MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 45 , Issue 4
Showing 1-50 articles out of 72 articles from the selected issue
  • Takashiro Ohyama, Hiroo Iwata, Yoshichika Kubo, Waro Taki
    2004 Volume 45 Issue 4 Pages 978-982
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The use of β-tricalcium phosphate (β-TCP) as osteoconductive and bone morphogenetic protein-2 (BMP-2) as osteoinductive bone graft substitutes has recently gained considerable research interest in spine surgery. However, whether the combination can be extrapolated to a successful interbody spinal arthrodesis remains uncertain. In this study, β-TCP combined with recombinant human BMP-2 was examined in the canine lumbar spine model as a substitute for autograft used for packing interbody fusion cages. The discectomy and interbody cage fusion were performed at three disc spaces in 8 dogs. The examination of microradiographs and histological sections of the lumbar spine at 16 weeks post-surgery revealed three fusions in autograft group (A), three β-TCP group (B), and five in β-TCP-BMP-2 (C). The mean percentage of trabecular bone area in the cages was 51.9% in group A, 48.8% in group B and 65.6% in group C. Statistical analyses of the results could not give significance. The young animal model used in this study might suppress difference between the groups. As mentioned, however, actual data of mean percentage of trabecular bone formation and of mechanical stiffness were largest in the cages filled with β-TCP and BMP-2. In clinical settings, we expect that a cage filled with β-TCP and BMP gives beneficial effects especially for patients with poor fusion statuses.
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  • Makoto Kitamura, Chikara Ohtsuki, Shin-ichi Ogata, Masanobu Kamitakaha ...
    2004 Volume 45 Issue 4 Pages 983-988
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    We attempted to fabricate α-tricalcium phosphate (α-TCP) ceramic porous body with interconnected continuous pores through conventional sintering process. Porous bodies were obtained by sintering the bodies prepared from slurry composed of β-TCP, potato starch and ultra-pure water. Distribution in pore size was uniform ranging between 10-100 μm in diameter. The pore size was mainly due to similarity of distribution in particle size of the potato starch. The porous body (CP-50), that is prepared from the slurry containing 50 mass% of starch, has 73.8% of porosity, and is able to be easy in secondary machining with surgical knife. Porosity of porous body increased with increasing the amount of potato starch added to the slurry. Compressive strength of porous bodies remarkably decreased with increasing the porosity of the porous body. Dissolution behavior was evaluated by released amounts of calcium and phosphate ions from the porous body in buffered solutions. Higher porosity of the ceramic body resulted in higher dissolution rate in the buffered solution. In vivo evaluation by peripheral quantitative computed tomography (pQCT) shows higher density of regenerated bone after the implantation of CP-50 than that of no specimen at defect in rabbit tibia, at four weeks postoperatively. α-TCP ceramic porous body was almost completely absorbed within four weeks after implantation. Consequently, we successfully fabricated α-TCP ceramic porous body with uniform pore distribution through a process with a direct casting method of slurry containing potato starch. This microstructure of the porous body gives high machinablity as well as bioresorbability.
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  • Hirotaka Maeda, Toshihiro Kasuga, Masayuki Nogami
    2004 Volume 45 Issue 4 Pages 989-993
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A novel sponge, coated with bonelike apatite (b-HA) on its skeleton surface, was prepared using a particle-leaching technique combined with a biomimetic processing. A powder mixture consisting of calcium carbonate/poly(lactic acid) composite (CCPC) and sucrose was hot-pressed and then the resulting compact was soaked in the simulated body fluid at 37°C. Within the first hour, the sucrose was completely dissolved out, resulting in the formation of large-sized pores in the compact, and subsequently, after 3 hours of soaking, b-HA formed on the skeleton consisting of CCPC. On the other hand, on a pore-free CCPC, the apatite started to form after 12∼18 hours. The induction period for b-HA formation on the skeleton of the CCPC sponge prepared using a particle-leaching technique is significantly shorter than that of the pore-free CCPC. The short period is suggested to originate from that a large amount of Ca2+ ion is rapidly supplied into the compartment space (pore) from the CCPC skeleton. The formed sponge has numerous, large pores of 450∼580 μm in diameter, which are connected with channels having a diameter in the range of 70∼120 μm, as well as a high porosity of 75%. Animal test using rats showed that the sponge has osteoconduction. The sponge is expected to be one of the promising candidates for osteoconducting fillers or tissue-engineering scaffolds.
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  • Akihiko Yoshida, Toshiki Miyazaki, Eiichi Ishida, Masahiro Ashizuka
    2004 Volume 45 Issue 4 Pages 994-998
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Natural bone is a kind of nanocomposites composed of orientated hydroxyapatite (HAp) along c-axis and fibrous collagen. Therefore, composites exhibiting composition and structure analogous to those of natural bone have been expected to be useful bone substitute materials. Organic polymer-HAp composites have been attracted much attention since they have interesting features such as bone-bonding ability, i.e. bioactivity and flexibility. In the present study, chitosan-HAp nanocomposites were prepared through mechanochemical reaction using conventional ball mill and subsequent aging. The obtained composites contained carbonate-containing HAp, and HAp nanocrystals in the composites aged at 25°C for 24 h showed a needle-like structure. They can form bone-like HAp on their surfaces after soaking in simulated body fluid (SBF), indicating potential for bioactivity in living body. The prepared chitosan-HAp composites are expected to be one of the useful bone substitute materials.
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  • Kyosuke Yoshimi, Mayumi Shoji, Tomohisa Ogawa, Akira Yamauchi, Takako ...
    2004 Volume 45 Issue 4 Pages 999-1004
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The microstructure and orientation distribution of aragonite crystals in the nacreous layer of cultured Pteria penguin are investigated in this paper. Helical patterns formed by growth forefronts of the nacreous layer for good-quality shells are observed using a laser microscope, whereas no clear pattern is observed on the nacreous layer surfaces of bad-quality shells. The observed aragonite crystals are plate-shaped and hexagonal for both the good and bad-quality shells, in which the top and bottom faces are parallel to the (001) plane and the side faces are parallel to the {110} and (010) planes. The aragonite crystals in the nacreous layer of good-quality shells seem to be harmonically oriented along a crystallographic direction. These orientation distributions basically indicate that the (001) basal planes are parallel to the inner shell surface, and the [100] and [010] axes are oriented in almost the same direction, respectively. Some of the aragonite crystals are rotated about the c axis by approximately ±60° from the basic orientation distribution. On the other hand, the aragonite crystals of bad-quality shells seem to be randomly oriented in the nacreous layer. These orientation distributions indicate that the (001) basal planes are parallel to the inner shell surface in a similar manner as those of good-quality shells, but their [100] and [010] axes are randomly oriented about the c axis. Therefore, it is considered that such different orientation distributions result in different qualities of pearls that are developed in the shells.
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  • Yoshimi Watanabe, Takashi Iwamoto, Akira Teramoto, Koji Abe, Yutaka Oh ...
