All issues
Volume 46, Issue 2
Displaying 1-17 of 17 articles from this issue
- |<
- <
- 1
- >
- >|
-
Hisashi Kawabe, Kaizo Kuwahara1982 Volume 46 Issue 2 Pages 117-125
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe strain amplitude (γ)-dependent damping characteristics in ferromagnetic metals have been represented by a mechanical model which is composed of a non-linear spring describing a magneto-mechanical hysteresis mechanism and of a mass. The model describes the following characteristics.
The envelope of its damped free oscillation curve is a bulge type decay curve, and the higher the damping capacity (Q−1), the more remarkable becomes such a peculiarity on decreasing amplitudes. The γ at the maximum Q−1 coincides with the critical strain (γc) in a magneto-mechanical hysteresis. At γ<γc, the Q−1 vs γ is more likely featured by a quadratic increasing function than by a linear increasing one that has so far been mentioned.
The vibration power-spectrum analyses of a commertial ferromagnetic damping metal show that the Q−1 consists not only of the γ-dependent damping but also of the frequency-dependent one, and the contribution of the latter component to damped free oscillation curves makes in particular their envelopes to be the so called exponential decay type.View full abstractDownload PDF (655K) -
Yuji Imashimizu, Jirô Watanabé1982 Volume 46 Issue 2 Pages 126-132
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDislocation etch pits on the (111) surface of Cu crystals have been observed to study the effects of the composition, stirring rate and temperature of etchants and the small addition of Al in Cu. The etchants are Young’s solutions containing (NH4)2S2O8, NH4OH and NH4Br. The dislocation etch pit morphology strongly depends on the composition of the etchants. It is shown that the pit size varies with the concentration of the etchant and the pit shape varies with the ratio of each components in the etchant. At a ratio (NH4)2S2O8:NH4OH:NH4Br nearly equal to 1∼1.5:6:0.3, the triangular pyramid pits surrounded with ⟨110⟩ sides are produced, while, off this ratio, the etch pits tend to become more or less rounded. On the other hand, the stirring of the etchant increases the pit size remaining its shape unchanged. Such a tendency is also indicated with an increase of etchant temperature from 260 to 300 K, except a slight rounding of etch pit at 300 K. Moreover, with the addition of Al, the etch pits become small and rounded, though the straight-sided pits are revealed when etched with etchant containing high concentration of (NH4)2S2O8. Some discussions about the effects of the etching condition are given in connection with the kink nucleation and motion at the surface steps.View full abstractDownload PDF (990K) -
Tokuzou Tsujimoto1982 Volume 46 Issue 2 Pages 132-140
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSComputer simulation for diffusion behavior of composition variations has been carried out by an iterative technique using a Fourier transformed diffusion equation. The driving force of diffusion, ∂χ⁄∂c, and the free energy, ΔfT, have been estimated from composition profiles. Here,
(This article is not displayable. Please see full text pdf.)
\ oindentwhere μ is the chemical potential, κ the gradient energy coefficient, M the mobility of atoms, Nv the number of atoms per unit volume, and D0, D1 and D2 are the diffusion constants. Q(h) is a Fourier spectrum representing a composition variation, and R(h), S(h) and T(h) are functions obtained by convoluting Q(h) once, twice and three times, respectively.
Diffusion always proceeds so that the free energy of the system may decrease. On the spinodal decomposition in high solute alloys the up-hill diffusion occurs even in the outside region of spinodal by the contribution of the second term in eq. (1) as a result of formation of adequate composition profiles, and it continues until χ becomes constant everywhere. In low solute alloys, the up-hill diffusion occurs at the high solute region in the composition profile and the down-hill diffusion occurs at the low solute region, which yields a uniform matrix and a composition peak. The region of the up-hill diffusion can expand up to the base of the composition peak if an adequate composition profile is formed. Then the solute atoms of the matrix are absorbed by the composition peak, and the latter develops into a nucleus. Otherwise, the composition peak decays out. Low solute alloys including composition variations over a wide region are at high levels of the free energy, and whether the phase separation occurs or not is determined at much higher energy levels than those of critical nuclei in the conventional theory.View full abstractDownload PDF (716K) -
Hideki Hagi, Yasunori Hayashi, Namio Ohtani1982 Volume 46 Issue 2 Pages 141-147
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe strain due to dissolved hydrogen atoms in electrolytic iron was measured by two independent techniques; a measurement of change in the electrochemical hydrogen permeation rate with the application of elastic tensile stress, and a measurement of change in the length of a specimen as a function of hydrogen concentration.
