MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 48 , Issue 11
Showing 1-41 articles out of 41 articles from the selected issue
  • Dmitri A. Molodov, Christian Bollmann, Peter J. Konijnenberg, Luis A. ...
    2007 Volume 48 Issue 11 Pages 2800-2808
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 05, 2007
    JOURNALS FREE ACCESS
    The impact of a magnetic field (17T) on texture and microstructure evolution in cold rolled (75%) commercially pure titanium was investigated. The specifically oriented titanium sheet specimens were heat treated at 1023 K in a magnetic field of 17 T for 60, 120, 180 and 240 minutes. X-ray diffraction and EBSD measurements were utilized to characterize the crystallographic texture and the grain microstructure. The magnetic annealing resulted in an asymmetry of the two major texture components that constantly increased with annealing time. This effect is attributed to a magnetic driving force for grain growth arising from the anisotropic magnetic susceptibility of titanium. Complementary computer simulations of 2D grain growth were employed to analyze the effect of a magnetic field on texture and microstruture evolution. EBSD measurements as well as the computer simulations revealed that a magnetic field affects the grain growth kinetics. Grains with energetically preferred orientations grow faster and their fraction becomes larger than the fraction of more slowly growing grains with disfavored orientations.
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  • Yan Wu, Xiang Zhao, Chang-Shu He, Yu-Dong Zhang, Liang Zuo, Claude Esl ...
    2007 Volume 48 Issue 11 Pages 2809-2815
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The effects of magnetic field annealing on microstructure and texture evolution at the initial stage of recrystallization in as-annealed interstitial-free (IF) steel sheet were investigated by the orientation imaging microscopy (OIM) and microhardness testing. The magnetic field annealing was conducted in a 12-tesla magnetic field at 650°C for different time spans (0, 10 and 30 min) to obtain partially recrystallized microstructure in specimens. It was found that the magnetic field annealing retarded the recrystallization process, and favoured the development of ⟨110⟩ texture components at the initial stage of recrystallization. Additionally, it is worth noting that, in the case of annealing for 10 min, we observed more pronounced {111}⟨123⟩ component associated with coarse grains in the magnetic field annealed specimen, which may suggest that this component was favoured by the applied high magnetic field in the early stage of nucleation and growth.
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  • Shou Jing Wang, Xiang Zhao, Yu Dong Zhang, Liang Zuo, Claude Esling
    2007 Volume 48 Issue 11 Pages 2816-2820
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The influence of a high magnetic field on the formation of ferrite in high purity Fe-0.52C (mass%) during austenite to ferrite transformation was studied. Results show that magnetic field can reduce the amount of Widmanstätten ferrite by enhancing the transformation driving force and make the ferrite grains elongate and align along the field direction.
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  • Sahar Farjami, Motohiro Yuge, Takashi Fukuda, Tomoyuki Terai, Tomoyuki ...
    2007 Volume 48 Issue 11 Pages 2821-2825
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: August 29, 2007
    JOURNALS FREE ACCESS
    Effect of magnetic field on γ(austenite)↔α(ferrite) transformation has been studied by using Fe-xRh alloys with x=2, 5, 10 at%. In this system, the Curie temperature Tc of the α-phase is either above the γ↔α transformation temperature or below it depending on the Rh content. In the former case, the transformation temperature increases linearly with increasing magnetic field, while in the latter case, it increases almost proportional to square of magnetic field. Such difference has been discussed quantitatively on the basis of a Clausius-Clapeyron-like equation by using the magnetization and latent heat measured in the study.
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  • Victoria A. Yardley, Sadahiro Tsurekawa, Hiromichi Fujii, Takashi Mats ...
    2007 Volume 48 Issue 11 Pages 2826-2832
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 05, 2007
    JOURNALS FREE ACCESS
    Recent work has shown that annealing amorphous alloys under an applied magnetic field can enhance the fraction of nanocrystalline phase formed and induce a strong texture. This effect has been attributed to the displacement of thermodynamic equilibrium by the energetic contribution from the applied field. In the present paper, an attempt is made to test the validity of this proposition in the Fe-Si-B(-Nb-Cu) system using equilibrium calculations in the framework of the CALPHAD (CALculation of PHAse Diagrams) methodology and a simple estimate of the energy supplied by the field. However, it is found that the magnetic energy term thus obtained is too small to produce the observed change in nanocrystalline phase fraction. Possible reasons for this discrepancy are discussed.
