MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 53 , Issue 11
Showing 1-42 articles out of 42 articles from the selected issue
  • P. G. Xu, K. Akita, H. Suzuki, N. Metoki, A. Moriai
    2012 Volume 53 Issue 11 Pages 1831-1836
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: July 11, 2012
    JOURNALS FREE ACCESS
    Different from electron back-scattering diffraction and X-ray diffraction, neutron diffraction enables to directly measure the bulk texture because of the high penetrability and the large spot size of neutron beam and easily investigate the preferred orientation distributions of multiphase materials, coarse-grained materials and low symmetric materials including hexagonal metals, ceramics and rocks. In this paper, the texture measurement technical environments of two angle dispersive neutron diffractometers were established and optimized respectively, and their reliabilities were quantitatively examined through evaluating the bulk textures of a warm-pressed magnesium alloy and a multilayered multiphase steel sheet. It is found that the MUSASI-L neutron diffractometer with a single tube detector through selecting the proper collimation angle may achieve the similar texture evaluation reliability to the RESA-2 neutron diffractometer with one-dimensional position-sensitive detector, so that both of them are available to directly measure the bulk textures of various materials. In addition, the estimation of thermal neutron absorption shows that if a measurement error about 5–8% is acceptable, a cubic sample or a cylinder samples whose diameters is equal to its height may be employed to directly measure its bulk texture through completely bathing it in the well-collimated uniform neutron beam without doing the correction of neutron absorption anisotropy.
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  • Toshiharu Morimoto, Fuyuki Yoshida, Yuji Kusumoto, Masahiko Oda, Jun Y ...
    2012 Volume 53 Issue 11 Pages 1837-1846
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    The ridging phenomenon of type 430 stainless-steel originates from the texture due to crystal plasticity anisotropy. Thus, to predict the antiridging property, we must continuously analyze the hot-rolling, hot-rolling and annealing, cold-rolling, cold-rolling and annealing textures. However, it has been previously difficult to analyze the recrystallization texture. We thus developed a model to predict the recrystallization texture coupled with the Taylor rolling model. Furthermore, the ridging index was calculated in order to estimate the plasticity in type 430 stainless-steels. The plasticity prediction method was applied to type 430 stainless-steel strips rolled at a low temperature with a high reduction rate in an actual tandem hot strip mill.
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  • Hiroshi Kaneko, Tatsuhiko Eguchi
    2012 Volume 53 Issue 11 Pages 1847-1851
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The influence of texture on the bendability in Cu–Ni–Si alloys was examined by using an age-hardened polycrystalline strip with various recrystallization textures. In multiple samples manufactured by adjusting conditions of rolling and heat treatment, the Cube orientation {100}<001>, the RD-rotated Cube orientation {012}<100>, the BR orientation {362}<853> and the R(S) orientation {231}<346>, which are the representative recrystallization textures of FCC metals, developed up to 40% in respective area fractions. The bendability was clearly dependent on texture. The sample that had a strongly developed Cube orientation showed the best bendability with respect to both the good and bad ways (GW, BW) in bending. In comparison, the samples in which the BR and the R orientations developed showed poor GW bendability. The sample having a comparably random orientation showed poor GW and BW bendability. The shape of the cracks generated by bending was linear, and these cracks developed in a direction about 40 degrees from the surface. Further, they developed along shear bands, and this result was confirmed by the EBSD measurement. Therefore, the cause of cracking resulting from bending was shear bands. The correlation between the good bendability and a low average Taylor factor was confirmed. More uniform deformation by crystalline slips through texture control was effective for restraining the shear bands, i.e., for obtaining excellent bendability.
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  • Hiroki Tanaka, Shingo Ikawa
    2012 Volume 53 Issue 11 Pages 1852-1857
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    It is known in aluminum alloy sheets that two ears on a cup formed by deep drawing in 0 and 180° to the rolling direction may grow up by cold rolling. In the previous reports, Goss and RD rotated cube textures were fingered as the cause of the 0°/180° earing. But the growth process of the 0°/180° earing is not clear. In the present work, texture analysis has been carried out in cold rolling process with AA 6016 aluminum alloy sheets that have a strong cube texture through the thickness and weak Goss texture at the center layer. RD rotated cube texture is formed at the surface layer by cold rolling whereas cube texture at the center layer decreases rapidly. It is indicated that RD rotated cube texture at the surface layer and persisting Goss texture at the center layer cause high 0°/180° earing. These texture factors are discussed by a crystal plasticity finite element analysis. The calculated earing profiles derived by the finite element analysis show much the same patterns of experimental earing profiles.
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  • Yohei Wadamori, Kentoku Hirayama, Hiroshi Fujiwara, Toshiyuki Uenoya, ...
    2012 Volume 53 Issue 11 Pages 1858-1862
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: July 25, 2012
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    Grain boundaries can change their misorientation by absorbing lattice dislocations at relatively high temperature under moderate straining. The same phenomenon is believed to occur during severe plastic deformation down to room temperature leaving grain boundaries in the nonequilibrium state. Direct evidence of misorientation change of the grain boundary during severe plastic deformation was obtained in copper bicrystals subjected to equal-channel angular pressing (ECAP) for one pass. Marked dependence of misorientaion change on the initial orientation was revealed, and is associated with the unique slip patterns of ECAP, where the shear deformation is restricted to the narrow zone parallel to the intersecting plane of the two channels. The degree of change can be related to slip geometry in terms of grain boundary plane orientation.
