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MATERIALS TRANSACTIONS Vol. 47 (2006), No. 3

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. 47 (2006), No. 3

Structure and Magnetism of Fe(Rh,Pd) Alloys

Kazuhiko Uebayashi, Hisashi Shimizu, Hideji Yamada

pp. 456-459

Abstract

First-principle band calculations of ordered 3d and 4d transition-metal alloys Fe(Rh,Pd) with the CsCl and CuAu-I type structures are carried out by a linear muffin-tin orbital method within an atomic sphere approximation, where Rh and Pd atoms are treated as virtual 4d-atoms with the atomic number averaged over the concentration. A generalized gradient correction for exchange-correlation potential is taken into account. Total energies for paramagnetic, ferromagnetic and three kinds of antiferromagnetic states are estimated as a function of lattice constants, a and c. Observed lattice constants and spin structures for the present alloys are well described by the present calculations.

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Structure and Magnetism of Fe(Rh,Pd) Alloys

Grüneisen’s Approach to Magnetovolume Effect of Itinerant Electron Ferromagnets

Yoshinori Takahashi, Takeshi Kanomata

pp. 460-463

Abstract

Interplay between magnetism and crystal volume in itinerant electron ferromagnets is reexamined paying particular attention on effects of spin fluctuations. By introducing Grüneisen parameters, magnetovolume properties are derived from the explicit volume dependence of the free energy. As the result, we have clarified the presence of new thermal expansions, giving rise to the enhanced T-linear coefficient of the thermal expansion coefficient at low temperatures around the magnetic instability point. We have also found that the magnetovolume coupling constant is temperature dependent and vanishes at the critical point. These results are compared with experiments.

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Grüneisen’s Approach to Magnetovolume Effect of Itinerant Electron Ferromagnets

Effect of Chemical Disorder on Half-Metallicity of Fe2CrZ (Z = IIIb, IV, Vb Element)

Shoji Ishida, Sou Mizutani, Sinpei Fujii, Setsuro Asano

pp. 464-470

Abstract

The electronic structures were systematically calculated for Heusler alloys X2YZ (X and Y = 3d transition element, Z = IIIb, IVb, Vb element). The results show that alloys Fe2CrZ have the high density-of-state at the Fermi energy in the majority-spin state and show high spin polarization. The effects of chemical disorder on the half-metallicity and magnetic moment are discussed on the basis of the electronic structures. Considering three types of chemical disorder, we show that among the alloys Fe2CrZ, there are high spin polarized materials insensitive to chemical disorder and that Fe–Cr chemical disorder may occur.

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Effect of Chemical Disorder on Half-Metallicity of Fe2CrZ (Z = IIIb, IV, Vb Element)

Magnetovolume Effect and Negative Thermal Expansion in Mn3(Cu1−xGex)N

Koshi Takenaka, Hidenori Takagi

pp. 471-474

Abstract

Metallic manganese nitrides Mn3AN (A=Zn, Ga, etc) are well-known for their large magnetovolume effect (MVE), i.e., a discontinuous volume expansion at the magnetic transition. However, MVE is exceptionally absent in Mn3CuN. We found that MVE is recovered by a small amount of Ge in the Cu site. This revival seems to coincide with recovery of the cubic structure. By further Ge doping, the volume expansion becomes gradual (ΔT∼100 K) and large negative thermal expansion (NTE) is exhibited around room temperature [α=−12×10−6 K−1 (α: coefficient of linear thermal expansion) for Mn3(Cu0.5Ge0.5)N]. Such a large, isotropic and non-hysteretic NTE is desirable for practical applications.

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Magnetovolume Effect and Negative Thermal Expansion in Mn3(Cu1−xGex)N

Electronic Structure of Ni3AlXy (X=B, C, H; 0<y<1)

Izumi Hase

pp. 475-477

Abstract

The electronic structures of anti-perovskite-type intermetallic compound Ni3AlXy (X=B, C, H; 0<y<1) have been calculated using coherent-potential approximation (CPA) within the local-density approximation (LDA). Ferromagnetic moment in Ni3Al rapidly decreases with increasing y for every dopant X, even though the lattice is more expanded than non-doped Ni3Al.

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Electronic Structure of Ni3AlXy (X=B, C, H; 0<y<1)

Concentration Dependence of Pressure Effect in La(FexSi1−x)13 Compounds

Asaya Fujita, Kazuaki Fukamichi, Tsuneaki Goto

pp. 478-481

Abstract

Effects of pressure P on the magnetic moment M and the Curie temperature TC have been investigated for La(FexSi1−x)13 above and below the magnetic phase boundary concentration x=0.86, where the ferromagnetic-paramagnetic transition at TC changes from the first-order (x≥0.86) to the second-order (x<0.86). The pressure coefficient of M exhibits a sluggish variation against concentration and no anomaly was observed at x=0.86, being consistent with the Landau expansion model. On the other hand, TC for the second-order transition has a large negative pressure coefficient dTCdP and its magnitude increases with increasing x. Above x=0.86, the magnitude of dTCdP for the first-order transition increases with x, contrary to the theoretical expectation. It has been revealed that the spin-wave dispersion coefficient becomes smaller when the first-order transition becomes clear by changing the concentration and also applying pressure. Consequently, it is plausible that dTCdP above x=0.86 is enhanced by the increase of instability of the ferromagnetic state.

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Concentration Dependence of Pressure Effect in La(FexSi1−x)13 Compounds

Control of Working Temperature of Large Isothermal Magnetic Entropy Change in La(FexTMySi1−xy)13 (TM=Cr, Mn, Ni) and La1−zCez(FexMnySi1−xy)13

Shun Fujieda, Naoyuki Kawamoto, Asaya Fujita, Kazuaki Fukamichi

pp. 482-485

Abstract

The Curie temperature TC of La(FexSi1−x)13 is increased by a partial substitution of Ni for Fe. On the contrary, TC is decreased by a partial substitution of Cr or Mn. In addition, a partial substitution of Ce for La in La(FexMnySi1−xy)13 causes the further decrease of TC. As a result, La0.65Ce0.35(Fe0.85Mn0.03Si0.12)13 exhibits a thermal-induced first-order transition at TC=60 K. This result means that TC of the La1−zCez(FexMnySi1−xy)13 is tunable in the temperature range between 60 and 180 K by adjusting composition with keeping the itinerant-electron metamagnetic transition. In the magnetic field change from 0 to 4 T in the vicinity of TC=60 K, the La0.65Ce0.35(Fe0.85Mn0.03Si0.12)13 shows the isothermal magnetic entropy change ΔSm=−13 J kg−1 K−1 and the relative cooling power RCP=458 J kg−1. Consequently, the La1−zCez(FexMnySi1−xy)13 compounds are useful for magnetic refrigerants working in a temperature range between 60 and 180 K.

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Control of Working Temperature of Large Isothermal Magnetic Entropy Change in La(FexTMySi1−xy)13 (TM=Cr, Mn, Ni) and La1−zCez(FexMnySi1−xy)13

Effects of Heat Treatment on the Magnetic Phase Transition and Magnetocaloric Properties of Mn1+δAs1−xSbx

Hirofumi Wada, Chie Funaba, Tetsuya Asano

pp. 486-491

Abstract

We studied effects of heat treatment on the magnetic transition and the magnetocaloric effects (MCEs) of Mn1+δAs1−xSbx with x=0.1 and 0.25. It is found that sintering at an appropriate temperature gives a sharp magnetic transition and hence giant MCEs for Mn1+δAs1−xSbx. In the bulk samples slowly cooled from a liquid state, free Sb was precipitated, which gives rise to compositional deviation. Quenching from a liquid state suppresses the precipitation of Sb. Subsequent annealing is effective to improve homogeneity, as a result, the sample undergoes a sharp magnetic transition. The optimum conditions of heat treatments of the present system for a sharp magnetic transition are discussed.

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Effects of Heat Treatment on the Magnetic Phase Transition and Magnetocaloric Properties of Mn1+δAs1−xSbx

X-ray Powder Diffraction Studies of Mn3Ga0.97Al0.03C in Magnetic Fields

Keiichi Koyama, Takeshi Kanomata, Tatsuo Watanabe, Takanobu Suzuki, Hironori Nishihara, Kazuo Watanabe

pp. 492-495

Abstract

We have performed the X-ray powder diffraction measurements for Mn3Ga0.97Al0.03C with a perovskite-type structure in the temperature range from 8 to 320 K in magnetic fields up to 5 T, in order to investigate the structural properties affected by the magnetic field. The compound has a successive magnetic phase transition below 160 K: the ferromagnetic (F)–intermediate (I)–antiferromagnetic (AF) phases for cooling process. The lattice parameter a abruptly increases by 0.23%, accompanied by the transition from the I to AF phases at TAF–I=130 K. In addition, we clearly observed that magnetic field induces the I phase with small a and suppresses the AF phase with large a below TAF–I.

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X-ray Powder Diffraction Studies of Mn3Ga0.97Al0.03C in Magnetic Fields

Magnetic Properties of Weak Itinerant Electron Ferromagnet CoVSb

Takeshi Kanomata, Toshiyuki Igarashi, Hironori Nishihara, Keiichi Koyama, Kazuo Watanabe, Klaus -U. Neumann, Kurt R. A. Ziebeck

pp. 496-500

Abstract

Precise magnetization measurements have been made on the weak itinerant electron ferromagnet CoVSb. The magnetic moment at 4.2 K and the Curie temperature TC are 0.16 μB/f.u. and 45 K, respectively. Below 10 K, the decrease in the square of the spontaneous magnetization Ms(T)2 is proportional to T2. However, over a wide temperature range from 24 K to the Curie temperature, the decrease in Ms(T)2 is proportional to T4⁄3. The results obtained are analyzed using spin fluctuation theory.

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Magnetic Properties of Weak Itinerant Electron Ferromagnet CoVSb

Pressure-Induced Metal-Insulator Transition in the Itinerant Antiferromagnet Nb12−xTixO29 (x=0 and 0.2)

Takashi Naka, Takayuki Nakane, Yuji Furukawa, Tadafumi Adschiri, Akiyuki Matsushita

pp. 501-503

Abstract

We have carried out resistivity measurements on itinerant antiferromagnets Nb12−xTixO29 (x=0 and 0.2) under pressure up to 2.5 GPa in order to investigate the pressure effects on these novel magnetic and metallic behaviors. The resistivity-temperature curves for both systems show metallic behavior at lower pressure, while the resistivity increases with decreasing temperature at higher pressure. These results indicate that a metal-insulator transition is induced by the application of the pressure in both systems. We will discuss the origin of the metal-insulator transition in terms of charge ordering and pressure-induced amorphization as have been suggested in other niobium oxides.

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Pressure-Induced Metal-Insulator Transition in the Itinerant Antiferromagnet Nb12−xTixO29 (x=0 and 0.2)

Effect of Annealing Temperature on Microstructure and Shape Memory Characteristics of Ti–22Nb–6Zr(at%) Biomedical Alloy

Jae Il Kim, Hee Young Kim, Tomonari Inamura, Hideki Hosoda, Shuichi Miyazaki

pp. 505-512

Abstract

Effect of annealing temperature on microstructure and shape memory characteristics of Ti–22Nb–6Zr(at%) biomedical alloys was investigated by using tensile tests, XRD measurement, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After severe cold-rolling, the plate was annealed at temperatures between 773 and 1173 K. The α⁄β transus temperature in this alloy was determined to be between 823 and 873 K. The specimen annealed at 823 K for 3.6 ks exhibited a fine subgrain structure. A fully recrystallized structure was observed in the specimens annealed above 873 K. The annealing temperature less affected the transformation temperature and recovery strain. However, the critical stress for slip decreased considerably with increasing annealing temperature, because the grain size increased. All specimens annealed above 823 K exhibited stable superelastic behavior at room temperature.

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Effect of Annealing Temperature on Microstructure and Shape Memory Characteristics of Ti–22Nb–6Zr(at%) Biomedical Alloy

Effects of Sn Content and Aging Conditions on Superelasticity in Biomedical Ti–Mo–Sn Alloys

Takashi Maeshima, Satoshi Ushimaru, Kiyoshi Yamauchi, Minoru Nishida

pp. 513-517

Abstract

The effects of Sn content and aging conditions on superelasticity in Ti–Mo–Sn alloys were investigated. Martensitic transformation temperature decreased with an increasing of Sn content. A large superelastic strain of 3.0% was obtained in a solution-treated Ti–5 mol%Mo–5 mol%Sn alloy in the tensile test. The superelasticity in the Ti–5 mol%Mo–5 mol%Sn at room temperature was improved by aging at 873 K for short periods between 180 and 420 s. A specimen aged at 873 K for 300 s exhibited superelasticity with a recovery strain of 3.5% in the tensile test. A recovery strain of 3.0% was consistently achieved in cyclic tensile deformations.