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  • Jae-hwa Lee, Takashi Fukuda, Tomoyuki Kakeshita, Koichi Kindo
    2007 Volume 48 Issue 11 Pages 2833-2839
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
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    Effects of external fields, such as temperature, magnetic field, stress and combination of these fields have been examined on martensitic transformation of SUS304 and SUS304L austenitic stainless steels. Following results are obtained: (i) No athermal martensitic transformation occurs in all the solution-treated and sensitized stainless steels. On the contrary, isothermal transformation occurs in the sensitized SUS304 (γ→α′) between about 150 K and 250 K. It also occurs in the solution-treated (γ→ε′→α′) and sensitized SUS304L (γ→ε′→α′ and γ→α′) between about 80 K and 160 K. The γ-phase in all the steels exhibits an antiferromagnetic transition at about 40 K. (ii) Magnetic field-induced martensitic transformation dose not occur in austenitic state of the solution-treated and sensitized SUS304 and SUS304L even when the pulsed magnetic field of up to 30 MA/m is applied in a wide temperature range between 4.2 K and 290 K. On the other hand, the solution-treated and sensitized SUS304L containing isothermally-induced ε′ martensite exhibit magnetic field-induced ε′ to α′ transformation at 4.2 K and 77 K. (iii) Deformation-induced γ→ε′→α′ martensite transformation easily occurs at 77 K for all the solution-treated and sensitized stainless steels. (iv) Magnetic field-induced ε′→α′ transformation does not occur in the ε′ martensite induced beforehand by deformation in all the steels.
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  • Takuro Kushima, Koichi Tsuchiya, Yasukazu Murakami, Daisuke Shindo, Yo ...
    2007 Volume 48 Issue 11 Pages 2840-2846
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
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    Phase transformation, microstructure and magnetic properties were investigated for Cu-(11-14) mol%Mn-20 mol%Ga. The structures of the magnetic domains were also investigated by Lorentz microscopy and electron holography. Plate-like martensite phase(ζM, ordered hcp) was observed in as-quenched Cu-12 mol%Mn-20 mol%Ga. Phase transformation from ζM martensite to ζ phase(hcp) occurred at around 540 K on heating. The ζ phase decomposed into ζ″(ordered hcp) and β(bcc) phase at around 700 K, then became the single β phase at around 840 K. By subsequent slow cooling, ζ phase was observed at room temperature. The results obtained from Lorentz microscopy and electron holography revealed that the twin plates of ζM martensite and the magnetic domain have one-to-one correspondence, suggesting high magneto-crystalline anisotropy energy of the martensite phase. The saturation magnetization and the Curie temperature increased with Mn content.
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  • Haruhiko Morito, Katsunari Oikawa, Asaya Fujita, Kazuaki Fukamichi, Ki ...
    2007 Volume 48 Issue 11 Pages 2847-2850
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 12, 2007
    JOURNALS FREE ACCESS
    The variations of the martensitic transformation starting temperature TMS and the Curie temperature TC in Ni-Fe-Ga alloys have been investigated by substituting with several kinds of the fourth elements. By partial substitution of Co or Cu for Ni, TC increases and TMS decreases. In particular, the increase of TC is remarkable in the Ni54−xCoxFe19Ga27 alloy, which is related to the strong Ni-Co and Co-Fe exchange interactions. For the Ni54Fe19−xMnxGa27 alloys, TC slightly increases with the increase of Mn content, in analogy with the Ni52FexMn21−xGa27 alloys. From the present study, it is demonstrated that both TC and TMS of the Ni-Fe-Ga alloys can be effectively controlled by selecting the substituents.
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  • Hideyuki Ohtsuka
    2007 Volume 48 Issue 11 Pages 2851-2854
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 12, 2007
    JOURNALS FREE ACCESS
    Effects of magnetic fields on transformation temperature, transformation behavior and transformed structure have been investigated for bainitic transformation in an Fe-3.6Ni-1.45Cr-0.5C steel and for transformation to lath martensite in 18Ni maraging steel. Bs temperature was determined by observing the transformed structure and Ms temperature was measured from the cooling curve of the specimen. It was found that both Bs and Ms temperatures increase with increasing applied magnetic field. Bainitic transformation behavior is accelerated by the applied magnetic field. Elongated and aligned structures were observed for austenite to ferrite transformation in an Fe-0.4C alloy, but no elongation or alignment of transformed structure has been observed for transformations to bainite and lath martensite.
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  • Tomohiko Tanase, Jun Akiyama, Kazuhiko Iwai, Shigeo Asai
    2007 Volume 48 Issue 11 Pages 2855-2860
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    Hydroxyapatite (HAp) is the main mineral component of bone and is used as a raw material for artificial bones and teeth, and as an adsorbent in liquid chromatography, among its other uses. As a result of its anisotropic crystal structure, HAp shows adsorption behavior that depends on the crystal plane. However, the differences between the a-plane and the c-plane of the HAp crystal in terms of their bioactivity, cell-propagation behavior, etc., have not yet been fully clarified. In this study, we fabricated highly crystallographically aligned samples of HAp by using a 10-T magnetic field, and we studied the effects of the specific crystal plane of HAp on its bioactivity by immersing the samples in a simulated body fluid.
    HAp is precipitated on both a-plane- and c-plane-aligned HAp sample surfaces. The rate of precipitation on a HAp sample immersed in the simulated body fluid depended on the crystal plane, especially during the first 24 h of immersion. Because the rate of precipitation on the c-plane is faster than on the a-plane, HAp is precipitated preferentially on the c-plane during the early stages of precipitation.
