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Volume 64, Issue 5
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Byung-Nam Kim, Keijiro Hiraga2000 Volume 64 Issue 5 Pages 275-278
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSSuperplastic deformation behavior is simulated in 2 dimensions by incorporating the mechanisms of grain boundary diffusion and concurrent grain growth of both static and dynamic growths. The relationship between microstructural changes and mechanical properties is examined under various loading conditions. Although grain boundary diffusion produces an increase in the aspect ratio of grains, for large grain boundary mobility, the increase is restricted by the rapid migration of the grain boundary. With increasing aspect ratio, the stress exponent decreases and the grain size exponent increases, which are 1 and 3 for equiaxed grains, respectively. From the observation of the simulated microstructures, it is also found that grain boundary sliding is related with the migration of grain boundaries.View full abstractDownload PDF (359K) -
Masahiko Ikeda, Shin-ya Komatsu, Koichiro Inoue, Hiroyuki Shiota, Toru ...2000 Volume 64 Issue 5 Pages 279-282
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn beta quenched Ti-Fe-Cr alloys prepared using ferro-chromium alloy, pure Fe or pure Cr and as targeting composition to electron-to-atom ratio (e/a) of 4.28, phase constitution and tensile properties were investigated by electrical resistivity measurement, X-ray diffraction and tensile testing.
In all alloys, beta phase was only identified by X-ray diffraction at room temperature. Resistivity and Vickers hardness decreased with increase in Cr content as a substitute for Fe on condition that 4.28 as e/a is maintained, whereas resistivity ratio increased with Cr content. These changes will be due to decrease in volume fraction of athermal omega with increase in Cr content.
Tensile strength slightly decreased with increase in Cr content, whereas elongation and reduction in area obviously increased. The tensile properties of the quenched Ti-Fe-Cr alloys were not worse than those of commercial beta Ti alloys, excepting Ti-7.1Fe alloy. It is considered that addition of Cr as a substitute for Fe will improve balance between tensile strength and ductility.View full abstractDownload PDF (423K) -
Yoshito Takemoto, Masahiro Nagae, Moritaka Hida, Akira Sakakibara, Jun ...2000 Volume 64 Issue 5 Pages 283-286
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSFine strain fields around TiN precipitates in Mo alloys, were analyzed by a newly proposed HOLZ (High Order Laue Zone) pattern method, using transmission electron microscopy. The shape of the TiN precipitates changed into three different types after heat treatment thin plate, rod and sphere. The thin foils for TEM observation were prepared by an electro-polish method. It was found in preliminary experiments using pure Mo that the appropriate condition to obtain a good HOLZ pattern for bcc materials was to choose an orientation which satisfied both low density and uniform distribution of reciprocal spots within the zero order Laue zone. The HOLZ patterns were therefore acquired from the [410] direction of the matrix at room temperature using a convergent electron probe 8.8 nm in diameter operated at 200 kV. Many HOLZ patterns were taken by shooting the electron probe within 150 nm × 150 nm areas that included a precipitate. These patterns were imported into a personal computer using a scanner. It was found that the HOLZ patterns hardly changed its configuration with position but moved as a whole within the center disk depending on position, suggesting lattice rotation of the matrix. The vector maps which indicated the degree and direction of lattice rotation around a precipitate were produced for three types of precipitates. The thin plate of TiN generated a symmetrical mountainous strain field. The rod yielded an asymmetrical valley strain field, and the sphere hardly influenced the matrix. It is considered that the difference in the form of the strain field depending on the shape of precipitate was caused by the degree of coherency between the matrix and the precipitates.View full abstractDownload PDF (995K) -
Masahiko Katagiri, Hidehiro Onodera2000 Volume 64 Issue 5 Pages 287-290
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe atomistic mechanism of Hydrogen-Induced Amorphization (HIA) of AB2 C15 Laves phase compounds was investigated via constant-pressure molecular dynamics (MD) method using empirical Lennard-Jones interatomic potentials. Present simulations have successfully reproduced the experimental results that the CeNi2 compound shows HIA while the YAl2 compound does not show it. Our results show the softening effect due to the incorporation of hydrogen in both systems; the non-linearity of the interatomic potential leads to the softening effect via volume expansion. In addition, the CeNi2 compound shows more softening effect due to the relaxations of atomic positions of Cerium and Nickel atoms, while the YAl2 compound does not show it. We suggest that the key to induce HIA is whether A and B atoms can relax simultaneously by releasing the contraction of A and the expansion of B in Laves phase as the CeNi2 compound is the case. Such relaxations give the reduction of bulk modulus, and may be an indication of the elastic lattice instability. The obtained amorphous structure is a potentially favorable one, and HIA causes the potential-energy decrease, indicating the driving force is the potential-energy decrease. In contrast, solid-liquid melting causes the potential-energy increase, indicating the driving force is the entropic effect.View full abstractDownload PDF (368K) -
Yasuyoshi Hidaka, Takahisa Nakagawa, Toshirou Anraku, Nobuo Ootsuka2000 Volume 64 Issue 5 Pages 291-294
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSHigh-temperature mechanical properties and deformation behavior of wustite scale were investigated.
