Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 60 , Issue 9
Showing 1-17 articles out of 17 articles from the selected issue
  • Masahiro Fujikura, Hiroya Sawairi, Takashi Sato
    1996 Volume 60 Issue 9 Pages 787-792
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Al and Ti contained as impurities in amorphous Fe-Si-B alloy ribbons induce surface crystallization during casting and resultantly degrade the magnetic properties. This paper describes the effect of the oxygen concentration in casting atmosphere on the surface crystallization caused by Al and Ti. For alloys with Al, the surface crystallization is restrained by casting in a low oxygen atmosphere. The resultant magnetic properties are improved. In case of alloys with Ti, the low oxygen atmosphere fails to suppress the surface crystallization, and further degrades the magnetic properties. For Al, the crystallization appears to be initiated by oxides at the surface of the ribbon, while for Ti, the surface crystallization occurs regardless of the concentration of oxygen.
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  • Hideki Hosoda, Akihiko Kamio, Tomoo Suzuki, Yoshinao Mishima
    1996 Volume 60 Issue 9 Pages 793-801
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    A method is proposed for predicting the substitution behavior of ternary elements (X) in B2-type intermetallic compounds (AB) having substitutional (antistructure) defects at offstoichiometric compositions. Calculations are carried out using the pseudo-ground state analysis based on the nearest-neighbor, pair-approximation. The results revealed that the site preference of X can be determined by both heat of formation and alloy concentration: X occupies A sites only in case of ΔHBX<ΔHAB+ΔHAX(ΔHAB stands for the heat of formation between A and B), X occupies B sites only in case of ΔHAX<ΔHAB+ΔHBX, and in cases, X occupies both or either A and/or B sites unfilled by constituent elements depending on alloy concentration. It is shown that: in NiTi, CoTi and FeTi, most 3A- and 4A-group elements occupy Ti sites only, and most 8A-, 4B-and 5B-group elements occupy Ni, Co and Fe sites only; while in NiAl, Co, Rh etc. occupy Ni sites only, and Si occupy Al sites only. These results are in good agreement with available data in the literature.
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  • Takashi Shibata, Yukoh Shudo, Yuichi Yoshino
    1996 Volume 60 Issue 9 Pages 802-808
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Ni-Fe-base wrought superalloy 706 is a relatively new alloy and has been used for high temperature services. However, the precipitation in this alloy system has not been well understood, making it difficult to interprete its strengthening behavior. Therefore, an intensive TEM study was conducted in the present study to characterize the precipitates in Alloy 706. Samples taken from a gas turbine disk forging were solution-treated at 1253 K for 3 h and stabilizing-treated in a range of 1053 to 1173 K for 1.5 h, followed by the double-aging at 993 K for 8 h and at 893 K for 8 h. Two types of γ′′ co-precipitates, not reported previously for Alloy 706, were identified in the grain matrix together with fine γ′′ and large γ phases. One was fine γ′′ co-precipitates having the core of γ being overlaid with γ′′ on its top and/or bottom, the other was large γ′′ co-precipitates having the core of γ being completely covered with γ′′. The η phase was identified at the grain boundary and found to be accompanied by a serrated grain boundary and denuded zone. The fine overlaid γ′′ co-precipitates and the fine γ′′ phase formed at the double-aging, whereas the relatively large cuboidal γ′′ co-precipitates, large γ phase and inter-granular η phase formed at the stabilizing treatment below 1113 K.
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  • Kenichi Yoshida, Baojun Pang, Ai Zhu, Kiyoshi Sakamaki, Hitoshi Takagi
    1996 Volume 60 Issue 9 Pages 809-815
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Yielding behavior of an aged Al-Li-Cu-Mg-Zr alloy was studied by the tensile test and acoustic emission and transmission electron microscopic observations, and the yield mechanism was discussed in detail. The continuous-type acoustic emission which can be related to the accelerating motion of dislocations was affected by the precipitates of a metastable δ phase and a metastable Al3Zr phase, and had its maximum value when the mean diameter of the δ phase was 12 nm. The reason was discussed in accordance with the frictional forces to the dislocation motion in the matrix and the δ phase, and the misfit strain of the Al3Zr phase in the δ phase. On the other hand, the burst-type acoustic emission which can be related to the shearing of the δ precipitates was also detected to be piled up above the continuous-type acoustic emission. Consequently, it was indicated that this alloy was plastically deformed by the dislocation motion with large planar slip and the shearing of the coherent ordered precipitates as the δ phase at the same time. Finally, it was shown that the burst-type acoustic emission also included the effect of the solute atom as the source of serration in addition to the shearing of the δ precipitates.
