MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 58 , Issue 4
Showing 1-32 articles out of 32 articles from the selected issue
  • Yen-Ting Chen, Fei-Yi Hung, Truan-Sheng Lui, Jia-Zheng Hong
    2017 Volume 58 Issue 4 Pages 525-529
    Published: April 01, 2017
    Released: March 25, 2017
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    Selective laser sintering (SLS) is an additive manufacturing (3D printing) technique that can be applied to the anode of lithium batteries to simplify the manufacturing process and enhance the production efficiency. The specific surface nanostructures and intermetallic compounds (IMC) induced by the SLS process can improve the capacity and cycle life. In this study, a stable anode for a lithium ion battery was successfully fabricated by the SLS process, the capacity of the battery exceeded 150 mAhg−1 after 10 cycles under a 0.1 C current rate at room temperature. Moreover, the capacity enhanced to 250 mAhg−1 after 10 cycles under a 0.1 C current rate at the high temperature of 55℃. The results show the potential of the SLS technique for application in the lithium ion battery industry.

  • Seong-Min Lee
    2017 Volume 58 Issue 4 Pages 530-534
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 24, 2017
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    This article demonstrates that the chipping damage resulting from silicon wafer separation can be more effectively suppressed by the adoption of hybrid dicing (a duel process that uses laser ablation prior to mechanical sawing) than single dicing, such as sawing. This work shows that the adoption of the hybrid dicing technique induces sacrificial fracture at the laser-induced groove tip to save the regions outside of the groove formed along the scribe region of the wafer. Particularly, this study details how a pre-existing groove (i.e., a laser-induced groove) on the front surface of the wafer interacts with the saw blade penetration-induced trench during the second step of the hybrid dicing process. According to the experimental results, the magnitude of the chipping damage in the chips diced from a wafer including a laser-induced groove with a larger aspect ratio was more effectively reduced at a more rapid sawing velocity. However, since a laser-induced groove with a larger aspect ratio could also have a bigger curvature in its tip, adopting a groove with the optimum shape was necessary for effective prevention of dicing-induced damage during hybrid dicing.

  • Tianzhu Mu, Fuxing Zhu, Bin Deng
    2017 Volume 58 Issue 4 Pages 535-538
    Published: April 01, 2017
    Released: March 25, 2017
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    Aiming at the problems of residual anode and free carbon generated in titanium oxycarbide electrolysis (TiC0.5O0.5), the phase composition and microstructure of TiC0.5O0.5 were characterized by XRD, SEM, EDS and POM. The results show that: titanium oxycarbide (TiC0.5O0.5) with similar crystal morphology and structure could be obtained by carbothermic reduction from TiO2 and sintering from TiC and TiO, which is composed of 15~21% gray-white titanium carbide, 56~69% yellow titanium oxycarbide and 13~25% aubergine titanium oxycarbide. The grain color of titanium oxycarbide is related to the content of carbon and oxygen. Gray-white titanium carbide contains 20~30% C, yellow titanium oxycarbide 10~50% C and 10~20% O, and aubergine titanium oxycarbide 5~10%C and 25~30% O. The structure of titanium oxycarbide is not uniformity, which results in the formation of residual anode and carbon. The gray-white and aubergine components in titanium oxycarbide are rich in TiC and TiO respectively, which generate free C, CO2, Ti2O3 and TiO2 after electrolysis.

  • Koji Kimura, Kouichi Hayashi, Koji Hagihara, Hitoshi Izuno, Naohisa Ha ...
    2017 Volume 58 Issue 4 Pages 539-542
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    We performed X-ray fluorescence holography measurements on a single crystal Mg85Zn6Y9 alloy, having a synchronized 18R long period stacking ordered structure, and successfully obtained Zn Kα holograms. The reconstruction shows “U”-shaped atomic images in remarkable contrast to the prediction of an existing model with Zn6Y8 L12 clusters. To explain this feature we calculated holograms using a model with positional fluctuations, and fit the reconstruction to the experimental results. It was found that large rotational fluctuations of the clusters can explain the “U”-shaped images.

  • Pei-Shan Chang, Chuen-Guang Chao, Tzeng-Feng Liu
    2017 Volume 58 Issue 4 Pages 543-548
    Published: April 01, 2017
    Released: March 25, 2017
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    In this work, the stress corrosion behavior of Mg–2 mass% Sn alloy in simulated body fluid solution was systematically investigated to determine its performance in a physiological environment. The effect of equal-channel angular extrusion (ECAE) on stress corrosion behavior of Mg–2 mass% Sn alloy was investigated using three-point bending test. ECAE process changed both grain size and Mg2Sn second phase distribution. The average grain size under homogenization annealing condition (about 123.61 μm) was significantly reduced to 34.32 μm after four ECAE passes. Mg2Sn phase formed more uniformly both in the grains and along the grain boundaries with ECAE process. The average volume fraction of Mg2Sn phase increased with increasing passes. The microstructure became more homogeneous with further ECAE passes. In bent-beam stress corrosion test, the average crack depths of samples underwent ECAE process were significantly lower than that of sample under homogenization annealing condition. This showed that the ECAE process could reduce crack propagation rate. The enhancement of stress corrosion resistance is attributable to uniform second phase distribution and grain refinement via ECAE process.