Tensile tests of oxide scale were performed from 600 to 1200°C under strain rates of 10−3∼10−5 s−1 in a gas atmosphere of H2-H2O-N2. Scale chemistry during the tensile test was maintained. Test specimens of wustite scale were prepared by complete oxidation of 99.999%Fe in a corresponding gas atmosphere before the tensile test.
Oxide scale of wustite deformed plastically above 700°C. Fracture elongation increased and tensile strength decreased as the temperature increase; elongation of 150% was obtained at 1200°C. Steady-state deformation, where the stress saturated, was recognized above 1000°C. Sub-boundary structure due to polygonization was observed for the test specimen after tensile test. The test results suggest that high-temperature deformation of wustite scale results from dynamic recovery associated with dislocation climb above 1000°C.View full abstractDownload PDF (762K) -
Hirofumi Homma, Hideyuki Saitoh, Toshihei Misawa, Toshiyuki Ohnishi2000 Volume 64 Issue 5 Pages 295-298
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSHydrogen distribution in pure vanadium, V-5 mol%Fe, V-50 mol%Ti and V-47.5 mol%Ti-5 mol%Fe alloys has been observed quantitatively by the tritium radioluminography to investigate the hydrogen behavior in them. Hydrogen concentration has been found to be non-uniform in the surface of each specimen depending on their microstructure. The cross sectional observation of the hydrogen distribution in the V-5 mol%Fe alloy has shown that the hydrogen concentration is low in the higher iron region in the specimen, i.e. the hydrogen concentration depend on the iron distribution in the specimen. It has been found that the iron addition into pure vanadium and V-50 mol%Ti alloys increases the hydrogen penetration rate. Surface hydrogen concentration in each specimen decreases during three days after hydrogen charging due to the hydrogen diffusion into the interior of the specimen. Observation of the local hydrogen concentration in the V-47.5 mol%Ti-5 mol%Fe alloy has shown that hydrogen concentration decreases rapidly in higher hydrogen concentration region in the specimen.View full abstractDownload PDF (646K) -
Keum-Yeon Hwang, Tetsumori Shinoda, Yoshihiro Oya-Seimiya2000 Volume 64 Issue 5 Pages 299-302
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effect of the Mo addition on the superconducting transition temperature, Tc, of the A15 Nb3Al alloy has been investigated on the basis of a general trend that Tc increases as the lattice parameter decreases for this kind of alloy series.
The lattice parameter of the A15 phase decreases monotonically with increasing Mo content. Tc of the Nb-20 mol% alloys in addition of 2 to 3.5 mol%Mo becomes higher than that of the Mo-free alloy, Tc(0), and attains a peak of 14.8 K at 2 mol%Mo, which is about 2 K higher than Tc(0). For Mo contents higher than 5 mol%, the enhancing effect of Mo on the Tc of N3Al alloy disappears.View full abstractDownload PDF (525K) -
Hiroaki Fukumura, Takao Mizushima, Akihiro Makino, Akihisa Inoue2000 Volume 64 Issue 5 Pages 303-306
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThermal stabilities of structure and soft magnetic properties were investigated for melt-spun Fe-Al-Ga-P-C-B-Si glassy alloy ribbon with various sample thicknesses. No change in structure and soft magnetic properties for Fe70Al6Ga1P11.4C4B4Si3.6 can be observed by holding at the starting temperature of endothermic reaction for glass transition (Tgonset) for 1.6 ks, which is much longer than those of conventional Fe-based amorphous alloys without supercooled liquid region. The thermal stability of Fe-based glassy alloy increases with increase of the width of supercooled liquid region. It does not, however, depend upon sample thickness. We can, therefore, hope that bulky Fe-Al-Ga-P-C-B-Si glassy alloy has a high workability without inferior of soft magnetic properties, because deformation and working processes are much easier in the supercooled liquid region owing to its low viscosity and ideal Newtonian flow.View full abstractDownload PDF (448K) -
Akemi Hayashi, Katsuya Hasegawa, Uichi Nakamura, Teruo Izumi, Yuh Shio ...2000 Volume 64 Issue 5 Pages 307-310
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSSm1+xBa2−xCu3Oy(Sm123) films were grown on MgO substrates by the Liquid Phase Epitaxy (LPE) process in air atmosphere using BaO-CuO solvents with Ba/Cu ratios of 3/5 and 3/4. The substitution ratios of Sm/Ba in Sm123 films were less than 0.02 for different growth conditions including temperature and Ba/Cu ratios of the solvent. Tc value of 94 K was obtained in the Sm123 films grown from the Ba/Cu=3/5 solvent in air after O2 annealing at 573 K for 100 h. These results suggest that the substitution ratio of Sm/Ba is smaller than that of Nd/Ba in Nd123 crystal and that the high Tc value would be obtained even grown from the melt of Ba/Cu=3/5 in the air atmosphere. Peak effects in the Jc-H curves were observed in the Sm123 films annealed by continuous cooling for oxygenation condition.View full abstractDownload PDF (307K) -
Ritsuko Nakajima, Kazuki Shimura, Munetsugu Matsuo2000 Volume 64 Issue 5 Pages 311-314
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA database of diffusion in solid on WWW is under development with the aim of supporting research activities on diffusion phenomena or materials design. It covers diffusion in metals and nuclear materials such as iron-, nickel-, or zirconium-alloys, and titanium alloys. The user interface and the functions are designed intelligibly, which enables even beginners to use this database properly. Some analyses by statistical approach have been performed to classify retrieved data with utilizing the functions of the system. The result shows that candidates for parameters to classify data and influential factors in isolated data can be suggested. A new advanced function based on this approach has been designed.View full abstractDownload PDF (354K) -
