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MATERIALS TRANSACTIONS Vol. 53 (2012), No. 10

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. 53 (2012), No. 10

Morphology and Magnetic Properties of Platelet γ-Fe2O3 Particles

Mikio Kishimoto, Tatsuya Oda, Yusuke Ohara, Ryoichi Miyamoto, Yoshimasa Akashi, Hideto Yanagihara, Nobuhiro Ohkochi, Eiji Kita

pp. 1711-1715

DOI:

10.2320/matertrans.M2012195

抄録

The morphology and magnetic properties of platelet α-FeOOH and γ-Fe2O3 particles were studied to use hysteresis-loss heating of ferromagnetic particles in magnetic hyperthermia or thermoablation. The platelet α-FeOOH particles were prepared through the formation of a precipitant followed by the hydrothermal treatment of the precipitant. The shape of the α-FeOOH particles changed from elongated to platelet-like depending on the quantity of ethanolamine in the precipitant. The size of the platelet α-FeOOH particles was reduced from 90–120 to 40–60 nm as the precipitant temperature was lowered in the range from 5 to −3°C. The formation of dimples was observed during the dehydrating process from α-FeOOH to α-Fe2O3, and was confirmed from the increase in the BET surface area of the α-Fe2O3 particles. The particle size and the coercive forces of the platelet γ-Fe2O3 particles were in the range 30–100 nm and 7.6 kA/m (96 Oe) to13.5 kA/m (169 Oe), respectively.

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Synthesis of Ni Carbide Nanoparticles with Ni3C-Type Structure in Polyol Solution Containing Dispersant

Shun Fujieda, Kozo Shinoda, Shigeru Suzuki, Balachandran Jeyadevan

pp. 1716-1720

DOI:

10.2320/matertrans.M2012160

抄録

Nanoparticles of Ni carbide of about 50 nm in diameter were synthesized by the reduction of Ni salt in a polyol solution in the presence of polyvinylpyrrolidone (PVP). It was found that the aggregation of nanoparticles was suppressed when PVP was added to the polyol solution during synthesis. Diffraction peaks of the fcc and hexagonal structures were observed for the specimen synthesized without PVP. On the other hand, no peaks assigned to the fcc structure and no spontaneous magnetization were observed for the specimen synthesized with 50 g/L PVP, although pure bulk Ni are fcc structure and ferromagnetic at room temperature. Additionally, small peaks were observed in the X-ray diffraction pattern at 2θ = 26.2, 35.7 and 47.8°, originated not from the impurity phase but from the hexagonal phase. The specimen synthesized with 50 g/L PVP was fundamentally identified as Ni carbide with a Ni3C-type structure, as small peaks mentioned above were assigned to super-lattice peaks. The structure parameters of the Ni carbide were refined by Rietveld analysis. It is concluded that the formation of the Ni carbide nanoparticles with Ni3C-type structure in the polyol solution is enhanced by the addition of PVP.

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Thermal and Electrical Transport Properties of Zr-Based Bulk Metallic Glassy Alloys with High Glass-Forming Ability

Rie Y. Umetsu, Rong Tu, Takashi Goto

pp. 1721-1725

DOI:

10.2320/matertrans.M2012163

抄録

Thermal and electrical transport properties, such as thermal diffusivity, the electrical resistivity and thermopower of the Zr-based bulk metallic glassy (BMG) alloys of Zr42Cu42Ag8Al8 and Zr55Al10Cu35−xNix (x = 0, 5 and 10) with high glass-forming ability were investigated. Thermal diffusivity is comparatively low at about 2 × 10−6 m2 s−1, reflecting the aperiodic crystal structure of the BMG, whereas it becomes higher and depends on the alloy compositions after their crystallization. The phonon contribution to the thermal conductivity of the BMG alloys is thought to be small, based on a comparison with the estimated value of the electronic contribution to the thermal conductivity from the Wiedemann–Franz law. The thermopower of the present Zr-based BMG alloys shows a small positive value around room temperature, which is a general feature of nonmagnetic amorphous alloys.

