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Volume 43, Issue 10
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[in Japanese]1996 Volume 43 Issue 10 Pages 1158
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (94K) -
Tatsuhiko Aizawa1996 Volume 43 Issue 10 Pages 1159-1164
Published: October 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSThe granular modeling has been developed not only to make direct simulation of powder compaction and forming for parts and members but also to consider the coupling between magnetic fields and powder flow for hard copy and powder compaction in the magnetic field. Through those successful analyses, our developed granular modeling is found to be an effective tool to describe powder flow and compaction behavior in actual powder forming. One of the most preferable features to this modeling should be its rational extention to fine-grained particle modeling through our developing averaging; this mesoscopic modeling on the basis of the granular modeling can be expected to be available to micro-rheological analysis of aggregated fine particles, various compounds and suspensions.View full abstractDownload PDF (3498K) -
Fujio Tsumori, Tatsuhiko Aizawa, Junji Kihara1996 Volume 43 Issue 10 Pages 1165-1170
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSNew sintering analysis method is proposed and developed by using the macro-micro coupling model with homogenization method for quantitative evaluation on the geometric changes of both green and brown materials. Together with description of deformed bulk work materials, this method enables us to make precise prediction of their microscopic structural change and shrinkage in sintering. Variational principle in the elasto-creep frame is utilized to make formulations for both macro and micro models and to simulate time history of geometric configuration, creep strain and stress in macro and micro models. Several numerical examples are employed to verify the validity and effectiveness of the present method and to investigate the effect of static pressure on the sintering process.View full abstractDownload PDF (3876K) -
Yukitaka Mizuno, Akira Kawasaki, Ryuzo Watanabe1996 Volume 43 Issue 10 Pages 1171-1176
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSintering shrinkage behavior is numerically simulated on stainless steel powder compacts prepared by metal powder injection molding (MINI). The MIM process is now highlighted because of its near-net-shape productivity of small mechanical parts having complex shape along with high relative density. In general, however, the initial packing density of the compacts is rather low to be around 55vol.% in relative density. This should cause large volume change during sintering, resulting in the possible nonuniform shrinkage in the compacts. Thus, in the MIM process, the prediction of geometric change of a compact is of extreme importance.
The numerical simulation involves finite difference analysis to determine temperature distribution in a compact set in a vacuum furnace, densification analysis by use of sintering rate equations, and finite element analysis to convert the shrinkage into the geometric change of the compact. Six rate equations for sintering mechanisms summarized by M.F.Ashby are used for the calculation. We have assumed that the six mechanisms are distinguishable and sintering rate is the sum of the six rate equations. It has been demonstrated that the density inhomogeneities due to local temperature differences contribute to the nonuniform shrinkage in the early stage of sintering; however, it attenuates reversely in the final stage.View full abstractDownload PDF (1608K) -
Grain Growth in Porous CompactsYoko Yamada, Ryuzo Watanabe1996 Volume 43 Issue 10 Pages 1177-1182
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe size distribution function for the steady-state grain growth in the presence of Zener-type restraint due to residual pares was derived and compared with the experiruental data. The calculation is based on the Hillert's hypothetical rate equation for the grain growth and the grain size distribution is calculated by classifying the grain growth rate into three regions : the first region where grain size is small compared to the critical size and the grains are shrinking, the second region where grain boundary movement is completety restrained by the residual pores and the grain growth rate is zero, and, the third region where grain size is large enough to grow at the expense of small grains. According to the present calculation, the increase of restraining force results in the displacement of the peak position of the grain size distribution towards the smaller size, as small as half of the critical grain size, and narrowing of the size distribution. Compared with the experimental data of carbonyl Ni and carbonyl Fe sintered compacts at various conditions, the predicted grain size distribution is in good agreement with the experimental data whose grain growth is restrained by residual pores intersected with grain boundaries.View full abstractDownload PDF (268K) -
Masato Otsuki, Koichi Yuri, Tohru Kohno, Akihisa Inoue1996 Volume 43 Issue 10 Pages 1183-1187
