Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Deep-ultraviolet continuous-wave photoluminescence spectroscopy is performed for nano-polycrystalline diamond (NPD) synthesized by a high pressure high-temperature technique. NPD exhibits clear deep-ultraviolet emissions, which originate from intrinsic excitonic transitions assisted by a momentum-conserving phonon with a photon. Surprisingly, the peak emission energy is about 30 meV higher than that of the single-crystalline diamond. Raman scattering spectroscopy indicates that the energy difference should originate from the excitonic properties of the NPD and not the phonon. Hence, NPD has a large bandgap compared to single-crystalline diamond.

DOI： 10.1080/08957959.2019.1702658

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Under high-temperature and high-pressure conditions, the long-period stacking-ordered structure in Mg85Y9Zn6 transforms to a dual-phase structure consisting of a hexagonal close-packed lattice and a face-centered cubic lattice. After further solidification at high-pressure, unique ultrafine microstructures are formed. The alloy recovered after subjected at 10 GPa and 973 K exhibited a fine lamella structure, and a 0.2% proof stress (sigma(0.2)) of 480 MPa obtained by the compression test. Further the alloy recovered after subjected at 10 GPa and 1273 K, a unique spherulite structure were formed, and its sigma(0.2) improved to 780 MPa. (C) 2019 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2019.01.080

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

©2018 The Japan Institute of Metals and Materials. Cast Mg 85 Y 9 Zn 6 has an 18R-type LPSO structure. However, Mg 85 Y 9 Zn 6 recovered after being subjected to a loading pressure of 7 GPa at 973 K shows a fine dual-phase structure composed of a face-centered cubic (fcc) structure showing a superlattice (D0 3 ), as well as a hexagonal close-packed structure (hcp:2H). The D0 3 /hcp structure transformed to 18R-type LPSO during heating at ambient pressure. In this research, the transformation process from the D0 3 /hcp structure to 18R-type LPSO structure was discussed by means of in situ XRD and first-principles calculation. At first, lattice volume of 2H increased with an increase in the temperature, because of the Zn and Y emitted from the D0 3 phase into the 2H lattice. After the volume expansion of 2H lattice, the structure collapsed due to insert of random stacking faults (SFs). Then, a formation of 18R-type LPSO structure occurred. Based on a first-principles calculation for pure Mg, volume expansion of the 2H lattice causes the transformation to an 18R structure. Furthermore, the results of free energy calculations for the hcp and fcc structures in the MgYZn ternary system show that the segregation of Y and Zn atoms on SFs occurs by the Suzuki effect. These segregated Y and Zn atoms in SF layers, which have a local fcc structure, create a synergy between the stacking and chemical modulations. Present result insists that the volume increase of 2H lattice takes place first, and then the transformation from the hcp structure to 18R stacking occurs. [doi:10.2320/matertrans.M2018213]

DOI： 10.2320/matertrans.M2018213

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

We propose a simple and easy electrode formation technique on nanopolycrystalline diamond (NPD) synthesized by a high-temperature and high-pressure technique. The stronger light absorption nature of NPD than of standard transparent diamond enables the laser irradiation process on NPD. Pulsed laser irradiation using an ArF excimer laser under atmospheric condition drastically reduced the resistance of the NPD surface by forming graphite. Repetition of the laser irradiation reduced the resistance, showing a resistance of 300 Omega for the laser-irradiated area of 100 x 150 mu m(2). These results indicate the applicability of pulsed laser irradiation to an NPD apparatus having a conductive electrode, as well as electronic device processes. (C) 2018 The Japan Society of Applied Physics

DOI： 10.7567/JJAP.57.118004

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Acta Materialia Inc  

The second example of a novel long-period superlattcie (LPSL) phase has been discovered in Mg97Zn1Yb2 alloys synthesized under high pressure (5 GPa) and at high temperature (673 K), whose superlattice dimensions are described as √3 × √ 3 × 2 with respect to the original hexagonal close-packed Mg structure. A model structure is constructed based on atomic-resolution electron microscopy and first-principles calculations, finding that the present LPSL structure is a long-range crystalline ordered version of the isolated Guinier-Preston-type zones reported in conventional age-hardening Mg-Zn-Gd alloys. Therefore, the present LPSL phase could be potentially stable configurations even under ambient conditions and hence formed for broad Mg alloys.

