MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 50 , Issue 4
Showing 1-39 articles out of 39 articles from the selected issue
  • Masaaki Fuse, Kenichi Nakajima, Hiroshi Yagita
    2009 Volume 50 Issue 4 Pages 703-710
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    This paper examines the traceability of resource movement across borders by quantifying the global flow of base metals (Fe, Al, Cu, Pb, and Zn) through the used passenger car trade in 2005 using trade statistics and vehicle composition data. An estimation method was developed to deal with the often problematic issues associated with trade statistics. This estimation shows that 3.4×106 metric tons of Fe, 3.1×105 metric tons of Al, 7.5×104 metric tons of Cu, 3.2×104 metric tons of Pb, and 2.7×104 metric tons of Zn in used passenger cars globally were not recycled in the country of origin, but rather moved in a global flow out of the country of manufacture. The destinations of these metals were mainly developing countries with rudimentary recycling technology. These results strongly indicate that in developed countries, many metal resources from automobiles that could have been utilized domestically were instead scattered and lost overseas.
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  • Masataka Hakamada, Akira Watazu, Naobumi Saito, Hajime Iwasaki
    2009 Volume 50 Issue 4 Pages 711-718
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    Compression tests were conducted at the temperature of 573 K with the true strain rates of 0.1 s−1 on Mg-9Al-1Zn-1Ca and Mg-9Al-1Zn (in mass%) alloys, and the dynamic recrystallization behaviors were examined. Superplastic deformation of the alloys at 573 K after the hot compression was also investigated. When the homogenized Mg-9Al-1Zn-1Ca alloy specimens were deformed to the true compressive strain of 1.6, a fully recrystallized microstructure with the grain size of approximately 5 μm was obtained. However, unrecrystallized regions were observed locally in the hot-compressed as-cast Mg-9Al-1Zn-1Ca and homogenized Mg-9Al-1Zn alloys, which is induced by initial microstructural heterogeneity. The superplastic deformation at 573 K of hot-compressed Mg-9Al-1Zn-1Ca was negligibly impaired by the second phase particles below the strain rates of 10−2 s−1 because the stress concentration due to the particles can be relaxed by diffusion. Microstructural observations of the hot-compressed Mg-9Al-1Zn alloy deformed to fracture suggested the detrimental effect of the unrecrystallized regions on the superplasticity.
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  • Masahiro Tahashi, Zunyi Wu, Hideo Goto, Youji Hayashi, Toshiyuki Ido
    2009 Volume 50 Issue 4 Pages 719-722
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Vanadium-doped ZnSe films were epitaxially grown on (100) GaAs substrates by metal-organic vapor phase epitaxy. The crystal structure and the state of vanadium in the ZnSe crystal were investigated using X-ray diffractometry, infrared absorption, and photocurrent. It was revealed that zinc sites in the ZnSe crystal were substituted by vanadium atoms on the basis of the results of infrared absorption which peaked around 2200 nm as a result of the presence of V2+, and the photocurrent which peaked at 860 nm as a result of the internal transition between V2+ and V3+. The magnetic properties were measured by using a superconducting quantum interface device at room temperature, and it was found that the magnetization curve of ZnSe was markedly changed by vanadium doping.
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  • Shota Nishio, Satoshi Sugimoto, Ryota Goto, Masashi Matsuura, Nobuki T ...
    2009 Volume 50 Issue 4 Pages 723-726
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
    JOURNALS FREE ACCESS
    Nd-Fe-B sintered magnets show high energy products and have started to be used for motors of hybrid electric vehicles (HEVs). For the use of the magnets, the understanding of the coercivity mechanism is required for obtaining high coercivity. The Nd-rich phase in Nd-Fe-B sintered magnets plays an important role in cleaning the surface of Nd2Fe14B grains for decreasing the number of nucleation sites of reverse domains, which leads to high coercivity. In this study, the phase equilibria including oxygen in Nd-Fe-B sintered magnets are discussed in view of the wettability between Nd-rich phase and Nd2Fe14B phase. It is considered that Cu addition decreases the free energy of Nd-rich liquid phase, which leads to the shift of liquidus line of Nd-O system to lower temperature and the increase in solubility limit of oxygen. Due to improvement of wettability and increase in solubility limit, Cu-added Nd-rich liquid spread easily and form homogeneous liquid phase during the sintering process. These phenomena enhance cleaning effect of Nd-rich phase and contribute to the increase in coercivity of Nd-Fe-B sintered magnets.
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  • Kota Kadoi, Norbert Babcsán, Hideo Nakae
    2009 Volume 50 Issue 4 Pages 727-733
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 11, 2009
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    TiH2 powder has been used to fabricate aluminum foams as a blowing agent for more than two decades. The aim of this paper is to understand the detailed decomposition behavior of TiH2 powder and to control the phenomenon by a heat treatment for the fabrication of fine aluminum foams by the melt route. TiH2 powders whose qualities were different, were characterized using TG-DTA and XRD. As heat treatment factors, temperature and time were applied. We have found differences in the decomposition behavior between the as-received TiH2 powders. Regardless of quality of TiH2 powder, increasing temperature and time of the heat treatment in air elevates the decomposition temperature and decreases the amount of released hydrogen during reheating due to the oxide barrier layer formed on the powder surface. The influence of the heat treatment temperature on the decomposition modification is more significant than that of the time. To control the decomposition phenomenon of TiH2 powder, the heat treatment condition has to be optimized taking into account the quality and the purity of the powder.
