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Volume 56, Issue 2
Displaying 1-14 of 14 articles from this issue
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Sadahiro Tsurekawa, Hideo Yoshinaga1992 Volume 56 Issue 2 Pages 133-141
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIt is well known that structural vacancies of carbon in nonstoichiometric titanium carbide form a long-range order structure in the carbon sublattice. For the superlattice structure of titanium carbide, two strucutres have been proposed; a cubic space group Fd3m and a rhomnohedral space group R\bar3m. However, it has not been definitely identified so far which of the two structures is the case. Therefore, in oder to identify the structure, we examined TiC0.59, for which superlattice spots are observed, by high resolution electron microscopy and micro-diffraction technique.
It is found that in each variant the superlattice has a periodicity along onle one ⟨111⟩ direction. From this result, it is concluded that the superlattice of titanium carbide is R\bar3m.View full abstractDownload PDF (3880K) -
Satoru Yamamoto, Masataka Mizuno, Atsushi Kirihata1992 Volume 56 Issue 2 Pages 142-147
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to study the influence of working and heat-treatment on work-softening of Al-Fe alloys, pure Al of 99.6, 99.99, and 99.999 mass%-purity, and Al-0.5, 1.0 and 1.7 mass%Fe alloys were prepared and investigated. Main results are as follows;
Work-softening was observed only in pure Al of 99.999 mass%-purity under all conditions of heat treatment, but not observed in pure Al of 99.6 and 99.99 mass%-purity.
In the case of Al-Fe alloys, work-softening was observed only in Al-Fe alloys annealed at 673 K after hot-rolling regardless of soaking conditions and recrystallized structures were observed.
The mechanism of work-softening was discussed based upon these results. Recovery and recrystallization was observed to occur at room temperature in 99.999 mass%Al due to the recrystallization-temperature lower than room temperature. On the contrary, in Al-Fe alloys, work-softening was observed only in the specimens in which Fe pre-dissolved in matrix was accelerated to precipitate due to hot-rolling and annealing under the existence of second phase, (Al3Fe). It seems that work-softening occurs by recovery and recrystallization because recrystallization-temperature is lowered remarkably by the precipitation of dissolved Fe accelerated by hot-rolling and annealing.View full abstractDownload PDF (961K) -
Masami Fujiwara, Tomoo Hirokawa1992 Volume 56 Issue 2 Pages 148-154
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSVickers microhardness tests were performed to find the crystallographic condition under which pencil glide occurrs only in the [001] direction of tin crystals impressing an indenter at room temperature. When a pyramid-shaped indenter was impressed on the (001) surface of a sheet crystal set on a quartz plate having a small hole, the impression on a top surface and the corresponding projection on a bottom surface with the same size and shape were formed. This phenomenon suggests that the deformation by the indentation is due to pencil glide in [001]{100} and [001]{110} slip systems. It was found that cross slip between the slip systems occurred because of wavy slip lines on the surface of projections. The size of impressions increased with increasing loading time and approached a critical value depending on applied load. The shear stress acting on the edge of impression corresponded to the yield shear strength of specimens.View full abstractDownload PDF (1243K) -
Masami Fujiwara, Tomoo Hirokawa1992 Volume 56 Issue 2 Pages 155-160
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIndentation tests were carried out to investigate the deformation mechanism of [001] pencil glide in tin crystals at the temperatures of 298, 333 and 373 K using a Vickers microhardness tester with a heating stage. To further examine the nature of the pencil glide, tensil tests were performed at various strain rates in the same temperature range. The steady state deformation of the pencil glide occurred in tension, in the range of strain rate and temperature. The size of the impression produced increased with increasing load and temperature. The activation energy and the activation volume of the pencil glide were 27∼41 kJ/mol and 2.1×10−25∼2.7×10−25 m3, respectively. It was concluded that the steady steate deformation due to the pencil glide was rate-controlled probably by cross slip between planes containing the [001] slip vector.View full abstractDownload PDF (1265K) -
Yutaka Hiraoka1992 Volume 56 Issue 2 Pages 161-167
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSEffects of rhenium and carbon additions on the fracture strength, ductility and fracture mode of powder-metallurgy molybdenum at low temperatures were investigated.
The results are summarized as follows:
(1) Low-temperature fracture strength of molybdenum indicated a maximum at 10 mass% rhenium. Rhenium addition enhanced both intergranular and transgranular fracture strengths. Carbon addition further enhanced the intergranular fracture strength in addition to the rhenium effect.
(2) Low-temperature ductility of molybdenum seemed to indicate a maximum at 10-13 mass% rhenium or more. This result is due to the lowering of yield strength as well as the increase of fracture strength. Further improvement of ductility by the carbon addition is due to the increase of intergranular fracture strength.
