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

MATERIALS TRANSACTIONS Vol. 53 (2012), No. 4

  • PREFACE

    pp. 583-583

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    DOI:10.2320/matertrans.MPR2012904

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    1. Mechanical Properties of Melt-Spun Amorphous Ni-Nb-Zr Alloys after Hydrogen Charging MATERIALS TRANSACTIONS Vol.47(2006), No.6
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  • Fabrication and Tensile Tests of Aluminum Foam Sandwich with Dense Steel Face Sheets by Friction Stir Processing Route

    pp. 584-587

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    DOI:10.2320/matertrans.ME201107

    An aluminum foam sandwich was fabricated by FSP route. In this process, both the fabrication of a foamable precursor and the metallurgical bonding between the precursor and a dense steel sheet can be simultaneously conducted. Although intermetallic compounds consisting of Fe2Al5 and FeAl3 were generated, tensile tests revealed that the bonding strength of the interface was relatively high compared with the tensile strength of the aluminum foam with a porosity of approximately 80%.
  • Effects of Low Rotational Speed on Crystal Orientation of Bi2Te3-Based Thermoelectric Semiconductors Deformed by High-Pressure Torsion

    pp. 588-591

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    DOI:10.2320/matertrans.ME201101

    Bi2Te3-based thermoelectric semiconductors were deformed by high-pressure torsion (HPT) using a low rotational speed of 0.1 rpm, which is less than the speed of 1 rpm used in our previous studies. The effects of different rotational speeds were investigated by metallographic and thermoelectric studies. Sample disks of p-type Bi0.5Sb1.5Te3.0 were cut from sintered compacts made by mechanical alloying (MA) followed by hot-pressing. The disks were deformed by HPT with 1, 3, and 5 turns at 473 K under 6.0 GPa of pressure at a rotational speed of 0.1 rpm. The preferred orientation was investigated using X-ray diffraction. The orientation factors of the disks changed from 0.054 for pre-rotation up to 0.653 for post-rotation samples. The maximum power factor of the disk using 5 turns and a speed of 0.1 rpm was 6.6 × 10−3 W m−1 K−2 at 363 K, which was larger than the reported power factors of 4.3 × 10−3 W m−1 K−2 for a disk using 5 turns and a speed of 1 rpm, and 4.6 × 10−3 W m−1 K−2 for melt-grown materials. Slow deformation by HPT was found to enhance the electrical conductivities and Seebeck coefficients of Bi2Te3-based thermoelectric semiconductors by producing a preferred orientation and grain refinement.
  • Synthesis of Zeolitic Material from Paper Sludge Ash Using Diatomite

    pp. 592-596

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    DOI:10.2320/matertrans.ME201104

    Paper sludge ash (PSA) was partially converted into zeolites by reaction with 3 M NaOH solution at 90°C for 24 h. The PSA had a low abundance of Si and significant Ca content, due to the presence of calcite that was used as paper filler. Diatomite, which contains amorphous silica and dissolves easily in alkali solution, was mixed with the ash, and then added to the NaOH solution to increase its Si content during alkali reaction and thus synthesize zeolites with high cation exchange capacity (CEC). The original ash without addition of diatomite yielded hydroxysodalite with CEC ca. 0.5 mmol/g. Addition of diatomite to the ash yielded zeolite-P with a higher CEC (ca. 1 mmol/g). The observed concentrations of Si and Al in the solution during the reaction explain the crystallization of these two phases. The reaction products were tested for their adsorption capacity for nutrients from liquid fertilizer, such as K+, NH4+ and PO43−. The product with zeolite-P exhibits high ability to adsorb these nutrients from liquid fertilizer, which is desirable for application in soil improvement.
  • Preparation of n-Type Bi2Te2.85Se0.15 Thermoelectric Semiconductor without Harmful Dopants

    pp. 597-600

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    DOI:10.2320/matertrans.ME201108

