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MATERIALS TRANSACTIONS Vol. 46 (2005), No. 10

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

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MATERIALS TRANSACTIONS Vol. 46 (2005), No. 10

Substructures of Gas-Ion-Irradiation-Induced Surface Blisters in Silicon Studied by Cross-Sectional Transmission Electron Microscopy

Shunsuke Muto, Naruaki Enomoto

pp. 2117-2124

Abstract

Internal structures of surface blisters and their precursors in Si formed by H+, D+ and He+ irradiation were examined by cross-sectional transmission electron microscopy (XTEM). The skin structures of H+-D+- and He+-blisters reflected the difference in the damage accumulation, and chemical interaction between the implant ion and silicon. These differences had a direct influence on the defect structures of the damaged layer, which played essential roles in the blistering mechanisms. It was found that blister skin thickness derived by grazing incidence electron microscopy (GIEM) and electron energy-loss spectroscopy (EELS) was underestimated compared to direct measurement by XTEM. The origin of this discrepancy is discussed.

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Substructures of Gas-Ion-Irradiation-Induced Surface Blisters in Silicon Studied by Cross-Sectional Transmission Electron Microscopy

X-ray Diffraction Analysis of the Recrystallization Behavior of SiCw/Al Composite at High Temperature

Chuan-hai Jiang, Chang-qing Ye, Bo Hong

pp. 2125-2128

Abstract

By using the method of in-situ X-ray diffraction and profile analysis, the variation of grain size and microstrain of the cold-rolled SiCw/Al composite at high temperature was measured, and the recrystallization behavior of the composite was investigated. Test results showed that the activation energy of grain growth after recrystallization and recovery at higher temperature of matrix in composite is close to the activation energy for self-diffusion of pure Al. It was verified that the recovery phenomenon was accompanied with the grain growth, and the whiskers cannot affect the grain growth and recovery of matrix in composite at higher temperature.

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X-ray Diffraction Analysis of the Recrystallization Behavior of SiCw/Al Composite at High Temperature

Improvement in Recrystallization Temperature and Mechanical Properties of a Commercial TZM Alloy through Microstructure Control by Multi-Step Internal Nitriding

Masahiro Nagae, Tetsuo Yoshio, Jun Takada, Yutaka Hiraoka

pp. 2129-2134

Abstract

In order to develop a molybdenum alloy with high recrystallization temperature and excellent mechanical properties, multi-step internal nitriding of a commercial TZM alloy (Titanium–Zirconium–Molybdenum alloy) was studied through optical and transmission electron microscopy, fractographic analysis and three-point bending tests. Two types of nitriding processes, a two-step and another four-step process, were carried out at temperatures between 1423 and 1873 K. Recrystallization was completely suppressed, even at the center of a 1-mm-thick specimen through four-step nitriding, whereas recrystallization proceeded at the specimen center in the case of two-step nitriding. The recrystallization temperature of the TZM alloy in vacuum was raised above 1973 K by four-step nitriding. The ductile-to-brittle transition temperature (DBTT) of the nitrided TZM alloy depended strongly on the thickness of the deformed microstructure. DBTT of the four-step nitriding specimen was below 130 K, which is about 70 K lower than that of the two-step nitriding specimen. The yield stress of the four-step nitriding specimen at 1773 K was about 2.6 times as large as that of the recrystallized specimen.

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Improvement in Recrystallization Temperature and Mechanical Properties of a Commercial TZM Alloy through Microstructure Control by Multi-Step Internal Nitriding

In-Situ Synthesis of Ti Matrix Composite Reinforced with Dispersed Ti5Si3 Particles via Spark Plasma Sintering

Masaki Sumida, Katsuyoshi Kondoh

pp. 2135-2141

Abstract

In this work, Ti matrix composite reinforced with dispersed Ti5Si3 particles was synthesized via spark plasma sintering starting with Ti and SiO2. Because reports on the equilibrium phase diagram show that there is a two phase region with O dissolved Ti, Ti(O), and Ti5Si3, Ti and small amount of SiO2 transform into Ti5Si3/Ti composite according to a reaction, Ti+SiO2=Ti(O)+Ti5Si3. Initial amount of SiO2 and sintering temperature were varied in ranges of 2.5–15 mass% and 800–1200°C, respectively. Their dependence on microstructure, bulk density, fraction of spatial occupation and Vickers hardness was studied systematically. From microstructure observation, composition and temperature range to yield Ti5Si3/Ti composite was identified. At low temperature sintering, however, SiO2 remained inside the Ti5Si3 envelope, indicating incompleteness of above reaction. A simple analysis was made on the phase transformation mechanism of Ti5Si3, supposing that the diffusion of Ti controls this process. Vickers hardness of the Ti5Si3/Ti composite increases with increase both in amount of SiO2 and temperature, but it is remarkably larger than that of commercial pure Ti. The bulk density and fraction of spatial occupation also increases with increase in temperature but decreases with increase in amount of SiO2. Taking into account the experimental and analytical results, microstructure formation and its effect on the properties are discussed briefly.

