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MATERIALS TRANSACTIONS Vol. 47 (2006), No. 6

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

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MATERIALS TRANSACTIONS Vol. 47 (2006), No. 6

The Phase Equilibria and Seebeck Coefficient of (Co,M)3AlC (M=Fe or Ni)

Tatsuya Maruoka, Ryosuke O. Suzuki

pp. 1422-1427

DOI:

10.2320/matertrans.47.1422

Abstract

The phase equilibria and the Seebeck coefficient were measured at the vicinity of the carbide (Co,M)3AlC (M=Fe or Ni) in the Co-Al-C, Co-Fe-Al-C and Co-Ni-Al-C systems. The samples were well annealed at 1473 K and examined through X-ray diffraction measurements, energy dispersive X-ray analysis and carbon analysis. Co3AlC with a perovskite structure did not exist at its stoichiometric composition, but was located within a narrow compositional range near Co3AlC0.67. The maximum Seebeck coefficient was 23.3 μV/K at 873 K for Co3AlC0.63. The replacement of a small amount of Co by Fe resulted in the expansion of the single-phase area of (Co,Fe)3AlCx, and the Seebeck coefficient of the single phase reached its maximum, 32.6 μV/K, at 873 K and Co3.506Fe0.025AlC0.77 in the quaternary Co-Fe-Al-C system. The addition of Ni did not stabilize this carbide, and the maximum Seebeck coefficient in the quaternary Co-Ni-Al-C system was 26.9 μV/K at 873 K.

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The Phase Equilibria and Seebeck Coefficient of (Co,M)3AlC (M=Fe or Ni)

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Thermoelectric Properties of Solution Grown β-FeSi2 Single Crystals

Hirokazu Suzuki, Haruhiko Udono, Isao Kikuma

pp. 1428-1431

DOI:

10.2320/matertrans.47.1428

Abstract

We have measured the Seebeck coefficient of single crystalline β-FeSi2 grown by a temperature gradient solution growth (TGSG) method using Ga solvent. Rectangular-like β-FeSi2 plates with the size of (3–6)×(1–2)×0.3 mm3, where the longitudinal axis was [011], were prepared from the grown ingots. Typical resistivity and hole concentration of the crystals were 4×10−4 Ωm and 2×1025 m−3 at room temperature (RT), respectively. The Seebeck coefficient measured along the [011] direction was approximately 350 μV/K at RT and showed the maximum value of 500 μV/K between 20 and 25 K. We also found that the solution grown single crystals had large power factors below RT. The value was 3.4×10−4 Wm−1 K−2 at RT, which was about three times larger than that of sintered poly-crystals and CVT-grown single crystals. The maximum power factor was 4.5×10−4 Wm−1 K−2 around 150 K. The value was more than one order of magnitude larger than reported values.

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Thermoelectric Properties of Solution Grown β-FeSi2 Single Crystals

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Thermoelectric and Thermophysical Characteristics of Cu2Te-Tl2Te Pseudo Binary System

Ken Kurosaki, Keita Goto, Atsuko Kosuga, Hiroaki Muta, Shinsuke Yamanaka

pp. 1432-1435

DOI:

10.2320/matertrans.47.1432

Abstract

We studied the thermoelectric and thermophysical properties of Cu2Te-Tl2Te pseudo binary system. Polycrystalline samples of CuTl9Te5, Cu2Te and Tl2Te were prepared and characterized. All samples indicated positive values of the Seebeck coefficient and very low values of the thermal conductivity. The values of the thermal conductivity of CuTl9Te5 and Tl2Te at room temperature were 0.49 and 0.35 Wm−1 K−1, respectively. These very low thermal conductivity values could be associated with the material’s thermophysical properties such as the average sound velocity. CuTl9Te5 was found to show relatively high thermoelectric figure of merit ZT; the maximum ZT value was 0.38 obtained at 592 K.

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Thermoelectric and Thermophysical Characteristics of Cu2Te-Tl2Te Pseudo Binary System

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Synthesis of La2S3 Thin Films by Sulfurization of LaCl3 and CS(NH2)2

Michihiro Ohta, Shinji Hirai, Hideyasu Asahi, Toshiyuki Nishimura, Yoichiro Uemura, Kazuyoshi Shimakage

pp. 1436-1439

DOI:

10.2320/matertrans.47.1436

Abstract

La2S3 thin films were prepared by dipping the substrates in methanol solutions of LaCl3·7H2O and CS(NH2)2, followed by sulfurization with CS2 gas in the temperature range of 773–1073 K. The effects of the substrate and the mole ratio of LaCl3·7H2O to CS(NH2)2 on the phase formation after sulfurization were investigated. When the mole ratio of LaCl3·7H2O to CS(NH2)2 was 2:3, the tetragonal β-La2S3 coatings were obtained on silica glass and Mo substrates for sulfurization at 1073 K. On the other hand, the cubic γ-La2S3 coating was obtained on a soda-lime glass substrate for sulfurization at 973 K. The thin films on Ta and Ti substrates were comprised of β-La2S3 and γ-La2S3 phases for sulfurization at 1073 K. The LaS2 phase was identified as an intermediate product of sulfurization at about 873 K. When the mole ratio of LaCl3·7H2O to CS(NH2)2 was 1:1, the γ-La2S3 coating was also obtained on silica glass substrate for sulfurization at 1073 K. Since the gaseous phases formed during sulfurization pass through the La2S3 layer, the thin films obtained were porous.