Yoshihiro Oya-Seimiya, Tetumori Shinoda, Yasuyoshi Fukui, Nobuyuki Yam ...2000 Volume 64 Issue 5 Pages 315
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA trial make Al-Si base multi-functionally gradient materials by means of centrifugal casting has been performed. The aim of this trial is to make an in-situ cylindrical composite in which the outer surface is enriched with Al of high heat conductivity, and the inner surface is abounded with Si-particles of high melting point.
As the consequence, the fine Si-particles disperse to the inner surface, as the rotation frequency of a mold increases. However, the Si-particles do not necessarily tend to distribute gradiently along the thickness direction of the cylindrical composite. This might be because the precipitation process of Si is complicatedly influenced by the centrifugal force. The rotation axis component of molten metal flow also acts as reducing the population of Si-particles at the inner surface because of carrying them to the both edges of the cylindrical composite.View full abstractDownload PDF (621K) -
Kazuhiko Noda, Masahiro Yamamoto, Hiroyuki Masuda, Toshiaki Kodama2000 Volume 64 Issue 5 Pages 319-322
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe corrosion characterization of the low alloy steel under seashore environment depends on the alloy elements. Rusting process and corrosion behavior of pure iron, Fe-3 mass%Ni and Fe-3 mass%Cr low alloy steel under corrosion cycle test were investigated by surface observation using optical microscope, laser microscope and AFM. Both Ni and Cr were effective to decrease the corrosion rate and the filiform corrosion type that is the same to the case of pure iron occurred on the alloys during rusting process. Form the result of removing the rust, the pitting corrosion was appeared under the rust on the Cr additive steel although the general corrosion occurred in the case of pure iron and Ni additive alloy. The difference of the corrosion type was explained by hydrolysis equilibrium. Fe and Ni anodic dissolution did not make the pH decline. When the anodic dissolution of Cr was carried out, it is easy to decline pH and severe condition was achieved at the local site. Therefore, localized corrosion produced on the Fe-Ce alloy.View full abstractDownload PDF (743K) -
Katsumi Nomura, Saburo Hoshi, Xin Yao, Yuichi Nakamura, Teruo Izumi, Y ...2000 Volume 64 Issue 5 Pages 323-326
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have investigated the in-plane homogeneity of the large LPE (liquid phase epitaxy) crystals in microstructure and the growth mode in order to clarify the growth mechanism. The growth rate distribution dependence on the crystal rotation was observed in 20×20 mm2 LPE films. In the YBa2Cu3O7−δ system the higher rotation rate caused a larger growth rate distribution. It was considered that the distribution of both the growth interface temperature and the solute diffusion boundary layer thickness was existed. In this paper, we have focused the effect of the heat flux from the bottom of the crucible (hot region) during the LPE growth. Investigation of the growth rate distribution in the NdBa2Cu3OX(NdBCO) system was effective in order to confirm the influence of the heat flux, since the influence was negligible for the LPE growth in the NdBCO system. The higher rotation rate in the NdBCO system caused a smaller growth rate distribution. These phenomena could be explained by the difference in the crystal rotation effect on the growth interface temperature.View full abstractDownload PDF (585K) -
Yasuhisa Yamamoto, Kenki Hashimoto, Takashi Kimura, Morihiko Nakamura, ...2000 Volume 64 Issue 5 Pages 327-330
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTo evaluate the room temperature ductility of Ti-rich titanium aluminide of L12-type (Al, Mn)3Ti, (Al, Cr)3Ti and (Al, Mn, Cr)3Ti alloys (where the composition changed from the L12-type (Al, Mn)3Ti to the L12-type (Al, Cr)3Ti ternary region), porosity distribution and bend ductility were examined for specimens heat-treated at 1500 K for 84.6 ks, by laser optical microscopy and a three point bending test, respectively. All of the specimens were confirmed to consist of a L12 single-phase microstructure, by laser optical microscopy. The area fraction and the average pore-size decreased with increasing Ti content, while both area fraction and pore size increased with increasing Cr content. The ternary (Al, Cr)3Ti alloys containing low Ti and high Cr contents exhibited a maximum bend ductility of 0.49% strain. On the fracture surface of the specimens where the bend ductility exceeded 0.3% strain, a few band-like contrast regions were observed which were parallel to the direction of the thickness of the test piece.View full abstractDownload PDF (756K) -
Jiangbo Sha, Hisatoshi Hirai, Tatsuo Tabaru, Akira Kitahara, Hidetoshi ...2000 Volume 64 Issue 5 Pages 331-334
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to examine the effect of carbon addition on the mechanical properties of niobium solid solution/niobium silicide eutectic alloys (in-situ composites), (Nb-xMo-22Ti-18Si)-yC(x=10 and 20 mol%, y=0, 1.0, 2.4, 4.8, 7.0, 9.1 mol%) alloys were prepared by arc melting and floating zone melting techniques. Each specimen was annealed at the temperature range from 1820 to 1870 K in a vacuum for 100 h. Vickers hardness was measured at room temperature and compressive strength was measured at 1670 K in a vacuum at an initial strain rate of 1×10−4 s−1.
