Materials Transactions, JIM
Online ISSN : 2432-471X
Print ISSN : 0916-1821
ISSN-L : 0916-1821
Volume 41 , Issue 11
Showing 1-38 articles out of 38 articles from the selected issue
  • Akira Takeuchi, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1372-1378
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Chemical mixing enthalpy (ΔHchem) and mismatch entropy normalized by Boltzmann constant (SσkB) corresponding to the three empirical rules for the achievement of high amorphous-forming ability (AFA) were calculated with thermodynamical functions for the gross number of 6450 alloys in 351 ternary amorphous systems. The ternary amorphous alloys have ΔHchem of −86 to 25 kJ/mol and SσkB of 1.0×10−3 to 5.7. The average values of ΔHchem and SσkB are calculated to be −33 kJ/mol and 0.33, respectively. The 30 alloys in 9 ternary amorphous systems including 10 alloys in Ag–Cu–Fe system have positive values of ΔHchem. Most of the ternary amorphous alloys have the values of ΔHchem and SσkB inside a trapezoid region in ΔHchem−log(SσkB) chart except mainly for the H- and the C-containing alloys, Si–W–Zr system and the 32 alloys having positive values of ΔHchem. The analysis of AFA was carried out for typical five ternary amorphous systems. The following four results are derived. 1) Al–La–Ni and B–Fe–Zr alloys have high AFA in accordance with the concept of the three empirical rules. 2) The further multiplication of alloy components causes an increase in the AFA of Al–B–Fe alloys. 3) Thermodynamical factors represented by melting temperature and viscosity at the melting temperature are required for evaluation of AFA for Mg- and Pd-based amorphous alloys. 4) A tendency for log(SσkB) to increase with decreasing ΔHchem is recognized in each alloys system, implying the stabilization of an amorphous phase against solid solution and intermediate phase.
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  • Eiichiro Matsubara, Shigeo Sato, Muneyuki Imafuku, Takahiro Nakamura, ...
    2000 Volume 41 Issue 11 Pages 1379-1384
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
      This paper has been retracted by the Editorial Committee with the first author’s agreement due to substantial overlap with the following paper previously received in another journal.

    Mater. Sci. Eng. A 312 (2001) 136-144
    Structural study of Amorphous Fe70M10B20 (M=Zr, Nb and Cr) alloys by X-ray diffraction
    E. Matsubara, S. Sato, M. Imafuku, T. Nakamura, H. Koshiba, A. Inoue, Y. Waseda (Received on May 8, 2000)

      And thus, it shall not be regarded as an original paper.

      Although this paper was submitted to the Special Issue on Bulk Amorphous, Nano-Crystalline and Nano-Quasicrystalline Alloys by the first author without understanding the bylaws of Materials Transactions, JIM, it was not an appropriate deed.

      The first author acknowledges the substantial overlap and his apologies have been accepted accordingly. The notice has been issued to all the authors to pay more careful attention in submitting papers.
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  • Tadakatsu Ohkubo, Takashi Hiroshima, Yoshihiko Hirotsu, Akihisa Inoue, ...
    2000 Volume 41 Issue 11 Pages 1385-1391
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    A change of atomic structure of amorphous La55Ni25A120 alloy in the course of annealing in the “supercooled liquid region” has been investigated by in-situ electron diffraction and high-resolution electron microscopy (HREM) using a specimen heating-stage in TEM. For recording electron intensities an imaging plate was used. In order to remove the inelastically scattered electrons an energy filter was used for recording electron diffraction patterns. No appreciable change was found in the in-situ HREM observation across the glass transition temperature on heating. However, atomic pair distribution function (PDF) analysis revealed a clear structural change in the “supercooled liquid region”. The observed structural change is concerned with the local development of strong atomic correlations especially for La–La and Al–Ni and also with the increase of structural volume. The atomic configurational change is closely related to the phase separation in the later crystallization stage.
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  • Takaomi Itoi, Hideya Onodera, Shigeyuki Miura, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1392-1396
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Structural change in the supercooled-liquid region of Fe58Co7Ni7Zr8B20 glassy alloy has been examined by Mössbauer spectroscopy. Analyses of the Mössbauer spectra showed that the hyperfine field distribution patterns in quenched states from supercooled-liquid state differ from that in the as-melt-spun state. As the quenching temperature increases, the hyperfine field distribution tends to show several peaks some of whose hyperfine field values seem to correspond well to those in crystalline Fe, Fe3B, Fe2B and Fe2Zr, although these distribution peaks are quite broad. These results as well as the initial crystallization behavior indicate that the thermal treatment in the supercooled-liquid region causes a compositional short-range order. It is, however, supposed that the chemical bond strengths are competitive among the Fe3B-, Fe2B-, FeZr2- and Fe–Zr–B-type compositional short-range order, and their growth frustrate each other in the supercooled-liquid region. This competitive frustration should be one of the reasons for the thermal stability against crystallization that occurs in the glassy alloys with a large supercooled-liquid region.
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  • Zhao Ping Lu, Hao Tan, Yi Li
    2000 Volume 41 Issue 11 Pages 1397-1405
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Glass formation and glass forming ability of six La-based La–Al–Ni–Cu–(Co) alloys have been studied systematically by Bridgman solidification and thermal analytical measurement. With increased Cu content the critical growth velocity for glass formation in La55Al25Cu20−xNix (x=0–20) alloys shows a steep minimum at 10 at%Cu, however, replacement of Ni by Co leads to a further decrease in the critical cooling rate for the La55Al25Ni5Cu10Co5 alloy. The thermodymics of these alloys was studied in the undercooled liquid and crystalline state by means of temperature-modulated DSC. Reduced glass transition temperature Trg given by TgTl (Tg the glass transition temperature and Tl the offset melting point) is found to show a stronger correlation with critical cooling rate for glass formation than that given by TgTm (Tm the onset melting point). The glass forming ability of these alloys is discussed in terms of microstructure selection and driving force for crystallization.