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  • Takeshi Hagio, Tomohiko Tanase, Jun Akiyama, Masanori Umino, Kazuhiko ...
    2009 Volume 50 Issue 4 Pages 734-739
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Hydroxyapatite ceramics has been demonstrated to be an appropriate material for biomedical applications owing to its bioactivity and high biocompatibility. It has an anisotropic crystal structure that belongs to the hexagonal system, and two types of crystal planes mainly appear on its crystal, which are a-plane and c-plane. Since these two crystal planes are very different in atomic elements, numbers and arrangements, they exhibit different nature (anisotropy). For this reason, it is said that crystal orientation might be intensifying its bioactivity and biocompatibility. However, the differences in biological features on these two crystal planes are not fully clarified yet. In this study, we have conducted an assessment to reveal anisotropic biological features of hydroxyapatite by using hydroxyapatite ceramics with controlled orientation fabricated by slip casting under a magnetic field. Tanase et al. have recently reported the difference in bioactivity on the two crystal planes by immersing crystal oriented hydroxyapatite ceramics into the simulated body fluid and found that c-plane oriented hydroxyapatite ceramics formed a precipitate layer earlier and thicker on its surface compared to a-plane oriented one. We first carried out Welch’s t-test on the difference in the thickness of the precipitate layer, reported previously to reveal the difference in bioactivity. Secondly, we conducted an osteoblast culture experiment on hydroxyapatite ceramics with controlled orientation to reveal the difference in initial cell attachment and cell morphology on the two crystal planes of hydroxyapatite using optical microscope observations. In the former case, the results of the Welch’s t-test indicated that the thickness of the precipitate significantly differed on each crystal oriented hydroxyapatite ceramics (P<0.05). In the latter case, initial cell attachment seemed to be better on the a-plane oriented hydroxyapatite ceramics and also the morphology of the osteoblasts seemed to be rounded on the a-plane oriented hydroxyapatite ceramics compared to the c-plane oriented one.
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  • Norikazu Yamamoto, Yoshiharu Murase, Johsei Nagakawa
    2009 Volume 50 Issue 4 Pages 740-743
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    In order to contribute to the development of first wall/blanket structural materials in nuclear fusion reactors, we have assessed the influence of nuclear-transmutational helium, which is widely known to often induce grain boundary embrittlement at high temperatures, on fatigue properties of a candidate reduced-activation martensitic steel, IEA (International Energy Agency) version of F82H (Fe-8%Cr-2%W-0.2%V-0.04%Ta). Utilizing α-particles from an accelerator, helium was introduced into specimens at 823 K to a concentration of about 100 appmHe. Through the subsequent fatigue tests at the same temperature, it has been demonstrated that both fatigue life and gauge extension to failure were not significantly deteriorated by helium. The appearance of fracture surfaces remained perfectly ductile and transgranular after helium implantation and no indication of grain boundary decohesion was detected. These results would reflect prominent resistance to the helium-embrittlement in this kind of steel and suggests their potential for future fusion applications.
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  • Yuhki Tsukada, Yoshinori Murata, Toshiyuki Koyama, Masahiko Morinaga
    2009 Volume 50 Issue 4 Pages 744-748
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Phase-field simulation is performed to examine the effect of elastic inhomogeneity between the γ and γ′ phases on microstructure evolution of the γ′ phase in Ni-based superalloys. For solving the elastic equilibrium equation numerically in the elastically inhomogeneous system, an iterative approach is used. In this simulation, both elastic anisotropy and shear modulus are varied independently based on the elastic constants of a practical Ni-based superalloy. Four different types of anti-phase domains in the γ′ phase are also considered in this simulation. The variation of elastic anisotropy affected significantly the manner of both morphology of the γ′ phase and distribution function of the γ′ particle size, whereas the variation of shear modulus did not affect them.
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  • Ting He, Jianlin Li, Lianjun Wang, Juanjuan Zhu, Wan Jiang
    2009 Volume 50 Issue 4 Pages 749-751
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Alumina/graphene composite powders were produced by ball milling alumina and graphite for different times. Transmission electron microscopy (TEM) was used to characterize the obtained powders. 3–4 nm graphene sheets were produced after 30 h milling time. Accelerative effect of alumina to ball milling was also studied. Graphene reinforced alumina-based composites were fabricated by spark plasma sintering (SPS) technique from as-prepared powders. Microstructural observation of fracture surface was conducted using scanning electron microscopy (SEM). It was found that adding graphene would hinder grain growth of alumina, making much finer particles.
