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

MATERIALS TRANSACTIONS Vol. 56 (2015), No. 1

  • Reaction-Mediator-Based Chlorination for the Recycling of Titanium Metal Scrap Utilizing Chloride Waste

    Yu-ki Taninouchi, Yuki Hamanaka, Toru H. Okabe

    pp. 1-9

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    DOI:10.2320/matertrans.M-M2014838

    Abstract

    In this study, a novel chlorination technique for metallic titanium (Ti) was devised in order to establish a recycling process that uses both Ti metal scrap and iron chloride (FeClx) waste, and its feasibility was demonstrated. Direct reaction between Ti and FeClx has drawbacks such as slow kinetics of Ti chlorination and high volatilization of FeClx. To overcome these, the authors proposed a chlorination technique utilizing a reaction mediator in molten salt. Based on thermodynamic analyses of lanthanoid chlorides, some fundamental experiments were carried out with samarium trichloride (SmCl3) as a reaction mediator. It was experimentally demonstrated that SmCl3 in molten magnesium chloride (MgCl2) can smoothly chlorinate Ti metal into gaseous titanium tetrachloride (TiCl4), and the by-product SmCl2 in the molten salt can be regenerated into SmCl3 by FeCl2. Thus, SmCl3 in a molten salt works efficiently as a reaction mediator, and the newly proposed chlorination technique has the potential to make the Ti recycling process more efficient and environmentally friendly.

  • Temperature Dependent Current-Voltage and Capacitance-Voltage Characteristics of an Au/n-Type Si Schottky Barrier Diode Modified Using a PEDOT:PSS Interlayer

    Zagarzusem Khurelbaatar, Kyu-Hwan Shim, Jaehee Cho, Hyobong Hong, V. Rajagopal Reddy, Chel-Jong Choi

    pp. 10-16

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    DOI:10.2320/matertrans.M2014263

    Abstract

    The temperature dependence of the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of an Au/n-type Si Schottky barrier diode (SBD) with a PEDOT:PSS interlayer was investigated. The SBD parameters, such as Schottky barrier height (ΦB), ideality factor (n), saturation current (I0), doping concentration (ND), and series resistance (Rs), were obtained as a function of temperature. The Richardson constant (A**) obtained from the In(Io/T2) versus 1000/T plot was much less than the theoretical value for n-Si. The mean Schottky barrier height (\barΦ bo) and standard deviation (σ0) calculated using the apparent Schottky barrier height (Φap) versus 1/2kT plot were 1.26 eV and 0.15 eV, respectively. From a fit of the modified Richardson plot of ln(I0/T2) − (qσ)2/2(kT)2 versus 1000/T, the A** was extracted as 134 A/cm2 K2, which was close to the theoretical value of the n-Si. The interface state densities obtained from the Au/PEDOT:PSS/n-Si SBD decreased with increasing temperature. Furthermore, the conduction mechanism dominating the reverse-bias leakage current in Au/PEDOT:PSS/n-Si SBD was described and discussed.

  • Influence of the Initial Texture on Texture Formation of High Temperature Deformation in AZ80 Magnesium Alloy

    Kwon-Hoo Kim, Kazuto Okayasu, Hiroshi Fukutomi

    pp. 17-22

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    DOI:10.2320/matertrans.L-M2014840

    Abstract

    The texture formation mechanism during high temperature deformation is investigated on AZ80 magnesium alloy. Three kinds of specimens with different initial textures were machined out from rolled plate having a ⟨0001⟩ texture. Plane strain compression tests were conducted at 723 K, 5.0 × 10−2 s−1 and strains ranging from −0.4 to −1.0. Development of (0001)<10\bar{1}0> component is confirmed regardless of the initial texture. It is concluded that the development of (0001)<10\bar{1}0> component can be attributed to the grain boundary migration during deformation. Besides (0001)<10\bar{1}0> component, several texture components appeared depending on the initial texture.

