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Volume 55, Issue 9
Displaying 1-18 of 18 articles from this issue
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Hideyuki Ikeda, Hidehiko Matsuda1991 Volume 55 Issue 9 Pages 909-914
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWe have simulated the phase decomposion processes in a substitutional bcc binary alloy with a crystal anisotropy by using a Monte Carlo method combined with static variational method. The two-body Johnson-type potentials are used for the interactions between the constituents.
Relaxing lattice distorsion, we have observed the spinodal decomposition in an alloy with higher concentration of vacancies and otherwise with lower concentration of vacancies.View full abstractDownload PDF (929K) -
Takeshi Haga, Toru Noguchi1991 Volume 55 Issue 9 Pages 915-921
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBending fatigue test was carried out on the Ni-Cr steel specimens quenched and tempered at various temperatures, and the compariative study was made on fatigue limit and crack extension rate, particularly with regard to the influence of tempering time.
The results were as follows:
(1) Fatigue strength was cleary infleuenced by tempering time, while hardness showed little variation with the tempering time. Specimens tempered at 623 K and 723 K showed the lowest fatigue limit at holding time of 2.4 ks, but it increased in specimens with both shorter holding time 1.2 ks and longer holding time 4.8 ks and 7.2 ks, showing that the fatigue strength was improved.
(2) However, the specimens tempered at 673 K and 873 K showed the highest fatigue strength at holding time 2.4 ks decreased with shorter and longer holding time.
(3) In all the specimens, the lowering fatigue strength was identified by characteristic microfracture appearance with quasi-cleavage facets in striation-like markings.
(4) With long holding time 7.2 ks, the m value, that characterizes crack propagation rate, was decreased to 1.4 for all the specimens as compared with the m value of 1.7 to 2.4 in specimens tempered for 2.4 ks. This suggested that crack propagation rate was late with tempering time.View full abstractDownload PDF (2117K) -
Keijiro Nakasa, Jianping Liu1991 Volume 55 Issue 9 Pages 922-927
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBending tests were carried out on a Ti-13V-11Cr-3Al alloy which was charged with hydrogen by an electrolytic method and a high-temperature high-pressure H2 gas method. Bending strengths σb of as-solution treated specimens as well as aged specimens decreased with increase in electrolytic hydrogen charging time. The decrease in σb was small when the charging current density ic was 500 A/m2, while it was large when ic were 1000 A/m2 and 3000 A/m2. The bending strength of the specimens charged with hydrogen at high temperatures and high pressures decreased with increase in hydrogen concentration in specimens. X-ray diffraction analysis of the fracture surface showed that the decrease in σb by the hydrogen charging was caused by a decrease in cleavage strength of the (100) plane due to the resolution of hydrogen atoms into metal.View full abstractDownload PDF (1532K) -
Hideaki Miyagawa, Syusuke Yoshitake, Hideharu Nakashima, Hideo Yoshina ...1991 Volume 55 Issue 9 Pages 928-936
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFor clarification of path dependence of flow stress in a solution hardened alloy at high temperature, stress-strain curves were measured at 573 K for several different deformation paths using an Al-5 at%Mg alloy.
A method for theoretical prediction of flow stress along an arbitrary deformation path was proposed based on the deformation mechanism in solution hardened alloys at high temperature, and the theoretical stress-strain curves were compared with the experimental ones.
The results are summarized as follows:
(1) The flow stress strongly depends on the deformation path.
(2) The flow stress in a steady-state stage for a constant strain rate is almost independent of the prior deformation history.
(3) The predicted stress-strain cuve based on the solute-atmosphere drag mechanism agrees well with the experimental one, as long as the drag mechanism operates.
