MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 49 , Issue 12
Showing 1-30 articles out of 30 articles from the selected issue
  • Shigeru Suzuki, Shotaro Senoo, Tadakatsu Maruyama, Kozo Shinoda
    2008 Volume 49 Issue 12 Pages 2755-2760
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 22, 2008
    JOURNALS FREE ACCESS
    Debye rings obtained by synchrotron X-ray diffraction were analyzed for investigating structural changes caused by stress-induced martensitic transformation and reverse transformation of a polycrystalline austenitic Fe-Mn-Si shape memory alloy. The chemical composition of the shape memory alloy was Fe-28 mass%Mn-6 mass%Si-5 mass%Cr. The results showed that a part of the austenitic γ phase was transformed to a martensitic ε phase by room-temperature tensile deformation, and the ε phase was reversely transformed by subsequent heating. Diffraction intensities in Debye rings changed non-uniformly on tensile deformation and heating, indicating that occurrences of the stress-induced and reverse transformation depend on the crystallographic orientations of grains with respect to the tensile direction. The optimum recovery strain induced by the reverse transformation was obtained for a sample deformed by about 10% tensile strain, which was consistent with the structural changes caused by the reverse transformation. X-ray diffraction lines were shown to be broadened by tensile strain. This indicated that irreversible deformation due to dislocations restricted the reverse transformation, leading to the optimum recovery strain.
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  • Hongwei Qin, Jifan Hu, Bo Li, Ming Zhao, Xing Liu, Juan Chen
    2008 Volume 49 Issue 12 Pages 2761-2764
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    Fe-Cu-V-Si-B nanocrystalline ribbons can be prepared using a melt-spinning technique without annealing processes. An appropriate addition of Cu improves the nucleation of α-Fe(Si) in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons. There is an optimal Cu content, about x=2.5, for obtaining largest permeability and lowest magnetostriction in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons. The permeability value (about 2.4×104) of as-spun Fe72Cu2.5V3Si13.5B9 (x=2.5) is much larger than that of Fe73.5Cu1V3Si13.5B9 annealed ribbons, due to the grain size of α-Fe(Si) for the former (12 nm) smaller than the later (41 nm). The smaller grain size of α-Fe(Si) for as-spun ribbon Fe72Cu2.5V3Si13.5B9 may be attributed to the refinement effect of Cu and the effect of high wheel speed in melt-spinning processes. Meanwhile, we have suggested that the capability of an element expelled from α-Fe(Si) and partitioned in the remaining amorphous phase is connected with the refinement of α-Fe(Si) grains. Based on Darken-Gurry solid solubility model, we have derived that the grain size of α-Fe(Si) reduces in order of Ta > Nb > Mo > W > V > Cr, which agrees to the experimental data very well. In addition, the DO3 ordered superstructure of α-Fe(Si) is observed in as-spun Fe74.5−xCuxV3Si13.5B9 ribbons, however it seems that the ordered degree of α-Fe(Si) grain is not a criterion for obtaining strong soft magnetic properties.
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  • Misako Iwasawa, Toshiharu Ohnuma, Naoki Soneda
    2008 Volume 49 Issue 12 Pages 2765-2769
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    The electronic structures of α-zirconium (Zr) and hydrogen (H) were calculated using density functional theory with the ultrasoft pseudopotential and generalized gradient approximation. The binding energy between a Zr vacancy and H, the migration energies of H in Zr with and without a Zr vacancy and the migration energy of a Zr vacancy with H were calculated, and the strong binding between a Zr vacancy and H was quantitatively demonstrated.