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  • Jun-ichi Hamada, Kazuyuki Agata, Hirofumi Inoue
    2009 Volume 50 Issue 4 Pages 752-758
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Planar anisotropies of r-values are calculated from crystallite orientation distribution functions (ODFs) by using the Taylor theory. These values are compared with experimentally obtained values for two kinds of ferritic stainless steel sheets with different planar anisotropies of the r-values and different texture gradients in the thickness direction. Moreover, the most suitable model for predicting the r-value of ferritic stainless steel sheets is examined. For a material with a remarkable texture gradient in the thickness, the ODF in a particular plane perpendicular to the normal direction was unsuitable for predicting the planar anisotropy of the r-value. On the other hand, r-value calculated using the average ODF through sheet thickness measured in a section perpendicular to the transverse direction shows good agreement with the experimentally obtained. The relaxed-constraints model, in which the shear strain components e13 and e23, are relaxed with a CRSS ratio of 1.1 in the {211}⟨111⟩ and {110}⟨111⟩ slip systems is the most suitable model for predicting the planar anisotropy of the r-value in ferritic stainless steel sheets.
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  • Keitaro Horikawa, Hiroaki Okada, Hidetoshi Kobayashi, Wataru Urushihar ...
    2009 Volume 50 Issue 4 Pages 759-764
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
    JOURNALS FREE ACCESS
    Hydrogen diffusion behavior of low alloy steel was visualized by means of hydrogen microprint technique. Effects of exposure time and temperature on the availability of hydrogen microprint technique were also examined. It was found that silver particles, which representing the emission site of hydrogen atoms, were distributed almost uniformly in the matrix after hydrogen charging, and that were arranged at the periphery of second phase particles such as MnS and Al2O3. Area density of the silver particles was clearly increased when the exposure time after cathodic hydrogen charging increased at room temperature or the exposure temperature was higher than room temperature, which was in agreement with the result obtained from the thermal desorption analysis. From a series of the heating experiments, it was also shown that hydrogen microprint technique would be applicable at temperatures below 120°C. After the long time exposure in the hydrogen-charged specimens, preferential accumulation of silver particles around the Al2O3 and MnS particles was identified. This suggested that hydrogen atoms were diffused not through the inside of the second phase particles but through the interface between the second phase particles and matrix phase.
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  • Tianmo Liu, Jianzhong Liu, Liwei Lu, Yu Liu, Zhongchang Wang
    2009 Volume 50 Issue 4 Pages 765-770
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    We report microstructure evolution and mechanical properties of Mg alloy AZ31 processed by a new severe plastic deformation technique, the change-channel angular extrusion (CCAE). Under all of the processing temperatures ranging from 523 to 723 K, grains of the extruded Mg alloys are found to be refined significantly, which is attributed to the grain subdivision and dynamic recrystallization induced by the drastic deformation. We have also found that lowering processing temperature is a relevant factor in yielding finer grain, which as a consequence, gives rise to higher micro-hardness, larger yield and ultimate compressive strength, and more enhanced compressive ratio. The improved mechanical properties of the AZ31 alloys deformed by the CCAE are comparable or even superior to those of the alloys subjected to the equal-channel angular extrusion with several passes, rendering the CCAE an effective and promising approach to impose drastic plastic deformation for further enhancing workability of Mg alloys.
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  • Meng-Shan Tsai, Pei-Ling Sun, Po-We Kao, Chih-Pu Chang
    2009 Volume 50 Issue 4 Pages 771-775
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    Equal channel angular extrusion (ECAE) is applied to an age-hardening Al-Mg-Si alloy at temperatures where concurrent aging (dynamic aging) can occur to form fine β″-Mg2Si precipitates, and an ultrafine-grained matrix with high dislocation density can be maintained. This microstructure results in significant strength enhancement with little sacrifice in tensile ductility. The large plastic strain imposed by ECAE causes a fraction of the precipitates to dissolve into the aluminum matrix, which re-precipitate during subsequent aging treatment.
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  • Hidekazu Sueyoshi, Yuki Yamano, Kensuke Inoue, Yoshikazu Maeda, Kosaku ...
    2009 Volume 50 Issue 4 Pages 776-781
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    Microstructure, tensile properties and Vickers hardness of the copper sulfide (Cu2S)-dispersed bronze produced by adding MoS2 to molten bronze consisting of Cu and Sn were examined. The amount of Cu2S and the number of casting defects increase with the amount of added MoS2. The Vickers hardness of Cu2S-dispersed bronze increases with the amount of added MoS2. This is because the solid-solution hardening owing to Mo and the hardening due to the dispersion of Cu2S are superior to the softening due to casting defects. The tensile strength of Cu2S-dispersed bronze decreases with increasing amount of added MoS2. This is because the softening due to casting defects outweights the solid-solution hardening due to Mo and the strengthening due to the dispersion of Cu2S. The fracture elongation of Cu2S-dispersed bronze decreases with the amount of added MoS2. This is because the number of casting defects increases and Cu2S acts as a nucleus of voids. To produce Pb-free bronze having excellent machinability and mechanical properties equivalent to those of CAC406 containing Pb and CAC902 containing Bi, adequate control of the amount and size of Cu2S and the number of casting defects is of great importance.
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  • Yanhong Cai, Degang Zhao, Xueying Zhao, Lidong Chen, Wan Jiang, Pengch ...
