All issues
Volume 46, Issue 4
Displaying 1-19 of 19 articles from this issue
- |<
- <
- 1
- >
- >|
-
Akira Tsukuda, Yoshihito Kondo, Kozo Yokota, Hisakazu Tomino, Jun-ichi ...1999 Volume 46 Issue 4 Pages 325-330
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSeveral kinds of sintered alumina with different porosity were produced by a cold press and a normal sintering using fine alumina powers. The grindarbility was undergone for these specimens using 2 kinds of diamond wheels with different abrasive grain sizes. To consider for effects of residual pore on grindarbility and grinding mechanism, normal grinding force were measured and ground surfaces were observed with SEM. The results were summarized as follows:
(1) The grinding mechanism of alumina with different porosity was changed by abrasive grain size of used grinding wheel. That is, in case of using grinding wheel with 800-mesh size, the grinding mechanism was dominated by plastic flow. On the other hand in case of using grinding wheel with 170-mesh size, that was governed by brittle fracture with large-scale cracks.
(2) The sintered alumina with high porosity gave a low normal grinding force, while the grinding mechanism was dominated by plastic flow in using grinding wheel with 800-mesh size.
(3) In chip generation by brittle fracture with large-scale cracks and plastic flow, using grinding wheel with 170-mesh size, the large-scale cracks were obstructed by residual pore, and the normal grinding force increased with increasing porosity at over 3.1vol% porosity.View full abstractDownload PDF (4849K) -
Hiroyuki Y. Suzuki, Kenji Shinozaki, Syunzo Tashima, Hidenori Kuroki1999 Volume 46 Issue 4 Pages 331-338
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSInfluence of microstructures on mechanical properties of high performance alumina is investigated focusing on density and mean grain size as microstructure characteristics. An alumina powder with a purity of 99.99 % and mean grain size of 0.22μm is dispersed in 25 mass % of ion-exchanged water, compacted applying a centrifugal force of 10, 000-20, 000 g for 3 ks, and sintered at 1423-1773 K for 0-172.8 ks in air.
It is shown that strength and hardness have one peak value respectively as microstructure develops during sintering, and those peaks appear on the same specimen with a relative density of about 99 % and grain size of about 1μm. For the specimens with density lower than 99 %, the strength and hardness decrease as density decrease, whereas for the ones with density higher than 99 %, those values decrease as grain size increase.
Furthermore, two empirical equations, which show the dependence of bending strength and hardness on both porosity and grain size, are derived by multivariate analysis. These equations provide contour lines which represent microstructures having the same strength or hardness on the grain-size/relative-density diagram. Superposing a trajectory line derived from grain size and density of various specimens on the diagram, the point where this trajectory and one of contour lines contact represents the best couple of grain size and relative density for the mechanical properties.View full abstractDownload PDF (670K) -
Akinori Katsui, Kazutoshi Iwamoto, Hideaki Ohtsuka1999 Volume 46 Issue 4 Pages 339-341
Published: April 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe diopside gels of the composition 25mol%CaO-25mol%MgO-50mol%SiO2 are prepared using a sol-gel route from Ca metal, Mg metal and tetrahydrofuran, and their structural changes with temperature are investigated using X-ray diffraction and Fourier transform infrared spectroscopy. The results indicate that the diopside glass and the glass-ceramics with the same silica network structure as the melted samples can be realized.View full abstractDownload PDF (207K) -
Haruki Kurokawa1999 Volume 46 Issue 4 Pages 342-347
Published: April 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe plate-like goethite particles were synthesized from a ferrous hydroxide solution with oxyalkylamine (OAA) in the course of oxidation. The ratio of the crystallite sizes of (010) and (110) direction, D010/D110, were determined and its correlation with particle morphology was discussed. The value of D010.D110 was 1.3 times higher than the value calculated from a0 and b0 using Gibbs' equation. It shows growth of the (100) plane was restricted due to adsorption of OAA. Titration of ferrous sulfate with NaOH in the presence of acicular or plate-like goethite particles show that formation of plate-like goethite particles is attributed to the prevention of crystal growth along c-axis. Synthesis of plate-like goethite is related to the preferred adsorption site of alcoholic part of OAA, since plate-like goethite particles have never been synthesized from ammonium. Adsorption of OAA on (100) and (001) decreases the rate of crystal growth of (100) and (001), especially when free OAA concentration exceeds 0.4mol/dm3.View full abstractDownload PDF (2569K) -
Jun-Gyu Kim, Koji Hayashi1999 Volume 46 Issue 4 Pages 348-357
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe compact of the mixture composed of (Ba, Sr)TiO3 ceramics powder and partially oxidized Ti powder (5.0mass% O) which was named TiO2(Ti) powder was found to show PTCR characteristic, when the compact was sintered in vacuum at 1623 K for 3.6 ks, and then heated in air at 853 K for 0.3 ks. Some properties of the sintered compacts were investigated.