Specimens containing more than 2.4 mol% carbon are composed of Nb solid solution, (Nb, Mo, Ti)5Si3 silicide and (Nb, Ti)C carbide, and the amount of carbide phase increases with increasing carbon content. A small amount of carbon addition lowers both Vickers hardness and 0.2% yield stress at 1670 K. By the addition of more than 4.8 mol% carbon, however, Vickers hardness and yield stress tend to increase. A certain amount of carbon must be soluble in the silicide phase, which possibly changes the crystal structure of the silicide, resulting the softening of this alloy.View full abstractDownload PDF (546K) -
Wen Shi, Makoto Kobashi, Takao Choh2000 Volume 64 Issue 5 Pages 335-338
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSGood wettability between molten metals and solid ceramics is important to fabricate metal matrix composites via a casting route. In this work, the wettability of molten magnesium on carbon and AlN substrate was evaluated. To stabilize the shape of the magnesium drop, the chamber was filled with magnesium vapor prior to the wettability measurement. A good wettability was observed from the magnesium-carbon system. Initial contact angles of molten magnesium on the vitreous carbon and the porous graphite at 973 K were 80° and 74°, respectively. However, the molten magnesium did not show good wettability with AlN. The initial contact angle of molten magnesium on AlN was 119°. The effects of aluminum and zinc addition on the contact angle were also measured. The contact angle of molten Mg-Al alloy on AlN substrate were almost constant (119°) for aluminum additions in the range of 0 to 3 mass%, but mildly reduced to 115° when 10 mass% of aluminum was added. The contact angle of Mg-10 mass%Zn alloy on AlN substrate was 107°, which again was slightly lower than that of pure magnesium.View full abstractDownload PDF (438K) -
Toshiyasu Nishimura, Akira Tahara, Toshiaki Kodama2000 Volume 64 Issue 5 Pages 339-342
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe rust formed on the 0.2 mass%Ru-bearing steel was analyzed by EPMA and XPS after wet/dry corrosion test using chloride solution. The Ru-enriched layers were found in the rust of the Ru-bearing steel, and the number of such layers were almost the same as those of test cycles. It is shown that Ru is zerovalent (metal) state at the Ru-enriched layer in the rust by EPMA and XPS. Ru ion could be dissolved into the solution with the ferrous ion from the base metal in wet process, and finally carried to around the interface of the outer and inner laylers due to the decrease of the water film in dry process, then Ru could become the metal state which was stable in this site in the iron rust.View full abstractDownload PDF (331K) -
Takahiro Hasegawa, Eiichi Higuchi, Keum-Yeon Hwang, Tetsumori Shinoda, ...2000 Volume 64 Issue 5 Pages 343-346
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSMethods for fabricating A15 type Nb3Al superconducting materials based on the solid Nb/liquid Al interfacial reaction have recently drawn the strong attention of workers in this field around the world. It seems, however, that the details of the formation process of the A15(Nb3Al) phase in these methods are not yet clear. Therefore, in the present study, we have performed some experiments in order to obtain some basic information about the processes involved. As a consequence, the following data were obtained; For Nb/Al composites with a single Al rod covered by a Nb tube heated at 1723∼2073 K for given times, 1) the σ (Nb2Al)-phase grows rapidly from the solid/liquid interface toward the interior of liquid Al, and 2) the A15 phase grows very gradually, with its grown width being about 40 μm at most for the sample heated at 2073 K for 1 h.View full abstractDownload PDF (732K) -
Tatsuya Ohmi, Kazuhiko Kirihara, Masayuki Kudoh2000 Volume 64 Issue 5 Pages 347-350
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCombustion synthesis and casting of Ni-25 mol%Al alloy and simultaneous joining to stainless steel, in the field of centrifugal force, have been investigated. In order to produce the Ni-Al alloy in the liquid state, the thermite type combustion synthesis process was adopted. In this process, the reaction temperature can be varied arbitrarily by changing the mixing ratio of the reactants, Ni, Al and NiO. In the present experiments, a cylindrical block of stainless steel was embedded in the basal part of a green compact of the reactants. The green compact was set in a centrifugal caster, and the combustion synthesis reaction was induced in the field of centrifugal force. This process, the centrifugal combustion synthesis, was successfully applied in joining the Ni-Al alloy and the stainless steel. On the other hand, joining did not succeed in the absence of a centrifugal force or close contact between the stainless steel and the green compact.View full abstractDownload PDF (767K) -
