MATERIALS TRANSACTIONS
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ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 56 (2015), No. 11

  • Tribocorrosion Behavior of Nanocrystalline Metals — a Review

    pp. 1759-1763

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    DOI:10.2320/matertrans.M2015280

    Nanocrystalline metal materials with ultra fine grains have many special mechanical, physical and chemical properties. Tribocorrosion is a material degradation or transformation process due to the combined action of wear and corrosion. Nanocrystalline materials could be obtained by artificial preparation or tribological/tribocorrosion process. In this paper, studies about the wear, corrosion and tribocorrosion behavior of nanocrystalline metal materials are reviewed. Nanocrystallization could enhance the wear resistance of materials by increasing the hardness and decrease the corrosion rate by forming continuous and compact passive layer. And the nanocrystallization could also enhance the tribocorrosion resistance of materials mainly by increasing surface hardness and forming protective and lubricating surface layers.
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  • Mechanical Properties and Fracture Behavior of Titanium-Aluminum/Titanium Micro-Laminate Sheet Deposited by EB-PVD

    pp. 1764-1770

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    DOI:10.2320/matertrans.M2015176

    A 110 µm thick micro-laminate sheet comprising 14 layers of TiAl/Ti3Al two phase compound and 15 layers of Ti was prepared by electron beam physical vapor deposition (EB-PVD), and its microstructures and mechanical properties were characterized. Results show that the hardness of interfacial region is about 7.029 GPa, higher than that of either component layer. After densification, room-temperature tensile strength and elongation are improved compared to single Ti-Al compound sample, reaching 656.89 MPa and 2.92%, respectively. Its tensile curve presents a distinct jagged feature. High-temperature tensile strength exhibits an abnormal increase with temperature, exceeding 440 MPa at 1023 K. The presence of Ti layers will lead to cracks stagger along the inter-laminar interface or the crack deflection and the micro-bridge connection caused by Ti layers, due to the TiAl-Ti3Al/α-Ti micro-laminate displaying a fine characteristic of delayed fracture.
  • Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

    pp. 1771-1780

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    DOI:10.2320/matertrans.L-M2015824

    Nanoclusters formed during natural aging cause the negative effect of the two-step aging in the age-hardenable Al-Mg-Si alloys. The relationship between the clustering behavior during natural aging and the two-step aging behavior was studied using the hardness, differential scanning calorimetry (DSC), electrical resistivity measurements, transmission electron microscopy (TEM) observation in the Cu-free and Cu-added Al-Mg-Si alloys. Three stages during the two-step aging are clearly revealed based on the hardness results. The hardness in the two-step aging with the natural aging time is decreased, increased and then decreased at the initial, middle and final stages, respectively. Si-rich clusters initially formed during natural aging do not transform into the β′′ phase and are thermally stable during the two-step aging at 170°C. On the other hand, Mg-Si co-clusters formed at the middle stage during natural aging transform into the β′′ phase and are thermally unstable during the two-step aging at 170°C. Much higher hardness is obtained in the Cu-added alloy than that of the Cu-free alloy during two-step aging when natural aging is performed for 3.6 ks belonging to the initial stage. The higher hardness is also found to be obtained during over-aging regardless of the natural aging time in the Cu-added alloy than that of the Cu-free alloy. The relationship between the clustering behavior during natural aging and the two-step aging behavior is discussed based on the observed age-hardening phenomena.
  • Texture and Lattice Distortion Study of an Al-6061-T6 Alloy Produced by ECAP

    pp. 1781-1786

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    DOI:10.2320/matertrans.M2015200

    Equal channel angular pressing (ECAP) is a severe plastic deformation (SPD) technique that produces nanostructured materials. Based on a remarkable grain size reduction, this process has led to improve mechanical properties, such as yield strength, fatigue, UTS, etc. In this work the characterization of the microstructure of the aluminum 6061-T6 alloy; plastically deformed up to ε ≈ 6, by the ECAP process, following route Bc, is presented. For this purpose, the ECAP processed samples were characterized by means of X-ray diffraction (for texture and line profile analysis) and transmission electron microscopy. The initial crystallographic texture vanished after one ECAP pass and a new, well defined, shear texture Cθ was generated. For the subsequent ECAP passes, more shear components: A*, Bθ and \bar{B}θ were also developed. From the orientation distribution function analysis, a shift (generally less than 15°) between some experimental maxima and the reported ideal shear texture positions was observed. From these results, it was found that the microstructure generated with this process was stabilized after the 5th ECAP pass. Finally, the micro-strain analyses, in addition to the texture and transmission electron microscopy, contributed to the understanding of the effect of the physical and mechanical processes that were activated during the SPD-ECAP technique.
  • Effect of TiB2 Particles on Microstructure of 7075 Al Alloy in Semi-Solid State Near Liquidus

    pp. 1787-1792

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    DOI:10.2320/matertrans.M2014447