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  • Tatsuya Fukino, Sadahiro Tsurekawa
    2008 Volume 49 Issue 12 Pages 2770-2775
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 16, 2008
    JOURNALS FREE ACCESS
    The in-situ SEM/EBSD technique has been applied to observe the dynamics of ferrite(α) → austenite(γ) phase transformation and to examine the orientation relationship between α and γ phases in an Fe-9.5 at% Ni alloy. Random grain boundaries and grain-boundary triple junctions were found to act as preferential nucleation sites for γ phase. The effectiveness of triple junctions as the γ phase nucleation site in phase transformation increased with increasing number of random boundaries intersecting at a triple junction. Approximately 90% of allotriomorphic γ phase possessed either a Kurdjumov-Sachs (K-S) or a Nishiyama-Wasserman (N-W) orientation relationship (OR) with the α parent grains. The γ allotriomorphs with a special OR with one of the adjoining α parent grains preferentially grew into the α grain having the special OR with them, while the allotriomorphs with special ORs with both of the α grains grew into both adjoining α grains symmetrically.
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  • Kai-Nan Lin, Shyi-Kaan Wu, Chia-Liang Tsai
    2008 Volume 49 Issue 12 Pages 2776-2780
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 29, 2008
    JOURNALS FREE ACCESS
    The effect of thermal cycling on B2→B19→B19′ transformations of cold-rolled and annealed Ti50Ni40Cu10 SMA was examined by DMA. Experimental results point out the transformation peak temperature and its tanδ peak value of B19→B19′ transformation are more suppressed by thermal cycling than those of B2→B19. This is because of the different microstructures between B19 and B19′ martensites in which B19 is a defect-free martensite but B19′ has plenty of twinning. Dislocations induced by thermal cycling can hinder the mobility of twin boundaries of B19′ martensite and cause different thermal cycling effects on B2→B19 and B19→B19′ transformations. Thermal cycling also shows an obvious effect on storage modulus E0 values of B19 and B19′ martensites and their E0 values increase with increasing thermal cycles.
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  • Yong Kuk Park, Jin-Gon Kim, Jae-Kon Lee
    2008 Volume 49 Issue 12 Pages 2781-2785
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    A new model for predicting the thermal conductivities of a composite with spherical microballoons is proposed and consists of two consecutive procedures, the computation of the thermal conductivity of the microballoon and the composite. The microballoon is first replaced by the equivalent filler of a known thermal conductivity, so the composite is treated as the matrix containing the equivalent fillers and its thermal conductivity is derived by using Eshelby model modified with Mori-Tanaka’s mean field approach. The present model is validated comparing the predicted, experimental, and numerical results from the literature. Parametric studies in terms of the microballoon volume fraction, its relative wall thickness, and the thermal conductivity ratio of the shell to the matrix have been made and their results are discussed.
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  • Hiizu Ochi, Yoshiaki Yamamoto, Takashi Yamazaki, Takeshi Sawai, Gosaku ...
    2008 Volume 49 Issue 12 Pages 2786-2791
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    The relationship between joint strength and deformation heat input at the upset stage and the relationship between joint strength and upset burn-off length were examined on friction welded joints of 1050 pure aluminum to C1100 tough pitch copper. Joint quality was evaluated from the tensile strength and fatigue strength. It was found that both the deformation heat input at the upset stage and the upset burn-off length correlated well with joint strength. Additionally, when the deformation heat input at the upset stage or upset burn-off length exceeded a certain value, stable tensile strength was obtained. The mixing layer, intermetallic compounds of Al-Cu were interpolated into A1050, formed at the weld interface, and joints having a thick mixing layer fractured at the weld interface. Joint efficiencies of sound joints for the fatigue limit of the A1050 base metal were 88–100%. Judging from the fatigue limit, sound joints could be produced when either the deformation heat input at the upset stage or the upset burn-off length exceeded a certain value.
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  • J. Koike, Y. Sato, D. Ando
    2008 Volume 49 Issue 12 Pages 2792-2800
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    In order to understand the origin of the anomalous twinning of the {10\\bar12} type, rolled sheets of AZ31 Mg alloy were deformed at room temperature in tension along the rolling direction. An excellent correlation was found between {10\\bar12} twinning tendency and basal dislocation slip activity. Calculation of strain tensor indicated that the diagonal strain components associated with the localized basal slip can be canceled completely by the {10\\bar12} twinning. The results led to the conclusion that anomalous {10\\bar12} twins were formed to accommodate the strain incompatibility caused by localized basal dislocation slip.
