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

MATERIALS TRANSACTIONS Vol. 53 (2012), No. 9

  • Relation of Shunting Current at Cracked Part to Critical Current and n-Value in Multifilamentary Bi2223 Composite Tape

    pp. 1549-1555

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    DOI:10.2320/matertrans.MAW201201

    Relation of transport current and n-value to collective crack-induced current shunting in BSCCO (Bi2223) multi-filamentary composite tape pulled in tension was studied experimentally and analytically. For analysis, the partial crack-current shunting model of Fang et al. was used by placing the collective crack as the partial one. It was shown that (a) collective crack-induced shunting current increases with increasing current (and voltage) and with increasing collective crack size, (b) the transport current normalized with respect to the transport current in non-cracked state is described with the modified ratio of non-cracked area to overall cross-sectional area of superconducting filaments at low voltage where shunting current is low, while it deviates upward from the modified ratio at high voltage where the shunting current is enhanced, and (c) the enhanced shunting current acts to reduce n-value at high voltage. These features were similar to those of cracked coated conductor.
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  • Light Absorption by Metals with Porous Surface Layer Formed by Oxidization–Reduction Treatment

    pp. 1556-1562

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    DOI:10.2320/matertrans.M2012139

    Metals with fine surface asperity show higher efficiency of sunlight absorption than those with flat surfaces. In the present study, ultraviolet–visible–infrared light absorption by metals with porous surface layers was examined. A three-dimensionally interconnected porous structure was formed on the surface of copper and iron substrates by oxidizing and then reducing. Pore size and layer thickness were dependent on oxidization and reduction temperatures and times. It was found that metals with porous surface layers exhibited higher efficiencies of light absorption over a wide wavelength range than those with mirror-polished surfaces. High light absorption efficiencies were obtained for metal substrates with fine porous structures. In particular, a very fine porous structure was formed on the surface of iron substrate by oxidizing and reducing it at low temperatures, and its light absorption reached 75–80% over a wide wavelength range corresponding to ultraviolet–visible–infrared light. This light absorption index is much higher than light absorption by conventional metal substrates with flat surface.
  • Magnetic Properties of Cluster/Thin-Film Laminated Hybrids of Fe–Pt and Fe–Co Alloys

    pp. 1563-1570

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    DOI:10.2320/matertrans.M2012120

    Both Fe–Pt cluster/Fe–Co film and Fe–Co cluster/Fe–Pt film laminated hybrids have been prepared by combination of a plasma-gas-cluster-deposition and a helicon-plasma sputter-deposition and studied by X-ray diffraction and magnetization measurements. In Fe–Pt cluster/Fe–Co film laminated hybrids, MS increases, while HC and BHMAX monotonically decrease with the Fe–Co film thickness. In Fe–Co cluster/Fe–Pt film laminated hybrids, MS, HC and BHMAX increase with the Fe–Co cluster layer thickness in comparison with those of simple Fe–Pt films. However, the remarkable improvement of their hard magnetic properties cannot be attained in these laminated hybrids owing to both the low packing density of Fe–Co clusters and the difficulty in the diffusion-control of Fe and Co atoms from Fe–Co to Fe–Pt layers.
  • Analysis of Dislocation Core Structure in B2 Ordered Phase by Cluster Variation Method

    pp. 1571-1577

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    DOI:10.2320/matertrans.MAW201214

    Theoretical framework of the Cluster Variation Method (CVM) is extended in two directions. One is the construction of a supercell in which the basic clusters are aligned in two dimensional directions. The other one is the introduction of the atomic displacement in the flexible lattice. These extensions of the conventional CVM enable us to calculate a core structure of two parallel superpartial dislocations in B2 ordered phase at finite temperatures. It is shown that a large stacking fault is formed inside the two superpartial dislocations at lower temperatures, while the stacking fault appears outside the superpartial dislocations at higher temperatures.
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  • Residual Stress Relaxation of Shot Peened Deformation Surface Layer on S30432 Austenite Steel under Applied Loading

    pp. 1578-1581

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    DOI:10.2320/matertrans.M2012111

