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MATERIALS TRANSACTIONS Vol. 58 (2017), No. 12

ISIJ International
belloff
オンライン版ISSN: 1347-5320
冊子版ISSN: 1345-9678
発行機関: The Japan Institute of Metals and Materials

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キーワードランキング

03 Dec. (Last 30 Days)

MATERIALS TRANSACTIONS Vol. 58 (2017), No. 12

Welding Characteristics and Effect of Gap Length on 2000 Series Aluminum Alloy Sheet Lap Joints Welded by Magnetic Pulse Welding

Takaomi Itoi, Syoichi Inoue, Keigo Okagawa

pp. 1629-1635

DOI:

10.2320/matertrans.L-M2017837

抄録

Effect of gap length on welding characteristics of 2000 series aluminum alloy sheets in magnetic pulse welding (MPW) was investigated. Collision time for the 2017-T3 sheet welded at gap length of 1.2 mm and 4.6 mm were 6.16 μs and 16.9 μs respectively, which were increased with increasing of gap length. The collision speed calculated from collision times increased as the gap length increased, showed a maximum value of 380 m/s with a gap length of 2.0 mm, and then the speed declined. This result indicates that it is possible to join sheets at a higher collision speed even with the same discharge energy by adjusting an appropriate gap length. Strong lap joint was achieved for the 2024-T3/2024-T6 and the 2024-T3/7075-T6 lap joint sheets by welding condition of gap length more than 1.0 mm. Thus, it could be possible to improve the weld strength by widening the gap length and performing MPW at high collision speed. SEM and HAADF-STEM observations showed no clear oxide films formed on the weld interface. From microstructure observation, it was considered that lap joints fabricated by MPW were welded at solid state. This Paper was Originally Published in Japanese in J. JILM 67 (2017) 423–429.

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He-Cavity Accumulation at Oxide Particle-Matrix Interface in Ni-Base ODS Superalloy

Azusa Konno, Naoko H. Oono, Shigeharu Ukai, Sosuke Kondo, Okinobu Hashitomi, Akihiko Kimura

pp. 1636-1639

DOI:

10.2320/matertrans.M2017142

抄録

Ni-based ODS superalloy is found to be an effective candidate for a core material of Gen. IV nuclear reactors by means of a Fe/He dual-ion bombardment simulation technique. It accumulates He cavities at the dispersed oxide particle/matrix interface, and avoids the aggregation of the cavities at the other sinks even after the irradiation up to 100.1 dpa at 1000℃. Swelling was reduced less than 1%. Cavity growth and sink strengths were estimated based on TEM observation and the rate theory. The estimations support the capability of the oxide particles for trapping the He cavities and suppressing their accumulation at grain boundaries.

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Mathematical Model for Predicting Flow Stress in Hot Rolling of Alloy Steel

Atsushi Matsumoto, Shunsuke Sasaki, Tatsuro Katsumura, Hiroki Ota

pp. 1640-1646

DOI:

10.2320/matertrans.P-M2017841

抄録

During the multipass hot processing of alloy steel, restoration processes such as static and dynamic recrystallization and recovery occur. Owing to these phenomena, flow stress characteristics are affected by various deformation conditions, such as temperature and accumulated strain. The objective of this research is to develop a mathematical model for predicting flow stress to represent these effects by simply considering the processing history and restoration. Hot compression experiments were conducted and the results were compared with the predicted results. It was found that the prediction accuracy can be improved by simultaneously considering the effects of accumulated strain and restoration.

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Extra Strengthening and Superplasticity of Ultrafine-Grained A2024 Alloy Produced by High-Pressure Sliding

Takahiro Masuda, Yoichi Takizawa, Manabu Yumoto, Yoshiharu Otagiri, Zenji Horita

pp. 1647-1655

DOI:

10.2320/matertrans.M2017242

抄録

In this study, the method of high-pressure sliding (HPS) was applied for grain refinement of an A2024 alloy. Sheet samples with 10–15 mm width and 100 mm length with 1 mm thickness were processed by HPS under pressures of 2–3 GPa. Microstructural observations revealed that the grain size was refined to ～200 nm. Tensile tests showed that the ultimate tensile strength reached 886 MPa with a total elongation of 7.1% and the anisotropy of samples was less developed in the HPS-processed samples. Extra strengthening was attained by aging at 423 K after HPS processing, leading to an ultimate tensile strength of 967 MPa at the peak aged condition. Superplastic elongation of more than 400% appeared when the A2024 alloy processed by HPS for 20 mm was deformed in tension at a testing temperature of 623 K with an initial strain rate of 1.0 × 10−3 s−1. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 80 (2016) 593–601. In order to convey the results more precisely, Fig. 3 included the average hardness and the standard deviation for each sample. Miller indices were also added in the selected area electron diffraction patterns in Figs. 4, 10 and 13.