    2009 Volume 50 Issue 4 Pages 782-790
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
    JOURNALS FREE ACCESS
    The temperature distribution and evolution of Mo/Ti/CoSb3 materials used as thermoelectric couples of devices during spark plasma sintering were simulated by finite element method, and the results agree well with the die interior temperature measured by thermocouple. The sample and punches have higher temperature in whole sintering process, the highest temperature region is existed in CoSb3 region, and the radial temperature gradient in CoSb3 region is obvious. It was confirmed by experiments that the temperature gradient in sample results in non-uniform microstructure and thermal conductivity difference. The temperature gradient increases with decreasing thermal conductivity and increasing electrical resistivity of CoSb3-based compound, from the point of view of the thermal conductivity and electrical resistivity, respectively, the optimization method of the combined mechanical property and thermoelectric property of CoSb3-based compound was proposed.
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  • Wencai Liu, Jie Dong, Ping Zhang, Chunquan Zhai, Wenjiang Ding
    2009 Volume 50 Issue 4 Pages 791-798
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    The effects of shot peening on surface characteristics and high cycle fatigue (HCF) performance of T5-treated high-strength magnesium alloy ZK60 (named after ZK60-T5) were investigated. The glass bead with an average diameter of 0.35 mm was adopted for shot peening and the Almen intensity was arranged from 0.02 to 0.40 mmN. The surface microstructure and texture of ZK60-T5 are greatly changed by shot peening, and residual compressive stress is produced in the surface deformation layer. The magnesium alloy ZK60-T5 shows a pronounced overpeening effect. A marked improvement in fatigue life is obtained at low Almen intensities, namely the fatigue strength (at 107 cycles) increases from 150 to 195 MPa at the optimum Almen intensity of 0.05 mmN. The fatigue crack nucleation site of ZK60-T5 is also found from surface regions to the subsurface.
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  • Vedarajan Raman, Toshiyasu Nishimura
    2009 Volume 50 Issue 4 Pages 799-805
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    To understand environmental factors in mortar, the Cl ion concentration and pH were monitored by inserting microelectrodes into artificial pores in the mortar. At the same time, the corrosion behavior of the reinforcing steel was investigated by EIS. In the EIS measurements of the reinforcing steel, Warburg impedance by diffusion was confirmed in the initial period, but it could no longer be observed after 35 days. In comparison with a 10 mm cover thickness, a 20 mm cover thickness showed a higher impedance behavior. The Cl ion concentration in the mortar was obtained using Ag/AgCl microelectrodes, showing that this behavior is generally controlled by diffusion. When the diffusion equation was used in this work, the diffusion coefficient (Dc) showed a high value of Dc=2×10−4 mm2/s. Similarly, the pH in the mortar was obtained using W/WOx microelectrodes. With a 20 mm cover thickness, pH was limited to approximately pH 11, but with a 10 mm cover thickness, pH continued to decrease to around pH 9.5. The latter phenomenon was considered to be the result of neutralization by penetration of the immersion solution from the surface. Based on the results of monitoring with the microelectrodes, solutions simulating those in the pores in mortar were prepared and used in EIS measurements. The charge transfer resistance Rct in the simulated solutions showed good correspondence with the impedance (Z2mHz) in the low frequency region (2 mHz) in the actual mortar. This is attributed to the fact that the corrosion of reinforcing steel was controlled by the solution conditions (mainly Cl concentration and pH) in the pores in mortar. If these solution conditions (Cl concentration, pH) exceed threshold values, it was found that the passivation film is destroyed, resulting in high corrosion.
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  • Sakiko Kawanishi, Takeshi Yoshikawa, Toshihiro Tanaka
    2009 Volume 50 Issue 4 Pages 806-813
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
    JOURNALS FREE ACCESS
    Fe-Si melt is a candidate for use as an alloy solvent for rapid liquid phase growth of SiC because of the high solubility of carbon in molten iron. In this work, the equilibrium phase relationship between SiC and the liquid phase of the Fe-Si-C system was studied to determine the optimal composition of a high SiC content solvent. The solubility of carbon in molten silicon was examined and the thermodynamic properties of the liquid phase in the Si-C system were reassessed. The phase relationship between SiC and Fe-Si melt was investigated by the equilibration technique at 1523–1723 K. It was found that Fe-36 mol% Si alloy equilibrates with SiC at the corresponding temperatures. The equilibrium phase relationship between SiC and various compositions of Fe-Si melts was studied by using thermodynamic calculations. The results indicated that SiC is far more soluble in iron-rich Fe-Si melt than in silicon-rich melt. The Fe-Si melt of Fe-36 mol% Si composition possessing high SiC solubility should be a suitable solvent for rapid liquid phase growth of SiC.
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  • Keiichiro Kashimura, Yoshiaki Kitayama, Kazuhiro Nagata
    2009 Volume 50 Issue 4 Pages 814-818
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    The transfer thermal plasma of argon (Ar) was deposited onto the surface of a Na2O-SiO2 molten slag at about 1200 to 1350°C, using a hybrid plasma furnace composed of transfer- and non-transfer plasma. Only the non-transfer plasma of Ar was deposited onto the slag, there was little vaporization of Na according to the thermodynamics. When the transfer plasma current was greater than 3 A, the amount of Na vaporized from the surface was seven times larger than the amount calculated by Faraday’s Law.
