MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 49 , Issue 2
Showing 1-26 articles out of 26 articles from the selected issue
  • Fengjuan Liu, Quanwen Yang, Shujie Pang, Chaoli Ma, Tao Zhang
    2008 Volume 49 Issue 2 Pages 231-234
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    Fe-based bulk metallic glasses (BMGs) with high glass forming ability (GFA) and excellent mechanical properties were synthesized in Fe-Ni-Mo-P-C-B alloy system by copper mold casting. Results show that the glass forming ability of Fe74−xNixMo6P10C7.5B2.5 alloys increases first and then decreases as Ni content, x, increases from 0 to 11.1 at%, with its climax being reached at x is between 3.7 and 5.0. Analyses indicate that either ΔTx and ΔHendo or Trg and γ can not illustrate the GFA of obtained alloys solely. With increasing Ni element in Fe74−xNixMo6P10C7.5B2.5 alloys, the yield strength and Vicker’s mircrohardness decline, while the plasticity increases, which implies that enhancing plasticity by adjusting the composition of alloys is followed with the loss of some strength. Serrated flow characteristics on the compressive stress-strain curves is observed for Fe74−xNixMo6P10C7.5B2.5 as x=11.1 at%, which is considered to relate to its lowest glass transition temperature. These mechanical properties of BMGs are illustrated with bonding nature between the constituent elements.
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  • Masahiro Kubota
    2008 Volume 49 Issue 2 Pages 235-241
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
    JOURNALS FREE ACCESS
    Characterization of the β′ and β precipitate phases formed in the aged Al-10 mass%Mg alloy with and without 0.5 mass%Ag at 200°C and 240°C has been carried out using TEM. The plate-like precipitate particles were formed in binary alloys aged from 2 h at 200°C. The plate-like particles had habit planes of {100}α, and were identified as the β′ phase. Whereas the very fine scale, uniformly distributed precipitate particles with a spherical shape were formed as the dominant precipitate particle in ternary alloy aged at 200°C for periods of 4 h and 6 h. These small spherical particles were identified to be icosahedral phase while no icosahedral phase was observed in the Ag-free alloys when samples were aged at 200°C. Formation of a precipitate cluster consisting of two distinguishable parts has been observed in binary alloys aged 5 h at 240°C, and these precipitate particles were identified as the equilibrium β and metastable β′ phases. Whereas a higher volume fraction of dispersed precipitate phases which comprised a mixture of a coarse-scale, rod-like particles and blocky particles, was observed in ternary alloy aged 5 h at 240°C. With further increase of ageing time up to 24 h at 240°C, the microstructure contained a high volume fraction of coarse-scale, globular precipitate particles, together with a secondary distribution of fine-scale spheroidal precipitates, these coarse globular particles were identified to be the equilibrium β phase.
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  • Yasuhiko Kawanami, Masanori Kajihara, Osamu Umezawa
    2008 Volume 49 Issue 2 Pages 242-249
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 27, 2007
    JOURNALS FREE ACCESS
    In order to examine the crystallography for diffusion-induced recrystallization (DIR) in the Ni(Cu) system, Cu/Ni/Cu diffusion couples were prepared by a diffusion bonding technique from a pure Cu single-crystal specimen and a pure Ni polycrystalline specimen, and then isothermally annealed at a temperature of 923 K for various times of 1–60 h. The Miller indices of the Cu specimen along the Cu/Ni interface are (111). The notation A(B) means that a solute B diffuses into a pure metal A or a binary A–B alloy with the A-rich single-phase microstructure. Due to DIR during annealing, a region with fine grains alloyed with Cu is produced into the Ni specimen from the Cu/Ni interface in the diffusion couple. The orientation relationship between the fine grain in the DIR region and the Cu or Ni specimen was analyzed by an electron backscattered diffraction technique as well as transmission electron microscopy. Orientation relationships close to but not identical to the cube/cube relationship exist between the Cu specimen and many fine grains in the DIR region. The chemical driving force for the formation of the DIR region, the boundary energy and the boundary diffusion coefficient were evaluated by mathematical models. According to the evaluation, it is likely that fine grains surrounded by small-angle boundaries are formed and grow moderately during DIR.
