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Shinichi Ohama
1996 Volume 43 Issue 4 Pages
407-414
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Composite materials offer many advantages when compared to an unreinforced matrix. The major advantage appears to be the ability to tailor mechanical and physical properties to meet specific needs.
Research and development of composite materials for gas turbine applications are being carried out by Research Institute of Advanced Material Gas-Generator. This paper introduces the outline of this project and presents outcome from initial three years of the program mainly manufacturing process deveropment of the gas turbine components of the composites.
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Masahiro Nawa, Syoichi Nakamoto, Keiichi Yamazaki, Tohru Sekino, Koich ...
1996 Volume 43 Issue 4 Pages
415-420
Published: April 15, 1996
Released on J-STAGE: December 04, 2009
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To compensate the definite disadvantages of ceria stabilized tetragonal zirconia polycrystal (Ce-TZP) as compared to Y-TZP ceramics, such as lower strength and lower hardness, we applied the idea of the nanocomposite to Ce-TZP/Al
2O
3 composite system. Zirconia matrix in these composites consisted of primarily the tetragonal phase and a small amount of the monoclinic phase. These composites partly possessed an intragranular nanostructure, in which fine alumina particles were trapped within the zirconia grains. At an optimum component for the 10Ce-TZP/30vol% Al
2O
3 composite sintered at 1500°C, strength of 730 MPa and very high toughness of 10.2 Mpa.m
1/2 (SEPB) were achieved. This toughness value was in excess of that (8.1 MPa⋅m
1/2) of WC/Co cermet. Therefore, it is suggested that this composite system would be expected as candidate for an attractive TZP ceramics, which have advantages of both high strength in Y-TZP and high toughness in Ce-TZP along with high resistance to low-temperature degradation.
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Yoshimasa Kobayashi, Jing-Feng Li, Akira Kawasaki, Ryuzo Watanabe
1996 Volume 43 Issue 4 Pages
421-425
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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It was recently found that SiC-AIN solid solutions can be formed over a wide compositional range and better mechanical properties were obtained particularly at room temperature for the SiC-AIN alloys than the end number materials. The present study was intended to investigate the high-temperature strength and deformation behavior of the SiC-AIN solid solution. For this purpose, superfine grained SiC-AIN solid solution and its composite samples were prepared by a reaction HIP-sintering process, and their fracture strength and deformation behavior were evaluated up to 1773K by using a newly-developed Small Punch (SP) testing method. It has been found that high fracture strength is obtained up to 1473K, and below this temperature the load-deflection curve is linear, indicating typically brittle behavior. At 1773K, plastic-like deformation behavior was observed and it intensified with decreasing strain rate. The fractographic observation suggested that the grain boundary sliding enhanced by the ultrafine grained-microstructure was predominately responsible for the appearance of the non-linear deformation at high temperature.
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Electrical and Mechanical Properties of Laminated Materials with Three Layers
Yoshiyuki Muraoka, Masaru Yoshinaka, Ken Hirota, Osamu Yamaguchi
1996 Volume 43 Issue 4 Pages
426-432
Published: April 15, 1996
Released on J-STAGE: July 12, 2010
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Well-densified composites with the compositions of ZrO
2(2Y)/WSi
2=60/40 and 80/20 mol% have been fabricated by hot isostatic pressing for 2 h at 1500°C and 196 MPa. Electric resistivities (ρ) between both composites change drastically; the former and latter composites correspond to the metallic and insulating materials, respectively. They are strongly dependent on the textures. Laminated materials with the compositions of ZrO
2(2Y)/WSi
2 =(60/40)/(80/20)/(60/40) mol% have been able to be prepared by the same technique. Overall electric resistivities in the perpendicular and parallel directions for the interfaces are determined to be ρ⊥≈1×10
11 and ρ//≈1×10
-4 Ω⋅cm, respectively. The residual stress as much as ≈200 MPa is induced in the interfaces. The fracture toughness (K
IC) is much affected by the residual stress.