  • Guisheng Gan, Bida Chen, Yiping Wu, Donghua Yang, Luxin Chi, Yingchun ...
    2017 Volume 58 Issue 4 Pages 549-553
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 03, 2017
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    Sn-xCu (x = 0.5, 0.7, 0.9, 1.1, 1.3) solders were prepared to investigate the influence of trace Cu on the microstructure, the spreadability and the oxidation resistance property of Sn-xCu lead-free solder. Researches have shown that the Cu content had a significant impact on the microstructure, the microstructure of Sn-0.7Cu solder was almost fine dendrites and others were composed of coarser dendrites. The liquidus temperatures of Sn-xCu were around 227℃, the peak of solidification temperature had vast difference and the biggest difference was 8.8℃. The peak of solidification temperature of Sn-0.7Cu was the smallest, with 192℃. The spreading rate of Sn-xCu solders greatly improved, in which Sn-0.5Cu improves by nearly 4 percents, Sn-0.7Cu improves by nearly 3 percents and the others improve by 2 percents around from 260℃ to 290℃. With the increase of Cu content, there were no obvious changes to solder with wetting power and wetting time, interfacial IMC thickness of Sn-xCu/Cu solders. The color of oxidation film deepened due to the serious oxidation with the increase of the temperature. The oxide slag of Sn-xCu solders decreased and then increased with the increase of Cu content, in which the oxide slag of Sn-0.7Cu solder was the lowest, about 18.5% of Sn-0.5Cu and 38% of Sn-1.3Cu.

  • Yasuaki Tanaka, Tomonari Inamura, Hideki Hosoda, Yoshihiro Suwa, Toshi ...
    2017 Volume 58 Issue 4 Pages 554-560
    Published: April 01, 2017
    Released: March 25, 2017
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    The temperature dependency of diffusional transformation texture development in steel sheet was investigated by electron backscatter diffraction. The site of the precipitated pro-eutectoid ferrite (PF) grains and the orientation relation with the surrounding austenite (γ) phase were affected by the transformation temperature. The PF on the triple junction, which has a Kurdjumov-Sachs relation (K-S) with the two surrounding γ phases (double K-S [DKS] relation) with high probability, predominated in the high-temperature transformation, whereas the PF on the grain boundary, which fulfills DKS with lower probability than the PF on triple junction, became predominant with decreasing temperature. The intensity of the variant selection on transformation decreased with decreasing transformation temperature. The texture predicted by the DKS model reproduced the measured PF texture, indicating that the intensity of the variant selection obeying DKS decreased with decreasing transformation temperature. Therefore, the intensity of the variant selection was affected by the degree of supercooling. The DKS rule operates strongly on the transformation in the high-temperature region, corresponding to a low degree of supercooling. However, the DKS rule has a small effect when the temperature decrease corresponds to a high degree of supercooling.

  • Misako Nakayama, Minho O, Masanori Kajihara
    2017 Volume 58 Issue 4 Pages 561-566
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 10, 2017
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    The kinetics of the solid-state reactive diffusion between Sn–Ag alloys and pure Ni was experimentally observed to examine effects of addition of Ag into Sn on the growth behavior of compound at the interconnection between the Sn-base solder and the multilayer Au/Ni/Cu conductor during energization heating. In this experiment, sandwich (Sn–Ag)/Ni/(Sn–Ag) diffusion couples with Ag concentrations of y = 0.011–0.033 were prepared by a diffusion bonding technique, and then isothermally annealed at temperatures of T = 453–473 K for various periods up to 3169 h, where y is the mol fraction of Ag. After annealing, an intermetallic layer consisting of Ni3Sn4 was recognized between the Sn–Ag and Ni specimens in the diffusion couple. Here, the concentration of Ag in Ni3Sn4 is negligible. The mean thickness of the intermetallic layer is proportional to a power function of the annealing time, and the exponent of the power function takes values of 0.33–0.43 at T = 453 K and those of 0.54–0.62 at T = 473 K. Thus, the growth of the intermetallic layer is controlled by boundary and volume diffusion at T = 453 K. In contrast, at T = 473 K, interface reaction and interdiffusion contribute to the rate-controlling process of the intermetallic growth. The addition of Ag into Sn accelerates the intermetallic growth within the experimental annealing times.

