All issues
Volume 39, Issue 7
Displaying 1-17 of 17 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kenji Abiko, Yunoshin Imai1975 Volume 39 Issue 7 Pages 657-666
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe precipitation of nitrogen during isothermal agings between 100 and 300°C in a quenched Fe-0.022 wt%N alloy was studied by means of electrical resistance measurement. The precipitation of α′′-phase and γ′-phase and the transition from α′′-phase to γ′-phase were elucidated by optical microscopy and transmission electron microscopy. The alloy was made by nitrogenizing molten iron with nitrogen gas.
The nucleation of α′′-phase is completed on dislocations and in ferrite matrix during quenching or the very early period of aging at below 225°C. The precipitation of nitrogen proceeds by a gradual growth of α′′-disks whose number decreases monotonously with aging time. The rate controlling process of the precipitation is considered to be the diffusion of single nitrogen atoms.
The nucleation of γ′-phase is completed before appreciable growth of the γ′-phase during aging at above 200°C. The rate of growth of γ′-phase is controlled by the diffusion of single nitrogen atoms as considered in the case of the α′′-phase precipitation. Plates of γ′-phase are formed on the grain boundary of ferrite, at the interface between inclusions and ferrite matrix and in the ferrite matrix in close succession with aging time. The size of an average γ′-plate is about 10μ in length, about 5μ in width and about 0.1μ in thickness. The precipitation of nitrogen proceeds by the increase in the number of γ′-plates with aging time.View full abstractDownload PDF (1829K) -
Takao Sawada, Takao Shibata1975 Volume 39 Issue 7 Pages 667-674
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA study of the constitutive equation σ=K\dotεm (K and m are constants) and the mechanical behavior of Zn-22Al superplastic alloy on the stress-strain curve was made with improvement of the usual method of the strain measurement (mean strain; εm) by using a short gage length. That is, the wire strain gage was used to obtain the strains smaller than 2% (wire strain; εw), and the elongation of the grid (0.5 mm) printed on the tensile specimen was measured to obtain the strains more than 1% (grid strain; εg). The compressive strains more than 2% were obtained by the displacement of the crosshead. Furthermore, the replicas from the specimen surface before and after deformation were observed, and the following results were obtained:
\ oindent(1) On the equation.
(i) The strain rate \dotεw increases with time in tension and compression at a constant crosshead speed at 20°C in the range of the strain hardening, and the equation holds for all cases.
(ii) The mean strain rate \dotεm decreases with time at a constant crosshead speed in tension at 20°C, while the grid strain rate \dotεg increases. However, the experimental equation, which has been obtained with \dotεm, can be also described by \dotεg in tension and compression in the range of the steady state plastic flow.
(iii) The value \dotεg is almost constant and equal to the initial value of \dotεm in tension at 250°C.
\ oindent(2) On the stress-strain curve at a constant strain rate.
(iv) Zn-22Al alloy does not harden with strain in the range of the steady state plastic flow at 20 and 250°C.
(v) With increasing tensile velocity, the value of the stress in the transition range more rapidly decreases from the strain hardening to the steady state plastic flow. It may be qualitatively ascribed to the stress relaxation and the generation of the necking.
(vi) The compressive stress is about 15% larger than the tensile stress at 20°C. This may be mainly due to the difference of the amount of cavities or voids which generate along the grain boundaries in tension and compression.View full abstractDownload PDF (723K) -
Hajime Hatano, Hiroshi Tanaka, Ryo Horiuchi, Noboru Niwa1975 Volume 39 Issue 7 Pages 675-679
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTensile tests of pure aluminum were used to measure stress wave emission (SWE) at room temperature for a better understanding of SWE during plastic deformation. The results were as follows: (1) In the case of a polycrystalline specimen, SWE had a maximum at the onset of macroscopic yielding and then decreased to a stationary level. The maximum value decreased with increasing grain size, and no peak was observed in the case of a single crystal. (2) It was found that the SWE energy per unit time increased linearly with strain rate. (3) The frequency spectrum of SWE, which was determined over the frequency range of 100 kHz to 2 MHz, showed a wide distribution and depended on the extent of deformation.View full abstractDownload PDF (434K) -
Tatsuhiko Ejima, Eiji Nakamura1975 Volume 39 Issue 7 Pages 680-686
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSurface tensions of MgCl2-KCl and KNO3-NaNO3 binary melts have been measured by means of the maximum bubble pressure method over the temperature ranges of 650∼875°C and 270∼405°C respectively.
