Materials Transactions, JIM
Online ISSN : 2432-471X
Print ISSN : 0916-1821
ISSN-L : 0916-1821
Volume 36, Issue 5
Displaying 1-16 of 16 articles from this issue
  • N. Saito, K. Abiko, H. Kimura
    1995 Volume 36 Issue 5 Pages 601-609
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Elements interacting attractively with carbon are considered to have two effects opposite to each other on the rate of ε-carbide precipitation: (a) they may decrease the diffusion rate of carbon and hence the rate of ε-carbide precipitation, and (b) they may act as preferential nucleation sites to increase the number density of the precipitates and hence the rate of precipitation. However, the whole effects of such elements on the rate of ε-carbide precipitation has not been determined as yet. The purpose of the present paper is to investigate the effects of small addition of titanium, vanadium and chromium, which interact attractively with carbon, on the rate of ε-carbide precipitation. High purity alloys made from 99.99% electrolytic iron were used to minimizes the effect of impurity atoms on the precipitation kinetics of ε-carbide. The kinetics of ε-carbide precipitation was investigated by measuring at 77 K the change in the electrical resistivity due to precipitation. The number density of precipitates was investigated by TEM. The activation energy for carbon atom diffusion was determined by slope change method.
    For the concentration investigated, only titanium increases the rate of ε-carbide precipitation by increasing the number density of ε-carbide particles. In the titanium containing alloys, fine precipitates of TiC which are present in the as-quenched condition act as the preferential nucleation sites for ε-carbide. Solute titanium after quenching decreases the rate of carbon diffusion. The decreasing effect, however, is small and the whole effect of tatanium addition is to increase the rate of ε-carbide precipitation.
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  • Hiroshi Fukutomi, Akiyoshi Nomoto, Toshio Ota
    1995 Volume 36 Issue 5 Pages 610-614
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    A method to control the lamellar arrangement in TiAl intermetallic compounds is proposed. It consists of the high-temperature deformation in the α region to construct a texture and the subsequent annealing in the two phase region to precipitate the γ phase in a lamellar form. The method was examined by experiments on Ti-41 mol%Al. The high-temperature deformation resulted in the formation of a fiber texture in the α2 phase. No significant change was observed in the texture of the α2 phase after the precipitation treatment of the γ phase. Formation of a fiber texture was found in the γ phase consisting lamellae. Crystallographic analysis revealed that the pole density distribution of the γ phase can be understood by the so called Blackburn’s relationship between the α2 and γ phases. It was concluded that the texture control at the high temperature α phase is effective to obtain the oriented arrangement of lamellae.
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  • K. S. Chan, T. S. Lui, L. H. Chen
    1995 Volume 36 Issue 5 Pages 615-619
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Al-7 mass%Si-Mg cast alloys can exhibit the Portevin-LeChatelier (PL) effect if excessive aging is prevented. In the present study, the PL effect of three Al-7Si-Mg cast alloys with 0.11, 0.26 and 0.46 mass% magnesium was compared with that of an Al-7 mass%Si cast alloy. Before conducting the tension test, part of the test alloys were solution treated at 813 K and the remaining were aged at 273 K. The critical strain for the onset of flow instability could be raised by increasing the magnesium content. For the solution-treated specimens tested in the low temperature regime where the critical strain decreases with temperature, the above result should be related to the attractive interaction between silicon and magnesium solutes since the apparent activation energy for the onset of flow instability increases with increasing magnesium content. For the solution-treated specimens tested in the high temperature regime, there occurs an aging effect which is more pronounced with increasing magnesium content and temperature. Consequently, the rate of increase of the critical strain for the ternary test alloys with respect to temperature is larger with higher magnesium content. For those specimens pre-aged at 273 K, the longer the aging time, the larger the critical strain. Also, the limiting aging time for which the flow instability still exists decreases with increasing magnesium content. Aging should play the role in depleting the quenched-in vacancies and solute atoms.