    Undoped n-type Bi2Te2.85Se0.15 compounds without harmful dopants were prepared by mechanical alloying (MA) and sintered by hot pressing (HP). Samples of the Bi2Te3-based materials had a nominal composition of Bi2Te2.85Se0.15. Dopants were not added to control the carrier concentration. The constituent elements, i.e., Bi (5 N), Te (6 N), and Se (5 N), were weighed according to the target composition and milled with silicon-nitride balls. MA was carried out for 30 h. The resulting MA powder was sintered by HP in the temperature range 573–673 K under a mechanical pressure of 147 MPa in an argon atmosphere. The Seebeck coefficient α and electrical conductivity σ were measured in the temperature range 300–473 K. The thermoelectric performance was evaluated from the power factor P, where P = α2σ. The obtained samples exhibited n-type conduction and the single-phase of Bi2(Te, Se)3. The power factor for an undoped sample sintered at 623 K was 4.4 × 10−3 W m−1K−2 at 313 K. This power factor was 88% of the value of 5.0 × 10−3 W m−1K−2 reported for single crystals of n-type doped Bi2Te2.85Se0.15. These results indicated that it is not necessary to dope Bi2Te2.85Se0.15 prepared by an MA–HP process with harmful halide dopants to achieve carrier control.
  • Nondestructive Assessment of Glass Fibre Composites by Mid-Wave and Near Infrared Vision

    pp. 601-603

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    DOI:10.2320/matertrans.I-M2011856

    The nondestructive testing (NDT) of composites is a critical step for the early detection and repair of industrial components. Infrared (IR) vision has demonstrated to be an attractive inspection technique, allowing a fast and straightforward examination of the integrity of materials and parts in a non-invasive and non-contact manner. In this study, mid-wave infrared (MWIR) thermography and near infrared (NIR) vision are investigated for the NDT inspection of a glass fibre sample with fabricated subsurface defects of different types. The main advantages and limitations of each technique are discussed and some comparative experimental results are provided.
  • Non-Destructive Evaluation of Weld Structure Using Ultrasonic Imaging Technique

    pp. 604-609

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    DOI:10.2320/matertrans.I-M2011857

    The welding penetration depth and width measured by destructive inspection are very important items to evaluate welding quality. However, the destructive method has some limitations and disadvantages. In this study, ultrasonic measurement technique which can make the image of cross sectional macro structure non-destructively was investigated. As a result, it is concluded that signal processing of ultrasonic back scattering is effective to measure the penetration depth of welds.
  • Fast Remaining Thickness Measurement Using a Laser Source Scanning Technique

    pp. 610-616

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    DOI:10.2320/matertrans.I-M2012801

    Fast remaining thickness measurement using Lamb wave is presented for the purpose of maintenance of large structures like oil storage tanks and pipe networks. This study used a laser ultrasonic source to perform a high resolution remote scanning over aluminum plates with grooved and circular defects that were modeled on corrosions in plate-like structures. The antisymmetric A0 and symmetric S0 modes of Lamb wave were used to obtain information of the plate thickness from amplitude distributions over the scanned areas on plates. The amplitude distributions of A0 mode provide better thickness distributions that those of S0 modes for grooved defects. For plates with circular defects, the amplitude distributions did not agree well with the thickness distribution due to the refraction around the defects, defect images were seen in both modes. Especially in the amplitude distribution of S0 mode, the defect images for the circular defect were clearly obtained.
  • In-Service Aged Composite Insulators at Transmission Line Investigated by the Micro-Computerized Tomography

    pp. 617-620

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    DOI:10.2320/matertrans.I-M2012802

    Composite insulators aged in-service for almost 10 years at the transmission line of 230 kV, in an area where brittle fracture of a composite insulator occurred, were inspected by the micro-computed tomography, µ-CT, and by the scanning electron microscope, SEM. As a result, several cracks with different depths under pollutant scale and confined in silicone housing were detected by the µ-CT. Surface of silicone housing was observed by the SEM. Many randomly oriented cracks from micrometers size were observed. However, larger cracks detected and evaluated by the µ-CT appear essentially perpendicular to the composite rod axis. In order to explain the evolution of those large cracks in composite insulators, a model based on µ-CT and SEM data was proposed.
  • Ultrasonic Imaging of Concrete by Synthetic Aperture Focusing Technique Based on Hilbert-Huang Transform of Time Domain Data

    pp. 621-626

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    DOI:10.2320/matertrans.I-M2012804