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSRapidly solidified AI-TM-Ln base alloy has excellent mechanical properties such as high specific strength or specific modulus. In this study, Al92Ni4.5Ti1.5CulZr0.8Ce0.2 (at%) alloy powders were directly forged using a double action forging press without preparing a compact preform that is difficult to consolidate because of the spherical shape and hardness of the powder. The tensile strength of above test pieces preheated at 723K for 3600s shows 670MPa and 2% elongation, which is comparable with the test pieces prepared by extrusion from the same powder. This process gives near net shape parts with excellent mechanical properties using the rapidly solidified Al-TM-Ln base alloy.View full abstractDownload PDF (3452K) -
Debinding Condition and Process in Supercritical DebindingToru Shimizu, Satoshi Mochizuki, Toshio Sano, Sadakatsu Fuchizawa1996 Volume 43 Issue 10 Pages 1188-1192
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMIM is an important method in the metal forming technology. Though, this process is incomplete, and still has problems in each processing step. Especially in the debinding step, there are many problems. In an actual producing process, the thermal debinding method is still used, and this method needs long debinding time. Also, the size of products is limited, and the metal powder is oxidized in this method. As a method to overcome these problems, the solvent debinding process is used recently. This method is an efficient debinding method. Though organic solvents are used in this method, they are poisonous. These solvents will harm human health and environment. For this reason, a debinding method which uses super critical dioxide(CO2) is desirable. Using this method, quick debinding is possible, and a thick green body can be debinded. Moreover, the solvent used in this method is safe and harmless for environment.View full abstractDownload PDF (1478K) -
Takekazu Nagae, Masateru Nose, Masaru Yokota1996 Volume 43 Issue 10 Pages 1193-1197
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSArgon gas atomized powder of Al-25mass%Si-3.5%Fe-3.5%Ni-1%Mg alloy was sintered by Spark Plasma Sintering (SPS) method. This powder and the bulk samples obtained by this sintering method were investigated by means of scanning electron microscopy, optical microscopy, X-ray diffraction and Rockwell hardness measurements. Results obtained were as follows;
(1) The most of powder particles have a structure consisting of Al-Si matrix and sphere like precipitates of metastable compounds enriched in Fe and Ni. The other particles have needle like shape in the precipitates of metastable compound. This metastable compound is presumed to be Alm(m=4.4) Fe structure in which a part of Fe is substituted by Ni.
(2) The Rockwell hardness of specimen sintered at 500°C by SPS method is higher than that obtained by the powder forging method. The higher hardness in the specimen procured by SPS method is attributed by the fine structure of compacts because of a completion of sintering in a short time.View full abstractDownload PDF (5038K) -
Takekazu Nagae, Masateru Nose, Masaru Yokota, Shigeoki Saji, Hiroshi S ...1996 Volume 43 Issue 10 Pages 1198-1202
Published: October 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSWe synthesized the Nb-Al alloy powder from Nb and Al elemental powders by Mechanical Alloying which provides the nanometer size crystals. Mixing ratio of Nb and Al was 7.5mass%Al corresponding to the Nb3Al composition. After 720 sec milling, the grain size of milled powder was about 3nm. Spark Plasma Sintering system was applied to sinter this MA powder. At the same time, the powder obtained by Plasma Melt Gas Atomize method (Nb-26.1at%Al) was sintered by SPS for comparison. Those SPSed compacts were investigated by SEM observation, EDX analysis, X-ray diffraction and Vickers hardness measurement at high temperature.
The results obtained were as follows;
(1) The MA powder, consisting of super saturated solid solution of Nb and Al, melted partially during SPS at 1773 K, however, the PMGA powder, consisting of mixed structure of Nb and Nb3Al, didn't melted at the same temperature.
(2) The compact of MA powder by SPS had a mixed structure of Nb and Nb2Al, which was too fine to determine by SEM. On the other hand, the mixed structure consisting of Nb2Al grains and Nb3Al grains was formed in compact of PMGA powder.
(3) Vickers hardness of SPSed compact of MA powder was higher than that of PMGA powder at R.T.-1 073K.View full abstractDownload PDF (3196K) -
Keizo Kobayashi, Kimihiro Ozaki, Akira Sugiyama, Teruo Haibara1996 Volume 43 Issue 10 Pages 1203-1207
Published: October 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSAl84Fe16, Al80Fe20, Al75Fe25, Al73Fe27 and Al70Fe30 were synthesized by mechanical alloying (MA) of Al powder and Fe powder using a planetary ball milling for 180ks in 35kPa argon gas atmosphere. The MA powders were consist of fine particles of about 20 μm diameter and granulated particles. The fine particles were obt Alned by flaking of the granulated particles. The MA powder of Al84Fe16 and Al80Fe20 formed Al liquid by heating.