  • Effects of Initial States on the Spinodal Decomposition of Quenched and Melt-Spun Cu-15Ni-8Sn Alloy

    Shin-ichiro Kondo, Akinori Masusaki, Kento Ogawa, Takao Morimura, Hiromichi Nakashima

    pp. 23-29

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    DOI:10.2320/matertrans.M2014234

    Abstract

    We investigate early stages of spinodal decomposition in a melt-spun Cu-15Ni-8Sn alloy (melt-spun samples) by X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and electron diffraction analysis through comparison against a non-melt-spun alloy of the same composition (quenched samples). In XRD measurements, no sidebands of (200) planes are found in the melt-spun sample after aging at 350°C for 120 min, whereas they are found in the quenched sample after a heat treatment at 350°C for 60 min. TEM observations of a quenched sample after aging at 350°C for 60 min indicate the presence of a modulated structure (λ = 5–10 nm) in the matrix, whereas those of a melt-spun sample after the same heat treatment also indicate the presence of a modulated structure (λ: too small to measure). Electron diffraction patterns reveal satellite structures in both samples, although with superlattice reflections from ordering phases visible in the quenched sample. These differences are presumably due to a difference in the size of clusters present in their respective quenched states; in melt-spun samples, cluster size was much smaller as a result of a high cooling rate (≈8 × 105°C/s).

  • Kinetics of Solid-State Reactive Diffusion in the (Pd–Cr)/Sn System

    Masaki Hashiba, Koji Masui, Masanori Kajihara

    pp. 30-39

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    DOI:10.2320/matertrans.M2014202

    Abstract

    The growth of compounds during energization heating at the interconnection between a Sn-based solder and a multilayer Pd/Ni/Cu conductor may be inhibited by alloying of Pd with Cr. To examine such influence of Cr on the compound growth, the kinetics of solid-state reactive diffusion in the (Pd–Cr)/Sn system was experimentally determined in the present study. Experiments were conducted using Sn/(Pd–Cr)/Sn diffusion couples with Cr mol fractions of y = 0.110, 0.215 and 0.323 which were prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed in the temperature range of T = 433–473 K for various times up to t = 360 h. During annealing, a compound layer consisting of different matrices and lamellar phases is formed at the original (Pd–Cr)/Sn interface in the diffusion couple. From the Pd–Cr side to the Sn side in the compound layer, the matrices are PdSn2, PdSn3 and PdSn4, and the lamellar phases are (Cr0.9Pd0.1)3Sn, (Cr0.95Pd0.05)2Sn, (Cr0.9Pd0.1)Sn and CrSn2. The total thickness of the compound layer is proportional to a power function of the annealing time. The exponent n of the power function is rather close to 0.5 independent of y at T = 453–473 K. At T = 433 K, however, n ≅ 0.5 for y = 0–0.110, but n = 0.7–0.8 for y = 0.215–0.323. Thus, the overall compound growth is controlled by volume diffusion for y = 0–0.323 at T = 453–473 K and for y = 0–0.110 at T = 433 K. On the other hand, for y = 0.215–0.323 at T = 433 K, the interface reaction at the moving interface contributes to the rate-controlling process. The overall growth rate of the compound layer is insensitive to y at y < yc but monotonically decreases with increasing value of y at y > yc, where yc = 0.1 and 0.2 at T = 433–453 K and 473 K, respectively. Consequently, the compound growth is actually decelerated by the addition of Cr with y > 0.2 into Pd in the multilayer Pd/Ni/Cu conductor.

  • Microstructure and Texture Evolution of the Al-20Sn Alloy Processed by Equal-Channel Angular Pressing Using Route C

    C. Hernández, I. A. Figueroa, I. Alfonso, C. Braham, P. Castillo, G. Gonzalez

    pp. 40-45

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    DOI:10.2320/matertrans.M2014225

    Abstract

    In this work, the microstructure and texture evolution of an Al-20Sn (mass%) alloy processed by Equal Channel Angular Pressing is presented. The evolution of dislocation cells into subgrains and the mechanical response of the deformed alloy have been emphasized. Samples were characterized by transmission electron microscopy, X-ray diffraction (for microstrain and texture measurements) and Vickers microhardness. It was found, that Al grains, suffered the highest degree of deformation during the ECAP process, however, the evidence showed that the deformation was largely heterogeneous, in terms of crystalline domain and feasibly in misorientation angles. The initial copper texture changes throughout the ECAP process forming an incipient shear texture component (111)[11-2]. The heterogeneity of the results obtained from the Vickers microhardness mapping could be associated to the microstructure resulted after the ECAP process.

