MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 54 , Issue 3
Showing 1-27 articles out of 27 articles from the selected issue
 
  • Shojiro Ochiai, Hiroshi Okuda, Takahiro Arai, Michinaka Sugano, Kozo O ...
    2013 Volume 54 Issue 3 Pages 269-275
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: December 28, 2012
    JOURNALS FREE ACCESS
    The influence of the volume fraction (Vf) of copper, plated at room temperature over a DyBa2Cu3O7−δ-coated conductor, on the tensile strain tolerance and stress tolerance of critical current at 77 K was studied over a wide range of copper Vf values. The copper plating exerts a tensile stress during cooling because copper has a higher coefficient of thermal expansion than the substrate conductor. Before application of tensile strain, the copper plated at room temperature yielded at 77 K when the copper Vf was lower than a critical value, and was in an elastic state at 77 K when the copper Vf was higher than the critical value. The strain tolerance of critical current increased with increasing copper Vf due to an increase in thermally induced compressive strain in the substrate tape. The stress tolerance of critical current decreased with increasing copper Vf because copper is softer than the substrate tape. These results, together with the trade-off between strain tolerance and stress tolerance (i.e., stress tolerance decreases with increasing strain tolerance), were analyzed by modeling. The results show that the restriction imposed by the trade-off, which limits the ability to simultaneously obtain a high strain tolerance and a high stress tolerance, can be relaxed by strengthening the copper.
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  • Kaoru Nakamura, Susumu Yamada, Toshiharu Ohnuma
    2013 Volume 54 Issue 3 Pages 276-285
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: January 25, 2013
    JOURNALS FREE ACCESS
    Possible combinations of alkali metal guest atoms and substitutional group-13 atoms in type-I Si clathrate and their thermoelectric properties were investigated using first-principles calculations. All alkali metals could be encapsulated as the guest element into a Si46 cage, and either Al or Ga was suitable for a substitutional atom. From the formation energy, possible clathrate compositions were selected as K8Al8Si38, K8Ga8Si38, Rb8Al8Si38, Rb8Ga8Si38, Cs8Al8Si38 and Cs8Ga8Si38. The thermoelectric properties of these compositions were calculated as functions of temperature and carrier density, using the Boltzmann transport equation and the calculated band energy. The obtained dependences of the Seebeck coefficient and electrical conductivity on the carrier density were discussed from the viewpoint of band structure. The thermoelectric properties were optimized to maximize ZT for each composition by controlling the carrier density. ZT ≈ 0.75 was predicted as the highest ZT value for hole-doped Cs8Ga8Si38.
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  • Wei Zhou, Yiming Tao, Li Liu, Lingti Kong, Jinfu Li, Yaohe Zhou
    2013 Volume 54 Issue 3 Pages 286-290
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    (Cu46Zr46Al8)100−xCox (x = 0, 1, 2, 3 and 4) bulk metallic glasses (BMGs) were synthesized by copper mold casting, and the effect of Co addition on the microstructure and mechanical properties of Cu46Zr46Al8 BMG was investigated. The existence of immiscibility gap between Co and the main component Cu is responsible for liquid separation to form droplet-type structure during solidification. The size scale for the droplet-type structure trends to increase with the Co concentration. Depending on the glass-forming ability of the separated liquid phase, amorphous/amorphous or amorphous/crystalline composite structure can be obtained. The results of compression test reveal that the plasticity and the fracture strength can be simultaneously enhanced with an appropriate amount of Co addition owing to nanoscale phase separation with the formation of Cu-rich and Co-rich glassy phases.
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  • Rie Y. Umetsu, Keita Endo, Akihiro Kondo, Koichi Kindo, Wataru Ito, Xi ...
    2013 Volume 54 Issue 3 Pages 291-296
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 16, 2013
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    Temperature dependence of the equilibrium transformation field (H0) for Ni50Mn34.4In15.6 metamagnetic shape memory alloy was precisely determined by electrical resistivity measurements using a pulsed magnet. The H0-T curve was found to exhibit a maximum at around 50 K, suggesting that the transformation entropy change becomes negative in the lower temperature region. The residual electrical resistivity in the field-induced parent phase at lower temperatures was about 10 × 10−8 Ω·m, being normal value as the ferromagnetic alloys, whereas that in the martensite phase was high of about 200 × 10−8 Ω·m. The temperature dependence of the magnetic field hysteresis can be well fitted with the Seeger’s theory proposed for plastic deformation by dislocations.