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  • C. S. Shieh, T. S. Lui, L. H. Chen
    1995 Volume 36 Issue 5 Pages 620-625
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The 300 to 693 K tensile characteristics of ADI with upper bainitic structure were studied by varying the austenitization temperature (1173 and 1223 K) and austempering temperature (643 and 693 K) of a spheroidal graphite cast iron which contains 3.6 mass% C and 2.4 mass% Si. The experimental results show that the flow stress decreases with increasing austenitization and austempering temperatures. The tensile characteristics can be divided into two temperature regimes. In the lower temperature regime below about 550 K, the presence of acicular ferrite should be the main factor which leads to the common features of dynamic strain aging including strengthening, elongation drop and flow instability. The flow instability, which occurs in the temperature range of about 373 to 493 K, is more distinct with coarser microstructure. The absence of flow instability for the specimens with the finest microstructure is probably caused by its nature of high dislocation density. In the higher temperature regime above 550 K where the flow stress decreases with increasing tensile temperature, the elongation starts to drop with temperature from about 600 K. The elongation drop, which should be due to the formation of quasi-continuous carbide particles from austenite during tensile deformation, can sometimes give rise to the appearance of quasi-cleavage fracture.
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  • Sadakichi Kitajima, Kazutoshi Shinohara, Masanori Kutsuwada
    1995 Volume 36 Issue 5 Pages 626-631
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The velocity of edge and screw dislocations moving in primary slip bands and the formation rate of primary slip bands were measured in stage I deformation of neutron-irradiated copper single crystals at different strain rates at room temperature using micro-cinematography and optical micrography. The average velocity of edge dislocations was larger at least by one order than that of screw ones, and that of screw dislocations did not depend so strongly on strain rate. The formation rate of primary slip bands was proportional to strain rate. From these results, it is concluded that (1) jogs produced on moving dislocations by cutting dislocation loops result in the difference in velocity between edge and screw dislocations and (2) the change in the density of mobile dislocations as well as velocity of dislocations is responsible for the change of plastic strain rate of a crystal.
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  • Koh-ichi Sugimoto, Mitsuyuki Kobayashi, Shin-ichi Yasuki, Shun-ichi Ha ...
    1995 Volume 36 Issue 5 Pages 632-638
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The influence of deformation temperature on the Bauschinger effect (BE) of a high-strength TRIP-aided dual-phase (TDP) steel containing retained austenite particles of 10 vol% was investigated in a temperature range between 27 and 200°C.
    The BE of the TDP steel depended significantly on the deformation temperature, although such a temperature dependence did not appear in a conventional ferrite-martensite dual-phase (DP) steel. Large BE, i.e., remarkable transitional softening and subsequent permanent softening proposed by Orowan, appeared at 100 and 200°C, at which the retained austenite particles were more resistant to the strain-induced martensite transformation (SIT) than those at 27°C. The Bauschinger stress obtained at 200°C was as high as that of the DP steel.
    The retained austenite particles as a hard phase increased the Bauschinger stress. The SIT, however, was expected to lower the Bauschinger stress by the following reason. Expansion and shear strains resulting from the SIT reduced both internal stresses in the retained austenite islands and in the ferrite matrix.
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  • Tsuneyuki Hashimoto, Yusuke Isobe, Naoto Shigenaka
    1995 Volume 36 Issue 5 Pages 639-644
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The role of interstitials in the radiation-induced segregation (RIS) process in a face-centered cubic (fcc) binary alloy is investigated with a newly developed model. The model considers three types of interstitial dumbbells, their diffusion and conversion via an interstitialcy migration, recombination with a vacancy, and vacancy diffusion through the position exchange with a lattice atom. Analysis of RIS kinetics in the Cu–Au alloy is used to verify the model, and good agreement is obtained with experimental measurements. The relationship is examined between the present model and the Wiedersich-Okamoto-Lam model (WOL model) in which the mixed dumbbell movement is neglected. Effective diffusion coefficients are derived which incorporate the effect of the mixed dumbbell into the WOL model formulation.