  • Plastic Deformation and Damage Behaviors of Fe-18Cr-18Mn-0.63N High-Nitrogen Austenitic Stainless Steel under Uniaxial Tension and Compression

    Chen-Wei Shao, Feng Shi, Wei-Wei Guo, Xiao-Wu Li

    pp. 46-53

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    DOI:10.2320/matertrans.M2014262

    Abstract

    Uniaxial tensile and compressive deformation behaviors of Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel were investigated at different strain rates. It is found that, with increasing strain rate, the yield strength of the steel increases either under tension or compression, while the ultimate tensile strength and the total elongation decrease under tension. The plastic deformation behavior prior to necking under uniaxial tension at different strain rates can be well described by the modified Ludwik relation. Under tensile deformation at the low strain rate of 10−4 s−1, microcracks prefer to initiate around the Al2O3 particles in the steel, whereas cracks nucleate at grain boundaries or along slip bands at the high strain rate of 10−2 s−1. Compressive deformation behavior of the steel is not so sensitive to the strain rate. The surface fluctuation is more serious under compressive deformation rather than tensile deformation. The tensile plastic deformation is mainly governed by the formation of planar slip bands and deformation twins, and deformation by twinning becomes more prominent with increasing strain rate, while dislocation slip featured by planar slip bands, dislocation bands and twin-like bands basically controls the compressive plastic deformation, and deformation twins are rarely formed.

  • Weibull Statistics of Tensile-Shear Strength of 5083 Aluminum Alloy after Friction Stir Spot Welding

    Chia-Wei Lin, Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen

    pp. 54-60

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    DOI:10.2320/matertrans.M2014281

    Abstract

    Friction stir spot welding has been adopted to replace resistance spot welding for Al alloys. This study investigates the effects of plunge depth, rotation speed, and welding duration on the microstructural characteristics of the weld, bonding strength and reliability of 5083 Al alloy. Bonding strength is evaluated using a tensile-shear test and the reliability is analyzed using a Weibull model. According to the experimental results, the major difference in the microstructure was the range of the stirring zone (SZ). The range of the SZ and the tensile-shear failure loading (TSFL) were enhanced when the welding duration or plunge depth was increased. The optimal rotation speed changed with plunge depth. Two fracture modes (tearing mode and cup pull-out mode) appeared for all parameter combinations. When the range of the SZ was deep and broad, the cup pull-out mode was the main fracture mechanism. The TSFL of the cup pull-out mode was higher than that of the tearing mode. Furthermore, the Weibull parameters of the cup pull-out mode were higher and the distribution curve shapes were better. Higher plunge depth, longer welding duration, and a suitable rotation speed made the fracture mode of the tensile-shear test be the cup pull-out mode and led to high bonding strength and good reliability.

  • Prediction of In-Plane Anisotropy of Bendability Based on Orientation Distribution Function for Polycrystalline Face-Centered Cubic Metal Sheets with Various Textures

    Hirofumi Inoue

    pp. 61-69

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    DOI:10.2320/matertrans.ME201405

    Abstract

    Bendability of sheet metals is strongly affected by crystallographic orientation and it has recently been found that the bendability has a correlation with the Taylor factor in Al-Mg-Si and Cu-Ni-Si alloy sheets. This paper has proposed an analytical method for predicting in-plane anisotropy of bendability in polycrystalline face-centered cubic metal sheets by using the mean value of Taylor factors for all grains calculated from an orientation distribution function. The calculation was performed on the assumption that a strain condition at the convex surface during bending deformation is close to plane strain tension. Using various ideal orientations with Gaussian distribution and various real textures of annealed aluminum or copper alloys, the normalized Taylor factor, which was defined as a ratio of the mean Taylor factor for a textured material to that for a randomly oriented one, was compared with some known experimental data on bendability at directions of 0° and 90° to the rolling direction. The results clearly showed that bendability was better at the bending direction with a lower normalized Taylor factor. Since the formation of shear bands at the sheet surface causes deterioration of bendability, the present analytical method based on the normalized Taylor factor will have the advantage of giving us a prediction of bendability at arbitrary directions in a sheet, if textures of metal sheets are measured on the surface without polishing by means of X-ray diffraction.