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  • Faqiang Guo, Sebastien Enouf, Gary Shiflet, Joseph Poon
    2000 Volume 41 Issue 11 Pages 1406-1409
    Published: 2000
    Released: May 23, 2007
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    The glass forming ability and thermal stability of the quenched amorphous phase are evaluated in Al87Ni7Gd6−x(Ca, Sr, Ba)x alloys in terms of large atomic size effects of Alkali metals. Thermal analysis indicates that the thermal stability of the quenched amorphous phase decreases with the addition of Ca and increases with the addition of up to 2 at%Sr and Ba, as seen in the change of primary crystallization peak temperature and activation energy for primary crystallization. However, the enhanced thermal stability of the quenched amorphous phase with the addition of Sr and Ba does not lead to easier glass formation. The critical thickness of the quenched ribbons with completely amorphous phase is found to decrease from 300 to 70 μm as the content of Alkali elements is increased at the expense of Gd. These results reveal the different effects of atomic size on the glass forming ability and the thermal stability of the quenched amorphous phase against crystallization.
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  • Yong Zhang, Ming Xiang Pan, De Qian Zhao, Ru Ju Wang, Wei Hua Wang
    2000 Volume 41 Issue 11 Pages 1410-1414
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Zr55Al15Ni10Cu20 bulk metallic glass is formed using low purity materials at a low vacuum with a small amount of yttrium addition. It is found that the glass forming ability, crystallization and melting process of the Zr55Al15Ni10Cu20 alloy are modified with yttrium addition, while the mechanical and elastic properties, such as hardness and Young’s Modulus, are not obviously changed. The positive effect of yttrium addition on the glassy formation of the Zr55Al15Ni10Cu20 alloy is clarified.
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  • Jürgen Eckert, Anette Kübler, Alexandra Reger-Leonhard, Anne ...
    2000 Volume 41 Issue 11 Pages 1415-1422
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    The effect of iron on the glass transition, the viscosity of the supercooled liquid and the crystallization behaviour of (Zr0.650Al0.075Cu0.175Ni0.100)100−xFex and (Zr0.55Al0.10Cu0.30Ni0.05)100−xFex metallic glasses (0≤x≤15) was investigated using parallel plate rheometry, differential scanning calorimetry and X-ray diffraction. Iron additions shift the glass transition as well as the crystallization to higher temperatures, and increase the viscosity of the supercooled liquid. Increasing iron content reduces the extension of the supercooled liquid region. This mainly results from a stronger composition dependence of the glass transition than the crystallization temperature. The results are discussed with respect to the kinetics and thermodynamics of the supercooled liquid suggesting that changes in the atomic arrangement and in the free volume are the microscopic origin for the differences in the viscosity and the thermal stability of the alloys. All investigated alloys are rather strong glasses as expressed by a relatively high melt viscosity, a low Vogel-Fulcher Tammann (VFT) temperature and a rather high fragility parameter, but in general (Zr0.55Al0.10Cu0.30Ni0.05)100−xFex alloys are slightly stronger glasses than (Zr0.650Al0.075Cu0.175Ni0.100)100−xFex alloys.
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  • Yong Zhang, De Qian Zhao, Ru Ju Wang, Ming Xiang Pan, Wei Hua Wang
    2000 Volume 41 Issue 11 Pages 1423-1426
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Zr/Nb-based bulk metallic glasses (BMGs) with excellent glass forming ability (GFA) and high thermal stability were obtained by water quenching method. The GFA of the alloys is sensitive to the Fe addition, and the highest GFA is achieved at 8 at% of Fe addition. It is found that ΔT defined by the difference between the onset temperature of the first crystallization event Tx and the glass transition temperature Tg (ΔT=TxTg) is more effective than Trg (Trg=TgTm, Tm, melting temperature) to reflect the GFA of the Zr/Nb-based BMGs. The elastic properties of the alloys are investigated by ultrasonic measurements.
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  • De Qian Zhao, Yong Zhang, Ming Xiang Pan, Wei Hua Wang
    2000 Volume 41 Issue 11 Pages 1427-1431
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Zr–Ti–Cu–Ni–Be–Fe bulk metallic glasses and metallic glassy matrix composites were produced by water quenching method. The effect of Fe addition on glass forming ability, hardness, magnetic susceptibility and thermal stability of the alloys was investigated. It was found that the glass forming ability and the properties of the alloys were sensitive to Fe content. A single amorphous phase was obtained in the alloys up to 8 at%Fe addition. These bulk metallic glasses exhibited high thermal stability, wide super-cooled liquid region, and anomalous magnetic susceptibility χ versus temperature in the supercooled liquid region. Metallic glassy composites consisting of nanocrystalline FeZr2 particles were obtained in the alloys with more than 10 at%Fe addition.