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Satoshi Emura, Masuo Hagiwara, Yoshikuni Kawabe
1996 Volume 43 Issue 4 Pages
433-437
Published: April 15, 1996
Released on J-STAGE: December 04, 2009
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To improve the high temperature performance of Ti
3Al intermetallics, 10wt% TiB ceramic particulate reinforced Ti-24Al-11Nb(at%) matrix composites have been produced by blended elemental (BE) powder metallurgy method. Pure titanium powder, Nb-Al master alloy powder and TiB2 ceramic powder were used as the starting materials. TiB particulate reinforcements were dispersed in-situ in the matrix during the vacuum sintering. By using finer starting powder (45μm) and sintering at higher temperature (1823K), homogeneous dispersion of TiB particulates was attained. The density of the composite was also increased with the decrement of the size of starting powders and the increment of the sintering temperature. The results of high temperature tensile and creep tests indicated that high temperature mechanical properties of Ti-24Al-11Nb/TiB composites were superior to those of the unreinforced Ti-24Al-11Nb.
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Tae Young Um, Yong Ho Park, Hitoshi Hashimoto, Shinchi Sumi, Ryuzo Wat ...
1996 Volume 43 Issue 4 Pages
438-443
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The aims of this study were to observe the microstructure and the tormed phases of Ti-Al intermetallic compound system composites made by spark plasma-combustion synthesis and to investigate the phase formation mechanism.
During the spark plasma sintering of the Ti:Al=1:1 powders, combustion synthesis was indicated by the abruptly shringkage in sample volume at Al melting point. The microstructure and the formed phase of spark plasma-combustion synthesized composites varied according to Ti particle size. For example, TiAl
3 phases were formed when 100μm Ti powders were used, and TiAl, Ti
2Al and Ti
3Al phases were formed when 10μm Ti powders were used (the sintering temperature was 973K). The formation mechanism of compounds using spark plasma sintering has two processes; combustion synthesis at Al melting point and diffusion in the high temperature region.
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Wan Jiang, Kenichi Tsuji, Tetsuo Uchiyama, Ryuzo Watanabe
1996 Volume 43 Issue 4 Pages
444-449
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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SiC whisker reinforced MoSi
2 composites were fabricated by hot pressing to more than 98% of theoretical density. Flexural strength and steady state creep strain rate of these composites exhibited substantial improvements over MoSi
2 matrix material. In the case of the MoSi
2-20vol% SiC whisker composites, the flexural strength was 1010 MPa (2.8 times MoSi2 matrix) at room temperature and 1420 MPa (3.7 times MoSi
2 matrix) at 1000°C; the steady state creep strain rate under a stress of 100 MPa at 1300°C was 2.2×10
-7/Sec (1/26 of MoSi
2 matrix). The material and microstructural characteristics contributing to these improvement mechanisms are discussed in this paper.
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Hidemi Watanabe, Osamu Kimura
1996 Volume 43 Issue 4 Pages
450-453
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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It is well known that a large thermal stress arise in a SiC whisker/Al2O3 composite. The compressive stress in the composite due to thermal expansion mismatch can introduce whisker clamping by the matrix during cooling, because the thermal expansion coefficient of the matrix is higher than that of the whisker. However, the possibility for existence of tensile stress is evaluated on the basis of a stress analysis, too. In this paper, analitical estimate of the stress was obtained by using E.Melan's theory. The caluculation has shown that a large tensile stress is generated in the surface of composite.
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[in Japanese]
1996 Volume 43 Issue 4 Pages
456
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Noriyoshi Shigaki
1996 Volume 43 Issue 4 Pages
457-463
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Fine grain cemented carbide having high hardness and toughness is used in various kinds of precision procecing industries such as semiconductor, electronic device, machine work. In order to make clear grain growth mechanism of WC phase for fine grain cemented carbide, a lot of studies have been done. However, there have been a few studies on formtion mechanism of ultrafine WC powder. We succeeded in manufacturing of ultrafine WC powder by direct carburizing method (direct reaction of W oxide powder with C). Particle diameter of WC powder made by direct carburizing method is mainly determined by the nucleation generated by the reaction from WO
2.72 to WO
2. Direct carburizaing method is advantageous to the manufacturing of ultrafine WC powder, and cemented carbide made from ultrafine WC by direct carburizaing method has higher hardness, strength and toughness than conventional cemented carbide.