(3) The present results support the “rhenium effect” reported by Klopp et al. and Lundberg et al. Molybdenum containing 13 mass% rhenium and 30 mass ppm carbon indicated a certain amount of ductility even at a temperature as low as −196°C.View full abstractDownload PDF (764K) -
Kaoru Tada, Yoshimi Hisatsune, Tetsuo Fujiwara, Masao Yamamoto1992 Volume 56 Issue 2 Pages 168-174
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to develop a new surface modification utilizing vapor pressure differences among alloy elements, the vaporization of Mn, which has high vapor pressure, from Fe-Cr-Mn alloy was studied. Fe-20%Cr-20%Mn alloy was heated in various atmospheres at temperatures ranging from 1173 to 1373 K. Mass changes for the samples during heat treatment and vaporized materials from the samples were examined. Concentration profiles of the alloy elements were measured before and after heat treatment.
The decreases in sample mass during heat treatments were measured. The mass loss was larger at a higher temperature and for a longer time. The materials vaporized from a sample contained Mn more than 98%. The Mn concentration on the sample surface, heat treated in a closed tube, was 13-15%. On the other hand, the Mn concentration on the sample surface, heat treated under a constant pressure using a vacuum pump, was less than 1%. The mass loss for a specimen heat treated at a constant vacuum pressure increased with the square root of heat time and the surface Mn concentration did not depend on the vacuum conditions, temperatures or time. A concentration gradient under a surface was produced by Mn vaporization. The concentration profiles split into two regions. The Mn concentration gradient was lower at the surface site and higher at the base metal side. The decrease of the Mn concentration is considered to cause the phase change from gamma to alpha.
Under the heat condition for a constant vapor pressure, the activation energy for Mn vaporization is 248 kJ/mol and is consistent with that for Mn diffusion in alpha iron. On tha assumption that the vaporization behavor is controlled by the diffusion of Mn, the Mn concentration profiles were calculated. The results agreed with the measured profiles for Mn concentration using EPMA.View full abstractDownload PDF (1651K) -
Toshio Shimoo, Yoshiharu Kakei, Ken-ichi Kakimoto, Kiyohito Okamura1992 Volume 56 Issue 2 Pages 175-183
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe mechanism of oxidation of amorphous Si-Ti-C-O fibers has been investigated. Using two types of fibers with different content of oxygen, T-1(18%O) and T-2(13%O), the rate of oxidation has been measured with thermo-balance in an oxygen atmosphere at temperatures from 873 to 1773 K.
The mass of the fiber was increased by the oxidation. The amorphous fibers was unchanged even at higher temperatures. The amorphous silica was formed at lower temperatures, while the cristobalite was formed at higher temperatures. The kinetics of the oxidation followed the contracting-disc formula rate for diffusion control: (1−X)ln(1−X)+X=kt. The oxidation rate of T-1 was sharply reduced by densification of the porous oxide film at 1073-1173 K. The activation energies for the oxidation of T-1 were 23 kJ/mol at 873-1073 K, and 72 kJ/mol at 1173-1773 K, and for the oxidation of T-2 it was 70 kJ/mol at 873-1173 K. It is considered that the oxidation rate oxidation rate of Si-Ti-C-O fiber is cotrolled by the gaseous diffusion through the micro-pores in the oxide film.View full abstractDownload PDF (1668K) -
Tetsu Go, Katsuhisa Sugimoto1992 Volume 56 Issue 2 Pages 184-190
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain high corrosion-resistant oxide filmes, Al2O3 films were formed on the Pt substrate by low pressure CVD technique using aluminum-tri-isopropoxide (ATI, Al(OC3H7)3) and oxygen. The changes in the composition, structure, and corrosion resistance of the films were investigated as functions of deposition and heat-treatment temperatures. The structure of the films was amorphous at deposition temperatures in the range of 473-773K. The refractive index of the films increased with increasing deposition temperature, showing the increase in density of the films. The corrosion resistance of the films in 1.0 and 12.0 kmol·m−3 HCl and 0.01 kmol·m−3 NaOH solutions increased with increasing deposition temperature. Films deposited at 623 K were transformed into γ-Al2O3 and α-Al2O3 by annealing at 1073 K and 1173 K, respectively. The crystallized films hardly dissolved in a 12.0 kmol·m−3 HCl solution.View full abstractDownload PDF (891K) -
Effect of Surface Modification of Al Particles on Alloying in Electrodeposited Ni-Al Composite FilmsMasanobu Izaki, Hidehiko Enomoto, Takashi Omi1992 Volume 56 Issue 2 Pages 191-197