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  • Nobuyuki Nishiyama, Maki Horino, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1432-1434
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    We measured the thermal expansion and specific volume of the Pd40Cu30Ni10P20 alloy by thermomechanical analyzer (TMA), fluid (H2O) displacement and volume dilatometric methods. At room temperature (293 K), the specific volumes of the Pd40Cu30Ni10P20 alloy in the relaxed glassy and crystalline states are 0.1070 and 0.1065 m3/Mg, respectively. The average linear coefficients of thermal expansion are 17.0×10−6 K−1 at 323 to 523 K in the relaxed glassy state (αrelax), 14.2×10−6 K−1 at 323–673 K in the crystalline state (αcry) and 39.9×10−6 K−1 at 873–1223 K in the liquid (αliq). Based on these results, the specific volume of the Pd40Cu30Ni10P20 alloy as a function of temperature, V(T), is estimated. The extrapolation line of the specific volume for the equilibrium liquid is smoothly connected to the specific volume for the supercooled liquid. On the other hand, the intersection point of the specific volume between the extrapolation of equilibrium liquid and crystal is evaluated at 527 K. In the assumption that the temperature of the intersection point corresponds to the entropic stability limit for the undercooled liquid, it is much lower than that of previous thermodynamic study.
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  • N. H. Pryds, M. Eldrup, M. Ohnuma, A. S. Pedersen, J. Hattel, S. Linde ...
    2000 Volume 41 Issue 11 Pages 1435-1442
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Bulk amorphous (Mg1−yAly)60Cu30Y10 alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs. time was recorded during the cooling and solidification process of the melt and compared with a spacial and temporal numerical simulation of that process. It is concluded that good thermal contact is maintained between the amorphous part of the solidified sample and the mould, while a rather poor contact develops between the crystalline part of the sample and the mould, probably due to the appearance of a narrow gap at the crystal-mould interface during crystallisation. The maximum amorphous layer thickness decreases from ∼3 mm to zero when the Al content increases in the range from 0 to about y=10%. The evolution of the microstructure of the initially amorphous phase was examined by x-ray diffraction (XRD) and differential scanning calorimetry (DSC) for different alloy compositions and annealing temperatures. On annealing into the supercooled liquid state (441 K), specimens with no Al content remain basically amorphous while nanoparticles are formed and remain stable also at higher temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg60Cu30Y10 specimen was determined experimentally by a combination of DSC data and temperature vs. time measurements to be 60–150 K/s, in agreement with estimates from the literature. The Vickers hardness (HV) of the amorphous material for y=2% is higher (∼360 kg/mm2) than for y=0 (∼290 kg/mm2). On crystallisation the hardness of the latter material increases to the 400 kg/mm2 level while the hardness of the former does not change.
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  • Shin Takeuchi, Tomohiro Kakegawa, Tatsuo Hashimoto, An-Pang Tsai, Akih ...
    2000 Volume 41 Issue 11 Pages 1443-1447
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Compression tests have been performed for bulk metallic glasses of La55Al25Ni20 (L-glass) and Zr41Ti15Ni12Cu11Be21 (Z-Glass) at temperatures from 4.2 K up to above the glass transition temperature. Shear fracture stresses are scattered between 0.75 GPa and 1.2 GPa in the L-glass, and between 1.3 GPa and 2.2 GPa in the Z-glass with a tendency of decrease towards both higher and lower temperatures from 77 K in L-glass and from 300 K in Z-glass. The normalized shear fracture stresses with respect to the Young’s modulus are around 0.02 in both glasses. The micro-plastic strain measured with the strain gauge for the L-glass is about 0.2% at the shear fracture stress at room temperature, decreases with decreasing temperature and is of the order of 0.01% below 77 K. The mechanism that determines the shear fracture stress is discussed.
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  • Kazutaka Fujita, Akihisa Inoue, Tao Zhang
    2000 Volume 41 Issue 11 Pages 1448-1453
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    A nanocrystalline (NC) bulk glass Zr55Al10Cu30Ni5 (at%) which contains nano-scale crystals embedded uniformly in a glassy matrix has both high tensile strength of 1.7 GPa and high ductility. It is therefore expected to find practical application in machines and structures. The fatigue crack propagation behavior of the NC bulk glass was examined. The threshold stress intensity factor range ΔKth was about 0.9 MPa\sqrtm, and the fatigue fracture toughness Kfc was about 13 MPa\sqrtm. Fatigue crack propagation rate dadn was approximately proportional to ΔK2. No significant difference in dadn between the NC glassy alloy and single phase amorphous alloys in literature was seen when they are compared on the basis of ΔK divided by Young’s modulus E. The dadn values were nearly the same as those for steels with the same tensile strength level. The dadn values were larger than those for low strength steels, Al alloys and Ti alloys in the low dadn range. When compared with the effective stress intensity factor range ΔKeff divided by E, the dadn values for crystalline alloys were almost coincident with those under different stress ratios for the NC glassy alloy. This indicates that the dadn values for the NC glassy alloy can be estimated on the basis of the dadn data for crystalline alloys.
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  • Tomoya Hirano, Hidemi Kato, Atsushi Matsuo, Yoshihito Kawamura, Akihis ...
    2000 Volume 41 Issue 11 Pages 1454-1459
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Bulk glassy Zr55Al10Ni5Cu30 composites containing ZrC particles up to 17.5 vol% were formed by the in-situ reaction between the Zr metal and graphite powder during melting-process. The glassy composites had a cylindrical form of 2 mm in diameter by a copper mold casting process. The in-situ reaction was effective for the homogeneous dispersion of ZrC particles and for the achievement of excellent wettability between pure glass and ZrC particles. Mechanical properties, particularly fracture strength and plastic elongation, were significantly improved in comparison with those of the pure glass as well as the similar bulk glassy composite formed by addition of ZrC particles. The present study has demonstrated that the in-situ reaction method is useful for the synthesis of the bulk glassy composites consisting of glassy matrix and dispersed reinforce particles with excellent mechanical properties.
