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

MATERIALS TRANSACTIONS Vol. 56 (2015), No. 4

  • PREFACE

    pp. 459-459

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    DOI:10.2320/matertrans.MPR2015901

  • Intermetallic Compound Nanoparticles Dispersed on the Surface of Oxide Support as Active and Selective Catalysts

    pp. 460-467

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    DOI:10.2320/matertrans.MF201408

    Preparation of nanoparticles of intermetallic compounds and their application to various catalytic reactions are summarized. On the surface of silica support, single-phase nanoparticles of intermetallics with various combinations of elements were obtained by co-impregnation and/or successive impregnation procedures. On alumina support, its strong interaction with metal species requires another preparation procedure, liquid-phase reduction, to obtain intermetallic nanoparticles with high phase purity. Most of the particles formed on both supports had diameters of 3∼20 nm. Thus prepared intermetallic nanoparticles were used as catalysts for various reactions such as H2-D2 equilibration, selective hydrogenation, dehydrogenation, oxidation and isomerization. The catalytic activity and selectivity of nanoparticles differed from each other depending on the combination and composition of two elements. In some cases, the intermetallic catalysts gave much higher activity and/or selectivity than their component monometallic catalysts. The unique catalytic properties of intermetallic compounds were discussed in terms of the electronic and geometric factors compared with pure metals.
  • Environment-Sensitive Thermal Coarsening of Nanoporous Gold

    pp. 468-472

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    DOI:10.2320/matertrans.MF201403

    In order to investigate environmental effects on the ligament/pore coarsening of nanoporous gold (NPG), we studied the thermal coarsening of NPG both in air and vacuum by ex situ observation, and found that it has high structural stability against heat treatment in vacuum. To clarify the nature of this phenomenon, we investigated the thermal coarsening of NPG by in situ environmental transmission electron microscopy. At an elevated temperature (400°C), the coarsening of ligaments/pores was triggered by introducing either pure N2 or O2 gas into the transmission electron microscopy (TEM) chamber (but not by Ar gas). We thus conclude with a discussion on the mechanism for thermal coarsening of NPG.
  • Preparation of Double Layer Membrane Combined with Palladium Metal and FAU Zeolite for Catalytic Membrane Reactor

    pp. 473-478

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    DOI:10.2320/matertrans.MF201402

    The preparation of a double-layer membrane by the combination of Pd metal and FAU zeolite was attempted to enhance the catalytic activity of the membrane reactor. The membrane was successfully synthesized on a porous α-Al2O3 support tube by the hydrothermal synthesis of the FAU zeolite layer followed by chemical vapor deposition of the Pd layer. The thicknesses of the FAU and Pd layers were ca. 5 µm and 1 µm, respectively. The membrane functioned efficiently as a hydrogen separation membrane without deterioration, due to the rigid connection of each layer. During the model reaction, such as the reaction of benzene and permeated hydrogen species from Pd membrane, the inner surface of the Pd layer that was in contact with the FAU layer exhibited high hydrogenation activity, in contrast to the outer surface. Scanning electron microscope observations reveal that one of the reasons for this observed difference is the roughness of the inner surface. Loading of Pd particles in the micropores of FAU zeolite layer by ion-exchange treatment resulted in enhancement of the hydrogenation activity. The FAU zeolite layer is suitable for loading of the highly dispersed active metal particles. The combination of Pd metal membrane and fine metal particles has potential for acceleration of catalytic membrane reactions.
  • Adsorption Structure and Electronic Structure of Ethylene on Pt3Ti(001) and PtTi3(001) Surfaces: a DFT Study

    pp. 479-484

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    DOI:10.2320/matertrans.MF201406

    Adsorption structure and electronic structure of ethylene on Pt3Ti(001) and PtTi3(001) intermetallic compounds surfaces are studied in terms of density functional calculations. In both intermetallic compounds, adsorption energy of bridge and hollow sites are larger than that of the atop sites. Moreover, obtained adsorption energy and the C-C separations at most sites on both intermetallic compounds are larger than those reported for Pt(111). Analyzing the surface LDOSs, it turns out that the bimodal density of states made by the occupied Pt d-states and unoccupied Ti d-states are effectively interact with the HOMO and LUMO of ethylene, which are bonding and anti-bonding states of the π-bond between carbon atoms, and then leading the elongated C-C bond and large adsorption energy. Larger adsorption energy at bridge and hollow sites is also understood in the same way. Although we found out the possibility that the bimodal density of states realized in intermetallic compounds composed of early and late transition metals is effective for molecular dissociation reaction generally, no clear evidence indicating the experimentally reported higher catalytic activity of Pt3Ti than PtTi3 and Pt in the ethylene hydrogenation is obtained in this study.
  • Efficient Hydrogen Generation from Ammonia Borane on Skeletal Cu Catalysts Prepared from Cu-Ti Amorphous Alloys

    pp. 485-489

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    DOI:10.2320/matertrans.MF201407