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Katsuhiro Nishiyama
1996 Volume 43 Issue 4 Pages
464-471
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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An experimental and analytical studies for obtaining high performance ceramics of TiB
2-and B
4C-based hard materials are inclusively presented in this paper. An improvement of sinterability and mechanical properties of TiB
2 and B
4C hard materials are achieved by using ultra-fine powders and sintering aids. First results obtained showed that the ultra-fine and size-controlled powders of TiB
2 can be produced by magnesium-thermic reduction method. Fabrication processing of TiB
2 using pressureless sintering was also investigated with special emphasis on the effect of doping Ni
7Zr
2, Ni
3B, NiB, and Co. The pore-free sintered compacts can be obtained by the addition of extreme small amount of Ni
7Zr
2. Moreover, sintering behavior and mechanical properties of B
4C-TiB
2 composites were investigated by pressureless sintering up to 2100°C in vacuum, resulting in a maximum density of 99% of the theoretical density. Tailored microstructures may be obtained in composites on the B
4C-TiB
2 system. The importance of microstructural features, resulting from precipitation phases from supersaturated solid solutions, for the improvement of sinterability and mechanical properties, is also addressed. Finally, sliding friction experiments were conducted on hard materials. A friction coefficient of B
4C-TiB
2 as low as 0.1 can be obtained because the oxidation of btmde produces a trapped-lubricating, glassy phase of boron oxide on the sliding surfaces.
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Katsuya Uchino, Akihiko Ikegaya, Toshio Nomura, Tsugio Miyagawa, Hiden ...
1996 Volume 43 Issue 4 Pages
472-477
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Steel coated with high wear-resistant and high corrosion-resistant hard materials are widely used, but this composite product does not always obtain the properties which coating materials originally have, mainly because coating materials with enough hardness could not be jointed densely and thickly as desired. It is possible to realize the aimed properties on the coated product if the cemented carbide could be coated in dense and thick way. In order to do so, over-coming the thermal stress between the steel and the cemented carbides is necessary, because the stress may cause the cracking of the product and the peeling of the cemented carbides from the steel. Study indicated that the coating the powder of different Co percentage of cemented carbides in multiple layers on steel and using the Spark Plasma Sintering process to sinter and joint the steel and cemented carbide simultaneously solves the problem. The characteristics of this process are low-temperature and short-time sintering. Crack-and peel-free coated product was realized from this process.
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Takahiro Fukushima, Saito Minoru, Osamu Terada, Hisashi Suzuki
1996 Volume 43 Issue 4 Pages
478-481
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Microstructures, hardness, cobalt and carbon contents of WC-Co alloys prepared commercially in different manufacturers for anvil and cylinder of high pressure apparatus were, in detail, examined. It was known that the above properties of anvil or cylinder were, at first sight, almost in the same way, in spite of the difference of manufacturers. On the other hand, it was noted that very coarse WC particles were usually observed in the microstructures of both parts of anvil and cylinder. It was also noted that the distribution of HV, cobalt and carbon contents throughout the parts were never uniform, with the fact that those properties differed distinctly between the surface layer and inside of the parts, in no relation to the sorts of manufacturers.
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Hideyuki Ogishi, Akiyoshi Mizuta, Hyoe Ono, Akira Tamura
1996 Volume 43 Issue 4 Pages
482-485
Published: April 15, 1996
Released on J-STAGE: December 04, 2009
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In the case of partial application of hard materials to wear-resistant components, it is difficult to insert by casting WC-based cemented carbide. In order to solve this problem, we studied WC- (high chromium cast iron) alloys that applied high chromium cast iron instead of cobalt as a binder of WC-based cemented carbide.
