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MATERIALS TRANSACTIONS Vol. 50 (2009), No. 2

ISIJ International
belloff
ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678
Publisher: The Japan Institute of Metals and Materials

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MATERIALS TRANSACTIONS Vol. 50 (2009), No. 2

High Temperature Grain Boundary Plasticity in Ceramics

Taketo Sakuma, Hidehiro Yoshida

pp. 229-235

DOI:

10.2320/matertrans.MOV2008254

Abstract

Superplasticity in fine-grained materials has been generally analyzed on the basis of their experimental strain rate-flow stress relationship. The phenomenological analysis based on a constitutive equation is effective for understanding the overall flow and fracture behavior and to speculate on the rate-controlling mechanism of superplastic flow. However, it has been recently pointed out that the high temperature superplastic flow and failure in ceramics is significantly influenced by the atomic structure and chemistry of grain boundary. Such phenomenon cannot be explained based on the classical phenomenological analysis. Our research group has therefore proposed to establish a new research field, grain boundary plasticity, to describe the superplastic deformation related to the grain boundary quantum structure. This paper aims to point out the importance of the quantum structure analysis of the grain boundary to understand the high temperature plasticity in ceramics.

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High Temperature Grain Boundary Plasticity in Ceramics

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Non-Equilibrium Thermodynamic Theory of 4-Component Lead-Free Solder

Kenichiro Suetsugu, Atsushi Yamaguchi, Kazumi Matsushige, Toshihisa Horiuchi

pp. 236-244

DOI:

10.2320/matertrans.MRA2008094

Abstract

We investigated non-equilibrium thermodynamic theories for 4-component lead-free solders based on classical thermodynamics using one-dimensional oscillator model to obtain their specific heat and the coefficient of linear thermal expansion.
We analyzed In and Sn reactions in SnAgBiIn solder as a representative lead-free material and experimentally obtained an Nc factor for expressing the state of non-equilibrium from the formation of metallic compounds. It was considered that the state of equilibrium did not occur experimentally, and that metallic compounds InSn4 formed in some parts of the 2-component eutectic solder. We then built a theory as one-dimensional oscillator model by approximating this Nc factor, as a representation of the non-equilibrium behavior of high temperature lead-free solder. Using this model representing the non-equilibrium state, the correlation between specific heat and coefficient of linear thermal expansion was derived theoretically, which was found to be linear in mathematical studies. In fact, it was learned that experimental results of this correlation also tended to be linear. This suggested that the derived non-equilibrium theory was practically useful, moreover other thermodynamic characteristics could be analyzed by this non-equilibrium thermodynamic theory using one-dimensional oscillator model.

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Non-Equilibrium Thermodynamic Theory of 4-Component Lead-Free Solder

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Dielectric Properties of Ba1−xCaxTi2O5 Prepared by Arc Melting

Xinyan Yue, Rong Tu, Takashi Goto

pp. 245-248

DOI:

10.2320/matertrans.MRA2008333

Abstract

b-axis-oriented CaO substituted polycrystalline BaTi2O5, Ba1−xCaxTi2O5 (BCT2, x=0 to 0.10), was prepared by arc melting. The dielectric property of BCT2 was investigated by an AC impedance method. The lattice parameters of BCT2 decreased with increasing CaO content in the range up to around x=0.08. The remnant polarization (Pr) and coercive electric field (Ec) of polycrystalline BCT2 at x=0.08 were 1.6×10−2 Cm−2 and 0.4×106 Vm−1, respectively. The Pr of polycrystalline BCT2 was larger than that of BaTi2O5 (BT2, Pr=0.9×10−2 Cm−2), while the Ec of BCT2 was smaller than that of polycrystalline BT2 (Ec=0.7×106 Vm−1). The permittivity of BCT2 showed the maximum value of 4950 at x=0.02 and a Curie temperature (Tc) of 736 K. The Tc of BCT2 decreased from 750 to 665 K with increasing CaO content from 0 to 0.10.

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Dielectric Properties of Ba1−xCaxTi2O5 Prepared by Arc Melting

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Theory of Instability Phenomena and Its Application to Melting of Cubic Metals

Yutaka Aikawa, Katsuhiko Fujii

pp. 249-253

DOI:

10.2320/matertrans.MRA2008229

Abstract

Melting temperature Tm of cubic metals is revaluated using the variation method, where anharmonicity of trial potential as well as crystal one is taken into account. The value of Tm is proportional to the dissociation energy D, and to the number of interactions between atoms which is properly estimated by using normal coordinates instead of each atomic displacement. We obtain the results which agree with the trend of the experiments that the straight line of Tm∝D for body centered cubic (BCC) is upper side than that for face centered cubic (FCC).