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Effects of Sn Content and Aging Conditions on Superelasticity in Biomedical Ti–Mo–Sn Alloys

Effect of Nb Addition on Shape Memory Behavior of Ti–Mo–Ga Alloys

Hee Young Kim, Yoshinori Ohmatsu, Jae Il Kim, Tomonari Inamura, Hideki Hosoda, Shuichi Miyazaki

pp. 518-522

Abstract

Effect of Nb addition on mechanical properties and shape memory behavior of Ti–Mo–Ga alloys was investigated by cyclic loading-unloading tensile tests, tensile tests at various temperatures and Vickers hardness tests. The martensitic transformation start temperature (Ms) decreased by 20 K with 1 at% increase of Nb content in the Ti–6Mo–3Ga(at%) alloy. The shape memory effect was observed in the Ti–6Mo–3Ga(at%) alloy. The superelastic strain increased with increasing Nb content. The increase of the yield stress during the cyclic deformation decreased the strain recovery rate in the Ti–6Mo–3Ga(at%) alloy. Aging at intermediate temperatures resulted in increase in hardness of the Ti–6Mo–3Ga–(0–4)Nb(at%) alloys. The increase in hardness decreased significantly with increasing Nb content because the addition of Nb was effective to suppress the ω phase hardening. The yield stress decreased and the strain recovery rate increased with increasing number of cycle in the Ti–6Mo–3Ga–4Nb(at%) alloy.

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Effect of Nb Addition on Shape Memory Behavior of Ti–Mo–Ga Alloys

Near Net-Shape Fabrication of Superelastic NiTi Devices by Sputtering and Photoetching

Holger Rumpf, Volker Wipperfürth, Christiane Zamponi, Eckhard Quandt

pp. 523-526

Abstract

NiTi-films were fabricated by DC magnetron sputtering from cast-melted disc targets. The obtained freestanding films revealed superelastic properties in tensile testing experiments. At 37°C superelastic properties were achieved showing a closed-loop hysteresis and a plateau of more than 5% strain. Photolithography and wet etching technology were applied in order to fabricate net-shaped devices. Achievable structure sizes range in the order of the NiTi film thickness, i.e. typically between 5 and 15 μm. Tensile testing experiments reveal a remarkable strain tolerance of these devices which summed up to a superelastic strain of up to 5%. It has been demonstrated that the deposition process can be transferred to the fabrication of NiTi tubes, which have high potential for application as vascular implants, e.g. stents.

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Near Net-Shape Fabrication of Superelastic NiTi Devices by Sputtering and Photoetching

A Microstructural Map of Crystallized NiTi Thin Film Derived from In Situ TEM Methods

Hoo-Jeong Lee, Hai Ni, David T. Wu, Ainissa G. Ramirez

pp. 527-531

Abstract

Sputtered-deposited nickel titanium thin films are commonly amorphous when synthesized and require annealing to crystallize them. The resulting microstructures, which are governed by nucleation and growth kinetics, dictate the actuation properties. The evolution of these microstructures was studied using in situ transmission electron microscopy (TEM) heating methods. The experimentally-determined kinetic values of nucleation and growth were inserted into a mathematical expression derived from the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory, which predicts the average grain size over a broad range of temperatures.

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A Microstructural Map of Crystallized NiTi Thin Film Derived from In Situ TEM Methods

A TiNiCu Thin Film Micropump Made by Magnetron Co-Sputtered Method

H. J. Zhang, C. J. Qiu

pp. 532-535

Abstract

Thin film SMAs have the potential to became a primary actuating mechanism for micropumps. In this study, a micropump driven by TiNiCu shape memory thin film is designed and fabricated. The micropump is composed of a TiNiCu/Si bimorph driving membrane, a pump chamber and two inlet and outlet check valves. The property of TiNiCu films and driving capacity of TiNiCu/Si bimorph driving membrane are investigated. The film surface shows a smooth and featureless morphology without any cracks, and the hysteresis width ΔT of TiNiCu film is about 9°C. By using the recoverable force of TiNiCu thin film and biasing force of silicon membrane, the actuation diaphragm realizes reciprocating motion effectively. Experimental results show that the micropump driving by TiNiCu film has good performance, such as high pumping yield, high working frequency, stable driving capacity, and long fatigue life time.

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A TiNiCu Thin Film Micropump Made by Magnetron Co-Sputtered Method

In-Situ TEM Study of the Thickness Impact on the Crystallization Features of a Near Equal-Atomic TiNi Thin Film Prepared by Planar Magnetron Sputtering

Xiaodong Han, Shengcheng Mao, Qun Wei, YueFei Zhang, Ze Zhang

pp. 536-539

Abstract

In-situ TEM studies were conducted to reveal the crystallization features of equi-atomic TiNi amorphous thin films. The TiNi amorphous thin film crystallization procedure can be divided to be two types: the in-homogenous nucleation and growth mode in the ultra thin regions and the homogenous polymorphous mode in the thick areas. In the thin regions, the thickness controls the in-homogenous nucleation mode. The formed nano-crystallites in the thin areas are with a size of 5–20 nm while in the homogenous nucleation and growth mode, the grain size drops to the range of sub-micron level. In general, the stabilized grain size is a function of thin film thickness and can be described as G=kx, where x is the thickness in nano-meter and k is a constant related to lattice parameter. An intermediate phase forms through the crystallization procedure in the thick region. The intermediate phase possesses a cubic structure with lattice parameter of a=9.03 A. The intermediate phase transforms to the stable B2 phase when the specimen being kept above the crystallization temperature for some time. The crystallization sequence in the thick region is determined to be: TiNi amorphous → intermediate phase → B2 + Ti3Ni4.

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In-Situ TEM Study of the Thickness Impact on the Crystallization Features of a Near Equal-Atomic TiNi Thin Film Prepared by Planar Magnetron Sputtering

Martensitic Transformation Behavior and Shape Memory Properties of Ti–Ni–Pt Melt-Spun Ribbons

Tomonari Inamura, Yohei Takahashi, Hideki Hosoda, Kenji Wakashima, Takeshi Nagase, Takayoshi Nakano, Yukichi Umakoshi, Shuichi Miyazaki

pp. 540-545

Abstract

Martensitic transformation behavior and shape memory properties of a Ti50Ni40Pt10 (TiNiPt) melt-spun ribbon fabricated by a single roll melt-spinning technique were characterized. The constituent phases of the as-spun ribbon were B2 (parent phase) and B19 (martensite phase) at room temperature. The B2–B19 martensitic transformation temperatures of the as-spun ribbon were 100 K higher than those of the bulk-material with the same chemical composition. The martensitic transformation temperatures of the as-spun ribbon were decreased with increasing the temperature of the heat-treatment made after the melt-spinning. The as-spun ribbon and the heat-treated ribbons exhibited shape recovery by heating and/or pseudoelasticity. The martensitic transformation temperatures determined from the temperature dependence of the 0.2% flow stress of the pseudoelastic deformation were in good agreement with those of B2–B19 martensitic transformation determined by DSC. It was confirmed that the observed shape recovery and pseudoelasticity are shape memory effect and superelasticity due to the B2–B19 martensitic transformation. Shape memory effect and superelasticity of melt-spun TiNiPt alloy were found to appear at higher temperatures compared to those of Bulk-material with the same composition.

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Martensitic Transformation Behavior and Shape Memory Properties of Ti–Ni–Pt Melt-Spun Ribbons

Severe Plastic Deformation of Melt-Spun Shape Memory Ti2NiCu and Ni2MnGa Alloys

Vladimir G. Pushin, Ruslan Z. Valiev, Yuntian T. Zhu, Dmitrii V. Gunderov, Alexander V. Korolev, Nikolai I. Kourov, Tatiana E. Kuntsevich, Eduard Z. Valiev, Lyudmila I. Yurchenko

pp. 546-549

Abstract

This paper describes the influence of severe plastic deformation (SPD) on the structure, phase transformations, and physical properties of melt-spun Ti2NiCu-based and Ni2MnGa-based shape memory intermetallic alloys. It was found that the SPD by high pressure torsion (HPT) at room temperature can be effectively used for the synthesis of bulk nanostructured states in these initially submicro-grained or amorphized alloys obtained by melt-spinning method in the form of a ribbon. The subsequent low-temperature annealing of HPT-processed alloys leads to formation of homogeneous ultrafine nano-grained structure. This is connected with a very high degree and high homogeneity of deformation at SPD in the whole volume of deformed samples.

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Severe Plastic Deformation of Melt-Spun Shape Memory Ti2NiCu and Ni2MnGa Alloys

Fabrication of TiNi Powder by Mechanical Alloying and Shape Memory Characteristics of the Sintered Alloy

Akira Terayama, Hideki Kyogoku, Masaru Sakamura, Shinichiro Komatsu

pp. 550-557

Abstract

This paper presents the fabrication condition of TiNi alloy powder by mechanical alloying and shape memory characteristics of the sintered alloy. The effect of mechanical alloying condition on the characteristics of mechanically alloyed powder (MA powder) was investigated. Also, the difference in sintering behavior between the MA powder and the elementally mixed powders by V-blender and the shape memory characteristics of the sintered alloys were also examined. The MA powder was fabricated by milling using a planetary ball mill in a rotational speed between 200 and 500 min−1 for various milling times in an atmosphere of Ar gas. These two types of powders prepared in different processes were sintered using a pulse-current pressure sintering equipment at various sintering temperatures. The powder agglomerated and its particle size became larger with an increase in milling time. The mixture of Ti and Ni powders changed into an amorphous state by processing for 3.6 ks over 300 min−1. The sintered alloy of the MA powder showed more uniform phase of TiNi than that of the elementally mixed powders sintered in a same manner, however, the former showed a lower density than the latter due to a larger particle size of the MA powder of before-sintering. It was found from the measurement of the transformation temperature of the sintered alloy of the MA powder using DSC that the alloy has shape memory characteristics, and the transformation temperatures of the alloy are higher than those of the alloy of the elementally mixed powders due to waste of Ni powder.

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Fabrication of TiNi Powder by Mechanical Alloying and Shape Memory Characteristics of the Sintered Alloy

Shape Recovery Characteristics of NiTi Foams Fabricated by a Vacuum Process Applied to a Slurry

Noriaki Sakurai, Junjiro Takekawa

pp. 558-563

Abstract

In order to fabricate the NiTi foams with greater than 80% porosity, a vacuum process applied to a slurry was developed. A mixture of elemental Ni and Ti powders was dipped into a solution of 7.5 mass% polyvinyl alcohol, and stirred to make the slurry. The lightly compacted lumps of slurry were then subjected to reduced atmospheric pressure to make foamed compacts. The green foams were debound and sintered under vacuum into NiTi sintered foams with 85% porosity. X-ray analysis showed alloying of NiTi was completed by the sintering at ≥1100°C. X-ray diffraction analysis and DSC measurement also indicated that the NiTi foams consisted of B2 austenite and B19′ martensite phases. Measurement of shape recovery strain showed the NiTi foams obtained by this process had the far excellent shape recovery characteristics compared with those of wrought NiTi alloys. Furthermore, repeated compressive deformation and heating greatly increased the shape recovery strains of these high-porosity NiTi foams.

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Shape Recovery Characteristics of NiTi Foams Fabricated by a Vacuum Process Applied to a Slurry

Elastic Energy Analysis of Carbide and Nitride-Type Precipitates in an Fe–Mn–Si–Cr Shape Memory Alloy

Susan Farjami, Hiroshi Kubo

pp. 564-570

Abstract

The application of the microscopic theory of elasticity in a discrete lattice model is made on the transitional metal carbide and nitride precipitates formed in the Fe–Mn–Si–Cr shape memory alloy in conjunction with the improvement of shape memory effect (strain) and the improvement of strength. Two distinguishable methods of analysis have been established using the microscopic theory of elasticity in a discrete lattice model: One is the establishment of the description of precipitate and misfit dislocations in Fourier space. The second is the rigorous estimation of interaction energies among precipitate and misfit dislocations. The results could successfully describe the shape of the precipitate observed in the experimental investigation. It was also concluded that the elastic strain energy increases with the lattice parameter of the precipitate. Among the transition carbides and nitrides under investigations, VN, which revealed the minimum value of the elastic energy, is manifested to be the most favored one for the precipitation enhanced Fe–Mn–Si–Cr shape memory alloy. Homogeneously precipitated VN containing materials could show large deformability, higher strength by precipitation hardening and the higher shape recovery strain due to the nucleation sites of the precipitates in its reverse phase transformation.

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Elastic Energy Analysis of Carbide and Nitride-Type Precipitates in an Fe–Mn–Si–Cr Shape Memory Alloy

Mechanical Properties of Fe–Mn–Si Based SMA and the Application

Akikazu Sato, Hiroshi Kubo, Tadakatsu Maruyama

pp. 571-579

Abstract

The SME (shape memory effect) in an Fe–Mn–Si based SMA is governed by motion of Shockley partial dislocations which carry the fcc↔hcp phase transformations. The degree of SME is determined by preservation of the partial dislocations whereas the strength is determined by the internal stress opposing against the dislocation motion. The increase in the internal stress tends to induce dislocation reactions which ruin the preservation of the Shockley partials and hence to decrease the degree of SME. Nevertheless, usage of this SMA for construction of a large structural product has recently gained much attention even with sacrifice in the degree of SME. Upon application of this SMA in such a field, the optimum condition has to be searched both in the mechanical properties of the SMA itself and the type of the usage in the sense of deformation mode such as elongation, contraction, bending, twisting and so on. In this paper, the dislocation motion responsible for a good SME with high strength will be discussed on the ground of the basic knowledge of the dislocation generation, the motion and the reactions.