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In-Situ Synthesis of Ti Matrix Composite Reinforced with Dispersed Ti5Si3 Particles via Spark Plasma Sintering

Temperature Dependence of Kinetics for Reactive Diffusion in a Hypothetical Binary System

Masanori Kajihara

pp. 2142-2149

Abstract

A hypothetical binary system consisting of two primary solid solution phases (α and γ) and one compound phase (β) was considered in order to analyze theoretically the temperature dependence of kinetics for reactive diffusion. Assuming that migration of interface is controlled by volume diffusion in neighboring phases, the growth of the β phase due to the reactive diffusion between the α and γ phases in a semi-infinite diffusion couple was mathematically expressed as a function of the interdiffusion coefficients and the solubility ranges of the α, β and γ phases. The assumption yields that the square of the thickness l of the β phase is proportional to the annealing time t according to the parabolic relationship l2=Kt, where K is the parabolic coefficient. The present attention was focused on the relationship between the temperature dependency of the growth rate and those of the interdiffusion coefficients, and hence the solubility ranges were assumed to be constant independently of the temperature and to take the same value for all the phases. On the contrary, the interdiffusion coefficient Dθ (θ=α,β,γ) was expressed as a function of the temperature T by an Arrhenius equation of Dθ=D0θexp(−QθRT). For simplicity, however, D0α, D0β and D0γ were considered equivalent. The temperature dependence of the parabolic coefficient K was described also by an Arrhenius equation of K=K0exp(−QKRT), and then K0 and QK were evaluated for various combinations of Qα, Qβ and Qγ. The evaluation yields that QK is equal to Qβ at Qα=Qβ=Qγ and close to Qβ at QβQα and QβQγ. Under such conditions, the temperature dependence of Dβ is estimated directly from that of K. On the other hand, QK is greater than Qβ at Qβ>Qα or Qβ>Qγ. In this case, such estimation becomes invalid.

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Temperature Dependence of Kinetics for Reactive Diffusion in a Hypothetical Binary System

Superplasticity and Superplastic Diffusion Bonding of a Fine-Grained TiAl Alloy

Hanliang Zhu, Bing Zhao, Zhiqiang Li, Kouichi Maruyama

pp. 2150-2155

Abstract

Superplasticity and superplastic diffusion bonding in a TiAl alloy with a fine-grained duplex microstructure have been investigated in order to fabricate TiAl alloy products using a combination process of superplastic forming with diffusion bonding. Superplastic tensile tests were carried out at temperatures ranging from 1000 to 1100°C, and at strain rates ranging from 10−5 to 10−3 s−1. A low superplastic flow stress of less than 25 MPa was observed at 1100°C and at a strain rate of 8.3×10−5 s−1. Under this condition, a tensile elongation of 300% and a strain rate sensitivity coefficient of over 0.5 were obtained. Furthermore, superplastic diffusion bonding under a low pressure of 10 MPa was conducted. Defect-free bonds were achieved at 1100°C for holding 1 h. It is suggested that the low superplastic flow stress at 1100°C allows a significant plastic flow between the two contacted surfaces, resulting in a full contact of the surfaces, which is necessary for the sound bonds. Finally, a two-sheet part of spherical dome was successfully produced from this alloy.

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Superplasticity and Superplastic Diffusion Bonding of a Fine-Grained TiAl Alloy

Effect of Ultrasonic Vibration on Infiltration of Nickel Porous Preform with Molten Aluminum Alloys

Yong Bum Choi, Gen Sasaki, Kazuhiro Matsugi, Osamu Yanagisawa

pp. 2156-2158

Abstract

In order to obtain the high-performance composites with high density, the influence of additional ultrasonic vibration on the infiltration of molten aluminum alloy (ASTM A336.0) into nickel porous preform by low-pressure and pressureless casting was investigated. There was no effect of ultrasonic vibration on infiltration distance under pressureless casting because of presence of surface oxide film on the molten alloy, even when the contact angle is reduced by ultrasonic vibration. However, infiltration distance increases upon applying ultrasonic vibration under low pressure. The infiltration distance appears to increase because of the decrease of the contact angle between the reinforcement and molten alloy upon applying ultrasonic vibration, as well as the reducing effect of oxide film on the surface of the molten alloy under low pressure. The improvement of infiltration by applying ultrasonic vibration under low pressure is applicable to the to infiltration of into nickel porous preform.

