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MATERIALS TRANSACTIONS Vol. 54 (2013), No. 8

ISIJ International
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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678
Publisher: The Japan Institute of Metals and Materials

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MATERIALS TRANSACTIONS Vol. 54 (2013), No. 8

Phase-Field Modeling of Phase Transformations in Platinum-Based Alloy Nanoparticles

Shunsuke Yamakawa, Ryoji Asahi, Toshiyuki Koyama

pp. 1242-1249

Abstract

A phase-field model that describes the phase decomposition and phase transformations inside platinum-based alloy nanoparticles is developed to elucidate the effects of particle size, alloy composition, and heat-treatment temperature on the microstructure formation. FePt, CoPt, NiPt, CuPt and IrPt binary alloy nanoparticles with diameters of less than 10 nm are investigated. The calculation results clearly show that surface segregation and atomic ordering are sensitive to the alloy components and particle size, and that the equilibrium nanostructure obtained varies according to the balance between the surface energy and chemical interaction between atomic components. Platinum-based alloy nanoparticles are expected to find applications as electrocatalysts in polymer electrolyte fuel cells. Thus, the proposed phase-field approach demonstrates its usefulness for the control of the radial distributions of each alloying component within a nanoparticle, leading to improvements in the activity and durability of the catalyst and reducing the required amount of platinum loading.

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Phase-Field Modeling of Phase Transformations in Platinum-Based Alloy Nanoparticles

Uncertainty Modeling in the Prediction of Effective Mechanical Properties Using Stochastic Homogenization Method with Application to Porous Trabecular Bone

Khairul Salleh Basaruddin, Naoki Takano, Hikaru Akiyama, Takayoshi Nakano

pp. 1250-1256

Abstract

A systematic modeling of uncertainty due to image processing, material characteristics and experimental works was developed in order to propose a novel stochastic image-based multi-scale method for heterogeneous media. The effective mechanical properties with application to three porous trabecular bone models were predicted by introducing the correction factor (β) to represent the miscellaneous errors or unknown factors. Finally, the probability density was obtained for the effective mechanical properties, which could evaluate the reliability of scattered experimental results. It has been concluded that variation in effective properties of heterogeneous media can be predicted even when only limited measured values are available by using the present extrapolation technique based on verified simulation results.

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Uncertainty Modeling in the Prediction of Effective Mechanical Properties Using Stochastic Homogenization Method with Application to Porous Trabecular Bone

Preferential Orientation of Collagen/Biological Apatite in Growing Rat Ulna under an Artificial Loading Condition

Jun Wang, Takuya Ishimoto, Takayoshi Nakano

pp. 1257-1261

Abstract

Mechanical loading plays a key role in altering macroscopic and microscopic bone structure through functional adaptation; however, the anisotropic micro-organization of collagen and biological apatite (BAp) in adaptively created bone tissue is not well understood in spite of its importance in the mechanical function of bone. In this study, we artificially applied axial compressive loading (15 N at 2 Hz) to a growing rat ulna 10 min/day for 3 weeks to induce new bone under increased mechanical stimulus. Artificial loading induced marked increases in the structural properties of the loaded ulna; the cortical bone area of the mid-shaft was 43.3% larger in the loaded ulna than the contralateral control ulna. The newly formed bone was located mainly on the medial periosteal surface of the ulnar mid-shaft, which experienced the highest compressive strain. The present study firstly clarified that new bone induced by an artificial load showed preferential orientation of collagen and BAp c-axis along the ulnar long axis, which is similar to the pre-existing bone, although the degree of orientation and bone mineral density (BMD) were still impaired after loading for 3 weeks. This anisotropic organization of collagen and BAp crystals corresponded to that of osteocytes, implying that osteocytes are involved in the formation of anisotropic bone micro-organization which is important aspect of bone mechanical function regarding material properties.

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Preferential Orientation of Collagen/Biological Apatite in Growing Rat Ulna under an Artificial Loading Condition

Theoretical Calculations of Segregation Behavior of Zinc and Magnesium at Hydroxyapatite Surface in Contact with Water

Masahiro Mori, Katsuyuki Matsunaga, Tomonori Kubota, Akira Goto, Kazuaki Toyoura, Atsutomo Nakamura, Isao Tanaka

pp. 1262-1267

Abstract

Density functional theory (DFT) calculations were performed to investigate atomic structures and segregation behavior of Zn2+ and Mg2+ ions at a (10\bar{1}0) surface of hydroxyapatite (HAp). In order to take account of aqueous solution environment surrounding the HAp surface, the conductor-like screening model (COSMO) was used. Ionic exchange energies of Zn2+ and Mg2+ at Ca sites around the surface were evaluated, under an assumption of chemical equilibrium between HAp and aqueous solution. It was found that Zn2+ can segregate energetically more favorably at the HAp surface, as compared to Mg2+. This may correspond to Zn2+ effects on inhibition of HAp crystal growth, as suggested by experiment.

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Theoretical Calculations of Segregation Behavior of Zinc and Magnesium at Hydroxyapatite Surface in Contact with Water

Compression Properties of Three-Layered Functionally Graded ADC12 Aluminum Foam Fabricated by Friction Stir Welding

Yoshihiko Hangai, Hiroto Kamada, Takao Utsunomiya, Soichiro Kitahara, Osamu Kuwazuru, Nobuhiro Yoshikawa

pp. 1268-1273

Abstract

Al foam is expected to be used as automotive components because of its light weight as well as its good energy absorption properties. When Al foam is applied to automotive components with complicated shapes, it is desirable to optimally distribute the low-plateau-stress and high-plateau-stress regions in a single Al foam, such as functionally graded (FG) Al foam, to realize components with superior and efficient energy absorption properties. In this study, two types of closed-cell FG Al foam, one composed of larger-smaller-larger three layers with different porosity and pore size to indicate lower-higher-lower plateau stress, and the other composed of smaller-larger-smaller three layers with different porosity and pore size to indicate higher-lower-higher plateau stress, were fabricated by varying the amount of blowing agent added. It was shown that the large-porosity and large-pore-size layers first deformed and, thereafter, the layers with small porosity and pore size deformed, regardless of the location of the large-porosity and large-pore-size layers in the compression test specimens. It was also shown that the first (lower) and second (higher) plateau regions appeared independently, which corresponds to the pore structures of each layer. Therefore, it was demonstrated that the plateau stress of Al foam can be controlled by varying the pore structures.

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Compression Properties of Three-Layered Functionally Graded ADC12 Aluminum Foam Fabricated by Friction Stir Welding

3-Dimensional Microstructural Evaluation of Wear-Induced Layer in Al–Al3Ti Functionally Graded Materials by Serial Sectioning

Hisashi Sato, Yusuke Noda, Yoshimi Watanabe

pp. 1274-1280

Abstract

The wear behavior of Al–Al3Ti functionally graded materials (FGMs) ring was investigated by 3-dimensional microstructural observations. The Al–Al3Ti FGMs ring was cast which contained platelet-shaped Al3Ti particles. The plane normal of the particles was parallel to the radial direction of the ring. The wear resistance of the Al–Al3Ti FGMs ring depended on the sliding direction of the wear tests because of the anisotropic distribution of the Al3Ti platelet particles. A wear-induced layer with a fine microstructure was formed just below the worn surface, and the formation behavior of the layer also depended on the sliding direction. However, the equivalent Hencky strain required to form the wear-induced layer was about 5, regardless of sliding direction. The anisotropy of the wear resistance in the Al–Al3Ti FGMs ring and the formation behavior of the wear-induced layer were explained by the shear strain distribution on the worn surface.