    2004 Volume 45 Issue 4 Pages 1005-1009
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The aim of this study is to develop a functionally graded material (FGM) of biodegradable poly (L-lactic acid) (PLLA) with a hardness gradient. For this purpose, the PLLA was extruded at elevated temperatures to introduce molecular orientation. Two types of extrusion, direct extrusion and equal channel angular (ECA) extrusion, were carried out. Heat treatment without extrusion was also carried out at 50°C, 60°C and 70°C. For the mechanical property characterization, the hardness distributions were investigated using a Vickers microhardness tester. Biodegradability of PLLA FGM was measured by evaluating the mass decreasing ratio after incubation in a physiological saline solution at 37°C. It was found that the PLLA FGMs with symmetric and asymmetric hardness gradients could be fabricated by direct extrusion and ECA extrusion at elevated temperature, respectively. Although in the initial state the mass of PLLA gradually increased with the softening of the FGM, it started to decrease after two weeks.
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  • Kazutoshi Tani, Fumio Watari, Motohiro Uo, Manabu Morita
    2004 Volume 45 Issue 4 Pages 1010-1014
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The differentiation of porcelain from tooh using fluorescence emission was investigated as a basic research for the visual detection of porcelain-restored teeth in mass dental health examinations. The fluorescence spectra were taken from the extracted human maxillary central incisors and five types of porcelain by excitation using the light 380-470 nm. There was a clear difference in fluorescence intensity between tooth and porcelain using excitation longer than 400 nm. Tooth and porcelain could be successfully distinguished on an image photographed by fluorescent light.
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  • Jose H. Santos, Naoki Matsuda, Zhi-Mei Qi, Takamitsu Yoshida, Akiko Ta ...
    2004 Volume 45 Issue 4 Pages 1015-1018
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A time-resolved evanescent wave absorption technique is employed in studying the adsorption of a mammalian protein (cytochrome c) from an electrolyte-free solution on a hydrophilic glass surface. The method combines the sensitivity of a fast-scan spectral analyzer and surface specificity of slab optical waveguide (SOWG) technique. While proteins are viewed to undergo an overall irreversible adsorption process brought about by structural changes that occur after the initial adsorption phase, we have used an SOWG technique to investigate the first stage of the adsorption process while no noticeable changes have taken place. Absorbance data within the first two seconds after contact fit well into the reversible adsorption model characteristic of Langmuir-type adsorption but the goodness-of-fit diminishes as the protein molecules spend more time on the surface.
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  • Makiko Yonehara, Tsutomu Matsui, Koichiro Kihara, Hiroaki Isono, Akira ...
    2004 Volume 45 Issue 4 Pages 1019-1026
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    This paper describes a quantitative evaluation method for metal surface texture. We used surface roughness and glossiness as parameters to describe surface texture. Specimen surface roughness was evaluated based on geometrical product specification data taken from japanese industrial standards. The effects of surface roughness on glossiness were investigated by aluminum alloys. The relationship between the glossiness and the roughness height, the period of the roughness profile and the slope for the surface roughness processed by a vertical milling machine were studied for determining if the topography of the surface roughness affects the glossiness. The surface of the specimens were polished using abrasive paper and blasted, so that the arithmetical mean deviation, Ra, was less than 1.00 μm. The effects of roughness on glossiness were investigated on polished surfaces and blasted surfaces. The results show that the surface roughness shape and the glossiness prove to be effective indices for evaluating the surface textures of aluminum alloys.
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  • Makiko Yonehara, Tsutomu Matsui, Koichiro Kihara, Hiroaki Isono, Akira ...
    2004 Volume 45 Issue 4 Pages 1027-1032
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    This paper describes the establishment of an evaluation method for metal surface texture. The evaluation parameters used for surface texture were roughness, glossiness and color. Seven sample materials were studied: aluminum alloys (A2017, A5052), stainless steel (SUS304) and copper alloys (tough pitch copper C1100, brass C2801, phosphor bronze C5191 and nickel silver C7541). The surfaces of all specimens were polished using waterproof abrasive papers. The correlation of the surface texture parameters for all specimens was investigated experimentally. The surface roughness of specimens was evaluated using the arithmetical mean roughness “Ra”. The method for evaluating surface color was assessed by using CIELAB color space. The CIELAB color space is one of a uniform color space defined by CIE (Commission Internationale de l'Eclairage) in 1976. The results indicated that as surface roughness value “Ra” decreased, as the glossiness value “Gs(60°)” increased exponentially. The lightness value “L*” of the CIELAB color space decreased, as surface roughness value “Ra” decreased. Thus, the relationship between the lightness value “L*” and surface roughness value “Ra” showed an inverse correlation with the glossiness value “Gs(60°)” and surface roughness value “Ra”. Moreover, the surface color showed that the blue hue increased, as the surface roughness value “Ra” decreased for all seven types of materials.
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  • Magda Kiyoko Yamada, Motohiro Uo, Shoji Ohkawa, Tsukasa Akasaka, Fumio ...
    2004 Volume 45 Issue 4 Pages 1033-1040
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A newly developed scanning electron microscope (SEM) installed with a 3D analyzer and a confocal laser scanning microscope (CLSM) were used to evaluate the images and surface profiles of enamel and dentin after CO2 laser irradiation. The surface roughness (Ra) was measured and the results were correlated with a stylus profilometer. Raman analysis was done and the laser irradiation effect after acid etching was also examined. Human intact extracted teeth were vertically sectioned. The laser was applied perpendicularly to non-etched and 35% phosphoric acid-etched teeth. The enamel resulted in a crater-like surface. The material was removed in the places where hydroxyapatite crystallites ran parallel to the irradiated surface. Non-etched dentin showed little change after irradiation, with some cracks mostly in the peritubular dentin; whereas in acid-etched dentin there was evaporation of collagen and melting of hydroxyapatite. The SEM and CLSM showed similar profiles and different image contrast. Ra levels obtained by the SEM and CLSM were similar to that obtained with the stylus profilometer. Raman analysis showed that bands of organic collagen matrix on dentin were lost and broad peaks due to carbon were observed. Both the SEM and CLSM provided non-contact evaluation of structural changes of teeth by laser irradiation through surface analysis in selected microareas, which was not possible using the stylus profilometer. Dentin showed more structural changes on the acid-etched surface by irradiation than on the non-etched one.
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  • Yasunari Ishikawa, Tadashi Sasada
    2004 Volume 45 Issue 4 Pages 1041-1044
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Frictional behavior of stainless steel cup against polyethylene head coated with dimethylacrylamide (DMAA) hydrogel was studied using a pendulum type friction tester. The friction coefficient of the pairs lubricated with Hyaluronic acid aq (HA) was as about 0.01, which is similar to that of living human hip or knee joint. The friction of the pair increased with loading time. When the coated head was immersed in the HA lubricant during an interval of repeated swing motions of the pendulum, the friction coefficient was above low value. The friction coefficient of the pair lubricated with a hydrophobic liquid (silicone oil) was as a high value of 0.4, close to the value without any lubricant. The friction coefficients of pairs lubricated with HA were not dependent on the load. The coefficients of friction lubricated with the biological factor (albumin, phospholipid) additive HA showed a little increase. Especially with albumin, the coefficient of friction increased with load. This behavior may be caused by the attachment albumin to hydrophilic high molecular chain by chemical adsorption. From these experimental observations, it is surmised that the low friction shown in coated PE head is caused by the formation of highly viscous zone through hydration of DMAA at the solid/liquid interface.
