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Volume 64, Issue 7
Displaying 1-15 of 15 articles from this issue
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Tatsuya Ohmi, Makoto Ueda, Youichi Itoh, Kiyotaka Matsuura, Masayuki K ...2000 Volume 64 Issue 7 Pages 483-489
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSSolidification structures of Al-Ni and Al-Ni-Si alloys produced by Centrifugal Duplex Casting (CDC process) have been investigated. The CDC process is applicable to the production of a cast pipe of an aluminum alloy with an in situ composite layer containing fine intermetallic crystals. In this process, two molten metals, i.e. “the first melt” (aluminum or a hypoeutictic aluminum alloy) and “the second melt” (a hypereutectic or hyperperitectic aluminum-transition metal alloy with a higher liquidus temperature), are poured in sequence at a given interval into a roating mold of a centrifugal caster. Because the first melt acts as a coolant, the second melt is rapidly quenched to precipitate extremely fine primary crystals when they are mixed in the mold.
When the first melt of an Al-5 mass%Ni alloy and the second melt of an Al-30 mass%Ni alloy were used, the composite layer in the CDC pipe consisted of the `“refined composite layer” with fine intermetallic particles and the “coarse composite layer” with relatively coarse particles. The coarse composite layer is subdivided into two sub-layers, i.e. the layer with accumulated flaky particles and that with freely grown particles.
The refined composite layer was not formed when the first melt was aluminum whose melting point is higher than the liquidus temperature of the Al-5 mass%Ni alloy. On the other hand, large clusters with fine Al3Ni crystals were formed when the first melt was an Al-12 mass%Si alloy whose liquidus temperature is lower than the Al-Al3Ni eutectic temperature. However, these clusters did not form the refined composite layer but coexisted with flaky particles of Al3Ni.View full abstractDownload PDF (952K) -
Han-Cheol Choe, Keum-Yeon Hwang, Kwan-Hyu Kim2000 Volume 64 Issue 7 Pages 490-494
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSCorrosion behavior of ion nitrided stainless steels (SS) containing Mo was investigated by electrochemical methods. The morphologies of ion nitrided stainless steel were analyzed using optical microscopy and scanning electron microscopy (SEM).
Pitting corrosion resistance is improved remarkably in the case of ion nitrided SS containing 4.05 mass% Mo at 653 K for 30 h because Mo acts to form a protective surface layer against Cl− ion and nitrited film such as Fe4N formed on the surface at low nitriding temperature. In the case of ion nitriding at 823 K, the pit nucleation rate and the number of pit decreased as the Mo content increased owing to retardation of the nucleation and growth of chromium carbide or nitride at the grain boundaries.View full abstractDownload PDF (467K) -
Goh Shimoike, Hirotsugu Ogi, Kazuki Takashima, Masahiko Hirao2000 Volume 64 Issue 7 Pages 495-501
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe complete elastic-stiffness tensor Cij comprising six independent components, and the corresponding internal friction Qij−1 for an SiCf/Ti cross-ply composite were measured with electromagnetic acoustic resonance (EMAR). Conventional resonance-ultrasound spectroscopy excites the eight possible groups of free vibration of a rectangular parallelepiped and identification of the vibration-mode was unclear. The EMAR, each vibration group was detected selectively and independently. This study shows that the EMAR is useful at elevated temperatures because of the contactless measurement. The temperature dependence of elastic stiffnesses up to 1000 K was also measured. The elastic stiffnesses decreased linearly up to near 650 K, and then showed anomalies around 700 K. This was attributed to the damaged interfaces, which were caused by oxidation between the fiber and matrix, and between the fiber core and coating materials surrounding the fiber.View full abstractDownload PDF (837K) -
Shinji Fujimoto, Takeshi Kato, Shigeji Taniguchi, Toshio Shibata2000 Volume 64 Issue 7 Pages 502-507
