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

MATERIALS TRANSACTIONS Vol. 56 (2015), No. 12

  • Potential Prospective Application of Zr-Based Bulk Metallic Glasses in Dental Implant

    pp. 1925-1929

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    DOI:10.2320/matertrans.M2015246

    Zr-based bulk metallic glasses (BMGs) are being studied widely in recent years due to their unique mechanical properties. In this paper, we will present the progress in the studies of corrosion resistance behavior and biomedical potential of the Zr-based BMGs, especially the in vitro and in vivo evaluation of their biocompatibility. Owing to their high resistance to corrosion in a physiological environment and the excellent biocompatibility that give them a passive, stable oxide film, Zr-based BMGs are considered the material of choice for intraosseous use. The aim of this paper is to give an overview of the available literature on the Zr-based BMGs and present a promising prospect for the application of oral implant.
  • Review on Thermo-Mechanical Fatigue Behavior of Nickel-Base Superalloys

    pp. 1930-1939

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    DOI:10.2320/matertrans.M2015323

    Nickel-base superalloys have become the key materials of hot-end components in the aeroengines over the past several decades. Nickel-base superalloys are easy to produce thermo-mechanical fatigue (TMF) behavior when withstanding the combined effects of high temperature, creep, oxidation, mechanical stress and thermal stress. The occurrence of TMF seriously affects the normal service for hot-end components. Thus, the investigation about TMF behavior is of great significance. The TMF test can be divided into in-phase (IP) tests and out-of-phase (OP) tests. The fatigue life was described and compared for IP-TMF and OP-TMF. The reasons for various lives were analyzed. The classical life prediction models were evaluated. Cyclic stress response behaviors and hysteresis loops were analyzed. Cyclic deformation mechanism was revealed in depth. Fatigue fractographs of crack initiation and propagation were characterized on the fracture surfaces of fracture specimens. Crack initiation mechanism and fatigue damage mechanism were revealed in depth for TMF.
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    Readers Who Read This Article Also Read

    1. Lower Protrusion of a Copper-Nickel Alloy in a Through-Silicon via and Its Numerical Simulation MATERIALS TRANSACTIONS Vol.56(2015), No.12
  • Retaining the ⟨001⟩ Orientation from Initial Columnar Grains and Magnetostriction in Binary Fe-Ga Alloy Sheets

    pp. 1940-1944

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    DOI:10.2320/matertrans.M2015282

    Sheets of binary Fe83Ga17 alloy were prepared by a method which involved rolling of specimens with ⟨100⟩ oriented columnar grains arranged initially along rolling direction. The ductility of the binary Fe83Ga17 alloy with ⟨100⟩ oriented columnar grains fabricated via directional solidification could be improved compared with that of the alloy with equiaxed grains. The orientation gradually rotated to a ⟨110⟩ from the ⟨100⟩ direction during the rolling process, and the final rolled texture was dominated by strong {100}⟨011⟩. The sharp {110}⟨001⟩ Goss orientation was confirmed in the final annealed sheets. Excluding the effects of inhibitors and surface energy on textural evolution, it is thought that the ⟨001⟩ orientation was obtained from the hereditary characteristics of the initial columnar grains. A high magnetostriction of 185 ppm without pre-stress was attributed to the strong Goss texture observed in the final recrystallized sheets.
  • The Decomposition Formula of ⟨001⟩ Symmetrical Tilt Grain Boundaries

    pp. 1945-1952

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    DOI:10.2320/matertrans.M2015277

    The general decomposition formula was established for the structures of symmetrical tilt grain boundaries with the tilt axis of ⟨001⟩. By investigating the underlying mathematical structure, we propose a novel algorithm to obtain the arrangement of structural units for any misorientation angle of the boundary with an arbitrary precision due to the Farey sequence.
  • Tribological Performance of Various Types of Biodiesel

    pp. 1953-1959

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    DOI:10.2320/matertrans.M2015263