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Synthesis of La2S3 Thin Films by Sulfurization of LaCl3 and CS(NH2)2

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Microscale Seebeck Scanning of Polycrystalline Samples of N-Type AgPb18SbTe20 and P-Type AgPb9Sn9SbTe20

Atsuko Kosuga, Ken Kurosaki, Hiroaki Muta, Christian Stiewe, Gabriele Karpinski, Eckhard Müller, Shinsuke Yamanaka

pp. 1440-1444

DOI:

10.2320/matertrans.47.1440

Abstract

We prepared polycrystalline-sintered samples of n-type AgPb18SbTe20 and p-type AgPb9Sn9SbTe20 and performed the microscale Seebeck scanning examination under room temperature conditions. Despite both samples appeared to be homogeneous by Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analyses, both samples contained apparently a microscale distribution of the Seebeck coefficient as observed by Seebeck microprobe analysis. The degree of the Seebeck coefficient distribution became larger in the order of PbTe, AgPb18SbTe20, and AgPb9Sn9SbTe20, indicating that an increase in the number of compositional elements of the materials led to a broader distribution of the Seebeck coefficient values. The statistical analysis of the Seebeck coefficient distribution of p-type AgPb9Sn9SbTe20 indicated a homogeneous phase seemed to appear only at the lowest Seebeck coefficient values (slightly above 50 μV/K).

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Microscale Seebeck Scanning of Polycrystalline Samples of N-Type AgPb18SbTe20 and P-Type AgPb9Sn9SbTe20

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Thermoelectric and Thermophysical Properties of TiCoSb-ZrCoSb-HfCoSb Pseudo Ternary System Prepared by Spark Plasma Sintering

Takeyuki Sekimoto, Ken Kurosaki, Hiroaki Muta, Shinsuke Yamanaka

pp. 1445-1448

DOI:

10.2320/matertrans.47.1445

Abstract

We studied the thermoelectric and thermophysical properties of TiCoSb-ZrCoSb-HfCoSb pseudo ternary system. Polycrystalline samples were prepared by a spark plasma sintering (SPS) technique, and their thermoelectric properties above room temperature and thermophysical properties at room temperature were measured. All the samples were identified as a half-Heusler compound by the X-ray diffraction analysis. The lattice parameter, electrical resistivity and thermoelectric power systematically change with the composition in the pseudo ternary phase diagram. All the samples indicated negative values of the thermoelectric power. Low thermal conductivity was achieved in the samples with the composition near the center of the pseudo ternary phase diagram where the effect of the alloy scattering becomes large. The maximum value of ZT was obtained to be 0.073 at 790 K for Ti0.25(Zr0.5Hf0.5)0.75CoSb.

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Thermoelectric and Thermophysical Properties of TiCoSb-ZrCoSb-HfCoSb Pseudo Ternary System Prepared by Spark Plasma Sintering

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Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO2−x Fabricated by Reduction Treatment Using Carbon Powder

Yun Lu, Mitsuji Hirohashi, Kenkichi Sato

pp. 1449-1452

DOI:

10.2320/matertrans.47.1449

Abstract

A reduction treatment using carbon powder for reducing TiO2 to fabricate non-stoichiometric titanium dioxide, TiO2−x, was proposed and performed. The carrier density and non-stoichiometric number were calculated by using thermogravimetry (TG) while heating and re-oxidizing TiO2−x in air. The thermoelectric properties of TiO2−x were measured and evaluated in air. The results show that TiO2−x can be simply and safely obtained by reducing insulating TiO2 through the proposed reduction treatment. The carrier density increases and non-stoichiometric number decrease with the temperature of the reduction treatment and have a good correspondence with the decrease in the electrical resistivity of TiO2−x. Significantly improved thermoelectric properties were observed as a consequence of the decreasing electrical resistivity of TiO2−x.

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Thermoelectric Properties of Non-Stoichiometric Titanium Dioxide TiO2−x Fabricated by Reduction Treatment Using Carbon Powder

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Substitution Effect on Thermoelectric Properties of ZrNiSn Based Half-Heusler Compounds

Hiroaki Muta, Takanori Kanemitsu, Ken Kurosaki, Shinsuke Yamanaka

pp. 1453-1457

DOI:

10.2320/matertrans.47.1453

Abstract

Thermoelectric properties of ZrNiSn based half-Heusler compounds, Zr0.7X0.3NiSn (X=Ti, Hf), ZrNi0.7Y0.3Sn (Y=Pd, Pt), and ZrNi1.05Sn were investigated from room temperature to 1000 K. All the substitutions and addition of the excess nickel drastically decreased the thermal conductivity. The experimental values at room temperature were in good agreement with those estimated by the disorder scattering theory. The thermal conductivity exhibited considerable increase above 700 K for all the samples. It was corresponding to the transition of electrical properties, indicating that the generated hole conduction at high temperatures provided the increase. The additional electronic thermal conductivity caused by the ambipolar diffusion effect is discussed.

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Substitution Effect on Thermoelectric Properties of ZrNiSn Based Half-Heusler Compounds

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Thermoelectric Properties of Cesium–Graphite Intercalation Compounds

Rika Matsumoto, Noboru Akuzawa, Yoichi Takahashi

pp. 1458-1463

DOI:

10.2320/matertrans.47.1458

Abstract

The thermoelectric properties of cesium–graphite intercalation compounds (Cs-GICs) and some other GICs were studied. The electrical conductivities of the Cs-GICs prepared from Grafoil were around 106 Ω−1 m−1, about 10 times higher than that of the host graphite, and the thermal conductivities were 50–100 Wm−1 K−1, about 1/4–1/2 of that of the host graphite. While the Seebeck coefficient of the host graphite was nearly zero, those of the Cs-GICs were found to be around −30 μV K−1. These properties were determined also for the Cs-GICs prepared from well-oriented PGS graphite sheets. Consequently, the figures of merit of the Cs-GICs were of the order of 10−5 K−1, approximately 105 times higher than that of the host graphite. The power factor of the Cs-GICs reached the order of 10−3 Wm−1 K−2, with the best datum at 6.5×10−3 Wm−1 K−2. The carrier density of the GICs increased as the concentration of intercalated species increased, whereas their lattice thermal conductivities decreased. It is suggested that highly concentrated GICs might be promising candidate thermoelectric materials.