    The relaxation of residual stress in shot peened surface layer on S30432 austenite steel under static and cyclic loading was investigated. The results revealed that the compressive residual stresses were relaxed under applied tensile stress. The relaxation of residual stresses in longitudinal direction was more obvious than that in transverse direction. And when applied stress was beyond the yield strength of the materials, the relaxation of the compressive residual stress was drastic. Under cyclic loading, the results showed that the relaxation behavior was determined by the applied loading and the number of cycles. And the fast relaxation of the compressive residual stress took place in the first few cycles then became stable gradually. Finally, a model was used to quantitatively predict the compressive residual stress under cyclic loading with different applied tensile stresses.
  • Microstructure and Local Density of States of Ruthenium Silicide on Si(001) Surface

    pp. 1582-1585

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    DOI:10.2320/matertrans.M2012154

    Using scanning tunneling microscopy, we observed the formation process of ruthenium silicide on a monolayer Ru-deposited Si(001) surfaces at high temperature. Ruthenium silicide islands of nanometer scale are formed after heating to 1400 K. They tend to be aligned in the [110] and [1\bar{1}0] directions. Locally observed spectroscopic results were compared with other spectral data. Large islands showed compositional inhomogeneity, with a widened band gap near the interface with the Si substrate, suggesting that growth of the islands occurs due to incorporation of Si atoms from the edges of nearby steps.
  • XPS and Magnetic Properties of CoFe2O4 Nanoparticles Synthesized by a Polyacrylamide Gel Route

    pp. 1586-1589

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    DOI:10.2320/matertrans.M2012151

    Cobalt ferrite CoFe2O4 nanoparticles were prepared via a polyacrylamide gel route and were characterized by XRD, SEM, XPS and VSM. It is demonstrated that the sample (designated S1) prepared without using the cross-linking agent bis-acrylamide has an average grain size of 45 nm, while the sample (designated S2) prepared by introducing an amount of bis-acrylamide which is about 1/5 times the amount of acrylamide has an average grain size of 23 nm. The two kinds of particles are shaped like spheres. The cation distribution is determined, from Co 2p3/2 and Fe 2p3/2 XPS spectra, to be (Co0.4Fe0.6)[Co0.6Fe1.4]O4 for both the samples, where (Co0.4Fe0.6) and [Co0.6Fe1.4] represent cations in the tetrahedral and octahedral sites, respectively. Magnetic measurement reveals a saturation magnetization of 67.3 A·m2·kg−1 for sample S1 and 62.3 A·m2·kg−1 for sample S2, but a similar coercivity of about 87.5 kA·m−1 for both the samples.
  • Transmission Electron Microscopy Study of Precipitation Behaviors in Cu–15 mass%Sn Alloy Annealed at 593 K

    pp. 1590-1597

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    DOI:10.2320/matertrans.MAW201206

    We have investigated precipitation behaviors of Cu–15 mass%Sn alloy annealed at 593 K by using transmission electron microscopy. Three kinds of precipitates with different morphologies have been observed. Inside grains, plate-like precipitates of approximately ten µm in length were found to display regular configuration. They are the equilibrium ε phase, and the orientation relationship with the matrix α phase can be expressed as (001)ε // (111)α, [100]ε // [1\bar{1}0]α, with (001)ε habit planes. At grain boundaries, Sn-rich precipitates of irregular shapes were found to precipitate. They are the δ phase, which is stable above 623 K. Some of them exhibit an incipient stage of growing cellular morphology brought about by diffusion induced grain boundary migration. In addition, there are intragranular particle-like grains of several µm or less, some of them are confirmed to be the δ phase. The observed precipitation behaviors are discussed from the viewpoints of crystallography of these phases.
  • Prediction of the Maximum Dislocation Density in Lath Martensitic Steel by Elasto-Plastic Phase-Field Method

    pp. 1598-1603

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    DOI:10.2320/matertrans.M2012067

    On the basis of the two types of slip deformation (TTSD) model of lath martensite, the martensitic transformation was simulated in Fe–0.1 mass% C steel by an elasto-plastic phase-field method. The TTSD model allowed us to predict the total dislocations for the necessity of the formation of lath martensite, which is taken as the upper limit of dislocation density in lath martensite. The calculated dislocation density by the simulation was reasonable to be higher than the observed dislocations in value but to be the same in order. This consistence indicates that the calculation method based on the TTSD model is credible, together with the calculation of the habit plane predicted by the TTSD model.
  • Local Reinforcement of 6061 Aluminum Alloy Bar Using High-Frequency Induction Heating Apparatus

    pp. 1604-1610

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    DOI:10.2320/matertrans.L-M2012820

