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MATERIALS TRANSACTIONS Vol. 51 (2010), No. 11

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

23 Nov. (Last 30 Days)

MATERIALS TRANSACTIONS Vol. 51 (2010), No. 11

Structure, Dye Degradation Activity and Stability of Oxygen Defective BaFeO3−x

Mengmeng Sun, Yinshan Jiang, Fangfei Li, Maosheng Xia, Bing Xue, Darui Liu

pp. 1981-1989

DOI:

10.2320/matertrans.M2010206

抄録

The structure, dye degradation activity and stability of oxygen defective BaFeO3−x was investigated. The pure perovskite BaFeO3−x was synthesized at 700°C. With further increase in temperature, the oxygen loss occurred, and then the instability of BaFeO3−x was improved due to the change in crystal structure. BaFeO3−x can degrade methyl orange in the dark, and the degradation rate can be improved under visible light due to the optical property of BaFeO3−x. This degradation was caused by the transformation from Fe4+ to Fe3+ to some extent which was related with the structural transition of BaFeO3−x. So the reducibility of BaFeO3−x functions in dye degradation. The oxygen loss accelerated the structural transition and the photo-assisted degradation activity of BaFeO3−x. The instable Ba2+ also improves the instability of BaFeO3−x.

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Core-Shell Formation and Juxtaposition in Fe and Si Hybrid Clusters Prepared by Controlling the Collision Stages

Naokage Tanaka, Kenji Sumiyama, Ryoji Katoh, Takehiko Hihara, Kazuhisa Sato, Toyohiko J. Konno, Ko Mibu

pp. 1990-1996

DOI:

10.2320/matertrans.M2010177

抄録

Fe and Si hybrid clusters are co-deposited on substrates in a double-glow-discharge-source-type plasma-gas-condensation system, and observed by transmission electron microscopy, scanning transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy. Core-shell Fe/Si clusters, in which chemically heterogeneous bcc Fe-Si cores are covered by amorphous-like Si shells, are obtained on the substrate when Fe and Si cluster nuclei collide with each other at an early stage (without setting the partition plate between the two sources). On the other hand, Fe and Si clusters are juxtaposed on the substrate when their nuclei collide with each other at a late stage (with setting of the partition plate). These results demonstrate that we can obtain various hybridized states of Fe and Si clusters by controlling the collision stages.

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Dynamic Electropulsing Induced Phase Transformations in a Furnace Cooled Zn-Al Based Alloy (ZA22)

S. To, Y. H. Zhu, W. B. Lee, X. M. Liu

pp. 1997-2004

DOI:

10.2320/matertrans.M2010130

抄録

Multi-phase identification and phase transformations in a dynamic electropulsing treated Zn-Al based alloy (ZA22) were studied by using backscattered scanning electron microscopy (BSEM) and electron back-scattered diffraction techniques (EBSD). By using EBSD, two hcp phases η′S and η′T with a small difference of about 1% in lattice parameters (c/a) were discriminated. Two stages of phase transformations: (a) η′S→η′T+ε′T+α′T and ε+α→T′+η (in a way of quenching), and (b) T′+η→ε+α and η′T+ε′T+α′T→η′S (in a way of up-quenching), were detected. It was found that dynamic electropulsing was less effective in accelerating phase transformations than static electropusling. The mechanism of dynamic electropulsing induced phase transformations is discussed from the point view of Gibbs free energy and electropulsing kinetics.

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Ab Initio Molecular Dynamics Study of Fe Adsorption on TiN (001) Surface

Chao Wang, Yongbing Dai, Haiyan Gao, Xiaoming Ruan, Jun Wang, Baode Sun

pp. 2005-2008

DOI:

10.2320/matertrans.M2010244

抄録

The adsorption energy of atomic Fe on TiN (001) surface was examined by first-principles calculations. The inter-atomic interaction mechanism between TiN crystal and Fe atom was investigated using ab initio molecular dynamics simulation. It was found that the N site is more preferable than Ti and bridge sites for Fe atom. These results may be of importance for further understanding heterogeneous nucleation mechanism.

