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Volume 48, Issue 1
Displaying 1-15 of 15 articles from this issue
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Zhongchun Chen, Keisuke Ikeda, Tadasu Murakami, Takenobu Takeda2001 Volume 48 Issue 1 Pages 3-8
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSZirconia, stainless steel powders and their composite powders have been extruded using an aqueous solution of a water-soluble polymer, hydroxypropyl methylcellulose (HPMC) as a binder. The powder-binder mixtures were extruded into pipes by a multi-billet coextrusion technique. The drying and debinding behavior of the extruded pipes was experimentally verified. The pore sizes and their distribution in dried extrudates obtained from composite powders depend to a large extent on the mixing proportion of the two powders. The pores due to evaporation of the moisture in the drying process accelerate the elimination of the HPMC polymer by promoting the diffusion of oxygen and degraded products. The presence of some oxygen is necessary in order to remove the HPMC polymer completely. The HPMC may be removed during the heating period of sintering operations without any special debinding treatments, provided some oxygen is present.View full abstractDownload PDF (2282K) -
Toshimi Yamane, Hirotaka Okubo, Nobuhiro Oki, Koji Hisayuki, Masaaki K ...2001 Volume 48 Issue 1 Pages 9-14
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSMixed copper and carbon powders were mechanically alloyed (MA) in a planetary ball mill. The supersaturated solid solubility of carbon in MA copper was 25at%C which was determined from lattice parameter change. The supersaturated copper powder consolidated by static compression of 1.4 GPa, has the relative density of 95%, and Vickers hardness of 121. Otherwise, that consolidated dynamically by a bullet of 90.1 g at the speed of 38.1 m/s after 0.4 GPa static compression, has the relative density of 96.3%, and Vickers hardness of 200. Keeping the MA effect more than half, MA powders could be consolidated by impact pressure.View full abstractDownload PDF (2328K) -
Katsushi Kusaka, Takanari Kurachi, Tetsuya Kondo2001 Volume 48 Issue 1 Pages 15-20
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSA fundamental study was subsequently made on the AC magnetic properties of Fe-Si type magnetic alloys, prepared by means of diffusion-sintering soft-iron/Fe-21(wt%)Si-B mixed powders. In this case, Fe-21Si (eutectic) mother alloy fines with B content: 0-0.4 wt% was made by high-pressure water atomization and was blended with soft-iron powder to Fe-0-8(wt%)Si compositions.
The results obtained were summarized as follows:
(1) Maximum flux density (Bm), specific permeability (μa) and core loss (Pcv) show almost the same dependence upon Si content and sintering temperature in the low frequency region.
(2) The maximum flux density (Bm), typical of AC magnetic properties, has the maximum value in the Si content:6-7 wt%, under roughly no influence of sintering temperature (1473-1623 K).
(3) This AC tendency of Bm-Si relationship, differently from the magnetic induction (B10)'s one of DC magnetic properties, is indicative of large dependence upon electrical resistivity (ρ) through the so-called skin effect.
(4) The maximum flux density (Bm) of Fe-6-7Si-B compacts sintered at 1573 K can be enhanced by-20% due to the small B ingredient which generally has some deoxidizing effect in liquid phase.