    A commercial 6061 aluminum alloy bar was partially reinforced using a high-frequency induction heating apparatus. One end of the bar was locally heated for solution treatment (local solution treatment). The power supplied to a heating coil was adjusted based on the surface temperature of the bar, which was measured using a radiation thermometer. The temperature profiles and hardness distributions in the longitudinal direction were investigated after the local solution treatment. The results of this study are as follows. The local solution treatment achieved a rapid heating rate of 80 K/s, overheating of about 2 K at the temperature transition stage from the heating to holding process, and a small-scale temperature fluctuation (below ±8 K) in the holding process. The reproducibility of the temperature profile during the local solution treatment was also sufficient. An increase in the hardness was achieved from solution treatment at 723 K or more. A holding time of 5 min or more was not very important for increasing in the hardness. The partial reinforcement of a 6016 aluminum alloy bar can be realized by applying an induction heating apparatus.
  • In-Situ Evaluation of Detwinning Behavior in Extruded AZ31 Mg Alloy by AE

    pp. 1611-1616

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    DOI:10.2320/matertrans.MAW201218

    Tension twinning readily occurs under compressive loading along extrusion direction because extruded AZ31 Mg plate has the texture with the basal planes parallel to the extrusion direction. Detwinning occurs in the twinned areas during tensile loading in the opposite direction. In this study, acoustic emission (AE) during the tensile test was investigated for the evaluation of detwinning behavior. Different AE features depending on the strain level were observed and detwinning behavior was divided into three stages. In the first stage, many AE signals with higher peak frequency were generated, then very few AE signals were observed in the second stage, and finally again some AE signals with lower peak frequency were observed in the third stage. In addition, EBSD analysis was conducted to identify phenomena in each stage. The results suggested that twin boundary starts to move in the first stage, then twin area shrinks in the second stage, and twin area disappears in the third stage. Deference of AE characteristics in each stage seems to be caused by these phenomena. It can be concluded that AE is an effective method for evaluation of detwinning behavior.
  • Effects of Sulfur Addition on the Formation of Inclusions and the Corrosion Behavior of Super Duplex Stainless Steels in Chloride Solutions of Different pH

    pp. 1617-1626

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    DOI:10.2320/matertrans.M2012194

    Effects of sulfur addition on the formation of inclusions and the corrosion behavior of super duplex stainless steels in chloride solutions of different pH were investigated using potentiodynamic and potentiostatic polarization techniques. As sulfur content increased, the corrosion resistance decreased due to the formation of numerous manganese sulfides deteriorating the corrosion resistance. The solutions used for this study are NaCl and NaCl + HCl solutions. The corrosion behavior is dominated by the pitting corrosion in NaCl solution of pH 7 and by both uniform and pitting corrosion in NaCl + HCl solution of pH 1. The pitting corrosion of the alloys was initiated at all types of inclusions of manganese sulfides, manganese oxy-sulfides and manganese oxides and then propagated to the ferrite phases, and finally propagated to the austenite phases.
  • The Influence of CoNiCrAlY Addition on the High Temperature Corrosion Behavior of CrSi2 Alloy in an Air–Na2SO4–NaCl Gas Atmosphere

    pp. 1627-1632

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    DOI:10.2320/matertrans.MAW201210

    In this study, an attempt has been made to improve the resistance of CrSi2 alloy toward high temperature corrosion and promote the formation of a continuous and slow-growing SiO2 scale on the alloy surface. For this purpose, spark plasma sintering was used to fabricate the CrSi2 alloys containing various amounts of CoNiCrAlY. The sintered alloys were then corroded isothermally in an air–Na2SO4–NaCl gas atmosphere at three different temperatures of 923 and 1073 K for up to 720 ks and at 1273 K for 72 ks. XRD, SEM and SEM-EDS were utilized to examine the alloy structures and compositions before and after the high temperature corrosion test. The influence of CoNiCrAlY addition on the high temperature corrosion behavior of the CrSi2 alloy was clarified.
  • Label-Free and Real-Time Immunodetection of the Avian Influenza A Hemagglutinin Peptide Using a Silicon Field-Effect Transistor Fabricated by a Nickel Self-Aligned Silicide Process

    pp. 1633-1637

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    DOI:10.2320/matertrans.M2012068