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Grain Refinement and Hardness Increase of Titanium via Trace Element Addition

J.-M. Oh, J.-W. Lim, B.-G. Lee, C.-Y. Suh, S.-W. Cho, S.-W. Lee, G.-S. Choi

pp. 2009-2012

DOI:

10.2320/matertrans.M2010175

抄録

The effect of trace Al, V, Sn and Si addition on the grain refinement, hardness, and lattice strain was discussed. From the results of variation in the average grain size, it was found that the growth restriction factor of individual additions is Si>Al>Sn>V in order of their magnitude. The c⁄a ratio of other Ti alloys except for the Ti-Si alloy were the same value of 1.587 as pure Ti, whereas that of the Ti-Si alloy was 1.581, the lattice strain of which affected the hardness increase. It was then suggested that Si addition to pure Ti plays an important role in the hardness increase, which can be explained by the lattice strain caused by c⁄a ratio reduction, the decrease in the grain size of Ti-Si alloy, and the formation of Ti silicide at higher Si content.

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Dependence of Microstructural Evolution of Nanoindented Cu/Si Thin Films on Annealing Temperature

Woei-Shyan Lee, Tao-Hsing Chen, Chi-Feng Lin, Yu-Liang Chuang

pp. 2013-2018

DOI:

10.2320/matertrans.M2010212

抄録

The nano-mechanical properties of as-deposited Cu/Si thin films indented to a depth of 2000 nm are investigated using a nanoindentation technique. The nanoindented specimens are annealed at a temperature of either 160°C or 210°C, respectively. The microstructures of the as-deposited and annealed samples are then examined via transmission electron microscopy (TEM). The results show that both the loading and the unloading regions of the load-displacement curve are smooth and continuous, which suggests that no debonding or cracking occurs during nanoindentation. In addition, the hardness and Young’s modulus of the Cu/Si thin films are found to vary with the nanoindentation depth, and have maximum values of 2.8 GPa and 143 GPa, respectively, at the maximum indentation depth of 2000 nm. The TEM observations show that the region of the Cu/Si film beneath the indenter undergoes a phase transformation during the indentation process. In the case of the as-deposited specimens, the indentation pressure induces a completely amorphous phase within the indentation zone. For the specimens annealed at a temperature of 160°C, the amorphous nature of the microstructure within the indented zone is maintained. However, for the specimens annealed at a higher temperature of 210°C, the indentation affected zone consists of a mixture of amorphous phase and nanocrystalline phase. Copper silicide (η-Cu3Si) precipitates are observed in all of the annealed specimens. The density of the η-Cu3Si precipitates is found to increase with an increasing annealing temperature.

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Refinement of Oxide Particles by Addition of Hf in Ni-0.5 mass%Al-1 mass%Y2O3 Alloys

Qingxin Tang, Takeshi Hoshino, Shigeharu Ukai, Bin Leng, Shigenari Hayashi, Yongming Wang

pp. 2019-2024

DOI:

10.2320/matertrans.M2010163

抄録

The effect of adding minor elements, such as Ti, Mg, Zr, Ca or Hf, on the size of oxide particles was investigated in Ni-based ODS alloy, Ni-0.5 mass%Al-1 mass%Y2O3. Among these elements, Hf is the most effective at refining the oxide particles, particularly at a concentration of 0.8 mass% Hf, as verified by TEM observation and hardness measurement. X-ray diffraction measurements indicate that the formation of Y2Hf2O7 is responsible for the refinement of oxide particles. The Hf is also effective for a commercial superalloy of PM1000.

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Determination of the Mechanical Properties of Extruded Pure Magnesium During Tension–Tension Low-Cycle Fatigue Using Ultrasonic Testing

Hideki Yamagishi, Mikio Fukuhara, Akihiko Chiba

pp. 2025-2032

DOI:

10.2320/matertrans.M2010188

抄録

The mechanical behavior of extruded pure magnesium during low-cycle fatigue at room temperature was investigated using ultrasonic reflection methods with longitudinal and shear waves. The sound velocities and calculated mechanical properties, Young’s and shear moduli, decreased by a large percentage with an increased number of cycles. However, Poisson’s ratio and bulk modulus increased before a macroscopic crack occurred. The fatigue behavior was compared with the high-cycle one from a previous study. The fatigue stress amplitude was normalized using 0.2% proof strength to provide a reasonable figure for the mechanical property degradation that would accompany the development of void defect mainly caused by cleavage crack. The damage phase data were determined using optical microscopy, scanning electron microscopy, and Vickers hardness tests.