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  • Minhaeng Cho
    2008 Volume 49 Issue 12 Pages 2801-2807
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    The flexural and tribological performance of polyphenylene sulfide (PPS) composites reinforced with multi-walled carbon nanotubes (MWCNTs) were studied as a function of carbon nanotube (CNT) proportion. The composites were prepared by compression molding and were tested for friction and wear in a pin-on-disk sliding configuration against hardened tool steel of a hardness of 55-60 HRC. The lowest specific wear rate of 15.86×10−6 mm3/Nm was obtained for the PPS-0.2%CNT composite. The variation in coefficient of friction was practically insignificant, irrespective of CNT proportion. The transfer films formed on the counterface during sliding were examined by optical microscopy and atomic force microscopy (AFM) to investigate the characteristics of transfer film in terms of topography and texture of transfer film. The worn pin surfaces were also examined by AFM to study the behavior of wear and friction of the composites. Three-point flexural tests and hardness measurements were carried out for PPS-CNT composites, where CNT concentration varied from 0.2 to 10 vol%. The highest flexural strength was observed in the PPS-0.2%CNT composite. The change in flexural strength with CNT proportion is discussed in terms of surface hardness and structural integrity of the composites examined by scanning electron microscopy (SEM).
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  • Yoshiyuki Nagatomo, Takeshi Kitahara, Toshiyuki Nagase, Yoshirou Kurom ...
    2008 Volume 49 Issue 12 Pages 2808-2814
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    Changes in the microstructure of the interface between an Al layer and an AlN plate during thermal cycling was studied to clarify the fracture mechanism of the Al/AlN interface. Observation of the interface with an ultra-sonic flaw detector indicated that a crack was generated at an edge of the Al layer after approximately 2000 thermal cycles. Cross-section observation using SEM-AsB (Angle Selective Backscattered electron detector) revealed that the crack propagated into the Al layer and ran along the interface. The grain size of Al around the crack tip is 0.2–1.0 μm. This size is much smaller than that in the initial Al layer, which was approximately 500 μm. It is considered that the refinement of Al grains was due to the accumulation of strains in the Al layer during the thermal cycling. Observations using SEM-AsB of higher magnification and TEM revealed that the crack was formed in the Al layer during thermal cycling, and propagated along the Al grain boundaries. SEM-EsB (Energy Selective Backscattered electron detector) image with a low accelerating voltage revealed that Si particles were precipitated in the Al layer during the thermal cycling. The Si particles were thought to be effective to hinder the progress of the refinement of Al grains.
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  • Nagatsugu Mukaibo, Yasuo Shimizu, Yuh Fukai, Toshiaki Hiroi
    2008 Volume 49 Issue 12 Pages 2815-2822
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    In an effort to realize the long-term stability of the magnetostrictive property of electrodeposited Ni-Fe alloy films, heat treatments needed for eliminating the possible effect of hydrogen and hydrogen-induced vacancies have been investigated, mainly by use of thermal desorption spectroscopy. While metal-atom vacancies begin to move only above ∼500 K, hydrogen atoms can undergo slow motion and concomitant changes of state at room temperature, and are therefore believed to be a major cause of the long-term drift of the magnetism. Hydrogen atoms dissolved on regular interstitial sites can be completely removed by high-frequency pulse heating to 668 K, and those trapped by vacancies with relatively low binding energies by additional heat treatments to 453 K for over 1 h. This combination of heat treatments was found to reduce substantially the change of state of hydrogen during subsequent aging tests (383 K for 400 h), and proved to be effective for ensuring the long-term stability of magnetostrictive Ni-Fe film sensors.