The hydrogen permeation rate increases with the application of stress but the diffusion coefficient of hydrogen is independent of stress, so that the stress application affects the solubility of hydrogen in iron. The logarithm of the ratio of the permeation rate in the stressed condition to that in the unstressed condition (ln(Jσ⁄J0)) is proportional to the applied stress (σ). The fractional increases of the permeation rate with increasing stress (ln(Jσ⁄J0)⁄σ) at ic=10−20 A/m2 are almost the same irrespective of the composition of the electrolyte.
The strain of a unit cell of the iron lattice containing one hydrogen atom can be calculated from change in the permeation rate of hydrogen with the applied stress by using the equation ln(Jσ⁄J0)⁄σ=a3ε⁄kT, where a is the lattice parameter and ε is an average of the diagonal elements of the strain tensor. The value of ε is 0.057 (at T=296 K).
The relative expansion of the iron specimen per atomic fraction of hydrogen dissolution corresponds to 2ε. The observed dilation of the iron specimen is the same within experimental error as that calculated from the above-mentioned value of ε and the hydrogen concentration.View full abstractDownload PDF (605K) -
Yoshinori Shirane1982 Volume 46 Issue 2 Pages 148-154
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMany activity measurements of components in liquid oxides have been reported in the field of slag chemistry. However, very little is known about the thermodynamic behavior of components in oxide solid solutions.
In the present paper, e.m.f.s of the following galvanic cells employing solid electrolyte ZrO2 (CaO) were measured over the entire range of composition of the solid solutions;
(This article is not displayable. Please see full text pdf.)
Activities of NiO in the solid solutions of (Mg1−xNix)O and (Mg1−xNix)2SiO4 (where 0≤x≤1) calculated from the results of e.m.f. measurements show considerable negative deviation from Raoult’s law whereas (Mg1−xNix)SiO3 (where 0≤x≤0.12) is slightly positive in the temperature range studied between 1073 and 1273 K.
In many nickel extraction processes such as segregation, preliminary reducing, chloridizing roasting, etc., we may be confronted with very complicated systems of the mineralogical types of garnierite ores involving a number of possible reactions. The present thermodynamic approach of the NiO-MgO and NiO-MgO-SiO2 systems enables us to predict the feasibility of the proposed process, and thus may contribute to a considerable saving in its cost.View full abstractDownload PDF (515K) -
Katsuhisa Sugimoto, Shiro Matsuda, Minoru Isshiki, Tatsuhiko Ejima, Ke ...1982 Volume 46 Issue 2 Pages 155-161
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe corrosion resistance of iron in acid and neutral chloride solutions has been investigated as a function of the purity of iron. Five kinds of iron having residual resistivity ratios, RRRH,4.2K, of 80, 150, 800, 1500 and 6000 were used as specimens. The former three with RRRH,4.2K 80, 150 and 800 were commercially available pure iron and the latter two with RRRH,4.2K 1500 and 6000 were high purity iron produced by a new method combining anion exchange and zone-refining processes.
In deaerated 0.5 kmol·m−3 H2SO4, the corrosion rate of iron decreased sharply with increasing purity; the corrosion rate of iron with RRRH,4.2K 6000 showed only 2% of that of the one with RRRH,4.2K 80. From the examination of cathodic polarization curves in the solution, it was confirmed that the increased hydrogen overpotential of high purity iron resulted in the decrease of corrosion rate.
Concerning the pitting corrosion in aerated 0.1 kmol·m−3 NaCl, the corrosion rate decreased slightly with increasing purity. The pitting potential and the induction time for pitting were, however, found to depend strongly on the purity of iron; the values of them measured in a pH 8.45 boric-borate buffer solution containing 0.01 kmol·m−3 NaCl increased sharply with increasing purity. This increased resistance against the initiation of pitting can be ascribed to the improved nature of passive films on high purity iron. The formation of thin compact films with low carrier concentration has been confirmed in situ by ellipsometric and impedance measurements on high purity iron in a pH 8.45 boric-borate buffer solution.View full abstractDownload PDF (604K) -
Satoshi Itoh, Mitsuhisa Hino, Takeshi Azakami1982 Volume 46 Issue 2 Pages 162-169
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSActivities of tin, indium and antimony in liquid Sn-As, In-As and Sb-As alloys have been measured by means of the e.m.f. method using # type cell container made of quartz. The cell constructions are as follows:
(This article is not displayable. Please see full text pdf.)
