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Volume 65, Issue 3
Displaying 1-19 of 19 articles from this issue
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Shunkichi Ueno, Satoshi Takata, Yasuhiro Tanabe, Masahiro Yoshimura, E ...2001 Volume 65 Issue 3 Pages 135-138
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFormation of the orientation relationship for uni-directionally solidified Al2O3/Ln3Al5O12 eutectic system at early stage of the solidification was examined. Ln3Al5O12 was the first phase to nucleate in the Al2O3/Ln3Al5O12 eutectic microstructure. When the Ln3Al5O12 phase nucleated as the primary phase, no specific orientation for the Al2O3 and Ln3Al5O12 phases with respect to the solidification direction was formed, and the coupled eutectic growth occurs like polycrystalline. On the other hand, in the case of Al2O3 phase nucleated as the primary phase, a specific orientation for Al2O3 and/or Ln3Al5O12 was easily formed. The orientation relationship ⟨100⟩Al2O3||⟨100⟩Ln3Al5O12||⟨solidification direction⟩ was obtained.View full abstractDownload PDF (466K) -
Masateru Yoshizumi, Yuichi Nakamura, Teruo Izumi, Yuh Shiohara, Yuichi ...2001 Volume 65 Issue 3 Pages 139-142
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to investigate solid state phase transformation in solid, Nd1+xBa2−xCu3O6+∂ powders with different compositions were annealed under different annealing conditions. The temperature-substitution ratio-oxygen content phase diagram of Nd1+xBa2−xCu3O6+∂ solid solution was constructed. The condition to occur Nd123ss phase separation was clarified by investigating the compositional fluctuation, XRD pattern, the time dependences of Tc properties and oxygen content. Solid state phase transformation of Nd123ss advances with two steps. Tetragonal orthorhombic phase transition due to oxygen introduction occurs at first, and then the orthorhombic phase with small x decomposes to the two phases by spinodal decomposition.View full abstractDownload PDF (360K) -
Hiroto Osono, Hiroshi Maeta, Kikuo Matsusaka, Takao Kino2001 Volume 65 Issue 3 Pages 143-146
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTo make a highly perfect aluminum crystal, high purity aluminum was melted in high vacuum of 2×10−7 Pa for 2 h using a cold-crucible induction furnace. The surface of as-melted ingot had a metallic luster and heavy oxidization was not observed on the surface. In the ingot, a large cylindrical-single crystal with a diameter of 60 mm and a length of 40 mm grew and dislocation density in the crystal was about 107 m−2. Purity of the melted aluminum was estimated to be near 99.9999% from the residual resistivity ratio. A large amount of highly perfect aluminum crystal with ultra-high purity was produced by only melting of melting once, under an ultra-high vacuum.View full abstractDownload PDF (540K) -
Mari Yonetsu, Yuji Yamasaki, Ken-ichi Takagi2001 Volume 65 Issue 3 Pages 147-150
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSNi-5 mass%B-53.25 mass%Mo-x mass%Mn model cermets with five levels of Mn content from 0 to 10 mass% were prepared to investigate the effects of Mn on the mechanical properties and microstructure of the Mo2NiB2 base cermets. The powder mixtures prepared form pure Mo and Mn, carbonyl Ni and MoB were ball-milled in acetone. After drying, the milled powders were pressed to green compacts and sintered in vacuum for 1.2 ks at temperatures between 1533 and 1593 K.
The cermets exhibit a two phase structure with a tetragonal Mo2NiB2 (M3B2) complex boride and a Ni base binder. Additions of 5 mass%Mn to the cermets resulted in refinement of the boride particles and remarkable improvement of mechanical properties such as transverse rupture strengh (TRS) and hardness. The maximum TRS of 2.45 GPa and hardness of 85.6 HRA were obtained at 5 mass%Mn. Fracture toughness slightly increase with increasing Mn content up to 7.5 mass% and exhibited steep increase between 7.5 and 10 mass%Mn, reaching 31 MPa·m1⁄2. The high fracture toughness was attributed to enhanced uniformity of the hard particle distribtuion as well as spheroidization and coarsening of the particles.View full abstractDownload PDF (411K) -
Tadashi Fukuda2001 Volume 65 Issue 3 Pages 151-154
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSEffects of morphology of titanium carbides on the ductility of Fe-30 mass%Cr alloys containing carbon and titanium were investigated by tensile test at low temperatures. Carbon and titanium contents vary from 0.011 to 0.071 mass%, and from 0.094 to 0.60 mass%, restectively. Ti/C ratio is about nine times. Three kinds of processes including heat treatments with or without solution treatment and cold rolling were adopted to obtain different types of morphology of fine grain boundary titanium carbides (0.05 μm), fine spheroidal titanium carbides (0.05 μm) within the grains, and coarse globular titanium carbides (0.5 μm) within the grains. Ductility was evaluated by transition temperatures in reduction of area.