    For non-destructive evaluation (NDE) of concrete, efficient and accurate imaging techniques are needed for a reliable evaluation of safety and serviceability of structures. Imaging of concrete structures is considered a very challenging task since it is a non-homogeneous material. In this paper, the acoustic (stress wave) technique was applied by using Ultrasonics and Synthetic Aperture Focusing Technique (SAFT).
    In ultrasonic NDE, the presence of coarse aggregates requires that the ultrasonic testing be conducted at relatively low frequencies in order to avoid excessive attenuation. The Hilbert-Huang Transform (HHT), based on Ensemble Empirical Mode Decomposition (EEMD), was used as a signal processing tool for interpreting and analyzing the ultrasonic waveforms taken from a concrete specimen with an embedded steel rod. SAFT images for both processed and unprocessed signals were obtained and compared. Results showed that the reflections from the bottom surface as well as the steel rod were successfully imaged when the processed signal were used. Therefore, anomaly or defect detection in concrete structures through ultrasonic imaging was greatly improved by the combination of HHT and SAFT.
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    Readers Who Read This Article Also Read

    1. Nondestructive Assessment of Glass Fibre Composites by Mid-Wave and Near Infrared Vision MATERIALS TRANSACTIONS Vol.53(2012), No.4
    2. Non-Destructive Evaluation of Weld Structure Using Ultrasonic Imaging Technique MATERIALS TRANSACTIONS Vol.53(2012), No.4
  • Numerical Analysis of Microwave NDT Applied to Piping Inspection

    pp. 627-630

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    DOI:10.2320/matertrans.I-M2012805

    Numerical simulations using finite element software were carried out to discuss the physical background of nondestructive inspections of pipes using microwaves. The simulations were conducted using an axisymmetric configuration modeling pipe with wall thinning to evaluate the effect of the profile of the wall thinning on the microwave propagation. Both rectangular and quasi-racetrack wall thinnings were considered. The numerical simulations showed the presence of wall thinning attenuates microwaves at particular frequencies. An empirical formula was proposed to evaluate the profile of wall thinning for the particular frequencies. Although the formula was based on the results of numerical simulations considering only rectangular wall thinning, it is also applicable to the evaluation of quasi-racetrack wall thinning.
  • Investigation of the Sound Field of Phased Array Using the Photoelastic Visualization Technique and the Accurate FEM

    pp. 631-635

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    DOI:10.2320/matertrans.I-M2012806

    In this study, we tried to obtain an accurate ultrasonic sound field of the commercial phased array system. For this purpose, the experimental photoelastic ultrasonic visualization system was improved to evaluate a phased array system and the analytical special large-scale finite element method (FEM) code for ultrasonic transmission was applied.
    As the results, an actual sound field of phased array system was much more complicate than that of the conventional industrial assumption based on a simple superposition. One of the causes of the difference might be the accuracy of the directivity for each element in the array transducer. Thus, the combination of photoelastic visualization method and FEM analysis was useful for the accurate sound field investigation of the phased array measurement.
  • Electronic Structures and Thermoelectric Properties of Sb-Doped Type-VIII Clathrate Ba8Ga16Sn30

    pp. 636-640

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    DOI:10.2320/matertrans.E-M2012807

    The type-VIII clathrate Ba8Ga16Sn30 shows a high figure of merit (ZT) in the middle temperature range 470–670 K. ZT enhancement through Sb doping has recently been reported in p-type Ba8Ga16Sn30. In this study, calculations to determine the electronic structures and thermoelectric properties of Sb-doped Ba8Ga16Sn30 are performed using the WIEN2k code. The energy derivative of density of states [∂ρ(ε)/∂εε=EF for valence band is lower in the Sb-doped Ba8Ga16Sn30 than in non-Sb-doped one, though the density of states [ρ(ε)]ε=EF of both system are almost the same as that for Ba8Ga16Sn30. Except for the signs, the calculated Seebeck coefficients for the p- and n-type Sb-doped and non-Sb-doped Ba8Ga16Sn30 are similar.
  • Temperature and Bias Voltage Dependencies of Spin Injection Signals for Co2FeAl0.5Si0.5/n-GaAs Schottky Tunnel Junction

    pp. 641-644

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    DOI:10.2320/matertrans.MBW201113