Yuichi Yamashita, Toshiyuki Matsui, Kenji Morii2000 Volume 64 Issue 5 Pages 351-354
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to synthesize thin films of a CoSb3 compound, thin Co/Sb multi-layered films were prepared by an ion-beam sputtering method, and annealed in a temperature range between 673 and 773 K for 1 to 3 h in a vacuum atmosphere. The effects of both chemical composition and annealing conditions on the CoSb3 phase evolution were evaluated by X-ray diffraction and transmission electron microscopy. The thermoelectric properties of the annealed films were studied at elevated temperatures. The results obtained are summarized as follows: In a rather wide composition range such as 70 to 85 at%Sb, thin films consisting of a CoSb3 single phase were successively synthesized. The CoSb3 films showed a p-type semiconducting character, and their thermoelectric transport properties were found to be nearly closed to those of bulk materials reported so far. It was also found that the grain size, electrical conductivity and Seebeck coefficient of the CoSb3 films were dependent on their chemical composition after annealing.View full abstractDownload PDF (712K) -
Akira Sugiyama, Keizo Kobayashi, Akihiro Matsumoto, Kimihiro Ozaki, To ...2000 Volume 64 Issue 5 Pages 355-358
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe formation process of a Mg2Si-MnSi1.73 thermoelectric device made by mechanical alloying (MA) and pulsed current sintering was investigated.
MA was performed in a planetary ball mill using two elemental powders of each material. The MA powders were consolidated by pulsed current sintering method. The Seebeck coefficient of Mg2Si sintered at 773 K under 250 MPa was −366 μV/K at room temperature. However, the electric conductivity of the obtained Mg2Si was very small and about 0.04 S/m. Therefore copper wires were mixed in order to improve the electric conductivity of Mg2Si. When the quantity of Cu wires was 5 vol%, the Seebeck coefficient kept the same value in spite of increasing electric conductivity to 0.65 S/m. A thermoelectric device with a laminated structure of Mg2Si and MnSi1.73 was made by sintering with a Cu sheet placed at the boundary surface of Mg2Si and MnSi1.73 and was not broken during cutting process.View full abstractDownload PDF (475K) -
Akira Yamauchi, Kazuya Kurokawa, Hideaki Takahashi, Yoshihisa Takada2000 Volume 64 Issue 5 Pages 359-362
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn order to clarify the influence of H2O vapor on growth behavior and morphology of scales formed on a stainless steel, SUS430 steel was oxidized for up to 3600 s at 1473 K in (N2-3%O2)-H2O atmospheres. The H2O contents were regulated to 6.9, 19.7, and 45.4%(vol%). The scale morphology showed that a uniform Cr2O3 scale formed in the initial stage, followed by the formation of iron-rich oxide nodules. Finally, the external scale of Fe2O3 and Fe3O4 and the porous inner scale of Fe(Fe, Cr)2O4 covered the entire specimen surface. The growth of the external and inner scales followed a linear rate law, and the thickness of each scale increased linearly with increasing H2O content. These results indicate that external and inner scales formed in H2O-containing atmospheres have high porosity and the formation of the inner scale is due to diffusion of H2O through the porous external scale.View full abstractDownload PDF (562K) -
Zhan-Jie Wang, Ryutaro Maeda, Kaoru Kikuchi2000 Volume 64 Issue 5 Pages 363-366
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSLead zirconate titanate (PZT) thin films were fabricated by a three-step heat-treatment process, which involves the addition of 20 mol% excess Pb to the starting solution and spin coating onto Pt/Ti/SiO2/Si substrate. Microstructure of the PZT film has been investigated using analytical and high-resolution electron microscopy. The film is crystallized in the perovskite phase with columnar grains and few pores on the order of nanometer are formed just below the layer interfaces. It is found that the presence of 1-2 nm layers of Pb-rich amorphous at grain boundaries. At the interface between PZT/Pt, second phases, such as PbO or PtxPb does not exist. It is considered that the (111) and (100) preferred orientation in the PZT film was not promoted by the PtxPb and PbO phases.View full abstractDownload PDF (1111K) -
Hideyuki Ogishi, Takeshi Suemitsu, Akira Takashima, Hyoe Ono, Hidemi U ...2000 Volume 64 Issue 5 Pages 367-370