  • Development of Manufacturing Technology for Direct Recycling Cemented Carbide (WC-Co) Tool Scraps

    Saharat Wongsisa, Panya Srichandr, Nuchthana Poolthong

    pp. 70-77

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    DOI:10.2320/matertrans.M2014213

    Abstract

    The objective of this research was to develop a sustainable industry manufacturing method for direct recycling cemented carbide tool scraps combining a hydrothermal and electrolysis process (CHEP). The research methodology was performed by studying the current recycling carbide tools, scrap industry and associated recycling technologies. A tungsten carbides (WC) recycling technology was designed by using an electrochemical cell comprising of a titanium cathode, titanium anode and hydrochloric acid (HCl) electrolyte under controlled temperature. Finally, the speed of binder phase removal, key process variables, WC leached and recovered WC purity rates were examined and identified. The results of this research indicated that this recycling process was effective in recycling cemented carbide from industrial cutting tools scraps. This technology can be used to purify the recovered WC rate to near virgin material, resulting in a more environmentally friendly process and reducing natural tungsten material usage.

  • Effects of Copper Addition on the Passivity and Corrosion Behavior of 27Cr-7Ni Hyper Duplex Stainless Steels in Sulfuric Acid Solution

    Soon-Hyeok Jeon, Hye-Jin Kim, Kyeong-Ho Kong, Yong-Soo Park

    pp. 78-84

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    DOI:10.2320/matertrans.M2014233

    Abstract

    The effect of the Cu addition on the passivation behavior of hyper duplex stainless steels in both the active and passive states was investigated using the electrochemical tests, a scanning electron microscope-energy dispersive spectroscope, a scanning Auger multi-probe analysis and an X-ray photoelectron spectroscopy analysis in sulfuric acid solution. In the active region of −0.2 VSCE, the Cu addition to the base alloy has a positive effect on the general corrosion resistance due to the novel Cu enriched on the surface. In the passive region of 0.6 VSCE, the Cu addition to the base alloy degraded the stability of passive film due to an increase of the formation of Cr enriched inclusion such as (Cr, Mn, Al) oxides and (Cr, Mn, Al, Fe) oxides acting as the defect in the passive film, resulting in deteriorating general corrosion resistance.

  • Effects of Silica Nanoparticle Co-Deposition on Macrothrowing Power of Zinc-Nickel Alloy Plating from an Acid Sulfate Bath

    Makoto Hino, Koji Murakami, Ken Muraoka, Norihito Nagata, Teruto Kanadani

    pp. 85-90

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    DOI:10.2320/matertrans.M2014329

    Abstract

    Zinc–nickel–SiO2 electrodeposits have been produced from an acid sulfate bath. The co-deposition behavior of SiO2 and the macro throwing power of plating baths were examined. The presence of SiO2 nanoparticles in the plating bath appears to change the alloy deposition behavior. The rate of nickel deposition was considerably decreased by the presence of SiO2 nanoparticles in the bath. The macro throwing power of plating was improved by adding SiO2 nanoparticles to the bath. At an early stage of electrodeposition, it seems that the SiO2 nanoparticles act as a nucleus for the precipitation. The SiO2 nanoparticles did not disperse uniformly in a plating film; they distributed only in a SiO2 rich layer (∼50 nm thick) that formed beneath the surface. In addition, this SiO2 rich layer can improve anticorrosive performance. Therefore, zincic use can be suppressed because film thickness can be reduced compared to zinc and zinc–nickel alloy electroplating.