The results obtained were as follows; (1)Obvious PTCR characteristic developed at TiO2(Ti) contents of 5-7vol%. (2)The transformation from tetragonal structure (ferroelectric phase) to cubic structure (paraelectric phase) of (Ba, Sr)TiO3 phase in the sintered and then annealed compact was suggested to occur only near the grain boundary and surface of the (Ba, Sr)TiO3 grains. (3)The dielectric constant ratio of ε ?? .540K/ε ?? t was 1/8, which was below the value (1/3) of (Ba, Sr)TiO3 air-sintered compact without TiO2(Ti), (4)The oxygen content of (Ba, Sr)TiO3 phase fairly decreased with increasing TiO2(Ti) content. (5)The densification and grain growth of the compact with 5-7vol% TiO2(Ti) hardly occured by the sintering. (6)The mechanism for the development of PTCR characteristic by the addition of TiO2(Ti) was discussed, based on Heywang-Jonker's model.View full abstractDownload PDF (2603K) -
Jun-Gyu Kim, Koji Hayashi1999 Volume 46 Issue 4 Pages 358-363
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of TiO2 contents (or thickness of TiO2 surface layer) in TiO2(Ti) powder and the grain size of Ti powder (or interparticle spacing of Ti particles) on the PTCR characteristic of the (Ba, Sr)TiO3 compact added with TiO2(Ti) or Ti, which were sintered in vacuum at 1623K for 3.6ks, were investigated.
The results obtained were as follows; (1)With increasing TiO2 content of the TiO2(Ti) from 12.5mass% to 25 and 37.5mass%, the range of metallic Ti content in TiO2(Ti) needed for the development of PTCR characteristic became 1.7 times larger at maximum. (2)For the sintered compact added with 2μm Ti powder, the range of Ti content needed for the development of PTCR characteristic was larger than that of the compact with 18μm Ti powder. (3)The above phenomena seemed to be due to the homogenization of oxygen ion concentration in (Ba, Sr)TiO3 particles which are caused by increasing thickness of TiO2 layer or decreasing interparticle spacing of Ti particles.View full abstractDownload PDF (528K) -
Jun-Gyu Kim, Koji Hayashi1999 Volume 46 Issue 4 Pages 364-370
Published: April 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe effects of sintering temperature (Ts; 1573-1748K) and time (ts; 0.6-14.4ks) and paste-baking-temperature or heating temperature (Tb or Th; 673-1273K; tb is 0.3ks) on PTCR characteristic were investigated for (Ba, Sr)Ti03 vacuum-sintered compact added with 3.9mass% TiO2(Ti) powder of 12.5mass% TiO2.