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  • Keiichi Yokoi, Kimihisa Ito, Masanori Tokuda
    1995 Volume 36 Issue 5 Pages 645-648
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Hexagonal boron nitride was synthesized from boron oxide using super critical ammonia and solid CaO below the melting point of B2O3 by the following reaction: B2O3(s)+2NH3 (super-critical fluid)+3CaO(s)=2BN(s)+3Ca(OH)2(s). The experiment was carried out at 623–753 K and the initial ammonia pressure was 3.0–40.0 MPa. The mean diameter of obtained BN particles was 0.2–0.3 μm. The yield of BN increased with increasing temperature, initial ammonia pressure and the addition of CaO. The thermochemical calculation showed that the CaO addition suppressed the decomposition loss of ammonia during the reaction.
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  • Tamas Kekesi, Kouji Mimura, Minoru Isshiki
    1995 Volume 36 Issue 5 Pages 649-658
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    In order to obtain a metallic product from the CuCl2-HCl solution purified by anion-exchange separation, the straightforward method of evaporation to dryness and reduction with H2 was investigated. Thermodynamic study of the probable reactions in the Cu-Cl-H-O system pointed out the feasibility of the direct reduction of CuCl2. In order to find out the practical reduction rates and effective recoveries, the process was tested under different conditions. The first step of reduction, which results in the conversion of CuCl2 to CuCl, is readily executable at temperatures slightly below the CuCl-CuCl2 eutectic point. The second step, which results in the metallic product, requires higher temperatures, though safely below the melting point of CuCl. Kinetic analysis of the critical second step provided an activation energy of 138 kJ mol−1 which could be interpreted in terms of a chemical reaction dominated mixed mechanism
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  • Emad A. Abd El Meguid, Takeo Oki
    1995 Volume 36 Issue 5 Pages 659-663
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Three layers of semibright nickel (SB–Ni), bright nickel (B–Ni) and dispersed SiO2-containing nickel (D–Ni) have been prepared from a Watts electroplating bath with some organic additives. The influence of the bath additives on the free corrosion potential of each as-plated nickel layer have been examined in 5 mass% NaCl and 6 mass% Na2SO4 solutions. Exposure time in the air after nickel layer preparation assisted more oxide film formation on semi-bright than on bright nickel surfaces. The anodic and cathodic polarization curves of as-plated nickel layers in chloride and sulphate solutions were investigated by using the potentiodynamic technique. In the chloride solution, all of these nickel layers exhibited pitting corrosion and the critical pitting potential, Epit, shifts less noble in the order: D–Ni>B–Ni>SB–Ni, while in the sulphate solution the nickel layers were passivated.
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  • Shinji Itoh, Fumio Hirose, Shin’ichi Hasegawa, Ryosuke Hasegawa
    1995 Volume 36 Issue 5 Pages 664-669
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Glow discharge mass spectrometric (GDMS) analysis of titanium alloys has been studied by using a VG 9000 instrument and pin samples. Alloying elements (Al, V, Cr, Fe, Zr, Mo and Sn) and trace impurities (Si, Ni, Cu and W) in the alloys were determined with accuracy comparable to that of ordinary XRF analysis. Examine were preliminary sputtering, optimum glow discharge conditions and spectral interference between vanadium argide (51V40Ar) and 91Zr. Relative sensitivity factor (RSF) of each analyte was evaluated by analyzing the standard reference materials: NIST SRMs, BS CRMs, IMI CRMs and the Ti alloys made in our Institute. The average RSF-values obtained were 3.33 for Al, 1.40 for V, 7.09 for Cr, 2.94 for Fe, 1.59 for Zr, 3.92 for Mo and 8.89 for Sn. Using these values, the GDMS analytical values were corrected on a personal computer to the values with an accuracy (σd) ranging from 0.065(V) to 0.16(Al).
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  • Jin Onuki, Masayasu Nihei
    1995 Volume 36 Issue 5 Pages 670-675
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    W film deposition by switching bias sputtering, which features alternating operation of standard and bias sputtering, was investigated to develop a process which better fits the requirements of ultra very large scale integration circuits applications. Step coverage is improved above 50% for the holes with 0.3 μm diameter and 1 μm depth by adopting most suitable conditions in this sputtering. The bias time ratio in this method is found to be a dominant factor to raise the step coverage. The quality of W films deposited by this method is the same level as that of deposited by conventional DC sputtering. It is found that the method does not produce damages during deposition but gives low contact resistances to n+ and p+ type Si. The W metallization using this method is considered to be quite promising for submicron LSIs.