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  • Yoshio Sakka, Kazuya Takahashi, Nobuyuki Matsuda, Tohru S. Suzuki
    2007 Volume 48 Issue 11 Pages 2861-2866
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    Hydroxyapatite (HAP, Ca10(PO4)6(OH)2) is a main component of bones and teeth, and a specific crystal orientation is required for biomaterial application. In this study, the effects of the processing parameters on the orientation, such as de-agglomeration by milling procedure, applied magnetic field and sintering temperatures, were examined. Using the de-agglomerated particle by a milling procedure, it is possible to control the particle orientation, but when using heavily agglomerated particles, it was impossible to control the particle orientation by applying a high magnetic field. Highly-textured HAP can be fabricated by slip casting using a well-dispersed suspension in a high magnetic field (above 4 T) followed by sintering above 1373 K.
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  • Takenori Kohama, Hiroki Takeuchi, Manabu Usui, Jun Akiyama, Mun-Gyu Su ...
    2007 Volume 48 Issue 11 Pages 2867-2871
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The crystal alignment behavior of bismuth particles in the presence of an imposed static magnetic field was examined in situ by X-ray diffraction. Because the c-plane of a bismuth crystal is aligned perpendicular to the direction of a magnetic field, the temporal variation in the (110) peak intensity of bismuth was measured by X-ray diffraction to determine the crystal alignment. The alignment time decreased as the magnetic field strength increased. This tendency is similar to that calculated for the relaxation time. The difference in the magnetic susceptibility between the magnetically easy and hard axes is the driving force for the crystal alignment, and aggregation of the bismuth particles decreases this driving force. The effective difference in magnetic susceptibility for aggregated bismuth particles was estimated by measuring the alignment time of the particles under magnetic fields of various strengths. The estimated effective difference in magnetic susceptibility generally increases with a decreasing magnetic field strength. Furthermore, the interference to crystal rotation caused by the interaction between the induced current and the imposed magnetic field is negligible in this study. To decrease the strength of the magnetic field required for alignment of crystals, the number of small particles should be reduced.
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  • Yasuhiko Sakaida, Kazuhiko Iwai, Shigeo Asai
    2007 Volume 48 Issue 11 Pages 2872-2876
    Published: November 01, 2007
    Released: October 25, 2007
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    It is well known that the transport of atoms, ions and holes in a material is induced by electromigration. This implies that electromigaration can control the structure of a material. In this study, an electric current was applied to a titanium sample that was subjected to a static magnetic field to investigate the effects of the electric current and the static magnetic field on crystal alignment in titanium.
    An intensity ratio of (002) peak to (100) peak in XRD analysis was introduced as a crystal alignment index.
    Because the magnetic susceptibility of titanium in the c-axis is larger than what it is in the a-axis, titanium crystals having a c-axis parallel to the magnetic field are stable from the viewpoint of magnetization energy. However, the numbers of these crystals decreased after the experiment. On the other hand, the c-axis of the titanium crystals aligned themselves itself to become perpendicular to the direction of flow of the electric current to reduce the Joule loss in the sample, because the specific resistance in the c-axis was larger than that in the a-axis. This agrees with the experimental result.
    Therefore, in this experiment the titanium crystals in the sample aligned themselves to reduce the Joule loss even though the magnetic energy was larger than the thermal fluctuation in this experiment.
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  • Hideaki Murase, Hideyuki Yasuda, Atsushi Nakahira
    2007 Volume 48 Issue 11 Pages 2877-2882
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 11, 2007
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    In this paper, the effect of high magnetic field on the development of property were investigated by calcination of MgFe-LDH (CO3) as a precursor of ferrite material under applied field of 10 T. Obtained products were identified by X-ray diffraction analysis (XRD) and their microstructures were observed using scanning electron microscopy (SEM). Furthermore, their magnetic properties were evaluated by a superconducting quantum interference device (SQUID). It was observed that the particle size of mixed oxide prepared by calcination under 10 T was homogeneous and small. Saturation magnetization of mixed oxide synthesized under 10 T was higher than that of zero field. Therefore, it was found that calcination due to imposition of high magnetic field affected phase transition to mixed oxide and provided enhancement of its property.
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  • Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio Sakka
    2007 Volume 48 Issue 11 Pages 2883-2887
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 12, 2007
    JOURNALS FREE ACCESS
    In general, the mechanical and physical properties of a crystal depend on the direction of the crystal axis. The controlled development of the crystallographic texture in ceramics is very useful for improvement of their properties. The preparation of the textured SiC polycrystal was achieved by colloidal processing in a strong magnetic field. The c-axis of the SiC was parallel to the direction of the applied magnetic field. The bending strength of the textured SiC depends on the crack-growth direction.
