 3030-3036

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    DOI:10.2320/matertrans.46.3030

    As a fundamental study to develop a new process for treating iron-lead base alloys, “speiss”, with a considerably high content of arsenic or antimony, which are produced in smelting lead ores or secondary materials of lead under a strongly reductive condition, the phase relations and the minor elements distribution of copper, silver, gold and platinum in the Fe–Pb–As and Fe–Pb–Sb systems saturated with carbon were determined at 1473 K by a quenching method. It was found that a miscibility gap composed of an iron-rich alloy phase with a very small content of lead and a lead-rich alloy phase with very few contents of iron and carbon extended over the wide concentration range. Arsenic was mostly distributed in the iron-rich alloy phase, while antimony almost evenly in both phases. For the distribution of precious metals, it was found that silver was mostly enriched in the lead-rich alloy phase, platinum in the iron-rich alloy phase, while gold and copper almost evenly in both phases. Based on the obtained data of the phase separation and using thermodynamic data for the Pb–As and Pb–Sb binary systems, the activity coefficients of arsenic and antimony in the Fe–As and Fe–Sb systems saturated with carbon at 1473 K were derived and expressed by a formula with the interaction parameters.
  • Controllability of Mesoscopic Surface Roughness of Sputtered Al and Al–N Films

    pp. 3037-3043

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    DOI:10.2320/matertrans.46.3037

    There is a concept that the surface roughness is the structure-type of the optical gradient function because the material volume fraction gradually changes along the surface normal from the vacuum (or air) to the material. In this sense, the controlling the surface undulations corresponds to the controlling the gradient-profile.
    Sputtered Al film, AlN film, and incompletely-nitrided Al film (Al–N film) has been investigated from the view point of forming the mesoscopic scaled surface roughness because it can be applied to, e.g., the solar absorption coating, the solar cell and/or the diffusive coloring. The surface structures have been characterized and the growth condition dependence, such as the degree of nitriding which is controlled by changing mixing ratio of N2 and Ar sputtering gases, the film thickness (df), and the substrate temperature (Tsub), are systematically investigated. The following controllable factors about surface structure are confirmed. The characteristic of the form of protuberances on the surface depends on the degree of nitriding. The height and the width of the protuberances can be controlled by df and/or Tsub.
  • Characterization of Si-Based Nanoparticulates Produced by Carbothermic Reduction of Silica-Containing Slag

    pp. 3044-3050

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    DOI:10.2320/matertrans.46.3044

    Si-based nanoparticles, nanochains and nanowires were synthesized by smelting reduction method which includes a high temperature carbothermic reduction of silica-rich melt to SiO vapor and transfer of the vapor with Ar carrier-gas to cooler surfaces inside the experimental reactor where the nanoparticulates were deposited. Features of the process have been discussed in our previous paper. In this paper, the synthesized nanoparticulates were characterized by using XRD, XPS, EDX, TEM and HRTEM analysis. The deposition temperature was found to be the crucial parameter governing the nanoparticulate morphology and phase composition. The nanowires were obtained in the high temperature range of 1320–1570 K. It is found that the as-obtained nanowires were composed of a SiC core and an amorphous sheath of silicon suboxide. The nanowires had diameter ranging from 20 to 60 nm and length up to several microns. The rounded nanoparticles of 30–50 nm in diameter were deposited at locations under temperatures lower than 920 K. They were mainly composed of amorphous silicon suboxide which could be decomposed under certain conditions yielding Si nanocrystallites embedded into the oxygen enriched suboxide matrix. The nanocrystallite size was estimated to be of 3–8 nm although much larger, up to 50 nm, Si crystals were detected at high temperature locations.
  • Pre-Treated Effect of Friction Stir Processing of Al Alloy 5052 on Vibration Fracture Behavior under Resonant Vibration