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  • T. Wadayama, H. Yoshida, S. Oda, N. Todoroki
    2009 Volume 50 Issue 4 Pages 819-824
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    This study investigates carbon monoxide (CO) adsorption and desorption behaviors on 0.1–0.6-nm-thick Cr-deposited Cu(100) surfaces using infrared reflection absorption (IRRAS) and temperature-programmed desorption (TPD) spectroscopic methods. The low-energy electron diffraction (LEED) pattern for the 0.1-nm-thick Cr-deposited Cu(100) surface indicates that distorted bcc-Cr(110) grows on fcc-Cu(100). The CO exposure to a clean Cu(100) at 90 K produces a single and sharp IR absorption band at 2090 cm−1 that is attributable to adsorbed CO on the on-top site of the Cu atoms’ on the surface. Two absorption bands are located at 2085 and 2105 cm−1 on the IRRAS spectrum for the CO-saturated 0.1-nm-thick Cr/Cu(110) surface. The former might originate from linearly bonded CO on the uncovered Cu substrate surface. With increasing Cr thickness, the latter high-frequency band becomes prominent. For the 0.3-nm-thick Cr surface, the band at 2117 cm−1 dominates all spectra through CO exposure. The TPD spectra of the Cr-deposited Cu surfaces show two remarkable features at 220–250 and 320–390 K, which are ascribable respectively to Cu-CO and Cr-CO bonds. Lower desorption peaks shift to higher temperatures with increasing Cr thickness. Based on TPD and IRRAS results, adsorption–desorption behaviors of CO on the Cr-deposited Cu(100) surfaces are discussed herein.
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  • Yoshimasa Noda, Akira Sato, Shogo Tobe, Masayuki Hara, Tsuginori Inaba
    2009 Volume 50 Issue 4 Pages 825-831
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    There are some problems for the environment and for the human body in a conventional blasting process when it is used for the pre-treatment of thermal spray. They are, for example, generation of noise and dust. One possible method to overcome these problems is a vacuum arc cleaning (VAC) process. It is possible for this technology to both surface cleaning and roughen surface. The VAC process is good for the environment as well as the human body, because this process takes place inside a chamber.
    In this study, the first aim is to establish the VAC process as the alternative of blasting, and the second aim is to develop ultra-high adhesive strength plasma spray coatings by employing blasting and the VAC process as the pre-treatment of plasma spray.
    The adhesive strength higher than 50 N/mm2 is achieved only by applying the VAC process as pre-treatment and higher than 90 N/mm2 is achieved by employing the VAC process after blasting.
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  • Kuk Hyun Song, Hidetoshi Fujii, Kazuhiro Nakata
    2009 Volume 50 Issue 4 Pages 832-836
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    To evaluate the dynamic recrystallization aspect and microstructures, electron back scattered diffraction (EBSD) analysis on friction stir welded Inconel 600 was employed. Friction stir welding (FSW) led to the dynamic recrystallization in all conditions as high angle grain boundaries were distributed more than 85% in fraction, with equiaxed grains, and the grain refinement was accelerated from average grain size of 19 μm in the base material to 3.4 μm in the stir zone by increasing the welding speed. Also, it increased microhardness by more than 20%, compared to base material microhardness, and the effect of grain size on the microhardness in the stir zones was satisfied with Hall-Petch relationship.
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  • Weizhi Luan, Chuanhai Jiang, Vincent Ji
    2009 Volume 50 Issue 4 Pages 837-840
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    The effect of stress peening on the surface layer characteristics of the TiB2/6351Al Composite including residual stress, microhardness and microstructures were investigated. The results show that the compressive residual stresses and microhardness were improved by stress peening. Microstructures investigation showed that, the deformation amount increased by stress peening which results in smaller domain size and higher density dislocations/microstrain. The more reinforcements distributed in the matrix played an important role in the compressive residual stresses increments and microstructures improvements. Stress peening is an effective method to improve the compressive residual stresses and the work-hardened state of the TiB2/6351Al Composite.
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  • Ryo Matsumoto, Michiaki Yamasaki, Masaaki Otsu, Yoshihito Kawamura
    2009 Volume 50 Issue 4 Pages 841-846
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    To develop a forging process for high strength Mg-Zn-Y alloys with a long period stacking ordered (LPSO) structure, the forgeability and flow stress of Mg97Zn1Y2 (at%) alloys were investigated with the upsettability test at an initial strain rate of 0.55 s−1. As-cast and extruded Mg97Zn1Y2 alloys can be successfully forged without fracture up to 0.5 and 1.0 respectively of average equivalent strain at a forging temperature of 773 K. To remove the influence of the temperature change during upsetting from the experimentally obtained flow stress curve, the isothermal flow stress curve was estimated by combining experimental results with finite element analysis. Furthermore, the mechanical properties of the forged Mg-Zn-Y alloys were measured, and the influence of microstructure on the forging properties was discussed.