The mixture of Fe Al composition was prepared by mixing of the mechanical alloyed Al80Fe20 powder and Fe powder. This mixture was sintered at 1200K after pressing at 938K. The sintered sample was composed of Fe Al phase. The addition of 0.5at%B to Al80Fe20 in MA process promoted to form the fine particles.View full abstractDownload PDF (1708K) -
Atsushi Hibino1996 Volume 43 Issue 10 Pages 1208-1214
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSCombustion synthesis process has been taken an interest in new synthesizing technology of intermetallic compound. However, the synthesized products tend to be porous and the process is not used practically. To realize the process, a method of synthesizing the dense product should be developed. In my previous paper, fabrication of Ni3Al intermetallic compound by pressureless combustion synthesis process was investigated. Consequently, it was found that density of the synthesized compound depended on initial powder particle sizes, and the nearly full dense product was obtAlned in case of using fine powders as initial substances. However, cause of the densification or mechanisms of the shrinkage have not been known. In this paper, numerical analysis of the process of Ni3Al was performed to clear the relationship between the densification and the compound formation stages in the combustion.
A Ni/Al compact which burned by the thermal explosion was divided into infinite elements, a numerical analysis model of combustion synthesis was derived under consideration of heat balance and material balance equations around the elements. The model was solved by LA.D. method, and the combustion synthesis behavior was analyzed.
The compound formation behavior during the combustion synthesis was able to be simulated. From the calculation, it is found that large quantities of liquid phases were formed in the Ni3Al synthesis. In the previous experiments of the combustion synthesis, the rapid shrinkage was observed during extremely short times. The quick densification might be caused by the large quantities of the liquid phases.View full abstractDownload PDF (488K) -
Atsushi Hibino1996 Volume 43 Issue 10 Pages 1215-1221
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo realize combustion synthesis process of intermetallic compound, a method of fabricating of full dense compound should be developed. In my previous paper, synthesis of Ni3Al intermetallic compound by pressureless combustion synthesis process was investigated. Consequently, it was found that density of the synthesized compound depended on initial powder particle size, and the nearly full dense product was obtained in case of using fine powders as initial substances. The densification might be caused by combustion temperature, compound formation ratio, quantities of liquid phases during the synthesis. However the details is not clear, to evolve the process, the cause of the densification and a course for producing the full dense compound should be established. In this paper, numerical analysis of the combustion synthesis of Ni3Al was performed as a continuation of the previous investigation, and the cause of densification was analyzed.
A Ni/Al premixed compact during thermal explosion combustion synthesis was divided into infinite elements, numerical analysis model was derived under consideration of heat balance and material balance equations around the elements. The model was solved by I. A. D. method, the combustion synthesis behavior was analyzed.
The compound formation behavior during the combustion synthesis was able to be simulated. The maximum combustion temperature or the ratio of compound formation at the each temperature during the synthesis did not depend on the powder particle sizes. However, the quantities of the liquid phases was greatly affected by the sizes, and it was guessed that the liquids is the cause of the densification. The quantities of the liquids were able to be increased by control of beginning temperature of the combustion, heat injection to the compact and enlargement of the compact size. Therefore, these countermeasures might be effective to synthesize the dense compound.View full abstractDownload PDF (460K) -
Shigeki Sato, Tomohiro Sogabe, Masahito Furukawa, Takeshi Nomura1996 Volume 43 Issue 10 Pages 1225-1230
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSEffect of sintering atmosphere on maximum energy capability of Pr-doped ZnO varistor has been studied. Distribution of electrical property and microstructure in ZnO varistor has been obtained with sliced sample. It is shown that donor density and interface states density increased with N2-Air sintering, and there is the close relationship between distribution of electrical property of grain boundary and maximum energy capability. Segregation of Pr and Cr at triple point was different with sintering atmosphere. The composition of segregation phase was Pr-rich PrCrO3, Pr4O7 and Pr2O3 with N2-Air sintering.View full abstractDownload PDF (1486K) -
Takeshi Kaneko1996 Volume 43 Issue 10 Pages 1231-1237
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThis report describes the results of investigation to evaluate the relation between charpy impact strength and mechanical properties of brittle materials as SiC, Sialon, Al2O3, AIN, B4C, WC-Co, TiC-TiN, Soda lime glass and Quartz glass. The charpy impact strength was obtained about the notched and unnotched specimens of these brittle materials. We analyzed correlation between the mechanical properties and charpy impact strength by the multiple regression method. The relation between microstructures of bending fracture surfaces and charpy impact strength of these brittle materials was also investigated.