    TiB2/7075 Al matrix composites were formed by in situ reaction, and effect of the TiB2 particles content on microstructure of 7075 Al alloy in semi-solid state near liquidus were investigated. The results have shown that the average grain size decreased with increased the amount of TiB2, and the microstructure became uniform rosette grains. The morphology of grains became big dendrite grains when the particles content were over 4.5 mass%. Globular grains of 7075 Al alloy whose size reached 94 µm can be got for 7.5 min at 630°C. The minimum grain size of 3 mass%TiB2/7075, 4.5 mass%TiB2/7075 and 9 mass%TiB2/7075 Al matrix composites at 630°C were 88 µm, 51 µm and 69 µm for 30 min, 20 min and 50 min, respectively. The TiB2 particles located in the grain boundary can hinder the Al atoms from diffusing within the semi-solid state of the 7075 Al alloy and restrain α-Al phase growth, but it can be conducive to improve the stability of semi-solid slurry in near-liquidus thixoforming.
  • Effect of Interlayer Thickness on Fatigue Behavior in A5052 Aluminum Alloy with Diamond-Like Carbon/Anodic-Oxide Hybrid Coating

    pp. 1793-1799

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    DOI:10.2320/matertrans.M2015302

    Anodic oxide layer was formed on A5052 aluminum alloy, and subsequently diamond-like carbon (DLC) was deposited to fabricate DLC/anodic-oxide hybrid coating. Plane bending fatigue testes have been performed using the hybrid-coated specimens with different thicknesses of anodic-oxide interlayer. The interlayer thicknesses were 10 and 50 µm, where the thickness of DLC film was fixed as 3 µm. The specimens without coating, with DLC single layer and with anodic-oxide single layer were also used for comparison. The fatigue strengths of the specimens with anodic-oxide single layer were lower than those of the substrate without coating because the corner edge cracking or pin-hole defects could be fatigue crack initiation sites. However, when DLC was deposited on the anodic-oxide layer, fatigue strengths were improved. The hybrid-coated specimens with the interlayer thickness of 10 µm had higher fatigue limit than the substrate and specimens with the interlayer thickness of 50 µm. Thin DLC layer with the thickness of 3 µm could have suppressed the cracking in interlayer, and led to the improvement of fatigue strengths than the substrate. When the interlayer became relatively thicker compared with the DLC film, such as 50 µm, DLC film could not suppress the cracking from the corner edge defects, resulting in the lower fatigue strengths in spite of the presence of hybrid coating.
  • Influence of Cold Rolling on Fundamental Properties of Ti-15V-3Cr-3Sn-3Al Alloy

    pp. 1800-1806

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    DOI:10.2320/matertrans.M2015247

    This study was conducted to investigate the influence of cold rolling on the fundamental properties of the typical β titanium alloy Ti-15V-3Cr-3Sn-3Al. Hot-rolled plates of the alloy were solution-treated and then cold-rolled under a rolling reduction of 30%. Cold rolling induced work hardening, increasing the hardness and the tensile strength. The developed texture caused anisotropy of the tensile strength. The cold-rolled material showed a unique anisotropy of yield strength because the activated slip system was switched or not switched, depending on the tensile direction against the cold rolling direction. The fatigue strength was also increased by cold rolling. However, fatigue cracks were generated from crystal grains having the same orientation regardless of the cyclic loading direction against the rolling direction. As a result, no clear anisotropy was found in the fatigue strength.
  • Low Temperature Nitriding of Commercially Pure Titanium with Harmonic Structure

    pp. 1807-1813

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    DOI:10.2320/matertrans.Y-M2015822