We conducted studies on the manufacturing method, mechanical properties, and powder abrasion properties of this WC- (high chromium cast iron) alloy and obtained the following results.
(1) Sound sintered products were obtained by sintering in a pressurized nitrogen atmosphere.
(2) Sintered products with a hardness similar to that of sintered WC-based cemented carbide were obtained.
(3) Sintered products with a flexural strength similar or superior to that of high chromium cast iron were obtained.
(4) Sinterd products with powder injection abrasion properties similar to those of sintered WC-based cemented carbide were obtained.
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Takayoshi Kuchiki, Noriaki Kikuchi, Mamoru Kodaka, Seiji Akiba, Yuichi ...
1996 Volume 43 Issue 4 Pages
486-492
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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We tried to experiment on the dry interrruptied cutting of austenitic stainless steel plates(SUS304) using power tools with cermet tipped-saw. The purpose of this paper was to investigate the effect of cutting speed on the cermet wear mechanism and wear damage of tip, and then to compare these results with those on cemented carbide. It was found that the cutting temperature of workpiece became 350-420K at the first cutting, and rapidly increased up to 1, 470 K at the end of tipped-saw life, and then the wear occurred by a repeat of adhesives formed in the built-up edge and spalling. Some discussions were made on these results.
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Cutting condition and Roughness of Finished Surface
Eiichi Sentoku, Hiroshi Tanaka, Hiroshi Kawabata
1996 Volume 43 Issue 4 Pages
493-497
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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In recent years, many ceramics with various kinds of properties have appeared on the market. Those ceramics are used for a few mechanical and electronic parts. The strength of alumina-ceramics piece is influenced by the residual crack of the finished surface on the green compact. The purpose of this paper is to clarify the machining performance of alumina-green compact. The machining performance of alumina-green compact is investigated and is discussed from view point of the relation between the flank wear of tool edge and the roughness of machined surface on the work-piece. In the cutting test by turning, the cutting speed was varied from 35 m/min to 150 m/min. The frequency of tool edge was measured by FFT(Fast Fourier Transform) analyzer, and worn parts of the tools were observed with the SEM and the microscope. The main results obtained are follows: (1) In the finish cutting for alumina-green compact, the best cutting condition was obtained as cutting speed of 100 m/min, feed 0.1 mm/rev, depth of cut 0.2 mm by tool of WC sintered carbide, and roughness Rmax of the machined surface was 7.10μm. (2)The tool life of this cutting was lager than other cutting. (3)The size of chip as cutting increased in proportion to the cutting length for 1/4 period of frequency on the tool edge.
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Yuji Yamasaki, Kazunori Nakano, Ken-ichi Takagi, Kazuyuki Koike
1996 Volume 43 Issue 4 Pages
498-503
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The properties of a complex (Mo, Ni) boride influenced by additions of W were investigated in Mo-Ni-Cr-W-B sintered alloys where the boride has the tetragonal crystal structure due to solid solutioning of Cr. Additions of W lead to partition of W primarily into the complex boride, resulting in a stoichiometric change of the tetragonal boride from Mo
2(Ni, Cr)B
2 to (Mo, W)
5-x(Ni, Cr)
xB
3 around 10mass%W. The alloys having the tetragonal Mo
2(Ni, Cr)B
2 boride with W in the boride maintained high levels of transverse-rupture strength(TRS) and hardness due to small particle size of the boride up to 5mass%W. The stoichiometric change of the boride by additions of W caused increase in hardness and decrease in TRS due to increased volume fractions of the boride at the given boron content.
