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Volume 48, Issue 8
Displaying 1-16 of 16 articles from this issue
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Masami Fujiwara, Tomoo Hirokawa1984 Volume 48 Issue 8 Pages 761-770
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSTo clarify the feature of dislocation motion in the pre-multiplication region in white tin single crystals, creep tests combined with an etch hillock technique were carried out at 288 K. Crystal plates were stretched in the [110] direction, and the motion of [100] (010) dislocations was revealed on the (001) surface by hillock traces which were formed along loci of individual dislocation movements. During 90 s under stretching, some of dislocations kept on moving, but others moved intermittently or stopped perfectly on the way. The standstill for more than 5 s in dislocation motion could be discerned on account of the difference in the trace width at the point. The length of the first free path (F.F.P.) of the dislocation to encounter an obstacle was measured, and its distribution was represented in a histogram. To explain the form of the distribution of F.F.P., the statistical analysis was performed on the basis of the assumption that point obstacles were scattered randomly on a slip plane. The deduced distribution function showed good agreement with the experimental histogram. The results of calculation suggested an adequate positive correlation between the density of obstacles and the initial dislocation density counted on the surface. The distribution of F.F.P. of the dislocations stopped perfectly at the obstacles was also represented in another histogram. By comparing these two histograms, the critical breaking angle of dislocation at the obstacle was deduced. From these results, it was inferred that obstacles for dislocation motion in the pre-multiplication region in the present crystals are forest dislocations of secondary slip systems.View full abstractDownload PDF (1701K) -
Shigeo Sakurai, Saburou Usami, Hiroshi Miyata1984 Volume 48 Issue 8 Pages 771-778
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSLow-cycle fatigue tests were carried out at various temperatures on copper specimens, in order to examine the effect of strain wave shapes on fatigue life and micro damage mode. The fracture surfaces and the internal damage modes of the failed specimens were observed by means of a scanning electron microscope as well as an optical microscope. Results obtained in this study were as follows:
(1) The temperature dependence of failure life in fast-fast (\dotε=10−3 s−1) wave shape had good correlation with the hardness and the 0.2% proof stress of the material.
(2) The failure lives in the slow-fast and the tensile hold wave shapes were decreased from those in the slow-slow and the fast-slow wave shapes above 473 K. In the tensile hold wave, the failure lives were almost stable above 573 K. The failure lives in the fast-slow wave shape was longer than those in the fast-fast wave above 673 K.
(3) At 673 K, detailed metallography revealed that life reduction was due to the accumulation of creep damage during the slow tensile straining. A lot of internal wedge type grain boundary cavities were observed in the slow-fast and the tensile hold wave shapes. In the fast-slow and the compression hold wave shapes, round type cavities were observed. The slow compressive straining recovered most of the damage. Those internal damage modes corresponded to the fatigue lives, that is, the fast-slow wave fatigue life was 20 times as great as the slow-fast strain wave.
(4) In the slow-fast wave shape, the failure life was dominated by crack initiation life, and possible mechanism of creep dominated fatigue failure was discussed.View full abstractDownload PDF (2140K) -
Tsuyoshi Kawashima, Syu Yamaguchi, Kazuhiro Nagata, Kazuhiro S. Goto1984 Volume 48 Issue 8 Pages 779-786
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNew chemical sensors to measure the oxygen pressure and the Na2O activity have been developed by using Na2O·11Al2O3 and ZrO2-MgO electrolytes. The chemical activity of sodium oxide in slag was measured at 1573 K during dephosphorization of carbon-saturated iron by soda-based fluxes. Simultaneously, the oxygen pressure at slag-metal interface and the sodium vapor pressure in gas phase were also measured.
In the case of Na2O·SiO2-Fe2O3 flux, the oxygen pressure rose rapidly to about 1×10−7 Pa and slowly fell down to about 3×10−10 Pa. The activity of sodium oxide was constant at about 1×10−5 during dephosphorization and then gradually increased.
In the case of Na2CO3 flux, the oxygen pressure fell down to much lower oxygen pressure of 1×10−13 Pa than that in carbon-saturated iron during dephosphorization. The activity of sodium oxide was nearly constant at 3×10−4, when the carbon-saturated iron with 0.35%P was used. However, it fell down to 2×10−6, when the carbon-saturated iron with a large P content of 2.52% was used. The sodium vapor pressure was constant at 6×104 Pa during dephosphorization and graclually lowered during rephosphorization.
In the case of Na2CO3 added Fe2O3 flux, both the activity of sodium oxide and the sodium vapor pressure were lower than those in the case of pure Na2CO3 flux.View full abstractDownload PDF (1113K) -
Hiroshi Nakai, Naotsugu Yamanouchi, Ken Okada1984 Volume 48 Issue 8 Pages 786-792
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe initial corrosion process of titanium in the H2-H2S atmospheres was investigated by thermogravimetry at 873 K to 1123 K in 5%H2S to 80%H2S; the reacting specimens were characterized by means of metallography, X-ray diffractometry and electron micro-probe analysis.