    We investigated the temperature and bias voltage dependencies of spin injection signals for Co2FeAl0.5Si0.5 (CFAS)/n-GaAs schottky tunnel junction. Clear voltage change was observed at 10 K for the junction by 3 Terminal Hanle measurements. The maximum voltage change, ΔVMAX, was decreased with increasing temperature and observed up to 100 K. The estimated spin relaxation time, τ, was 290 ps at 10 K and was also decreased with increasing temperature. In addition, temperature dependency of τ was lower than that of ΔVMAX. The ΔVMAX was increased with increasing bias voltage, and the sign of ΔVMAX was reversed by opposite bias voltage direction. Moreover, bias dependency of ΔVMAX became insensitive with increasing temperature.
  • Oxide Particle Refinement in 4.5 mass%Al Ni-Based ODS Superalloys

    pp. 645-651

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    DOI:10.2320/matertrans.M2011251

    Oxide particle refinement, which improves high temperature strength in Ni-based oxide dispersion strengthened (ODS) superalloys, was investigated by employing Hf addition during mechanical alloyed (MA) process. TEM micrographs show that 2 mass% Hf addition makes the smallest oxide particles and shortest separation in the base alloy (Ni–4.5 mass%Al–1 mass% Y2O3). Formation of Y2Hf2O7 is confirmed to be responsible for the oxide particle refinement with XRD analysis. By the calculation and comparison based on hardness and Orowan mechanism, the improvement of hardness by Hf addition attributes to the dispersion strengthening of oxide particles.
  • Effects of Two-Step Cold Rolling on Recrystallization Behaviors in ODS Ferritic Steel

    pp. 652-657

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    DOI:10.2320/matertrans.M2011301

    The recrystallization behaviors of Fe–15Cr ODS ferritic steels underwent two different processing routes were compared; (a) 1st 70% cold rolling + intermediate annealing, (b) 1st 70% cold rolling + intermediate annealing at 1100°C to make a recrystallization structure +2nd 70% cold rolling + final annealing. Hardness and texture changes during rolling and isochronal annealing were investigated. Results show that the recrystallization temperature of 70% cold rolled specimen is 950°C and the recrystallization texture is {111}<112>. On the contrary, in the case of specimen which was cold rolled for two times, the recrystallization temperature increases to 1100°C, and the recrystallization texture changes to {111}<110>. These changes are ascribed to the different routes of crystalline rotation during 1st and 2nd cold rolling, which produce different cold rolling texture. Higher {100}<110> content induced by 2nd cold rolling after intermediate recrystallization which has low stored energy increases the recrystallization temperature. And the difference in texture intensity along γ fibre after 1st and 2nd cold rolling results in different recrystallization texture.
  • Irregular or Smooth Grain Boundaries Evolved after Secondary Recyrstallization of Fe–3%Si Steel

    pp. 658-661

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    DOI:10.2320/matertrans.M2011268

    Irregular or smooth grain boundaries after secondary recrystallization are formed depending on whether interpass aging is adopted or not during cold rolling of Fe–3%Si steel. Interpass aging induces the primary texture of high intensity of {111}⟨112⟩ and {411}⟨148⟩ orientations, which have a ∑9 relation with respect to the Goss orientation and therefore are favorable for Goss grains to grow by solid-state wetting. Under this condition Goss grains come in contact with each other by wetting without leaving any small grains in between, resulting in irregular boundaries.
  • Wettability Model Considering Three-Phase Interfacial Energetics in Particle Method

    pp. 662-670

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    DOI:10.2320/matertrans.M2011330

    Wettability of a solid by a liquid plays a key role in achieving the purpose of the process in moving bed-type reactors. In recent years, particle method has been proposed for the design of processes which include multiphase flows. Using this method, it is possible to analyze a free surface flow without explicitly tracking the interface. Although surface tension and wettability models using the particle method have already been proposed, the complexity of calculations of normal line and curvature of the surface particle has been pointed out as a problem. In this study, surface tension and wettability model were introduced in terms of interparticle potential, and theoretical and experimental verifications were performed for a 3-dimensional particle method which stabilizes the internal pressure distribution in fluids. The analytical solution for the droplet oscillation period by this method showed good agreement with the theoretical solution, and the surface tension between a gas and liquid could be calculated correctly. Because the difference in the number density of a liquid phase and solid phase becomes remarkable in a 3-dimensional space, a technique which corrects for this in particles at a three-phase interface was introduced. Time change in the droplet shape was compared with the experimental results by changing the droplet impact velocity to obtain agreement of the Weber number. It is considered possible to express the droplet shape correctly during rotating falling on a solid surface.
  • Detection of AE Events due to Cracks in TBC during Spraying Process

    pp. 671-675

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    DOI:10.2320/matertrans.MBW201118