DOI： 10.1016/j.scriptamat.2018.02.043

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We investigated inherent electronic properties of ultra-hard nano-polycrystalline diamond (NPD) synthesised at 15 GPa and 2300 °C. NPD exhibited a p-type semiconducting property with a resistivity of 1 × 106 and 4 × 102 Ω cm at 400 °C and 800 °C, respectively, with activation energies as high as 1.2 eV. The mobility was 2 cm2/Vs at 800 °C. The observed transport was considered to be attributed to grain boundary. Cathodoluminescence spectra show defect-related peaks with dominant peaks at 2.8 eV close to band-A and peaks below 2 eV, which is possibly related to crystal defects. In contrast, photoluminescence excited with a wavelength of 405 nm resonantly excited peaks having energies lower than 2.1 eV. The large density of crystalline defects such as grain boundaries and impurities in the NPD would result in the characteristic electronic and optical properties.

DOI： 10.1016/j.diamond.2018.03.007

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© 2018 Author(s). By combining theoretical predictions and in-situ X-ray diffraction under high pressure, we found a novel stable crystal structure of Li3PS4 under high pressures. At ambient pressure, Li3PS4 shows successive structural transitions from γ-type to β-type and from β-type to α type with increasing temperature, as is well established. In this study, an evolutionary algorithm successfully predicted the γ-type crystal structure at ambient pressure and further predicted a possible stable δ-type crystal structures under high pressure. The stability of the obtained structures is examined in terms of both static and dynamic stability by first-principles calculations. In situ X-ray diffraction using a synchrotron radiation revealed that the high-pressure phase is the predicted δ-Li3PS4 phase.

DOI： 10.1063/1.5011401

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

A novel long-period superlattice Mg77Zn9Yb14 phase, whose dimensions are described as root 3 x root 3 x 3 with respect to the original hexagonal close-packed Mg lattice, has been found in Mg97Zn1Yb2 alloys synthesized under high pressure (5 GPa) and at high temperature (723 K). A preliminary model structure is constructed based on atomic-resolution electron microscopy and first-principles calculations, providing local configurations around Yb atoms whose sizes appear to be smaller than those of a divalent Yb. This may be reasonably attributed to an applied high-pressure effect (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2016.04.022

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We recently succeeded in fabricating a new type of synchronized long-period stacking ordered (LPSO) phase crystal with the 10H crystal structure in the Mg-Zn-Y system. In the 10H LPSO phase, the long-range order of the Zn/Y-enriched L1(2)-like cluster was more significantly developed than that in the previously reported 18R LPSO phases in the Zn/Y concentrated layer. As the operative deformation mode in the 10H phase, (0001)<11<(2)over bar>0> basal slip was found to predominate. In addition, the formation of deformation kink bands was confirmed under conditions in which the operation of basal slip was macroscopically hindered. These features were similar to those observed in the 18R phase, but some differences were also observed in the deformation behavior owing to the development of in-plane ordering in the Zn/Y concentrated layers. The formation of a deformation kink band was localized in the deformation of the 10H crystal, and the localization of the kink-band formation was more enhanced in a specimen annealed at 500 degrees C for 24 h, in which the long-range order of the L1(2)-like cluster was pronounced. In addition, the operation of nonbasal slip was hindered in 10H crystals during deformation at high temperatures. The localization of kink-band formation and the prohibition of nonbasal slip induced the frequent formation of microcracks during the deformation of the 10H crystal, which led to fracture in the early stage of deformation. Experimental results demonstrated that the development of in-plane ordering of the L1(2)-like cluster in the Zn/Y concentrated layer is significantly detrimental to the ductility of the synchronized LPSO phase. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.actamat.2016.02.037