  • Yoshiki Takamatsu, Minho O, Masanori Kajihara
    2017 Volume 58 Issue 4 Pages 567-573
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 10, 2017
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    The kinetics of reactive diffusion in the Co/Zn system was experimentally examined at solid-state temperatures. In this experiment, sandwich Zn/Co/Zn diffusion couples were prepared by a diffusion bonding technique, and then isothermally annealed in the temperature range of 523–573 K for various times up to 211 h. Owing to annealing, an intermetallic layer consisting of the γ, γ1 and γ2 phases was formed at the original interface in the diffusion couple, where the thickness is much smaller for the γ and γ1 phases than for the γ2 phase. Thus, the γ2 phase predominantly governs the overall growth of the intermetallic layer. The total thickness of the intermetallic layer increases in proportion to a power function of the annealing time. The exponent of the power function takes values of 0.54–0.56 at 523–548 K and that of 0.85 at 573 K. Consequently, volume diffusion mainly controls the layer growth at 523–548 K, but interface reaction as well as volume diffusion contributes to the rate-controlling process at 573 K.

    Fig. 3 The total thickness l of the intermetallic layer versus the annealing time t at T = 523, 548 and 573 K shown as open rhombuses, squares and circles, respectively. Fullsize Image
  • Tatsuya Okada, Hirofumi Tai, Minoru Tagami
    2017 Volume 58 Issue 4 Pages 574-579
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    The objective of the present study was to characterize early-stage recrystallization in copper single crystals. Two crystals with different front surfaces, i.e., {110} or {112}, were deformed in tension along the <111> direction to a tensile strain of 0.2. The deformation was uniform without deformation bands. Thin disk specimens prepared from the deformed <111>{110} and <111>{112} crystals were heated in a high vacuum to a set temperature with a holding time of 10 s, and subsequently observed. This process was repeated by raising the heating temperature for each step until the first detection of recrystallized grains. In all specimens, recrystallization was found after annealing at almost the same temperature, about half of the melting point in the absolute temperature scale. Each recrystallization aggregate was composed of a pair of major recrystallized grains with a coherent twin boundary. Small annealing twins were detected inside the larger recrystallized grains but not in the smaller grains. The present results suggest that recrystallization in copper begins with the formation of pairs of twin-related recrystallized grains, followed by the introduction of annealing twins.

    Fig. 4 (a) SEM/EBSD inverse-pole-figure orientation map of a pair of major recrystallized grains (RG1 and RG2) in the annealed <111>{110} specimen. (b) The 111 pole figure of RG1 and RG2. The common 111 pole is represented by a red circle. Fullsize Image
  • Eva Hasenhuetl, Ryuta Kasada, Zhexian Zhang, Kiyohiro Yabuuchi, Akihik ...
    2017 Volume 58 Issue 4 Pages 580-586
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 10, 2017
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    The local strain rate (LSR) dependence of nanoindentation (NI) hardness was investigated by using standard constant strain rate (CSR) test method and strain rate jump (SRJ) test method for W single crystal with the surface orientation of {001} before and after 6.4 MeV Fe3+ irradiations (nominal damage level of 0.1, 1 and 2 dpa, 573 K). The effect of ion-irradiation on the LSR sensitivity of NI-hardness at room temperature (RT) was evaluated by changing LSR between 0.3 s−1 and 0.01 s−1 or 0.03 s−1 and 0.001 s−1. Under these experimental conditions, ion-irradiation increases NI-hardness and slightly decreases LSR sensitivity of NI-hardness for all damage levels. The effect is more pronounced with increasing damage level. The LSR sensitivity values are ranging between 0.015 and 0.04 in SRJ tests, and between 0.0425 and 0.06 in CSR tests, indicating that the deformation of bcc W{001} at RT is controlled by a high lattice friction stress. The decrease in LSR sensitivity by ion-irradiation could be attributed to the increase in the athermal stress caused by ion-irradiation induced defect structures, which is reflected to a decrease in the activation volume of dislocation motion in ion-irradiated W{001}.

  • Kazutaka Fukuda, Yuta Koyanagi, Masayuki Tsushida, Hiromoto Kitahara, ...
    2017 Volume 58 Issue 4 Pages 587-591
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 10, 2017
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    With a hexagonal close packed structure, magnesium has many slip systems. Pure shear tests were carried out to evaluate their critical resolved shear stresses (CRSS). As a result, the CRSS for the basal slip was 0.7 MPa, and it was close to conventional values. When the shear stress of 40 MPa was applied in parallel to the prismatic plane, the {1012} twin deformation occurred only, and the prismatic slip deformation did not occur.