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3-Dimensional Microstructural Evaluation of Wear-Induced Layer in Al–Al3Ti Functionally Graded Materials by Serial Sectioning

Mass Loss and Ion Elution of Biomedical Co–Cr–Mo Alloys during Pin-on-Disk Wear Tests

Kyosuke Ueda, Kaori Nakaie, Shigenobu Namba, Takashi Yoneda, Keita Ishimizu, Takayuki Narushima

pp. 1281-1287

Abstract

Pin-on-disk wear tests using biomedical Co–Cr–Mo alloy pins and alumina disks were conducted in Kokubo and 1% lactic acid solutions. The mass loss and elution of metallic ions were measured and the surface of the pin was observed after the wear test. Mass loss of the alloy pins in 1% lactic acid solution was 10 times higher than the mass loss in Kokubo solution. In Kokubo solution, the as-cast pins exhibited higher mass loss and higher total amount of eluted ions than solution-treated pins. The Cr and Mn ion content in Kokubo solution was lower than expected, based on the chemical composition of the alloy. The incorporation of Cr and Mn ions into the calcium phosphate detected on the wear track of disks is the possible reason for the small amount of these ions in Kokubo solution.

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Mass Loss and Ion Elution of Biomedical Co–Cr–Mo Alloys during Pin-on-Disk Wear Tests

Damping Capacity of Fe–17mass%Mn High Damping Alloy with Variant Controlled Microstructure

Yoshimi Watanabe, Yuusuke Suga, Hisashi Sato, Hideaki Tsukamoto, Yoichi Nishino

pp. 1288-1294

Abstract

In our previous study, it is reported that damping capacity as well as hardness of an Fe–20 mass%Mn alloy can be improved by the thermo-mechanical training featured by rolling deformation. In this study, the thermo-mechanical training of an Fe–17 mass%Mn alloy is carried out with bending mode, since vibration manner of the internal friction measurement refers to bending mode. An anisotropic damping capacity is observed for samples subjected to bending mode training. Moreover, the trade-off between the damping capacity and hardness can be overcome by thermo-mechanical training. To be concluded, the thermo-mechanical training is useful for enhancement of damping properties and hardness of Fe–Mn alloys.

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Damping Capacity of Fe–17mass%Mn High Damping Alloy with Variant Controlled Microstructure

Effects of Alloying Elements on the HAp Formability on Ti Alloys after Alkali Treatment

Ken Cho, Mitsuo Niinomi, Masaaki Nakai, Junko Hieda, Xiaojie Tao

pp. 1295-1301

Abstract

This work presents a study on the relationship between the alloying elements such as niobium (Nb), tantalum (Ta) or zirconium (Zr) and the hydroxyapatite (HAp) formability on the surfaces of titanium (Ti) alloys subjected to alkali treatment process that is developed to form a HAp layer. The HAp formability on the surfaces of pure Ti, Ti–Nb alloys, Ti–Ta alloys, Ti–Zr alloys, pure Nb, pure Ta and pure Zr subjected to alkali treatment in 1 mol/L NaOH solution at 363 K for 259.2 ks was investigated.
The pure Ti, Ti–10Nb alloy and Ti–10Zr alloy have a good HAp formability because sodium titanate is formed on the surface after the alkali treatment. However, the HAp formability is decreased with increasing Nb and Zr contents. A layer including sodium titanate and sodium tantalate is formed on the surfaces of Ti–Ta alloys after the alkali treatment. Therefore, the Ti–10Ta, Ti–20Ta, Ti–30Ta and Ti–40Ta alloys have a good HAp formability. On the other hand, a sodium niobate layer and a thick crystalline sodium tantalate layer are formed on the surfaces of pure Nb and pure Ta, respectively, after the alkali treatment. Moreover, there is no component change on the surface of pure Zr after the alkali treatment. Therefore, the HAp formability on the surfaces of pure Nb, pure Ta and pure Zr is significantly low after they are soaked in a simulated body fluid for 1 week.

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Effects of Alloying Elements on the HAp Formability on Ti Alloys after Alkali Treatment

Formation of Anatase on Commercially Pure Ti by Two-Step Thermal Oxidation Using N2–CO Gas

Nobuyuki Umetsu, Shota Sado, Kyosuke Ueda, Kazuki Tajima, Takayuki Narushima

pp. 1302-1307

Abstract

The phase of a TiO2 layer formed on commercially pure Ti by two-step thermal oxidation using N2–CO gas was investigated. The oxidation process comprised two steps: treatment in an N2–(0.1, 1 and 5)%CO atmosphere and treatment in air. A Ti(C,N,O) phase was formed after the first-step treatment conducted at 873–1123 K. In the second step, the oxidation of this phase at 573–773 K resulted in the formation of an anatase phase, while its oxidation at 873 K resulted in the formation of a single rutile phase. An increase in the CO partial pressure in the first step lowered the temperature for anatase phase formation. Further, in the second step, a single-phase anatase layer was formed at temperatures of 623 and 673 K.

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Formation of Anatase on Commercially Pure Ti by Two-Step Thermal Oxidation Using N2–CO Gas

Improved Corrosion Resistance and Thinner Alpha-Case Layer on Titanium Casting Using Al2O3–5Ti as Investment Material

Ji-Woon Lee, San Kang, Woon-Suk Hwang, Byong-Pil Lee, Myoung-Gyun Kim, Young-Jig Kim, Soong-Keun Hyun

pp. 1308-1312

Abstract

Suppression of the reaction between molten Ti and the investment material could limit the formation of the alpha-case layer, which influences the mechanical properties of the casting. This study investigated the influence of the investment material on the composition of the alpha-case layer and the corrosion behavior of Ti castings prepared in Al2O3-based molds by plasma arc melting. The micro-Vickers hardness of the castings was evaluated both on the surface and in the matrix. The corrosion behavior was investigated in 1 M HCl solution by electrochemical tests. The results show that the alpha-case layers formed when using Al2O3–5Ti molds are thinner than those formed when using Al2O3 molds, because the reaction with the molten metal is suppressed. Further, Al2O3–5Ti molds produce castings with better corrosion behavior, although this behavior is still poorer than that of pure Ti. Thus the corrosion behavior of Ti castings is affected by the composition of the alpha-case layer.

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Improved Corrosion Resistance and Thinner Alpha-Case Layer on Titanium Casting Using Al2O3–5Ti as Investment Material

Recent Progress in Ti-Based Metallic Glasses for Application as Biomaterials

Guoqiang Xie, Fengxiang Qin, Shengli Zhu

pp. 1314-1323

Abstract

Ti-based bulk metallic glasses are of great interest in biomedical applications due to their high corrosion resistance, excellent mechanical properties and good biocompatibility. This article reviews recent progress in the development of Ti-based metallic glasses for the application as biomaterials. Ti-based (Ti–Zr–Cu–Pd, Ti–Zr–Cu–Pd–Sn, and Ti–Zr–Cu–Pd–Nb) bulk metallic glasses without toxic and allergic elements have been developed. These glassy alloys exhibited high glass-forming ability, high strength, large plasticity, good corrosion resistance and excellent biocompatibility, which open possibilities to create Ti-based metallic glass implants. Using a spark plasma sintering process, large-size Ti-based bulk metallic glasses and the composites with hydroxyapatite, as well as porous glassy alloys having approximate Young’s modulus with that of bone were developed.