    Electrical immunodetection of the avian influenza A (H5N1) hemagglutinin (HA) peptide, the IN peptide, with anti-HA antibody was demonstrated using a field-effect transistor (FET) with an n-type silicon (Si) channel and a nickel (Ni) self-aligned silicide source/drain that was fabricated by a conventional top-down process. The specific binding of the IN peptide with anti-HA antibody in phosphate buffered saline (PBS) occurs on the patterned SiO2 surface through covalent linkage. Positive ions in the buffer create majority carriers in the n-type Si channel, leading to a rapid increase in current across that channel. However, specific binding of the negatively charged antigens on the SiO2 surface overlaying the Si channel results in the reduction of electrons induced in the Si channel by the positive ions, causing a significant decrease in the channel current. The settling time for obtaining a stable signal change, driven by the negatively charged antigens bound to antibody, extrapolates to approximately 32 s.
  • Microstructure and Properties of 6061 Aluminum Alloy Brazing Joint with Al–Si–Zn Filler Metal

    pp. 1638-1643

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    DOI:10.2320/matertrans.M2012110

    Ternary Al–Si–Zn filler metals were designed in order to join the 6061 aluminum alloy. The microstructure, phase constitution and fracture morphology of the brazed joint were investigated. Results of the microstructure observation showed that eutectoid α(Al) + η(Zn), α(Al) solid solution, as well as Si particles formed in the filler metal. The melting points of these filler metals are much lower than Al–12Si alloy. The η(Zn), α(Al) solid solution, and the primary Si particles were found in the 6061 Al brazing seam when using Al–0.2Si–78Zn and Al–2Si–62Zn filler metal, while the Al–Si eutectic were found when using Al–6.5Si–42Zn alloy. Results also indicate that the tensile strength of the 6061 Al brazed joints using Al–0.2Si–78Zn, Al–2Si–62Zn and Al–6.5Si–42Zn is 101, 109, 129 MPa, respectively. The fracture morphology of the brazed joints showed intergranular fracture mode while some transgranular fracture could be found in the joint of Al–6.5Si–42Zn filler metal.
  • Reinforcement Behavior in Laser Welding of A356/TiB2p MMCs

    pp. 1644-1647

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    DOI:10.2320/matertrans.M2011385

    TiB2p behavior was systematically studied in laser welding of A356/TiB2p metal matrix composites (MMCs). TiB2 particles encountered three different types of evolution under the direct irradiation of laser, including oxidization, escaping out of the bead and immigration in the welding pool. TiB2 particles remained solid state in the welding pool. The clusters of solid TiB2 particles were pushed into smaller clusters size and dispersive TiB2 particles by the outflow of Al plasma. After solidification, the distribution of TiB2 in the bead got more homogeneous than pre-welding. TiB2 and Al matrix bonded in strong semi-coherent relationship.
  • Influence of Sintering Temperature on the Microstructure of TiB2 Sintered with Al3Ti Additive

    pp. 1648-1651

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    DOI:10.2320/matertrans.M2012113

    Titanium diboride (TiB2) has been sintered using spark plasma sintering (SPS) with the addition of titanium tri-aluminide (Al3Ti) at the temperature between 1273 and 1573 K. By the X-ray diffraction measurements, it has been shown that TiB2–Al3Ti composites can be obtained by the sintering at 1273 K. Vickers hardness of the specimen increases as the amount of Al3Ti increases up to 30% by the sintering at 1273 K, and TiB2–30 mass% Al3Ti composite has the relative density of around 96% and Vickers hardness as high as 2100 Hv. On the other hand, Al3Ti evaporates during sintering above 1473 K. TiB2 sintered with 10 mass% Al3Ti at 1573 K has the relative density of 94% and Vickers hardness 2100 Hv, while TiB2 sintered without Al3Ti has the relative density as low as 76%. This fact indicates that Al3Ti accelerates the diffusion of TiB2 causing densification of sintered TiB2 specimens in the sintering above 1473 K.
  • A Cell-Automaton Model for Eutectic Growth of a Ternary Alloy System with a Dilute Third Element

    pp. 1652-1656

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    DOI:10.2320/matertrans.M2012147

