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Volume 46, Issue 8
Displaying 1-19 of 19 articles from this issue
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Osamu Kohmoto, Hiromichi Nakagawa, Fumihisa Ono1999 Volume 46 Issue 8 Pages 797-800
Published: August 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSEffects of O2 partial pressure at sputtering on the crystal structures and magnetic properties of Ni-O films werestudied. The film thicknesses were 150 nm for Ni and 500 nm for NiO. The following results were obtained. (1)Below 10% of O2 partial pressure [O2/(Ar+O2)], single-phase Ni films were obtained; above 10%, single-phase NiO films were obtained. (2)Lattice constants of both Ni and NiO were larger than those ofbulk Ni and NiO. (3)The saturation magnetization Ms is 90% that of the bulk. Anisotropy of magnetic susceptibility x was observed, andaverage value is the same as that of the bulk. (4)Coercive force(Hc)of the Ni film at O% is 1.1 kA/m at easy albs and O.9 kA/m at hard axis. (5)Electric resistivity ρ for Ni tends to increase with O2 partial pressure. The ρ of NiO which indicates semiconductor properties is only by four order larger than that of Ni, and is by four order smaller than thatof bulk NiO. It is thought that the NiO film composition is not stoichiometric, and the film is Ni-defect type (P-type) semiconductor.View full abstractDownload PDF (284K) -
Katsuyoshi Kondoh, Atsushi Kimura, Yoshinobu Takeda1999 Volume 46 Issue 8 Pages 801-810
Published: August 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn-Situ direct nitriding process to produce AIN in aluminum alloy powder by utilizing the reaction between aluminum and nitrogen gas at temperatures below 823K has been developed. Topmost-surface analysis by X-ray Photoelectron Spectroscopy using Synchrotron Radiation (SR-XPS) was conducted and chemical bonding changes on aluminum powder surface during heating were investigated. Deoxidization of aluminum oxide (Al2O3) surface film by Mg contented in the powders occurred over 670K and Al2O3 film was deoxidized and reduced. After the deoxidization of Al2O3 surface film, aluminum in powder reacted with nitrogen gas and AIN layer was produced upon the powder surface. In-Situ reacted AIN had a good bonding with aluminum matrix and showed a laminar structure with a layer thickness of 20-30nm. The content of reacted AIN strongly depends on a period of heating in nitrogen gas and on surface area of raw powder.View full abstractDownload PDF (6504K) -
Satoshi Sugiyama, Atsunori Kamegawa, Hitoshi Takamura, Masuo Okada1999 Volume 46 Issue 8 Pages 811-815
Published: August 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL FREE ACCESSZnO-Pr6O11 varistors exhibit non-ohmic current-voltage characteristics due to the double Schottky barrier formed at the interface between ZnO grains and intergranular phases of Pr6O11. In this paper, the I-V characteristic of ZnO/Pr6O11 multilayerd films with different thickness fabricated by pulsed laser ablation method are studied. In spite of decreasing the film thickness, the films with 5000-500Å thickness exhibit nonlinear I-V characteristic. The values of breakdown voltage (Vb) and non-linear coefficient (a) are estimated as Vb=0.19-0.30V, α=2.5-4.1. Therefore, thin ZnO/Pr6O11 multilayered films prepared by PLD method show lower breakdown voltage.View full abstractDownload PDF (381K) -
Nobuyuki Tamari, Isao Kondoh, Takahiro Tanaka, Masakazu Kawahara, Masa ...1999 Volume 46 Issue 8 Pages 816-819
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAlumina ceramics were fabricated by spark-plasma-sintering (SPS) and hot-pressing at 1100 to 1600°C under 30 MPa for 5 min. The room temperature mechanical properties were measured. The SPS brought about dense alumina ceramics at a sintering temperature lower than that in the hot-pressing. The alumina ceramics obtained by SPS had strength, hardness and fracture toughness higher than those by hot-pressing. The alumina grains in the sintered bodies prepared by SPS grew larger than those by hot-pressing.View full abstractDownload PDF (2149K) -
Hideshi Miura1999 Volume 46 Issue 8 Pages 822
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDownload PDF (99K) -
Jin Kon Kim, Byoung-Kee Kim1999 Volume 46 Issue 8 Pages 823-829
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effect of liquid-liquid phase-separation (LLPS) on the crystallization behavior and mechanical properties of poly(ethylene-ran-vinyl acetate) (EVA) and paraffin wax blend was investigated. The blend of EVA and the wax became homogeneous at temperatures greater than its upper critical solution temperature (UCST) (371K), and an LLPS was observed between UCST and the melting point of 361 K for EVA in the blend. The degree of crystallinity of EVA in the blend, judged from a melting endothermic peak in differential scanning calorimeter (DSC) thermograms obtained during heating runs, decreased with increasing duration time in the LLPS region.