  • Enhancement of Visible Light Absorbance and Hydrophobicity by Sputter-Coating of PTFE onto Fine Protrusions Formed by Sputter-Etching of Steels

    Rongguang Wang, Keijiro Nakasa, Takashi Kubo, Akihiro Yamamoto, Junya Kaneko

    pp. 91-98

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    DOI:10.2320/matertrans.M2014270

    Abstract

    Argon ion sputter-etching was applied to type 316 stainless steel and AISI M2 (JIS SKH 51) steel, and the sputter-coating of polytetrafluoroethylene (PTFE) film was carried out onto the sputter-etched surface. The sputter-etching of the steels formed fine and dense ridge- or column-shaped protrusions with a diameter of 100 nm to 1 µm on the surface. The protrusions of as-sputter-etched type 316 and M2 steels specimens showed low reflectance of visible light smaller than 8.5% and 4.4% respectively, and the sputter-coating of PTFE film reduced the reflectance further to 5.3% and 2.8% as long as the thickness of the film is thin. In addition, the protrusions of both steels sputter-coated with PTFE films showed superhydrophobicity with a contact angle of a water droplet of more than 165°. The superhydrophobicity of the type 316 specimen was still preserved after an ultrasonic vibration test of 3.6 ks in water.

  • Grain Refinement of Al3Ti Dispersed Aluminum Matrix Composites by Reaction Centrifugal Mixed-Powder Method

    Kazuya Yamauchi, Takahiro Kunimine, Hisashi Sato, Yoshimi Watanabe

    pp. 99-107

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    DOI:10.2320/matertrans.L-M2014841

    Abstract

    Aluminum matrix composites having dispersoids of Al3Ti intermetallic compounds can be obtained by reaction centrifugal mixed-powder (RCMP) method. It is reported that Al3Ti intermetallic compounds act as grain refiners, since the disregistry value between Al3Ti intermetallic compound phase and Al matrix is smaller than 10%. In terms of lattice registry between Al matrix and Al3Ti phase, it is expected that the grain structure of Al matrix in Al-Al3Ti composites becomes more refined than that of centrifugally cast pure Al. In this study, Al-Al3Ti composites have been cast by the RCMP method. Effects of the Al3Ti phases around Ti particles formed by reaction between Al and Ti particles during RCMP method on grain refinement behavior of Al matrix have been systematically investigated. Moreover, grain refining performance of Al cast by Al-Ti refiner with grain shaped Ti particles was also studied.

  • Diamond-Reinforced Metal Matrix Bulk Materials Fabricated by a Low-Pressure Cold-Spray Process

    Hansang Kwon, Seungchan Cho, Akira Kawasaki

    pp. 108-112

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    DOI:10.2320/matertrans.M2014145

    Abstract

    Fully densified diamond-reinforced aluminum (denoted as Al-D) matrix bulk materials were successfully fabricated using a low-pressure cold-spray process. Two different temperatures of the processing gas were used in order to deposit the Al-D composite powders, and the thermophysical properties of the Al-D bulk materials were investigated. The interfaces between the matrix and reinforcement were observed by scanning electron microscopy in order to understanding of the relationship between the thermophysical properties and microstructure. The thermophysical properties of the Al-D bulk materials were better than those of pure Al processed under the same conditions. We believe that this cold-spray process can be successfully applied for fabricating Al-D bulk materials.

  • Welding of AA 6028 Aluminum Alloy and Its Nanocomposite Using Different Filler Materials

    Hashem F. El-Labban, Essam R. I. Mahmoud

    pp. 113-119

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    DOI:10.2320/matertrans.M2014283