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  • SeongNyeong Kim, JaeHwang Kim, Hiroyasu Tezuka, Equo Kobayashi, Tatsuo ...
    2013 Volume 54 Issue 3 Pages 297-303
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: December 21, 2012
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    In this paper, nanocluster formation behavior in Al–Mg–Si alloys with different Mg and Si concentration was studied by differential scanning calorimetry (DSC), micro-Vickers hardness and electrical resistivity measurements. Two exothermic peaks were detected in the alloys with different Mg and Si concentration in the DSC results, and separated using the Gaussian function method in order to analyze the Cluster (1) and Cluster (2). It is found that both of Cluster (1) and Cluster (2) formation are enhanced with the higher Mg + Si and the Mg/Si ratio close to 1.0. Especially, it is suggested that the formation sequence of Cluster (1) during natural aging is classified into three regions from the results of hardness and electrical resistivity measurement. These results mean that the composition of Cluster (1) is initially Si-rich then gradually becomes enriched in Mg by the incorporation of Mg. The growth rate of Cluster (1) is not high, whereas of Cluster (2) is higher and the composition becomes Mg/Si ≃ 1.0.
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  • Ssu-Ta Chen, Truan-Sheng Lui, Li-Hui Chen
    2013 Volume 54 Issue 3 Pages 304-307
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    Anisotropic deformation behaviors of the friction stir processed dynamic recrystallized commercial pure aluminum alloys were studied in this study. Recrystallized and refined grain size can be acquired after friction stir process is conducted. However, this is not guaranteed of isotropic deformation characteristics. Microhardness profile within the friction stir processed region is crystallographic orientation dependence. This dependence is manifested properly by the corresponding average Taylor factors.
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  • Meichuan Chen, Daisuke Terada, Akinobu Shibata, Nobuhiro Tsuji
    2013 Volume 54 Issue 3 Pages 308-313
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
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    In this study, an identical area of a SUS304 austenitic stainless steel specimen was observed by electron backscattering diffraction measurements at different strains in tensile test at ambient temperature, in order to investigate the details of deformation-induced martensitic transformation. Firstly, a number of thin deformation twins were formed in austenite grains. Most of the martensite crystals were observed either near grain boundary triple junctions or inside the deformation twins. Secondly, it was found that martensite crystals preferentially appeared in the austenite grains whose < 001> crystal directions were close to the tensile direction. Furthermore, when austenite grains had several martensite crystals inside, only one or two variants were observed among 24 variants possible under Kurdjumov-Sachs orientation relationship, which indicated the existence of variant selection rules. Patel and Cohen model and Bogers–Burgers model were examined to understand the variant selection, but both models could not explain the variant selections. The result suggests that complicated stress states govern the deformation-induced martensitic transformation in polycrystalline austenite.
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  • Yoshikazu Tanabe
    2013 Volume 54 Issue 3 Pages 314-318
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: January 25, 2013
    JOURNALS FREE ACCESS
    The crack energy density causes a new expression of fracture toughness for brittle fracture, together with the concept of Barenblatt’s characteristic distance dc of cohesive zone at the edge of the crack. The Griffith’s formula for fracture toughness is modified by the ratio of σTT, which σT is the true fracture stress and ΣT the maximum strength of the material obtainable by ordinary processing. The fracture toughness of elastic-plastic material, KIc* for brittle fracture is described by the product of σT and the root of the observed absorption energy by Charpy impact test corrected for instrumental effect, \sqrt\smashIcpcorrected\mathstrut . The characteristic distance dc depends linearly on the released elastic energy, which is the physical basis of above-mentioned estimation formula.
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  • Rong-Tan Huang, Wen-Han Chen, Leu-Wen Tsay
    2013 Volume 54 Issue 3 Pages 319-325
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    The notch tensile strength (NTS) of Ti–15V–3Cr–3Sn–3Al (Ti-15-3) aged at temperatures ranging from 426 to 600°C was determined at elevated temperatures, and correlated to microstructure. Notch tensile tests were conducted in laboratory air at the room temperature, 150, 300 and 450°C. The base metal specimen aged at 426°C formed elongated α precipitates interlocked in a basket-weave like structure and then had peak hardness but inferior notch tensile strength at room temperature due to the trans-granular quasi-cleavage fracture seperated along the α/β interface in the aged specimen. As the aging and test temperature increased, the coarse Widmanstätten α in the specimen aged at 540°C was facilitated to perform high NTS owing to crack deflection or microcrack formation in Ti-15-3 alloy under 300°C, while the improved ductility and notch blunting of the specimen aged at 426°C reduced the notch brittleness and resulted in a remarkably improved NTS tested at 450°C. The NTS of the specimen aged at 426°C was much higher than that of the other aged specimen tested at 450°C. This result suggested that the basket-weave-like structure was more resistant to the softening of substance than the coarse Widmansttäten structure at 450°C.