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Influence of Precipitation Behavior of Different Crystalline Phases for Embrittlement Behavior of Several Zr-Based Metallic Glasses

Ichiro Seki, Hisamichi Kimura, Kazuhiro Nakata, Akihisa Inoue

pp. 2033-2038

DOI:

10.2320/matertrans.M2010195

抄録

We have examined difference in embrittlement behavior of characteristic Zr-based metallic glasses of Zr55Cu30Al10Ni5, Zr59Cu31Al10 and Zr65Cu17.5Ni10Al7.5. All of the metallic glasses are embrittled with the precipitation of crystalline phases, and the crystalline phases for the Zr55Cu30Al10Ni5 metallic glass change in annealing temperatures of Tg-15 K and Tx-50 K. The embrittlement behavior is relating well with the behavior of the precipitated crystalline phases and is caused with step-wise process when the several kinds of crystalline phases are precipitated continuously and complexly. The precipitation of crystalline seems to relate to formation of shear band with the embrittlement behavior. Especially, CuZr2 phase causes much shear band near fracture point with bending test.

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Generalized Self-Consistent Model for Predicting Thermal Conductivity of Composites with Aligned Short Fibers

Jae-Kon Lee, Jin-Gon Kim

pp. 2039-2044

DOI:

10.2320/matertrans.M2010249

抄録

Thermal conductivities of aligned short fiber composites in the longitudinal and transverse directions are derived by extending the generalized self-consistent model proposed by Benveniste and Miloh. Their final forms are semi-explicitly expressed as functions of constituents’ thermal conductivities, fiber aspect ratio, and the aspect ratio of the matrix surrounding the fiber. The results are proved to be consistent with those of composites with extreme shapes of fillers such as sphere and continuous fiber by simply changing a confocality variable. The present results for aligned short fiber composites are compared with Wu’s upper and lower bounds to be validated. Finally, the predictions by the present model and modified Eshelby model are compared in terms of the thermal conductivity ratio of constituents, fiber aspect ratio, and fiber volume fraction and their accuracy for the predictions are evaluated by the experimental results from the literature.

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Application of Dual-Energy K-Edge Subtraction Imaging to Assessment of Heat Treatments in Al-Cu Alloys

Hiroyuki Toda, Kazuyuki Shimizu, Kentaro Uesugi, Yoshio Suzuki, Masakazu Kobayashi

pp. 2045-2048

DOI:

10.2320/matertrans.L-M2010819

抄録

Dual-energy K-edge subtraction imaging technique has been employed to analyze the spatial distribution of copper and its change in three-dimensions quantitatively during a solution treatment. In order to realize it, some preliminary investigations on the verification and assurance of accuracy and repeatability have been performed. Inhomogeneous Cu concentration distribution is revealed even after the solution treatment for a sufficiently long period of time at a high temperature in an Al-Cu alloy. The present technique has a unique potential to realize four-dimensional chemical-concentration mapping.

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Factors Influencing Tensile Ductility of OFHC Cu Having Different Ultrafine Grained Structures

Lee Ju Park, Hyung Won Kim, Chong Soo Lee, Kyung-Tae Park

pp. 2049-2055

DOI:

10.2320/matertrans.M2010089

抄録

Tensile ductility of OFHC Cu with the different ultrafine grained (UFG) structures, which were fabricated by the different routes of equal channel angular pressing (ECAP), was associated in detail with the microstructural characteristics developed by ECAP. OFHC Cu having the lamellar and equiaxed UFG structures was prepared by ECAP of routes A and Bc, respectively up to 8 and 16 passes. Their microstructures were closely examined by transmission electron microscopy and orientation image mapping. Tensile tests at room temperature were conducted on the ECAPed samples under the quasi-static condition of 10−3 s−1 and 1 s−1. Uniform elongation of the lamellar UFG samples decreased with increasing the ECAP passage while both uniform and total elongations of the equiaxed UFG samples increased. In the case of route A producing the lamellar UFG structure, the fractions of high angle grain boundaries and grains less than 0.5 μm increased significantly but an analysis revealed that the dislocation free length decreased with increasing the ECAP passage. For route Bc resulting in the equiaxed UFG structure, the fraction of high angle grain boundaries increased but the grain size distribution and the dislocation free length remained nearly unchanged with increasing the ECAP passage. From the present experiments and analyses, it was found that tensile ductility of lamellar UFG OFHC Cu is primarily controlled by the dislocation free length and that of the equiaxed one is mainly dependent on the fraction of high angle grain boundaries.

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Synthesis of Fe Based Metallic Glass–Pd Based Metallic Glass Composite by Slightly Pressured Liquid Phase Sintering

N. Yodoshi, R. Yamada, N. Morita, A. Kawasaki, R. Watanabe

pp. 2056-2062

DOI:

10.2320/matertrans.M2010197

抄録

To consolidate [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass powder to full density, a pressurized liquid phase sintering was employed, which was intended to promote densification by an enhanced wetting of a liquid phase with solid particles. Pd42.5Ni7.5P20Cu30 metallic glass powder, which has been reported to have a high glass forming ability and the lowest critical cooling rate of glass formation of 0.067 K/s, was chosen as a liquid phase component. The melting point of the Pd42.5Ni7.5P20Cu30 metallic glass alloy of 763 K is lower than the glass transition temperature of the [(Fe0.5Co0.5)0.75Si0.05B0.2]96Nb4 metallic glass alloy of 808 K. However, the wettability of this alloy with the Pd42.5Ni7.5P20Cu30 alloy was revealed to be poor. Therefore, sintering pressure was applied to the compacts to promote a viscous flow deformation of solid particles and also to enhance the intergranular permeation of the liquid phase. A specially designed micro-hot press was devised for the pressure-sintering experiment. A pseudo-wettability was observed during pressure-sintering, and the liquid phase was found to fill completely the intergranular space of the powder compact. The relative density of 64–95%, as well as the sintering structure, could be controlled by the punch displacement to squeeze out a part of the liquid phase from the compact. The compressive fracture strength of the obtained metallic glass composite was found to be as high as 2051 MPa, and the fracture was observed to be intragranular type, suggesting a good bonding in the particle-binding phase interface.

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Grain Orientation and Texture Evolution in Pure Titanium Lap Joint Produced by Friction Stir Welding

Hong Liu, Kazuhiro Nakata, Naotsugu Yamamoto, Jinsun Liao

pp. 2063-2068

DOI:

10.2320/matertrans.M2010242

抄録

Pure titanium lap joints were produced by friction stir welding, and the grain orientation and texture evolution were investigated as well as the mechanical property of the lap joint. The grain orientation changes obviously after welding, and the strong P1 texture formed in the stir zone suggests that the metal flow can be characterized by a simple shear deformation. The shear plane in the center and bottom parts of the stir zone is shown to be a spherical crown surface, which is nearly similar to the bottom shape of the probe. The vertical flow of stirred metal is slight and it may be a reason why the welding condition is narrow. The hardness in the stir zone is distinctly higher than that in the base metal due to the grain refinement after FSW, and the shear tensile strength is so high that the fracture happens at the base metal, resulting from both the hardness increase in the stir zone and the sufficient width of lap zone.