    Abstract

    The 6000 series aluminum alloys and its composites welded joints suffer from solidification cracking and loss of strength in their fusion zone. Formation of fine equiaxed grains in weld fusion zones is considered one of the best solutions to avoid such problems. AA 6028 aluminum alloy and its nanocomposite (reinforced with 2 mass% Al2O3) have been gas-tungsten arc welded with different four filler metals. The first one was Al-12%Si piston alloy. The second, third and fourth ones are Al-6% Si-based reinforced with TiB2 and Al3Ti nano-constituents produced from addition of Al-Ti5-B1 master alloy with different percentages (1, 2, and 3%). The microstructures of the base and weld zones were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the weld zone were evaluated using a microhardness tester. All the weld joints were successfully welded without any cracks, large pores or solidification cracks. In case of Al-12%Si piston alloy filler metal, the weld metal shows fine dendritic eutectic structure for the AA 6028 alloy and its nanocomposites base metals. The hardness of the weld zone was increased almost as twice as the base metals. For the filler metals that treated with Al-Ti5-B1 master alloy, the weld zone structure shows fine dendrite eutectic morphology structure inside α – Al grains in addition to TiB2 and TiAl3 precipitates distributed within the weld zone of the AA 6028 base metal. In case of the nanocomposite base metal, the weld metal was consisted of fine and equiaxed grains with modified eutectic structure and reinforced with TiB2 precipitates and in-situ TiAl3. The hardness distributions inside the weld zone were almost homogenously as high as twice as the base metal. As the amount of Al-Ti5-B1 master alloy increased in the filler metal, the hardness will increased.

  • An Investigation of Reflection Coefficients of the T(0,1) Mode Guided Waves at Axisymmetric Defects and Inverse Problem Analyses for Estimations of Defect Shapes

    Hideo Nishino

    pp. 120-128

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    DOI:10.2320/matertrans.M2014331

    Abstract

    The frequency dependences of the reflection coefficients at gradual step-down axisymmetric defects were experimentally evaluated for the investigation of the reflection phenomena of the T(0,1) mode guided waves. Different frequency dependences were observed depending on the axial profile of the defect. A mathematical model using the characteristic acoustic impedance for calculating the reflection coefficients at axisymmetric defects was introduced. The reflection coefficients for the gradual step-down axisymmetric defects were confirmed to be in good agreement with the calculation results. By utilizing the mathematical model, a reflection mechanism was explained precisely and was verified. An inverse problem analysis for estimating the shape of an axisymmetric defect was also proposed based on the experimental reflection coefficients as a function of frequency together with the calculation model. Experimental verification of the proposed estimation method was performed using circular concave axisymmetric defects inside pipe specimens. The estimation results and accuracy were discussed in terms of the relation between the frequency range and the axial length of the defects.

  • Effects of Hydrogenation-Disproportionation-Desorption-Recombination Processing Parameters on the Particle Size of Ultrafine Jet-Milled Nd-Fe-B Powders

    Michihide Nakamura, Masashi Matsuura, Nobuki Tezuka, Satoshi Sugimoto, Yasuhiro Une, Hirokazu Kubo, Masato Sagawa

    pp. 129-134

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    DOI:10.2320/matertrans.M2014273

    Abstract

    The effects of variations in the hydrogenation-disproportionation-desorption-recombination (HDDR) processing parameters on the size of Nd-Fe-B ultrafine powders were investigated. The ultrafine powders were fabricated by hydrogen decrepitation and jet milling of the HDDR alloys. Before pulverization, the crystal grain size of the HDDR alloys obtained by changing the HD processing temperature (THD) varied from 0.27 to 0.55 µm, and decreased as THD was lowered. The ultrafine powder of the HDDR alloy became finer as THD decreased, with sizes in the range of 0.33 to 0.58 µm.

  • Toxicity Assessment of Fe-Mn-Al Ternary Alloys Using a Probit Dose-Response Model and an Augmented Simplex Design

    Shih-Hang Chang, Bor-Yann Chen, Chin-He Chiang

    pp. 135-139

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    DOI:10.2320/matertrans.M2014108

    Abstract

    This study establishes a toxicity assessment of the mixture of Fe3+, Mn2+, and Al3+ ions by employing a Probit dose-response model and an augmented simplex design. The toxicity of individual Fe3+, Mn2+, and Al3+ metal ions with respect to Escherichia coli DH5α is in the order of Mn2+ > Fe3+ > Al3+. The mixture of Fe3+, Mn2+, and Al3+ ions shows a hump region and a saddle region in the IC50 values contour plot. Fe-Mn-Al ternary alloys may possess a lower toxic risk when the ratio of released metal ions approaches the hump region of the contour plot. Fe-Mn-Al ternary alloys may present an increased toxic risk when the ratio of released metal ions gets close to the saddle regions of the contour plot.