    Cracks may occur inside a top coating or at an interface between the top and bond coating of the thermal barrier coating (TBC) during atmospheric plasma spraying (APS) process. The acoustic emission (AE) method is suitable for detection of the generation and propagation of these cracks because it is an in-situ non-destructive evaluation technique. However, AE monitoring of APS process is prevented by large acoustic noise at elevated temperature on a specimen due to heating by the plasma jet. Therefore, a non-contact laser AE method with a newly developed measurement and analysis system was used for monitoring of the top coating process. Several types of noise reduction processes such as soft-thresholding were applied to continuously recorded AE waveform. Experiments were conducted with various preheating temperatures and scanning speeds of the plasma torch. AE events due to cracking were detected only during spraying, on the other hand no events were detected after spraying. The effect of preheating temperature and scanning speed of the plasma torch on the development of cracks were estimated. A correlation was observed between the density of delamination cracks and the number of AE events.
  • Composition Dependence of Pd–Ag Alloy Proton Injection Layer on Optical Switching Properties of Electrochromic Switchable Mirror

    pp. 676-680

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    DOI:10.2320/matertrans.M2011177

    We fabricated electrochromic switchable mirror glass with a Pd–Ag alloy proton injection layer to investigate the relationship between the composition of the proton injection layer and the optical switching properties, in an attempt to reduce the cost and the amount of palladium used in the fabrication of these devices. The composition of the layer was easily controlled by co-sputtering of palladium and silver metal targets with various power ratios. A device with a Pd86Ag14 layer showed the maximum transmittance in the transparent state, and similar switching speed between the reflective and transparent states to a palladium-only reference device. Changing the silver content in the layer effectively controlled the reflectance of the device. The maximum reflectance in the reflective state increased with increasing silver content, due to the high reflectance of silver. However, the maximum transmittance in the transparent state decreased, and the high silver content prevented smooth switching of the device. In this work, although Pd86Ag14 displayed the best properties as a proton injection layer, the performance was insufficient for commercial use. Therefore, more suitable fabrication conditions and proton injection materials will be the subject of future investigation.
  • Influence of Substrate Temperature on Structure and Adhesion Strength of Fe–Cr–P–C Amorphous Coating Films Produced by Thermal Spraying Technique

    pp. 681-689

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    DOI:10.2320/matertrans.M2011261

    The influence of the substrate temperature on the structure, the pore distribution, and the adhesion strength of Fe-10Cr-based amorphous coating films has been examined. The amorphous coating films have been produced by a thermal spraying technique using our developed cylindrical nozzle on SS400 substrates. The splat morphology of the sprayed particles changed drastically from an irregular splash shape to a disk shape at a transition temperature of about 325°C. When the substrate temperature increased to the transition temperature region, between 325 and 350°C, the porosity in the boundary regions between the sprayed coating films and the substrates drastically decreased to about 6%, which may be due to the drastic increase in the wettability of the sprayed particles accompanied with the change of morphology from the splashed shape to the disk shape. When the substrate temperature increased from the transition temperature of 325°C up to 400°C, the porosity decreased gradually, and the volume fraction of the amorphous phase increased with increasing substrate temperature, resulting in an increase in the adhesion strength up to about 15 MPa.
  • Strain-Controlled Fatigue Behavior in Thin Pure Copper Sheet for Smart Stress-Memory Patch

    pp. 690-695

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    DOI:10.2320/matertrans.MBW201117

    A new sensing method called “smart stress-memory patch” has been proposed for fatigue damage evaluation of structures. This patch estimates the number of cycles and stress amplitude using its crack length. In this study, fatigue crack growth behavior in thin pure copper sheet was investigated under strain-controlled testing to evaluate the sensor characteristics when the patch is attached to structure. Electrodeposited (ED) copper of 99.96% purity with an average grain size of 2 µm provided a stable crack propagation and easy observation of crack length. The relationship between stress intensity factor range and crack growth rate was fitted on one curve regardless of strain amplitude. The scattering in fatigue crack growth was evaluated by a stochastic model, and it demonstrated that the error of fatigue cycles estimated by the patch is small enough. Furthermore, stress transfer between the patch and structure was calculated on the simple assumption that the patch is perfectly bonded on the structure, and it was shown that the patch attached to structure can estimate the number of cycles and stress amplitude on the structures.
  • Observation of Electric Potential Distribution in Model Capacitor Sample Using Electron Holography

    pp. 696-699

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    DOI:10.2320/matertrans.MBW201108

