Materials Transactions, JIM
Online ISSN : 2432-471X
Print ISSN : 0916-1821
ISSN-L : 0916-1821
Volume 40, Issue 1
Displaying 1-13 of 13 articles from this issue
  • Kazuyoshi Sekine, Jun Wang
    1999 Volume 40 Issue 1 Pages 1-6
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    The aim of this paper is to clarify the difference in textural behavior during rolling between low and very low stacking fault energy fcc materials. The rolling texture developments of pure silver and Ag–Zn solid solution alloys containing 8 mass% and 18 mass%Zn were investigated in detail by means of the X-ray texture analysis including the reliable calculations of the orientation distribution function for a wide range of rolling reduction. At higher reductions in thickness (>95%), the terminal textures in all specimens of Ag and Ag–Zn alloys were almost similar, and they exhibited the typical brass type rolling texture in which the dominant {110}⟨112⟩ was developed with the minor component of {110}⟨001⟩. However, it was found at medium degrees of reduction (approximately 50%–75%) that the Ag–Zn alloys having very low stacking fault energies behaved in remarkably different fashion compared to the silver alloy with a moderately low value of stacking fault energy. In such a medium region of rolling reduction, the formation of {111}⟨011⟩ type component which should be considered as a distinct texture component of very low stacking fault energy alloys, such as Ag–Zn alloys, were enhanced with increasing Zn content. This characteristic feature appearing in the rolling texture of very low stacking fault energy alloys is discussed in terms of “the non-Wassermann effect” of deformation twinning which has been suggested by one of the authors already.
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  • Eiichiro Matsubara, Ryoji Kakiuchi, Kaku Asada, Asaya Fujita, Kazuaki ...
    1999 Volume 40 Issue 1 Pages 7-12
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    The concentration dependence of transition metals Cr and Mn on atomic structures in amorphous La(Co1−xCrx)13 and La(Co1−xMnx)13 alloys has been studied by X-ray diffraction. The concentrations x are varied from 0.05 to 0.30 and from 0.05 to 0.40 in amorphous La(Co1−xCrx)13 and La(Co1−xMnx)13 alloys, respectively. The fundamental unit structure is a Co(Cr) icosahedron in the amorphous La(Co1−xCrx)13 alloys, which consists of 12Co(Cr) atoms at its vertices and a Co atom at its center. The distribution of the icosahedra around a La atom in the near neighbor region resembles that in the crystalline LaCo13 phase and is gradually changed at longer distance. The atomic structure shows no significant change up to x=0.30 in the amorphous La(Co1−xCrx)13 alloys. The atomic structure is also composed of the Co(Mn) icosahedra randomly distributed around a La atom in the amorphous La(Co1−xMnx)13 alloy. The atomic distance of the first neighbor Co–Co pairs, however, increases and the icosahedral cluster is gradually deformed with the Mn concentration. The difference of the concentration dependence of the atomic structure between the amorphous La(Co1−xCrx)13 and La(Co1−xMnx)13 alloys is understood by a balance of the size difference between Cr and Mn atoms, and the allowed size of an atom substituting for Co atoms located at the vertices of the icosahedron without any significant deformation.
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  • Hidekazu Sueyoshi, Kazuto Hamaishi, Takayuki Shiomizu
    1999 Volume 40 Issue 1 Pages 13-19
    Published: 1999
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Three types of austenitic stainless steels, SUS304, SUS316 and SUS310 were preheated in air in a temperature range of 573 to 973 K for 1 h, followed by nitriding in NH3 gas in a temperature range of 773 to 873 K. The influences of nitriding temperature and time on nitriding behavior were examined in connection with the kinetics of the nitriding reaction.
    The nitriding reaction occurs locally at an early stage of the nitriding treatment. The whole surface becomes covered with a nitrided layer by coalescence of nitrided regions. Thereafter, the nitrided layer with a uniform thickness is formed by the growth in the depth direction.
    Diffusion of nitrogen through the nitrided layer is the rate-determining process in the growth of the nitrided layer. Atmospheric preheating has no influence on the growth of the nitrided layer. On the other hand the nucleation of the nitriding reaction is greatly accelerated by atmospheric preheating. This is attributed to both considerable dissociation of NH3 gas and the rapid diffusion of nitrogen through the surface film due to the change in the composition of the surface film with atmospheric preheating. The hardness of the nitrided layer decreases with increasing nitriding temperature. This tendency is especially significant for SUS304 and SUS316 steels.