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Thermoelectric Properties of Cesium–Graphite Intercalation Compounds

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Quality Improvement of Steel Pipes Produced by Seam Welding with New Magneto-Dielectric Impeder

Miroslav Milicevic, Zoran Radakovic

pp. 1464-1468

DOI:

10.2320/matertrans.47.1464

Abstract

The standard technology of steel pipe production is the high frequency (HF) inductive welding. A mechanically formed profile is introduced into an inductor. Inside the pipe, in the position of the inductor there is an impeder, whose function is to form a suitable distribution of the electromagnetic and temperature field. In previous paper of the authors, the new magneto-dielectric (MD) material for the impeder is proposed and results of extraordinary energy saving are shown.
This paper treats the aspect of the pipe quality, which represent the essential parameter in a production technology. The analyses were made for the widely spread ferrite impeder and for the proposed MD impeder. From this point of view, the MD impeder appeared to be advantageous material also. In addition to the standard mechanical tests of pipes quality, extensive chemical and physical analyses of the material in the weld, as well as in the basic section of the pipe, have been performed. The aim of the investigation was to explain the bad results in the standard flattening and hydrostatic testing of pipes produced using the ferrite impeder of TDK-IP1 type.

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Quality Improvement of Steel Pipes Produced by Seam Welding with New Magneto-Dielectric Impeder

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Electron-Irradiation Induced Phase Transformation of Amorphous, Supercooled Liquid and Crystalline Phases in Zr66.7Cu33.3 Metallic Glass

Takeshi Nagase, Yukichi Umakoshi

pp. 1469-1479

DOI:

10.2320/matertrans.47.1469

Abstract

Electron-irradiation induced phase transformation of amorphous, supercooled liquid and crystalline phases in Zr66.7Cu33.3 alloy was investigated. The amorphous phase and supercooled liquid were not stable under 2.0 MV electron-irradiation, and electron-irradiation induced crystallization occurred. The C11b-Zr2Cu crystalline phase was precipitated from the supercooled liquid phase and the amorphous phase at and above 552 K, while an f.c.c. solid solution was precipitated from the amorphous phase at and below 298 K. Crystal-to-glass or crystal-to-supercooled liquid transition of the C11b-Zr2Cu crystalline phase in Zr66.7Cu33.3 metallic glass was not observed at and above 552 K. Phase stability of crystalline phases against electron-irradiation is a dominant factor for phase selection in electron-irradiation induced crystallization of Zr66.7Cu33.3 metallic glass.

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Electron-Irradiation Induced Phase Transformation of Amorphous, Supercooled Liquid and Crystalline Phases in Zr66.7Cu33.3 Metallic Glass

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Quantitative Evaluation of Interdiffusion in Fe2Al5 during Reactive Diffusion in the Binary Fe–Al System

Masanori Kajihara

pp. 1480-1484

DOI:

10.2320/matertrans.47.1480

Abstract

Using Al/Fe/Al diffusion couples prepared by a diffusion bonding technique, the reactive diffusion in the binary Fe–Al system was experimentally examined in a previous study. The diffusion couple was isothermally annealed at temperatures of T=823–913 K, and then a compound layer of Fe2Al5 was observed to form at the interface. The observation indicates that there exists the parabolic relationship between the mean thickness of the Fe2Al5 layer and the annealing time. The parabolic relationship means that the growth of the Fe2Al5 layer is controlled by volume diffusion. A mathematical model for the reactive diffusion controlled by volume diffusion was used in order to analyze numerically the growth rate of the Fe2Al5 layer. Through the analysis, the interdiffusion coefficient D of Fe2Al5 was evaluated to be 5.93×10−16, 1.18×10−14 and 2.92×10−14 m2/s at T=823, 873 and 913 K, respectively. Expressing the temperature dependence of D as D=D0exp(−Q⁄RT), values of D0=2.34×102 m2/s and Q=276 kJ/mol were obtained by the least-squares method.

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Quantitative Evaluation of Interdiffusion in Fe2Al5 during Reactive Diffusion in the Binary Fe–Al System

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Cold Rolling Texture of Ni-Based L12 Ordered Intermetallic Alloys

Yasuyuki Kaneno, Akira Takahashi, Takayuki Takasugi

pp. 1485-1491

DOI:

10.2320/matertrans.47.1485

Abstract

Cold rolling textures of three kinds of Ni-based intermetallic alloys with L12 ordered structure (i.e., Ni3(Si,Ti), Ni3Al, and Ni3Fe) were investigated by the orientation distribution function (ODF). For comparison, the rolling texture of pure nickel with fcc disordered structure was also determined. The rolling textures of the 70% and 90% cold-rolled L12 alloys as well as fcc nickel are composed of the α-fiber ({011}⟨100⟩ (G) − {011}⟨211⟩ (Bs)) and β-fiber ({112}⟨111⟩ (C) − {123}⟨634⟩ (S) − {011}⟨211⟩ (Bs)) components, but the {011}⟨211⟩ (Bs) (and also the {011}⟨100⟩ (G)) orientation is remarkable in the L12 alloys while the {123}⟨634⟩ (S) (and also the {112}⟨111⟩ (C)) orientation is prominent in fcc nickel. Moreover, the intensity of rolling texture in the L12 alloys depended on materials (i.e., constituent elements). The observed rolling texture of the L12 ordered alloys was discussed in terms of cross slips of extended dislocations whose width was estimated by the energies of stacking-fault-like defect (SFLD) (i.e., antiphase boundary (APB) in the case of L12 ordered structure and stacking fault (SF) in the case of fcc disordered structure).