(4) The predicted values of the stress exponent of strain rate, n, and the contribution of the internal stress to the flow stress, σi/σ, for steady-state deformation agree well with the experimental ones.View full abstractDownload PDF (1223K) -
Zhu Hong-Min, Toshihito Saito, Yuzuru Sato, Tsutomu Yamamura, Kazuyosh ...1991 Volume 55 Issue 9 Pages 937-944
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe ultrasonic velocity and absorption coefficient, α in molten alkali metal nitrates and carbonates have been measured by a pulse transmission method. The adiabatic and isothermal compressibilities, internal pressure and bulk viscosity were derived from the ulltrasonic velocity and absorption coefficient. The results obtained are summarized as follows.
(1) The ultrasonic velocity and the value of α/f2 decrease with increasing temperature, but they are not dependent on frequency, f, in the frequency range investigated (5∼75 MHz).
(2) The compressibility increases and the internal pressure decreases with increasing cation size in the series of molten alkali carbonates. The compressibility and internal pressure show similar cation size dependence in the series of molten alkali nitrate, except LiNO3.
(3) The bulk viscosities of alkali metal carbonates and nitrates have negative temperature dependence, and the value of ηB/ηS increases with increasing cation size in the series of molten alkali nitrates and carbonates.
(4) The compressibilities calculated on the basis of a hard sphere model agree well with the experimental values, but the bulk viscosities calculated are obviously smaller than the experimental values.View full abstractDownload PDF (1060K) -
Noriyuki Tatsumi, Shunsuke Toyoda, Ryokichi Shimpo, Yasushi Nakamura1991 Volume 55 Issue 9 Pages 945-950
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTwo-phase equilibria of Ga/GaS and GaS/Ga2S3 for Ga sulfides, and of In/InS, InS/In6S7 and In6S7/In2S3 for In sulfides were studied. Equilibria between these two-phases and H2S-H2 mixture were measured with a thermobalance by changing H2S content of H2-H2S mixture. From the obtained values of equilibrium content of H2S, standard Gibbs free energy changes for the formations of these sulfides were calculated as follows:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (812K) -
Kazuo Kameda, Katsunori Yamaguchi1991 Volume 55 Issue 9 Pages 951-956
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe emf measurements of the following galvanic cells have been carried out to determine the standard free energy of formation of PbO (s) and the thermodynamic quantities of liquid Pb-Tl alloys:
(This article is not displayable. Please see full text pdf.)
\ oindentThe standard free energy of formation of PbO(s) was determined as follows:
ΔGPbO(s)°⁄J·mol−1=−217580+98.7 T±200 in the temperature range 810-1104 K.
Activity of lead in liquid Pb-Tl alloys at 850 and 950 K show slightly smaller positive and negative deviations from the Raoult’s law. The activity of thallium at the same temperature exhibits a smaller negative deviation from the Raoult’s law over almost all the concentration range except for the thallium rich region. It is nearly in agreement with the ideality in the thallium rich side of the system. The γPb° and γTl° values are estimated to be 0.62 and 0.69 at 850 K and 0.65 and 0.74 at 950 K, respectively. The α functions of lead against NPb never show a constant value, suggesting no regular solution behavior.