    The electrical potential distribution in a model capacitor specimen, made of single-crystalline BaTiO3 and thin Pt plates, has been revealed by electron holography. In order to represent the inherent potential distribution related to the capacitance, undesired phase information was eliminated by the analysis of electron holograms acquired in various conditions of applied voltage; the undesired information includes signals due to electrical charging, thickness variation, and modulation of the reference electron wave by a long-range electric field. The observation of electric potential showed reasonable agreement with simulation for the model specimen.
  • Corrosion of Calcium Phosphate Coated AZ31 Magnesium Alloy under a Salt Spray Test

    pp. 700-706

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    DOI:10.2320/matertrans.M2011346

    The corrosion resistance and adhesiveness of a hydroxyapatite (HAp)-coated AZ31 magnesium alloy rolled plate were evaluated by a salt spray test (SST: JIS Z 2371) and a cross-cut test (CCT: JIS K 5600), respectively. The length of the HAp coating solution treatment was 4 or 6 h. A HAp coating consisting of an inner continuous layer and an outer porous layer uniformly covered the surface regardless of the treatment period. After the SST for 7 days, the HAp-coated surfaces showed no significant delamination but several visible pits. The HAp coating in the non-corroded area retained its original morphology after the SST by a SEM observation. The rating number (RN) for the HAp-coated specimens was over 9, which was much higher than RN 4 observed for the chemically polished specimen covered almost entirely with filiform corrosion. The RN of HAp-coated specimen increased slightly with a longer treatment period. The adhesiveness of the HAp coating was not influenced by the SST according to the CCT. After removing the corrosion products and HAp coating from the non-corroded area, small pits with a diameter of a few hundred micrometers appeared; however, general corrosion did not take place underneath the HAp coating. The HAp coating shows high corrosion resistance and good adhesiveness to the AZ31 substrate.
  • Investigation of Flotation Parameters for Copper Recovery from Enargite and Chalcopyrite Mixed Ore

    pp. 707-715

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    DOI:10.2320/matertrans.M2011354

    A flotation pre-treatment study for the separation of enargite (Cu3AsS4) from chalcopyrite (CuFeS2) ores of different origins was investigated in this work. The copper ore bearing enargite mineral contained 5.87 mass% As and 16.50 mass% Cu while the chalcopyrite bearing ore contained 0.32 mass% As and 21.63 mass% Cu. The two ore samples were mixed at 7 : 3 (enargite : chalcopyrite) by weight ratio to prepare a mixed ore sample with As content at 3.16 and 18.25 mass% Cu for the flotation study. Effect of particle size, slurry pH, flotation time, collector type, collector addition or dosage and depressants were investigated to evaluate efficiency of enargite separation from chalcopyrite and recovery of both minerals as separate concentrates. For enargite single ore flotation, the 38–75 µm size fraction showed that over 98% of enargite was selectively recovered within 5 min at slurry pH of 4 and As content in the final tailings was reduced to 0.22 mass%. In mix ore (enargite + chalcopyrite) flotation, 97% of enargite was first removed at pH 4 followed by chalcopyrite flotation at pH 8, and over 95% recovery was achieved in 15 min flotation time. The As content in the final tailings was reduced to 0.1 mass%.
  • Fine Grains Forming Process, Mechanism of Fine Grain Formation and Properties of Superalloy 718

    pp. 716-723

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    DOI:10.2320/matertrans.M2011337

    The mechanical properties of Inconel 718 superalloy are determined primarily by its microstructure and grain size. The grain structure of Inconel 718 is traditionally refined by aging treatment, and a high volume fraction of acicular δ phase precipitates before the structure forms. During the following static or dynamic recrystallization process, the existing δ phase inhibits recrystallized grain growth and acquires a fine grain structure. In the proposed approach, the Inconel 718 specimens are re-solution heat treated at a temperature higher than the δ solvus temperature to ensure thorough dissolution of the precipitated δ phase into the austenite matrix and produce a niobium oversaturated matrix. The specimens are then cold compressed to produce a dislocation saturated matrix and are finally recrystallized at 950°C to induce the precipitation of fine δ phase. The δ phase precipitates exert a strong grain-boundary pinning effect, and thus a fine grain structure is obtained despite the high recrystallization temperature. The average grain size in the refined microstructure is found to be 2–3 µm, which is around half that of the grain size in the specimens prepared using the conventional process. Hardness testing and tensile testing at 25 and 650°C revealed its superior mechanical properties.
  • Cell Proliferation, Corrosion Resistance and Mechanical Properties of Novel Titanium Foam with Sheet Shape

    pp. 724-732

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    DOI:10.2320/matertrans.M2011325