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Mechanical Properties of Fe–Mn–Si Based SMA and the Application

Development of Prestressed Concrete Using Fe–Mn–Si-Based Shape Memory Alloys Containing NbC

Takahiro Sawaguchi, Takehiko Kikuchi, Kazuyuki Ogawa, Setsuo Kajiwara, Yosaku Ikeo, Masarou Kojima, Takatoshi Ogawa

pp. 580-583

Abstract

This article reports the mechanical properties of concrete prestressed by the Fe–Mn–Si-based shape memory alloys containing NbC that exhibit an excellent shape memory effect without the so-called ‘training’ treatment. A thermomechanically treated Fe–28Mn–6Si–5Cr–0.53Nb–0.06C (mass%) alloy was used for this purpose. Four square bars of the alloy were embedded in mortar, and heated above their reverse martensitic transformation start temperature after hardening of the mortar matrix. Three-point bending tests were performed for the mechanical property characterization. It was found that prestressing by the shape memory alloys increased the bending strength and cracking stress of the mortar.

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Development of Prestressed Concrete Using Fe–Mn–Si-Based Shape Memory Alloys Containing NbC

The Synthesis of Composite Particles in Molten Salts

Ruisong Yang, Lishan Cui, Yanjun Zheng

pp. 584-586

Abstract

A novel process for synthesizing composite particles, named the high temperature molten salts method, is discussed in this paper. The molten salts are a reaction medium that do not take part in the chemical reaction and can be easily dissolved by water washing. By this method, composite particles were prepared in molten salts at 680–850°C. The heat released from the chemical reaction was found playing an important role to obtain the desired composite particles. The reverse martensitic transformation of the NiTi particles is confirmed in these composite particles by differential scanning calorimetry (DSC).

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The Synthesis of Composite Particles in Molten Salts

Free-Energy Density of the Shape-Memory Alloy AuZn

Jason C. Lashley, Hassel Ledbetter, Tim W. Darling, Avadh Saxena, Artur Malinowski, Michael F. Hundley, James L. Smith, Dan J. Thoma

pp. 587-593

Abstract

The shape-memory alloy AuZn transforms martensitically (TM=65 K) from a cubic B2 (Pm\\bar3m) to a rhombohedral R-phase (P3) through softening of the TA2[110] phonon branch. We report elastic constants, specific heat, and thermal expansivity measurements through the transition. A large elastic anisotropy, A=9 at TM, associated with softening of the TA2[110] phonon branch accompanied with a volume change ΔVV of 0.25% characterize the transition. We find that specific heat and thermal expansion are well represented by adding low-energy Einstein modes to the harmonic lattice. On the basis of these measurements, combined with established group-theoretical symmetry criteria, the free-energy density is presented with atomic shuffle displacements as the primary order parameter, Q. We use this free-energy model to explain the atomic displacements in the R-phase.

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Free-Energy Density of the Shape-Memory Alloy AuZn

Electronic Structure of B2-Type Ti–Ni–Fe Alloys Exhibiting Second-Order-Like Structural Transformation

Takuya Yamamoto, Takashi Fukuda, Tomoyuki Kakeshita

pp. 594-598

Abstract

We have calculated electronic structure of B2-type Ti–(50−x)Ni–xFe (0≤x≤28) alloys in order to understand the concentration dependence of the phase stability of the B2-type structure in this system. The Fermi surface of each alloy shows a nesting with a sharp peak of generalized susceptibility χ(q) at a nesting vector of q=[ζζ0]2π⁄a. The value of ζ at the peak position decreases linearly as the Fe content increases. On the contrary, the peak height of χ(q) does not change monotonically but shows a maximum value for Ti–44Ni–6Fe alloy. This result is consistent with the experimental results obtained by resistivity and specific heat measurements. In addition, we found that although the χ(q) shows a local maximum near 1⁄3[110]2π⁄a in Ti–44Ni–6Fe alloy, it shows a saddle point near 1⁄3[110]2π⁄a in TiNi.

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Electronic Structure of B2-Type Ti–Ni–Fe Alloys Exhibiting Second-Order-Like Structural Transformation

The Electronic Structure and Magnetic Properties of Full- and Half-Heusler Alloys

Svetlana E. Kulkova, Sergey V. Eremeev, Tomoyuki Kakeshita, Sergey S. Kulkov, Gennadiy E. Rudenski

pp. 599-606

Abstract

The electronic structure of the full- and half-Heusler alloys have been studied by ab-initio calculations using full potential augmented plane-wave-method (FLAPW). It was shown that obtained equilibrium lattice parameters and magnetic moments agree well with available experimental data. The influence of vacancies on the electronic structure and magnetic properties of Ni2−xMnGa and Co2−xZrSn is analyzed.

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The Electronic Structure and Magnetic Properties of Full- and Half-Heusler Alloys

Acoustic Emission as a Probe of the Kinetics of the Martensitic Transformation in a Shape Memory Alloy

Stefanus Matheus Cornelis van Bohemen, Jilt Sietsma, Roumen Petrov, Marcel Joseph Marie Hermans, Ian Malcom Richardson

pp. 607-611

Abstract

The kinetics of the martensitic transformation in a CuAlMn shape memory alloy (SMA) has been studied using the acoustic emission (AE) technique. It is demonstrated that the volume fraction of martensite as a function of time and temperature can be derived from the measured AE power. The fraction data obtained can be described by the Koistinen and Marburger (Acta Metall. 7 (1959) 59) equation with high accuracy, which indicates that the nucleation of martensite takes place heterogeneously and that the average volume of martensite crystals is constant over the extent of the transformation. The martensite-start temperature determined from the measured AE data is in good agreement with the value found by differential scanning calorimetry (DSC). Furthermore, the results of AE experiments on the SMA are compared with optical Confocal Laser Scanning Microscopy (CLSM) observations of the surface of the SMA. The observations show that both small and large martensite plates are formed both at the beginning and at the end of the transformation, which is in agreement with the assumption of a constant average volume of martensite crystals used in the Koistinen and Marburger model.

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Acoustic Emission as a Probe of the Kinetics of the Martensitic Transformation in a Shape Memory Alloy

Magnetic Properties and Martensite Structures of Ni50Mn28Ga22 Ferromagnetic Shape Memory Alloy

Feng Chen, Zhi Y. Gao, Wei Cai, Lian C. Zhao

pp. 612-614

Abstract

Magnetic properties and martensite structures of Ni50Mn28Ga22 ferromagnetic shape memory alloy (FSMA) haven been investigated by physical properties measurement system (PPMS), magnetic force microscope (MFM) and transmission electron microscope (TEM) in the present paper. Magnetization-magnetic field (MH) curves and MFM images show that the martensite has stronger magnetic anisotropy than the parent phase. The typical martensite with twin substructures is observed in Ni50Mn28Ga22 alloy, while another type martensite substructure showing stripe like morphology is also found. It is assumed that such martensite structure may affect the magnetic field induced strain (MFIS) of Ni50Mn28Ga22 alloy.

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Magnetic Properties and Martensite Structures of Ni50Mn28Ga22 Ferromagnetic Shape Memory Alloy

Two-Way Shape Memory Effect and Micromachine of Rapidly Solidified Ferromagnetic Fe–Pd Ribbon

Harunobu Tomita, Teiko Okazaki, Yasubumi Furuya

pp. 615-618

Abstract

Ferromagnetic Fe–Pd alloy is a magneto-thermoelastic actuator material that has a large magnetostriction and the shape memory effect. In order to use the Fe–Pd alloy for a micromachine, we investigated the behavior of the shape memory effect for rapidly solidified Fe–29.6 at% Pd alloy ribbons. From the results, the ribbon exhibited a reversible two-way shape memory effect (TWSME) in the temperature range of 273 to 403 K, where the transformation from the martensite phase to austinite phase is found. On the basis of the development of an actuator of rapidly solidified Fe–29.6 at% Pd ribbon, a small simple-structured micromachine system was fabricated. A wireless micromachine is controlled remotely by an alternating magnetic field: it is able to swim in a fine liquid pipe with the aid of the gripping motion of a small ball. The ball is released by heating it to 340–350 K. This unique fishlike swimming micromachine will be applicable to medical curing devices in the body and as a nondestructive investigation tools for industrial machines and structures.

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Two-Way Shape Memory Effect and Micromachine of Rapidly Solidified Ferromagnetic Fe–Pd Ribbon

Martensitic Transformation and Microstructure of Sputter-Deposited Ni–Mn–Ga Films

Volodymyr A. Chernenko, Manfred Kohl, Victor A. L’vov, Volodymyr M. Kniazkyi, Makoto Ohtsuka, Oliver Kraft

pp. 619-624

Abstract

The martensitic transformation and microstructure of Ni–Mn–Ga films deposited on an alumina substrate and annealed at 1073 K for 36 ks are studied. Electrical resistivity and calorimetry measurements reveal a non-monotonous thickness dependence of the martensitic start temperature, Tms, at submicron film thickness. Focused Ion Beam (FIB) and standard SEM techniques are used to clarify the film microstructure. A martensitic morphology of films is confirmed by the FIB imaging to be a laminated twin structure aligned almost parallel to the film plane in each crystallite as a consequence of {110}-type crystallographic texture. A thermodynamic model based on the Landau formalism taking into account the substructure of the film and the elastic interaction between film and substrate describes the essential features of the thickness dependence of Tms.

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Martensitic Transformation and Microstructure of Sputter-Deposited Ni–Mn–Ga Films

Magnetic-Field Induced Two-Way Shape Memory Effect of Ferromagnetic Ni2MnGa Sputtered Films

Makoto Ohtsuka, Yuya Konno, Minoru Matsumoto, Toshiyuki Takagi, Kimio Itagaki

pp. 625-630

Abstract

The shape memory effect (SME) induced by the magnetic field is interesting and important for physics and application. The ferromagnetic Ni2MnGa films with various compositions were deposited on a poly-vinyl alcohol (PVA) substrate with a radio-frequency (RF) magnetron sputtering apparatus using four kinds of Ni–Mn–Ga targets. After separating from the substrate, the films were heat-treated at 1073 K for 3.6 ks for homogenization and aged at 673 K for 3.6 ks in a constraint condition. The reversible two-way SME by the thermal change was confirmed for the constraint-aged films with various compositions. The gradient of the strain–temperature curve, the amount of strain accompanied by the two-way SME and the width of thermal hysteresis were dependent on the composition of the films. The strain–temperature curve shifted to a high temperature region and the martensitic phase was stabilized by the applied magnetic field. Furthermore, the two-way SME by the magnetic field was observed around the martensitic transformation temperature on cooling for the constraint-aged film, which showed the large gradient and small thermal hysteresis in the strain–temperature curve.

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Magnetic-Field Induced Two-Way Shape Memory Effect of Ferromagnetic Ni2MnGa Sputtered Films

Magnetic Emission During Austenite-Martensite Transformation in Ni2MnGa Shape Memory Alloy

Zoltán Balogh, Lajos Daróczi, Lajos Harasztosi, Dezsö L. Beke, Thomas A. Lograsso, Deborah L. Schlagel

pp. 631-634

Abstract

The magnetic emission signals, accompanying the martensitic transition in Ni2MnGa magnetic shape memory alloy, are studied. The width (duration) and height (amplitude) distributions of the signals exhibit a power-law behaviour, with exponents α and β respectively. The values of α and β are characteristic of the magnetic noise originating from the transition itself and both have the value of 3.0±0.15.

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Magnetic Emission During Austenite-Martensite Transformation in Ni2MnGa Shape Memory Alloy

Martensitic Transformation in Ni–Mn–Ga Alloy Under High Magnetic Fields

Volodymyr A. Chernenko, Victor A. Lvov, Takeshi Kanomata, Tomoyuki Kakeshita, Keiichi Koyama, Stefano Besseghini

pp. 635-638

Abstract

An effect of magnetic field on the martensitic transformation (MT) temperature in ferromagnetic shape memory Ni49.4Mn27.7Ga22.9 single crystal with the MT temperature 285 K is studied by measuring and theoretical treatment of the magnetization versus temperature dependencies in a wide range of the high magnetic fields higher than saturating one. In this way, a linear approximation of the field dependence of MT temperature was proved for the high-field range. The linear increase of transformation temperature is characterized by the slope of 3.5×10−2 K/kOe. This value is essentially larger than the value 2×10−2 K/kOe reported by Gonzales-Comas et al. [Phys. Rev. B 60 (1999) 7085–7090] for the Ni49.5Mn25.4Ga25.1 alloy with a low MT temperature. This difference is in an agreement with the predictions of the Landau theory.