  • Effect of Distance between Orifices in Column Type Pneumatic Separator for Waste Electronic Devices

    Naohito Hayashi, Tatsuya Oki

    pp. 140-148

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    DOI:10.2320/matertrans.M-M2014839

    Abstract

    When recycling important rare metals (such as tantalum) from the printed circuit boards of waste electronic equipment, electronic devices must first be delaminated from the boards. The devices are then separated into individual device types. We previously developed a double-tube pneumatic separator for practical use in the separation process. One of the features of this equipment is the introduction of orifices in a pneumatic separation column, and experiments and an airflow simulation were conducted to clarify its effect. This study investigated the effects of the length of the distance between the orifices (separation room) and the airflow rate on the airflow velocity profile in the separation room and the separation characteristics of tantalum capacitors and quartz resonators focusing on the length of the separation room in the separation column. The results suggested that the separation column could be divided into four typical zones where the velocity profiles changed toward the top of the column: (1) high velocity zone where floating particles were forced to accelerate, (2) maintaining a relatively uniform velocity profile, (3) changing to a more uniform velocity profile, and (4) changing to a velocity profile with a slightly higher velocity around the column center. The main reason for the formation of zones (2)–(4) was that the internal airflow in the column had yet to become a fully developed turbulent flow. In these zones, there was relatively little difference between the velocity at the column center and that around the center to form a uniform velocity profile. Therefore, there was possibly a high-accuracy separation based on the difference in particle density. We defined these zones as ‘separation zones’. Under the experimental conditions used, and applying the optimum separation velocity for the airflow, which was estimated by performing a floating–falling experiment on each electronic device, it transpired that a high separation efficiency was obtained when the separation room was longer than 300 mm. In addition, when using 4% less than the optimum airflow rate, if the length of the separation room was 300–500 mm, that is the length of the separation zone was 50–250 mm, separation could also be achieved with high efficiency.

  • Effects of Chemical Properties and Roughness on Anisotropic Wetting Observed on Machined Surfaces

    Shu Liming, Liang Yande, He Fuben, Zhang Hongzhe

    pp. 149-153

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    DOI:10.2320/matertrans.M2014337

    Abstract

    Anisotropic wetting of machined surfaces occurs in many industrial applications, but there has not been much work on it. In this paper, based on the analysis of the influencing factors of anisotropic wetting from the orthogonal directions, experiments investigating anisotropy wetting have been performed on machined surfaces with a wide range of roughness on four kinds of materials. It is found that roughness and chemical properties of materials exert significant effects on anisotropic wetting on machined surface. Generally, it increases with the mean slop of roughness profile Kr, and decreases with intrinsic contact angle. Anisotropic wetting on hydrophilic materials is distinctly stronger than that on hydrophobic materials. These efforts on researching the effects on anisotropy wetting on machined surfaces have shown practical significance in oil recovery, lubrication and sealing.

  • Application of High Pressure Gas Jet Mill Process to Fabricate High Performance Harmonic Structure Designed Pure Titanium

    Mie Ota, Sanjay Kumar Vajpai, Ryota Imao, Kazuaki Kurokawa, Kei Ameyama

    pp. 154-159

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    DOI:10.2320/matertrans.M2014280

    Abstract

    Through many years, conventional material developments have emphasized on microstructural refinement and homogeneity. However, “Nano- and Homogeneous” microstructures do not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a “nano- and homo-”microstructure design, we have proposed “Harmonic Structure” design. The harmonic structure has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro- but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to pure-Ti via a novel powder metallurgy route consisting of controlled severe plastic deformation of the fine-sized powder particles via jet milling and subsequent consolidation by SPS. At a macro-scale, the harmonic structure materials exhibited significantly better combination of strength and ductility, under quasi-static tensile loadings, as compared to their homogeneous microstructure counterparts.