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  • Hsin-Wen Huang, Bin-Lung Ou, Cheng-Ting Tsai
    2008 Volume 49 Issue 2 Pages 250-259
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    This investigation studies 3003 aluminum alloys for automobile heat exchangers. The effects of precipitation in homogenization treatments, recrystallization in extrusion and brazing on extrusion forming ability and final material properties are examined. At first, fine second phase particles were precipitated during the 460°C × 9 h homogenization treatment and coarse particles were precipitated by homogenization treatments with 600°C × 9 h. Second, when the precipitation were not plentiful and fine enough during extrusion, the amount of solution dominated the extrusion breakout pressure, and recrystallization was easier; on the contrary, the domination state was replaced by plentiful and fine precipitated particles, and recrystallization became more difficult. Additionally, the hardness after extrusion was lower in the complete recrystallization position, and higher in the incomplete recrystallization position. Finally, in brazing, the sample under the 460°C × 9 h condition (a) underwent full recrystallization from partial recrystallization with a reduction in strength; the local position of the edge of the sample under the 600°C × 9 h → 460°C × 3 h condition (c) exhibited a second recrystallization and a significant drop in hardness.
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  • Sang-Hak Lee, Naoyuki Nomura, Akihiko Chiba
    2008 Volume 49 Issue 2 Pages 260-264
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
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    An improvement in the mechanical properties of a biomedical Ni-free Co-Cr-Mo alloy under as-cast condition has been examined by means of tensile tests and microstructure observations. The solubility of N in Co-Cr-Mo alloys increases with increasing Cr content from 29 to 34 mass%. This results in a significant improvement in mechanical properties such as yield stress, tensile strength, and fracture elongation. The improvement in the mechanical properties results from the γ phase stabilization and inhibition of the σ phase formation due to N addition. Increasing the Cr content also has contributed to the improved mechanical properties.
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  • Takeshi Nagase, Akihiro Nino, Yukichi Umakoshi
    2008 Volume 49 Issue 2 Pages 265-274
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
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    Formation of nano-structure in melt-spun ternary Fe-Nd-B alloys was examined focusing on electron irradiation induced crystallization. In Fe82.2Nd7.1B10.7 (Fe/Nd/B = 23/2/3), Fe77Nd4.5B18.5 and Fe71Nd9B20 alloys, melt-spun amorphous phase changed to a crystalline phase during electron irradiation and nano-structure was formed. The crystalline phase in melt-spun Fe86Nd9B5 and Fe82.4Nd11.8B5.8 (Fe/Nd/B = 14/2/1) alloys was unstable under electron irradiation and electron irradiation induced amorphization occurred. With the further irradiation, crystallization from the amorphous phase was induced resulting in forming nano-crystalline structure. The onset total dose for the irradiation induced crystallization, namely, stability of the amorphous phase against electron irradiation depends strongly on the Fe-ratio, crystallization temperature, mismatch entropy and mixing enthalpy of the alloys.
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  • Bo Hong, C. H. Jiang, X. J. Wang
    2008 Volume 49 Issue 2 Pages 275-277
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
    JOURNALS FREE ACCESS
    The copper films were electrodeposited from aqueous and organic solutions in the presence and in the absence of ultrasound. The internal stress and texture in copper films were studied using the X-ray diffraction (XRD). The results showed that the internal stress and texture of the copper films were reduced on the effect of ultrasound. The surface morphology of copper grains was investigated using scanning electron microscopy (SEM). The results showed that the porous structure was formed on the surface of copper grains deposited in organic solution under ultrasonic radiation.