    The catalytic performances of skeletal Cu prepared from Cu-Ti amorphous alloy heated at various temperatures were tested for the hydrogen generation from ammonia borane. The catalytic activity per surface area decreased with increasing heating temperatures of Cu-Ti amorphous alloy. The thermal treatment of Cu-Ti amorphous alloy leads to the high surface area of skeletal Cu. A skeletal Cu catalyst prepared from heated Cu-Ti amorphous alloy at 300°C which is a moderate temperature somewhat lower than crystallization temperature, exhibited a higher catalytic activity in this reaction.
  • Formation of Amorphous Pt Oxides: Characterization and Their Catalysis

    pp. 490-494

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    DOI:10.2320/matertrans.MF201410

    Amorphous Pt oxides (am-PtOx) were formed by the leaching of copper from a Cu3Pt alloy in concentrated HNO3 at 323 K for 12 h. The resulting am-PtOx was characterized using synchrotron X-ray powder diffraction, hard X-ray photoelectron spectroscopy, thermal analysis (TG-DTA, TPD) and the BET method. This material had a high specific surface area with micropores (61.7 m2/g) and decomposed to form Pt and O2 at approximately 720 K. The catalytic performance of the am-PtOx during CO oxidation was superior to that of a conventional Pt black catalyst. This study demonstrated a novel method of preparing am-PtOx with applications as a catalyst.
  • Formation of an Icosahedral Quasicrystal and Its Approximant in Au-Al-Sc System

    pp. 495-499

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    DOI:10.2320/matertrans.M2014421

    The formation of the icosahedral (i-) and 1/1-approximant (1/1-) phases in the Au-Al-Sc system has been investigated. A primitive-type i-phase was found to form in an Au45Al40Sc15 alloy. This i-phase was shown to be thermodynamically stable at 973 K. A stable 1/1-phase was found to form at 1173 K for compositions of Au44+xAl41−xSc15 (x = 0, 1, 2, 3). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) revealed that the 1/1-phase consists of Tsai-type icosahedral clusters. Similar local structures were observed in the HAADF-STEM image for the i-phase, indicating that the i-phase consists of Tsai-type clusters identical to the clusters in the 1/1-phase. The composition of the Au-Al-Sc i-phase is consistent with the formation conditions, including those in the valence electrons per atom ratio and in the atomic size factor, which has been shown previously for other Tsai-type i-phases. This fact demonstrates the importance of these conditions for stabilization of Tsai-type i-phases.
  • Effects of the Pre-Aging Period on the Formation Behavior of Nanoclusters in an Al-Mg-Cu Alloy

    pp. 500-506

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    DOI:10.2320/matertrans.L-M2015801

    The effects of the pre-aging period on the formation behavior of nanoclusters during two-step aging in an Al-3.0Mg-1.0Cu (mass%) alloy has been investigated by the hardness, differential scanning calorimetry (DSC) and electrical resistivity measurement. Two-step aging which consists of pre-aging and final aging results in an increase of the peak hardness. When the pre-aging is conducted at 323 K for 1.2 ks, the hardness dramatically increases after the final aging treatment. This pre-aging period corresponds to the incubation stage which is one of the hardening stages in an Al-Mg-Cu alloy. During the pre-aging, no clear hardness and electrical resistivity increase are obtained, however a certain structural change is considered to occur. In this study, co-clusters are assumed to be formed during pre-aging. On the contrary, when the pre-aging period is 345.6 ks, the hardness and electrical resistivity decrease in the beginning of final aging. It is attributed to the reversion of nanoclusters. In this case, the pre-aging period corresponds to the first stage of hardening. The first stage of hardening, which occurs rapidly (e.g. within 60 s at 443 K) and contributes 60% of the total hardening, is attributed to solute clustering rather than to the formation of GPB zones.
  • Effect of Dispersoids in β-Sn Matrix on Creep Properties of Chip Scale Packages Joined by Sn-xAg-0.5 mass%Cu (x = 1, 2, 3 and 4 mass%) Solder Alloys

    pp. 507-512

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    DOI:10.2320/matertrans.MBW201406

