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Volume 59, Issue 1
Displaying 1-17 of 17 articles from this issue
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Fuyuki Yoshida, Junji Sugamoto, Hideharu Nakashima, Hideo Yoshinaga1995 Volume 59 Issue 1 Pages 1-7
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the originating mechanism of threshold stress for high temperature deformation of precipitation-strengthened alloys with incoherent dispersoids, the threshold stress was measured by the stress abruptly loading test (SAL test) and the creep test at 673, 623 and 573 K, using an Al-0.7 at%Mn alloy with incoherent Al6Mn precipitates. Further, the possibility of temperature dependence of threshold stress was discussed by estimating the activation energy for dislocations to detach the dispersoids. The main results are as follows.
(1) At all the test temperatures, the threshold stress obtained by the SAL test decreased from the Orowan stress to the void-hardening stress as the time elapsed under load. (2) The relation of Zener-Hollomon parameter Z to the modulus-compensated creep stress in steady state could be expressed by a single master curve irrespective of the test temperature. (3) The calculated energy for a dislocation to detach the dispersoids was very high compared to the thermal energy, predicting that the threshold stress is almost independent of temperature, which agreed with the experimental observations.
From the above results, it is concluded that the originating mechanism of the threshold stress is the Srolovitz’s one, and the temperature dependence of the threshold stress is insignificant.View full abstractDownload PDF (827K) -
Tatsuya Morikawa, Toshihiro Okazaki, Hideharu Nakashima, Hideo Yoshina ...1995 Volume 59 Issue 1 Pages 8-14
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to establish the prediction method of high temperature deformation behavior, a bcc solution-hardened Fe-3.5 at%Mo alloy was deformed in tension at temperatures from 1050 K to 1150 K along three different paths of constant strain rate and continuously varying strain rate, and it was inspected whether or not the prediction method proposed for fcc solution-hardened Al-Mg alloys could be applied to the deformation behavior of the bcc alloy.
It is found that the method can be applied to the bcc alloy with some modification of the parameters used for the prediction, and the limiting conditions of the applicability can be explained by the break away of dislocations from the solute atmosphere in the same way as that for fcc alloys.View full abstractDownload PDF (573K) -
Katsutoshi Yamada, Syouichi Sekiguchi, Keizo Hashimoto, Tsugio Ishida1995 Volume 59 Issue 1 Pages 15-22
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of interfacial strength between the carbon fibers and the aluminium matrix on the bending strength (tensile strength) of the carbon fiber reinforced aluminium alloys (CFRM: PAN based high modulus (CF, Vf=70%) fabricated by pressure infiltration method has been studied. The CFRM with a matrix of Al-7.8%Mg alloy (CF/Al-Mg) having a high bending strength of 1250 MPa and a low compressive strength of 600 MPa shows pull-out fibers on the fracture surface of a bending test specimen under SEM observation, as the CFRM with a matrix of Al-7.1%Si-0.36%Mg alloy (CF/Al-Si-Mg) having a low bending strength of 600 MPa and a high compressive strength of 1000 MPa exhibits a flat fracture surface and high resolution TEM identified Al4C3 precipitates on the interface.
The cracked surfaces of bending specimens with a notch parallel to the fibers were analyzed using Auger Electron Spectroscopy(AES). The depth profile of the content of Al, C, Mg and Si at the aluminium matrix side of the surface revealed that the fractured position near the interface is in the interior of the carbon fiber. The distance of the fractured position from the interface in the case of CF/Al-Mg is comparatively shorter than the case of the CF/Al-Si-Mg. This means the interfacial strength of the CF/Al-Mg is low.
