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Volume 52, Issue 4
Displaying 1-10 of 10 articles from this issue
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Masuhiro Fukaya, Takao Kozakai, Toru Miyazaki1988 Volume 52 Issue 4 Pages 369-374
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMicrostructures of various Fe-rich Fe-Si-V and Fe-Si-Co ordering alloys were extensively investigated by means of transmission electron microscopy (TEM), and the phase diagrams consistent with the TEM observations were proposed. The results obtained are as follows:
(1) The phase separation into A2+DO3, which has not been experimentally found in the Fe-Si binary system, is observed in Fe-Si-V ordering alloys. This two-phase range is spreading over a wide region connecting low V content Fe-10 to 15 at%Si ternary alloys with the Fe-Si-V alloys including V solute atoms over 20 at%.
(2) For the Fe-Si-Co ordering alloys, the B2 single phase region of the Fe-Si binary system is simply connected with that of the Fe-Co binary system. The A2, B2 and DO3 single phase regions exist in a wide region. On the other hand, the phase separation into B2+DO3 is observed in the ternary alloys whose compositions lie in the low Co range with Fe-10∼15 at%Si and in the high Co range with Fe-14.3 at%Si-28.3 at%Co, respectively.View full abstractDownload PDF (1325K) -
Hiroshi Okuda, Kozo Osamura, Yoshiyuki Amemiya, Hiroo Hashizume1988 Volume 52 Issue 4 Pages 375-382
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe reversion process below the miscibility gap has been investigated for Al-Zn binary alloys by means of in-situ Synchrotron radiation small-angle X-ray scattering (SR-SAXS). In the present study, it was made clear that the structure change during the reversion below the miscibility gap was divided into two processes, i.e., the reversion process and the coarsening process. Also, in the reversion process there were two stages. The early stage of reversion was characterized by the decreasing solute concentration and a constant volume fraction of the zones. The later stage was characterized by the decreasing volume fraction and a constant solute concentration of the zones. Comparison with a model calculation based on two-phase Stephan problem suggested that the two-phase model could describe well the structure of the G.P. zone during the reversion below the miscibility gap as well as above it.View full abstractDownload PDF (1048K) -
Akira Sakakibara, Teruto Kanadani, Masuo Yamada, Mutsuo Ohta1988 Volume 52 Issue 4 Pages 383-387
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of the vacancies supplied from the free surface and the secondary defects on the reversion in an Al-10 mass%Zn alloy were studied by Vickers hardness measurements. Specimens were quenched from 823 K or 873 K where a large number of secondary defects such as dislocation loops were formed, or from 723 K where a small number of them were formed, and then aged for 120 ks at 293 K. These specimens were reverted at 353 or 403 K. At every stage of the reversion at 353 K until 18 ks, the hardness number near the surface is always smaller than that in the interior of the grain, regardless of the quenching temperature, because more vacancies are supplied from the surface than from the interior sources. Also the surface is always softer than the interior of the crystal when the specimen aged after quenching from 723 K is annealed at 403 K where the secondary defects decay rapidly. But the hardness number near the surface is equal to that in the interior when the specimen aged after quenching from 873 K is reverted at 403 K. These results show that the secondary defects, in addition to the surface, supply free vacancies effectively, when the reversion temperature is high enough for the secondary defects to decay.View full abstractDownload PDF (688K) -
Kiyohito Ishida, Masato Ohkubo, Myeong Yong Wey, Taiji Nishizawa1988 Volume 52 Issue 4 Pages 388-394
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe spheroidization of lamellar pearlite in annealing at temperatures between 600 and 700°C has been studied by quantitative micrography. It was found that the rate of spheroidization is described by a cubic law; (1⁄S)3−(1⁄So)3=ks·t, where S is the total area of the interface between ferrite and cementite per unit volume and S0 is the initial value. The rate constant ks is approximated by ks=k0⁄(3f)3, where k0 is the rate constant in the Ostwald ripening of cementite particles, and f is the volume fraction of cementite. The effect of alloying elements on the Time-Temperature-Spheroidization curve was estimated on the basis of the analysis of Ostwald ripening, and it was shown that the small additions of Cr, Mn and Mo remarkably retard the spheroidization mainly due to the concentration of these elements into cementite.View full abstractDownload PDF (1275K) -
