All issues
Volume 37, Issue 6
Displaying 1-15 of 15 articles from this issue
- |<
- <
- 1
- >
- >|
-
Factors for Milling Rate and ContaminationMasamitsu Nishida, Hamae Ando, Koichi Kugimiya1990 Volume 37 Issue 6 Pages 827-831
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFactors of milling rates and contamination due to abrasion of balls were investigated in order to obtain ultrafine powder of pure piezoelectric ceramics.
Higher milling rates and lower contamination from balls were obtained for smaller balls. Calcined piezoelectric powders of 1μm in mean particle diameter were milled into the fine powders of 0.2μm for about 7 min. It was estimated that milling rates of this case (0.4 mm PSZ balls) was about 105 times as that of ball mill (ball size 10 mm). Even smaller ultrafine particles of 19 nm in mean particle diameter were obtained by milling for 90 min.View full abstractDownload PDF (283K) -
Shinya Nariki, Shigeru Ito, Kenji Baba, Nobuyuki Koura, Noboru Yoneda1990 Volume 37 Issue 6 Pages 832-836
Published: August 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSCo-containing γ-Fe2O3 is not prepared by solid state reaction of γ-Fe2O3 and CoO at high temperature but is prepared by wet method, because γ-Fe2O3 transforms into α-Fe2O3 above 400-500°C. However, γ-Fe2O3 is stabilized by the addition of potassium. To be reported here is a finding that the solid state reaction of acicular γ-Fe2O3 and Co(NO3)2⋅6H2O can be accomplished by the addition of K2CO3. When a mixture of γ-Fe2O3:Co(NO3)2⋅6H2O:K2CO3=5:1:0.2(molar ratio)was heated at 500-600°C, the coercivity of the product was above 1000 Oe. In addition, the magnetic property was also improved in the squareness ratio compared with the original γ-Fe2O3. The particle morphology of the obtained Co-containing γ-Fe2O3 was maintained acicular even after the heat treatment.View full abstractDownload PDF (1414K) -
Osami Kamigaito1990 Volume 37 Issue 6 Pages 837-844
Published: August 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSIdeal Strength, aid as a function of temperature was found to be approximated by the following formula:
σid≥σid=∫TxT3αE/(1-2μ)dT=3αE(Tx-T)/(1-2μ)
where Tx stands for the minimum value of transformation points (melting, sublimation, solid to solid, and brittle to ductile), and α, E, μ respectively for the coefficient of linear thermal expansion, Young's modulus and Poisson's ratio. The formula's error is less than 20%, expressed in the term of error compared with whisker's strength at RT. It was also compared with literature data on high temperature strength of sapphire monofilament, which proved the compatibility of the formula.
σid is estimated as 9 GPa for SiC and 3.5 GPa for Si3N4 at 1, 400°C, 1 GPa at 2, 200°C for SiC, and 1 GPa at 1, 700°C for Si3N4. These values prove the usefulness of the materials as high temperature gas turbine components. The formula tells also us that the ideal strength can be well approximated by a straight line regardless of material.
The Young's modulus plotted against temperature can be converted to Young's modulus plotted against strain, ε, by using ε=3∫α/(1-2μ)dT, which can not be given directly from experimental measurement due to the occurrence of fracture in the material. The tangent of the curve for MgO was proved to agree well with the value given by a classical solid state theory. The range of binding force acting across material surface was estimated by using the ideal strength, giving 0.5-1 nm for SiC and Si3N4 and 0.1-0.5 nm for MgO and Al2O3. The allowable atomic distance difference between neighboring layerd material in coherently multilayered films, which has no defect was also estimated to be less than 3% from the ideal fracture strain.View full abstractDownload PDF (515K) -
Masato Ito, Kanji Ueda, Tadaaki Sugita1990 Volume 37 Issue 6 Pages 845-850
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis study is to evaluate the thermal shock fracture reliability of partially stabilized zirconia components in laser heating. To elucidate the thermal shock cracking, the stress distribution and the thermal stress intensity factor are analyzed using the finite element method, and the results of analysis are compared with the thermal shock experiments by the laser heating. From the analysis, it seems that the maximum principal stress direction shifts from the Z-axis direction under the irradiated surface to the tangential direction outside the irradiated area. As the irradiation energy increases, the thermal stress intensity factor increases. On the other hand, some experimental results show that the thermal crack is initiated on the surface and propagates to the radial direction of the irradiated area, although the cracking is arrested after the critical length. Also, there is no crack initiation below the critical irradiation energy. These observed cracking behavior corresponds with the analytical results. Finally, the thermal shock fracture toughness is obtained from the critical irradiation energy and the thermal stress intensity factor analysis. The thermal shock fracture toughness is smaller than the fracture toughness in the same temperature.View full abstractDownload PDF (2344K) -
Tamotsu Ueyama, Takashi Yamamoto1990 Volume 37 Issue 6 Pages 851-856
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper treats the influences of the W-particle size and the firing temperature on the metallization bonding strength of the W-metallized alumina substrate co-fired in the wet reduced atmosphere. As the result, it has been revealed that there is an optimum firing temperature at which the metallization bonding strength becomes the maximum and that this temperature increases with the increase of the W-particle size.View full abstractDownload PDF (2718K) -
Wet CuttingEiichi Sentoku, Mikito Kumagai, Yoshio Fujimura1990 Volume 37 Issue 6 Pages 857-860
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSGlass ceramics consisting of fluor-phlogopite can be machined with tight tolerance with conventional metal working equipments and tools. The purpose of this paper is to study flow rate of cutting fluids and to find the mechanism of wear of tools with high efficiency.