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  • Takayuki Hama, Masato Takamura, Akitake Makinouchi, Cristian Teodosiu, ...
    2008 Volume 49 Issue 2 Pages 278-283
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    In this study, the effect of tool-modeling accuracy on a finite-element simulation of a square-cup deep-drawing process is examined. First, the accuracy of tool modeling using a conventional approach, in which polyhedral surfaces are used, is compared with that of an alternative approach, in which the quadratic parametric surfaces proposed by Nagata [Nagata, Comput. Aided Geom. D 22 (2005) 327–347] (Nagata patch) are used. It is clear that the Nagata patch yields a much more accurate tool geometry than the conventional approach with regard to the shape and normal vectors of the tool. Next, simulations of the square-cup deep-drawing process are carried out for die models with various numbers of tool elements. It was found that a polyhedral model with at least 10 divisions at the die shoulder is required to carry out accurate simulations. The simulated result of the Nagata patch model with two patches at the die shoulder corresponds well to that of the polyhedral model with more than 10 patches. From this point of view, it is concluded that the number of tool elements can be markedly decreased using the Nagata patch model. In the present case, the number of tool elements can be reduced to about 10% of that of the polyhedral model.
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  • Masahito Uchikoshi, Koutarou Kawai, Michihito Sasagaki, Kouji Mimura, ...
    2008 Volume 49 Issue 2 Pages 284-288
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 19, 2007
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    The demand for high-purity Mn is growing in the field of advanced electronics devices. Chromatographic separation using chelating resins is useful for pre-concentration of metal ions prior to the determination of metallic elements by chemical analysis. This separation technique can be applied to the recovery of hazardous substances from industrial waste. In the present study, this separation technique was applied to the purification of Mn for the first time. Separation was carried out in an ammonium chloride medium because Mn can be recovered by electrowinning in the final step. Ammonium chloride added to the electrolyte is useful for improving the current efficiency during electrowinning of Mn. The optimum separation process was examined according to the recovery ratio of Mn and the elimination ratio of each impurity derived from the elution curves.
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  • Susumu Miyamoto, Masatoshi Watanabe, Takayuki Narushima, Yasutaka Iguc ...
    2008 Volume 49 Issue 2 Pages 289-293
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 19, 2007
    JOURNALS FREE ACCESS
    The deoxidation behavior of NiTi alloy melts with metallic barium was investigated. Metallic barium was added to the NiTi alloy melts held in lime (CaO) crucibles at 1673 K, and the concentrations of oxygen, barium and calcium in the melts were quantitatively measured. The oxygen content in a raw NiTi alloy bar was 660 ppm, and the oxygen content in the NiTi alloy melts just before barium addition was around 1100 ppm. Oxygen was introduced into the melts by the dissolution of lime during melting.
    The addition of barium lowered the oxygen content in the melts with the formation of deoxidation product, which might be barium oxide. The oxygen content was measured to be around 350 ppm 120 s after barium addition. The barium and calcium contents were less than 10 ppm and 12 ppm, respectively, indicating that the deoxidation product was removed from the melts in a very short period of time. These results suggest that barium is an effective deoxidation element for NiTi alloy melts. Furthermore, the interaction between oxygen and barium cannot be ignored in thermodynamic considerations of the deoxidation process.