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Influence of Yttrium Addition on Plastic Deformation of Magnesium

Hiroaki Rikihisa, Takashi Mori, Masayuki Tsushida, Hiromoto Kitahara, Shinji Ando

pp. 1656-1663

DOI:

10.2320/matertrans.M2017265

抄録

Tensile tests of single crystalline and polycrystalline Mg-Y alloys were carried out at room temperature to investigate the influence of yttrium on activation of <c+a> slip systems and to clarify the relationship between ductility of magnesium and the activation of <c+a> slip systems. Tensile directions of single crystals and polycrystals were parallel to (0001) and their rolling direction, respectively. Mg-(0.6–1.1)at%Y alloy single crystals yielded due to the first order pyramidal <c+a> slip (FPCS). Yield stress and ductility of Mg-(0.6–1.1)at%Y alloy single crystals were higher than those of pure magnesium. Mg-0.9at%Y alloy polycrystals showed higher ductility than pure magnesium. The number of grains where second order pyramidal slips were activated was the largest in those where non-basal slips were activated in pure magnesium, while those where FPCS were activated increased with increasing strain in Mg-0.9at%Y alloy. High ductility of Mg-0.9at%Y alloy would be caused by activation of FPCS due to yttrium addition. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 81 (2017) 458–466.

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Precise Density Measurement of Liquid Titanium by Electrostatic Levitator

Shumpei Ozawa, Yu Kudo, Kazuhiko Kuribayashi, Yuki Watanabe, Takehiko Ishikawa

pp. 1664-1669

DOI:

10.2320/matertrans.L-M2017835

抄録

Density of liquid titanium was measured free from any contamination over wide temperature range of 1640 and 2090 [K] including the undercooling condition by electrostatic levitator (ESL). When the diameter of upper electrode of ESL was modified to be smaller than that of lower one, it was decreased the uncertainty contribution of the droplet volume estimated from its image with respect to the density measurement by 30% through the suppression of the horizontal movement of the levitated droplet. The expanded uncertainties of the measurement plot were less than only ±1.4% when the coverage factor k = 2 was selected. Furthermore, it was evaluated the expanded uncertainty in the temperature dependence of density for liquid titanium expressed by a primary approximation of the plots.

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Electro-Wetting Behavior of Sodium Chloride Aqueous Solution on Hydrophobic Surfaces of Stainless Steel and Its Influence on Polarization

Rongguang Wang, Junya Kaneko, Keijiro Nakasa, Akihiro Yamamoto, Yunhan Ling

pp. 1670-1678

DOI:

10.2320/matertrans.M2017224

抄録

Hydrophobic polyethylene (PE) and perfluorodecyltriethoxysilane (PFDS) were deposited on stainless steels and the contact angle of aqueous NaCl solution on these surfaces was measured before and after applying different currents through a Pt wire. The polarization curves on some surfaces were measured and their relationship to electro-wetting behaviors was determined. Negative rather than positive current greatly reduced the contact angles on both the plane surface of polished SUS304 steel and the rough surface of sputter-etched SUS316 steel (SUS316SE), which were deposited with PE and PFDS, respectively. On rough surfaces, the negative current-induced reduction in contact angle was greater on SUS316SE-PE than on SUS316SE-PFDS specimens. Prior cathode polarization reduced the pitting potential on SUS316SE-PE specimens, but had no effect on 316SE-PFDS specimens. This difference was likely related to the difference in solution invasion into the root of protrusions, from which chromium was depleted by sputter etching.

