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Volume 37, Issue 4
Displaying 1-15 of 15 articles from this issue
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Kohmei Halada, Hiroo Suga1990 Volume 37 Issue 4 Pages 492-499
Published: June 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSAtomizing parameters for cerntrifugal atomization of metal powder is theoretically investigated. Predictional formulas of average diameter by the disintegration mechanism of direct-drop-formation and stopping distance of atomized particle are derived as d=3.25 (ω2R)-1/2 (σ/ρ)1/2 and L5=1.29ρ1/4σ3/4ω-1R-1/4S-1ρg-1/2μg-1/2, respectively, where ω: revolution rate, R: radius of rotating disk, σ1: surface tension, ρ: density, μ: viscosity, and subscript g means the character of atmospheric gas. Cetnrifugal atomization diagram which shows the predominating mechanism of disintegration in a given atomizing condition is proposed. According to the diagram, metallic liquids are mainly located in the area of unstable column-formation-disintegration. It is predicted that the production of fine and uniform-sized metallic powder requests much more powerful rotating conditions than usual.View full abstractDownload PDF (526K) -
Katsuhiro Nishiyama1990 Volume 37 Issue 4 Pages 500-507
Published: June 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA newly developed method to prepare the ultrafine and size-controlled powders of TiB2 based on magnesium-thermic reduction was described. The preparation of TiB2 powders from TiO2 and B2O3 by magnesium-thermic reduction with MgO was examined in the temperature range from 500°C to 1000°C at Mg/TiO2 (molar ratio)=3 to 7 and at B2O3/TiO2=0.6 to 3 under flowing argon gas. The TiB2 was formed above 525°C. The TiB2 powders were washed with 10%NH4Cl water-solution, then 10%HNO3 water-solution, followed by water washing and drying. The average sizes of TiB2 powders thus obtained were in the range of 0.35-2.5 ftm with plate-like crystallite. The composition of TiB2 was approximately equal to the stoichiometry.View full abstractDownload PDF (4054K) -
Tetsuo Uchikoshi, Yoshio Sakka, Satoru Ohno1990 Volume 37 Issue 4 Pages 508-512
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSPalladium ultrafine powders were prepared by a hydrogen plasma-metal reaction method. After exposure of the prepared powders to air, gas evolution characteristics were examined by a temperature programmed desorp-tion method. Main evolved gases detected with a quadrupole mass spectrometer were H2O, CO and CO2. H2O and CO2 evolution peaks were appeared at temperatures of approximately 420 and 620 K. CO evolution peaks were appeared at temperatures of approximately 440, 510, 610 and 770 K. From the results of gas evolution behaviour after exposure to specific gases such as O2, CO and H2O, the origins of those peaks were discussed. The result was interpreted as follows; Palladium oxide (PdO), hydroxide (or its precursor) and impurity carbon existed on the surface. The evolution of H2O, CO and CO2 were due to the desorption of adsorbed species on the surface of the above compounds and the production by surface reactions.View full abstractDownload PDF (1205K) -
Masato Ohtsuki, Tohru Kohno1990 Volume 37 Issue 4 Pages 513-520
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSP/M forging of some rapidly solidified aluminum alloy powders was investigated in order to develop an inexpensive production process of high strength parts with complex shapes. The results of this study are summarized as follows:
1. The investigation of several P/M forging process for Al-18%Si alloy powders showed that mechanical properties of this alloy produced by the rigid die hot coining, followed by the rigid die hot forging are as good as those produced by extrusion.
2. Forging of Al-25%Si-3%Cu-1%Mg-1%Fe alloy and of Al-10%Fe-1.5%Mo-1%V alloy powders for production of wear resistance parts of and for heat resistance parts, respectively were investigated, the mechanical properties of those parts were as good as those produced by extrusion. In the case of production of complicated shape parts, the powder forging technique gives good production yield and cost savings in comparison with the powder extrusion, since the powder forging produces a part in its final form directly without machining step.View full abstractDownload PDF (3938K) -
Masato Imamura, Akira Yanagisawa, Hiroyuki Noguchi, Takeo Nakagawa1990 Volume 37 Issue 4 Pages 521-525
Published: June 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe production method of composite material having a large amount of porosity, relatively high-strength and small dimensional change during sintering has been proposed by the authors. The composite material can be obtained by sintering a mixture of metal powder and ceramic powder containing vanishing binder in the oxidizing atmosphere. And it is already employed as molds for vacuum forming of plastic sheets and molding of ceramics utilizing its permeability of air and water.