The scaling kinetics shows a linear rate laws. In all experimental conditions, corrosion products were identified as Ti1+xS2 by X-ray diffractometry. In this temperature range, the activation energy calculated from Kl data was about 104 kJ/mol, which was almost in agreement with the rate mainly controlled by the reaction of surface. Furthermore, in this experimental conditions, the behavior of H2 and H2S varied according to the theory of Langmuir. As a result, we concluded that H2S was strongly adsorbed to titanium.View full abstractDownload PDF (1355K) -
Makoto Kishimoto, Setsuo Mishima, Katsumi Mori, Yasuji Kawai1984 Volume 48 Issue 8 Pages 793-797
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to know the interdiffusivity of FeO-MnO in FeO-MnO-SiO2 melts contained in an iron crucible, electrochemical measurements have been made at 1540 to 1673 K. The experimental technique was the chronopotentiometry at constant currents to the cell;
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\ oindentThe necessary transference number of manganese was determined experimentally and was found to be equal to the molar ratio of manganese to the total of iron and manganese. The interdiffusivities of two slags in composition of FeO 36.9-MnO 16.9-SiO2 46.2 mol%, and FeO 46.3-MnO 13.4-SiO2 43.0 mol%, were almost the same within experimental uncertainty and expressed as follows:
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\ oindentwhich is in a fair agreement with an estimated value from the electric conductivity.View full abstractDownload PDF (686K) -
Yoshiaki Iguchi, Yoshikazu Aoki, Hirofumi Yamanami, Jiro Hirao1984 Volume 48 Issue 8 Pages 798-802
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSMgO is added as a flux to iron-ores in the sintering and pelletising processes. MgO diffused into wustite influences the reduction of wustite. In order to understand the dissolution rate of MgO, diffusion experiments were conducted by means of the FeO-MgO diffusion couple method. The diffusivity \ ildeD was obtained in the range of Fe cation-site fraction (NFe) from 0.3 to 0.85 and relatively lower temperatures (1188∼1529 K). \ ildeD increases exponentially with NFe in the range of NFe from 0.3 to 0.6, but in the range more than 0.6, the increasing tendency becomes weak gradually. The variation of \ ildeD with NFe can be interpreted due to the facts that \ ildeD is proportional to 1.6 powers of vacant cation-site fraction (NV) and that the NV increases exponentially with an increase in NFe, but the increase in NV shows the tendency to be suppressed in the range of NFe more than 0.6. The experimental results can be represented by the equation, log\ ildeD=A(logPO2+8)+B. A and B are shown in Figs. 5 and 6, respectively.View full abstractDownload PDF (626K) -
Yoshiaki Iguchi, Jiro Hirao1984 Volume 48 Issue 8 Pages 802-807
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDense metallic-nickel shells are formed on each particle of NiO-MgO solid solution during the reduction with hydrogen. This is confirmed by microscopy. By doping of the oxide solid solution with FeO, however, porous metallic-nickel shells are formed. The change in the metallic-nickel morphology by doping with FeO can be interpreted in terms of the magnitude of vacancy fraction in the oxide solid solution by use of Ilschner’s one-dimensional model for metal formation during the reduction of metal-oxides. According to the model, the spacing between nuclei of the metal increases, as the vacancy fraction in the oxide increases. Doping of the NiO-MgO solid solution with FeO which is known to possess a very large fraction of vacancy introduced the increment in vacancy fraction. The metallic-nickel particles are more difficult to be sintered, as the size of metal grains and the spacing between them increase.View full abstractDownload PDF (1521K) -
Masahiro Yamane, Yasunari Kaneko, Kazuichi Mizoguchi, Yukio Suginohara1984 Volume 48 Issue 8 Pages 808-812
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn a previous paper, three kinds of oxygen, i.e. O0, O− and O2− in binary silicate glasses were analyzed quantitatively by using XPS. In the present paper, the effect of TiO2 on the silicate structure was investigated for CaO-SiO2-TiO2 glasses in the same way as analyzed previously. It was found that the O1s spectra obtained by XPS was able to be separated into four kinds of oxygen ions spectram according to specification for binding state of oxygen ions, that is, Si-O-Si, Si-O−…Ca2+, Si-O-Ti (or Si-O−…Ti4+) and Ti-O−…Ca2+. The rate for existence of these oxygen ions analyzed from the O1s spectra was in good agreement with the distribution of oxygen ions, which was calculated from the existence ratio of tetrahedrally coordinated Ti4+ ion (Ti(4)) to octahedrally coordinated Ti4+ ion (Ti(6)) with reference to the results of electrical conductivity measurement of CaO-SiO2-TiO2 melts.