    Commercially pure titanium with harmonic structure, which consists of a coarse-grained structure surrounded by a network structure of fine-grains, was produced by sintering mechanically milled powders to achieve high strength and high ductility. The effect of subsequent nitriding on the commercially pure titanium with harmonic structure was investigated. Nitriding was performed at relatively low temperatures of 773, 873 and 973 K (500, 600 and 700°C). The surface microstructures of the nitrided specimens with harmonic structure were characterized using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and a non-contact scanning white light interferometry. The nitrided titanium specimen with harmonic structure had higher hardness than a nitrided-only titanium specimen because the fine-grained structure in the harmonic structure accelerated the formation of titanium nitrides during nitriding. Furthermore, fine grains created by mechanical milling were not coarsened during the nitriding process. These results indicate that low temperature nitriding is effective to increase the surface hardness of commercially pure titanium with harmonic structure while grain-coarsening is also suppressed.
  • Corrosion Resistance of a Free-Cutting Soft-Magnetic Stainless Steel in Pure Water

    pp. 1814-1820

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    DOI:10.2320/matertrans.M2015222

    The corrosion resistance of a new free-cutting soft-magnetic stainless steel containing Ti4C2S2 instead of MnS was examined by immersion corrosion tests in pure water and anodic polarization measurements in 0.1 M Na2SO4. The Ti4C2S2 inclusions hardly dissolved in pure water at 353 K and did not suffer anodic dissolution in the passivity region of stainless steel in 0.1 M Na2SO4. In contrast, conventional free-cutting soft-magnetic stainless steels with (Mn,Cr)S inclusions caused the significant release of Mn species during immersion in pure water, and showed a marked increase in the dissolution current of MnS under anodic polarization in 0.1 M Na2SO4. The thermodynamic stability of Ti, Mn and Cr oxide films on the inclusions makes the difference in the corrosion resistance of Ti4C2S2 and (Mn,Cr)S, with no dissolution of Ti from Ti4C2S2 and the selective dissolution of Mn from (Mn,Cr)S.
  • Adhesive Force Improvement of Polyethylene Terephthalate (PET)/Epoxy Resin Joint by Electron Beam to PET Prior to Assembly

    pp. 1821-1826

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    DOI:10.2320/matertrans.M2015082

    Adhesive 2-layer lamination joints of polyethylene terephthalate (PET)/epoxy resin were prepared without the use of hot press using a new adhesion method of applying homogeneous low energy electron beam irradiation (HLEBI) to the PET prior to assembly by hand pressure. HLEBI treatment within the range of 0.13 to 0.43 MGy increased the adhesive force of peeling (oFp) substantially over the untreated. The largest oFp values at optimal dose 0.30 MGy were 12.4, 37.2 and 190 Nm−1, which were more than 2.2, 2.8 and 9.5 times larger than 5.76, 13.5 and 20.0 Nm−1 of the untreated at low-, median- and high peeling force accumulative probability, Pp of 0.06, 0.50 and 0.94, respectively. The statistically lowest oFp for safety design (Fs at Pp = 0) iterated by the 3-parameter Weibull equation was raised from zero for the untreated to 10.7 Nm−1 for the 0.30 MGy samples indicating increased reliability by the HLEBI. XPS (X-Ray Photoelectron Spectroscopy) observations of the peeled 0.30 MGy HLEBI PET revealed generation of a C-O peak at 286 eV possibly explaining the increased adhesion. Therefore residual epoxy deposition is apparently found to be retained on the PET sheet by inter-matrix fracture of epoxy resin further into the thickness. This can be explained by the adhesion force from crosslinking between PET/epoxy being stronger than the cohesive force of epoxy polymer itself. Since the experimental data shows the optimum HLEBI dose is about 0.30 MGy, above which at 0.43 MGy the oFp begins to drop, carefulness in optimization is highly recommended when applying in industry to insure safety.
  • Effect of Particle Size Distribution on SiC Ceramic Sinterability

    pp. 1827-1833

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    DOI:10.2320/matertrans.Y-M2015823