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  • Noriyuki Hirota, Soma Hara, Yoshio Sakka
    2007 Volume 48 Issue 11 Pages 2888-2892
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The effect of magnetic fields on electroless silver deposition was investigated through in situ microscopic observation using a periscope system developed on the basis of a confocal scanning laser microscope. At the growth front of a silver dendrite, under a 12 T magnetic field applied perpendicularly to the sample plane, a straight silver branch was grown for a while; then, a given length of the branch at the neighbor of the tip started moving rapidly and was bent in an integrated manner. As a result of the process, a dense silver dendrite in the shape of a vortex was formed. When the sample space was narrowed, the branch did not bend due to the increase in the static friction between the branch and the glass plates. Judging from these observations, the mechanism underlying the formation of a dense vortex dendrite was thought to be the effect of the Lorentz force acting on the branch due to the electric current flowing through the branch itself accompanied by the silver deposition and the copper dissolution reactions. Furthermore, the reason that the silver dendrite grown under high magnetic fields looked denser by macroscopic observation was investigated by evaluating the reaction amount and the microstructure of the silver branch. No significant difference was observed in the reaction amount between the experiments with and without magnetic fields. On the other hand, the microstructures of the silver branch were significantly different from each other. The silver branch grown under high magnetic fields had a low-density structure, which seems to account for its denser appearance in the macroscopic observation. This low-density structure may be formed because of the interference of the static crystal growth due to the rapid bend of the silver branches.
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  • Chiaki Uyeda, Shun Kano, Keiji Hisayoshi, Akio Nakanishi, Kenji Kimoto
    2007 Volume 48 Issue 11 Pages 2893-2897
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    Oscillation of magnetically stable-axis with respect to a static field below 20 kOe occurred for various solids without spontaneous magnetic moment. The oscillation was caused by anisotropy of magnetic susceptibility Δχ. According to theoretical consideration on the origin of diamagnetic and paramagnetic anisotropy, Δχ values of ordinary solid is expected to range over 6 orders of magnitude. These Δχ values can be obtained from period of the above-mentioned oscillation; small Δχ values were detectable because effect of restoration torque of a fiber that suspended the sample was excluded in the measurement. Δχ above 1×10−9 emu/g were detected at terrestrial gravity in a field below B=20 kOe. The fiber itself was excluded by floating a sample in microgravity, for the purpose of detecting Δχ below 1×10−9 emu/g. Alignment of micron-sized crystals dispersed in fluid at room temperature is achieved below 2 Tesla for most of the solids since their Δχ value is above 1×10−9 emu/g. Efficiency of magnetic alignment is enhanced considerably for ordinary oxide when resultant Δχ is increased by paramagnetic impurity ions up to level of 10−5 emu/g.
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  • Chih-Chun Hsieh, Dong-Yih Lin, Ming-Che Chen, Weite Wu
    2007 Volume 48 Issue 11 Pages 2898-2902
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 28, 2007
    JOURNALS FREE ACCESS
    The purpose of this study was to discuss the microstructure, recrystallization, and mechanical property evolutions in the heat-affected zones and fusion zones during dissimilar stainless steels welding. The morphology, quantity and chemical composition of the δ-ferrite were analyzed by using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and electron probe micro-analyzer (EPMA), respectively. The recrystallization phenomenon was evident with the second pass heat-affected zone (HAZ-2) and indicated equiaxed grains after second pass welding. The contents of δ-ferrite exhibited the highest value of all situations in the first pass fusion zone (FZ-1) during the first pass welding. Furthermore, the solidification mode of fusion zones transformed from massive as well as acicular δ-ferrite into lathy and skeletal structures as increased the welding pass number from 1 to 3.
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  • Jun Du, Jian Yang, Mamoru Kuwabara, Wenfang Li, Jihua Peng
    2007 Volume 48 Issue 11 Pages 2903-2908
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    The effect of iron on the grain refinement of Mg-3Al alloy modified with and without carbon powder has been investigated in the present study. Significant grain refinement could be obtained for Mg-3 mass%Al alloy modified with either Fe or carbon. The Al-C-O and Al-Fe particles were observed which should be the potent nuclei for Mg grains. The high segregating power of Fe was also proved as an important factor which determines the grain size of Mg-Al alloys. Refining efficiency could be further obtained by the combination of Fe and carbon. Both Al-C-O-Fe-rich and Al-Fe-rich intermetallic particles were observed in the samples modified by the combination of Fe and carbon. The Al-C-O-Fe-rich intermetallic particles should play a very positive role in grain refining for Mg-Al alloys. The combination of Al-C-O-Fe and Al-Fe intermetallic compounds produced more powerful nuclei for Mg grains, and thus caused grain refinement.
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  • Yoshiaki Yamamoto, Hiizu Ochi, Takeshi Sawai, Hiroshi Yamaguchi, Koich ...
    2007 Volume 48 Issue 11 Pages 2909-2913
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The Ono’s rotary bending fatigue test and the cantilever rotary bending fatigue test were carried out on friction-welded 6061 aluminum alloy joints, and the relationship between the deformation heat input in the upset stage or the upset burn-off length and fatigue strength was examined. In the Ono’s type test, sound joints, which fractured in the heat affected zone in the tensile test, fractured in the heat affected zone also and the fatigue limit of these joints was slightly lower than that of 6061 aluminum alloy base metal. This is because joints fractured in the softened area in both tensile test and Ono’s type test using smoothed test specimens. While, in the cantilever type test, the fatigue limit of sound joints was a little more than or a little less than that of 6061 aluminum alloy base metal. It seems that a weld and a structure at the weld interface affected fatigue strength in the cantilever type test using notched test specimens. Judging from the fatigue limit obtained, sound joints could be produced when either the deformation heat input in the upset stage or the upset burn-off length exceeded a certain value.