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  • Man Seung Lee, Jin Young Lee, J. Rajesh Kumar, Joon Soo Kim, Jeong Soo ...
    2008 Volume 49 Issue 12 Pages 2823-2828
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    We have conducted solvent extraction of Pt(IV) from HCl solution with Alamine336. Solvent extraction reaction in our system was determined from the experimental results by graphical method. The equilibrium constant of the solvent extraction reaction was estimated from our experimental results by considering the activity coefficients of chemical species present in the aqueous phase with Bromley equation. Bromley interaction parameter between hydrogen ion and PtCl62− was evaluated from the solvent extraction data reported in the literature. Solvent extraction of PtCl4 by Alamine336 and the corresponding equilibrium constant in our experimental range can be represented by PtCl62−+R3NH2Cl2,org=PtCl6R3NH2,org+2Cl, Kex=1.9×103. The measured distribution coefficients of Pt(IV) agreed well with those calculated in this study.
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  • Koji Murakami, Makoto Hino, Masao Takamizawa, Kiyomichi Nakai
    2008 Volume 49 Issue 12 Pages 2829-2836
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    Generation and growth of whiskers on tin electroplating was studied by scanning electron microscopy and X-ray diffraction. When the surface of the plating, whose thickness was 1 μm, was etched by argon ion beam to remove native oxide scale and kept in a vacuum, whiskers were rarely observed but many nodules were formed. While residual stress of tin plating (1 μm) and the number of whiskers increased with the amount of Cu6Sn5 formed between the tin plating and copper substrate, the 10 μm thickness specimen showed no meaningful change and no whiskers were found. The orientation of whiskers was shown to be identical throughout a crystal by electron backscattering diffraction even when kinked. The mechanism of generation and growth of whiskers is considered to be due to diffusion of tin atoms induced by inhomogeneous strain field, formation of vacancies, and the resulting increase in volume of the grain receiving the tin atoms. Energy change in the growth of whiskers was modelled and calculated, and the main factor determining the growth was found to be the formation enthalpy of a vacancy and the entropy of configuration.
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  • Hidetoshi Fujii, Yasufumi Yamaguchi, Shoji Kiguchi, Kiyoshi Nogi
    2008 Volume 49 Issue 12 Pages 2837-2843
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    A new surface hardening technology for cast irons was developed by applying the Friction Stir Processing (FSP) in which the matrix can be controlled in the solid state. Flake graphite cast iron (FC300) and spheroidal graphite cast iron (FCD700) were used to investigate the validity of this new method. As a result, it has been clarified that a Vickers hardness of about 700 HV is obtained for both the flake graphite cast iron and the spheroidal graphite cast iron, and that the hardness depends on the size and the density of the martensite phase. Moreover, the hardness can be controlled down to about 500 HV by changing the stirring degree. For previous hardening methods, post surface-processing was required because a large distortion was generated. However, with this new method, many advantages, such as a higher surface hardness and unnecessary post surface-processing, could be obtained.
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  • Shinji Fukumoto, Taiju Matsuo, Daisuke Kuroda, Atsushi Yamamoto
    2008 Volume 49 Issue 12 Pages 2844-2849
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 16, 2008
    JOURNALS FREE ACCESS
    The feasibility and microstructural development of high-nitrogen-containing nickel-free austenitic stainless steel by small-scale resistance spot welding were studied. Almost fully austenitic cellular microstructure was developed in weld nuggets because the cooling rate of approximately 105 Ks−1 was much faster than that in conventional fusion welding processes. Only a small amount of delta ferrite was formed at the gamma grain boundary in the weld, and chromium nitride precipitation was observed both in the gamma grains and at the grain boundary. No significant defects and sensitization were observed in the weld nugget and in the heat affected zone, respectively, and an adequate joint strength was obtained.
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  • Song Li, Guoqiang Xie, Dmitri V. Louzguine-Luzgin, Ziping Cao, Noboru ...