In this report, the sintering behavior and the mechanical properties of this composite material was examined with the use of iron powder as metal powder and mullite powder as ceramic powder. It was clarified that iron changes into a-Fe2O3 during sintering process, and the interaction of expansion and shrinkage of iron particles caused by oxidation and sintering produces relatively high strength and small dimensional change. The sintered body consists of twe layers, outer sintered hard layer has high strength and smooth surface, and inner non-sintered layer has large porosity and superior permeability. It is an advantageous feature for the mold of several forming and molding process.View full abstractDownload PDF (1987K) -
Influences of Grain-boundary in Two-particles System on ShrinkageHidetsugu Yagi, Yuzo Mori, Takasi Ide, Hirosi Kajita1990 Volume 37 Issue 4 Pages 526-531
Published: June 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe mechanism of shirinkage of a two-particles system was described. A paired spherical copper particles, which had been sieved so that the particle size is 53-45 μm, were sintered at 1223 K for 21.6 ks. It was clarified that the values of the amount of shrinkage dispersed between the theoretical values due to the variable-constantradius-interpenetration mechanism. It was also clarified that the scattering caused by the location of the grain boudary in the particles. The amount of shrinkage was at its maximum when the grain boundary existed in the neck between the particles and at its minimum when the grain boundary did not exist in the particles. Furthermore it was also shown to be possible, by energy calculation, for the grain boundary to be shifted or even eliminated depending on the ratio of each particle.View full abstractDownload PDF (1648K) -
Takashi Sato1990 Volume 37 Issue 4 Pages 532-538
Published: June 25, 1990
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMagnetic properties of cores formed from amorphous powder prepared by rapid quenching water atomiza-tion were studied. It was found that the increase of particle size and relative density of compressed core enhances d.c. magnetic properties and deteriorates a.c. magnetic properties, and that the magnetic properties depend on alloy compositions, which is not the pronounced tendency though. Furthermore, it was found that the variation of the coercivity can be explained by the magnitude of stress variation.View full abstractDownload PDF (373K) -
Masaru Yokota, Kohei Otani, Hideki Moriguchi, Hiroshi Nagai1990 Volume 37 Issue 4 Pages 539-545
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn fluence of cold rolling and annealing on the damping capacity of Fe sintered compacts, infiltrated with Pb was investigated by measuring internal friction. Infiltration volume ratio of Pb in sintered Fe compacts and draft of the specimens were up to 31.6% and 40%, respectively, and annealing temperatures were mainly 473 K. Results obtained were as follows:
(1) Internal friction of Fe sintered compacts, infiltrated with Pb increased with the increase of infiltration volume ratio of Pb. Work of cold rolling enhanced the internal friction of specimens remarkably, but in the case of low volume ratio of infiltrated Pb in Fe sintered compacts, the internal friction tended to saturate at a certain draft.
(2) Ultimate tensile strength of the specimens increased with the increase of draft, showed a maximum value, and then decreased with the increase of draft. Maximum value of ultimate tensile strength of the specimen tend-ed to shift to higher draft with the increase of Pb infiltration volume ratio.
(3) Internal friction of cold rolled Fe sintered compacts fell down to that before cold rolling with annealing time at 473 K. On the contrary, in the case of cold rolled Fe sintered compacts, infiltrated with Pb, higher inter-nal friction was retained to prolonged annealing time. The origin of decrease of internal friction by annealing is thought to be the recovery of internal stress in Fe matrix by cold rolling.
(4) Internal friction of Fe sintered compact, infiltrated with 30 vol%Pb and cold rolled at 40% of draft was approximately the same as that of flaky graphite cast iron. Whereas, ultimate tensile strength of this specimen was comparatively lower value of approximately 13 kgf/mm2.View full abstractDownload PDF (2501K) -
Keiichi Kobori, Mitsuo Ueki, Astushi Fukawa, Hisashi Suzuki1990 Volume 37 Issue 4 Pages 546-550
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSFor the application of milling ductile cast iron (FCD60), effect of microstructure and composition of substrate on cutting performance of cemented carbide tools coated with TiC by 2μm thickness were studied. It was suggested that the properties of coatings including adherence force to the substrate did not change, even when the structure and composition of substrate, and the surface-flatness of coatings were varied under a fixed content of binder. It was found that cutting performance of coated tools became superior, as the carbide grain size of substrate decreased.View full abstractDownload PDF (3180K) -
Junichi Matsushita, Hideo Nagashima, Hajime Saito1990 Volume 37 Issue 4 Pages 551-555
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSinterability, Vickers hardness and fracture toughness of TiB2-ZrO2 composites, with ranging from 10 to 60 wt% of 3 mol% Y2O3⋅ZrO2, produced by pressureless sintering at 1600°C to 1900°C were investigated. In the cases of the content of more than 40 wt%ZrO2 and the sintering temperature of more than 1700°C, the composites having relative density of more than 95% were obtained. The Vickers hardness of TiB250 wt%-ZrO250 wt% composite was about 15 GPa. The fracture toughness of TiB260 wt%-ZrO240 wt% composite was about 8.5 MPa√m.View full abstractDownload PDF (3128K) -
Takeji Hachisuka1990 Volume 37 Issue 4 Pages 556-561
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTo clarify solution mechanism of chromium carbide in TiC-Cr3C2 system, the compacts of carbide mixtures containing up to 12.5 mol% Cr3C2 embedded in carbon black were solution treated in vacuo at temperatures below melting point of Cr3C2.