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Effect of Ultrasonic Vibration on Infiltration of Nickel Porous Preform with Molten Aluminum Alloys

Finite Element Analysis of the Onset of Necking and the Post-Necking Behaviour during Uniaxial Tensile Testing

Hyoung Seop Kim, Sung Ho Kim, Woo-Seog Ryu

pp. 2159-2163

Abstract

Tensile deformation and post-necking behaviour were investigated using the elasto-plastic finite element method. Necking at the specimen centre could be reproduced by applying a radial constraint at the loading points without assuming initial imperfections or plastic instability theory. It was found from the calculated results that for strain hardening materials Hart’s criterion overestimates the necking onset strain a little, probably due to the end effect.

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Finite Element Analysis of the Onset of Necking and the Post-Necking Behaviour during Uniaxial Tensile Testing

The Twinning Microstructure and Damping Behavior in Mn–30Cu (at%) Alloy

Fuxing Yin, Takuya Sakaguchi, Qingchao Tian, Atsuko Sakurai, Kotobu Nagai

pp. 2164-2168

Abstract

The twin boundary damping peak and the transformation damping peak constitute the temperature dependent damping behavior in Mn–Cu alloys. In order to observe the effects of twinning microstructure on the twin boundary damping behavior, a Mn–30 at%Cu alloy was finally treated by furnace cooling (FC) and aging after water-quenching (AG), respectively. Regular twin bands with the similar widths along some {101} twin boundary were observed in FC treated condition, while intersected twin bands with pointed fronts belonging to different {101} twin boundaries occurred in the AG treated specimens. Meanwhile, the twin boundary damping features were obtained based on dynamic mechanical analyzer (DMA) measurement, and increased activation energy and decreased peak damping capacity were found in the AG treated alloy. The distortion state of the interfaces enclosing the decomposed nanometer regions was considered to influence the twinning microstructure formation and hence alter the damping features of the twining microstructure.

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The Twinning Microstructure and Damping Behavior in Mn–30Cu (at%) Alloy

Effect of Zincate Treatment on Adhesion of Electroless Ni–P Plated Film for 2017 Aluminum Alloy

Makoto Hino, Koji Murakami, Minoru Hiramatsu, Keiko Chen, Atsushi Saijo, Teruto Kanadani

pp. 2169-2175

Abstract

The present authors have investigated the changes in adhesion of electroless Ni–P plated films on an aluminum alloy substrate (JIS A2017P-T3, Al–4 mass%Cu) from the viewpoint of the preceding zincate treatment and the subsequent heat treatment. The precipitation state of zinc and adhesion of Ni–P plated film differed with the number of zincate treatments. Without zincate treatment, some of the Ni–P plated film peeled off during the plating process, and the film obtained after the single zincate treatment also showed poor adhesion to the substrate. The highest adhesion was obtained by the double zincate treatment, and the triple zincate treatment resulted in a poorer adhesion. Existence of aluminum at the surface of the zincate film was shown to be necessary to obtain higher adhesion of the Ni–P plated film, on the other hand, excess zinc obtained by the triple zincate caused lower adhesion. Interdiffusion of aluminum and nickel between the Ni–P plated film and the substrate through the medium of zincate film with an appropriate thickness is thought to promote strong bond between the Ni–P plated film and the substrate.

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Effect of Zincate Treatment on Adhesion of Electroless Ni–P Plated Film for 2017 Aluminum Alloy

Characterization of Electroplated Platinum–Iridium Alloys on the Nickel-Base Single Crystal Superalloy

Yingna Wu, Aya Suzuki, Hideyuki Murakami, Seiji Kuroda

pp. 2176-2179

Abstract

As a high temperature protective layer, platinum–iridium alloys were electroplated on the nickel-base single crystal superalloy TMS-82+ from amidosulfuric acid solutions by the direct current method. It was found that Ir content in the films was always lower than the ratio of concentration ([Ir3+]/([PtCl62−] + [Ir3+])) in the electrolytes, indicating that preferential deposition of Pt occurred in this study. The as-deposited Pt–Ir films formed an fcc single phase structure with a granular surface. When Ir content exceeded 3 at%, Pt–Ir films exhibited the ⟨111⟩ preferred growth orientation. It was also found that pre-deposition of Ni and Pt promoted the deposition rate and changed composition of overlaying Pt–Ir films.