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Mechanical properties and failure characteristics of Mg97Y2Zn1 (at%) alloys, prepared by gravity casting and extrusion processes, are examined experimentally. High tensile and fatigue strengths are obtained for extruded Mg97Y2Zn1 alloys, with the values being approximately twice as high as those for cast Mg97Y2Zn1 alloys. Such high strengths are attributed to the high internal stress arising from the complicated microstructure and severe lattice strain in the alpha-Mg and long-period stacking order phases. On the other hand, a high fracture strain is obtained for cast Mg97Y2Zn1 alloy, which is affected not only by the lower internal stress, but also severe kink deformation. The failure characteristics, e.g., crack growth characteristics are examined via direct observation during tensile and fatigue tests at micro- and nano-scales. Meandering fatigue crack growth is obtained for the cast Mg97Y2Zn1 alloys. The mean roughness of the fracture surface for cast Mg97Y2Zn1 alloys is more than twice as high as that for commercially available AM60 and AZ91 cast alloys. A coarse fracture surface that was observed in the cast Mg97Y2Zn1 alloys would make severe roughness-induced crack closure, leading to high fatigue strength. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.msea.2015.11.069

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Curie temperature, T-C, of the Fe-Ni Inyar alloys increase due to irradiation with electron and some kinds of ions. In this study, proton irradiation effects upon magnetism in an Fe65Ni35 alloy have been investigated. It is found that the increment of T-C, Delta T-C, increases with increasing fluence. The magnetic hysteresis curve of the alloy was found to be unaffected by irradiation. Comparing Delta T-C and the calculated energy transfer from the ions to the sample, it seemed that Delta T-C was found to be related to the number of vacancies formed in nuclear collision events. In addition, Delta T-C was influenced by the fluence rate, i.e., the deposited energy per unit time. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2015.06.050

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High pressure and high temperature state of long period stacking order structure (LPSO) synchronized with chemical concentration in Mg85Zn6Y9 alloy have been investigated. A stripe-patterned nanostructure consisting of D0(3) and hcp phases is formed in Mg85Zn6Y9 alloy by high pressure and high temperature treatments. The nanostripe patterns are created by the phase separation of LPSO synchronized with chemical concentration. A pressure-temperature phase diagram is given in this research. LPSO is stable below 673 K, the D0(3)+ hcp mixed phase dominant above 973 K under the pressure up to 20 GPa. Phase separation under high pressure is useful for the fabrication of nanostructured metallic materials. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2015.04.086

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A zero thermal expansion in a wide temperature range including room temperature has been achieved in a cubic perovskite oxide SrCu3Fe4-xMnxO12 for x = 1.5. Partial substitution of Mn for Fe in SrCu3Fe4O12 systematically changes the linear thermal expansion coefficient from negative [-6.4(2), -5.7(5), and -1.88(11) ppm/K for x = 0.5, 1, and 1.25, respectively] to almost zero [0.67(15) ppm/K for x = 1.5] to positive [2.97(17) ppm/K for x = 1.75] and the operational temperature window shifts to higher temperature ranges above room temperature. Crystal structure analysis and Mossbauer spectroscopy reveal that the zero thermal expansion for x = 1.5 composition is induced by intermetallic charge transfer between Cu and (Fe, Mn) ions. These results display the high potential of SrCu3Fe4-xMnxO12 for the development of zero thermal expansion materials. (c) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4918293