    An effect of dispersoids in β-Sn matrix on creep properties of chip scale packages joined by Sn-xAg-0.5 mass%Cu (x = 1, 2, 3 and 4 mass%) solder alloys were investigated by stress relaxation tests performed at 298, 348 and 398 K. Creep behavior observed can be described by the power law at all temperatures tested, and solders with higher silver contents had better creep properties. It is considered that lattice diffusion of β-Sn affected the creep deformation of the solders because activation energy of the observed creep properties was about 100 kJ/mol, which is close to that for lattice diffusion of β-Sn. Stress exponents estimated from Norton’s law were larger than seven for all the solders tested, and the solders which showed better creep properties had more submicron-size dispersoids. Therefore, submicron-size dispersoids are considered to be useful to strengthen the β-Sn matrix and increase the creep properties of the solders tested.
  • Enhancement of Fatigue Life in TiNi Shape Memory Alloy by Ultrasonic Shot Peening

    pp. 513-518

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    DOI:10.2320/matertrans.MBW201408

    The fatigue property of shape memory alloy (SMA) is one of the most important subjects in view of evaluating functional characteristics of SMA elements. In the present study, ultrasonic shot peening (USP) was applied to induce compressive residual stress on the surface layer of TiNi SMA tape and the influence of USP on the bending fatigue life was investigated. The fatigue life of USP-treated tape is longer than that of the as-received tape. The fatigue life of the tape USP-treated with high coverage is longer than that with low coverage. The fatigue life of the USP-treated tape increases in proportion to the hardness on the surface of the tape.
  • Impact of Effective Pressure on Threshold Pressure of Kazusa Group Mudstones for CO2 Geological Sequestration

    pp. 519-528

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    DOI:10.2320/matertrans.M-M2014849

    During carbon dioxide (CO2) injection process, overpressure within targeted reservoirs might occur because of changes in stress related to the CO2 pressure, which could lead to deformation of the surrounding rocks, including caprocks which are geological formations with low permeability overlying a CO2 storage reservoir. The understanding for impact of effective pressure (i.e., the difference between confining pressure and pore pressure) on hydraulic parameters (i.e., threshold pressure and permeability) of such caprocks has a critical role in the safe implementation of CO2 geological sequestration. The purpose of this study was to examine the hydraulic properties of mudstones, which were taken from Otadai (OTD), Ohara (OHR), and Namihana (NMH) formations of Kazusa group, depending on effective pressure at 40°C and effective pressures of the range from 1–20 MPa. Change in porosity as a function of effective pressure was also investigated in order to infer the critical pressure, which provided an insight into the relationship between threshold pressure and permeability. Our results demonstrated that with increasing effective pressure, OHR mudstone exhibited a steeply decreasing trend in permeability at around 5 MPa, whereas OTD and NMH mudstones exhibited a monotonous decrease. All data of threshold pressure as a function of effective pressure exhibited linear correlation with permeability data on a log-log scale, except for the OTD and OHR mudstones at below the inferred critical pressure. It was suggested that the relationship between threshold pressure and permeability depends strongly on changes in pore structures as a function of effective pressure for each mudstone tested. The results highlighted that the presence of microfractures could be critical in characterizing the hydraulic parameters of mudstones, and mudstones with crack-like pores and/or microfractures such as the OTD and OHR mudstones might be significantly more susceptible to decreasing threshold pressure compared with fracture-less structures under below the critical pressure condition. However, considering CO2 injection process which means that CO2 is injected into the targeted reservoirs within normal stress states, all the obtained data above the critical pressure could be explained fully by the linear correlation between threshold pressure and permeability, even if the mudstones incorporated microfractures.
  • Effects of Electron Beam Irradiation on Shear Strength of Laminated Sheet of Bio-Adaptable Polydimethylsiloxane (PDMS) and Polytetrafluoroethylene (PTFE) with Fracture Toughness

    pp. 529-533

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    DOI:10.2320/matertrans.MBW201411