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  • Ehsan Borhani, Hamidreza Jafarian, Akinobu Shibata, Nobuhiro Tsuji
    2012 Volume 53 Issue 11 Pages 1863-1869
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 17, 2012
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    Evolution of textures in the solution treated and aged Al–0.2Sc alloy heavily deformed by ARB process and subsequently annealed was investigated using pole figure and orientation distribution functions (ODF) that were determined by electron backscatter diffraction (EBSD) technique. Three kinds of starting materials were prepared before the ARB process: solution treated (ST) material, 300°C-aged material including fine Al3Sc precipitates, and 400°C-aged material having coarse Al3Sc precipitates. The results of deformation texture indicated that at early stage of ARB S {123} <634> orientation component developed and it changed to Copper {112} <111> and Taylor {4 4 11} <11 11 8> components at later ARB cycles in both ST-ARB and Aged-ARB specimens. However, in the Aged-ARB specimens after 5-cycle ARB process, Copper {112} <111> component decreased and Taylor {4 4 11} <11 11 8> component did not developed. Cube {100} <001> component strongly developed in the 400°C Aged-ARB specimen by annealing at high temperature, whereas Cube component did not develop in the ST-ARB and 300°C Aged-ARB specimen. Such a difference was understood as the effect of Al3Sc precipitates.
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  • Jinuk Kim, Kazuto Okayasu, Hiroshi Fukutomi
    2012 Volume 53 Issue 11 Pages 1870-1875
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 17, 2012
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    The formation behavior of textures during high temperature plane strain compression deformation is experimentally studied on AZ80 magnesium alloy. Three kinds of specimens with different initial textures are prepared from the extruded bars having a <10\bar{1}0> fiber texture. Plane strain compression is conducted at 723 K, 5.0 × 10−2 s−1 and strains ranging from −0.4 to −1.0. New grains appeared after the deformation up to −0.4 in true strain. Initial texture gradually changes with increasing strain. After the deformation up to −1.0 in true strain, (0001)<10\bar{1}0>, {11\bar{2}0}<10\bar{1}0>, (0001)<11\bar{2}0> and {10\bar{1}0}<0001> appeared depending on the initial texture. (0001)<10\bar{1}0> and {11\bar{2}0}<10\bar{1}0> are formed irrespective of the initial texture. Simple crystallographic examination showed that all the texture components are orientations stable for the plane strain compression.
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  • Yong Choi, Hirofumi Inoue
    2012 Volume 53 Issue 11 Pages 1876-1880
    Published: November 01, 2012
    Released: October 25, 2012
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    Thin nickel sheets were fabricated by electroforming, and cold rolled to improve their strength. The thin nickel sheets have very fine grains with a {001}<uv0> fiber texture. Cold rolling results in evolving a {001}<110> orientation and the formation of a weak {111}<uvw> fiber component. Micro-hardness of the nickel sheet on the surface normal to the normal direction (ND) was increased from 247.8 to 354.4 Hv by cold rolling with 87.5% reduction. The corrosion potential and corrosion rate of the nickel sheet in artificial sea water were in the ranges of −27 to −12 mVSCE and 4.2 × 10−7–1.8 × 10−6 A cm−2, respectively. The change in corrosion behavior with cold rolling on the surface normal to ND has little relation to crystallographic texture because of a stable {001} texture during rolling, unlike nickel bulk samples.
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  • Yuki Tokumoto, Hyun-Jae Lee, Yutaka Ohno, Takafumi Yao, Ichiro Yonenag ...
    2012 Volume 53 Issue 11 Pages 1881-1884
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: September 05, 2012
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    Annealed low-temperature GaN layers grown on r-plane sapphire substrates were examined by X-ray diffraction pole figure measurements. The GaN layers were mainly a-plane oriented, in which misoriented grains with four different orientations were detected. The c-axes of the misoriented grains are tilted from the surface normal by about 35°, which are along the bonds not parallel to the c-axis of the a-plane oriented layers. There was a difference among the peak intensities corresponding to the c-planes of the misoriented grains with the four different orientations. Considering the difference, the relative amount of misoriented grains with each orientation can be predicted. The evolution of the misoriented grains is expected to be controlled by the major polarity.
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  • Masaomi Nishimura, Yosuke Iwasaki, Masahiro Arai
    2012 Volume 53 Issue 11 Pages 1885-1891
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    We have attempted to reveal the deformation mechanism of amorphous metals by local lattice instability analysis, based on the positive definiteness of the atomic elastic stiffness coefficients, Bijα. In our previous study, changes in inhomogeneous structure are explained by the observation of the stability-switching or transition between detBijα > 0 and detBijα < 0. In this study, we have performed the indentation simulation on a binary amorphous metal, and discussed the inelastic deformation in the amorphous metal by Voronoi polyhedra analysis and the stability-switching of local lattice instability. The indentation simulation predicts that rearrangements of atoms occur not only on structures below the indentation point but also inside the amorphous metal structure. These structural changes produce a significant volume change in the Voronoi polyhedra, the stability-switching based on local lattice instability analysis, and a local volume reduction evaluated within scales of a few hundred atoms.
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  • Ping Wang, Dong-yan Liu, Dong-sheng Li
    2012 Volume 53 Issue 11 Pages 1892-1895
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    We report the nanostructures and gas-sensing properties of Zinc oxide nanosheets prepared by hydrothermal method. In particular, needle-like Zinc oxide was also prepared for comparison. The morphology and structural properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Subsequent gas-sensing measurement between Zinc oxide nanosheets and Zinc oxide nanoaciculars indicated that the nanosheets exhibited higher gas response to ethanol. The enhanced gas sensing properties of Zinc oxide nanosheets suggests that governing the shape and the surface structure of nano Zinc oxide is a significant approach for developing high performance gas sensors.