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Laser-Generation Based Imaging of Ultrasonic Wave Propagation on Welded Steel Plates and Its Application to Defect Detection

Shigeki Yashiro, Nobuyuki Toyama, Junji Takatsubo, Tetsuro Shiraishi

pp. 2069-2075

DOI:

10.2320/matertrans.M2010204

抄録

This study investigated nondestructive testing of welded steel plates by imaging ultrasonic wave propagation based on laser generation. The specimens were scanned by a pulsed laser, and the signals were received by a fixed piezoelectric transducer. A moving diagram of wave propagation from the fixed point was obtained directly from the collected signals. Wave scattering due to a weld defect (e.g., toe crack or root crack) was successfully imaged on weld specimens, and was easily recognized by visual observation in the measured moving diagrams. These experiments demonstrated the ability of the imaging technique to inspect a large area in a short time and to reliably detect a defect. Furthermore, the position-time-amplitude maps (B-scope images) were reconstructed from the moving diagram along some lines perpendicular to the defect, and the location and the size of a root crack were evaluated based on the B-scope images.

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Fabrication of Porous High-Purity Iron with Directional Pores by Continuous Zone Melting Technique

S. K. Hyun, M. Uchikoshi, K. Mimura, M. Isshiki, H. Nakajima

pp. 2076-2079

DOI:

10.2320/matertrans.M2010219

抄録

Lotus-type porous iron rods were fabricated by continuous zone melting technique under the pressure of 2.5 MPa of hydrogen, using iron with three different purities: 99.5%, 99.9% and 99.999%. It was found that the pore size in lotus iron with high purity (99.999% pure) is much larger than that in lotus iron with lower purity (99.5% and 99.9% pure), while the porosity in lotus iron with high purity is lower than that in lotus iron with lower purity. The transfer velocity does not affect the porosity in all lotus iron, but may affect the pore size; the pore diameter decreases with increasing transfer velocity. Thus, it is apparent that the purity of iron significantly affects the pore morphology and the impurities in iron serve as the nucleation sites of pores to increase the pore number density and also suppress the growth of pores due to slower diffusion of hydrogen.

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Corrosion Behavior of Magnesium with Hydroxyapatite Coatings Formed by Hydrothermal Treatment

Sachiko Hiromoto, Masanari Tomozawa

pp. 2080-2087

DOI:

10.2320/matertrans.M2010192

抄録

Corrosion resistance of magnesium alloys must be improved for their applications to orthopaedic bioabsorbable devices. Since hydroxyapatite (HAp) is chemically stable in the body and is the main component of bones, HAp coatings have been well studied to improve the corrosion resistance and osteoconductivity of magnesium alloys. In this study, highly crystallized HAp coatings were formed on pure magnesium with a single-step hydrothermal treatment using a C10H12CaN2Na2O8 solution with various pH values. Morphology of the HAp coating varied depending on the pH value. Corrosion behavior of the HAp-coated magnesium was investigated by anodic polarization, impedance and immersion tests in a simulated body fluid. It was revealed that the corrosion resistance of pure magnesium was improved more than 10 times with the HAp coatings. Stable localized corrosion was prevented with the HAp coatings although the occurrence and moderation of unstable localized corrosion appeared to take place at the defects of the HAp coatings. The initial protectiveness of the HAp coating depended on the treatment condition. During 4-day immersion, the precipitated HAp sealed the defects of the HAp coatings, resulting in the negligible release of magnesium ions regardless of the treatment conditions.

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Microstructure Evolution of Dual-Directional-Extruded Mg Alloy AZ31: An Experimental and Simulation Study

Liwei Lu, Tianmo Liu, Yong Chen, Liguang Wang, Zhongchang Wang

pp. 2088-2093

DOI:

10.2320/matertrans.M2010198

抄録

Combining the finite-element analytic technique with the microscopic observation, we have investigated microstructures and stress-strain distributions of the Mg alloys AZ31 processed by a new extrusion method, dual-directional extrusion. We have found that grains in the extruded alloys are refined significantly, which is attributed to the deformation-induced grain subdivision and dynamic recrystallization. Such well refined grains play a critical role in the enhancement of the long-standing poor mechanical properties of the relevant engineering Mg alloys AZ31.