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  • Hidekazu Sueyoshi, Kensuke Inoue, Yuki Yamano, Yoshikazu Maeda, Kosaku ...
    2009 Volume 50 Issue 4 Pages 847-852
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    Molybdenum sulfide (MoS2) was added to molten bronze consisting of Cu and Sn. Then, the machinability of the obtained bronze was examined from the viewpoints of cutting force, chip disposability and finished surface roughness. Copper sulfide (Cu2S)-dispersed bronze is produced by adding MoS2 to molten bronze. The dispersion of Cu2S reduces the coefficient of friction on the rake surface and increases the shear angle, resulting in a decrease in cutting force. The Cu2S-dispersed bronze has a good chip disposability because Cu2S acts as a chip breaker. The dispersion of Cu2S has no influence on the finished surface roughness. Thus, the Cu2S-dispersed bronze has an excellent machinability equivalent to those of CAC406 containing Pb and CAC902 containing Bi.
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  • Nittaya Keawprak, Rong Tu, Takashi Goto
    2009 Volume 50 Issue 4 Pages 853-858
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    Ca-Ir-O compounds in various molar ratios of Ir to Ca (RIr/Ca) from 0.2 to 1.2 were synthesized by solid-state reaction and compacted by spark plasma sintering (SPS). Ca4IrO6 and CaIrO3 with a small amount of second phase were obtained at RIr/Ca=0.25 and 1.0, respectively, whereas Ca2IrO4 in a single phase was obtained at RIr/Ca=0.5. The electrical conductivity was 4×10−4 to 150 Sm−1 at room temperature and exhibited a semiconducting behavior for all the samples. The Seebeck coefficient at RIr/Ca=0.4 to 0.7 showed negative values whereas samples with RIr/Ca=0.25 and 0.9 to 1.2 showed positive values. The thermal conductivity was 1.1 to 2.7 Wm−1K−1 at room temperature and slightly decreased with increasing temperature. The highest ZT value of p-type was 0.006 at 1023 K and RIr/Ca=1.1 and 1.2, while that of n-type was 0.0022 at 800 K and RIr/Ca=0.5.
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  • Masatoshi Takahashi, Masafumi Kikuchi, Osamu Okuno
    2009 Volume 50 Issue 4 Pages 859-863
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    The purpose of this study was to improve the grindability of titanium by alloying with zirconium. The grindability of dental cast Ti-Zr alloys (10, 20, 30, 40 and 50 mass% Zr) was evaluated using a carborundum wheel. The Ti-Zr alloys up to 30 mass% Zr formed an α structure, and the 40 mass% Zr and 50 mass% Zr alloys formed an α′ structure. The Ti-40 mass% Zr alloy at up to 1000 m/min and the Ti-50 mass% Zr alloy at up to 1250 m/min exhibited significantly higher grindability than titanium. More than twice the volume of metal was removed from the alloys than from titanium per minute. The improved grindability could be attributed to the α′ structure in addition to the decrease in elongation. The Ti-Zr alloys, which formed an α′ phase structure, are candidates for use as machinable biomaterial in dental applications.
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  • Wook Jin Lee, Bong Gyu Park, Ik Min Park, Yong Ho Park, Jeong Jung Oak ...
    2009 Volume 50 Issue 4 Pages 864-871
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
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    This paper presents the experimental and analytical investigation on the thermal fatigue fracture mechanism of Al18B4O33/Mg systems in the temperature range of 150–350°C. Three types of functionally graded Al18B4O33/Mg composites which consisted of 2, 3 and 4 layers and where volume fractions of Al18B4O33 were gradually changing from 0 to 35% were fabricated using graded preform and squeeze infiltration process. A simple quenching method of thermal shock test was used to simulate the operating state of the automotive composite cylinder liner system. On the other hand, thermal stress intensity factors in FGMs were obtained by the ANSYS finite element code. Through the study of the microstructure in thermal fatigue test, it was found that the thermally induced cracks appeared in two forms, vertical crack and interfacial crack. By the comparison between numerical and experimental results, the vertical cracks considered to be generated by the mode I stress intensity due to the coupled effect of thermal stress and temperature gradient in FGM systems. The depth of the vertical cracks may correspond to a location of mode I stress intensity being equal to the fracture strength of the FGMs. The interfacial cracks were fatigue cracks which were initiated and extended by thermal loads in mixed I and II mode. Both the mode I and II stress intensities were largely reduced with the number of FGM layer. As the stress intensity decreased, the thermal fatigue resistance of Al18B4O33/Mg system was clearly increased with the number of the layer.
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  • Takeshi Nagase, Koichi Kinoshita, Takayoshi Nakano, Yukichi Umakoshi
    2009 Volume 50 Issue 4 Pages 872-878
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 11, 2009
    JOURNALS FREE ACCESS
    Ti-Zr binary metallic wires without toxic elements were developed by an arc-melt-type melt-extraction method for potential application as biomedical materials. The Ti-Zr binary alloy showed high wire forming capability during the melt-extraction process, independent of the Ti concentration. Therefore, it was possible to form rapidly quenched wires using Ti100−xZrx (x=10 at% to 80 at%) alloys. Continuous binary Ti-Zr alloy wires had good white luster, negligible surface roughness, high tensile strength, and high bending ductility.
