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Volume 47, Issue 2
Displaying 1-12 of 12 articles from this issue
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Hideyuki Ikeda, Hidehiko Matsuda1983 Volume 47 Issue 2 Pages 91-98
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe clustering processes at the early stage of aging on a quenched two-dimensional substitutional binary alloy have been investigated in a similar stochastic model that Flinn and McManus dealt with the order-disorder problems by the Monte Carlo method. The investigation was carried out with an assumption of the constant vacancy concentration during aging. The results obtained are as follows:
(1) The vacancies accelerate clustering, and the number of clusters is independent of vacancy concentration. These results agree well with the experimental ones.
(2) The number of clusters increases at the beginning and then decreases after reaching its maximum value with time evolution.
(3) The maximum value at lower aging temperature is greater than that at higher aging temperature.
(4) The size distribution of clusters at lower aging temperature is consistent with a log-normal curve.
(5) The time dependence of the number of free solute atoms remaining in the matrix is in good agreement with the reaction of the second order.View full abstractDownload PDF (1329K) -
Yoshie Matsuo, Kaoru Takahashi, Akira Nagasawa1983 Volume 47 Issue 2 Pages 99-103
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo elucidate a dynamical mechanism of the transformation of a metastable ordered β1-phase into a ζ-phase in AgZn alloy, the effect of additional elements on the elastic behavior was examined. The temperature dependence of the elastic constants for AgZn alloys doped with Cu, Cd or In was measured in a temperature range between 150 K and 400 K, using an ultrasonic pulse-echo overlapping method. It is found that with increasing temperature, the elastic constants C11, CL[111]=(C11+2C12+4C44)/3 and C44 decrease linearly while C′=(C11−C12)/2 first varies only slightly and then rapidly decreases. Furthermore, CL[111] which is mainly related to the β1 to ζ transition mechanism predominantly depends on e/a and the transition temperature Tc. That is, for the doped specimens CL[111] and Tc fall with increase in e/a while for the non-doped specimens they rise with increase in e/a. These phenomena support strongly that CL[111] plays an important role in the β1→ζ transition. In the case of the doped alloy systems, hysteresis phenomena of the elastic constant are not observed, while the non-doped alloy shows a characteristic temperature hysteresis. Discussion is given on these phenomena using a model of dynamical process of the β1→ζ transition.View full abstractDownload PDF (684K) -
Yasumasa Koyama, Osamu Nittono1983 Volume 47 Issue 2 Pages 104-113
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPhase changes during aging of indium-(30-40 at%) lead alloys have been studied by means of X-ray diffractometry and metallographic techniques. These indium alloys, when cooled from a high-temperature phase and then aged at a moderate temperature, show two kinds of phase change as follows: (a) fcc0→fcc+fct(c/a<1) and (b) fct0(c/a<1)→fcc+fct(c/a<1). In the former case, the precipitation of the fct(c/a<1) phase from the fcc phase is accompanied by both needle-like and banded surface relief structures, and a fine twin structure parallel to {110} planes is observed inside the needle-like precipitates. The precipitation is a kind of the Bainite transformation and it takes place by a mechanism involving macroscopic cooperative movements of atoms, being quite similar to a martensitic transformation in indium-rich alloys. On the contrary, in the latter case the precipitation of the fcc phase from the fct(c/a<1) takes place by a diffusion process and it occurs along grain boundaries without being accompanied by any surface relief structure. These structural changes can be well explained in terms of free energy curves as a function of Pb concentration for both fcc and fct(c/a<1) phases. The characteristic features of the fcc→fct phase change during aging are also discussed on the basis of the Landau theory applicable to martensitic transformations in indium-rich alloys, and it is shown that this phase change takes place in the form of an athermal process.View full abstractDownload PDF (5175K) -
Toshio Shimoo, Shigeru Ando, Hiroshi Kimura1983 Volume 47 Issue 2 Pages 114-120
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe evolution rates of Mg and SiO from CaO-SiO2-MgO slag melted in a graphite crucible were measured at 1823 to 1923 K by means of a thermo-balance, particularly, in order to investigate the reaction mechanism of Mg evolution.
The mass loss was linear with the reaction time. The stoichiometric calculation indicated that the mass loss was caused by both the following over-all reactions:
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\ oindentThe rates at 1873 K were 2.2×10−5∼4.8×10−4 mol/m2·s for Mg evolution and 1.0×10−4∼1.5×10−3 mol/m2·s for SiO evolution.
The rate data for Mg evolution applies to the following equation which is derived on the assumption that the rate is controlled by the dissociation of MgO adsorbed on the slag-graphite interface;
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\ oindentwhere k1 and k2 are constants.
As to the evolution of SiO, its rate was in proportion to aSiO2, and the apparent activation energy varied from 270 to 500 kJ/mol with the slag composition. The rate is mixed-controlled by the break-down of Si-O bonds and the transport of SiO2 in slag.View full abstractDownload PDF (892K) -
Yoshifumi Kita, Mitsuru Ueda, Zen-ichiro Morita, Kazuhiko Tsuji, Hiroh ...1983 Volume 47 Issue 2 Pages 120-126
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe angular distribution of positron annihilation N(θ) has been measured for molten binary alloys containing transition metal or noble metal (i.e., molten Fe-Ge, Ni-Ge, Ni-In, Ag-Ge and Au-Ge alloys) at temperatures near the liquidus.