The tests of cutting mica-ceramics were performed with K10 of sintered carbide tool by turning. It was observed that there were specific phenomena in worn surface of tool in wet cutting test. The main results obtained are as follow: (1) Wet cutting test might bring about high cutting speed of about 200 m/min. (2) The large width of worn surface increased roughness of machining surface. (3) When the value of cutting speed corresponded to that of the velocity of cutting fluid, there existed an area without fluid on the tool. (4) In this cutting test, tool life and surface roughness were better than in dry cutting test.View full abstractDownload PDF (3442K) -
Takeji Hachisuka1990 Volume 37 Issue 6 Pages 861-868
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn order to clarify the effects of sintering property of TiC and the dissolving of metallic impurities into lowchromium carbides, the sintering mechanism in TiC-Cr3C2 ceramic composite containing metallic impurities about 1 % was investigated as a function of Cr3C2 content.
It has been confirmed that densification of TiC was substantially improved by composing with Cr3C2. In the ceramic system, solid solution reaction of Cr3C2 into.TiC plays an important role in densification process. As a result completely dense bodies of TiC-Cr3C2 ceramic composite could be obtained by normal sintering below 1600°C. Metallic impurities were fully dissolved into low-chromium carbides before complete densification.
Cr3C2 content which is to be contained for the compact of complete densification and of full dissolution of metalic impurities were calculated on the basis of the previous and present results.View full abstractDownload PDF (4488K) -
Mitsuo Ueki, Yasuro Taniguchi, Kozo Kitamura, Hisashi Suzuki1990 Volume 37 Issue 6 Pages 869-872
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe two-phase TiC-34 vol%TiN-(7-14) vol% WC-7 vol%Co-3.5 vol%Ni alloys with different carbon contents were sintered in vacuum at 1500°C for 1 hr, cooled to room temperature and then annealed at temperatures ranged from 950 to 1250°C. It was found that the two-phase region of each alloy became narrower by the annealing, because of the precipitation of η or WC phases. The strength and cutting performance of the alloys affected by the annealing were examined. The reason why the alloys of as sintered state were not stable was in detail discussed.View full abstractDownload PDF (2340K) -
Hisashi Suzuki, Osamu Terada, Nobuyuki Kitagawa, Nobujiro Tsuchiya1990 Volume 37 Issue 6 Pages 873-877
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe microstructure of Mo2C or Mo2C and WC contained cermet was studied using optical microscope and SEM. It was found by SEM that extremely fine carbides which had never been observed by optical microscope, co-existed with the carbides with surrounding structure usually observed by optical microscope. Formation mechanism of the former carbides seemed to be the same as that of the latter carbides. It was demonstrated in nitrogen free cermets that, by means of decreasing the size of usually observed carbides, the structure finer than that of nitrogen contained cermets was easily obtained.View full abstractDownload PDF (6720K) -
Takashi Sakamoto1990 Volume 37 Issue 6 Pages 878-884
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe addition of small amount of special metal powders to Mo powder compact is known to be effective for getting high sintered density.
This paper describes the sintering characteristics of Mo powder compacts containing up to 0.8%Ni, 2.0%Fe and 0.6%Co powders, studied by use of density measurement and dilatometric methods. The result obtained is that Ni powder is quite more effective to densificate Mo powder compacts than Fe and Co powders. For example, the dimensional shrinkage of Mo-Ni powder compact starts at low temperature in comparison with Mo-Fe and Mo-Co powder compacts during heating up to 1573 K.