    2008 Volume 49 Issue 12 Pages 2850-2853
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 22, 2008
    JOURNALS FREE ACCESS
    Microwave (MW) heating and sintering of Ni-based bulk metallic glass matrix composite, consisting of gas-atomized Ni52.5Zr15Nb10Ti15Pt7.5 glassy alloy and tin powders, was performed without external pressure by using a single-mode applicator. These powders could be heated well in the magnetic field maximum, but not heated enough in the electric field maximum. A bulk sintered body with the retention of the amorphous phase was obtained below 783 K in an inert atmosphere. The addition of Sn particles promoted the densification of the sintered Ni52.5Zr15Nb10Ti15Pt7.5 glassy specimen. The results suggest that the MW sintering of metallic glasses offers a flexibility of fabricating bulk metallic glasses and metallic glass matrix composites.
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  • Hiroshi Kimura, Takashi Uchino
    2008 Volume 49 Issue 12 Pages 2854-2860
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    The isothermal compressive forming is carried out in the cylindrical nanocrystalline tetragonal (ZrO2·3 mol%Y2O3)80(Al2O3)20 sample, as prepared by consolidating the attrition milled amorphous powder in the absence of any additive, using the thermo-mechanical processing equipped with electric current heating, in order to provide a quantitative analysis for the superplastic flow inherent to the nanocrystalline ceramics. The nanocrystalline tetragonal (ZrO2·3 mol%Y2O3)80(Al2O3)20 sample shows a large decrease in true plastic strain rate (\\dotε) up to a high compressibility of 0.75 with a decrease in true stress (σ) without void formation and grain growth at the temperature from 1440 to 1590 K. The strain rate sensitivity exponent (m) as defined by the relationship of the form, m=∂lnσ⁄∂ln\\dotε shows the constancy of 0.7 at a higher level of the strain rate compensated by temperature and reciprocal true stress, \\dotεσ−1exp(QkT), following an increase from approximately 0.3 at a lower level of the parameter, for the superplastic flow in nanocrystalline (ZrO2·3 mol%Y2O3)80(Al2O3)20. The flexural strength of consolidated tetragonal (ZrO2·3 mol%Y2O3)80(Al2O3)20 with the longitudinal crystallite size of approximately 40 nm is greatly enhanced by compressive forging relative to that of consolidated sample, and then characterized by the size effect with aspect ratio of sample width (W) to height (H) having nearly 2 GPa at the maximum in the case of WH=1.
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  • Hideo Nishino, Shuichi Masuda, Kenichi Yoshida, Masakazu Takahashi, Hi ...
    2008 Volume 49 Issue 12 Pages 2861-2867
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    Theoretical and experimental investigations of transmission coefficients of longitudinal waves through metal plates immersed in air have been carried out for noncontact and nondestructive testing (NDT) of metal plates. Transmission coefficients through metal plates in water and through polymer plates in air have also been shown for comparisons. Theoretical relations between the transmission coefficients and the Lamb wave dispersions were described. It was confirmed that the transmission coefficients took high values when the Lamb waves were generated without exception. Quantitative evaluations for the transmission coefficients were investigated for the use of the air-coupled ultrasounds. The experimental verifications were carried out using 1-, 3-, and 5-mm-thick aluminum plates. The experimental results of the transmission coefficients were in fairly good agreement with the theoretical predictions.
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  • Lihua Zhang, Tsuyoshi Tosho, Noriyuki Okinaka, Tomohiro Akiyama
    2008 Volume 49 Issue 12 Pages 2868-2874
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: October 29, 2008
    JOURNALS FREE ACCESS
    Thermoelectric properties of Al-doped ZnO prepared by solution combustion synthesis using urea as fuel and sintered by spark plasma sintering were investigated for developing an energy- and time-saving synthesis method to decrease its thermal conductivity without a significant deterioration in other thermoelectric properties. The desired materials were successfully synthesized and sintered. The thermoelectric properties of the synthesized products subjected to planetary ball milling (PBM) treatment before sintering were compared with those of synthesized products not subjected to PBM treatment; the results showed that the former products had a larger power factor and higher thermal conductivity than the latter products. The thermal conductivity of all as-synthesized products was in the range of 8.3–19.7 W·m−1·K−1 at room temperature, which was significantly lower than that of the products synthesized by a conventional solid-state reaction method. (Zn0.99Al0.01)O obtained by PBM had the highest dimensionless figure of merit ZT of 0.050 at 863 K. From these results, it is inferred that solution combustion synthesis is an effective method for synthesizing Al-doped ZnO with relatively low thermal conductivity for high-temperature thermoelectric applications.
