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Volume 36, Issue 2
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[in Japanese]1989 Volume 36 Issue 2 Pages 76
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (72K) -
Junichi Hojo, Osamu Sagawa, Hideyoshi Kimura, Akio Kato1989 Volume 36 Issue 2 Pages 77-80
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAl2O3 particles (mean diameter: 250μm) were coated with fine Ni particles (mean diameter: 5μm) by an agglomeration coating technique. The Ni content was 40-50vol%. The compact of the coated particles was sintered at a temperature of 1200°-1500°C. The use of the coated particles resulted in uniform dispersion of Al2O3 particles in Ni matrix. The pre-coating of Al2O3 particles with fine W particles (mean diameter: 1μm) was effective to improve the adhesion and wettability of Ni to Al2O3. Although the relative density of the sintered body was 70-80%, the dense composite was produced by the infiltration of molten Ni into the porous sintered body.View full abstractDownload PDF (4019K) -
Junichi Hojo, Shinji Asao, Atsushi Takamatsu, Akio Kato1989 Volume 36 Issue 2 Pages 81-84
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSiC or TiC particles having the average sizes of 0.27-5.8μm were codeposited in amorphous Ni-P alloy coating on mild steel substrate from chemical Ni plating bath and the wear resistance of the composite coating was investigated using emery abrasion paper as counter material. The wear resistance increased with an increase in the content of ceramics particles and showed the maximum at about 1μm for the size of ceramics particles. When the composite coating was heat-treated at 400°C, the wear resistance was remarkably improved, which may be caused by the crystallization of Ni and Ni3P phases. At 600°C, SiC composite coating was significantly degraded owing to the reaction of SiC with metal phase, whereas TiC composite coating was stable and kept the high wear resistance.View full abstractDownload PDF (2391K) -
Teruo Takahashi, Yasuhiko Hashimoto1989 Volume 36 Issue 2 Pages 85-89
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe mechanical alloying was carried out using pure electrolytic copper, amorphous boron and graphite powders as starting materials, and the solid solutions or ultra fine mixtures of Cu-B-C system were obtained. These powders were altered to a boron carbide-dispersion-strengthened copper by the subsequent heat-treatment in a vacuum below the temperature of 1323 K. The mean particle sizes of B4C precipitates are about 100-300 nm. The hardness values of B4C-dispersion-strengthened coppers increased with volume percentage of B4C. In the alloy with constant volume percentage of B4C, the maximum hardness value was obtained by the heat-treatment at 873 K. The separation of copper from the boron carbide-dispersion-strengthened copper did not take place by heat-treatment at 1323 K for 7.2 ks, so the present boron carbide-dispersion-strengthened copper is excellent in thermal stability than other particle-dispersion-strengthened coppers.View full abstractDownload PDF (5370K) -
Katsuhiro Nishiyama, Yoshiyasu Matsuda, Sokichi Umekawa1989 Volume 36 Issue 2 Pages 90-94
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of the addition of cobalt metal on the densification and the mechanical properties of TiB2-Co alloys under the pressureless-sintering as well as the hot-pressing conditions were examined. A dense TiB2-based alloy could be obtained by the addition of Co by either the pressureless-sintering or the hot-pressing process. The TiB2-2vol% and 6vol%Co alloys hot-pressed at the temperature from 1600 to 1800°C for 1 hr in vacumm under 6OMPa had the bending strength of 940MPa. The TiB2-l0vol%Co alloy pressure-less sintered at the temperature of 1800°C for 1 hr in vacuum had the bending strength of 64OMPa. The hot-pressed alloys with Co had a finer grain size compared with the pressureless-sintered alloys. The hardness of the pressur-less sintered TiB2-Co alloys were higher than that of TiB2. In the TiB2-Co system, Co metal changes completely to borides.View full abstractDownload PDF (1259K) -