    This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 334–339.

  • Hyo Kyu Kim, Hyung Guin Kim, Byung-Soo Lee, Seok-Hong Min, Tae Kwon Ha ...
    2017 Volume 58 Issue 4 Pages 592-595
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    In order to improve wear resistance of pure titanium fabricated by additive manufacturing, its surface was hardened by atmosphere gas carburizing. For the study, the pure titanium was fabricated by electron beam melting system. The microstructures and wear properties of the as-built and carburized titanium were investigated. After carburizing, hardness was increased and titanium carbides were precipitated in the surface region. The friction coefficients of the both specimens were estimated by dry sliding friction tests; the friction coefficient of carburized titanium is lower than that of as-built titanium. The improvement of wear property would be a result of high surface hardness and the slippery nature of titanium carbide formed on the surface.

  • Shigehiro Arita, Takashi Ogihara, Masahiro Harada, Yasuhiko Furukawa
    2017 Volume 58 Issue 4 Pages 596-599
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    A large-scale spray pyrolysis apparatus in which the mist is pyrolyzed by a flame using a gas burner was developed for the mass production of Ag powder. Forty ultrasonic vibrators with a frequency of 1.6 MHz generated 4 dm3/h of mist. The thermal stability of the ultrasonic vibrators was improved using water-cooling. Spherical Ag powder was continuously produced, and the yield of the powders remained above 95% over 60 hours of continuous production with starting solution concentrations of up to 1.5 mol/dm3. Scanning electron microscopy (SEM) analysis showed that the particles were sub-micrometer in size with a dense microstructure, and they did not aggregate. Powder X-ray diffraction (XRD) demonstrated that the as-prepared Ag powder exhibited high crystallinity. The particle size of the Ag powder was approximately in agreement with the predicted size, calculated under the assumption that one Ag particle was formed from one droplet of mist. Moreover, 7 kg of Ag powder was produced over 12 h at 1.5 mol/dm3. This apparatus exhibited good reliability for the continuous mass production of Ag powder.

  • Yasuhiro Morizono, Sadahiro Tsurekawa, Takateru Yamamuro, Sohshi Yoshi ...
    2017 Volume 58 Issue 4 Pages 600-605
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 03, 2017
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    We developed a new surface modification technique called “iron-powder pack (IPP) treatment”. A layer of titanium carbonitride, Ti(C, N), was formed on the surface of a titanium sample embedded in a mixture of iron, graphite, and alumina powders and held around 1273 K in a nitrogen flow. In this work, IPP treatment using a 4:6:3 (volume ratio) mixture of iron, graphite, and alumina powders was applied to titanium plates, and the effects of the heating temperature and nitrogen gas flow rate on the microstructures near the titanium surface were investigated. The Ti(C, N) layer was observed on the titanium plate heat-treated at 1173 K for 3.6 ks at a nitrogen flow rate of 0.5 L/min. This layer became uniform and thick as the heating temperature increased. At 1373 K, a Ti(C, N) layer with a thickness of more than 30 μm that increased the hardness of the titanium surface to an HV value of about 1500 was obtained. In addition, an increase in the nitrogen flow rate increased the surface hardness further. Spherical titanium powder was treated at 1273 K to examine the growth of the Ti(C, N) layer. The layer thickness increased with the holding time. Because the average diameter of the spherical powder was unchanged after heating, the Ti(C, N) layer grew toward the inside of the titanium via the diffusion of carbon and nitrogen from the powder mixture and the atmosphere.

  • Yuki Sato, Satoshi Oue, Shinichi Heguri, Hiroaki Nakano
    2017 Volume 58 Issue 4 Pages 606-612
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    This study investigated the effect of dissolved impurities on the lightness, surface morphology, and current efficiency of deposited nickel during electrowinning. Nickel electrodeposition was performed at a current density of 300 A·m−2 and 7.2 × 105 C·m−2 of charge in an unagitated chloride solution containing Mn2+, Cr3+, and SO42− ion impurities with a pH from 1 to 3, at a temperature of 333 K. Solutions containing 10 g·dm−3 of Mn2+ resulted in a slight decrease in current efficiency for nickel deposition and smaller crystal sizes in the deposited nickel. The lightness of deposited nickel decreased for Mn2+ concentrations exceeding 1 g·dm−3. When nickel deposition was performed using a soluble nickel anode to prevent the formation of MnO2 at the anode, greater nickel lightness resulted than with an insoluble anode, suggesting that MnO2 produced by the insoluble anode caused decreased lightness of nickel. In solutions containing Cr3+, the current efficiency of nickel gradually decreased with increasing Cr3+ concentrations and significantly decreased at Cr3+ concentrations above 0.1 g·dm−3. The lightness of deposited Ni greatly decreased with increasing concentrations of Cr3+ above 0.001 g·dm−3. Formation of Cr(OH)3 at the cathode layer is presumed to suppress nickel deposition, resulting in some codeposition of NiO and Ni(OH)2 along with Ni, which causes the nickel current efficiency and lightness to decrease. Conversely, solutions containing SO42− resulted in a moderate decrease in nickel current efficiency at SO42− concentrations above 50 g·dm−3 and a significant decrease above 100 g·dm−3. The lightness of deposited nickel increased slightly at SO42− concentrations of 20 g·dm−3 and strongly increased above 20 g·dm−3. Because the overpotential for nickel deposition increases with the concentration of SO42−, the surface of the deposited nickel becomes smooth, resulting in greater lightness.