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Acoustic Emission Measurements on Palladium Hydrogenation Process by Using New Gas Pressure Cell

Shuji Harada, Takanori Otake, Jiaxiang Piao

pp. 1726-1731

DOI:

10.2320/matertrans.M2012177

抄録

A hydrogenation process of palladium has been studied by acoustic emission (AE) methods with a new gas pressure cell. By using noble Ar gas, the AE events were observed intermittently for the stepwise pressurization. On the repetition of the re-pressurization, the AE events showed the Kaiser effect, i.e., a dislocation motion induced effect. The typical power spectrum of AE signal by noble gas demonstrated the fundamental signal modes of 250 and 550 kHz. By the hydrogen gas re-pressurization, the characteristic AE behavior was recognized as following: (1) The continuous AE events were observed by the stepwise pressurization, (2) in the early stage of primary H solid solution of Pd, the fundamental AE modes were measured as 250 and 550 kHz, (3) in the hydride formation stage, the continuous AE events were also observed, and the typical AE mode was changed to 250 kHz mainly. The hydride formation mechanism was discussed on the basis of the dislocation theory.

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Effect of Serine and Arginine on the Phase Transition from Amorphous CaCO3 and CaCO3·6H2O to Calcite Film

Seung-Woo Lee, Yong-Il Kim, Kyubock Lee, Jun-Hwan Bang, Chi-Wan Jun, Young-Nam Jang

pp. 1732-1738

DOI:

10.2320/matertrans.M2012164

抄録

Calcium carbonate, ubiquitous throughout nature, is one of the most biologically significant minerals. It is known that the organic matrix of biological materials controls the phase transition of CaCO3, but much remains undiscovered regarding its pathway from an amorphous to crystalline solid. In this study, examination of the initial formation of CaCO3 films has been proposed as a new methodology to identify the phase transition of CaCO3. We have identified a significant role for both serine and arginine in the synthesis of CaCO3 and have found them to be important for the stabilization of amorphous calcium carbonate and CaCO3·6H2O. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy have been used for the identification of crystalline phase and surface structure. This study presents information useful for understanding the phase transition of CaCO3 and the function of organic molecules in the formation of biological materials.

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Metastable Phases in Al80Fe10Ti5Ni5 Alloy Fabricated by Non-Equilibrium Processes

M. Tavoosi, F. Karimzadeh, M. H. Enayati, H. S. Kim

pp. 1739-1743

DOI:

10.2320/matertrans.M2012061

抄録

In this study, the metastable phases that can be formed in Al80Fe10Ti5Ni5 alloy by melt spinning and mechanical alloying techniques have been investigated. The produced samples were examined by X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The results showed that the phases in Al80Fe10Ti5Ni5 alloy during rapid solidification are Al13(Fe,Ni)4, Al3Ti and amorphous phases. The formation of equilibrium phases was completely suppressed by mechanical alloying. It is of note that supersaturated solid solution, decagonal, and amorphous phases are three separated phases that can be formed during mechanical alloying of an Al–10%Fe–5%Ni–5%Ti powder mixture.

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Effects of Fe, W and Mo on Kinetics of Discontinuous Precipitation in the Ni–Cr System

Shigeki Ueta, Masahiro Hida, Masanori Kajihara

pp. 1744-1752

DOI:

10.2320/matertrans.M2012132

抄録

The effects of Fe, W and Mo on the kinetics of discontinuous precipitation in the Ni–Cr system were experimentally examined using a binary Ni–38Cr alloy and ternary Ni–38Cr–0.9Fe, Ni–38Cr–3.2W and Ni–38Cr–1.7Mo alloys. These alloys were homogenized at 1423 K for 3 h, solution treated at 1423 K for 1 h, and then isothermally annealed in the temperature range of 873–1023 K for various times up to 2300 h. Due to the solution heat treatment, all the alloys show the polycrystalline single-phase microstructure of the Ni-rich solid-solution (γ) phase with the face-centered cubic structure. During isothermal annealing, however, the cell of the lamellar microstructure consisting of the γ phase and the Cr-rich solid-solution (α) phase with the body-centered cubic structure is formed along the grain boundary of the γ matrix and then grows into the γ matrix. At each annealing temperature, the migration distance of the moving cell boundary is proportional to the annealing time. Hence, the growth rate of the cell is constant independent of the annealing time. The growth rate and the interlamellar spacing of the cell almost monotonically increase with increasing annealing temperature at 873–1023 K. The cell growth is decelerated by W and Mo but not by Fe. The deceleration is more remarkable for Mo than for W. A kinetic model for the binary discontinuous precipitation controlled by boundary diffusion was used to analyze quantitatively the experimental result. According to the analysis, W and Mo retard the boundary diffusion of Cr along the moving cell boundary, but Fe slightly hastens that. Such influence of the alloying component on the boundary diffusion is ascribable to the thermodynamic interaction between Cr and the alloying component in the moving cell boundary. As a consequence, it is concluded that the retardation of the Cr boundary diffusion causes the deceleration of the cell growth.