Yasuhiko Hashimoto, Koichiro Koyama, Kenji Suzuki, Hiroshi Arai, Masan ...1989 Volume 36 Issue 2 Pages 95-99
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSo as to develop an alloy having high electrical conductivity and high-temperature-strength used for such as the spot welding electrode material, reaction sintering of Cu-Ti-B-C alloy was investigated by heating the mixed powder compacts prepared from copper powder, titanium hydride powder and boron carbide powder(fine or coarse) at temperatures higher than the melting point of Cu. Cu-TiC-TiB2 three-phase alloy was obtained when the atomic ratio of Ti:B:C in the starting mixture was near 2:2:1. When fine B4C powder was used, a frame structure composed of fine granular TiC and TiB2 crystals was formed in the Cu matrix; on the other hand, when coarse B4C powder was used and reaction-sintered at 1373 K, network structure of whisker- or fibre-type TiB2 was formed in the Cu matrix.View full abstractDownload PDF (2006K) -
Shiro Torizuka, Hiroaki Nishio1989 Volume 36 Issue 2 Pages 100-104
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSFull dense TiB2 sintered body containing ZrO2 between 0wt % and 40wt % was fabricated by glass encapsulation HIP method. Three point bending strength of TiB2 increased drastically by adding 10wt % ZrO2, compared to that of monolithic TiB2. Three point bending strength and Vickers hardness of TiB2-10wt %ZrO2 sintered body were 1.17GPa and 23.4GPa, respectively. Such an amount of ZrO2 was effective to fabricate high strength and high hardness of TiB2 sintered body.
However, three point bending strength decreased with increasing ZrO2 content. On the other hand, fracture toughness increased linearly with increasing ZrO2 content. TiB2-30wt%ZrO2 sintered body exhibited a high fracture toughness of 8.2MPam1/2. The amount of monoclinic ZrO2 increased with increasing ZrO2 content. This increase resulted in the decrease in strength, while the fracture toughness increased.View full abstractDownload PDF (3388K) -
Tomio Nisimura, Osamu Ishibashi, Kiyoshi Terasaki, Kei Tokumoto1989 Volume 36 Issue 2 Pages 105-109
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCemented carbides are used for bearing parts as well as cutting tools, but their sliding ability is not sufficient for severe conditions. In order to improve their ability, an introduction of pores into cemented carbide was attempted by means of addition of spherical resin to the milled powder. The specimens were fabricated by conventional methods. Their microstructures, mechanical properties and dynamic coefficient of friction were investigated. The results obtained were as followes:
(1) pores were homogeneously dispersed in specimens, and their shapes and dimensions corresponded to the added resins, (2) the hardness was decreased with the increase in pore content and transverse-rupture strength was decreased with the increase in pore content and their dimensions, and (3) the dynamic coefficient of friction between the pore dispersed cemented carbide and a conventional cemented carbide was smaller than that between conventional cemented carbides.View full abstractDownload PDF (1523K) -
Tomio Nishimura, Osamu Ishibashi, Shuichi Imasato, Kohjiro Takechi, Ke ...1989 Volume 36 Issue 2 Pages 110-114
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSWC-Ni cemented carbides tended to be cracked in vacuum presintering and also to have heterogeneous carbon distribution both in vacuum and H2 atmosphere presintering, compared with WC-Co cemented carbides. H2-CH4 atmosphere presintering of WC-(15, 18) mass%Ni was attempted to solve these problems. Carbon contents of presintered compacts were investigated as a function of CH4 concentration of (5.6-30)vol%CH4 and the distance from the surface (0-15mm).