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Characterization of Electroplated Platinum–Iridium Alloys on the Nickel-Base Single Crystal Superalloy

Effects of Coexisting Oxygen and Antimony in Molten Copper on Rate of Arsenic Elimination from the Copper Phase by the Use of Na2CO3 Slag

Mitsuru Tanahashi, Takeru Fujinaga, Zhijian Su, Kunihiko Takeda, Hong Yong Sohn, Chikabumi Yamauchi

pp. 2180-2189

Abstract

The rate of As elimination from molten copper by the use of Na2CO3 slag was measured at 1523 K. The results obtained, under the experimental conditions of this study, show that As in molten copper is eliminated in a pentavalent form and that its elimination rate increases with increasing initial oxygen concentration in molten copper. Based on the results obtained in the present study, the overall rate of As elimination is probably controlled by mass transfer in molten copper. The mass-transfer coefficient of As in molten copper at 1523 K was determined to be 1.3(±0.4)×10−4 m·s−1 based on the material balances of As and oxygen in the molten copper and slag phases, and the equilibrium relationship of the As elimination reaction at the slag-metal interface. In addition, the behavior of the simultaneous elimination of As and Sb, which coexist as impurities in molten copper at 1523 K, were also investigated from a kinetic viewpoint. The results show that the elimination rate of As is much higher than that of Sb, and two types of elimination behaviors are observed depending on the initial oxygen concentration in molten copper. At relatively low initial oxygen concentrations, As is preferentially eliminated with an initial plateauing of Sb elimination. On the other hand, both elements are eliminated simultaneously at relatively high initial oxygen concentrations. These behaviors were examined from the viewpoint of the oxygen concentration at the slag-metal interface.

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Effects of Coexisting Oxygen and Antimony in Molten Copper on Rate of Arsenic Elimination from the Copper Phase by the Use of Na2CO3 Slag

Influences of Potential and pH on Initiation of Environment-Assisted Cracking of Ti–6Al–4V

Takumi Haruna, Masaya Hamasaki, Toshio Shibata

pp. 2190-2196

Abstract

We have investigated the influences of potential and pH on environment-assisted cracking (EAC) of Ti–6Al–4V in aqueous solutions. The EAC test was conducted by slow strain rate technique. Solution pH was controlled from 1 to 7, and applied potential was fixed between −1.8 and +0.2 VSHE. In the solutions of pHs 3 and 7, mechanical properties of the material was almost independent of applied potential. This means that the material shows almost no EAC susceptibility in the potential-pH region for the EAC test period. At pH 1, however, both maximum stress and fracture strain changed with applied potential, and showed minimum values at an applied potential of about −1.0 VSHE. According to surface analyses by scanning electron microscopy and X-ray diffraction technique, some cracks and Ti hydride were detected from only the specimens fractured at about −1.0 VSHE in the solution of pH 1. Therefore, it can be concluded that Ti–6Al–4V is most susceptible to the EAC at about −1.0 VSHE and a pH less than 1. The EAC region was in good agreement with Ti ion stable region in a potential-pH diagram of Ti/water system, and was quite similar to that on the EAC of TiAl.

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Influences of Potential and pH on Initiation of Environment-Assisted Cracking of Ti–6Al–4V

Effect of Topography on Glossiness and Surface Color for a 5052 Aluminum Alloy

Makiko Yonehara, Koichiro Kihara, Yoshihito Kagawa, Hiroaki Isono, Toshio Sugibayashi

pp. 2197-2203

Abstract

The effect of topography on the glossiness and surface color of aluminum alloy A5052 specimens was experimentally investigated. The surfaces of the specimens were machined using either a vertical milling machine, a horizontal milling machine or a shaping machine. Four specimens were produced by each machine so that the arithmetical mean roughness value, Ra, was less than 1 μm under four different cutting conditions. The experimental results revealed that the vertical and horizontal milling glossiness values were nearly the same, while the glossiness values of the shaped surface was less than half of this value. The surface color of all of the specimens was gray, although the lightness value of the surface color, L*, for the horizontal milling surface had the highest value. Based on the experimental results, it was determined that the surface texture of specimens produced by these machines could be characterized by their glossiness and surface color. These results could prove an effective indicator for choosing the most appropriate machining method by providing surface texture values.

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Effect of Topography on Glossiness and Surface Color for a 5052 Aluminum Alloy

Gas Pore Formation in Lost Foam Casting of AZ91H Mg Alloy in Comparison with A356 Al Alloy

Seung-Ryoul Shin, Sang-Won Han, Kyong-Whoan Lee

pp. 2204-2210

Abstract

Castings performed under reduced pressure and atmosphere were used to investigate the formation of pores in lost foam casting (LFC) of the AZ91H Mg alloy, and the results are compared with the results of a previous work on the A 356 Al alloy.
In LFC, although the pouring temperature of the AZ91H alloy melt was higher than that of the A356 alloy, the amount of porosity in the AZ91H alloy after solidification was much lower than that of the A356 alloy. The lower porosity was caused by the extra hydrogen solubility. The pore formation mechanism of the AZ91H alloy in LFC was similar to that of the A356 alloy but the critical temperature for generating a different mechanism of pore formation is higher in the A356 alloy by as much as about 323 K. The mold evacuation promotes lower porosity and shrinkage defects due to the easy removal of polystyrene products. However, the exceeded vacuum degree severely entraps polymer pyrolysis products, thereby leaving large pores after solidification.