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  • Kenji Amiya, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1460-1462
    Published: 2000
    Released: May 23, 2007
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    Magnesium-based bulk amorphous alloys with a diameter of 7 mm for Mg65Y10Cu15Ag5Pd5 were produced by a metallic mold casting method. The glass transition temperature (Tg), crystallization temperature (Tx), the temperature interval of the supercooled liquid region (ΔTx=TxTg) and the melting temperature (Tm) are measured to be 437, 472, 35 and 707 K, respectively, for the Mg65Y10Cu15Ag5Pd5 alloy. The simultaneous addition of Ag and Pd to Mg–Y–Cu system causes a steep decrease in Tm and an increase in the reduced glass transition temperature (TgTm), leading to an increase in the glass-forming ability. The Mg–Y–Cu–(Ag, Pd) bulk amorphous alloys have a high compressive fracture strength of 770 MPa. The simultaneous addition of Ag and Pd is useful for the improvements of glass-forming ability and fracture strength.
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  • Tao Zhang, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1463-1466
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    A rotating disk casting has been developed as a new method of producing an amorphous alloy wire. The rotating disk, which is made of copper, has a semicircular groove on its upside surface. The amorphous alloy wires with large diameters from 0.5 to 1.5 mm in the Zr–Al–Ni–Cu alloy system with high glass-forming ability have been prepared by the new method. The cross-section of the wires is nearly circular, because the melt is quenched to an amorphous state at the contact with an inner surface in the groove of the rotating disk. The cast amorphous alloy wires exhibit the same thermal stability and mechanical properties as those for the melt-spun amorphous alloy ribbon with the same composition. The formation of the amorphous alloy wires with large diameters is attributed to the high glass-forming ability of the alloy. In any event, the success of forming amorphous alloy wires by the present casting method is important for the future extension of application fields of amorphous alloys.
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  • Cang Fan, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1467-1470
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    DSC curves show that the crystallization reactions change from a single exothermic peak to two exothermic stages by adding Ti up to 5 at% to Zr–Ni–Cu–Al amorphous alloys and bulk amorphous composites containing nanocrystalline particles were produced by annealing cast Zr70−xyTixNi10Cu20Aly (x=5–7.5 and y=10–15 at%) amorphous alloys. The microstructure after the precipitation of a primary crystalline phase consists of the crystals less than 10 nm in size embedded in the amorphous matrix. Both the compressive strength and plastic strain increased significantly with increasing volume fraction of nanocrystals, and the maximum plastic strain was obtained in the early stage of nanocrystallization. High-resolution electron microscopy showed that the bulk nanocrystalline Zr53Ti5Ni10Cu20Al12 alloy with the maximum plastic strain includes nanocrystals with a much smaller grain size of about 2.5 nm.
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  • Akihiro Makino, Akihisa Inoue, Takao Mizushima
    2000 Volume 41 Issue 11 Pages 1471-1477
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    A large supercooled liquid region over 50 K before crystallization were obtained in amorphous Fe–(Al, Ga)–(P, C, B, Si), Fe–(Cr, Mo, Nb)–(Al, Ga)–(P, C, B) and (Fe, Co, Ni)–(Zr, Hf)–M–B (M = Ti, Hf, V, Nb, Ta, Cr, Mo, W) systems and their bulk glassy alloys were produced in a thickness range below 2 mm for the Fe–(Al, Ga)–(P, C, B, Si) system and 6 mm for the Fe–Co–(Zr, Nb, Ta)–(Mo, W)–B system by copper mold casting. The ring-shape glassy Fe–(Al, Ga)–(P, C, B, Si) alloys produced by copper mold casting exhibit much better soft magnetic properties than the ring-shape alloy made from the melt-spun ribbon as a result of the formation of a unique domain structure. The bulk Fe–(Al, Ga)–(P, C, B, Si) alloys were also produced by consolidating the amorphous powders using an electric-pulse-sintering method. The large elongation in the supercooled liquid region enables production of the bulk samples with relatively higher density and better soft magnetic properties than those of the sintered Fe–Si–B bulk amorphous sample. The bulk glassy (Fe, Co, Ni)70M10B20 (M = Zr, Hf) systems exhibit large supercooled liquid regions of 72 K for M = Zr, and of 82 K for M = Hf. The replacement of Zr or Hf by 2 at%Nb or Ta causes a further increase in the supercooled liquid region. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material.
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  • Baolong Shen, Hisato Koshiba, Hisamichi Kimura, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1478-1481
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The effect of the addition of the transitional metal Mo, on the glass-forming ability, mechanical strength and magnetic properties of Fe78−xMoxGa2P12C4B4 glassy alloys was investigated. The addition of 4 to 6 at%Mo was found to be effective for the extension of the supercooled liquid region (ΔTx) defined by the difference between the glass transition temperature (Tg) and crystallization temperature (Tx). The ΔTx value is 30 K for the Fe78Ga2P12C4B4 alloy and increases to 60 K for the 4 at%Mo alloy. These glassy ribbon alloys exhibit good soft magnetic properties of 1.13 to 1.34 T for saturation magnetization and 2.2 to 3.8 A/m for coercive force. Based on the large ΔTx values, we tried to prepare bulk glassy Fe74Mo4Ga2P12C4B4 rods in a cylindrical form with different diameters. The glassy single phase was obtained in the diameter range of 1.0 to 2.0 mm. These bulk glassy alloys also exhibit high saturation magnetizations of about 1.20 T as well as a high compressive strength of 2685 MPa.