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Theory of Instability Phenomena and Its Application to Melting of Cubic Metals

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Evaluation of Phase Diagrams for the Al2O3-CaO-SrO System by In-Situ Observation Using Confocal Laser Microscope

Tomonori Kuroki, Yoshitoshi Saito, Taijiro Matsui, Kazuki Morita

pp. 254-260

DOI:

10.2320/matertrans.MRA2008352

Abstract

Phase relations for the Al2O3-CaO-SrO ternary oxide system were clarified. This ternary system has a high liquidus temperature in most compositions and contained many types of solid solutions with a wide composition range. Hence, it was difficult to predict the precise phase diagrams by using conventional techniques such as chemical equilibration method. In fact, the phase diagram reported formerly contains a considerable amount of prediction and surmise and is far from satisfaction. In the present study, an in-situ observation at increasing temperatures was performed using a high temperature observational system that included a confocal scanning laser microscope (CSLM) in combination with an infrared image furnace as a heating device. As a result, definite images of the samples during melting were obtained, and the advantages of this method for the measurement of this type of ternary oxide system were confirmed. Further, a more appropriate ternary phase diagram and its 1973 K isothermal cross section were predicted.

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Evaluation of Phase Diagrams for the Al2O3-CaO-SrO System by In-Situ Observation Using Confocal Laser Microscope

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Microstructure Evolution in the Rolled Mg97Zn1Y2 Alloy with Long-Period Stacking Phase upon Annealing

Baishu Wang, Yongbing Liu, Zhenguo Su, Zhanyi Cao

pp. 261-265

DOI:

10.2320/matertrans.MRA2008278

Abstract

Mg97Zn1Y2 alloy (at%) has been studying nearly ten years as an elevated temperature creep resistant Mg-based alloy with long-period stacking (LPS) phase. The deformation processing had been performed upon the alloy so that a highly non-equilibrium state was looked forward to provide particularly advantageous material property profiles for it. Thus the texture evolutions in Mg97Zn1Y2 alloy processed by rolling and annealing the as-cast alloy at different temperatures, are investigated thoroughly. The microstructures of the alloy had been examined using general optical microscopy (OM), laser optical microscopy (LOM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM); the textures were analyzed by X-ray diffraction (XRD). The result shows that the second recrystallization texture had developed primarily when a preliminary annealing treatment of 500°C for 2 hours was performed to the rolled alloy and that part of the LPS phase had evolved into another phase with hexagonal superstructure which is an approximant to a quasicrystal and even the quasicrystal.

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Microstructure Evolution in the Rolled Mg97Zn1Y2 Alloy with Long-Period Stacking Phase upon Annealing

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Influence of Ag on Kinetics of Solid-State Reactive Diffusion between Pd and Sn

Taro Sakama, Masanori Kajihara

pp. 266-274

DOI:

10.2320/matertrans.MRA2008292

Abstract

The influence of Ag on the kinetics of the solid-state reactive diffusion between Pd and Sn was experimentally examined using Sn/(Pd–Ag)/Sn diffusion couples with a Ag concentration of 75 at% in the present study. The diffusion couples were isothermally annealed at temperatures of 433, 453 and 473 K for various periods up to 1365 h. During annealing, a compound layer dominantly consisting of polycrystalline PdSn4 and Ag3Sn lamellae is formed at the (Pd–Ag)/Sn interface in the diffusion couple. The square of the thickness of the compound layer increases in proportion to the annealing time. This relationship is called the parabolic relationship. On the other hand, the interlamellar spacing in the compound layer is proportional to a power function of the annealing time, and thus grain growth occurs in the compound layer. The exponent of the power function is close to 1/3. The parabolic relationship of the layer growth and the occurrence of the grain growth guarantee that the growth of the compound layer is controlled by volume diffusion. The addition of Ag with 75 at% into Pd decreases the parabolic coefficient by 93, 88 and 78% at 433, 453 and 473 K, respectively. Hence, Ag works as an effective suppressant against the growth of the compound during the solid-state reactive diffusion between Pd and Sn.

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Influence of Ag on Kinetics of Solid-State Reactive Diffusion between Pd and Sn

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Characteristics of Retained Austenite in Quenched High C-High Cr Alloy Steels

Muneo Yaso, Shuhei Hayashi, Shigekazu Morito, Takuya Ohba, Kunichika Kubota, Kouji Murakami

pp. 275-279

DOI:

10.2320/matertrans.MRA2008161

Abstract

In this paper, the morphologies of martensite and retained austenite for 1.5 mass%C-12 mass%Cr and 1 mass%C-8 mass%Cr steels were observed by means of optical microscopy, XRD, SEM/EBSD and TEM. The amount of retained austenites was quantitatively investigated and compared with XRD, EBSD and TEM observation methods. The retained austenites were distributed in the form of a block type and a film type in the martensite structures. For the 1.5 mass%C-12 mass%Cr steel, the amount of block type retained austenite and film type one are almost equal in three distinct regions of carbide; primary carbide, secondary carbide and without carbide. In the case of 1 mass%C-8 mass%Cr steel, as to film type retained austenite there are not so much differences among those regions. However, block type retained austenites are distributed with much amount, especially in the region around primary carbide.