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Cold Rolling Texture of Ni-Based L12 Ordered Intermetallic Alloys

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Evaluation of Displacive Models for Bainite Transformation Kinetics in Steels

María Jesús Santofimia, Francisca G. Caballero, Carlos Capdevila, Carlos García-Mateo, Carlos García de Andrés

pp. 1492-1500

DOI:

10.2320/matertrans.47.1492

Abstract

Several kinetic models for bainite transformation have been widely applied in industry and research. The majority of these models, that do not consider the effect of cementite precipitation during bainite transformation, were validated in high silicon bainitic steels in order to avoid the interference of cementite precipitation during bainite formation. In this work, displacive models for bainite transformation have been validated in bainitic steels with different silicon content with the aim of evaluating their applicability on steels where cementite precipitation may play an important role on bainite formation. It has been found that these models fail in the calculus of the maximum volume fraction of bainite of lean silicon steels, but lead to a reasonable accuracy in high silicon steels. This is not surprising since cementite formation reduces the carbon content in the residual austenite, stimulating the formation of a further quantity of ferrite. Likewise, an imprecise estimation of the nucleation rate of bainite must be the reason for the poor correlation in the predictions of the bainite transformation kinetics in high silicon steels. This entails a better treatment of autocatalytic nucleation, still unresolved issue in the bainite transformation kinetics theory.

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Evaluation of Displacive Models for Bainite Transformation Kinetics in Steels

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Surface Modification of Cast Iron Containing 6 mass% Aluminum and Its Wear Property

Susumu Takamori, Yoshiaki Osawa, Xinbao Liu, Takashi Kimura

pp. 1501-1507

DOI:

10.2320/matertrans.47.1501

Abstract

Flake graphite cast iron containing aluminum is known to have excellent heat resistance. In this research, the characteristics of a surface modification process and the wear property of surface-modified aluminum alloyed cast iron were investigated.
When flake graphite cast iron containing 6 mass% aluminum was heat-treated at 1273 K in air, alumina precipitated at the positions where graphite existed, showing the same shape as flake graphite. The thickness of the alumina dispersed layer reached about 1 mm by heat-treating for more than 72 ks at 1273 K. This material was evaluated by the pin-on-disc method, and showed excellent wear property compared to normal flake graphite cast iron. The surface-modified layer showed excellent wear resistance especially at a test speed of 1.0 m/s. Also, at a test speed of 0.1–0.5 m/s, this layer showed better wear resistance than normal cast iron. Apparently the material surface transforms into an oxidized wear state due to the adhesion of oxides including alumina, resulting in improved wear resistance.
This is a new surface modification method applying decarburization of graphite and the easy oxidation feature of aluminum. The method is easy to perform as it uses only heat-treatment in air, and suggests that cast iron having new characteristics may be created by substituting other substances for the included graphite.

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Surface Modification of Cast Iron Containing 6 mass% Aluminum and Its Wear Property

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Influence of Iron Oxide Particles on the Strength of Ball-Milled Iron

Donald R. Lesuer, Chol K. Syn, Oleg D. Sherby

pp. 1508-1517

DOI:

10.2320/matertrans.47.1508

Abstract

Detailed microstructural and mechanical property studies of ball-milled iron, in the powder and consolidated states, are reviewed and assessed. The analyses cover three and one-half orders of magnitude in grain size (from 6 nm to 20 μm) and focus on the influence of oxide particles on the strength. The study includes the early work of Jang and Koch, Kimura and Takaki and continues with the more recent work of Umemoto et al. and Belyakov, Sakai et al. It is shown that the major contributors to strength are the nano-oxide particles. These particles are created by adiabatic shear banding during ball-milling leading to a bimodal distribution of particles. The predicted strength from particles, σp, is given by σp=B·(Ds*)−1⁄2 where Ds* is the surface-to-surface interparticle spacing, and B=395 MPa·μm1⁄2. A model is proposed that accounts for the influence of the bimodal particle size distribution on strength.

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Influence of Iron Oxide Particles on the Strength of Ball-Milled Iron

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Compressive Deformation Behavior of Nanocrystalline Al Alloys at High Temperatures

Wonsik Lee, Jin Man Jang, Se-Hyun Ko, Chang-Woo Lee

pp. 1518-1522

DOI:

10.2320/matertrans.47.1518

Abstract

Three kinds of nanocrystalline materials, pure Al, Al-1.5Mg and Al-0.7Mg-1.0Cu, were compressive deformed at 300°C. In load-displacement curves, sharp drop of load after yielding was observed in Al-1.5Mg and Al-0.7Mg-1.0Cu alloys while slight increase of load in pure Al. The load drop results from effective grain boundary sliding, which indicates that alloying elements, Mg and/or Cu, assist the occurrence of grain boundary sliding. Plateau region where load is constantly sustained appeared following load drop, especially at strain rate of 1×10−3 s−1 in Al-1.5Mg and Al-0.7Mg-1.0Cu alloys. During deformation in plateau region grains were highly refined from 100 nm to about 10 nm and then, the refined grains grew again up to 100 nm by subsequent deformation. All nanocrystalline Al alloys including pure Al showed strain softening phenomenon due to grain boundary sliding at 300°C regardless of strain rate.