The results obtained are summarized as follows:
(1) Transition temperatures of the specimens containing grain boundary titanium carbides are remarkably higher than those of the specimens containing titanium carbides within the grains.
(2) Transition temperatures of the specimens containing fine spheroidal titanium carbides within the grains are lower than those of the specimens containing coarse globular titanium carbides.
(3) Transition temperatures of the specimens containing spheroidal titanium carbides (≤0.5 μm) within the grains do not increase with increasing the volume fraction of titanium carbides.View full abstractDownload PDF (423K) -
Hiromasa Kakimi, Toshiyuki Matsui, Kenji Morii2001 Volume 65 Issue 3 Pages 155-158
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have prepared Mn-doped CoSb3 thin films by the annealing of ion-beam sputtered Co/Mn/Sb multi-layers at 673 K for 1h in vacuum, and studied the effects of the amount of doped Mn on the thermoelectric properties of the films. Mn atoms are assumed to be substituted for Co sites since the Mn-doped samples indicated no apparent shifts in the lattice parameter from the non-doped sample obtained by X-ray diffraction. Thermoelectric properties of the thin films were evaluated by measuring DC conductivity and Seebeck coefficients at elevated temperatures. The non-doped CoSb3 samples showed a p-type semiconducting character with the conductivity of about 7×103/Ωm irrespective of their chemical composition to be Sb-rich or Sb-deficient. The Seebeck coefficient of the sample was about 160 μV/K at 540 K. In contrast, the samples doped with 1-2 at%Mn exhibited a rather low conductivity of about 1×103/Ωm and their conduction behavior was changed to n-type with the Seebeck coefficient of about −70 μV/K at 500 K.View full abstractDownload PDF (444K) -
Masahiko Katagiri, Hidehiro Onodera2001 Volume 65 Issue 3 Pages 159-162
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMechanism of Hydrogen-Induced Amorphization (HIA) was studied by Molecular Dynamics method (MD). C15 Laves AB2 compounds were examined. The HIA phenomenon is experimentally observed for Laves phase with contracted A atoms and expanded B atoms, in comparison with their atomic size in stable pure crystals. Aim of our study is to reveal the atomic size effect in the occurrence of HIA. Our previous MD simulation shows that hydrogenation makes the elastic constants soft. It comes from the nonlinearity of the interatomic potentials during volume expansion by hydrogenation. In HIA, another origin is observed for the softening. We suggested that the latter softening facilitates the bulk-modulus instability and HIA occurs. In present study, MD simulation under isotropic tensile load was performed instead of hydrogenation. We investigated the elastic stability change due to the volume expansion. We defined a stability criterion of sublattice and evaluated the elastic stability in sublattice. In HIA, the bulk-modulus stability of expanded B-atom sublattice is low. Its instability occurs before instability of total lattice. Once hydrogen is incorporated in such AB2 crystal, atoms relax. As a result, the pressure-fluctuation term of elastic constant increases negatively and the bulk modulus is reduced. Such a bulk-modulus instability gives HIA.View full abstractDownload PDF (579K) -
Hirofumi Homma, Hideyuki Saitoh, Toshihei Misawa, Toshiyuki Ohnishi2001 Volume 65 Issue 3 Pages 163-166
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTritium radioluminography has been applied to the quantitative observation of hydrogen distribution in a V-5 mol%Fe alloy. Hydrogen distribution in the specimen has been found to be non-uniform. By comparing the hydrogen distribution with iron-mapping image obtained from a wavelength dispersive X-ray microanalyzer (WDX), it has been found that the hydrogen distribution correlates with iron segregation formed in the arc-melting specimen. The cross sectional observation of the hydrogen distribution has shown that the hydrogen concentration depends on the iron concentration in the specimen. The hydrogen concentration decreases gradually as iron concentration increases from 3 mol% to 4.3 mol%. Using both the radioluminography and WDX, simultaneously, it has been found that the relation between the local hydrogen concentration and the alloy composition in the specimen can be obtained.View full abstractDownload PDF (664K) -