Because of the high vapor pressure of arsenic, measurements for the tin-arsenic, indium-arsenic and antimony-arsenic systems were limited in the range up to NAs=0.401, 0.499 and 0.400, respectively. Therefore, the activities of arsenic were not derived by the usual graphical Gibbs-Duhem integration, because the integration constant could not be fixed. As the lower limit of the integration, the activities of arsenic at NAs=0.273 and 0.212 obtained by using the isopiestic method were used for the tin-arsenic and indium-arsenic systems, respectively. For the antimony-arsenic system, the linear relation between logγSb and NAs2 at 1173 K was derived by the method of least squares. Based on this relation, the value of γAs at any composition were calculated by the Gibbs-Duhem integration.
The activities of arsenic obtained for the tin-arsenic and indium-arsenic systems show negative deviations from Raoult’s law, and the γAs0 values at 1173 K are estimated as 0.22 and 0.12 for both systems. For the antimony-arsenic system, the activity of arsenic shows a slight positive deviation from Raoult’s law. The value of γAs0 is estimated 1.3 at 1173 K. In addition, for the indium-arsenic system the liquidus curve in the indium-rich region was obtained from the e.m.f. measurements and compared with published data.View full abstractDownload PDF (622K) -
Munetaka Kuribayashi, Hisayoshi Okabayashi1982 Volume 46 Issue 2 Pages 170-175
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to examine the influence of γ-ray radiation on stress corrosion cracking of sensitized austenitic stainless steel, the SCC tests were conducted with γ-ray radiation in boiling 12%NaCl solution, pH adjusted to 3 with HCl, and in high temperature pure water (230°C (503 K)).
Obtained results are as follows:
(1) γ-ray radiation increased intergranular stress corrosion cracking (IGSCC) susceptibility of sensitized type 304 stainless steel in boiling 12%NaCl solution, pH adjusted to 3 with HCl. The ferric ions (Fe3+) are radiolytically formed by γ-ray radiation from the ferrous ions (Fe2+) in acid solution, and this phenomenon is the widely known principle of Fricke’s Dosimeter. The ferric ions may act as strong oxidizing agent and may increase the susceptibility to IGSCC in the acid boiling chloride solution.
(2) γ-ray radiation increased IGSCC susceptibility of sensitized type 304 stainless steel also in high temperature oxygenated pure water.View full abstractDownload PDF (484K) -
Takehiro Dan, Keikichi Nakamura1982 Volume 46 Issue 2 Pages 176-183
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWhen palladium is coated onto group Va metals such as niobium, the hydrogen absorption rate becomes comparable to that in the diffusion-controlled case, and various problems relevant to the generation of stresses are expected to arise due to the existence of hydrogen concentration gradient during the absorption-desorption cyclings. One of these problems hitherto observed is the occurrence of hydrogen induced rupture during the cyclings carried out at temperatures sufficiently higher than that of α+β→α transition.
In order to investigate into these problems in detail, the hydrogen absorption rates were controlled by coating palladium and nickel onto niobium substrates and the resultant specimens were subjected to the hydrogen absorption-desorption cycling at 723 K and PH2≤37 kPa. Following the cycling the topology of the specimen was examined to see whether fracture occurred or not. Then the coated layer was removed and changes in the hardness and X-ray diffraction half-width were measured along the depth direction of the niobium substrate.
Results obtained are summarized as follows:
(1) Remarkable increase in the hardness of niobium was observed, especially in the vicinity of its surface, when the palladium coated one was subjected to the cycling. On the contrary, increase in the hardness of nickel coated niobium following the cycling was negligibly small.
(2) However, when palladium coated niobium was subjected to step by step absorption and desorption, the increase in hardness was also very small.
(3) The changes of X-ray diffraction half-width behaved similar to those of hardness. The remarkable increases in both hardness and half-width might be due partly to the stress generation mentioned above.
(4) Fracture was observed in palladium coated niobium and not in nickel coated one. It originated from heavy worked regions such as marked or welded zone of niobium, whenever niobium had not been annealed after these working processes.View full abstractDownload PDF (897K) -
Norio Sanada, Osamu Asano, Jun Ikeuchi1982 Volume 46 Issue 2 Pages 183-190
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAs pumps, valves and pipes are damaged by cavitation attack, the method of evaluating resistance of materials, of which these apparatuses and pipes are composed, has been of considerable concern. The vibratory test is one of the widely used methods to evaluate resistance of materials to cavitation damage. However, there is no enough knowledge to determine by this vibratory method the resistance which materials will offer during exposure to cavitation attack in various surrounding conditions.
The present paper deals with the cavitation damage of carbon steels and stainless steels, of which pumps, valves, and pipes consist. All steels were tested with a 17.7 kHz vibratory unit at an amplitude of 35 μm (peak-to-peak) in water at 298 K under pressure conditions from the atmospheric pressure to 0.3 MPa.