    Lubricity is a critical property of diesel fuel because it affects engine performance. Current and future regulations are expected to reduce the sulfur content of diesel fuel. Low lubricity (i.e., low sulfur content) increases diesel engine wear and damages the fuel injection system. Alternative types of fuel have reduced diesel engine exhaust emissions and improved the friction and wear properties of engine parts.
    Four types of diesel fuel, pure petrodiesel, soybean oil, palm oil, and waste edible oil (WEO), were compared for their fuel properties, engine performance, and emission characteristics. A series of tests was performed using various types of diesel fuel. The ball-on-ring wear testing method was used as an analytical tool for this purpose. The lubricating efficiency of the fuels was estimated using a photomicroscope to measure the average width of the wear scar produced on the test ring.
    The wear experiments showed that the wear scar widths were 3.48 mm, 2.76 mm, 2.90 mm, and 2.93 mm for lubrication of the pure petrodiesel, soybean oil, palm oil, and WEO, respectively. Lubricities of this diesel are as follows: soybean oil > palm oil > WEO > pure petrodiesel. The ability of biodiesel to be highly biodegradable and its superior lubricating property when used in compression ignition engines make it an excellent fuel. This detailed experimental investigation confirms that biodiesel can substitute mineral diesel without any modification in the engine. The use of biofuels as diesel engine fuels can play a vital role in helping the developed and developing countries to reduce the environmental impact of fossil fuels.
  • Effect of Precipitation of Impurities during Annealing on the Rate of Recovery and Recrystallization in 1050 Aluminum Hot-Rolled Sheets

    pp. 1960-1967

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    DOI:10.2320/matertrans.L-M2015830

    It is well known that the recovery and recrystallization of commercially pure aluminum are influenced by the dissolved impurities, iron and silicon. In this study, we assumed that the dissolved impurities precipitate on the cell boundaries and subgrain boundaries during annealing and control the rate of recovery and recrystallization in the commercially pure aluminum and adopted a new rate equation developed by Yamamoto, which contains the term of the particle number that exponentially changes. It was found that the entire reaction was divided into two reactions, i.e., the recovery and recrystallization, which processes were analyzed by this equation. The entire reaction was expressed by superimposing the two processes. For the recovery process, the value of the time exponent is 0.5, which means control of the dislocation pipe diffusion, by which impurities precipitate on the dislocation cell boundaries. For the recrystallization process, the value of the time exponent is 1, which means control of the grain boundary diffusion, by which impurities precipitate on the subgrain boundaries. Therefore, our assumption was verified by this new equation. Based on the activation energy, we consider that the precipitation of silicon during the recovery and that of iron during the recrystallization control the reaction rate.
  • Relevance of Primary γ′ Dissolution and Abnormal Grain Growth in UDIMET 720LI

    pp. 1968-1976

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    DOI:10.2320/matertrans.M2015283

    The relevance of the dissolution behavior of the primary γ′ phase and abnormal grain growth in UDIMET 720LI (U720LI) alloy was studied under various heat treatment conditions and through corresponding simulation based on the classical dynamic model using MATLABTM. The results indicated that the dissolution kinetics and volume fraction of the dissolved primary γ′ phase increased by increasing the dissolution temperature. Additionally, an increase temperature promoted abnormal grain growth. Fine and coarse grains randomly mixed during the temperature range of 1155°C to 1170°C. The dissolution mechanism was rationalized, with the elastic splitting of the primary γ′ phase involved in the early stage of the dissolution process. The dissolution process of the primary γ′ phase was dominated by the diffusion mechanism in the latter stages. The dissolution-sensitive temperature range which should be avoid to inhibit the abnormal grain growth was given. Simulation results were consistent with the experimental data and thus the classical dynamic model was further used to investigate the influence of Al and Ti content on the dissolution behavior of the primary γ′ phase. With an increase in Al and Ti content, the full dissolution time decreased, whereas volume fraction of the primary γ′ phase increased. Volume fraction of the primary γ′ phase was more affected by variation of Al content than Ti content. In terms of the impact on the full dissolution time of the primary γ′ phase, there was no obvious difference between same variation of Al content and Ti content. Trends in the changes of the dissolution-sensitive temperature range under various Al and Ti contents were also given in this paper.
  • An In Situ Three-Point Bending Study on Pre-Notch 7075 Aluminium Alloy with Acoustic Emission

    pp. 1977-1983

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    DOI:10.2320/matertrans.M2015279