Tatsuya Ohmi, Junji Yanoma, Masayuki Kudoh2001 Volume 65 Issue 3 Pages 167-170
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMelting behavior of the reaction products during a thermite-type combustion synthesis of Ni-25 mol%Al alloy (Ni3Al) has been investigated. The thermite-type combustion synthesis reaction is represented by the following equation: 3aNiO+3(1−a)Ni+(1+2a)Al=Ni3Al+aAl2O3. In this process, the reaction temperature can be varied arbitrarily by changing the value of a. The reaction sequence and the melting behavior of the products are summarized as follows: (1) The thermite-type combustion synthesis reaction of Ni3Al is a two-step reaction of the combustion synthesis reaction between Ni and Al; and the thermite reaction between the Ni-Al melt and NiO. (2) When the temperature of the specimen rises over the melting temperature of NiAl at the first reaction stage, the thermite reaction takes place and then the fluid products are produced.View full abstractDownload PDF (613K) -
Takahiro Hasegawa, Tetsumori Shinoda, Yoshihiro Oya-Seimiya2001 Volume 65 Issue 3 Pages 171-174
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFormation process of A15 Nb3Al phase at the interface between Nb(solid) and Al(liquid), together with the corresponding change in superconducting transition temperature, Tc, was pursued by varying the heating time to 1/3, 1 and 3 h at 2073 K on the Nb/Al composite made of roughly the same volume of Al and Nb rods inserted in a Nb tube, cold rolled to give a 25% reduction in diameter. The results are as follows. (1) Al oxide particles are concentrically arrayed in the vicinity of the inner circumference of the Nb tube of the composite, which might be formed at the solid/liquid interface in the initial stage of the reaction. (2) On the outside of those “circularly arrayed oxides”, the layer of A15 phase grows, as well as a lamellar mixture of (A15+the Nb-Al solid solution) adjacently, towards the outer side of the Nb tube, and, on the inside nearby the “circularly arrayed oxides”, σ (Nb2Al) phase is precipitated agglomeratively when the heating time is less than 1 h. (3) When the heating time is increased to 3 h, the inner part of the “circularly arrayed oxides” is as a whole transformed into a fine mixture of (A15+σ) phases. (4) The onset Tc values of the composite attain to 16.5 K, 17.3 K, and 18.0 K, respectively, after heated for 1/3, 1 and 3 h at 2073 K, followed by the annealing at 1173 K for 3 h, furnace cooled.View full abstractDownload PDF (755K) -
Katsumi Nomura, Saburo Hoshi, Yuichi Nakamura, Teruo Izumi, Yuh Shioha ...2001 Volume 65 Issue 3 Pages 175-178
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSHetero-epitaxial growth of YBa2Cu3Oy (YBCO) crystals on MgO substrates has been investigated by comparing with the homo-epitaxial growth on a YBCO substrate, in order to clarify the initial growth mechanism of the liquid phase epitaxy (LPE). It was found that the slope angle of the growth grain varied with growing the crystal in the initial growth of the LPE. In the case of the hetero-epitaxial growth, the slope angle increased with growing the crystal. On the other hand, in the homo-epitaxial growth, the slope angle decreased with growing the crystal. These phenomena could be explained by considering the difference in step-advancing rates between hetero-epitaxial and homo-epitaxial interfaces. It was found that the hetero-epitaxial interface strongly affected the quality of the LPE film. The guideline for the high quality LPE film by the hetero-epitaxial growth could be obtained.View full abstractDownload PDF (409K) -
Keizo Kobayashi, Toshiyuki Nishio, Akihiro Matsumoto, Kimihiro Ozaki, ...2001 Volume 65 Issue 3 Pages 179-182
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTi-1 at%Si, Ti-5 at%Si, Ti-10 at%Si and Ti-20 at%Si powders were synthesized by mechanically alloying (MA) of pure elemental Ti and Si powders using a planetary ball milling for 360 ks. Si addition was effective to produce large amount of Ti-based MA powder without adhesion to the vial wall and the surface of the milling balls. After milling for 360 ks, the amount of recoverable powder increased with increasing Si content in the MA powder. The formation of an amorphous phase was observed at Ti-5 at%Si and Ti-10 at%Si powders after 360 ks milling.