    Effects of homogeneous low voltage electron beam irradiation (HLEBI) without glue on the adhesive force of tensile shear strength (τB) at each shear probability (Ps) of laminated PDMS/PTFE sheets of polydimethylsiloxane (PDMS) and Polytetrafluoroethylene (PTFE) were investigated. Although τB of shear at low and mid Ps of 0.06 and 0.50 were 0.015 and 0.04 MPa before treatment, 0.22 MGy-HLEBI enhanced the τB up to the largest values of 0.098 and 0.11 MPa of the laminated sheets, respectively. They were more than 6 and 3 times larger than those before treatment. On the other hand, additional HLEBI apparently reduced the τB of laminated sheets irradiated at more than 0.43 MGy as usual radiation damages. The effects of HLEBI on adhesion force of τB can be explained by the enhancement of cross-linking at PDMS/PTFE interface. When HLEBI cut the chemical bonds and generated active terminated atoms with dangling bonds at cross-linked PDMS and PTFE polymers, strengthening the bonding force of cross-linking polymers was induced by the chemical bonding and intermolecular attractive force.
  • Numerical Simulation for Cavitation Bubble Near Free Surface and Rigid Boundary

    pp. 534-538

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    DOI:10.2320/matertrans.M2014348

    In order to investigate a single vacuum bubble collapse near the free surface and the rigid boundary, the moving particle simulation (MPS) method has been used. Liquid and gas phase were defined by the moving particles and bobble shape was determined by the position of interface particle. The calculation was performed with four parameters; bubble radius, distances from free surface or rigid boundary to and viscosity of the liquid, to estimate the effect of these parameters on the bubble dynamics. The results showed that the bubble collapse time near the free surface is shortened, while the one with near the rigid boundary become prolonged. These four parameters significantly affect to the bubble interface velocity. To evaluate the accuracy of this model, the results are compared with the theoretical model and experimental results. A good agreement between present model and other results were obtained and validity of the present model to the vacuum bubble dynamics was confirmed.
  • High Sensitive Surface Plasmon Resonance (SPR) Sensor Based on Modified Calix(4)arene Self Assembled Monolayer for Cadmium Ions Detection

    pp. 539-544

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    DOI:10.2320/matertrans.M2014366

    In this work, a new chromogenic calix(4)arene was functionalized onto self assembled monolayer (SAM) of cysteamine for cadmium ions detection and tested by using SPR measurement. The functionalization of modified SPR sensor is based on the oxidation of calixarene-SAM alcohol group to quinone. Four interfering ions were used Cu2+, Co2+, Mg2+ and Ca2+. pH of sensor in which the sensitivity of sensor is higher was optimized for cadmium ions and detection of ions was made in basic solution. Detection limit reached for Cd2+ is lower than 10−11 M with a dynamic response time of about 16 s when changing from 10−6 M cadmium to 10−5 M.
  • The Third Law Entropy of Strontium Molybdates

    pp. 545-549

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    DOI:10.2320/matertrans.M2014470

    The heat capacities, Cp,m° , for SrMoO4 at 200-300 K were measured by the relaxation method. The third law entropy, Sm° , and the Debye temperatures, ΘD, were determined from the measured Cp,m° . The obtained thermodynamic properties were: Sm° (SrMoO4(cr), 298.15 K)/J K−1 mol−1 = 136.56 ± 1.37; ΘD(SrMoO4(cr))/K = 373 ± 6. Such thermodynamic properties can be used for evaluating the hierarchy for formation of the yellow phase related-substances in the nuclear waste glasses.
  • The Effect of Bio-Coal on the Carbothermic Reduction of Laterite Ores

    pp. 550-555

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    DOI:10.2320/matertrans.M2014315