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Gas Pore Formation in Lost Foam Casting of AZ91H Mg Alloy in Comparison with A356 Al Alloy

Effect of Welding Process Parameters on Mechanical Property of FSW Lap Joint between Aluminum Alloy and Steel

Kittipong Kimapong, Takehiko Watanabe

pp. 2211-2217

Abstract

This paper investigated the effect of a tilt angle and a pin diameter of the tool on the tensile shear load of lap joints between A5083 aluminum alloy and SS400 steel produced by Friction Stir Welding. The main results obtained are as follows:
The joint shear strength could not be increased with the increase of a tool tilt angle due to the formation of intermetallic compound at the joint interface. The increase of a tool tilt angle caused the concentration of aluminum in the intermetallic compound increased, resulting in the decrease of the joint strength. The increase of a pin diameter of a tool also could not increase the shear strength of the joint due to a void defect and a thicker intermetallic compound formed at the interface. The size of the void increased as the pin diameter increased. The effect of a pre-hole, which was opened at the pin inserting position of an aluminum plate before welding, was investigated to obtain the higher shear strength of the joints. It was concluded that the joint interface temperature was slightly decreased and the thickness of the intermetallic compound at the interface decreased with the increase of pre-hole diameter. The optimal pre-hole indicated the shear strength of about 77% that of the aluminum base material. The interface microstructure examination showed no intermetallic compound was formed at the joint interface.

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Effect of Welding Process Parameters on Mechanical Property of FSW Lap Joint between Aluminum Alloy and Steel

New Ti-Based Bulk Metallic Glasses with Significant Plasticity

Hua Men, Shujie Pang, Akihisa Inoue, Tao Zhang

pp. 2218-2220

Abstract

Formation of Ti-based bulk metallic glasses was investigated in (Ti,Zr)–(Cu,Ni) pseudobinary system. It was found that glass-forming ability was significantly improved by the addition of Zr and Ni to the Ti–Cu binary alloys. For Ti50Zr5Cu40Ni5, Ti45Zr5Cu45Ni5, Ti42.5Zr10Cu42.5Ni5 and Ti42.5Zr7.5Cu45Ni5 alloys, glassy alloy rods with diameters of 2 and 3 mm can be obtained by a copper mold casting method. The glassy alloys exhibit high compressive fracture strength of about 2 GPa, and the bulk glassy Ti45Zr5Cu45Ni5 alloy shows distinct plastic strain of 0.018.

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New Ti-Based Bulk Metallic Glasses with Significant Plasticity

Microstructure and Mechanical Properties of a Rheo-Diecast Mg–10Zn–4.5Al Alloy

Yuqin Liu, Ma Qian, Z. Fan

pp. 2221-2228

Abstract

High zinc content Mg–Zn–Al alloys have the potential to be used as high pressure die casting (HPDC) alloys for applications up to 150°C. However, these alloys show high tendency to hot tearing and microporosity. Rheo-diecasting (RDC) is an innovative semisolid HPDC process, which can effectively eliminate the formation of primary magnesium dendrites and convert them into fine, globular particles. This very positive change in the morphology and distribution of the primary phase reduces the subsequent formation of various casting defects. In this study, a composition of Mg–10Zn–4.5Al was selected from the Mg–Zn–Al system and processed with both HPDC and RDC. It is shown that, samples produced by the RDC process exhibit substantially reduced hot cracks, few gas pores, and a nearly uniform distribution of fine, globular primary particles. These microstructural changes resulted in much improved strength and elongation, which are comparable to those of AZ91D, while the processing temperature is much lower. It is concluded that high zinc content Mg–Zn–Al alloys have good potential to be exploited as commercially useful alloys by the RDC process.

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Microstructure and Mechanical Properties of a Rheo-Diecast Mg–10Zn–4.5Al Alloy

Image-Based Mechanical Analysis of Multifilamentary Microstructure Formation in Al–Fe Heavily Deformed In-Situ Composites

Hiroyuki Toda, Hiroto Mizutani, Toshiro Kobayashi, Toshikazu Akahori, Mitsuo Niinomi

pp. 2229-2236

Abstract

It has been reported that nano-scale multifilamentary microstructure, which has been readily available in Al–Nb systems, was hardly realized in Al–Fe heavily-deformed composites systems. In the present study, state-of-the-art techniques are applied to gain basic insight into the necessary requirement for the texture development of the Al–Fe composites. Three-dimensional finite element meshes were generated to monitor local stress and strain distributions in real materials. The approach taken in this study may be characterized as new type of the reverse engineering which is based on the visualization of microstructural features of materials. It has been clarified that local stress elevation occurs where the Fe phase is constricted or gnarled with flection when cutting chips are used as a matrix. Hydrostatic stress varies significantly in the Fe phase thereby promoting the plasticity of the Fe phase. Both sufficient strengthening of aluminum and irregular distribution of the embedded Fe phase are identified essential for multifilamentary microstructure formation.