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  • Masaru Okuyama, Jun Kobayashi, Seisho Take, Yasuhiko Itoi
    2004 Volume 45 Issue 4 Pages 1045-1053
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Sealing treatment for the porous titanium layers was performed in attempt to prevent cytotoxic nickel ions releasing from porous titanium plasma-sprayed Ni-Ti alloys due to the existence of chloride ions in the body liquid. Two types of sealants were used for this purpose, one was a group of biocompatible polymer resins and the other was metallic titanium. As polymer sealants, 4 kinds of resins (silicone, cyanoacryl resin, epoxy resin and polyamide resin) were used. The first three sealants were soaked into the porous coating layers after dilution by organic solvents, while the thermoplastic polyamide resin was melted and then penetrated into them. On the other hand, physical evaporation deposition (PVD) technique was employed for sealing with titanium metal. The effect of combination of the thickness of the plasma-sprayed layers and the amount of titanium deposited by PVD was investigated. The effectiveness of the sealants was evaluated by electrochemical polarization measurement. The adhesion test of the coating layer to the alloy substrate was also carried out. Among the polymer sealants, the polyamide resin showed excellent performance. As for the titanium PVD sealing, optimum combinations of the thickness of the coating layers and the amount of titanium PVD existed for both corrosion resistance and adhesion strength.
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  • Allan E Jacobs, Stephanie H Curnoe, Rashmi C Desai
    2004 Volume 45 Issue 4 Pages 1054-1059
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Domain patterns in several classes of ferroelastics are studied using a Landau expansion in the strains and their derivatives. Examination of the local rotation, the non-order-parameter strains and the local energy density reveals the wedge and other disclinations responsible for the complexity of the patterns in (1) tetragonal-orthorhombic materials, and (2) hexagonal-orthorhombic and related materials. At temperatures where the parent phase is unstable and so has negative stiffness, simulations of hexagonal-orthorhombic systems yield pockets where the order parameter is much reduced; if the parent phase exists experimentally under these conditions, it might give rise to extreme damping. For cubic-tetragonal materials, perturbing the parent phase at a temperature well below its stability limit gives an inhomogeneous noncompact product.
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  • Yoshinori Tanaka, Shoji Ishida, Setsuro Asano
    2004 Volume 45 Issue 4 Pages 1060-1064
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    For many years, many researchers had taken it for granted that the martensitic phase of Ni2MnGa was the tetragonal structure. The common knowledge as regads the magnetic moment of the Heusler alloys including Mn was around 4.0 μB per formula unit (f.u.). However, Brown et al. newly observed the super-cell structure as the martensitic phase and reported the small magnetic moments on Mn in Ni2MnGa. In this paper, the electronic structures are calculated and magnetic moments are estimated for Ni2MnGa in the L21 and martensitic super-cell structures. In our calculation, we obtained a variety of magnetic moments on Mn in the martensitic structure and that values are largely different each other.
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  • Shoji Ishida, Shingo Kawakami, Setsuro Asano
    2004 Volume 45 Issue 4 Pages 1065-1069
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    To theoretically examine the existence of half-metals in Co-Cr-Fe-Al alloys, band calculations were carried out for these alloys. Seeing energy dispersion curves E(k) of Co2CrAl with the Heusler structure, we find that the Fermi level intersects the E(k) curves in the majority-spin state but is located at the energy gap in the minority-spin state, that is, it is predicted that this stoichiometric Co2CrAl alloy is half-metallic. On the other hand, the half-metallic properties are not observed in the electronic structures of Co2FeAl. The composition dependence of electronic structures of Co2(Cr1−xFex)Al (x = 1/8—7/8) indicates that the alloys have the tendency to become half-metallic in the range of x < 5/8.
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  • Yasuhito Ogata, Masaya Takatugu, Takeshi Kunimasa, Keisuke Uenishi, Ko ...
    2004 Volume 45 Issue 4 Pages 1070-1076
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    In order to investigate the applicability of laser micro welding to the fabrication of medical devices, Ti-Ni shape memory alloy wires with pseudo-elasticity were micro spot melted by using YAG laser. By changing the melting parameters, such as laser power or pulse duration, the evolution in microstructure, tensile strength and pseudo-elasticity was investigated. Melted metal width decreased with decreasing the input energy and pulse duration. The microstructure of melted areas was cellular dendrite structures and that of heat affected areas was grown cell structure with a cell size of about 3∼10 μm. Tensile strength of spot melted wires was 30% lower than that of base metal, and the fracture occurred in melted areas with a brittle fracture surface. Although melted areas and heat affected areas did not show a pseudo-elasticity due to the larger grain size, minimizing the width of melted metal improved the overall pseudo-elasticity of spot melted samples. For the sample wires that were prepared by spot melting of cold rolled wires and by the subsequent heat treatment for shape memorizing, the pseudo-elasticity was improved because heat affected zone recrystallized to form fine grains.
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  • Yusuke Fukui, Tomonari Inamura, Hideki Hosoda, Kenji Wakashima, Shuich ...
    2004 Volume 45 Issue 4 Pages 1077-1082
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Ni-free Ti-base shape memory alloys (SMA) have been systematically developed by our group for biomedical applications in order to replace Ti-Ni SMAs which posses the possibility of Ni-hypersensitivity. In this study, superelastic behavior of solution-treated Ti-24 mol%Nb-3 mol%Al alloy was investigated by means of tensile tests at room temperature (RT) as well as microstructural observation. The alloy was fabricated by Ar arc-melting followed by a homogenization at 1273 K and then cold-rolled with the reduction of 99% in thickness without intermediate annealing. The cold-rolled sheets were solution treated at 1273 K for 1.8 ks in vacuum. Then, cyclic loading-unloading tensile tests were performed at RT. In the tensile tests, the tensile direction was systematically changed from rolling direction (RD) to transverse direction (TD) in the plane of the cold-rolled sheets. It was found by the tensile tests that the superelastic behavior strongly depends on the tensile direction and the number of deformation cycles. The solution-treated alloy after 99% cold rolling exhibits the best superelasticity when loaded along RD. The nature of the anisotropy in the superelastic behavior is discussed related with the texture developed during the fabrication process. It is concluded that the thermo-mechanical treatment performed in this study is quite useful as a superelastic treatment for the Ti-base SMAs, and that this alloy should be used industrially by taking into account such anisotropy of superelasticity.
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  • Tomonari Inamura, Yusuke Fukui, Hideki Hosoda, Kenji Wakashima, Shuich ...
