All issues
Volume 52, Issue 7
Displaying 1-15 of 15 articles from this issue
- |<
- <
- 1
- >
- >|
-
Toshio Tomida, Yasuhiro Maehara, Yasuya Ohmori1988 Volume 52 Issue 7 Pages 623-631
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to reveal the mechanism of the ferrite→austenite phase transformation during rapid quenching, the microstructure of melt-quenched δ⁄γ duplex stainless steel ribbons has been investigated by means of transmission electron microscopy. Two types of plate-like transformation products are observed within δ-ferrite columner grains. One involves plenty of stacking faults on close-packed planes, and the diffraction pattern shows 18R stacking of close packed structure. The other comprises α-ferrite and γ phase, where the ferrite is surrounded by the thin γ films, and the orientation relationship between them is close to that of the Kurdjumov-Sachs. These plates are considered to be formed by the martensitic transformation from δ-ferrite to the close-packed structure or δ-ferrite to austenite and again from austenite to α-ferrite. The lattice invariant shear strain of the former transformation could be the stacking faults on close packed planes.View full abstractDownload PDF (4379K) -
Shicheng Liu, Hisasi Kuwano, Yoshikazu Hamaguchi1988 Volume 52 Issue 7 Pages 632-638
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe precipitation reaction in supersaturated Fe-27Mo and Fe-16Mo alloys during the aging was studied mainly by means of X-ray diffraction, electron diffraction and transmission electron microscopic observation. The principal results obtained are as follows:
(1) A metastable R-phase was precipitated in the early stage of aging at 873-1453 K in both Fe-27Mo and Fe-16Mo alloys. In the later stage the R-phase was transformed to equilibrium phases, the μ-phase at 1213-1453 K and the Laves-phase at 873-1213 K respectively.
(2) The crystallographic structure of the metastable R-phase was rhombohedral with lattice parameters a=0.8977 nm, α=74.1°. The chemical analyses showed that the Mo content in the metastable phase was about 48 mass%. The above results are the same as those in the stable R-phase in the Fe-Mo system in the higher temperature range.
(3) The origin of age hardening in the early stage of aging is not the precipitation of the equilibrium μ- or Laves phase but that of the metastable R-phase.View full abstractDownload PDF (1657K) -
Toshitada Shimozaki, Yoshinori Wakamatsu, Masami Onishi1988 Volume 52 Issue 7 Pages 639-645
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA technique for the numerical calculation of the concentration-penetration profile in multiple phase diffusion couples has been proposed in consideration of the concentration dependence of interdiffusion coefficients and molar volumes on the basis of the so-called ξ coordinate. The concentration dependence of interdiffusion coefficients and the concentrations at phase boundaries in pure Ag-pure Zn diffusion couples have also been determined experimentally. By using these experimental values as well as those on molar volumes, the concentration-penetration profile in the diffusion couple has been calculated numerically. The results are in good agreement with the values obtained experimentally.View full abstractDownload PDF (1059K) -
Hideharu Nakashima, Hironobu Hukushima, Shoji Goto, Hideo Yoshinaga1988 Volume 52 Issue 7 Pages 646-653
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to clarify the yielding mechanism and the character of threshold stress for high temperature deformation of dispersion strengthened alloys, three kinds of Al-Mg-Mn alloys with different dispersion parameters were prepared. Their deformation behaviour and threshold stresses were analysed by means of the tensile test and the stress relaxation test during the steady state deformation at strain rates from 3×10−5 s−1 to 3×10−3 s−1 at 673 K.
Their threshold stresses were very close to the calculated Orowan stresses. The dependence of the threshold stress on the interparticle spacing was quite similar to the dependence of the Orowan stress.
From the analysis of their deformation behaviour and microstructure after deformation, it is found that the threshold stress is not determined by the Orowan mechanism but determined by the attractive interaction of dislocations with dispersed particles.View full abstractDownload PDF (1822K) -
Toshio Shimoo, Fusago Mizutaki, Shigeru Ando, Hiroshi Kimura1988 Volume 52 Issue 7 Pages 654-662
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn relation to the smelting reduction as a new process of producing Fe-Cr alloys, the mechanism of reduction of Cr2O3-Fe2O3 mixtures with solid carbon has been investigated by means of thermogravimetry and metallography. The rate of reduction was measured at high temperatures from 1673 to 1923 K under an argon atmosphere.
In the early stage of reduction, Fe2O3 was preferentially reduced to FeO, which immediately reacted with Cr2O3 to yield chromite. Subsequently, nearly simultaneous reduction of FeO and Cr2O3 in the chromite occurred.