    Some types of congenital and machining-induced defects remain in a material, such as cracks and crack notches generated in a series of machining processes. Such structural defects will probably lead a reduction in the material’s service life, and even a huge accident. It is important to investigate the influence of crack initiation, crack growth and crack failure in relation to the downgrading and failure of materials. We have employed the acoustic emission (AE) signal to identify the 7075 Aluminium alloy (7075 Al) crack initiation and crack growth unilateral pre-crack, bilateral pre-cracks, unilateral V notch and bilateral V notches under three-point bending (TPB) conditions. At the same time the tip morphology of notch specimens is obtained by the opto-digital microscope. Comparing the in situ images with the AE signals, the results indicate that the AE signals can effectively predict the crack initiation, crack growth and crack rapid instability during TPB test. In addition, the geometrical shape of the specimen is relative to the intensity of AE signals. The AE signal of a no notch specimen is much higher than that of other notch specimens. The intensity of the AE signal of pre-crack specimens is lower than the V notch specimens. A pre-crack specimen causes failure more easily than the V notch specimen in the process of bending. Specimens with no notch, unilateral pre-crack, bilateral pre-cracks, unilateral V notch and bilateral V notches can be characterized by the intensity of AE signals. The position of the crack can be determined by the linear position of the AE signals.
  • Hot Tensile Deformation and Fracture Behavior of a Nitrogen Alloyed Ultralow Carbon Austenitic Stainless Steel

    pp. 1984-1991

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    DOI:10.2320/matertrans.M2015221

    The hot tensile deformation and fracture behavior of a nitrogen alloyed ultralow carbon austenitic stainless steel were studied by a Gleeble-1500D thermo-mechanical simulator with the temperature range of 1173–1473 K and strain rate range of 0.01–1 s−1. Microstructural evolution was analyzed in terms of fractography at various deformation temperatures and strain rates. The tensile true stress-true strain curves after necking were calculated by the heuristic method. The fracture threshold values of the studied steel were estimated by finite element method (FEM). The final load-stroke curves obtained from the FEM simulation were found to have a good agreement with the experimental load-stroke curves. The quantitative relationship between fracture threshold value and Zener-Hollomom parameter was also established. The results are beneficial to the understanding of hot deformation behavior of a wide range of stainless steels.
  • Dynamic Strain Aging Behavior of Alloy 600 in a High Temperature Coolant Environment

    pp. 1992-1999

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    DOI:10.2320/matertrans.M2015160

    The slow strain rate tests were conducted on cold-worked Alloy 600 at a nominal strain rate 1 × 10−6 s−1 in air and in a simulated BWR coolant environment. The dynamic strain aging phenomenon at 200°C, 250°C, 275°C and 300°C was studied. The jerky flows of small and large serration amplitude observed on the stress-strain curves were respectively categorized as type B and D serrations. The serrated flow is more significant for those specimens with lower cold work levels tested at higher temperatures than those with higher cold work levels tested at lower temperatures. For the cold-rolled SSRT specimens tested in the 200°C water environment, the largest reduction of area along with the smallest elongation was observed. It could be accounted for by the localized deformation induced by dynamic strain aging. The strain hardening exponent generally increases with increasing the test temperature and decreases with an increase of the cold work level.
  • Correlation between Bound Water and Stability of Anodic Oxide Film on Aluminum

    pp. 2000-2005

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    DOI:10.2320/matertrans.L-M2015831