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Corrosion Behavior of Lead-Free Copper Alloy Castings and Their Crystallized Substances of Cu2S and Bi

Yoshinobu Yasuda, Hiroyuki Abe, Ryozo Matsubayashi, Toru Maruyama, Takumi Haruna

pp. 1679-1686

DOI:

10.2320/matertrans.M2017196

抄録

In this study, we aimed to understand the corrosion behavior of Pb-free Cu alloys (Japan Industrial Standards (JIS) CAC411 and CAC901) and their crystallized substances (Cu2S and Bi, respectively) particles in a 3.0 mass% NaCl aqueous solution, in comparison with those of a Cu alloy (JIS CAC406), its crystallized substance (Pb) particles, and a Cu alloy (JIS CAC403) with no crystallized substances. A Cu2S specimen was produced via sintering Cu2S powders, and a Bi specimen was produced by Bi electro-plating on a Cu substrate. The measured corrosion potentials of CAC411, CAC901, and CAC403 were close to that of Sn instead Cu. The current density peak near the corrosion potential of CAC403, which was the highest Sn concentration, was the largest in comparison with those of the other Cu alloys. Conversely, rapid increase in the current density, which was shown for all the Cu alloy at the potential above −0.20 V vs. Ag/AgCl, was similar to that of Cu. Therefore, it was concluded that these increase in current densities of Cu alloys was due to the dissolution of the Cu matrix. Cu2S was converted into CuS during the anodic reaction. However, the corrosion potential of Cu2S was higher than those of Cu and CAC411. Therefore, it was concluded that the Cu2S particles in CAC411 act as cathodic sites and remain stable during the natural corrosion. The corrosion potential of Bi was higher than that of CAC901 and slightly lower than that of Cu. Further, at the potentials below −0.10 V vs. Ag/AgCl, Bi was thought to be covered with the passive film of Bi2O3 that was expected to protect Bi from corrosion. Therefore, it was concluded that the Bi particles in CAC901 hardly suffer severe corrosion. The corrosion potential of Pb was lower than those of the Cu and Cu alloys expect for CAC406. In addition, Pb exhibited a large anodic current density and dissolved actively around the corrosion potential of Cu. Therefore, it was concluded that the Pb particles dissolved preferentially during the corrosion of CAC406 owing to the galvanic corrosion. It was finally concluded that the Cu2S and the Bi particles in CAC411 and CAC901, respectively, hardly suffer severe corrosion than the Pb particles in CAC406 in chloride-containing aqueous solutions like sea water.

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Monitoring the Early Stage of Degradation of Epoxy-Coated Steel for Ballast Tank by Electrochemical Impedance Spectroscopy

Hitoshi Hayashibara, Eiji Tada, Atsushi Nishikata

pp. 1687-1694

DOI:

10.2320/matertrans.M2017243

抄録

The early stages of the degradation of thick epoxy-coated steels used for water ballast tanks were monitored by electrochemical impedance spectroscopy (EIS). 200-μm-thick epoxy-coated steels were exposed to accelerated corrosion tests containing humid air at 70℃ for 246 days before immersion in a NaCl solution at 70℃ for 79 days. They were removed from the corrosion test chamber during the test so that EIS measurements could be performed in order to determine the coating resistance (Rf) and the coating capacitance (Cf). In addition, the water volume fraction (XV) and the diffusion coefficient (DH2O) in the coating were determined from the Cf vs. t1/2 curves during the water desorption process. These parameters were compared with the degradation morphology of the coated steel after a pull-off test. Only “physical aging” of coating was observed for first 80 days. After 190th day, Rf decreasing, Cf and XV increasing started. Underlying corrosion also initiated between 80th and 190th day. On the other hand DH2O did not indicate the clear change associated with the degradation. The changes in Rf, Cf, and XV were closely correlated with the progress of the degradation of the coated steels.

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Comparison of Suppressing Effect for Soldering Reactions by Surface Modifications Using Nitriding and Amorphous Carbon Film in Zinc Alloy Die Casting

Mai Mizubayashi, Takuya Sakuragi, Naoki Watanabe, Kenji Matsuda, Masateru Nose

pp. 1695-1701

DOI:

10.2320/matertrans.M2017239

抄録

In zinc alloy die casting, the thin oxide layer generated on a mold surface causes soldering reactions, and the outer surface becomes coarser as the soldering proceeds. To minimize casting defects such as zinc deposits, we propose a surface modification of the mold to prevent soldering reactions. In this study, we observed the diffusion state of constituents generated between a molten zinc alloy (ZDC1) and the surface-modified mold material (maraging steel) using secondary ion mass spectrometry (SIMS). Furthermore, we analyzed the interfacial reaction layer between the surface-modified mold and the zinc deposits observed on the mold by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), and considered the effect of surface modification on suppressing soldering reactions.