     

    This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 539–545.

  • Masahito Watanabe, Fumiya Sato, Kyosuke Ueda, Daisuke Matsuwaka, Takay ...
    2017 Volume 58 Issue 4 Pages 613-618
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    Oxygen removal from Ti–Si melts (Si: 9.1–30 mass%) during arc melting was investigated. High-purity Si was added to either Ti with a high oxygen content (High O Ti, O: 1.6 mass%) or commercially pure Ti (CP Ti, O: 0.104 mass%) melted under Ar or He gas flow conditions at atmospheric pressure. At Si additions of 23 mass% and 30 mass%, the oxygen content of the Ti–Si ingots decreased. After melting, Si and amorphous SiO2 powders were observed in the chamber, which suggested that the oxygen in the melts was removed in the form of SiO gas. The oxygen content of the Ti–Si ingots after melting varied as a function of position within the ingot; the residual oxygen content was lowest in the top section of the ingots and highest in the bottom section. Under the Ar gas flow, the oxygen content of the High O Ti–30Si ingot decreased to 0.136 mass% and 0.609 mass% in the top and center sections of the ingot, respectively; similarly, the oxygen content of the CP Ti–30Si ingot decreased to 0.030 mass% and 0.051 mass% in the top and center sections, respectively. After melting under He gas flow, the oxygen contents of the CP Ti–30Si ingot in the top, center, and bottom sections were 0.020 mass%, 0.021 mass%, and 0.029 mass%, respectively. Better uniformity of oxygen distribution in the ingots was achieved under the He gas flow than under the Ar gas flow because the melted region is extended in the depth direction by using He gas. During melting, no significant evaporation of Ti and Si occurred, which is an advantage of arc melting that operates at atmospheric pressure over electron beam melting that occurs in vacuum.

  • Tomonori Kimura, Naoya Tokoo, Makoto Ogata, Masafumi Nojima, Kosuke Ku ...
    2017 Volume 58 Issue 4 Pages 619-622
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    A chromium-based duplex alloy is proposed for a novel class of alloys for hot and harsh environments. The alloy is defined as a duplex microstructure comprised of a hard and high-strength chromium-based BCC (α) phase and a ductile FCC (γ) phase to overcome the brittleness of the conventional α-Cr alloy. The candidate composition of the alloy was selected from a Cr-Fe-Ni ternary system, and the mechanical properties were evaluated. The abrasion and corrosion properties of a surface-remelted chromium-based duplex alloy were compared with those of a Co-based cladding alloy (Bishilite® No. 6), and the results suggested its potential use as a wear and corrosion resistant cladding.

  • Masayuki Horie, Kenji Hirata, Junichi Tateno, Naoki Nakata
    2017 Volume 58 Issue 4 Pages 623-628
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 24, 2017
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    A plan view pattern control method for plate rolling called the Mizushima Automatic Plan View Pattern Control System (MAS) or Dog Bone Rolling (DBR) was developed. In this method, the slab is given a non-uniform thickness profile in the width direction to obtain non-uniform elongation at following flat rolling. In order to make the plate more rectangular under various rolling conditions, prediction of elongation at following flat rolling is necessary. In this research, the influence of the width of the dog-bone (overly thick part at the slab width edge) on the fish-tail length (over-elongation at the slab end) is investigated. The fish-tail length increases as the dog-bone width increases and the dog-bone width ratio decreases. These phenomena are related to the following behavior of the restriction of excessive elongation in the dog-bone because of existence of unrolled volume before roll gap entrance: As the dog-bone width increases and the dog-bone width ratio decreases, the working length of restricting stress increases. Hence, restricting stress is released earlier and the rolling length for fish-tail formation increases. As a result, the fish-tail length increases. Therefore, in prediction of the plan view pattern, not only the dog-bone thickness, but also the dog-bone width and dog-bone width ratio should be considered.

