All issues
Volume 60, Issue 5
Displaying 1-14 of 14 articles from this issue
- |<
- <
- 1
- >
- >|
-
Koichi Kitazono, Eiichi Sato, Kazuhiko Kuribayashi1996 Volume 60 Issue 5 Pages 441-445
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMaterials containing second phases show superplastic behavior during thermal cycling (internal stress superplasticity). The authors recently proposed a quantitative model using continuum micromechanics theory for the superplastic behavior. In the present study, this theoretical model has been verified by compression creep tests under thermal cycling conditions using a Be particle dispersed Al matrix alloy as an ideal material. The thermal cycling creep rates were much higher than the isothermal creep rates and proportional to the applied stress at low stresses. However they approached the isothermal creep rates at high stresses. This behavior agrees well with a theoretical prediction, and the value of the thermal cycling creep rate at low stresses coincides with the theoretical one. Therefore it was concluded that the internal stress superplasticity model was applicable to particle dispersed metal matrix composites.View full abstractDownload PDF (714K) -
Kensuke Kuroda, Kazuhiko Matsuyama, Koji Kato, Toshiharu Fujisawa, Chi ...1996 Volume 60 Issue 5 Pages 446-451
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of the solute precipitation or the compound precipitation of solute with solvent on the solid state electransport (SSE) was examined by using the Fe-C system from the viewpoint of the purification of metallic materials.
The experiments were carried out under the conditions of the initial carbon concentration=1.3 and 2.1 mass% and the temperature=1223 and 1273 K.
Carbon transported toward the cathode end of the Fe-C alloy specimen by SSE-treatment. When the carbon content reached the saturation content at the cathode end, carbon precipitated there as a graphite. The concentration profile of carbon was fastened to the saturation content at the cathode end. In a short time treatment, a less purification degree was achieved compared with the hypothetical calculation without precipitation. In a longer time treatment, on the other hand, a higher purification degree was achieved by the precipitation.
Even when the specimen with cementite (Fe3C) precipitates was treated, SSE phenomena was observed. The cementite particles near the anode end disappeared and accumulated near the cathode end. In this case, graphite was also precipitated at the cathode end.View full abstractDownload PDF (756K) -
Kazuo Kameda, Katsunori Yamaguchi, Toshiyuki Gomi1996 Volume 60 Issue 5 Pages 452-456
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe activities of indium in liquid In-Bi-Ag and In-Bi-Te alloys have been determined by the emf measurement using zirconia electrolyte at 896∼1297 K and 816∼1111 K for 15 and 18 compositions of the alloys, respectively. Combining the binary data of In-Bi and In-Ag alloys in In-Bi-Ag system, In-Bi and In-Te alloys in In-Bi-Te system for this study, isoactivity curves at 1100 K and 1200 K. 900 K and 1000 K were obtained in the whole composition range, respectively. There seem no published data to be compared with.View full abstractDownload PDF (575K) -
Hideshi Sumiyoshi, Yuji Ikeda1996 Volume 60 Issue 5 Pages 457-462
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe high temperature oxidation mechanism of Fe-20Cr alloys with various amounts of Y2O3 dispersion was investigated by means of optical reflectance measurement together with conventional methods. Mechanically alloyed samples were cyclically oxidized at 1100 K in O2 for up to 82 cycles. The surface reflectance of oxidized samples decreased with decreasing Y2O3 content. The variation in the reflectance was much more sensitive than the mass change. The reflectance method will be useful for the study of initial oxidation. Dispersed Y2O3 is considered to retard the diffusion of alloying elements into the oxide film. The inhomogeneous distribution of Y2O3 and its insufficient dispersion generated numerous oxide nodules.View full abstractDownload PDF (674K) -
Shin Ishikawa, Masa-aki Kohno, Chizuko Maeda, Kazuhide Ishii, Jun-ichi ...1996 Volume 60 Issue 5 Pages 463-468
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAl2O3 scales formed on Fe-20Cr-5Al alloys by oxidation at 1473 K for 72 ks in air atomosphere were investigated by a transmission electron microscope (TEM) equipped with a field emission gun and an energy-dispersive X-ray spectrometer (EDX).
Segregation of La to the grain boundaries in Al2O3 scales was observed in the alloys containing 0.064 or 0.11 mass%La, while that of La and Zr to those was also found in the alloy containing 0.077 mass%La and 0.083 mass%Zr. In the latter, the concentration of Zr was higher than that of La. Cross-sectional TEM analysis showed that La segregated at the columner grain boundaries near the scale/alloy interface in higher concentration than at the equiaxed ones near the surface of the scale.
