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Volume 53, Issue 6
Displaying 1-10 of 10 articles from this issue
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Shigeo Sugawara, Jirô Watanabé1989 Volume 53 Issue 6 Pages 565-570
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of the concentration of (NH4)2S2O8 and NH4OH on dissolution of the copper (111) surface in Young’s etchant ((NH4)2S2O8-NH4OH-NH4Br) was studied by utilizing the etch-pits of edge dislocations. The dissolved thickness S of the matrix surface was first measured by two-beam interferometry. The two quantities H and D correlating with the dissolution of the copper (111) surface in lateral and normal directions at the dislocation sites were determined from S and the width h and depth d of the edge dislocation etch pit which were measured by replica electron microscopy.
As the concentration of (NH4)2S2O8 and NH4OH in the etchants was increased, the following features were confirmed: (a) the lateral dissolution at the edge dislocation sites, H, increased gradually, (b) the normal dissolution at the edge dislocation site, D, showed a maximum at a certain concentration and (c) the matrix dissolution, S, increased slightly.
These results were discussed on the basis of the two-dimensional nucleation theory of crystal dissolution.View full abstractDownload PDF (1481K) -
Ryo Shimizu, Jirou Harase1989 Volume 53 Issue 6 Pages 571-578
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTexture evolution by grain growth in the presence of precipitates of MnS and AlN in Fe-3%Si alloy has been investigated by SEM-ECP technique. The two texture groups A and B are evolved by grain growth from the primary texture (grain diameter of 6 μm) composed mainly of {111}⟨112⟩. The group A (gtain diameter of 2600 μm) is mainly composed of the Goss orientation and its rotated orientations of about 0.26 to 035 rad around the ND axis, while the group B (grain diameter of 700 μm) had the intensity level of about one-fifth of that of the group A and has near {112}⟨110⟩ orientations. The group A has a low intensity of Σ1 and has either the highest frequency of Σ9 or a higher value of the product of its intensity and the intensity of Σ9 in the primary texture. The group B has a higher intensity of Σ1 and a higher value of the product of its intensity and the intensity of Σ9 in the primary texture. The mechanism of the texture evolution mentioned above can be explained in terms of the preferential migration of Σ9 boundaries in the presence of the precipitates and under the inhibitor effect of grain boundary migration by Σ1 boundaries.View full abstractDownload PDF (1160K) -
Yoshimasa Takayama, Tatsumi Tozawa, Hajime Kato, Chihiro Katsumata, No ...1989 Volume 53 Issue 6 Pages 579-584
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe interrelationship between grain size and hardness distributions during grain growth has been investigated for a pure iron. It was shown that the geometric mean grain diameter Dg increased during grain growth, while the standard deviation for lnD, lnσg decreased, where the grain diameter D was defined as the equivalent volume diameter. The (arithmetic) mean Vickers hardness \barHV decreased during recrystallization and growth, showing a common sigmoidal curve in the plots of \barHV versus annealing time, and the variation coefficient of hardness σHV⁄\barHV expressing the spread of the distribution also tended to decrease. The mean hardness \barHV had a better correlation with Dg−1⁄2 than with \barl−1⁄2, where \barl was the arithmetic mean length of linear intercept. Therefore, it is concluded that Dg, which is one of the mean grain sizes in three dimensions, is a more significant value of the mean grain size than \barl. It was also pointed out that the value of σHV⁄\barHV has a trend to increase with the increment of lnσg.View full abstractDownload PDF (808K) -
Shouichi Ochiai, Toshio Suzuki, Yo Kojima, Masaru Kobayashi, Yasunori ...1989 Volume 53 Issue 6 Pages 585-592
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of Y content on the oxidation behavior of Ni3Al alloys in air has been studied in the cyclic oxidation between 1273, 1373 or 1473 K and room temperature as well as in the isothermal oxidation at 1373 K by means of mass gain measurements, optical micrography, scanning electron microscopy, X-ray diffraction, and electron pyobe microanalysis.