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Martensitic Transformation in Ni–Mn–Ga Alloy Under High Magnetic Fields

Ferromagnetic Shape Memory Microactuators

Manfred Kohl, Berthold Krevet, Makoto Ohtsuka, Daniel Brugger, Yong Liu

pp. 639-644

Abstract

The technologies for fabrication, micromachining and integration of Ni–Mn–Ga thin films are developed in order to create novel microactuators and sensors. These devices simultaneously make use of the electrical, thermoelastic and ferromagnetic properties of the thin films allowing a new level of multifunctionality and, as a consequence, particularly compact designs. By adjusting the Ni-content of the thin films, the martensitic and ferromagnetic transformation temperatures are tuned close to each other above 373 K, which has important consequences on the device performance such as actuation stroke and response time. This article focuses on the mechanisms, fabrication technologies as well as typical performance characteristics of Ni–Mn–Ga microvalves and microscanners. The present state-of-the-art of FSMA microactuators is highlighted.

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Ferromagnetic Shape Memory Microactuators

Effect of Heat Treatment Atmosphere on Multistage R-Phase Transformation in an Aged Ti–51.0 at%Ni Alloy

Minoru Nishida, Kentarou Ishiuchi, Kousuke Fujishima, Toru Hara

pp. 645-649

Abstract

The present study systematically investigates the effect of heat treatment atmosphere on the multistage R-phase transformation (MRT) in an aged Ti–51.0 at%Ni alloy. No MRT occurs when the heat treatments were completed under the regulated atmosphere. On the other hand, the MRT is observed in the specimen heat treated under the unregulated atmosphere. It is apparent from transmission electron microscope observations that the first and the second transformations take place around the grain boundary and at the grain interior, respectively. We conclude that the MRT is extrinsic, and is an artifact during the heat treatment, rather than intrinsic in nature.

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Effect of Heat Treatment Atmosphere on Multistage R-Phase Transformation in an Aged Ti–51.0 at%Ni Alloy

Mechanical Properties of Ti–50(Pt,Ir) High-Temperature Shape Memory Alloys

Yoko Yamabe-Mitarai, Toru Hara, Seiji Miura, Hideki Hosoda

pp. 650-657

Abstract

To develop high-temperature shape memory alloys, Ti–50(Pt,Ir)mol% compounds are noted because of their martensitic transformation from B2 to B19(2H) or 4H(4O) structures above 1273 K. A thermal expansion measurement and loading-unloading compression test were performed for Ti–50(Pt,Ir) to determine if the shape memory effect or superelasticity was shown. The thermal expansion measurement indicated the shape recovery in some of the compounds. The maximum shape recovery was about 4% by reheating at the above martensite transformation temperature after a loading-unloading compression test. Superelasticity was also observed in ternary compounds. The potential of Ti–50(Pt,Ir) as a high-temperature shape memory alloy is discussed.

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Mechanical Properties of Ti–50(Pt,Ir) High-Temperature Shape Memory Alloys

Transformation and Damping Characteristics of NiTi/NiTi Alloys Synthesized by Explosive Welding

Tingyong Xing, Yanjun Zheng, Lishan Cui

pp. 658-660

Abstract

The present work aims to investigate transformation and damping characteristics of a Ni51Ti/Ni50.2Ti alloy synthesized by explosive welding. The DSC results showed that the two endothermic peaks of the unprestrained specimen corresponded to the reverse transformation of each NiTi component. The reverse transformation temperature of Ni50.2Ti increased with increasing prestrain level, whereas the reverse transformation peak of Ni51Ti was split up into two independent endothermic peaks. Meanwhile, the internal friction results showed that the temperatures of the internal friction peaks of the Ni51Ti/Ni50.2Ti alloy and the range of reverse transformation temperature increased with increasing of prestrain level, which is consistent with the DSC results. Explosive welding is confirmed an effective method to fabricate chemical heterogeneous shape memory materials.

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Transformation and Damping Characteristics of NiTi/NiTi Alloys Synthesized by Explosive Welding

Vacuum Induction Melting of Ternary NiTiX (X=Cu, Fe, Hf, Zr) Shape Memory Alloys Using Graphite Crucibles

Zhonghua Zhang, Jan Frenzel, Klaus Neuking, Gunther Eggeler

pp. 661-669

Abstract

In the present study we investigate vacuum induction melting (VIM) of prominent ternary NiTiX (X=Cu, Fe, Hf, Zr) shape memory alloys using graphite crucibles. We apply a melting procedure which was recently developed for binary NiTi alloys and which keeps the carbon pick-up during melting at a minimum. We investigate the microstructures of the as-cast and homogenized alloys using scanning electron microscopy (SEM) in combination with energy dispersive X-ray analysis (EDX). Differential scanning calorimetry (DSC) was performed to study the phase transformation temperatures of the as-cast and homogenized materials. The results show that VIM processing in graphite crucibles provides ternary NiTiX shape memory alloys with good chemical homogeneity and acceptable impurity contents.

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Vacuum Induction Melting of Ternary NiTiX (X=Cu, Fe, Hf, Zr) Shape Memory Alloys Using Graphite Crucibles

Superelastic Deformation Behaviors Based on Phase Transformation Bands in TiNi Shape Memory Alloy

Elzbieta A. Pieczyska, Hisaaki Tobushi, Stefan P. Gadaj, Wojciech K. Nowacki

pp. 670-676

Abstract

Properties and characteristics of superelastic deformation behavior based on Lüders-Like phase transformation bands in TiNi shape memory alloy (SMA) are presented. Temperature distributions accompanying the stress-induced phase transformations in the SMA are found using the infrared technique and employed for the investigation into nucleation and further development of the bands of martensitic and reverse transformations. Based on the temperature and the relevant mechanical characteristics it is noticed that just after crossing a certain threshold stress, narrow bands of considerably higher temperature, about 8 K, corresponding to the martensitic phase, appear starting from the central part of the specimen and developing towards the both specimen borders. A few such bands parallel to each other occur at higher stresses and move towards the specimen grips, as well as their next generation, developing in almost perpendicular direction. The heterogeneous field of the temperature distribution was observed also during the unloading process, while the reverse transformation occurred, also inhomogeneous and related to the significant temperature decrease. Based on the tests carried out with various strain rates, an influence of the strain rate on the mechanical behavior was presented. Thermomechanical aspects of the martensitic and the reverse transformations were discussed.

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Superelastic Deformation Behaviors Based on Phase Transformation Bands in TiNi Shape Memory Alloy

Root-Mean-Square Displacements of Atoms in the B2-Phase of Titanium Nickelide

Vyacheslav M. Gundyrev, Vitaly I. Zel’dovich

pp. 677-681

Abstract

Using of MoKα radiation, on a single crystal of a titanium nickelide intensities of 15 structural and 11 superstructural reflections of the B2-phase are measured. Structural factors of scattering for these reflections are calculated, and root-mean-square displacements of atoms of nickel and atoms of titanium from positions of equilibrium are determined. The mean square of displacements of atoms of nickel is equal ⟨u2Ni=(8.7±0.6)×10−4 nm2, atoms of titanium −⟨u2Ti=(3.9±0.3)×10−4 nm2.

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Root-Mean-Square Displacements of Atoms in the B2-Phase of Titanium Nickelide

SMA for Dampers in Civil Engineering

Antonio Isalgue, Francisco C. Lovey, Patrick Terriault, Ferran Martorell, Rosa Maria Torra, Vicenç Torra

pp. 682-690

Abstract

The necessary physical properties for CuAlBe and, also tentatively, for NiTi alloys are analyzed at mesoscopic scale via static and dynamic contributions. The long time scale of the civil engineering (more than 10 or 20 years) requires analysis of the diffusion effects acting on microscopic scales. Simplified models for CuAlBe and NiTi dampers are built inside the ANSYS software scheme ensuring faster simulation for a three arch (or portico) in a family house. The dynamic simulation using accelerations of actual quakes (i.e., El Centro) shows that the SMA dampers reduce the amplitude of free oscillations by, at least, a factor two.

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SMA for Dampers in Civil Engineering

Surface Characterization and Blood Compatibility of Diamond-Like Carbon (DLC) Films on the NiTi Alloys

Jiehe Sui, Wei Cai, Ailian Liu, Zhixue Wang, Liancheng Zhao

pp. 691-693

Abstract

Diamond-like carbon (DLC) films are fabricated on the NiTi alloys at room temperature using plasma immersion ion implantation and deposition (PIIID). The effects of the substrate bias on the characteristics of the DLC films are systematically examined to correlate to the blood compatibility. The results show both the IDIG ratio (inverse trend in the sp3sp2 ratio) and the G peak position first decrease and then increase, while the nano-hardness first increases and then decreases with the increase of the substrate bias, and the blood compatibility of the coated sample is better than that of the uncoated sample and the DLC films on the NiTi alloys deposited at the substrate bias of 25 kV possesses better blood compatibility than the films deposited at other substrate bias. It can be concluded that the blood compatibility of the DLC films on the NiTi alloys is influenced by the sp3sp2 ratio.

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Surface Characterization and Blood Compatibility of Diamond-Like Carbon (DLC) Films on the NiTi Alloys

Effect of Severe Plastic Deformation on the Behavior of Ti–Ni Shape Memory Alloys

Vladimir G. Pushin, Ruslan Z. Valiev, Yuntian T. Zhu, Dmitrii V. Gunderov, Nikolai I. Kourov, Tatiana E. Kuntsevich, Alexei N. Uksusnikov, Lyudmila I. Yurchenko

pp. 694-697

Abstract

The nanostructured TiNi-based shape-memory alloys were synthesized by severe plastic deformation (SPD), including high pressure torsion, equal-channel angular pressing, and multi-step SPD deformations (SPD plus cold rolling or drawing). It is found that the SPD processing changed the morphology of the martensite and temperature of martensite transformation. Also, we found that the mechanical and shape memory properties can be enhanced by forming nanostructures in these alloys. SPD processing renders higher strength, higher yield dislocation strength and in results—higher recovery stress (up to 1.5 GPa) and maximum reverse strain (up to 10%) of shape memory, which are desirable in various practical application.

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Effect of Severe Plastic Deformation on the Behavior of Ti–Ni Shape Memory Alloys

PM Processing of Single-Phase NiTi Shape Memory Alloys by VPCR Process

Bernard Bertheville

pp. 698-703

Abstract

Single-phase nickel–titanium alloys were successfully synthesized by using a powder metallurgical process based on the use of a calcium reductant source during sintering in argon atmosphere (VPCR process). This process allows avoiding secondary phase formation during the NiTi compound forming reaction. The experimental results show that both heating rate and sintering temperature play a significant role on the final porosity. Different sintering stages at temperatures below TE(Ti2Ni), between TE(Ti2Ni) and TE(Ni3Ti), and above TE(Ni3Ti) were investigated in order to elucidate the influence of the two liquid eutectics on the densification. By choosing a slow heating rate of 0.5 K/min and a long time sintering at 1193 K, an almost dense single-phase NiTi compact was obtained with austenite ↔ martensite transformation heats comparable to those found in melt-cast NiTi alloys.

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PM Processing of Single-Phase NiTi Shape Memory Alloys by VPCR Process

Constitutive Equation with Consideration of Slip-Deformed Martensite in the Deforming of Ti–Ni Shape Memory Alloy

Toshio Sakuma, Yuji Mihara, Yasuo Ochi, Kiyoshi Yamauchi

pp. 704-710

Abstract

The modeling of the transformation and deformation behavior of a shape memory alloy has been investigated by many researchers. However, there are few reports that investigate plastic deformation of shape memory alloys. To design an actual product, the modeling in consideration of plastic deformation is indispensable. In this work, plastic deformation after pre-deformation is investigated using the volume fraction of slip-deformed martensite. New kinetics and constitutive equations are proposed for the reverse transformation process. The material constants in the proposed equations are determined from the results of tensile and heating/cooling tests on Ti–50 at%Ni alloy. The calculated results describe well the deformation and transformation behavior affected by pre-strain.

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Constitutive Equation with Consideration of Slip-Deformed Martensite in the Deforming of Ti–Ni Shape Memory Alloy

A Study on the Low Temperature Internal Friction Relaxation Peak in a Ti49.8Ni50.2 Alloy

Shyi-Kaan Wu, Hsin-Chih Lin, Tung-Sheng Chou

pp. 711-715

Abstract

The low temperature relaxation peak appearing around 200 K in Ti49.8Ni50.2 shape memory alloy is a multiple relaxation process with activation energy Q=0.39 eV and frequency factor f0=6.2×109 s−1 and is associated with the interaction of dislocations with pinning vacancies. Due to the increase of dislocation density and the annihilation of quenched-in vacancies after thermal cycling, the height of relaxation peak PR decreases with increasing the number of thermal cycling. Higher amounts of dislocation-vacancy reaction cause a higher relaxation damping under the condition of higher quenching temperature. The quenched-in vacancies can have a significant effect on the transformation rate, and thus the heights of transformation peaks PH1 and PC1 decrease with increasing quenching temperature. Dislocations introduced by both thermal cycling and quenching from high temperature will depress the martensitic transformation, and hence decrease the peak temperatures of PH1 and PC1.

