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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 42 (2001), No. 9

  • Formation and Soft Magnetic Properties of (Fe, Co)-RE-B Glassy Alloy with Large Thickness

    Wei Zhang, Akihisa Inoue

    pp. 1835-1838

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    DOI:10.2320/matertrans.42.1835

    Abstract

    The glass-forming ability, thermal stability and magnetic properties have been investigated for a Fe67Co9.5Nd3Dy0.5B25 glassy alloy with a large supercooled liquid region of 56 K prepared by the melt-spinning technique. The glassy phase is formed in the wide sheet thickness range from 19 to 203 \\micron. The glass transition temperature (Tg), crystallization temperature (Tx), supercooled liquid region (ΔTx=Tx−Tg) and heat of crystallization (ΔHc) remain almost unchanged in the thickness range below 203 \\micron. The Fe62Co9.5Nd3Dy0.5B25 glassy alloy annealed at 773 K for 600 s exhibit good soft magnetic properties of 1.41 T for saturation magnetization (Is), 2.6 A/m for coercive force (Hc), and 12000 for permeability (μe) at 1kHz in a thickness of 19 \\micron. The Is, Hc and Curie temperature (Tc) remain unchanged in the thickness range up to about 200 \\micron, but the μe at 1 kHz gradually decreases to 6700 for the thick sheet with a thickness of 203 \\micron.

  • TEM/AFM Observation of Crack Tip Plasticity in Silicon Single Crystals

    Masaki Tanaka, Toru Fukui, Toshitaka Yamagata, Tatsuya Morikawa, Kenji Higashida, Ryuta Onodera

    pp. 1839-1842

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    DOI:10.2320/matertrans.42.1839

    Abstract

    Crack tip plasticity in silicon single crystals has been investigated using both high voltage electron microscopy (HVEM) and atomic force microscopy (AFM). Cracks were introduced into a (001) silicon wafer at room temperature by Vickers indentation method. The specimen temperature was increased to more than 873 K to activate dislocation generation around the crack tip under a residual stress due to the indentation. In specimens without the heat-treatment, no dislocations were observed around the crack, while in specimens with the heat-treatment, characteristic dislocation configurations were observed near the crack tip. AFM observations showed that slip bands were formed around the crack tip in the heat-treated specimens, and that the step heights of those slip bands were around one nanometer. Such crack tip plasticity is considered to be caused by mainly mode I tensile load, and contribute to increasing fracture toughness.

  • Local Electronic Structure of Si Semiconductor Surface

    Takashi Yamauchi, Yoshihiro Takahara, Nobutaka Narita

    pp. 1843-1845

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    DOI:10.2320/matertrans.42.1843

    Abstract

    Local electronic structure around Si-adatoms on Si(111)-7×7 surface has been investigated using the methods of STM (scanning tunneling microscopy), STS (scanning tunneling spectroscopy) and the molecular orbital calculation for the cluster of local structure around each adatom. In view of the difference of surrounding local structure, the adatoms are classified into four types, i.e., the corner- and center-adatoms in a faulted half (F) cell, and the corner- and center-adatoms in an unfaulted half (UF) cell. In the STS spectra for each type of adatoms, significant differences are revealed. The intensity of the STS spectrum near the HOMO (highest occupied molecular orbital) level for a coner- and center-adatoms in the F cell is larger than for the respective adatoms in the UF cell. The calculation of local electronic structure indicates the main constitution of the HOMO by the atomic orbitals of adatoms and rest-atoms and also the charge transfer from the adatom to the rest-atom. The charge transfer leads to the intensity difference in the STS spectra near the HOMO between corner- and center-adatoms, because the corner- and center-adatoms have one and two rest-atom neighbors, respectively. The energy gap between the HOMO and LUMO (lowest unoccupied molecular orbital) in STS spectra for the corner-adatom in a F cell is larger than that in an UF cell. Similar results are obtained for the center-adatom. The change of the energy gap by the presence of stacking fault is demonstrated by the calculation using the cluster models with and without the stacking fault.

  • Detection of Defects in Thermal Barrier Coatings by Thermography Analyses

    Hua-nan Liu, Michiru Sakamoto, Kazushi Kishi, Kazuhisa Shobu, Tatsuo Tabaru, Hiroshi Tateyama, Yoshio Akimune

    pp. 1845-1850

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    DOI:10.2320/matertrans.42.1845

    Abstract

    Thermographic imaging under steady-state heat flow was used to nondestructively detect the defects in thermal barrier coatings (TBCs). The finite element method (FEM) analyses and the experimental thermography observations were performed using artificially grooved ZrO2 plates and the indentation-tested TBC-metal specimens. The FEM results show that: (1) Defects (nonuniformity or internal cracks) of the TBC can be effectively detected by the thermographic imaging method; (2) The apparent thermal images would be far greater than the real sizes of the defects, but the half-height sizes of the temperature profile were found to give good estimates for the latter; and (3) The higher value of heat flow would contribute to the detections. Besides these results, the influence of the defect situations (morphology, size and position) on the thermal images was also predicted by the FEM analysis. Although, due to some difficulties in preparing the test specimens, the quantitative comparison between each FEM result and that of the actual measurement was not performed, however, the experimental results of the grooved ZrO2 plates were found to be in good agreement with the FEM predictions. For the thermographic experiments of the indentation-tested specimens, both the internal-cracks and the thickness-nonuniformity of the TBCs were successfully observed, and the smallest cracks detectable had a diameter far less than 1 mm.

  • Effect of Interface Behavior between Particles on Properties of Pure Al Powder Compacts by Spark Plasma Sintering

    Guoqiang Xie, Osamu Ohashi, Takayuki Yoshioka, Minghui Song, Kazutaka Mitsuishi, Hidehiro Yasuda, Kazuo Furuya, Tetsuji Noda

    pp. 1846-1849

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    DOI:10.2320/matertrans.42.1846

    Abstract

    Pure Al powder was sintered by spark plasma sintering (SPS) process at various sintering temperatures and loading pressures. The density, electrical resistivity, tensile properties and microstructure of powder compacts were investigated. The powder compacts with the similar properties as base aluminum metal was obtained at sintering temperature above 873 K, loading pressure above 23.5 MPa. For the powder compacts with the similar density but with the large difference in the electrical resistivity and tensile properties, the interfaces between Al powder particles were investigated using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS). Two types of interfaces, with metal/metal bonding and metal/oxide film layer/metal bonding, were observed in Al powder compacts. The properties of powder compacts were mainly subject to the behavior of oxide film between the powder particles.