From the results of the above analysis, the behaviour of TiO2 was explained in the range of three compositions as follows:
(1) In the case of CaO/SiO2=1, Ti(4) existed at the same ratio as Ti(6). It means that TiO2 added to the CaO-SiO2 system did not act as network former or modifier on the silicate anions but existed as titanate ions having Ti-O−…Ti4+ bond.
(2) In the case of CaO/SiO2<1, it was found that the amount of Ti(6) was more than that of Ti(4) and the excess Ti(6) acted as a network modifier on the silicate anions.
(3) In the case of CaO/SiO2>1, the amount of Ti(4) became larger than that of Ti(6), and the excess Ti(4) constituted titanate anions and made Ti-O−…Ca2+ bond.View full abstractDownload PDF (774K) -
Kenji Matsuki, Mitsugu Tokizawa, Norio Takatsuji, Kazuo Murotani1984 Volume 48 Issue 8 Pages 813-822
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDirect hot extrusion tests of a high strength Al-5 mass%Mg alloy billet, a clad billet composed of a core of the alloy and a sleeve of pure aluminium and also a clad billet with pure aluminium plate placed adjacent to the die face were carried out at various extrusion conditions. The extrudability of these billets were investigated by metallographic observation and flow pattern analysis, in order to clear the effects of the pure aluminium sleeve and plate on the metal flow and the surface tearing formation behaviour of the Al-5 mass%Mg alloy. Main results obtained are as follows:
(1) The surface tearing formation occurred frequently during hot extrusion of the Al-5 mass%Mg billet even at low extrusion speed because of severe friction between the extrusion tool and the billet.
(2) During the extrusion of the clad billet, the shear deformation due to the friction along the container face was concentrated on the pure aluminium sleeve with high deformability, and thus the extrusion pressure was reduced remarkably in comparison with that of the Al-5 mass%Mg billet. However, the surface defects formation could not be prevented also in the extrusion of the clad billet, because the Al-5 mass%Mg alloy contained in the dead metal zone was extruded gradually as the adhering layer on the surface of the extrusion rod coated with pure aluminium.
(3) The extrusion of the clad billet with the plate, of which the thickness is large enough to form the dead metal zone composed of only pure aluminium, was found to be very effective not only to reduce the extrusion pressure but also to achieve a better surface finish of the extrusion rod at higher extrusion speed. This is based on the relatively uniform metal flow which was achieved by the effect of continious flow of pure aluminium on the surface of the extrusion tool and the dead metal zone composed of only pure aluminium.View full abstractDownload PDF (2645K) -
Toshinori Ohshima, Li Wanlin, Tadayoshi Takahashi1984 Volume 48 Issue 8 Pages 823-828
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe present study has been made to clarify the relationship between the quality of ingot and the feedability during solidification. An Al-3 mass%Si alloy melted in a graphite crusible was cooled continuously to the temperature corresponding to a certain fraction of solid, and then quenched after 300 s holding at this temperature. The quality of ingots was evaluated by density measurement, tensile testing and scanning electron micro-fractography.
The results are summarised as follows.
During solidification, the density of quenched ingots decreased by three steps with increasing fraction of solid. This revealed the existance of three kinds of solidification zones, named effective feed zone (EFZ), restricted feed zone (RFZ) and ineffective feed zone (IFZ) in order of feedability. The ingots were highly sound in the EFZ, but they were subjected to transitional deterioration during RFZ owing to increase in porosity resulting from the reduction of feedability and remained unchanged as they passed through the IFZ.View full abstractDownload PDF (1397K) -
Tetsuyuki Ikeda, Seiki Nishi, Jungi Sugimoto1984 Volume 48 Issue 8 Pages 829-835
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSA continuous casting mechine in new wheel-chain belt systems was manufactured by way of trial. A continuous caster which is different from the conventional casters enables one to cast Al alloys with a wide range of the solidification temperature. The cast band can be cast continously by rotating asynchronously the wheel and chain belt at the high speed. In addition, band materials are cut and separated to a suitable length, and the cast strips with uniform width could be produced. An experiment for continuous casting was made for Al-20%Sn and Al-8%Pb-4%Si alloys. Strips of good castability were produced at a casting speed from 0.15 to 0.25 m/s and a velocity ratio from 1.5 to 4.5. Also, the cooling and solidification processes are strongly dependent on casting conditions. Therefore, by the effect of rapid cooling and inversion of band materials during casting the fine structure was formed and the gravity segregation was suppressed.View full abstractDownload PDF (1680K) -
Kazuyoshi Nakao, Yotaro Murakami, Kishio Hidaka, Yoshitaka Matsumura1984 Volume 48 Issue 8 Pages 836-843
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe machinability of leaded brass is well known to be affected by the microstructural properties of its matrix and microconstituents, particularly by the size and distribution of lead particles, and of course, by variation in machining conditions. The behavior of precipitation and coarsening of Pb particles during solidification and subsequent annealing of α- and β-single phase pure leaded brass was initially assessed by conventional metallographic methods. The size distribution was treated by a new statistical method. The results were later extended to α+β phase commercial leaded α+β brasses.