    It has been investigated that the tiny amount of bound water in anodic oxide film on Al was quantitatively measured by thermal gas desorption spectroscopy (TDS) and correlation between the amount of bound water in the film and stability of the film was discussed. Al wire specimens were anodically polarized at 20.5 V in sulfuric acid solution to prepare the anodic oxide film on the specimen. The specimen with the film was then subjected to the film-modification process in which an anodic potential from 1.0 to 2.0 VAg/AgCl was applied to the specimen for 180 s in chloride solution. The specimens for which pitting corrosion did not occur were subjected to the four tests; measurements of thickness of barrier layer in the film, pitting potential, the amount of bound water in the film by the TDS and the amount of water in the porous layer by grow discharge optical emission spectroscopy (GD-OES). As a result, the thickness of the anodic oxide film formed on Al at 20.5 V was about 25 µm and independent of the modification potential. The amount of bound water was quantitatively detected by the TDS, and increased with a rise in the modification potential. However, depth profile of hydrogen, which is considered to correspond to water, in the porous layer of the film detected by the GD-OES was independent of the modification potential. The findings suggested that the bound water is included in the barrier layer. The pitting potential exhibited the maximum value when a modification potential of about 1.5 VAg/AgCl was applied to the specimen. According to the correlation between the amount of bound water in the film and the pitting potential, the pitting potential rose with an increase in the amount of bound water in smaller amount range, and the amount beyond the small range induces the pitting potential higher. The evidence suggests that control of the amount of bound water is key factor for improving stability of the anodic oxide film on Al.
  • Influence of PMSA-Based Polymer on the Settling Velocity of CNT in Aqueous Media

    pp. 2006-2009

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    DOI:10.2320/matertrans.Y-M2015828

    The preparation of a stable suspension dispersing carbon nanotube (CNT) in aqueous media using polystyrene maleic acid (PSMA)-based polymer as surfactant was attempted to be subsequently used in the fabrication of high-performance ceramic matrix composites. Settling velocity under centrifugation analysis was experimentally evaluated as one of the stability criteria of the dispersion and pulsed nuclear magnetic resonance was used to evaluate the adsorbed molecules. The settling velocity decreased considerably with the PSMA concentration up to the saturation at around 7 mass%, then further decreased gradually with PSMA. The former was thought to be based on the dissociation of CNT agglomerate and the latter would be attributed to the surfactant-induced network structure formed in the aqueous media.
  • Relationship between Fatigue Limit and Defect Size in Spheroidal Graphite Cast Iron with Different Graphite Spheroidization Ratios and Microstructures

    pp. 2010-2016

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    DOI:10.2320/matertrans.F-M2015826

    The purpose of this study is to investigate that effects of graphite spheroidization ratio and microstructure on the characteristics of fatigue limit in spheroidal graphite cast iron. Ferritic spheroidal graphite cast iron (FDI), pearlitic spheroidal graphite cast iron (PDI) and austempered spheroidal graphite cast iron (ADI) were used as specimens. The graphite spheroidization ratio was varied between 63∼94% by the addition of a spheroidizing agent. Tensile test was carried out in air at room temperature. The experiment conformed to JIS (Japan Industrial Standards). Rotating bending fatigue test was also carried out using these materials. The experiment conformed also to JIS. Stress ratio R was −1, and the specimen used was type 1(JIS) with a diameter of 8 mm. The test was carried out in air at room temperature. The relationship between fatigue limit and graphite spheroidization ratio was investigated, as well as the correlation between fatigue limit and defect size.
    When the graphite spheroidization ratio was over 80%, the fatigue limit was not influenced. Fracture origins were micro-shrinkage, aggregate graphite, and unspheroidized graphite. When graphite spheroidization decreased, the ratio of unspheroidized graphite at the fracture origin increased. The defect size that transitioned from region I to II differed according to the microstructure: the defect size of PDI was the smallest, and that of FDI was larger than ADI. When there are no large defects in FDI, the fatigue limit can be estimated by tensile strength. However, in PDI and ADI, it must be estimated taking into account the size of existing defects in specimens.
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    1. Aluminum-Alloyed Cast Iron as a Versatile Alloy MATERIALS TRANSACTIONS Vol.43(2002), No.3
    2. Diffusion Bonding of TiAl Intermetallic Compound to Ti-6Al-4V Alloy and Pure Titanium QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY Vol.22(2004), No.4
  • Molten Metal Surface Pattern and Its Generating Mechanism in Gray Cast Iron

    pp. 2017-2022

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    DOI:10.2320/matertrans.F-M2015827