  • Synthesis of New Hydrides with Cubic Structures in Mg-Ca-Ni Systems by Using High Pressure

    Yasuyuki Goto, Hirofumi Kakuta, Atsunori Kamegawa, Hitoshi Takamura, Masuo Okada

    pp. 1850-1853

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    DOI:10.2320/matertrans.42.1850

    Abstract

    Phases and thermal stability of new hydrides synthesized by using under a high pressure of 5 GPa in Ca–Mg–Ni–H systems were studied. The high-pressure synthesis was carried out at 1073 K–1223 K for 2 h under 5 GPa by using an anvil-type apparatus. A series of (Ca1−xMgx)2NiHδ was found to form solid solution in the range of x=0–0.4. This hydride decomposed around 646 K regardless of Mg content. In CaH2-X%MgH2 systems, hydrides with BCC structure were obtained in the range of X=50–67. Lattice constant of the BCC phase decreased from 0.4032(9) nm (X=50) to 0.3988(3) nm (X=67) with increasing Mg content. The decomposed temperature of the BCC phase increased from 650 K (X=50) to 673 K (X=67) with increasing Mg content, in other words, with decreasing the lattice constant of BCC phase.

  • Fabrication of Continuously Porous Alumina Body by Fibrous Monolithic and Sintering Process

    Taek-Soo Kim, In-Cheol Kang, Takashi Goto, Byong-Taek Lee

    pp. 1851-1856

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    DOI:10.2320/matertrans.42.1851

    Abstract

    A continuously porous alumina sintered body was successfully fabricated using by the fibrous monolithic process, in which carbon and flour were used as a pore forming agent. An equation was driven for anticipating the microstructural change during extrusion as a function of the extrusion ratio, and it was identified that the resultant microstructure obtained from using the fibrous monolithic process agreed well with the calculated size using the equation. The third passed and sintered alumina body includes continuous pores of about 42.5 μm in diameter at an intended direction, while the second one consists of 228 μm. Fine pores were also found to form along the alumina surfaces with 0.1–10 μm in diameter. There was no shape change during binder burning out and sintering processes.

  • Hydrothermal Synthesis of Vanadium-Based Layered Compound with 1 nm Basal Spacing

    Junji Yamanaka, Shigehiro Mori, Yoshikazu Kaneko

    pp. 1854-1857

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    DOI:10.2320/matertrans.42.1854

    Abstract

    Vanadium-based layered compounds were synthesized from a reaction between ammonium vanadate and supercritical/non-supercritical water. The hydrothermal conditions were as follows: treatment temperature of 773 K and pressure of 30 to 100 MPa. We characterized specimens by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffractometry, transmission electron microscopy and thermogravimetry. Then we determined the condition of repeatable synthesis of the layered compound with a 0.98 nm basal spacing. The compound included no impurity, at least at the sensitivity of EDX . The compound showed good stability up to 500 K . We infer the chemical formula of the compound to be V2O5·0.5H2O.

  • Improved Strength in Carbon Fiber Reinforced Plastics due after Electron Beam Irradiation

    Akihiro Mizutani, Yoshitake Nishi

    pp. 1857-1860

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    DOI:10.2320/matertrans.42.1857

    Abstract

    Carbon fiber reinforced plastics (CFRPs), with their advantages of light weight and high strength, are increasingly being applied as structural materials in the fields of aerospace engineering and rapid transport engineering. To strengthen CFRPs, electron beam (EB) irradiation is performed homogeneously. EB irradiation enhances the bending fracture stress and the bending fracture strain, and also slightly enhances the bending elasticity of CFRP. The analysis based on the Law of Mixture Strength for composites suggests that EB strengthening of CFRPs is chiefly attributable to ductility enhancement of the epoxy resin and carbon fiber.

  • Microstructures and the Magnetic Properties of Fe3B/(Nd, Dy)2Fe14B Nanocomposite Microalloyed with Cu and Zr

    Kagehisa Kajiwara, Kazuhiro Hono, Satoshi Hirosawa

    pp. 1858-1861

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    DOI:10.2320/matertrans.42.1858

    Abstract

    The effect of Zr and Cu addition to a Nd3.4Dy1Fe72.3B18.5Cr2.4Co2.4 alloy on the microstructure and the magnetic properties of Fe3B/Nd2Fe14B nanocomposite has been investigated by a three-dimensional atom probe (3DAP) and transmission electron microscopy (TEM). Addition of a small amount of Zr and/or Cu is effective in improving the hard magnetic properties of the base alloy. Cu atoms form clusters in the early stage of crystallization, and Zr atoms are segregated at the interfaces of Fe3B/Nd2Fe14B being rejected from the Fe3B soft magnetic phase on the optimal heat-treated condition. This causes refining the nanocomposite microstructure, resulting in improved hard magnetic properties compared to those of the base alloy.

  • Microstructure and Dry Sliding Wear of Ti-50Al Alloy and Ti-47Al-3W/Ti2AlC Composite Produced by Reactive Arc-Melting

    Janakarajan Ramkumar, Santa Kumar Malhotra, Ramalingam Krishnamurthy, Hiroshi Mabuchi, Kei Demizu, Atsushi Kakitsuji, Hiroshi Tsuda, Toshiyuki Matsui, Kenji Morii

    pp. 1861-1865

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    DOI:10.2320/matertrans.42.1861

    Abstract

    To study dry sliding wear behavior and its relation to microstructure, Ti–50Al alloys and Ti–47Al–3W alloy and its composite with varying reinforcement of Ti2AlC were prepared by reactive arc-melting. Dispersion of fine B2 particles is obtained by the addition of tungsten to TiAl alloy, which improves both the hardness and wear resistance of the matrix. By adding carbon to Ti–47Al–3W alloy, composite can be produced having a random distribution of reacted rod-like Ti2AlC particles and smaller Ti2AlC precipitates with fine B2 particles in the matrix. The Ti–47Al–3W/3.5 vol%Ti2AlC intermetallic composite features excellent wear resistance compared to 10 and 18 vol% composites, and fine dispersion of the Ti2AlC and B2 particles in the matrix has improved the wear resistance properties.