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Phase transformation of the long period stacking order (LPSO) synchronized with the chemical concentration in Mg85Zn6Y9 has been investigated during both heating and cooling via in situ X-ray diffraction analysis. With increasing temperature, above 800 K, 10H-type LPSO phase collapsed firstly. 10H structural modulation collapsed earlier than the chemical modulation of 5 layers per period. The in plane ordering consisted of aligned L1(2)-type clusters vanished before the collapse of chemical and structural modulation of 18R-type LPSO. After, the chemical and structural modulation of 18R-type LPSO show synchronize collapse.
During cooling, the 14H-type LPSO emerged in addition to the 18R-type LPSO. The growths of chemical and structural modulation start at the same temperature. After that, the formation of in plane order consisting of aligned L1(2)-type Zn-Y clusters emerged. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2014.12.021

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The crystal structures of Mg85Zn6Y9 alloy under 3 GPa were investigated between room temperature and 973K using in situ X-ray diffraction (XRD). In addition, the crystal structures and microstructures of Mg85Zn6Y9 alloys that were recovered after being heated at various temperatures under 3 GPa were also investigated. The in situ XRD analysis results indicated that 10H- and 18R-type long-period stacking orders (LPSOs) were stable below 673K under 3 GPa; however, the D0(3) and alpha-Mg structures, which were not observed at ambient pressure, emerged at 873K in the sample under 3 GPa. When the temperature was increased to 973 K, the D0(3) and alpha-Mg phases fused. The D0(3) and alpha-Mg phases were also confirmed to be present in Mg85Zn6Y9 alloy that was recovered after being heated at 873K under 3 GPa. In contrast, the XRD pattern of the Mg85Zn6Y9 alloy that was recovered after being heated at 973K under 3 GPa indicated the presence of the 18R-type LPSO, D0(3), and alpha-Mg structures. These results indicate that three phases-18R-type LPSO, D0(3), and alpha-Mg-were formed during cooling from the molten state at 3 GPa. These results further suggest that the D0(3), alpha-Mg, and 18R-type LPSO are energetically very similar under 3 GPa.

DOI： 10.2320/matertrans.MH201413

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A highly ordered long-period stacking order (LPSO) structure of 10H-type is found to form in Mg75Zn10Y15 (at.%) alloys annealed at 773 K, with a remarkably developed in-plane long-range order of Zn/Y atoms. The degree of order of the present 10H-LPSO Mg-Zn-Y phase is similar to that of the Mg-Al-Gd alloys, the structural characteristics of which are described according to order/disorder-type intermetallic polytypes. The measured composition Mg77.2Zn9.7Y13.1 appears to be precisely consistent with an ideal stoichiometry of the 10H-Mg23Zn3Y4 (Mg76.7Zn10Y13.3) phase. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2014.01.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature Publishing Group  

Silicon dioxide has eight stable crystalline phases at conditions of the Earth's rocky parts. Many metastable phases including amorphous phases have been known, which indicates the presence of large kinetic barriers. As a consequence, some crystalline silica phases transform to amorphous phases by bypassing the liquid via two different pathways. Here we show a new pathway, a fracture-induced amorphization of stishovite that is a high-pressure polymorph. The amorphization accompanies a huge volume expansion of ∼100% and occurs in a thin layer whose thickness from the fracture surface is several tens of nanometers. Amorphous silica materials that look like strings or worms were observed on the fracture surfaces. The amount of amorphous silica near the fracture surfaces is positively correlated with indentation fracture toughness. This result indicates that the fracture-induced amorphization causes toughening of stishovite polycrystals. The fracture-induced solid-state amorphization may provide a potential platform for toughening in ceramics.