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Hybridization of FePt/ZnS Nanocore-Shell Structure with DNAs of Different Sequences

Ho Chang, Sheng-hong Wu

pp. 2094-2098

DOI:

10.2320/matertrans.M2010181

抄録

This study attempts to develop a nanocore-shell structure with photomagnetic nature. The structure is then allowed undergo conjugation reaction with the DNAs of different sequences so that it can be applied to target-based drug therapy and biomedical-related areas. First of all, iron platinum (FePt) magnetic nanofluid with an average particle size of 2–3 nm is prepared by a chemical method. After that, zinc sulfide with a fluorescent nature is used to modify the surface of the nanoparticles so as to form a core-shell structure. The shell thickness in this kind of core-shell structure can be controlled at 5–10 nm by a fabrication process. The FePt nanoparticles being modified by zinc sulfide not only can enhance the dispersed suspension of nanoparticles, but also have good optical nature. The prepared nanocore-shell structured particles are conjugated with two groups of DNA of different sequences respectively. Nanoparticles before and after being conjugated and the structure of DNA are not deteriorated or altered because of the principle of positive and negative charges attraction. Conjugation efficiency is 64% and 77% respectively. A bridge DNA and two groups of DNA of different sequences are conjugated. Moreover, the occurrence of hybridization is proven through the analyses of the UV-vis spectrum. Analyses by fluorescence spectrometer show that the luminescence for modified ZnS and nanoparticles after hybridization respectively increases significantly.

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Fine-Sized Etching of Flexible Substrates Using Nano Particle Deposition System (NPDS)

Woojin Song, Yang-Hee Kim, Min-Saeng Kim, Sung-Hoon Ahn, Caroline Sunyong Lee

pp. 2099-2103

DOI:

10.2320/matertrans.M2010221

抄録

Nano Particle Deposition System (NPDS) was used to etch flexible substrates, such as SU-8 and indium tin oxide (ITO) substrates using nickel powders using micronozzles. The stand-off distance (SoD) was changed in order to find out the optimal distance on etching behavior. The results showed that the etching capability was influenced by the SoD and the types of substrate. Especially, the etching depth of the substrate was the largest when the SoD was 500 μm. This phenomenon related to the variation of SoD can be explained by the flow behavior at which the powder-gas mixture injected from the nozzle where the particles are most highly accelerated at that point. The etching capability is also affected by the types of substrates. Especially, the hardness of the substrate mainly determines the etching depth. The result suggests that the NPDS gives an alternative way of micromachining suitable for fine-sized etching on flexible substrates.

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Extraction of Plastic Properties of Aluminum Single Crystal Using Berkovich Indentation

Jui-Chao Kuo, I-Hua Huang

pp. 2104-2108

DOI:

10.2320/matertrans.M2010132

抄録

An alternative to extract representative stress-strain curves from a set of indentation data measured with the Berkovich indenter is developed in this study. The “yield” depth in the representative strain is identified by a double logarithm plot of indentation data, and it enables the establishment of a representative stress-strain curve. Comprehensive analyses are demonstrated using the new method proposed to capture the yield strength and the strain hardening exponent for an aluminum single crystal.

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A Comparison of the Effects of Pre-ECAR and Post-ECAR Aging on Microstructure and Strengthening in 7050 Al Alloy Sheet

Jun-Hyun Han

pp. 2109-2112

DOI:

10.2320/matertrans.M2010236

抄録

Effects of the post-ECAR aging treatment on the microstructural evolution and strengthening were compared with those of the pre-ECAR aging for a wrought 7050 Al alloy sheet that was subjected to severe plastic deformation (SPD) through multiple equal channel angular rolling (ECAR). The post-ECAR aging treatment led to the formation of a nanocrystalline structure with a grain size of ∼100 nm through the precipitation of fine MgZn2 particles during post-ECAR aging, which pinned the grain boundary motion, and more effectively strengthened the 7050 Al alloy than the pre-ECAR aging.