  • Protium Absorption Properties of Ti-Cr-V Alloys in Low Hydrogen Pressure Regions

    Takuya Tamura, Atsunori Kamegawa, Hitoshi Takamura, Masuo Okada

    pp. 1862-1865

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    DOI:10.2320/matertrans.42.1862

    Abstract

    Ti–Cr–V alloys are known to absorb about 3.8 mass% of protium, but to desorb about 2 mass% because of the formation of stable protorides in low hydrogen pressure regions. However, few protium storage properties of the alloys in low hydrogen pressure regions were reported. This paper aims to clarify the protium absorption properties of Ti–Cr–V alloys in low hydrogen pressure regions. It was found that first low pressure plateau regions were coexistence regions of two different BCC phases for 20 at% V alloys. Decreasing V content and increasing Cr content turned out to shift the beginning of the second high pressure plateau regions to low protium concentration in unstabilizing the protorides in the first plateau regions. As a result, the Ti–52 at%Cr–20 at%V alloy was designed and found to have about 2.4 mass% protium desorption capacity in the width of the second plateau region at 273 K.

  • Continuous Displacement Cluster Variation Method and Diffuse Scattering Intensity Calculation

    Hideyuki Uzawa, Tetsuo Mohri

    pp. 1866-1869

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    DOI:10.2320/matertrans.42.1866

    Abstract

    Continuous Displacement Cluster Variation Method within the pair approximation is combined with Lennard-Jones type potential and we investigate local atomic displacements for a binary ordering system in the two dimensional square lattice at 1:1 stoichiometry. The order-disorder transition temperature is reduced by the introduction of the local atomic displacement, while the second order nature of the transition is conserved. The distribution of unlike pair is localized in the vicinity of the rigid lattice points, which is explained as the deepest pair potential characteristic for the ordering system. The obtained information of atomic displacements in the real space is Fourier transformed to calculate diffuse scattering intensity spectrum in k-space. The maximum intensity contribution from the linear term is attained at (kx∗, ky∗) with kx∗=ky∗<0.5 in k-space, while the maxima of the short range order diffuse intensity appears at (0.5, 0.5). This is interpreted based on the concept of displacement wave.

  • Secondary Electron Emission Characteristics of MgO Thin Films Prepared by an Advanced Ion-Plating Method

    Kazuo Uetani, Hiroshi Kajiyama, Akira Kato, Akiko Takagi, Takanobu Hori, Isao Tokomoto, Yasuhiro Koizumi, Koichi Nose, Yasushi Ihara, Ken-ichi Onisawa, Tetsuroh Minemura

    pp. 1870-1873

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    DOI:10.2320/matertrans.42.1870

    Abstract

    We measured the secondary electron emission (SEE) and the film microstructures of the MgO thin films. The films were deposited by the advanced ion-plating (AIP) method we developed and also a conventional electron beam evaporation (EB) method for reference. The secondary electron yield, γ, defined as a ratio of irradiated ion current to emitted electron current of the samples was measured to be 0.55 for the AIP film and 0.35 for the EB film. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations revealed that the AIP film had well-defined columnar structures which were grown from the substrate interface to the film surface. The AIP film with thickness of a 100 nm had (111) preferred orientation, while the crystal orientation of the EB film was not detected. We supposed that the γ value was greatly improved due to the improved crystallinity as well as (111) preferred orientation.

  • Effect of Cooling Process on Critical Current Density of Bi-2223/Ag Superconductive Tapes Prepared by Dip-Coating

    Masaki Sumida, Akiyoshi Matsumoto, Hiroaki Kumakura

    pp. 1872-1876

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    DOI:10.2320/matertrans.42.1872

    Abstract

    In this paper, effect of the cooling process is examined for the superconductive properties of high Tc Bi-2223/Ag tapes prepared by dip-coating. The short tapes are cooled after the isothermal heat treatment at a controlled temperature profile, which can refine the microstructure. The cooling rate and the slow cooling range are varied, showing that the optimum condition is found where the enhanced Jc is obtained compared to that of normal furnace cooling. Contrarily, Tc did not show an optimum under this condition but increased monotonously with a decrease in the cooling rate and an increase in the slow cooling range. From phase identification, microscopic observation, and quantitative analysis, the microstructure formation in the polycrystalline oxide layer during this process and its relation to these properties are discussed.

  • Cross-Sectional Observation of Surface Graphitization in Furan-Resin-Derived Carbon

    Junji Yamanaka, Eiichi Yasuda, Hidekazu Migita, Yasuhiro Tanabe

    pp. 1874-1877

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    DOI:10.2320/matertrans.42.1874

    Abstract

    Carbons synthesized from thermosetting resins are generally grouped into nongraphitizable carbons. Furan-resin-derived carbon is one of the well-known nongraphitizable carbons. We investigated the microstructures of furan-resin-derived carbon by cross-sectional transmission electron microscopy, and found that graphitization occurred at the surface. This is the first cross-sectional observation of surface graphitization in furan-resin-derived carbon. The surface graphite layer was approximately 20 or 30 nm in thickness in the specimen heat-treated at 3273 K for 1800 s. Atomic stacking in the layer was parallel to the specimen surface. The interior of the specimen was not graphitic but a cage structure.

  • Field Study on Heavy Metal Accumulation in a Natural Wetland Receiving Acid Mine Drainage

    Keiko Sasaki, Tagiru Ogino, Yuji Endo, Kunihiko Kurosawa

    pp. 1877-1884

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    DOI:10.2320/matertrans.42.1877

    Abstract

    The mechanism of surface water remediation in a natural wetland that is receiving heavy metal-rich acidic mine drainage was investigated. Selective sequential extraction was useful to derive the mechanisms of heavy metal removal in the wetland. In the upstream portion of the wetland, dissolved Fe was removed mainly as oxide-bounded mineral phases, such as hydroxides. These are important for the subsequent removal of other heavy metals. Other ion-exchangeable and carbonate-bounded heavy metals are also observed in the upstream, associated with Fe oxides. Organic matter and Fe–Mn oxides in the upstream remove Cu and Zn ions from the drainage, respectively. In the middle of portion of the wetland the removal of heavy metal ions in relatively low concentrations occurs by the emergent vegetation. Greater clay abundance and higher microbial activity of sulfate reducing bacteria in the downstream parts achieved low-level removal of metals. Multi-cell wetlands are recommended for the treatment of acidic metal bearing surface water drainage, if sufficient land area and expenses are available to construct.