Carbon contents of these two presintered compacts increased with the increase in CH, concentration, and homogeneous carbon contents were obtained in H2-(5.6-10)vol%CH4 atmosphere presintering.View full abstractDownload PDF (1253K) -
Masao Komai, Ken-ichi Takagi, Tadao Watanabe1989 Volume 36 Issue 2 Pages 115-120
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe corrosion behavior of sinterd Mo2FeB2 base hard alloys was studied in oxidizing and non-oxidizing acid solutions. The behavior of the alloys varies depending on its composition and corrosive environments. The addition of Ni increases the corrosion resistance in a non-oxidizing acid solution, whereas the addition of Cr increases the resistance in an oxidizing acid solution. Transition of the preferentially attacked phase of the alloy from a ferrous binder to a Mo2FeB2 complex boride occurs with increasing Cr content, associated with the active-passive transition of the ferrous binder in an oxidizing acid solution. The Mo2FeB2 base hard alloy has a good corrosion resistance through selection of a suitable composition for a given corrosive. The Mo2FeB2 base hard alloy has potential utilities as a corrosion-resistant material in various corrosive environments.View full abstractDownload PDF (3393K) -
Chip ShapeEiichi Sentoku, Takahiro Sato, Yoshio Fujimura1989 Volume 36 Issue 2 Pages 121-124
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMachinable ceramics can be machined to tight tolerance with conventional metalworking equipment and tools. These machinable ceramics have been widely applied to electronic parts, medical appliances, etc.
The purpose of this paper is to study roles of chip shapes and to investigate the cutting mechanism to the chip shape in high efficient cutting. The main results obtained are as follows: (1) Using the cutting tool with large nose radius, high efficient cutting can be performed and the tool life becomes long. (2) Decrease in cross-sectional area of uncut chip or the mean grain size of chip, makes the specific cutting force larger. (3) A few consideration of the chip formation mechanism can be obtained from the study of chip shapes.View full abstractDownload PDF (3361K) -
Eiichi Sentoku, Yoshio Fujimura1989 Volume 36 Issue 2 Pages 125-129
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSSince cBN tool shows good cutting performance to the hardened steel, the authors has been considering to replace the grinding by the turning.
This paper presents new results of cutting tests performed on the orthogonal cutting with the cBN tool. Machining tests were conducted to find the most effective cutting conditions with long tool life for the finishing. Cutting speed was varied from 0.8 m/s to 3.3 m/s and rake angle ranged from -10° to -35°. The principal studies were carried out the relationship between edge shape and cutting mechanism, especially 'WHITE-LAYER' on the sawtoothed chip often observed at high cutting speed with large negative rake angle. The main results obtained are as follows: (1) The main cutting force and chip thickness has few influences to a variety of rake angle, and the cutting ratio comes near 1. Therefore, adoption of large negative rake angle for protection of the edge breakage has good advantages in the finishing. (2) It is concluded that the white-layer consists of an amorphous layer which is produced as a result of severe plastic defomation and rapid cooling.View full abstractDownload PDF (3253K) -
Keiichi Kobori, Mitsuo Ueki, Atsushi Fukawa, Hisashi Suzuki1989 Volume 36 Issue 2 Pages 130-133
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe strength and cutting performance of the cemented carbide tools coated with titanium carbide(called TiC) by CVD process were studied in relation to the amount of βtWC-TiC-TaC solid solution) and the grain size of substrate carbides. It was found that the strength of coated alloys having the same amount of βt and the same thickness of coated layer was improved with increasing grain size of carbides. The result of milling test for 2μmTiC-coated alloy showed that the resistance to fracture of cutting edge was improved and the resistance to flank wear was decreased with decreasing the amount of βt and increasing grain size of carbides. It was suggested that CVD-coated cemented carbide tool showing a long life time could be obtained, when the amount of βt and the grain size of carbides of substrate are controlled appropriately.View full abstractDownload PDF (1094K) -
Nobujiro Tsuchiya, Osamu Terada, Hisashi Suzuki1989 Volume 36 Issue 2 Pages 134-138
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe microstructure, hardness and adhesive strength of titanium carbide (TiC) layer coated on WC-10mass%Co alloy were studied as a function of carbon content of the alloy substrate.