The free energy of mixing at 950 K shows slightly smaller negative values than ΔGid, and the peak value of ΔG is −6.3 kJ/mol at about NPb=0.49. The heat of mixing shows very small negative values. The peak value of ΔH is −1.3 kJ/mol at about NPb=0.50.View full abstractDownload PDF (788K) -
Osamu Endo, Katsuhisa Sugimoto1991 Volume 55 Issue 9 Pages 957-961
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain high corrosion-resistant SiO2 films by a CVD process using tetraethylorthosilicate (TEOS) and O3, changes in the growth rate, composition and corrosion resistance of the films with deposition temperature have been investigated. The growth rate increased with increasing deposition temperature up to 573 K, whereas it decreased above 573 K. The number of Si-OH bonds in films decreased with increasing deposition temperature and the bond hardly existed at temperatures above 573 K. The films deposited at temperatures between 423 K and 673 K were amorphous. The corrosion resistance of the films in a buffered HF solution increased with increasing deposition temperature, especially at the temperatures above 573 K. The films showed no susceptibility to corrosion in 5.0 kmol·m−3 HCl. However, they suffered from the exfoliation from substrates in the solution.View full abstractDownload PDF (692K) -
Kazuo Yamanaka1991 Volume 55 Issue 9 Pages 962-969
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe initial repassivation processes of anodic reaction on newly created surfaces of high nickel alloys containing 0-30 mass% chromium were investigated by a rapid straining electrode technique in a 10%Na2SO4+H2SO4 (pH at room temperature=3.0) solution at 553 K at constant anodic potentials. The results obtained are as follows:
(1) The decrease in current density with time after rapid straining was stopped consists of two stages. Namely, current density in a short period (within around 20 ms) after rapid straining was stopped decays to the formula of i∝exp (−tn) (i: current density, t: time, n: constant), and then the density at least up to 1000 ms decays to the formula of i∝t−n.
(2) The repassivation rate increased with increasing chromium content, and so the amounts of charge caused by the metal dissolution decreased with increasing chromium content.
(3) It was considered that the reason for which nickel-base alloys containing high chromium content such as Alloy 690 (60%Ni-30%Cr-10%Fe) had high SCC resistance in a high temperature acidic solution containing sulfate ions is due to both the promotion of the repassivation and the suppression of the film dissolution by the formation of the chromium oxide film.View full abstractDownload PDF (959K) -
Takeshi Kobayashi, Kunikazu Ide, Haruno Okochi, Yasushi Shimada1991 Volume 55 Issue 9 Pages 970-974
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAn analytical method has been established for the determination of trace amounts of acid soluble and insoluble aluminium in iron and steels by graphite furnace atomic absorption spectrometry. A sample was dissolved with aqua regia, and the solution was filtered. After adding sulfuric acid, acid soluble aluminium in the filtere was determined. The residue was used for the determination of acid insoluble aluminium. After the solution (20 mm3) was pipetted into a L’vov platform in a graphite furnace, it was ashed and atomized in argon as a purge gas. Atomic absorption of aluminium was measured at 309.3 nm. The effect of diverse elements (Fe, Ni, Cr, Co, Mn, V, Mo, Mg) was supressed by peak area measurement. The relative standard deviation of the proposed method was within 3.2% at 12.5 ppm of acid soluble aluminium and 2.8% at 13.3 ppm of acid insoluble aluminium in high purity irons. The limit of detection (3σ of blank value) was 0.3 ppm of acid soluble aluminium and 0.1 ppm of acid insoluble aluminium, when 0.5 g of the specimen was used.View full abstractDownload PDF (730K) -
Ryo Inoue, Hideaki Suito1991 Volume 55 Issue 9 Pages 975-980
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe method for the determination of oxygen in iron containing aluminum was studied by use of the inert gas fusion-infrared absorptiometry as a function of flux, temperature and heating pattern. The double graphite crucibles containing Sn, more than four times of the sample weight, were first degassed at 3000 K and the temperature was reduced to 2630-2760 K. Then the sample enclosed by a nickel capsule was dropped into the tin bath and fused for 30 s. This analytical procedure made the oxygen determination in an Fe-10∼15 mass%Al alloy possible without observation of the “gettering effect” due to aluminum. The recovery of oxygen was confirmed to be almost 100% by the analysis of alumina powder. The results for the oxygen in a Ti-25∼51 mass%Al alloy was also discussed.View full abstractDownload PDF (825K) -
Masahiro Okumiya, Yoshiki Tsunekawa, Itaru Niimi, Masahiko Hamada, Mic ...1991 Volume 55 Issue 9 Pages 981-985
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLow-alloy steel (SCr42O) bulk specimens were plasma-carburized in methane/hydrogen mixed gas. The carburizing gas near a specimen was collected by a sampling cylinder and a piston system, and the retained methane in carburizing gas was measured by gas chromatography. The influences of treating temperature, plasma energy and vacumm-pumping speed on the retained methane were studied.