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Characteristics of Retained Austenite in Quenched High C-High Cr Alloy Steels

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In-Situ Observation of Grain Growth of Steel at High Temperature

Yasuhiro Yogo, Kouji Tanaka, Koukichi Nakanishi

pp. 280-285

DOI:

10.2320/matertrans.MRA2008387

Abstract

An in-situ observation method for structures at high temperature is developed. The new observation device proposed in the present paper can reveal grain boundaries at high temperature and enables dynamic observation of these boundaries. Grain growth while maintaining microstructure at high temperature is observed by the new observation device with only one specimen for the entire observation, and grain sizes are quantified. The quantifying process reveals two advantages particular to the use of the new observation device: (1) the ability to quantify grain sizes of specified sizes and (2) the results of average grain size for many grains have significantly less errors because the initial structure is the same for the entire observation and the quantifying process.

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In-Situ Observation of Grain Growth of Steel at High Temperature

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Interfacial Morphology of Magnetic Pulse Welded Aluminum/Aluminum and Copper/Copper Lap Joints

Mitsuhiro Watanabe, Shinji Kumai

pp. 286-292

DOI:

10.2320/matertrans.L-MRA2008843

Abstract

In order to investigate interfacial morphology and their welding condition dependency, Al/Al and Cu/Cu lap joints were fabricated by magnetic pulse welding under various discharge energies. A part of flyer plate along the longitudinal direction of the coil bulged toward a parent plate and hit the parent plate. Two parallel seam-welded areas were formed along the side edges of coil, but the area between them was left un-welded. The welding interface exhibited characteristic wavy morphology, which was similar to that of explosive welding. Wavelength and amplitude of the interfacial wave were not uniform, but gradually changed through the interface. In addition, the maximum wavelength and amplitude increased with increasing discharge energy. Both macro- and microscopic features of interfacial morphology are considered to be due to the oblique collision behavior between the plates, in which traveling velocity, collision angle and collision pressure of the plates gradually change during the welding for a few microseconds.

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Interfacial Morphology of Magnetic Pulse Welded Aluminum/Aluminum and Copper/Copper Lap Joints

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Electric Flame-Off Characteristics and Fracture Properties of 20 μm Thin Copper Bonding Wire

Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen, Yi-Chang Lin

pp. 293-298

DOI:

10.2320/matertrans.MRA2008145

Abstract

In the present study, the neck fracture properties of annealed wire with φ=20 μm (0.8 mil) at 225°C for 1 hour and un-annealed wire were compared. In addition, the microstructural characteristics, the mechanical properties and the texture transition using EBSD methods before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that the recrystallization temperature of the as-drawn wire was ∼225°C, and the annealed copper wires possessed a fully annealed structure. Through recrystallization, the matrix structure transferred from long, thin grains to equiaxed grains and a few annealed twins. The microstructure of the free air ball (FAB) after an EFO process consisted of column-like grains, and grew from the heat-affected zone (HAZ) to the Cu ball. For the annealed and un-annealed wires, their preferred orientations on the wire and the neck were ⟨100⟩||AD. Under the thermal effect of EFO, the orientation of the Cu balls were mainly ⟨101⟩||AD and ⟨111⟩||AD for annealed wires. Additionally, the hardness of the Cu balls and the strength of the neck sites of the EFO wires were able to affect the reliability of the copper wire bonding.

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Electric Flame-Off Characteristics and Fracture Properties of 20 μm Thin Copper Bonding Wire

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Postbuckling Behavior of Composite Laminated Plates with Initial Imperfections under Biaxial Compression

Keiichi Nemoto, Hirakazu Kasuya, Hisao Kikugawa, Takashi Asaka

pp. 299-304

DOI:

10.2320/matertrans.MRA2008250

Abstract

Advanced fiber-reinforced laminated plates have been used for structural members in various fields, by virtue of their high specific strength and stiffness. This paper considers, by use of Galerkin’s methods, the postbuckling behaviors of angle-ply laminated plates with initial deflection under biaxial compression that is simply supported along four edges. The inevitability of postbuckling behaviors is proved analytically, and the effects of various factors, such as initial imperfection, lamination angle, biaxial compressive load ratio, and postbuckling deflection pattern, are clarified.

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Postbuckling Behavior of Composite Laminated Plates with Initial Imperfections under Biaxial Compression

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Effect of Different Preservative Methods on Fracture Behavior of Bovine Cortical Bone

Masahiro Kuninori, Hisao Kikugawa, Takashi Asaka, Hirakazu Kasuya

pp. 305-312

DOI:

10.2320/matertrans.MRA2008375

Abstract

Bone specimens used for evaluating the mechanical properties of bone may not have been necessarily preserved by the same method before they become available. To this end, the mechanical properties of bone may be affected by freezing, a common preservation method, as well as by formalin and other preservation solutions. In this study, bone specimens were preserved by different methods (i.e., freezing, preservation in saline, preservation in ethanol, and preservation in formalin) to examine the effects of each preservation method on the fracture characteristics of bovine femoral cortical bone. Regarding the crack extension behavior in the fracture toughness test, microcracks accumulated at the top of the slit in the low-load region before the maximum load was reached. When such accumulated microcracks grew to a visible size, a crack was formed from the top of the slit, and then grew with subsequent expansion of the processing zone. The fracture toughness values of the bone groups preserved in formalin and neutral buffered formalin were significantly lower than those of the bone groups preserved by other methods. As the fracture surface by scanning electron microscopic observations was smoother with a loading rate of 20 mm/min than with 1 mm/min, cracks were considered to develop easily, resulting in a lower fracture toughness value. Scanning electron microscopic observations of a test section subjected to a low loading rate showed that the fracture surface of the bone groups preserved in formalin or neutral buffered formalin was flat and smooth. In the other preservation groups, the lamellae adjacent to the top of the slit had undulating contours with plastic deformation.