The W and C atoms in the substrate were apt to diffuse into TiC layer during CVD, as the carbon content of substrate increased. This resulted in the formation of network structure of TiC-WC solid solution (β-phase) inside the layer near the interface, and also in the formation of thin cobalt layer and micro-pores inside the substrate near the interface. It was clearly shown that the hardness and adhesive strength of TiC layer were varied according to the carbon content of the substrate.View full abstractDownload PDF (4285K) -
Kazuo Higuchi, Shoji Noda, Osami Kamigaito1989 Volume 36 Issue 2 Pages 139-142
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSIn the present study, we investigated deposition of diamond films on both Si substrates pre-treated with diamond powder by an ultrasonic vibrator and also further ion-implanted. The pre-treatment with diamond powders increased a density of diamond nucleation on Si substrate by five-order of magnitude against to the untreated substrate. 280keV Ar+ ion implantation at 90K to the pre-treated substrate significantly reduced the density of the diamond nucleation while the implantation at 773K scarcely affected the density. It is proposed that healing of micro-flaws, which are thought to work as the nucleation sites, is an important mechanism to reduce the diamond nucleation density by ion implantation.View full abstractDownload PDF (2954K) -
Hirohide Nakamatsu, Kazuhiko Hirata, Shichio Kawai1989 Volume 36 Issue 2 Pages 143-146
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEpitaxial SiC films grow on α-Al2O3(0001) substrates under the irradiation of UV light from an ArF excimer laser or a deuterium discharge lamp. The irradiation of laser beam is effective to assist the formation of the interface between the SiC film and the Al2O3 substrate. Epitaxial SIC films which are very adhesive to the substrate, are grown at a low temperature. Irradiation to the substrate is essential to these effects. At an initial stage of film growth, nucleation density is increased and the contact between SiC and α-Al2O3 is improved by the irradiation. The irradiation of the light with the wavelength shorter than about 380nm is effective to obtain the adhesive epitaxial films. This wavelength is discordant with the light absorption range for the reaction gases(Si2H6, C2H2), Al2O3 and SIC. The light absorbents which exist only at the substrate surface (as possible examples, SIC clusters and surface states of Al2O3) improve the film growth on the substrate.View full abstractDownload PDF (1248K) -
[in Japanese]1989 Volume 36 Issue 2 Pages 148
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
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Tsuneta Inaba, Shozo Nagai, Osamu Iwatsu, Norihiko Nakanishi, Toshihik ...1989 Volume 36 Issue 2 Pages 149-152
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe making process of Cu-Zn-Al shape memory alloys by powder-metallurgycal (P/M) method were studied, being expected that the functional properties would be superior to those of normal method such as melting method. The results obtained were as follows: 1) The properties of the sintered compact obtained by master-alloyed method were better than those by both elemental and pre-alloyed methods. 2) The relative density of the alloy by the master-alloyed method attained to about 98% when it was added 0.1% of A1F3 as a sintering accelerator and was sintered at 1173K. 3) The grain size of the alloy by P/M method was 20-100um, and was much finer than that by the normal method.View full abstractDownload PDF (2173K) -
Norihiko Nakanishi, Toshihiko Shigematsu, Tsuneta Inaba, Shozo Nagai, ...1989 Volume 36 Issue 2 Pages 153-157
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPurposes to prepare Shape Memory Alloys by the powder-metallurgical(P/M) method are to precisely control the alloy composition and to obtain fine grain sizes in especially Cu-based alloys. These P/M-SMA's are useful for the high damping property and complicated shape materials. The authors deal with the following items using P/M Cu-25Zn-9.25Al(at%) alloys: 1) Comparison of shape memory characters between the melted(normal process) and the P/M-process alloys, i.e., the transformation temperatures(Ms, Mf, As and Af) and their hys-teresis, and stress-strain relations upon shape memory and superelastic treatments and also upon cyclic(load-unload) treatments. 2) Effect of aging treatment on the transformation temperatures.
The experimental results obtained are briefly discussed.View full abstractDownload PDF (210K) -
1989 Volume 36 Issue 2 Pages 158
Published: 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (20K) -
[in Japanese]1989 Volume 36 Issue 2 Pages 160
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (53K) -
Nobuyasu Kawai, Hiroshi Takigawa1989 Volume 36 Issue 2 Pages 161-169
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA new method to produce bimetallic cylinders for injection molding of engineering plastics has been developed. Co based alloy was designed to improve corrosion-and wear-resistance, and fine powders having this composition were made by Ar gas atomization. Prealloyed powders were bonded to the inner surface of the cylinder body by the HIP process.