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIt is known that the heat exchanger tubes exposed to severely corrosive conditions including sulfuric acid and hydrochloric acid in waste incineration plants. Therefore, there is a pressing need for a new materials with much higher acid corrosion resistance than that of conventional dewpoint-corrosion-resistant steel and stainless steel. In this study, amorphous Fe-Ni-Cr-Ta alloys prepared by using a sputtering technique were evaluated by immersion tests in a high temperature concentrated sulfuric acid solution, and the corrosion scale formed on the alloys was analyzed using X-ray photoelectron spectroscopy. The corrosion resistance of the amorphous Fe-Ni-Cr-Ta alloys was found to be 1000 times higher than that of Type 316L stainless steel. In addition, thin layers which contained a large amount of tantalum and tantalum compound were found. This surface tantalum rich layer was considered to contribute for increasing of corrosion resistance.View full abstractDownload PDF (414K) -
Makoto Sato, Yasushi Hasegawa, Taro Muraki, Kouichi Maruyama2000 Volume 64 Issue 5 Pages 371-374
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThis paper aims at discussing the role of W in creep strength of high chromium ferritic steels with a tempered martensitic lath structure. Creep tests of a 9Cr-1.8W-MoVNb steel (NF616) were performed at 923 and 973 K at stresses ranging from 80 MPa to 120 MPa. Microstructural degradation (recovery of subgrain structure and agglomeration of M23C6 carbides and Laves phases) in the course of creep was studied by TEM and SEM observations. The experimental results were compared with those of a Mod.9Cr-1Mo steel without W and an 11Cr-2.6W-MoNNb steel (TAF650). The most noticeable change in microstructure during the creep of the high Cr ferritic steels is the recovery of subgrain structure. Subgrain width increases and dislocation density within subgrains decreases with the progress of creep deformation. The growth rate of subgrain width in the W containing steels is slower than that of the steel without W, and the growth rate decreases with increasing W concentration. The fine and stable subgrain structure of the W containing steels suppresses the accumulation of creep strain, resulting in their longer rupture lives. Precipitation of Laves phase and M23C6 carbide on sub-boundaries retards the recovery of subgrain structure. The W addition stabilizes the M23C6 carbides, and the number of the carbides increases with increasing W concentration. These facts are the origin of the stable subgrain structure of the W containing steels. The number of M23C6 carbides in a unit area is 5 to 10 times larger than that of Laves phases, suggesting that the stability of M23C6 carbides is more important in the strengthening of the ferritic steels.View full abstractDownload PDF (372K) -
Masaaki Ishio, Tsuyoshi Hasegawa, Hiroshi Ohyama, Hirofumi Inoue, Kenj ...2000 Volume 64 Issue 5 Pages 375-378
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSWe have advanced the research of the texture control to improve the drawing formability of clad metals that are used as the anode cases of button type batteries. In this study, the effect of the thickness of each layer on the texture formation of the Cu/18Cr-8Ni-Fe clad metals was investigated by using specimens with different Cu bonding ratios ranging from 11 to 33%. A shear type rolling texture described as the ⟨110⟩\varparallelRD fiber from {001}⟨110⟩ to {111}⟨110⟩ forms to the Cu surface but the β fiber is little observed. The former texture especially develops after cold rolling the clad metal with a thinner Cu layer that was roll-bonded using the annealed Cu as a starting material. In the case of a thicker Cu layered specimen, the β fiber forms in the center of the Cu layer. A sharp cube texture of the Cu layer formed in the annealed state remains even after cold rolling to high reduction for the thinner Cu layer. On the other hand, there is no difference of the texture formation corresponding to the clad ratio for the 18Cr-8Ni-Fe layer in contrast to the Cu layer, while the texture evolution of the 18Cr-8Ni-Fe layer is suppressed by the effect of the Cu layer.View full abstractDownload PDF (533K) -
Atsuko Sekiguchi, Junichi Koike, Kouichi Maruyama2000 Volume 64 Issue 5 Pages 379-382
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCopper thin films have been considered as alternative materials to Al in ULSI metallization. Under various processing conditions, Cu films experience thermal stress that often cause stress-induced failure. Although cavity formation has been reported in Cu thin films, its mechanism has not been understood up to now. The present work is aimed at understanding the cavitation mechanism in relation to deformation and stress concentration mechanisms.