    Silicon Carbide has drawn a significant attention in recent decades for its excellent properties such as high oxidation resistance, high hardness and low density. However, an important drawback for SiC manufacturing is its poor sinter ability due to its highly covalent nature of bonding. This work investigates the effect of dispersion in Particle Size Distribution on the sinter ability of SiC ceramics. In the present work, two types of SiC powders, consisting powders of sizes 0.3 µm and 2.5 µm, were subjected to mechanical milling in order to produce various patterns of particle size distributions. Subsequently, milled powders were sintered by spark plasma sintering. This sintering technology is used in account of its rapid heating and short time sintering. This work also suggests the usage of coefficient of variation, Cv as an appropriate parameter to indicate the dispersion level in PSD range investigated.
  • A Practical Investigation of the Production of Zr-Cu-Al-Ni Bulk Metallic Glasses by Arc Melting and Suction Casting

    pp. 1834-1841

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    DOI:10.2320/matertrans.M2015235

    The successful fabrication of bulk metallic glasses (BMG) through suction casting based on the existing literature is a difficult task due to the sensitivity of glass-forming ability (GFA) to small changes in processing variables. We report processing challenges and process modifications required in the successful and consistent production of Zr-Cu-Al-Ni BMGs by arc melting and suction casting. Focus was placed on homogenization methods, elemental yields, and the effect of argon purge gas and Zr purity on GFA. A “cut and re-cast” homogenization method used to reduce oxidation produced good overall homogeneity but resulted in the entrainment of an oxide-rich surface layer into the bulk of the alloy. Homogenization by multiple melting iterations and prolonged melting times was ultimately found to be the most effective method. Zr loss was observed in the bulk of the samples post-production. This has been attributed to the formation of a Zr/ZrO2 surface layer during melting. Using X-ray diffraction and isochronal DSC, both argon gas purity and Zr purity were shown to markedly affect GFA. GFA was optimized within a specific oxygen concentration range. The highest GFA was obtained when using high purity argon (Grade 6.0) and low Zr purity (99.5%). The optimization of GFA in Zr-based BMGs at a critical oxygen concentration has not been shown in previous work.
  • Ultrasonic Weldability of Al Ribbon to Cu Sheet and the Dissimilar Joint Formation Mode

    pp. 1842-1851

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    DOI:10.2320/matertrans.M2015251

    This work aims to investigate the ultrasonic weldability of Al ribbon (width 2.0 mm × thickness 0.2 mm) to Cu sheet (thickness 1.0 mm) using a WC tool of 2.0 mm × 1.0 mm (sonotrode tip size) and to understand joint formation process by examining joint microstructures and fracture behavior for different bonding times. For the selected conditions of 20 W power, 30 N clamping force, 0.1–0.8 s bonding time, it was found that sound lap joints could be readily obtained when the bonding time reached and exceeded 0.4 s, which fractured within Al ribbon, but not along interface, owing to the formation of dense and thin alloying layer of 2∼3 µm thickness with a continuous composition gradient. When such bonding has been established, the actual slipping motion shifted upwards to the top of Al ribbon. On the other hand, both microstructure and fracture surface observations indicated that in the early stage, localized adhesion occurred accompanied by the detachment of just adhered Al part from remaining Al ribbon body, leading to a cracking (called secondary interface) within weak Al ribbon. Thus, USW of Al ribbon to Cu sheet was achieved through a series of slipping at three kinds of transient interfaces: localized adhesion at original interface and alloying of the adhered Al together with detachment within Al ribbon (forming the secondary interface); re-bonding at the secondary interface together with further bonding at original interface under resisted slipping and high frictional coefficient as a result of surface roughening by previous isolated compound formation at original interface; and final upwards shifting of slipping to the third interface between top surface of Al ribbon and tool end.
  • Metal–Metal Joining by Unusual Wetting on Surface Fine Crevice Structure Formed by Laser Treatment

    pp. 1852-1856

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    DOI:10.2320/matertrans.M2015301

    We have investigated metal–metal joining using “unusual wetting”, in which a liquid metal spreads by capillary action on a porous metal surface layer formed under atmospheric oxidation–reduction. Although oxidation–reduction creates an adequate porous structure for “unusual wetting”, it is difficult to subject only a specific area to atmospheric oxidation–reduction treatment, and region-selective “unusual wetting” and joining are not achieved. In this work, we propose the use of laser, which is able to treat regions selectively, to form a suitable structure for “unusual wetting”. A fine asperity structure was observed on the Cu substrate surface after laser treatment. This structure was termed a “surface fine crevice structure”. The wettability of the laser-treated Cu substrate by liquid Bi was determined to confirm region-selective “unusual wetting” on the “surface fine crevice structure”. We also joined two Cu substrates by “unusual wetting” after creating a “surface fine crevice structure”.
  • The Tuning of Phase, Morphology and Performance of Graphene Oxide/Manganese Oxide for Supercapacitors

    pp. 1857-1862

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    DOI:10.2320/matertrans.M2015101