    The surface patterns called Bamboo-leaf type, Pine needle type and Hexagonal type appear at around 1350°C on the molten iron. These patterns are known to be used to examine the condition of the molten cast iron in a cupola. In this study, the developing mechanism of the surface patterns was examined.
    The origin of the surface patterns is a surface SiO2 film which formed by the oxidation of Si with CO. The difference in radiation rate between SiO2 and molten iron makes the patterns visible. The addition of 0.02% mass% S reduces the surface tension remarkably. As a result, a complex Marangoni convection occurs beneath the surface and it generates the complex surface patterns. The characteristics of the molten iron get better in the order of Bamboo-leaf, Pine needle and Hexagonal pattern. The Hexagonal pattern becomes finer by the inoculation.
  • Synthesis of Thermoelectric Mg2Si by Reactive Sintering Utilizing Directly Applied Current Sintering

    pp. 2023-2028

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    DOI:10.2320/matertrans.Y-M2015829

    Synthesis of the thermoelectric Mg2Si sintered body was tried by reactive pulsed current sintering (PCS) using graphite punches and a nonconductive quartz glass die (directly applied current sintering). The mechanically milled powder mixture of Mg and Si was heated by directly applied current sintering, the densification behavior, Mg2Si phase formation and the power consumption during sintering, and the relative density and the microstructure of the sample were compared to those of a sample sintered by the conventional PCS (using graphite punches and a graphite die). When the mechanically milled powders were heated by directly applied current sintering, the densification of a powder compact became larger during heating and the density of a sintered body was also significantly higher as compared to those of the sample sintered by the conventional PCS. The relative density of a compound sintered in a quartz die at 973 K for 10 min was 99.3%, which is almost the same as that of the sample sintered by the conventional PCS at 1073 K for 60 min, 99.6%. Furthermore, directly applied current sintering is found to accelerate the reaction between Mg and Si to form Mg2Si phase.
  • Improvement of Electric Field Induced Compressive Electrostriction of Polyurethane Composites Film Homogeneously Dispersed with Carbon Nanoparticles

    pp. 2029-2033

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    DOI:10.2320/matertrans.M2015252

    To obtain the high compressive electrostriction indicated by maximum strain (Smax) at low electric field (Emax), a dependence of solidification thickness on Smax was investigated for carbon nanoparticles dispersed polyurethane (PU) composite films. The thickness dependent Smax at 20 MV/m from 7.52% for 143 µm thickness to 47.7% for 21 µm thickness exhibited linear relationship, which was parallel to that of pure PU. Both thinning and nanoparticles addition enhanced the Smax within the linear relationship. Considering with crystalline volume fraction and crystalline periodicity, the thickness dependent Smax was explained. Effects of nanoparticles addition on Smax were probably contributed by the polarization enhancement induced by increasing the capacitance.
  • Lower Protrusion of a Copper-Nickel Alloy in a Through-Silicon via and Its Numerical Simulation

    pp. 2034-2041

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    DOI:10.2320/matertrans.M2015335