Samples consist of layer of Cu/Ta/SiO2/Si. A Ta layer was deposited as a diffusion barrier layer. Stress change was measured in copper thin films during thermal cycling at heating and cooling rates of 0.056 K/s in a temperature range of R.T. to 723 K. Morphological change was observed by SEM and TEM. Analysis of stress-temperature curves indicated that the stress state is in tension during cooling and in compression during heating. The obtained stress-temperature curve was compared with a calculated deformation mechanism map. It was found that deformation occurs mainly by a dislocation-glide creep mechanism during cooling and by a grain-boundary-diffusion creep mechanism during heating. Microstructure observation revealed that cavities were formed at twin/twin and twin/grain-boundary intersections. Based on the obtained results, the cavity formation mechanism can be understood as follows. Elastic anisotropy of neighboring twin variants gives rise to the concentration of shear stress at twin interfaces. This, in turn, causes the twin interfaces to be preferential dislocation glide planes, leading to dislocation pile up and cavitation at the intersection.View full abstractDownload PDF (481K) -
Zhan-Jie Wang, Ryutaro Maeda, Kaoru Kikuchi2000 Volume 64 Issue 5 Pages 383-386
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSPZT films were fabricated using the addition of 10% excess of Pb to the starting solution and spin coating onto Pt/Ti/SiO2/Si substrates. The effect of the thickness on texture of the films was investigated, and it is clear that the (100) texture gradually increases and the (111) texture decreases with increasing film thickness. A PtxPb intermetallic metastable phase was observed by X-ray diffraction, and it is found that the position of this peak shifted from 2θ=38.30° (d=0.2348 nm) to 2θ=37.10° (d=0.4213 nm) with increasing firing temperature from 350°C to 550°C. The (111) preferred orientation in the PZT film was not attributed to the metastable PtxPb phase. The temperature of pyrolysis of the PZT films influences the preferred orientation of the film: 250°C favored a (111) orientation, whereas 400°C favored a (100) orientation.View full abstractDownload PDF (358K) -
Nobuaki Mukai, Masataka Masuda, Yasunori Hayashi2000 Volume 64 Issue 5 Pages 387-390
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTo investigate the effect of the substrate surface roughness on the magnetic properties of Co1−XPtX alloy films (X\fallingdotseq0.73), the alloy films were prepared on various sputter-etched silicon substrates. The alloy films were produced by molecular beam epitaxy at various substrate temperatures (from 200°C to 400°C) and the magnetic properties of the films were examined by using vibrating sample magnetometry. We found out that the substrate surface roughness strongly affected the magnetic properties of alloy films. Actually, some alloy films on rough surface substrate showed larger values of effective perpendicular anisotropy Keff, coercivity Hc, and the squareness factor Mr/Ms than the film on smooth surface substrate. The magnetic properties of the alloy film prepared at 350°C on 5 min-etched substrate were comparable to those of the epitaxial Co/Pt multi-layer film. The structure of the alloy films was characterized by Atomic Force Microscopy, X-ray diffraction, transmission electron microscope and X-ray photoelectron spectroscopy.View full abstractDownload PDF (378K) -
Takushi Goto, Shinji Ando, Hideki Tonda2000 Volume 64 Issue 5 Pages 391-394
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCore structures of a-screw dislocation in hcp metals have been investigated using molecular dynamics simulation. Lennard-Jones(LJ) type and Finnis-Sinclair(FS) type potentials were employed to obtain dislocation core structures. In the case of the LJ potential, a-screw dislocation has expanded core on the basal plane at 0 K. At higher temperature, the core width becomes narrow and expanded to the prismatic plane. Core structures of titanium, magnesium and beryllium were investigated at 300 K with FS potential. The core structures of titanium and magnesium were expanded on the prismatic and basal planes, respectively. These results correspond to the slip of the real metals behavior. The core structure of beryllium was expanded on the prism plane. This result was different from real metal slip behavior. The a-screw dislocation in titanium began to move at 0.009 strain in [\bar2110] tensile, and at 0.006 strain in [0\bar110] tensile.View full abstractDownload PDF (336K) -
Masafumi Noda, Kunio Funami, Masaru Kobayashi2000 Volume 64 Issue 5 Pages 395-399
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSTo improve the mechanical properties of Al alloys, grain refinement is one of the useful methods. In this study, grain refinement of 3004Al alloy was carried out by heavy plastic working i.e. warm or cryogenic forging, which induced high stored strain energy. It was possible to be rolled up to 98% reduction ratio by using cryogenic rolling with forging as prework process. Annealing was finally performed for rapid recrystallization in a salt bath at recrystallization temperature. As the result, Vickers hardness, tensile strength and yield stress of specimens worked up to 98% were HV160, 450 and 390 MPa, respectively. The specimens having annealing treatment at 583 K, 300 s produced fine grain structures with about 5 mm in grain size. It was found that the yield stress and tensile strength were 1.6 and 1.2 times compared with that of initial material regardless of forging condition. In the case of shorter annealing time, i.e. 30 s, the grain size was 3∼4 μm and yield stress increment of 2.5 times was obtained. This working process is more practical and easy to enhance its mechanical properties.View full abstractDownload PDF (632K) -