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Recent Progress in Ti-Based Metallic Glasses for Application as Biomaterials

Production of Ni-Based Glassy Alloy-Coated Bipolar Plate with Hydrophilic Surface for PEMFC and Its Evaluation by Electrochemical Impedance Spectroscopy

Shin-ichi Yamaura, Ken-ichi Katsumata, Masatomo Hattori, Toshinobu Yogo

pp. 1324-1329

Abstract

In this study, Ni65Cr15P16B4 glassy alloy-coated bipolar plates with a hydrophilic surface were produced and the power generation properties of a single fuel cell with such plates were investigated, SUS316L and graphite bipolar plates also being produced for comparison. The fuel cell with the glassy alloy-coated bipolar plates showed good I–V performance after repeated I–V scans for membrane activation as did the cell with the graphite bipolar plates. After 30 I–V scans for activation, a long-time power generation test for 100 h was conducted at a current density of 0.2 A·cm−2. As a result, it was found that the fuel cell with the glassy alloy-coated bipolar plates showed stable power generation behaviour, maintaining the cell voltage at around 0.6 V. Impedance measurements were also conducted for the cells and it was found that it was possible to understand the difference of I–V behaviour between the cells with three different bipolar plate materials by calculating the impedance parameters.

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Production of Ni-Based Glassy Alloy-Coated Bipolar Plate with Hydrophilic Surface for PEMFC and Its Evaluation by Electrochemical Impedance Spectroscopy

Hydrogen Permeable Nb-Based Amorphous Alloys with High Thermal Stability

H. Y. Ding, W. Zhang, S. I. Yamaura, K. F. Yao

pp. 1330-1334

Abstract

In this work, the Nb-based Nb42Ni40Co18−xZrx (x = 0, 4, 12) and Nb42Ni32Co6Zr12M8 (M = Ta, Ti, Zr) amorphous alloy ribbons were successfully prepared by single roller melt-spinning technique. These amorphous alloys exhibit high thermal stability with the crystallization temperature (Tx) exceeding 850 K. It has been found that Tx of the Nb42Ni40Co18 alloy decreased with Zr addition, while hydrogen permeability increased linearly with Zr content. The hydrogen permeability of the Nb42Ni40Co18, Nb42Ni40Co14Zr4, Nb42Ni40Co6Zr12 and Nb42Ni32Co6Zr20 amorphous alloys at 673 K are 0.03 × 10−8, 0.23 × 10−8, 0.69 × 10−8 and 1.40 × 10−8 mol·m−1·s−1·Pa−1/2, respectively. It is noticed that hydrogen permeability of the Nb42Ni32Co6Zr20 alloy is comparable with that of Pd–23%Ag alloy (1.14 × 10−8). Meanwhile, permeability of the above mentioned alloy decreased to 60% of the initial value while it still maintains amorphous structure after 24 h long term durability test. Both thermal stability and hydrogen permeability are enhanced by substituting 8 at% Ni with Ta or Ti in the Nb42Ni40Co6Zr12 alloy. The present result indicates that the Nb-based amorphous alloys possess the potential of applying as a kind of hydrogen permeable membrane at high temperature.

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Hydrogen Permeable Nb-Based Amorphous Alloys with High Thermal Stability

Ti Particles Dispersed Ti-Based Metallic Glass Matrix Composite Prepared by Spark Plasma Sintering

Shengli Zhu, Guoqiang Xie, Fengxiang Qin, Xinmin Wang, Takao Hanawa

pp. 1335-1338

Abstract

Using spark plasma sintering (SPS) process, Ti particles dispersed Ti40Zr10Cu36Pd14 metallic glass (MG) matrix composites were fabricated. The X-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and compressive tests were used for examining the microstructure and properties of the composites. The experiment results showed that the as-sintered composite exhibited mainly dense structure. The Ti-based MG and pure Ti particles were coalesced together closely. There was no distinct gap or interface between the Ti-based MG matrix and pure Ti particles. No crystallization was observed in the Ti-based glassy matrix. The addition of Ti particles improved the plasticity of the Ti-based MG composite, while had no significant influence on the thermal stability of MG matrix.

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Ti Particles Dispersed Ti-Based Metallic Glass Matrix Composite Prepared by Spark Plasma Sintering

Effect of Hydrogen Absorption on Electrical Transport Properties for Ni36Nb24Zr40 Amorphous Alloy Ribbons

Rie Y. Umetsu, Hajime Yoshida, Mikio Fukuhara, Shin-ichi Yamaura, Makoto Matsuura, Toshio Sasaki, Tetsushi Sekiguchi, Mikiko Saito, Jun Mizuno, Hiroshi Kawarada

pp. 1339-1342

Abstract

Electrical resistivity measurements in the temperature range from 6 to 300 K were carried out in order to investigate the effects of the hydrogen absorption on the transport properties of Ni36Nb24Zr40 amorphous alloy ribbon. The electrical resistivity basically behaved negative temperature dependence in all prepared specimens of (Ni0.36Nb0.24Zr0.40)100−xHx with 0 ≤ x < 15. The absolute value of temperature coefficient of the resistivity, TCR, increased with increasing the amount of the absorbed hydrogen. In addition, it was also clear that the electrical resistivity gradually increased with the time just after electrochemically charging, and tended to saturate after about 800 ks at 300 K. The behavior of the gradual increase in the electrical resistivity with the time was explained by the model including two kinds of the relaxation times, being associated with the migration of the hydrogen from the sample surface.

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Effect of Hydrogen Absorption on Electrical Transport Properties for Ni36Nb24Zr40 Amorphous Alloy Ribbons

Solution Process for Synthesizing Bioactive Nano-Mesh Layer on Ti-Based Bulk Metallic Glasses

Yuriko Fukushima, Ken-ichi Katsumata, Zhu Shengli, Xie Guoqiang, Mitsuo Niinomi, Kiyoshi Okada, Nobuhiro Matsushita

pp. 1343-1346

Abstract

Ti based Bulk Metallic Glasses (BMGs) were treated by Hydrothermal (H), Electrochemical (E) and Hydrothermal-Electrochemical (H-E) processes in NaOH solution and all of these processes enabled fabrication of titanate nano-mesh structures on their surfaces. XPS data suggested that the amount of cytotoxic Cu was drastically decreased for the samples treated by H-E process. Specimens having nano-mesh structures on their surface were immersed in Simulated Body Fluid (SBF) for 12 days. The results of the SBF test supported the fact that nano-mesh structures fabricated by these three methods have bioactivity. However, only the specimen treated by H-E process exhibited very good adhesion performance between the induced hydroxyapatite layer and substrate with intermediated titanate nanomesh layer. These results indicated that the H-E process was the best among three to fabricate a low cytotoxic bioactive nano-mesh layer on Ti-based BMG which enabled to induce hydroxyapatite layer with strong adhesion.

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Solution Process for Synthesizing Bioactive Nano-Mesh Layer on Ti-Based Bulk Metallic Glasses

Electrochemical Properties of Porous Pd-Based Bulk Metallic Glasses

Fengxiang Qin, Guoqiang Xie, Takeshi Wada, Shengli Zhu, Zhenhua Dan

pp. 1347-1350

Abstract

The corrosion behavior of porous Pd42.5Cu30Ni7.5P20 bulk metallic glasses with various porosities in Hanks’ solution was investigated. The results revealed that all bulk metallic glasses exhibited similar corrosion behavior. The bulk metallic glasses with the porosity of 0 and 18% were spontaneously passivated with passive current densities between 10−2 and 10−1 A/m2 in anodic polarization curves. The bulk metallic glasses with 40 and 55% porosity exhibited an anodic process with the current density increasing gradually. As the anodic potential increasing, no obvious passivity breakdown occurred in the anodic polarization process. The polarization resistance decreased with the increasing of the porosity from 0 to 55%. The breakdown potential of the passive film for the bulk metallic glass with 55% porosity was about 100 mV lower than that of the 0% porosity Pd42.5Cu30Ni7.5P20 bulk metallic glass.