Currently, these new cylinders are actually operating in the Japanese engineering plastic industry and are showing a good performance.
And further, a new valve-body was produced by the same HIP process and the various properties were also discussed.View full abstractDownload PDF (4713K) -
Hiroji Ogawa1989 Volume 36 Issue 2 Pages 170-173
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIt has gone already 1.5 decade, since the MIM⋅Process had been introduced as a new noteworthy Powder Metallurgical Technology in US., APMI & PMIF had established MIM Assoiation in 1987. In general MIM Process has many superiorities in products; free in geometry; considerable productivity; high material qualities due to the high sintered density by using fine quality powders. In the otherhand MIM Process has some important demerits such as: troublesome debindering: limited dimensional accuracy caused by large sintered shrinkage: weight limitation and price problems of products because of expensive raw material powders. Here it is important to develope the MIM Process, to reconsider the metal powders and the sintering, refering past studies, standing back to the original point of Powder Metallurgy. Initial consideration is begun from the classification of recent MIM products, and are added some recomendations for the developement of Metal Injection Molding as the conclusion.View full abstractDownload PDF (280K) -
Characterization of Debinding ProcessYoshitaka Ohyama, Norio Kasahara, Yasunari Kaneko, Hiromichi Iwasaki, ...1989 Volume 36 Issue 2 Pages 174-177
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe Alumina powder mixed the each organic binder(A, B, C) were molded rod like test pieces by a screw injection-molding machine. The binder(A) consisted of polystylene (PS), polybutylmethacrylate(PBMA), stearic acid(St) and paraffin wax(WAX); (B) consisted of PS, PBMA, St, WAX and atactic polypropylene(APP); (C) consisted of PS, PBMA, St, APP. The test pieces which were made of the binder(B), (C) cracked easily during the debinding process, but those which was made of the binder(A) didn't crack. From the above fact, one of the reasons was shown that owing to the radical thermal decomposition of the APP at the about 200°C, the rate of debinding of the binder(B), (C) were rapider than that of binder(A). So that it was clear that the causing cracks within the test pieces resulted from the rising rate of debinding at about 200°C.View full abstractDownload PDF (178K) -
Selection of BinderNorio Kasahara, Yoshitaka Ohyama, Yasunari Kaneko, Hiromichi Iwasaki, ...1989 Volume 36 Issue 2 Pages 178-182
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFor the injection molding of metallic powder, the binder which consists of polystylene, polybutyl-methacrylate, wax, and stearic acid was used. When the molding compound was injected in the mold, wax was separated from the other binder. To prevent the separation of wax, the addition of APP(atactic polypropyrene) was very effective. Because APP has good compatibility with other polymers, APP plays a roll to bind wax with other binder. The effect of the addition of APP varied with the ratio of APP and wax, how much molecular weight APP has, and what structure APP has. The green part was debinded by the thermal way, heating from room temperature to 320°C in the air for 49 hours. The debinded part was sintered at 1320°C under a vacuum of 10 ?? Torr for 2 hours. The sintered part has a relative density of 95-96%. A little decrease of Cr was caused by this debinded and sintered process. But after the surface protection was given, it doesn't matter to the corrosion resistance.View full abstractDownload PDF (243K) -
Yasunari Kaneko, Kei Ameyama, Hiromichi Iwasaki, Masaharu Tokizane, Yo ...1989 Volume 36 Issue 2 Pages 183-187
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe injection molding of S-50C powder(19.7μm in average diameter)was carried out with the SA(special-acrylate copolymer)-APP(atactic polypropyrene)-Wax binder system.S-50C powder was mixed with the binder at 140°C.The molding composition was 54.2%S-50C powder, 19.5%SA, 10.7%APP, 11.3%Wax and 4.3%dibutyl phthalate in volume.The green body was debinded during heating from room temperature to 320°C in the air.The debinded specimen was sintered at 1100 to 1220°C under vacuum of 10-4 Torr.The main results are summmarized as follows:
1)This binder system has good mixing, molding and binder removal characteristics.