The results are as follows.
(1) Charpy impact strength increased in order of WC-Co, TiC-TiN, Al2O3 and SiC.
(2) The charpy impact strength showed close correlation with static bending strength of these brittle materials by the multiple regression methods.View full abstractDownload PDF (2317K) -
Osamu Kimura, Masafumi Matsumoto, Mitsuo Sakakura1996 Volume 43 Issue 10 Pages 1238-1241
Published: October 15, 1996
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSThe magnetoplumbite ferrite with the composition of 2Co0⋅3Ba0.6Sr0.5 0⋅10.8Fe2O3 was reported to reveal enhanced dispersion frequency.
This paper aims to enhance the dispersion frequency of this ferrite, using calcined powder finerly pulverized. The resonance frequency corresponding to μ″ maximum of the sample hot-pressed at 1110 °C in an oxygen atmosphere extendes to 3.4 GHz, which is almost the vale theoretically predicted, although its permeability is only only 4.4. The resonance frequency decreases and the permeability increases with increasing hot-pressing temperature. Moreover annealing of the hot-pressed sample at higher temperature results in almost the same result.View full abstractDownload PDF (4940K) -
Masao Morishita, Koichiro Koyama, Masahiko Morinaga, Hirohiko Adachi1996 Volume 43 Issue 10 Pages 1242-1246
Published: October 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSLocal electronic states around Ni atom in NiMo2B2 having an orthorohmbic crystal structure were investigated using the DV-X a molecular orbital calculation. It was found that the ionicity of Mo was positive and that of B was negative by the charge transfer from Mo atom to B atom. Ni acted as an accepter of electrons from Mo and a donor of electrons to B, and consequently its ionicity was neutral. The bond orders of Ni-B, Mo-B and Ni-Mo were very high. That is, covalent bonds of these pairs were very strong. The partial densities of states for 3d of Ni, 4d of Mo, and 2s and 2p of B were mutually widely overlapped. This is probably the reason for the high strength of the covalent bonds among Ni, Mo and B. The Fermi level existed near the peaks of the partial densities of states of 4d of Mo and 2p of B, indicating that the phase transformation of NiMo2B2 from the orthorohmbic to tetragonal structure may be caused by substitution of Cr for a part of Ni.View full abstractDownload PDF (316K) -
Hiroyasu Araki, Akira Ishikawa, Hitoshi Ishii, Keiichiro Tohgo1996 Volume 43 Issue 10 Pages 1247-1252
Published: October 15, 1996
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTi powder and TiC particles were blended by two methods of simple blending and mechanical alloying. Hot pressing was applied after the blending and mechanical properties of these Ti base composites with 0 to 20 mass % TiC were studied. Tensile strength of the simply blended composite showed a peak at 5 mass % TiC and it decreased by further adding of TiC. On the other hand, tensile strength of the mechanically alloyed composite increased with the content even above 5 mass % of TiC. Sharp decrease in elongation occurred at 3 mass % TiC, and elongation of the mechanically alloyed composite was always slightly larger than that of the simply blended composite. Young's modulus of the composite increased linearly with TiC content along with a rule of mixture. Debonding at the matrix/particle interface did not occur during tensile deformation, but relatively large TiC particles were observed to be cracked easily. Mechanical alloying is a useful method for the strengthening of Ti base composites with TiC particles, as the structure having small TiC particles of uniform dispersion is made by this method.View full abstractDownload PDF (7525K) -
Gil-Geun Lee, Dong-Won Lee, Gook-Hyun Ha, Byoung-Kee Kim1996 Volume 43 Issue 10 Pages 1253-1258
Published: October 15, 1996
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSTumbler-ball milling of Al powder was carried out to investigate the effect of milling conditions on the characteristics of Al flake powder particles for fingerprint detection. Initial powder of under 25μm was more easily developed to flake particles have high specific surface area than under 19μm one. With an increase in the ball size from 4.8 to 16mm, the specific surface area of the milled powder particles increases and then decreases at 16mm. The specific surface area of the milled powder particles increased with increasing mill container rotation speed. The excellent fingerprint detection qualities were obtained in milling condition of under 25μm initial powder, 9.5mm ball size, 80rpm mill container rotation speed and 40 hours milling time. The diameter of the flake particles estimated from the impact velocity of the balls based on the milling ball dynamics and the Hertz contact theory was compared with the measured one.View full abstractDownload PDF (5104K)
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