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  • Leu-Wen Tsay, S. T. Chang, Chun Chen
    2013 Volume 54 Issue 3 Pages 326-331
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    In this study, the fatigue crack growth rate (FCGR) of a Ti–15V–3Cr–3Al–3Sn (Ti-15-3) alloy, which was aged at a temperature range of 371 to 593°C, was measured in air at room temperature. The specimen aged at 371°C showed clear serrations in the crack growth curve at a stress ratio (R) of 0.1, and it also exhibited a larger Paris law gradient than the other aged specimens at R = 0.5. The peak-aged (426°C aged) specimen had the highest FCGR of the specimens, regardless of the stress ratio. A gradual decrease in the FCGRs with increasing aging temperature, from 482 to 593°C, was observed for the over-aged specimens. Cleavage-like fracture was more likely to occur in the under- and peak-aged specimens as compared to the transgranular fatigue in the over-aged specimens. It seemed that the coarse α platelets with lowered hardness in the over-aged specimens resulted in a higher resistance to fatigue crack growth in the Ti-15-3 alloy.
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  • Moo-Chin Wang, Ching-Tsung Lin, Chi-Shiung Hsi, Tao-Chih Chang, Ming-K ...
    2013 Volume 54 Issue 3 Pages 332-336
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    Using an organic solderability preservative (OSP), the morphology and microstructure of Sn–9Zn–1Al (SZA) and Sn–8Zn–3Bi (SZB) lead-free solder pastes used to assemble BGA packages with Sn–3.8Ag–0.7Cu (SAC) solder balls on a printed circuit board (PCB) were investigated. The scallop-shaped (Cu,Ag)5Zn8 intermetallic compound (IMC) is formed in both SZA and SZB solder joints, and the belt-shaped (Cu,Ag)5Zn8 IMC is also formed at the interfaces of both SZA/Cu and SZB/Cu. At 125°C, the Zn atoms in the IMC layer have sufficient energy to diffuse towards the Cu pad and react with it. The IMC belt composed of island-shaped compounds formed in the SZA and SZB solder joints and the size of island-shaped compounds and amount of microvoids increased after 1,000 times thermal cycling.
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  • Akira Toda, Pornthep Chivavibul, Manabu Enoki
    2013 Volume 54 Issue 3 Pages 337-343
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 08, 2013
    JOURNALS FREE ACCESS
    An electroless Ni–Co–P plating solution, which composed of lactate-citrate-ammonia as buffering and complexing agents, has been prepared. Various electroless Ni–Co–P coatings were deposited from this solution to investigate the effects of ion concentrations, pH and bath temperatures on the chemical composition of the deposited coating. The results showed that the present electroless Ni–Co–P plating solution has a potential for depositing Ni–Co–P coatings with an average composition of 71 mass% Ni, 17 mass% Co and 12 mass% P. The plating solution showed a good stability to deposit the coatings with a small deviation in compositions over wide ranges of pH values in acid region, bath temperatures, cobalt-ion and hypophosphite-ion concentrations. The nickel content of the Ni–Co–P coating could be tailored by varying nickel-ion concentrations of plating bath. The Ni content increased with increasing nickel-ion concentration while the opposite trend was observed for Co content. However, plating in the alkaline region showed significant changes in coating composition and plating behavior. Systematic UV–visible absorption measurement showed the change of complex ions from acid to alkaline regions, which could explain the different plating behavior in those regions.
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  • Shoichi Kikuchi, Takahiro Fukuoka, Takuma Sasaki, Jun Komotori, Kengo ...
    2013 Volume 54 Issue 3 Pages 344-349
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    In order to increase surface hardness of AISI 1045 steel, a new hybrid surface modification; combination of atmospheric-controlled induction-heating fine particle peening (AIH-FPP) and plasma nitriding, was developed. Surface microstructures of plasma nitrided specimens pre-treated with AIH-FPP using Cr shot particles were characterized by an optical microscope, a scanning electron microscope (SEM), an energy dispersive X-ray spectrometer (EDX) and X-ray diffraction analysis (XRD). As results, the nitrided layer was formed at the surface of the specimen with Cr diffused layer induced by AIH-FPP. This nitrided layer showed higher hardness than that of without AIH-FPP specimen. This was because CrN was formed at the surface of the AIH-FPP/Plasma nitriding treated specimen. And, the surface hardness of the nitrided layer tended to increase as the Cr concentration in the surface layer decreased. It was clarified that the pore formation during the AIH-FPP/Plasma nitriding treatment was inhibited by decreasing Cr concentration. These results suggest that the proposed hybrid surface treatment remarkably increases surface hardness of AISI 1045 steel.