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  • Wei Zhang, Mitsuhide Matsusita, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1482-1485
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The thermal stability, crystallized structure and magnetic properties of melt-spun Fe70−xCo10PrxB20 (0≤x≤6) amorphous alloys have been investigated. The glass transition followed by a supercooled liquid region (ΔTx) was observed in the composition range of 2 to 5 at%Pr and the value of the ΔTx is in the range of 23 to 43 K. The good hard magnetic properties were obtained for the alloys containing 2.5 to 5 at%Pr subjected to an optimum heat treatment. The ΔTx and reduced glass transition temperature (TgTm) of the 3.5 at%Pr alloy are 43 K and 0.57, respectively. The crystallized structure consists of (Fe, Co)3B, α-(Fe, Co) and Pr2(Fe, Co)4B phases and their average grain sizes after annealing for 420 s at 863 K are about 25 nm. The remanence (Br), coercivity (iHc) and maximum energy product (BH)max of the optimally annealed the 3.5 at%Pr alloy are 1.36 T, 211 kA/m and 107 kJ/m3, respectively. The good hard magnetic properties in the crystallized state of the Fe–Co–Pr–B amorphous alloys with high glass-forming ability indicates the possibility of future fabrication of a bulk hard magnetic material by the simple process of the formation of a bulk amorphous alloy followed by crystallization.
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  • Keita Isogai, Tadashi Shoji, Hisamichi Kimura, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1486-1489
    Published: 2000
    Released: May 23, 2007
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    It was found that an amorphous Mg62Ni33Ca5 alloy absorbs a large amount of hydrogen at 323 K and the hydrogen content is much larger than that of the corresponding crystalline alloy. The maximum absorption concentration of hydrogen at 323 K is 2.3 mass% in the amorphous phase and 1.3 mass% in the crystalline state. The Mg-based amorphous alloy with 2.3 mass%H2 crystallizes through the process of Am → Am′+Mg2Ni → Mg2Ni+Mg2Ca+MgNi2+Mg2NiH4. The crystallization process is different from that (Am → Mg2Ni+Mg2Ca+MgNi2) of the as-quenched amorphous phase. The onset temperature and the completed temperature for crystallization is 453 and 532 K, respectively, for the as-quenched amorphous alloy and 475 and 572 K, respectively, for the amorphous phase containing 2.3 to 3.0 mass%H2. The absorption of hydrogen causes a significant increase in the thermal stability of the amorphous phase, presumably because of the necessity of a larger amount of hydrogen for the crystallization of the remaining amorphous phase which is coexistent with Mg2Ni. The retardation of the crystallization reaction of the Mg-based amorphous alloy by absorption of hydrogen is encouraging for future application to hydrogen-storage materials. It is concluded that the hydrogen can be used to control the thermal stability and crystallization process of Mg-based amorphous alloys.
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  • Shujie Pang, Tao Zhang, Hisamichi Kimura, Katsuhiko Asami, Akihisa Ino ...
    2000 Volume 41 Issue 11 Pages 1490-1494
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The melt-spun glassy Zr60−xNbxAl10Ni10Cu20 (x=0, 5, 10, 15, 20 at%) alloys were found to exhibit a large supercooled liquid region (ΔTx) exceeding 42 K before crystallization. The largest ΔTx for the glassy alloys containing Nb reaches as large as 82 K for the Zr55Nb5Al10Ni10Cu20 alloy. The glass transition temperature (Tg) increases and the ΔTx value decreases with increasing Nb content. The corrosion behavior of the Zr–(Nb)–Al–Ni–Cu glassy alloys was examined by mass loss (=weight loss) and electrochemical measurements. In 1N HCl solution at 298 K, the addition of Nb for replacing some portion of Zr is effective in improving the corrosion resistance of the investigated Zr-based glassy alloys. The corrosion rate significantly decreases with increasing Nb content. The pitting potential and open circuit potential rise with Nb content. In 3%NaCl solution, the addition of Nb effectively increases the pitting potentials of the glassy alloys. In 1N H2SO4 solution, the corrosion rates of the glassy alloys are 10−4∼10−3 mm·y−1 (1 mm·y−1=0.317 pm·s−1). They are spontaneously passivated and have a wide passive region with significantly low passive current density. The open circuit potential increases with an increase in Nb content.
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  • Kimihiro Ozaki, Akihiro Matsumoto, Akira Sugiyama, Toshiyuki Nishio, K ...
    2000 Volume 41 Issue 11 Pages 1495-1500
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Amorphous Mg75Ni15Si10 powders synthesized by mechanical alloying were consolidated into bulk pieces by pulsed current sintering. An investigation was also done on the corrosion behavior of the pieces by measuring the corrosion rate and the polarization curve. The mechanically alloyed powder was examined by X-ray diffraction and TEM with selected area electron diffraction and differential scanning calorimetry. The amorphous powder could be made by milling for 2520 ks. However, the powder included Si particles and nano-crystals in addition to the amorphous phase. The composition of the amorphous phase has been determined to be Mg71.5Ni13.5Si15.0 by TEM-EDS. The crystallization temperature was 571 K. The bulk alloys sintered at 473 K and 523 K kept the amorphous phase, but Mg crystals grew in the alloy. The sintering density increased with increasing die pressure and reached to at 94% under 500 MPa at 473 K. The real density was calculated to be 2588 kg/m3. No corrosion of the bulk amorphous alloy could be observed when exposed to 5 mass%NaCl solution for a period of 86.4 ks (24 h) because of the passive film formed on the surface of the amorphous alloy. It was confirmed by the measurement of the polarizaiton curve in 5 mass%NaCl solution that the corrosion rate of the amorphous alloy was a quarter or one-fifth that of AZ91D alloy.
