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Volume 51, Issue 8
Displaying 1-14 of 14 articles from this issue
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Tomoshi Takahashi, Michitomo Katoh, Yoritoshi Minamino, Toshimi Yamane1987 Volume 51 Issue 8 Pages 701-709
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInterdiffusion experiments of Cu-rich α Cu-Ni-Mn alloys have been performed in a temperature range from 1023 to 1133 K. The concentration profiles indicate that the diffusion distance of Mn is longer than that of Ni in these solid solutions. The interdiffusion fluxes evaluated from the equations of Dayananda and Kim show that the zero-flux planes exist in the diffusion zones of the Cu-Ni-Mn couples, The influence of the indirect fluxes becornes larger with the increase in Ni or Mn concentration. The diffusion paths show S-shaped curves. The direct coefficients \ ildeDMnMnCu and \ ildeDNiNiCu are positive, and the indirect coefficients \ ildeDMnNiCu and \ ildeDNiMnCu are negative. The four interdiffusion coefficients are very sensitive to the Ni and Mn concentrations, The temperature dependence of \ ildeDMnMnCu, \ ildeDMnNiCu, \ ildeDNiNiCu and \ ildeDNiMnCu at the concentration of Cu-16.2 at%Ni-15.2 at%Mn can be expressed by the following equations:
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\ oindentThe frequency factor D0 Mn(Cu-Ni)∗ and the activation energy QMn(Cu-Ni)∗ for impurity diffusion of Mn in the Cu-Ni alloys are given by
(This article is not displayable. Please see full text pdf.)
\ oindentwhere K0 and K1 are constants, Tm and Tm Cu are the melting points of the Cu-Ni alloys or the pure Cu, respectively, XNi is the atomic percentage of Ni, and D0 Mn(Cu)∗ and QMn(Cu)∗ are diffusion characteristics of Mn in Cu. From the estimated values of interaction parmeters, it is considered that the interaction energy of Ni-Mn bonds is much larger than those of the Cu-Ni and Cu-Mn bonds.View full abstractDownload PDF (1120K) -
Hajime Suto, Taketo Sakuma, Noboru Yoshikawa, Yoshikatsu Higuchi1987 Volume 51 Issue 8 Pages 710-714
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUsing specimens prepared by arc-melting and by sintering, anti-phase boundaries (APB’s) in yttria partially stabilized zirconia were observed by means of transmission electron microscopy. Results obtained are as follows: (1) APB’s are introduced in tetragonal phase during cubic-tetragonal displacive transformation on cooling. (2) Inter-APB’s distance decreases with Y2O3 content, but in the range of 5 to 7 mol%Y2O3, it is kept at a constant value of about 0.05 μm. (3) In an 8 mol%Y2O3 specimen, APB’s cannot be observed. (4) When a quenched tetragonal specimen is annealed, APB’s density decreases and APB’s becomes flattened lying on {111} planes.View full abstractDownload PDF (2766K) -
Keijiro Hiraga, Keisuke Ishikawa1987 Volume 51 Issue 8 Pages 715-722
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of austenitic phase (γ) stability on the low temperature tensile and Charpy impact properties of γ′-strengthened iron-based alloys have been investigated by using transmission electron microscopy and magnetic techniques. The mechanical tests at 4, 77 and 300 K were conducted on a series of Fe-(16-28.5)Ni-(14, 16)Cr-2.4Ti-(1.5, 2)Mo (mass%) alloys after aging at 973 K for 172.8 ks which yieled the same hardness level of 320-330 Hv.
The (18.5-21)%Ni alloys showed an enhancement in ductility at 4 and 77 K due to transformation-induced plasticity (TRIP), while the yield and tensile strengths and Charpy absorbed energy were almost independent of the γ-phase stability of the alloys. The tensile deformation characteristics at 4 K of the metastable alloys have been discussed on the basis of the morphology of the α′ phase as follows:
(1) Fine lath-like α′ formed at the intersections of microscopic {111}γ shear bands. The formation of the α′ is accompanied by a decrease in work-hardening rate at an eary stage of deformation and continues to near necking point for the alloys that cause the TRIP.