The variation of the constituent ionic species with composition for the MgCl2-KCl binary system has been estimated by comparing the results obtained with those determined for the KNO3-NaNO3 binary system having relatively strong ionic characters. The results obtained are summarized as follows:
(1) For both systems, the surface tension shows an approximately linear decrement with increasing temperature at each composition. The surface tension and its temperature coefficient of molten MgCl2 are considerably low as compared with those of other chlorides but these are markedly increased by the addition of KCl. These trends are considered to be indicating the associating property as in the case of molten ZnCl2 previously studied by the authors.
(2) The variation of the surface tension at the melting point with composition is well corresponding to the phase diagram for the KNO3-NaNO3 system, but not for the MgCl2-KCl system, particularly on the MgCl2-rich side. The temperature coefficient of surface tension corresponding to the surface entropy per unit area and the surface enthalpy per unit area vary monotonously with composition in the KNO3-NaNO3 system, but show notable inflections at about 30 and 80 mol%KCl in the MgCl2-KCl system. The surface heat of mixing per unit area for the MgCl2-KCl system shows a maximum and a minimum at about 30 and 90 mol%KCl.
(3) The surface tensions calculated from a modified Guggenheim equation agreed very well with the experimental values for KNO3-NaNO3 binary melts, indicating that this system can be treated as a nearly ideal solution.
(4) It is also found that the variations of the surface properties with composition are well corresponding to the changes of the other physicochemical properties in the MgCl2-KCl system.View full abstractDownload PDF (526K) -
Tatsuhiko Eijima, Toshio Mitsuhashi1975 Volume 39 Issue 7 Pages 687-696
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSAbsorption and velocity of ultrasonic waves in molten MgCl2-KCl and CaCl2-KCl mixtures have been measured by using the double-transducer pulse method. The results obtained are summarized as follows:
The relation between the ultrasonic velocity and the experimental temperature can be represented by a straight line having a negative temperature gradient over the entire range of composition for these systems.
Since the temperature dependences of the volume viscosity coefficient, ηB, and the ratio of volume and shear viscosity coefficients, ηB⁄ηs, are nearly equal to the values found in the organic liquids having associated properties, it is possible to assume that the absorption in excess of Stokes’ absorption is attributed to the existence of structural relaxation caused by a time lag in structural rearrangement.
Variations of the volume viscosity coefficient, ηB, and the adiabatic compressibility, ηs, calculated from the measured sound velocity with composition can be explained by considering the change in the consitituents existing in the melt, and the present results are well supporting the presumption derived from the results of density and surface tension measurements which are reported in the previous papers.View full abstractDownload PDF (843K) -
Akinori Matsuda, Koichi Nakajima1975 Volume 39 Issue 7 Pages 697-703
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMost of investigations on plastic deformation of metal single crystals have only considered the resolved shear stress component of the operating slip system and have ignored the existence of the normal stress component.
The present experiments were carried out with a simple shear tetst to investigate the plastic deformation behavior of iron single crystals, with greater emphasis on the deformation in {110}⟨111⟩ and {112}⟨111⟩ slip systems.
The results obtained are summarized as follows:
(1) Three-stage hardening in stress-strain curve was observed at 300 and 195°K with shear tests on the (112) plane. The work hardening rate in stages I and II increased and strains for the two stages decreased as the shearing direction deviated from the [11\bar1].