In the cyclic oxidation, the scales formed on the Ni3Al base alloy spalled markedly during cooling, resulting in a very complicated construction of oxides consisting of NiO, NiAl2O4 and Al2O3. On the other hand, the alloys containing 0.03 and 0.5 at%Y showed no spalling of the surface oxides in any of the oxidation conditions studied. In the isothermal oxidation, the surface oxide on the base and Y-added alloys was predominantly Al2O3 and the mass gain slightly increased with increasing Y content.
The scales were very adherent on the Y-added alloys. This was attributed to the annihilation of Kirkendall voids formed at the scale/alloy interface. The deeply penetrating Al2O3 layer along the alloy grain boundaries was observed in the 0.5 at%Y alloy. There is a possibility that this protruding oxide leads to the operation of the so-called keying mechanism. But less adhesion of the scale on the 0.5%Y alloy than on the 0.03%Y alloy may be associated with the formation of YAG particles in the vicinity of the scale/alloy interface on the former alloy. The present results indicate the existence of optimum Y content for the best oxidation resistance.View full abstractDownload PDF (2549K) -
Toshio Oishi, Takayuki Nishi, Yasuhiro Kondo, Katsutoshi Ono1989 Volume 53 Issue 6 Pages 593-600
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe experimental studies on the basis of theoretical informations have been carried out for the removal of trace oxygen and sulfur in liquid copper.
Analytical values of oxygen in copper were compared with those calculated from emf values of a zirconia solid electrolyte galvanic cell. The oxygen in copper could be removed to around 1 mass ppm by either hydrogen gas or carbon reduction.
The sulfur in copper could be removed to less than 0.05 mass ppm by adding oxygen and exhausting as SO2 gas.
This method was proved to be a simple and efficient pyro-metallurgical process for the removal of trace gas elements in liquid copper.View full abstractDownload PDF (962K) -
Koji Hayashi, Tai-Whan Lim1989 Volume 53 Issue 6 Pages 601-607
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe relative density of the H2 gas-sintered compact (Ds) from Cu-10.8 mass%Sn or Cu-10.8 mass%Ni alloy fine powder of 5-15 μm in grain size and the effect of the addition of iron powder on Ds were investigated, compared with the previous result on Cu fine powder.
The results obtained were as follows: (1) The Ds of both alloy sintered compacts did not reach 100%, irrespective of the fabrication condition, as in the case of the Cu sintered compact. The reason was attributed to the high equilibrium gas pressure ratio of H2O/H2 in the reduction reaction of Cu or Ni oxide with H2. (2) The addition of iron powder to the Cu-Sn alloy powder was effective for the complete densification of the sintered compact in the same way as that of Cu powder, but not effective for the Cu-Ni alloy powder. This difference was thought to be due to the fact that unlike Cu and Sn, Ni dissolved in large quantities in the iron phase of the sintered compact and oxides with high equilibrium gas pressure ratio of H2O/H2 were formed in the Cu-Ni-Fe compact. (3) Therefore, the H2O/H2 equilibrium gas pressure ratio which is used as the criterion for the reduction of the oxide in the powder was considered to be a key parameter for the densification of the sintered compact after the isolation of pores.View full abstractDownload PDF (1755K) -
Koji Hayashi, Tai-Whan Lim, Hideatsu Komine1989 Volume 53 Issue 6 Pages 608-613
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn the previous study, the relative density (Ds) of the hydrogen-sintered compact obtained from Cu, Cu-10.8 mass%Sn or Cu-10.8 mass%Ni fine powder of 5-15 μm used for injection molding was found to tend to saturate at 95-97% and this phenomenon was suggested to be caused by the high equilibrium gas pressure ratio of H2O/H2 in the reduction reaction of the oxides, although the content of oxygen retained in the sintered compact was as small as 0.02 mass%. In this study, the cause for the above phenomenon was investigated in more detail.