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Sakae Takahashi, Kimitaka Maruyama
1996 Volume 43 Issue 4 Pages
504-509
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The effects of Si contents on the mechanical properties and microstructures of Ni-2.2 mass%B-(0-6.4)mass%Si-30mass%WC-15mass%Mo alloys were studied. The transverse-rupture strength ( TRS ) declined as the Si contents increased after the TRS reached its peak (2.0GPa) at 3.2 mass% Si. The TRS values of the alloys increased with dissolution of Si into binder phase and with dispersion of fine Ni
3Si particles. In the case of coarse Ni
3Si, Ni
31Si
12 particles were formed in the binder phase, the TRS decreased.
The hardness increased as Ni
3Si, Ni
31Si
12 was formed in the binder phase. The maximum hardness of HRA87.5 was obtained at 6.4 mass% Si.
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Kazunori Nakano, Masaru Inoue, Kazuyuki Koike, Ken-ichi Takagi
1996 Volume 43 Issue 4 Pages
510-514
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Ternary Cr
3C
2-Ni-WB cermets can be sintered to full density at temperatures lower than 1450K. The lower densification temperatures, compared with the Cr
3C
2-Ni system (1550K), were attributed to the liquid phase formation as the results of WB-Ni quasi-eutectic reaction prior to Cr
3C
2-Ni reaction. The bonding of the interface proceeds during the liquid phase sintering of the cermets. A direct reaction between the Cr3C2 particles and the substrate material should be avoided for a satisfactory sintered body of the cermet and sufficient interface bonding strength. In case of the cermets without WB, an excessive reaction occurred due to higher sintering temperatures than the reaction temperature at the interface. The direct reaction between the Cr
3C
2 and S45C generates a large amount of a liquid phase and causes remarkable grain coarsening of the carbides. The coarsened carbide particles were identified as a M
7C
3 type containing W and Fe.
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Dong-Gil Ahn, Yong-Ho Park, Akira Kawasaki, Ryuzo Watanabe
1996 Volume 43 Issue 4 Pages
515-519
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The purpose of this study is to investigate the formation of a new phase in TiB
2-W cermets during HIP sintering and to evaluate the influence of this new phase on the mechanical properties. Green compacts of TiB
2-W with compositions between 5 and 40vol%W were densified by HIP at a pressure of 200MPa and temperatures above 2023K, which yielded the cermets with a relative density of more than 99%. Analysis of these semples by XRD, EPMA and Auger, showed the presence of TiB
2, β-WB and WTiB
2, however no metallic W was detected between 5 and 30vol%W. The Vickers hardness, fracture toughness and Young's modulus increased with the formation of the WTiB
2 phase, and its volume fraction increased at W-rich compositions. The highest fracture toughness of 7.8MPam
1/2 and Young's modulus of 571GPa, were obtained for the TiB
2-25vol%W composition. The Vickers hardness value of all specimens was above 20GPa. The fracture toughness values of the higher W compositions were greater than those of the lower W compositions.
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Pablo Wally, Masanori Ueki, Peter Ettmayer
1996 Volume 43 Issue 4 Pages
520-525
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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In order to study the phase stability of the hard particle grains in cermet cutting materials (Ti, Mo)(C, N)-Ni cermets were heat treated at 1393K for 7.2 × 10
3 ks (2000h). The microstructurel changes were compared to the changes observed in nitrogen free (Ti, Mo)C-Ni cermets under otherwise identical conditions. (Ti, Mo)C-Ti(C, N) and (Ti, Mo)C-TiC diffusion couples were also prepared and heat treated at 2023 and 2173 K. Surprisingly, the (Ti, Mo)C-Ti(C, N) diffusion couple showed faster diffusion kinetics than the (Ti, Mo)C-TiC couple. A mechanism based on the chemical interaction of Mo and N atoms was proposed for this phenomenon.