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  • Masanori Kajihara
    2012 Volume 53 Issue 11 Pages 1896-1904
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 03, 2012
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    If a binary Fe–C alloy with a single-phase microstructure of the austenitic γ phase is isothermally annealed in an appropriate decarburization atmosphere, a layer of the ferritic α phase is formed on the surface of the γ phase and gradually grows into the γ phase. The kinetics for the growth of the α layer during the decarburization was quantitatively analyzed using a diffusion model at annealing temperatures between 1011 and 1185 K. In the analysis, the diffusion coefficient of C in each phase is considered independent of the chemical composition. According to the model, the square of the thickness l of the α layer is proportional to the annealing time t as described by the relationship l2 = Kt. This relationship is called the parabolic relationship. As the initial concentration xγ0 of C in the γ phase increases from the minimum value to the maximum value for the γ single-phase region at each annealing temperature T, the parabolic coefficient K monotonically decreases from the maximum value Kdmax to the minimum value Kdmin. As T decreases, Kdmax decreases, but Kdmin increases. However, both Kdmax and Kdmin vary depending on T in a complicated manner. Thus, an Arrhenius equation is not applicable even to the temperature dependence of Kdmax in the whole annealing temperature range. At a constant value of xγ0, K monotonically decreases with increasing value of T. This means that the growth of the α layer takes place faster at lower annealing temperatures than at higher annealing temperatures. Such temperature dependence of the kinetics coincides well with experimental observations.
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  • Elzbieta A. Pieczyska, Hisaaki Tobushi, Karol Kulasinski, Kohei Takeda
    2012 Volume 53 Issue 11 Pages 1905-1909
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    In this study, the thermomechanical coupling effects accompanying stress-induced martensitic transformation in TiNi shape memory alloy subjected to compression test were investigated. The mechanical characteristics were elaborated and the temperature changes related to the exothermic martensitic forward transformation and the endothermic reverse one were measured in a contactless manner by a fast and sensitive infrared camera. The obtained temperature changes of the specimen depend on the strain rate applied. At higher strain rate, greater temperature changes were observed, because the heat flow to the surroundings was lower and the process was closer to adiabatic conditions. The temperature changes of the shape memory alloy significantly influence its stress–strain characteristics. Moreover, the energy dissipated during a compression cycle was calculated for various strain rates. The study revealed that both the loading work and recoverable strain energy increase with increasing strain rate, while the dissipated energy fraction decreases.
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  • Yongjun Zhang, Jianguo Li
    2012 Volume 53 Issue 11 Pages 1910-1914
    Published: November 01, 2012
    Released: October 25, 2012
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    The microstructure evolution and microsegregation behavior of alloying elements in a Ni-based superalloy at a series of growth rates under super-high thermal gradient directional solidification were quantitatively characterized. Both microstructure and dendritic segregation are functions of growth rate. The high growth rate solidification leads to refinement in primary (λ1) and secondary (λ2) dendrite arm, decreased size of γ/γ′ eutectics and γ′ phase, as well as reduced microsegregation degree of alloying elements. Also with the growth rate increased, the morphology of γ′ precipitates changes from irregular shape to a cuboidal one. The electron probe microanalysis (EPMA) reveals that Cr, Mo and γ′ forming elements (Al, Ta and Nb) all partition to interdendritic region, while W and Re both preferably segregate to dendrite core. Thus at fast growth rates (or high cooling rates), finer dendrites, uniformly coherently cuboidal γ′ precipitates and decreased segregation favorable to the performance of superalloys are obtained. These quantitative results provide a basis for the establishment of cast and heat treatment process.
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  • Minwoo Kang, Minsu Jung, Hyongjik Lee, Young-Kook Lee
    2012 Volume 53 Issue 11 Pages 1915-1921
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The effects of a slow heating rate and a long austenitizing time with various cooling rates on the carbide dissolution and phase transformations of a 5% Cr work roll steel was investigated based on actual austenitization and quenching conditions and a large roll size using transmission and scanning electron microscopy, dilatometry, and thermodynamic calculations. When the roll temperature reached the austenitization temperature of 1173 K, the dissolution of pre-existing carbides was nearly complete due to the slow heating rate of 100 K/h, indicating that the austenite matrix had an equilibrium chemical composition at 1173 K before quenching. After quenching at cooling rates ranging from 0.1 to 3.0 K·s−1 along the radial direction of the roll, the core of the roll contained ferrite, pearlite, bainite and undissolved carbides, while the surface consisted of martensite and undissolved carbides.
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  • Lin Zhang, Xuanhui Qu, Mingli Qin, Rafi-ud-din, Xinbo He, Ye Liu, Dan ...
    2012 Volume 53 Issue 11 Pages 1922-1928
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    Co–Ni–Al–W-base alloy, strengthened by nanosized oxide and γ′ precipitate is a novel type of high-temperature structural material. The microstructural evolution of the alloys during heat treatment was investigated, and the γ–γ′ misfit and the coarsening kinetics of γ′ precipitate were discussed. The alloys consisted of γ/γ′ two-phase region, discontinuously formed area and several secondary phases (AlxCo, Co3W and Co7W6). An increase in the solution temperature and Ni contents favored the precipitation of γ′ phase due to the enhanced solid solubility of Al and W in cobalt matrix. The ordered arrangement of near cuboidal γ′ precipitates was observed, and the γ–γ′ misfit was calculated to be 0.57%. The coarsening kinetics of γ′ precipitates conformed to the L-S-W model. The Arrhenius analysis yielded the activation energy of 188 KJ·mol−1.