(2) Temperature dependence of the critical stress in shear deformation was markedly different from that in tensile deformation, being smaller in the former. This suggests that the normal stress component is an important factor for controlling the mechanism of deformation. Moreover, in the shear deformation for the {112}⟨111⟩ and {110}⟨111⟩ slip systems, the variation of the critical stresses with temperature were remarkably different. This means that Schmid’s law does not hold for BCC metal crystals, particularly at low temperatures.View full abstractDownload PDF (661K) -
Shizuo Mukai, Makoto Fujiwara1975 Volume 39 Issue 7 Pages 704-706
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn Fe-Si steel, the relationship between the micro-crack transition temperature, Tm and the temperature, TV*=0 at which the activation volume apparently equals zero in V* vs T1⁄2 curve, is discussed using tensile strain-rate controlled tests. The results obtained are as follows:
(1) V* can be plotted as a function of the square root of temperature.
(2) The following equation between TV*=0 and Tm was obtained:
(This article is not displayable. Please see full text pdf.)
Tm can be taken by the above equation, finding TV*=0 in a temperature range below 173°K where the fit cooling baths are a little difficult to be used.View full abstractDownload PDF (222K) -
Hirofumi Miyaji, Satoshi Watanabe1975 Volume 39 Issue 7 Pages 707-710
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe characteristics of the structure formed by quenching in textured sheets of austenitic Fe-32.86 and 30.65 wt%Ni alloys were investigated by optical and electron microscopy. The results obtained are as follows:
(1) The plate-liked α′ martensite grew through the recrystallized austenite grain boundaries when the orientation of adjacent those grains was within some narrow range varying with the sheet width and cold rolling reduction.
(2) Stacking faults were observed in the Fe-32.86 wt%Ni alloy, and a structure, which seems to be hcp structure, was observed in the Fe-30.65 wt%Ni alloy. The hcp structure satisfies the orientation relationship between the austenite and hcp martensite lattices.View full abstractDownload PDF (457K) -
Seiichi Ikeda, Goro Ito, Shigeo Ohashi1975 Volume 39 Issue 7 Pages 710-717
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOxidation tests were conducted for zircaloy-2 in steam at temperature ranging from 900 to 1300°C to clarify its oxidation kinetics as a nuclear fuel cladding materials in case of a loss-of-coolant accident.
The influence of maximum temperature and heating rate of the specimen on its oxidation rate in steam was investigated. The changes in mechanical properties of the specimens after oxidation tests are also studied.
The results obtained were summarized as follows:
(1) The weight of the specimen after oxidation in steam increased two times as the time required to reach the maximum temperature increased from 1 to 10 mins.
(2) The kinetics of oxidation of zircaloy-2 in steam were not affected by the difference in the surface condition before test such as chemical polishing or pre-oxidation in steam.
(3) The dominant growth of oxide film on the surface of zircaloy-2 was observed at the initial stage of oxidation in steam. However, the thickness of oxygen-rich solid solution layer under the film increased gradually with the progress of oxidation and the ratio of oxygen in oxide to that in solid solution has a constant value of 8:2.
(4) The breakaway took place only in the specimen subjected to 900°C repeated heating. This penomenon was caused by the local growth of the oxide below a crack of the oxide film resulting from the reheating of the specimen.
(5) The results of bending tests showed that the deflection until fracture of the specimen was smaller for the one heated at a higher temperature even if the weight increase was of the same order of magnitude for both specimens.
(6) It was concluded that the ductility of zircaloy-2 decreased remarkably at a heating temperature in excess of 1100°C for more than 5 min.View full abstractDownload PDF (1099K) -
Tsuneo Nakanishi1975 Volume 39 Issue 7 Pages 718-725
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSExperimental studies have been made on a breakaway oxidation and the determination of the post breakaway oxidation rate of 9Cr-1Mo steel in the pressurized carbon dioxide.
Non-protective oxidation which is characterized by the cracking of the oxide along the edges of specimens was observed on STPA 26 and STBA 26 with the ferritic structure, but not on HT 7 and HT 9 with the martensite structure exposed to the carbon dioxide of 30 atm at 700°C.