For the CF/Al-Mg, bending stress continues to increase long after the first Acoustic Emission(AE) signal is obtained and fracture of the specimen occurs finally when the stress of the total fibers reached maximum. This shows that the crack initiating from the fractured fiber can not propagate easily through the fiber. Fracture of bending specimen of the CF/Al-Si-Mg occurs very soon after the first AE signal is obtained, thus showing that the crack propagate through the fibers very easily.View full abstractDownload PDF (681K) -
Akira Muto, Shoji Goto, Michihiro Tagami, Setuo Aso1995 Volume 59 Issue 1 Pages 23-30
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSHot deformation and high ductility in fine-grained structures were studied via tensile tests of 70-30 brass specimens with different grain sizes (from 0.009 mm to 0.209 mm) at temperatures up to 803 K and at a strain rate of 6.7×10−4 s−1. The shapes of stress-strain curves were characterized by serrated flow and high temperature yielding phenomena. The shapes of stress-strain curves, yield stresses and tensile stresses strongly depended on initial grain size and temperature. Yield stresses, as well as tensile stresses at intermediate temperatures, increase in the region of finer grain, but decrease in the region of coarser grain with increasing grain size. The values of stress exponent n and activation energy Q in a mechanical equation [\dotε=A·σn·exp(−Q⁄RT)] for fine-grained specimens were 3.9 and 120 kJ/mol, respectively. It is concluded from the above results that hot deformation as well as high ductility of α brass at intermediate temperatures can be controlled by the enhancement of grain boundary sliding and dynamic recrystallization.View full abstractDownload PDF (868K) -
Hirohisa Masuda, Yoshio Ohta, Kenji Morinaga1995 Volume 59 Issue 1 Pages 31-36
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAntimony oxide is known as a network-former of glass. There are, however, few reports on this glass and most of those include some other network-former oxide or intermediate oxide.
In this paper, the determination of the glass forming region and the measurement of X-ray fluorescence spectra and infrared spectra are carried out to clarify the structure of glass in binary antimonate system with alkali and alkaline earth oxide.
Glass is obtained in the Li2O, Na2O, K2O, CaO, SrO, BaO-Sb2O3 system, but not in the MgO-Sb2O3 system and the Sb2O3 single oxide. From the measurement of X-ray fluorescence spectra and infrared spectra, the structure of the antimony complex anion in these glasses is identified as the same structure as stibiotantalite type which consists of tri-valent and penta-valent ions in the same amount.View full abstractDownload PDF (616K) -
Takayuki Narushima, D. Sajuti, Katsuyuki Saeki, Shin-ya Yoshida, Yasut ...1995 Volume 59 Issue 1 Pages 37-43
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe oxygen solubility in liquid gallium or liquid indium equilibrated with solid Ga2O3 or In2O3, respectively, was determined in an alumina crucible which was less reactive than the silica one. After establishment of an equilibrium between the liquid metal (gallium or indium) and an oxide (Ga2O3 or In2O3) formed on the surface of the metal during melting, the oxygen content in quenched gallium or indium was analyzed by the inert gas fusion-IR absorption method. The optimum conditions for oxygen extraction were decided for a furnace power and a bath composition. The temperature dependence of oxygen solubility in liquid gallium or liquid indium was expressed as the following equations:
(This article is not displayable. Please see full text pdf.)
\ oindentUsing the temperature dependence of the oxygen solubility in the present work and the standard free energy of formation of Ga2O3 or In2O3 in the literature, the standard free energy change for oxygen dissolution in liquid gallium or liquid indium could be represented as follows:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (486K) -
Takaaki Hatano, Toshiaki Yano, Masahiro Tsuji, Tsugio Ogura1995 Volume 59 Issue 1 Pages 44-49
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to search for a desulfurizing method for molten copper and copper alloys in the remelting process, oxidizing desulfurization by oxygen gas or oxidizing flux and reducing desulfurization by magnesium or basic fluxes (CaO or BaO, Na2CO3 system) were studied with molten Cu-8%Sn-0.1%P alloy.