    A cell-automaton model for eutectic growth has been extended from a binary alloy case into a ternary alloy case with a dilute third element. Quasi-stable ranges with an oscillatory growth mode of lamellar spacings have been obtained for lower growth velocities which can be distinguished from unstable ranges of spacing. The lower limit of the quasi-stable range decreases with the increase of the growth velocities, and the range becomes narrower with the increase of the content of the third element. The upper growth temperatures of the quasi-stable pattern decrease compared with the liquidus temperatures with the increase of the growth velocity. The quasi-stable growth pattern might be an instability pattern which would develop into a cellular-eutectic growth if lamellar branching were possible.
  • Effects of Electron Beam Irradiation on Adhesive Force of Laminated Sheet of High Strength Polytetrafluoroethylene (PTFE) and Bio-Adaptable Polydimethylsiloxane (PDMS)

    pp. 1657-1664

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    DOI:10.2320/matertrans.M2012124

    The effects of homogeneous low voltage electron beam irradiation (HLEBI) on the adhesive force of peeling (oFp) and peeling resistance energy (oEp) at each peeling probability (Pp) of laminated sheets of bio-adaptable polydimethylsiloxane (PDMS) with transparency and high strength polytetrafluoroethylene (PTFE) with sterilization were investigated without glue. Although both oFp and oEp of peeling at low Pp of 0.06 were 0.2 N·m−1 and 4.0 × 10−2 J·m−1 before treatment, HLEBI enhanced the oFp and oEp up to the largest values of 11 N·m−1 and 2.2 J·m−1 of the laminated sheets irradiated at 0.13 MGy, respectively. They were more than 55 times larger that those before treatment. On the other hand, additional HLEBI reduced the oFp and oEp of laminated sheets irradiated at more than 0.22 to 0.86 MGy, although they were apparently larger than those before treatment. In order to investigate the influence of EB irradiation on oFp and oEp, electron spin resonance (ESR) signals related to dangling bonds were observed. When HLEBI cut the chemical bonds and generated dangling bonds with nonbonding electrons in PTFE and PDMS, the electrons induced the chemical bonding and intermolecular attractive force. HLEBI induced strong adhesive force of laminated sheets was explained by the discussion. Therefore, it was concluded that HLEBI was a useful tool for quick lamination of bio-adaptable PDMS and high strength PTFE.
  • Microwave Absorption Properties of Highly Filled Polymer Composites with Amorphous Fe–B Particles

    pp. 1665-1668

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    DOI:10.2320/matertrans.MAW201203

    In this study, polymer composites containing amorphous Fe–B particles with large particle size distribution were fabricated. A polymer composite of mixed particles showed a high relative permeability of μ ’r = 9.3 at 1 GHz. In addition, the composite exhibited good microwave absorption properties (R.L. < −20 dB) in the frequency range of 0.6–1.1 GHz for absorber thickness of 2.4–4.2 mm. Thus, this polymer composite can be used for fabricating microwave absorbers that are effect in the 0.7–1.0 GHz band, and would result in microwave absorbers thinner than any other microwave absorbers reported to date.
  • Effects of Vacuum Annealing on the Charge–Discharge Characteristics of Eutectic Al–Si/Al Thin Film as Anode Material for Li-Ion Batteries

    pp. 1669-1673

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    DOI:10.2320/matertrans.M2012086