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  • Yuichiro Kurokawa, Takehiko Hihara, Kenji Sumiyama
    2012 Volume 53 Issue 11 Pages 1929-1932
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    Sn1−x/Six cluster assembled films have been prepared by a plasma-gas-condensation cluster beam deposition apparatus. Transmission electron microscope images indicate that individual clusters have core–shell morphology, where Sn cores are covered by Si shells. Temperature dependence of electrical resistivity exhibits a metallic behavior and a superconducting transition at low temperature for 0 < x < 0.20, while a semiconductor-type behavior and no superconductivity down to 2 K for x > 0.29. These results indicate that the cluster network and/or core–shell morphology Sn1−x/Six cluster assembled films changes with x.
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  • Masashi Yoshida, Takafumi Yumitate
    2012 Volume 53 Issue 11 Pages 1933-1937
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: September 26, 2012
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    Composites of TiB2-tetragonal Al3Ti and TiB2-cubic (Al,Ni)3Ti have been fabricated using spark plasma sintering method at the temperature between 1173 and 1573 K. When TiB2–(Al,Ni)3Ti specimens were sintered between 1273 and 1373 K, (Al,Ni)3Ti filled in space between TiB2 grains and dense samples were obtained. On the other hand, when TiB2–(Al,Ni)3Ti specimens were sintered at above 1473 K, (Al,Ni)3Ti evaporated and monolithic TiB2 were obtained. A similar results have been obtained for the TiB2–Al3Ti composites. The highest bending strength of TiB2–(Al,Ni)3Ti specimens were 660 MPa obtained for TiB2–30 mass%(Al,Ni)3Ti sintered at 1373 K. The highest bending strength of TiB2–Al3Ti composites were 610 MPa obtained for TiB2–30 mass%Al3Ti sintered at 1473 K. The Vickers hardness of TiB2–(Al,Ni)3Ti composites increased as the sintering temperature increased and the maximum value of 2100 Hv were obtained by the sintering at 1573 K.
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  • Tatsuro Morita, Hidemasa Nakaguchi, Syo Noda, Chuji Kagaya
    2012 Volume 53 Issue 11 Pages 1938-1945
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    This study investigated the effects of fine particle bombarding (FPB) on the surface characteristics and fatigue strength of commercial pure titanium. For comparison, conventional shot peening (SP) was also performed. The surface microstructure was nano-crystallized by FPB and SP. The grain size of nano-crystals reduced with decreasing particle diameter or increasing air pressure for accelerating particles. The surface hardness and compressive residual stress markedly increased by FPB. The surface layers were uniformly generated along the surface, and effectively suppressed the initiation of fatigue cracks. As a result, the fatigue strength greatly increased. Since the surface layers acted as a barrier to subsurface cracks, its improvement ratio was closely related to the surface characteristics.
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  • Hiroaki Nakano, Shingo Arakawa, Yuya Takada, Satoshi Oue, Shigeo Kobay ...
    2012 Volume 53 Issue 11 Pages 1946-1951
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    Electrodeposition behavior of Zn–Ni alloys was investigated at current densities of 10–500 A·m−2 and a charge of 5 × 104 C·m−2 in an unagitated zincate solution containing triethanolamine, which forms a stable complex with Ni2+ ions at 308 K. At low current densities, the Zn–Ni alloy exhibited normal codeposition, wherein electrochemically more noble Ni deposited preferentially, while at high current densities, it exhibited anomalous codeposition, wherein less noble Zn deposited preferentially. Ni deposition and H2 evolution were significantly suppressed in the region of anomalous codeposition at higher current densities, showing the formation of an inhibitor for deposition, which results from Zn2+ ions in the cathode layer. In contrast, in the region of normal codeposition at lower current densities, the underpotential deposition of Zn apparently occurred with Ni. Because Zn–Ni alloys are composed of a stable intermetallic compound of Ni5Zn21, the activity coefficient of Zn in the deposit appears to decrease remarkably.
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  • Koichi Imagawa, Hidetoshi Fujii, Yoshiaki Morisada, Yasufumi Yamaguchi ...
    2012 Volume 53 Issue 11 Pages 1952-1955
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: September 26, 2012
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    The authors clarified that various cast irons can be hardened by friction stir processing (FSP) in a previous study. However, the high applied tool load was indispensable for obtaining the hardened layer. In this study, the effect of the tool geometry on the applied tool load was investigated for forming the hardened layer by the FSP with a lower applied tool load. As a result, the applied tool load could be reduced by 36% using a concave tool.
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  • Dai Yamamoto, Takanori Iida, Kazushi Arii, Kensuke Kuroda, Ryoichi Ich ...
    2012 Volume 53 Issue 11 Pages 1956-1961
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    Surface hydrophilicity is considered to have a strong influence on the biological reactions of bone substituting materials. However, the relationship between hydrophilicity and osteoconductivity has not been discussed quantitatively. In this study, Ti substrates were coated with TiO2 having different water contact angles, using anodizing in aqueous solutions containing different types of solute ion, and the quantitative relationship between hydrophilicity and osteoconductivity was investigated.