(2) Blocky or large lath-like α′ which grow from the fine α′ at a later stage of deformation where the amount of α′ phase exceeds about 4 mass%. This phase is hardener for the suppression of necking but acts as a site for stress concentration in subsequent straining.View full abstractDownload PDF (1955K) -
Toshiro Kobayashi, Kenji Matsunuma, Hideki Ikawa, Kenya Motoyoshi1987 Volume 51 Issue 8 Pages 723-729
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAlthough there are many researches on static fracture toughness tests of ceramics in the literature, the testing method has not yet been standardized. On the other hand, only a few reports dealt with dynamic fracture toughness tests of ceramics have been observed. Moreover, it becomes a problem that conventional methods of static fracture toughness testing have been applied mainly to specimens without precracking. Therefore, the values of static fracture toughness obtained by the methods are lacking in reliability. Moreower, it is very difficult to measure the real fracture load in the dynamic fracture toughness test because of a remarkable inertial loading effect.
In the present study, static fracture toughness of ceramics was measured by a three-point bending test using precracked specimens. The results were compared with those obtained by the conventional methods. Moreover, the dynamic fracture toughness of ceramics was measured by the impact response curve method using a strain gage attached to the specimen in the instrumented Charpy impact test.
As a result, it has been shown that the static fracture toughness test using precracked specimens can evaluate the lower limits of static fracture toughness in contrast with the conventional methods. Dynamic fracture toughness Kd in partially stabilized zirconia has been observed to increase monotonously with loading rate \dotK, while Kd in Si3N4 decreases at first and then increases with increase of \dotK. This phenomenon suggests the existence of a minimum Kd value in ceramics. It has also been made clear that a rather good correlation exists between Kd and the total absorbed energy Et of the unnotched impact test specimen when the latter value is corrected by the fracture unit distance.View full abstractDownload PDF (1054K) -
Akira Nozue, Dai Ikegaya, Tadatsune Okubo1987 Volume 51 Issue 8 Pages 730-736
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA better understanding is required to identify the effects of the Ti-6Al-4V alloy structure on hydrogen embrittlement behavior. Microstructural factors appear to be the volume ratio of primary alpha phase to the matrix phase consisting of retained beta and martensite, the structures of the matrix phase, the configuration of the matrix phase, and the primary alpha grain size. The purpose of the present study is to clarify the effects of these structures on the hydrogen embrittlement behavior.
Compact tension specimens were cathodically charged in a 50 mol/m3 H2SO4 solution under the condition of a current density of 2 kA/m2 during sustained loading. No aging treatment was carried out to simplify the structures. The time to a given crack growth length was evaluated as the susceptibility to the hydrogen embrittlement on stage II in the relation between crack growth rate and stress intensity factor, by eliminating the region of unstable crack growth and initial crack growth.
The susceptibility to the hydrogen embrittlement of the present alloy is found to be enhanced by the increase in the volume ratio of the primary alpha phase to the matrix phase, the continuity of the beta phase, and the multiplication of the primary alpha grain size.View full abstractDownload PDF (2443K) -
Yoshitaka Tamou, Toyonobu Yoshida, Kazuo Akashi1987 Volume 51 Issue 8 Pages 737-742
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSUltrafine silicon carbide powder was synthesized from SiCl4 and CH4 through thermal plasma CVD using a “hybrid plasma”, characterized by the superimposition of a DC arc jet on a radio-frequency plasma. For a better understanding of the process, thermodynamic equilibrium compositions for the Ar-H-C-Si-Cl system were calculated up to 6000 K.
The reactants of SiCl4 and CH4 mixed with H2 were injected into an arc jet and a tail flame of the hybrid plasma through a narrow ring-slit, respectively. By this method, the productive reaction zone of SiC is very limited to the space at the slit level, leading to a homogeneous reaction history of each particle. The ratio of [C]/[Si] in the product depended upon the molar ratio of [CH4]/[SiCl4] and the total flow rate of H2 used as a quenching gas. Under appropriate conditions, nearly stoichiometric whitish gray β-SiC powder about 30 nm in size was obtained. Moreover, it was found that the particle size could be controlled by regulating the quenching process.
