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Volume 69, Issue 10
Displaying 1-14 of 14 articles from this issue
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Shinji Ando, Masayuki Tsushida, Hideki Tonda2005 Volume 69 Issue 10 Pages 855-858
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSTo understand the deformation mechanism due to non-basal slip in hcp metals, the core structure of edge dislocation with Burgers vector (c+a) was investigated by molecular dynamics simulation using a Lennard-Jones type pair potential. A perfect (c+a) edge dislocation was introduced along [1100] direction at the center of the model crystal. In the case of [0001] tensile, a core structure of the (c+a) perfect edge dislocation (Type-A) changed into {1121} twin-like structure with increasing strain. The Type-A moves at the tensile stress of 6.8 GPa with twin structure. The (c+a) edge dislocation consisted with two partial dislocations (Type-B) moves along (1122) plane with increasing strain. The critical tensile stress of the Type-B was about 3.4 GPa. In the case of [0001] compression, although the both type of dislocations moved in the opposite direction as the Type-B, the critical stress in compression was smaller than that in the tensile. This explains how the mobility of (c+a) edge dislocations seen in our tensile tests depends on the direction of applied stress. A temperature dependence of the critical stress has been demonstrated, so that when the temperature was raised from 0 K to 30 K, the stress decreased rapidly in all case.
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Yuta Shimizu, Toshio Itami2005 Volume 69 Issue 10 Pages 859-862
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSThe 7Li NMR Knight shift was measured for liquid Li-Tl alloys. Prior to this NMR measurement, DSC measurements were carried out to know the exact liquidus temperatures. Except for some trivial points, the phase diagram determined is almost same as the previous one; the solid compound at the maximum liquidus temperature was observed at 50 at%Tl; the eutectic point was detected at 84.8 at%Tl. The 7Li Knight shift, K, decreases rapidly with the addition of Tl up to 20 at%Tl. In the concentration range from 20 to 50 at%Tl, the K keeps a constant value, which is 60% of 7Li Knight shift for the pure liquid Li. Such a decrease of the K is considered as an indication for the strong charge transfer from Li to Tl. The Zintl ion formation is expected in this concentration range of liquid Li-Tl alloys. These tendencies are similar to the previous studies for liquid Li-Ga and Li-In alloys. However, beyond 50 at%Tl, the K increases slightly and reaches to the constant value (70% of 7Li Knight shift for the pure liquid Li). Such a back donation of charge is absent for liquid Li-Ga and Li-In alloys. It is considered that the tendency of the Zintl ion formation for liquid Li-Tl alloys is slightly weaker compared with the cases of liquid Li-Ga and Li-In alloys.
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Masahiro Ishimaru, Hiromitsu Ino2005 Volume 69 Issue 10 Pages 863-866
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSPhase stability of FexNi1-x alloys (x=0.65~x=0.90) prepared by milling was investigated, together with the magnetic transition of the FCC phase. In as-milling state the BCC single phase was obtained in x=0.84 and higher Fe samples, and the FCC single phase in x=0.65. Between these two compositions, FCC and BCC mixed phase appeared. After the heat treatment at 1073 K for 300 sec, the FCC single phase was obtained in x≦0.84 and the BCC and FCC mixed phase in x=0.85 and 0.88. The BCC-FCC phase transformation temperatures both for heating and cooling rose with Fe concentration. It was shown that the Curie temperature of the FCC phase decreased with Fe concentration.
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J-H. Park, Mitsuharu Kanda, Noriyuki Tsuchida, Yo Tomota2005 Volume 69 Issue 10 Pages 867-873
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSEffect of nitrogen addition on strain rate dependence of flow stress in austenitic stainless steel (SUS310S) was investigated. It is made clear that both thermal and athermal flow stress components are increased with increasing of nitrogen concentration. The flow stress was described by using the Kocks-Mecking (KM) model, where the KM parameters were determined from the data obtained by tension tests at low strain rates below RT. The flow stress at a high speed, 2×103 s-1 measured by the Hopkinson split-bar method agrees well with the prediction by the KM model. High nitrogen bearing steel is characterized by higher flow stress with a considerably large work-hardening at high speed deformation, which has never been achieved in ferritic steels. Because microstructure evolution is influenced by deformation temperature, flow stress shows the deformation history dependence in nitrogen bearing steels.