The flexural modulus of the blend became maximum at the 35wt% EVA. This behavior can be explained by the fact that this blend composition has the largest relative degree of crystallinity of EVA measured by DSC. We found that the flexural modulus of the binder itself is directly related to that of a feedstock consisting of larger amounts of metal powder and the binder, which can help someone to develop a suitable binder system for a powder injection molding process.View full abstractDownload PDF (3979K) -
Byung Ohk Rhee, Sang-hoon Lee1999 Volume 46 Issue 8 Pages 830-836
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe rheological characterization with capillary rheometer requires three major corrections named as the Rabinowitsch, Bagley and Mooney corrections. Due to the amount of time and effort needed to complete the correction procedure, some engineers may avoid the corrections. However, engineers who want to avoid it should understand how much the theological data is affected by influencing factors. In this article, the correction values made by the Rabinowitsch and Bagley corrections were analyzed for PIM feedstocks in terms of particle shape and size, powder concentration, binder composition, temperature, shear rate and capillary length. Two types of SUS powders with irregular and round particle shapes and a zirconia powder were used with wax-based binders. As results, particle shape and size were the major influencing factor followed by powder concentration. Also a longer capillary is recommended for less error as long as it does not cause thixotropic phenomenon. Without extensive experiment, a feasible result could be obtained only by the Rabinowitsch correction for feedstocks with round particle shape at a relatively low powder concentration. However, the correction is strongly recommended for feedstocks with irregular particle shape at a relatively high powder concentration.View full abstractDownload PDF (2548K) -
C.J. Hwang, T.H. Kwon1999 Volume 46 Issue 8 Pages 837-843
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPowder Injection Molding (PIM) filling process is one of the key processes towards a successful PIM. In this regard, the methods of slip characterization of powder-binder mixtures and a quasi-3-dimensional finite element simulation program based on Hele-Shaw approximation has been presented.
In contrast to conventional injection molding of thermoplastics, there are many PIM parts that include thick regions. To simulate such thick PIM parts properly, a full 3-dimensional simulation program is needed. In this regard, we have been developing a full 3-dimensional finite element program for PIM filling process with the slip phenomena taken into account. For a computational efficiency, a pre-meshed finite element mesh was used with a scalar fill-factor to automatically update the computational domain during the filling.View full abstractDownload PDF (2983K) -
Nakatsukasa Eiji1999 Volume 46 Issue 8 Pages 844-848
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSSHIMADZU Vacuum Debinding and Sintering Furnace is designed for debinding and sintering of the green parts of MIM (Metal Injection Molding). The furnace is not contaminated by the vapor of the binder during the debinding process and it realizes clean atmosphere in the sintering process. The user set a high valuation on this feature as equipment for mass-production of MIM parts. We present recent technical trends of the furnace based on our results of the supplies.View full abstractDownload PDF (3157K) -
Detlef Gonia1999 Volume 46 Issue 8 Pages 849-852
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSDue to the improvements in the production process for metal injection molding (MIM) parts produced by this method, especially light weight parts with very complex shape have become very competitive against other technologies. The introduction of the catalytic debinding process is an important improvement since it decreases the debinding time greatly and allows the use of a continuous process, in which debinding as well as sintering is performed in one furnace. MIM parts for automotive applications can be found increasingly at least on the European market.View full abstractDownload PDF (2335K) -
Hideki Kyogoku, Hideki Nakayama, Shinichiro Komatsu1999 Volume 46 Issue 8 Pages 853-857