On the other hand, a mounded oxide produced on the smooth surface in the carbon dioxide of 42 atm was also found to be non-protective.
An appreciable amount of carbon was contained in the breakaway oxide, resulting in the carburizing and hardening of the underlying metal. It seemed that a difference from a breakaway phenomenon of mild steel was owing to the difference in strength of oxide films. The oxidation rate of HT 7 and HT 9 showing no breakaway at 700°C was almost zero after 176 hr exposure and was reduced remarkably after a long exposure even at 600°C.View full abstractDownload PDF (1053K) -
Teishiro Oda, Makoto Nakamura, Hiroshi Kawakami1975 Volume 39 Issue 7 Pages 725-735
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe method for determining the notch toughness KIC from the results of the conventional mechanical tests with small specimens was studied. The following correlation was found between the notch toughness KIC and the tensile and impact properties:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere k is a non-dimensional constant, σT a true fracture stress, ICP a Charpy impact value and E is Young’s modulus.
The analysis of the published data by the above equation revealed that those data showed different tendencies according to the authors and/or the test methods. Similar equation proposed by other authors was also discussed.View full abstractDownload PDF (874K) -
Mitsuo Kido, Keijiro Nakasa, Hideo Takei1975 Volume 39 Issue 7 Pages 735-741
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe influence of fatigue accumulation given by pulsating tensile stress (bending) on the delayed fracture crack initiation was studied with notched specimens of Ni-Cr-Mo steel (SNCM 8) quenched and tempered at 200 or 400°C. The results obtained are as follows.
(1) When tempering temperature is 200°C, the time to crack initiation in delayed fracture decreases as the fatigue accumulation stress and the amount of the fatigue accumulation are increased, but the critical stress below which no crack initiation occurs is not changed by the fatigue accumulation.
(2) When tempering temperature is 400°C, both the time to crack initiation and the critical stress are decreased by the fatigue accumulation.View full abstractDownload PDF (501K) -
Kazuo Suzuki, Tetuo Fujiwara1975 Volume 39 Issue 7 Pages 742-748
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of alloying composition on the shrinkage behaviour of prealloyed stainless steel powder compacts were examined by the sintering experiment in vacuum at 900 to 1300°C for 1 hr.
It is found that the linear shrinkage of prealloyed powder compacts are changed with sintering temperature and specimen composition.
Linear shrinkage of ferritic (Fe-Cr) stainless steel is much greater than that of austenitic (Fe-Cr-Ni) stainless steel.
Shrinkage behaviour of stainless steel powder compacts mainly depends upon the nickel content in alloy composition and it decreases with increasing nickel content.
It is reasonable to consider that the difference in the shrinkage behaviour between austenitic and ferritic stainless steel compacts is mainly due to the difference between the diffusion coefficients of iron in the alpha and gamma phases.View full abstractDownload PDF (994K) -
Hisashi Suzuki, Teruyoshi Tanase1975 Volume 39 Issue 7 Pages 749-753
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present authors recently reported that the strength of conventional WC-Co cemented carbide is directly controlled by structural defects, in particular by residual pores up to about 150μφ, suggesting that the strength should remarkably increase even by eliminating the coarse pores only. In this investigation, therefore, the strength of WC-10%Co alloy free from coarse residual pores (more than about 30μφ) which are usually contained in coventional alloys was studied in detail in relation to sintering conditions and carbon contents in the alloy.
As a result, it was confirmed that the strength of the alloy easily increased to such a high value as 350∼370 kg/mm2 (according to the JIS) as expected. It was also confirmed that the strength of the present specimen was not sensitive to sintering conditions and that in the scope of this experiment the strength of low carbon two-phase alloy was surely superior to that of high carbon alloy.View full abstractDownload PDF (477K) -
Hisashi Suzuki, Kozi Hayashi1975 Volume 39 Issue 7 Pages 754-759
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of residual compressive stress (σro) due to surface-grinding on the transverse-rupture strength (σm) of WC-Co cemented carbide were studied in detail. Specimens of WC-(10∼30)%Co high carbon two-phase alloys which were free from residual pores of more than about 20μφ were made by vacuum sintering. The sintered specimens were ground by using diamond-wheels with a diamond grain size of about 70 and 150μ (abbreviated as G-specimen), or sufficiently polished so as to remove the surface layer associated with σro (P-specimen).