    All of the anodized coatings were anatase-type TiO2 with a fine surface roughness. Most of the solute ions were included in the coatings, but they did not influence the hydrophilicity of the anodized coatings. However, the surface hydrophilicity of the anodized coatings depended on the pH of the aqueous solution. The amount of hard tissue formed on TiO2-coated specimens (denoted as RB-I) depended on the water contact angle on their surface. For water contact angle between 20 (deg.) and 55 (deg.), the value of RB-I increased as water contact angle decreased. On the other hand, for water contact angle between 55 (deg.) and 70 (deg.), the value of RB-I increased as water contact angle increased.
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  • Hiroyuki Nakayama, Kenta Takagi, Kimihiro Ozaki, Keizo Kobayashi
    2012 Volume 53 Issue 11 Pages 1962-1966
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 03, 2012
    JOURNALS FREE ACCESS
    The consolidation of Sm2Fe17N3 powder was examined by pulsed current sintering below its decomposition temperature. Although decomposition of the powder was not observed, its coercivity decreased dramatically. Annealed powder was observed by transmission electron microscopy in order to clarify the mechanism for the reduction in the coercivity. In powder annealed at 673 K, a thin nanostructured layer was formed around the Sm2Fe17N3 particles. The crystal structure of this thin layer had a crystallographic symmetry higher than that of the Sm2Fe17N3 structure. This higher symmetry layer appeared to have a smaller magnetic anisotropic energy, allowing it to act as a nucleation site for a reverse magnetic domain, when a reverse magnetic field is applied to the magnetized powder. Therefore, the coercivity of the powder decreased below its decomposition temperature. Irregular growth of the thin layer was observed in powder annealed above the decomposition temperature, and the grown region was confirmed to be an iron phase.
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  • Togo Fukada, Masashi Matsuura, Ryota Goto, Nobuki Tezuka, Satoshi Sugi ...
    2012 Volume 53 Issue 11 Pages 1967-1971
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 03, 2012
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    The relationship between coercivity and the microstructural parameters α and Neff for grain refined Nd–Fe–B sintered magnets was examined. The parameter α describes the effect of grain misalignment and a decrease in the magnetocrystalline anisotropy of the Nd2Fe14B grains on the coercivity. The parameter Neff describes the influence of the demagnetizing field on the coercivity. These parameters were evaluated for Nd–Fe–B sintered magnets with three different grain sizes and the same composition. Neff decreased with grain refinement, while α varied only slightly with grain size. This implies that the decrease in the demagnetizing field increased the coercivity through grain refinement. Grain shape and asperity were then evaluated by the aspect ratio, angle of the grain to the direction of magnetization, and reverse circularity. Although the aspect ratio and angle of the grains were not related to the changes in Neff, variation of the average reverse circularity corresponded to the changes in Neff with grain refinement. Therefore, improving the asperity should increase the coercivity through grain refinement.
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  • Gong-An Lan, Truan-Sheng Lui, Li-Hui Chen
    2012 Volume 53 Issue 11 Pages 1972-1975
    Published: November 01, 2012
    Released: October 25, 2012
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    Electric current-induced liquation feature of cast pure β-tin under alternating current (AC) was investigated in this study. According to the experimental results, the initial fusion emerges from grain interior. Since the fusion paths traverse the grain boundaries preferentially in a high-angle manner, their track inside a grain tends to be curved and thus longer than the grain size. Continued electrification leads fusion paths to form network-like interconnected fusion structure with most triple junctions residing within grain interior. Lateral thickening of the interconnected fusion paths leads to final failure. The result that the network-like fusion structure is rather equiaxed can eliminate the effect of crystal anisotropy on the fusion behavior if it exists.
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  • Donghun Kim, Ken Kurosaki, Yuji Ohishi, Hiroaki Muta, Shinsuke Yamanak ...
    2012 Volume 53 Issue 11 Pages 1976-1980
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 17, 2012
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    InSb is known to be a good candidate as a thermoelectric (TE) material owing to its high carrier mobility and narrow band gap of around 0.18 eV. However, a high ZT value has not been achieved in InSb because of its high lattice thermal conductivity (κlat). In order to reduce the κlat of InSb, In3+ ions in InSb were partly replaced by Zn2+ and Ge4+ ions to form the ZnIn18GeSb20 alloy. Polycrystalline samples of ZnIn18GeSb20 were prepared by a powder metallurgy process combining mechanical alloying and hot pressing followed by water quenching or slow cooling. The TE properties of the quenched and slow-cooled samples were examined over the temperature range of room temperature to 723 K. The κlat values of the quenched and slow-cooled samples at room temperature were 2.70 and 2.83 W m−1 K−1, respectively. These values were approximately 6 times lower than that of InSb, presumably due to grain refinement through MA and effective alloy scattering from the multi-component system. The present study confirmed that the relatively large secondary phase would played an important role for the decreased the thermal conductivity in the Zn–In–Ge–Sb system unlike the AgPbmSbTem+2 (LAST-m) system, in which nano-sized Ag–Sb inclusion are embedded in the PbTe matrix.
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  • Hiroyuki Tada, Tokujiro Yamamoto, Xinmin Wang, Hidemi Kato
    2012 Volume 53 Issue 11 Pages 1981-1985
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The effect of Al content on superelastic properties of Ti75−xNb15Zr10Alx (x = 0–6 at%) quaternary β Ti alloys were investigated. And the effects of baking for coating or plating on superelastic properties were also studied. The alloys containing 3 and 4 at% of Al clearly exhibited superelastic behavior after aging at 453 and 553 K, which are appropriate temperatures for industrial coating and plating, respectively. Ti72Nb15Zr10Al3 alloy exhibited the largest recovery strain of 2.5% due to superelastic behavior even after industrial coating and plating. In this quaternary alloy system, strange non-monotonical change of superelastic behavior as a function of Al content was also found.