The results obtained were as follows; (1)PTCR characteristic developed at all TS (ts=3.6ks, Tb=853K). The electrical resistivity at room temperature (ρrt) showed a minimum value of 1.8x 102Ω⋅cm and the ρmax/ρrt showed a maximum value of about 106 at 1723K. (2)For all ts(Ts=1623K, Tb=853K), PTCR characteristic developed. The ρrt showed a minimum value of 2.6x 103Ω.cm at 7.2ks. (3) At Tb above 823K (Ts=1623K, ts=3.6ks), PTCR characteristic developed. The ρrt showed a minimum value of 1.0x l03Ω⋅cm. (4)The ρ-T curve of (Ba, Sr)Ti03+TiO2(Ti) vacuum-sintered compact was affected more largely by TS, ts and Tb than that of (Ba, Sr)Ti03 air-sintered compact. This was considered to be mainly due to the porous and fine grained microstructure in the former compact.View full abstractDownload PDF (535K) -
[in Japanese]1999 Volume 46 Issue 4 Pages 372
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (105K) -
Nobuaki Asada, Yoshiharu Yamamoto, Tadashi Igarashi, Yoshihiko Doi, Ko ...1999 Volume 46 Issue 4 Pages 373-377
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe powders of the mono-nitride and mono-carbonitride of W and Mo in VIa group of the periodic table of elements have not been commercialized. The main reason seems to be in the fact that the nitrides of W and Mo can not be synthesized by heating those metals in nitrogen gas of normal pressure. We tried to synthesize WN and W(C, N) by heating W powder and W+C mixed powder respectively in nitrogen gas of high pressure up to 190 MPa, and found that the powder of tungsten carbonitride, i.e., W(C, N) with nitrogen content up to about 20 at% could be synthesized, while WN could not.View full abstractDownload PDF (2174K) -
Teiichi Kimura, Hirotsugu Takizawa, Kyota Uheda, Tadashi Endo1999 Volume 46 Issue 4 Pages 378-382
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe products from Ti and Al metal powder via 28 GHz-microwave irradiation in air were investigated. The high frequency microwave (28 GHz in this work) is known to inhibit the electric discharge between particles in contrast to the low frequency microwave (2.45 GHz, for example) which induces the discharge that causes melting and/or joining of particles. The product from Ti powder was a-type interstitial compound with nitrogen and oxygen, and the content of nitrogen increased more rapidly than that of oxygen with increasing the irradiation time. In the case of Al, however, the contents of nitrogen and oxygen did not change during irradiation even heated up to the near melting temperature.View full abstractDownload PDF (2245K) -
Shigeaki Sugiyama, Koichi Asari, Hitoshi Taimatsu1999 Volume 46 Issue 4 Pages 383-389
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSReactive spark plasma sintering technique was applied to the synthesis of TiB2-TiNx composites from BN and Ti powders and the simultaneous consolidation of them. The nonstoichiometry of synthesized TiNx (x=0.6-1.0) was controlled by the change of the molar ratio of BN and Ti starting
powders and the resulting displacement reaction 2BN+(1+2/x)Ti→(TiB2+2/xTiNx. When x is 0.9 and below, the relative density of composites reached more than 99.6 % at a sintering temperature of 2000°C, because of the good sinterability of nonstoichiometric TiNx. For dense composites, Young's
modulus increased with x, but hardness decreased. The composite at x=0.9 had the highest values for Young's modulus (476 GPa) and fracture toughness (3.2 MPa m1/2)as well as good sinterability.View full abstractDownload PDF (5554K) -
Minoru Saito, Hiroo Ito, Hisashi Suzuki1999 Volume 46 Issue 4 Pages 390-395
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSome properties of WC-Co alloy as well as those of WC powder were studied relating to the carbonizing temperature of starting WC powder having the same grain size (2.5μm) . The WC powder carbonized at low temperature (L-WC) appeared to be pulverized more easily, compared with the powder carbonized at high temperature (H-WC). In other words, sintered alloys prepared by using L-WC showed often the micro-structure containing coarse WC grains which anomaly grew, suggesting that H-WC was more stable than L-WC. However, the H-WC seemed to be not necessarily advantageous, considering that the above result was changeable according to manufacturing history of the alloy.View full abstractDownload PDF (7172K) -
Kazuo Hamashima, Yasuo Shinozaki1999 Volume 46 Issue 4 Pages 396-401
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe Mo-Ni-B cermets were sintered in cans at various temperature by the hot isostatic pressing (HIP), to obtain the thick layers of the cermet securely bonded with steel. The bonding strength between cermet and steel HIPed at 1393-1523K was enough, but the mechanical properties of HIPed cermet were inferior to those of the vacuumsintered cermet. Especially, the fracture toughness (K1C value) was 65% of the latter.