DOI： 10.1038/srep06558

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The magnetic properties of Fe-Ni Invar alloys are significantly affected by ion irradiation. Au3+ with the energy of 16 MeV irradiation effects on the magnetism of Fe66Ni34 have been reported in this paper. Considering from the temperature variations of AC susceptibility of irradiated Fe66Ni34, Curie temperature of a part of sample increase with increasing incident ion fluence, and the magnetization of irradiated Fe66Ni34 is also increase. The FCC structure of Fe66Ni34 is not changed by ion irradiation; however peaks become broader with increasing ion fluence. It means that lattice fluctuations are generated owing to ion irradiation. However it cannot be considered that lattice fluctuations observed X-ray diffraction measurements are enough to increase the Curie temperature observed in AC susceptibility measurements. Then, we suggest as the considerable origin of increasing T-C, atomic mixing effects owing to the ion irradiation. It might change the chemical ordering reported in the diffused scattering, such as Fe-Fe coupling. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nimb.2013.05.037

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The magnetism of Fe-Ni Invar alloys is very sensitive to the lattice constant, stress, and the number of nearest-neighbor Fe-Fe atomic pairs. Ion irradiation is a useful tool to alter the local atomic structure of a given material. Therefore, the effects of low-energy and light-ion irradiation on the magnetism of a Fe66Ni34 Invar alloy were investigated in this study. The Fe66Ni34 Invar alloy was irradiated with 50-keV protons at a fluence of 1 x 10(15) ions/cm(2) at room temperature. The Curie temperature was found to increase from 465 K (before irradiation) to 535 K (after irradiation). The X-ray absorption analysis of the fine structure of the alloy revealed that irradiation had no effect on the atomic structures surrounding Fe and Ni. (C) 2012 Elsevier BY. All rights reserved.

DOI： 10.1016/j.jmmm.2012.12.043

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Nanocrystalline bulk stishovite, with pure SiO2 composition, was synthesized under high pressure and temperature. We found that this material has an extremely high fracture toughness (similar to 13 MPa m(1/2)), nearly eight times higher than that of stishovite single crystal. The measured Vickers hardness of this material was similar to 29 GPa and stishovite is known to be one of the hardest oxides. This new material has potential to be used for industrial purposes because of its combination of very high hardness and toughness. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.scriptamat.2012.08.028

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We investigate the mechanical strength of ceramic/metal composites subjected to cyclic thermal loading. First, test samples of Cu/AlN systems are prepared via brazing. Next, short-term thermal cycle tests (25, 50, and 100cycles) are conducted at temperatures ranging from -40 to 125°C. Four-point bending tests are conducted to evaluate the residual strength. Further, thermal stress analysis is performed using the finite element method in order to examine the thermal stress behaviors during cyclic heating. The results reveal that the residual strength increases during 0∼20cycles because of residual thermal stress relaxation. This relaxation is generated by the cyclic softening of the metals owing to combined hardening. In contrast, relatively long-term thermal cycling (20∼100cycles) reduces the residual strength owing to damage growth to AlN. The AlN plates exhibit variability in residual strength, and the distribution of the residual strength for each cycle number conforms to the two-parameter Weibull curve. The variability in residual strength increases with the cycle number, and it is attributed to variabilities in the pre-existing crack size and damage accumulation. We conclude that the residual strength of the Cu/AlN composites depends on the thermal stress behavior and damage growth to the AlN plates. © 2012 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.61.530

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The effects of brazing filler metal diffusion on the mechanical strength of a ceramic/metal composite are described. First, a specimen of a SUS304/Cu/Si 3N 4 system, including brazing filler metals of AgCu and/or AgCuTi, was prepared by brazing in a vacuum furnace. Next, the vicinity of the joint parts was observed using field emission scanning electron microscopy. The brazing filler metals were found to diffuse into the Cu interlayer and ramify. In addition, a crack due to thermal stress resulting from a mismatch in thermal contraction between the materials present was observed around the AgCuTi/Si 3N 4 boundary. Energy-dispersive X-ray spectroscopic analysis revealed that Ag atoms diffused into the Cu interlayer to form the solid solutions of Ag and Cu. Micro-Vickers hardness tests were conducted on the surface of the Cu interlayer in order to examine the effects of brazing alloy diffusion on the hardening of the Cu interlayer. It was found that the diffusion of the brazing filler metals enhanced the hardness of the Cu interlayer. Finally, numerical simulations were performed to verify the increase in thermal stress due to hardening of Cu, and this behavior was discussed using simple equations. The results of the experiments and numerical simulations showed that the mechanical strength of the SUS304/Cu/Si 3N 4 composite is subjected to the diffusion of brazing filler metals. © 2012 The Society of Materials Science Japan.