     

    This Paper was Originally Published in Japanese in J. JSTP 57 (2016) 347–352.

  • Yuichi Motoyama, Tomoyuki Ozasa, Toshimitsu Okane
    2017 Volume 58 Issue 4 Pages 629-634
    Published: April 01, 2017
    Released: March 25, 2017
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    New pouring equipment was developed for the measurement of copper alloy fluidity. The fundamental characteristics of the developed equipment are the pouring cup system, which has high heat-retention, a stopper system without preheating, and a pouring temperature determination system. In the evaluation of the developed device, the temperature of the molten copper alloy was decreased by 30 K from pouring to the stability of the measurement of the molten alloy temperature in the pouring cup. The rate of temperature decrease of the molten copper alloy in the pouring cup until the pouring temperature was 3.5 K/s. Experimentally obtained results demonstrated that the linearity between the superheat above liquidus temperature and flow length improved compared with that reported from earlier studies. The standard deviation of flow length in the equipment was 20 mm. These results indicate that the effect of the casting conditions on flow length of the copper alloys will be evaluated accurately with the developed equipment.

     

    This Paper was Originally Published in Japanese in J. JFS 87 (2015) 855–860.

  • Sadatoshi Koroyasu
    2017 Volume 58 Issue 4 Pages 635-640
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    The effect of coat permeability on mold filling for thin wall aluminum alloy castings in the expendable pattern casting (EPC) process was investigated experimentally. Thin wall aluminum alloy plates were cast by the EPC process, using eight kinds of coats with different permeabilities. The fluidity length and melt velocity were measured. The use of thin expendable polystyrene (EPS) pattern led to shorter fluidity length of melt. When the coat permeability was less than approximately 2, the fluidity length of the melt and melt velocity increased with increasing coat permeability. When the coat permeability was greater than approximately 2, even when the coat permeability increased, the fluidity length of the melt and melt velocity did not increase so much. The application of high expansion ratio of EPS pattern or high pouring temperature, led to long fluidity length of the melt. The distances of melt flow stop were predicted based on the heat transfer from the molten metal to the mold through the coat using measurement melt velocity values. The predicted values more or less agreed with experimental values for fluidity length.

     

    This Paper was Originally Published in Japanese in J. JFS 88 (2016) 192–197.

  • Wei Li, Jiuhao Ge, Yanyun Wu, Xiaokang Yin, Guoming Chen, Xinan Yuan, ...
    2017 Volume 58 Issue 4 Pages 641-645
    Published: April 01, 2017
    Released: March 25, 2017
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    Subjected to hoop stress and land movement load, the orientation of cracks on the surface of pipeline may be axial direction, circumferential direction or the others. In this paper, an electromagnetic Helmholtz-coil probe is presented to detect the oriented cracks on the surface of pipeline. A structure of equal-spaced TMR sensor array of the Helmholtz-coil probe is applied to scan the full circumference of the pipeline simultaneously in a single pass. The simulation and experiment results indicate that using the combination effect of the electric current perturbation and the magnetic flux leakage, the oriented crack can be mapped clearly.

  • A. Takeuchi, K. Takenaka, Y. Zhang, Y.C. Wang, A. Makino
    2017 Volume 58 Issue 4 Pages 646-654
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 24, 2017
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    Molecular dynamics (MD) simulations were performed for an Fe50Ni50 (at.%) alloy with NTp ensemble to keep the number of atoms (N), temperature (T = 673 K), and pressure (p ∼ 101.325 kPa) constant under a GrujicicZhou-type MD potential from an Embedded Atom Method scheme with a cut-off distance of 1 nm. An Fe50Ni50 alloy was initially created as a hypothetical chemically-ordered B2 structure with a 12 × 12 × 12 supercell comprising 3456 atoms. Subsequently, it was annealed at 673 K, without the application of stress, and then under a uniaxial tension of ∼290 MPa, and shear stresses of ∼570 and ∼2940 MPa. The results revealed that stress contributed to a change in the transformation scheme to the L10 phase from partially to fully of the system with a reduction of time. On the other hand, an as-quenched amorphous phase under a shear stress of ∼680 MPa, transformed to a disordered fcc-derivative phase. Therefore it is clear that stresses in MD simulations play a crucial role in enhancing the atomic motion during a transformation.