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Powder Forming Process from Machined Titanium Chips via Heat Treatment in Hydrogen Atmosphere

Junko Umeda, Takanori Mimoto, Hisashi Imai, Katsuyoshi Kondoh

pp. 1702-1707

DOI:

10.2320/matertrans.Y-M2017833

抄録

The recycling process of the coarse machined chips from the commercial Ti-6%Al-4%V (Ti-64) alloy products to fine powders available for powder metallurgy (PM) components was established. The brittle TiH2 compounds formation in Ti chips via heat treatment in hydrogen gas atmosphere significantly improved their milling ability. TG-TDA and XRD analysis suggested the hydration and dehydration behavior of pure Ti and TiH2 powders. The suitable hydration temperature over 873 K in H2-Ar mixed gas successfully caused TiH2 compounds synthesis in Ti-64 chips, and resulted in reproduction of fine Ti-64 powders with a median particle size of 120 µm from the machined spiral chips by mechanical milling process. The green compact of reproduced Ti-64 powder after vacuum sintering at 1273 K showed a relative density of about 93%, larger than that of the sintered material in using the commercial Ti-64 powder. The hydrogen and oxygen contents of the sintered specimen using reproduced Ti-64 powder were satisfied with JIS-60. Accordingly, the machined Ti alloy chips were directly recycled as valuable starting materials to reproduce PM components via combination of hydration-milling-dehydration process. This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 64 (2017) 81–87.

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Evaluation of the Form-Forming Mechanism for High-Tensile-Strength Steel Plate

Kouji Kanno, Souichiro Nishino, Kunio Ohya

pp. 1708-1714

DOI:

10.2320/matertrans.P-M2017840

抄録

Steel plate with tensile strengths of from 440 MPa to 980 MPa is increasingly being adopted for the structural elements of automobile bodies to both reduce weight and increase collision safety. However, the use of such material brings defects in press forming and other problems. The research reported here focuses on the form-forming method, which is effective for forming high tensile strength steel plate. To clarify the features of form-forming, we used eight types of steel plate having tensile strengths of from 270 MPa to 980 MPa in three forming processes, draw-forming, one-step form-forming, and two-step form-forming, to evaluate the shape freezing property. The results showed that the shape freezing property depends on the mechanical properties of the material; specifically, a correlation with tensile strength, 0.2% proof stress, and elongation was seen. The effectiveness of form-forming for materials of higher strength was confirmed. Improved shape freezing by dividing the form-forming process into two steps was also confirmed. For draw-forming, the entire shaped surface was affected by unbending, so form-forming effectively suppresses unbending. The spatial distribution of unbending was evaluated quantitatively by measuring the residual stress distribution, confirming that residual stress serves as a useful index for clarifying the forming mechanism.

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Effects of Shot Blasting on Corrosion Properties after Electrodeposition and Fatigue Properties of Arc Welds in Automotive Steel Sheets

Hiroki Fujimoto, Koji Akioka, Masatoshi Tokunaga

pp. 1715-1720

DOI:

10.2320/matertrans.P-M2017838

抄録

In this study, we investigated the effect of shot blasting on the corrosion properties after electrodeposition and the fatigue properties of the arc welds in automotive steel sheets. The corrosion properties of arc welds after electrodeposition were significantly improved by shot blasting due to the removal of slag and fume, which can cause painting defects. Also, the fatigue strength of welded joints was enhanced by shot blasting, because the mean stress effect due to compressive residual stress improved the fatigue properties. These results suggest that shot blasting has the potential to reduce the thickness of arc welded steel parts in automobile chassis. This Paper was Originally Published in Japanese in J. JSTP 58 (2017) 299–303.