The decomposing speed of methane being quite slow, the partial pressure of methane was extremely higher than the equilibrium partial pressure in plasma-carburizing. Since the methane was decomposed by heating, the retained methane decreased as treating temperature increased. It also decreased by plasma energy. As the retentive time of the carburizing gas in the furnace decreased with increasing pumping speed, the retained methane increased.
The influences of the retained methane, treating temperature, pressure, time and pumping speed on the surface carbon content of specimen were also studied. The surface carbon content of the specimen was determined by the retained methane in the temperature range of 1203 and 1373 K. It increased as the retained methane increased. Under the stable glow discharge, it increased as the chamber pressure, pumping speed and treating time increased.
The number of carbon atoms which were permeated into the specimen would agree with that of the dissociated carbon from the methane by plasma energy.View full abstractDownload PDF (715K) -
Jun Su Kim, Junichi Kaneko, Makoto Sugamata1991 Volume 55 Issue 9 Pages 986-993
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSiC whisker reinforced composites with Zn-22Al alloy matrix were fabricated by high pressure infiltration of the alloy melt and hot extrusion of the composite ingots eutectoid heat-treated to produce superplastic fine grain structures. Structures and mechanical properties at room temperature were examined on the obtained composites. The composites were shown to be hot-extruded under lower extrusion pressure than aluminum alloys such as 2024 and 7075. Less damage of whiskers during hot extrusion and hence a higher strengthening effect of whiskers than the composites with aluminum alloy matrix were observed. The elastic modulus and tensile strength of the Vf 20% composites at room temperature were 152 GPa and 488 MPa, respectively.View full abstractDownload PDF (1765K) -
Jun Su Kim, Makoto Sugamata, Junichi Kaneko1991 Volume 55 Issue 9 Pages 994-1001
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSiC whisker reinforced composites with Zn-22Al alloy matrix were fabricated by high pressure infiltration and subsequent hot extrusion. Deformation behavior at elevated temperatures was examined under various conditions, and hot compressive forming of the composite ingots into various shaped parts was carried out by using closed dies. Superplasticity was not observed on the composites, whereas the Zn-22Al matrix alloy showed tensile elongation as high as 1200% at 553 K. Metallographic inspection of the elongated specimens revealed formation of voids in the composites. The existence of SiC whiskers as the reinforcement significantly affects deformation and fracture behavior of the composites at elevated temperatures. The strain rate exponent (m-value) of the composites decreased with an increase of whisker volume fraction. At 543 K, the measured m-value was 0.28 for 13% Vf and 0.16 for 20% Vf, while that of the Zn-22Al matrix alloy was 0.44. The highest elongation of the composites was 80% for 13% Vf and 50% for 20% Vf. These elongation values were shown to be high enough to carry out hot forming. Cup- and gear-shaped products of the composites were obtained by compressive forming.View full abstractDownload PDF (1919K) -
Yutaka Takahashi, Hideki Takagi, Tadatomo Suga, Borris Gibbesch, Gerha ...1991 Volume 55 Issue 9 Pages 1002-1010
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAluminum/aluminum joints were prepared by means of the surface activation room temperature bonding technique in following different vacuum conditions. The relationship among microstructure, mechanical property and electrical property of the interface was clarified.
(1) When surfaces are activated by argon beam sputtering in ultra-high vacuum (10−9 Pa), indeally clean surfaces are adhered in the atomic scale.
(2) In a vacuum of 10−5 Pa, surfaces are attacked by residual gases such as H2O during argon beam sputtering. A crystalline altered layer in about 5 nm thickness is formed on the surface before bonding. The layer affects the interfacial microstructure, but the tensile strength is more than 100 MPa and the interface electrical resistivity is as low as less than 10−12 Ω·m2 in such a joint.