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Compressive Deformation Behavior of Nanocrystalline Al Alloys at High Temperatures

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Mechanical Properties of Melt-Spun Amorphous Ni-Nb-Zr Alloys after Hydrogen Charging

Asahi Kawashima, Shinji Yamaura, Naofumi Ohtsu, Hisamichi Kimura, Akihisa Inoue

pp. 1523-1526

DOI:

10.2320/matertrans.47.1523

Abstract

The effect of pre-charged hydrogen on the mechanical behavior of melt-spun amorphous Ni-Nb-Zr alloys was investigated. A substantial increase in the tensile fracture strength is observed even in hydrogen content up to about 46 at%. The Vickers hardness gradually increases with an increase in hydrogen content up to about 27 at%, and keeps almost the same value in the higher content more than 46 at%. It might be said that the amorphous (Ni0.6Nb0.4)70Zr30 alloy is not embrittled distinctly even in the high hydrogen content at room temperature. The amorphous alloy ribbons always curled during hydrogenation and the outer side of the curled ribbon corresponds to the roll side due to preferential absorption of hydrogen. XPS study revealed that the zirconium content in the surface film of the roll side surface is lower than that of the top side surface. The difference in surface composition as well as higher surface roughness of the roll side surface seems responsible for the preferential hydrogen absorption.

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Mechanical Properties of Melt-Spun Amorphous Ni-Nb-Zr Alloys after Hydrogen Charging

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High Temperature Deformation of ZrC Particulate-Reinforced Nb-Mo-W Composites

Y. Tan, C. L. Ma, R. Tanaka, J.-M. Yang

pp. 1527-1531

DOI:

10.2320/matertrans.47.1527

Abstract

The effect of incorporating ZrC particulates on the microstructure and mechanical behavior of Nb-Mo-W ternary alloy prepared through a powder metallurgy route was investigated. Microstructure of the alloy was examined by optical microscopy, X-ray diffractometry and electron probe microanalysis. Tensile tests were conducted from room temperature up to 1773 K. The results revealed that the incorporation of a small amount of ZrC particle is effective in improving the tensile strength and ductility of Nb-Mo-W alloy at elevated temperature. A transition of fracture mode from a brittle transgranular mode to ductile intergranular mode was observed in the composite with ZrC particles at elevated temperature.

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High Temperature Deformation of ZrC Particulate-Reinforced Nb-Mo-W Composites

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Relation between Strength, Fracture Toughness, and Critical Frontal Process Zone Size in Ceramics

Hideo Awaji, Takuya Matsunaga, Seong-Min Choi

pp. 1532-1539

DOI:

10.2320/matertrans.47.1532

Abstract

In order to improve the fracture toughness of inherently brittle ceramics, a new material design concept must be developed. One suitable concept involves the use of dislocation activities. Intra-type ceramic-based nanocomposites use dislocation activities to enhance strength and fracture toughness. The dislocations are generated by residual stresses induced during sintering process around the second-phase nanoparticles dispersed within the matrix grains. In this paper, first, we proposed an indirect technique for estimating a critical frontal process zone (CFPZ) size for ceramics and clarified the relation between the strength, fracture toughness, and CFPZ size. The fracture toughness of ceramics is closely related to the CFPZ size because ceramics with larger CFPZ size consume higher fracture energy during crack extension and consequently have higher fracture toughness. Second, we fabricated toughened alumina-nickel nanocomposites using a soaking method to construct an intra-type nanostructure, and found that the appropriate annealing conditions after sintering could achieve toughened nanocomposites. Finally, we discussed the relation between the experimentally obtained fracture toughness and the CFPZ size of monolithic alumina, as-sintered nanocomposites, and annealed nanocomposites. The results revealed that nanocomposites showed the largest CFPZ size and the highest fracture toughness after appropriate annealing: the sessile dislocations ahead of a crack tip in a nanocomposite are thought to serve as stress concentration, create many nanocracks in the CFPZ, and expand the CFPZ size.

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Relation between Strength, Fracture Toughness, and Critical Frontal Process Zone Size in Ceramics

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Partition Equilibria of Lead and Antimony between Liquid Copper and MgO Saturated Cu2O-SiO2, Cu2O-CaO and Cu2O-CaO-SiO2 Systems

Yang Cui, Xing-Hong Du, Tasuku Hamano, Fumitaka Tsukihashi

pp. 1540-1545

DOI:

10.2320/matertrans.47.1540

Abstract

The partition ratios of Pb and Sb between liquid copper and MgO saturated Cu2O-SiO2, Cu2O-CaO and Cu2O-CaO-SiO2 systems were measured from 1523 to 1673 K.
For Cu2O-SiO2-MgOsatd. system at 1573 K, the effect of SiO2 content on partition ratios of Pb and Sb was small and their partition ratios were lower than 20. For Cu2O-CaO-MgOsatd. system, the partition ratio of Pb was not affected by the CaO concentration, while the partition ratio of Sb and the activity coefficient of SbO1.5 were dependent on the CaO concentration. When CaO concentration increased, the partition ratio of Sb increased and the activity coefficient of SbO1.5 decreased.
For Cu2O-CaO-SiO2-MgOsatd. system, two liquid phases, which one was calcium silicate rich phase and another was Cu2O rich phase, were observed at 1573 K. The partition ratios of Pb and Sb between calcium silicate phase and liquid copper were dependent on the ratio of (mass%CaO)/(mass%SiO2). When the ratio (mass%CaO)/(mass%SiO2) increased, the partition ratio of Pb decreased and that of Sb increased.

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Partition Equilibria of Lead and Antimony between Liquid Copper and MgO Saturated Cu2O-SiO2, Cu2O-CaO and Cu2O-CaO-SiO2 Systems

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The Relationship between Microstructure and the Thermal Equilibrium Diagram of Au-Co Alloy Electrodeposit

Koichiro Inoue, Nobuto Sasaki, Takashi Sasadaira, Tohru Watanabe, Takeshi Nakata

pp. 1546-1549

DOI:

10.2320/matertrans.47.1546

Abstract

An Au-Co alloy with an extensive composition range was electrodeposited from a gold sulfite and cobalt sulfate mixture. The Au-Co alloy electrodeposits were analyzed by XRD and TEM and the relationship between the phase and thermal equilibrium diagrams was investigated. The Au-Co alloy electrodeposits formed a solid solution over an extensive composition range. It was also revealed that the composition of the electrodeposited Au-Co alloy was equal to that of the quenched phase at a high temperature, about 950°C.