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Grain Boundary Related Deformation in ODS Ferritic Steel during Creep Test

Yoshito Sugino, Shigeharu Ukai, Bin Leng, Naoko Oono, Shigenari Hayashi, Takeji Kaito, Satoshi Ohtsuka

pp. 1753-1757

DOI:

10.2320/matertrans.M2012143

抄録

Oxide dispersion strengthened (ODS) ferritic steel developed as a fast breeder reactor fuel cladding is an advanced heat-resistant steel, and its high-temperature strength depends on not only transgranular deformation but also intergranular deformation. The objective of this study is to elucidate the grain boundary deformation process using 15CrODS ferritic steel. From the double logarithm plot for stress and strain rate at 800°C, the stress exponent n becomes over 10, and the real strain rate is an order of 105 lower than that which suggests that the simple grain boundary sliding. The serration structure, which is aggregation of micro-cracks perpendicular to the stress axis, was clearly observed along coincident site lattice boundaries. Also, sub-grains are produced along grain boundaries. From these observations, the localized deformation near grain boundary is considered to be the dominant deformation process of 15CrODS ferritic steel.

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Dynamic Shear Properties of Alloy 718 over Wide Temperature Range

Woei-Shyan Lee, Chi-Feng Lin, Tao-Hsing Chen, Chi-Sheng Huang

pp. 1758-1764

DOI:

10.2320/matertrans.M2012073

抄録

In this study, a split Hopkinson torsional bar was utilised to study the dynamic shear deformation behaviour of Alloy 718 at shear strain rates of 1000, 1500 and 3200 s−1 and temperatures of −150, 25 and 300°C. It was found that the mechanical behaviour of Alloy 718 is sensitive to both the strain rate and the temperature. The yield shear stress and work hardening coefficient increased with increasing strain rate, but decreased with increasing temperature. In addition, the fracture shear strain increased with increasing strain rate and temperature. The strain rate sensitivity and temperature sensitivity increased with increasing strain and strain rate, but decreased with increasing temperature. It was found that the high strain rate plastic deformation of Alloy 718 alloy can be adequately described using the Kobayashi and Dodd constitutive equation. Finally, the fracture surfaces were found to contain multiple dimple-like features. The dimple density increased with increasing strain rate and temperature. Thus, it was inferred that the ductility of Alloy 718 increases at higher strain rates and temperatures.

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Fabrication of Ultrafine Nanoporous Copper by the Minor Addition of Gold

Zhenhua Dan, Fengxiang Qin, Yu Sugawara, Izumi Muto, Nobuyoshi Hara

pp. 1765-1769

DOI:

10.2320/matertrans.MAW201204

抄録

Ultrafine nanoporous Cu was successfully fabricated through the dealloying of amorphous Ti60Cu40−xAux (x = 0, 1, 2 at%) ribbon alloys in 0.65 M HF solution under free immersion conditions. A bicontinuous nanoporous structure of Cu formed on Ti60Cu40, Ti60Cu39Au1 and Ti60Cu38Au2 ribbons with pore sizes of 134, 8.9 and 7.4 nm, respectively. The pore size of the nanoporous Cu dealloyed from Au-added alloys was more than one order smaller than that of the Ti–Cu alloy, which resulted from the 5-order decrease in the surface diffusivity through alloying of Au into Ti60Cu40 ribbons. The Au content increased rapidly during the dealloying process and eventually formed binary Cu–Au solid solution and Au nanoparticles. Modifying the surface diffusivity by adding Au made it possible for the formation of the ultrafine nanoporous Cu structure.