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe present study aims at clarifying the mechanism by which the oxidation resistance of TiAl intermetallic compound was much improved by a small addition of Zr. TiAl and TiAl-0.2 mass%Zr were oxidised at 1273 K in O2 of 0.013 Pa for up to 28.8 ks. The oxide scales and the layers beneath them were examined for the both specimens by TEM, EDS, AES, SEM and EPMA. The scale formed on the TiAl specimen consists mainly of a continuous α-Al2O3 layer (virtually Al2O3 scale) of varying thickness with a few TiO2 grains on it. An Al depleted layer is formed beneath the scale. With the progress of oxidation of TiAl, TiO2 grains are formed in the Al2O3 scale and grow. This was considered to be the onset of breakaway oxidation. The addition of Zr results in lower oxidation rates with the formation of Al2O3 scales of uniform thickness. Contrary to the TiAl specimen, there was no sign of formation of TiO2 grains in the scales, although a few TiO2 grains formed in the very initial stage remain on the scales. The Al-depleted layer found with the TiAl specimen is very similar to the Z-phase shown in the literature. However, the growth manner of this layer was much changed by the addition of Zr. The length to thickness ratio for TiAl is around unity and decreases gradually with time, while this ratio becomes significantly large for the TiAl-Zr specimen. The addition of Zr modifies the nature of the initially formed Al2O3 layer and the Al-depleted layer.View full abstractDownload PDF (759K) -
Ken’ichi Miura, Itsuo Ishigami, Tomoyuki Mizukoshi2000 Volume 64 Issue 7 Pages 508-517
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSAttempts have been made to clarify the influence of process parameters on oxygen concentration in titanium nitride films. The films were deposited onto substrates of high speed steel, SKH51. Oxygen concentration was determined through the quantitative analysis method proposed before for electron probe microanalysis. Hardness was measured by Vickers hardness indentation at 0.098-0.49N loads. Most of the oxygen should originate from the gasses adsorbed on walls in a chamber. Higher deposition temperatures reduced the oxygen concentration because the walls were baked out on heating the substrate up to a temperature prior to deposition. Extension of depositing time also enhances the baking out, thereby making oxygen concentration decrease in the surface region of the film. The oxygen concentration decreased remarkably by applying a little bias voltage to the substrate; this may suppress the contribution of negative oxygen ions to the reaction. A decrease in nitrogen partial pressure brings about a high oxygen concentration. There was a large amount of oxygen in the film containing α-Ti. It seems that the adsorption energy of oxygen on titanium is higher than that on titanium nitride. An increase in oxygen concentration offered finer grains to TiN films, and hence their hardness increased. Precipitation of α-Ti in the films containing Ti2N causes the hardness to decrease. For single-phase α-Ti, an increase in the nitrogen+oxygen concentration gave rise to a remarkable increase in the hardness.View full abstractDownload PDF (926K) -
Yoshiharu Doi, Hitoshi Akimoto, Kenji Matsuki, Tetsuo Aida, Shouichi O ...2000 Volume 64 Issue 7 Pages 518-526
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSA Ni3Al(γ′) and NiAl(β) two phase nickel aluminide (Ni-33.9 mol%Al-0.1 mol%B) powder material was fabricated from Ni and NiAl raw powders by mechanical alloying (MA) process followed by hot pressing. The effects of process control agents for milling on the suppression of oxidation and microstructure refinement in powders as well as compaction have been investigated.
It was found that hexane as a milling agent was very effective to suppress the oxidation. Especially, a very fine γ′ and β two phase microstructure was obtained by hot pressing after a wet milling process using a large quantity of hexane enough to separate the powders by the organic agent. The average grain size was about 1.2 μm. Oxygen content was as low as about 0.37 mass%. The change of X-ray diffraction patterns with the heating of the wet MA powders indicated that the (γ′+β) two phase microstructure was formed at above 773 K by the reaction between the finely dispersed Ni and NiAl phases in the powders.