    The reduced graphene oxide (rGO)/manganese oxides (MnO2) composites are obtained from GO/MnO2 precursor by the microwave-assisted reducing procedures. Characterization indicates that the phase and morphology transformation have been discovered in GO/MnO2 composite for the first time, and this transition can be explained by a “dissolution-precipitation” model. The capacitive properties of the rGO/MnO2 electrodes are measured using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests. The rGO/Mn3O4 in hydrazine hydrate (H-rGO/Mn3O4) exhibits a specific capacitance as high as 324.9 F/g, which is about four times as the GO/MnO2 precursor (81.25 F/g). It is deduced that the diversity of ionic state of Mn3O4, the large specific surface area, and the large reduction degree of GO are favorable to the enhancement of the electrochemical performance. The results show that the H-rGO/Mn3O4 nanocomposite from GO/MnO2 can be used as electrode material for high performance supercapacitors.
  • Separation of Platinum(IV) and Rhodium(III) from Hydrochloric Acid Solutions Using Diaion Resins

    pp. 1863-1867

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    DOI:10.2320/matertrans.M2015254

    Pt and Rh in HCl solutions were separated by adsorption with strong basic resins (Diaion SA10A, Diaion SA20A, and Diaion PA308) in the HCl concentration range 0.1–5 mol/dm3. The molar ratio of Pt to Rh in the feed solution was fixed at 5 : 1, based on the composition of spent automobile catalysts. The resins used had selectivity for Pt over Rh, and the adsorptions of both metals were clearly affected by the acid concentration. Batch experiments indicated that it is possible to separate Pt from Rh at low acid concentrations with these resins; Diaion SA10A was the most effective. The feasibility of separation of Pt and Rh with Diaion SA10A was verified using continuous column experiments. The loaded Diaion SA10A resin was regenerated by elution with a mixture of HCl and thiourea.
  • Effects of Cu Addition on Microstructure Characteristics and Tensile Behaviors of Metal Inert-Gas Arc Welded Mg-Steel Dissimilar Joints

    pp. 1868-1874

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    DOI:10.2320/matertrans.M2015249

    The joining of AZ31B Mg alloy to Q235 steel was realized by metal inert-gas arc welding. Microstructure characteristics and tensile behaviors of Mg-steel joints with and without Cu addition were investigated and compared. Results show that the microstructure and tensile strength were improved with the addition of Cu interlayer. The IMC Mg2Cu with rod-like structure was generated in both the whole weld zone and Mg/steel interfacial zone. The maximum tensile strength of Cu-added joint can reach to 185 MPa, which partly fractured at the weld seam of Mg alloy instead of the Mg/Fe interface. The increase of the joint strength and microhardness profile with addition of Cu can be explained in terms of improvement of wettability of Mg alloy to steel and the formation of fine IMC Mg2Cu.
  • Preparation of Zirconium Powder Through ZrCl4 Bubbling in Mg-MgCl2 Bath

    pp. 1875-1879

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    DOI:10.2320/matertrans.M2015248

    An alternative process has been studied for zirconium production through chemical reaction between ZrCl4 bubbles and magnesium melt floating on molten MgCl2 salt. The preparation of pure zirconium in the form of powder was successfully accomplished by cleaning process consisting of washing with distilled water and pickling with hydrochloric acid solution. The purity of zirconium powder increased with dense concentration of hydrochloric acid solution and longer pickling time by removing residual magnesium, MgCl2 and other impurities except for zirconium. The sufficiently high level of purity was achieved by pickling for 6 hours using 3 mass% of hydrochloric acid solution. It was noteworthy that purity of zirconium powder was deteriorated with the formation of intermetallic compounds when alumina or iron was used for apparatus material. Meanwhile, a sound quality without any intermetallic compound and high purity were achieved when MgO material was used. It was found that there were no significant differences in purity and morphology of zirconium powder depending on reaction temperature. However, mean particle size was increased by increasing reaction temperature.
  • Segregation of Dopants at WC/Co and WC/WC Interfaces in Solid-State-Sintered WC-VC-Cr3C2-Co Cemented Carbides

    pp. 1880-1886

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    DOI:10.2320/matertrans.M2015198