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Effect of Different Preservative Methods on Fracture Behavior of Bovine Cortical Bone

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Pop-in Crack Propagation Monitoring for AA2024-T3 Ductile Alloy

H. C. Lin, T. Y. Kuo, H. T. Lee

pp. 313-320

DOI:

10.2320/matertrans.MRA2008275

Abstract

This paper demonstrates the use of temperature change, induced by thermo-mechanical effect, as a means of monitoring the pop-in crack propagation of ductile materials. Center crack tensile (CCT) tests are performed at room temperature using 1/4″ thick AA2024-T3 aluminum alloy specimens at different loading speeds. The temperature variation in the vicinity of the crack tip is measured and correlated with the changes in the applied load and fractographs. The results show that the load and temperature curves comprise three distinct regions, corresponding to the initial thermo-elastic stage, a stable cracking extension stage, and an unstable cracking extension stage, respectively. The load and temperature characteristics in each stage are highly distinctive and therefore provide a reliable means of monitoring the state of the crack propagation process.

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Pop-in Crack Propagation Monitoring for AA2024-T3 Ductile Alloy

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Immobilization of Arsenic from Novel Synthesized Scorodite—Analysis on Solubility and Stability

Tetsuo Fujita, Ryoichi Taguchi, Hisashi Kubo, Etsuro Shibata, Takashi Nakamura

pp. 321-331

DOI:

10.2320/matertrans.M-MRA2008844

Abstract

The solubility of scorodite synthesized in a novel atmospheric process was investigated. Stable scorodite (FeAsO4·2H2O) particles were produced by introducing oxidizing gas into a reaction mixture containing ferrous sulfate and high-concentration arsenic (V) to convert ferrous ion to ferric ion. The obtained scorodite crystals released a very low, almost negligible concentration of arsenic in the pH range of 3 to 6, suggesting its long-term stability. The thermodynamic parameters for the dissolution reaction of scorodite, Ksp and ΔGf, were similar to those reported previously. The results show scorodite released a considerably high concentration of arsenic under specific leaching conditions. In particular, the combination of CaO and NaCl present in the alkaline leaching solution had a significant effect on the mobilization of arsenic. Although this study did not cover all possible natural environments in which scorodite would be stored, it seems practically impossible to develop conditions that would completely prevent the dissolution of arsenic from scorodite. It is crucial to develop scorodite storage methods that will minimize the risk of environmental arsenic contamination based on accurate evaluation of the conditions for the leaching of arsenic.

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Immobilization of Arsenic from Novel Synthesized Scorodite—Analysis on Solubility and Stability

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Effect of O2 Pretreatment on Fluorinated Carbon Film Surfaces

Mi Ryn Seong, Gye Young Lee, Si Hyeong Cho, Hyun Woo Lim, Jin Goo Park, Caroline Sunyong Lee

pp. 332-334

DOI:

10.2320/matertrans.MRA2008295

Abstract

Fluorocarbon (FC) film is used in micro-electro-mechanical system (MEMS) processes as an anti-stiction layer. We studied the effect of O2 pretreatment on FC film using an X-ray photoelectron spectroscope (XPS) and atomic force microscope (AFM) to measure the surface roughness and to characterize the composition of the film. CF and CF3 were observed for all temperatures at 6.67 Pa. A high oxygen concentration was found in the film deposited at 250°C. An AFM analysis of the surface roughness showed agglomeration on the film surface, while none was found on the films deposited at 25°C and 100°C. Therefore, the O2 pretreatment seemed to facilitate oxidation at a deposition temperature of 250°C. Since our results showed that a smooth anti-stiction layer could be deposited at 100°C without any oxidation occurring, the optimum conditions for FC deposition were 100°C at a pressure of 6.67 Pa. Therefore, this study showed an important relationship between O2 pretreatment and deposition temperature.

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Effect of O2 Pretreatment on Fluorinated Carbon Film Surfaces

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Effect of the Electrodeposition Temperature on the Cyclic-Oxidation Resistance of Ni Aluminide Containing Zr Formed by Molten-Salt Electrodeposition

Michihisa Fukumoto, Takashi Suzuki, Motoi Hara, Toshio Narita

pp. 335-340

DOI:

10.2320/matertrans.MRA2008293

Abstract

The effect of the Al electrodeposition temperature on the cyclic oxidation resistance of Ni aluminide containing Zr formed by molten salt electrodeposition was investigated. Zr and Al were deposited by molten salt electrolysis. For the sample treated with the Al deposition at 1073 K, a layer consisting of Ni2Al3 was uniformly formed. On the other hand, for the sample treated by Zr deposition, followed by Al deposition at 1073 K, a layer consisting of Ni2Al3 and a Ni aluminide layer containing Zr on the Ni2Al3 layer were formed. Furthermore, when the Al electrodeposition temperature was changed, the concentration of Zr in the Ni aluminide layer containing Zr changed. When the Al electrodeposition was carried out at 1153 and 1173 K, the Zr was scarcely observed in the surface region of the Ni aluminide layer. The cyclic oxidation test showed that for the sample treated with only the Al deposition and the sample treated with the Zr deposition, followed by Al deposition at 1073 K, a mass reduction due to scale exfoliation took place, whereas for the samples treated with the Zr deposition, followed by Al deposition at 1153 and 1173 K, no mass reduction was observed. For these samples, after the cyclic oxidation test, a scale consisting of α-Al2O3 adhering to the substrate was formed. Consequently, it was found that the cyclic oxidation resistance of Ni was improved by Zr deposition, followed by Al deposition at 1153 and 1173 K.