Ti-10 at%Si powder prepared by milling for 360 ks, which consisted of amorphous phase and fine Ti particles, was consolidated using a pulsed current sintering (PCS) apparatus under a high pressure of 1568 MPa. The compact consolidated at 733 K was almost densified with the retention of non-equilibrium structure. The Ti-10 at%Si powder milled for 360 ks with a hardness of 378 Hv was suitable for a consolidation under a high pressure with a deformation of powder.View full abstractDownload PDF (492K) -
Wen Shi, Akira Kamiya, Jun Zhu, Toru Nonami, Akira Watazu2001 Volume 65 Issue 3 Pages 183-186
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTitanium matrix composites reinforced with alumina short fiber were fabricated by the hot-press method. Altex fiber (85 mass% γ-alumina, 15 mass% silica) was used in this study. A reaction layer was observed at the interface between Altex fiber and the titanium matrix of the composite sintered at 1023 K. Tensile test results indicated that the tensile strength was affected by fiber volume fraction and interfacial reaction of the composite. Tensile strength of the titanium composites containing 3 vol% Altex fiber fabricated by hot-press at 1023 K for 20 min was 30% higher than that of pure titanium. However, the tensile strength of the composite did not increase for 30 min sintering time and decreased for 50 min sintering time due to excessive interfacial reaction.View full abstractDownload PDF (971K) -
Shinji Ando, Nobushiro Iwamoto, Takayuki Hori, Hideki Tonda2001 Volume 65 Issue 3 Pages 187-190
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe fatigue crack growth behavior of pure magnesium has been investigated in laboratory air at room temperature. Two type of compact specimens were prepared from magnesium polycrystalline ingot, and two type of compact specimens with different notch orientations were also prepared from magnesium single crystal made by the Bridgeman technique. Two types of fatigue crack propagation behavior were observed in the magnesium crystals. When a notch is normal to basal plane, a fatigue crack propagates though zigzag route with many basal slip. In the case of notch parallel to basal plane, a fatigue crack propagates through straight route with {10\={1}2} twin, and the value of ΔKth is smaller than that of fatigue crack propagation with basal slip.View full abstractDownload PDF (681K) -
Yusuke Ide, Tsuneki Takahashi, Arata Tsukamoto, Katsuji Nakagawa, Akiy ...2001 Volume 65 Issue 3 Pages 191-194
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe giant magneto resistance (GMR) effect in Co/Cu multilayers is one of the important issues for achieving a highly sensitive magnetic head. It is commonly known that GMR effect depends on the nanostructure at the interface and the grain size in the polycrystalline multilayers. For the purpose of clarifying the nanostructure at the surface during the film formation process, we performed molecular dynamics (MD) simulations for fabrication processes. Two different simulations were given for the Cu deposition behavior for both (1) on a Cu (111) single crystal substrate and (2) on a polycrystalline ⟨111⟩ textured Cu substrate. The MD simulation was also applied to the polycrystalline substrate for the quench process after melting at 1357 K. After the deposition of 0.6 Cu atoms monolayer on a single crystal substrate, [ABC] and [AB/A] structures were observed at the surface. With increasing the thickness of the deposition layer, [ABC] and [AB/A] structures contacted each other, and stacking faults appeared inside the third deposition layer. Then the grain structure appeared inside the fourth deposition layer merely over the area where the stacking faults were observed inside the third deposition layer. In case of deposition on the polycrystalline substrate, grain structures were observed in the deposition layer, which is similar to the grain structures of the substrate.View full abstractDownload PDF (735K) -
Kazutomo Ayabe, Takuji Okabe2001 Volume 65 Issue 3 Pages 195-198
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMechanical alloying (MA) of powder mixtures of Ni-33 mol%Al-x mol%B(x=0−2.0) was performed for various milling times, and the effect of MA on combustion synthesis under air and vacuum heating conditions was investigated for the MA powders. The nature of combustion synthesis changed dramatically with MA conditions (milling duration, quantity of B-doping, etc.), and suitably produced MA powders induced combustion synthesis in air (room temperature) and vacuum heating (near 673 K). The addition of B inhibited the combustion of the MA powders. By X-ray diffraction (XRD) analysis, it was found that intermetallic compounds such as NiAl, Ni3Al and Al3Ni2 were formed. The increase in relative intensity of XRD peaks for the intermetallic compounds was greater for vacuum heating than for air. It is suggested that combustion in air for the MA powders in the present study is led by the heat of formation from the oxidation reaction between mechano-chemically activated fine Al powders and oxygen. That is, the heat becomes a trigger for combustion synthesis between reactant species of Ni and Al. The above mechanism in air differs from that in vacuum heating where the MA powders themselves directly cause the exothermic reaction and combustion synthesis.View full abstractDownload PDF (755K) -