Compression tests were carried out for the compacted specimens at temperatures of 1173 and 1273 K at an initial strain rate range from 1.4×10−4 s−1 to 5.6×10−2 s−1. The strain rate sensitivity exponent m was estimated as high as 0.36 to 0.38 at 1173 K and 1273 K, respectively. These results suggest that the compacted specimen can deform superplastically at the strain rate range higher than 10−2 s−1.View full abstractDownload PDF (1458K) -
Kazuyoshi Tatsumi, Teruyasu Mizoguchi, Masato Yoshiya, Isao Tanaka, Hi ...2000 Volume 64 Issue 7 Pages 527-534
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSElectronic structures of 3d transition metal-boron systems are calculated using molecular orbital (MO) theory in order to interpret their B-K ELNES (electron energy loss near edge structure). The ELNES is analyzed from two points. One is the absolute transition energy and the other is the spectrum shape. The former is investigated using the simplest model, i.e. M6B (M=3d transition elements) clusters. The energy shows systematic chemical shifts depending on M elements. The origin of the chemical shift is found to be two-fold : 1) The strength of M-B anti-bonding interactions, and 2) the electronegativity of M. The spectrum shape is discussed for M2B (M=Ti, Fe, Co and Ni) compounds, since their spectra are experimentally available. These spectra show four distinct peaks in common, except for the case of Ti2B. Among the four peaks, electronic origins of the three peaks can be understood by the analogy of the results by the M6B clusters; they are determined by M-B interactions. The other remaining peak originats from B-B interactions. Although the B-B bond-lengths in the M2B compounds are approximately 20% larger than the bond-lengths in pure B, MB and MB2, the B-B interaction affects the spectram shape. This fact can be explained by the spatial delocalization of the wave functions in the unoccupied bands.View full abstractDownload PDF (719K) -
Minoru Tagami, Keizo Kashihara, Tatsuya Okada, Fukuji Inoko2000 Volume 64 Issue 7 Pages 535-542
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESS99.99 mass% ⟨111⟩ and ⟨001⟩ aluminum single crystal specimens were deformed in tension to strains of about 20%. Multiple slipped structures without deformation bands were observed. In the ⟨111⟩ aluminum single crystal deformed at room temperature, short and wavy slip traces are observed because of the difficulty of cross slips which comes from the orientation-dependence. The microstructure shows layered cell structures composed of dense dislocation walls. In ⟨001⟩ aluminum single crystal deformed at liquid nitrogen temperature 77 K, short and wavy slip traces similar to those in the above ⟨111⟩ ones are also observed because of the difficulty of cross slips which comes from the temperature-dependence. The microstructure presents small cell structures with high dislocation density even in the cells as well as along the cell walls. In the above two kinds of deformed aluminum single crystals, the formation of recrystallized grains is very easy. On the other hand, in the ⟨001⟩ aluminum single crystal deformed at room temperature, many cross slips with long-distance steps are observed because each of eight primary slip systems has the corresponding cross (another primary) slip system. The microstructure gives polygonal cells with loose dislocations. After annealing no recrystallized grain forms. The stress values at 20% strains of the stress-strain curves in the ⟨001⟩ (room temperature), ⟨111⟩ (room temperature) and ⟨001⟩ (77 K) aluminum single crystals are 22, 71 and 106 MPa, respectively.View full abstractDownload PDF (1217K) -
Akemi Tsuchiyama, Mamoru Minami, Yasuyuki Takatani, Yasunori Hayashi, ...2000 Volume 64 Issue 7 Pages 543-550
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe electrochemical corrosion tests of DLC films formed on aluminum substrates by ionization deposition method have been performed to evaluate their ability as a protective coating for electronic devices. In addition, the testing results of DLC/Al obtained in this work have been compared with those of SiO2/Al and SiN/Al. The main results obtained in this study are as follows; (1) The electrochemical corrosion behavior of DLC/Al becomes considerably similar to that of SiN/Al and different from that of SiO2/Al. It has excellent anti-corrosion property. (2) Some corrosion pits under the pinhole defects of DLC/Al after potentiodynamic anodic polarization of DLC/Al are linked together. In other words, the morphological character of DLC/Al shows mixed types of SiO2/Al and SiN/Al. (3) According to the above results, the authors have proposed three type of corrosion models about DLC/Al, SiO2/Al and SiN/Al, respectively.View full abstractDownload PDF (902K) -
Osami Seri, Katsunori Satoh, Kazunao Furumata2000 Volume 64 Issue 7 Pages 551-558
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIt is well known that iron and silicon are major elements in an industrial pure aluminum 1100 where they form Al-Fe-Si ternary intermetallic compounds.
The 1100 plate specimen and the ternary cast specimens containing aluminum, silicon and iron are electrochemically investigated in NaCl and AlCl3 solutions.