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Effect of the Electrodeposition Temperature on the Cyclic-Oxidation Resistance of Ni Aluminide Containing Zr Formed by Molten-Salt Electrodeposition

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Simultaneous Determination of the Composition and Size of Oxide Particles in Solid Materials by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

Andrey V. Karasev, Ryo Inoue

pp. 341-348

DOI:

10.2320/matertrans.MRA2008301

Abstract

Laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) has been used for the determination of the composition and size of oxide particles consisting of SiO2, MnO, Al2O3, MgO and CaO on the surface of a glass or metal sample. The composition and size of multicomponent oxide particles such as MnO-SiO2, CaO-Al2O3 and CaO-Al2O3-MgO evaluated by LA-ICP-MS are compared with those obtained by chemical analysis and by SEM observation. It is confirmed that LA-ICP-MS method has prospects to be applied for quick and simultaneous measurement of the composition and size of particles on the surface of metals in steelmaking industry. The difference between the particle size determined by LA-ICP-MS and that by SEM ranges from 6 to 13% on an average in the range of dV=7∼40 μm.

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Simultaneous Determination of the Composition and Size of Oxide Particles in Solid Materials by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

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Microstructures and Mechanical Properties of Mg96Zn2Y2 Alloy Prepared by Extrusion of Machined Chips

Syuichi Fudetani, Takaomi Itoi, Tetsuo Kubo, Yoshihito Kawamura, Mitsuji Hirohashi

pp. 349-353

DOI:

10.2320/matertrans.L-MRA2008842

Abstract

Hot extrusion of machined chips of Mg96Zn2Y2 (at%) alloy was carried out at 623 K, and microstructures and mechanical properties of the extruded Mg96Zn2Y2 alloy were investigated. The alloy consisted of α-Mg, Mg12ZnY, and Mg3Zn3Y2 phases, and the Mg grains had a mean grain size of 450 nm. The Mg12ZnY phase was frequently observed inside the fine Mg grains. In addition, oxidation occurred around cavities remaining after extrusion. The extruded alloy exhibited a high 0.2% proof strength of 495 MPa and elongation of 3% at room temperature. The Mg grain refinement and dispersion of Mg12ZnY and Mg3Zn3Y2 phases caused by hot extrusion led to high strength at room temperature. Further, the extruded alloy also exhibited superplasticity at temperatures of 623 and 723 K with initial strain rates from 2×10−1 S−1 to 2×10−3 S−1. The maximum elongation was 450% at 723 K with an initial strain rate of 2×10−3 S−1. Grain boundary sliding of Mg grains is the dominant deformation mechanism for the alloy at high temperature ranges.

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Microstructures and Mechanical Properties of Mg96Zn2Y2 Alloy Prepared by Extrusion of Machined Chips

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Effect of Strontium, Magnesium and Iron Content on Mechanical Properties of Rheocast Al-7 mass%Si-Mg Alloys

Satoru Sato, Yasunori Harada, Naoki Ishibashi, Mitsuru Adachi

pp. 354-360

DOI:

10.2320/matertrans.F-MRA2008845

Abstract

Newly developed Rheocasting process makes semi-liquid slurry in metallic vessel without stirring process. Semi-liquid castings made by this process show good mechanical properties. The effects of strontium, magnesium and iron contents on the mechanical properties of Rheocast and squeeze cast Al-7 mass%Si-Mg alloys were investigated. Elongation of Al-7 mass%Si-Mg alloy Rheocastings was higher than those of squeeze castings when strontium was not added or iron content was up to 0.27 mass%. Both Rheocastings and squeeze castings increased in strength but decreased in elongation with increasing magnesium content in Al-7 mass%Si-xmass%Mg (x=0.23–0.64) alloy.