  • Thanit Meebupha, Sudsakorn Inthidec, Prasonk Sricharoenchai, Yasuhiro ...
    2017 Volume 58 Issue 4 Pages 655-662
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    The effect of the Molybdenum (Mo) content on the heat treatment behavior of multi-alloyed white cast iron was investigated. The cast iron with varying Mo contents from 0.12 to 7.66% under the basic alloy composition of 5% Cr, W and V each was prepared. After annealing at 1223 K for 18 ks, the test specimens were austenitized at 1373 K for 3.6 ks in a vacuum furnace and subsequently hardened by a jet-spray of liquid nitrogen. The tempering was carried out at temperatures from 673 to 873 K at 50 K intervals for 12 ks. It was found that the hardness in the as-hardened state was increased progressively with an increase in the Mo content. The volume fraction of the retained austenite (Vγ) decreased markedly when the Mo content was increased over 1.17%. In the tempered state, the hardness curve showed clear secondary hardening due to the precipitation of fine secondary carbides and a reduction of the Vγ. The Vγ value in each specimen decreased gradually as the tempering temperature was elevated, but reduced greatly when tempered at 748 to 823 K. The maximum tempered hardness (HTmax) was obtained in the specimen tempered at 798 K where the Vγ was less than 10%. The HTmax increased first, and then subsequently decreased with an increase in the Mo content. The highest HTmax value, 946 HV30, was obtained in the specimen with 4.98%Mo. It was found that the 15–37%Vγ in the as-hardened state was necessary to get the hardness over 900 HV30 by tempering. The degree of secondary hardening (ΔHs) increased as the Mo content rose from 0.12 to 4.98% where the difference between the Vγ in the as-hardened state and that at HTmax (ΔVγ) was 22–23%.

  • Kun Zhou, Tao Zhang
    2017 Volume 58 Issue 4 Pages 663-667
    Published: April 01, 2017
    Released: March 25, 2017
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    The feasibility of a novel metalloid-free Ni57Zr20Ti17Al5Sn1 (at.%) amorphous filler metal for 304 SS brazing was investigated by induction brazing. The joining process can be completed within seconds in argon atmosphere due to the sensitive response of induction heating. The effects of joining time on the microstructure of joints and the joint shear strength were investigated. The results indicate that the joints brazed for 5 s and 10 s exhibit good wetting between the base metal and the filler metal. Overheating occurred due to skin effect for the holding time of 20 s. The brazed seam of 5 s is composed of Ni-rich phases while the brazed seam of 10 s is composed of Fe-rich phases indicating the gradual homogenization of the bonding region with the base metal as a function of holding time. Shear strength of as high as 235 MPa was obtained when brazed for 10 s.

  • Chaojie Zhang, Yanping Bao, Min Wang, Lechen Zhang, Hanghang An
    2017 Volume 58 Issue 4 Pages 668-672
    Published: April 01, 2017
    Released: March 25, 2017
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    In order to improve heat prevention property of insulation board used in hot top during casting of steel ingot, thermal conductivities of insulation boards of solid structure and porous structure with different porosities were investigated using numerical simulation and calorimetric techniques. A heat transfer model used to calculate the thermal conductivity of insulation boards was developed, and the accuracy of the model was verified by calorimetric experiment. A series of porous insulation boards made of floating beads with different porosities were designed and effect of porosity on thermal conductivity of porous insulation board was investigated by numerical simulation. It was found that porous insulation board performs a better heat prevention property than insulation board of solid structure. Thermal conductivity of porous insulation board decreases notably with the increase of porosity. By contrast, the sizes of pores almost have no influence on the thermal conductivity of porous insulation board.

    Fig. 3 Photographs of porous insulation board made with floating beads, (a) Porous insulation board with no magnification, (b) Porous insulation board with 7 times normal magnification, (c) Floating beads with 7 times normal magnification, (d) Floating beads with 50 times normal magnification. Fullsize Image
  • Youqiang Yao, Zhefeng Xu, Kenjiro Sugio, Yongbum Choi, Kazuhiro Matsug ...
    2017 Volume 58 Issue 4 Pages 673-678
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    Magnesium-calcium alloy composites reinforced with nickel-coated vapor-grown carbon fibers (VGCFs) were fabricated using a compo-casting process. Then, the microstructures and mechanical properties of these composites were investigated. The Mg-5Al-3Ca (AX53) alloy exhibited a dendritic microstructure with a coarse lamellar (Mg, Al)2Ca phase along the grain boundaries instead of the irregular β-Mg17Al12 phase found in the Mg-5Al alloy. For the 0.5% Ni-coated VGCF-reinforced AX53 alloy composite, the VGCFs were well dispersed in the matrix, with the nickel coating diffused into the metal. Al3Ni compounds formed both inside the grains and on the grain boundaries. The ultimate tensile strength (UTS) and strain-hardening of the AX53 alloy, in comparison with the Mg-5Al alloy, were improved significantly to the point of fracture. Furthermore, an increase in the UTS of the composite was achieved with the addition of 0.5% VGCFs, along with an increase in the total elongation, which could mainly be attributed to the strain hardening during a larger strain. The 0.2% yield stress was slightly improved as a result of the small amount of introduced Ni-coated VGCFs. However, the elongation dropped for the 1.0% VGCF-reinforced AX53 alloy composites, which led to a low strength similar with that of the AX53 alloy.