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSNickel-Aluminium composites were produced by electrodeposition from a diluted Watts-type Ni bath containing Al particles which were as-atomized, water-boiled, or plated with Ni-B alloy. Structural changes of Ni-Al particle composites on heating at 873 K were studied by X-ray diffraction and electron probe microanalysis. Thin Al(OH)3 layer of 0.5 μm thick was found between as-atomized Al particles and Ni matrix. One to 3 μm thick Al(OH)3 layers were also found between boiled Al particles and Ni matrix. Aluminium particles plated with Ni-B alloy directly adhered to Ni matrix. After heating at 873 K, preferential formation of Ni3Al phase was found as a result of reaction of Ni-B-plated Al particles with Ni matrix. Formation Ni3Al and NiAl phases were found along with Al2O3 particles as a result of the reaction of as-atomized Al particles with Ni matrix. However, any alloy phases did not form in composites of Ni boiled Al particles; instead, NiAl2O4 and NiO oxide layers formed between Al particles and Ni matrix, which inhibited the alloying.View full abstractDownload PDF (2428K) -
Tadakazu Ohnishi, Yasuhiko Noguchi, Masatoshi Nishiyama, Tsuyoshi Naka ...1992 Volume 56 Issue 2 Pages 198-203
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe structure of the alloy layers formed by hot-dip aluminum coatings on SUS316 stainless steel has been studied. The fundamental construction of the coating layer was found to be the SUS316-substrate/FeAl3/FeAl6/adhered-aluminum-layer. The formation of FeAl6 has not been reported so far. The thickness of the alloy layer was found to increase logarithmically with dipping time up to about 3 min in the case of coating at 700°C and thereafter to decrease gradually. The effect of coating temperature on the formation of the alloy layer was a little up to about 760°C, but at higher temperatures the thickness of the alloy layer decreased gradually. Diffusion heating treatment after coating resulted in the disappearance of the adhered aluminum layer and FeAl6, and in the formation of a mixture alloy layer of FeAl3 and Fe2Al5.View full abstractDownload PDF (1119K) -
Kohei Amano, Katsuhisa Sugimoto1992 Volume 56 Issue 2 Pages 204-209
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to obtain high corrosion-resistant oxide films, ZrO2 films were formed on Pt substrates by low pressure CVD technique using zirconium-tetra-isopropoxide (ZTI; Zr(O-i-C3H7)4) and oxygen at temperatures between 523 K and 773 K. The changes in the growth rate, structure and corrosion resistance of the films were investigated as a function of deposition temperature. The growth rate increased with increasing deposition temperature. The films deposited below 523 K were amorphous and those deposited above 573 K had monoclinic crystalline structures. The corrosion resistance of the crystalline films in 12.0 kmol·m−3 HCl and 10.0 kmol·m−3 NaOH solutions were much higher than those of amorphous films. The corrosion resistance of both the amorphous and crystalline films increased with increasing deposition temperature. The crystalline films showed no sign of dissolution in a 10.0 kmol·m−3 NaOH solution.View full abstractDownload PDF (965K) -
Suk-won Lim, Takao Choh1992 Volume 56 Issue 2 Pages 210-217
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effect of alloying elements on SiC particulate dispersion into molten magnesium was investigated. The incorporation time is defined as the time required for dispersion of solid particles into molten metal.
The incorporation time of SiC particles into molten pure magnesium was remarkably shorter and the particulate dispersion was more uniform than that of pure aluminum which was reported previously. The reason for this is the good wettability of SiC to molten magnesium, because of the low surface tension of molten magnesium. Moreover, through the reaction of Mg2Si formation from magnesium and SiC, the wettability is improved. The incorporation time was not influenced by the addition of Ce, Mn, Zr, Bi. Pb, Sn or Zn and was prolonged by the addition of Al, Cu or Si. By alloying with Ca, the incorporation time was also prolonged, and agglomerates of a large number of SiC particles were formed.View full abstractDownload PDF (1856K) -
Kazuhiko Magima, Makiko Hasegawa, Masaru Yokota, Shin Mishima, Hiroshi ...1992 Volume 56 Issue 2 Pages 218-224
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn this experiment, the microstructural changes during sintering of Ni-Zn ferrites used as the substrate for magnetic recording heads of thin films have been studied by SEM, XRD and XPS. The results obtained are sammarized as follows.
(1) No precipitates were recognized on the specimen furnace-cooled from 1423 K during sintering in air. ZnO precipitates, however, were observed at the grain boundary, especially at the triple point of the specimen furnace-cooled from 1453 K. These precipitates have been elongated along grain boundaries of the specimen furnace-cooled from 1453 K after holding at this temperature for 10.8 ks.
(2) While the above mentioned ZnO precipitates were not observed on the specimen sintered in O2 atmosphere, the grain coarsening was observed and the residual pores were also recognized inside the grain.
(3) The existence of Ni3+ ion was detected by XPS on the specimen prepared by HIP process at 1373 K for 18 ks under 120 MPa after sintering in air at 1453 K for 10.8 ks, where the ratio of Ni3+/(Ni2++Ni3+) was confirmed to be 3%.View full abstractDownload PDF (1527K) -
1992 Volume 56 Issue 2 Pages 225
Published: 1992
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPlease see pdf. Wrong:Fig. 2 Right:Fig. 2View full abstractDownload PDF (306K)
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