    In this study, radio frequency magnetron sputtering was used to prepare eutectic Al–Si/Al bi-layered films as anode materials and the effect of vacuum annealing in the charge–discharge capacity characteristics at different temperatures were discussed. For the purpose of 400 nm Al–Si film can possess the lowest crystallization temperature, the eutectic composition was adopted. The pre-sputtered 40 nm Al thin film not only reduced the resistivity of the composite anode film, but also diffused to prevent peeling between the Al–Si films and Cu foils after vacuum annealing. While the annealing temperatures were elevated (RT ∼ 400°C), indexes of crystalline (IOC) and resistivities of specimens were changed. The properties of materials containing ASEC-400 (at RT) and ASEC-200 (at 55°C) had outstanding charge–discharge characteristics. The morphology transformation at the surface and cross section resulted from annealing at different temperatures and cycling testing were examined by Focus Ion Beam (FIB). Besides, the relationship between cycling performances and electrochemical characteristics of Al–Si/Al film anodes were also investigated by Cyclic Voltammetry and Electrochemical AC Impedance Spectroscopy (EIS).
  • Relationship between Porosity and Interface Fracture on Aluminum Foam Sandwich with Dense Steel Face Sheets Fabricated by Friction Stir Processing Route

    pp. 1674-1679

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    DOI:10.2320/matertrans.MAW201212

    An aluminum foam sandwich consisting of an aluminum foam core with two dense metallic face sheets is expected to be used as a lightweight structural component with good energy and vibration absorption properties. In this study, by the friction stir processing route, aluminum foam sandwiches with porosity of approximately 55–85% and metallurgical bonding between the aluminum foam and dense steel sheets were successfully fabricated. Moreover, tensile tests were carried out on the fabricated aluminum foam sandwiches. Through the test results, it was shown that, although a brittle intermetallic compound layer exists at the interface, fracture in the aluminum foam part with porosity above 65% occurs and the bonding strength of the interface is higher than the tensile strength of the aluminum foam.
  • Preparation and Purity Evaluation of 5N-Grade Ruthenium by Electron Beam Melting

    pp. 1680-1684

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    DOI:10.2320/matertrans.M2012155

    In this study, we carried out an electron beam (EB) melting purification process to obtain a 5N-grade high-purity Ru ingot from commercial Ru powder. The first step was to primarily sinter Ru powder compact by means of vacuum heat treatment at 1,773 K. Vacuum sintering was employed to ensure a high vacuum condition during EB melting by the removal of remaining gaseous elements between the compact powders. The second step was to obtain Ru ingots by EB melting of the sintered Ru compact. The purity of the Ru raw powder was 99.962 mass% and the purity of a premelted Ru button ingot obtained by EB melting was 99.9873 mass%. The purities of the respective Ru button ingots remelted for 2 and 4 min were 99.9988 and 99.9992 mass%, respectively. As a result, the sum of metallic impurities in the Ru ingot refined for 6 min was 5.3 mass ppm and the purity of the ingot considerably increased up to 99.9995 mass%, which means that a 5N-grade high-purity Ru ingot can be obtained by the EB melting purification process. Furthermore, the EB-melted Ru ingot showed an excellent ability to remove interstitial impurities.
  • Designing Experimental Methods to Predict the Expansion Ratio of EVA Foam Material and Using Finite Element Simulation to Estimate the Shoe Expansion Shape

    pp. 1685-1688

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    DOI:10.2320/matertrans.M2012178

    Correcting and quickly predicting the shrink mold shape in the sport shoe industry for direct injection-expanded foam molding manufacturing procedures are critical. Traditional methods rely on the engineer to guess the initial shrink mold shape when manufacturing the actual shrink mold and shoe sole product. The artificial experience is then used to compare the original large 3D model with the shoe sole product to modify the shrink mold, requiring numerous iterations to complete. In this study, we designed a series of rectangular specimens varying with z-thickness, and measured the density in the middle location of these specimens and transferred them into an expansion ratio. Furthermore, we performed a heat transfer simulation to determine the temperature–time curve in these locations and correlated the expansion ratio with the curve. We then used the heat expansion finite element method to simulate the expansion behavior. Finally, we used the actual shoe sole to verify our algorithm; with the precision meeting the shoe sole requirement. Therefore, this algorithm can reduce the number of iterations.
  • Sintered Behaviors and Electrical Properties of Cr50Cu50 Alloy Targets via Vacuum Sintering and HIP Treatments

    pp. 1689-1694

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    DOI:10.2320/matertrans.M2012150