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  • Jonkion M. Font, Mitsuhisa Hino, Kimio Itagaki
    1999 Volume 40 Issue 1 Pages 20-26
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    As a contribution to the understanding of oxygen-blowing smelting of the nickel-copper-iron matte, the phase equilibrium and the distribution of minor elements between the iron-silicate base slag saturated with silica and the Ni3S2–Cu2S–FeS matte with a Ni:Cu molar ratio of 1 was investigated in a magnesia crucible under controlled partial pressures of SO2 at 10.1, 50.7 and 101.3 kPa and 1573 K. At a given matte grade, the solubility of copper in the slag is found to be independent of pSO2 while the solubility of nickel is dependent on pSO2 and these behaviors are analyzed thermodynamically based on a concept of oxidic and sulfidic dissolutions of the components in the slag. The distribution ratio of X, LXs/m, is defined as (mass%X in slag)/{mass%X in matte}. At a fixed pSO2, the distribution ratios of As and Sb decrease remarkably with increasing matte grade, and in the case of Bi, LBis/m decreases with increasing matte grade up to about 55 mass%Ni and then increases slightly in the higher range. When the matte grade is specified, the distribution ratios of As, Sb and Bi increase with increasing pSO2. The results for the present Ni3S2–Cu2S–FeS matte system were compared with those for the Cu2S–FeS and Ni3S2–FeS matte systems.
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  • Ichiro Aoi, Makoto Yoshida, Hideharu Fukunaga, Hideo Nakae
    1999 Volume 40 Issue 1 Pages 27-33
    Published: 1999
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    In order to study the influence of gravity on the eutectic growth of Ag–Si and Al–Si alloys, both the downward (direction of gravity) and upward (opposite to direction of gravity) unidirectional solidifications were carried out. In the case of the downward U.D.S., the molten metal is confined between the crucible and solid. This inevitably produces the shrinkage cavity at the solid/liquid interface during solidification. In this study, the zone-melting technique was used to avoid this cavity formation. The results of this study were as follows:
    (1) In the case of the downward U.D.S. of the Ag–Si alloy, the eutectic silicon phase grew discontinuously and dispersed in the α-Ag phase with a diameter of several micrometers. This is caused by the large difference in specific density between silver and the silicon phase. On the other hand, in the case of the upward U.D.S., the silicon phase grew continuously and its morphology showed the typical faceted/non-faceted eutectic.
    (2) The eutectic silicon phase of the Al–Si alloy grew continuously regardless of growth direction. There was no morphological difference between the upward and downward U.D.S. specimens.
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  • Peter Ratchev, Bert Verlinden, Peter De Smet, Paul Van Houtte
    1999 Volume 40 Issue 1 Pages 34-41
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    Artificial ageing of several Al–Mg–Cu alloys for car-body applications has been studied. The Cu:Mg ratio was between 0.14 and 0.29 (in mass) and the ageing temperatures were in the range 60–180°C. Strengthening curves during ageing at 140 to 180°C show several typical stages, namely an initial jump compared to the as-annealed state, followed by a linear increase and finally a peak in strength which appears after considerable ageing time. A two-fold precipitation sequence has been confirmed. On one side S″- and further on S′-phase (precursors of the Al2MgCu phase) precipitate heterogeneously on dislocation loops and helices, on the other hand a homogeneous precipitation sequence in the matrix of the type: Cu/Mg clusters (GPB zones)→S″→S′ has also been observed. The ageing at 60°C follows the same scheme but at much lower speed, so up to three months only the first precipitation stages (i.e. clusters in the matrix and S″ on dislocations) were found. An increased amount of Cu increases the bake hardening response, not only at the peak but over the whole ageing curve. Increasing the amount of Mg (or lowering the Cu:Mg ratio), retards the precipitation sequence which increases the stability against natural ageing. It does not severely decrease the precipitation hardening response since for this practical application the hardening is given by the initial jump. This last appears promptly in the first minutes of ageing at 140–180°C, irrespective of the Mg content. Decreasing the baking temperature from 180 to 140°C is also not affecting the first two hardening stages which means that traditional baking temperatures (160–180°C) can be decreased to 140°C and may be less.