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Electrochemical Properties of Porous Pd-Based Bulk Metallic Glasses

Structural Features of the Extraordinary Low Glass Transition Temperature for Au65Cu18Si17 Bulk Metallic Glass

Makoto Matsuura, Wei Zhang, Shinichi Yamaura, Takashi Fujita, Koji Ohara, Shinji Kohara, Jun Mizuno

pp. 1351-1355

Abstract

Au65Cu18Si17 bulk metallic glass (BMG) exhibits an extraordinary low glass transition temperature (<100°C) and a wide supercooled liquid region. In order to elucidate the structural features of the extraordinary low glass transition temperature and high glass forming ability of the Au65Cu18Si17 BMG, high-energy X-ray diffraction (HEXRD) and Extended X-ray Absorption Fine Structure (EXAFS) measurements were carried out using synchrotron radiation. A sharp first peak and oscillation of the structure factor S(Q) up to the high wave number Q can be attributed to the dominant weighting factor of the Au–Au correlation over others. A reverse Monte Carlo (RMC) simulation was applied simultaneously to the HEXRD and EXAFS data. The obtained RMC model shows a quite highly dense packed structure with large amount of icosahedral type clusters around Au atoms while small ones around Si atoms. The partial Cu–Cu pair distribution function gCu,Cu(r) shows a sharp peak at a short interatomic distance, i.e., 2.38 Å. The Cu–Cu pairs with short interatomic distances and the large thermal fluctuation around Cu atoms are considered to be one of the structural characteristics of the low glass transition temperature of the Au65Cu18Si17 BMG.

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Structural Features of the Extraordinary Low Glass Transition Temperature for Au65Cu18Si17 Bulk Metallic Glass

Cooling Rate and Composition Dependences of Magnetic Susceptibility for Zr54−xCu30+xAl8Ag8 Glassy Alloys

Ichiro Seki, Rie Y. Umetsu, Guo-Qiang Xie, Naoyuki Nomura, Xin-Min Wang, Takao Hanawa

pp. 1356-1360

Abstract

Cooling rate and composition dependences of the magnetic susceptibility for Zr54−xCu30+xAl8Ag8 glassy alloys which are candidate materials for magnetic resonance imaging (MRI) were investigated. Lower magnetic susceptibility was achieved by reducing Zr content in the present series of the alloys, and also by higher cooling rate during the preparing glassy alloys. The magnetic susceptibility values were hard to be explained by the simple free-electron model. It is suggesting that the effects of the enhancement of the density of states by 4d-conduction band should be taken into the consideration. The results obtained by utilizing the pair correlation functions suggested that the different magnetic susceptibilities between the ribbon and bulk glassy alloys were originated from the structural difference in the middle range order caused by the different cooling rates.

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Cooling Rate and Composition Dependences of Magnetic Susceptibility for Zr54−xCu30+xAl8Ag8 Glassy Alloys

Effect of Oxide Particles Formed through Addition of Rare-Earth Metal on Mechanical Properties of Biomedical β-Type Titanium Alloy

Junko Hieda, Mitsuo Niinomi, Masaaki Nakai, Ken Cho, Shigeki Nagai

pp. 1361-1367

Abstract

In order to improve the mechanical properties of Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy without increasing Young’s modulus for application in bone prostheses, dispersion strengthening of TNTZ using yttrium oxide (Y2O3) particles was studied. The formation of well-dispersed Y2O3 particles inside grains of Y-added TNTZ is achieved through the reaction of added Y with the oxygen contained in TNTZ. The size and its standard deviation of obtained Y2O3 particles increased at Y concentrations of 0.2 and 0.5 mass%. The addition of Y led to a decrease in the grain size in Y-added TNTZ. Low Young’s modulus was retained in the Y-added TNTZ subjected to cold rolling. The tensile strength and 0.2% proof stress slightly increased in Y-added TNTZ with Y concentrations below 0.1 mass%, whereas they decreased significantly in Y-added TNTZ with Y concentrations of 0.2 and 0.5 mass%. Large Y2O3 particles that formed in Y-added TNTZ with Y concentrations of 0.2 and 0.5 mass% worked as sources for the formation of voids during fracture, which resulted in a decrease in the tensile strength and 0.2% proof stress. Elongation tended to decrease in the Y-added TNTZ as compared to that of TNTZ without any Y addition. As a result, it is found that Y-added TNTZ with improved mechanical properties was obtained at a Y concentration of 0.05 mass% in this experiment. The fatigue strength of Y-added TNTZ was also improved at the Y concentration of 0.05 mass%.

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Effect of Oxide Particles Formed through Addition of Rare-Earth Metal on Mechanical Properties of Biomedical β-Type Titanium Alloy

Glass-Forming Ability, Corrosion Resistance and Mechanical Properties of Zr60−xAl15Ni25TMx (TM = Nb and Ta) Bulk Metallic Glasses

Y. H. Li, W. Zhang, C. Dong, S. Yamaura, A. Makino

pp. 1368-1372

Abstract

The thermal stability, glass-forming ability (GFA), corrosion resistance and mechanical properties of Zr60−xAl15Ni25TMx (TM = Nb and Ta, x = 0–6) bulk metallic glasses (BMGs) were investigated. The added Nb and Ta greatly increase the glass transition temperature of the base BMG whereas reduce the supercooled liquid region. Minor addition of Nb enhances the GFA of the base alloy, and Zr56Al15Ni25Nb4 BMG exhibits the largest critical diameter of 20 mm. Additions of Nb and Ta efficiently improve the corrosion resistance of the BMGs in chloride-ion-containing solutions due to the formation of highly protective surface film. In addition, the compressive yield strength of the BMGs increases gradually with increasing Nb and Ta contents.

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Glass-Forming Ability, Corrosion Resistance and Mechanical Properties of Zr60−xAl15Ni25TMx (TM = Nb and Ta) Bulk Metallic Glasses

Characteristics and Effects of Particle Morphology and Tensile Ductility Resulting from FSP of Al–Si–Cu–Ni Casting and Forging Piston

Hsu-Chi Chuang, Truan-Sheng Lui, Li-Hui Chen

pp. 1373-1380

Abstract

The aim of this work was focused exclusively to clarify the diversification of tensile ductility between the friction stir processed (FSPed) casting and forging Al–Si–Cu–Ni heat resistant piston alloy. Experimental results show that though a single-pass FSP can improve tensile ductility of hot forging piston alloy, but still not enough to achieve sufficient refinement. Microstructural refining and homogenization will play an important role on the variation of tensile properties, also governed by the particles dissolution effect of Al3CuNi (δ phase) after performed friction stir process resulted in disappearance of the potential nucleation sites for precipitation. The present investigations through conducted different combination of abovementioned casting, extrusion-forging and FSP process to verify the variation of tensile deformation behavior and tensile ductility.

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Characteristics and Effects of Particle Morphology and Tensile Ductility Resulting from FSP of Al–Si–Cu–Ni Casting and Forging Piston

Supramolecular Interaction of Side-Chain Crystalline Block Co-Polymer and Its Thermal Rheological Function

Shigeru Yao, Toru Okuma, Chihiro Kumamaru, Hiroshi Sekiguchi, Satoshi Ichikawa, Daisuke Tatsumi

pp. 1381-1384

Abstract

Recently, we polymerized a block copolymer that was constructed of side-chain crystalline monomer and a solvent-compatible monomer, which we referred to as a side-chain crystalline block copolymer (SCCBC). This SCCBC has a specific melting point. We found that this SCCBC was adsorbed onto polyethylene (PE) crystal by via supramolecular interaction. In addition, through this supramolecular interaction, the SCCBC acts as a dispersant for a concentrated PE particle dispersion, and this dispersion can be considered a Thermal Rheological Fluid.
By using this novel supramolecular interaction, we can easily modify the surface properties of high crystalline polymers (PE, polytetrafluoroethylene (PTFE), etc.), which have been thought to be inert. Especially, we can modify the inner surface properties of porous membranes without using physical methods (such as UV irradiation or plasma irradiation). Furthermore, these modified surface properties can revert to those in the non-modified state under changes in temperature. It may possible to develop intelligent materials with use of this supramolecular interaction in the near future.