According to equilibrium calculations, SiCl4 is completely dissociated in the plasma, and the main reaction for the formation of β-SiC is believed to be the reaction: Si(g)+CHx. Moreover, there was no possibility for the condensed phase except β-SiC to appear during the cooling process from the plasma. Accordingly, the synthesis of very pure SiC powder would not be so difficult if complete reaction occurred in the plasma tail flame. These thermodynamic considerations were consistent with the experimental results.View full abstractDownload PDF (1135K) -
Junji Shibata, Hiroshi Sawai, Makoto Sano, Sanji Nishimura1987 Volume 51 Issue 8 Pages 743-748
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExtraction of Cu, Ni, Co(II) and Co(III) from ammoniacal solution was carried out by using Versatic Acid 10, D2EHPA, PC-88A, LIX64N, SME529 and KELEX100 as extractants, in order to investigate the difference in extraction suppresion by the extractants used.
When the acidic extractants such as Versatic Acid 10, D2EHPA and PC-88A were applied to the extraction from the aqueous solution containing ammonia at high concentration, the strong extraction suppresion was caused by the formation of stable metal-ammine complexes. Metal ions of Cu, Ni and Co were not extracted at all in the pH region of 7-9.5. On the other hand, the extraction suppresion was weak and the extraction of Cu and Co(II) occurred even in the pH range over 10 when chelating extractants such as LIX64N, SME529 and KELEX100 were used for the extraction from the ammoniacal solution. The extent of extraction suppresion is dependent on the sort of metal ions, the ammonia concentration and the sort of extractants. The difference of the extraction suppresion with the sort of extractants seems to be determined by the relation between stability constants of metal ions and extractants and those of metal ions and ammonia.View full abstractDownload PDF (814K) -
Junji Shibata, Makoto Sano, Hiroshi Ohmori, Sanji Nishimura1987 Volume 51 Issue 8 Pages 749-754
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe extraction of Pr and Nd was carried out by using D2EHPA as an extractant and by adding the additives such as TBP, TOPO and amine to the organic phase or the additives such as dimethylsulfoxide and dimethylformamide to the aqueous phase.
If it is assumed that D2EHPA exists as dimer in the organic phase, the extraction equilibria of Pr and Nd with D2EHPA diluted in kerosene or toluene are expressed as follows:
In the case of kerosene dilution,
(This article is not displayable. Please see full text pdf.)
In the case of toluene dilution,
(This article is not displayable. Please see full text pdf.)
The difference in extraction equlibrium with the diluents is due to the assumption that the association number of D2EHPA in the organic phase is equal to 2.0 irrespective of the sort of diluents. The composition of the extracted species of both Pr and Nd is, therefore, considered to be the same form of MR33HR.
The separation factor of Pr and Nd increses in D2EHPA/LIX63 and D2EHPA/BEHAA systems, while the additives except LIX63 and BEHAA cause a decrease in the separation factor. When the water soluble additives such as acetonitrile, dimethylformamide and dimethyl sulfoxide are added to the aqueous phase the extraction of Pr and Nd is strongly affected. The separation factor increases up to 5.06 in the extraction of Pr and Nd from the feed solution containing 70 vol% acetonitrile.View full abstractDownload PDF (820K) -
Yoshiki Ono, ltsuo Ohnaka, lsamu Yamauchi1987 Volume 51 Issue 8 Pages 755-761
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThin Cu-Mn-Al Heusler alloy wires with the minimum diameter attainnable of 35 μm could be produced relatively easily by the In-Rotating-Water-Spinning Process (INROWASP). This spinnability was due to the lack of reaction between the molten alloy and the quartz nozzle and also due to the tight and thin oxide films of Al and Mn around the melt jet. Wires about 130 μm in diameter were polycrystalline and brittle. As the wire diameter decreased, some parts of the wire had only one grain across its cross section; wires with so called “bamboo structure” were obtained, which were composed of many single-crystals elongated to the wire axis. As the wire diameter became about 50 μm. the bamboo structure were dominantly observed. It was possible for the wire with the bmboo structure to be bent 180°. In most bamboo structure each single-crystal was found to be formed by the grain growth radially, or in a fan-like fashion, from one end of the molten jet surface. The polycrystalline wire also turned to the bamboo strucure by suitable heat treatments. The values of the fracture stress and elongation of wires with the bamboo structure were scattered in the range of 325-632 MPa and 3-20%, respectively. It suggested that the deformation behavior depended on the number of single-crystal, its orientaion and the morphology of grain boundary inside of a specimen length. The saturation magnetization was comparable to that obtained by O. Heusler, but the electric resistivity and its temperature coefficient showed slightly different values from the equated ones.View full abstractDownload PDF (1646K) -
Noboru Yoshikawa, Hajime Suto1987 Volume 51 Issue 8 Pages 762-768
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCommercial ZrO2 powders containing 2 and 2.5 mol%Y2O3 (PSZ) (grain size ∼20 nm) were dispersed in nitric acid aqueous solution at pH 3 with the aid of high power (1 kW) ultrasonic agitation. Centrifugal force (accerelation>20000 G) was applied not only for sedimentation but for effective compaction of the powder. Semi-transparent sintered body was obtained after sintering of the powder at 1573 K for 14.4 ks, which turned out to have very low porosity (less than 0.5%).