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Image-Based Mechanical Analysis of Multifilamentary Microstructure Formation in Al–Fe Heavily Deformed In-Situ Composites

Fabrication of Fe-Based Bulk Amorphous Alloys Using Hot Metal and Commercial Ferro-Alloys

Seonghoon Yi, Ki Buem Kim, Ho Sang Sohn

pp. 2237-2240

Abstract

For commercial applications of Fe-based bulk amorphous alloys as structural materials, Fe-based bulk amorphous alloys that can be cost-effectively and massively produced have been developed using hot metal and ferro-alloys from a steel plant. The alloy Fe68.0C10.5Si4.4B6.5P8.6Al2.0 can be cast into a fully amorphous rod of 3 mm in diameter through a suction casting method. Upon heating the amorphous rod, a sequential crystallization behavior starting with the precipitation of fcc-Fe phase were observed. Since the crystallization kinetics was sluggish, the Fe-based bulk amorphous alloy can be used as a precursor for the fabrication of bulk nanostructured Fe alloy.

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Fabrication of Fe-Based Bulk Amorphous Alloys Using Hot Metal and Commercial Ferro-Alloys

Effects of Electron Beam Irradiation on Impact Value for Soda Glass

Yoshitake Nishi, Keisuke Iwata

pp. 2241-2245

Abstract

Influences of electron beam (EB) irradiation on the impact value for soda glass were studied by a standard Charpy impact test. EB irradiation below 0.0432 MGy, which was one of short-time treatments of dry process at low temperature, increased impact values of the glass. As the EB irradiation generated dangling bonds at the weaker-bonded metal–oxygen atomic pairs in the soda glass, partial relaxation occurred at points of residual strain near dangling bonds in the network structure mainly constructed with the stronger-bonded metal–oxygen pairs. If the inter-atomic distance of the stronger-bonded metal–oxygen pairs became to be optimum potential curves of the sodium glass, the relaxation should increase the bonding energy of the network structure. Evidently, the increased impact value was mainly due to an increase in the bonding energy for the stronger-bonded metal (Si or Al)–oxygen atomic pairs in the atomic network structure, as well as a relaxation of the network structure.

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Effects of Electron Beam Irradiation on Impact Value for Soda Glass

Preparation of Calcium Phosphate Films by Radiofrequency Magnetron Sputtering

Takayuki Narushima, Kyosuke Ueda, Takashi Goto, Hiroshi Masumoto, Tomoyuki Katsube, Hiroshi Kawamura, Chiaki Ouchi, Yasutaka Iguchi

pp. 2246-2252

Abstract

Calcium phosphate films were prepared on titanium substrates by radiofrequency (RF) magnetron sputtering at RF powers from 75 to 150 W. Hot-pressed β-tricalcium phosphate (β-TCP) plates with a high density (>99.6%) were used as a sputtering target. The substrate was not intentionally heated. The films consisted of amorphous calcium phosphate and oxyapatite (Ca10(PO4)6O) phases. The ratio of the oxyapatite phase depended on the sputtering conditions of RF power, oxygen gas concentration in the sputtering gas (CO2) and total pressure in the chamber. The (002) preferred orientation of oxyapatite phase was observed. The deposition rate of films increased with increasing RF power and decreasing CO2. The highest deposition rate was 0.143 nm·s−1 (0.515 μm·h−1).

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Preparation of Calcium Phosphate Films by Radiofrequency Magnetron Sputtering

Hydrogen Permeability in Nb–Ti–Ni Alloys Containing Much Primary (Nb,Ti) Phase

Weimin Luo, Kazuhiro Ishikawa, Kiyoshi Aoki

pp. 2253-2259

Abstract

In order to develop high hydrogen permeability alloys, structural changes induced by hydrogenation, microstructures and hydrogen permeability Φ were investigated for samples on the straight line connecting the eutectic and the primary phase in the Nb–Ti–Ni phase diagram. Φ was measurable in the alloys containing much amount of the eutectic phase, indicating that the eutectic microstructure suppresses the hydrogen embrittlement. The value of Φ increased with increasing Nb content and the volume fraction of the primary (Nb,Ti) phase. The most Nb-rich Nb68Ti17Ni15 alloy showed the highest Φ of 4.91×10−8 (mol H2m−1 s−1 Pa−0.5) at 673 K, which is 2.5 times higher than that of the Nb39Ti31Ni30 alloy, which has been reported to be highest in the Nb–Ti–Ni alloys. The present work demonstrated that the hydrogen permeable alloys are extended on the straight line connecting the eutectic and the primary phase to the Nb-rich side in the Nb–Ti–Ni system.