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Supramolecular Interaction of Side-Chain Crystalline Block Co-Polymer and Its Thermal Rheological Function

Crystal Structure and Pseudo-Mackay Clusters of R-AlPdCo

Rayko Simura, Shota Suzuki, Kunio Yubuta, Kazumasa Sugiyama

pp. 1385-1391

Abstract

The structure of the rhombohedral (R-) AlPdCo phase was determined by single-crystal X-ray diffraction: space group R−3 (No. 148), a = 2.91019(8) nm and c = 1.31854(4) nm, V = 9.6709(5) nm3, atoms/cell = 660, F(000) = 12820, R = 0.0481 for the observed 3354 reflections measured by Mo Kα radiation (λ = 0.071069 nm). R-AlPdCo has two types of pseudo-Mackay clusters (pMCs) around Co(12) at 18f and Al/Pd(14) at 3a. The first shell of Co(12)-pMC consists of nine Al sites. The second shell of the Co(12)-pMC is a combination of (M, Co)-icosahedron (ICO) and Al-icosidodecahedron (IDO), where M is a mixed site of Pd, Co or Al. On the other hand, the first shell of the other pMC around Al/Pd(14) consists of two sub-shells: an M-cube and Al-octahedron. The outer shell of the Al/Pd(14)-pMC consists of an M-ICO and Al-IDO. These pMCs interpenetrate each other by sharing the edges of the second ICO shells and their interstitial space is filled by Al-ICOs around M(1) and M(2). These structural features suggest that the structure of R-AlPdCo is realized by linking the Co(12)- and Al/Pd(14)-pMCs together with two types of smaller Al-ICO around the M(1) and M(2) sites.

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Article Title

Crystal Structure and Pseudo-Mackay Clusters of R-AlPdCo

Crystal Structures and Spin Injection Signals of Si/Mg/MgO/Co2FeAl0.5Si0.5 Junctions

Takashi Onodera, Masahiro Yoshida, Nobuki Tezuka, Masashi Matsuura, Satoshi Sugimoto, Yoshiaki Saito

pp. 1392-1395

Abstract

We investigated the crystal structures and the spin injection signals of Si/Mg/MgO/Co2FeAl0.5Si0.5 (CFAS) junctions deposited by molecule beam epitaxy. The (001)-orientation and the structural ordering of CFAS thin films changed by heating deposition of CFAS and the insertion of Mg layer into Si/MgO interface. Spin injection signals observed at 10 K for the junctions by 3 terminals Hanle measurements. The maximum voltage change, ΔVMAX, was increased by heating deposition of CFAS and the insertion of Mg layer. It is supposed that the enhancement of spin polarization by the improvement of structural ordering of CFAS or coherent tunneling by (001)-oriented MgO barrier caused the increment of ΔVMAX.

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Crystal Structures and Spin Injection Signals of Si/Mg/MgO/Co2FeAl0.5Si0.5 Junctions

An Advanced Fitting Method for Crystallographic and Morphological Analyses of EBSD Data Applied for Low-Carbon Steel Martensite

Anh H. Pham, Takuya Ohba, Shigekazu Morito, Taisuke Hayashi

pp. 1396-1402

Abstract

Some essential modifications were introduced to the ordinary fitting method to make it become a powerful tool for thorough crystallographic and morphological analyses of lath martensite based on electron backscatter diffraction (EBSD) data. A large area of martensite which covers a whole prior austenite grain can be effectively analyzed. The austenite orientation and orientation relationship between martensite and austenite can be obtained by fitting from martensite orientations. The fitting procedure is fast with high precision up to 0.5 degrees for austenite orientation and 0.2 degrees for the orientation relationship. The output data are also modified for automatically indexing martensite variants and visual plotting of the results.

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An Advanced Fitting Method for Crystallographic and Morphological Analyses of EBSD Data Applied for Low-Carbon Steel Martensite

Microstructure and Properties of Rapidly Solidified Cu–0.81Cr–0.12Zr Alloy

Zhenya Pan, Jiangbiao Chen, Wei Zhou, Jinfu Li

pp. 1403-1407

Abstract

Cu–0.81 mass%Cr–0.12 mass%Zr alloy was spun into ribbon and then aged at different temperatures for different time. The microstructure, microhardness and electrical conductivity were investigated. It is found that the mother alloy ingot solidified under conventional conditions consists of three phases: Cu matrix, Cr and Cu5Zr. Rapid quenching makes Cr and Zr fully dissolve into the copper matrix. As the aging proceeds, Cr and Cu5Zr phases precipitate again from the matrix. The ribbon aged at 773 K for 15 min possesses the best property: a microhardness of 212 HV and an electrical conductivity of 78.9% IACS. Compared with the conventional process (homogenization treatment of a bulk alloy ingot followed by aging), the use of rapid quenching doubles the microhardness while only slightly decreasing the electrical conductivity.

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Microstructure and Properties of Rapidly Solidified Cu–0.81Cr–0.12Zr Alloy

Variation of Oil Introduction Behaviour during Oil-in-Water Emulsion Rolling

Hironobu Nakanishi, Kozo Saiki, Tomoko Hirayama, Takashi Matsuoka

pp. 1408-1415

Abstract

In the cold rolling of steel plates and the hot rolling of aluminium plates, an oil-in-water emulsion is used as the rolling oil, both as a coolant and a fire retardant. Understanding the formation mechanisms of the oil film that formed in a roll bite is important for controlling the lubricity and surface quality of the product. This film is formed by introducing oil that spreads on the rolls and strip, which is called “plate-out”, and by introducing oil droplets into the inlet zone. However, the effects of these two oil introduction methods on the oil film that formed in the roll bite and the relationship between them have not yet been clarified. In our previous study, oil-film thickness was estimated from the volume of the tracer left on the strip after rolling and the proportion of the volume to that of the oil introduced. The mutual relationships between the volume of the introduced oil and the emulsion particle size, the oil concentration of the emulsion, and rolling velocity were determined. In this study, the effect of plate-out volume on the oil film that formed between the rolls and the strip was investigated by comparing oil-film thickness and plate-out volume. In addition, the behaviour of the introduction of oil droplets for various plate-out volumes was investigated by controlling the supply conditions of the oil-in-water emulsion and the velocity of rolling on a test mill. The effect of plate-out volume was found to decrease and that of oil-droplet introduction was found to increase with an increase in rolling velocity.

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Variation of Oil Introduction Behaviour during Oil-in-Water Emulsion Rolling

ZrCu-Based Metallic Glass Matrix Composites with Ta Dispersoid by In Situ Dealloying Method

Wei Guo, Kunio Yubuta, Hidemi Kato

pp. 1416-1422

Abstract

Zr48Cu36Al8Ag8-based bulk metallic glass matrix composites (BMGCs) with in situ dispersed Ta-rich particles surrounded by microcrystalline phases were fabricated successfully by both the conventional arc melting and a new dealloying methods followed by copper mold casting. The microstructures and uniaxial compressive mechanical properties of as-cast ϕ3-mm rods fabricated by the two different methods were compared. The size and dispersion of the Ta-rich particles and the mechanical properties of the as-cast BMGC rods obtained using the new dealloying method were smaller, finer and better than those of the rods obtained using the conventional arc-melting method. Both the compressive and tensile plastic strain increased from almost 0% for monolithic Zr48Cu36Al8Ag8 bulk metallic glass to about 7 and 1%, respectively, for as-cast BMGC rods with 5 at% Ta formed by the in situ dealloying method. These in situ Ta-rich particles are considered as obstacles that restrict shear band propagation. An obvious work-hardening phenomenon can be observed in compression tests considerably due to work hardening of the Ta-rich particles restricted by the surrounding microcrystals.