The experimental results for molten Fe-Ge, Ni-Ge and Ni-In alloys showed that the broad component of N(θ) arising from annihilation with d-electrons hardly increased even for the concentration of 37 at%Fe(Fe37Ge63) or 33 at%Ni(Ni33Ge67), and only a little increased for the concentration of 50 at%Ni(Ni50Ge50 and Ni50In50). On the other hand, for molten Ag-Ge and Au-Ge alloys, the broad component increased rapidly and monotonously with increasing concentration of Ag or Au.
These results correspond well with the feature of ionic structure obtained from X-ray diffraction for molten Ni-Ge and Ag-Ge alloys, and also with the results of XPS measurements for amorphous Fe-Ge, Ni-Ge, Ag-Ge and Au-Ge alloys. The difference in the concentration dependence of N(θ) between molten binary alloys containing transition metal and those containing noble metal may be ascribed to the difference in the ionic structure and the extension of d-wave function in these molten alloys.View full abstractDownload PDF (949K) -
Shigeo Sumita, Ken-ji Morinaga, Tsutomu Yanagase1983 Volume 47 Issue 2 Pages 127-131
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe density and the surface tension of Na2O-Fe2O3 and RO(R=Ca, Sr, Ba)-Fe2O3 melts have been measured to investigate the structure of these melts. Fe3+-ions may be amphoteric ions in these melts, that is, an oxygen 4 coordinated Fe3+ ion forms an oxygen complex anion such as SiO2 and an oxygen 6 coordinated Fe3+ ion acts as a cation. The size of oxygen complex anion which can be calculated from the density and the surface tension using the Reiss’s theory is about 0.5−1.5×10−9 m and increases with increasing RO content. Especially in the BaO-Fe2O3 system the size of oxygen complex anion has a maximum value at 50 mol%BaO. Infrared absorption spectra of quenched glassy samples show a good correspondence to the dependence of complex anion size upon the composition.View full abstractDownload PDF (676K) -
Hideo Ohno, Kazuo Igarashi, Yoshiki Takagi, Hisayoshi Toratani, Kazuo ...1983 Volume 47 Issue 2 Pages 132-141
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structure of glassy and molten states of the PbO-SiO2 system was investigated by X-ray diffraction analysis. In the glass, the Pb-O bond has the ionic charactor in the SiO2-rich region and has more of the covalentic charactor with increasing PbO concentration. The atomic distance of Pb-Pb pair with 3.75×10−10 m is not changed with the PbO concentration, and Pb atoms are considered to be arranged with local order in the glass. The Pb-Pb peaks in the SiO2-rich region correspond roughly to multiples of 3.75×10−10 m, and Pb atoms seem to be arranged in a simple and straight chain. However, the arrangement probably consists of twisted and zigzag PbO4 chains as increasing PbO concentration. In the molten state, a part of the three dimensional network structure of covalentic Pb-O bond seems to be destroyed and, the concentration of Pb2+ ion which is free in the melt increases. Then Pb-Pb pairs with the distance around 5×10−10 m increase due to increase in straight chains such as ionic Pb2+-O2−-Pb2+ which hardly exist in the glass.View full abstractDownload PDF (1206K) -
Masayasu Kawahara, Yutaka Mitsune, Yoshinori Shirane1983 Volume 47 Issue 2 Pages 142-147
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe solid state reaction in 2FeO-SiO2, Mg2SiO4-2FeO and Ni2SiO4-2FeO systems were studied by means of X-ray diffraction analysis, and the reaction of 2FeO+SiO2→Fe2SiO4, Mg2SiO4+2FeO→Fe2SiO4+2MgO and Ni2SiO4+2FeO→Fe2SiO4+2NiO were kinetically discussed.
Composition dependence of unit cell parameters of (Mg, Fe)2SiO4, (Mg, Fe)O and (Ni, Fe)2SiO4 solid solutions were examined by means of X-ray diffraction. The results indicated that these systems formed complete solid solutions.
A mixture of 2FeO+SiO2, Mg2SiO4+2FeO or Ni2SiO4+2FeO was heated at temperatures between 1173 and 1573 K for a fixed time up to 36 ks, and the rate of reaction in 2FeO+SiO2→Fe2SiO4, Mg2SiO4+2FeO→Fe2SiO4+2MgO or Ni2SiO4+2FeO→Fe2SiO4+2NiO was determined by means of X-ray diffraction analysis. The results indicated that these reactions followed Carter’s or Ginstling-Brounshtein’s equation of diffusion controlled reaction. In this experimental condition, the apparent activation energies (E) of these reaction were as follows:
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Kunio Nagaoka, Toyojiro Isano1983 Volume 47 Issue 2 Pages 147-152
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSChange in the tensile strength of an Al-Zn-Mg alloy, which was subjected to the Stress-Corrosion (SC) treatment in 3%NaCl aqueous solution containing K2Cr2O7 was examined in relation to aging temperature, tesile load applied in the SC treatment, and the solution temperature (Ts). The observation of fracture surfaces was also performed by scaning electron microscopy. Results obtained are:
(1) The relation between the reciprocal of the solution temperature in the SC treatment and aging time intervals (tb) up to minimum tensile strength is conjectured approximately as: tb∝Nexp(κ⁄Ts), where N and κ are constant.