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  • Jian-Hua Liu, Wei-Hua Gui, Yong-Fang Xie, Zhao-Hui Jiang
    2013 Volume 54 Issue 3 Pages 350-356
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    In the present contribution, a scheme to solve transient cost-related optimization problem of dynamic transient procedure for copper flash smelting process is investigated. Taking the actual copper flash smelting process at a Smelter in China as the research object, the transient cost-related optimization problem is presented by integrating transient time, transient resources consumption and the state fluctuation constraint. Then, it was considered as the operational parameters trajectories optimization problem that generates minimum-time and minimum-resources consumption during dynamic transient procedure. The dynamic relationship and the working state fluctuation are constructed in the form of constraints in the resulting optimization problem formulation. The Legendre Pseudospectral method is used to solve the constrained, nonlinear optimization problem. The results of numerical experiments of dynamic transient procedure for copper flash smelting process are given to illustrate the proposed scheme.
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  • Xiao Xu, Ineko Katakura, Takumi Kihara, Masashi Tokunaga, Wataru Ito, ...
    2013 Volume 54 Issue 3 Pages 357-362
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: December 21, 2012
    JOURNALS FREE ACCESS
    In situ microscopic study was carried out on Ni44.3Co5.1Mn31.4Al19.2 metamagnetic shape memory alloy under a pulsed magnetic field up to 35.5 T. Magnetic field-induced reverse martensitic transformation was directly observed. The critical magnetic fields were determined from the contrast change of the microstructure, where good agreement had been found by magnetization measurement in a previous study. Comparison of the micrographs during thermal and magnetic field cycles between Ni45Co5Mn36.7In13.3 and Ni44.3Co5.1Mn31.4Al19.2 was conducted. It is concluded that though the energy barrier related to thermal activation strongly effects the martensitic transformation of Ni45Co5Mn36.7In13.3, its effect is very small on Ni44.3Co5.1Mn31.4Al19.2. Qualitative discussion yielded a reasonable understanding of the results of microstructure observation.
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  • Tao Jin, Conghang Li, Jiale Huang, Ke Tang, Lixin Chen
    2013 Volume 54 Issue 3 Pages 363-366
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    High specific heats of the magnetic regenerative material, at the temperatures lower than 20 K, is crucial for a regenerative cryocooler to reach a liquid-helium temperature. The hydrogenation of the magnetic regenerative materials ErNi and ErNi2 may change their structures, magnetic properties and specific heats, which will be investigated in this paper. XRD patterns show that crystalline and amorphous phases can both be formed in the hydrogenation at 293 K. The insertion of hydrogen atoms can lead to a larger specific heat, measured by a physical property measurement system (PPMS), in some higher temperature ranges. But the peak values of specific heat of the hydrides are lower than those of their parent compounds below 15 K, which indicates that the idea of regenerative material hydrogenation should be left out in the efforts of regenerator performance enhancement.
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  • Hiroyuki Hosokawa, Koji Shimojima, Akihiro Matsumoto, Kiyotaka Kato, T ...
    2013 Volume 54 Issue 3 Pages 367-370
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    Wetting tests for Ni on (Ti0.95Mo0.05)(C0.5N0.5), (Ti0.9Nb0.1)(C0.5N0.5) and (Ti0.85Nb0.1Mo0.05)(C0.5N0.5) ceramics were carried out at 1823 K and compared with those for the previous data. The larger the Mo content was, the smaller the contact angles were. The contact angle for (Ti0.85Nb0.1Mo0.05)(C0.5N0.5) was smaller than for (Ti0.95Mo0.05)(C0.5N0.5). No new phase was observed on cross sections of the wet tested samples and microstructures could be divided into three regions: a Ni-rich region, reactive region, and substrate region. The depth of reactive region/height of Ni-rich region ratios for titanium carbonitrides containing Nb were larger than those for them containing Mo, and (Ti0.85Nb0.1Mo0.05)(C0.5N0.5) had the largest ratio in all the samples.