    In order to investigate the effect of bio-coal on the carbothermic reduction of laterite ores, carbothermic reduction experiments of two type laterite ores mixed with bio-coal were conducted in this research. The reduction experiments were carried out at 1173–1673 K for 1800 s in Ar. Compared reduction results of coal and bio-coal show increasing the nickel content with increasing temperature. Bio-coal had become the reductant, the nickel content of limonite specimens and saprolite specimens had been raised from 1.18 mass% (before reduction) to 1.64 mass% (after reduction at 1373 K for 1800 s) and from 3.43 mass% (before reduction) to 4.93 mass% (after reduction at 1473 K for 1800 s), respectively. The major phases of limonite specimens were Fe1.833(OH)0.5O2.5 and Fe2SiO2. After the reduction at 1473 K for 1800 s, the major phase was metal Fe. The major phases of the saprolite specimens were Fe(CO3), Fe3O4, Fe2SiO4 and Al3S4. After the reduction at 1473 K for 1800 s, the major phases were Fe, Fe0.64Ni0.36 and α-Fe10.8Ni. The morphological observation of limonite and saprolite specimens shows that the pellet-shaped specimen became a dense area and the core of the pellet had loose structure at 1173–1374 K for 1800 s. The core of pellet was produced small spherical metal phase at 1473 K for 1800 s, this temperature was the soft melting temperature. Finally, the pellet produced nickel-iron alloy phase and iron was separated from the oxide phase at 1673°C for 1800 s.
  • Evaluation of the Gas Nitriding of Fine Grained AISI 4135 Steel Treated with Fine Particle Peening and Its Effect on the Tribological Properties

    pp. 556-562

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    DOI:10.2320/matertrans.M2014448

    The effect of fine particle peening (FPP) on the gas nitriding of AISI 4135 chromium-molybdenum steel was investigated. Surface microstructures of nitrided specimens pre-treated with FPP were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and glow discharge optical emission spectroscopy (GDOES). The nitrided layer formed on the fine grained specimen treated with FPP was thicker than that on the nitrided-only specimen, because the fine grains created by FPP accelerate the formation of iron nitride during the nitriding process. Furthermore, FPP reduces the concentration of chromium near the nitrided surface, which suppresses the formation of cracks and pores in the compound layer. Therefore, a nitrided specimen pre-treated with FPP has higher hardness than a nitrided-only specimen. Reciprocating ball-on-disk friction tests were performed at room temperature to investigate the tribological properties of the nitrided AISI 4135 steel. The nitrided specimen pre-treated with FPP had a lower friction coefficient and exhibited less wear loss due to the presence of a thick compound layer without cracks and pores. Therefore, a hybrid surface modification that employs FPP as a processing step prior to gas nitriding is effective for improving the tribological properties of AISI 4135 steel.
  • Application and Characteristics of Low-Carbon Martensitic Stainless Steels on Turbine Blades

    pp. 563-569

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    DOI:10.2320/matertrans.M2014307

    410M1 (0.17%C-11.6%Cr-0.18%Nb) and 410M2 (0.17%C-10.2%Cr-0.38%Nb-0.84%Mo-0.2%V-0.05%N) martensitic stainless steels are modified from the basic martensitic stainless steel 410 (0.12%C-12%Cr). They contain Nb and are utilized in the blades of turbines for generating power. This study investigates the heat treatment characteristics, microstructure and secondary hardenability of 410M1 and 410M2.
    The precipitation hardening of 410 occurs at 400°C but that of 410M1 or 410M2 occurs earlier at 300°C. The peak hardening of 410 occurs at 450°C but that of 410M1 or 410M2 occurs at 500°C. Clearly, addition of Nb improves the mechanical properties of steel at high temperature.
    Under quenching conditions, 410M1 and 410M2 are lath martensites. 410M2 contains not only Nb but also Mo, V, and N, which improve its secondary hardenability over that of 410M1. From the characteristic chart of quenching and tempering, the tempering softening and the increase in impact toughness of 410M2 are delayed as a high tempering temperature range of 650°C to 670°C is reached. This phenomenon is observed by FE SEM and proves that NbC-carbide with 20∼40 nm are precipitated in the matrix. This investigation studies the effect of alloy design on its toughness, secondary hardenability, microstructure and applications.
  • In-Beam Stress Corrosion Behavior of Welded 308 Stainless Steel at 473 K in Aerated and Hydrogenated Water Conditions

    pp. 570-575

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    DOI:10.2320/matertrans.MBW201404