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A Green Approach to Synthesis of Nanoparticles of Sn–3.0Ag–0.5Cu Lead-Free Solder Alloy

Siu-kwong Pang, Kam-chuen Yung

pp. 1770-1774

DOI:

10.2320/matertrans.M2012112

抄録

Sn–3.0Ag–0.5Cu nanoparticles can provide a potential solution to the high soldering temperature problem of lead-free solder alloy because the nanosize effect can depress the melting temperature. In this paper, a green approach to the synthesis of Sn–3.0Ag–0.5Cu nanoparticles by chemical reduction at room temperature is reported. A safe organic solvent, ethanol, was used to prevent the formation of tin oxide during synthesis without the help of capping agents and N2 purging. Vigorous stirring instead of the use of capping agents was applied to the reaction mixture to reduce agglomeration of particles during the reaction time. Owing to not having capping agents on the nanoparticles and no detection of tin oxide, the subsequent steps for eliminating them are not necessary. Ag3Sn revealed by the XRD pattern and the electron diffraction pattern confirmed the successful alloying of Sn and Ag during synthesis. The TEM image showed that the nanoparticles were composed of a crystalline core embedded by an amorphous matrix. The average particle diameter was 53.3 nm with a standard deviation of 8.9 nm. An onset melting temperature of 187.3°C and a peak melting temperature of 212.7°C were achieved. This simple, safe and environmentally friendly method can reduce the production cost of nanosolder and may be applicable to the synthesis of other metal nanoparticles.

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Effects of Injection Speed and Fraction Solid on Tensile Strength in Semisolid Injection Molding of AZ91D Magnesium Alloy

Yuichiro Murakami, Kenji Miwa, Naoki Omura, Shuji Tada

pp. 1775-1781

DOI:

10.2320/matertrans.F-M2012822

抄録

Semisolid injection molding is expected to be increasingly utilized as a forming process applicable to highly flammable magnesium alloys, since it can be carried out at temperatures lower than those of die casting. In this study, we investigated the effects of molding conditions on the tensile strength and internal casting defects of AZ91D magnesium alloy. Semisolid injection molding was conducted at injection speeds of 220, 300 and 400 mm·s−1 and fraction solids of 0.0, 0.3, 0.4 and 0.5. Whereas the volume fraction of casting defects decreased together with the decrease of injection speed, the mechanical strength reached a maximum at an injection speed of 300 mm·s−1. The investigation results show that in the solidification microstructure, α-Mg and β-Mg17Al12 phases, which were liquid during injection, were refined at higher injection speeds, suggesting that the tensile strength increases together with the injection speed if there are no casting defects. This trend might be due to the increased heat transfer coefficient between the mold and the slurry from the higher flow rate. On the other hand, the volume fraction of casting defects increased together with injection speed, and as a result the tensile strength deteriorated. When the injection speed was increased, the effects of decreased strength due to the increase in the volume fraction of casting defects counterbalanced the effects of increased strength due to the refinement of α-Mg + β-Mg17Al12 mixed phase. For this reason, the mechanical strength is considered to reach a maximum at an injection speed of 300 mm·s−1. Thus, we demonstrated that the tensile strength of semisolid products is affected not only by the volume fraction of casting defects, but also by the microstructure of the residual mixed phase precipitated, which is refined by increasing the injection speed.

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Inverse Problem for Shape Reconstruction of Plate-Thinning by Guided SH-Waves

Bin Wang, Sohichi Hirose

pp. 1782-1789

DOI:

10.2320/matertrans.I-M2012823

抄録

In this paper, a new method for shape reconstruction of local plate thinning from reflection coefficients of guided SH-waves, based on guided wave scattering theory, is presented. The Green’s function for the SH-wave problem is used to express the reflected wave field in an integral form in terms of the surface shape of flaw and the total wave displacement. By introducing the Born approximation and the far-field approximation into the integral form of the reflected wave, the depth of plate thinning is obtained as a function of the horizontal coordinate by performing the inverse Fourier transform of the reflection coefficients at various frequencies. Numerical examples are given and the accuracy of proposed inverse approach is discussed by means of parametric comparisons for different wave modes, frequency ranges and various thinning shapes.