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Numerical Simulation and Experimental Validations of Planar Solidification Process for Large Ingot by Using Moving Dense Sprues

Shao Bo, Zhang Haitao, Qin Ke, Cui Jinazhong

pp. 1721-1728

DOI:

10.2320/matertrans.M2017249

抄録

A mathematical model based on commercial finite volume package FLUENT has been developed to describe the melt flow and heat transfer during planar solidification casting process of 7050 alloy ingot with cross-section size of 600 × 600 mm. The effects of two fixed sprues and two movable sprues served as the feeding system on the temperature field and velocity field of planar solidification were investigated. Moreover, the model has been verified by the temperature measurements obtained from experiments. The numerical results reveal that the effect of feeding system on melt temperature field is dominating during planar solidification casting process and the movable sprues are significantly superior to the fixed sprues. The characteristics of planar solidification front and uniform temperature field are achieved by movable dense sprues. According to the numerical results, an ingot without V- shaped shrinkage and crack on the surface, and with uniform microstructure and small difference in composition was casted successfully.

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In Situ Observation of Nonmetallic Inclusion Formation in NiTi Alloys

Fumiyoshi Yamashita, Masamitsu Wakoh, Koji Ishikawa, Hiroyuki Shibata

pp. 1729-1734

DOI:

10.2320/matertrans.M2017156

抄録

It is well recognized that the fatigue characteristics of NiTi alloys are greatly influenced by the presence of nonmetallic inclusions. A high fatigue strength is required for the application of these alloys to medical devices, especially stents, to allow them to withstand the repeated processes of pulsation-induced expansion and contraction. In this study, the phases and morphology of the inclusions in commercially produced NiTi alloy were investigated. The inclusions in an as-cast ingot consisted of a single phase of Ti(C, O) and possessed a fiber shape with a diameter of about 0.5 µm, and were formed during the solidification of the NiTi alloy. In situ observation by confocal laser scanning microscopy revealed that the inclusions formed and grew in the region of residual melt (consisting of concentrated Ti, C, and O) during the solidification process.

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Microstructure and Properties of High Temperature Titanium Alloys with a High Si Content Prepared by Powder Metallurgy

Q.B. Kuang, L.M. Zou, Y.X. Cai, X. Liu, H.W. Xie

pp. 1735-1741

DOI:

10.2320/matertrans.M2017248

抄録

The objective of this paper is to improve the performance of high temperature titanium alloys with a high Si content by powder metallurgy. Firstly Ti-6.5Al-1.4Si-2Zr-0.5Mo-2Sn alloy powders were prepared using two different rotating speeds by plasma rotating electrode process (PREP). Then two sintering temperatures were selected to fabricate titanium alloys by hot isostatic pressing (HIP). The relationship between rotating speed and particle size distribution was investigated. X-ray diffraction, SEM, and OM were used to characterize the phase compositions, morphologies, and microstructures of the powders and titanium alloys. The mechanical properties of titanium alloys were investigated at room temperature,300℃ and 600℃. The results show that high quality titanium alloy powders were prepared by PREP. The mechanical properties of titanium alloy fabricated by powder metallurgy were superior compared to casting.And the strength is higher than typical Ti-1100 high temperature alloy.

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Development of Manufacturing Principle of Porous Iron by Carbothermic Reduction of Composite of Hematite and Biomass Char

Taichi Murakami, Takayuki Takahashi, Shoko Fuji, Daisuke Maruoka, Eiki Kasai

pp. 1742-1748

DOI:

10.2320/matertrans.M2017232

抄録

Iron-based porous metals have several advantages such as high strength and low cost compared with aluminum alloy foams. In recent years, a number of manufacturing technologies for iron-based porous metals have been proposed. However, a practical process could not be developed because of lower porosity, higher cost of raw materials, and so on. In this study, a new manufacturing principle of porous iron was proposed by applying carbothermic reduction using a composite of hematite and carbonaceous material. In the reduction experiment, graphite, coal, and three different charcoals were used as reductants. Based on the results, the characteristics and mechanism of the volume change of the composite were investigated under different pressures.Reduction behavior significantly varied among the different types of reductants. The composites containing graphite and coal shrank during the reduction process when heated up to 1373 K. However, swelling behavior was observed for the composite prepared using charcoal containing some amounts of sodium and sulfur as ash components. When this composite was heated up to 1273 K at a rate of 0.167 K s−1 at 0.3 MPa, porous iron with a maximum porosity of 97.7% was successfully obtained. The bulk density of the composite changed during the reduction of wustite to metallic iron and formed iron whiskers. The formation of the whiskered iron texture led to a considerable swelling of the composite. On the other hand, the composite prepared using charcoal with low sodium and sulfur concentrations in the ash did not swell after the formation of metallic iron. Furthermore, when such elements in the charcoal were preliminarily removed, the composite did not swell.