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Yutaka Yanaba, Koji Hayashi
1996 Volume 43 Issue 4 Pages
526-530
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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In our previous study, we have theoretically derived an equation of σ
m=ψK
ICS
mf1/2 based on the fracture theory for general hard materials, where σ
m is the flexural strength of test piece, ψ is a factor, K
IC is the fracture toughness and S
mf is the total macroscopic area of fracture surfaces of all fragments of one test piece, and also experimentally confirmed it's validity on two kinds of hard materials, i.e., WC-Co cemented carbides and Si
3N
4 base ceramics. In this study, the error due to stopped cracks (cracks which do not cause the formation of fragments, but generate internal fracture surfaces) in the relative value of K
IC estimated by using the above equation was investigated on WC-10mass%Co cemented carbide (the size of test piece is 4×3×36mm
3 and the span of ii e is 30mm).
The results obtained were as follows; (1)The total macroscopic area of internal fracture surfaces formed by stopped cracks (S
c) increased from 4.7 to 9.3mm
2 with increasing σ
m. However, the ratio of S
c/S
mf was almost constant; 0.05-0.06. (2)A linear correlation was found between σ
m and (S
m ?? +S
c)
1/2 in similar manner to σ
m-S
mf1/2 relation. The slope of the correlation line (ψK
cIC; K
cIC is the fracture toughness estimated by taking into consideration S
c) was nearly the same as that of σm-Smf1/2 correlation line (ψK
IC) in accordance with the results that K
cIC/K
IC expressed as {S
mf/(S
mf+S
c)}
1/2 was 0.97-0.98 and the error estimated by equation (K
IC-K
cIC)/K
cIC is about 2.5%. Therefore, it was concluded that the error due to stopped cracks or S
c is negligible.
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Formation of L12-Al3 Ti Phase by the Addition of Cu
Masao Morishita, Koichiro Koyama, Masahiko Morinaga, Hirohiko Adachi
1996 Volume 43 Issue 4 Pages
533-539
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The mechanism of the crystal structure transformation of Al
3Ti from DO
22 to a high symmetry Ll
2 by the addition of Cu was investigated using the DV-X α molecular orbital calculation. The calculation suggested that Ti atoms were able to locate at the 2nd neighbor sites of Ti atoms by substitution of Cu atoms for a part of Al atoms, namely, the 1st neighbor sites of Ti atoms. This atomic configuration is the mechanism for the stabilization of the Ll
2 crystal structure of Al
3Ti by the addition of Cu. Therefore, Cu was added to improve the ductility of a new reaction sintered Al-Ti-N alloy which consists of Al
3Ti and AlN phases. The added Cu transformed the crystal structure of Al
3Ti from DO
22 to a high symmetry Ll
2, and as a result, decreased the hardness of the alloy.
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Nobuhiro Tsujii, Genryu Abe, Kenzo Fukaura, Hisakichi Sunada
1996 Volume 43 Issue 4 Pages
540-544
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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Effects of the quenching temperature on the high temperature low cycle fatigue property of P/M hot work tool steel, which is a newly developed 4.2Cr-2.5Mo-V-Nb steel, were investigated in comparison with conventional ingot metallurgy products of the same grade. The fatigue life of P/M material quenched from 1403K was longer than that from standard quenching temperature, 1303K, while I/M material showed opposite tendency. The improvement of fatigue life of P/M material by quenching from high temperature was due to the finer grain and the increase of slip deformation stress because of the fine dispersion of carbides. The coarsening of grain, which was observed in I/M materials quenched from high temperature, promoted initiation and propagation of fatigue cracks and brought a decrease of the fatigue life. It was clarified that the grain size and high temperature hardness were important factors for high temperature low cycle fatigue property of hot work tool steels.
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Satoshi Uenosono, Shigeru Unami, Kuniaki Ogura
1996 Volume 43 Issue 4 Pages
545-549
Published: April 15, 1996
Released on J-STAGE: May 22, 2009
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The effect of graphite retained in the pore sites of sintered steels on machinability was investigated. Sintered steels containing retained graphite were obtained by sintering green compacts made from sulfur-containing iron powder with copper and graphite. Retained graphite in the pore sites of sintered steels in amounts of 0.1 to 0.3wt% resulted in 10 times longer drilling tool life and no significant impact on tensile strength.
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