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Fabrication of Porous Aluminum Alloy with Aligned Unidirectional Pores by Dipping Pipes in Base Metal Melt

Junichi Ichikawa, Shinsuke Suzuki, Tatsuro Hayashida, Ryosuke Yahara, Hideo Nakae

pp. 1790-1794

DOI:

10.2320/matertrans.MAW201211

抄録

A pure aluminum pipe was dipped into Al–13 mass%Si melt at 873 K. After holding time, the specimen was cooled and solidified. With holding time shorter than 360 s, the pipe was connected with the base metal without melting of the inner wall. Aligned 37 pipes with internal diameter of 3 mm were dipped into the base metal, also. Even the distance between the pipes was as small as 0.5 mm, the melt of the base metal penetrated among the pipes. The result of the EPMA analysis showed metallic bonding between the pipe and the base metal by Si diffused into the pure aluminum pipe side. It became possible by this method to fabricate porous aluminum alloys with aligned unidirectional pores by controlling the porosity, pore diameter and pore distribution.

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Strain Heterogeneity, Recovery and Recrystallization of Nanostructured ODS Alloys during Cold Deformation

Chun-Liang Chen, You-Ming Dong, Shu-Mei Fu

pp. 1795-1800

DOI:

10.2320/matertrans.M2012197

抄録

Nanostructured ferritic oxide dispersion strengthened (ODS) alloys are promising materials for high-temperature applications as they contain uniform nano-oxide dispersoids, which exert a Zener pinning force to inhibit dislocation movement and retard the recrystallization process. Recrystallization behaviour of iron-based ODS alloys is complicated and strongly depends on the deformed state of severely strained materials. In the present work, the effect of cold rolling followed by annealing on the development of recrystallized grain structures was investigated. A different level of cold deformation introduces the heterogeneous distribution of stored energy in the material. Inhomogeneous microstructure stimulates nucleation of recrystallization. This paper investigates variations of stored energy and dislocation density with varying levels of strain using DSC and TEM. The results indicate that heavy deformation alters the amount of stored energy and the number of effective nuclei and therefore it affects the rate of recrystallization. In addition, the change in stored energy is related to the number and configuration of the dislocations in the material.

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Influence of Addition of Alumina Nanoparticles on Thermoelectric Properties of La-Filled Skutterudite CoSb3 Compounds

Takashi Itoh, Masaki Matsuhara

pp. 1801-1805

DOI:

10.2320/matertrans.E-M2012821

抄録

The CoSb3-based compound is a promising thermoelectric material useful in the temperature range of 600–900 K. It, however, has a higher thermal conductivity. Thus, reducing the thermal conductivity causes improvement of the thermoelectric performance. In this work, we tried to reduce the thermal conductivity by both filling La and dispersing alumina nanoparticles (ANPs) into the compound. The raw powders of LaSb, Co, Ni, Sb and Te were prepared. The n-type La-filled compound was synthesized from the raw powders using a planetary ball mill. Then, ANPs were added to the combined powder and further mixed using the planetary ball milling. The mixture was sintered by a pulse-discharge sintering method. The combining phases of the samples were characterized by X-ray diffraction analysis. The thermoelectric properties were measured for the samples. Influence of addition of ANPs on the properties was studied. Adding 0.05 mass% ANPs reduced the thermal conductivity. The sample added 0.5 mass% or more ANPs increased both the electrical resistivity and the thermal conductivity. As a result, the sample added 0.05 mass% ANPs had the maximum performance of ZT = 1.15 at 873 K.