In oxidizing desulfurization, a considerable loss in copper, tin and phosphorus took place. Desulfurizing effect by magnesium was small. Desulfurization reaction was not observed in addition of CaO only, while it proceeded by co-operative effects of the addition of CaO sintered with CaF2 and strong stirring. Using CaO-NaCl fluxes desulfurization took place rapidly. In CaO-Na2CO3 fluxes, the degree of desulfurization was determined by the quantity of Na2CO3, and CaO had a suppressing effect of sulfur reversion. BaO-BaF2 fluxes showed the highest ability of desulfurization, and the rate of desulfurization increased with increasing BaF2 content or with stirring. In the treatment by using the basic fluxes, no losses of copper and tin were found, a certain amount of phosphorus, however, was lost after the treatment.View full abstractDownload PDF (661K) -
Hideki Katayama, Kazuto Yagi, Atsushi Nishikata, Tooru Tsuru1995 Volume 59 Issue 1 Pages 50-56
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe AC impedance method has been applied to the study of degradation processes of organic-coated SUS304 stainless steel with a macroscopic line defect. A corrosion test of the coatings was conducted by 0∼7 day exposures to 0.5 kmol/m3 NaCl solutions containing 3 vol%H2O2. The impedance was measured in 0.5 kmol/m3 NaCl solution over the frequency range of 10 mHz to 100 kHz. For the comparison with the impedance results the delaminated area of the coating from the substrate was determined by a delamination test with an adhesive tape after the corrosion test.
The delamination propagates in the direction normal to the macroscopic line defect during the corrosion test and a thin water layer is formed under the delaminated coatings. The equivalent circuit can be constructed by a parallel combination of the circuits for a macroscopic defective part and for delaminated part. The later can be expressed by one dimensional distributed constant circuit. The parameters in the equivalent circuit were determined by the fitting of the theoretically calculated curve to the impedance data. The calculated double layer capacitance well correlates with the actual delaminated area.View full abstractDownload PDF (685K) -
Yutaka Ishiwata, Yoshiyasu Itoh, Takahiro Okuhata, Ryuzo Watanabe1995 Volume 59 Issue 1 Pages 57-64
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSintering behavior and bending strength of the Y2O3 dispersed W composite were investigated, and the sintering mechanism has been discussed. W powders with 10 vol% and 20 vol%Y2O3 were compacted by cold isostatic pressing (CIP), and sintered at 1673-2273 K for 28.8 ks in vacuum (<6.7×10−4 Pa). The relative density of the Y2O3/W compacts were remarkably increased after sintering at 1773 K, and in the relative density over 99% was obtained at 2073 K, which is to be compared with the relative density of 84% for elemental W powder attained under the same sintering condition. This observation shows that Y2O3 addition has remarkable effect to enhance the sintering densification of W powder.
The reaction phase, identified as Y2(WO4)3 by X-ray diffraction, was observed between W grains in the Y2O3/W compacts. The melting point of Y2(WO4)3, 1713 K, is almost equal to the sintering temperature at which densification enhancement was observed. Thus, the sintering mechanism of the Y2O3/W composite is considered to be a liquid phase sintering with Y2(WO4)3 liquid.
From AES (Auger electron spectroscopy) analyses, an appreciable amount of phoshorus (P) was detected at the interface between W matrix and Y2O3 particle in the Y2O3/W compact. It is reported that the melting point of YP5O14, which is formed by the reaction between Y2O3 and P2O5, is 1130 K. It may be considered that Y2(WO4)3 is formed through the reaction with the YP5O14 glassy phase during sintering.