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  • Akira Furuto, Masanori Kajihara
    2008 Volume 49 Issue 2 Pages 294-303
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 27, 2007
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    A hypothetical binary system composed of one intermetallic compound and two primary solid-solution phases has been considered in order to examine the kinetics of the reactive diffusion controlled by boundary and volume diffusion. If a semi-infinite diffusion couple initially consisting of the two primary solid-solution phases with solubility compositions is isothermally annealed at an appropriate temperature, the compound layer will be surely produced at the interface between the primary solid-solution phases. In the primary solid-solution phases, however, there is no diffusional flux. Furthermore, we suppose that the compound layer is composed of a single layer of square-rectangular grains with an identical dimension. Here, the square basal-plane is parallel to the interface, and hence the height is equal to the thickness of the compound layer. Under such conditions, the growth behavior of the compound layer has been analyzed numerically. In order to simplify the analysis, the following assumptions have been adopted for the compound layer: there is no grain boundary segregation; and volume and boundary diffusion takes place along the direction perpendicular to the interface. When the size of the basal-plane remains constant independently of the annealing time, the thickness of the compound layer is proportional to the square root of the annealing time. In contrast, the growth of the compound layer takes place in complicated manners, if the size of the basal-plane increases in proportion to a power function of the annealing time. Nevertheless, around a certain critical annealing time, the thickness of the compound layer is approximately expressed as a power function of the annealing time. For each grain, the layer growth is associated with increase in the height, and the grain growth is relevant to increase in the size of the basal-plane. The exponent for the layer growth almost linearly decreases with increasing exponent for the grain growth.
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  • Shigehiro Kawamori, Terufumi Machida
    2008 Volume 49 Issue 2 Pages 304-309
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 19, 2007
    JOURNALS FREE ACCESS
    To improve the mechanical properties of magnesium alloys, hot pressing was performed to produce a silicon carbide-dispersion-strengthened magnesium (SiCp/Mg), in which SiC particles (SiCp) were milled with pure Mg using an attritor ball mill to reinforce the Mg. In this study, the silicon carbide dispersion strengthening of magnesium using the mechanical alloying (MA) method was investigated. The experimental results are summarized as follows. By increasing the milling energy of the ball mill in which the pAl2O3/Mg MA powder of a previous study was fabricated, the density of the SiCp/Mg was able to be increased to a value higher than that of the pAl2O3/Mg. The SiCp/Mg is about two-thirds as dense as commercial aluminum alloys. The hardness of the SiCp/Mg was about 1.5-fold that of the pAl2O3/Mg and exceeded that of AZ91D, which has the best mechanical properties of all the commercial Mg alloys. The highest value obtained was 95 HV. The bending strength of the SiCp/Mg was better than that of the pAl2O3/Mg. The results of XRD analysis and SEM-EDAX of the SiCp/Mg suggest that SiCp is almost uniformly and finely dispersed in the Mg and that the grain size of the matrix becomes finer with the dispersion.
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  • Masahiro Sasada, Naoki Koura, Isamu Aoki
    2008 Volume 49 Issue 2 Pages 310-316
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    In this paper, we discuss the clearance compensation effect in precision shearing. This effect is based on the hypothesis that unbalanced clearance is automatically compensated by the bending of a punch when shearing is performed using a long and thin punch. We also discuss the compensation mechanism through various experiments and an elastic-plastic finite element method. When the clearances on the right and left sides differ, the shearing and horizontal forces acting on both punch sides also differ slightly. These forces result in moments that bend the punch. The clearance compensation effect depends on the magnitude and direction of these moments. In other words, the effect is due to not only the horizontal force but also the shearing force. In most cases of double-sided shearing, the existence of the compensation effect was apparent.
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  • Jin Kawakita, Norio Maruyama, Seiji Kuroda, Sachiko Hiromoto, Akiko Ya ...
    2008 Volume 49 Issue 2 Pages 317-323
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 27, 2007
    JOURNALS FREE ACCESS
    Metallic glasses are highly attractive because of their superior strength, relatively low Young’s modulus and superb corrosion resistance[S1], etc. By combining a metallic glass with different materials, synergy effect can be expected in the mechanical properties and corrosion resistance, for example. Fabricating a thick metallic glass layer on a substrate material by thermal spray process is one way to bond these materials. In such practice, however, the temperature of the sprayed metallic glass and that of the substrate must be kept relatively low in order to avoid crystallization and/or oxidation of the amorphous deposits. Warm Spray is a modified version of HVOF spraying developed by National Institute for Materials Science (NIMS) suited for spraying of heat sensitive feedstock materials. In the process, high-velocity solid particles heated to the temperatures below its melting point are projected on to the substrate. A Zr-base metallic glass powder was warm sprayed onto cylindrical substrates of 316L stainless steel to various thicknesses. Negligible crystallization and oxidation were observed in the deposited layer of the glass alloy. The linear relationship between the thickness of the glass alloy layer and the Young’s modulus of the composite bar demonstrated that the mechanical property of such composite structures can be controlled.