Yoshikiyo Ogino, Mitsuru Nagahama, Tetsu Yamada1988 Volume 52 Issue 4 Pages 395-404
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFor the purpose of separative determination of trap parameters for some types of H-trapping sites in a 35 pct-reduced high purity iron, a study has been performed with use of a two-steps electrochemical permeation technique. Two types of trapping sites, T I and T II, have been confirmed to exist. The T I sites have a binding energy of 63.1 kJ·mol−1 and a density of 1×1023 m−3. They are mostly annihilated by recovery annealing at temperatures below about 673 K. The sites T II have a binding energy of 46.4 kJ·mol−1 and a density of 7×1023 m−3. They are also significantly reduced on annealing at temperatures below about 573 K, but a final reduction occurs at around 730 K accompanied by recrystallization. The sites T II are believed to be core sites of edge dislocations. The significant reduction of T II on annealing at low temperatures suggests that the segregation of interstitial impurity atoms to dislocation-core sites precludes their occupancy by hydrogen. Another type of trapping sites, T III, having a binding energy roughly of 30 kJ·mol−1 are also pressumed to exist. The concentration and temperature dependency of H-diffusivity in the deformed iron can be well explained in terms of the coexistence of the three types of trapping sites.View full abstractDownload PDF (1691K) -
Manabu Enoki, Teruo Kishi, Junji Kihara1988 Volume 52 Issue 4 Pages 405-413
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn infinitesimal deformation in a material can be described by a moment tensor in the “eigenstrain method” of micromechanics. In the present treatment, a microcracked region was modeled as a dislocation source with moment tensor components. The advanced acoustic emission (AE) technique was developed to evaluate AE signals quantitatively and to characterize AE sources. A method to determine moment tensor components from the signals recorded by six multi-transducers was developed. This method was applied to analyze quasicleavage facets of an embrittled Cr-Mo-V steel (A470) during the fracture toughness testing. A dynamic response function of the compact tension specimen for each AE source location was calculated by a finite difference method. An iterative deconvolution algorithm was developed and moment tensor components were determined. Deconvolution results showed that mixed mode microcracks with about 60 μm across were generated at the crack tip, and these microcracks which nucleated prior to macroscopic crack extension were identified to be responsible for the embrittlement of the steel.View full abstractDownload PDF (1597K) -
Hitoshi Matsuda, Osamu Takano1988 Volume 52 Issue 4 Pages 414-419
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe magnetic and electrical of properties electroless Co-Zn-P films were studied as a function of composition and thickness of films.
The coercivity of Co-Zn-P films which was measured by B-H loop tracer increased with increasing zinc content of the films and reached 9.7×104 A/m at a zinc content of 1.7%.
High coercivity and resistivity were maintained at a film thickness of 20 μm in Co-Zn-P films, whereas they decreased markedly as the film thickness increased in Co-P films.
Upon heat treatment at 400 K, the coercivity and resistivity of Co-Zn-P films were observed to decrease drastically.
From the experimental date of ESCA and thermo-analysis, it seems to be the most probable that the co-deposited zinc exsisted as hydroxide in electroless Co-Zn-P films.View full abstractDownload PDF (1614K) -
Nobuyuki Morito, Chizuko Maeda, Toshiko Suzuki, Takako Yamashita1988 Volume 52 Issue 4 Pages 420-427
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of annealing atmosphere on magnetic properties of Fe78.5B13Si8.5 amorphous alloy has been studied. Annealing in N2, Ar, H2 and N2+20%O2 atmospheres improved significantly the iron loss of the rapidly quenched amorphous ribbon, being much better than that after annealing in H2+H2O atmosphere. The purpose of this paper is to make clear the mechanism of this deleterious effect of annealing in a H2O containing atmosphere.