    2004 Volume 45 Issue 4 Pages 1083-1089
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Textures of severely cold-rolled Ti-24 mol%Nb-3 mol%Al superelastic alloy were examined by X-ray pole figure measurements for the bcc parent phase (β) and the relationship between transformation strain and loading direction was evaluated on the basis of the lattice correspondence and change in the potential energy of an external stress. A well-developed recrystallization texture of ‹110›β{112}β type was confirmed by X-ray pole figure measurements for the material which was 99% cold-rolled followed by a solution-treatment at 1273 K. Crystallographic analysis showed that the maximum dilatation component of the martensitic transformation from β to α″ is ‹110›β parallel to the rolling direction (RD). An energy consideration revealed that only one α″-variant (lattice-correspondence variant) can be induced by the tensile stress along RD when the recrystallization texture appears. The transformation strain generated under the RD tension was about three times larger than that generated under the tension along transverse direction (TD). These calculations were in good agreement with experimental evidences.
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  • Hee Young Kim, Yoshinori Ohmatsu, Jae Il Kim, Hideki Hosoda, Shuichi M ...
    2004 Volume 45 Issue 4 Pages 1090-1095
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Mechanical properties and shape memory behavior of Ti-Mo-Ga alloys were investigated in order to develop Ni-free biomedical shape memory alloys. The Ti-Mo-Ga alloys were fabricated by arc melting method. The ingots were cold-rolled up to 95% reduction in thickness. The cold-rolled specimens were heat treated in the temperature range 673—1273 K for 60 s—3.6 ks. The martensitic transformation temperature decreased with increase in Mo and Ga content. The maximum shape recovery strain was obtained in a solution treated Ti-6 at%Mo-3 at%Ga alloy. Mechanical properties and shape memory behavior strongly depend on heat treatment condition in the Ti-6 at%Mo-3 at%Ga. Premature failure was observed in specimens heat treated in the temperature range 673—773 K. Ultimate tensile strength decreased and fracture strain increased with increasing heat treatment temperature. Shape memory effect was obtained in specimens heat treated in the temperature range 1073—1273 K. The shape memory effect was due to the stress induced martensitic transformation yielding tensile deformation and the reverse transformation upon heating after unloading. The martensitic transformation start temperature increased and the yield stress decreased with increasing heat treatment temperature and time. Stable superelastic behavior was obtained in a Ti-7 at%Mo-4 at%Ga alloy at room temperature by cyclic tensile tests. The recovery strain exceeding 4% was achieved in the pre-strained Ti-7 at%Mo-4 at%Ga alloy.
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  • Takashi Maeshima, Minoru Nishida
    2004 Volume 45 Issue 4 Pages 1096-1100
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Shape memory properties of Ti-Mo-Ag and Ti-Mo-Sn alloys consisting of biocompatible elements were investigated. The alloys with appropriate combination of Mo and Ag or Sn showed nearly perfect shape memory effect in convenient bending and heating tests. Recoverable tensile strain is more than 3% in some of Ti-Mo-Ag and Ti-Mo-Sn alloys. Microstructure observations and X-ray diffraction measurements before and after tensile test revealed that stress induced β to α″ martensitic transformation was origin of the shape memory effect.
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  • Takashi Maeshima, Minoru Nishida
    2004 Volume 45 Issue 4 Pages 1101-1105
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Ni-free Ti-Sc-Mo shape memory alloys are designed as a substitute for Ti-Ni alloys in the biomedical field. From results of bending and recovery test with heating, Ti-Sc-Mo alloys were found to have superior shape memory effect. The optimum composition for the shape memory effect was Ti-4.0 to 6.0Sc-6.0Mo alloys. The maximum shape recovery strain in the Ti-5.0Sc-6.0Mo alloy was 5.3% measured through cyclic tensile deformation. Vickers hardness and 0.2% proof stress were remarkably decreased and elongation was increased with Sc content. The marked grain refining was also achieved. The relationship between microstructure and mechanical properties was briefly discussed. Microstructure observations and XRD measurements before and after tensile deformation showed that the shape memory effect was associated with the stress induced β to α″ transformation.
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  • Masahiko Ikeda, Shin-ya Komatsu, Yuichiro Nakamura
    2004 Volume 45 Issue 4 Pages 1106-1112
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Using Ti-50Ta, Ti-50Ta-Sn and Ti-50Ta-Zr alloys, the effects of Sn and Zr additions on phase constitution in the solution treated and quenched state and aging behavior were studied by electrical resistivity and Vickers hardness measurements and X-ray diffactometry. All alloys were solution treated at 1173 K for 3.6 ks and then quenched into ice water (STQ). STQed specimens were isochronally aged at temperatures up to 1323 K in Ti-50Ta-Sn alloys and 1173 K in Ti-50Ta-Zr alloys. Shape recovery test was also performed in bent Ti-50Ta, Ti-50Ta-Sn and Ti-50Ta-Zr alloy specimens. In the STQed state, only reflections of orthorhombic α″ martensite were observed by XRD in Ti-50Ta and Ti-50Ta-4Sn alloys. In STQed Ti-50Ta-10Zr alloy, coexistence of α″ and β (bcc) phases were found by XRD. In STQed Ti-50Ta-8Sn and Ti-50Ta-20Zr alloys, only β phase was identified. In Ti-50Ta, Ti-50Ta-4Sn and Ti-50Ta-10Zr alloys, resistivity at liquid nitrogen temperature and resistivity ratio increased with isochronal aging up to a certain temperature. It is considered that these increases are due to reverse-transformation of α″ into metastable β phase. Shape-recovery test confirmed the shape memory effect of Ti-50Ta, 50Ta-4Sn and 50Ta-10Zr alloys.
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  • Nobuhito Sakaguch, Mitsuo Niinomi, Toshikazu Akahori
    2004 Volume 45 Issue 4 Pages 1113-1119
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The composition of Ti-30Nb-10Ta-5Zr, which is simplified that of the Ti-29Nb-13Ta-4.6Zr alloy developed for biomedical applications, was selected, and then Nb content in the basic composition was varied from 20 to 35%. The deformation mechanisms of such Ti-Nb-Ta-Zr system alloys were investigated by loading-unloading tensile tests and characterizing deformed microstructures. The behavior of unloading and reloading of the stress-strain curves up to strain about 2% of Ti-20Nb-10Ta-5Zr and Ti-25Nb-10Ta-5Zr alloys is similar to that obtained in metastable β type titanium alloys where the stress induced martensite transformation occurs. This indicates that the stress and strain induced martensite transformation occurred in these alloys. Furthermore, the elastic deformation of Ti-30Nb-10Ta-5Zr alloy disobeys Hooke's law. However, the behavior of stress or strain-induced martensite transformation does not recognized in the stress-strain curve up to strain about 2% of this alloy. The main deformation mechanism up to fracture of Ti-20Nb-10Ta-5Zr alloy, Ti-25Nb-10Ta-5Zr alloy and Ti-35Nb-10Ta-5Zr alloy is identified as the deformation - induced martensite transformation of β phase to α″ phase, deformation-induced martensite transformation of β phase to α″ phase and deformation twin, and slip, respectively. The deformation mechanisms for Ti-30Nb-10Ta-5Zr alloy are not explained by slip, deformation twining and deformation-induced martensite transformation. However, the super elastic behavior observed in this alloy is expected to occur without deformation-induced martensite transformation.