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Effect of Strontium, Magnesium and Iron Content on Mechanical Properties of Rheocast Al-7 mass%Si-Mg Alloys

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Effects of Process Conditions of Melting Furnace on Alkali-Free Glass Cleanliness

Chien-Chih Yen, Meng-Chun Wu, Weng-Sing Hwang

pp. 361-367

DOI:

10.2320/matertrans.MRA2008394

Abstract

In this study, the effects of process conditions such as air bubbling, top radiation heating and electrode heating in a melting furnace on the cleanliness of alkali-free glass, which is characterized by the residence time and trajectories of tracer particles, is investigated by a reduced physical model. The reduced physical model was made of an acrylic tank, which is similar in shape of the actual glass melting furnace but one tenth in size, with heating electrodes, top radiation heating and air bubbling devices. Silicon oil was used to simulate molten glass. The gas flow rate was set at 6.67×10−7 Nm3/s. The electrode and radiation temperatures were set at 298 K, 323 K, 353 K and 373 K. Residence time, which is the time required for tracer particles to flow from inlet to outlet, was measured to evaluate the cleanliness of the molten glass. The results showed that the effect of bubbling on residence time is larger than that of top radiation heating which is then larger than that of electrode heating when one single process variable is considered. For the effect of the coupling of two process variables, the dual effect of bubbling and radiation is better than that of bubbling and electrode which is in turn better than that of radiation and electrode. As all three devices were all turned on, it was found that the most desirable condition to obtain clean glass is bubbling with electrode temperature of 323 K and radiation temperature of 373 K.

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Effects of Process Conditions of Melting Furnace on Alkali-Free Glass Cleanliness

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Effects of Nd Content on the Dynamic Elastic Modulus and Mechanical Properties of Titanium-Neodymium Alloys

Ying-Long Zhou, Mitsuo Niinomi

pp. 368-372

DOI:

10.2320/matertrans.MRA2008260

Abstract

The microstructures, dynamic elastic modulus, and mechanical properties of Ti-Nd alloys with Nd contents of 1.5, 3, 4.5, and 6 (mass%) were investigated in this study in order to assess whether Nd was an effective alloying element for decreasing the elastic modulus of a Ti alloy and simultaneously increasing its strength for its potential use in biomedical applications. The microstructures were examined by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The dynamic elastic modulus was measured by the vibration resonance method and the mechanical properties were determined from uniaxial tensile tests. Experimental results indicate that all the Ti-Nd alloys exhibit hexagonal structures of both α Ti and α Nd. An increase in the Nd content decreases the elastic modulus of the Ti-Nd alloys by a small amount and gradually increases their strength. The residual stress caused by cold rolling has a slight effect on both the elastic modulus and the mechanical properties of the Ti-Nd alloys. From this investigation, it can be concluded that Nd is not an effective alloying element for decreasing the elastic modulus of Ti alloys and simultaneously increasing their strength for their potential use in biomedical applications.

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Effects of Nd Content on the Dynamic Elastic Modulus and Mechanical Properties of Titanium-Neodymium Alloys

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Effect of Microscopic Internal Structure on Sound Absorption Properties of Polyurethane Foam by X-ray Computed Tomography Observations

Tsuyoshi Yamashita, Kazuhiro Suzuki, Hideki Adachi, Souichiro Nishino, Yo Tomota

pp. 373-380

DOI:

10.2320/matertrans.MRA2008207

Abstract

We investigated several conditions for manufacturing polyurethane foam for motor vehicle application to clarify the effect of the material structure on sound absorption performance in the low-frequency region. The objective is to reduce material weight without reducing noise absorption performance. We investigated the relationship between the internal microscopic structure and absorption performance by 3D analysis of X-ray computed tomography scanning observations. We found that the microscopic structural parameters of the material cells affect the sound absorption frequency and that they have a strong relationship with tortuosity, which is an acoustic parameter of porous materials. We also found that reducing cell size and making the cell frames thicker shifts the peak frequency of the sound absorption coefficient downward.

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Effect of Microscopic Internal Structure on Sound Absorption Properties of Polyurethane Foam by X-ray Computed Tomography Observations

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Microstructural Characteristics and the Charge-Discharge Characteristics of Sn-Cu Thin Film Materials

Chao-Han Wu, Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen

pp. 381-387

DOI:

10.2320/matertrans.MER2008291

Abstract

In this study, radio frequency magnetron sputtering was used to prepare Cu6Sn5 film anodes. The effects of the thickness of the film and its index of crystallinity (IOC) on the charge-discharge capacity characteristics are discussed. Increasing the thickness of the film anode from 500 to 1500 nm, not only raised the IOC, but also improved the migration of lithium ions and electrons because of the lower resistivity. So, the cyclability of the as-adopted film was enhanced with increasing the film thickness. After recrystallization, the IOC rose and the resistivity fell. However, cracks on the film induced by thermal strain increased the area of the passive film, resulting in reduced cyclability. Also, prolonging the duration of sputtering (5000 nm) led to a deterioration in the charge-discharge capacity.

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Microstructural Characteristics and the Charge-Discharge Characteristics of Sn-Cu Thin Film Materials

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Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr-(Ti,Nb)-Al-Ni-Cu System

A. Inoue, Q. S. Zhang, W. Zhang, K. Yubuta, K. S. Son, X. M. Wang

pp. 388-394

DOI:

10.2320/matertrans.MER2008179

Abstract

Bulk glassy alloy rods with a diameter of 20 mm were produced for Zr61Ti2Nb2Al7.5Ni10Cu17.5 and Zr60Ti2Nb2Al7.5Ni10Cu18.5 by a tilt casting method. The replacement of Zr by a small amount of Ti and Nb caused a distinct increase in the maximum diameter from 16 mm for Zr65Al7.5Ni10Cu17.5 to 20 mm, accompanying the decrease in liquidus temperature and the increase in reduced glass transition temperature. The primary precipitation phase from supercooled liquid also shows a distinct change, i.e., from coexistent Zr2Cu, Zr2Ni and Zr6NiAl2 phases for the 65%Zr alloy to an icosahedral phase for the 61%Zr and 60%Zr alloys. These results allow us to presume that the enhancement of the glass-forming ability is due to an increase in the stability of supercooled liquid against crystallization caused by the development of icosahedral short-range ordered atomic configurations. The 60%Zr specimens taken from the central and near-surface regions in the transverse cross section at the site which is 15 mm away from the bottom surface of the cast glassy rod with a diameter of 20 mm exhibit good mechanical properties under a compressive deformation mode, i.e., Young’s modulus of 81 GPa, large elastic strain of 0.02, high yield strength of 1610 MPa and distinct plastic strain of 0.012. Besides, a number of shear bands are observed along the maximum shear stress plane on the peripheral surface near the final fracture site. The finding of producing the large scale Zr-based bulk glassy alloys exhibiting reliable mechanical properties is encouraging for future advancement of bulk glassy alloys as a new type of functional material.

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Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr-(Ti,Nb)-Al-Ni-Cu System

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Effects of HIP Treatment on the Microstructure and Properties of Cr35-Si65 Target

Chung-Hung Tam, Shih-Chin Lee, Shih-Hsien Chang, Fong-Cheng Tai

pp. 395-400

DOI:

10.2320/matertrans.MER2008259

Abstract

Hot Isostatic Pressing (HIP) can be used for upgrading castings, densifying pre-sintered components, consolidating powders, and interfacial bonding. Hot pressing is a good method for fabricating on high melting materials with better mechanical properties. Commercial as-hp treated Cr35-Si65 targets are used throughout this study. The aim of this paper is to discuss the methods and to find a suitable HIP treatment for the as-hp treated Cr35-Si65 target. Meanwhile, we also to evaluate the effects of HIP treatment on the microstructure and properties of Cr35-Si65 target. The experiment results show that HIP treatment at 1100°C under 175 MPa for 2 hours of Cr35-Si65 target is the most suitable condition. It can reduce the open pore porosity by 20% and close pore porosity by 30%. The density could be increased to 3.64×10−3 kg/m3.

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Effects of HIP Treatment on the Microstructure and Properties of Cr35-Si65 Target

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The Effect of Ultrasonic Treatment on Microstructural and Mechanical Properties of Cast Magnesium Alloys

Yeong-Jern Chen, Wen-Nong Hsu, Jhih-Ren Shih

pp. 401-408

DOI:

10.2320/matertrans.MER2008273

Abstract

Magnesium alloys are important light metals. In recent years, they have been widely applied in the aerospace and automotive industries, and in the manufacture of communication devices, consumer-electronics appliances and computer products. However, cast magnesium and magnesium alloys are subject to problems due to gas pores, inclusion particles, oxide films, and so on. How to reduce the harm caused by these defects and refine the structure to improve casting quality has become an important topic. In this study, we evaluate the effect on casting quality of an ultrasonic method for treating the melt. The method is based on the generation of cavitation bubbles from ultrasonic treatment of the melt, which induces dispersion and degassing action. Analysis of the microstructure and determination of the mechanical properties of the resultant castings are the basis for identifying the quality of the magnesium and magnesium alloys. The microstructure was evaluated using an optical microscope and scanning electron microscopy (SEM). The elemental constituents of the inclusion particles and oxide films were identified using scanning electron microscopy in conjunction with an X-ray energy dispersive spectrometer and electron probe microanalyzer (EPMA). Finally, the mechanical properties of the magnesium and magnesium alloys, including the tensile strength, the elongation and the hardness, were also determined and discussed. In addition, variations in mechanical properties of cast aluminum and magnesium alloys by ultrasonic treatment are also discussed.

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The Effect of Ultrasonic Treatment on Microstructural and Mechanical Properties of Cast Magnesium Alloys

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Characteristics of the Treated Ground Calcium Carbonate Powder with Stearic Acid Using the Dry Process Coating System

Soo-Bok Jeong, Young-Cheol Yang, Young-Bae Chae, Byoung-Gon Kim

pp. 409-414

DOI:

10.2320/matertrans.MRP2008351

Abstract

This study examined the surface properties, fluidity, flowability and floodability of untreated ground calcium carbonate (GCC) powder and treated GCC powder with stearic acid (SA) using a dry process coating system. The surface of GCC powder is generally hydrophilic, but was changed to a hydrophobic surface when coated with SA. The contact angle of water on the coated GCC powder surface increased with increasing concentration of SA. The contact angle and hydrophobicity on the GCC powder treated with 1.0 mass% SA was 105° and 100%, respectively. The dispersive component of the surface free energy, γSD of the untreated GCC powder determined using inverse gas chromatography (IGC) was 103 mJ·m−2 at 100°C. However, that of the GCC powder treated with 1.0 mass% SA was 34.8 mJ·m−2. Kawakita’s equations were used to characterize the properties of the powder. The fluidity index was increased from 18.60 to 30.39 when the surface of GCC powder was modified with SA. On the other hand, the characterization based on the method suggested by Carr showed that the flowability and the floodability of the GCC powder treated with SA increased from 45 to 53 and from 30 to 69, respectively. Therefore, the flowability and floodability of the GCC powder treated with SA were superior to the untreated GCC powder.