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Norio Shinya, Junro Kyono2005 Volume 69 Issue 10 Pages 874-879
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSCompositions of type 304 austenitic stainless steels were modified with the addition of boron, cerium and titanium. The addition of cerium and titanium removed mobile sulfur almost completely by formation of sulfides (Ce2O2S2 and Ti4C2S2). Boron nitride precipitated during creep tests on creep cavity surfaces in sulfur-free samples. Auger electron spectroscopic analyses of the chemistry of creep cavity surfaces, exposed by breaking the creep exposed specimens at liquid nitrogen temperature under impact loading, revealed the precipitation of boron nitride on creep cavity surface. The boron nitride suppressed creep cavity growth and provided the steel with higher rupture strength and higher rupture ductility.
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Jun Mabuchi, Yoichi Nishino2005 Volume 69 Issue 10 Pages 880-885
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSThe mechanical properties of (Fe1-xVx)3Al alloys including the Heusler-type Fe2VAl (x=1/3) have been investigated using high-temperature compression tests with attention to an increase in the D03(L21)-B2 transition temperature Tc by the V substitution. The yield stress peak substantially shifts to higher temperatures with increasing Tc and can be found at around 1270 K for Fe2VAl. The strain rate sensitivity exponent m is near zero in the temperature range where the plateau with a rather low yield stress appears, but rises sharply around the peak temperature, reaching m=0.40 at 1300-1400 K for Fe2VAl. Thus superplastic behavior is always expected to occur in the (Fe1-xVx)3Al system when deformed at temperatures above that of the yield stress peak under a strain rate range of 10-4-10-3 s-1. In spite of large-grained Fe2VAl, the grain size becomes much finer after deformation up to a strain of 120%: from about 400 μm to 30 μm. Dynamic recovery and recrystallization process similar to that in Fe3Al is proposed as the superplastic deformation mechanism.
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Shingo Kurosu, Naoyuki Nomura, Katsunori Yamaguchi, Shigeo Fujinuma, A ...2005 Volume 69 Issue 10 Pages 886-891
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSIn order to investigate the effects of 5th element addition to Co-29Cr-6Mo-1Ni alloys on metal ion release, Co-29Cr-6Mo-1Ni-X(X=Ti, Nb, Al, Zr) alloys were immersed in 1 mass% lactic acid solution at 37°C for 7 days and released metal ions were examined by ICP-AES. All of the 5th element added alloys showed less Ni ion quantities released from various alloys than that released from the original Co-29Cr-6Mo-1Ni alloy. This result suggests that Ni ion release could be suppressed by Ni-fixation mechanism due to the formation of Ni-X compounds (X=Ti, Al, Nb, Zr). Furthermore, the quantities of Co ion from Co-29Cr-6Mo-1Ni-X(X=Ti, Zr) alloys were a half less than that from the original. Each metal ion quantity released from Co-Cr-Mo-Ni alloys consisting hcp phase is lower than that from the alloys consisting fcc phase. From the relationship between microstructure and released metal ion quantity, Co-Cr-Mo-Ni alloys consisting hcp phase exhibit low released metal quantities compared to those consisting fcc phase. Therefore, it is likely that metal ion release is suppressed by controlling microstructure through the alloying method.
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In-Joon Son, Hiroaki Nakano, Satoshi Oue, Shigeo Kobayashi, Hisaaki Fu ...2005 Volume 69 Issue 10 Pages 892-898
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSThe effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al and Al-Mg alloy was investigated by means of polarization curves in solutions containing 300 ppm of Cl- and by surface analysis. The potentials for pitting corrosion of Al and Al-Mg alloy were evidently shifted to the noble direction by ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observation revealed that the pitting corrosion occurred near the impurity precipitates and the size of impurity precipitated decreased with ECAP process. The time-dependence of corrosion potential and the polarization resistance determined by AC impedance technique suggested that the formation rate of Al oxide films was increased with ECAP process. The improvement in pitting corrosion resistance of Al and Al-Mg by ECAP seems to be attributable to the decrease in the size of impurity precipitates and the increase in the formation rate of Al oxide films.
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Satoshi Sunada, Masanori Kariba, Kazuhiko Majima, Katsuhisa Sugimoto2005 Volume 69 Issue 10 Pages 899-906
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSAn SCC test was carried out in aqueous solutions containing both H2SO4(0~5.5 kmol/m3) and NaCl(0~4.5 kmol/m3) as solutes, in order to study the influence of the environment on the corrosion type of an SUS304 steel. The both solutes of H2SO4 and NaCl have synergistic influence on the corrosion type, and SCC occurs within a specific concentration region and general corrosion occurs at the other concentrations. For a constant H2SO4 concentration the corrosion mass loss decreases with increasing NaCl concentration up to a certain value and then increases. This tendency makes a V-shape curve when the mass loss is plotted against the NaCl concentration. On the other hand, SCC crack length increases with increasing NaCl concentration up to a certain value, passes a maximum, and then decreases. This tendency is just like an inverse V-shape curve. In addition, the NaCl concentration ranges for the minimum mass loss and maximum crack length are almost equal. It was also confirmed that these NaCl concentration regions are inversely proportional to the H2SO4 concentration.