Three-point bending tests with the span length of 15 mm were carried out for the specimens of 1.5 mm×2 mm×20 mm fabricated by the above method. The highest strength was 1.9 GPa in the case of a specimen containing 2 mol%Y2O3.
From observations of the microstructure it was evident that coarse agglomerates were condensed at the bottom of the consolidated body, and that no segregation of Y2O3 took place along the centrifugal direction. Application of high centrifugal force (accerelation>200000 G) was found to be effective for further compaction.View full abstractDownload PDF (2768K) -
Hajime Suto, Jing-feng Li1987 Volume 51 Issue 8 Pages 769-773
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is well-known that 2 to 3 mol%Y2O3-ZrO2 has high toughness because of the stress-induced tranrformation from the tetragonal to the monoclinic phase. In the present investigation on the mechanical properties of 2 and 3 mol%Y2O3 bearing partially stabilized ZrO2 (Y-PSZ) prepared with coprecipitation powders, it was found that the maximum toughness was obtained by sintering for several hundred ks at 1573 K. In order to understand this, structural analysis was performed by means of TEM-EDS and XRD. Results obtained are as follows: (a) In the specimen sintered at 1573 K for 3.6 ks, each grain consisted of an almost average composition of the specimen. (b) After prolonged sintering the grain size was kept under 1 μm, but the composition of each grain began to change continuously toward the equilibrium values of the tetragonal or cubic phase alternatively. This type of phase separation in ultra-fine polycrystals is considered to be spinodal decomposition without modulated structure. (c) With the decrease of Y2O3 content in the tetragonal phase, the stability of Y-PSZ decreased and consequently the toughness changed.View full abstractDownload PDF (1688K) -
Tomoaki Sakurai, Kimiyoshi Goto, Tetsuo Inoue1987 Volume 51 Issue 8 Pages 774-777
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMagnetite (Fe3O4) colloidal solutions suitable for the colloid-SEM method for observing fine magnetic domains have been prepared. Fe3O4 powders were co-precipitated from FeSO4, FeCl3 and NaOH solutions in a magnetic field of about 200 kA/m. The particle size of about 76% of Fe3O4 powders thus prepared was in a range of 6∼16 nm, which was measured on electron micrographs. Among colloidal solutions prepared with many dispersing ingredients, several useful solutions have been chosen. Examples of domain patterns using some of these solutions are shown for a Sm(Co0.64Fe0.28Cu0.06Hf0.022)7.1 sintered magnet and small SmCo5 particles, and an example of recorded patterns on a Co-24 mass%Cr film is also shown.View full abstractDownload PDF (975K) -
Determination of the Thermal Activation Parameters by Stress Relaxation Test at Constant Gage LengthKoji Tanoue, Junichi Ishimaru, Hidehiko Matsuda1987 Volume 51 Issue 8 Pages 778-779
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (278K) -
1987 Volume 51 Issue 8 Pages 780
Published: 1987
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPlease see pdf. Wrong:[in Japanese] Right:[in Japanese]View full abstractDownload PDF (31K)
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