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ZrCu-Based Metallic Glass Matrix Composites with Ta Dispersoid by In Situ Dealloying Method

Effect of ECAE on Microstructures and Mechanical Properties of Solution Heat Treated Mg–5(mass%) Sn Alloy

Hao-Jan Tsai, Chin-Guo Kuo, Chuen-Guang Chao, Tzeng-Feng Liu

pp. 1423-1428

Abstract

The microstructures and mechanical properties of the Mg–5(mass%) Sn alloy subjected to a solution heat treatment (SHT) were investigated by using equal channel angular extrusion (ECAE). The average grain size was significantly refined from 147 µm (as-cast) to 16 µm by ECAE four passes. Further, the fine Mg2Sn particles were uniformly distributed in the matrix by dynamic precipitation after ECAE four passes. The yield strength (YS), ultimate tensile strength (UTS) and elongations also showed notable improvements at room temperature and high temperatures (100 and 200°C) on account of the ECAE process. Further, the tensile strength and elongations were better than those of the ECAE without SHT alloy. Those results show that SHT is a useful way to enhance the effect of ECAE on the mechanical properties of Mg–5(mass%) Sn alloy.

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Effect of ECAE on Microstructures and Mechanical Properties of Solution Heat Treated Mg–5(mass%) Sn Alloy

Behavior of High-Temperature Embrittlement and Its Mechanism in Heat-Affected Zone of Low-Carbon Alloy Steels

Suguru Yoshida, Teruhisa Okumura, Hiroshi Kita, Kohsaku Ushioda, Yoshio R. Abe

pp. 1429-1436

Abstract

For the purpose of understanding the mechanism of high-temperature embrittlement, especially in the heat-affected zone of B-bearing low-carbon alloy steel, the role of B addition is studied in terms of grain-boundary segregation and nitride precipitation of B. BN precipitates at the prior austenite grain boundary are supposed to be the dominant cause of the embrittlement of steel when tensile stress is applied at 600°C, followed by heat cycle of welding, where a fire environment is simulated. After hot rolling, followed by reheating to 600°C for a tensile test, intragranular TiN is changed to intergranular BN at the prior austenite grain boundary after reheating to 600°C following the heat cycle of welding. Consequently, the grain-boundary fracture takes place in the specimens that are subjected to the heat cycle of welding when tensile stress is applied after reheating to 600°C because the intergranular BN leads to the formation of cavity along the prior austenite grain boundary. This mechanism is experimentally verified by the fact that high-temperature embrittlement can be prevented by either the addition of Zr or the addition of more Ti, which may fix nitrogen to a more stable nitride state and inhibit the dissolution of nitride during welding heat cycle.

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Behavior of High-Temperature Embrittlement and Its Mechanism in Heat-Affected Zone of Low-Carbon Alloy Steels

Post-Buckling Stability Analysis of Composite Laminated Flat Plates with Initial Deflection under Biaxial Compression

Keiichi Nemoto, Hirakazu Kasuya, Hisao Kikugawa, Tooru Kohiga

pp. 1437-1443

Abstract

Advanced fiber-reinforced laminated plates have been used as structural members in various applications by virtue of their high specific strength and stiffness. This paper considers, by use of the second variation of the total potential energy, secondary buckling of cross-ply laminated plates with an initial deflection under biaxial compression that is simply supported along four edges. The occurrence of secondary buckling is proven analytically and the effects of the initial deflection, outer lamination angle, number of layers, biaxial compressive load ratio and post-buckling deflection pattern are discussed.

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Post-Buckling Stability Analysis of Composite Laminated Flat Plates with Initial Deflection under Biaxial Compression

Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride

Jungshin Kang, Toru H. Okabe

pp. 1444-1453

Abstract

A selective chlorination process using magnesium chloride (MgCl2) as chlorinating agent was investigated with the aim of developing a process for removing iron directly from ilmenite, which is a low-grade titanium ore known as FeTiO3. Two crucibles, one consisting of titanium ore and the other consisting of a mixture of titanium ore and MgCl2, were placed in a gas-tight quartz tube, and then both crucibles were heated to 1000 K. In some experiments, H2O vapor was introduced in the quartz tube. HCl gas produced from the MgCl2/titanium ore mixture reacted with the iron present in the titanium ore placed in the other crucible to produce TiO2. Iron present in the titanium ore of the titanium ore/MgCl2 mixture reacted with MgCl2, and MgTiO3 and MgO were obtained. Iron in the titanium ore present in both crucibles was removed as FeCl2 (l,g). In these experiments, the effects of the particle size of the titanium ore and the atmosphere on selective chlorination were investigated. In addition, titanium ores produced in Vietnam, Australia and China were used as feedstocks. By the chlorination process, 97% TiO2 was obtained directly in one step from the low-grade titanium ore containing 51% TiO2 under certain conditions, thus demonstrating the feasibility of the selective chlorination process for producing high-purity titanium dioxide from low-grade titanium ore.

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Removal of Iron from Titanium Ore through Selective Chlorination Using Magnesium Chloride

Surface Hardening of Titanium by Using a Simplified Carbon and Nitrogen Diffusion Technique with Steel and Carbon Powders

Yasuhiro Morizono, Yuka Kawano, Sadahiro Tsurekawa, Takateru Yamamuro

pp. 1454-1459

Abstract

Commercially pure titanium plates were embedded in mixtures of steel and activated carbon powders and then heated at 1273 K for 3.6 ks in a nitrogen flow. During this simplified treatment, a Ti(C, N) layer with a thickness of approximately 10 µm formed on the titanium surface. The surface hardness of the titanium plates coated with the Ti(C, N) layer was more than HV = 1000 regardless of the steel powder ratio in the mixture. Although a Ti(C, N) layer formed upon heat treatment with the activated carbon powder alone, addition of the steel powder led to an increase in the surface hardness and layer thickness. From X-ray diffraction results, Ti(C, N) began to form on the titanium plate heat-treated at 1073 K and became a complete layer at higher heating temperatures. Instead of activated carbon, the use of graphite with added alumina as a reliable anti-sintering agent had no negative effects on the formation of the Ti(C, N) layer.

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Surface Hardening of Titanium by Using a Simplified Carbon and Nitrogen Diffusion Technique with Steel and Carbon Powders

Solvent Extraction of Zirconium and Hafnium from Hydrochloric Acid Solutions Using Acidic Organophosphorus Extractants and Their Mixtures with TOPO

Ling Yun Wang, Hwa Young Lee, Man Seung Lee

pp. 1460-1466

Abstract

Solvent extraction of Zr and Hf from hydrochloric acid solution was performed by using acidic organophosphorus extractants and their mixtures with TOPO. In the HCl concentration range from 1 to 4 mol/dm3, solvation reaction was responsible for the extraction of Zr and Hf by single acidic organophosphorus extractants, such as D2EHPA, PC88A and Cyanex272. Although the extraction percentage of both metals by single and mixture of extractants increased with the increase of HCl concentration, the dependence of separation factor on the HCl concentration showed opposite behavior in both extractant systems. Synergistic extraction of Zr and Hf was obtained by the mixtures. Single Cyanex272 and a mixture of Cyanex272 and TOPO were found to be the most efficient in separating the two metals.