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  • M. de Oliveira, W. J. Botta F., A. R. Yavari
    2000 Volume 41 Issue 11 Pages 1501-1504
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Shaping of Bulk metallic glasses (BMG) and BMG-based composites into various complex forms has been achieved by a new electromechanical process. Bulk metallic glasses have large supercooled regions between the glass transition temperature Tg and the crystallisation temperature Tx up to some hundred degrees higher. In this range, the undercooled liquid in principal deforms in a Newtonian way, allowing thermomechanical shaping in the low viscosity range as applied to oxide glasses. Electromechanical shaping technology allows rapid shaping at low applied stresses by eliminating the thermal mass of the furnace and and the need to heat the deformation dies. Joule heating is efficiently used thanks to the high electrical resistivity of bulk metallic glasses. Here it is shown that large shape changes (high deformations) can be achieved without crystallisation. For example, crosses and other mechanically resistant complex forms are achieved from two amorphous rods or an amorphous rod and a crystalline bar.
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  • Junji Saida, Mitsuhide Matsushita, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1505-1510
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    We examined the nucleation and grain growth kinetics of a nano icosahedral phase formed as a primary phase in the Zr65Al7.5Ni10Cu17.5−xPdx (x=5, 10 and 17.5) glassy alloys by differential scanning calorimetry and transmission electron microscopy. The nano icosahedral grains are distributed homogeneously, indicating the homogeneous nucleation mode. The grain growth rate of the icosahedral phase is nearly constant at the initial stage and much lower than that of the cubic Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 glassy alloy. The growth rate decreases with increasing Pd content. It is (4.5±0.4)×10−9 m s−1 at x=5 and decreases to (8.3±0.8)×10−10 m s−1 at x=17.5. The homogeneous nucleation rate at crystallization temperature, Tx, changes drastically with Pd content, and is (1.1±0.3)×1020 m−3 s−1 in the Zr65Al7.5Ni10Cu7.5Pd10 glass, which is approximately 102 times higher than that in the Zr65Al7.5Ni10Cu12.5Pd5 glass and 104 times higher than that of the Zr2Ni phase in the Zr65Al7.5Ni10Cu17.5 glass. Thus, it is clarified that with increasing the Pd content, the nucleation rate of the primary phase increases significantly and its growth rate decreases. The addition of Pd is effective for the increase in the number of nucleation sites and the suppression of grain growth. The formation of the nano icosahedral phase by the addition of Pd implies the existence of icosahedral short-range order in the glassy state of the Zr–Al–Ni–Cu alloy.
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  • Akihisa Inoue, Tao Zhang, Junji Saida, Mitsuhide Matsushita
    2000 Volume 41 Issue 11 Pages 1511-1520
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    This article was retracted. See the Notification.
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  • Chunfei Li, Junji Saida, Akihisa Inoue
    2000 Volume 41 Issue 11 Pages 1521-1525
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The crystallization processes of (Zr0.64Ni0.36)100−xAlx (x=5, 7.5 and 10) and (Zr0.64Ni0.36−0.0xCu0.0x)95Al5 (x=0, 6, 10, 13 and 16) metallic glasses were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). For the (Zr0.64Ni0.36)100−xAlx (x=5 and 7.5) and (Zr0.64Ni0.36−0.0xCu0.0x)95Al5 (x=0, 6, 10 and 13) alloys, crystallization proceeds through double-stage exothermic reactions. The first exothermic reaction corresponds to the precipitation of a metastable face-centered cubic Zr2Ni (F–Zr2Ni). For the (Zr0.64Ni0.36)100−xAlx (x=10) and (Zr0.64Ni0.36−0.0xCu0.0x)95Al5 (x=16) alloys, crystallization proceeds through a single-stage exothermic reaction, corresponding to the precipitation of stable crystalline phases. Accompanying the above changes in crystallization mode, the supercooled liquid region ΔTx, defined as the temperature interval between the glass transition temperature Tg and the crystallization temperature Tx, increases from 39 K for (Zr0.64Ni0.36)95Al5 to 64 K for the (Zr0.64Ni0.36)90Al10 in (Zr0.64Ni0.36)100−xAlx (x=5, 7.5 and 10) alloy series, and from 39 K for (Zr0.64Ni0.36)95Al5 to 70 K for (Zr0.64Ni0.20Cu0.16)95Al5 in the (Zr0.64Ni0.36−0.0xCu0.0x)95Al5 (x=0, 6, 10, 13 and 16) alloy series. The reason for the stabilization of the supercooled liquid state at higher Al concentrations in the (Zr0.64Ni0.36)100−xAlx (x=5, 7.5 and 10) alloy series and at higher Cu concentrations in the (Zr0.64Ni0.36−0.0xCu0.0x)95Al5 (x=0, 6, 10, 13 and 16) alloy series is discussed.
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  • Muneyuki Imafuku, Shigeo Sato, Hisato Koshiba, Eiichiro Matsubara, Aki ...