  • Analysis of Microstructures and Magnetic Domain Structures in Nd-Fe-B Nanocomposite Magnets by Analytical Electron Microscopy and Lorentz Microscopy

    Young-Gil Park, Daisuke Shindo, Hirokazu Kanekiyo, Satoshi Hirosawa

    pp. 1878-1881

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    DOI:10.2320/matertrans.42.1878

    Abstract

    By analytical electron microscopy and Lorentz microscopy, microstructures and magnetic domain structures of Nd–Fe–B nanocomposite magnets prepared by the melt-spun technique which consists of a mixture of hard and soft magnetic phases were investigated. By energy dispersive X-ray spectroscopy elemental mapping for the neodymium element, hard (Nd2Fe14B) magnetic grains were distinguished from soft (Fe3B or α-Fe) magnetic grains. The Fe3B grains could be further distinguished from the α-Fe grains by investigating the boron K-edge in electron energy-loss spectroscopy, despite the strong background in the spectra. From bright-field electron microscopy coupled with energy dispersive X-ray spectroscopy elemental mapping, the grain size distribution of constituent phases in a Nd4.5Fe77B18.5 magnet annealed at 973 K was evaluated. An average grain size of Fe3B and Nd2Fe14B grains was evaluated to be about 32 nm and 35 nm, respectively. Through Lorentz microscopy study on the Nd4.5Fe77B18.5 magnet annealed at 973 K, the size of the magnetic domain formed through the exchange interaction was found to be 100–150 nm being much larger than the grain sizes of Fe3B and Nd2Fe14B phases.

  • Quantitative Evaluation of Charging on Amorphous SiO2 Particles by Electron Holography

    Chang-Woo Lee, Daisuke Shindo, Kon-No Kijiro

    pp. 1882-1885

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    DOI:10.2320/matertrans.42.1882

    Abstract

    The amount of the electric charge in spherical SiO2 particles with 1 \\micron diameter has been evaluated quantitatively by using electron holography. The charging effect was found to depend on not only the incident electron intensity but also the insertion of an objective aperture. The amount of the electric charge in a SiO2 particle is estimated to be 1.5×10−16 C under the current density of incident electron beam at 0.5 A/m2 without an objective aperture. This electric charge is equal to the net loss of about 940 electrons from the amorphous SiO2 particle. In the case of inserting an objective aperture, the amount of the electric charge on SiO2 particles decreases by 30–40%. The results are compared with the cases of Au coated particles and the small particles of 250 \\micron in diameter.

  • Hydrogen Permeation Characteristics of Melt-Spun Ni-Nb-Zr Amorphous Alloy Membranes

    Shin-ichi Yamaura, Yoichiro Shimpo, Hitoshi Okouchi, Motonori Nishida, Osamu Kajita, Hisamichi Kimura, Akihisa Inoue

    pp. 1885-1890

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    DOI:10.2320/matertrans.42.1885

    Abstract

    We prepared the melt-spun (Ni0.6Nb0.4)100−xZrx (x=0 to 40 at%) and other amorphous alloy membranes and examined the permeation of hydrogen through those alloy membranes. The interatomic spacing in the Ni–Nb–Zr amorphous structure increased with increasing Zr content. The crystallization temperature of the Ni–Nb–Zr amorphous alloys decreased with increasing Zr content. The hydrogen flow increased with an increase of the temperature or the difference in the square-roots of hydrogen pressures across the membrane, Δ\\sqrtp. At relatively higher temperature up to 673 K or at relatively higher hydrogen pressure difference, Δ\\sqrtp up to 550 Pa1⁄2, the hydrogen flow was more strictly proportional to Δ\\sqrtp. This indicates that the diffusion of hydrogen through the membrane is a rate-controlling factor for hydrogen permeation. The permeability of the Ni–Nb–Zr amorphous alloys was strongly dependent on alloy compositions and increased with increasing Zr content. However, it was difficult to investigate the hydrogen permeability of the (Ni0.6Nb0.4)60Zr40 amorphous alloy in this work due to the embrittlement during the measurement. The maximum hydrogen permeability was 1.3×10−8 (mol·m−1·s−1·Pa−1⁄2) at 673 K for the (Ni0.6Nb0.4)70Zr30 amorphous alloy. It is noticed that the hydrogen permeability of the (Ni0.6Nb0.4)70Zr30 amorphous alloy is higher than that of pure Pd metal. These permeation characteristics indicate the possibility of future practical use of the melt-spun amorphous alloys as a hydrogen permeable membrane.

  • Shape Memory Effect of Sputtered Ni-rich Ni2MnGa Alloy Films Aged in Constraint Condition

    Shinji Isokawa, Motohiko Suzuki, Makoto Ohtsuka, Minoru Matsumoto, Kimio Itagaki

    pp. 1886-1889

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    DOI:10.2320/matertrans.42.1886

    Abstract

    The intermetallic compound Ni2MnGa has a shape memory effect and a ferromagnetic property. Films of this compound may be applied for an actuator of micro-machines. The Ni-rich Ni2MnGa films with a nearly 5 \\micron thickness were deposited on an Al2O3 substrate by a radio-frequency magnetron sputtering apparatus with a Ni52Mn24Ga24 target. The sputtering power was 400 W and the substrate temperature was kept at 323 K by cooling water. The composition of the deposited films was Ni–23.4 mol%Mn–23.0 mol%Ga. They were annealed at 1073 K for 36 ks for homogenization and ordering, and slowly cooled down in the furnace. Martensitic transformation temperatures of the films were measured by a differential scanning calorimeter, and the results were Ms=315 K, Mf=311 K, As=316 K and Af=321 K . To induce a shape memory effect, the annealed films were aged at 573–773 K for 0.9–3.6 ks in a constrained condition. It was found that they showed the two-way shape memory effect by thermal cycling.

  • Structure and Superconductivity of High Pressure Synthesized Sr-Ca-Cu-O System

    Kazuhiko Ohmori, Masashi Sakamoto, Hidefumi Asano, Masaaki Matsui

    pp. 1890-1892

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    DOI:10.2320/matertrans.42.1890

    Abstract

    A new superconducting cuprate (Sr0.7Ca0.3)3Cu2O5+δ has been synthesized under high pressure. CaO2 has been used to make a homogeneous oxidizing atmosphere. X-ray diffraction measurements on the bulk sample revealed that (Sr0.7Ca0.3)3Cu2O5 (325-type) phase was found in the top surface of the columnar sample, (Sr0.7Ca0.3)4Cu3O7 (437-type) phase in the bottom surface and 325-type+437-type mixed phase in a cross section parallel to the column axis. Segregations of 325-phase and 437-phase were supposed to take place in the upper and lower parts of the sample, respectively. Nearly single phase samples of 325-type and 437-type crystal were gained by grinding from the upper part and the lower part of the sample, respectively, using abrasive papers. Magnetic susceptibility measured by SQUID and electrical resistivity measurements showed that superconductive transition temperatures are 106 K in the 325-phase and 110 K in the 437-phase.