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  • Toshihiro Omori, Naoki Koeda, Yuji Sutou, Ryosuke Kainuma, Kiyohito Is ...
    2007 Volume 48 Issue 11 Pages 2914-2918
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The microstructure and superplastic behavior at 450°C and 500°C in Cu-Al-Mn-based shape memory alloys were investigated using optical microscopy and a tensile test. It was found that a fine α (fcc) + β (bcc) two-phase structure with a grain size of 3 μm in diameter can be obtained in Cu-Al-Mn-Ni alloy by annealing at 600°C. The flow stress of Cu-Al-Mn-Ni alloy depends on the strain rate and the strain rate sensitivity is over 0.3 with an elongation of over several hundred percent, which shows that the Cu-Al-Mn-Ni shape memory alloy exhibits superplasticity. For the test temperature at 500°C and a strain rate of 5×10−4 s−1, a maximal elongation of 1150% was obtained. The formation of cavity stringers lying parallel to the tensile axis was observed and the size of the cavity was larger as the specimen was more highly deformed.
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  • Hongqi Li, Peter K. Liaw, Hahn Choo
    2007 Volume 48 Issue 11 Pages 2919-2922
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    The uniaxial compression tests were conducted on an amorphous Zr-based alloy at room temperature. The results show that this alloy exhibited the typical features of metallic glasses and the stress-strain curve is extensively serrated within the plastic regime. The analysis reveals that for all the shear band events, the maximum stresses remained approximately constant during the course of plastic deformation, and the minimum stresses began to decrease when the deformation enters the late stage. This phenomenon is probably associated with the different shear-banding behaviors within various deformation stages. Calculations find that the stress accumulation sections in the stress-strain curve are parallel to each other, indicating that such reloading processes are elastic in nature. Therefore, there are elastic and plastic sections in the stress-strain curve. Further analysis discloses that the plastic strain component carried by each shear band event increases with the applied strain within the late deformation stage.
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  • Futoshi Shimizu, Shigenobu Ogata, Ju Li
    2007 Volume 48 Issue 11 Pages 2923-2927
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses (Acta Mater. 54 (2006) 4293), based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis. The model predicts the existence of a critical lengthscale ∼10 nm, above which melting could occur in shear-alienated glass. Large-scale molecular dynamics simulations with up to 5 million atoms have directly verified this prediction. When the applied stress exceeds the glue traction (computed separately before in a shear cohesive zone, or an amorphous-amorphous “generalized stacking fault energy” calculation), we indeed observe maturation of the shear band embryo into bona fide shear crack, accompanied by melting. In contrast, when the applied stress is below the glue traction, the shear band embryo does not propagate, becomes diffuse, and eventually dies. Thus this all-important quantity, the glue traction which is a property of shear-alienated glass, controls the macroscopic yield point of well-aged glass. We further suggest that the disruption of chemical short-range order (“chemical softening”) governs the glue traction microscopically. Catastrophic thermal softening occurs only after chemical alienation and softening in our simulation, after the shear band embryo has already run a critical length.
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  • Ryuji Sugiura, A. Toshimitsu Jr. Yokobori, Shinjyu Takamori, Masaaki T ...
    2007 Volume 48 Issue 11 Pages 2928-2936
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The life of creep crack growth for W-strengthened 9–12%Cr steel is sensitive to the alloying additions and to differences in material microstructure, such as lath martensitic structure and grain size caused by differences in cooling rates in the steel ingots during the manufacturing process, which results in the large scatter of experimental data from the law of creep crack growth life. In the present study, creep crack growth tests were conducted using W-strengthened 9–12%Cr steels with various contents of alloying additions and the dimensions of micro-nano structures. The effects of the composition of alloying additions and material microstructures on the life of creep crack growth for W-strengthened 9–12%Cr steel were clarified.
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  • Taichi Murakami, Kensuke Ohara, Takayuki Narushima, Chiaki Ouchi
    2007 Volume 48 Issue 11 Pages 2937-2944
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 28, 2007
    JOURNALS FREE ACCESS
    A new method for manufacturing iron foam using CO and CO2 as foaming gases was studied. This method consists of three stages: (1) mixing powders of pure iron, graphite, and hematite; (2) preparing the precursor by cold pressing the mixed powders; and (3) foaming by heating the precursor at temperatures between the liquidus and solidus in the Fe–C binary system. Molten iron containing carbon is foamed by gases generated by a reduction reaction. Optimizations of both the composition of the precursor and the heating conditions are required to produce the iron foam with high porosity. It was found that the content and powder size of hematite in the precursor significantly affect the porosity and pore diameter of the iron foam. Iron foam with a porosity of 55% and average pore diameter of around 500 μm is obtained by heating the precursor of Fe-3.1 mass%C-1.0 mass%Fe2O3 at 1543 K.