    The segregation of V and Cr at WC/Co and WC/WC interfaces in ultrafine-grained WC-0.7VC-1.4Cr3C2-10Co (mass%) cemented carbides produced through solid-state sintering and semi-sintering was investigated. This segregation was compared against that of a liquid-state-sintered specimen to elucidate the mechanism by which WC grain growth is inhibited by V and Cr. The V and Cr were found to segregate at the WC/Co and WC/WC interfaces during solid-state sintering and semi-sintering, but no differences were observed in the V and Cr concentrations at the interfaces among the liquid-state-sintered, solid-state-sintered and semi-sintered specimens. Furthermore, these concentrations were unchanged by quenching of the solid-state-sintered specimen. From these results, it was concluded that (V,W,Cr)Cx segregation layers are stably formed at the WC/Co and WC/WC interfaces at a temperature below the solidus of the Co phase, but almost dissolve in the liquid Co phase once the temperature exceeds its liquidus. Thus, the (V,W,Cr)Cx segregation layers observed at the WC/Co and WC/WC interfaces at room temperature are formed during the cooling that follows the liquid-state sintering. This supports the finding that WC grain growth is inhibited by the adsorption of dopant atoms onto steps/kinks on the WC surface during liquid-state sintering, as well as by the segregation layers formed on the WC surface during solid-state sintering.
  • Investigation of Thermal Conductivity and Mechanical Properties of Mg-4Zn-0.5Ca-xY Alloys

    pp. 1887-1892

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    DOI:10.2320/matertrans.M2015304

    The thermal conductivities of quaternary Mg-Zn-Ca-Y alloys have been investigated by evaluating the effect of adding Y on the Mg-4Zn-0.5Ca alloys, with an emphasis on developing new Mg alloys without compromising their thermal conductivities, processabilities, and mechanical properties.
    In this study, to improve the mechanical properties of the Mg-4Zn-0.5Ca alloy, Y was chosen as a strengthening element, and the effect of adding Y on the thermal and mechanical properties of the alloy was investigated. The thermal conductivities slightly decreased as the Y-content increased. However, the tensile yield strength and ultimate tensile strength improved as the Y-content increased. In addition, the average spiral flow lengths of the Mg-Zn-Ca-xY alloys were almost the same as that of the Mg-Zn-Ca alloy. The results of this study indicate that Mg-Zn-Ca alloys with more than 1 mass% Y exhibit better mechanical properties and thermal conductivities than gravity-cast AZ91 alloys.
  • Numerical Simulation and Preparation of Cladding Billet by Direct Chill Semi-Continuous Casting

    pp. 1893-1900

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    DOI:10.2320/matertrans.M2015229

    This study presents an innovative direct chill semi-continuous casting process to prepare AA4045/AA3003 cladding billet using numerical simulation and experiments. The influence of casting speed on temperature field in cladding billet has been investigated by the commercial software FLUENT and validated by experiments. The cladding billet was examined by methods of metallographic examination, field emission scanning electron microscopy (FESM) and universal testing machine. The results show that the experiments are in good agreement with the simulation results. Cladding billets can be obtained at the casting speeds ranging from 110 mm/min to 150 mm/min. Excellent metallurgical bonding of the two alloys could be achieved at the casting speed of 130 mm/min and 150 mm/min. With the increase of casting speed, increasing contact temperature promotes the interdiffusion of alloy elements. The tensile strength and shear strength of interface reaches 106 MPa and 77 MPa respectively. Moreover, fracture position moves to AA3003 side from the interface in tensile test, while fracture mode changes to the ductile from the brittle as casting speed increases.
  • Angle–Torque Transmission Characteristics of Ti–Ta–Sn Alloy Guidewire

    pp. 1901-1904

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    DOI:10.2320/matertrans.M2015261