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  • Namil Um, Tetsuji Hirato
    2012 Volume 53 Issue 11 Pages 1986-1991
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The conversion of cerium (IV) oxide into cerium (IV) sulfate in sulfuric acid solutions was studied in a batch-type glass reactor under atmospheric pressure. The effects of agitation speed, acid concentration, reaction temperature, initial amount of cerium (IV) oxide per sulfuric acid solutions (C/S), and particle size on the conversion process were investigated. All experiments were carried out in the range of 8–14 mol/dm3 for sulfuric acid concentration, 105–135°C for reaction temperature, 0.04–0.28 mol/dm3 for C/S, and 2.5–112.5 µm for average particle size. The conversion process involves the dissolution of cerium (IV) oxide and the precipitation of cerium (IV) sulfate. Cerium (IV) oxide reacted with sulfuric acid very slowly and then dissolved cerium (IV) in a saturated condition directly formed cerium (IV) sulfate indicating that the conversion rate was controlled by the dissolution rate of cerium (IV) oxide. Increases in sulfuric acid concentration and reaction temperature increased the dissolution rate, whereas increase in particle size decreased it. However, the C/S had no effect on the dissolution rate. In terms of the yield of precipitated cerium (IV) sulfate after reaction equilibrium, increases in sulfuric acid concentration and C/S increased the yield. However, the particle size and the reaction temperature had no effect on the yield of precipitated cerium (IV) sulfate. The kinetics of cerium (IV) oxide dissolution, under various conditions of sulfuric acid concentration, reaction temperature, C/S, and particle size, was interpreted by a shrinking core model with chemical reaction. The variation of rate constant upon dissolution with temperature obeyed the Arrhenius equation with an activation energy of 123 kJ/mol.
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  • Namil Um, Tetsuji Hirato
    2012 Volume 53 Issue 11 Pages 1992-1996
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The conversion of cerium oxide (CeO2) into sodium cerium sulfate (NaCe(SO4)2·H2O) in Na2SO4–H2SO4–H2O solutions was studied at elevated temperatures using a batch-type glass reactor under atmospheric pressure. Sodium sulfate (Na2SO4) concentration, sulfuric acid (H2SO4) concentration and reaction temperature were chosen as dependent variables, and the effects of these three variables on the conversion of cerium oxide into sodium cerium sulfate in Na2SO4–H2SO4–H2O solutions were investigated. The conversion includes two chemical reactions: cerium oxide dissolution and sodium cerium sulfate synthesis. The experimental data showed that increases of sodium sulfate concentration and sulfuric acid concentration decreased the conversion rate, whereas the conversion rate increased with increasing reaction temperature. The conversion kinetics of cerium oxide into sodium cerium sulfate for these three variables was analyzed and the fitted equation to the experimental data was determined. The variations of rate constant in dissolution and synthesis with temperature obeyed the Arrhenius equation with activation energies of 120 and 200 kJ/mol, respectively. In addition, the rate constant of cerium oxide dissolution was a function of the sodium sulfate concentration and sulfuric acid concentration at N−0.3 and C6.5, respectively, and for sodium cerium oxide synthesis at N−0.2 and C−4.3.
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  • Chiharu Tokoro, Yutaro Yamaoka, Sei Yuki, Tomohiro Shiozawa, Shuji Owa ...
    2012 Volume 53 Issue 11 Pages 1997-2003
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    The effects of attrition on sandy and silty Pb-contaminated soil from shooting ranges were quantitatively investigated. The abrasion rate could be quantitatively evaluated using a population balance model from the size distribution of soil particles before and after attrition in an intensive mixer. The maximum abrasion rate was 0.047 µm/s in the first stage of attrition (1 min of grinding), and then declined between 2 and 4 min of grinding. The two samples had similar maximum abrasion rates, but the decline in the abrasion rate was larger in the silty soil, which would have a thinner soft layer on the surface of the soil particles, than the sandy soil. The incremental change in the mass fraction of Pb in the <20 µm particle size fraction increased proportionally with the abrasion thickness from the surface of the soil particles. Although the Japanese regulatory standard for the Pb concentration in soil (150 mg/kg) was not met for either sample, the Japanese regulatory standard for the concentration of leached Pb (0.01 mg/L) was met for silty soil after attrition. Sequential extraction using Tessier’s procedure for the >20 µm size fraction before and after attrition showed the attrition was more effective for the oxides or organic-bound species and carbonate species of Pb chemical forms.
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  • Sradhanjali Singh, Bansi Dar Nayak, Rama Chandra Mohanty, Swaranjit S. ...
    2012 Volume 53 Issue 11 Pages 2004-2010
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
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    Malanjkhand copper project, Madhya Pradesh, India, generates a lot of lean sulphidic ores containing chalcopyrite (∼0.3% of copper) with traces of oxidized, semi-oxidized and secondary sulfides. EPMA analysis shows that the granitic rock samples have plagioclase feldspar, orthoclase feldspar and quartz as major constituents within which the ore minerals are sparsely distributed. Due to the complex structure and low solubility of the sulphide-bearing granitic rock, the dissolution of copper from the hard matrix is difficult. The present study deals with change in crystallographic and chemical nature of the mineral system present in the host rock. In an attempt to increase copper recovery, the ore was subjected to heating at 600°C under normal atmospheric conditions. This heat treatment resulted in enhanced copper recovery, up to 98% within 60 days of progressive leaching.