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A Study on the Low Temperature Internal Friction Relaxation Peak in a Ti49.8Ni50.2 Alloy

Effects of Cerium Addition on Martensitic Transformation and Microstructure of Ti49.3Ni50.7 Alloy

Wei Cai, Ailian Liu, Jiehe Sui, Liancheng Zhao

pp. 716-719

Abstract

In order to study the effect of Cerium on martensitic transformation and microstructure of Ti49.3Ni50.7 alloy, a group of TiNiCe alloys with different content of Ce addition were prepared. The microstructure and the martensitic transformation behavior of TiNiCe ternary alloys were investigated by optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the microstructure of Ti49.3Ni50.7 alloy is changed obviously by Ce addition, and there are many Ce-rich phases dispersing in the TiNi matrix. One step martensitic transformation due to B2↔B19′ transformation occurs during the cooling and heating processes of the TiNiCe ternary alloys. The phase transformation temperatures increase remarkably when the content of Ce is less than 2 at%. However, when the content of Ce is further increasing, the phase transformation temperatures increase slowly and tend to stable.

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Effects of Cerium Addition on Martensitic Transformation and Microstructure of Ti49.3Ni50.7 Alloy

Theoretical Prediction on Martensitic Transformation Start-Strain of Nitinol

Wenge Zhang, Klaus Hackl

pp. 720-723

Abstract

The martensitic phase transformation (MT) start-strain of NiTi shape memory alloy under uniaxial tension is predicted theoretically on the basis of micromechanics. Results directly show that the martensitic transformation start-strain depends on three kinds of parameters: lattice correspondence strain (Bain strain), mechanical constants of Nitinol (Young’s module, Poisson ratio) and chemical energy difference between austenite and martensite phase (temperature dependence parameters). Comparison of this new prediction with other methods and experimental data is also given.

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Theoretical Prediction on Martensitic Transformation Start-Strain of Nitinol

Two-Way Shape Memory Effect and Its Stability in a Ti–Ni–Nb Wide Hysteresis Shape Memory Alloy

Xianglong Meng, Feng Chen, Wei Cai, Liming Wang, Liancheng Zhao

pp. 724-727

Abstract

The effect of training strain, deformation temperature and number of training cycles on the two-way shape memory effect (TWSME) and its stability have been investigated systematically in a Ti46.3Ni44.7Nb9 (at%) wide hysteresis shape memory alloy (SMA). The experimental results indicate that two-way shape memory strain increases with increasing the training strain up to 14.5% and then decreases with further increasing the training strain. When the training strain is less than 12%, the two-way shape memory strain increases with the increase of number of training cycles in the Ti46.3Ni44.7Nb9 alloy deformed at the room temperature. Compared with TiNi binary alloy, the TWSME is smaller and the training strain to get the maximum TWSME is larger in the Ti–Ni–Nb alloy due to the deformation of β-Nb soft particles during training. However, the Ti–Ni–Nb alloy exhibits excellent stability of TWSME during the thermal cycling.

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Two-Way Shape Memory Effect and Its Stability in a Ti–Ni–Nb Wide Hysteresis Shape Memory Alloy

Effect of Pre-Strain on Transformation and Deformation Behavior in Ti–50 at%Ni Shape Memory Alloy

Toshio Sakuma, Yuji Mihara, Yasuo Ochi, Kiyoshi Yamauchi

pp. 728-734

Abstract

In many cases that shape memory alloys are applied to engineering and medical fields, it is necessary to deform them in martensitic phase and after that, to recover them by heating. However, if a slip-deformation occurs, a shape recovery does not occur completely even if heated up above a reverse transformation finish temperature Af. It is reported that transformation temperatures are changed by pre-deformation and in constrained strain condition. Therefore, it is important to investigate the relationship between the pre-deformation and the deformation and transformation characteristics such as the recovery stress, the transformation temperatures and so on. The purpose of this paper is to clarify the influence of the pre-deformation on the recovery strain, the recovery stress and the transformation temperatures in a Ti–Ni shape memory alloy. The material used in this study is Ti–50 at%Ni alloy annealed at 1103 K for 60 s. The variation of the recovery strain, the recovery stress and the transformation temperatures by the pre-straining are investigated experimentally, and also the variation of the transformation and deformation characteristics by the pre-straining is discussed in relation to the volume fraction of slip-deformed martensite.

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Effect of Pre-Strain on Transformation and Deformation Behavior in Ti–50 at%Ni Shape Memory Alloy

Effect of Cyclic Loading on Apparent Young’s Modulus and Critical Stress in Nano-Subgrained Superelastic NiTi Shape Memory Alloys

Shengcheng Mao, Xiaodong Han, Ming. H. Wu, Ze Zhang, Fei Hao, Danmin Liu, YueFei Zhang, Bihui Hou

pp. 735-741

Abstract

A series of uni-axial tensile cycling tests were conducted at room temperature in superelastic NiTi strip specimens with nano-grain size. The NiTi superelastic strip specimen’s Apparent Young’s Modulus (AYM) and the critical stress decrease when the specimen is subjected to an external uni-axial stress and the strain being higher than 1.5%. Both of the AYM and the critical stress become steady after 10-time cycling. The number of the (111)[1\\bar43] oriented grains increases with extending the strain value. The sub-grain size grows with increasing mechanical cycling number due to the annihilation of the small angle boundaries. The AYM-softening is related to the grain re-orientation (texture evolution) and the formation of irreversible-stabilized B19′ martensitic variants. The softness of the critical stress is principally attributed to the aspect that the grains re-orient to align along the two textural components (111)[1\\bar10] and (111)[1\\bar43] when the external stress being applied. The rotation of grains towards the observed orientation gives higher Schmid factor for the transformation and is one of the reasons for the decrease in AYM and critical stress. The orientation relationships between B2 parent phase and the strain-induced B19′ martensite are observed to be: [111]B2||[10\\bar1]M, (1\\bar10)B2||(010)M and [111]B2||[\\bar110]M and (1\\bar10)B2||(001)M.

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Effect of Cyclic Loading on Apparent Young’s Modulus and Critical Stress in Nano-Subgrained Superelastic NiTi Shape Memory Alloys

Atomic Dynamics and Energetics of Martensitic Transformation in Nickel–Titanium Shape Memory Alloy

Ken-ichi Saitoh, Tomohiro Sato, Noboru Shinke

pp. 742-749

Abstract

Microscopic mechanism of martensitic transformation in nickel (Ni)–titanium (Ti) alloy is investigated by molecular dynamics (MD) simulation using embedded atom method (EAM) potentials. The computational parallelepiped specimen with nano-size dimension is surrounded by Ti-terminated free surfaces and constrained regions for loading. The detection method of martensite phase is newly exploited. The crystalographic B19′ monoclinic crystal form can be identified as martensite phase by checking up atomic lengths and angles of neighborhood and by comparing them with possible values of lattice parameters already proposed. In tensile loading, the specimen shows a kind of stress-induced transformation from parent phase (B2 structure) to martensite phase (B19′ structure). Outbreak of martensitic transformation occurs immediately after stress reaches maximum value. In outbreak of martensite, distortion of unit structure is observed as an actual change in atomic coordinates. It is found that there are two major transformation paths both resulting in martensite structure, each of which has contrary sequence of changes in atomic length or angle. There is also the other route of atomic movement for completing martensitic transformation with relatively long-range atomic migration. The EAM potential used in the present study is discussed as to crystalline energies of periodic B2 or B19′ unit structures. Dynamic energies in transformation are also obtained from MD results and they show that there are energy barriers in martensitic transforming. Static evaluation of energy, on the assumption of uniform transformation, is carried out and is compared with energy change obtained by MD method.

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Atomic Dynamics and Energetics of Martensitic Transformation in Nickel–Titanium Shape Memory Alloy

Suggestion of Pipe Coupling Method for Maximum and Uniform Joining Stress

K. K. Jee, J. H. Han, W. S. Jung, W. Y. Jang

pp. 750-752

Abstract

A new method of pipe joining using shape memory alloys (SMAs) is proposed in this study to obtain the maximum and uniform joining stress. Fe-based SMAs, regarded as potential alloys for pipe couplings, is not so widely industrialized as anticipated. The major obstacle is error of pipe size, which causes a gap between deformed SMA joint and pipes to be joined prior to heating. Since the recoverable strain of Fe SMAs is comparable to the gap, most of the strain is wasted as free recovery. In this study, the problem is settled by deforming simultaneously SMA coupling and pipes to be joined with the coupling inserted in the pipes. By doing so, there is always no gap between coupling and pipes prior to heating. The new method makes it possible to apply alloys with a poor shape memory effect (SME) to pipe couplings. Some other expected advantages and disadvantages will be discussed.

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Suggestion of Pipe Coupling Method for Maximum and Uniform Joining Stress

Appearance of Two-Way Strain in Shape Memory Effect of Ti–Ni–Nb Alloy —Influence of Applied Strain on Two-Way Strain—

Keisuke Okita, Nagatoshi Okabe, Tomoyuki Sato, Takashi Nakao

pp. 753-758

Abstract

A promising field for applications of shape memory alloys (SMAs) in the near future is the micro-actuator technology. Especially, two-way shape memory effect (TWSME) is the most suitable to apply in actuators, because a pre-determined response can be obtained very easily by thermal changes against shape memory elements.
In this paper, the TWSME in Ti–Ni–Nb alloy was investigated quantitatively by applying various levels of pre-deformation. The deformation in a complete martensite phase was applied by a thermo-mechanical treatment in order to obtain the two-way memory strain. The experimental results indicated that the deformation mechanism in a martensite phase was just the martensite reorientation accompanied by the dislocation slip. The dislocation due to the slip deformation is the origin of the internal stress field that is necessary to generate the two-way memory strain. However, excessive introduction of the dislocation decreases the two-way memory strain. The maximum two-way memory strain observed in this experiment was 2.1% at an applied strain of 18%. In addition, pre-deformation increases the temperature of reverse transformation, but decreases the temperature of martensitic transformation. These experimental results can be explained by using the series-parallel combined model that has been suggested in our previous work.

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Appearance of Two-Way Strain in Shape Memory Effect of Ti–Ni–Nb Alloy —Influence of Applied Strain on Two-Way Strain—

Influence of Strain Ratio on Bending Fatigue Life and Fatigue Crack Growth in TiNi Shape-Memory Alloy Thin Wires

Ryosuke Matsui, Yoshiyasu Makino, Hisaaki Tobushi, Yuji Furuichi, Fusahito Yoshida

pp. 759-765

Abstract

The influence of strain ratio on bending fatigue properties of TiNi shape-memory alloy thin wires and the process of fatigue crack propagation were investigated. The results obtained are summarized as follows. (1) The martensitic transformation stress of a superelastic thin wire is higher than that of a shape memory wire, resulting in shorter fatigue life of the superelastic wire. The maximum bending strain of fatigue limit is the martensitic-transformation starting strain. (2) The plane-bending fatigue life curve is expressed by a power function of maximum strain εmax and the number of cycles to failure. The smaller the strain ratio, the shorter the fatigue life. (3) In both rotating bending and plane bending, fatigue cracks nucleate on the surface of the wire. One fatigue crack grows preferentially and the fatigue-crack propagated region of fracture surface is fan-shaped. (4) If εmax is larger than 1%, εmax during the rotating-bending fatigue test becomes a little smaller than that of the initial value. (5) The fatigue crack length can be estimated by measuring increase in electric resistance based on decrease in cross-sectional area due to fatigue crack propagation. (6) The fatigue crack length of the notched wire is expressed by a power function of the number of cycles.

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Influence of Strain Ratio on Bending Fatigue Life and Fatigue Crack Growth in TiNi Shape-Memory Alloy Thin Wires

Local Strain Distribution Arising in Shape Memory Alloy Composite Subjected to Thermal Loading

Go Murasawa, Satoru Yoneyama

pp. 766-771

Abstract

The main purpose of the present research is the measurement of local strain distributions generated in a shape memory alloy composite (SMAC) under thermal loading. In the present study, firstly, the test system is constructed on the basis of Digital Image Correlation (D.I.C.) in order to measure local strains all over the surface of object. Then, local strain distributions generated in SMAC are measured under heating. Results in present study are as follows: (1) Longitudinal local strain reveals inhomogeneous deformation behavior during austenite transformation of SMA fiber, and shows distribution along to x and y direction after austenite transformation. Also, we can see that the state of distribution is different between x and y directions after austenite transformation. (2) Lateral local strain begins to generate around fiber during austenite transformation of SMA, and shows distribution along to only y direction after austenite transformation. This distribution is caused by thermal expansion of matrix. (3) Shearing local strain begins to generate at fiber edge during austenite transformation of SMA fiber, and shows distribution along to x and y direction after austenite transformation.