  • Microstructure in Zn-Al Alloys after Equal-Channel-Angular Extrusion

    Tsutomu Tanaka, Hiroyuki Watanabe, Kenji Higashi

    pp. 1891-1894

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    DOI:10.2320/matertrans.42.1891

    Abstract

    Experiments were conducted to evaluate the grain refinement in Zn–22Al alloys subjected to equal-channel-angular extrusion (ECAE) under three different conditions. In the first condition (Route 1), ECAE was performed during the phase transformation at room temperature. In the second condition (Route 2), ECAE was carried out after the phase transformation at room temperature. In the third condition (Route 3), ECAE was performed after the phase transformation at 373 K. The average grain sizes after ECAE exhibited 0.35, 0.3 and 0.6 μm for Route 1, 2 and 3, respectively. Route 1 was efficient to develop the material with a finer microstructure, and reduce the processing time. It was also verified that reasonably equiaxed and homogeneously distributed grains were obtained by ECAE after solution treatment without rolling process.

  • Microstructures and Magnetic Properties of Nd-Fe-B-X (X=Co, Zr) Alloys Produced by a Metallic Mold Casting Method

    Shunpei Ozawa, Tetsuji Saito, Tetsuichi Motegi

    pp. 1893-1896

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    DOI:10.2320/matertrans.42.1893

    Abstract

    The microstructures and magnetic properties of Nd4Fe77.5B18.5 and Nd4(Fe-X)77.5B18.5 (X=Co, Zr) alloys produced by a metallic mold casting were investigated. The resulting Nd4Fe77.5B18.5 alloys had a cylindrical shape with 1 mm in diameter and 50 mm in length and had fine equiaxed grains. The cylindrical sample contained some metastable Fe3B and amorphous phases together with the stable Fe2B, Nd2Fe14B, and α-Fe phases. However, the coercivity of the cylindrical sample was as low as that of the original ingot. The substitution of Co or Zr for Fe in Nd4Fe77.5B18.5 alloy resulted in a drastic change in the microstructures. These cylindrical samples showed a slightly higher coercivity than the Nd4Fe77.5B18.5 counterparts.

  • Structure and Properties of Melt-Spun Mg-Pd Binary Alloys

    Shin-ichi Yamaura, Hisamichi Kimura, Akihisa Inoue

    pp. 1895-1898

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    DOI:10.2320/matertrans.42.1895

    Abstract

    Amorphous alloys in the Mg–Pd binary system were formed in a composition range of 10 to 35 at%Pd by melt-spinning technique. The crystallization temperature and tensile strength of the amorphous Mg100−xPdx (x=10, 20 and 30 at%) alloys are in the range from 417 to 535 K and 440 to 650 MPa, respectively. There is a tendency for the crystallization temperature and the tensile strength to increase with increasing Pd content. Vickers hardness also increased with increasing Pd content. Their compositional dependence is attributed to an increase in the number of Mg–Pd atomic pairs with large negative mixing enthalpy. Crystallized structure of the Mg–Pd amorphous alloys was also examined in correlation with equilibrium phases.

  • Microstructure and Mechanical Properties of TiAl/Ti2AlN Composites Prepared by Combustion Synthesis

    Atsushi Kakitsuji, Hiroki Miyamoto, Hiroshi Mabuchi, Hiroshi Tsuda, Kenji Morii

    pp. 1897-1900

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    DOI:10.2320/matertrans.42.1897

    Abstract

    TiAl/Ti2AlN composites were prepared by a reactive arc-melting technique using elemental powders of Ti, Al, and AlN . Ti2AlN particles synthesized by the combustion reaction synthesis were dispersed in the lamella grains, with rod-like shapes with sizes of 1–3 \\micron width and 5–15 \\micron length. The grain size of the matrix was decreased and the deviation of the grain size was converged by the distribution of the Ti2AlN . The lamella grains in the matrix were decomposed both into TiAl and very fine Ti2AlN particles by the homogenizing treatment. The bending strength of these composites was larger than that of TiAl single-phase material and it was improved by increasing the Ti2AlN content. Their ductility kept the same level of that of TiAl. Fracture toughness values were enhanced by the dispersion of Ti2AlN, since crack propagation can be deviated by such dispersoids in the composite materials.

  • Some Aspects of Elevated-Temperature Deformation of Single-Phase Alloys

    Hiroshi Oikawa

    pp. 1901-1912

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    DOI:10.2320/matertrans.42.1901

    Abstract

    Some critical discussions on creep behavior and deformation mechanisms of single-phase metallic materials are presented. Subjects dealt with are deformation mechanism diagrams and strain-hardening and recovery rates in pure metals, effects of solute atoms (the Cottrell atmosphere and the Suzuki atmosphere) and their limitation in disordered solid solution alloys, and creep characteristics and the strength of single phase materials and two-phase mixture of Ti–Al intermetallics.

  • The Behaviour of Structural Steels at Elevated Temperatures and the Design of Fire Resistant Steels

    Wei Sha, Brian R. Kirby, Fergal S. Kelly

    pp. 1913-1927

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    DOI:10.2320/matertrans.42.1913

    Abstract

    This paper reviews the current understanding of the characteristics of structural steels at elevated temperatures typical of those experienced in a fire and the design of fire-resistant steels for building construction. Following a commercial view of the requirements and market for steels with enhanced properties at elevated temperatures, the microstructure/property relationships and the influence of these upon high temperature strength are discussed in detail. Steel composition and processing variables can be controlled to modify grain size, the presence of second phases and precipitation, ferrite/austenite transformation temperature, dislocation density and weldability. These are reviewed as well as the important issues concerning structural aspects that determine the fire resistance of steels. The microstructure and property requirements of fire resistant steels are outlined and the ways in which these may be achieved are discussed including those that have already been developed.