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  • Jiyoung Yu, Junghyun Shim, Sehun Rhee
    2012 Volume 53 Issue 11 Pages 2011-2018
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    For the last few decades, formability and weldability of steels have been intensively investigated to increase the productivity and the safety in automotive companies. Recently, steel which has both high ductility and high tensile strength is required to reduce vehicle weight. Twin induced plasticity (TWIP) steel has high tensile strength as well as improved ductility and is applicable to automobiles. Since, TWIP steel is an austenitic alloy which contains high content of Mn, it would have different resistance spot welding characteristics comparing with dual phase (DP) steel. In this work, TWIP steel, the newly developed steel, was introduced. To identify the resistance spot welding characteristics of 1 GPa grade TWIP steel, the experiments for both DP and TWIP steels were conducted. Resistance and power signals were measured to analyze the welding characteristics. The suitable welding ranges were also obtained with the lobe diagrams for these steels. In order to analyze the weld, shear tension and hardness tests, and a microstructure analysis were conducted. Both steels show a different microstructure in base metal, heat affected zone, and nugget. Because of the different microstructures between the two steels, the two steels showed different hardness distribution and tensile shear strength in the weld. Also, the differences in dynamic resistance signal, welding power signal, and welding heat input are shown between the two steels. These distinctions in microstructure and welding process characteristics caused the difference in suitable welding range. As well, this study provides guidelines to the application of DP and TWIP steels in resistance spot welding for vehicle manufacturing process.
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  • Zhifeng Wang, Yuan Yao, Xiaoqing He, Yang Yang, Lin Gu, Yanguo Wang, X ...
    2012 Volume 53 Issue 11 Pages 2019-2022
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    Elastic strain plays an important role in modifying physical properties such as the mobility of charge carriers in semiconductors. Strain analyses reveal that the reduction of the total strain and the elastic strain could be as large as 30 and 65%, respectively in a very thin transmission electron microscopy (TEM) specimen. The strain and thin film relaxation in a cross-sectional transmission electron microscopy (XTEM) specimen of GeSi/Si strained-layer superlattice has been investigated by dark-field electron holography with a large holographic field of view (FOV) to 150 nm achieved by moving the specimen down below the front-focal plane of the objective lens in free lens control mode.
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  • Cheng-Shun Chen, Sheng-Yao Lin, Nai-Kuan Chou, Yih-Sharng Chen, Sheau- ...
    2012 Volume 53 Issue 11 Pages 2023-2027
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    Stents are commonly inserted into coronary arteries for treating cardiovascular diseases. Nonetheless, the process of manufacturing metal stents is challenging owing to the geometric design, the optimization of machining methods and the materials involved. Fiber lasers were used as the laser cutting technology for cutting stents. The experiment revealed the importance of precise technical parameters, including the lens’ focal length, focus position, pulse frequency, cutting speed and pulse width. These parameters strongly influence the kerfs width and the quality of the cutting seam surface. Our results indicate that the width of the kerfs increases with an increase in the pulse frequency and pulse width, whereas it decreases or shows minimal change at higher cutting speeds. The surface roughness for stent laser cutting was Ra 43.5 nm, which essentially meets the design requirement for further performance evaluation. Finally, high-quality cutting of a 316LVM stainless steel vascular stent was achieved.
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  • Chung-Seok Kim
    2012 Volume 53 Issue 11 Pages 2028-2033
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    The creep of heat-resistant steel (12Cr–3.45W alloy) is experimentally characterized to estimate damages using a nonlinear ultrasonic technique. The finite amplitude method has been used to measure the ultrasonic nonlinearity parameter in all creep damaged specimens by through transmitted longitudinal wave. The microstructure showed significant changes in precipitate size and dislocation density during creep. The normalized ultrasonic nonlinearity decreases significantly in stage I and decreases monotonously in stage II and stage III. However, the ultrasonic nonlinearity increase due to the formation of creep voids in the vicinity of the creep failure region. The correlation between the microstructural changes and ultrasonic nonlinearity is discussed.
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  • Sung-Ho Joo, Young-Uk Kim, Jin-Gu Kang, J. Rajesh Kumar, Ho-Sung Yoon, ...
    2012 Volume 53 Issue 11 Pages 2034-2037
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    Ion exchange separation of rhenium using Purolite A-170 and Purolite A-172 was carried out from the dust leach solution of molybdenite concentrate. Different parameters such as effect of contact time, equilibrium pH, and solid liquid ratio were investigated. The optimum absorption condition for Purolite A-172 resin was determined, and the absorption efficiency of Re and Mo were obtained to be about 90 and 0%, respectively. From results, it was evident that, the performance of Purolite A-172 resin was more effective than Purolite A-170 resin, towards the selective recovery of Re from the molybdenite dust leach solution.
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  • Sung-Ho Joo, Young-Uk Kim, Jin-Gu Kang, Ho-Sung Yoon, Dong-Su Kim, Shu ...
    2012 Volume 53 Issue 11 Pages 2038-2042
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    A study has been conducted for the separate recovery of molybdenum and rhenium from alkali leaching solution of molybdenite roasting dust by a selective precipitation method. Two kinds of synthetic alkali leaching solutions were employed and more than 85% of molybdenum was recovered as a precipitate in the experimental conditions of 243.15 K, pH 2.2, 200 rpm of agitation speed, 7,200 s of reaction time, and 1.5 of equivalence ratio between NH4OH and NaOH for NaOH leaching solution. Regarding NH4OH leaching solution, the optimal conditions for the formation of molybdenum precipitate were found to be 243.15 K, pH 2.5, 100 rpm of agitation speed, and 18,000 s of reaction time. The precipitation efficiency of molybdenum was higher than 99% in these conditions and molybdenum was observed to be precipitated as ammonium molybdate. Contrary to the precipitating behavior of molybdenum, rhenium was precipitated very little in the given conditions, which suggested a possibility for the selective recovery of molybdenum and rhenium.