    The application of Cu-filled through-silicon via (TSV) in 3-D integrated circuit packaging faces several fabrication and reliability issues. In this study, we introduced a Cu-Ni alloy for TSV filling with a high filling speed and a reduced TSV protrusion. In particular, the characteristics of Cu-Ni via protrusions at various annealing temperatures (∼200–450°C) were investigated with experimental and numerical analysis and compared with Cu-filled vias. High speed Cu-Ni alloy filling into the vias was achieved without any defects by an electroplating process that used a periodic pulse reverse current waveform. The Cu-Ni alloy TSV showed lower via protrusion than the Cu TSV. The simulated protrusion heights of the Cu-Ni vias were in good agreement with the experimental results. The simulation results also indicated that the Cu-Ni TSVs has smaller protrusions than the Cu TSVs. As the annealing temperature was varied from 200 to 450°C, the protrusions increased gradually and became significant at an annealing temperature of 350°C. When the temperature was increased further, the protrusions became larger due to severe creep deformation. The von Mises stress also increased with increasing annealing temperature, and increased substantially at a temperature of 300°C due to the creep effect. In summary, the Cu-Ni alloy TSVs showed smaller protrusions relative to the Cu TSVs. The stress level of the Cu-Ni via was lower than that of the Cu via. These results indicate that the Cu-Ni alloy TSV had advantages in terms of high speed filling and smaller protrusions, demonstrating its promise as an alternative to current Cu TSV technologies.
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    1. Review on Thermo-Mechanical Fatigue Behavior of Nickel-Base Superalloys MATERIALS TRANSACTIONS Vol.56(2015), No.12
  • Effects of Heat Treatment on the Morphology of Long-Period Stacking Ordered Phase and the Corresponding Damping Capacities of Mg-Cu-Mn-Zn-Y Alloys

    pp. 2042-2046

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    DOI:10.2320/matertrans.M2015234

    Different cooling processes of solid solution treatment, such as quenching in water and cooling in furnace, were introduced to Mg–3Cu–1Mn–1.8Zn–10Y (mass%) alloy. The morphology of long-period stacking ordered (LPSO) phase and the corresponding damping capacities were investigated in the present study. The block-shaped and the lamellar-shaped LPSO phases can be obtained through different cooling processes. Furthermore, the lamellar-shaped 14H LPSO phase grew and ran through the whole grains. Comparison of the damping capacities of the alloys with different morphologies, it reveals that the lamellar LPSO phases precipitated in the matrix are more conducive to the damping capacity that Q−1 ≥ 0.052 at strains exceeding 1 × 10−3. The grain size is almost same and no new phase is found after the processes. Meanwhile, it can conclude that the sample cooled in the furnace exhibits higher damping capacity due to the coarse grains and formation of lamellar-shaped 14H LPSO phase.
  • Effect of HF and HNO3 Concentration on Etching Rate of Each Component in Waste Crystalline Silicon Solar Cells

    pp. 2047-2052

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    DOI:10.2320/matertrans.M2015293

    In order to maximize the recovery of silicon wafer in waste crystalline silicon solar cells, chemical treatment has been carried out by using the mixed solution of hydrofluoric acid (HF) and nitric acid (HNO3). The effect of HF and HNO3 concentrations on etching rates of several components such as silver (Ag), aluminum (Al), anti-reflection film made of silicon nitride (AR) and silicon (Si) in the solar cells has been made clear. The etching rates of Ag, Al and Si are held almost constant with time and become larger with the increasing HF concentration and the etching temperature. All of the etching rates of Al, AR and Si have peaked at the HF mole fraction of about 0.8. The dependency of HF concentration on Al, AR and Si etching rates becomes larger than that of HNO3. As the best solution composition for the Si recovery yield, the following relation has been found in this study: (number of AR moles)/(number of Al moles) = 7.62 × 10−4 CHNO30.59CHF0.74 where CHNO3, CHF: HNO3, HF concentration (kmol/m3).
  • The Application of a Natural Zeolite for Acid Mine Drainage Purification

    pp. 2053-2057

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    DOI:10.2320/matertrans.M2015292