    Stress corrosion tests were performed for welded 308 stainless steel under proton irradiation at 473 K in aerated water (DO: 0.15–0.22 ppm, DH: <10 ppb) and hydrogenated water (DH: 1.0–1.4 ppm, DO: <5 ppb) conditions. The in-beam loading condition was 0 and 300 MPa in tension under an irradiation dose rate of 1.3 × 10−7 dpa/s. In situ measurement of electrochemical corrosion potential (ECP) and subsequent SEM analysis were also conducted for all the specimens. In the aerated water condition, the process of stress corrosion cracking (SCC) was significantly accelerated under irradiation, while the in-beam effect on SCC was suppressed in the hydrogenated water condition. The in-beam stress corrosion behavior is discussed in terms of both water radiolysis and radiation-induced microstructures.
  • Investigation of Static and Fatigue Behavior of Periodic Mesh Plates Using Acoustic Emission Method

    pp. 576-580

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    DOI:10.2320/matertrans.M2014404

    Yield and fatigue strength of pure titanium periodic plates were investigated for three different mesh designs using acoustic emission (AE) method. Simulations of tensile test were also conducted to estimate yield strength numerically and compare with experiments. By analyzing AE during deformation, it was found that the origin of multiple AE count rate peaks is due to various yielding locations inside the specimens. For fatigue experiments, AE was used to detect the time of first fracture as it corresponds to the failure of a single cell. However, the difference in time with the final fracture of the plate was not significant, especially for low stress amplitude.
  • Precipitation Behaviors and Strengthening of Carbides in H13 Steel during Annealing

    pp. 581-586

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    DOI:10.2320/matertrans.M2014452

    Deploying optical microscopy, transmission electron microscopy, electron diffraction and energy dispersive spectrometer analysis. This article analyze the categories and shapes of carbides of three different positions in H13 ingot after annealing: upside, middle and bottom of ingot. It is found that the microstructure of H13 after annealing is composed of granular pearlite+ small amounts of ferrite and carbide phase. The categories of carbides mainly include M23C6 and MC, precipitation temperatures of which are figured out through thermodynamic calculation. Through the test of mechanical properties, it is found sample at the bottom has the optimal mechanical property. Through statistics of amounts and average sizes of precipitates and calculation of precipitation strengthening, it is found that, from upside to bottom of H13 after annealing, the size of precipitates decreases with increase of precipitation volume fraction, and contributions of precipitates to yield strength enhance gradually.
  • Acoustic Emission of Hydrogen Bubbles on the Counter Electrode during Pitting Corrosion of 304 Stainless Steel

    pp. 587-592

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    DOI:10.2320/matertrans.M2014373

    An acoustical investigation into the hydrogen bubbles on the counter electrode during pitting corrosion of 304 stainless steel has been carried out with the potentiodynamic method. After reaching the pitting potential, there was a short time delay before an Acoustic Emission (AE) signal was detected. Given this, the obtained cumulative AE counts were divided into three distinct stages showing their own unique behavior in terms of rise time and duration. The bubble evolution characteristic in each different stage was supposed to be responsible for the feature of AE signal. In the AE Stage III, the cumulative counts of the AE signals provided empirical correlations with both the total number and the total volume of corrosion pits, thus demonstrating the potential of utilizing the AE signal of hydrogen bubble on the counter electrode as a non-intrusive monitoring tool of pitting corrosion.
  • Electrochemical Characterization of Passive Films on Ni-Based Alloys in Acidic and Neutral Solutions

    pp. 593-599

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    DOI:10.2320/matertrans.M2014384

    The present work reports the structure, chemical composition and electronic properties of passive films formed on Alloy 600 and Alloy 690 in borate buffer and sulfuric acid solutions. Photoelectrochemical response from passive films varied depending on the alloy substrates and the solutions. XPS analysis revealed that the passive films formed on Alloy 600 and Alloy 690 consisted of an outer hydroxide layer and an inner oxide layer in the borate buffer solution as well as the sulfuric acid solution. The chemical composition of the layers was relatively different depending on the solutions, that is, more Fe was incorporated into the passive films formed in the borate buffer solution.
  • Oxidation Behavior of Au-55 mol%Ti High Temperature Shape Memory Alloy during Heating in Ar-50 vol%O2 Environment

    pp. 600-604

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    DOI:10.2320/matertrans.M2014468