In order to reveal the diffusion processes of Mo powder compacts, diffusion couples of Mo-Ni, Mo-Fe and Mo-Co powder compacts are heated in vacuum up to 1573 K for 3.6 ks, and diffusion zones are examined using EPMA. The result is interpreted as that the mass flow in Mo-Ni diffusion couple is larger than that in Mo-Fe and Mo-Co diffusion couples.View full abstractDownload PDF (4129K) -
Takeshi Kaneko1990 Volume 37 Issue 6 Pages 885-892
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis report describes the effects of microstructure on mechanical properties of sintered W-Ni-Fe alloys. Tungsten heavy alloys have a useful combination of density and mechanical properties for several applications. The microstructure consists of a rounded tungsten phase (typically 50 μm in diameter) surrounded by a matrix phase containing dissolved tungsten. This paper focusses on the density, strength and ductility variations at high tungsten concentrations (91.3 to 97.0 wt%W).
Following the increase of W content, contiguities between W grains become higher, and when W content ex-ceeds 97.0 wt%, tensile strength and elongation decrease drastically. During tensile testing, cracks form on the surface of the specimens at W-W grain boundaries. The chemical additions are measured for heavy alloys which increase the solubility of tungsten in the matrix during sintering.
These results were discussed in terms of microstructures, size of fracture source, toughness of alloy, etc..View full abstractDownload PDF (5688K) -
Katsushi Kusaka1990 Volume 37 Issue 6 Pages 893-897
Published: August 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe objective of this work is to evaluate practically the potential of TiAl type P/M alloys for higher temperature structural applications. TiAl alloys mainly containing 1.4%Si (0.06%B), previously reported to have a good oxidation resistance, were investigated in the light of mechanical properties and plastic deformation (processing) at higher temperature.
The results were summarized as follows:
(1) TiAl type alloys investigated here have a ductile-brittle transition temperature in the vicinity of 800°C. The tensile behavior of TiAl specimens with and without Si content are much the same in the strength but fairly different in the strain for fracture at higher temperature.
(2) Flow stress (deformation) appears to be controlled superplastically (strain rate sensitivity m≥0.3) at lower strain rate in the refined grain size of a few μm, in both tension and compression, where its dependence on strain rate is influenced by Si additive, besides powder particle size and temperature as usual.
(3) Siliconizing TiAl P/M parts using the pack-cementation process may be recommended for almost no Si-in-fluence on mechanical properties, though Si alloyed to TiAl (B) lowers its tensile elongation at 1000°C or more. (Received January 18, 1990)View full abstractDownload PDF (3556K) -
Katsuhiro Nishiyama1990 Volume 37 Issue 6 Pages 898-902
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFabrication processing of TiB2 using pressureless sintering was studied with special emphasis on the effect of doping Ni7Zr2. The pore-free compacts were obtained by the addition of extreme small amount of Ni7Zr2 under the condition of heating at 2100°C for 1 h in vacuum (-0.13 Pa). The prosity of obtained specimens were below 10-3 volume percent.View full abstractDownload PDF (3713K) -
Katsuhiro Nishiyama1990 Volume 37 Issue 6 Pages 903-905
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSinterability of ultra-fine TiB2 powder with 0.6 μm prepared by magnesium-thermic reduction and of coarse TiB2 powder with 6 μm obtained from a commercial source were examined in pressureless-sintering under the condition of heating at 2100°C for 1 hr in vacuum. The blending effect of same powders on the sintered density was also investigated. The results are summarized as follows:
(1) Sinterability of fine powder with 0.6 μm is superior to coarse powder with 6 μm in pressureless-sintering.
(2) In the blending of fine and coarse powders the maximum value of the sintered density exsisits near the blending ratio of 0.7.View full abstractDownload PDF (3401K) -
Katsuhiro Nishiyama1990 Volume 37 Issue 6 Pages 906-908
Published: August 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMilling effect and contamination of titanium diboride powder by centrifugal-type ball-milling carried out in a WC-Co pot, with WC-Co balls were examined. The average particle-size of the as-recieved powder with 6μm decreased to 2.5μm by ball-milling for 3 hr. However, the contamination quantities of WC, Co and O2 remarkably increased with the lapse of the milling times.View full abstractDownload PDF (1520K)
- |<
- <
- 1
- >
- >|