The reduction of Cr2O3-Fe2O3 mixture in a graphite crucible as a reductant was retarded at low temperatures, since the solid reduction product was formed at the oxide-graphite interface and the rate of reduction was controlled by the diffusion of carbon through the solid product. At high temperatures, the samples was reduced rapidly by forming a molten Fe-Cr-C alloy. The reduction was accelerated by decreasing the Cr/Fe ratio and by the addition of graphite powder. When Cr2O3-Fe2O3 mixtures with a low Cr/Fe ratio were reduced by powdered graphite, the molten Fe-Cr-C alloy was finely dispersed apart from the graphite particle. It is considered that the reduction rate would be under a mixed control of the Boudouard reaction and the counter-current of CO and CO2 between the oxide and the graphite particles. In the sample with a high Cr/Fe ratio, the graphite particle was surrounded by the Fe-Cr-C alloy having a high melting point.View full abstractDownload PDF (2162K) -
Kiyoshi Nogi, Koji Ikeda, Shuzo Shimada, Kazumi Ogino1988 Volume 52 Issue 7 Pages 663-669
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe wettability of the single crystal of α-SiC by liquid pure metals (Cu, Sn, Ge, Al, Au and Si) was measured by the sessile drop method. The obtuse contact angles between liquid metals and α-SiC were obtained except for the liquid Cu and Al/α-SiC systems.
A characteristic wetting was observed in the liquid pure Cu/α-SiC system under limited experimental conditions. At a low temperature (<c.a. 1440 K) and under low pressure (<10 Pa), the hexagonal wetting was observed in the liquid pure copper/α-SiC system and a normal wetting was observed at high temperature and under high pressure. The liquid pure (Sn, Ge, Al, Au, and Si)/α-SiC systems always showed the normal wetting.
Hexagonal etching at the interface between solidified Cu and α-SiC was detected when the hexagonal wetting was observed.
It has been concluded that the hexagonal wetting is closely related to the surface structure of α-SiC.View full abstractDownload PDF (1549K) -
Woon Suk Hwang, Katsuhiko Mushiake, Noboru Masuko1988 Volume 52 Issue 7 Pages 670-676
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of three kinds of cations such as Cr(II), Ti(III), and Ti(IV) ions on the stability of passivated titanium in sulfuric and hydrochloric acid solutions of 1 kmol·m−3 was investigated by immersion tests. The open-circuit reduction of the passive film was accelerated by Cr(II) and Ti(III) ions, and retarded by Ti(IV) ion. In relatively dilute solutions of the cations, the reciprocal of the self-activation time exhibited a linear dependence on the cation concentration. A galvanostatic reduction test was also conducted with an electronic current regulation device and showed that the inverse value of the self-activation time increased linearly with the increase of the applied cathodic current. These results were compatible with each other and the cation concentration-applied current plot derived from them was used to calculate the rate constant of the ions in the reduction of the passive film. The value of the rate constant so obtained was 5×10−7 m·s−1 for Cr(II), 2×10−8 m·s−1 for Ti(III) and 2.4×10−7 m·s−1 for Ti(IV) in the sulfuric acid solution, and 1×10−8 m·s−1 for Ti(III) in the hydrochloric acid solution. The rate of the self-activation of the passivated titanium in the sulfuric acid solution was also estimated to be 0.74×10−2 A·m−2, twice the value in the hydrochloric acid solution. Additions of Ti(IV) ions of 3 mol·m−3 or above prevented the self-activation in the sulfuric acid solution, attributed to the inhibition of the film dissolution. These observations explained a relatively rapid initiation and cessation of crevice corrosion in sulfuric acid solutions. The potential-time curves at temperatures of 313 K to 328 K yielded a linear relation between logarithm of the rate of the self-activation and the inverse value of temperature, and from the slope of the straight line activation energy for the anodic dissolution of the metal was estimated to be 78 kJ·mol−1.View full abstractDownload PDF (884K) -
Seiichi Iwata, Naoki Yamamoto, Nobuo Hara, Akira Ookawa1988 Volume 52 Issue 7 Pages 677-684
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is not easy to evaluate thin film/substrate adhesion and to characterize the thin film/substrate interface when adhesion is strong. For this purpose, a new method (scratch-ESCA test), which is a combination of the scratch test, the peeling (by adhesive tape) test, and the ESCA (electron spectroscopy for chemical analysis) measurement, has been developed and is applied to the study of CVD (Chemically vapor deposited) WSix (tungsten silicide)/poly (polycrystalline) Si adhesion. In addition to the conventional adhesion evaluation by the scratch test, it is possible to evaluate adhesion by measuring (with ESCA) the amount of WSix film peeled off from poly Si by an adhesive tape after the scratch test. At the same time, WSix/poly Si interface can be characterized from the results of this ESCA measurement.
The results of the above adhesion evaluation are found to have a good correlation with the tendency of WSix films to delaminate or peel during semiconductor device manufacturing processes. The interface characterization by ESCA shows that the WSix adhesion is affected by the presence of such elements as F, O, C and N at this interface.