The size and distribution of Pb particles were quite different in the two types of brasses. In as-cast conditions, Pb particles in α-brass were much coarser and precipitated mainly on grain boundaries, while the distribution of Pb particles in β phase brass was relatively homogeneous and its size was much smaller.
The diffusion path and preferred nucleation sites of Pb atoms such as dislocations, sub-boundaries and grain boundaries were needed to the coarsening of Pb particles.
The solid solubility of Pb was likely to be larger in β-phase than in α-phase, and therefore, the distribution of Pb particles in β-phase was more homogeneous than in α-phase.
It was concluded that the size and distribution of Pb particles in commercial leaded brass are determined through the change in the grain structure of α and β phases.View full abstractDownload PDF (3800K) -
Tsutomu Kojima, Katashi Masumoto, Isao Nishida1984 Volume 48 Issue 8 Pages 843-847
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe phase transformation from a sintered eutectic alloy consisting of ε-FeSi and α-Fe2Si5 to β-FeSi2 has been studied by metallographic observations, by X-ray quantitative analysis techniques, and by measuring the resistivity and thermoelectric power corresponding to various annealing temperatures and times. It is found that the resistivity increases with increasing amount of β-FeSi2 and two maximum values occur at 1123 and 1133 K in the relationship between the resistivity and the annealing temperature. A drastic decrease in the resistivity can be also confirmed in the temperature range from 1123 to 1133 K. Two different reactions separately occur in the regions below 1123 and above 1133 K. Below 1123 K β-FeSi2 is formed mainly by the decomposition reaction, α→β+Si, and followed by the subsidiary reaction, Si+ε→β; above 1133 K β-FeSi2 is produced by the peritectoid reaction, ε+α→β. In the former reaction, the complete β-FeSi2 is obtained by an effective annealing at 1113 K for 3.6×104 s.View full abstractDownload PDF (1391K) -
Shin’ichi Towata, Sen’ichi Yamada1984 Volume 48 Issue 8 Pages 848-853
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe thermal expansion behavior of SiC fiber/Al alloy composites prepared by squeeze casting was studied between room temperature and 653 K. Pure Al, Al-Si, and Al-Cu alloys were used as the matrix metals.
The results are as follows:
(1) Hysteresis was observed in the thermal expansion and contraction curves.
(2) Transition points corresponding to elastic to plastic deformation of the matrix were observed; TA and TC in the expansion and contraction curves, respectively.
Transition points corresponding to plastic deformation to plastic flow of the matrix were observed; TB and TD in thd expansion and contraction curves, respectively.
TA and TC were dependent on the yield stress of the matrix.
(3) Variation of the thermal expansion coefficient between TA and TB was explained by modification of Turner’s equation.
(4) The average thermal expansion coefficient of the composites increased with Si or Cu content of the matrix as long as the yield stress of the matrix increased.
(5) The degree of the hysteresis increased with the temperature range investigated.View full abstractDownload PDF (737K) -
Hisashi Suzuki, Motohiro Kanno, Toshiyuki Ohsako1984 Volume 48 Issue 8 Pages 854-860
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe IIIa element such as Sc, Y, La, Ce or Sm was added to commercially available pure copper (containing sulfur impurity of 6 mol ppm) in the range up to about 800 mol ppm, and annealing characteristics of cold-worked coppers with additional elements were examined by means of hardness and electrical resistivity measurements and structural observations.
The half-softening temperature (TH) of cold-worked coppers with additional elements became commonly lower than that of pure copper; but in the case of Sc and Y, the TH became higher, when the additional amount exceeded a certain value. The lowering of TH was attributed to the reduction in the amount of sulfur impurity dissolved in pure copper, because additional elements trapped sulfur atoms to form their sulfides; this is the same as a previous result by the authors on Ti, Zr or V added copper. Cold-worked coppers with lowered TH as well as cold-worked pure copper containing sulfur impurity less than 1 mol ppm easily recrystallized during leaving at 303 K. On the other hand, coppers with additional Sc more than about 110 mol ppm showed markedly high TH. The reason would relate to the fact that precipitation on dislocation lines occurred in those alloys.View full abstractDownload PDF (1533K) -
Tetsuo Inoue, Kimiyoshi Goto1984 Volume 48 Issue 8 Pages 861-862
Published: 1984
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (856K)
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