Changes in lattice parameter of δ phase were occurred at temperature not more than 1300°C, due to solution of any chromium carbide. At the same time, the formations of Cr7C3 and Cr23C6 were observed. At higher temperatures Cr3C2 was disappeared because of complete solution, and δ phase showed constant lattice parameter. On the other hand, Cr7C3 and Cr23C6 were vaporized from the bodies resulting increased weight loss. But small amount of them remain in the bodies even after complete solution of Cr3C2 into δ phase.
It was confirmed from these results that the solute substance into δ phase in TiC-Cr3C2 system was cubic CrC. Approximate lattice parameter of CrC calculated based on the results was 3.88Å.View full abstractDownload PDF (2528K) -
Nobujiro Tsuchiya, Osamu Terada, Akira Sasaki, Hisashi Suzuki1990 Volume 37 Issue 4 Pages 562-565
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe microstructure, mechanical properties, etc. of WC-TiN-Co alloy were studied in comparison with those of WC-TiC-Co alloy. The WC-(0-15)mass%TiN (TiC)-10 mass%Co alloys were used as specimens. It was found that the amount of β (WC-TiC S.S) phases formed in the structure was less in the TiN contained alloy under the same addition amount of TiN or TiC, leading to the higher strength and lower hardness in the TiN contained alloy. The thickness of surrounding structure formed on the TiN core became markedly thin, probably owing to the negative affinity between nitrogen and tungsten at elevated temperatures.View full abstractDownload PDF (2257K) -
Yuji Katsumura, Toshiyuki Takahashi, Hirotaka Kiso, Hisashi Suzuki1990 Volume 37 Issue 4 Pages 566-570
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe Al2O3-TiC ceramics tools having 10-50 mass% TiC and different grain size were prepared by hot-pressing and the cutting performance of the tools were studied. The results obtained were briefly summarized as follows; The flank wear in turning tests of grey cast iron became smaller with decreasing TiC content and coarser TiC grain size, and that in the tests of ductile cast iron became smaller with increasing TiC content in no relation to TiC grain size. The tool having 20-30 mass%TiC and finer TiC grain size showed a superior resistance to flaking and an optimum cutting performance in turning test of alloyed tool steel. Discussion on flaking mechanism and the flank wear being different according to the kinds of works was given.View full abstractDownload PDF (3208K) -
Tomohiro Yanai, Atsushi Nakahira, Katsuaki Suganuma, Koichi Niihara1990 Volume 37 Issue 4 Pages 571-574
Published: June 25, 1990
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe influence of SiC dispersion on the sintering behavior and mechanical properties has been investigated for the B4C/SiC composite system. Nearly full dense composites were obtained by hot-pressing in an argon atmosphere at 2200°C for 30 min. The maximum bending strength and francture toughness were obtained for the compsite containing 20 vol%SiC prepared hot-pressed at 2200°C for 30 min. The bending strength increased from 620 MPa for the monolithic B4C to 750 MPa for the B4C/20 vol%SiC compositee and fracture toughness showed a similar trend from 3.9 to 4.9 MN/m3/2. Scanning electron microscopy was used to analyze crackmicrostructure interactions. Fractography indicated that the crack deflection and bridging by SiC particles might be the main toughening mechanisms for this composite system.View full abstractDownload PDF (3383K) -
Takeshi Sadahiro, Mitsuya Fujimoto1990 Volume 37 Issue 4 Pages 575-577
Published: June 25, 1990
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSCalculation of stress intensity factors (K) for the three-point bend specimen by the FEM was investigated. The accuracy and reliability of K calibrations from FEM for the ratio of support span to specimen width, S/W=8, agrees with the literature.
Stress intensity factor, KI for the three-point bending, single edge cracked beam specimen is
KI=σ√a(1.73-0.76α2+1.78α2-0.31α3+10.15α4)
for 0≤a=a/W≤0.7, where σ=stress, W=specimen width, α=crack length and S=support span (=2.5 W).View full abstractDownload PDF (162K)
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