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  • Hiromi Nagaumi, Satoru Suzuki, Toshimitsu Okane, Takateru Umeda
    2008 Volume 49 Issue 2 Pages 324-330
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 27, 2007
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    In this study, the effect of Mn and Cr addition on high temperature mechanical properties of a machinable 2xxx alloy with high Sn content was systematically investigated. Tensile test during solidification was carried out, using an electromagnetic induction heating tensile test machine. Stress-strain curve, tensile strength, fracture strain (elongation), Zero Strength Temperature (ZST) and Zero Ductility Temperature (ZDT) were evaluated. To determine the solidification range of the 2xxx alloy with high Sn content, the specific heat were continuously measured in the range from room temperature to 700°C using an insulating type measuring device of specific heat. It was found that the tensile strength during solidification steeply increased with Mn and Cr addition, and the temperature range between ZST and ZDT became wider, in comparison with those without Mn and Cr addition. It was presumed that the crack susceptibility of the alloy increased by Mn and Cr addition. Fractography on the high temperature clearly distinguished the fracture property and fracture behavior of the alloys with and without Mn and Cr addition. Formation of intermetallic compounds at later stage of solidification was different from with and without Mn and/or Cr addition. Furthermore, by comparing the tensile strength with the casting practice, the effect of Mn and Cr addition on the crack susceptibility of direct-chill cast billets was severely attributed to crystallization of these compounds.
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  • Ming-Hsiu Tsai, Weng-Sing Hwang
    2008 Volume 49 Issue 2 Pages 331-338
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
    JOURNALS FREE ACCESS
    The dynamics of droplet formation of liquid in a piezoelectric inkjet printing process with bipolar pulse and drop-on-demand (DOD) mode is investigated in this study. Two liquids with different viscosities and surface tension coefficients; alcohol and ethylene glycol, are studied. The effects of pulse voltage on the droplet formation are also examined. A piezoelectric actuated inkjet printhead with a nozzle orifice of 30 μm in diameter is employed to conduct the investigations at room temperature (25°C). The complex morphologies of the droplets during their formation, which include ejection and stretching of liquid, contraction of liquid column, pinch-off of liquid column from nozzle exit, breakup of liquid column into primary droplet and possible satellites, and combination of primary drop and satellites, are demonstrated. The droplet size is in the range of 23–37 μm. The investigations also show a workable pulse voltage range; between 28 and 40 volts, exists for the droplets to be smoothly generated and ejected for alcohol where viscosity and surface tension coefficient are smaller. The range is between 30 and 50 volts for ethylene glycol. Within this workable voltage range, one single droplet for each pulse can be achieved with lower voltage. For the intermediate voltage, two droplets are generated initially and collide into one during the flying stage. For the higher voltage, multiple droplets are formed without recombination. It is also found that the velocities of the main droplet and satellite droplet in the different voltage ranges are responsible for whether the multiple initial droplets can be recombined.