    Oxidation behavior and subsequent phase decomposition of Au-55 mol%Ti high temperature shape memory alloy are investigated for heating oxidation up to 1773 K in Ar-50 vol%O2 using a simultaneous thermogravimetry combined with differential scanning calorimetry (TG-DSC). Au-55 mol%Ti powder specimen begins to be oxidized at 802 K and the oxidation reaction is most active at 1150 K. Since the oxidation start temperature is comparable to the martensitic transformation temperatures, the oxidation must be a problem for practical high-temperature long-term applications. An equilibrium phase reaction appears near 1346 K which is melting of Au produced by the reaction of AuTi + O2 → Au + TiO2. The oxidation reaction and products assessed by the TG-DSC measurement are in good agreement with those obtained by X-ray diffraction analysis.
  • Effect of Stain Rate on Microstructure Evolution and Compressive Deformation Behavior of High-Strength Aluminum Coating Materials Fabricated by the Kinetic Spray Process

    pp. 605-609

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    DOI:10.2320/matertrans.M2014371

    The effects of strain rates on compressive deformation behavior and microstructure evolution of kinetic sprayed pure aluminum were investigated. The initial microstructure showed a highly deformed structure with high-dislocation density. This material exhibited higher yield strengths from 200 to 224 MPa with different strain rates and low strain rate sensitivity (0.012) compared to those of conventional pure aluminum. Strain softening occurred at lower strain rates, even at room temperature, and strain hardening at high strain rates.
  • Recovery of Cobalt Ion into Polyethyleneglycol (PEG) Gel Phase as Thiocyanato Complex

    pp. 610-616

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    DOI:10.2320/matertrans.M2014428

    This study outlines the recovery of cobalt (Co) ion as a gel phase consists of PEG and Co-thiocyanato complex (Co(NCS)42−) from aqueous solution. Taking advantage of gel precipitation with composition written as (PEG)nCo(NCS)4K2, a novel process for the efficient recovery of Co was proposed. Composition of gel phase and load capacity of Co ion in it was investigated by fundamental experiment. Gel precipitation from aqueous solution of nickel sulfate (NiSO4), cobalt sulfate (CoSO4) and potassium thiocyanate (KSCN) was observed by mixing it with polyethyleneglycol (PEG#4000, molar weight; 2,700∼3,500) aqueous solution. The results confirmed the large load capacity of Co (6.8 × 10−4 mol/1 g of gel phase) compared to the sorption to polyurethane foam reported in the past. Percentage of Co ion to the total amount of Ni and Co ions in gel phase were more than 99.6 at%, revealing excellent condensation efficiency for Co. Furthermore, Co ion was extracted and separated from SCN and PEG in gel phase, by utilizing solvent extraction. From the set of experimental results, feasibility of the proposed process was discussed.

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16 Jan. (Last 30 Days)

  1. A Review of the Chemistry, Structure and Formation Conditions of Silico-Ferrite of Calcium and Aluminum (‘SFCA’) Phases ISIJ International Vol.58(2018), No.12
  2. Improving Blast Furnace Raceway Blockage Detection. Part 1: Classification of Blockage Events and Processing Framework ISIJ International Advance Publication
  3. Phase Transformation Behavior of Oxide Scale on Plain Carbon Steel Containing 0.4 wt.% Cr during Continuous Cooling ISIJ International Vol.58(2018), No.12
  4. Hydrogen Embrittlement Susceptibility Evaluation of Tempered Martensitic Steels Showing Different Fracture Surface Morphologies Tetsu-to-Hagané Vol.105(2019), No.1
  5. Improvement of Sinter Productivity by Control of Magnetite Ore Segregation in Sintering Bed ISIJ International Vol.58(2018), No.12
  6. Gasification and Migration of Phosphorus from High-phosphorus Iron Ore during Carbothermal Reduction ISIJ International Vol.58(2018), No.12
  7. Effect of TiO2 and MnO on Viscosity of Blast Furnace Slag and Thermodynamic Analysis ISIJ International Vol.58(2018), No.12
  8. Effect of Coke Size on Reducing Agent Ratio (RAR) in Blast Furnace ISIJ International Vol.58(2018), No.12
  9. High Temperature Thermal Diffusivity Measurement for FeO Scale by Electrical-Optical Hybrid Pulse-Heating Method ISIJ International Vol.58(2018), No.12
  10. Improving Blast Furnace Raceway Blockage Detection. Part 3: Visual Detection Based on Tuyere Camera Images ISIJ International Advance Publication

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16 Jan. (Last 30 Days)

  1. blast furnace
  2. blast furnace permeability
  3. blast furnace productivity
  4. 鉄と鋼
  5. continous annealing
  6. laser welder
  7. titanium
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  9. activity feo
  10. argon steel