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  • Naoya Tsuchikura, Michael C. Faudree, Yoshitake Nishi
    2013 Volume 54 Issue 3 Pages 371-379
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    Experimental results showed homogeneous 100 keV-class low voltage electron beam irradiation (HLEBI) prior to lamination assembly (our new method) often improved the Charpy impact values (auc) of the sandwich structural CFRP/ABS/CFRP (carbon fiber reinforced epoxy polymer) and (acrylonitrile butadiene styrene) with low volume fraction of carbon fibers for cost reduction and safety. The auc values at each Pf of CFRP/ABS/CFRP laminated by both high-strength and light structural CFRP plies and ABS core separately irradiated from 0.04 to 0.30 MGy-HLEBI before lamination were mostly higher than that without HLEBI. Although carefulness for aircraft parts would be necessary since higher doses of 0.30 and 0.43 MGy HLEBI applied to the CFRP sheets and ABS core before lamination assembly reduced the lowest impact value at Pf = 0 (as) calculated by 3-parameter Weibull equation, the low dose of 0.04 MGy-HLEBI before lamination assembly apparently boosted the as almost 3 times, ∼200%, over the untreated samples from 15 to 44 kJ m−2. Moreover, applying the low dose of 0.04 MGy-HLEBI before instead of after lamination apparently improved the as 76% from 25 to 44 kJ m−2. Furthermore, applying the medium doses of 0.13 MGy or 0.22 MGy HLEBI before rather than after lamination appeared to improve the as remarkably from 0 to 40, and 0 to 42 kJ m−2, respectively. The new method of applying HLEBI prior to lamination allows for more efficient beam contact to the inner core and its surface permitting deeper areas in thick laminated composites such as CFRP/ABS/CFRP to be treated generating dangling bonds, hence strengthening the bulk materials and the CFRP-ABS interface of the thick laminated CFRP/ABS/CFRP constructed with thin or thick surface sheet and thick core can be expected.
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  • Wantae Kim, Kwanho Kim, Hoon Lee, Minchul Shin, Sangbae Kim
    2013 Volume 54 Issue 3 Pages 380-383
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: January 25, 2013
    JOURNALS FREE ACCESS
    β-eucryptite (Li2O·Al2O3·2SiO2) was prepared by mechanochemical activation followed by calcination of the powder mixture containing pyrophyllite, gibbsite and lithium carbonate. XRD and FT-IR results showed that the crystallization of β-eucryptite occurred from the milled mixture by calcination. Dry milling using a planetary mill promoted the amorphization of the mixture. The crystallization of β-eucryptite increased with increment of milling time and calcination temperature. Trace amount of undesired phases such as cristobalite and quartz disappeared completely at 950°C in the mixture milled for 120 min. The thermal expansion behavior characteristics were found to be strongly influenced by the milling time of the constituent powder mixture and calcination temperature.
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  • J. Mizuguchi, Y. Tsukada, H. Takahashi
    2013 Volume 54 Issue 3 Pages 384-391
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    A novel system for the recovery of reinforcing fibers from fiber reinforced plastics (FRP) and their recycling technology has been developed on the basis of the thermal activation of semiconductors (TASC). TASC is our new technology characterized by the use of oxidative properties of defect electrons (i.e., hole) of semiconductors. The present technology enables us to totally decompose a polymer matrix in FRP into H2O and CO2 in 10–20 min at about 400–500°C in air, yielding only embedded reinforcing fibers in their original form. Characterization of the recovered glass fibers or carbon fibers has also been carried out by optical microscope, scanning electron microscope (SEM), X-ray photo-electron spectroscopy (XPS), X ray diffraction (XRD), as well as thermogravimetric analysis and differential thermal analysis (TGA/DTA). The analysis revealed that no noticeable difference is recognized between the virgin reinforcing fibers and the recovered ones, but the sizing agent has also totally been removed. Therefore, it is necessary to coat a sizing material again when the recovered fibers are reused for recycling.
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  • Kazutaka Suzuki, Yasumasa Chino, Xinsheng Huang, Motohisa Yuasa, Mamor ...