It is believed that this scratch-ESCA test will be a powerful tool for the adhesion evaluation of well-adhering thin films, determination of various factors influencing adhesion, and characterization of interfaces in general.View full abstractDownload PDF (1211K) -
Yuzo Hosoi, Noboru Wade, Kouzi Kakehi, Mitsuru Tanino, Hazime Komatsu1988 Volume 52 Issue 7 Pages 685-693
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA study has been made on the effect of microalloying with phosphorus(P) and carbon(C) on creep and high-temperature tensile properties of a modified type 316 austenitic stainless steel which has a similar composition to a candidate alloy for the first wall application in the fusion reactor.
The P addition up to 0.1 mass% increases markedly the creep life and decreases the steady state creep rate. P is more effective than C, and the combined addition of P and C is most helpful in increasing the creep strength. Void formation at grain-boundaries during creep is considerably suppressed by P and C additions. Finely dispersed Laves phases by the P addition and M23C6 type carbides by C and P-C additions are precipitated on the crept specimen, resulting in improvement of the creep strength. The P addition contributes to enhance the fine dispersion and stabilization of the precipitates. Cold working and aging are also effective for increasing the high-temperature tensile strength. The following relationship between effective stress, (σ−σi) and creep rate, \dotε, is confirmed by measuring the internal stress σi:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere, σ is the applid stress and B a constant.
The relation suggests the Orowan type precipitation strengthening mechanism.View full abstractDownload PDF (2779K) -
Masakazu Mohri, Kohji Kitazawa1988 Volume 52 Issue 7 Pages 694-700
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe solidification structure of 9%Ni cast steel and the effect of electro-magnetic stirring on its structure and mechanical property were examined.
9%Ni molten steel was poured into an exothermic mold and was solidified unidirectionally without stirring. Using the ingot, measurements were made of the primary and secondary dendrite arm spacings. Next, 9%Ni molten steel was solidified unidirectionally in a rotary magnetic field. The relation ship between primary arm spacing(S1; μm), secondary dendrite arm spacing(S2; μm) and average cooling rates (Va; K/s) was as follows:
(This article is not displayable. Please see full text pdf.)
And it was also confirmed that the as-cast ductility was greatly improved by this stirring, though this cast steel grade had no ductility as cast.View full abstractDownload PDF (1463K) -
Kuniyasu Gemma, Mamoru Kawakami1988 Volume 52 Issue 7 Pages 701-710
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA sudden decrease of the nitriding rate at about 873 K and a markedly promoted nitriding rate below this temperature were investigated. SUS304, 309 and 310 austenitic stainless steels were nitrided in ammonia gas in the temperature range 661∼1123 K for 0.9∼25.2 ks. In this paper, an explanation for understanding of the abnormal phenomena is attempted on the basis of a fact that the standard free energy of formation of chromium nitrides (Cr2N and CrN) intersects at about 703 K. The experimental results were as follows: (1) A discontinuity of the nitriding rate was observed at about 693∼713 K near the intersection temperature of the free energies, and the promotion of nitriding began above the temperature of the discontinuity. (2) A supersaturated solid solution (fcc, a0\fallingdotseq0.406 nm), containing approximately 33 atomic percent of nitrogen estimated from its lattice paramater, was detected from the surface of SUS304 steel nitrided by X-ray diffractometry, and transformation of this phase into γ′-(Fe, Ni)4N and CrN was observed in the temperature range where the nitriding has been promoted. (3) The structure under the surface of SUS304 steel nitrided varied from [γ′-(Fe, Ni)4N+CrN] to [austenite+CrN] between 923 and 973 K. (4) All the nitriding rates of SUS304, 309 and 310 steels showed a sudden decrease at about 873 K irrespective of the compositions. From the above results, it is concluded that the sudden decrease of the nitriding rate is a phenomenon as a result to caused upon termination of the effect of nitriding at approximately 873 K.View full abstractDownload PDF (1800K) -
Sunao Takeuchi, Tomohisa Okada, Toyonobu Yoshida, Kazuo Akashi1988 Volume 52 Issue 7 Pages 711-718
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe main objective of this study is to investigate the effectiveness of a radio-frequency plasma (rf) for spraying processes. In order to develop a suitable torch design for plasma spraying, the effects of swirl velocity on temperature and flow fields in the assumed torches are systematically examined. The most important result derived here is the finding of the conditions for an axial injection of particles without hindering the stability of plasma. Based on these calculations, a new rf plasma torch for spraying was designed. Feasibility of the design was examined by preliminary experimental investigations, and the proper function of the torch was verified. By using the torch, particle flatterning tests were performed systematically on three graded Al2O3 powders in order to investigate the effect of initial particle size on deformation. It was revealed that powders of 80-100 μm diameter were most flattend due to homogeneous melting prior to impingement on the substrate. Based on these results, spraying experiments were made for Ni, Mo, and Al2O3 powders, and dense coatings were obtained. Especially in Ni, Mo coatings on the high-temperature substrates, no particle boundaries were observed. Most of the thick Al2O3 layers deposited on the non-blasted stainless steel substrates, however, came off themselves after deposition, except for a few cases which showed the possibility of adhesion. The adhesion problem remains yet to be studied. It is noteworthy that the low particle velocity of the order of 10 m/s does not deteriorate the quality of the coatings. These theoretical and experimental investigations have confirmed that the rf plasma spraying processes will open new fields of spraying.View full abstractDownload PDF (1374K) -
Ryuuji Watanabe, Hisashi Andoh, Kiyoji Iwashita, Yukio Kurosawa, Hidea ...1988 Volume 52 Issue 7 Pages 719-724
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCo based electrode materials for vacuum circuit breakers were prepared, and the microstructures and various electric properties of the electrode were investigated. Sintered porous Co was impregnated with Ag-10 mass%Te and this impregnated alloy consisted of three phases: Co matrix, Ag and an intermetallic compound Ag2Te. The chopping currents of the Co-40∼60 mass%(Ag-Te) alloys were approximately 3 A, which were found to be much smaller than those of conventional Cu-Pb electrodes.