  • Dynamic Recrystallization in Pure Magnesium

    Oleg Sitdikov, Rustam Kaibyshev

    pp. 1928-1937

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    DOI:10.2320/matertrans.42.1928

    Abstract

    Microstructural evolution of commercial grade pure magnesium was studied during plastic deformation by torsion under high pressure at ambient temperature and by compression at temperatures ranging from 293 to 773 K and at a strain rate of 3×10−3 s−1. Grain refinement takes place by operation of dynamic recrystallization (DRX) at all examined temperatures. The mechanisms of DRX change with temperature and strain. As a result, unusual dependencies of recrystallized grain size against strain and recrystallized volume fraction against temperature are observed. In the temperature interval of 293–623 K the deformation twinning results in “twin” mechanism of DRX, which processes strain softening at an initial stage of deformation. At T≤423 K the other mechanism of low temperature DRX takes place at high strains. Such DRX is accompanied by strain hardening. In contrast, continuous DRX (CDRX) yielding a steady-state flow operates frequently at temperatures ranging from 523 to 773 K . CDRX occurs mainly in overall recrystallization process at elevated temperatures. Discontinuous DRX (DDRX) takes place by bulging of boundaries of coarse recrystallized grains evolved from twins at T=723 K . DDRX occurs repetitively, but gives an insignificant contribution into total recrystallization process. The present results suggest that the mechanisms of DRX and the deformation mechanisms are closely related.

  • Electron Backscatter Diffraction Analysis of Recrystallized Grains Formed in Deformation Band in Aluminum Single Crystal

    Tatsuya Okada, Leona Ikeda, Xiaoxu Huang, John A. Wert, Keizo Kashihara, Fukuji Inoko

    pp. 1938-1944

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    DOI:10.2320/matertrans.42.1938

    Abstract

    An aluminum single crystal of ⟨110⟩ {110} orientation was deformed in tension and annealed to obtain partial recrystallization. In a special type of band of secondary slip (SBSS), many recrystallized grains (RGs) were formed. The orientation and the morphology of RGs were examined by an electron backscatter diffraction method. Many RGs exhibited elongated morphology along the trace of primary or sub-primary slip plane. The RGs elongated along the primary slip trace exhibited crystal rotation with respect to the average SBSS crystal orientation, about axes close to the primary plane normal. For the RGs elongated along the sub-primary slip trace, the crystal rotation axes were close to the sub-primary plane normal. In the interior of the sample, about 250 \\micron beneath the original surface, only one RG was detected. This interior RG had an orientation similar to that of the majority of RGs formed at the original surface. The rotating angle was almost exactly 40° (40° ⟨111⟩ rotation) for the interior RG, while the rotating angles for the surface RGs distributed in relatively wide range.

  • Solid State Bonding of Graphite to Inconel 718

    Hidekazu Sueyoshi, Tomoyuki Nishida

    pp. 1945-1951

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    DOI:10.2320/matertrans.42.1945

    Abstract

    Graphite was bonded to Inconel 718 in a vacuum using an RF-induction furnace. The influence of joining conditions on the bending strength of the graphite/Inconel 718 joint, and changes in the microstructure and hardness of Inconel 718 near the joining interface, were investigated. Thermal stress induced in the joint was estimated using the finite element method. Good-solid-state bonding becomes feasible with annealing at temperatures higher than 1173 K under compressive stress of 35 MPa. The adequate joining temperature and joining compressive stress in graphite/Inconel 718 bonding are higher than those in graphite/nickel bonding. This is because fracture of passive-oxide film on the surface due to plastic deformation of Inconel 718 and the resulting direct contact of graphite with matrix of Inconel 718 are required on solid-state bonding. The bending strength of the joints is nearly equal to or greater than that of graphite. This is because the compressive stress induced on the surface of graphite by the plastic deformation of Inconel 718 after bonding and the resulting elastic deformation of graphite in the radial direction relaxes the tensile thermal stress induced on the surface of graphite during cooling or the compressive stress remains. Heat treatment is required to recover the strength of Inconel 718 since intermetallic compounds precipitated in Inconel 718 dissolve in the matrix during annealing and age hardening disappears.

  • Microstructural Characteristics and Wear Resistance of Electromagnetic Casting Aluminum Alloys

    Sug-Won Kim, Hai Hao, Ui-Jong Lee, Kee-Do Woo, Jun-Ze Jin

    pp. 1952-1958

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    DOI:10.2320/matertrans.42.1952

    Abstract

    Direct chill casting (DCC) has some demerits such as oscillation and subsurface segregation. Electromagnetic casting (EMC) technology was used to solve these problems. The electromagnetic force prevented the metal from touching the mold, which contributes to leaving the ingot surface very smooth. Moreover, the electromagnetic stirring and joule heating made the structure become more homogeneous over the entire cross-section. It results in the EMC ingots having distinct merits.The 2024 and 5182 Al alloys were made using EMC and DCC technology. Parts of them were used for specimens. OM and SEM were carried out to analyze the microstructures. Hardness and wear resistance tests were carried out in order to investigate mechanical properties. On the other hand, the solution and aging treatment effects on mechanical charaterization were compared between EMC and DCC ingots. Micrographs show that EMC ingots have a very fine and uniform grain structure, which makes the EMC ingots have high strength and good ductility. The EMC specimens have twice the hardness of DCC specimens in the as-cast state. They also express excellent wear resistance characteristics.

  • Distribution of Ni, Cr, Mn, Co and Cu between Fe-Ni Alloy and FeOX-MgO-SiO2 Base Slags

    Hector M. Henao, Mitsuhisa Hino, Kimio Itagaki

    pp. 1959-1966

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    DOI:10.2320/matertrans.42.1959

    Abstract

    The distribution of nickel and minor elements such as chromium, manganese, cobalt and copper between the Fe–Ni alloy and the FeOX–MgO–SiO2 base slag in a magnesia crucible was studied at 1773 and 1873 K under controlled partial pressure of oxygen in a range between 1.8×10−5 and 3.2×10−2 Pa using CO–CO2 gas mixtures. The effect of adding lime (CaO/SiO2 molar ratio of about 1) and alumina (AlO1.5/SiO2 molar ratio of about 0.25) to the plain FeOX–MgO–SiO2 slag was also investigated. The distribution ratios of chromium and manganese, defined by (mass%X in slag)/[mass%X in alloy] where X is the minor element, for the plain slag at 1773 K have large values greater than 100 and 1000, respectively. These are 4 and 5 orders of magnitude larger than that of nickel, while those of cobalt and copper are of a magnitude similar to that of nickel. It was clarified that the addition of lime reduces the distribution of chromium and manganese into the slag while the addition of alumina increases the dissolution of chromium though it reduces the dissolution of nickel, cobalt and copper.