  • Thermal and Mechanical Properties of Aluminum Alloy Composite Reinforced with Potassium Hexatitanate Short Fiber

    Kazunori Asano, Hiroyuki Yoneda, Yasuyuki Agari, Mitsuaki Matsumuro, Kenji Higashi

    pp. 160-166

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    DOI:10.2320/matertrans.M2014284

    Abstract

    To develop a machinable aluminum alloy composite with high strength, high rigidity and low thermal expansion rate, potassium hexatitanate short fibers were selected as the reinforcements for the composite. JIS-AC8A alloy was used as the matrix metal, and two kinds of potassium hexatitanate short fibers were used as the reinforcements. The composites were fabricated by squeeze casting. The microstructure, thermal conductivity, thermal expansion behavior, and mechanical properties under compressive stress of the composites were investigated. These properties of the composites were compared with those of the unreinforced AC8A alloy and the composites reinforced with various reinforcements such as potassium titanate whisker and aluminum borate whisker. Optical microscopy revealed that the reinforcements were three-dimensionally arranged in the alloy matrix, and no agglomeration of the reinforcements or porosity was observed, indicating that the melt infiltration into the reinforcement preform was perfectly accomplished. The thermal conductivity of the composite decreased as the reinforcement volume fraction increased, and the value of the short fiber-reinforced composite is similar to that of the potassium titanate whisker-reinforced composites. This tendency can be roughly estimated by Landauer’s model. The average thermal expansion coefficient of the composite decreased as the volume fraction increased, and the experimental values were in good agreement with the theoretical values calculated using the Shi’s model. Although the compressive elastic modulus and 0.2% proof stress increased due to the reinforcement at both room temperature and 523 K, the increase in the volume fraction from 25 vol% to 45 vol% had a small effect on improving these mechanical properties for the short fiber-reinforced composite.

  • Preparation of Ti Ternary Alloys by Addition of Si to Ti-Mo Alloy Scraps for Carbonitride Application

    Jung-Min Oh, Ki-Min Roh, Hanjung Kwon, Back-Kyu Lee, Chang-Youl Suh, Jae-Won Lim

    pp. 167-170

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    DOI:10.2320/matertrans.M2014285

    Abstract

    In this study, Ti-Mo-Si ternary alloy ingots were prepared by the addition of Si (0.25–2.0 mass%) to Ti-10Mo alloy scraps in order to produce the raw materials for titanium carbonitride composites. To investigate the effects of Si addition, the prepared alloys were subjected to hardness, tensile strength, grain size, and phase analyses. The Si-added alloys showed no major changes in their O, N, and C impurity contents. Their hardness increased remarkably in proportion to an increase in the Si content, from 435 Hv to 601 Hv at 2.0 mass%. The tensile strength increased with Si addition up to a maximum of 1.0 mass%, reaching 883 MPa, but after this peak, it decreased sharply because of the brittleness that arose by the formation of titanium silicide.

  • Mechanochemical Synthesis and Fast Low-Temperature Consolidation of Nanostructured Ni-ZrO2 Composite and Its Mechanical Properties

    Ju-Kwon Lee, In-Jin Shon

    pp. 171-174

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    DOI:10.2320/matertrans.M2014265

    Abstract

    ZrO2 has been used for hip and knee joint replacements because of the excellent combination of biocompatibility, low density and corrosion resistance. However the low fracture toughness of ZrO2 ceramic limits its wide application. One of the most obvious tactics to improve the mechanical properties has been to formulate a nanostructured composite materials. Nanopowders of Ni and ZrO2 were synthesized from NiO and Zr by high energy ball milling. A highly dense nanostructured 2Ni-ZrO2 composite was consolidated by pulsed current activated sintering within 2 min under 1 GPa pressure. This process allows very quick densification to near theoretical density and prohibits grain growth in nano-structured materials. The grain sizes of Ni and ZrO2 in the composite were calculated. Finally, the average hardness and fracture toughness values of nanostructured 2Ni-ZrO2 composite was investigated.
  • © 2015 The Japan Institute of Metals and Materials

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