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  • Kazuhiko Takahashi, Tetsuo Shoji, Mikiko Nakajima
    1996 Volume 60 Issue 9 Pages 816-825
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    In powder-forged ferrous materials, surface defects such as decarburized layers, surface roughness, and non-sintered areas (NSA) are observed. These NSA, peculiar to this material, play the most important role in determining the mechanical properties.
    In order to understand the behavior of NSA in dynamic conditions, fractography and measurement of the NSA distribution on the fatigue origin were investigated. The behavior of crack initiation and propagation was observed during fatigue tests by using ACPD (the alternative current potential drop method) measurement and the thermoelastic stress analysis system. The effects of NSA on fatigue properties were discussed on the basis of fracture mechanics.
    As a result, the mixture of static fracture with fatigue in fatigue origin indicates that process of fatigue fracture consist of 3 stages as follows:
    1st stage; effective crack initiation (combination of NSAs by static and fatigue fracture)
    2nd stage; propagation of effective crack
    3rd stage; final rupture
    Observations of fatigue crack initiation and propagation with the crack growth monitoring system show that the fatigue fracture process consist of 3 stages mentioned above and effective crack initiation occurred at the beginning of less than 10% of fatigue life. From the measurement of NSA distribution of fatigue origin, the fatigue behavior of this material can be treated with fracture mechanics based on the effective crack length equal to the depth of NSA distribution of which NSA ratio is 14%.
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  • Satoshi Uchida, Ryouhei Suzuki, Masanori Tokuda
    1996 Volume 60 Issue 9 Pages 826-833
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The dissolution behavior of metallic tin plates in aqueous sodium hydroxide solutions was investigated. The dissolution rate was measured by weight changes of the samples under the conditions of 0.01∼1.0 mol/l-H2O NaOH concentrations, 0∼750 rpm rotation speeds and 4∼87°C. The dissolution rate was mainly controlled by the diffusion of dissolved oxygen at temperatures higher than 30°C and the NaOH concentrations higher than 0.1 mol/l-H2O. It was found that the dissolution rate of tin increases with increasing temperature and rotation speed, while its maximum rate was observed as the NaOH concentration increased.
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  • Osamu Inoue, Satoshi Itoh, Takeshi Azakami
    1996 Volume 60 Issue 9 Pages 834-840
    Published: 1996
    Released: April 04, 2008
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    Phase relations and the equilibrium oxygen partial pressures in the Fe-Ti-O ternary system at 1373 K have been studied using a thermogravimetric technique in various atmospheres buffered by a CO-CO2 gas mixture and X-ray diffraction technique. The results indicate that at 1373 K ilmenite(FeTiO3) can be reduced and decomposed to iron and rutile(TiO2). Consequently upgrading ilmenite to a rutile substitute is possible in principle.
    From the present results, the standard Gibbs energy of the following reactions was calculated to be −184.7, −196.0 kJ·mol−1 at 1373 K, respectively.
    (This article is not displayable. Please see full text pdf.)
    \ oindentBoth the activities of magnetite and ulvöspinel in the Fe2TiO4-Fe3O4 spinel solid solutions coexisting with metallic iron at 1373 K obtained exhibit negative deviations from Raoult’s law.