2)A specimen sintered at 1220°C for 90min has a relative density of 92.2% and shows average tensile strength of 23.8Kg/mm2
3)Sintered specimen are observed decarburization from surface under vacuum sintering.View full abstractDownload PDF (2230K) -
Yoshihiko Seyama, Eiji Horikoshi, Tsutomu Iikawa, Kaoru Hashimoto, Tak ...1989 Volume 36 Issue 2 Pages 188-191
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSMetal injection molding was used to produce near-net-shape parts made of an Fe-6.5%Si soft magnetic alloy having a low workability due to its high degree of hardness and brittleness.
We attempted metal injection molding using powders with the larger, 20 μm (-350 mesh) average particle size generally used in powder metallurgy. We studied the effects of different powder properties on kneadability and moldability. Results of experiments showed that the 20 μm average particle size can be used in injection molding if given a high tap density.View full abstractDownload PDF (2976K) -
Kei Miyamoto, Yuzuru Takahashi, Suguru Inamura, Hiroki Miyamoto1989 Volume 36 Issue 2 Pages 192-194
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA transparent mold with a window of a strengthened glass was devised. This mold enables to visualize the dynamic flow of the Si3N4 slurry through the glass window by VTR. A turbulent flow of the slurry was observed, when the flow rate increses abruptly. It was made clear that this turbulence gives rise to a lot of voids in the Si3N4 green compact, which result in low Weibull constant of bending strength of Si3N4 sintered body.View full abstractDownload PDF (4269K) -
Takaaki Matsuoka, Jun-ichi Takabatake, Akihiko Koiwai, Yoshinori Inoue ...1989 Volume 36 Issue 2 Pages 195-198
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSFiber orientation induced during injection mold filling of fiber filled thermoplastics causes material properties to be anisotropic and molded parts to warp. Predicting fiber orientation is important for parts and mold designs to produce sound molded parts. A computer program has been developed to predict planar fiber orientation in thin walled molded parts by using Folgar and Tucker's orientation model for concentrated suspensions. Computed result was compared with experimental one for an injection molded square plate of glass fiber reinforced polypropylene.View full abstractDownload PDF (209K) -
[in Japanese]1989 Volume 36 Issue 2 Pages 200
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (64K) -
Takeshi Sadahiro1989 Volume 36 Issue 2 Pages 201-206
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTo measure the fracture toughness, KIC of a material, the specimen must have a pecrack of sharp, simple geometry. It is very difficult to use the fatigue precracking method for brittle materials. Therefore, an alternative precracking method is needed and various methods had been examined. But, these methods required a special equipment and a selected specimen to obtain the meaningful fracture toughness value. So, a new simple and effective testing method for brittle materials has been developed. This indentation precracking method (Bridge Indentation method) utilizes a two-step preparation process (primary precracking and pop-in cracking). The fracture toughness values obtained show small scattering and are reliable.View full abstractDownload PDF (325K) -
Titanium Diboride CeramicsKatsuhiro Nishiyama, Hideyuki Someya, Sokichi Umekawa, Mamoru Omori1989 Volume 36 Issue 2 Pages 207-213
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper is concerned with the developments for the application of indentation techniques to determine fracture toughnesss of the hot-pressed boron carbide - titanium diboride ceramics. The single edged pre-cracked beam(SEPB) technique was chosen as the primary method to study in detail the effects of experimental parameters on K1c determinations for the hot-pressed boron carbide - titanium diboride ceramics. Obsevations of the induced crack in the specimens and estimation of the fracture toughness data obtained for the same specimens by the SEPB technique provided a suitable calibration of the indentation coefficient. The calibrated equation of indentation toughness are also demonstrated to be capable of predicting the median and radial growth characteristics observed in other ceramic materials.View full abstractDownload PDF (2656K) -