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Effects of the Edm Combined Ultrasonic Vibration on the Machining Properties of Si3N4

Chaiya Praneetpongrung, Yasushi Fukuzawa, Shigeru Nagasawa, Ken Yamashita

pp. 2113-2120

DOI:

10.2320/matertrans.M2010194

抄録

The authors have previously performed numerous experiments on the machining of insulating materials using the assisting electrode method. However, the machining performance was inferior to that of the electrically conductive materials. To overcome this inferiority, for this research, an ultrasonic vibration system was combined with electrical discharge machining (USEDM) and applied with the assisting electrode method. Rotational machining was also added. A cylindrical copper tungsten bar was used as the electrode material for machining the sintered Si3N4 insulating ceramic. The effects of the electrode polarities, the effects of the amplitude on machining performance, the generation of a conductive layer and the discharge waveforms were investigated. The results were then compared to the conventional electrical discharge machining (normal EDM). The finishing process was performed by combining the ultrasonic vibration and various abrasive suspensions to remove the conductive layers and the craters. The results show that the material removal rate improved by a factor of approximately two over the normal EDM, and the surface roughness increased when the ultrasonic vibration was applied. The conductive layers and the craters were removed by the ultrasonic vibration using an abrasive (US+abrasive) method. The surface roughness of the workpiece was greatly improved by using the proposed method.

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Quantitative Analysis of Titanium Ions in the Equilibrium with Metallic Titanium in NaCl-KCl Equimolar Molten Salt

Hidehiro Sekimoto, Yoshitaro Nose, Tetsuya Uda, Hiroyuki Sugimura

pp. 2121-2124

DOI:

10.2320/matertrans.M2010238

抄録

The equilibrium between titanium ions (Ti2+, Ti3+) and metallic titanium (Ti) in NaCl-KCl equimolar molten salt was investigated using TiCl3 and Ti. Equilibrium experiments were carried out in metal container of titanium or stainless-steel at 740°C. The concentrations of titanium ions were determined by chemical methods consisting of continuous three steps. Ti2+ and Ti were quantitated by H2 evolution method. Ti3+ was quantitated with titration by Fe3+. As the result, the concentration of Ti2+ was higher than that of Ti3+. The concentration quotient, Kc=(xTi3+)2⁄(xTi2+)3, depends on the concentration of Ti2+. The value of Kc at 740°C is recommended to be 5.9 at xTi2+=0.02 and 2.6 at xTi2+=0.07 respectively.

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Electrical Wire Explosion of Cr-Coated Ti Wire in N2 Gas

Wonbaek Kim, Sujeong Lee, Chang-yul Suh, Sung-wook Cho, Taegong Ryu, Je-shin Park, In-Jin Shon

pp. 2125-2128

DOI:

10.2320/matertrans.M2010205

抄録

Cr-coated Ti wire was electrically exploded in N2 gas. The diameter of Ti wire was 0.289 mm and the thickness of Cr coating was 0.033 mm, which corresponds to the average composition of about 25 at% Cr. X-ray diffraction and FE-TEM study revealed that the explosion products consisted of cube-shaped TiN, sphere-shaped Cr2N, and clusters of extremely fine particles. The average particle size of TiN and Cr2N was about 35 and 38 nanometers, respectively. The size of the fine particles was small as a few nanometers and clustered heavily. Therefore, it was not possible to examine individually. The particles contained about 28 at% Cr. In some part of the high resolution TEM image, cubic structure could be recognized. The lattice parameter of the particles calculated assuming cubic structure was smaller than TiN and larger than CrN. As a result, it was concluded that the fine particles are (Ti,Cr)N.

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Rapid Consolidation of Nanostructured TiCu Compound by High Frequency Induction Heating and Its Mechanical Properties

In-Jin Shon, Na-Ri Kim, Song-Lee Du, In-Yoong Ko, Sung-Wook Cho, Wonbaek Kim

pp. 2129-2131

DOI:

10.2320/matertrans.M2010251

抄録

Nanosized TiCu powders were synthesized by high energy ball milling of micron-sized Ti and Cu powders. Dense TiCu could be consolidated by high frequency induction sintering method within 1 min using both horizontally milled elemental powders of Ti+Cu and mechanically synthesized powders of TiCu. The consolidation was accomplished under the combined effect of induced current and applied mechanical pressure. The grain size, sintering behavior and hardness of TiCu sintered from both powders were examined.

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