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Local Strain Distribution Arising in Shape Memory Alloy Composite Subjected to Thermal Loading

Effects of Applied Strain and Subsequent Heat Treatment at Intermediate Temperature on Mechanical Properties of a Thin Plate Ti–51 at% Ni Shape Memory Alloy

Hiromasa Semba, Nagatoshi Okabe, Toru Yamaji, Keisuke Okita, Kiyoshi Yamauchi

pp. 772-779

Abstract

Attempts have been made to develop new types of seismic devices using shape memory alloys. They are a single-stage bellows which are processed from thin-walled tubes by employing the rubber bulge method and then are annealed at 400°C for the shape-memory treatment. As strain distribution is induced on the bulged part due to the process, it is significant to know the effects of pre-strain and the subsequent heat-treatment on the mechanical properties of the material for tube when designing the bellows shapes for the seismic structures. Thus, tensile tests and thermal analysis were conducted before and after the heat treatment on rectangular specimens cut from the tubes.
In this paper, the oxidization method was first attempted to observe distinctively both regions of the stress induced martensite (SIM) transformation and twin deformation generated while applying strain to the specimens. It became clear that the micro-structure in the SIM area had a changed R phase from the austenite phase at room temperature after being annealed at 400°C. From the experimental and analytical results for the specimens, the mechanical behavior was classified broadly into two conditions as follows: (1) the mechanical behavior can be formulated on the basis of a series-model consisting of areas of both R phase and austenite considering the area-ratio of these phases until the SIM transformation has expanded over the whole specimen, and (2) after that, the mechanical behavior can be formulated using the exponential function for the applied strain as a parameter.

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Effects of Applied Strain and Subsequent Heat Treatment at Intermediate Temperature on Mechanical Properties of a Thin Plate Ti–51 at% Ni Shape Memory Alloy

Influence of Cyclic Loading on Inhomogeneous Deformation Behavior Arising in NiTi Shape Memory Alloy Plate

Go Murasawa, Satoru Yoneyama, Toshio Sakuma, Masahisa Takashi

pp. 780-786

Abstract

The aim of present paper is the investigation of relationship between inhomogeneous deformation behavior and macroscopic deformation behavior arising in SMA during cyclic loadings. Firstly, a test system was constructed on the basis of Digital Image Correlation in order to measure inhomogeneous deformation behavior. Secondary, measurements of the inhomogeneous deformation behavior (local strain distribution) arising in 50.5Ni49.5Ti plate were tried during cyclic tensile loading–unloading in the region of pseudoelastic temperature. From some results, it is seen that the inhomogeneous deformation behavior sensitively changes according to the state of loadings (i.e., number of cycle, history of loading and so on). Also, the macroscopic deformation behavior for SMAs is strongly affected by the inhomogeneous deformation behavior. It is very important for application of SMA to investigate the relationship between macroscopic deformation behavior and inhomogeneous deformation behavior.

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Influence of Cyclic Loading on Inhomogeneous Deformation Behavior Arising in NiTi Shape Memory Alloy Plate

Effect of Cold Working on Transformation and Deformation Behavior after Pre-Deforming in Ti–50 at%Ni Shape Memory Alloy

Toshio Sakuma, Yuji Mihara, Hirotada Toyama, Yasuo Ochi, Kiyosi Yamauchi

pp. 787-791

Abstract

It is reported that the transformation characteristics of Ti–Ni shape memory alloys (SMAs) are influenced by manufacturing conditions, such as composition, heat-treatment temperature, cold working, and so on. To understand correctly the effects of these manufacturing conditions on transformation characteristics of Ti–Ni SMAs make it possible to control the transformation temperature and recovery stress. The purpose of this work is to clarify the effect of cold working ratio on transformation and deformation behavior after pre-deforming SMA. The specimens were Ti–50 at%Ni annealed at 673 K for 3.6 ks. The variation of the recoverable strain, recovery stress and transformation temperature with cold working ratio was investigated experimentally. The solution treated material was also used as a reference material. The effect of cold working ratio on the transformation and deformation behavior is discussed in relation to the volume fraction of the residual martensite subjected to slip deformation.

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Effect of Cold Working on Transformation and Deformation Behavior after Pre-Deforming in Ti–50 at%Ni Shape Memory Alloy

Influence of Carburization on Dynamic Impact Behavior of NiTiCu Alloy

RenBo Xu, LiShan Cui, YanJun Zheng

pp. 792-794

Abstract

The dynamic impact behavior of bare and carburized NiTiCu shape memory alloy was studied using a home-built impact testing system in this paper. The contact force and contact time between impactor and specimen at different impact energy were measured in real time by force sensor, and predicted formulae about parameters during impact process were presented. The results showed that the contact force and contact time of carburized specimens were less than these of bare specimens, and the absorbed energy of carburized specimens due to stress-induced martensitic transformation was higher than that of bare specimens. These results indicated that the carburization process could reduce contact force and material damage of NiTiCu alloy during impact process.

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Influence of Carburization on Dynamic Impact Behavior of NiTiCu Alloy

Structure and Properties of the Ti–50.0 at%Ni Alloy after Strain Hardening and Nanocrystallizing Thermomechanical Processing

Vladimir Brailovski, Sergei D. Prokoshkin, Irina Yu. Khmelevskaya, Karine E. Inaekyan, Vincent Demers, Sergei V. Dobatkin, Evgeny V. Tatyanin

pp. 795-804

Abstract

The thermomechanical processing consisting in cold work (true strain e=0.3–1.9) followed by a post-deformation annealing (200–700°C temperature range) is applied to the equiatomic Ti–Ni alloy. The evolution of the structure, substructure and functional properties of the material is studied. For all levels of cold work, the maxima of the free recovery strain and constraint recovery stress are obtained after annealing in the 350–400°C temperature range. For a moderately cold-worked material (true strain e=0.3), this temperature range corresponds to polygonization; for a severely cold-worked material (e=1.9), it corresponds to the material nanocrystallization, while for a highly cold-worked material (e=0.88), the structure is mixed. An increase in the cold-work strain leads to an increase in the completely recoverable strain above 8% and in the maximum recovery stress up to 1450 MPa, as well as to the widening of the superelastic temperature range.

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Structure and Properties of the Ti–50.0 at%Ni Alloy after Strain Hardening and Nanocrystallizing Thermomechanical Processing

One-Dimensional Anti-Phase Structures Based on an Mg12Ce (Mn12Th-Type) Structure in an Mg91Ce6Zn3 Alloy, Studied by High-Resolution Transmission Electron Microscopy and High-Angle Annular Detector Dark-Field Scanning Transmission Electron Microscopy

Masahiko Nishijima, Kenji Hiraga, Takaomi Itoi, Mitsuji Hirohashi

pp. 805-810

Abstract

The crystal structure of a new phase with an approximate composition of Mg91Ce7Zn2, which is formed as a main phase in an Mg91Ce6Zn3 alloy, has been determined by atomic-scale observations of high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The structure of this phase can be described as a one-dimensional incommensurate structure with an orthorhombic unit cell of a=1.03 nm, b=1.03 nm and c\\fallingdotseq3.7 nm, formed by insertion of anti-phase boundaries in the fundamental Mg12Ce (Mn12Th-type) structure with a tetragonal unit cell of a0=1.03 nm and c0=0.60 nm. The anti-phase boundaries are parallel to the (001) plane of the fundamental tetragonal structure, and an average interval of the boundaries along the [001] direction is about 3.1c0. Also, a commensurate structure with an interval of 5.5c0 is observed as a coexisting phase with the incommensurate structure.

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One-Dimensional Anti-Phase Structures Based on an Mg12Ce (Mn12Th-Type) Structure in an Mg91Ce6Zn3 Alloy, Studied by High-Resolution Transmission Electron Microscopy and High-Angle Annular Detector Dark-Field Scanning Transmission Electron Microscopy

111Cd(←111In) Time Differential Perturbed Angular Correlation (TDPAC) Spectroscopy in Fe/Ag Films

Takashi Otomo, Saburo Nasu, Shotaro Morimoto, Koji Baba, Masayoshi Nishiyama, Tadashi Saito

pp. 811-816

Abstract

We have investigated the magnetic properties of Cd atoms decayed from 111In at the interfaces of Fe/Ag evaporated films. In order to determine the magnetic properties of the films, we have measured 111Cd(←111In) time differential perturbed angular correlation (TDPAC) spectra at room temperature as a function of distance from the interface. Fe and Ag were evaporated using electron beam evaporation, and small amounts of radioactive 111In were evaporated by resistance-heating. The evaporated films had the following stacking orders on kapton polyimide film substrate: (1) polyimide/Fe 50 nm/111In/Fe x nm/Ag 20 nm (x=0.2,0.3,1,3,5,10), (2) polyimide/Fe 50 nm/Ag x nm/111In/Ag 20 nm (x=0,0.2,1). We used an Ag layer as a cap layer in order to prevent oxidation in air. TDPAC spectra were measured using a four-detector arrangement. The hyperfine magnetic field tends to be slightly larger when 111In is close to the interface of the Fe/Ag layer. The intensity of perturbation damps rapidly as 111In is close to the interface of Fe and Ag. These behaviors are thought to depend on electric field gradients and the influence of the surface roughness.

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111Cd(←111In) Time Differential Perturbed Angular Correlation (TDPAC) Spectroscopy in Fe/Ag Films

Shear-Band Deformation in Amorphous Alloys and Composites

Cang Fan, Laszlo Kecskes, Tong Jiao, Hahn Choo, Akihisa Inoue, Peter Liaw

pp. 817-821

Abstract

The deformation of monolithic bulk-metallic glasses (BMGs), nanocrystal-containing, and micrometer-sized, ductile-particle-reinforced bulk metallic glass composites (BMGCs) has been investigated. The number density of shear bands, the interaction of shear bands with the particles, as well as the apparent plasticity was found to be significantly different in three types of samples before failure occurred. The interaction of shear bands with the micrometer-sized particles implied that shear bands can be initiated by stress concentration at the particle boundaries and, at the same time, absorbed by the deformation of particles. It is hypothesized that the observed number density and motion of shear bands could arise from the interaction of rotational sliding of medium range order (MRO) or dense-packed clusters, fine crystals, and the free volume in the material. An estimate of the shear band thickness, based on the size of particles or grains near and in the shear bands of the BMGs, BMGCs, and ultra-fine structured materials is consistent with this conjecture.

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Shear-Band Deformation in Amorphous Alloys and Composites

Fast Penetration of Sn into Ag by Diffusion Induced Recrystallization

Toshio Takenaka, Masanori Kajihara

pp. 822-828

Abstract

At interconnection between a Ag-base conductor alloy and a Sn-base solder alloy, fast penetration of Sn into the conductor alloy occurs due to diffusion induced recrystallization (DIR) during solid-state heating under usual energization conditions. Like formation of binary Ag–Sn compounds, the penetration of Sn deteriorates the electrical conductivity at the interconnection. In order to examine the penetration rate of Sn into the conductor alloy, the kinetics of DIR in the Ag(Sn) system was experimentally observed in the present study. The experiment was carried out using Sn/Ag/Sn diffusion couples prepared by a diffusion bonding technique. The diffusion couples were isothermally annealed at temperatures of T=433–473 K for various times up to t=1100 h in an oil bath with silicone oil. Due to annealing, a region alloyed with Sn is formed in Ag due to DIR at T=453 and 473 K. At T=433 K, however, the DIR region could not be recognized clearly. The concentration of Sn in the DIR region is about half of the solubility of Sn in Ag. The mean thickness l of the DIR region reaches to 4 μm for t=1100 h at T=453 K and 5 μm for t=890 h at T=473 K. The experimental results were theoretically analyzed using mathematical models. The analysis indicates that the growth of the DIR region is controlled by the interface reaction at the moving boundary of the DIR region within the experimental annealing times. At longer annealing times, however, the interface reaction is no longer the bottleneck for migration of the moving boundary and the grain boundary diffusion across the DIR region governs the growth of the DIR region.

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Fast Penetration of Sn into Ag by Diffusion Induced Recrystallization

Quantitative Explanation for Uphill Diffusion of Sn during Reactive Diffusion between Cu–Sn Alloys and Nb

Tomomi Yamashina, Masanori Kajihara

pp. 829-837

Abstract

In a bronze method, uphill diffusion of Sn takes place from a binary Cu–Sn alloy to Nb3Sn during reactive diffusion between the Cu–Sn alloy and Nb at temperatures around 1000 K. In order to account for the occurrence of the uphill diffusion quantitatively, the phase equilibria in the ternary Cu–Nb–Sn system were theoretically analyzed using a thermodynamic model for phases with different sublattices. In this ternary system, there is no ternary compound and the solubility of the third component is very small for all the phases. Consequently, the ternary interaction was assumed negligible, and thus the Gibbs energy of each phase was expressed with the thermodynamic parameters of the relevant binary systems. In an isothermal section calculated at 1053 K, the three-phase equilibrium of Cu + Nb + Nb3Sn appears at an activity of Sn with 0.0047. If the activity aSnb of Sn for the binary Cu–Sn alloy is greater than the activity aSnc of Sn for the three-phase equilibrium of Cu + Nb + Nb3Sn, Nb3Sn is spontaneously produced owing to the reactive diffusion. As a result, the uphill diffusion of Sn occurs from the Cu–Sn alloy to Nb3Sn. The chemical driving force ΔGSn for the uphill diffusion is evaluated by the equation ΔGSn=RTln(aSnbaSnc). This equation semi-quantitatively explains the growth behavior of Nb3Sn.