(5) This small amount of B: 0.05-0.1 wt% tends to remove impurities and hence, to clean the microstructure of sintered specimens but excess B may possibly pin the domain wall in AC magnetic field as inclusions.View full abstractDownload PDF (3545K) -
Shinichi Sakano, Hisataka Takenaka, Toshihiko Sato2001 Volume 48 Issue 1 Pages 21-26
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe morphology and magnetic properties of ultrafine Co1-xCaxFe2O4 particles prepared by chemical coprecipitation have been investigated. For particles heat treated at 800°C, an incremental linear relationship was found to exist between the lattice constant, ao, and the nominal composition of CaFe2O4, X, for 0≤X≤0.7. The curie temperature, Tc, of these ferrites also increases from 518°C to 550°C for 0≤X≤0.5. The saturation magnetization, σs, of ultrafine CoFe2O4 particles is 75 emu/g at 300 K. Curves of σs vs. X appear convex with no linearity at all for 0≤X≤1. These results on a0, Tc, and σs indicate that ultrafine Co1-xCaxFe2O4 particles form as a solid solution, at least when X is in the range 0≤X≤0.7. In samples heat treated at 600°C or more, the grain size drops markedly as X increases. For example, for an 800°C treatment the size is 63 nm when X=0, but only 33 nm when X=0.2. In addition, the amount of a Fe2O3 formed by heat treatment increases as X increases. The largest value of the coercivity, IHc, obtained is 2750 Oe (0.2≤X≤0.3) for a sample heat treated at 800°C. This value is approximately equal to the intensity of the anisotropic magnetic field, Ha, calculated from the crystalline magnetic anisotropy constant, K, , of bulk CoFe2O4. There are two possible causes of the high IHc. One is that the single-domain CoFe2O4 particles might be separated by α-Fe2O3 particles, the other is that, as X increases, the K, of Co1-xCaxFe2O4 particles might become increasingly higher than the value for bulk CoFe2O4.View full abstractDownload PDF (2156K) -
Norimitsu Hirose, Shin-ichi Tanaka, Junichi Asami, Tohru Kohno2001 Volume 48 Issue 1 Pages 27-33
Published: January 15, 2001
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe relationships among elastic modulus, sound velocity and porosity (P) were investigated by theoretical elastic model and experimental results obtained by acoustic pulse method. Young's modulus (shear modulus) decreased with increasing P as (E0-KE⋅P)·(1-P), where KE and E0 are experimental constants.
The square of sound velocity was as a function of P. The calculated sound velocity using the relation corresponded to the measured sound velocity against P. Furthermore, it was clarified that elastic modulus against P can be calculated using the square of sound velocities at P=0 and two experimental constants.
In these relations, the experimental constants of elastic modulus and sound velocity changed at critical porosity where pore morphology changes. When the critical porosity was considered to the fitting curve calculated using the equation derived in this study, good agreement with the fitting curve and measured data of Poisson′s ratio was obtained.View full abstractDownload PDF (470K) -
Daisuke Iwanaga, Yukie Nakano, Mari Miyauchi, Takako Hibi, Takeshi Nom ...2001 Volume 48 Issue 1 Pages 34-38
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe effect of thinning dielectric layers on the insulation resistance of MLCCs with Ni-electrode has been studied with special reference to the microstructure. Thinning dielectric layers is effective to achieve large capacitance MLCCs. In this study, MLCCs which are consisted of 1.9μm dielectric layer thickness with one grain are evaluated. The insulation resistance (IR) of MLCCs with a 1.9μm active layer thickness changed from 105 to 1011 Ω·cm by reoxidation treatment. In order to explain the increase of the IR after annealing, the distribution of element was investigated using TEM-EDS and EPMA. As a result of analysis, segregated Mn in active layer has disappeared after annealing. These phenomena suggested that the IR faults were caused by the segregated phases.View full abstractDownload PDF (5954K) -
Satoshi Hironaka, Toshihiro Tsuchiyama, Setsuo Takaki2001 Volume 48 Issue 1 Pages 39-44
Published: January 15, 2001