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  • Yoshiyuki Sato, Motoi Hara, Yutaka Shinata, Toshio Narita
    1996 Volume 60 Issue 9 Pages 841-847
    Published: 1996
    Released: April 04, 2008
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    High temperature oxidation behavior of Fe-1, 2, 5 and 18 mass%Cr alloys was examined by thermogravimetry in 1%HCl-50%O2-N2 and 100%O2 atmospheres at temperatures between 973 and 1173 K. Corrosion products were analyzed by XRD and EPMA. The mass gain of Fe-Cr alloys increased with time and temperature, and it decreased with the Cr content in the alloys. The mass gains for Fe-Cr alloys at various temperatures in a 1%HCl-50%O2-N2 atmosphere were larger than those in 100%O2, while the Cr content dependence of mass gains of Fe-Cr alloys in 1%HCl-50%O2-N2 had almost the same tendency as that in 100%O2. Namely, the mass gain decreased with the Cr content of the alloy and the 18 mass% addition of Cr was effective to reduce the corrosion rate. In the 1%HCl-50%O2-N2 atmosphere, the scale formed on Fe-5%Cr alloy consisted of two layers of thick and dense Fe oxides and a porous Fe-Cr spinel oxide (FeCr2O4). The scale formed on the Fe-18%Cr alloy was a single layer of Fe oxides with segregation of Cr2O3 in the bottom part of the scale. From the results obtained and a thermodynamic discussion, it was suggested that the accelerated oxidation was due to the formation of volatile FeCl2 in addition to the oxidation of Fe and Cr, and that the Cr addition to the alloy led to reduce the corrosion rate because of the formation of a protective FeCr2O4 layer or a Cr2O3 layer in the scale.
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  • Kiyoko Takeda, Hiroyuki Anada, Haruhiko Kajimura
    1996 Volume 60 Issue 9 Pages 848-852
    Published: 1996
    Released: April 04, 2008
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    Zircaloy-4 is used as materials for nuclear fuel rods in PWR plants. Zircaloy-4 is oxidized by the inward diffusion of the oxygen ions through the oxide on the surface in high temperature water and/or steam. Therefore, the structure of the oxide films should affect the corrosion resistance of Zircaloy-4. However, the relationship between the crystal structure of the oxide films and the corrosion resistance of Zircaloy-4 has not been clear. Zircaloy-4 shows a rapid increase in corrosion rate during the corrosion process. This phenomenon was called “transition”. However, a relationship between the crystal structure of the oxide films and the transition has not been clear. A purpose of this paper is to clarify the relationships. The materials used for corrosion tests were Zircaloy-4 sheets with two different intermediate annealings at 903 and 1053 K. The corrosion tests were carried out in static steam at 673 K. The oxides in the vicinity of an oxide-to-metal interface were observed in the cross-section using transmission electron microscopy. The main results are as follows: (1) The oxide films just before the first transition consisted of a two-layered structure. The outer layer was the monoclinic structure and the inner layer adjacent to the oxide-to-metal interface was the tetragonal structure. (2) Zircaloy-4 with intermediate annealing at 1053 K had better corrosion resistance and a thicker tetragonal layer than that with intermediate annealing at 903 K. (3) The tetragonal layer of both materials disappeared just after the transition. The oxide films of both materials consisted of only the monoclinic structure. “transition” corresponded to this structure transformation from the tetragonal to the monoclinic structure. (4) The acceleration of the corrosion rate at the transition could be caused by the formation of diffusion paths for the oxygen ions in the monoclinic layer by the volume expansion with the transformation.
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  • Ken-ichiro Suzuki, Koji Nishikawa, Hiroyuki Matui, Sirou Watakabe
    1996 Volume 60 Issue 9 Pages 853-862
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The melt flow and mold filling in precision casting of a Ti-6Al-4V alloy has been examined by casting trials, in which the molten alloy with an amount intentionally adjusted to be less than that for complete filling is poured into mold cavities under some centrifugal force. By rotation of the tree on the horizontal plane, the molten alloy flows into the mold cavities keeping contact with one of the vertical inside walls of a gate and a mold cavity. Solidification in the mold cavity proceeds mainly in a manner of directional solidification by accumulating the solidifying layer from the far end of a mold cavity where the centrifugal force is maximum to the gate at which the force is a minimum. The centrifugal force imposed on the melt enhances separation of gas bubbles which may evolve during pouring the melt into the mold cavity, reduces the number of gaseous defects to a level negligibly small at 30G, and improves mechanical properties of castparts. Detailed observation of the defects showed that dendrites appears at the bottom of porosity where the inter-dendritic melt is sucked to the half thickness side surface by solidification shrinkage. Micro segregation of solute in a dendrite tip seems to be caused not during solidification but during transformation from the β to α phase by mapping analysis.