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  • Narrowing of Al2O3, Y3Al5O12 and ZrO2 Eutectic Lamellae by Rapid Solidification in Al2O3 Based Eutectic Composites

    Jose M. Calderon-Moreno, Masahiro Yoshimura

    pp. 1967-1968

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    DOI:10.2320/matertrans.42.1967

    Abstract

    The fabrication of bulk ceramic composites with homogeneous structure in the nano-scale is a difficult challenge. Multi-step methods based on synthesis and sintering of ceramic nanopowders, or methods using deposition from gas phases are complex and require high energy input with very low energetic efficiency, so they are not practical. However, bulk ceramic composites with a naturally self-assembled structure may be formed by solidification from eutectic melts. Smaller eutectic spacing may be obtained by using rapid solidification. We report here the rapid solidification in an arc-image furnace of eutectic melts in the system alumina-Y3Al5O12-zirconia. Ceramic eutectic composites grown from melt have homogeneous bulk structure and lamella sizes in the submicron to the nanoscale range.

  • Relationship between the Crystallographic Structure of Electrodeposited Fe-Zn Alloy Film and Its Thermal Equilibrium Diagram

    Xintan Hu, Tohru Watanabe

    pp. 1969-1976

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    DOI:10.2320/matertrans.42.1969

    Abstract

    The microstructures and morphologies of Fe–Zn alloys electrodeposited at different chloride bath compositions have been studied in detail by using TEM, SEM, XRD, and compared to those appearing in the Fe–Zn thermal equilibrium phase diagram. The results indicate that the α, Γ, Γ1 and η phases appear in the Fe–Zn electrodeposits, whereas δ and ζ phases which appear in the thermal equilibrium phase diagram do not appear. The surface appearance and microstructure of the intermetallic phases in Fe–Zn alloy electrodeposits depend on the Zn content in the Fe–Zn alloy deposit. It was also found that there is an orientation relationship among the Γ, Γ1 and η phases when these three phases appear simultaneously.

  • In-house Anomalous X-ray Scattering Analysis for the Amorphous Zr60Al15Ni25 Alloy

    Shigeo Sato, Muneyuki Imafuku, Eiichiro Matsubara, Akihisa Inoue, Yoshio Waseda

    pp. 1977-1980

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    DOI:10.2320/matertrans.42.1977

    Abstract

    In-house anomalous X-ray scattering (AXS) analysis coupled with white radiation produced from a rotating anode X-ray generator and a solid state detector has been tested by obtaining the environmental structure around Zr in the amorphous Zr60Al15Ni25 alloy. The AXS measurement with the conventional X-ray source was successfully carried out with a newly constructed system by enhancing the intensity of incident X-rays. The present AXS data for Zr in the amorphous Zr60Al15Ni25 alloy was found to agree well with the previous results obtained by monochromatic X-rays produced from a synchrotron radiation source.

  • Eutectic Solidification Mode in Sodium Modified Al-7 mass%Si-3.5 mass%Cu-0.2 mass%Mg Casting Alloys

    Kazuhiro Nogita, Stuart David McDonald, Jacob Wesley Zindel, Arne Kristian Dahle

    pp. 1981-1986

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    DOI:10.2320/matertrans.42.1981

    Abstract

    The influence of sodium (Na) on nucleation and growth of the Al–Si eutectic in a commercial hypoeutectic Al–Si–Cu–Mg foundry alloy has been investigated. The microstructural evolution during eutectic solidification was studied by a quenching technique. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites by EBSD, the eutectic solidification mode could be determined. The results show that the eutectic solidification starts near the mould wall and evolves with front growth opposite the thermal gradient on a macro-scale, and on a micro-scale with independent heterogeneous nucleation of eutectic grains in interdendritic spaces. Na-modified alloys therefore behave significantly differently from those modified by other elemental additions.

  • Process of Nanocrystallization and Partial Amorphization by Cold Rolling in TiNi

    Hiroyuki Nakayama, Koichi Tsuchiya, Zhi-Guang Liu, Minoru Umemoto, Koichi Morii, Takayoshi Shimizu

    pp. 1987-1993

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    DOI:10.2320/matertrans.42.1987

    Abstract

    TiNi alloy is vulnerable to solid-state crystalline-amorphous transformation by many means, such as particle irradiation, shot peening, compression and cold rolling. In the present study a process of structural refinement and partial amorphization by cold rolling was studied on Ti–50.2 at%Ni. Crystal structures and microstructures were characterized by X-ray diffractometry, optical microscopy and electron microscopy. Differential scanning calorimetry revealed that the introduction of high density of dislocations and resultant structural refinement by cold rolling suppressed martensitic transformation. In the transversal section of cold rolled samples, microscopic and macroscopic shear band formation was observed after 40–50% rolling. Transmission electron microscopy observations revealed that amorphous bands exist in the sample with rolling reduction over 40%. The amorphous bands form about 35–45 degrees with respect to the rolling direction. This suggests that a part of the shear bands becomes amorphous.

  • Precipitation Behavior on Carbon Steel Modified by Double Glow Plasma Surface Alloying with W and Mo

    Bin Zhao, Jiansheng Wu, Zhong Xu, Zhonghou Li, Xiaoping Liu

    pp. 1994-1997

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    DOI:10.2320/matertrans.42.1994

    Abstract

    Many brittle precipitates appeared in the alloyed layers which were formed in surface modified carbon steel by DGPSA (Double Glow Plasma Surface Alloying) with W and Mo because of the slow cooling rate in the alloying furnace. As a result, the mechanical properties of these alloys were significantly degraded by precipitation of the brittle phase. Phase analysis of the electro-extracted precipitates by X-ray diffraction (XRD) revealed that they were mainly composed of the μ-phase and a small amount of carbide, M6C . In the present study, their microstructures were characterized by optical microscopy (OM) and scanning electron microscopy (SEM). It was concluded that the chemical components, temperature and time were the main thermodynamic factors influencing their deposition. The isothermal transformation (IT) diagram of the precipitates showed that there were two transforming climaxes. Based on the IT diagram, a technique was developed to depress the precipitate deposition.