The results obtained were as follows. (1) The effects of σro were confirmed to exist in this case, differing from the case of conventional alloys. The effects of σro were remarkable in the alloy with lower Co contents, so that the dimension of the defect acting as a fracture source and the distance from the tension surface to the defect increased generally in G-specimen; and the σm of G-specimen was higher than that of P-specimen by about 25 and 15 kg/mm2 in 10 and 20%Co alloys, respectively. (2) These effects of σro were discussed in terms of the dimension of the defect, the resulting stress developed in the specimen when the transverse-rupture stress was applied, the surface strength of the specimen, etc. (3) In addition, the anomalous phenomenon that the external stress acting on the defect at the moment of fracture never increases and attains a definite value, when the dimension of the defect decreases to a value less than about 8μ, was reasonably explained by the influence of residual tensile stress in the resulting stress mentioned above.View full abstractDownload PDF (558K) -
Yasutoshi Saito1975 Volume 39 Issue 7 Pages 760-767
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe isothermal oxidation of uranium dioxide was studied by thermogravimetry and X-ray diffraction of partially oxidized samples at temperatures from 175 to 360°C in the oxygen atmosphere diluted with inert gas. The oxidation proceeded in two steps. In the first step UO2 was oxidized to U3O7 in the parabolic form of the rate curves implying the diffusion-controlled process. In the second step the oxidation of U3O7 to U3O8 occurred in the S-shaped form preceded by an induction period, which was characteristic of the processes of nucleation and growth. The changes in X-ray diffraction profiles during the oxidation were well interpreted in terms of the formation of two tetragonal phases, α-U3O7 (a=5.46 Å, c=5.40 Å, c⁄a=0.989) and β-U3O7 (a=5.38 Å, c=5.55 Å, c⁄a=1.031), identified by Hoekstra et al. α-U3O7 was detected in the relatively early stage of the first oxidation step. As the oxidation progressed, intensities of diffraction peaks for α-U3O7 increased at the expense of UO2 present. The orthorhombic U3O8 phase was detected together with β-U3O7 in the products of the second oxidation step, indicating that U3O8 was formed after the conversion of α-U3O7 to β-U3O7.
The X-ray and kinetic analyses favored a mechanism in which the rate-controlling process of the first oxidation step was the diffusion of oxygen through the product layer of the tetragonal phase. The Jander equation of the form [1−(1−f)1⁄3]2=kt was applicable to the first step, where f=fraction of conversion, k=constant and t=time, giving the apparent activation energy of 24.5 kcal/mol. The rate data of the second oxidation step were analysed by the Avrami-Erofeev equation of the form −ln(1−f)=(kt)n with n=3, and the apparent activation energy of 30.5 kcal/mol was obtained.View full abstractDownload PDF (786K) -
Koji Kazuoka, Teruo Tanabe, Yoshio Kondo1975 Volume 39 Issue 7 Pages 767-771
Published: 1975
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe extraction equilibria of cerous, terbium and yttrium nitrates into Versatic Acid 911 were studied. The organic phase was diluted with benzene, and the ionic strength of the aqueous solutions was maintained at unity by adding NaNO3. Radioactive isotopes of these elements were used as the tracer. The compositions of the extracted species were CeR3·4RH·H2O, TbR3·4RH·H2O and YR3·4RH·H2O, and the apparent equilibrium constants of extraction were 9.14×10−15, 3.90×10−14 and 1.70×10−14, respectively.View full abstractDownload PDF (358K)
- |<
- <
- 1
- >
- >|