(3) When the activated surface is exposed before joining, the bonding properties deteriorated due to the surface contamination of a residual gas. The interface is fully covered with an intermediate amorphous layer of a few nm in thickness in a specimen exposed for 7.3 ks in a vacuum of 2.7×10−5 Pa. As a result, the interface resistivity increased drastically (∼10−10 Ω·m2) and the tensile strength decreased to 50 MPa. It should be emphersized, however, that a macroscopic bonding is obtained in the Al/Al system in such a contaminated condition suggesting that a clean and/or atomically activated surface is not necessarily essential to the mechanism of the room temperature bonding.View full abstractDownload PDF (3491K) -
Shuichi Kamota, Masahiro Sakai, Yasuki Miyakoshi, Kohsuke Tagashira, K ...1991 Volume 55 Issue 9 Pages 1011-1017
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of Cr and B contents on properties of Ni base self-fluxing alloys were investigated in order to develop trial alloy particles for bonding of cast iron and mild steel. The chemical compositions of the trial particles were determined to be bal. Ni-5.0Cr-3.5Si-1.5B-1.0Fe-3.0Cu (mass%) considering the mechanical properties as well as the melting temperature and wettability of the alloy.
The tensile strength of the joints bonded with thermal spray coatings using the trial particles was higher than that of the joints bonded using the commercial particles (Ni base self-fluxing alloys of high Cr and C contents). A eutectic phase, which looked like net work structures surrounding primary granular αNi, was observed in the sprayed layer of the bonded region. Almost the same tensile strength was obtained regardless of the surface roughness of the sprayed layer. However, the influence of layer thickness was remarkable and the strength was decreased with decreasing the layer thickness under 0.1 mm.View full abstractDownload PDF (1856K) -
Hiroyuki Kon, Yasutoshi Noda, Yoshitaka Furukawa, Isao Nishida, Katash ...1991 Volume 55 Issue 9 Pages 1018-1022
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe thermoelectric properties of Sb-doped n-type and Ag-doped p-type Mg2Si0.6Ge0.4 samples were investigated in the temperature range 300 to 900 K. The scattering factor was determined as 0.0 by measuring the temperature dependence of Hall mobility. Thermoelectric power and electrical conductivity were measured, and thermal conductivity was evaluated using the measured value at 300 K. The maximum figure-of-merits Z’s were estimated to be 1.61×10−3 K−1 at 663 K for the n-type and 2.67×10−3 K−1 at 629 K for the p-type, respectively. From the fact that the dimensionless figure-of-merits ZT’s exceeded unity, the Mg2Si1−xGex solid solution semiconductors can be expected as a new promissing material for high-efficiecy thermoelectric energy conversion in the middle-temperature range.View full abstractDownload PDF (611K) -
Mitsuo Niinomi, Toshiro Kobayashi, Kazunori Ryugoh, J. C. Williams, W. ...1991 Volume 55 Issue 9 Pages 1023-1030
Published: 1991
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAccurate fracture toughness test methods on the Nb added titanium-based intermetallic compound Ti3Al using three point bending specimens were examined. Then, microfracture mechanism of this intermetallic compound was also studied.
Load-deflection curves indicated elastic-plastic behavior in both static and dynamic fracture toughness tests. Crack-initiation points were evaluated by the acoustic emission (AE) method, the compliance change rate method and the multiple specimen method. It was found that there was good agreement among them under static conditions. Fracture toughness values obtained using notched specimens with various root radii were in good agreement with those obtained using fatigue-precracked specimens tested under both static and dynamic conditions. Microcracks, debonding of α2 (Ti3Al)-βo (Ti2NbAl) interface, planar slip bands and a planar dislocation structure were observed near the crack tip. The planar dislocation structure in the α2 phase had a trend to concentrate to near the α2-βo, interface under dynamic conditions.View full abstractDownload PDF (2495K)
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