Results obtained are summarized as follows:
(1) Under pressure conditions beyond the atmospheric pressure, the cavitation erosion behavior of tested steels, described by means of the mean depth penetration rate (MDPR) versus eroded volume, was classified into three zones; (a) a transition zone, (b) a zone with maximum erosion rate, and (c) a zone in which the erosion rate decreases.
(2) The experimental equation was derived which describes the correlation between the MDPR and the testing pressure (P) as Max (MDPR)=a·Pn (a, n: const.).View full abstractDownload PDF (1040K) -
Takanori Ohira, Hiroshi Homma, Teruo Kishi1982 Volume 46 Issue 2 Pages 190-198
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe acoustic emission technique was applied to the elastic-plastic fracture toughness tests of the compact tension specimens with various thicknesses in the 60 kg grade high tensile strength steel in order to investigate effects of the mechanical condition on the microscopic fracture processes. Since the high AE activity was confined to the fracture process before the macroscopic crack growth point, JIc, these AE events can be related with the deformation or the microscopic fracture events within the crack tip plastic zone. However, AE event counts did not directly depend on the specimen thickness or the plastic zone size. Then the volume of plane strain plastic zone was estimated by the three-dimensional plastic zone model, and AE event counts were shown to be proportional to this volume independent of the specimen thickness.
Furthermore, change in the AE activity is given by a dimensionless parameter, α=E′J⁄Bσy2, and corresponds well to the transition of deformation mode from the hinge type to the shear type based on the Dugdale-Muskhelishvili model.
From these results, the emission source can be attributed to the initiation of microcrack such as cracking or decohesion of the second phase particles which predominantly occurs within the plane strain plastic zone prior to the macroscopic crack growth.View full abstractDownload PDF (842K) -
Hiroshi Mabuchi, Yutaka Nakayama1982 Volume 46 Issue 2 Pages 198-204
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSBehaviors of grain boundary during high temperature tensile deformation have been studied in polycrystalline magnesium. In particular, the grain boundary sliding, the grain boundary migration and the cell formation in a region adjacent to the grain boundary, becoming significant modes of deformation in creep at elevated temperature, were observed mainly by optical microscopy as functions of the testing temperature (473, 573 and 673 K) and the strain rate (4.2×10−5, 4.2×10−4 and 4.2×10−3 s−1). Results obtained are summarized as follows.
(1) At 473 K, the grain boundary sliding is accompanied by the localized grain boundary migration and the cell formation due to polygonization. A “broadening” of grain boundary is observed. Such broadening develops into the band region of grain boundary with increasing tensile strain. The intergranular fracture always takes place in the band region of grain boundary by the formation of microvoids.
(2) At 573 K and above, the amount of grain boundary migration is more extensive, and the cell structure is not remarkably formed in comparison with the case at 473 K: the band region of grain boundary is not observed. In this case, the intergranular fracture takes place when the strain rate is the lowest, and voids appear at a triple point or at a knee of the wavy grain boundary.
These results indicate that the interaction between the sliding and migration of grain boundary, and the cell formation in a region adjacent to the grain boundary is important in the high temperature deformation and the intergranular fracture of polycrystalline matals.View full abstractDownload PDF (1024K) -
Tomei Hatayama, Takuzi Okabe, Hideo Takei, Yosiyuki Hodo1982 Volume 46 Issue 2 Pages 205-210
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relation between the fracture strain and the strain rate sensitivity index m is analized, and it is compared with experimental results obtaind from Al-Cu eutectic and Zn-Al eutectoid alloys. The results are as follows: (1) Most of the fracture strain is made in the strain rate region where the m-value of the non-uniform part of the specimen is approximately equal to that at a given strain rate. (2) Using the m or M-value at a given strain rate, the fracture strain εf is described by the following theoretical equations:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere Am and AM are constants which depend not only on the m-value at a given strain rate \bar\dotε but on the distribution-curve of the m-values to the strain rates. They become larger, the higher the ratio of the strain rate \dotε∞′ at m=0 to a given strain rate (\dotε∞′⁄\bar\dotε) and the more gradual the change in the m-value with the strain rate. (3) It is indicated that the uniform strain εh depends on the m or M-value as the following equations:
(This article is not displayable. Please see full text pdf.)View full abstractDownload PDF (443K) -
Takuzi Okabe, Tomei Hatayama, Hideo Takei1982 Volume 46 Issue 2 Pages 211-216