The bending strength of the Y2O3/W composite is 680 MPa at 973 K and 510 MPa at 1573 K, which are about three and five times higher than those of pure W, respectively.View full abstractDownload PDF (1141K) -
Katsuo Saitou, Mitsushige Nakayama, Jyuzo Shibata1995 Volume 59 Issue 1 Pages 65-70
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNickel ultrafine particles were produced using the Ar-H2 arc plasma method under constant electric power. The factors which affect the ultrafine particle generation process were chosen as the hydrogen content in a mixed gas and the electrode angle. The generation rate of ultrafine particles depends on the electrode angle. The mean diameter of ultrafine particles converted from a specific surface area increases with increasing hydrogen content and electrode angle. In order to explain these phenomena, a new idea was proposed on the basis of a mass transport in the arc plasma.View full abstractDownload PDF (376K) -
Yoshiharu Waku, Narihito Nakagawa, Hideki Ohtsubo, Yasumasa Ohsora, Ya ...1995 Volume 59 Issue 1 Pages 71-78
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to develop stable composite materials in air atmosphere above 1673 K, fabrication of unidirectional solidification of Al2O3/Y2O3 mixed powders (82/18 mol ratio) was carried out in 10−5 mmHg vacuum at the 5 mm/h down speed using advanced alloy crystalline structure controlling equipments at Japan Ultra-high Temperature Materials Research Center. The microstructures of the unidirectional solidified eutectic composites were composed of single crystal (110) Al2O3 and single crystal (420) YAG containing no colony and porosity. No temperature dependence of flexural strength of the composites from room temperature to 1973 K was observed and the flexural strength is 360∼500 MPa. It is found that the composites have superior creep resistance at 1873∼1973 K, oxidation-resistance and thermal stability at 1973 K for 50 h in air atmosphere.View full abstractDownload PDF (1887K) -
Masaaki Naka, Jicai Feng1995 Volume 59 Issue 1 Pages 79-83
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPressureless-sintered (PLS) SiC was joined to Nb by solid state bonding at 1790 K for 0.6∼144 ks and 7.26 MPa in vacuum. Interfacial reaction layers and microstructures were investigated by an electron probe microanalyser and X-ray diffractometry. The hexagonal Nb2C phase in the Nb side and the mixture of hexagonal Nb5Si3C and tetragonal Nb5Si3 phases in the interface of Nb2C and SiC were formed at 1790 K for 0.6∼7.2 ks. With increasing joining time, the Nb2C containing small amounts of NbC changed to NbC. At the long joining time of 72 ks, the hexagonal NbSi2 phase appeared at the interface between NbC adjacent to SiC and Nb5Si3C. The fracture shear strength of SiC/Nb/SiC couples showed the maximum of 187 MPa at room temperature, where a uniform thin layer of NbC at the interface adjacent SiC at 1790 K for 36 ks was formed. The couples exhibited the stable strength at temperatures up to 973 K.View full abstractDownload PDF (879K) -
Masahiro Fukumoto, Hiroaki Murakami, Isao Okane, Hiroshi Harada1995 Volume 59 Issue 1 Pages 84-88
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe ring shear test was modified to evaluate the adhesion properties of plasma sprayed coatings. To ensure the ring shear test to be reliable, the conditions of some main factors, such as coating thickness, coating width and rod-jig clearance, for the evaluation of the adhesion strength were evaluated.
The results obtained in this research are summarized as follows:
1) In order to develop the accuracy of the loading exactly along the specimen’s axial direction, the loading stress uniformity on the coating and the uniformity of the clearance between rod and jig, the conventional ring shear test was modified in shapes of both the shearing jig and the specimen and the loading manner. Consequently, the reproducible results with less scattering were obtained by using the modified ring shear test.
2) To ensure this modified ring shear test as the method to evaluate the adhesion strength of plasma sprayed coating, the necessary conditions of some main factors were evaluated. It was found that coating width, coating thickness and rod-jig clearance should be fixed to some moderate values.View full abstractDownload PDF (658K) -
Tetsuo Yano, Toshihiko Ooie, Masafumi Yoneda, Munehide Katsumura1995 Volume 59 Issue 1 Pages 89-93
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLow temperature bonding of a Cu specimen on a Si3N4 plate was examined. Si3N4 plates were irradiated with KrF excimer laser beam in vacuum. The energy density of laser was 0.3 J/mm2. At the laser irradiation area Si3N4 was decomposed into Si and N2 and then thin Si layer was formed on Si3N4. XPS analysis revealed that the thickness of the thin Si layer was 0.04 μm. An Ar ion sputtered Cu specimen was pressed on a Si3N4 plate through thin Si layer at temperatures of 560∼630 K for 3.6 ks in vacuum. The bonding strength was 100-200 MPa and the Si layer was essential for low temperature bonding of Cu and Si3N4.View full abstractDownload PDF (1216K) -
Hiroyuki Toda, Toshiro Kobayashi, Yoshiharu Wada1995 Volume 59 Issue 1 Pages 94-102
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA simulation program based on the fracture mechanics was constructed to evaluate crack initiation and growth characteristics in discontinuously-reinforced MMCs.