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  • Yong-Jai Kwon, Ichinori Shigematsu, Naobumi Saito
    2009 Volume 50 Issue 4 Pages 879-884
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: February 25, 2009
    JOURNALS FREE ACCESS
    The surface region of electric-discharge-machined aluminum foams was modified by the friction-surface-modifying and rolling (FSMR) process. A new surface was successfully obtained through the FSRM process, which was considerably smoother and denser than that of the unprocessed aluminum foam. In the FSMR process, the amount and morphology of the residual pores are mainly dominated in the surface of metallic foams by the friction surface modification (FSM) process stage. The smoothest surface, however, was formed for the friction-surface-modified (FSMRed) aluminum foam, which was attributed to the additional rolling process after the FSM process. This result demonstrates that the FSMR process is a very effective technology in controlling the surface morphology of the metallic foams through the cell structure control of the surface region. For the FSMRed aluminum foam, the highest average bonding strength, yield strength and toughness were obtained, which were nearly equivalent to 1.4, 2 and 1.6 times the values of the unprocessed aluminum foam, respectively. This result shows that, in the FSMR process, the additional rolling process after the FSM process is very effective in enhancing the bonding characteristics of the metallic foams by smoothening the surface. In addition, the above-mentioned bonding characteristics were remarkably increased with the decrease in the surface roughness, suggesting the surface morphology is a very important parameter in controlling the bonding characteristics of the metallic foams. The experimental results revealed that the FSRM process is a very effective technology for the improvement of the bonding characteristics of the metallic foams through the control in the surface morphology.
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  • Chung-Hung Tam, Shih-Chin Lee, Shih-Hsien Chang
    2009 Volume 50 Issue 4 Pages 885-890
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Commercial as-hp (hot pressing) and canning HIP (Hot Isostatic Pressing) treated Cr-Si targets are used throughout this study which with two different compositions: Cr35-Si65 and Cr50-Si50. To evaluate the effects of as-hp and canning treated Cr-Si targets by HIP process, SEM, XRD, microstructure and porosity inspections were performed. The experimental results show that the Canning HIP Cr35-Si65 targets had reduced the porosity about 40% compared with the as-hp ones, and the Cr50-Si50’s even decreased about 65% after HIP treatment. Both nitrogen and oxygen concentrations of the targets were also reduced after Canning HIP treatment. This was especially true for the single silicon in Cr-Si targets such as Cr35-Si65.
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  • En-Yu Wu, Keng-Liang Ou, Shih-Fu Ou, Klaus D. Jandt, Yung-Ning Pan
    2009 Volume 50 Issue 4 Pages 891-898
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 11, 2009
    JOURNALS FREE ACCESS
    In this study, the effect of O2-plasma treatment with various powers on the surface characteristics and also the cell response of the Ti-30Nb-1Fe-1Hf alloy were investigated. Surface characteristics of Ti-30Nb-1Fe-1Hf alloy were evaluated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray powder diffractometer (XRPD) and wettability test. The results show that the surface roughness of the alloy decreases after O2-plasma treatment, and also with increased plasma power. By XPS analyses, both Ti valence states of Ti2+, Ti3+ and Ti4+ as well as Nb valence states of Nb2+, Nb4+ and Nb5+ can be detected in the oxide films. Also, the concentrations of TiO2 and Nb2O5 increase with increasing O2-plasma power. The results also show that the contact angle decreases as the alloy is modified by O2-plasma treatment, and therefore, the treated alloys can be expected to be more hydrophilic. On the other hand, for the evaluation of cell response, cell (MG-63) culture was performed. The results show that the oxidation effect on the alloy surface brought about by O2-plasma treatment enhances the spreading of cells. In addition, in vitro tests suggest that cell spreading on Ti-30Nb-1Fe-1Hf alloy is similar to that on Ti-6Al-4V alloy, whereas, cell adhesion on Ti-30Nb-1Fe-1Hf alloy is better than that on Ti-6Al-4V alloy.
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  • Hwa-Teng Lee, Wen-Yeong Huang
    2009 Volume 50 Issue 4 Pages 899-908
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 11, 2009
    JOURNALS FREE ACCESS
    This paper examines the effects of the thermal storage time and Cu addition on the adhesive strength and microstructure of lead-free Sn-3.0 mass% Ag-1.5 mass% Sb-xCu solder joints. The experimental results show that the adhesive strength of the as-soldered specimens increases with increasing Cu addition and increasing strain rate. Meanwhile, for the aged specimens, the adhesive strength increases with increasing strain rate, but decreases with increasing storage time or with increasing Cu addition beyond 1.0 mass%. The microstructures and fracture morphologies of the solder specimens are analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The observations reveal that the Cu6Sn5 and Ag3Sn particles within the solder microstructure coarsen following high temperature storage and thus reduce the adhesive strength of the solder. Finally, it is found that the prolonged aged specimens with a Cu addition of 0.5 mass% or 1.0 mass% fracture in a combined brittle and ductile failure mode, while those with a Cu addition of 1.5 mass% fail as a result of cleavage after following 200 hours of thermal storage and a strain rate of over 1 s−1, but otherwise these fracture in a combined brittle and ductile failure mode.