    We had developed novel titanium (Ti) foam sheet with original slurry foaming method. The products had an average pore size under 500 µm in diameter, volumetric porosities over 80%, and chemical composition corresponding to grade 4 in ISO 5832-2; Implants for surgery — Metallic materials. The Ti foam had the tensile strength of 9 to 20 MPa similar to cancellous bone strength and anisotropic characteristics. Considering the application of our Ti foam for surface modification of hip or knee prostheses, we prepared Ti foam sheet joined with CP Ti, Ti–6Al–4V, or Zr–2.5Nb plate to evaluate the effect of joined solid metals on cell proliferation and corrosion resistance. Plate materials did not show any significant difference on cell proliferation test but affected the anode corrosion rates. Our novel Ti foam exhibited high applicability to the surface modification not only of Ti but also of Ti–6Al–4V and Zr–2.5Nb orthopedic implants.
  • Microstructural Characteristics of InGaZnO Thin Film Using an Electrical Current Method

    pp. 733-738

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    DOI:10.2320/matertrans.M2011312

    This research studied the microstructural characteristics and electronic properties of IGZO1114 films (atomic ratio In : Ga : Zn : O = 1 : 1 : 1 : 4) with different annealing conditions. The solid-state electrical current method was used in the IGZO/In films (In layer was a channel) and the interface effect on the electrical current mechanism was discussed. The experimental results show the effect of the annealing temperature was larger than that of the deposition oxygen flow rate for the film resistances. IGZO film which was annealed at 575 K was able to stabilize the composition of the matrix. The electrical current experiment at room temperature confirmed that the diffusion of the IGZO/In film occurred through an electric current induced crystallization (EIC). The In layer not only assisted the recrystallization behavior of the IGZO film, but also improved the electrical resistance.
  • The Effect of Phases in Nanoparticles Produced by Electrical Wire Explosion on Arsenic(III) Removal

    pp. 739-744

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    DOI:10.2320/matertrans.M2011381

    Nano-sized iron oxide particles were prepared by electrical wire explosion (EWE) for As(III) removal. The electrical explosion of Fe wire in Ar–5%O2, Ar–10%O2, and Ar–30%O2 produced a wide spectrum of iron–oxide phases from wüstite to hematite depending on the oxygen partial pressure in the chamber. An increase in oxygen partial pressure tended to shift the iron oxides towards higher oxidation states. The major phase of the explosion product was verified as the magnetite (Fe3O4)–maghemite (γ-Fe2O3) mixture through the step scan of (511) and (440) peaks. The As(III) removal capacity and saturation magnetization were found to be proportional to the amount of zero-valent iron (ZVI) in the particles. The As(III) adsorption capacity (qmax, mg/g) calculated from the Langmuir isotherm was 19.7, 9.46, and 3.55 mg/g for particles synthesized in Ar–5%O2, Ar–10%O2, and Ar–30%O2, respectively. The EWE process could be utilized to produce nano-sized adsorbent particles with a wide range of As(III) removal capability simply by varying the gas mixture. The eco-friendly nature of EWE process combined with the magnetic separation option would add to the list of the successful As(III) removal adsorbents.
  • Effects of Thermal Erosion and Wear Resistance on AISI H13 Tool Steel by Various Surface Treatments

    pp. 745-751

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    DOI:10.2320/matertrans.M2011360