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The Relationship between Microstructure and the Thermal Equilibrium Diagram of Au-Co Alloy Electrodeposit

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TEM-EDX Observations of the Microstructure of Electrodeposited Ni-Sn Alloys

Satoshi Oue, Hiroaki Nakano, Ryo Kuroda, Shigeo Kobayashi, Hisaaki Fukushima

pp. 1550-1554

DOI:

10.2320/matertrans.47.1550

Abstract

The microstructure of Ni-Sn alloys electrodeposited at 50–5000 A/m2 from 65°C chloride solutions containing 5–40 metal% of Sn were analyzed by TEM-EDX. Ni-Sn alloy deposition showed a characteristic behavior in that Ni and Sn were codeposited at an atomic ratio of 1:1 under a wide range of solution compositions and current densities. Ni and Sn EDX mapping images of a cross section of Ni-50 at% Sn alloy deposited at over 1000 A/m2 showed a lamellar pattern parallel to the interface between substrate and deposit, indicating the alternate deposition of Ni-Sn alloys with different compositions. The Ni-Sn alloys were identified by EDX line analysis as Ni3Sn4 and Ni3Sn2. It was concluded that Ni-50 at%Sn alloys deposited over 1000 A/m2 were not composed of the previously reported metastable-phase NiSn single alloy, but instead consisted of both Ni3Sn4 and Ni3Sn2 alloys in a thermodynamically stable phase.

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TEM-EDX Observations of the Microstructure of Electrodeposited Ni-Sn Alloys

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Standard Gibbs Energy of Formation of Zn8La Determined by Solution Calorimetry and Measurement of Heat Capacity from Near Absolute Zero Kelvin

Masao Morishita, Hiroaki Yamamoto, Kohei Tsuboki, Yasutomo Matsumoto

pp. 1555-1559

DOI:

10.2320/matertrans.47.1555

Abstract

The thermodynamic properties of Zn8La were investigated by calorimetry. The standard entropy of formation at 298 K, ΔfS298°, was determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, ΔfH298°, was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, ΔfG298°, was determined from these data. The results obtained were as follows: ΔfH298°(Zn8La)/kJ·mol−1 = −297.18±18; ΔfS298°(Zn8La)/J·mol−1·K−1 = −25.02±3.60; ΔfG298°(Zn8La)/kJ·mol−1 = −289.71±18. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn8La was small, indicating that decrease of the density of states for 4f component of the lanthanum atom in the vicinity of EF.

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Standard Gibbs Energy of Formation of Zn8La Determined by Solution Calorimetry and Measurement of Heat Capacity from Near Absolute Zero Kelvin

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Control of Hardness Distribution in Friction Stir Welded AA2024-T3 Aluminum Alloy

Saad Ahmed Khodir, Toshiya Shibayanagi, Masaaki Naka

pp. 1560-1567

DOI:

10.2320/matertrans.47.1560

Abstract

AA 2024-T3 Aluminum alloy plates of 3 mm thickness were friction stir butt welded at a constant rotation speed of 1250 min−1 and welding speeds of 50 and 100 mm/min. Three types of backing materials such as SUS304, pure copper block, and a combination of copper-block with 0.5 mm SUS304 were used. Controls of temperature history were achieved and their effects on microstructures, hardness distributions, and tensile properties of the joints were investigated. Grain size of the stir zone decreased from 7.4 μm in the case of stainless steel to 4.4 and 1.7 μm for the cases of a combination backing type and copper-block respectively. As a result of higher heating/or cooling rates, both higher welding speed and copper-block backing material resulted in increased hardness in HAZ and a maximum value was achieved for the combined backing plate at 100 mm/min of welding speed. Higher peak temperature was beneficial for higher hardness in stir zone while lower one in HAZ. A maximum tensile strength of the joint was achieved at a welding speed of 100 mm/min when the combined backing type was used. The joint efficiency of this case was 93.6% and this value was the highest among the present joints.

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Control of Hardness Distribution in Friction Stir Welded AA2024-T3 Aluminum Alloy

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Bulk Amorphous Formation and Magnetic Properties of Nd-Fe-Co-Al Alloys by the New Gas Jet Flow Type Levitating Process

Shuji Azumo, Seishi Utsuno, Katsuhisa Nagayama

pp. 1568-1571

DOI:

10.2320/matertrans.47.1568

Abstract

The amorphous formation ability and the magnetic properties of Nd60Fe30−xCoxAl10 (x=10, 15, 20 or 30) alloys in the containerless process were studied by the new gas jet flow type levitating process. The gas jet flow type levitating process enables solidification without any container wall by the inert gas jet. The samples were solidified at the cooling rate of around 100 K/s. Then, the undercooling of samples exhibits high values (ΔT=60–150 K). From X-ray diffraction measurements, the Nd60Fe30−xCoxAl10 samples exhibit a typical broad diffraction pattern for an amorphous structure. The DTA curves of x=10, 15 and 20 showed an exothermic peak due to the crystallization. That is, it was revealed that the Nd60Fe30−xCoxAl10 samples formed bulk amorphous. Also, the coercivity is 1.6, 3.3 and 3.6 kOe for the Nd60Fe20Co10Al10, Nd60Fe15Co15Al10 and Nd60Fe10Co20Al10, respectively. From the thermomagnetic curves, the Curie temperature is determined to be 463, 482 and 482 K for the Nd60Fe20Co10Al10, Nd60Fe15Co15Al10 and Nd60Fe10Co20Al10, respectively. In the M-H loops and the thermomagnetic curves, this difference between x=10 and x=15, 20 may depend on the microstructure.