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Hydrogen Permeability in Nb–Ti–Ni Alloys Containing Much Primary (Nb,Ti) Phase

Improved Biocompatibility of Titanium–Zirconium (Ti–Zr) Alloy: Tissue Reaction and Sensitization to Ti–Zr Alloy Compared with Pure Ti and Zr in Rat Implantation Study

Yoshiaki Ikarashi, Kazuhiro Toyoda, Equo Kobayashi, Hisashi Doi, Takayuki Yoneyama, Hitoshi Hamanaka, Toshie Tsuchiya

pp. 2260-2267

Abstract

Titanium–zirconium (Ti–Zr) binary alloy has better corrosion resistance and mechanical properties than commercially pure Ti. The present study was designed to determine the biocompatibility of Ti–Zr alloy by an implantation test in animal bodies in comparison with pure Ti, Zr, and chromium (Cr) implants as positive controls. Sample specimens were placed in a subcutaneous position in rats for 8 months. No significant decreases in body weight, the weight of any organ, or the weight of any organ relative to body weight were found in the implant groups compared to a no-implant control group. On hematological examination, small differences in several parameters were found in some groups, but these changes were not attributable to the materials implanted. Mitogen-induced blastogenesis was observed in similar degrees among all implant groups. These results suggest that the implantation of test samples did not cause systemic toxicity or a decrease in immune activity. The fibrous capsule membranes around the Ti and Ti–Zr alloy implants were thinner than those around Cr implants. The numbers of macrophages, inflammatory cells, and other cells involved in immune responses in and around the fibrous capsules of the Cr- and Ti-implant groups were higher than those of the Ti–Zr alloy- and Zr-implant groups. The Ti–Zr alloy had the lowest total score of tissue responses among the materials tested. None of the animals from the Ti-, Zr-, and Ti–Zr alloy-implant groups exhibited a skin reaction following exposure to Ti or Zr salt solutions. These results indicate the Ti–Zr alloy has better biocompatibility than Ti for use as an artificial surgical implant.

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Improved Biocompatibility of Titanium–Zirconium (Ti–Zr) Alloy: Tissue Reaction and Sensitization to Ti–Zr Alloy Compared with Pure Ti and Zr in Rat Implantation Study

Effect of Mg Content on Vibration Fracture Resistance of Friction Stirred Al–Mg Alloys

Kuo-Tsung Huang, Truan-Sheng Lui, Li-Hui Chen

pp. 2268-2275

Abstract

In this study, the effect of Mg content on friction stirred Al–Mg alloy is discussed, and the experimental results indicate that grains of parent plate which are refined through FSP (friction stir processing) are effective in enhancing tensile properties of materials through FSP and improving the vibration fracture resistance of friction stirred specimens. It should be noted that the deterioration of vibration fracture resistance can be recognized as Mg content increases, the grain size actually has been refined by FSP. From crack propagation result, an intergranular crack propagation feature can be recognized in the specimen with higher Mg content, and it is reasonable to suggest that the precipitation of β phase plays an important role in the deterioration of vibration fracture resistance. However, all cross-sectioned microstructures at stir zone show that distinct finer grains which can be acquired by dynamic recrystallization during FSP. That meaningful improvement of uniform elongation on friction stirred specimens can be recognized is not only resulted from controlling the grain size factor, but also microstructural characteristics factor which are resulted from high temperature shear deformation.

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Effect of Mg Content on Vibration Fracture Resistance of Friction Stirred Al–Mg Alloys

Electrical Characteristics of a New Class of Conductive Adhesive

Woo-Ju Jeong, Hiroshi Nishikawa, Daisuke Itou, Tadashi Takemoto

pp. 2276-2281

Abstract

Conventional conductive adhesives are composed of micro-sized filler metal and polymer matrix. Currently, the conductivity of conventional conductive adhesives is generated by small contact points formed among the particles during the curing process and by the tunneling effect. Therefore, conventional conductive adhesives generally exhibit higher electrical resistance than metal solder materials. In this study, a new class of conductive adhesive, composed of nano-particles and micro-particles in epoxy, was developed to improve electrical conductivity. This study used four conventional conductive adhesives (CCA1 to 4) and three hybrid conductive adhesives (HCA1 to 3). Scanning electron microscopy (SEM) observation was used to investigate the configuration of nano-particles and micro-particles. The electrical resistance of HCA1 to 3 was investigated and compared to CCA1 to 4 using a four-point probe method. When 2 mass% of nano-particle content was added to the micro-particle (HCA1), the electrical resistance decreased compared to CCA3. At 4 mass% of nano-particle content (HCA2), the electrical resistance value was similar to CCA3. However, at 8 mass% of nano-particle content (HCA3), the electrical resistance continued to increase, and exceeded that of CCA3.