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Quantitative Explanation for Uphill Diffusion of Sn during Reactive Diffusion between Cu–Sn Alloys and Nb

Deformation and Recrystallization of Aluminum Bicrystals Having Asymmetric Tilt Grain Boundary

Tatsuya Okada, Masashi Kotaka, Tetsuya Wada, Minoru Tagami, Fukuji Inoko

pp. 838-844

Abstract

Two types of aluminum bicrystals (Bicrystal 1 and 2) having an asymmetric tilt grain boundary were grown. In Bicrystal 1, the orientations of component grains were related to each other by 45° rotation about the normal of the wide surface of the tensile specimen. In Bicrystal 2, although the primary slip planes were symmetric about the grain boundary plane, the component grains were related to each other by 180° rotation about the tensile axis of the specimen. The specimens were deformed to a tensile strain of 0.3 and subsequently annealed. In both bicrystals, deformation bands were not formed symmetrically about the grain boundary. After annealing, no strain induced boundary migration was found. Recrystallization occurred through ⟨111⟩ rotation mechanism. These results were compared with the deformation and recrystallization in aluminum bicrystals having a symmetric tilt grain boundary.

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Deformation and Recrystallization of Aluminum Bicrystals Having Asymmetric Tilt Grain Boundary

Microstructure Characterization and Mechanical Properties of TiSi2–SiC–Ti3SiC2 Composites Prepared by Spark Plasma Sintering

Chao Qin, Lianjun Wang, Wan Jiang, Shengqiang Bai, Lidong Chen

pp. 845-848

Abstract

Dense TiSi2–SiC and TiSi2–SiC–Ti3SiC2 composites in which SiC particles in 200–300 nm disperse, were reactively synthesized through spark plasma sintering (SPS) technique using TiC, Si, and C powders in micrometer as starting reactants. The phase constituents and microstructures of the samples were analyzed by X-ray diffraction, field emission scanning electron microscopy and transmission emission microscopy. The hardness, fracture toughness and bending strength of TiSi2–SiC and TiSi2–SiC–Ti3SiC2 composites were tested at room temperature. The fracture toughness and bending strength of TiSi2–SiC–Ti3SiC2 composites reach 5.4±0.3 MPa·m1⁄2 and 700±50 MPa, respectively. The factors leading to the improvement of the mechanical properties were discussed.

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Microstructure Characterization and Mechanical Properties of TiSi2–SiC–Ti3SiC2 Composites Prepared by Spark Plasma Sintering

Synthetic Process of Titanium Dioxide Coating on Aluminum by Chemical Conversion Method

Takayoshi Fujino, Teppei Matzuda

pp. 849-853

Abstract

Titanium dioxide (TiO2) coatings were prepared by chemical conversion treatment of aluminum in (NH4)2TiF6 with H2O2, and the sintering of the coating was prepared to immobilize the photocatalyst on aluminum. Coatings were also formed in this solution at room temperature. To identify the coating structure, coating analysis was carried out using an infrared absorption spectrum analyzer. Based on the infrared absorption results, a component of the coating was found in the hydrolysis product of peroxo titanium fluoride. Furthermore, the coating analysis was carried out using X-ray diffractometry (XRD), and non-sintered coating was amorphous; however, the coating sintered by 673 K was anatase-type titanium dioxide.
In the forming process of the conversion treatment in (NH3)2TiF6 and H2O2, first, the generated F in the bath reacted with the aluminum. At the same time, hydrogen ions on the aluminum surface were consumed because hydrogen gas was generated. Thus, the pH of the interface became alkali. The hydrolysis of the titanium peroxo fluoride was deposited on the aluminum because pH increased on the surface.
The coating sintered at 473 K had the highest activity. The photocatalytic activity of the coating sintered at 623 K was lower than the coating heated at 473 K, which is attributed to TiO2 aggregation This forming process of the coating is low cost because of the useless electrolytic decomposition process. Furthermore, practical industry is expected because immobilized substances on aluminum can easily be decomposed at low temperatures.

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Synthetic Process of Titanium Dioxide Coating on Aluminum by Chemical Conversion Method

Activity of Iron Oxide in Magnesiowüstite in Equilibrium with Solid Metallic Iron

Masakatsu Hasegawa, Tatsuro Tsukamoto, Masanori Iwase

pp. 854-860

Abstract

By employing an electrochemical technique incorporating magnesia-stabilized zirconia electrolyte, the activities of iron oxide, FexO, were measured in magnesiowüstite, FexO–MgO solid solution, in equilibrium with solid metallic iron at temperatures between 1373 and 1573 K. The sub-regular solution model was applied to the FexO activities, and the calculated FexO activities were in good agreement with the experimental values in this study and the literatures at temperatures between 1073 and 1573 K with an accuracy of ±0.02.

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Activity of Iron Oxide in Magnesiowüstite in Equilibrium with Solid Metallic Iron

Relationship between X-ray Intensity and Electric Bias on Al2O3 Surface during Low Energy Ga+ Irradiation

Jiancun Rao, Minghui Song, Renchao Che, Masaki Takeguchi, Kazuo Furuya

pp. 861-863

Abstract

Low-energy characteristic X-ray emission is detected during bombardment of positive low energy ions onto insulator materials. The phenomenon is considered to be related to surface charge-up. To study further the mechanism, the characteristic X-rays was studied during 30 keV Ga+ ions bombardment onto Al2O3 monocrystalline specimens applied with a direct current (DC) bias in the present work. The applied DC voltage builds an electric field parallel to the surface of the specimen. The results show that the characteristic X-rays of O-Kα and Al-Kα increased with the increasing of the applied DC voltages.

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Relationship between X-ray Intensity and Electric Bias on Al2O3 Surface during Low Energy Ga+ Irradiation

Separation of Fe and Sn–Cu Phases in an Fe–Sn–Cu–B System

Hideki Ono-Nakazato, Kenji Taguchi, Daisuke Kawauchi, Tateo Usui

pp. 864-867

Abstract

Scrap metal often includes a large amount of copper and tin. It is important to recover copper and tin from this scrap metal for recycling. Separation into two liquid phases, namely Fe and Sn(–Cu) phases, has been investigated at 1523 K in Fe–Sn–B and Fe–Sn–Cu–B systems. In the Fe–Sn–B system, the tin content of the Fe-rich phase and the iron content of the Sn-rich phase are 13.7 and 11.7 mass%, respectively, when [mass%B](in Fe)=3.62. Boron widens the miscibility gap of the Fe–Sn binary system. The isothermal section diagram of the Fe–Sn–Cu–2.66 mass%B quaternary system at 1523 K is described. In the Fe–Sn–Cu–B system, separation into two liquid phases, Fe-rich and [Sn–Cu]-rich, is found over all ratios of [mass%Sn]/[mass%Cu]. The separation region is enlarged as the [mass%Sn]/[mass%Cu] ratio is decreased. By using the separation into two liquid phases, iron can be enriched in the Fe-rich phase and copper and tin can be enriched in the [Sn–Cu]-rich phase. It is possible to recover copper and tin effectively from Fe–Sn–Cu alloy.

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Separation of Fe and Sn–Cu Phases in an Fe–Sn–Cu–B System

Enhancing Effect on Photocatalitic Activity of TiO2/Pt/Al2O3 and TiO2/Sn/Al2O3 Films on Anodically Oxidized Aluminum

Takanori Hattori, Takayoshi Fujino

pp. 868-873

Abstract

Aluminum was anodized in a Na3PO4 solution, and then platinum and tin were electrodeposited into nano pores of anodic oxidation film in H2PtCl6 and SnSO4 solutions. Titanium (IV) oxide (TiO2) thin film was immobilized on electrolytically colored anodic oxide coating of aluminum. The photocatalytic activity of prepared films was analyzed for photolysis of the malachite green. In the results, the photocatalytic activity of Pt loaded TiO2 (TiO2/Pt/Al2O3) film was highest in all films, and the relation between the amount of metallic colloid and photocatalytic activity was confirmed. Photocatalytic activity improved with increase of the electrodeposition amount, and activity was highest when the amount of platinum was about 4.2×10−5 kg·m−2. But photocatalytic activity began to decline when the amount of platinum exceeded 4.2×10−5 kg·m−2 because the platinum had a recombination center and decreasing surface area by electrodeposition. The photocatalytic activity of Sn loaded TiO2 (TiO2/Sn/Al2O3) film didn’t reach that of the TiO2/Pt/Al2O3 film. However, that indicated photocatalytic activity of about 1.6 times compared with TiO2/Al2O3 film. SnO2 manifested photocatalysis as well as TiO2 because it was confirmed that sintered tin was SnO2 in the results of XPS.
Therefore, anodic oxidation film and electrolytically colored anodic oxide coating were effective substrates of photocatalytic films.

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Enhancing Effect on Photocatalitic Activity of TiO2/Pt/Al2O3 and TiO2/Sn/Al2O3 Films on Anodically Oxidized Aluminum

Mechanical Properties of 5052/2017 Dissimilar Aluminum Alloys Deposit by Friction Surfacing

Hiroshi Tokisue, Kazuyoshi Katoh, Toshikatsu Asahina, Toshio Usiyama

pp. 874-882

Abstract

5052 aluminum alloy plate used for substrate and 2017 aluminum alloy bar used for coating rod, both monolayer and multilayer friction surfacing were done using a numerical controlled full automatic friction welding machine. Effects of the surfacing conditions on structure and mechanical properties of both monolayer and multilayer deposits were investigated. It was clearly observed that the circular pattern appeared on the surface of both monolayer and multilayer deposits by the rotation of coating rod, and the interval of circularly pattern become narrower with increasing of the rotation of coating rod. The monolayer deposit has a tendency to incline toward right side (Retreating side) further than center of deposit for the feed direction of coating rod. And, the 2nd surfacing of multilayer deposit recognized to incline toward the 1st deposit side. A little of incomplete welds was observed at both sides of monolayer deposit. The incomplete parts of welds 1st deposit in multilayer deposit were disappeared by 2nd surfacing. Microstructures of both monolayer and multilayer deposits were finer than those of the substrate and coating rod. The deposition efficiency of 2nd surfacing in multilayer deposit showed higher value than that of the monolayer deposit. Hardness of both deposits showed higher value than that of the substrate and same value of coating rod. The softened area was recognized at 2.5 mm distance from the weld interface of substrate and coating rod. The tensile strength of multilayer deposit showed higher value than that of the monolayer deposit, and both deposits showed higher value than that of the substrate.

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Mechanical Properties of 5052/2017 Dissimilar Aluminum Alloys Deposit by Friction Surfacing

Effect of Die-Surface Treatment on Magnesium Alloys Fluidity

Lu Hsueh-Shang, Jun Yaokawa, Koichi Anzai

pp. 883-888

Abstract

Magnesium alloy offers an outstanding combination of light weight, ease of manufacturing, and good engineering properties. The most common method to manufacture magnesium alloy products is die-casting; however defect rate for magnesium alloy die-casting is still relatively high. Especially in case of thin-sectioned die-casting, mold filling may not be accomplished occasionally due to its fast solidification rate. As a result, fluidity (i.e. the ability of filling a cavity) becomes very essential.
In this study, a unique “melt droplet experiment” is proposed and conducted to examine the fluidity performance of magnesium alloys on various mold surfaces treatment, including plain SKD61 molds, vacuum nitration treated SKD61 molds and 4 other types of ceramic coating on SKD61 molds, TiAlN, CrN, AlCrN and CrC. In the beginning a variety of magnesium alloys with known fluidity are examined to validate this method’s legitimacy. The effect of mold surfaces coating treatment on fluidity of magnesium alloy AZ91D was studied.
Different types of surface coatings are applied on mold to distinguish the influence on fluidity performance. It is realized that surface coatings have certain enhancement towards fluidity length. For example, fluidity on the TiAlN coated molds was about 40 mm, while non treated plain molds exhibited 29 mm of fluidity, although their microscopic structure and surface roughness are similar. The difference of fluidity performance between them is about 35%. From the experimental results and heat transfer point of view, thermal properties of mold surface coating may be related to the fluidity difference.

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Effect of Die-Surface Treatment on Magnesium Alloys Fluidity

Building Ultra-Thin Layers by Ceramic Laser Sintering

Hwa-Hsing Tang

pp. 889-897

Abstract

The layer thicknesses of rapid prototyping 3D parts must be minimized to reduce the dimensional tolerance and improve the surface roughness. This paper studies the thinnest layer feasible by Ceramic Laser Sintering (CLS) and analyzes the reasons why ultra-thin layers could be built with CLS.
Manufacturing a work piece with a proper scanning parameter (3200 mm/s scanning speed, 33 W laser power) verified a 20-layer square work piece could be made successfully with 0.015 mm layer thickness, which is the thinnest layer made by a powder-based process.
Regarding the feasible layer thickness, effects of the following four significant influential parameters were discussed: (1) powder particle size, (2) paving force carrying capacity of paved layer, (3) upward deformation of the property transformation zone, and (4) anti-fracture strength of the property transformation zone.
The reasons why CLS could build ultra-thin layers were: (1) layers were built with slurry; (2) the inherent solid green support could withstand the paving force and prevent excessive upward deformation; (3) the lowest working temperature was decreased from 1800°C of Ceramic Laser Fusion to 1200°C.