Spatial patterns of reinforcement are quantified by using one of the three statistical probability functions. Reinforcement strength is assumed to vary according to the three-parameter Weibull distribution function. The crack-tip stress field is computed by HRR singularity for both stationary cracks and growing cracks. It was identified by preliminary in-situ CODs measurement. The results of FEM analysis are used for computing the extent of stress concentration around the reinforcement in the HRR field, and adequate criteria for microcrack initiation are defined. Shielding effects and crack deflection are taken into consideration. Finally, the strain energy density factor is used as a criterion for crack initiation and growth.
Microcrack formation ahead of a major crack-tip and crack deflection towards the microcracks, which has been often observed in-situ in the discontinuously-reinforced MMCs, are well simulated by the numerical calculation. Parametric studies were carried out to evaluate crack initiation and growth through an Al alloy composite reinforced with SiC whiskers.View full abstractDownload PDF (1177K) -
Yukiko Itou, Yasuji Fukui, Takashi Kitayama, Yoshiro Iwama, Takao Koba ...1995 Volume 59 Issue 1 Pages 103-107
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMicrostructures and magnetic properties of the Nd-Fe-B magnets sintered by adding Dy compound powder are examined. The Nd15Fe77B8 powders are mixed with Dy40Al30Cu30 compound powders and then sintered, followed by an appropriate heat treatment. It is found by EPMA analysis that the R2Fe14B main phase is composed of a Dy-poor core region surrounded with a Dy-rich shell region. As a result, the coercivity is increased and the value is higher than that of the magnet sintered by conventional process, in which there is a homogeneous distribution of Dy. The effect is enhanced by thinning the Dy-rich region by controlling the diameter of magnet powder of Nd15Fe77B8, as well as the sintering time.View full abstractDownload PDF (830K) -
Yoshimitsu Okazaki, Yoshimasa Ito, Tetsuya Tateishi, tsuo AIto1995 Volume 59 Issue 1 Pages 108-115
Published: 1995
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTi-15 mass%Zr-4%Nb-4%Ta-0.2%Pd and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd alloys not containing harmful V and Al for surgical implantation in response to recent concerns about the long term safety of Ti-6%Al-4%V ELI (Extra low interstitial, ASTM specified for surgical implantation) were cast by plasma electron beam melting. The effect of heat treating on room temperature strength was investigated by aging treatment after solution treatment. The alloys were forged in their α and α+β regions, and then solution-treated at 953∼1173 K for 3.6 ks. Vickers hardness in the range below β transition temperature increases with increasing solution treating temperature and change of Vickers hardness in the range over its temperature is small. Optimized solution treatment conditions are 1038 K-3.6 ks for Ti-Zr alloy and 1098 K-3.6 ks for Ti-Sn alloy containing 15∼20 vol% primary α phase. After solution treatment under the optimized condition aging treatment was done at 623∼873 K for 600 s∼36 ks. Vickers hardness in aging below 723 K increases with increasing aging temperature and aging time. Optimized aging conditions for Ti-Zr and Ti-Sn alloys were at 673 K for 36 ks and at 723 K for 36 ks, respectively. The room temperature strengths of those alloys are superior to those of Ti-6%Al-4%V ELI for medical implants. It is revealed by transmission electron macroscopic observation that fine α phase precipitates in the α′ martensitic matrix are responsible for the age hardening.View full abstractDownload PDF (1693K)
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