Akira Muto, Kiyoshi Sato, Shoji Goto, Michihiro Tagami2000 Volume 64 Issue 5 Pages 399-402
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA fine grain size Cu-30 mass%Zn specimen revealed an anomalous type of creep curves in which the strain rate at the 3rd creep stage increased with increasing strain, attained a peak value at the end of the 3rd creep stage and then decreased during our newly discovered 4th creep stage, which we call quaternary creep. These constant stress creep tests were conducted in an intermediate temperature range. The specimens with a grain size of 12 μm were creep tested at 723 K under various stresses. TEM observations were conducted for the specimens crept under a stress of 19.6 MPa at various creep stages. The dislocation density increased rapidly at the 1st and the 4th stages. Hardening rates are discussed in terms of increased dislocation density associated with the creep deformation. The occurrence of the 4th stage results from work-hardening.View full abstractDownload PDF (449K) -
Mitsuhiko Matsui2000 Volume 64 Issue 5 Pages 403-406
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRecently sodium ionic conductors such as NASICON (Na3Zr2Si2PO12) have been used as the solid electrolyte for EMF(electromotive force) type CO2 sensors. However, it has been hard to obtain a sufficiently high quality in this type of sensor, partly due to the low humidity-resistance of NASICON and partly because of its poor initial response of EMF to CO2 pressure.
For the purpose of improving the humidity-resistance and the initial response of EMF of the solid electrolyte CO2 sensors, Li2TiSiO5 is employed as the sensing material instead of NASICON. It is composed of the following electrochemical cell:
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The electrochemical reaction is in good agreement with the Nernst equation, and reacted electron is calculated as 2.04. The sensor fabricated with Li2TiSiO5 shows good linearity when it is exposed to an atmosphere of 90% relative humidity at 60°C. The initial 90% response of EMF is steadied within 4 min. These experimental results make it possible to use the sensor in the environments.View full abstractDownload PDF (321K) -
Kohsuke Tagashira, Kiyoto Kikuchi, Toshiaki Tanaka2000 Volume 64 Issue 5 Pages 407-412
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe solidification texture of weld metal was investigated for laser irradiated aluminum. Both cold rolled and recrystallized specimens of 1.2 mm thickness were irradiated using a 1.2 kW CO2 laser, at three different welding speeds; 41.7, 62.5 and 83.3 mm/s. The following results were obtained. (1) The main components of the solidification texture, both for the cold rolled and for the recrystallized specimens are (001) [100] and {112}⟨111⟩-{123}⟨634⟩, which is almost the same as the usual recrystallization texture for cold rolled aluminum. These are independent of welding speeds. (2) In the recrystallized specimens, the columnar grains in the bead grow from matrix grains adjacent to the fusion boundary by keeping the same orientation as if matrix grains are seed crystals. (3) In the cold rolled specimens, recrystallized grains in the heat affected zone due to laser irradiation act as the seed crystals for the growth of the columnar grains in the beads.View full abstractDownload PDF (1115K) -
Toshio Yonezawa, Toshihiko Iwamura, Koji Fujimoto, Kazuhide Ajiki2000 Volume 64 Issue 5 Pages 413-422
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe authors have reported that the primary water stress corrosion cracking (PWSCC) in baffle former bolts made of austenitic stainless steels for PWR after long-term operation is caused by irradiation-induced grain boundary segregation.
The resistance to PWSCC of simulated austenitic stainless steels whose chemical compositions are simulated to the grain boundary chemical composition of 316 stainless steel after irradiation increased with decrease of the silicon content, increases of the chromium content, and precipitation of M23C6 carbides at the grain boundaries.
In order to develop resistance to irradiation assisted stress corrosion cracking in austenitic stainless steels, optimized chemical compositions and heat treatment conditions for 316CW and high-chromium austenitic stainless steels for PWR baffle former bolts were investigated.
For 316CW stainless steel, ultra-low-impurities and high-chromium content are beneficial. About 20% cold working before aging and after solution treatment has also been recommended to recover sensitization and make M23C6 carbides coherent with the matrix at the grain boundaries. Heating at 700 to 725°C for 20 to 50 h was selected as a suitable aging procedure. Cold working of 5 to 10% after aging produced the required mechanical properties.
The optimized composition of the high-chromium austenitic stainless steel contents 30% chromium, 30% nickel, and ultra-low impurity levels. This composition also reduces the difference between its thermal expansion coefficient and that of 304 stainless steel for baffle plates. Aging at 700 to 725°C for longer than 40 h and cold working of 10 to 15% after aging were selected to meet mechanical property specifications.View full abstractDownload PDF (1116K)
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