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  • Yoshimi Watanabe, Hisashi Sato, Tetsuro Ogawa, Ick-Soo Kim
    2007 Volume 48 Issue 11 Pages 2945-2952
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 12, 2007
    JOURNALS FREE ACCESS
    In present study, the Al-Al2Cu functionally graded material (FGM) ring was fabricated from Al-3 mass%Cu initial master alloy by the centrifugal in-situ method. In the case of Al-3 mass%Cu alloy, the density of the primary α-Al crystal is larger than that of the molten Al alloy. Therefore, the solid α-Al phase migrates towards the outer periphery of the ring when the centrifugal force is applied in the early stage of solidification. Consequently, since the Cu concentration within the FGM ring monolithically increases towards the ring’s inner position, the FGM ring, whose density increases toward inner region, can be successfully fabricated by the centrifugal in-situ method from dilute Al-Cu alloy. It is also found that the hardness increases towards the inner region of the ring within the Al-Al2Cu FGM ring. The hardness of the fabricated specimens at the inner region of the ring increases in a large scale by the heat treatments, since Guinier-Preston (GP) zones would be formed by aging.
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  • Akihiko Ito, Hiroshi Masumoto, Takashi Goto
    2007 Volume 48 Issue 11 Pages 2953-2959
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 28, 2007
    JOURNALS FREE ACCESS
    BaRuO3 (BRO) thin films were prepared by laser ablation at substrate temperature (Tsub) ranging from room temperature to 973 K in a high vacuum (10−6 Pa) and in O2 at oxygen pressures (PO2) of 0.13 to 130 Pa. The relationship between deposition conditions, microstructure, binding state and electrical conductivity was investigated. 9R-type BRO thin film with well-crystallized fine grains was obtained at PO2=13 Pa and Tsub>773 K. BaRu6O12 was co-deposited with BRO at P=10−6 Pa and Tsub>573 K. The electrical conductivity (σ) of the BRO thin films positively correlated with Tsub and PO2. Highly conductive (σ>104 S·m−1) BRO thin films showed metallic conduction whereas less conductive (σ<104 S·m−1) BRO thin films showed semiconducting behavior. BRO thin film prepared at PO2=13 Pa and Tsub=773 K exhibited a maximum σ of 7.7×104 S·m−1 at room temperature.
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  • Jaeryeong Lee, M. T. Le, H. S. Chung
    2007 Volume 48 Issue 11 Pages 2960-2963
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 11, 2007
    JOURNALS FREE ACCESS
    The inner surface of a steel pipe could be lined with ceramics by means of a SHS reaction under centrifugal force. Some physical characteristics of the ceramic layer were investigated with the change of filling ratio (thermit mixture, Fe2O3 and Al) and the addition of silica.
    Two compositions, α-Al2O3 and FeAl2O4, were detected in the dispersed phase. The size of alumina grains became larger towards the pipe innermost side at high mixture filling ratios. Additionally, it was found that amorphous silicate materials formed by the addition of silica makes the layer dense significantly. The apparent density and hardness of the ceramic layer were improved from 2.9 g/cm3 and 1,430 Hv to 3.7 g/cm3 and 1,700 Hv with the effect of additive, silica.
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  • Yoshitake Nishi, Haru-Hisa Uchida, Kenichi Numazaki
    2007 Volume 48 Issue 11 Pages 2964-2968
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 12, 2007
    JOURNALS FREE ACCESS
    In order to obtain a large movement with high power and responsiveness, a hydrogenation operated bimetal device made of La-Ni alloy film deposited on a thin copper (Cu) substrate foil, has been successfully developed. The sample of La-Ni film deposited on the Cu thin foil exhibits about 50% larger bending displacement than that on a thick sheet of polyimide substrate within 50 s. The influence of load on bending motion has also been investigated. The moving yield of the La-Ni film deposited on the Cu thin foil is larger than that on a polyimide thick sheet.
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  • Yoshitake Nishi, Mitsuru Hirano
    2007 Volume 48 Issue 11 Pages 2969-2972
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 11, 2007
    JOURNALS FREE ACCESS
    An influence of elastic tensile stress on electrical resistivity of carbon fiber has been investigated as a basic research to develop a strain sensor. The initial elastic stress reversibly decreases the electrical resistivity, although the large stress causing irreversible deformation increases the resistivity. In addition, a linear relationship between initial stress and reduced electrical resistivity is obtained in the initial elastic stress zone. As the initial elastic stress probably enhances the periodicity of graphite structure, decreasing in the electrical resistivity with tensile elastic stress is explained.
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  • Cheng Shun Wang, Cheng Yao Tsai, Chuen Guang Chao, Tzeng Feng Liu
    2007 Volume 48 Issue 11 Pages 2973-2977
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 11, 2007
    JOURNALS FREE ACCESS
    The corrosion behaviors of the as-quenched austenitic Fe-9%Al-30%Mn-(3,5,6.5,8)%Cr-1%C (in mass%) alloys in 3.5% NaCl solution have been examined. Passivation could be observed for all of the four alloys. The corrosion potential (Ecorr) and pitting potential (Epp) increased pronouncedly as Cr content increased from 3 to 5%, and decreased as Cr content up to 6.5 and 8%. The decrease of Ecorr and Epp of alloys containing 6.5 and 8% Cr was due to the formation of (Fe,Mn,Cr)7C3 carbides within the austenite matrix and on the grain boundaries. The present result indicates that the Fe-9%Al-30%Mn-5%Cr-1%C alloy exhibited the highest corrosion resistance in 3.5% NaCl solution. It is worthy to note that the corrosion behaviors of the austenitic FeAlMnCrC alloys with higher Cr (≥3%) content have never been reported in previous literature.