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe effects of sintering conditions and heat-treatment conditions on the mechanical properties of sintered tool steel(AISI D2)compacts were investigated. An AISI D2 gas atomized powder and polyamide binder were mixed well and injection molded into metallic molds for transverse test specimen. These injection-molded compacts were debound at 593 K and then sintered at various temperatures between 1473 K and 1483 K. The sintered compacts were annealed at 1173 K and quenched from 1293 K, and then were tempered at various temperatures between 453 K and 803 K. The relative density increased with increase in sintering temperature and showed to be more than 99 in the case of 1483 K. The hardness decreased with elevating the tempering temperature and showed to be larger than 58 HRC in the case of 543 K. The transverse rupture strength of the compacts sintered at 1473 K and 1478 K showed to be larger than 3000 MPa regardless the tempering temperatures. The tool steel compacts of which mechanical properties were equivalent to those of the wrought tool steels could be fabricated by controlling the sintering and heat-treatment conditions precisely.View full abstractDownload PDF (3619K) -
Hideshi Miura, Mari Yonetsu, Junko Nuka1999 Volume 46 Issue 8 Pages 858-864
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSMetal injection molding (MIM) process allows nearly full dense and net shaping of a variety of engineering materials. Especially, the application of MIM process to hard and brittle materials such as Fe-Si-Al (Sendust) alloy demonstrates the potential of this novel process.
This study considers the processing of Sendust alloy compacts through the MIM techniques using different types of powders, gas and water atomized powders. Soft magnetic properties were strongly influenced by the grain size and retained oxides. By the continuous process combining the debinding and sintering steps together, high performance soft magnetic properties due to the reduction of oxides and coarse grain size were obtained by using gas atomized powder.View full abstractDownload PDF (5506K) -
Kiyotaka Kato1999 Volume 46 Issue 8 Pages 865-869
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe preparation of pure-Ti compacts by metal injection molding (MIM) process was described in this paper. To reduce contamination at sintering process, the sintering was performed at low temperature range from 1198K to 1348K. On this sintering condition, the properties of sintered compacts were investigated.
When HDH powder (average particle size is 23μm) was used as the material, the compacts sintered at more than 1298K had high tensile strength (630MPa<) in spite of low density (92.5-94.5%). When gas-atomized powder (average particle size is 15μm) was used, the sintered compact had high density (-95%) and high elongation (15-20%) at low sintering temperature range (1248K-1298K).View full abstractDownload PDF (4983K) -
Hidefumi Nakamura, Tokihiro Shimura, Kouei Nakabayashi1999 Volume 46 Issue 8 Pages 870-876
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPure Ti, which is used in the field of Metal Injection Molding (MIM), can be used to produce parts with complicated shapes. But, since oxidation, nitrogen and carbonization are generated during the debinding-sintering process, the mechanical properties of the sintered material cannot achieve the same level as those of the ingot material. Accordingly, we have studied the debinding and sintering methods by using various binder systems. This paper reports on the mechanical properties required by customers (0.2%proof stress of 216 MPa or more, tensile strength of 343 to 510 MPa, and elongation of 10% or more)and the development of the parts production process.View full abstractDownload PDF (3810K) -
Junnjiro Takekawa, Noriaki Sakurai1999 Volume 46 Issue 8 Pages 877-881
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSTo examine the applicability of the powder injection molding (PIM) process to the Ti alloy system, a basic study was performed using premixed powder. A Ti-12Mo alloy, in which the βphase is stable, was selected as test material because of its high corrosion resistance and strength.
It was shown that the relative densities of the PIM compacts were more than 2% higher than those of the PM (traditional powder metallurgy) compacts, beside the PIM compacts showed higher strengths than the PM compacts compared under the same sintering conditions. The compacts showed the maximum strength at 94% in theoretical density, in both the PIM and PM process. It was also shown that the TiC precipitates strengthened the PIM compacts when they were fine and uniformly precipitated.