  • Plastic Deformation by Slip on (001)[100] in Ni3Nb Single Crystals with D0a Structure

    Koji Hagihara, Takayoshi Nakano, Yukichi Umakoshi

    pp. 1998-2002

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    DOI:10.2320/matertrans.42.1998

    Abstract

    Plastic deformation by slip on (001)[100] in Ni3Nb single crystals was investigated. The yield stress, strain rate sensitivity of the flow stress, shape of the stress-strain curve, morphology of slip markings and deformation substructures varied strongly depending on temperature. Temperature dependence of their behavior was classified into three regions. Anomalous increase in the yield stress was observed between 500 and 800°C. The anomalous strengthening is caused by dynamic strain aging, the so called Portevin-Le Chatelier effect.

  • Effects of Reflow Processing and Flux Residue on Ionic Migration of Lead-Free Solder Plating Using the Quartz Crystal Microbalance Method

    Hirokazu Tanaka, Fumitaka Ueta, Sachio Yoshihara, Takashi Shirakashi

    pp. 2003-2007

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    DOI:10.2320/matertrans.42.2003

    Abstract

    To investigate the ionic migration, quite a new measurement method has been developed by the authors, which enables real time monitoring of the growth process of ionic migration using a QCM (Quartz Crystal Microbalance). This research has focused on the QCM method to study the growth process of ionic migration in various types of lead-free solder plating and the effects of the reflow processing and flux residue of soldering processes. In addition, we investigated the anode dissolution characteristics of the elements in each type of solder alloy by measuring the current-potential curve in 0.1 kmol m−3 KNO3 solution. When using Sn–3.5 mass%Ag solder plating, reflow processing segregates the stable compound Ag3Sn layer and Sn layer. The Sn layer selectively promotes the anode dissolution reaction, increasing the occurrence of migration. When using Sn–9 mass%Zn solder plating, the Sn effectively prevents the excessive dissolution reaction of Zn. However, since reflow processing causes each element to separate out, reflow processing lessens the effectiveness of Sn, thus promoting the occurrence of migration. The flux processing of lead-free solders suppresses anode dissolution and effectively prevents the occurrence of migration. However, with Sn–9 mass%Zn, the lowered adhesion between the flux film and the electrodes is a factor in speeding the growth of migration.

  • Relationship between Phason Strain and Approximant Crystal Structure in Co-Rich Al-Ni-Co Decagonal Phase

    Yoshie Matsuo, Yutsuki Nishimura, Kazuki Yamamoto, Yasushi Ishii

    pp. 2008-2012

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    DOI:10.2320/matertrans.42.2008

    Abstract

    Peak broadening and the peak positions of the Bragg reflections were studied with the high-resolution X-ray diffraction method for the decagonal Al72.7Ni8.5Co18.8 quasicrystal. The full-widths at half-maximum (FWHM) of the Bragg reflections along the longitudinal direction (L), which is perpendicular to the periodic axis, have no Q|| or Q⊥ dependences. On the other hand, notable peak shifts from ideal Bragg peak positions with linear Q⊥ dependence were observed. This means that the Al72.7Ni8.5Co18.8 decagonal phase has linear phason strains. According to the absolute values of the linear phason strains, the transformation from the decagonal phase to an approximant crystal is discussed.

  • Effect of Cross Slips on Deformation Microstructure and Recrystallization in < 111> and < 001> Al Single Crystals

    Minoru Tagami, Keizo Kashihara, Tatsuya Okada, Fukuji Inoko

    pp. 2013-2020

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    DOI:10.2320/matertrans.42.2013

    Abstract

    ⟨111⟩ and ⟨001⟩ aluminum single crystal specimens with 99.99 mass% purity were deformed in tension to strains of about 20%. In all specimens, multiple slip structures without deformation bands were observed. In ⟨111⟩ specimen deformed at room temperature of 293 K (RT), fine wavy slip traces are recognized because of the difficulty of cross slips. The difficulty is due to the tensile-orientation dependence of cross slips. The dislocation structure shows layered cell structures composed of cell walls with high dislocation density. In ⟨001⟩ specimen deformed at liquid nitrogen temperature of 77 K (LNT), complex fine slip traces similar to those in the case of ⟨111⟩ RT specimens are also observed because of the difficulty of cross slips. This difficulty is due to the temperature dependence of cross slips. The dislocation structure is composed of small isotropic cells with high dislocation density around their cell walls. In the above two kinds of deformed aluminum single crystals, the formation of recrystallized grains (RGs) is very easy. On the other hand, in the ⟨001⟩ specimen deformed at RT, many cross slips with large steps are seen because all the eight primary slip systems have an appropriate cross (i.e. another primary) slip system geometrically. The dislocation structure gives polygonal cells with low dislocation density. After annealing no recrystallized grain is formed in the specimen. The stress values of the stress-strain curves in the ⟨001⟩ (RT), ⟨111⟩ (RT) and ⟨001⟩ (LNT) specimens are 22 MPa at 25% strain, 71 MPa at 22% and 106 MPa at 20%, respectively.

  • Velocity of Sound in Liquid 3d Transition Metals near the Melting Point

    Isao Yokoyama

    pp. 2021-2023

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    DOI:10.2320/matertrans.42.2021

    Abstract

    A hard-sphere model, which has been successfully applied to the calculations of excess entropy, self-diffusion coefficient, shear viscosity coefficient and surface tension, is shown to give a quantitative description of the velocity of sound in liquid 3d transition metals if a uniform background potential is properly taken into account.

  • Recovery Stage of Polycrystalline-Si Prepared by Excimer Laser Annealing

    Naoto Matsuo, Hisashi Abe, Naoya Kawamoto, Yoshio Miyai, Hiroki Hamada

    pp. 2024-2025

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    DOI:10.2320/matertrans.42.2024

    Abstract

    By irradiating the multi-pulse excimer laser with the energy density smaller than 200 mJ/cm2 on the amorphous silicon (a-Si), the crystallinity of the Si increases, as increasing the number of the pulse. During the first laser irradiation some part of the melted a-Si becomes the polycrystalline (poly)-Si which corresponds to the nucleus, and after the second irradiation the poly-Si does not melt and the remaining a-Si becomes the poly-Si. The crystal growth of the poly-Si proceeds by the solid phase crystallization (SPC). Crystal growth of poly-Si by excimer laser annealing (ELA) is discussed by considering the recovery stage. This stage is examined from the relationship between the amorphous Si area and the total irradiation time. The fact that the measured data coincides with the theoretical data indicates that the recovery proceeds during the ELA at the low energy density.
  • © 2001 The Japan Institute of Metals and Materials

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