(1) The effect of reduction time (0-32.4 ks) at 773 K in H2 gas on Ds or the oxygen content was not observed for each powder, suggesting that the limited amounts of oxides near the center of the powder particles are not easily reducible at low temperatures. (2) The addition of 1 mass%Al2O3 powder inhibited the crystal grain growth of the sintered compact, but the Ds also saturated at about 95%, indicating that the phenomenon is not related to the grain boundary acting as the sink of atomic vacancy. (3) The sintering in vacuum resulted in the complete densification. (4) Taking account of these results and the calculated value of the H2O gas pressure in the isolated pores, the cause for the above phenomenon was considered to be due to the high value of the equilibrium gas pressure ratio of H2O/H2 as suggested in the previous study.View full abstractDownload PDF (2766K) -
Tetsuo Uchikoshi, Yoshio Sakka, Eiichi Ozawa1989 Volume 53 Issue 6 Pages 614-620
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe initial sintering and gas release characteristics were examined for the slow oxidation treated Ag ultrafine powders. The sintering characteristics were examined by measuring the surface areas and the dimensional changes. The neck growth of the Ag ultrafine powders occurred at room temperature, and the densification occurred at temperatures above 473 K.
The released gases detected with a quadrupole mass spectrometer were mainly CO, CO2, H2O and H2. The peaks of these gases were observed in the neighborhood of 370, 480, 530, 620 and 710 K. These desorption peaks were explained as follows. (1) The peak at 370 K was the release of CO and CO2 produced by the reaction of adsorbed oxygen with surface carbon impurity. (2) The peak at 480 K was the release of CO2 due to the decomposition of the adsorbed surface carbonate CO3 (a). (3) The peak at 620 K was the release of CO, CO2, H2O and hydrocarbon accompanied with the decomposition of Ag2O. (4) The peak at temperatures above 710 K was the release of CO and CO2 by the reaction of sub-surface oxygen with surface carbon impurity.View full abstractDownload PDF (1554K) -
Mitsuyoshi Shimaoka, Itsuo Ohnaka1989 Volume 53 Issue 6 Pages 621-627
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe In-Rotating-Water Spinning Process, in which a molten metal jet is injected into a rotating water bath, can produce rapidly solidified crystalline or amorphous wires with round cross-section. In order to estimate the cooling rate of solidifying wire in the process and to get some nature of the process variables, the water flow around the jet and the microstructure of the obtained wires were examined. The temperature profile of the jet was simulated, and the result was compared with the temperature calculated from the luminance of the jet. Molten Cu85Be11Fe4 (in at%) alloy jet was injected into a water bath of 20 mm depth formed on the inner surface of a drum of 500 mm diameter which rotated at 300 r.p.m.. Separation of water around the jet and around a stainless wire at room temperature which simulates the metal jet was observed by a stroboscopic photograph. The length of the water separation along the stainless wire increased with decreasing wettability of the wire by water. The heat transfer in the region of the water separation from the jet seemed to be forced convectional film boiling. The dendrite arm spacing of the Cu-Be-Fe wire increased with increasing water temperature and was not so much affected by the ejection temperature. The cooling rates of the jet during solidification was estimated to be about 105 K/s from the dendrite arm spacing and this was supported by the simulation. It was found that the temperature profile of the metal jet could be estimated from the luminance of the jet which was measured from the photographic paper. Epstein and Hauser’s equation for the forced convectional film boiling heat transfer would be applicable to the heat transfer in this spinning process.View full abstractDownload PDF (939K) -
Haruhiko Sugimoto, Kei Ameyama, Teruhiko Inaba, Masaharu Tokizane1989 Volume 53 Issue 6 Pages 628-634
Published: 1989
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mixture of elemental powders of Ti(64 mass% (50 at%)) and Al(36 mass% (50 at%)) was offered to a mechanical alloying process. The processed powder was vacuum hot pressed at 1173 K for 3.6 ks under 100 MPa. The compact having relative density of 99.8% was obtained.
The results of X-ray diffraction, TEM observation and energy dispersive X-ray analysis indicated that the compact has an ultra-fine grain (average grain diameter=0.1 μm) structure mainly consisting of TiAl intermetallic compound. Grain growth up to 1∼2 μm in diameter occurred in the compact annealed at 1473 K for 36 ks.
As-hot pressed compact was extremely brittle in spite of its noticeable high compressive strength (0.2% proof stress=2770 MPa).
Improved combination of high strength (0.2% proof stress=1189 MPa) and good ductility (higher than 20% reduction in height) by the compression test at room temperature was attained by annealing the compact at 1473 K for 36 ks.
The compressive deformation of the compact at 1173 K was presumed to proceed by superplastic flow.View full abstractDownload PDF (2484K)
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