The gas evaporation from the cermet was investigated during the sintering in Ar, and evaporation of CO and boride gas at 1300K-was clarified. In HIP process, this evaporation could not occur sufficiently. The remained carbon reacted with Ta, W or Mo, and the brittle complex carbides were formed certainly. It is thought that the poorness in mechanical properties of HIPed cermet is due to the excess of carbon, oxygen and so on.View full abstractDownload PDF (3908K) -
Shuichi Imasato, Shigeya Sakaguchi, Kazumitu Sugano, Yasunori Hayashi1999 Volume 46 Issue 4 Pages 402-408
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWC-Ni-Cr cemented carbides have been used even under corrosive condition because of its excellent corrosion resistance. The corrosion characteristics of this alloy in acidic and neutral solution had been investigated by immersion test and polarization test, and reported that corrosion resistance was improved in the low carbon and high Cr3C2 content alloy.
In this report, these corrosion tests were carried out in 1N NaOH solution. In immersion test, most of the dissolved element in the solution was W. The corrosion rate of WC-Ni-Cr was the higher with the lower carbon and the lower Cr3C2 contents, and these results were quite opposite to the tendency in acidic and neutral solutions. In polarization test, a large difference in polarization curves by the change of carbon content was not observed. The passivation region, which was observed in acidic solution, was not observed. In the vicinity of the corrosion potential, the corrosion current density (irorr) decreased with the increase in the carbon and Cr3C2 contents. The difference of corrosion rate with carbon and Cr3C2 contents of WC-Ni-Cr in 1N NaOH solution was considered to be caused by the difference in the amount of W dissolved in the binder Ni phase.View full abstractDownload PDF (4249K) -
Kenji Nakahara, Kei Tokumoto, Shigeya Sakaguchi, Yasunori Hayashi1999 Volume 46 Issue 4 Pages 409-416
Published: April 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe corrosion behavior of TiCx (X=0.55, 0.75, 1.0) and TiC phase in Ti-20mass%Mo-33mass%TiC alloy (TM-2) prepared through P/M technology was studied by corrosion test and electrochemical measurements. The immersion tests in 35%HCl and 3%NaCl solutions showed that the TiC phase in TM-2 alloy and TiCx (X=0.55, 0.75, 1.0) had excellent corrosion resistance in these solutions. The corrosion rates of TM-2 alloy and TiCx (X=0.55, 0.75, 1.0) in 5%HNO3 solution were over 10 times larger than that in 35%HCl solution because of dissolution of the TiC phase. From the potentiodynamic polarization curves, it was thought that the dissolution reaction of the TiC phase in TM-2 alloy and TiCx (X=0.55, 0.75, 1.0) in 5%HNO3 solution was not only an electrochemical reaction, but also a chemical reaction without the electron transfer. The main corrosion of TM-2 alloy was due to the dissolution of a-Ti phase in 35%HCl and 3%NaCl solutions, and the dissolution of TiC phase in 5%HNO3 solution, respectively.View full abstractDownload PDF (4279K) -
Cutting Force on Orthogonal CuttingEiichi Sentoku, Keiichi Eida, Atsushi Yamamoto1999 Volume 46 Issue 4 Pages 417-421
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn recent years, many ceramics have been developed for the uses to mechanical and electronic parts. The strength of alumina ceramic pieces is influenced by the residual crack of the machined surface which generates due to the action of force on the cutting process. The purpose of the study is to clarify the cutting mechanism of alumina green compact by the orthogonal cutting test. The cutting mechanism is discussed from a view point of the relation between specific cutting force and depth of volume or chamfer angle. In the cutting test by a new type testing machine, the cutting conditions are cutting speed 0.8m/s and depth of cut 0.05mm to 0.4mm. The chamfer angle of tool shape was varied from -20°to 5°in grinding. The main results obtained are follows; (1)The specific cutting force of the alumina green compact is affected by depth of cut volume and chamfer angle. (2)In small depth of cut, main crack propagates to inside of a granule, while other crack propagates along grain boundary in large depth of cut.View full abstractDownload PDF (4640K) -