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Bulk Amorphous Formation and Magnetic Properties of Nd-Fe-Co-Al Alloys by the New Gas Jet Flow Type Levitating Process

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Topographical Mapping of Surface and Interface Profiles by Using Acoustic Interferometry

Hiroshi Kato, Satoru Ohmura, Satoru Toyooka, Yoshiaki Kawada, Kensuke Kageyama

pp. 1572-1576

DOI:

10.2320/matertrans.47.1572

Abstract

The model is presented to explain formation of interference fringes appearing in acoustic images obtained by the acoustic microscopy. In the model, the residual vibration in the vibrator is overlapped by the vibration due to the ultrasonic wave reflected from the surface of the solid. The model was confirmed by the periodical change in the output of the vibrator with the water path. Then acoustic images of an inclined glass plate were observed to examine the influence of the inclination angle, the focal position and the wave frequency on the fringe spacing. A height difference corresponding to the fringe spacing was about a half wavelength of the ultrasonic wave in water. The interference fringes were also observed with a specimen with a deep notch under bending test and showed a good agreement with moiré fringes. The presented model suggests that the interference fringes are also formed corresponding to profiles of a reverse surface and a boundary between dissimilar substances. This was confirmed by acoustic images of copper plates with a tapered edge and a shallow groove on the reverse surface, and also those of a copper plate with a dint on the reverse surface, covered by tin alloy solder.

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Topographical Mapping of Surface and Interface Profiles by Using Acoustic Interferometry

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Component Candidacy of Second Side Reflow with Lead-Free Solder

Yueli Liu, David A. Geiger, Dongkai Shangguan

pp. 1577-1583

DOI:

10.2320/matertrans.47.1577

Abstract

For double-sided assemblies, the solder joints on the topside of the board are inverted and reflowed again. During the second reflow, the components are held in place by the surface tension, which may prevent the components from falling off under the gravitational force. A method is needed to determine a component’s candidacy for bottom-side attachment based on the component weight and total pad area.
In this paper, a theoretical model was introduced to determine the critical value for component fall-off during the second reflow. Design of Experiments (DOE) and ANOVA analysis for lead-free solder boards were performed to examine the main process factors which have different effects on the component fall-off for different components, and comparison was made between lead-free and SnPb solders. Optical inspection and cross-sectioning were carried out for further investigation. The test results indicated no significant difference of Cg⁄Pa value between SnPb and lead-free solders.

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Component Candidacy of Second Side Reflow with Lead-Free Solder

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Evolution of Solidification Structures in Fe-Mn-Si-Cr Shape Memory Alloy in Centrifugal Casting

Kenichiro Ito, Ryoji Sahara, Susan Farjami, Tadakatsu Maruyama, Hiroshi Kubo

pp. 1584-1594

DOI:

10.2320/matertrans.47.1584

Abstract

In aiming at obtaining thin columnar structures in the centrifugal casting of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy (SMA), evolution of solidified macroscopic structures is investigated by solidification experiments and simulation using a coupled finite volume-cellular automaton (FV-CA) model.
In the temperature gradient-crystal growth rate (G-V) diagram of solidification, the columnar to equi-axed transition (CET) line that indicates the boundary of two different structural regions is identified from the simulation calculation. The macroscopic structure of joining pipes of Fe-28Mn-6Si-5Cr SMA produced by centrifugal casting is elucidated to reside in a deep region of columnar structure in the G-V diagram. It is concluded that finer columnar structure could be obtained by increasing the rotation speed of centrifugal casting mould and by increasing the cooling rate of the casting.

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Evolution of Solidification Structures in Fe-Mn-Si-Cr Shape Memory Alloy in Centrifugal Casting

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Ultrahigh Strength and High Electrical Conductivity Characteristics of Cu-Zr Alloy Wires with Nanoscale Duplex Fibrous Structure

Hisamichi Kimura, Akihisa Inoue, Naokuni Muramatsu, Keesam Shin, Tokujiro Yamamoto

pp. 1595-1598

DOI:

10.2320/matertrans.47.1595

Abstract

The cold drawing of cast Cu100−xZrx (x=3, 4 and 5 at%) alloys to the reduction ratio of 99.7% was found to cause simultaneous achievement of ultrahigh tensile strength of 1350 to 1800 MPa and high electrical conductivity of 30 to 45%IACS (International Annealed Copper Standard). The cold-drawn Cu95Zr5 alloy wire has a well-developed fibrous structure of fcc-Cu and tetragonal Cu9Zr2 phases. The volume ratio of the fcc-Cu phase was evaluated to be about 76%. A very high density of internal defects was observed inside the Cu9Zr2 phase in the cold-drawn Cu95Zr5 alloy. The microstructure data suggest that the Cu fibrous phase with high aspect ratios is the origin for the achievement of high electrical conductivity and the well-developed fibrous structure contributes to the high tensile strength. The success of synthesizing the Cu-Zr alloy wire with simultaneously high tensile strength and high electrical conductivity exceeding the best combination of all Cu-based alloys reported up to data is expected to be used as a new type of high-strength and high conductivity material because of some advantages of energy saving, low materials cost and simple production process.