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Solvent Extraction of Zirconium and Hafnium from Hydrochloric Acid Solutions Using Acidic Organophosphorus Extractants and Their Mixtures with TOPO

Cyclic Voltammetric and Chronoamperometric Deposition of CdS

Yongkuk Kim, Jaegoo Jung, Seunghun Kim, Won-Seok Chae

pp. 1467-1472

Abstract

CdS was electrochemically deposited on ITO using cyclic voltammetry (CV) and chronoamperometry (CA) in aqueous solution. To fabricate the CdS thin films, a potential ranging from −0.3 to −1.2 V was applied for CV and a constant potential of −1.1 V was applied for CA (Ag|AgCl). The deposited CdS thin films were characterized in detail using XRD, AFM and SEM. UV/Vis-transmittance was used to determine the band-gap energy (Eg) of the films. The dopant densities and flat band-potentials (Efb) were determined using Mott-Schottky plots. The CdS film obtained by CV deposition was observed to be rougher and sparser than that obtained by CA deposition. This was attributed to the alternating reduction–oxidation, corresponding to deposition–dissolution of CdS. The carrier density of the CdS film deposited by CV was measured to be as much as 17%.

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Cyclic Voltammetric and Chronoamperometric Deposition of CdS

Effects of Solution-Annealing Temperature on the Precipitation of Secondary Phases and the Associated Pitting Corrosion Resistance in Hyper Duplex Stainless Steel

Soon-Hyeok Jeon, Soon-Tae Kim, Se-Young Kim, Min-Seok Choi, Yong-Soo Park

pp. 1473-1479

Abstract

The effects of the solution-annealing temperature on the precipitation of secondary phases and the associated pitting corrosion resistance in hyper duplex stainless steel after aging at 1123 K were investigated in a highly concentrated chloride solution. Increasing the solution annealing temperature from 1333 to 1413 K retarded the formation of the secondary phases owing to a decrease in both the number of preferential precipitation sites such as the ferrite/austenite interface and the activities of Cr, Mo and W. The slow rate of degradation of the pitting corrosion resistance of the alloy with the increase in the solution annealing temperature appears to be caused by the retardation of the precipitation of the sigma phase. Based on the results of the precipitation of secondary phases and electrochemical tests, the optimal solution annealing temperature was determined to be 1373 K.

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Effects of Solution-Annealing Temperature on the Precipitation of Secondary Phases and the Associated Pitting Corrosion Resistance in Hyper Duplex Stainless Steel

Effects of High Pressure Heat Treatment on Thermal Conductivity and Electrical Conductivity of CuAlBi Alloy

Ma Yu-quan, Lin Hong-ju, Zhang Li-hong

pp. 1480-1483

Abstract

The thermal conductivity and electrical conductivity of CuAlBi alloy before and after 1–6 GPa high pressure treatment were measured by thermal constant tester and conductivity gauge when it was heated at 700°C and lasted for 30 min. And the effects of high pressure heat treatment on thermal conductivity and electrical conductivity of CuAlBi alloy were discussed by its microstructure. The results show that the thermal conductivity variation trend of CuAlBi alloy before and after 3 GPa pressure heat treatment is almost the same in range of 25–600°C, high pressure can reduce the thermal conductivity and electrical conductivity of CuAlBi alloy, the thermal conductivity and electrical conductivity of the alloy decrease with the increment of pressure in less than 3 GPa, when the pressure is over 3 GPa, the variation of thermal conductivity and electrical conductivity are not obvious.

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Effects of High Pressure Heat Treatment on Thermal Conductivity and Electrical Conductivity of CuAlBi Alloy

Effects of the Mn/Fe Ratio and Cooling Rate on the Modification of Fe Intermetallic Compounds in Cast A356 Based Alloy with Different Fe Contents

Zhijun Zhang, Hiroyasu Tezuka, Equo Kobayashi, Tatsuo Sato

pp. 1484-1490

Abstract

In cast Al–Si alloys, the platelet β type Fe intermetallic compound has been considered as most detrimental Fe compounds to their mechanical properties, especially ductility. When the Fe is inevitable, to enhance the properties of the cast aluminum alloys, the modification of Fe compounds from the platelet β type Fe compound to a more compact and less harmful α type Fe compound having the Chinese script morphology becomes the efficient and important way. This work mainly investigated how did three factors, Fe content, Mn/Fe ratio and cooling rate combined influence this modification process in cast A356 (JIS, AC4C) based alloys. The results revealed that with increasing the Fe content in the alloy without Mn addition, the size of the platelet β type Fe compound increases significantly under the same cooling rate. The Mn addition was effective to modify the platelet β type Fe compound to more compact Chinese script and/or polyhedral shape α type Fe compound. The ratio of these two kinds of α type Fe compounds mainly depends on the Mn/Fe ratio and the cooling rate in a given Fe level. The further research work about the solidification sequence of Fe compounds during casting revealed that in the alloys without Mn addition, the Fe compounds only appeared as a platelet shape. With Mn addition, the Fe compound crystallized as the platelet β type compound at the beginning of the solidification. With the solidification proceeding, the Chinese script α type Fe compound became the dominant one. The formation of the polyhedral shape α type Fe compound mainly came from the growth of the Chinese script α type Fe compound. The ratio of these three Fe compounds was greatly influenced by the Mn/Fe ratio and cooling rate in a given Fe content.

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Effects of the Mn/Fe Ratio and Cooling Rate on the Modification of Fe Intermetallic Compounds in Cast A356 Based Alloy with Different Fe Contents

Computer-Aided Designs of Die and Thermal Control for Fabrication of A356 Wheels

Xiu Song Huang, Zhi Gang Lv, Liang Ju He, Guang Bao Mi, Pei Jie Li

pp. 1491-1495

Abstract

Horizontal squeeze casting (HSC) is a potential method for casting aluminum alloy wheels. In this study, the process for HSC of an A356 wheel was modeled and simulated. After analysis of the velocity and temperature fields during the casting process, the designs of the die and thermal control were modified and the effects of the design modifications on two key characteristics of HSC were studied: slow filling and squeeze feeding. An increase in the gate size and the use of exhaust slots reduced the tendency for gas to become entrapped. Furthermore, the increase in the gate size and application of thermal control allowed squeeze feeding for the wheel hub to be achieved successfully. Finally, experiments were performed to verify the results of simulation.

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Computer-Aided Designs of Die and Thermal Control for Fabrication of A356 Wheels

Synthesis of Noble Metal-Doped Cu Nanoparticles by Ultrasonication

Hiroaki Koubu, Yamato Hayashi, Jun Fukushima, Hirotsugu Takizawa, Ichihito Narita, Satoru Yoshioka

pp. 1496-1501

Abstract

Cu nanoparticles doped with small amounts of noble metals were synthesized by ultrasonication. The noble metals selected were Pd, Pt, Ru, Rh and Ir. Mean particle size was most reduced for Cu nanoparticles doped with Pd, with Cu–Pd nanoparticles of approximately 50 nm in diameter being obtained. X-ray absorption, near-edge spectroscopy and extended X-ray absorption were used to conduct fine structure analysis, and these techniques confirmed that Cu–Pd nanoparticles possessed Cu–Pd bonds. High-angle annular dark-field scanning transmission electron microscopy and energy dispersive X-ray spectrometer mapping were used to show that Cu–Pd nanoparticles were dispersed as Pd clusters inside Cu nanoparticles. It was supposed that the surfaces of Cu–Pd nanoparticles were Cu-rich, and Pd clusters were dispersed inside these particles. It is proposed that heterogeneous nucleation of Cu onto Pd nuclei resulted when nucleation of Pd occurred.