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  • Guo He, Masuo Hagiwara
    2004 Volume 45 Issue 4 Pages 1120-1123
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A group of multicomponent Ti-Cu-Ni(Cr, Fe, Co)-Sn-Ta(Nb) alloys were investigated in terms of the microstructure and the mechanical properties. A composite microstructure with a micrometer-sized dendritic bcc-β-Ti(RM) (RM = Nb, Ta) phase dispersed in a matrix was obtained. The TEM observation on the Ti60Cu14Ni12Sn4Ta10 alloy shows that the matrix is composed of a nano/ultrafine bcc-phase with the size of 50—100 nm which is isolated by a tetragonal-phase. The designed Ti alloy exhibit very high yield strength (1050—1472 MPa) and relative lower Young's modulus (67—105 GPa). Such combined properties, not easily achievable in previous Ti alloys, make these new designed Ti alloys promising candidates as biomedical materials.
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  • Huanlong Li, Scott M. Oppenheimer, Samuel I. Stupp, David C. Dunand, L ...
    2004 Volume 45 Issue 4 Pages 1124-1131
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Successful bone formation which leads to functional osseointegration is determined by the local mechanical environment around bone-interfacing implants. In this work, a novel porous titanium material is developed and tested and then impact of porosity on mechanical properties as a function of bone ingrowth is studied numerically. A superplastic foaming technique is used to produce CP-Ti material with rounded, interconnected pores of 50% porosity; the pore size and morphology is particularly suitable for bone ingrowth. In order to understand the structure-property relations for this new material, a numerical simulation is performed to study the effect of the porous microstructure and bone ingrowth on the mechanical properties. Using ABAQUS, we create two-dimensional representative microstructures for fully porous samples, as well as samples with partial and full bone ingrowth. We then use the finite element method to predict the macroscopic mechanical properties of the foam, e.g., overall Young's modulus and yield stress, as well as the local stress and strain pattern of both the titanium foam and bone inclusions. The strain-stress curve, stress concentrations and stress shielding caused by the bone-implant modulus mismatch are examined for different microstructures in both elastic and plastic region. The results are compared with experimental data from the porous titanium samples. Based on the finite element predictions, bone ingrowth is predicted to dramatically reduce stress concentrations around the pores. It is shown that the morphology of the implants will influence both macroscopic properties (such as modulus) and localized behavior (such as stress concentrations). Therefore, these studies provide a methodology for the optimal design of porous titanium as an implant material.
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  • Shoji Ohkawa, Kuniyoshi Ishii, Motohiro Uo, Toshi Sugawara, Fumio Wata ...
    2004 Volume 45 Issue 4 Pages 1132-1139
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The feasibility of using slip casting of titanium powder as a method for manufacturing dental prosthetic appliances was examined. Slips with water-powder (W/P) ratios, 0.318, 0.354 and 0.391, and with minimum viscosities were cast in plaster molds. Castings were sintered in an argon atmosphere at 1373, 1473 and 1573 K for 3.6, 7.2 and 10.8 ks, respectively. Green densities and strengths of castings were 2.20 kg/m3 and 2.31—3.82 MPa, respectively. Linear shrinkages and relative densities of sintered castings varied from 17.6 to 20.8% and 0.82 to 0.97 of the theoretical density of titanium, respectively. Tensile strengths and Vickars hardness of the sintered castings were 199.5—315.4 MPa and 233.0—247.7, respectively. There was almost no elongation. Decreasing porosity and crystal grain growth were found in the microstructures of sintered castings and rod-like precipitates of TiC with α-titanium were also observed. Concentrations of carbon and oxygen in the microstructures of sintered castings were higher than those in wrought titanium. Fractured surfaces showed ridge patterns typical of brittle fracture. Further modification of the sintering atmosphere and the additives for the slip is needed to improve the microstructure of slip-cast sintered titanium.
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  • Keiji Iwasaki, Shoji Ohkawa, Motohiro Uo, Tsukasa Akasaka, Fumio Watar ...
    2004 Volume 45 Issue 4 Pages 1140-1146
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The performance of laser welding of Ti and two dental precious alloys (Ag-Pd-Au, Au-Pt-Ag) was investigated by mechanical testing and microscopic observation, using butt joint as design. The laser irradiation was done using a commercial Nd:YAG dental laser-welding device in a single pulse mode with output currents 150, 200, 250, 300 A, spot diameters 0.6, 0.9, 1.2 mm, and pulse duration 10 ms. The average welding fracture strength of the dissimilar metals were 108.9 and 137.2 MPa for Ti and Ag-Pd-Au alloy, and Au-Pt-Ag alloy, respectively. The average welding fracture strength of the same metals were 594.9, 648.8 and 312.9 MPa for Ti, Ag-Pd-Au alloy and Au-Pt-Ag alloy. The hardness increased in weld zone, compared with the base metals. Penetration depths were affected by the welding conditions such as the output currents and spot diameters. The welding cracks and porosity were observed in microstructures of the welds. Mapping by EPMA showed the remarkable heterogeneity of the component metals concerned. The welding cracks, porosities and granular precipitates similar to metallic compounds in the weld zones were suggested as the cause for lower welding fracture strength in the dissimilar welds, compared with the similar metals.
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  • Shigeru Fujino, Hirofumi Tokunaga, Eduardo Saiz, Antoni P. Tomsia
    2004 Volume 45 Issue 4 Pages 1147-1151
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Silicate glass coatings on Vitallium®, a Co-Cr alloy were prepared using a simple enameling technique. The composition of the glasses in the SiO2-Na2O-K2O-MgO-CaO-P2O5 system has been tailored to match the thermal expansion of the alloys. The optimum glass composition and firing conditions (temperature and time) needed to fabricate homogeneous coatings with good adhesion to the alloy were determined. The final coating thickness ranged between 40 and 60 μm. Coatings fired under the optimum conditions do not delaminate during indentation tests of adhesion. Excellent adhesion to the alloy has been achieved through the formation of 150 nm thick interfacial layers (CrOx). The silicate glass can be successfully coated to Co-Cr alloy and formed hydroxyapatite on the glass surface when immersed in a simulated body fluid (SBF) for 30 days.