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt has been confirmed that sintered Ti-mass%(%)Cr alloy with martensitic structure exhibits superplasticity, at around 1023 K. Mechanical properties of the sintered material can be improved with rising density by superplastic deformation. In this study, superplastic deformation behaviors of Ti-4%Cr-Al ternally alloys were investigated for the purpose of fabricating a sintered Ti alloy with higher strength. Ti4%Cr-6%Al alloy with martensitic structure exhibited superplasticity (about 350% elongation) on condition that the phase ratio a to β is about 1:1. However, the superplastic elongation could not be obtained in the Ti-4%Cr-(2, 4)%Al alloys. It is important for an exhibition of superplasticity in Ti-4%Cr-Al alloys to do alloy design that the phase ratio a to β is about 1:1 at temperature which equiaxization of acicular α grains finishes, and Ti-4%Cr-6%Al is suitable for the compotion. Mechanical properties of densificated Ti-4%Cr-6%Al alloy are in not at all inferior to those of Ti-6Al-4V alloy produced by ingot metallurgy.View full abstractDownload PDF (5961K) -
Atsushi Aruga, Hajime Katsuta2001 Volume 48 Issue 1 Pages 45-50
Published: January 15, 2001
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe effects of additives on the densification of vanadium nitride (VN) ceramics were prechecked by sintering. So we selected Y2O3 as a sintering aid among several oxides (Al2O3, CaCO3, MgO, SiO2, TiO2, WO3, Y2O3, etc.). VN ceramics were prepared by pressureless sintering at 1800 to 2200°C for 2h in N2 atmosphere. A sample added 5vol% Y2O3 sintered at 2000°C gave the relative density (dr) of 96.2% and its Vicker's hardness reached 16.2 GPa. As its spesific resistance is 1.2×10-4 Ωcm at room temperature, it is possible to cut this by using of an arc cutting machine. The optical reflectivity of polished samples is light beige with metallic luster. It is concluded that polished samples (dr>95%) can be used for ornament.View full abstractDownload PDF (2138K) -
Satoshi Kinoshita, Takeshi Saito, Masaki Kobayashi, Koji Hayashi2001 Volume 48 Issue 1 Pages 51-60
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSWe have developed an economical new fabrication process of WC-Co base cemented carbides with highly oriented plate-like triangular prismatic WC grains by using special W+C mixed powder instead of conventional WC powder, and already reported that the new alloy has superior room-temperature mechanical properties, compared with the conventional alloy.
In this study, the mechanism of such WC grain formation was investigated in detail. It was clarified that the formation has its origin in both the flattening of W granular particles to plate-like shape by ball-milling and their highly unidirectional orientation by die-pressing, and is assisted by both the formation of highly unidirectional plate-like Co-W-C compounds (CoxWyCz) particles and its change to highly unidirectional plate-like triangular prismatic WC grains during solid state heating. Such formation of WC grains is attributed to both the higher nucleation and/or growth rate of WC grains having (0001) crystal plane parallel to the geometrical basal plane of plate-like CoxWyCz particles. Furthermore, the formation is also assisted by non-collapse of such WC grains configuration during the appearance and solidification of Co-W-C liquid phase.View full abstractDownload PDF (9831K) -
Akihiro Yamazaki, Junichi Kaneko, Makoto Sugamata2001 Volume 48 Issue 1 Pages 61-66
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSPure magnesium powder was mechanically alloyed with SiO2 powder by using a planetary ball mill under an Ar atmosphere. After mechanical alloying, the powder was consolidated to the P/M material by vacuum hot pressing. Solid state reaction in the mechanically alloyed powder and the P/M material of the Mg-SiO2 system was studied by XRD, DSC and TEM. In this system, the solid state reaction started to occur during MA processing between Mg and SiO2 and in-situ formation of MgO and Mg2Si was attained in the Mg matrix. Such solid state reaction progressed further during hot-pressing and heating of the P/M material. The hardness increase was observed during heating of the P/M material at 773 K, and thus the Mg-SiO2 P/M material can be strengthened by in-situ formation of MgO and Mg2Si.View full abstractDownload PDF (3256K) -
[in Japanese]2001 Volume 48 Issue 1 Pages 68
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (106K) -
Atsushi Hibino, Shinichi Matsuoka2001 Volume 48 Issue 1 Pages 69-76
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe combustion synthesis of dense TiAl intermetallic compound with Co/Al sintering additive was investigated.The raw Ti/Al (Ti:Al=1:1) powder mixed with Co/Al (Co:Al=1:1) was prepared from elemental Ti, Al, and Co powders. The compacts made from the powders were reacted by the thermal explosion combustion synthesis. After this, density, phases, microstructure, and mechanical properties (Vickers hardness, compressive strength of the obtained product) were measured.