    As a simulated blood vessel circuit, a silicone tube was introduced into the groove of a circuit constituted by a curved line of 90° combined with a radius of curvature of R20 mm. The rotational angle trackability and torque transmission performance in this simulated blood vessel circuit were compared for core material bases of stainless steel and Ni–Ti alloy commercial guidewires and of a Ti–Ta–Sn alloy. According to the load–deflection curve, on protruding by 2 mm, the highest load was measured for stainless steel; however, plastic deformation was observed after unloading. The Ni–Ti alloy exhibited higher load values than the Ti–Ta–Sn alloy, the latter showing a load as small as 2.2 N; however, after unloading, the displacement was fully recovered in both cases. The best and worst rotational angle trackabilities were observed for Ti–Ta–Sn and Ni–Ti alloys, respectively. The proximal tip side torque was large in the stainless steel and Ni–Ti alloy, whereas the Ti–Ta–Sn alloy exhibited a small value. The distal tip side torque was the largest in stainless steel, whereas Ni–Ti and Ti–Ta–Sn alloys showed almost similar values. Comparing the results of torque loss, Ni–Ti and Ti–Ta–Sn alloys exhibited the largest and smallest torque losses, respectively. The results indicated that the rotational angle trackability of the Ti–Ta–Sn alloy is higher than that of a commercially available guidewire core, while showing the smallest torque.
  • The Thermal Stability and Strength of Highly Alloyed Ni3Al

    pp. 1905-1910

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    DOI:10.2320/matertrans.M2015298

    In this study the L12 gamma prime phase (based on Ni3Al) has been highly alloyed with Cr, Co, W, and Ta in order to examine the effects on strengthening and thermal stability. The order-disorder transition temperature of gamma prime is decreased with higher alloying content. Thermodynamic calculations show that the ordering enthalpy decreases as the entropy term increases. Conversely, the hardness can be 1.5 times higher comparing to that of a conventional Ni-based superalloy. This indicates that the strengthening effect of designing a gamma prime composition toward higher entropy is significant, due to greater lattice distortion and higher anti-phase boundary energy of gamma prime.
  • Synthesis of Hierarchical SnO2 Microflowers Assembled by Nanosheets and Their Enhanced Photocatalytic Properties

    pp. 1911-1914

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    DOI:10.2320/matertrans.M2015287

    Hierarchical SnO2 microflowers assembled by aggregative sheets have been successfully synthesized via a facile one-pot hydrothermal method. The crystal structure and optical properties of the product were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SEAD), Raman spectroscopy, UV–vis absorption and photoluminescence (PL) spectroscopies. By utilizing the SnO2 microflowers as a photocatalyst, improved photocatalytic degradation was observed towards rhodamine B (RhB) dye under UV light illumination. The improved photocatalytic activity may be attributed to their unique morphology and surface defects.
  • Effect of FeAl on Mechanical Properties and Consolidation of Nanostructured (W,Ti)C by the High Frequency Induction Heating

    pp. 1915-1918

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    DOI:10.2320/matertrans.M2015227

    In the case of cemented (W,Ti)C, Ni or Co is added as a binder for the formation of composite structures. However, the high cost and the low hardness of Ni or Co, and the low corrosion resistance of the (W,Ti)C-Ni and (W,Ti)C-Co cermets have generated interest in recent years for alternative binder phases. In this study, FeAl was used as a novel binder and consolidated by the high frequency induction heated sintering (HFIHS) method. The method was found to enable not only the rapid densification but also the inhibition of grain growth preserving the nano-scale microstructure. Highly dense (W,Ti)C and (W,Ti)C-FeAl with a relative density of up to 99% was obtained within 3 min by HFIHS under a pressure of 80 MPa. The addition of FeAl to (W,Ti)C enhanced the toughness without great decrease of hardness due to crack deflection and nanostructured phase.
  • Reduction of Titanium Oxide by Molten Silicon to Synthesize Titanium Silicide

    pp. 1919-1922

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    DOI:10.2320/matertrans.M2015264

    Titanium silicide was synthesized via the reaction of titanium oxide bearing slag and molten silicon. Results indicated that titanium oxide in slag was reduced by silicon with an intermetallic bulk being formed. This novel synthesis method is a three-layer refining process that is much simpler and could reduce the cost of titanium silicide production significantly. Moreover, this novel and low-cost synthesis method of Ti5Si3 provides a new way to produce high purity titanium.
  • Erratum

    pp. 1923-1923

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    DOI:10.2320/matertrans.ERM201503

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