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  • Kuo-Chih Feng, En-Yu Wu, Yung-Ning Pan, Keng-Liang Ou
    2007 Volume 48 Issue 11 Pages 2978-2985
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: September 28, 2007
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    Alkali solution- and heat-treatments were employed to modify the surfaces of Ti-6Al-4V, Ti-40Nb-1Hf and Ti-30Nb-1Fe-1Hf alloys, and then the surface characteristics and the biocompatibility of the treated alloys were analyzed. The formation of porous surfaces that contain numerous nano-pores and irregular cracks, together with the increase in hydroxyl, TiO2 and Nb2O5 contents in the surface layer of the treated Ti-40Nb-1Hf and Ti-30Nb-1Fe-1Hf alloys, have been found to enhance biocompatibility which was evaluated by the osteoblast cell culture in vitro. In addition, the biocompatibility of both Ti-40Nb-1Hf and Ti-30Nb-1Fe-1Hf alloys are comparable to that of Ti-6Al-4V alloy. Alkali solution- and heat-treatments are believed to enhance bone-bonding ability of both Ti-40Nb-1Hf and Ti-30Nb-1Fe-1Hf alloys, and therefore are useful for surface modification practice.
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  • Yoshihito Kawamura, Michiaki Yamasaki
    2007 Volume 48 Issue 11 Pages 2986-2992
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
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    We investigated the formation and mechanical properties of Mg97Zn1RE2 alloys with long-period stacking ordered (LPSO) structures by examining RE = Y, La, Ce, Pr, Sm, Nd, Gd, Dy, Ho, Er, Tb, Tm and Yb. The LPSO phase developed for RE = Y, Dy, Ho, Er, Gd, Tb and Tm. LPSO Mg-Zn-RE alloys are either type I, in which the LPSO phase forms during solidification: Mg-Zn-Y, Mg-Zn-Dy, Mg-Zn-Ho, Mg-Zn-Er and Mg-Zn-Tm, or type II, in which the LPSO phase is nonexistent in as-cast ingots but precipitates with soaking at 773 K: Mg-Zn-Gd and Mg-Zn-Tb. The criteria for REs that form an LPSO phase in Mg-Zn-RE alloys are discussed. Mg-Zn-RE alloys with an LPSO phase, which were worked by hot extrusion, include high strength both at ambient and elevated temperatures, and good ductility. Their tensile yield strength, ultimate strength and elongation were 342–377 MPa, 372–410 MPa and 3–9%, respectively at ambient temperature, and 292–310 MPa, 322–345 MPa and 4–13% at 473 K. The LPSO Mg-Zn-RE alloys are promising candidates for lightweight structural materials.
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  • Chun-Wei Su, Chuen-Guang Chao, Tzeng-Feng Liu
    2007 Volume 48 Issue 11 Pages 2993-2996
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 11, 2007
    JOURNALS FREE ACCESS
    As-quenched microstructure of the Fe-23 at% Al-7 at% Ti alloy was a mixture of (A2+D03) phases. When the as-quenched alloy was aged at 1073 K for moderate times, D03 domains grew preferentially along ⟨100⟩ directions and extremely fine B2 particles occurred at a/2⟨100⟩ anti-phase boundaries (APBs). After prolonged aging at 1073 K, the B2 particles would grow to occupy the whole a/2⟨100⟩ APBs. Consequently, the stable microstructure of the alloy at 1073 K was a mixture of (B2+D03) phases.
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  • Kojiro Akiba, Mitsutoshi Ueda, Kenichi Kawamura, Toshio Maruyama
    2007 Volume 48 Issue 11 Pages 2997-3006
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    Quantitative prediction of voids formation is demonstrated for CoO scale formed at 1373 K. Calculations of ion fluxes and their divergence in CoO scales can predict the void formation in the scale which mostly occurs in the vicinity of the metal/oxide interface. The volume fraction of voids is found to be maximum at the initial surface. These predictions are in good agreement with the observed morphology of CoO scale obtained in high temperature oxidation of cobalt at 1373 K.
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  • F. Nozoe, H. Matsumoto, T. K. Jung, S. Watanabe, T. Saburi, S. Hanada
    2007 Volume 48 Issue 11 Pages 3007-3013
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    Superelasticity of β Ti-16 at%Nb-4.8 at%Sn alloy consisting of non- (or minimal-) cytotoxic elements was investigated for biomedical applications as functions of deformation temperature and aging heat treatment after quenching. As-quenched Ti-16Nb-4.8Sn having Af (the reverse martensitic transformation finish temperature) of 266 K exhibits superelasticity at human body temperature (310 K) with an elastic recovery strain of 3.2%. Af decreases with increasing aging temperature in the range of 353 to 423 K or with increasing aging time at 423 K. It is confirmed from TEM observation and Young’s modulus measurements that ω transformation occurs on aging at 423 K for 500 h. Stress for inducing martensitic transformation, σM, increases with aging. Stress-strain curves showing superelasticity are quite similar to each other when as-quenched or aged samples are deformed at such temperatures that they have the same σM. It is concluded that maximum superelastic recovery strain can be obtained at intended temperature, e.g. human body temperature, in β Ti-Nb-Sn alloys by aging at relatively low temperatures.