The nearly full dense product could be obtained by moderate addition of the Co/Al additive. The product was consisted of TiAI, Ti3Al, and solidified Ti-Al-Co melt phases with about 20-25 mm grain size. The Vickers hardness of the product was about Hv=330, and the fracture strength was σf=1350MPa (εf=0.25).
In a previous experiment, the nearly full dense compound could be synthesized by addition of Ni/Al powder. The present product is softer than the previous compound with the Ni/Al powder addtion, and showed a slight plastic deformation. Therefore, the sintering additive affected the strength of the TiAl compound. However, the product was still too brittle to use for structure materials, and it is necessary to improve the brittleness.View full abstractDownload PDF (8125K) -
Kazuo Isonishi, Masahiro Asano2001 Volume 48 Issue 1 Pages 77-81
Published: January 15, 2001
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSEffect of phase change from unstable phase to stable phase on densification process by pressure sintering was studied by using mechanically alloyed powders. Powder mixtures of Ti and Si having the composition of Ti-37.5mol%Si were milled for 360ks and 3600ks. The latter powder showed homogeneous microstructure and amorphous-like XRD profile, although the former showed (Ti+Si) lamellar microstructure. Milled powders were vacuum hot pressed at a heating rate of 20 K/min up to 1273 K with applying constant pressure from 10 to 200 MPa, then kept for 10.8 ks. It was observed that the density of compacts increases suddenly at the temperature range between 869K and 900K for 3600ks MAed powder. This temperature range showed good agreement with that of the phase formation from amorphous to Ti5Si3. 360 ks MAed powder densified faster during heating stage, however 3600 ks MAed powder obtained higher final density after 10.8 ks holding at 1273 K due to the very fine spherical grains. It is concluded that fine grain superplastic deformation and internal superplastic deformation act an important roll in densification of MA powder having amorphous-like structure.View full abstractDownload PDF (4140K) -
Susumu Takizawa, Ryuzo Watanabe, Akira Kawasaki2001 Volume 48 Issue 1 Pages 82-86
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNon-uniform sintering shrinkage is a critical issue in MIM which the size and shape of the compacts are to be precisely controlled. To overcome this problem, we need to know how the green compacts shrink during sintering. In-situ measurement system with digital image correlation method enables us to measure the non-uniform sintering shrinkage, in two-dimension on non-contact and real time basis. In this paper, we report the measurement of the shrinking behavior of a metal-injection-molded using the digital image correlation method. The digital image correlation method is based on the principle that the brightness distribution is specific at each point on the surface of an object and moves with the surface displacement. The MIM sample was found to show a non-uniform shrinkage; the shrinkage beneath curved surface is lager than that beneath flat surface. This non-uniform shrinkage was attributed to the difference in packing density.View full abstractDownload PDF (5343K) -
Mitsuru Nakamura, Takashi Umemura, Takeshi Ohba, Yoshimi Sugaya2001 Volume 48 Issue 1 Pages 87-93
Published: January 15, 2001
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThis study of rapid sinteing method within a few minutes is to investigate under nitrogen atmosphere. Specimens were composited 0.8mass%C-1.5mass%Cu-bal.Fe powders and used by the high frequency induction heating instrument. In this case, it was important to release an adsorbed gas in iron powder particle surface. The product of decarburized layer on specimen surface was a problem because of reduce of mechanical properties. As a result, it was possible to keep about 40μm at a minimum as the decarburized layer when the constant sintering condition (1523 K-30s, LT 1323 K-60s and heating rate 10 K/s). This method was finished to sinter only 3.5 minites, and the radial crushing strength (R.C.S) was obtained almost same value compared to conventional furnace method.View full abstractDownload PDF (7190K)
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