    In this study AISI H13 steel was treated with oxynitriding, CrN coating, and CrN coated with oxynitriding to investigate the molten loss for melting A380 aluminum alloy and wear resistance. The experimental results indicate that the minimum melting loss appeared in duplex surface treatments of CrN coated with oxynitriding after a 3 h erosive test. Weight loss was only 0.8%; however the untreated specimen was 3.2%. In addition, all specimens following the different surface treatments, showed a higher wear resistance after the wear test. The untreated specimen showed obvious traces of plough cracks. Conversely, other surface treated specimens experienced very shallow wear. This result shows that the wear resistance of AISI H13 can be effectively improved by performing various surface treatments. The lowest coefficient of friction also appeared in the duplex surface treatment of CrN coated with oxynitriding. The average value of frictional coefficient was 0.28.
  • Electromotive Force of the High-Temperature Concentration Cell Using Al-Doped CaZrO3 as the Electrolyte

    pp. 752-759

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    DOI:10.2320/matertrans.M2012020

    In order to clarify the electrochemical properties of the Al-doped CaZrO3 system, a gas concentration cell was assembled adopting 0.4 mol%Al-doped CaZrO3 polycrystalline sintered material as the electrolyte and its electromotive force (emf) was measured for various oxygen and hydrogen chemical potential gradients. The measurements were performed in a hydrogen-rich atmosphere for the temperature range from 973 to 1473 K. For almost all the conditions in the experiment, the measured emf’s were well explained by regarding that the substantial predominant charge carrier is the proton. Under the conditions that the transport number of proton is less than unity, the agreement was examined between the measured emf and the theoretical one estimated based on the conduction parameters determined by the conductivity measurement reported in the previous work. It was confirmed that they well coincide with each other in all experimental conditions.
    This fact shows that the conduction parameters of CaZr0.996Al0.004O3−α and also the model of defect structure reported in the previous work were reasonable. The proton conduction domain of Al-doped CaZrO3 in the oxygen-hydrogen chemical potentials plane was examined based on these conduction parameters and it was found to be a little wider than that of In-doped CaZrO3 system.
  • Simultaneous Recovery of Gold and Iodine from the Waste Rinse Water of the Semiconductor Industry Using Activated Carbon

    pp. 760-765

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    DOI:10.2320/matertrans.M2012009

    This research work focused on the simultaneous recovery of gold (40.5 mg/dm3) and iodine (748 mg/dm3) from the waste rinse water of the semiconductor industry using activated carbon. A batch study was conducted to optimize process parameters, such as contact time and carbon dose, for the recovery of gold and iodine from the waste water. The loading capacity of the activated carbon for adsorption of gold and iodine was found to be 33.5 mg Au/g carbon and 835 mg I2/g carbon, respectively. Gold was found to exist on the activated charcoal surface in two forms: ionic gold and elemental gold. Aqua regia was used to convert metallic gold to its ionic form, and the iodine and the small amount of ionic gold were removed from the activated carbon by elution with aqua regia. Gold was recovered from the eluate by reduction with hydrazine. Iodine from the diluted aqua regia was then precipitated by adding sodium hydrosulfite (Na2S2O4). A complete process flow sheet was developed to recover both gold and iodine from the waste water of the semiconductor industry, which conserves the resources while meeting environmental pollution requirements.
  • Microstructure Characterization and Thermal Stability of Nanocrystalline Cu Powders Processed via Cryomilling

    pp. 766-769

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    DOI:10.2320/matertrans.M2011374

    Nanocrystalline Cu powders with a grain size of about 32 nm have been successfully synthesized using cryomilling technique. The effect of cryomilling time on the particle size, grain size, and structure of cryomilled Cu powders were investigated. The thermal stability of cryomilled Cu powders was studied and the study described the enthalpy change due to grain growth and stress relaxation of cryomilled Cu particles by annealing. The stress relaxation process associated with reordering of the grain boundaries was found to occur at 280°C. The grain growth process was found at 330°C and the thermal release of the grain growth was detected by differential scanning calorimetry analysis.
  • Structure of Deposits Obtained from Urea-Based Melt Bath Containing Co and La

    pp. 770-772

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    DOI:10.2320/matertrans.M2011379

    Electrodeposition was performed in an unagitated solution from a urea-based melt bath containing Co and La under galvanostatic (10–40 mA·cm−2) and coulostatic (10 C·cm−2) conditions at 403 K, and the structure of the deposits was investigated. Co deposited in a metallic state at 10 mA·cm−2, whereas it was incorporated into deposits mainly as an oxide at high current densities of 30 and 40 mA·cm−2. La codeposited with Co as an oxide irrespective of current density. The content of La2O3 increased with current density. The deposits showed a granular crystal structure and became nonuniform crystals comprising large localized granules at high current densities.

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