It is supposed that the segregation of La and Zr to the grain boundaries in the scale suppresses the diffusion of oxygen via grain boundaries and decreases the oxidation rate of the alloy.View full abstractDownload PDF (1412K) -
Seiichi Iwata, Naoki Yamamoto, Fumiko Yano1996 Volume 60 Issue 5 Pages 469-475
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSince very small amounts of defects or impurities influence Si MOS (Metal-Oxide-Semiconductor) device characteristics, it is usually difficult to detect them in the SiO2/Si structures used for these devices by ordinary surface characterization. We therefore tried to resolve this problem with a different approach. In an effort to detect electron and hole traps in SiO2/Si samples, the electric current that flows from the sample to the ground was measured as a function of the X-ray irradiation time during ESCA (Electron Spectroscopy for Chemical Analysis) measurements. The transient of this current was found to be due to electric charges supplied to the Si side of the SiO2/Si interface. The number of these charges increases as the electric charges of the opposite sign become trapped at oxide traps in the SiO2. This transient was found to be the sum of the exponential functions of the X-ray irradiation time with different time constants. Various types of traps can be distinguished by these time constants and the sign of the current. Our first experiment showed that traps whose concentration is of the order of 1014 m−2 can be detected by this method, whereas they cannot be easily detected with such sensitivity in an ESCA spectra because the ESCA detection limit is of the order of 1016 m−2. This new method was used to compare two different kinds of thermally oxidized silicon, namely, that oxidized in O2/N2 and that oxidized in pyrogenic steam. The present method is expected to be useful in the process development of MOS devices using ultra-thin SiO2 films.View full abstractDownload PDF (911K) -
Hidetoshi Saitoh, Jun Satoh, Takashi Ishiguro, Kiichiro Kamata, Yukio ...1996 Volume 60 Issue 5 Pages 476-481
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBoron nitride deposits were prepared on Si substrates using a glow discharged plasma chemical vapor deposition apparatus with a gas mixture of BCl3-N2-H2-Ar and characterized using some evaluation techniques for their morphology, atomic composition, crystal structure and mechanical properties. The deposition apparatus used in this study is equipped with an rf plasma source for Ar-N2 gas mixture excitation, and a heater for decomposition of BCl3. This films were deposited on the substrate at the conditions of a total gas pressure of 266 Pa and an rf power of 100 W for the plasma operation. The dendritic aggregation of hexagonal BN (h-BN) and amorphous boron-rich boron nitride film were contained in the deposits. The dendritic aggregation of h-BN had a size of approximately 10 μm and grew along the scrached mark. In addition, the boron-rich amorphous film had a thickness of 3 μm as a result of 1.8 ks-deposition. A substrate temperature of ≥673 K and a negative bias voltage applied to the substrate of ≥350 V are required in obtaining high deposition rate of amorphous films. The surface of amorphous films indicated a Knoop hardness of Hk6000-8000 at a loading force of 98 mN. Furthermore, the scratching test revealed that the critical load of the amorphous films was larger than that of diamond-like carbon films prepared on the Si substrate. These results suggest that the amorphous boron nitride film obtained in this work is one of the candidates for hard coating material.View full abstractDownload PDF (1412K) -
Makoto Yoshida, Takao Tsujimura, Toru Tsukagoshi, Hideo Nakae1996 Volume 60 Issue 5 Pages 482-489
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of rod to lamella transition with increasing growth rate was studied. The relationship between γ phase ⟨100⟩ direction and the α-phase microstructure was examined using the back-reflection Laue method. The influence of growth rate on the transition was also estimated by increasing the rate in the middle of directional solidification. The experimental results revealed that both the growth rate and the deviation of γ⟨100⟩ from the growth direction amplified the aspect ratio of the transverse α-phase microstructure. A mechanism of the transition was proposed and summed up as follows.
At first, we assume that the following two control factors exist for the decision of the microstructure:
(1) tendency to organize low energy habit planes.
(2) eutectic second phase tends to grow perpendicular to the S/L interface (parallel to the growth direction).