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  • Nobuyuki Mori, Takeshi Kitaoka, Hirofumi Miyahara, Keisaku Ogi
    1996 Volume 60 Issue 9 Pages 863-869
    Published: 1996
    Released: April 04, 2008
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    To clarify the solidification mechanism of thin alloy films between solid plates, the effects of the film thickness and the growth conditions on the unidirectional solidification structures of Al-Cu alloys were studied. The primary arm spacings of the thin film specimens, whose thicknesses were less than or equal to the secondary arm spacings, were twice or three times larger than those of bulk Al-15%Cu specimens. This phenomena were interpreted through the quantitative estimation of the influence of solid plates on the solute diffusion process in the liquid near dendrite tips. Two diffusion models were proposed, and the calculated ratios (DhD1) of the primary arm spacing Dh of the film and D1 of the bulk specimen were: (1) Columnar diffusion layer model: (DhD1)={(4π⁄3)⁄(2hD1)}1⁄2, (2) Hemispherical diffusion layer model: (DhD1)={(1⁄(2hD1)}1⁄3. The intermediate value of the above models showed good agreement with the experimental ratios (dhd1) of the film dh and the bulk d1.
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  • Hiroaki Sakamoto, Naoki Okumura, Yoshiharu Inoue, Toshio Yamada
    1996 Volume 60 Issue 9 Pages 870-877
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    Microstructures of thick Fe80.5Si6.5B12C1 amorphous ribbons which were crystallized by the addition of 0.01 mass%Aluminum have been examined. The ribbons with the thickness of 66-74 μm were cast by using a multiple slotted nozzle in a conventional single roll method. The microstructures of the as-cast ribbons were as follows: The region near the free surface of the ribbon was fully crystallized. The confirmed phases were primarily α-Fe which forms dendritic structures, Fe2B and orthorhombic-Fe3B. The roll side of the ribbons was primarily amorphous with α-Fe. The middle region in the ribbon thickness direction was primarily amorphous with only a trace of α-Fe. In the free side surface, it was found that (110) orientation of the dendritic α-Fe occurred by the addition of Aluminum and it is considered that the α-Fe formed directly from the molten alloy during casting.
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  • Masateru Nose, Takekazu Nagae, Masaru Yokota, Shigeoki Saji, Masahiro ...
    1996 Volume 60 Issue 9 Pages 878-883
    Published: 1996
    Released: April 04, 2008
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    Pure Nb and pure Al powders were mechanically alloyed in a planetary ball mill in Ar gas atmosphere, at the maximum centrifugal acceleration of 30 g (“g” is the gravitational acceleration). Nb and Al were mixed corresponding to the NbAl3, Nb2Al and Nb3Al compositions with the mass% of Al being 46.6, 12.7 and 7.5, respectively. Mechanical alloying (MA) processes of Nb-Al mixed powders were investigated by means of SEM and X-ray diffraction. The results obtained were as follows:
    (1) In the mechanical alloying process of the Nb and Al mixed powders, the coalescences of both powders are produced during the first stage, and then formation of the solid solution proceeds from perimeter of the coalescences.
    (2) NbAl3 intermetallic compound is formed in the mixed powders corresponding to NbAl3 composition in the early stage of the mechanical alloying process. However, in the case of the mixed powders of Nb2Al and Nb3Al compositions, no intermetallic compound is formed even after milling for 1440 ks. α-Nb solid solution is formed after 10.8 ks milling and then an amorphous-like pattern is observed after milling for 720 ks in the mixed powders of Nb2Al composition. On the other hand, only Nb-Al supersaturated solid solution has been confirmed in the powder of Nb3Al composition obtained by mechanical alloying.
    (3) These formation tendencies of intermetallic compounds during mechanical alloying correspond to the standard enthalpy value of the intermetallic compound formation (ΔH298°).