    A natural zeolite from Serbia was employed for the removal of heavy metals from acid mine drainage (AMD) generated in the area of copper mine. The efficiency of the natural zeolite samples was tested on AMD that contained manganese, copper, zinc, nickel and cadmium ions in the concentrations above the maximal allowed, according to existing legislation. The results of X-ray diffraction (XRD) analyses of natural zeolite having a particle size of −1 + 0.3 mm, confirmed that the clinoptilolite (Al1.6H30Ca2.06O47.56Si16.4) is a dominant mineral of mine tuff. A dynamic method was used for the experiments in order to simulate real conditions in an industrially relevant environment. The effect of the flow rate of AMD, type of columns and zeolite classes on the degree of adsorption of the heavy metals from AMD was investigated. The results of chemical analyses of treated AMD samples at a flow rate of 0.0033 dm3 s−1 which corresponds to the spontaneous outflow from the real accumulation indicate that concentrations of heavy metals are not decreased below that allowed for defined recipient class, except for copper. Also, these results show that the heavy metal ion removal serie for the industrially relevant environment can be given as: Cu > Zn > Cd > Mn > Ni.
  • Effect of Alternating Magnetic Field on the Microstructure and Solute Distribution of Cu–14Fe Composites

    pp. 2058-2062

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    DOI:10.2320/matertrans.M2015244

    The influence of a low frequency alternating magnetic field (LFAMF) during solidification was investigated for Cu-14Fe composites. The microstructure was investigated by optical microscope; the solute distribution in different phases was analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy; the oxygen content was tested by oxygen & nitrogen analyzer; the conductivity was measured by eddy current conductivity meter; and the micro-hardness was measured by Vickers hardness tester. AMF treatment reduced rod shape and large size Fe dendrites, changed some Fe dendrites into club shape and equiaxed grains, and promoted the homogenization of Fe phase distribution. In addition, AMF treatment increased the Cu content in Fe phase and decreased the Fe content in Cu matrix. The effect of AMF during solidification was discussed from the view of thermodynamics and kinetics. This was attributed to the refinement of primary Fe dendrites and the precipitation of Fe atoms from Cu matrix.
  • Effect of Quenching Rates on Microstructure and Impact Ductile of X12CrMoWVNbN10-1-1 Steel

    pp. 2063-2069

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    DOI:10.2320/matertrans.M2015107

    The effect of the quenching rates on microstructure and impact ductile of X12CrMoWVNbN10-1-1 steel was investigated. The samples were heated to 1080°C for 16 h and quenched with different rates to room temperature, then tempered at 700°C for 24 h. It was found that the critical quenching rate of suppressing the precipitation of Cr-rich M2N and Fe-rich M3C was faster than 1.5°C/min and 10°C/s, respectively. And the critical quenching rate for the precipitation of ferrite was in the range of 1∼1.5°C/min. The impact energy began to decrease when the tempered sample was quenched with a rate of 1.5°C/min due mainly to the precipitation of Cr-rich M2N based on the careful conducted analysis of the microstructure and fractography.
  • Effects of Curvature on the Flow Characteristics and Particle Behavior in the Flame Spray Process

    pp. 2070-2077

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    DOI:10.2320/matertrans.M2015299

    The present study investigates numerically the thermal and flow characteristics and transient particle behavior in the conventional flame spray process by using the computational fluid dynamics (CFD) code (ANSYS Fluent V. 16.1). From geometrical consideration, it is noted that the deposition angle of a particle decreases drastically on a curved surface because of the curvature effect, and significantly affects the normal impact velocity of the particle. Numerical results indicated that the normal component of the particle impact velocity on the curved surface was lower than that on a flat surface by up to 5.7%. This result is significant with regard to the adhesive characteristics, as binding energy with the substrate is proportional to the square of the particle’s normal impact velocity. The influence of spray distances and radius of the curved substrate were examined and the corresponding results would be useful in finding optimal operating conditions for the curved substrate. It was observed in this study that the spray distance exhibited a more dominant effect on the particle impact velocity, substantially associated with the coating quality of the deposited layer.
  • Corrosion Behavior of Alloy 600 Coupled with Electrodeposited Magnetite in Simulated Secondary Water of PWRs

    pp. 2078-2083

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    DOI:10.2320/matertrans.M2015322