Jin Pan, Akihiro Okamoto, Sang Pill Lee, Gen Sasaki, Makoto Yoshida, H ...2001 Volume 65 Issue 3 Pages 199-206
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA new surface treatment method for aluminum borate whisker was developed in order to suppress the interfacial reaction between the whisker and aluminum alloy. By depositing Mg on the whiskers under 10 Pa at 650°C for 3.6 ks, and heating them in air at 800°C for 1.8 ks, a uniform MgAl2O4 layer with a thickness of 10-20 nm covered the whisker. MgAl2O4 layer had a close bonding to the whisker. No treatment whisker, SiO2 binder added whisker, Mg coated whisker and MgAl2O4 coated whisker reinforced AC4CH aluminum alloy composites were fabricated by squeeze casting, respectively. Compressive strength of the whisker preforms having Mg coat and MgAl2O4 coat increased remarkably. The deformation of the preform was avoided during squeeze casting. Tensile strength of Mg coat whisker reinforced composites did not decrease, and that of MgAl2O4 coat whisker reinforced composites was enhanced by 37% after aging treatment (T6). The interface having MgAl2O4 coat showed a stable state. MgAl2O4 coat can be regarded as a good barrier to prevent the interfacial reaction between aluminum borate whisker and aluminum alloy matrix.View full abstractDownload PDF (2227K) -
Takeshi Yamada, Takayuki Tsuzuku, Hiroaki Sato2001 Volume 65 Issue 3 Pages 207-216
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn development of continuous fiber reinforced titanium alloy matrix composites (TMCs) for practical applications there are some difficulties due to the enormous production cost resulting from preliminary forming and elaborate tooling for consolidation. One of the promising approaches to reducing the production cost is to apply a superplastic forming technique in manufacturing TMC parts. In the present study, superplastic-formable TMC sheets, SiC/Ti-4.5Al-3V-2Mo-2Fe (SCS-6/SP-700) composites, were newly developed, and their consolidation conditions, deformation characteristics and cavitation behavior were investigated. The TMCs were fabricated by foil/fiber/foil lamination using SP-700 sheets 0.12 mm in thickness and 4-ply SCS-6 preforms; they were consolidated by hot isostatic pressing under an Ar-gas pressure of 150 MPa at 973 to 1073 K for 2 h. In the case of the TMCs consolidated at a temperature above 1023 K, foil/foil and foil/fiber interfaces were successfully bonded, and their tensile strength at room temperature showed better reproducibility than that in the case of the TMCs consolidated at a temperature below 998 K. In preliminary tensile tests in the direction perpendicular to the fiber orientation at 1048 K, the TMCs consolidated at 1023 K showed a maximum true strain exceeding 69%. Thus, 1023 K was selected as the consolidation temperature. Deformation properties were tested by tensile tests in the direction perpendicular to the fiber orientation under a constant strain of 5×10−5 to 1×10−3 s−1 at temperatures in the range of 1023 to 1073 K. The TMC showed superplasticity with the maximum m-value of 0.58 at 1048 K. A maximum true strain exceeding 69% was achieved under a constant strain of 5×10−5 s−1 at 1048 K. Cavitations observed in specimens after deformation were classified into three types; one of these strongly depends on the forming conditions, but the other two do not. SCS-6/SP-700 composites were successfully bent both in the longitudinal direction and in the transverse direction at 1048 K.View full abstractDownload PDF (1678K) -
Yuichiro Sudo, Kenji Yajima, Yoshiharu Mae2001 Volume 65 Issue 3 Pages 217-222
Published: 2001
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRecent trends toward smaller diameter in fine copper wire and smaller thickness in rolled copper foil require improvement in workability of materials. Generally, workability can be estimated by the strain hardening exponent obtained from the true stress-true strain curve in the tensile test.
In this work, work hardening behavior of three kinds of recrystallized commercial pure coppers was investigated. The effect of the increase in the annealing temperature is summarized as follows.
(1) In oxygen free copper, the flow stress increases due to the locking hardening by sulfur, but the strain hardening exponent does not change.
(2) In phosphorus deoxidized copper, the flow stress decreases and the strain hardening exponent increases due to phosphorus in the solid solution.
(3) In electrolytic tough pitch copper, the flow stress decreases due to the coarsening of Cu2O particles and the strain hardening exponent increases due to oxygen in solid solution.
The difference in work hardening behavior between three kinds of commercially pure coppers seems to be brought about by the difference in the interaction between dislocations or stacking faults and atoms of the above trace elements.View full abstractDownload PDF (1216K)
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