(2) The relation between tensile load applied in the SC treatment and tb is conjectured as: tb∝N′exp(−κ′σ), where N′ and κ′ are constant.
(3) The relation between the reciprocal of aging temperature (Ta) and tb is conjectured as: tb∝N″exp(κ″⁄Ta), where N″ and κ″ are constant.
(4) It is assumed that grain boundary precipitates formed by aging grow up with prolonged aging time, and in due course, they are decomposed to particles, and are absorbed into three ajacent grain-boundaries.
(5) The area of dimples on a fracture surface is small near the surface but large in the center for the specimen just after the SC. With passage of aging time, the area of dimples seems to move gradually from surface side to center, and after prolonged time, the area is very small near the surface. This phenomenon could be explained as the change in the embrittlement region by hydrogen diffusion.View full abstractDownload PDF (1625K) -
Eiji Fukushima, Sadao Kobatake, Itsuo Arima, Mikio Morita1983 Volume 47 Issue 2 Pages 153-158
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSCorrosion tests were made on various stainless steels to make geothermal power plants of binary cycle systems available for dilute acidic geothermal brines. Corrosion tests were made in a hydrochloric acid type brine at Onikobe in Miyagi prefecture and in a sulfuric acid type brine at Kurokawa in Kumamoto prefecture. Using test results and assuming the service period for 15 years, rough values of pit depth and reduction of plate thickness by uniform corrosion of evaporator tubes which were especially under severe corrosion conditions were presumed.
A brief summary of main results is as follows.
(1) Approximate values of maximum pit depth of evaporator tubes including weld joints after 15 years usage were presumed to be 0.6 mm for SUS 316 and 1.0 mm for 19Cr-2Mo steel.
(2) Approximate values of maximum pit depth of SUS 410 and SUS 304 were presumed to be larger than those of SUS 316 and 19Cr-2Mo steel. Particularly deep pits were presumed to be found on SUS 304 immersed in the brine at Kurokawa for 15 years, according to oxygen dissolved in the brine.
(3) Reduction of plate thickness by uniform corrosion is quite smaller than pit depth. Especially the former of SUS 316 and 19Cr-2Mo steel after the 15 years service period was presumed to be negligible compared with the latter.View full abstractDownload PDF (842K) -
Shin’ichi Towata, Sen’ichi Yamada1983 Volume 47 Issue 2 Pages 159-165
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSSiC fibers produced from organosilicon polymer were incorporated into pure aluminum and Al-Si alloy matrixes by the squeeze casting method. The tensile strength of the obtained composites were 500-750 MPa and the tensile modulus agreed with the rule-of-mixture. By use of the composites, the reactions between SiC fibers and aluminum alloys were investigated by differential thermal analysis, scanning electron microscopy and X-ray diffraction analysis.
Aluminum carbide and elemental silicon were formed by the exothermic reaction at temperatures above the melting point of aluminum alloy matrix. The activation energy of the exothermic reaction was determined by Kissinger method to be about 200 kJ/mol. It was shown that the Si content (0-15%) in the matrix has little effect on the exothermic peak position in the D.T.A. diagram and the activation energy of the reaction. In the composite with Al-20%Si matrix, aluminum carbide and crystalline silicon carbide were formed by the exothermic reaction.View full abstractDownload PDF (2034K) -
Jun Takada, Shin-ya Miyawaki, Kazuo Kamata, Masao Adachi1983 Volume 47 Issue 2 Pages 166-174
Published: 1983
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe deformation behavior of ⟨001⟩Cu-Al2O3 alloy single crystals with various particle distribution (particle diameter and spacing) has been studied for the purpose of making clear the mechanism of the high temperature deformation of the dispersion hardened alloys. These alloys have been tested in tension at temperatures between 823 and 923 K and at initial strain rates between 10−5 and 10−3 s−1.
The main results are summarized as follows:
(1) The steady-state deformation is realized at small amounts of deformation, and the specimen axis does not rotate, because multiple slip takes place from the begining of the deformation.
(2) The strain rate in the steady-state deformation is represented as a power of stress normalized by the Young’s modulus. Values of the stress exponent and the activation energy for high temperature deformation are 7-9 and about 196 kJ·mol−1, respectively. The latter is close to that for self-diffusion in copper. The applied stress mainly consists of the internal stress. These results suggest that the high temperature deformation of these alloys is controlled by a recovery process.
(3) The stress and particle distribution dependences of the strain rate in steady-state deformation for Cu-Al2O3 alloys have been discussed on the base of creep models for dispersion hardened alloys so far. The local climb model seems to be adequite to the creep of these alloys.View full abstractDownload PDF (1516K)
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