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  • Toshio Narita, Shigenari Hayashi, Shohei Hata
    1996 Volume 60 Issue 9 Pages 884-889
    Published: 1996
    Released: April 04, 2008
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    Metals of Ni or Cu joined to Si3N4 ceramics with Ag- or Ni-brazing filler (Ag-Cu-Ti and Ni-Cu-Ti) were thermally cycled in vacuum between room temperature and the temperatures of 573, 723 and 873 K, and then the surface distortion and fracture strength of the joints were measured using scanning acoustic microscopy and a four-point bending test.
    In the case of the RT-573 K cycling there was little change in the joints, whereas Ni and Cu metals swelled at both of the RT-723 K and RT-873 K cycles and Ni swelling was much larger than that of Cu due to Ni plate sliding at the Ag-rich layer formed within the brazing filler. The fracture strength decreased significantly after the thermal-cyclings, because of the crack formation near the ceramic/filler interface.
    In the case of the Si3N4/Ni joint the Ni metal shrank at the early stages of the thermal cycling and then it tended to swell with the crack formation near ceramic-filler interfaces. The integrity of ceramic/metal joints could be controlled by the mechanical properties of metal components at the elevated temperatures.
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  • Yoshimitsu Okazaki, Sethumadhavan Rao, Shigeo Asao, Tetsuya Tateishi, ...
    1996 Volume 60 Issue 9 Pages 890-896
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effects of Ti, V and Al concentrations on the relative growth ratios of L929, MC3T3-E1 cells and on the colony formation ratio of V79 cells by cell culture method with metallic powders were investigated. These powders were sterilized under U.V. lamp for 14 ks(4 h), suspended in the medium and were extracted for 173 ks(48 h), 259 ks(72 h) and 346 ks(96 h) in the incubator under a 95% air-5%CO2 atmosphere. The medium not containing any metallic powder (control) was also extracted under similar conditions. After filtering with a 0.2 μm filter, 1.0×104∼5.0×104 L929 cells/ml, 5×104 MC3T3-E1 cells/ml and 102 V79 cells/ml were seeded in control and in the filtrates of the medium containing metallic powder. The number of cells were counted using a coulter counter from 86 ks(1 d) to 605 ks(7 d). The number of L929 cells after 346 ks(4 d) of incubation were almost similar for Ti extraction and control, whereas in the case of Al and V extractions the number of cells were too low as compared to that of control. The relative growth ratios of L929 cells for Ti, Al and V after 346 ks (4 d) of incubation were about 1, 0.05 and 0.02 respectively. Also, similar trends were observed for MC3T3-E1 and V79 cells. The relative growth ratio (number of cells in test medium/number of cells in control) of L929 cells for Ti powder was almost equal to one in 1∼10 g of Ti powder. On the contrary, the relative growth ratio of L929 cells for Al decreased with the increase in the weight of Al powder from 1 g to 3 g for both Eagle’s MEM (Minimum Essential Medium not containing fetal bovine serum and 7.5%NaHCO3) and Eagle’s medium extractions. No colonies of V79 cells were found for Al. Further, the concentration of Al in the medium increased with the increase in the weight of the Al powder. The relative growth ratio of L929 cells decreased as the initial number of L929 cells increased. Moreover, dilutions from 1 to 10 times in the case of Al and from 1 to 5000 times in the case of V were made. The relative growth ratios of L929, MC3T3-E1 and V79 cells became equal to 1 at 5 times dilution for Al and at 4000 times dilution for V. As the metallic concentration of Al and V ion in the medium increased from 0.2 to 0.5 mass ppm, the relative growth ratio of L929 and colony formation ratio of V79 cells decreased from 1 to almost 0. But, for MC3T3-E1 cells, the effect from a much lower concentration of V ion (0.02 ppm) was observed.