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Ultrahigh Strength and High Electrical Conductivity Characteristics of Cu-Zr Alloy Wires with Nanoscale Duplex Fibrous Structure

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Performance and Mechanism of a Multi-Functional Superplasticizer for Concrete

Qianping Ran, Changwen Miao, Jiaping Liu, Shishan Wu, Jian Shen

pp. 1599-1604

DOI:

10.2320/matertrans.47.1599

Abstract

Shrinkage reducing admixtures (SRA) have been used for several years to reduce the shrinkage of concrete. However, because their prices are very expensive and their dosages are very large, it is not economical for their practical application. Another problem of SRA is the degradation of compressive strength of concrete with SRA. In order to solve the two problems, a new polycarboxylate based superplasticizer with shrinkage reducing function was developed and its mechanism was investigated. According to experimental results, the admixture named JM-PCA (IV) reduces shrinkage of concrete effectively and reduces water content effectively. JM-PCA (IV) at a dosage of 0.25% decreases the shrinkage of concrete by about 40 to 55 percent at 28 days and 60 days when compared with sulfonated naphthalene formaldehyde condensate superplasticizer at a dosage 0.74%. The possible reason is that a shrinkage reducing component (SRC) and long ethylene oxides(EO) side chain were introduced into the molecular structure. The adsorption-reduction of interface tension is thought to be its main action mechanism of the reduction of shrinkage of JM-PCA (IV).

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Performance and Mechanism of a Multi-Functional Superplasticizer for Concrete

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Quantitative NDE of Surface Cracks in Ceramic Materials by means of a High-Frequency Electromagnetic Wave

Mikiko Suzuki, Kazuhiro Ogawa, Tetsuo Shoji

pp. 1605-1610

DOI:

10.2320/matertrans.47.1605

Abstract

Ceramic materials have excellent corrosion, wear, and heat resistant properties etc. However, due to their brittleness, it is essential for all ceramic products to be checked during the manufacturing process in order to maintain safely. Therefore, it is important that detecting cracks, which exist on the surface or inside the ceramic materials, by means of an accurate and speedy non-destructive evaluation (NDE) technique. Moreover, if the crack can be evaluated quantitatively, it is identified whether the crack is permissible or not. However, the NDE technique that is capable of quantitatively evaluating cracks for the ceramic materials has not been found yet.
This paper shows that high-frequency electromagnetic wave transmission characteristics of the ceramics can provide a new NDE technique with the possibility of quantitatively evaluating cracks on the ceramic surfaces. This technique is hereafter called the High-Frequency Transmission (HFT) technique. The HFT technique is one of the NDE techniques by means of electromagnetic wave such as an eddy current testing. The electromagnetic wave signal with higher than 1 GHz frequency can penetrate easily through the ceramic materials. Accordingly, the HFT technique can detect defects more sensitively than the other electromagnetic techniques.
Specifically, experiments have been performed with specimens made of alumina, containing an artificial and a natural crack. As a result of the detection of the artificial crack, whose width is 0.5 mm and depth is 1 mm, the signal changed approximately 18 dB. From measuring the different depth crack, it was clarified that this change of the electromagnetic wave signal was caused by the depth of crack on the alumina ceramic. A numerical analysis was applied to discuss about the factors, which affect the variation in the electromagnetic wave signal. It was found that electric field was changed by existence of the crack. In addition, the naturally closed crack was measured by the HFT technique. As a result, it could also be found that the naturally closed crack changed the signal.

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Quantitative NDE of Surface Cracks in Ceramic Materials by means of a High-Frequency Electromagnetic Wave

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A New Laser-Arc Hybrid Welding Technique Based on Energy Conservation

Liming Liu, Xinfeng Hao, Gang Song

pp. 1611-1614

DOI:

10.2320/matertrans.47.1611

Abstract

Aiming at the problem of energy loss in the process of welding at present, a new hybrid welding technique that low powered laser (about 400 W) combined with arc was put forward. Taking magnesium alloys as objects, it was found that the new technique had many advantages such as high welding speed, deep penetration and high quality welded joint comparing with that welded by laser or arc alone. Besides, the mechanical properties of the welded joint were improved remarkably. Comparing with high powered laser (about 2000 W)-arc hybrid welding, the laser used in the new technique was about 400 W, which was about 1/5 of that of the former, so the welding costs could be reduced markedly, while a great deal of energy was saved. In the research of arc behaviors, a new hybrid mechanism was proposed, in which the ability of arc to discharge was improved mainly because the laser pulse acted on the negative arc (electrode was positive and the specimen was negative) during the hybrid welding.

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A New Laser-Arc Hybrid Welding Technique Based on Energy Conservation

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Fe-(Cr,Mo)-(C,B)-Tm Bulk Metallic Glasses with High Strength and High Glass-Forming Ability

Kenji Amiya, Akihisa Inoue

pp. 1615-1618

DOI:

10.2320/matertrans.47.1615

Abstract

The glass-forming ability and mechanical properties of (Fe,Co)-(Cr,Mo)-(C,B)-Tm glassy alloys have been investigated. The (Fe,Co)48Cr15Mo14C15B6Tm2 glassy alloys were prepared in a cylindrical form with a diameter of 10 mm. These alloys have high glass forming ability (GFA) enough to produce a single glassy rods with a diameter above 10 mm. The largest supercooled liquid region before crystallization in (Fe1−xCox)48Cr15Mo14C15B6Tm2 alloys is 90 K for Co48Cr15Mo14C15B6Tm2. These glassy alloys have high fracture strength of over 4100 MPa for the entire composition range and the strength level is almost independent of Co content. The high GFA is attributed to the retardation of precipitation of the crystallized phases caused by the formation of the stabilized glassy local structure in which short-range ordered trigonal prisms are connected through glue effect of Tm element. The combination of high strength and high glass-forming ability indicates high possibility of applying the (Fe,Co)-(Cr,Mo)-(C,B)-Tm glassy alloys to various industrial materials.

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Article Title

Fe-(Cr,Mo)-(C,B)-Tm Bulk Metallic Glasses with High Strength and High Glass-Forming Ability

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