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSFlow and fracture behaviors of superplastic Al-Cu eutectic and Zn-Al eutectoid alloys are investigated under various conditions of the strain rate sensitivity index m. The main results are as follows: (1) The normalized strain rate \dotεn*⁄\bar\dotε at fracture, where \dotεn* is the apparent fracture strain rate in the non-uniform part of the specimen and \bar\dotε is a given strain rate, decreases as \bar\dotε approaches the strain rate \dotε∞′ at m=0 in a higher strain rate side. (2) In the typical superplastic conditions well-developed dimples are found. This fact suggests that grain deformations on the fracture surfaces are remarkably high, and that the fracture part passes through the higher strain rate region where the deformation mechanism is not the grain boundary sliding but the dislocation motion in grains. (3) The fracture diameter, which depends not only on the m-value at a given strain rate \bar\dotε but on the distribution-curve of the m-value to the strain rates, shows a lower value for the higher ratio of \dotε∞′⁄\bar\dotε and for the more gradual change in the m-value with the strain rate. (4) On the basis of the above results, it seems reasonable to consider that the fracture of superplastic materials occurs when a fracture part gets the strain rate \dotε∞′.View full abstractDownload PDF (595K) -
Naomi Matsumura, Masaharu Tokizane1982 Volume 46 Issue 2 Pages 217-224
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of minor addition of niobium (0.039 mass%) on the tempering process of 0.15 mass% carbon steel were examined by a hardness test and optical- and electron-microscopy. All the specimens were solution-treated at 1523 K and then quenched to form lath martensite. Some of them were deformed 50% by cold rolling prior to the tempering at 923 K.
Experimental results obtained are summarized as follows: The recovery process of the lath martensite was markedly suppressed by the presence of niobium. In the case of the as-quenched lath martensite recrystallization was not observed, while in the case of the deformed lath martensite recrystallization occurred rapidly during the tempering. The recrystallization, however, was considerably retarded by niobium addition. Such effects of niobium on the recovery and the recrystallization behavior may be related to the precipitation of niobium carbide during the tempering.View full abstractDownload PDF (1739K) -
Yoshitaka Mori, Ishi Miura1982 Volume 46 Issue 2 Pages 224-232
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMorphological changes in equiaxed grain structures have been studied. Two-dimensional grain structures are generated by computer simulation on the basis of assumptions of random nucleation sites and constant growth rate. The nucleation rate is assumed to (a) be kept constant, (b) to obey the normal distribution law, or (c) to increase or (d) to decrease with time. Coefficients of variation in grain area and grain size distributions increase with increasing grain growth rate. Average morphological characteristic values, 4πA⁄P2, LD⁄BR and CP⁄P, are calculated for each case, where A, P, LD, BR and CP represent the grain area, perimeter, longest dimension, breadth and convex perimeter, respectively. The values of 4πA⁄P2 and CP⁄P decrease markedly with increasing grain growth rate, particularly for a large grain having more than double the average grain area of each structure. Compared with polycrystalline ferrite structures, the coefficients of variation suggest that the ferrite structures are formed at the growth rates of 0.05 to 0.2, while the morphological characteristic values of the grain structures generated in this range of growth rate deviate markedly from the values observed on the ferrite structures.View full abstractDownload PDF (994K) -
Tomotoshi Sato1982 Volume 46 Issue 2 Pages 232-236
Published: 1982
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo examine the relationship between the primary dendrite arm spacing and solidification conditions, experiments were performed with Al-2.0%Cu, Al-4.0%Cu, Al-6.0%Cu, and Al-2.0%Si alloys which were unidirectionally solidified in three ways, i.e., by rapid cooling, by slow cooling, and by alternating rapid and slow cooling. The results are summarized as follows:
(1) When the average cooling rate V ranged between 1.6 K/s and 12.6 K/s, the primary dendrite arm spacing Z1 (10−3 m) was proportional to (G2R)−1⁄4 which was expected from Hunt’s theory, G (103 K/m) is the temperature gradient in liquid and R (10−3 m/s) is the growth rate.
(2) When the average cooling rate V for most of the slowly cooled specimens was lower than 1.6 K/s, the value n in the equation Z1∝(G2R)−n became smaller than 1⁄4.
(3) When the temperature gradient in the solid-liquid coexisting region was expressed as Gs (103 K/m), the primary dendrite arm spacing Z1 was proportional to Gs−0.70R−0.35 for all the specimens.
(4) For the specimens solidified by rapid cooling and slow cooling, the relationship between Z1 and the cooling rate V was expressed as Z1∝V−1⁄2. But for the ones solidified by alternating rapid and slow cooling, Z1 was not proportional to V−1⁄2.
(5) For all the specimens, Z1 was proportional to (GsR)−1⁄2.View full abstractDownload PDF (474K)
- |<
- <
- 1
- >
- >|