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  • Akihisa Inoue, Akira Takeuchi, Akihiro Makino, Tsuyoshi Masumoto
    1995 Volume 36 Issue 5 Pages 676-685
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    When an amorphous Fe90Nd7B3 alloy subjected to annealing for 60 to 180 s at temperatures between 923 and 1023 K consists of a mixed structure of bcc-Fe, Fe3B, Fe14Nd2B and remaining amorphous phases, the (BH)max and remanence were found to have maximum values of 113 kJ/m3 and 1.17 T, respectively. Their crystallites which precipitated through the process of Am→Am′+bcc-Fe→Am″+bcc-Fe+Fe3B→Am'″+bcc-Fe+Fe3B+Fe14Nd2B have the particle sizes of 20 to 60 nm and the thickness of the intergranular amorphous layer is 5 to 30 nm. The Fe14Nd2B phase is surrounded by the bcc-Fe and remaining amorphous phase in the optimally annealed state because it precipitates from the remaining amorphous phase which surrounds the bcc-Fe particles. The further increase in annealing temperature and annealing time causes the increase in particle size of their precipitates as well as the disappearance of the residual amorphous phase, leading to the significant decrease in (BH)max. The existence of the residual amorphous phase was also recognized for all other Fe-Nd-B alloys with maximum (BH)max values obtained by annealing the amorphous phase. The intergranular amorphous phase as well as the bcc-Fe phase is presumed to act as an effective magnetic exchange-coupled medium. This information is extremely important for the subsequent development of permanent magnet materials by the utilization of magnetic exchange-coupled state as well as for the interpretation of the appearance of hard magnetism in the use of the rapidly solidified Fe-rich amorphous phase as a precursor.
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  • Takashi Ohishi, Daisuke Shindo, Kenji Hiraga, Jun-ichi Kudoh
    1995 Volume 36 Issue 5 Pages 686-688
    Published: 1995
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    By using the imaging plate, electron diffraction patterns of an Au thin film were observed quantitatively by changing the temperature. Intensity of both Bragg reflections and the background in the electron diffraction patterns contributed from thermal diffuse scattering as well as plasmon scattering were measured accurately. It was shown that the background contributed from the thermal diffuse scattering in the electron diffraction patterns increased monotonously with the increase of temperature. The change in the observed intensity of the thermal diffuse scattering with the change in temperature was briefly discussed in terms of a theoretical model.
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  • Akihisa Inoue, Yoshinori Miyauchi, Tsuyoshi Masumoto
    1995 Volume 36 Issue 5 Pages 689-692
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Good soft magnetic properties and high saturation magnetization (Bs) were obtained for the Fe87Zr7Si4B2 and Fe86Zr7Si4B3 alloys with the partially crystallized structure consisting of nanoscale bcc grains surrounded by the remaining amorphous phase. These alloys consist only of an amorphous phase and have good bending ductility in the as-quenched state and the partial crystallization to the nanocrystalline structure by annealing for 3.6 ks at 873 K causes the simultaneous achievement of 1.6 T for Bs, 14000 for permeability at 1 kHz (μe) and <1×10−6 for magnetostriction (λs). No zero magnetostriction is obtained for nanoscale bcc Fe90Zr10 and Fe90Zr7B3 alloys and the addition of about 4 at% Si is essential for the achievement of the zero magnetostriction in the Fe–Zr base alloys. The glass formation at the new alloy compositions, the good ductility in the as-quenched amorphous state and the good soft magnetic properties in the partially crystallized state allow us to expect that the present alloys develop subsequently as a new type of soft magnetic material.
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  • P. Markondeya Raj, K. T. Jacob
    1995 Volume 36 Issue 5 Pages 693-694
    Published: 1995
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
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