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Synthesis of Bi0.5Sb1.5Te3 Sintered Composite with Dispersed Ionic Liquid and Investigation of Thermoelectric Properties

Shigeru Katsuyama, Yusuke Kusafuka, Toshihiro Tanaka

pp. 1749-1753

DOI:

10.2320/matertrans.Y-M2017836

抄録

The sintered composite of Bi0.5Sb1.5Te3 and ionic liquid, BMImTFSI, was synthesized by sintering the mixture of Bi0.5Sb1.5Te3 powder and BMImTFSI at 573 K by hot pressing, and its microscopic structure and thermoelectric properties were investigated. The dispersed micropores, where BMImTFSI occupied, were observed by SEM observation on the cross-section of Bi0.5Sb1.5Te3-BMImTFSI sintered composite. With increasing the amount of BMImTFSI, the Seebeck coefficient of the composite generally decreased, while the electrical resistivity increased and the electrical resistivity of the composite with 0.5 ml of BMImTFSI is about two times larger than that of Bi0.5Sb1.5Te3 with no BMImTFSI. The thermal conductivity of the composite with 0.01 ml of BMImTFSI was reduced by about 20% compared to that of Bi0.5Sb1.5Te3 with no BMImTFSI. These results indicate that the dispersed BMImTFSI in the composite acts as a scattering center for electric carrier and phonon. As a result, the dimensionless figure of merit ZT of the composite with 0.01 ml of BMImTFSI showed a maximum value of 0.70 at 373 K, which was about 20% larger than that of Bi0.5Sb1.5Te3 with no BMImTFSI. This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 63 (2016) 719–724.

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Using Recycled Bismuth-Tin Solder in Novel Machinable Lead-Free Brass

Pemika Suksongkarm, Surasit Rojananan, Siriporn Rojananan

pp. 1754-1760

DOI:

10.2320/matertrans.M2017227

抄録

The aim of this work was to create and apply a recycled bismuth-tin (Bi-Sn) solder in novel machinable lead-free brass. The Bi-Sn alloys were obtained from a recycled solder used in the electronics industry to reduce cost and to partially solve electronic waste issue. The relationship between mechanical properties, microstructures and machinability of the brass were investigated. The results showed that a based lead-free Cu-38Zn-0.5Si brass without Bi-Sn alloy addition exhibited highest tensile strength, required the highest machining force and produced an undesirable long continuous chip type. An addition of 1–3 mass% Bi-Sn alloy resulted in significant decrease of both the tensile strength and the machining force. The chip formation changed from an undesirable long continuous chip to a discontinuous chip in moderate size. On the other hand, the addition of 4 and 5 mass% Bi-Sn alloy slightly increased the tensile strength and the machining force, the chip formation changed from a moderate chip size to a very short chip under every test condition. The lead-free brass with 3 mass% Bi-Sn alloy showed the best effective machinability as it required the lowest machining force and produced a short chip. Furthermore, the mechanical properties were about the same as those of the commercial EnviroBrass®III. Thus, the recycled Bi-Sn alloy can be used to improve the machining properties of lead-free brass and offers a possibility for new and better lead-free brass alloys.

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Preparation of Metaettringite from Ettringite and Its Performance for Boron Removal from Boric Acid Solution

Atsushi Iizuka, Miyuki Takahashi, Takashi Nakamura, Akihiro Yamasaki

pp. 1761-1767

DOI:

10.2320/matertrans.M-M2017839

抄録

Metaettringite was prepared by heat treatment of ettringite, and its boron removal performance from solutions at low concentrations (25 mg/L boron (mg-B/L)) was investigated. With a calcination temperature of > 65℃, amorphous metaettringite formed, and this showed better boron removal performance than ettringite. The dominant mechanism for boron removal by metaettringite was incorporation of B(OH)4− in the ettringite structure during its regeneration from metaettringite by hydration. The highest uptake was 15.1 mg of boron per gram of metaettringite. Boron in solution could be effectively removed by metaettringite over a wide initial pH range of 5.22 to 11. Residual boron concentrations were lower than those specified by the Japanese effluent standard (10 mg-B/L) even when using metaettringite with a large particle size. Boron removal was strongly suppressed by high temperatures, but a residual boron concentration lower than 10 mg-B/L was obtained when the mass concentration of adsorbent in the boron solution was increased.

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