    2013 Volume 54 Issue 3 Pages 392-398
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    Mg–1.5 mass%Mn (M1) alloy is known for its high damping properties. In this study, effects of process parameters such as rolling and annealing temperatures on the texture formation in rolled M1 alloys were investigated for the purpose of enhancing their room-temperature formability. Specimens were pre-annealed, warm-rolled and then finally annealed. Pre-annealing at temperatures of 773–813 K and subsequent warm-rolling at temperatures of 373–523 K resulted in the formation of basal textures with low intensities. The (0002) pole was inclined towards the rolling direction. The specimens annealed at 473 K in the final step showed a high Erichsen value of 7.9, while the values for specimens annealed at temperatures higher than 623 K were lower. This deterioration in the Erichsen values was attributed to the occurrence of abnormal grain growth accompanied by recrystallization. It is suggested that iterating the protocol involving pre-annealing at high temperatures and the subsequent warm-rolling promoted the formation of extensive twinning, which contributed to the formation of basal textures with low intensities. The internal friction of the M1 alloy sheets was found to be 70% of that of pure Mg.
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  • Shih-Hsien Chang, Chih-Chien Ko
    2013 Volume 54 Issue 3 Pages 399-404
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    In this study, different amounts of fine TiC powders (0, 10, 15 and 20 mass%) were mixed and added to cobalt-based alloy powders. Then, the mixed composite materials (cobalt-based alloy and TiC powders) were vacuum sintered at 1260, 1270, 1280 and 1290°C for 1 h, respectively. The experimental results showed that the highest TRS value of 1485.1 MPa was obtained by the addition of 15 mass% TiC powder and sintering at 1280°C for 1 h; while the highest hardness value of HRA 80.4 was obtained by 20 mass% TiC powder sintered at 1290°C for 1 h. In addition, two types of carbide precipitates appeared in the microstructure. Without added TiC powder of the specimen, fine plate-like precipitates of M6C and M23C6 carbides were obvious on the grain boundary; but when TiC powder was added to the specimens, only M23C6 carbides were observed after sintering treatment. The result also showed that a suitable amount of TiC additive (15 mass%) effectively inhibits carbide precipitation and growth.
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  • Yoshihiko Hangai, Kousuke Saito, Takao Utsunomiya, Soichiro Kitahara, ...
    2013 Volume 54 Issue 3 Pages 405-408
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 01, 2013
    JOURNALS FREE ACCESS
    Functionally graded (FG) aluminum foam containing A1050 pure aluminum and ADC12 aluminum alloy was fabricated. The FG foam has the potential for its location of deformation to be controlled. Moreover, a FG foam with plateau regions and stresses corresponding to those of the uniform A1050 and ADC12 foams was obtained.
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  • Joong-Hwan Jun
    2013 Volume 54 Issue 3 Pages 409-411
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: January 25, 2013
    JOURNALS FREE ACCESS
    The effects of a small amount of CaO addition (0.3 mass%) on the microstructure and damping properties of AM50 casting alloys have been investigated. The added CaO contributes to the formation of an Al2Ca phase but reduces the total amount of compound particles by decreasing the β phase content. The AM50–CaO alloy shows a slightly higher damping level within the strain-amplitude dependent region than does the alloy without CaO. The lower number density of compound particles acting as strong pinning points for dislocations is thought to be responsible for the improvement in the damping capacity.
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  • Jingchao Tao, J. Wang, Anping Dong
    2013 Volume 54 Issue 3 Pages 412-414
    Published: March 01, 2013
    Released: February 25, 2013
    [Advance publication] Released: February 08, 2013
    JOURNALS FREE ACCESS
    The thermodynamic properties of 3%mol zirconia doped ceria nano-size powders prepared by sol–gel were studied by thermogravity analysis. The entropy and enthalpy extracted from the data of thermogravity experiment of 3%mol zirconia doped ceria compared with undoped ceria were analyzed. The data of Gibbs free energy calculated by the data of entropy and enthalpy of 3%mol zirconia doped ceria compared with undoped ceria and water were investigated. The temperature range and the heat energy required of dissociating water obtained from the data of Gibbs free energy of 3%mol zirconia doped ceria compared with undoped ceria were shown as the result of this study.
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  • John J. Jonas, Suresh Shrivastava
    2013 Volume 54 Issue 3 Pages 415-416
    Published: March 01, 2013
    Released: February 25, 2013
    JOURNALS FREE ACCESS
    One of the problems associated with the use of the Hencky equivalent strain in the analysis of experiments in large shear is that it cannot be paired with a work-conjugate equivalent stress. A further problem is associated with the observation that the textures developed in shear differ sharply from those formed during tension or compression, so that the rates of work hardening are also different. The effects of these differences on the von Mises equivalent stress/equivalent strain flow curves determined by testing are discussed.
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  • 2013 Volume 54 Issue 3 Pages 417
    Published: March 01, 2013
    Released: March 01, 2013
    JOURNALS FREE ACCESS
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