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  • Cang Fan, Akira Takeuchi, Akihisa Inoue
    1999 Volume 40 Issue 1 Pages 42-51
    Published: 1999
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    Bulk nanocrystalline alloys with good ductility and high tensile strength (σf) in Zr–Al–Cu–Pd and Zr–Al–Cu–Pd–Fe systems were formed by partial crystallization of cast bulk amorphous alloys. The nanostructure alloys consist of nanoscale Zr2(Cu, Pd) compound surrounded by the remaining amorphous phase. The particle size and interparticle spacing of the compound are less than 10 and 2 nm, respectively. The crystallization of a ternary Zr60Al10Cu30 amorphous alloy occurs by the simultaneous precipitation of Zr2Al and Zr2Cu phases with large particle size of about 500 nm and hence the addition of Pd is essential for formation of the nanostructure. The nanostructure alloys in the cast cylinder of 2 to 3 mm in diameter keep good ductility in the volume fraction (Vf) range of the compound phase below 20 to 40%. The σf, Young’s modulus (E) and fracture elongation (ε) increase from 1760 MPa, 81.5 GPa and 2.10%, respectively, at Vf=0% to 1880 MPa, 89.5 GPa and 2.17%, respectively, at Vf=40% for the Zr60Al10Cu20Pd10 alloy and from 1750 MPa, 81.1 GPa and 2.21%, respectively, at Vf=0% to 1850 MPa, 85.6 GPa and 2.28%, respectively, at Vf=28% for the Zr60Al10Cu15Pd10Fe5 alloy. The formation of the bulk nanostructure alloys with high σf and good ductility in coexistent with the compound is presumably because the remaining amorphous phase can contain a number of free volumes by water quenching from the supercooled liquid region. The synthesis of the high-strength bulk amorphous alloys containing nanoscale compounds is important for future development of a new type of high-strength material.
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  • Nobuya Shinozaki, Masami Suenaga, Kusuhiro Mukai
    1999 Volume 40 Issue 1 Pages 52-56
    Published: 1999
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    A basic research study for improvement of the galvanizing process has been conducted. The contact angle and surface tension of the molten zinc/oxide ceramic systems were measured at 873 and 973 K by the sessile drop method. The measurement became possible by using sponge titanium as deoxidizer under vacuum. It was found that zinc didn’t react or wet zirconia and alumina significantly. The surface tension of molten zinc decreased slightly with increasing temperature. On the basis of the work of adhesion, it was presumed that the dispersion force was predominant for the bond at zinc/zirconia and zinc/alumina interface.
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  • Seiji Saikawa, Kiyoshi Nakai, Yasuo Sugiura, Akihiko Kamio
    1999 Volume 40 Issue 1 Pages 57-63
    Published: 1999
    Released on J-STAGE: June 01, 2007
    JOURNAL FREE ACCESS
    The relationship between hydrogen gas content of molten metal and the porosity generated during solidification of Al–Li–Mg–Zr–Ti alloys with or without the addition of lithium was investigated. All alloys were cast into stepped-form metal mold in an argon atmosphere by the melting-casting machine. In the Al-1.90%Mg-0.15%Zr-0.11%Ti alloy step-castings, the maximum and minimum porosity were 0.77% and 0.05%, respectively, when the hydrogen gas content of the molten metal at the time of pouring was (0.19−0.60)×10−7 m3·kg−1. On the other hand, in the Al-2.36%Li-1.76%Mg-0.15%Zr-0.11%Ti alloy castings, the maximum and minimum porosities were 0.35 and 0.09%, respectively, even when the hydrogen gas content of the molten metal was (1.05−1.23)×10−7 m3·kg−1. In both types of alloys with or without Li, the locations at which porosity was generated were either grain boundaries or dendrite cell gaps. The size of the pores decreased as the hydrogen gas content decreased, and their shape changed from spherical to flake-like. The critical hydrogen gas content in the molten metal at which no porosity was generated, were (0.70−0.98)×10−7 m3·kg−1 for the 2.36%Li-added alloy and (0.12−0.28)×10−7 m3·kg−1 for the no-Li-added alloy, respectively. Therefore, the alloying of 2.36%Li increased the critical hydrogen gas content by (0.58−0.70)×10−7 m3·kg−1.