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  • Toshiaki Morita, Yusuke Yasuda, Eiichi Ide, Yusuke Akada, Akio Hirose
    2008 Volume 49 Issue 12 Pages 2875-2880
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    We investigated a new bonding technique utilizing micro-scaled silver-oxide (Ag2O) particles. The results of our investigations revealed that bonding between electrodes using for semiconductor modules can be accomplished by adding myristyl alcohol to silver-oxide particles, followed by heating the mixture in air at 300°C under a pressure of 2.5 MPa. Since this bonding technique produces silver particles with a size of a few nanometers when the silver oxide is reduced by the presence of the alcohol, low-temperature sintering and bonding can be achieved.
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  • Hidekazu Sueyoshi, Ryosuke Ishii, Hisayoshi Fukudome, Shinji Mizokuchi ...
    2008 Volume 49 Issue 12 Pages 2881-2886
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    In order to develop an advanced soldering material, the Cu/Fe alloys were produced by using powder metallurgy and the soldering properties were examined. Thermal conductivity of Cu/Fe alloy decreased with the increase in the volume fraction of pores, while it increased with the increase in the volume fraction of Cu particles. Wettability of Cu/Fe alloy was better than that of conventional Fe plating. Comparing the consumption amounts under the same wettability, the amount of Cu/Fe alloy consumed was smaller than that of Fe plating consumed.
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  • Xue Li, Chuntao Chang, Takeshi Kubota, Chunling Qin, Akihiro Makino, A ...
    2008 Volume 49 Issue 12 Pages 2887-2890
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    The effect of Cr addition on the glass-forming ability (GFA), the magnetic properties, and corrosion resistance of (Fe0.76Si0.096B0.096P0.048)100−xCrx (x=0, 2, 4 and 6) bulk glassy alloys (BGAs) with high Fe contents was investigated. 4% Cr addition makes the alloy composition to approach towards a eutectic point, which could result in an increase in the GFA. The BGA rod with diameters up to 3 mm was produced by copper mold casting. These BGAs exhibit a rather high saturation magnetization of 1.10–1.50 T and lower coercive force of 1.4–2.4 A/m. A significant improvement in corrosion resistance was observed with increasing Cr content. Furthermore, these Fe-based BGAs exhibit super high strength of ∼3.3 GPa and Young’s modulus of 168 GPa.
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  • Takashi Ueda, Chinatsu Okamura, Kazuhiro Hasezaki
    2008 Volume 49 Issue 12 Pages 2891-2894
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    This article was retracted. See the Notification.
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  • Shuji Harada, Hiroyuki Tanaka, Hideaki Araki, Minoru Kubota
    2008 Volume 49 Issue 12 Pages 2895-2898
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    The hydrogen outgassing of a Pd-H specimen is greatly accelerated by the presence of oxygen. Details of the outgassing process of Pd-H systems are investigated by gravimetric method as a function of lapse time and of various atmospheric conditions. The acceleration of the outgassing by oxygen was restricted when the palladium specimen is exposed with a preferred surface orientation (111). The face dependence and acceleration mechanism have been discussed on the basis of surface science.