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  • Yoshimitsu Okazaki, Shin-ichi Katsuda, Yuko Furuki, Tetsuya Tateishi
    1996 Volume 60 Issue 9 Pages 897-901
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effects of surface treatments of Ti and Al on the relative growth ratio of L929 and the colony formation ratio of V79 cells were investigated. Ti and Al were oxidized inside the heating oven at 453 K(180°C) for 7.2 ks. These powders were suspended in the medium and were extracted for 173 ks(48 h) in the incubator with 95% air-5% CO2 atmosphere. The medium not containing any metallic powder (control) was also extracted under similar conditions. After filtering with a 0.2 μm filter, 1.5×104 L929 cells/ml and 102 V79 cells/ml were seeded in control and in the filtrates of the medium containing metallic powder. It was observed that, upon oxidation, the relative growth ratio of L929 cells for oxidized Al powder became almost equal to 0.8 after 346 ks(4 d) of incubation. This shows that a relatively strong oxide film is formed over the surface of Al powder, thus preventing Al ions to be released in the medium and, hence the relative growth ratio of L929 cells markedly increases. Anodic polarization measurements showed an excellent corrosion resistance for Ti in medium solution, whereas, the corrosion resistance for Al was found to be very low in medium solution. In the investigations of the colony formation of V79 cells, well formed colonies were observed for Ti with mirror-like finishing, but, no colony exists in the case of Al with mirror-like finishing. However, the colony appeared when the plate was etched with NaHCO3 and C2H4O2. Also, a similar result was observed when the plate is polished with #240 water proof emery paper. Hence, the colony formation of V79 cells strongly depends on the surface treatment of Al plate. The oxide film formed on the surface of Ti and Al after 0.6 Ms(7 d) of incubation with V79 cells were investigated by X-ray photo electron spectroscopy. It was observed that, the peak for Ca and P were observed for Ti. On the other hand, such peaks were small for Al. The peaks for Ti resembles the peaks of those of hydroxyapatite, thus exhibiting excellent biocompatibility. It is important to note that no peak resembling hydroxyapatite was observed for Al.
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  • Yoshimitsu Okazaki, Shigeo Asao, Sethumadhavan Rao, Tetsuya Tateishi
    1996 Volume 60 Issue 9 Pages 902-906
    Published: 1996
    Released: April 04, 2008
    JOURNALS FREE ACCESS
    The effects of metallic concentrations of Zr, Sn, Nb, Ta, Pd, Mo, Co, Cr, Si, Ni and Fe in the medium on the relative growth ratios of fibroblasts L929, osteoblasts MC3T3-E1 cells and the colony formation ratio of fibroblasts V79 cells were investigated. The change in the relative growth ratio of L929 cells after 346 ks(4 d) of incubation in different extraction time, namely, 86 ks(24 h), 173 ks(48 h), 259 ks(72 h), 346 ks(96 h) and 432 ks(120 h) were estimated. It was observed that, the relative growth ratio of L929 cells was equal to unity for Ti, Zr, Sn, Nb, Ta, Cr and Si, whereas, the relative growth ratio was approximately equal to 0 for Mo, Ni, Co, and Fe. Also, the relative growth ratio of L929 cells became equal to 0 at the extraction time of 346 ks(96 h) for Pd. From the anodic polarization studies in the medium solution, it can be seen that Ta, Nb and Si exhibited excellent corrosion resistance. On the other hand Cr, Ni, Co and Fe exhibited a relatively low corrosion resistance. These results were in good match with the results of the relative growth ratios of L929, MC3T3-E1 and V79 cells. The effect of the weight from 1 to 5 g of Nb, Ta and Zr powders on the relative growth ratios of MC3T3-E1 cells in α-MEM (α-modified Minimum Essential Medium not containing fetal bovine serum and 7.5% NaHCO3) solution and α-Medium extractions were also examined. The relative growth ratios of MC3T3-E1 cells were equal to unity for Nb at all weights from 2.5 to 5 g. A marked decrease in the relative growth ratio of MC3T3-E1 cells was observed for Zr and Ta as the weight increased from 2.5 to 5 g. Since Mo, Pd, Co, Ni, Fe and Si were released in the medium, the effects of dilution on the relative growth ratio of L929 and MC3T3-E1 cells were carried out. The relative growth ratios of L929 and MC3T3-E1 cells markedly decreased at a metallic concentration of more than 3 mass ppm for all the metal powders used.
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