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  • Byong-Taek Lee, Swapan Kumar Sarkar, Ho-Yeon Song
    2008 Volume 49 Issue 2 Pages 339-344
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    In this paper development of novel ceramic microstructures by the fibrous monolithic process were reported. Attempts were made to tailor the microstructures of these advanced ceramics by introducing fibrous or layered morphology to incorporate multi-toughening mechanisms. Fabrication and characterization of four different kinds of microstructure, termed in this manuscript as network type, double network type, functional gradient microchanneled and functional gradient microchanneled double network type microstructure, were reported. In network and double network type microstructure developments the two phase Al2O3-(m-ZrO2) cores were embedded within network-type frames of t-ZrO2 single phase. In the double network type microstructure, an additional thicker network-type t-ZrO2 enclosure surrounded a network-type micro-assembly. Unidirectionally aligned continuously porous HAp-Al2O3-ZrO2 tri-phase ceramic composites were fabricated by the same method to incorporated functional gradient for improved functionality and depress processing defects. The microstructure had three layers of HAp/HAp-(Al2O3-(m-ZrO2))/Al2O3-(t-ZrO2) around the continuous pore with compositional gradient. In the functionally gradient micro-channeled HAp/HAp-(Al2O3-(m-ZrO2))/Al2O3-(t-ZrO2) composites, the size and distribution of micro-channels were homogeneously controlled. Detailed morphological analyses of the resulting microstructures were studied.
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  • Tsuyoshi Yamashita, Kazuhiro Suzuki, Souichiro Nishino, Yo Tomota
    2008 Volume 49 Issue 2 Pages 345-351
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    Recently, the application of porous soundproof materials to automobiles is changing from the use of sound insulation materials to the use of sound absorption materials. A method for attaining high absorption performance in the low-frequency region without increasing the material weight is thus needed. We investigated the use of X-ray computed tomography (CT) scanning for investigating the microscopic structure of soft urethane foam, a low specific gravity resin material, in a nondestructive manner. Our testing reveals that it is an effective tool for observing the microscopic organizational structure of a low specific gravity resin material and that the cell size of urethane foam, as measured by X-ray CT, affects the sound absorption characteristics. It also shows that reducing cell size shifts the peak frequency of the sound absorption coefficient downward.
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  • Jong-Jin Pak, M. Bahgat, Bo-Ho Kim, Min-Kyu Paek
    2008 Volume 49 Issue 2 Pages 352-359
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: December 19, 2007
    JOURNALS FREE ACCESS
    Two Molar ratios 1:1 and 1:2 of AR grade nickel oxide and iron oxide powder was mixed and compacted. The fired compacts were isothermally reduced in pure hydrogen at 500, 550, 600 and 650°C. Based on thermogravimetric analysis, the reduction behavior and kinetics reaction mechanism were studied comparatively for the different mixed oxides ratios. The initial fired powder and the various reduction products were characterized by XRD, SEM, TEM and reflected light microscope to reveal the effect of hydrogen reduction on composition and microstructure of produced Ferronickel alloy. Synthesis of nanocrystalline Fe1−xNix alloy with 33 and 20 at% Ni for reduction of 1:1 and 1:2 NiO/Fe2O3 ratios was detected respectively. The activation energy values were calculated from Arrhenius equation and the approved mathematical formulations for the gas solid reaction were applied. It was found that for NiO/Fe2O3 of both 1:1 and 1:2 ratios, the initial reduction stages is controlled by the combined gaseous diffusion and interfacial chemical reaction mechanisms while at the final reduction stages the reaction is controlled by the interfacial chemical reaction mechanism.
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  • Teiko Okazaki, Yosinori Iwai, Yasubumi Furuya
    2008 Volume 49 Issue 2 Pages 360-364
    Published: February 01, 2008
    Released: January 25, 2008
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    The Fe-Pd ferromagnetic shape memory alloy is a multifunctional material. We investigated the behavior of the superelastic properties of rapidly solidified Fe-Xat%Pd (X=29.3, 29.6, 30.2 and 30.4) alloy ribbons to develop biomedical materials applicable to orthodontics and medical instrumentation. The appearance of a stress-induced martensite phase under the loading stress was confirmed by X-ray diffraction measurements. Stress-strain curves were drawn from results obtained using a tensile testing machine at temperature of 290 and 313 K. The Fe-Xat%Pd (X=29.6, 30.2, 30.4) ribbons exhibited superelastic strain of 3.0–3.5%. Moreover, when these Fe-Pd alloy ribbons were treated in Hanks’ solution for 150 days, they exhibited good biocorrosion resistance.