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  • Salvatore Grasso, Yoshio Sakka, Giovanni Maizza
    2008 Volume 49 Issue 12 Pages 2899-2906
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    In recent years the number of publication on SPS has grown exponentially although the process itself is still not completely understood. The SPS process is governed by a complex bulk and contact multiphysics. The contact resistance between SPS system elements is crucial to understand the overall current and temperature distribution. This work is undertaken in order to improve our fundamental understanding on the contact resistance behaviour in the SPS system. The effect of the initial punch-die clearance is experimentally investigated for the first time during SPS heating. The results are given in terms of temperature-time and voltage-time profiles for various clearance values. It is shown that the initial punch-die clearance is a key SPS parameter to be specified when different SPS experiments or apparatus features have to be compared and offers another means to control the temperature gradient along the radius.
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  • Hideo Murata, Takuya Ohba
    2008 Volume 49 Issue 12 Pages 2907-2911
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    Sputter deposited Cr-Mo alloy films have been investigated in electrical properties and microstructures. The resistivity of the films decreased with the Mo concentration from 20 to 40 at% and increased up to 80 at%Mo and showed lowest value at Mo film. This resistivity change was discussed with microstructure observations, XRD and recoiled Ar concentration. SEM and TEM images indicated that several grains were combined and form lager aggregated grains and columnar structure. Stress in the films was discussed also with relationship of Mo concentration.
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  • Hanbin Chen, Bin Yang
    2008 Volume 49 Issue 12 Pages 2912-2915
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    A bulk nanostructured Al-Zn-Mg-Cu alloy with high contents of alloy elements was fabricated by cryomilling followed by spark plasma sintering (SPS) techniques. Higher strain and lower strength were obtained in the SPS-processed Al-Zn-Mg-Cu alloy samples. This is due to the agglomeration of MgZn2 precipitated on the contact zones of powders during the SPS process. The strength of the Al-Zn-Mg-Cu alloy can be improved further by an optimize heat treatment technique, after which the precipitation-hardening effect of MgZn2 particles precipitated homogeneously in grain interiors was enhanced. The experimental results have shown that modifying the MgZn2 size and distribution is beneficial to improve the mechanical property of the nanostructured Al-Zn-Mg-Cu alloy.
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  • Yasumasa Chino, Kensuke Sassa, Mamoru Mabuchi
    2008 Volume 49 Issue 12 Pages 2916-2918
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
    Texture and stretch formability of Mg-1.5 mass%Zn-0.2 mass%Ce alloy rolled at different rolling temperatures were investigated. The Mg-Zn-Ce alloy rolled at 723 K and annealed at 623 K tended to produce a TD-split texture. The TD-split texture contributed to the low average r-value and high tensile elongation, resulting in the significant high stretch formability corresponding to the commercial Al alloys.
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  • J. C. Qiao, Z. P. Xi, H. P. Tang, J. Y. Wang, J. L. Zhu
    2008 Volume 49 Issue 12 Pages 2919-2921
    Published: December 01, 2008
    Released: November 25, 2008
    [Advance publication] Released: November 12, 2008
    JOURNALS FREE ACCESS
    Porous sintered fiber metals with different relative densities were successfully prepared by using vacuum sintering process. Compressive property and energy absorption capacity of porous sintered fiber metals were investigated under quasi-static conditions. The results indicate that compressive stress-strain curves of porous sintered fiber metals exhibit three distinct deformation regions: elastic region, stress plateau region and densification region. The compressive property of porous sintered fiber metals can be interpreted by the Gibson-Ashby theory. It is found that compressive property, energy absorption capacity and energy absorption efficiency of porous sintered fiber metals present significant relative density sensitivity. The energy absorption capacity of the samples rises from 7.17 to 25.75 MJ·m−3 when relative density increases from 0.177 to 0.355.
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  • Susumu Miyamoto, Masatoshi Watanabe, Takayuki Narushima, Yasutaka Iguc ...
    2008 Volume 49 Issue 12 Pages 2922
    Published: December 01, 2008
    Released: November 25, 2008
    JOURNALS FREE ACCESS
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