After many interruption tests, their chopping currents were constant and at a low level. It can be considered that the Ag2Te compound film forms at the surface layer of the electrode. Further, this electrode has a high withstand-voltage and good interruption-ability.
The materials may have a considerable potential for the low surge vacuum circuit breaker.View full abstractDownload PDF (1511K) -
Yoshinobu Sato1988 Volume 52 Issue 7 Pages 725-732
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInvestigations have been made on the effect of small additions of the non-ferromagnetic elements, Cu, Ag, Al, Ti, Zr, Si, Ge, Sn, Nb, Ta, Cr, W and Mn, 2% on the magnetic properties of a 83%Ni-11%Fe-6%V alloy and the optimum short-range ordering heat treatments at low temperature to obtain high permeability. Specimens used in this study were prepared from each alloy sheet less than 0.2 mm thick subjected to the various heat treatments in a pure H2 atmosphere.
In the case of the addition of each of Si, Ti, Sn, Ge, W, Nb and Ta varying from 1 or 2%, a higher value of dc initial permeability and a lower value of coercive force than those of the Ni-Fe-6%V base alloy are obtained. Mn exhibits such an advantageous characteristic effect that the lowering in saturation magnetic induction by the addition does not occur. The effective permeability μe in a higher frequency field of the base alloy can be improved by the additions of Sn, Si, Nb and Ta. Especially Sn raises remarkably the value of μe. For example, an alloy containing 2%Sn exhibits a nearly 25% higher value of μe at 100 kHz for the alloy specimen 0.025 mm in sheet thickness. The additions of the elements such as Al, Si, Ti and Mn, which are very susceptible to the oxidation, or Sn bring about the reduction in optimum duration of the ordering heat treatment for the highest permeability inversely with the amount of the additions. These two types of the shortening effect are considered to be due mainly to the generation of excess vacancies which accelerate the ordering, by the formation of the oxidized surface layer and the concentration of segregated Sn atoms on the sheet surface, respectively.View full abstractDownload PDF (1056K) -
Nobuyuki Morito, Shinji Kobayashi, Yohko Kitano1988 Volume 52 Issue 7 Pages 733-741
Published: 1988
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe impurity Ti (0.02-0.2 mol%) in Fe-B-Si amorphous alloys prepared by the melt spinning method was found to deteriorate extremely the iron loss, W13⁄50, and the magnetic flux density at 100 A/m, B1.
When the Ti concentration in an amorphous alloy strip was more than 0.05%, the α-Fe crystalline layer was detected on the free-side surface of the as-cast strip by X-ray diffraction, but not on the roll-side surface. This surface crystalline layer results partially in the deterioration of the magnetic properties through the magnetostriction, because it applies the compressive stress to the strip. According to X-ray diffraction and differential thermal analysis, the as-cast strip was in an amorphous state except the surface crystalline thin layer.
The magnetic property of Ti-containing amorphous alloy strip annealed in the magnetic field was not improved to the extent of the pure Fe-B-Si amorphous strip, even after removal of the surface crystalline layer by chemical polishing. The internal magnetic field and the direction of the magnetic moment in the amorphous alloys changed with the addition of a small amount of Ti according to the Mössbauer spectra, so it was suggested that the main mechanism of the deterioration was the solute Ti in the amorphous alloys, but not the crystallization.View full abstractDownload PDF (1165K)
- |<
- <
- 1
- >
- >|