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  • Akihisa Inoue, Wei Zhang, Junji Saida
    2004 Volume 45 Issue 4 Pages 1153-1162
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A glassy phase containing cubic phase particles with a size of 3—5 nm was formed in cast Cu60Zr30Ti10 and Cu60Hf30Ti10 bulk alloys. The cubic phase is in a metastable state and its lattice parameter (a0) is 0.45 nm for the former alloy and 0.51 nm for the latter. These bulk alloys exhibit good mechanical properties of 2000—2130 MPa for tensile strength (σt,f), 2060—2160 MPa for compressive strength (σc,f) and 0.008—0.017 for compressive plastic strain (εc,p). The temperature interval of the supercooled liquid (SL) region prior to crystallization is 37 K for Cu60Zr30Ti10 and 67 K for Cu60Hf30Ti10. The primary crystallization occurred by precipitation of cubic CuZr (a0 = 0.35 nm) in a diffusion-controlled growth mode of nuclei and an orthorhombic Cu8Hf3 phase in an interface diffusion-controlled growth of nuclei with decreasing nucleation rate. The difference in the precipitation modes is interpreted to be the origin of the difference in the SL region. Furthermore, the addition of Al to Cu-Zr and Cu-Hf alloys caused the formation of a glassy single phase in the rod form with diameters up to at least 3 mm, though bulk glassy alloy rods with critical diameters up to 1.5 mm and σc,f of 1920—2260 MPa were formed in Cu-Zr and Cu-Hf binary systems. The ternary bulk glassy alloys exhibited high σc,f of 2100—2370 MPa with εc,p of 0.002—0.006. The addition of Pd, Pt, Ag or Au increased ΔTx and a large ΔTx of 102—110 K was obtained for the Cu-Hf-Al-M (M=Pd or Ag) glassy alloys. The synthesis of Cu-based bulk glassy alloys with good mechanical properties and large ΔTx in glassy single, and mixed glassy and cubic phase states, is important for future applications of bulk glassy alloys.
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  • Masato Shimono, Hidehiro Onodera
    2004 Volume 45 Issue 4 Pages 1163-1171
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Criteria for estimating the glass-forming ability accessible by the molecular dynamics simulations are proposed. The enthalpy of the glassy phases and the density of the supercooled liquid phases can be the criteria, the former reflects the energetics and the latter reflects the dynamics. The relaxation behavior of the glassy phases suggests that the cooling rate dependence of the glass transition temperature also could be the criterion as to explore the ‘energy landscape’ and the phase stability for both supercooled liquid and glassy phases.
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  • Yoshihiro Takahara, Nobutaka Narita
    2004 Volume 45 Issue 4 Pages 1172-1176
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Local electronic structures of Zr-based metallic glasses have been calculated using the discrete variational Xα cluster molecular orbital method. The cluster models are constructed for Zr-Cu, Zr-Ni and Zr-Pd metallic glasses on the base of local structure parameters determined by extended X-ray absorption fine structure analysis. The valence-band X-ray photoelectron spectra computed from the local electronic structures agree well with experimental spectra. Based on the feature of chemical bonds in those glasses evaluated from the electronic structures, we discuss the relationship between the chemical bond and the stability of supercooled liquid state. The strength of the Zr-Ni bond is larger than that of Zr-Cu bond, while the Cu-Cu bond strength is nearly equal to the Ni-Ni bond. Moreover, the Zr-Zr bond strength is larger in Zr-Cu glass than in Zr-Ni glass. This indicates that the formation of primary crystalline phase is more difficult in Zr-Cu glass than in Zr-Ni glass. The difficulty contributes to the relative stabilization of supercooled liquid state in Zr-Cu glass compared with that in Zr-Ni glass. It is also shown that local atomic structures of Zr-Pd glass are well described by the icosahedral atomic configuration.
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  • Chuang Dong, Yingmin Wang, Jianbing Qiang, Dehe Wang, Weirong Chen, Ch ...
    2004 Volume 45 Issue 4 Pages 1177-1179
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    In this paper, we will discuss and apply the formation rules for bulk metallic glasses, originated from quasicrystals composition rules, by combining two most common factors, atomic size factor and electron concentration (e/a) factor. According to literature survey, to our experience on quasicrystal formation, and to our own experimental verification, we propose two criteria, based on atomic size and electron concentration e/a respectively. The first criterion is quantified as the Rav-constant criterion, Rav being the average atomic radius, and the second one the e/a-constant criterion. In a given alloy system the optimum BMGs and their crystalline counter parts tend to share the same Rav and e/a values. These criteria have been applied to determine the ideal BMGs in Zr-Al-Cu-Ni system.
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  • Yingmin Wang, Chan Hung Shek, Jianbing Qiang, Chi Hung Wong, Qing Wang ...
    2004 Volume 45 Issue 4 Pages 1180-1183
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Composition optimization for the largest glass-forming ability has been performed in the Zr-Al-Ni(Co) systems in this investigation. Two guiding criteria, termed respectively the e/a-constant criterion and the e/a-variant criterion, are applied. They are incarnated into the e/a = 1.5 composition line and the Zr9Ni(Co)4-Al composition line. Bulk metallic glasses are obtained by suction casting alloy melts of compositions within an e/a span of 1.3∼1.5, with their thermal stabilities and glass forming abilities being increased with increasing e/a. The intersecting point of the two lines gives the composition Zr53Al23.5Ni(Co)23.5 with the largest glass-forming ability.
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  • Osami Haruyama, Hisamichi M. Kimura, Nobuyuki Nishiyama, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1184-1188
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The structural relaxation process was investigated for a Pd42.5Cu30Ni7.5P20 metallic glass (bulk and ribbon samples) isothermally annealed at 566 and 573 K just below glass transition temperature Tg = 576 K. The relaxation process was examined by differential scanning calorimetry (DSC) and electrical resistmetry. Then, the resistivity of bulk glass was exactly estimated from the resistance and the geometry of the sample. Although the DSC absorption peak appeared just after glass transition became larger with the progress of the relaxation, the growth was terminated after annealing for 6 × 103 s at 566 K or 6 × 102 s at 573 K, meaning that the free volume content reached a constant value and a fully relaxed state was attained. The corresponding change was also seen in the room temperature residual resistivity ρ(300) during relaxing at 566 K. Then, the ρ(300) increased with time for initial 6 × 103 s and was constant during further 6 × 104 s.
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  • Tetsu Ichitsubo, Eiichiro Matsubara, Kazuhiro Anazawa, Nobuyuki Nishiy ...
    2004 Volume 45 Issue 4 Pages 1189-1193
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    We have studied the elastic and anelastic behavior of fully structural-relaxed Pd40Ni40P20 and Zr55Al10Ni5Cu30 bulk metallic glasses using high-frequency ultrasound vibrations at elevated temperature, and found that the structural anomaly is induced by ultrasound vibrations in a supercooled liquid region. The electromagnetic acoustic resonance and resonant ultrasound spectroscopy methods were employed to measure the resonant spectra and ultrasonic attenuation coefficients. When the glassy samples are subjected to sub/low-MHz ultrasound vibrations during heating process, the crystallization is accelerated around their glass transition temperatures, and with this abrupt structural change, irregular Λ-shaped internal friction peaks appear. From the standpoint of ultrasonic echography, the glass transition and crystallization temperatures are considerably lowered by ultrasound vibrations in the present measurements.
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  • Takeshi Hanada, Yoshihiko Hirotsu, Tadakatsu Ohkubo
    2004 Volume 45 Issue 4 Pages 1194-1198
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Advanced techniques of electron microscopy were employed for analyzing a local structure of an as-formed Fe70Nb10B20 metallic glass. From nano-diffraction with an electron probe size of 1 nm, diffraction patterns of bcc-Fe and Fe-boride were observed which indicated an occurrence of nano scale phase separation in the glass. Atomic pair distribution function (PDF) analysis of the glass was also performed by means of precise electron diffraction intensity analysis taking advantage of energy-filter and imaging plate techniques. An atomic structure model was constructed using reverse Monte-Carlo calculation followed by Voronoi polyhedral analysis in order to know local atomic arrangements in the glass structure. The Voronoi analysis revealed atomic arrangements with bcc-Fe-like and B-centered trigonal prism polyhedral structures in this glass, which is consistent with the local structural study by nano-diffraction.