If no confliction between the two tendencies occurs at the S/L interface, a rod structure will be formed. However, when the derivation of γ⟨100⟩ from the growth direction exists, the rod structure will induce the confliction between the two tendencies proportional to the growth rate. In such a case, in order to avoid the confliction, the lamella structure will become metastable with an increase in α⁄γ interfacial energy and undercooling.View full abstractDownload PDF (1625K) -
Tatsuya Ohmi, Yoshiaki Kimura, Youichi Itoh, Masayuki Kudoh, Kiyotaka ...1996 Volume 60 Issue 5 Pages 490-496
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA novel process named Centrifugal Duplex Casting has been proposed: it is a manufacturing process of aluminum cast pipes with in-situ composite layer which contains fine intermetallic compounds. In this process, two kinds of molten metals, i. e. molten aluminum (first melt) and molten Al-Cr alloy with higher liquidus temperature (second melt), are cast in sequence at a given interval in a rotating mold. The second melt collides with the meniscus of the spinning first melt, and is dispersed as fine fluid clumps. These fluid clumps are rapidly quenched, migrate toward the outer periphery, and accumulate to form the composite layer. The intermetallic compounds in this composite layer are much smaller in particle size than the Al-Cr alloy centrifugally cast by the conventional process. The solidification structure of the cast pipe produced by Centrifugal Duplex Casting is controlled by cooling capacity of the first melt. For instance, when the first melt has superheat at the time of the pouring of the second melt, coarse intermetallic particles grow inside of the refined composite layer. On the other hand, when the first melt has partially been solidified, the growth of the particles is suppressed. Therefore, the time interval from first to second pouring is an important parameter in this process.View full abstractDownload PDF (2260K) -
Katsumi Miyama, Masaya Ito, Toshio Narita1996 Volume 60 Issue 5 Pages 497-503
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSilicon nitride ceramics were brazed to nickel sheet by active brazing with nickel-copper-titanium solder under various heating rates. Properties of the reacted products were analyzed by using a scaning electron microscope, an electron probe microanalyzer, an X-ray diffraction meter, and a transmission electron microscope. Joining strength was measured by the 4-point bending test. Joining strength was improved with increasing heating rate. While fracture occured at the whole interface between ceramic and metal, fracture partially propagated into the ceramic in the case of the highest heating rate. The fracture occurred in the reacted products formed at the interface between silicon nitride and the nickel-copper-titanium solder. As a result of electron probe microanalysis of the reacted products on the metal-side fracture surface, silicon was detected with aluminium and oxygen, which serve as the sintering aid of silicon nitride. The silicon intensity of the reacted products increased with increasing joining strength. However, as a result of X-ray diffraction, titanium nitride in the form of a crystalline phase was detected, but no silicon compounds were detected. These results suggest that silicon in the reacted products exists as the amorphous phase with aluminium-oxide in the grain boundary of silicon nitride.
It is considered that the titanium nitride and the silicon-aluminium oxide amorphous phase are both formed as the reacted products between silicon nitride and nikel-copper-titanium solder, and the silicon-aluminium oxide amorphous phase substantially controls joining strength.View full abstractDownload PDF (1239K) -
Takeshi Mohri, Makoto Kobashi, Naoyuki Kanetake, Takao Choh1996 Volume 60 Issue 5 Pages 504-511
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTaCp/Al alloy composites were fabricated by the melt stirring method. The composites can be fabricated up to 40 vol% reinforcement and can be cast up to 30 vol%. Very few reaction products between TaCp and the matrix alloy can be detected by scanning electron microscopy. The tensile strength, 0.2% proof stress and Young’s modulus of TaCp/pure Al composites increase and the uniform elongation decreases with increasing volume fraction. The strength of TaCp/Al-3 mass%Mg composites increases up to 20 vol% reinforcement but decreases with more than 20 vol% because they have some pores. The theoretical calculation based on the Eshelby’s inclusion model can explain the feature of strain hardening of experimental stress-strain curves, but the calculated stress values are much lower than the experimental ones. To improve the theoretical prediction of stress-strain curves of composites, the calculation model was modified by taking into account the effects of the residual stress caused by mismatch in coefficients of thermal expansion (CTE) and the change of matrix properties caused by grain refining into the yield stress of matrix alloy in composites. The modified calculation can fairly explain the experimental stress-strain curves, though these effects on the matrix yield stress are different with respect to the particle volume fraction. The predicted stress values are higher than the experimental ones in the composites with small volume fractions and are lower in the composites with high volume fractions.View full abstractDownload PDF (1384K) -