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Synthesis of Noble Metal-Doped Cu Nanoparticles by Ultrasonication

Non-Monotonic Aging Temperature Dependence of Superelasticity of Ti72Nb15Zr10Al3 Quaternary Alloys

Hiroyuki Tada, Tokujiro Yamamoto, Xinmin Wang, Hidemi Kato

pp. 1502-1509

Abstract

The influence of aging on the superelastic behavior of Ti72Nb15Zr10Al3 alloy (which is associated with the martensitic transformation from β to α″ martensite) was investigated. The precipitation of ω phase during aging significantly affects the mechanical properties. A non-monotonic change in the stress required for martensitic transformation was observed as the aging temperature changed from 453 to 603 K. This variation in stress may be attributed to two factors: change of chemical composition in the matrix and internal strain because of ω phase formation. The likely variation in the stress for martensitic transformation associated with each of these effects was estimated. As the volume fraction of ω phase increased, the change in the chemical composition produced a greater effect than the change in the internal strain.

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Non-Monotonic Aging Temperature Dependence of Superelasticity of Ti72Nb15Zr10Al3 Quaternary Alloys

Effect of Accelerated Carbonation on the Leaching Behavior of Cr in Municipal Solid Waste Incinerator Bottom Ash and the Carbonation Kinetics

Namil Um, Seong-Young Nam, Ji-Whan Ahn

pp. 1510-1516

Abstract

The accelerated carbonation process with CO2 absorption to confirm the leaching behavior of Cr in municipal-solid-waste incinerator (MSWI) bottom ash was investigated. This investigation was performed by placing samples in a CO2 chamber. Only the temperature of the chamber at atmospheric pressure was varied and the CO2 concentration was kept constant at 30% while the water-to-solid ratio was held at 0.3 dm3/kg. The result of an XRD analysis indicated that CO2 could combine with portlandite, ettringite and hydrocalumite to form mainly an amorphous Al-rich material and calcite. Comprehension of the Cr leaching behavior during the carbonation reaction was gained by understanding the results obtained in this study. The carbonation kinetics includes a two-step process with a phase-boundary chemical reaction and diffusion through the product layer. As the carbonation process proceeds, the rate-controlling step was switched from a chemical reaction to diffusion by means of product layer control. The experimental data showed that the increase in the reaction temperature increased the carbonation rate. The carbonation kinetics of two types of mechanisms for varying temperatures was analyzed and an equation fitted to the experimental data was formulated. The variations of the rate constant with the temperature obeyed the Arrhenius equation with activation energies of 13.82 and 21.98 kJ/mol. Approximately 34 g/kg CO2 was sequestrated in MSWI bottom ash with a particle size of less than 0.15 mm after a carbonation time of 120 min.

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Effect of Accelerated Carbonation on the Leaching Behavior of Cr in Municipal Solid Waste Incinerator Bottom Ash and the Carbonation Kinetics

Oxidation of MoSi2-Coated and Uncoated TZM (Mo–0.5Ti–0.1Zr–0.02C) Alloys under High Temperature Plasma Flame

Joon Sik Park, Jeong Min Kim, Seong Hyun Cho, Young II. Son, Daeseung Kim

pp. 1517-1523

Abstract

Oxidation of coated and uncoated TZM alloys has been investigated under high temperature plasma flames with varying exposure time. TZM alloy specimens were pack-cemented in a powder mixture of Si, NaF and Al2O3 (25, 5 and 70 mass%) in an Ar atmosphere at 1173 K, resulting in the formation of MoSi2 and Mo5Si3 layers on the TZM alloy. When the uncoated alloy was exposed to the flame for up to 4 min, the TZM alloy specimen showed a significant weight loss. However, the MoSi2-coated TZM alloy specimen did not exhibit a measureable weight loss during the same exposure time due to the presence of the MoSi2 layer. The effect of coating layers on the oxidation of TZM alloy under the dynamic flame is discussed based on the surface morphology and the microstructural observations, together with the weight changes during the test.

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Oxidation of MoSi2-Coated and Uncoated TZM (Mo–0.5Ti–0.1Zr–0.02C) Alloys under High Temperature Plasma Flame

Energetic Analysis of Deformation Twins and Twinning Dislocations in Magnesium

Daisuke Matsunaka, Akira Kanoh, Yoji Shibutani

pp. 1524-1527

Abstract

Twin boundaries and twinning dislocations for (10\bar{1}2) and (10\bar{1}1) twins in Mg are investigated, using the generalized-embedded-atom-method interatomic potential. The twin boundary energy for the (10\bar{1}2) twin is found to be larger than that for the (10\bar{1}1) twin. On the other hand, both the dislocation energy and the Peierls barrier of the twinning dislocation are low for the (10\bar{1}2) twin. This implies that the (10\bar{1}2) twin is capable of having a winding morphology and can grow easily.

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Energetic Analysis of Deformation Twins and Twinning Dislocations in Magnesium

Copper Casting Layer Prepared by Jet Electroforming

Chen Jinsong

pp. 1528-1531

Abstract

Jet electroforming technology was used to make copper casting layer. The effects of current density, electrolyte jet speed and nozzle scanning speed on the surface morphology of copper casting layer have been investigated. Results show that higher current density, scanning speed and lower jet speed produced a compact and smooth copper casting layer with finely deposited particles. However, for opposite electroforming conditions, the copper casting layer was composed of cellular particles growing in dendrite morphology with poor surface smoothness.

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Copper Casting Layer Prepared by Jet Electroforming

Dehydriding Property of LiBH4 Combined with Mg2FeH6

Guanqiao Li, Motoaki Matsuo, Stefano Deledda, Ryutaro Sato, Bjørn C. Hauback, Shin-ichi Orimo

pp. 1532-1534

Abstract

A dehydriding property of xLiBH4 + (1 − x)Mg2FeH6 (x = 0.1–0.83) was investigated. The dehydriding reactions of pure LiBH4 and Mg2FeH6 start at approximately 650 and 450 K, and 12.5 and 4.3 mass% hydrogen are released, respectively. The property drastically changes by combining LiBH4 and Mg2FeH6. Within the composition range 0.1 ≤ x ≤ 0.5, LiBH4 and Mg2FeH6 simultaneously release hydrogen. The reaction temperatures and quantities of released hydrogen alter with x. The lattice parameter of the Mg2FeH6 phase measured by in-situ high-resolution synchrotron diffraction measurements suggest the possibility of forming LixMg2−2x(BH4)x(FeH6)1−x with both double-cation and double-anion.

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Dehydriding Property of LiBH4 Combined with Mg2FeH6

Magnetoelastic Anomalies Exhibited by Ni–Fe(Co)–Ga Polycrystalline Ferromagnetic Shape Memory Alloy

Patricia Lázpita, Volodymyr A. Chernenko, Jose M. Barandiarán, Jon Gutiérrez, Hideki Hosoda, Jose A. Rodríguez-Velamazán

pp. 1535-1538

Abstract

The martensitic transformation (MT) as well as the structure, magnetic and magnetostrain properties of a polycrystalline Ni50.1Fe18.6Ga27.2Co4.1 (at%) ferromagnetic shape memory alloy are investigated. The studied alloy exhibits a martensitic ferromagnetic phase near room temperature that shows a non-modulated tetragonal structure with a tetragonality ratio of c/a > 1. Strain measurements reveal a complex spontaneous change at MT amounting to about 0.15% that increases up to 0.22% at 5 T of the applied magnetic field indicating orientation influence of the field on the martensitic variants growth. Magnetostrain measurements enable evaluation of the magnetic field-induced strain effect in the vicinity of MT. The sample shows moderate deformation achieving values of 70 ppm related to the magnetization rotation and volume magnetostriction that does not saturate at applied magnetic field of 5 T.

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Magnetoelastic Anomalies Exhibited by Ni–Fe(Co)–Ga Polycrystalline Ferromagnetic Shape Memory Alloy

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