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  • Jae Bin Lee, Dong Hwan Shin, Joo Hyun Moon, Seong Hyuk Lee
    2012 Volume 53 Issue 11 Pages 2043-2048
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    In this work, experimental results on the morphology and adhesive characteristics of flame-sprayed Ni–20 mass%Cr coating layers deposited on preheated SCM415 surfaces are presented. The flame spray distance was varied from 100 to 200 mm so as to investigate the change in the adhesive strength of the deposited layers. Commercially available Ni–20 mass%Cr particles with a mean diameter of 45 µm were employed in the experiments, and computational fluid dynamics (CFD) simulations using a commercial code (FLUENT) were conducted so as to estimate the temperature and velocity distributions of continuous and discrete phases before impact on the substrate. From FE-SEM images of the deposited layers, it was observed that, as the flame spray distance decreased, the metal particle morphology exhibited a splash-like pattern and a short, stretched shape. Such morphological characteristics were induced by the higher particle momentum associated with very high gas velocities. In addition, as the flame spray distance decreased, the adhesive strength between the deposited layer and the substrate increased due to the stronger momentum of the molten metal particles.
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  • F. Y. Hung, T. S. Lui, Z. S. Hu, S. J. Chang, L. H. Chen, K. J. Chen
    2012 Volume 53 Issue 11 Pages 2049-2055
    Published: November 01, 2012
    Released: October 25, 2012
    JOURNALS FREE ACCESS
    Silver film is widely used in optoelectronic and semiconductor industries, but its stress problem has not been verified. Sputtered Ag films of different thicknesses were used to investigate the effect of the crystallization on their solidification residual stress and electrical properties. From XRD data (2θ > 90°), an increase the thickness of the Ag film from 30 to 400 nm, not only raised the index of crystallization, but also obtained a lower resistivity. However, the peak (331) had a dissolution tendency due to the residual stress. The grain size of Ag films with greater thickness had grown because of the longer sputtering duration. Due to variations in the crystallized texture, the 30 and 110 nm films showed no sign of elasticity under nano-indentation testing. Under low-energy XRD (30 kV-20 µA), the 30 nm film not only had more residual stress, but also formed a new plane of diffraction at 104.2° of 2θ and the actual compressive stress value was 14.94 MPa. After an electrical current induced crystallization (EIC) test, the resistivity and residual stress of Ag film were improved.
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  • Kyungsun Song, Sujeong Lee, Chang-Yul Suh, Wonbaek Kim, Kyung-Seok Ko, ...
    2012 Volume 53 Issue 11 Pages 2056-2059
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 17, 2012
    JOURNALS FREE ACCESS
    Iron oxide nanoparticles were prepared using a wire explosion method. Pure Fe wire was exploded in Ar–5%O2, Ar–10%O2 and Ar–30%O2 gas mixtures. The variation in the oxygen partial pressure in the explosion chamber resulted in a full spectrum of iron oxide nanoparticles, the sizes of which ranged from 10 to 200 nm. The phases in the explosion products were augmented in the order FeO → magnetite (Fe3O4) → maghemite (γ-Fe2O3) → hematite (α-Fe2O3) as the oxygen partial pressure was increased. Among the oxide phases, magnetite (Fe3O4) and maghemite (γ-Fe2O3) were the major phases, and the identification and relative quantification of both phases was possible through a step-scan and peak deconvolution routine. The presence of the magnetite-maghemite phase mixture was also substantiated by a field-emission transmission electron microscopy (FE-TEM) study on individual particles. The average particle size and phase ratio (maghemite/magnetite) decreased with increasing oxygen partial pressure.
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  • Y. B. Choi, T. Hinoki, K. Ozawa, Y. Katoh, K. Matsugi, T. Kelimu
    2012 Volume 53 Issue 11 Pages 2060-2063
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 17, 2012
    JOURNALS FREE ACCESS
    SiC/SiC composite is a candidate material for demonstration fusion power reactor (DEMO). To identify the inherent anisotropy of composites, it requires predicting axial/off-axial mechanical properties by various failure modes. This study evaluated failure behavior of SiC/SiC composites by various mode tests such as tensile, Inter-laminar shear and Trans-thickness tensile modes. To provide strength anisotropy maps and discussed a method to predict this trend analytically. The identification of various fabric orientations from strength anisotropy maps clearly indicate that the composites failed by the mixed modes. The strength anisotropy can be described satisfactorily.
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  • Joong-Hwan Jun
    2012 Volume 53 Issue 11 Pages 2064-2066
    Published: November 01, 2012
    Released: October 25, 2012
    [Advance publication] Released: October 11, 2012
    JOURNALS FREE ACCESS
    Influences of Bi addition on microstructures and damping capacities of Mg2Si/Mg–Al–Si–(Bi) composites have been investigated. The Bi addition is beneficial to modify Mg2Si phase from coarse Chinese script shape to fine polygonal shape. Even though the Bi-containing alloy has modified polygonal Mg2Si compounds, its damping capacity shows similar level with that of the Bi-free alloy. This would be attributed to the increased solute concentration related to high solubility of Bi in Mg, which eventually offsets the damping increment in response to Mg2Si modification.
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