Toshihiko Nishida, Takeshi Shiono, Atsuo Nagai, Tomozo Nishikawa1989 Volume 36 Issue 2 Pages 214-216
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFracture toughness(K1c) of polycrystalline silicon carbide was evaluated using a single edge precracked beam(SEPB) method. A Knoop indentation microcrack was introduced into a specimen, and then a sharp pop-in precrack was developed by applying the bridge indentation technique. The precrack length was varied by changing the indentation load and/or the support groove width. The precracked specimens were fractured by three-point bending under a cross-head speed of 0.5mm/min at room temperature. K1c values for silicon carbide decreased with the increase of the indentation load. The indentation load dependence on the K1c values was discussed from the consideration of the residual stress around the indentation crack.View full abstractDownload PDF (169K) -
Akira Kawasaki, Ryuzo Watanabe, Hee Don Jeong, Hideaki Takahashi1989 Volume 36 Issue 2 Pages 217-221
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis paper reports an evaluation of the fracture behavior of metal/ceramic composites by small punch test. A specific material combination of a stainless steel and a zirconia was employed. Disk specimens for small punch test of metal/ceramic composite having definite metal/ceramic ratios were prepared by powder metallurgical method. Small punch test was conducted at room temperature. A specific transition behaviors from ductile to brittle fracture have been found to depend on the composition and microstructure. The ductile-brittle transition was observed to take place at a zirconia volume fraction of 0.4-0.6. The microstructural investigation of the fracture behaviors
was also made. It has been found that fracture behaviors are strongly dependent on the continuity of the stainless steel phase; that is, the skeletal to dispersive structural transition determines the fracture behaviors.View full abstractDownload PDF (2278K) -
Hideshi Miura, Masahiro Kai, Tadatoshi Honda1989 Volume 36 Issue 2 Pages 222-228
Published: March 25, 1989
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSEffects of alloying elements and heat treatment on the fracture toughness of sintered alloy steels have been investigated by means of three-point bending test, optical and scanning electron microscopies.
The fracture toughness (KO) of sintered steels increased with an increase of carbon content. In Fe-Cu-1%C, the KO was somewhat increased by an addition of 1%Cu, but it was constant with Cu above 1%. This is explained in terms of the formation of pores at the original location of the Cu powders. On the other hand, the KO of Fe-Ni-1%C showed a peak with an addition of 3%Ni. This is attributed to the appearance of Ni rich martensitic phase with Ni above 3%, although Ni is effective to the densification of iron compacts. The KO of these compacts were also increased with yieled strength by heat treatment.
A remarkable feature of the obtained results was that the KO increased simultaneously with the yield strength, which was contrary to the general behaviour of wrought materials. The origin of this mechanism is clarified from SEM observation, that is, the fracture process of sintered alloy steels is the necking down between the crack tip and adjacent pores.View full abstractDownload PDF (2877K) -
Haeng-Nam Ko1989 Volume 36 Issue 2 Pages 229-232
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA four-point bending test was carried out on sintered Si3N4 at room temperature to investigate the effect of pre-compression on the static strength of ceramics. The static strength distribution for virgin specimens was compared with that for pre-compression specimens by Weibull plot, and the fracture features of both specimens were examined. It was known that the strength of virgin specimens was not decreased by pre-compressive stress. On the contrary, the pre-compressive stress seemed to increase the strength of virgin specimens under a certain condition.View full abstractDownload PDF (2031K) -
[in Japanese]1989 Volume 36 Issue 2 Pages 233-238