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  • Shih-Hsien Chang
    2009 Volume 50 Issue 4 Pages 909-916
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    This paper discusses the effect of pressure and soaking time of HIP on 713LC cast superalloy. In this study, the HIP temperature was kept at 1453 K. Two different pressures, 150 and 175 MPa, were applied, and the soaking times were 2 and 4 h. The results of the experiment showed that the HIP treatment for 713LC superalloy at the temperature of 1453 K, pressure of 175 MPa, and soaking time of 2 h yielded the optimal results. Porosity was decreased to 60.3%. At fast strain rate (0.001 s−1), it increased the tensile strength by 8.8% at 298 K, 13% at 813 K, and 13.6% at 923 K. The elongation increased 32.9% at 298 K, 21.6% at 813 K, and 99.5% at 923 K in the tension tests. The treatment also increased the strength by 10% at 298 K and 17% at 813 K in the bending test. HIP treatment was proven to enhance the MC carbide precipitation on grain boundary, improve the grain size and the uniformity of size, and decrease the segregation phenomenon of 713LC casting.
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  • Sa-Woong Kim, Takahisa Shobu, Satoshi Ohtsuka, Takeji Kaito, Masaki In ...
    2009 Volume 50 Issue 4 Pages 917-921
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    Nanometer size oxide particles in 9Cr-ODS steel are dispersed finely and densely in a matrix by the hot-solidification process. The size and density distribution of dispersed oxide particles is recognized as one of the main issues for ensuring good microstructural stability and high temperature strength in a high temperature (<700°C) and neutron irradiation (250 dpa) environment. However, the behavior of oxide particles in the hot-solidification process has not been determined yet. This study evaluated the correlation between nano-size oxide particles and the heat treatment temperature and time in order to characterize the mechanism of formation and the behavior during growth and coalescence of these particles in 9Cr-ODS steel raw powder. XRD and SAXS measurements were made using high-energy synchrotron radiation X-rays in SPring-8. This is the first report of the oxide complex particles (Y2Ti2O7 and Y2TiO5) being formed from 800 to 960°C, and they were observed to grow and coalesce on increasing both heat-treatment temperature and time.
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  • K. J. Chen, F. Y. Hung, S. J. Chang, S. J. Young
    2009 Volume 50 Issue 4 Pages 922-925
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    ZnO thin films were prepared on a quartz substrate by sol-gel method and a UV photodetector was constructed on the ZnO thin films, with a circular spiral structure in contact with 30 nm IrO2 electrodes. The ZnO thin films were crystallized at various crystallized temperature (600∼700°C) for 1 hour in pure oxygen atmosphere, and were then analyzed by X-ray diffraction (XRD) and the scanning electron microscopy (SEM) to investigate the thin film crystallized structures. From photoluminescence (PL) and I-V measurement, the 650°C thin film not only possessed a better crystallization but also had nanopillar structures that revealed an excellent characteristic of UV photodetector.
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  • Sang Hun Lee, Jeom Yong Choi, Won Jong Nam
    2009 Volume 50 Issue 4 Pages 926-929
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 04, 2009
    JOURNALS FREE ACCESS
    The hardening behavior of a 304 stainless steel containing deformation-induced martensite during static strain ageing was investigated. Tensile strength increased with the increase of aging temperature. The results of DSC measurements showed that the aging mechanisms would be related to carbon diffusion to dislocations in α′-martensite and carbon diffusion in austenite. It is found that the increase of strength during strain aging would be attributed to hardening of austenite as well as α′-martensite.
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  • Tadayoshi Fujioka, Zenji Horita
    2009 Volume 50 Issue 4 Pages 930-933
    Published: April 01, 2009
    Released: March 25, 2009
    [Advance publication] Released: March 18, 2009
    JOURNALS FREE ACCESS
    A new processing technique, called in this study as high-pressure sliding (HPS), was developed as a process of severe plastic deformation (SPD). It is then demonstrated that HPS can be used for grain refinement of metallic sheets with a rectangular shape which was difficult with a conventional high-pressure torsion utilizing disk samples. Application of HPS to pure Al (99.99%) showed that the grain refinement is achieved with the extent similar to other SPD techniques.
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  • K. Oikawa, R. Saito, K. Anzai, H. Ishikawa, Y. Sutou, T. Omori, A. Yos ...
    2009 Volume 50 Issue 4 Pages 934-937
    Published: April 01, 2009
    Released: March 25, 2009
    JOURNALS FREE ACCESS
    Low-frequency elastic modulus, internal friction, tensile stress-strain loops, and thermally-induced strain recovery of single-crystal fibers obtained by pulling-down method from the melts of NiFeGaCo alloys were studied. A minimum of the elastic modulus and the maximum peak of the internal friction were obtained at the martensitic transition temperature. A large super-elastic strain of about 10% was obtained in the fiber of the Ni49Fe18Ga27Co6 alloy. Thermodynamic estimation by the Clausius-Clapeyron equation was consistent with the experimental results.
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