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  • Nobuyuki Nishiyama, Akihisa Inoue
    1999 Volume 40 Issue 1 Pages 64-71
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    The viscous flow of the supercooled liquid for a bulk amorphous Pd40Cu30Ni10P20 alloy was examined as a function of temperature and applied stress. The flow rate increases linearly with increasing applied stress, but the viscosity is independent of stress. Thus, the viscous flow of the supercooled liquid occurs via the Newtonian flow mechanism. The viscosity at the temperature just before crystallization is as low as 8.3×105 Pa·s and the low viscosity reflects the high resistance of supercooled liquid against crystallization. The viscosity (η) measured by thermomechanical analysis is independent of applied stress and heating rate and can be expressed as a function of temperature by equation; η=9.34×10−3exp[4135⁄(T−447)] (Pa·s). The Pd-based amorphous alloy heated at a heating rate of 0.33 K/s up to 600 K can retain the supercooled liquid state with a low viscosity of about 108 Pa·s for 1 ks. The die-forging into a three-stage die with pitch circle diameters of 4, 5 and 6 mm and a module of 0.3 was made for 120 s at 610 K under a compressive stress of 10 kPa and a three-stage gear was formed. The shape and dimension of the gear agree with the inner size of the die within a scattering of ±1%. The utilization of viscous flow in the supercooled liquid was found to be useful for secondary working of the bulk amorphous alloys which can produce a final product with near-net shape.
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  • Osvaldo A. Lambri, Andrea V. Morón Alcain, Griselda I. Lambri, ...
    1999 Volume 40 Issue 1 Pages 72-77
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    The occurrence of precipitation processes in Cu–Li alloys, produced by electrodeposition, with lithium concentrations close to 18 at%, has been studied. Analytical methods employed include the following techniques: thermogravimetry, differential scanning calorimetry, thermo-electric power, X-ray diffraction, amplitude-dependent damping and modulus measurements.
    A precipitation process at low temperatures occurs in the range 325 to 425 K. Subsequently, these precipitates disappear at temperatures between 425 and 525 K. Furthermore, another precipitation process at higher temperatures around 525 K was observed.
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  • Wei Zhang, Akihisa Inoue
    1999 Volume 40 Issue 1 Pages 78-81
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    A supercooled liquid region before crystallization was found in wide composition ranges of 0 to 65 at%Co and 1.5 to 7 at%Ln in Fe90−xyCoxLnyB20 (Ln=Nd, Sm, Tb or Dy) amorphous alloys. The supercooled liquid region shows the largest value of 41 K for the Fe47Co30Sm3B20 alloy. Besides, an internal equilibrium state leading to the disappearance of the previous thermal history is achieved within a temperature interval of 15 K. Furthermore, the Fe–Co–Ln–B amorphous alloys exhibit soft ferromagnetism with saturated magnetization (Bs) of 0.84 to 1.66 T and coercivity (Hc) of 5.0 to 36 A/m at room temperature. In addition, a high magnetostriction (λs) exceeding 40×10−6 was observed in the composition range of 0 to 10 at%Co and 1.5 to 3 at%Ln (Ln=Sm, Tb or Dy) while the highest λs reaches 58×10−6 for Fe68.5Co10Ln1.5B20 (Ln=Sm or Tb), which is higher than the highest value (44×10−6) for previously reported amorphous alloys. All the Fe68.5Co10Ln1.5B20 amorphous alloys have good bending ductility. The tensile fracture strength, Vickers hardness and Young’s modulus of the Fe68.5Co10Sm1.5B20 amorphous alloy are 3220 MPa, 990 and 76.5 GPa, respectively. The good combination of high λs, high Bs, low Hc, large ΔTx, good ductility and high mechanical strength is a promising new type of ferromagnetic bulk amorphous alloy.
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  • Chan Tung Chen, Tien Shou Lei
    1999 Volume 40 Issue 1 Pages 82-85
    Published: 1999
    Released on J-STAGE: May 23, 2007
    JOURNAL FREE ACCESS
    A PC-controlled vacuum heat treating system was used to austemper an alloyed ductile iron with 0.77%Cu and 0.5%Ni at 400°C after austenitizing at 850°C. During the progress of isothermal transformation, the resistivity of austempered ductile iron vs. time was recorded and then analyzed to determine the processing window. X-ray diffraction, heat tinting technique, and microstructural examination were conducted to examine the suitability of this processing window in terms of microstructural changes. The data of mechanical properties of the ductile iron from the same casting batch and same austempering were extracted from a concurrent work to discuss the suitability of this processing window. Both the evaluation of microstructures and mechanical properties confirmed the suitability of this processing window. A slow rate transformation during the time interval of processing window was observed which was associated with the continuous decomposition of blocky austenite and resulted in a slight variation of the mechanical properties.
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