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  • Eiichiro Matsubara, Satoshi Tanaka, Akihiro Makino, Te-Hsuan Chiang
    2004 Volume 45 Issue 4 Pages 1199-1203
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Structures of amorphous Fe84Nb7B9 (FN7) and Fe85Nb6B9 (FN6) alloys were investigated by high-energy X-ray diffraction. The structures of FN6 and FN7 contain a relatively large amount of bcc-Fe like clusters. This cluster size seems to grow larger for FN6 than for FN7. From the lattice parameters of αFe precipitates, the crystallization behavior of both alloys were discussed. The αFe precipitates contain supersaturated Nb and B. These solute atoms are removed from αFe by annealing at elevated temperature and stabilize the amorphous matrix. This appears to prevent the growth of αFe to maintain nano-scale αFe particles.
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  • Shintaro Sobu, Hisamichi Kimura, Dmitri V. Louzguine, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1204-1209
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Glassy type Al-based alloys, with a distinct glass transition and a supercooled liquid region before crystallization, were formed in (Al0.84Ni0.1Ce0.06)100−xBx (x = 0 to 10 at%) and (Al0.84Ni0.05Y0.09Co0.02)100−xBx (x = 0 to 3 at%) systems by melt spinning. The addition of an optimum amount of B was found to increase the temperature interval of supercooled liquid region from 18 K to 23 K at 6%B for the former system and from 28 K to 31 K at 1.5 and 2%B for the latter system. The similar increase with B content was also recognized for Vickers hardness (Hv) and tensile fracture strength (σf) and the highest values of Hv and σf are 400 and 1060 MPa, respectively, at 6%B and 375 and 1140 MPa, respectively, at 1.5%B. The maximum phenomena of temperature interval of supercooled liquid region (ΔTx = TxTg), Hv and σf at optimum B contents can be interpreted in the framework of the three empirical component rules for the stabilization of supercooled liquid and the formation of bulk glassy alloys. The crystallization occurs through two stages of glass → Al + metastable phase → Al + Al3Ni + Al4Ce for the Al-Ni-Ce-6%B alloy and through three stages of glass → Al + glass → Al + metastable phase + glass → Al + Al9Co2 + Al3Y + Al4NiY + Al-Y-Ni-Co quaternary compound for the Al-Ni-Y-Co-2%B alloy. The finding of Al-based glassy alloys with large ΔTx values above 30 K is encouraging for future development of Al-based alloys as a high strength material with light weight.
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  • Wei Zhang, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1210-1213
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    High-strength Cu-based bulk glassy alloys with a large supercooled liquid region in Cu-TM-Al (TM=Zr, Hf) ternary and quaternary systems were synthesized by copper mold casting. The maximum diameter was 3.0 mm for the Cu50Zr45Al5, Cu52.5Hf40Al7.5, Cu50Hf42.5Al7.5 and Cu50Hf22.5Zr22.5Al5 alloys. The glass transition temperature (Tg), temperature interval of supercooled liquid region ΔTx(=TxTg) and reduced glass transition temperature (Tg/Tl) are in the range from 701—781 K, 54—91 K and 0.61—0.63, respectively. The Cu-based bulk glassy alloys exhibit good mechanical properties, i.e., 102—128 GPa for Young's modulus, 1885—2370 MPa for compressive fracture strength, up to about 0.6% for compressive plastic elongation, and 550—670 for Vickers hardness. The finding of the new Cu-based bulk glassy alloys with large supercooled liquid region above 54 K, high reduced glass transition temperature above 0.60, and high fracture strength above 1885 MPa is encouraging for future development as a new type of bulk alloys which can be used as structural materials.
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  • Kenji Amiya, Akiri Urata, Nobuyuki Nishiyama, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1214-1218
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The glass-forming ability and mechanical properties of Fe-B-Si-Nb glassy alloys have been investigated. The Fe72B20Si4Nb4 glassy alloy was prepared in a cylindrical form with a diameter of 2 mm. Young's modulus, compressive fracture strength and plastic elongation of the bulk metallic glass were 200 GPa, 4200 MPa and 1.9%, respectively. Many shear bands were observed along the shear plane, which was declined by about 43 degrees to the direction of applied load, and the fracture occurred along the shear plane. The local-ordered regions were recognized in the high-resolution TEM image of the Fe72B20Si4Nb4 bulk metallic glass with a diameter of 2 mm. The good mechanical properties are attributed to the suppression effect of the local-ordered regions on the propagation of shear bands.
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  • Teruo Bitoh, Akihiro Makino, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1219-1227
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The density and the magnetization process of the melt-spun glassy Fe-(Al, Ga)-(P, C, B, Si) alloys are investigated to clarify the origin of low coercivity of the glassy alloys. The differences of the density (Δρc) between the crystalline and the amorphous phases of glassy Fe-(Al, Ga)-(P, C, B, Si) alloys are much smaller than those of the ordinary amorphous Fe-B(-Si) alloys. The H−1-power law behavior of ΔJ (= JsJ, where Js is the saturation magnetization) is observed for both the glassy and ordinary amorphous systems in the magnetic field (H) range of 20—25 < μ0H ≤ 50 mT. In the high magnetic field range of 50 ≤ μ0H < 70 mT, ΔJ of both the alloy systems obeys the H−2-power law. The length of the effective Burgers vector and width of quasi-dislocation dipole (QDD) type defects are nearly independent of the alloy system. This means that the local volume contraction is independent of the alloy system, but the density of QDDs in the glassy alloys is much smaller than the ordinary amorphous alloys because the glassy alloys exhibit much smaller Δρc than the ordinary amorphous alloys. Since the coercivity originates from elastic stress of QDDs is proportional to (Δρc)1/2, the origin of low coercivity of the Fe-(Al, Ga)-(P, C, B, Si) glassy alloys is the low density of QDDs which corresponds to low density of the domain-wall pinning centers.
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  • Hyoung Seop Kim, Hidemi Kato, Akihisa Inoue, Ho-Sou Chen, Sun Ig Hong
    2004 Volume 45 Issue 4 Pages 1228-1232
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Microforming can be a good application for bulk metallic glasses. It is important to simulate the deformation behaviour of the bulk metallic glasses in a supercooled liquid region for manufacturing micromachine parts. For these purposes, a correct constitutive model which can reproduce viscosity results is essential for good predicting capability. In this paper, we studied deformation behaviour of the bulk metallic glasses using the finite element method in conjunction with the fictive stress constitutive model which can describe non-Newtonian as well as Newtonian behaviour. A combination of kinetic equation which describes the mechanical response of the bulk metallic glasses at a given temperature and evolution equations for internal variables provide the constitutive equation of the fictive stress model. The internal variables are associated with fictive stress and relation time. The model has a modular structure and can be adjusted to describe a particular type of microforming process. Implementation of the model into the MARC software has shown its versatility and good predictive capability.