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Electrical Characteristics of a New Class of Conductive Adhesive

Local Structure and Glass Transition in Zr-Based Binary Amorphous Alloys

Tetsu Ichitsubo, Eiichiro Matsubara, Junji Saida, Ho-Sou Chen

pp. 2282-2286

Abstract

The physical significance of the glass transition observed by differential scanning calorimetry (DSC) in the metallic glasses was considered through the measurements of the heating-rate, β, dependence of the glass transition temperature, Tg, and the crystallization temperature, Tx, in the Zr70Cu30 and Zr70Ni30 amorphous alloys and X-ray study of their structures in as-quenched and crystallized states. Zr70Cu30 exhibits the glass transition before crystallization, but Zr70Ni30 is immediately crystallized at heating rates of conventional time scale in the DSC measurement. The heating rate βc at the intersection of the two linear curves of Tg and Tx against logβ provides us with a significant measure to determine the glass-forming ability or thermal stability of the metallic glasses. By heating at β larger than βc, the crystallization is suppressed and the glass transition is clearly observed even in Zr70Ni30. The thermal stability of the Zr70Cu30 amorphous alloy is caused by retardation of crystallization due to the amorphous structure that is different from the Zr2Cu crystalline phase. In contrast, the thermal instability of Zr70Ni30 is attributed to the structural similarity to the Zr2Ni crystalline phase. Thus, suppressing the crystallization is shown to be a key to enhance the thermal stability of the present amorphous alloys.

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Local Structure and Glass Transition in Zr-Based Binary Amorphous Alloys

Development of Constitutive Equation on Superplastic RS P/M Mg–Y–Zn Alloy

Masato Tsujikawa, Hidetoshi Somekawa, Sung Wook Chung, Kenji Higashi

pp. 2287-2290

Abstract

A constitutive equation of rapid solidification (RS) powder metallurgy (P/M) magnesium alloy was constructed analytically from normalized strain rate-stress plots. Data related to RS P/M magnesium alloy showed deviation from those of conventional superplastic magnesium alloys; they indicated greater strength or lower strain rates than conventional superplastic magnesium alloys because the grains have a unique structure on superplastic flow. A constitutive equation for superplastic flow was developed using a metal matrix composite model.

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Development of Constitutive Equation on Superplastic RS P/M Mg–Y–Zn Alloy

Ce-Rich Misch Metal-Based Bulk Metallic Glasses with High Glass-Forming Ability

Ran Li, Shujie Pang, Hua Men, Tao Zhang

pp. 2291-2294

Abstract

Ce-rich misch metal (Mm)-based bulk metallic glasses (Mm consists of Ce, La, Pr and Nd) with high glass-forming ability are developed in Mm–Co–Al alloy system. The critical diameter for glass-formation is 10, 5 and 3 mm, and the supercooled liquid region ΔTxTx=TxTg, Tx is crystallization temperature and Tg is glass transition temperature) are 27, 90 and 79 K for Mm65Co25Al10 (Mm65), Mm60Co20Al20 (Mm60) and Mm55Co25Al20 (Mm55) alloys, respectively. Reduced glass transition temperature Trg (Trg=TgTm, where Tm is melting temperature) is 0.62, 0.65 and 0.69 for Mm65, Mm60 and Mm55, respectively. The employment of the misch metal, which comprises multi-rare earth elements, instead of pure Ce in the Ce–Al–Co system can improve the glass-forming ability in spite of the tiny atomic size difference of the rare earth metals. The present alloy system is an exception to the criteria of ΔTx, TgTm and different atomic size distribution as well as negative heat of mixing used for evaluating the relative GFA.

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Ce-Rich Misch Metal-Based Bulk Metallic Glasses with High Glass-Forming Ability

Surface Evolution during Focused Ion Beam Micro-Machining in (001) Plane of Single-Crystalline Ni and Amorphous Nickel Alloy

Hiroyuki Hosokawa, Takeshi Nakajima, Koji Shimojima, Mamoru Mabuchi

pp. 2295-2297

Abstract

A focused Ga+ ion beam (30 keV and 187 pA) have been irradiated at doses of 8.92×1016–2.68×1018 ions/cm2 in (001) plane of a single-crystalline Ni and an amorphous Ni75B15Si10 alloy and their surface evolution was investigated by atomic force microscopy. The root-mean-square (rms) roughness increased with increasing ion dose and the transition of surface morphology from dot structure to ripple structure occurred during FIB machining in the single-crystalline Ni. However, the amorphous Ni75B15Si10 alloy showed no such transition of surface morphology and held the rms roughness almost constant in an ion dose range more than about 1×1017 ions/cm2. Therefore, it is suggested that surface diffusion, which is the primary smoothing mechanism for crystalline surfaces, plays an important role in smoothening during FIB machining when the ion dose is low, while viscous flow, which is dominant for amorphous surfaces, contributes to smoothening when the ion dose is large.

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Surface Evolution during Focused Ion Beam Micro-Machining in (001) Plane of Single-Crystalline Ni and Amorphous Nickel Alloy

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