According to infrared reflection spectra of the Fe78.5B13Si8.5 amorphous alloy ribbon annealed in the H2+H2O atmosphere, boron in the alloy is found to be oxidized selectively to form B2O3 film with the thickness of several 10 nm on the ribbon surface.
Auger electron spectroscopy analysis shows that any depletion zone is not formed on the ribbon surface after annealing in the N2, Ar, H2 and N2+O2 atmospheres. On the other hand, the boron-depletion zone is detected under the oxide film formed during annealing in H2+H2O. The alloy composition in this boron-depletion zone is approximately 0-3 mol%B and 9-11 mol%Si, that suggests a significant decrease of the crystallization temperature.
The α-Fe crystalline phase is detected only on the ribbon surface after annealing in the H2+H2O atmosphere by means of thin film X-ray diffraction.
We propose the mechanism on the deleterious effect of annealing in the H2+H2O atmosphere that H2O in the atmosphere oxidizes selectively boron in the amorphous alloy to form B2O3 film and the boron-depletion zone, and then the alloy in this zone is crystallized into α-Fe, and this surface crystalline layer induces the perpendicular magnetic anisotropy in the amorphous alloy to deteriorate the iron loss.View full abstractDownload PDF (1032K) -
Hideo Nakae, Hideki Yamaura, Tooru Shinohara, Kazuhiro Yamamoto, Yoshi ...1988 Volume 52 Issue 4 Pages 428-433
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFor meassuring the wetting of ceramics by liquid metals with Meniscograph, at first we examined the wetting of copper by liquid mercury at 353∼383 K. It has become clear that there are three stages in the wetting process. The first stage is the early wetting and is related to the process of wetting. The second stage is the period of equilibrium for the early wetting in a period of 10∼100 s after dipping. The third stage is the wetting accompanied by the chemical reaction between Cu/Hg, where the value of adhesion tension varies with time. The values obtained from many previous studies about the wetting were observed in this stage.
To determine the wetting speed, a model was introduced. In this model, the samples were dipped into Hg at a high speed to avoid the wetting of the samples with Hg during the dipping. The surface tension of Hg, γlv, acts on the samples at t=0, then the wetting starts and proceeds with time exponentially. According to this model, the wetting speed is given by the following equation: γlvcosθ=−(γlv+C)exp(kt)+C
C; equilibrium adhesion tension, k; constant of wetting speed, t; time after dippingView full abstractDownload PDF (853K) -
Takeaki Sakai, Takehiko Sato, Zenzo Henmi1988 Volume 52 Issue 4 Pages 434-439
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relationship between magnetic properties and structure of Fe-3 mass%Si alloy sintered at various temperatures has been studied. Electrolytic iron powder and Fe-17 mass%Si master-alloy powder were used as the material powder. The compacted Fe-3 mass%Si specimens were sintered over the temperature range between 1173 and 1673 K. Magnetic hysteresis loop, induction at 800 AT/m (B8), maximum permeability (μm) and coercive force (Hc) were measured using a recording fluxmeter, and core loss (W5⁄50) was measured at frequency of 50 Hz and maximum induction of 0.5 T. Structure was examined using an electron probe microanalyzer.
The results are summarized as follows:
(1) The sintered alloy shows a hysteresis loop suitable for block-shape magnetic cores at the sintering temperature range between 1473 and 1673 K. At this temperature range, B8 increases from 1.22 T to 1.41 T and μm increases from 9×10−3 H/m to 1.5×10−2 H/m linearly with the density of the sintered alloy. On the other hand, Hc decreases from 84 AT/m to 48 AT/m linearly with the density. In this case, round pores are formed in the sintered alloy.
(2) W5⁄50 is improved at sintering temperatures higher than 1473 K and is almost constant (25.0 W/kg) at sintering temperatures up to 1673 K.
(3) Grain growth of the sintered alloy does not affect the coercive force contrary to expectation, since intermetallic inclusions are formed in the sintered alloy.View full abstractDownload PDF (1936K)
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