    Powder metallurgy is the conventional process for the production of Cr–Cu alloys. Enhanced vacuum sintering techniques and the use of HIP processes can be applied to obtain higher densities and decreased porosity in the sintered parts. In this study, the optimal sintering process of Cr50Cu50 alloy targets is 1270°C for 1 h; a high density and low electrical resistivity of the alloy targets is obtained. The experimental results also indicate that the relative density of the Cr50Cu50 vacuum sintering targets can reach 99.42%, and that apparent porosity decreases to 0.54% after 1050°C at 175 MPa for 4 h of HIP treatments. The crystal property of sintered Cr–Cu alloy is improved, and the resistivity decreased to 589 × 10−8 Ω·cm; IACS is also enhanced to 29.27% via HIP optimal treatment. This study shows that the high density and optimum properties of sintered Cr50Cu50 alloy targets can be produced by utilizing a suitable HIP treatment.
  • The Influence of Organic Additives on Surface Microroughness of Copper Deposits from Cuprous Solution under Potentiostatic Conditions

    pp. 1695-1698

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    DOI:10.2320/matertrans.M2012095

    In this study, surface roughness values of electrodeposits from chloride solution (0.1 mol/L CuCl, 0.05 mol/L HCl and 4.0 mol/L NaCl electrolytes) under potentiostatic conditions were characterized in terms of root mean square roughness (RMS roughness) using a Mirau interferometer, an optical microscope, and computer software analysis. A variety of organic additives were used to study their influence on RMS roughness values. The surface roughness of copper electrodeposits in the presence of gelatin (RMS roughness = 0.38 µm) is significantly lower than in the absence of additives (RMS roughness = 15.19 µm). The use of gelatin also resulted in lower roughness than other additives (RMS roughness ranging from 16.75 to 3.30 µm). The copper electrodeposition tests were performed under rotating disk electrodeposition conditions (100 mV cathodic overpotential for 1 h under argon purging at 500 rpm). The effect of additive concentration on RMS roughness values was also evaluated. As cathodic overpotential and deposition time increased, the RMS roughness increased at low overpotential and deposition time. RMS roughness did not increase significantly at longer deposition times in the presence and absence of gelatin.
  • Segregation of Alkali and Alkaline Earth Metals at Σ11(113)[110] Grain Boundary in Aluminum from First-Principles Calculations

    pp. 1699-1705

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    DOI:10.2320/matertrans.M2012108

    The grain boundary segregation energies of Mg, Na, Ca, K and Sr at a symmetric tilt Σ 11(1\bar{1}3)[110] grain boundary were investigated in aluminum using the first-principles calculation. The relationship between the grain boundary segregation energies and the volume size factors were examined to understand the role of elastic strain energy in the grain boundary segregation energy. The grain boundary segregation energy decreased with the increase in the volume size factor. It has been explained that the solute atom larger in size than Al, which stores greater strain energy in the bulk, prefers the looser site at the grain boundary plane rather than in the bulk, to release the elastic strain energy. Furthermore, on the basis of the Rice–Wang model, the effects of grain boundary segregation on the embrittlement at the grain boundary were studied. The embrittlement potency indicates that the Mg, Na, Ca, K and Sr atoms serve as embrittler in the grain boundary.
  • Development of Manufacturing Method for Porous SiO2 Using Decarburization Process

    pp. 1706-1709

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    DOI:10.2320/matertrans.M2012181

    The objective of this work is to develop a manufacturing method for porous SiO2. Porous SiO2 was fabricated by decarburization after sintered at 1472 K with carbon particles. Porosity of C20SiO2 (added carbon particles of 20 vol%), C40SiO2 (added carbon particles of 40 vol%), C60SiO2 (added carbon particles of 60 vol%) and C80SiO2 (added carbon particles of 80 vol%) were 20.4 ± 0.4, 40.5 ± 0.4, 60.6 ± 0.3, and 80.7 ± 0.3 vol%, respectively. It is to say that the porosity of the porous SiO2 could be controlled by less than ±1% of the amount of carbon particles. In addition, pore size of porous SiO2 could be controlled by the size of the carbon particles. Furthermore, pore-size of the porous SiO2 depends on the size of carbon particles instead of the quantity of the carbon particles. Decarburization processing method is a simple and economical manufacturing method to controlled porosity and pore size of porous SiO2.

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