    2000 Volume 41 Issue 11 Pages 1526-1529
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The phase transformation of Fe90−XNb10BX (X=10 and 30) amorphous alloys by annealing was studied by differential scanning calorimetry (DSC) and X-ray diffraction. The Fe60Nb10B30 alloy exhibits a large supercooled liquid region (i.e. the difference between the glass transition temperature (Tg) and the onset of crystallization temperature (Tx)), ΔTx (=TxTg) of 67 K, whereas the Fe80Nb10B10 amorphous alloy transforms directly into crystalline phases. New metastable crystalline phases were found during the crystallization process of these alloys. In the crystallization process of the Fe80Nb10B10 alloy, the structure of the primary precipitation phase is α-Mn type, which transforms into α-Fe phase at a higher temperature. In case of Fe60Nb10B30 alloy, another metastable phase, Fe23B6-type structure, is formed corresponding to the first exothermic peak in the DSC curve. Although the metastable phases in the two alloys are completely different, the dissociated phases of α-Fe, Fe3B and Fe2B are formed in both alloys after the final stage of crystallization. The local atomic ordering structure in the α-Mn type is similar to that in an amorphous state of the Fe80Nb10B10 alloy. On the other hand, the formation of the Fe23B6-type structure requires a significant change in the geometrical rearrangements with relatively long-range ordering of the Fe60Nb10B30 alloy, which may be attributed to the high stability of the supercooled liquid.
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  • Jan Schroers, William L. Johnson
    2000 Volume 41 Issue 11 Pages 1530-1537
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Crystallization of the undercooled bulk metallic glass forming Zr41Ti14Cu12Ni10Be23 melt is investigated. Isothermal crystallization studies are performed between the liquidus and the glass transition temperature and a time-temperature-transformation diagram is determined. The various solidification products of samples solidified from different levels of undercooling are examined by electron microprobe. The investigations reveal the morphology and typical length scale of the microstructure as well as the primarily solidified phases after crystallizing at different degrees of undercooling. The typical length scale, the size to which one nucleation event grows, decreases continuously with increasing supercooling over 5 orders of magnitude. The number density of nuclei during primary crystallization is estimated from the microstructure. Repeated isothermal undercooling experiments are performed to investigate the scattering of the time to reach crystallization. These results suggest that at low undercooling crystallization takes place by a classical nucleation and growth mechanism. At high undercooling a diffusion controlled mechanism can explain the results. In addition, constant heating and cooling experiments are performed. Crystallization is found to be history dependent in this system. A rate of about 1 K/s is sufficient to suppress crystallization of the melt upon cooling from the equilibrium is nore liquid. During heating of amorphous samples, in contrast, a rate of about 200 K/s is necessary to avoid delectable crystallization. The crystallization temperature upon reheating depends on the minimum temperature to which the liquid was cooled prior to reheating as well as on the cooling rate by which the liquid was cooled into the amorphous state.
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  • B. S. Murty, K. Hono
    2000 Volume 41 Issue 11 Pages 1538-1544
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    This paper reports the crystallization sequence of ternary Mg65Cu25Y10, Mg80Cu10Y10 and Mg80Cu15Y5 amorphous alloys. Nanodispersions of Mg2Cu, hcp-Mg and fcc-Mg ranging from 5 to 20 nm have been observed in the melt-spun Mg65Cu25Y10, Mg80Cu10Y10 and Mg80Cu15Y5 alloys, respectively. The brittleness of melt-spun Mg–Cu–Y based alloys appears to be due to the nanodispersions of Mg2Cu intermetallic phase. On the other hand, nanodispersions of terminal solid solution such as hcp-Mg or fcc-Mg in the amorphous matrix lead to good ductility in the melt-spun Mg-rich alloys. The results also indicate that the glass forming ability and the thermal stability of amorphous phase are not improved by additions of quaternary elements such as Ni, Al, Zn and Mm to Mg–Cu–Y based alloys.
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  • Akihiro Matsumoto, Keizo Kobayashi, Makoto Takagi, Toru Imura
    2000 Volume 41 Issue 11 Pages 1545-1549
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    Ti-37.5 at%Si powder mixtures were mechanically alloyed in a planetary ball mill under an argon atmosphere. The powder milled for 180 ks consisted of amorphous and nano-sized titanium and/or silicon grains. Crystallization temperature of the powder was about 780 K. It was consolidated using a cubic-type anvil apparatus under a high hydrostatic pressure of 5.4 GPa (HHPC method). The obtained compact consolidated at below 663 K was fully densified with the retention of amorphous phase, while the compact prepared at above 723 K almost crystallized. The compressive strength of the compact prepared by HHPC method at 623 K was measured to be 2.52 GPa at room temperature. The value was about 0.5 GPa higher than that of the compact prepared by HHPC method at 723 K. It suggests amorphous phase is attributed to toughening of the compact.
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  • Hisamichi Kimura, Akihisa Inoue, Kenichiro Sasamori
    2000 Volume 41 Issue 11 Pages 1550-1554
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    By using the conventional powder metallurgy technique, P/M Al–V–Fe and Al–Fe–M–Ti (M=V, Cr, Mn) alloys with a diameter of 8 mm and a length of 300 mm were prepared by extrusion of the atomized powders at an extrusion ratio of 10 and extrusion temperatures (Te) of 623, 673 and 723 K. The structure of the P/M Al94V4Fe2 alloys is identified as fcc-Al (Al)+icosahedral quasicrystal (Q.C.) at Te=623 K, Al+Q.C.+Al11V at Te=673 K and 723 K. The structure of the P/M Al93Fe3Cr2Ti2 alloy is Al+Q.C.+Al23Ti9 at Te=673 K. The ultimate tensile strength (σUTS), 0.2% proof stress (σ0.2), plastic elongation (εP), Young’s moduli (E), Vickers hardness (Hv) and specific strength (σUTS⁄ρ) of the P/M Al93Fe3Cr2Ti2 alloy at room temperature are 660 MPa, 550 MPa, 4.4%, 85 GPa, 192 and 2.20×105 N m·kg−1, respectively. After heating for 300 s at 573 K, the σUTS, σ0.2 and εP are 360 MPa, 330 MPa and 1.5%, respectively. The Q.C. structure in the P/M Al93Fe3Cr2Ti2 alloy remains almost unchanged even after annealing for 720 ks at 573 K and the good wear resistance against S50C steel is also maintained for the extruded alloy tested at the sliding velocity of 0.5 to 2 m/s.