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Solidification Thickness Dependent Electrostriction of Polyurethane Films

Masae Kanda, Kaori Yuse, Benoit Guiffard, Laurent Lebrun, Yoshitake Nishi, Daniel Guyomar

pp. 1806-1809

DOI:

10.2320/matertrans.MAW201208

抄録

To obtain large electrostriction (Smax) at low electric filed (Emax), a dependence of the solidification thickness (L) on Smax was investigated for polyurethane films. Thinning the films remarkably enhanced Smax at high Emax at 20 MV/m, whereas thick films apparently exhibited higher Smax at low Emax of less than 3 MV/m. The L dependent Smax from 5.01% for 140 µm thickness to 30.99% for 28 µm thickness exhibited linear relationship of pure polyurethane. Considering crystalline volume fraction and crystalline periodicity, the L dependent Smax was explained.

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Formation of Through-Silicon-Vias Using Pressure Infiltration of Molten Tin

Min-Young Kim, Sung-Kyu Kim, Tae-Sung Oh

pp. 1810-1815

DOI:

10.2320/matertrans.M2012158

抄録

Formation of through-silicon-via (TSV) was examined by pressure infiltration of molten Sn into Si via-holes with variations of the infiltration pressure, infiltration time and via-hole size. Contrary to the conventional Cu TSV process which requires complicate and long Cu electroplating, the method using pressure infiltration of molten Sn is fast enough to complete via-filling within 5 s regardless of the via-hole size. The ratio of the unfilled volume to the initial volume of a via-hole versus the external infiltration pressure well satisfied the Boyle’s law. TSVs of different diameters in a wide range of 10–200 µm could be easily formed at once by infiltration of molten Sn at an external pressure of 4 MPa for 5 s.

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Recovery of Mechanical Property on Nano-Co Particles Dispersed Al2O3 via High-Temperature Oxidation

Daisuke Maruoka, Tsuyoshi Itaya, Tai Misaki, Makoto Nanko

pp. 1816-1821

DOI:

10.2320/matertrans.MAW201202

抄録

Recovery of mechanical strength in α-Al2O3-based hybrid materials with 5 vol% dispersed nano-Co particles was carried out via a thermal oxidation process. Three Vickers indentations were conducted at 49 N for 10 s in air to introduce pre-cracks on the sample surface. The bending strengths of as-sintered and as-cracked samples were approximately 710 and 159 MPa, respectively. Bending strength value increased to 636 MPa when as-cracked specimens with introduced surface cracks were heat-treated at 1200°C for 6 h in air. Surface cracks disappeared completely through formation of the oxidation product, CoAl2O4. Specimens heat-treated at 1200°C for 6 h in air did not fracture through the surface cracks introduced by the Vickers indentation during three-point bending test. Specimens heat-treated at 1200°C for 6 h in an Ar–10%H2 gas flow, in which metallic Co is stable, were broken along the surface crack introduced by the Vickers indentation. The recovery of mechanical strength was obtained by surface cracks filling with CoAl2O4.

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Phase Field Simulation of the Sub-Block Microstructure in Lath Martensitic Steels

Zhenhua Cong, Yoshinori Murata, Yuhki Tsukada, Toshiyuki Koyama

pp. 1822-1825

DOI:

10.2320/matertrans.M2012250

抄録

The formation mechanism of the sub-block microstructure in lath martensite is explained by a two-type-slip deformation (TTSD) model. To simulate the sub-block structure morphology, the TTSD model is coupled with the phase field method resulting in the elastoplastic phase field model. The sub-block structure of lath martensite in Fe–0.1C mass% steel is simulated in 3-D by employing the elastoplastic phase field model, which helps with the understanding of the formation mechanism of the sub-block structure in lath martensite.

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Development of Ductile B2-Type Fe–Co Based Alloys

Mitsuhiro Matsuda, Kozo Yamashita, Ryutaro Sago, Kenji Akamine, Kazuki Takashima, Minoru Nishida

pp. 1826-1828

DOI:

10.2320/matertrans.M2012205

抄録

We investigated the mechanical properties of B2-type Fe–Co based alloys containing minor amounts of Ni or Pd to improve their tensile ductility at room temperature. The yield and tensile stresses of the new alloys showed remarkable increases. Fe–Co–Ni alloys showed high total elongation of over 10% at room temperature. Co50Fe40Pd10 alloy displayed a tensile strength of 1250 MPa and a high total elongation of 16%. The substitution of Ni or Pd into Fe–Co based alloys is therefore an extremely effective means of improving their room-temperature ductility.

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