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  • Norio Maruyama, Sachiko Hiromoto, Masato Ohnuma, Takao Hanawa
    2004 Volume 45 Issue 4 Pages 1233-1238
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    A fretting fatigue test was carried out with commercially available Zr-based amorphous alloy (7.6Ni-12.3Cu-3.5Al-76.6Zr in mass%) in air and in a pseudo-body fluid, PBS(-). The fracture behaviors were investigated. The fretting fatigue test was performed under load control using a sinusoidal wave with a stress ratio of 0.1, a frequency of 20 Hz in air or 2 Hz in PBS(-) and a fretting contact pressure of 30 MPa. The 107-cycle fretting fatigue strength in air was one-third the 107-cycle plain fatigue strength. On the other hand, the 2 × 106-cycle fretting fatigue strength in PBS(-) was approximately two times the fretting fatigue strength in air. However, there was little difference between the friction coefficients in air and PBS(-). SEM observations showed that the actual contact area damaged by fretting in air due to the roughness of the surfaces became smaller than that in PBS(-). Thus, it can be considered that the fretting fatigue strength was decreased since in air the actual contact pressure caused by the roughness became higher than the apparent contact pressure. Also, based on the observation that film-forming elements in PBS(-) were different from those in air, it is believed that the surface film can affect the frictional wear characteristics and contribute to the suppression of fretting fatigue crack initiation.
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  • Mamoru Ishida, Hideki Takeda, Daichi Watanabe, Kenji Amiya, Nobuyuki N ...
    2004 Volume 45 Issue 4 Pages 1239-1244
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The fillability and imprintability of a Ni-based bulk metallic glass (BMG) prepared by the precision die-casting was investigated. A three-dimensional microgear made of Ni-based BMG is successfully prepared by the precision die-casting technique. The cast Ni-based BMG has excellent fillability against a microindentation formed by Vickers indentation, and the filling area obtained using a confocal scanning microscope reaches 99%. In addition, the cast Ni-based BMG exhibits excellent imprintability of the die surface even on a nanometer scale. It is therefore concluded that the Ni-based BMG is suitable as a material for micromachines due to its superior fillability and imprintability.
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  • Nobuyuki Nishiyama, Kenji Amiya, Akihisa Inoue
    2004 Volume 45 Issue 4 Pages 1245-1250
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    By use of excellent properties of bulk metallic glasses, some industrial products were practically prepared and their performances were investigated. Ni-based BMG microgear prepared by injection casting exhibits nano-imprintability against the surface roughness of mold. Linear actuator constructed by a set of Fe-based BMG yokes generates relatively large driving force due to the Lorentz force. The newly developed alloy with a nominal atomic composition of Ti52Cu23Ni11Mo7Fe7 exhibits high yield strength of 1250 MPa, high fracture strength of 2740 MPa and large plastic elongation of over 20%. These results for the industrial products made of BMGs are promising for future developments as industrial materials with high performance.
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  • Hongwei Qin, Jifan Hu, Juan Chen, Luming Zhu, Hongdong Niu
    2004 Volume 45 Issue 4 Pages 1251-1254
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    The Nd doping effect on the room temperature magnetoresistance in manganites (La1−xNdx)0.67Sr0.33MnO3 was investigated. With increasing Nd doping content in manganites (La1−xNdx)0.67Sr0.33MnO3 the room temperature magnetoresistance ΔR/R0 decreases for low Nd content x < 0.1, which may be mainly due to the sharp reduction of the room temperature saturation magnetization MS. For x > 0.1, an enhancement of the room temperature magnetoresistance can be obtained. Such enhancement of the room temperature magnetoresistance is correlated with the shift of the Curie temperature to near room temperature and the slow change of the room temperature saturation magnetization MS induced by the appropriate Nd doping. The ΔR/R0 become small again at large Nd doping contents. The drop of ΔR/R0 may be attributed to their lower metal-insulator transition temperature TMI far from the room temperature and the smaller MS value at room temperature. Values of the room temperature magnetoresistance ΔR/R0 for manganites (La1−xNdx)0.67Sr0.33MnO3 depend not only on the Curie temperature TC but also on the metal-insulator transition temperature TMI and the room temperature saturation magnetization MS.
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  • Kazuki Yamamoto, Wang Yang, Yutsuki Nishimura, Naoshi Ikeda, Yoshie Ma ...
    2004 Volume 45 Issue 4 Pages 1255-1260
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Peak broadening and peak shifts of Bragg reflections were studied with the synchrotron single-crystal X-ray diffraction method for an Al72.7Ni8.5Co18.8 decagonal quasicrystal classified as the 5f state. From the Q and Q|| dependences of the full width of half maximum (FWHM) of the Bragg reflections along the longitudinal direction, the coexistence of random phason strains with phonon strains was observed. High-resolution synchrotron X-ray measurements could present quantitative estimations of these strains. The value of the random phason strain component is 0.0054 ∼ τ−11. The asymmetrical broadening due to the phonon strain shows that the single crystal may be constructed with two kinds of grains that have A5D values of 0.6273 and 0.6265 nm.
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  • Tsutomu Tanaka, Kenji Higashi
    2004 Volume 45 Issue 4 Pages 1261-1265
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Equal-Channel-Angular extrusion (ECAE) has been conducted at room temperature in order to develop an ultrafine-grained structure in a Zn-22 mass% Al eutectoid alloy. The microstructures had an equiaxed and homogeneously distributed Al-rich and Zn-rich duplex-phase and its average grain size was about 0.35 μm. This alloy exhibited a large elongation of 240% albeit at room temperature and a high strain rate of 10−2 s−1. A grain-size-dependent phenomenon was also observed at lower strain rates. The activation energy was close to that for grain boundary diffusion. It was apparent that the deformation behavior at room temperature is consistent with that observed in conventional superplasticity. From the results, it was concluded that the dominant deformation mechanism was grain boundary sliding accommodated by dislocation movement controlled by grain boundary diffusion.
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  • Sung Wook Chung, Hiroyuki Watanabe, Woo-Jin Kim, Kenji Higashi
    2004 Volume 45 Issue 4 Pages 1266-1271
    Published: 2004
    Released: June 24, 2005
    JOURNALS FREE ACCESS
    Creep deformation behavior of coarse-grained Mg-Al based solid solution alloy (AZ31) was studied in a wide strain rate range of 2 × 10−5∼7 × 10−2 s−1 at temperature range of 573∼673 K. Viscous glide controlled creep (VGC), dislocation climb creep (DCC) and power law breakdown (PLB) showed up in order with increasing stress as the flow rate-controlling process. From the former results for Mg-Al and Mg-Al-Zn alloys, the creep mechanisms of VGC and DCC in Mg and Mg alloys are confirmed. Moreover, several theories presented for DCC and VGC are applied to convey the creep mechanisms in Mg and Mg alloys by analytical way. Transitions in Mg alloys are analyzed also by comparing experimental results and theories. Alloying effects on creep strength and transitions of deformation mechanism are analyzed.
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