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Characteristics of the Treated Ground Calcium Carbonate Powder with Stearic Acid Using the Dry Process Coating System

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Ti-Coated Al2O3 Balls Prepared by Fine Particle Bombardment and Their Reductive Properties

Daigo Yamaguchi, Shigeru Suzuki, Jin Mizuguchi

pp. 415-418

DOI:

10.2320/matertrans.MER2008386

Abstract

Ti-coated Al2O3 balls with a proposed structure of TiO2/TiOx/Al2O3 (0<x<2) prepared by fine particle bombardment (FPB) had previously been reported to possess a catalytic effect for durability improvement of oils or mileage increase of diesel fuels due presumably to the well-known oxidative effect of titanium dioxide. On the contrary, we believed that the durability improvement of oils can more reasonably be explained by reductive properties (i.e. antioxidant) of the Ti-coated Al2O3 balls. For this reason, reductive properties of Ti-coated Al2O3 balls have been studied in the present investigation in terms of electrical measurements of the balls, X-ray photoelectron spectroscopy (XPS) analysis of the surface, as well as reduction indicator using a viologen compound. The reductive properties are found to arise from a thin TiOx layer which can gradually be dissolved into water-containing media, leaving behind electrons on the Al2O3 balls. These electrons may serve as the antioxidant (i.e. reducing agent: electron donor) for durability improvement of oils or mileage increase of diesel fuels.

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Ti-Coated Al2O3 Balls Prepared by Fine Particle Bombardment and Their Reductive Properties

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Ferromagnetic Properties of Co-Cu Alloy with Nanoscale Lamellar Structure

Motohiro Yuasa, Hiromi Nakano, Yoshiaki Nakamoto, Masataka Hakamada, Mamoru Mabuchi

pp. 419-422

DOI:

10.2320/matertrans.MRP2008220

Abstract

Co-Cu alloys containing a nanoscale lamellar structure with a spacing of 3 nm were produced by electrodeposition, and the effects of annealing on the ferromagnetic properties of the electrodeposited Co-Cu alloys were investigated at room temperature. Both the saturation magnetization and the coercivity were decreased by annealing. This is related to a change in the lamellar structure upon annealing. It is suggested that in the d6-dependence range of coercivity, the lamellar boundaries play a different role from the grain boundaries.

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Ferromagnetic Properties of Co-Cu Alloy with Nanoscale Lamellar Structure

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Anomalous Thermal Expansion of Cold-Rolled Ti-Nb-Ta-Zr Alloy

Masaaki Nakai, Mitsuo Niinomi, Toshikazu Akahori, Harumi Tsutsumi, Xiaoliang Feng, Michiharu Ogawa

pp. 423-426

DOI:

10.2320/matertrans.MRP2008380

Abstract

Negative thermal expansion, i.e. a type of shrinkage that occurs during heating, was observed in cold-rolled Ti-29Nb-13Ta-4.6Zr alloy (mass%) (TNTZ). The reduction ratio of cold rolling and the angle of the longitudinal axis of specimens with respect to the cold-rolling direction were systematically changed, and then the thermal expansion rate was measured using a dilatometer. Further, the cyclicity of thermal expansion was examined for the cold-rolled TNTZ. From the results, it is observed that with an increase in the reduction ratio of cold rolling, the thermal expansion rate of TNTZ cold-rolled parallel to the rolling direction (RD) decreases, but it increases in TNTZ cold-rolled parallel to the transverse direction (TD). With regard to the anisotropy of thermal expansion, the thermal expansion rate increases with the angle between the longitudinal axis of the specimens and RD. Further, the cyclicity of the above-mentioned anomalous thermal expansion is observed in a temperature range below 473 K, but it is not observed when the specimen is heated above 573 K in the first cycle.

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Anomalous Thermal Expansion of Cold-Rolled Ti-Nb-Ta-Zr Alloy

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Effects of Pore Characteristics Finely-Controlled by Spacer Method on Damping Capacity of Porous Aluminum

Masataka Hakamada, Hiroyuki Watanabe, Tetsunume Kuromura, Youqing Chen, Hiromu Kusuda, Mamoru Mabuchi

pp. 427-429

DOI:

10.2320/matertrans.MRP2008389

Abstract

The room-temperature damping properties of porous aluminum fabricated by the spacer method were investigated using the method of lateral resonant vibration in cantilever holding. In particular, the effects of the porosity and pore size, which are the representative parameters of porous metals and can be controlled well by spacer method, on the damping properties were focused on. The damping capacity increased with increasing porosity and pore size. Local stress concentration arising from the heterogeneity of porous structures seems responsible for the enhanced damping capacity under the condition in which the main damping mechanism is amplitude-dependent dislocation damping. The present results point out the importance of the porous structure control in damping properties.

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Effects of Pore Characteristics Finely-Controlled by Spacer Method on Damping Capacity of Porous Aluminum

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