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Mitsuru Hirano, Hiroyuki Kobayashi, Yoshitake Nishi2005 Volume 69 Issue 10 Pages 907-910
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSTo develop high temperature sensor, the change in an electrical resistivity of carbon fiber according to the stress increasing was measured as basic research. It was confirmed that the stress in the low stress zone decreased electrical resistivity, whereas the excess stress increased the electrical resistivity in the high stress zone.
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Yoshiyasu Itoh, Shoko Suyama, Hideyasu Andoh, Takahiko Shindoh2005 Volume 69 Issue 10 Pages 911-916
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSTungsten/copper composites had already been used for electric arc resistance parts. However, the arcing resistant properties of tungsten/copper composites, were not clarified. Therefore, the surface damage behaviors of tungsten/copper composites were investigated by electric arcing test. In this study, the electric arcing test apparatus with a cooling function was newly developed for the arcing resistant evaluation of tungsten/copper composites. As a result, it was verified using the electric arcing test apparatus that the surface damage of tungsten/copper composites could be evaluated. Also, it was confirmed by SEM observation and X-ray diffraction analysis that the surface erosion of tungsten/copper composites was extremely increased in case of the positive polarity and Ar+SF6 atmosphere and this phenomenon was caused by the reaction with the decomposed gas of SF6.
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Masaaki Yamada, Kiyohide Hibino, Masanori Suzuki, Kazuhide Tanaka, Ats ...2005 Volume 69 Issue 10 Pages 917-922
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSTwo-dimensional distribution of adsorbed and absorbed hydrogen in Mg-Ni alloys with two-phase structure was observed by scanning electron-stimulated desorption microscopy (or scanning “protoscope”). In the time-of-flight (TOF) spectrum, the desorbed hydrogen ions exhibit two-peak components, for which hydrogen ion images were measured discriminately. It has been found that, in hydrogen-adsorbed alloys, the desorbed hydrogen ions with longer TOF (lower kinetic energy Ek) represent hydrogen from Mg2Ni phase, whereas those with shorter TOF (higher Ek) from selectively oxidized Mg phase. On the other hand, in hydrogen-absorbed alloys, the desorbed ions from both Mg2Ni hydride and Mg hydride comprising the eutectic phase were observed, exhibiting longer and shorter TOF components, respectively.
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Tadashi Fukuda2005 Volume 69 Issue 10 Pages 923-927
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSEffects of Ti carbide precipitates on the ductility and toughness of 30 mass%Cr steels containing above 0.1%C and 1%Ti were investigated by tensile and impact tests at low temperatures. Two kinds of heat treatment of aging after solution treatment (process SA) and annealing without solution treatment (process A) were performed for the test pieces. The ductility and toughness were evaluated by ductile-brittle transition temperature (DBTT) in reduction of area and DBTT in absorption energy, respectively. Both the processes SA and A produce coarse globular Ti carbide particles within the grains in the 2 μm size range and cluster-like coarse globular Ti carbides at grain boundaries. The process SA does not bring about numerous fine grain boundary Ti carbides for the specimens containing above 0.1%C, which is contrary to those for the specimens containing below 0.07%C. DBTTs determined by the tensile test for the specimens with above 0.1%C after the process SA are lower than those of the specimens in a range from 0.04% to 0.07%C, while DBTTs determined by the impact test for the former specimens are higher than those of the latter specimens. The effect of morphology of Ti carbide on the DBTT determined by the tensile test and that on the DBTT determined by the impact test are different. The numerous fine grain boundary Ti carbides exert detrimental effect on the former DBTT. On the other hand, the numerous fine grain boundary Ti carbides and the coarse globular Ti carbides exert detrimental effect on the latter DBTT.
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Keijiro Hiraga, Koji Morita, Byung-Nam Kim, Yoshio Sakka2005 Volume 69 Issue 10 Pages 928-932
Published: 2005
Released on J-STAGE: October 20, 2005
JOURNAL FREE ACCESSIn yttria-stabilized cubic zirconia, the addition of 0.15-5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and at multiple junctions. For a grain size of 0.75 or 1.7 μm, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the fracture toughness measured by an indentation method. The latter result arises because the decrease in the elastic modulus-to-hardness ratio is compensated by a decrease in the crack length for a given indentation load. Inspection of crack-propagation paths indicates that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.
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