The PIM process showed to be successfully applicable to premixed Ti-12Mo powderView full abstractDownload PDF (7610K) -
Yongchan Kim, Nack J. Kim, Taesik Yoon, S. Ahn1999 Volume 46 Issue 8 Pages 882-886
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSPowder Injection Molding (PIM) of Ti-48Al was attempted with a special interest in its densification behavior at different processing conditions such as debinding atmosphere, sintering temperature and time. Specimens debinded in H2 showed high densification rate, resulting in 97% density after sintering at 1350°C in vacuum for 3 hours. Fine Al2O3 particles about 1 μm size were observed along the prior particle boundaries of the sintered specimens. Specimens debinded in Ar and sintered in vacuum at 1350°C and 1400°C for 3 hours resulted in similar densifications of 91.7% and 91.5%, respectively. The microstructures were, however, quite different; Sintering above α/(α+γ) transus temperature showed a fully lamellar microstructure with a coarse grain size, whereas sintering at 1350°C showed a fine grained duplex microstructure. Presintering at 1000°C for 3 hours eliminated the macro pores and improved densification to 93.4% when the specimen was subsequently sintered at 1350°C for 3 hours. Densification was improved as the sintering time increased, reaching a near full density of 98.8% after 30 hours sintering at 1350°C.View full abstractDownload PDF (7332K) -
Hwan-Jin Sung, Taesik Yoon, S. Ahn1999 Volume 46 Issue 8 Pages 887-892
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe objective of this study is to examine the feasibility of manufacturing WC-Co milling insert by PIM process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were limited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom in design.
P30 grade WC powder (WC-Co-TiC-TaC system) was mixed with RIST-5B 133 binder and injection molded into milling inserts (Taegu Tech. Model WCMX 06T308). The mean particle size of the powder was about 0.8μm. Injection molded specimens were debinded by solvent extraction and thermal degradation method at various conditions. The specimens were sintered at 1400°C for 1 hr in vacuum. Carbon content, weight loss, dimensional change, and macro defects of the specimen were carefully monitored at each stage of the PIM process.
PIMed WC-Co milling inserts reached 100% full density after sintering. Its mechanical properties and micro-structures was comparable with the press and sintered milling insert. Carbon content of the sintered WC-Co insert was mainly determined by the atmosphere of thermal debinding. By controlling powder loading and injection molding condition, dimensional accuracy could be obtained within 0.4%. We confirm that PIM can not only be an alternative manufacturing method for WC-Co parts economically but also provide a design freedom for more efficient cutting tools.View full abstractDownload PDF (4572K) -
Young Do Kim, Sung-Soo Ryu, In-Hyung Moon1999 Volume 46 Issue 8 Pages 893-897
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSA study was carried out to investigate the possibility whether MIM process could be applied to the compacting process of W-Ni-Fe heavy alloy in order to obtain an intricate shape. The multi binder system of 45PW+30PE+15BW+10SA was used for injection molding and compacts from the powder-binder mixture of metal powder fraction of 60 vol.% were studied for debinding and sintering behaviors. In debinding process, heating rate in temperature range from 120°C to 290°C had an important effect on the weight loss of the binder. The binder could be fully removed by three stage debinding treatment. The microstructure of the sintered specimen was dependent on the sintering atmosphere. The W-4.9wt.%Ni-2.1wt.%Fe alloy of full sintered density was obtained by sintering at 1470°C for 1 h in a wet hydrogen atmosphere and there was no difference in microstructure compared to that of W heavy alloy by die compaction.View full abstractDownload PDF (4458K) -
Eui-Sik Yoon, Ji-Hun Yu, Jai-Sung Lee1999 Volume 46 Issue 8 Pages 898-903
Published: August 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSThe densification process and related microstructure evolution during sintering of the powder injection molded (PIMed) W-15wt%Cu nanocomposite powder have been investigated. The densification process of the PIMed composite powder was analyzed in terms of dilatometry, shrinkage anisotropy and microstructure. Especially, the sintering behavior of the W-Cu composite powder compact was in-situ analyzed during heat up, which might be closely related to gas evolution in the early stage of sintering. It was found that residual carbon reduces oxides, that hydrogen is unable to reduce, forming CO gas at 700-1000°C. Such carbon effect resulted in enhancement of the solid state sintering as well as formation of inhomogeneous microstructure of the PIMed W-Cu nanocomposite powder. Based on the measurement of gas evolution, the most effective removal of residual impurities and the best consolidation were achieved without promoting solid state sintering.View full abstractDownload PDF (6059K)
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