Toshi Ishii, Nobuhiko Shima, Hiroshi Ueda, Masayuki Gonda, Shirou Okay ...1999 Volume 46 Issue 4 Pages 422-426
Published: April 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe microstructure of highly adhesive CVD coated α-Al2O3 films on cemented carbide cutting tool inserts have been investigated. These inserts are coated with a TiN layer, a MT(moderate temperature)-Ti(C, N) layer, a bonding layer, and a α-Al2O3 layer by using CVD.
SEM, TEM, and TEM-EDX were used to characterize the coatings, and following characteristics were found.
(1) The bonding layer is composed of Ti, C, N, and O or of Ti, C, and O. Its crystal structure is a face centered cubic one with a lattice parameter of 0.431nm.
(2) Each grain in the bonding layer continues crystallographically from the MT-Ti(C, N) layer grains.
(3) There are crystalline planes running between a grain of the bonding layer and a grain of the a-Al2O3 layer.
(4) Vertical-plane-shape projections are formed on the surface of bonding layer.
The last three characteristics are considered to be the cause for improved α-A12O3 layer adherence and longer tool life.
A crystallographical model shows that the above mentioned microstructure is consistent to X-ray diffraction result which shows the (110) plane of α-Al2O3 layer is oriented to the parallel of the insert's surface.View full abstractDownload PDF (6086K) -
Kamada Koichi, Toshiaki Sasaki, Ikuo Takahashi1999 Volume 46 Issue 4 Pages 427-431
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe have studied properties of the coating using grinded scraps of hard metal by the high velocity flame spray method. It was possible to make scraps thermal spray powders which was reduced at 1073K, and graphite was added so that the total content become 6mass%, and then presintered at 1473K in hydrogen. The coating using the scraps was similar to the coating using commercial powders in the microstructure and hardness of the coating. But the wear rate of the coating using the scraps was three times larger than the coating using commercial powders. This is considered to mainly result from the increase of the roughness of coating surface due to ununiformity of the particle size of the scraps.View full abstractDownload PDF (7052K) -
Yutaka Yanaba, Koji Hayashi1999 Volume 46 Issue 4 Pages 432-437
Published: April 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWe investigated whether our new estimating method of fracture toughness (KIC) by use of equation of σm-ψKIC Smf1/2 (σm; three point bending fracture strength, ψ, a material factor, Smf; total macroscopic area of bending fracture surface of all fragments for one test piece) is applicable to high speed steel (HSS) having KIC and σm values higher than those of WC-l0mass%Co hardmetal. It was found that a linear relation was observed between σm and Smf1/2 for three kinds of HSS specimens (SKH12, SKH51 and SKH55, according to JIS G4403), respectively, and that the values (KEIC) of fracture toughness (about 21, 20 and 18MPam1/2, respectively) estimated from the slopes of the regression lines between σm and Smf1/2 coincided well with the values (KMIC) of fracture toughness measured with SEPB method. Therefore, it was concluded that this new estimating method of KIC is also applicable to HSS.View full abstractDownload PDF (5671K)
- |<
- <
- 1
- >
- >|