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSFormula to estimate the ideal strength of brittle material was derived from the consideration of the relationship between the fracture under uniform tensile stress and the transformations of the material, sublimation, melting and solid to solid transformation. The validity of the formula was examined by comparing the ideal strength with the fracture stress of whiskers. The accuracy of the formula was within ± 30% for the material whose ionicity is less than 50%. The fracture stress of the whisker whose ionicity is more than 50% is about 1/3 to 1/5 of the value given by the formula. The discrepancy in the ionic materials seems to come from the possible occurence of shear fracture in the materials. From the formula, mullite is concluded that it would have the fracture stress similar to silicon nitride.View full abstractDownload PDF (339K) -
Atsushi Nakahira, Koichi Niihara, Junn Ohkijima, Toshi Hirai1989 Volume 36 Issue 2 Pages 239-242
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAl2O3/Si3N4 composites were prepared by hot-pressing the mixtures of finer Al2O3 and Si3N4 powders at 1600°C in N2 atmosphere. Transmissiom electron microscopic observation revealed that most of Si3N4 particles were dispersed within Al2O3 grains. The fracture toughness of this nanocomposites increased from 3.25 to 4.6 MPam1/2 and the fracture strength showed a similar trend from 350 to 530 MPa. The most striking finding in this composite system was that the degradation in hardness and strength at elevated temperatures were significantly improved by the nanoscale dispersion of Si3N4 into the Al2O3 grains. The effcts of Si3N4 dispersions into Al2O3 grains on the mechanical properties such as hardness, toughness and strength were discussed.View full abstractDownload PDF (1339K) -
Koichi Niihara, Takeshi Hirano, Atsushi Nakahira, Katuaki Suganuma, Ka ...1989 Volume 36 Issue 2 Pages 243-246
Published: March 25, 1989
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe Si3N4, /SiC composites were prepared by hot-pressing the Si-C-N powder pre-cursors from CVD. Transmission electron microscopic observations indicated that SiC particles finer than -0.1μ m were dispersed mainly within the matrix grains whereas large SiC dispersions were located at the grain boundaries. No apparent impurity phase was observed at the interface of Si3N4, and SiC. The coefficient of thermal expansion of the composites increased with SiC content according to the composite law, while the thermal conductivity decreased up to about 20 vol% SiC and increased with the increase of SiC dispersion. Thus, the slightly decreased-thermal-shock-fracture-resistance, ΔTc, was observed for the composites as compared with pure Si3N4, although the fracture strength (also toughness) was improved significantly by the SiC dispersions.View full abstractDownload PDF (1678K) -
Haruo Doi, Shoji Noda, Tatsumi Hioki, Osami Kamigaito1989 Volume 36 Issue 2 Pages 247-252
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESS400KeV Ag+ ions were irradiated to the (100) surfaces of 9.5m% Y2O3 stabilized ZrO2 with the doses ranging from 5×1015 ions/cm2 to 5×1017 ions /cm2 at room temperature in order to investigate the correlations between the state of implanted Ag and the suppression of crack initiation.
1) Ag precipitated as particles in orienting the (200) face of Ag. The sizes of the Ag particles were ranging from 2nm(5×1016ions/cm2)to 11nm (5×1017ions/cm2).
2) Knoop hardness of the surface of ZrO2 increased by about 20-30% by Ag+ ion-irradiation at the doses less than 5×1016ions/cm2 and decreased at the doses larger than 1×1017ions/cm2.
3) Vickers indentation crack at a loads of 0.25N was completely suppressed in the surface of ZrO2 irradiated to a dose of 5×1017ions/cm2.
4) The suppression of the crack initiation may be ascribed to the influence of the nanometer composite layer containing max. 23at% Ag.View full abstractDownload PDF (1362K) -
Kazuo Higuchi, Shoji Noda, Osami Kamigaito1989 Volume 36 Issue 2 Pages 253-256
Published: March 25, 1989
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA carbon film of 200nm thickness was vacuum-deposited on Si wafer at 573 K. The carbon film was implanted with 280keV Ar+ to doses up to 1×1017/cm2. Implantation temperatures were 90 K to 773 K. Raman and XRD studies showed that the as-deposited carbon was graphite-like amorphous carbon, and implantation above 523 K resulted in growth of graphite microcrystals in the film while implantation below 213 K destroyed graphite-like structure in the film.View full abstractDownload PDF (260K)
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