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  • Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen, Cheng-Wei Chan
    2007 Volume 48 Issue 11 Pages 3014-3020
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The effect of Ni content on the microstructure, as well as the tensile and vibration fracture mechanisms of a potential lead-free solder, Sn-3.0Ag-0.5Cu-xNi (0.02, 0.07, 0.1, 0.2 and 0.3 mass%), are examined in this study. The results show that both Sn-Ni-Cu and Sn-Cu-Ni-Ag intermetallic compounds (IMC) increased with increasing the Ni content. The IMCs mostly formed in the eutectic zones and a few in proeutectic Sn-rich phases. Notably, the Ni content of the bar-like Sn-Ni-Cu compounds was higher than that of the particle-like Sn-Cu-Ni-Ag compounds. In addition, the tensile deformed resistance of Sn-3.0Ag-0.5Cu-xNi solders decreased when the Ni content was increased. Adding Ni obtained finer structures, however the hard massive Sn-Ni-Cu in the eutectic zone deteriorated the tensile deformation resistance. For the lower Ni content specimens, the 0.07Ni specimen not only possessed finer structures but a large number of compounds which congregated were able to increase the crack tortuosity, which in turn increased the crack propagation resistance and the vibration life.
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  • P. Vizureanu, M. Agop
    2007 Volume 48 Issue 11 Pages 3021-3023
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    Using the fractal space-time theory (scale relativity theory), the dynamics of the fluid/nano-particle interface was analyzed. In the general case, the heat transfer through the interface reproduces a d.c. or an a.c. Josephson effects of thermal type, while in the linear approximation, the standard form of heat transfer is given. Consequently, a negative differential thermal conductance appears and an increase in of heat transfer in nanofluids results.
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  • Akihiro Makino, Takeshi Kubota, Chuntao Chang, Masahiro Makabe, Akihis ...
    2007 Volume 48 Issue 11 Pages 3024-3027
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    Among many kinds of bulk metallic glasses (BMGs), Fe-based BMGs with good magnetic properties, high strength and low materials cost should have great potential for wide variety of applications. However, the glass-forming metal elements such as Al, Ga, Nb, Mo, Y and so forth in the Fe-based BMGs significantly decrease saturation magnetization (Js) which is a essential property as soft magnetic materials and also increase the material cost.
    The coexistence of high Fe content and high glass-forming ability (GFA) has been earnestly desired from academia to industry. We report a novel Fe76Si9B10P5 (at%) bulk metallic glass with unusual combination of high Js of 1.51 T due to high Fe content and high GFA leading to a glassy rod with a diameter of 2.5 mm despite not-containing any glass-forming metal elements. This alloy composed of familiar and low-priced elements, also exhibiting very excellent magnetic softness and rather high strength, has a great advantage for engineering and industry, and thus should make a contribution to conservation of earth resources and environment through energy saving.
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  • Chung Seok Kim, Sook In Kwun
    2007 Volume 48 Issue 11 Pages 3028-3030
    Published: November 01, 2007
    Released: October 25, 2007
    JOURNALS FREE ACCESS
    The influence of microstructure on the magnetic properties was experimentally investigated to estimate the creep damage in ferritic 11Cr-3.45W steel as an applicable research for the structural health monitoring. The microstructure showed significant changes in precipitate size (dp), precipitate number (N), dislocation density (ρ) and martensite lath width (ω) during creep. The magnetic coercivity decreased with creep duration and depended strongly on precipitate number and lath width. However, the magnetic saturation and remanence did not change after 500 h creep duration. The correlation between the microstructural changes and coercivity was discussed.
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  • Qingsheng Zhang, Wei Zhang, Akihisa Inoue
    2007 Volume 48 Issue 11 Pages 3031-3033
    Published: November 01, 2007
    Released: October 25, 2007
    [Advance publication] Released: October 18, 2007
    JOURNALS FREE ACCESS
    Glass-forming ability (GFA) of Cu36−xPdxZr48Ag8Al8 alloys was examined with the aim of developing a bulk glassy alloy with large critical diameter. It was found that the addition of 2 at% Pd significantly improved the GFA of the Cu36Zr48Ag8Al8 alloy. The fully glassy alloy rod with a diameter of 30 mm was successfully fabricated for the Cu34Pd2Zr48Ag8Al8 alloy using a copper mold casting method. The further increase of Pd content causes the decrease in the GFA. For the Cu36−xPdxZr48Ag8Al8 alloys, the Tg and Tx increase monotonously with increasing Pd content, while Tl shows a minimum value at 2 at% Pd, resulting in a maximum γ (=Tx⁄(Tg+Tl)) value at 2 at% Pd. The increase of γ parameter may be the reason for the significant improvement of the GFA of the quinary alloy.
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