    The corrosion behavior of Alloy 600 coupled with magnetite was investigated in simulated secondary water of pressurized water reactors using a potentiodynamic polarization test and zero-resistance ammeter. Passive film formed on the surface of Alloy 600 was also analyzed using X-ray photoelectron spectroscopy. Alloy 600 was the anodic element of the galvanic pair since its corrosion potential was less noble than that of the magnetite. Galvanic coupling increased the corrosion current density of Alloy 600 due to the shifting of the potential of Alloy 600 to the positive value. The passive film of coupled Alloy 600 was more slowly stabilized and was thinner and less protective than that of non-coupled Alloy 600.
  • Thermally Activated Deformation of Gum Metal: A Strong Evidence for the Peierls Mechanism of Deformation

    pp. 2084-2087

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    DOI:10.2320/matertrans.M2015271

    Compression deformation and stress relaxation tests have been made over a wide temperature range for Ti-based bcc alloy single crystal of Gum Metal composition to elucidate the deformation mechanism. The shear yield stress decreases rapidly with increasing temperature with decreasing slope above room temperature, tending to level off. Activation analysis showed that the activation volume becomes smaller than 10 b3 (b: the Burgers vector) at high stress, indicating that the deformation is controlled by the Peierls mechanism at low temperature. Similar results have been obtained also for severely cold-swaged polycrystalline Gum Metal with the similar composition. These results contradict the generally accepted dislocation-free mechanism of Gum Metal.
  • The Corrosion Behavior of an Ag43Cu37Zn20 Alloy in the Natural Seawaters

    pp. 2088-2091

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    DOI:10.2320/matertrans.M2015284

    We investigated the effects of natural seawater on the corrosion of an Ag43Cu37Zn20 alloy. The alloy was a commercial brazing filler alloy of composition (BS1845:1984 Ag5) and belongs to the class of Cd-free silver brazing alloys. The Ag-Cu-Zn system is corrosion resistant in chloride solutions has not been widely examined. In this study, the corrosion behavior of the alloy has been investigated using the open circuit potential measurements, Tafel plots and anodic potentiodynamic curves. By comparing different samples of marine water indicates that salinity is the primary influence on corrosion behavior near the open circuit potential. At higher anodic potentials, the impact of mineral composition becomes significant.
  • A New Hole-Filling Technique onto Thin Aluminum Alloy Sheets Using a Rotational Consumable Tool

    pp. 2092-2094

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    DOI:10.2320/matertrans.M2015313

    We have developed a new hole-filling technique that differs from conventional techniques, the friction hydro pillar processing (FHPP) and friction taper stud welding (FTSW), which fill holes by utilising friction welding. The new method friction welds a hole using a rotating consumable tool with a diameter larger than the hole diameter. The new method can be applied to soft alloys such as aluminium alloys and is suitable for making holes in thin sheets to disappear and is superior to FHPP and FTSW in these aspects. In addition, unlike the hole-filling method using nonconsumable tools, the new method does not reduce sheet thickness. Observations of sections of the samples created using the new method shows that the hole has disappeared because of compressive deformation. In addition, no defects were observed inside the samples. Observation of the grains demonstrated the weld line by the friction welding between the workpiece and tool, and micro-grains derived from dynamic recrystallization were observed.
  • Application of a Chamfered Slab to Reduce Risk of Edge Straight Crack on Hot Rolled Strip Surface

    pp. 2095-2097

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    DOI:10.2320/matertrans.M2015331

    Major losses of steel were due to edge straight crack for hot rolled IF steel strip products. A chamfered slab with 30° chamfered angle was adopted to improve the defect. The deformation and temperature change processes were simulated with dynamic explicit FEM. The temperature of chamfered slab edge and side was higher, and the distribution was more even than rectangle slab. Due to this temperature field and the chamfering shape, the ‘dog bone’ shape of chamfered slab rolled after vertical roll achieved a lower level, and the corner shape changed to circular arc shape. These deformation characteristics in turn brought the advantageous for temperature holding. The chamfered slab used in hot strip rolling experiment reduced the defect ratio from 50% to 7%.

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