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  • Toshikazu Akahori, Mitsuo Niinomi, Masaaki Nakai, Toshihiro Kasuga, Mi ...
    2008 Volume 49 Issue 2 Pages 365-371
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    Beta-type titanium alloys used in biomedical applications have been developed all over the world. In particular, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) is one of beta-type titanium alloys for biomedical applications that has been developed by the authors in Japan. Although TNTZ is composed of non-toxic elements such as niobium, tantalum, and zirconium, it still lacks bioactivity, which is the ability to form chemical bonds with living bones. The stems that are parts of artificial hip joints, dental implants, etc., which are made of metallic materials, etc. are required to bond strongly with living bones. However, these stems, dental implants etc., cannot form chemical bond with living bones by themselves. The bioactive surface modification of metallic materials by the application of ceramics is effective in improving the biocompatibility of TNTZ. Calcium phosphate ceramics such as hydroxyapatite (Ca10(PO4)6OH2; HAP) and β-tricalcium phosphate (β-Ca3(PO4)2; β-TCP) possess bioactivity. In this study, the characteristics and morphology of TNTZ coated with a calcium phosphate invert-glass-ceramic (CPIG) layer by dip-coating treatment or with a sodium titanate layer by alkali solution treatment are investigated before and after soaking it in a simulated body fluid (SBF).
    The bonding strength between a CPIG layer with a thickness of around 5 μm and a specimen surface of TNTZ is around 25 MPa. No cracks or exfoliations are observed along the boundary between the CPIG layer and the specimen surface. This is the reason why the difference in the thermal expansion coefficients between CPIG layer and TNTZ reduced due to a compositional gradient zone with a thickness of around 3 μm in CPIG layer. HAP is formed on the entire surface of the TNTZ specimen after soaking it in the SBF for more than 1728 ks. The fatigue properties of TNTZ coated with a CPIG layer are similar to those of as-solutionized TNTZ. A reticulate structure with a thickness of 400 to 800 nm is formed on the TNTZ specimen surface after soaking it in 3 to 10 kmol/m3 NaOH solution for 86.4 ks and 172.8 ks. HAP is completely formed on the entire surface of the TNTZ specimen when it is soaked in the SBF for 1209.6 ks after being soaked in 5 kmol/m3 NaOH solution for 172.8 ks.
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  • Koji Fujita, Yoshihiro Takahara, Yoshinori Chikaura
    2008 Volume 49 Issue 2 Pages 372-375
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
    JOURNALS FREE ACCESS
    We have studied the refining effects of refining agents and ultraviolet transmitting property of soda lime glass, for the purpose of developing ultraviolet transmitting glass with soda lime glass composition which is one of an inexpensive glasses. It was found that for glass that requires ultraviolet transmitting property, antimony oxide, which is commonly used as a refining agent, cannot be used because it has an ultraviolet absorption band. In addition, it turned out that it becomes possible to actualize both bubble quality and ultraviolet transmitting property by adding a small amount of iron oxide and making the glass reductive. The transmission of the bubble-free glass sample obtained in this study was 78% at 260 nm, which is not problematic for practical applications.
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  • Chang Joon Yang, Moon Gi Cho, Hyuck Mo Lee
    2008 Volume 49 Issue 2 Pages 376-381
    Published: February 01, 2008
    Released: January 25, 2008
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    A Pb-free combination solder structure was successfully attained from a high-melting 80Au-20Sn solder alloy completely wrapped in a low-melting 42Sn-58Bi solder paste (the numbers of which are all in mass% unless specified). The phases of (Au,Ni)3Sn4 and AuSn4 were observed at the interface between Sn-Bi solder and Cu/Ni/Au UBM, whereas the (Au,Ni)3Sn2 phase was observed at the interface between Au-Sn solder and Cu/Ni/Au UBM. The interfacial reaction between the Au-Sn solder and the Sn-Bi solder resulted in the formation of AuSn2 on the side of the Sn-Bi solder and AuSn on the side of the Au-Sn solder. All of these interfacial reactions were explained with relevant equilibrium phase diagrams. Moreover, we found that there is a limit in the optimum solder volume for a well-defined combination solder structure that can be applied to organic substrates with an increased remelting temperature.