Katsutoshi Takagi, Takashi Ohnishi, Kazuo Yoshikawa1996 Volume 60 Issue 5 Pages 512-518
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of Si content on resistivity were investigated in sputtered Al-Ta-Si alloy films. Al-2.3 mol%Ta-x mol%Si (x=0.8-3.6) and Al-2.3 mol%Ta alloy films with 1.0 μm thickness were deposited on glass substrates by DC magnetron sputtering using mosaic Al-Ta-Si and vacuum-melted Al-Ta alloy targets. The resistivity of the films which were as-deposited or annealed at 523-673 K for 1.8-25.2 ks was measured by the four-point probe method, after the films were patterned into 100-μm-wide and 10-mm-long lines. Moreover, their structure was examined by transmission electron microscopy, electron diffractometry and X-ray diffractometry. The resistivity of as-deposited Al-Ta-Si alloy films increases in proportion to the Si content, because conduction electrons are scattered by the Si dissolved in the Al matrix. The resistivity of Al-Ta-Si alloy films, however, decreases by annealing at temperatures over 523 K for more than 1.8 ks, and is lower than that of Al-Ta alloy films after the annealing. The decrease in resistivity is due to the precipitation of the Si and Ta into TaSi2, which are dissolved in the Al matrix and cause an increase in resistivity after the deposition. The resistivity of Al-Ta-Si alloy films also depends on a decrease in resistivity due to the precipitation of TaSi2 and an increase in resistivity due to the scattering of conduction electrons by TaSi2, and can therefore be minimized by optimizing the Si content and annealing at temperatures over 523 K for more than 1.8 ks. These results can be applied to decrease the resistivity of Al-Ta alloy films for the interconnections of liquid crystal displays.View full abstractDownload PDF (1973K) -
Fumiyoshi Kirino, Shigekazu Otomo, Nagatsugu Koiso, Fumiko Yano1996 Volume 60 Issue 5 Pages 519-528
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe crystallization mechanisms of Fe-Ta-C alloy films added Nb and Cr were studied in terms of changes in the crystal structure and magnetic properties. The Fe-Ta-C thin films as prepared by sputtering have an amorphous like X-ray diffraction profile. However, microcrystals of TaC of about 5 nm size were observed by TEM. Through DSC measurement, the crystallization temperature of the Fe alloy film was determined to be 753 K. However, the diffraction peak of α-Fe started to appear at 713 K, and the complete crystallization of the film occurred at 753 K. The sturation induction Bs of a Fe-Ta-C thin film before annealing was 0.76 T. The α-Fe grain size of the Fe-Ta-C thin film after annealing was 5 to 12 nm. The coercive force was 720 A/m befor annealing at 823 K for 1800 s. After annealing this film at 823 K for 3600 s, the coercive force was 32 A/m, but in the magnetic film, a component with higher coercive force was formed. To control the Fe grain size, Cr which dissolves into α-Fe was added. To control the grain size of TaC, Nb which reacts to the carbon was added. When Nb and Cr were added to Fe-Ta-C, no microcrystal such as TaC was observed under TEM in the as deposited film, indicating that the film is in an amorphous state. The DSC measurements of the Cr- and Nb-doped films showed that the crystallization temperature is 787 K, higher than that in Fe-Ta-C films. The complete crystallization of Cr- and Nb-doped Fe-Ta-C alloy thin films occurred at the same temperature. The magnetic properties also changed at 787 K. The Bs value of the as-deposited Fe-Ta-Cr-Nb-C film was 0.1 T. This is smaller than that of the Fe-Ta-C thin film.
This is consistent with the TEM observation of the as-deposited film. The coercivity Hc was 16 A/m, which is smaller than 32 A/m of the Fe-Ta-C thin film. High coercive force component as was seen in the Fe-Ta-C was not formed in the Fe-Ta-Nb-Cr-C film. Controlling the crystallization by adding elements such as Cr and Nb, we significantly improved the soft magnetic properties of Fe-Ta-C films.View full abstractDownload PDF (1671K) -
Shigekazu Otomo1996 Volume 60 Issue 5 Pages 529-536
Published: 1996
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe dependence of induced anisotropy on the composition of Co-TM-Zr(TM=Nb, Ta, Mo, W, and Ni) amorphous sputtered films is investigated. The anisotropy field, Hk of the amorphous films increases with increasing the saturation magnetic flux density, Bs. The anisotropy field, Hk is the largest in Co-Ni-Zr films and the strength of Hk decreases in the order of Co-Ta-Zr, Co-W-Zr, Co-Mo-Zr and Co-Nb-Zr films, when Hk is compared among the films with the same Bs. The composition dependence of induced anisotropy in Co-TM-Zr films can be understood by the pair-ordering model assuming that a pseudodipole interaction between a cobalt atom pair depends on the magnetic moment of the Cobalt atom. The relaxation time of anisotropy changes in Co-Nb-Zr and Co-W-Zr films increases by 2 to 3 orders of magnitude by pre-annealing at 400°C, and the activation energy of 3.2 to 3.4×10−19 J(2.0 to 2.1 eV), being one of the highest activation energies for the amorphous alloys, is determined by the analysis based on a Gaussian distribution for the relaxation time.View full abstractDownload PDF (871K)
- |<
- <
- 1
- >
- >|