  • Shojiro Ochiai, Hiroshi Okuda, Noriyuki Fujii
    2017 Volume 58 Issue 4 Pages 679-687
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 03, 2017
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    Influences of crack size-distribution and specimen length on the critical current and n-value of heterogeneously cracked superconducting tapes were studied by a Monte Carlo simulation method combined with a model of crack-induced current shunting. In simulation, model specimens, constituted of a series of sections having cracks with different size to each other, were used. It was shown by the present simulation that (i) both of the critical current and n-value decrease with increasing width of crack size distribution, (ii) n-value decreases more sensitively to the increase in width of crack size distribution in comparison with the critical current, and (iii) the features (i) and (ii) stated above are enhanced with increasing specimen length. Also, the experimentally observed feature that the width of distribution of critical current decreases with increasing length in heterogeneously cracked superconducting tapes was realized by the present simulation. This result was in good accordance with the reported feature that local information of critical current values in a specimen is diluted when the voltage tap distance is large.

  • Kazuki Nishinaka, Osamu Terakado, Haruki Tani, Masahiro Hirasawa
    2017 Volume 58 Issue 4 Pages 688-691
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 24, 2017
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    Pyrometallurgical chlorination process has been examined for the recovery of gallium from gallium nitride, GaN, a promising semiconductor material. It was found that gallium was successfully recovered as volatile gallium chloride by thermal treatment of GaN powder in the presence of ammonium chloride. All gallium could be recovered as volatile species at 500℃. The results indicate that gallium can be extracted from complex mixture of semiconductor materials or wastes through this process. The influence of reaction conditions, such as reaction temperature and composition of ammonium chloride, was examined.

  • Kota Sasaki, Takuya Katagiri, Noritaka Yusa, Hidetoshi Hashizume
    2017 Volume 58 Issue 4 Pages 692-696
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 24, 2017
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    This study evaluated the applicability of nondestructive microwave testing method for the long-range detection of inner-surface cracks in metallic tubes. Two seamless straight tubes 7 m in length and 23.0 mm in inner diameter were prepared, and artificial circumferential slits penetrating the tube walls were introduced. A probe to propagate microwave inside the tube, designed based on three-dimensional finite element simulations, was attached to an end of the tube, and the reflections of the microwave propagating inside the tube were measured using a network analyzer. The experiments confirmed clear reflections due to the slits situated 6 m away from the probe. Furthermore, imposing a signal processing method to compensate for the dispersion of the microwave clarified the reflections and enabled the slit to be localized quantitatively from the time-of-flight of the reflections.

  • Abdelrahman Farghali, Tatsuhiko Aizawa
    Type: Rapid Publication
    2017 Volume 58 Issue 4 Pages 697-700
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: February 17, 2017
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    A high density plasma nitriding experiment was performed on a circular disk specimen of martensitic stainless steel at the temperature of 673 K for 14.4 ks. The nitrided thickness was 80 μm in depth from the surface with a high surface nitrogen concentration of 31 at%. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and, electron backscattering diffraction (EBSD) were used to analyze the microstructure, the nitrogen content distribution, the phase formation, the grain size, and the straining in the specimen. Phase transformation from martensitic to austenitic phases took place together with high straining as well as grain size refinement.

  • Tsuyoshi Masumoto, Shigehiro Ohnuma, Kazuyuki Sugawara, Hisamichi Kimu ...
    Type: Rapid Publication
    2017 Volume 58 Issue 4 Pages 701-704
    Published: April 01, 2017
    Released: March 25, 2017
    [Advance publication] Released: March 10, 2017
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    In the present study, both excellent Elinvar and Invar characteristics have been found in the antiferromagnetic Fe-Mn based alloys consisting of about 25 mass%Mn and a small amount of Mo, W, Nb, Ta, Ti, Zr and Hf which are belonging to the 4~6 families in the periodic table. The best characteristics obtained in the present study were constant Young's modulus (Elinvar characteristics) of 1 × 10−6 K−1 and a small thermal expansion coefficient (Invar characteristics) of 8 × 10−6 K−1 in the temperature range of 293~353 K under appropriate treatment of cold working and annealing. Such alloys will be expected as applications in a wide field such as precision instruments, electromagnetic devices and controlling devices.

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