The SEM surface observation, EPMA analysis and electrochemical measurements reveal that (1) the iron content of the compounds is mainly responsible for the initiation of pitting attack: the higher content of iron in the compounds is, the more easily occurs the initiation of pitting attack, and (2) an appearance of the compound in the bottom of the cavity, whether the iron content of the compound is higher or not, stimulates the further propagation of pitting attacks.View full abstractDownload PDF (932K) -
Yi Tan, Hisao Tanaka, Chaoli Ma, Akio Kasama, Ryohei Tanaka, Yoshinao ...2000 Volume 64 Issue 7 Pages 559-565
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe effect of alloying on the solid solution strengthening and compressive strength of Nb-X (X=Ta, V, Mo and W) binary alloys was studied by Vickers hardness measurements at room temperature and compression tests at high temperature up to 1873 K. The changes of lattice parameter caused by alloying were investigated by X-ray diffractometry. It is found that the solid solution strengthening in the binary alloys primarily depends on atomic size misfit. No apparent solid solution strengthening is observed in Nb-Ta binary alloys up to 1873 K. In V added alloys, the 0.2% flow stress increases with increasing V content below 1600 K, but solid solution strengthening disappears above 1600 K. In Mo or W added alloys, the 0.2% flow stress increases with increasing Mo or W content at temperatures ranging from room temperature to 1873 K. The ductility of Nb-X binary alloys decreases with increasing alloying content, but it is improved by increasing temperature. In the alloys with less than 20 mol%Mo, 10 mol%W and 10 mol%V, large compressive ductility is recognized.View full abstractDownload PDF (592K) -
Yi Tan, Hisao Tanaka, Chaoli Ma, Akio Kasama, Ryohei Tanaka, Yoshinao ...2000 Volume 64 Issue 7 Pages 566-570
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe room- and high-temperature strength of Nb-Mo-W ternary alloys consisting of a bcc solid solution were studied by compression tests up to 1873 K. It is found that the compressive strength increases with Mo and W additions due to solid solution strengthening, and the effect of the strengthening is retained to very higher temperature. On the other hand, the compressive ductility decreases with increasing Mo+W content. Alloys with Mo+W content less than 25 mol% possess both high temperarture compressive strength and large room temperature ductility.View full abstractDownload PDF (468K) -
Yasushi Ikai, Muneki Nagai, Shinichi Shimomura2000 Volume 64 Issue 7 Pages 571-577
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSThe difficulties which are often encountered in using a data base, which deals with continuous variables and objective quantities, are (1) the data is missing where one wants to be refered, (2) the reliability of the data is not clear, and, (3) there may exist some miss-inputed data. In order to resolve these points, an interpolation technique, which gives the smoothest curved surface exactly passing all of given points, is applied to a data base.
An algorithm was shown to obtain a curved surface, to pass a smaller number of “representative points” among the data distributed with scatter. Once this curve is obtained, the difficulties above mentioned can be resolved. The amount of numerical values of a data base may be reduced into several per cent without reducing its information.
Practical applications of this technique to a glass data base INTERGLAD were carried out in three examples such as hardness, crystallization temperature, and refractive index. This technique showed better approximations of data bases than that by statistical linear regressions.View full abstractDownload PDF (478K) -
Min Ho Lee, Hyung Ho Park, Byung Il Kim2000 Volume 64 Issue 7 Pages 578-583
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSIn this investigation, conventional Ti, Ti-6Al-4V specimens with and without surface treatment with alkali-and heat-treatment were used as implanted material in mice. Conventional SUS316L was also used for comparison. The implanted site was in the abdominal connective tissue. The implants were kept there for three months and then their biocompatibility was evaluated by in vitro and in vivo experiments. The main results obtained were as follows:
(1) When evaluated by immersing in Hank’s solution, which has similar ion concentrations to those of human blood, the alkali-treated specimens are much better because an apatite layer is formed, which accelerates the connection with the bone.
(2) The number of macrophage, which is known to increase as the inflammation reaction proceeds, is much less for the alkali-treated specimens than the others.
(3) The average thickness of the fibrous capsule formed around the implant is much thinner for the alkali-treated specimens than the others.
These results show that the surface-treatment performed by the present study is very effective for the improvement of biocompatibility.View full abstractDownload PDF (1068K) -
Hidehiko Kamide, Hitoshi Komagata2000 Volume 64 Issue 7 Pages 584-589
Published: 2000
Released on J-STAGE: April 24, 2008
JOURNAL FREE ACCESSRelationship between crack propagation rate and dissolution rate of type 310 stainless steel was studied to clarify the effect of the lattice defects on crack initiation and crack propagation in H2SO4-NaCl solutions.
Stress corrosion morphology changed in order of general corrosion, localized corrosion, stress corrosion cracking with increasing NaCl concentration. Stress corrosion cracking was observed at the potential range of active region on an anodic polarization curve. Dissolution rates of prestrained specimens were increased with increasing the dislocation density. Optical micrograph showed the formation of corrosion grooves and dissolution rates of these corrosion grooves are close to the crack propagation rates under low initial stress intensity. Transmission electron microscopic observation showed the existence of bundle structure that is high dislocation density region like a plane. As the dissolution rate was accelerated with increasing the dislocation density, this corrosion grooves might be formed by the preferential dissolution of bundle structure.
From these results, it is thought that the crack initiation and the propagation are accelerated with preferential dissolution of bundle structure.View full abstractDownload PDF (627K)
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