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  • Chung-Hung Tam, Shih-Chin Lee, Shih-Hsien Chang, Tzu-Piao Tang, Hsin-H ...
    2008 Volume 49 Issue 2 Pages 382-386
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    Hot Isostatic Pressing (HIP) is a process that uniquely combines higher pressure and temperature to produce materials and parts with substantially better properties than those fabricated by other methods. Commercial as-hp (hot pressing) treated Cr50-Si50 targets are used throughout this study. The aim of this paper is to discuss the methods and to find a suitable HIP treatment for the as-hp treated Cr50-Si50 target. Otherwise, we also to find the effects of microstructure on the mechanical properties of HIP treated Cr50-Si50 target. To evaluate the effects on microstructure and properties of the Cr50-Si50 target by HIP process, SEM, TEM and porosity, density inspections were performed. The experiment results show that HIP treatment at 1373 K under the pressure of 175 MPa and 4 hours for Cr50-Si50 target is the optimum condition. In this study, HIP treatment reduced the porosity of the target about 60%.
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  • Makoto Matsuura, Kazuya Konno, Mitsuhiko Yoshida, Masahiko Nishijima, ...
    2008 Volume 49 Issue 2 Pages 387-389
    Published: February 01, 2008
    Released: January 25, 2008
    [Advance publication] Released: January 17, 2008
    JOURNALS FREE ACCESS
    Unique precipitates with novel structures have been found in melt-quenched (MQ) Mg98Cu1Gd1 alloys by transmission electron microscopy (TEM). Amorphous spherical particles with 50–200 nm sizes are uniformly embedded in Mg grains of an MQ Mg98Cu1Gd1 alloy prepared with a relatively higher cooling rate. So-called LAL precipitates, which consist of an amorphous core sandwiched by long period stacking (LPS) phase, are formed in an MQ Mg98Cu1Gd1 alloy prepared with a lower cooling rate. TEM observations show that LAL precipitates transform into LPS phases by annealing above 450 K. DSC results show that amorphous cores in LAL particles and amorphous particles crystallize at around 450 K, and partial melting of the LPS phase occurs at around 710 K prior to the melting of the Mg matrix. The composition of amorphous particles is 68 at%Mg, 26 at%Cu and 6 at%Gd, which is close to that having the highest glass forming ability (Mg65Cu25Gd10). Limited solubility of Cu and Gd in Mg and large negative mixing enthalpy between Cu and Gd are responsible for the formation of unique precipitates in rapidly solidified Mg-Cu-Gd alloys.
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  • Yong Bum Choi, Kazuhiro Matsugi, Gen Sasaki, Shunsaku Kondoh
    2008 Volume 49 Issue 2 Pages 390-392
    Published: February 01, 2008
    Released: January 25, 2008
    JOURNALS FREE ACCESS
    Porous preform reinforced aluminum alloy composite were prepared by the infiltration of molten metal using a low-pressure casting. The infiltration behavior of the filling pattern and the velocity profile obtained for alloys fabricated by the low-pressure casting process was investigated. The infiltration times in the case where a barrier palate was placed on the preform and at the pressure acceleration times of 1, 2 and 5 s were experimentally investigated under a constant applied pressure of 0.4 MPa. The infiltration at the pressure acceleration time of 1, 2 and 5 s ended in 5.36, 5.8 and 6.2 s, respectively. Hence, the infiltration time was short if the pressure acceleration time was short.
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