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Building Ultra-Thin Layers by Ceramic Laser Sintering

Heating of Metal Particles in a Single-Mode Microwave Applicator

Noboru Yoshikawa, Etsuko Ishizuka, Shoji Taniguchi

pp. 898-902

Abstract

Microwave (MW) heating behavior of various metal particles was investigated using a single-mode applicator. Considering the distributions of the electromagnetic fields in the wave guide, specimens were placed at four specific positions with respect to the electric and the magnetic fields of MW. They were heated at conditions of constant power input.
It was demonstrated that iron particles were heated well in the magnetic field, and that ferro-magnetic metal particles having the higher Curie point was heated the better. It was possible to heat iron bulk particles (∼3 mm) in a magnetic field without occurrence of electric discharge. In the range of nickel particle size between 45 and 150 μm, the particles with the smaller size were heated the better.
Nickel oxide (NiO) was heated well only in the position of large electric field, which indicates that the heating was caused by the different (dielectric heating) mechanism from the metal particles.
From these results, contribution of magnetic field to heating metal particles was discussed, considering the heating mechanisms of the magnetic loss and the eddy current loss. The dependence of the heating rate of metal particles on their size was discussed in terms of the heat transfer rate.

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Heating of Metal Particles in a Single-Mode Microwave Applicator

Microwave Dielectric Properties of the (1−x)La2⁄3TiO3xLa(Ti1⁄2Mg1⁄2)O3 System

Aimin Yang, Huixin Lin, Lan Luo, Wei Chen

pp. 903-906

Abstract

(1−x)La2⁄3TiO3xLa(Mg1⁄2Ti1⁄2)O3 ceramics with x ranging from 0.1 to 0.9 were prepared by conventional solid-state reaction. La2⁄3TiO3 and La(Mg1⁄2Ti1⁄2)O3 were found to form a solid solution over the whole compositional range. However, the second phase La2Ti2O7 existed for x=0.1 and 0.3. As the x value increased from 0.1 to 0.9, the dielectric constant εr decreased from 65.1 to 28.4. The oxygen vacancies were the main factor affecting the Q×f values of the (1−x)La2⁄3TiO3xLa(Mg1⁄2Ti1⁄2)O3 ceramics. A τf value of −5 ppm/°C can be obtained at x=0.3.

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Microwave Dielectric Properties of the (1−x)La2⁄3TiO3xLa(Ti1⁄2Mg1⁄2)O3 System

In Situ Observations of Magnetization Process in Alnico Magnets by Electron Holography and Lorentz Microscopy

Joong Jung Kim, Hyun Soon Park, Daisuke Shindo, Satoshi Hirosawa, Hideyuki Morimoto

pp. 907-912

Abstract

The magnetic microstructure of Alnico 5 and Alnico 8 and their magnetization process were investigated systematically at a nanometer scale by means of electron holography and Lorentz microscopy. In particular, the magnetization process in Alnico alloys was visualized for the first time by utilizing a sharp magnetic needle made of sintered Nd2Fe14B in a transmission electron microscope. It was found that the direction of lines of magnetic flux changed at the boundaries between the α1 and α2 phases which were aligned in the direction of the magnetic field applied in the thermomagnetic treatment. In the Lorentz microscope image, these boundaries were observed as white lines and black bands, whose shapes reflected the difference in the shape anisotropy between Alnico 5 and Alnico 8. With an increase in the magnetic field induced by the magnetic needle, the magnetization direction of the domains magnetized in the direction opposite to that of the approaching needle was reversed, and finally a large reversed domain was formed. In both Alnico 5 and Alnico 8, it was shown that the magnetization process was accomplished through an entire magnetization reversal in each grain of the α1 phase.

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In Situ Observations of Magnetization Process in Alnico Magnets by Electron Holography and Lorentz Microscopy

Eco-Efficiency (Factor X) for Electrical and Electronic Products and a Case Study on Home Appliances in a Household

Taeko Aoe

pp. 913-922

Abstract

Many institutes and companies are currently researching into eco-efficiency and Factor X as evaluation methods for environmentally conscious design. However, no standard method has been established. Moreover while the eco-efficiency of each home appliance is being improved, the increasing number and size of such home appliances may increase the overall environmental impact. This paper begins with describing a practical eco-efficiency (Factor X) indicator developed to evaluate environmentally conscious products or services. This indicator gives a rationalized relationship between their functional performance and environmental impacts. Next, the paper presents a brief case study of Factor X done in Japan that compared home appliances from 2003 with those from 1990 using such indicators. The number of home appliances used in a household increased 1.2 times from 65 to 79. However, GHG (greenhouse gas) emissions per year was 0.64 times the former amount, dropping from 8456 to 5383 kg–CO2eq/year, and the new resources and discarded resources per year became 0.99 times the previous amount, dropping from 231 to 228 kg/year. Therefore, GHG Factor X was 1.9 and Resource Factor X was 1.2. Although based on a restricted evaluation model, these results quantitatively show the potential to improve functional performance (as evaluated by the number of home appliances) and at the same time reduce their environmental impacts (as evaluated by GHG emissions and new resources and discarded resources). These results also show that Resource Factor X is more difficult to improve than GHG Factor X. Improving Resource Factor X and establishing a sound material-cycle society requires not only technological innovation and reform of the social system, but also a significant change in people’s awareness.

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Eco-Efficiency (Factor X) for Electrical and Electronic Products and a Case Study on Home Appliances in a Household

Preparation and Characterisation of Mg–Al Layered Double Hydroxides Intercalated with 2-Naphthalene Sulphonate and 2,6-Naphthalene Disulphonate

Tomohito Kameda, Masami Saito, Yoshiaki Umetsu

pp. 923-930

Abstract

A Mg–Al layered double hydroxide (Mg–Al LDH) has been modified with aromatic anions by a coprecipitation technique. This method is based on the anion-exchange characteristics of the hydrotalcite-type compound which intercalates various anions, including anions of organic acids, in the interlayer. The Mg–Al LDHs are intercalated with 2-naphthalene sulphonate (2-NS) and 2,6-naphthalene disulphonate (2,6-NDS2−) ions, which contain a naphthalene ring with one and two sulphonate (–SO3) groups in their structures, respectively. They are formed by the dropwise addition of a mixed aqueous solution of Mg(NO3)2 and Al(NO3)3 (Al/Mg mole ratio = 1/3) to a solution containing the individual organic anion at a constant pH of 10.0. The Mg–Al LDHs modified with aromatic anion are expected to recognize and selectively uptake hazardous aromatic compounds, such as bisphenol A, from aqueous solutions. The composite materials prepared were characterized by X-ray diffraction, FT-IR spectroscopy and chemical analyses.
2-NS was observed to be intercalated into the interlayer almost fully up to the accommodation expected based on the neutralisation of the positive charge of the host lattice. The intercalation of 2,6-NDS2− was approximately 80% of the expected value, however. IR analysis results show that the organic anions are intercalated into the Mg–Al LDH without any significant change in their intrinsic structure.
The X-ray diffraction data suggest that the intercalation of the organic anions under consideration was accompanied by an expansion in the basal spacing of the LDHs. The X-ray diffraction patterns of the 2-NS-modified LDH suggested the formation of two types of LDHs showing different basal spacing at higher 2-NS content. On the other hand, the 2,6-NDS-modified LDH showed diffraction peaks, which corresponded to the basal spacing, with widely spreading peak angles and reduced intensity, suggesting the widely varying basal spacing of the Mg–Al LDH.

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Preparation and Characterisation of Mg–Al Layered Double Hydroxides Intercalated with 2-Naphthalene Sulphonate and 2,6-Naphthalene Disulphonate

Hydriding Chemical Vapor Deposition of Metal Hydride Nano-Fibers

Itoko Saita, Takeshi Toshima, Satoshi Tanda, Tomohiro Akiyama

pp. 931-934

Abstract

Here we show a novel chemical vapor synthesis technique, which uses high-pressure hydrogen and produces needle-shaped single crystalline made of metal hydride of MgH2. The principle of this method is based on the gas phase reaction of vaporized metal with high pressure hydrogen sublimating into solid metal hydride (Mg(g) + H2(g) → MgH2(s)). This can directly produce pure single-phased metal hydride of MgH2, while the conventional solid-gas reaction (Mg(s) + H2(g) → MgH2(s)) can hardly produce high purity hydride. The X-ray spectrum of as-synthesized product was MgH2 with rutile structure. The scanning electron micrographs showed the interesting figure of the product; needle-shaped nano fibers with diameter less than 500 nm and length larger than 100 μm. Transmission electron micrograph and related electron diffraction pattern provided that the needle-shaped product was single crystalline of MgH2 growing into [1 0 1] direction, into which Mg-layers and H-layers are alternately stacked up. The results appealed a revolutionary productive route for metal hydride, which offers many benefits for simplifying the productive procedure, minimizing processing time, saving energy, and upgrading the product.

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Hydriding Chemical Vapor Deposition of Metal Hydride Nano-Fibers

Effect of Heat Treatment on Characteristics of Plasma Sprayed Hydroxyapatite Coatings

Chun-Cheng Chen, Shinn-Jyh Ding

pp. 935-940

Abstract

Bioactive hydroxyapatite (HA)-coated implants plasma sprayed on Ti6Al4V substrates have been widely used in load-bearing applications because of their biocompatibility and their intimate contact with bone. The improvement of the characteristics of HA coatings is concerned. The purpose of this work was to evaluate corrosion behavior and bond strength of HA coatings after post-deposition heat treatment at 500–700°C. The results indicated that the heat treatment led to recrystallization of amorphous calcium phosphate of as-sprayed HA coatings. The reduction of layer defects associated with plasma-sprayed coatings and the enhancement of the resistance to corrosion took place after heat treatment. Bond strength of the heat-treated coatings was sensitive to the treatment temperature. It is concluded that the heat treatment at 600°C for 1 h in air, endowing with increased crystallinity and the reduced defects without significantly reduced bond strength, provided a better corrosion protection than the other two treatment temperatures.

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Effect of Heat Treatment on Characteristics of Plasma Sprayed Hydroxyapatite Coatings

Atmospheric Pressure Plasma Treatment and Non-Flux Lead-Free-Soldering of Cu Wire and Strand

Tomohiro Okumura, Mitsuo Saitoh, Kazutaka Nishikawa, Akio Furusawa, Kenichiro Suetsugu

pp. 941-947

Abstract

There has been an intensive effort in the industries in recent years to replace leaded solder with lead-free process in order to minimize the emission of toxic materials. However, leaded solder is still used in many cases where no alternative lead-free process is currently available. Leaded soldering of the wire terminals is one of the worst examples as it causes cross contamination of lead into the lead-free solder bath during the successive process. To avoid this problem, it is important to develop a new process of successfully removing polymer film coated on a copper wire. We have investigated the use of atmospheric pressure plasma as a solution for the polymer removal in conjunction with lead-free solder plating. The atmospheric plasma technology has some unique advantages compared with the conventional low pressure plasma processes such as low cost operation and high speed processing as the chemical reaction tends to be more enhanced at higher pressure. An atmospheric micro-plasma source was thus developed for this purpose and its high etching rate of more than 100 μm/min with fluorine gas mixture was demonstrated. Furthermore, it was found that the copper wires processed by this plasma could be readily plated with lead-free solder at low temperature of 250°C without any use of fluxes even at 168 h after removing the polymer film.

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Atmospheric Pressure Plasma Treatment and Non-Flux Lead-Free-Soldering of Cu Wire and Strand

In-Situ Laser Cladding of Al2O3 Reaction Coating on Aluminium Alloy 7075 for Corrosion Resistance Improvement

T. M. Yue, K. J. Huang, H. C. Man

pp. 948-951

Abstract

The microstructure and corrosion behaviour of the thermite reaction coatings for the systems of Al–CuO–SiO2, Al–Cr2O3–SiO2, and Al–TiO2–SiO2 that produced by laser cladding on aluminium alloy 7075 have been studied. The results of the XRD analysis show that in all the three reaction coatings, α-Al2O3 and γ-Al2O3 phases were present together with various intermetallic phases and the corresponding reduced metal. A comparison of the polarisation curves of the untreated and the various coated specimens shows that except for the Al–CuO–SiO2 system, the corrosion current density of the coated specimens was one order of magnitude lower than that of the untreated specimen, also a higher corrosion potential was obtained. The inferior corrosion resistance of the Al–CuO–SiO2 system is attributed to galvanic corrosion occurred between the reduced metal, the intermetallic compounds and aluminium.

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In-Situ Laser Cladding of Al2O3 Reaction Coating on Aluminium Alloy 7075 for Corrosion Resistance Improvement

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