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  • Weijie Lu, Di Zhang, Xiaonong Zhang, Renjie Wu, Takao Sakata, Hirotaro ...
    2000 Volume 41 Issue 11 Pages 1555-1561
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    TiB and TiC reinforced titanium matrix composites have been produced by non-consumable arc-melting technology utilizing the self-propagation high-temperature synthesis reactions between titanium and B4C, graphite. X-ray diffraction (XRD) was used to identify the phases in the composites. Microstructures of composites have been observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The results show that there are three phases in the composite: TiB, TiC and titanium matrix alloy. Reinforcements are distributed uniformly in the matrix. TiB grows in short-fiber shape and TiC grows in dendritic, equiaxed shapes. The interfaces between reinforcements and titanium matrix alloy are very clean. There is no any interfacial reaction. There are high-density dislocations around TiC particle. Mechanical properties have been improved due to the incorporation of reinforcements. The addition of aluminum not only strengthens the titanium matrix alloy by solid solution strengthening, but also improves the mechanical properties of composites by refining the reinforcements and matrix alloy.
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  • María Teresa Pérez-Prado, Maria Carmen Cristina, Oscar R ...
    2000 Volume 41 Issue 11 Pages 1562-1568
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    The texture evolution of the Al–Li alloy 8090 has been investigated in order to analyze the microscopic mechanisms operative during deformation under different conditions of temperature and strain rate. A through-thickness texture gradient is present in the as-received material. As will be seen, the predominant deformation mechanisms are different in the mid layer and in the outer regions of the 8090 sheet alloy. In the outer regions, the texture intensity decreases with deformation and no significant changes in the main components were observed, indicating the predominance of grain boundary sliding (GBS). In the mid-layer, however, texture sharpens with straining and major changes in the main texture components were detected, revealing that crystallographic slip (CS) plays an important role in the deformation of this zone. CS takes place mainly in two slip systems and causes the orientations to move along the β-fiber in Euler space, towards the Copper component in longitudinal tests and towards the Brass component in transverse tests. The comparably small ductility of the 8090 alloy, with respect to other similar superplastic aluminum alloys, may be due to the operation of CS in the mid-layer.
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  • Guang Sheng Song, Min Ha Lee, Won Tae Kim, Do Hyang Kim, Zhen Zhong Zh ...
    2000 Volume 41 Issue 11 Pages 1569-1574
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    The correlation between dendritic microstructure and melt undercooling is investigated to present a new technique for rapid single crystal growing, or high undercooling directional solidification (HUDS). In a certain range of undercooling for stable dendrite growth in a negative temperature gradient, this new technique is employed to prepare single crystal Ni50Cu50 bars of approximately 10 mm in diameter and 65 mm in length. Optical metallography and X-ray diffraction experiments indicate that the resulting single crystals in the directionally solidified bars are composed of dendrites approximately parallel to each other and growing mainly in the ⟨100⟩ directions. The formation process and growth velocity of single crystals in an undercooled liquid are analyzed according to the obtained results and calculated by a current dendrite growth theory, respectively. A comparison of the HUDS technique with the as-proposed autonomous directional solidification (ADS) process is made also in the present paper.
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  • Jafar Mahmoudi, Hasse Fredriksson
    2000 Volume 41 Issue 11 Pages 1575-1582
    Published: 2000
    Released: May 23, 2007
    JOURNALS FREE ACCESS
    A series of solidification experiments using DTA furnace were performed on different Cu–Sn alloys. The undercooling, cooling rates of the liquid and the solid states, solidification times and temperatures were evaluated from the curves. The cooling curves for different samples and alloys were simulated using a FEM solidification program. The heat transfer coefficient and the heat of fusion were evaluated. The calculated fraction of solid formed before quenching has been compared with the experimental result. It was found that the calculated values of the heat of fusion were much lower than the tabulated ones. The fraction of solid was also found to be much higher than those calculated theoretically. It is proposed that a large number of vacancies form during rapid solidification and that they condense during and after the solidification. The influence of these defects on the thermodynamics and solidification of the alloys has been evaluated.
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  • Yoshihiko Yokoyama, Ryunosuke Note, Kenzo Fukaura, Hisakichi Sunada, K ...
    2000 Volume 41 Issue 11 Pages 1583-1588
    Published: 2000
    Released: June 01, 2007
    JOURNALS FREE ACCESS
    Phase relations between the liquid and the solid icosahedral (I-) phases were examined at different temperatures to determine the growth condition of a single Al–Cu–Fe I-quasicrystal using the Czochralski method. The composition of the single I-quasicrystal was chosen to be Al64Cu23Fe13 due to the superior thermal stability. We found that the liquid composition, which equilibrates to the Al64Cu23Fe13 I-phase at 1073 K, was Al57.7Cu37.7Fe3.5Si1.1. Based on the phase relation, production of a single Al64Cu23Fe13 I-quasicrystal was attempted by using the Czochralski method. As a result, we succeeded in the growth of a single Al64Cu23Fe13 I-quasicrystal, and we also measured the Vickers hardness of annealed single I-quasicrystal samples with different anneal times to estimate the structural improvement by annealing.
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