DOI： 10.2472/jsms.61.197

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DOI： 10.1016/j.jmmm.2011.08.041

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DOI： 10.1016/j.jmmm.2011.08.041

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We investigate the mechanical characteristics of S45C/Cu/Si_3N_4 structures subjected to thermal loadings. First, thermal loading tests are conducted under various heat conditions. Next, four-point bending tests are conducted to evaluate the stress-strain curves and residual strength. The results reveal that thermal loadings cause fatigue damage to the Cu interlayers and its amount increase with increases in the cycle number and temperature range of thermal loading. The increases in the cycle number and temperature range promote reductions of fracture ductility, Young's modulus and residual strength for S45C/Cu/Si_3N_4 structures. It is found that the reductions of the mechanical characteristics of the S45C/Cu/Si_3N_4 structures are affected by the fatigue damage of the Cu interlayers.

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The effects of thermal loading conditions on the mechanical properties of S45C/Cu/Si 3N 4 composites with brazing filler metals of AgCu and AgCuTi are described. Thermal loading tests were conducted on test samples under various heat conditions, after which the joint parts of the samples were observed with a focus on the Cu interlayers using an optical microscope. Four-point bending tests were conducted on the samples to evaluate the residual strength and stress strain characteristics of the samples. In addition, fracture surfaces and the origins of the fractures were observed using an optical microscope. The results showed that thermal loading of the S45C/Cu/Si 3N 4 composites caused fatigue damage to the Cu interlayers and its amount increased with increases in the cycle number and temperature range of thermal loading. In the case of relatively-mild thermal loading conditions, fracture initiation regions were observed at the Cu/Si 3N 4 boundary. In contrast, fracture initiation regions were observed in the Cu interlayer for the samples subjected to relatively-extreme thermal loading conditions. The increases in the cycle number and temperature range of thermal loading promoted reductions of residual strength, resilient modulus and residual fracture ductility for the samples. The reductions of the mechanical properties of the S45C/Cu/Si 3N 4 composites were affected by the fatigue damage of the Cu interlayers. It was concluded that continuous operation (no start-stop system) is suitable for long-term use of ceramic/metal composites including interlayers in order to minimize reduction of their mechanical strength. © 2012 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.61.292

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Bronization and carburization of fine-grain superplastic stainless steel is reviewed, and new experimental results for fine grain Ti88.5Al4.5V3Fe2Mo2 are reported. In superplastic duplex stainless steel, the diffusion of carbon and boron is faster than in non-superplastic duplex stainless steel. Further, diffusion is activated by uniaxial compressive stress. Moreover, non-superplastic duplex stainless steel shows typical grain boundary diffusion; however, inner grain diffusion is confirmed in superplastic stainless steel. The presence of Fe and Cr carbides or borides is confirmed by X-ray diffraction, which indicates that the diffused carbon and boron react with the Fe and Cr in superplastic stainless steel. The Vickers hardness of the carburized and boronized layers is similar to that achieved with other surface treatments such as electro-deposition. Diffusion of boron into the superplastic Ti88.5Al4.5V3Fe2Mo2 alloy was investigated. The hardness of the surface exposed to boron powder can be increased by annealing above the superplastic temperature. However, the Vickers hardness is lower than that of Ti boride.

DOI： 10.3390/ma4071309

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We have investigated the pressure variation of the volume and structure of an FCC Fe64Mn36 anti-ferromagnetic Invar alloy. The inclination of the pressure-volume (P-V) curve of the FCC structure becomes discontinuous at a pressure of 4 GPa. According to the bulk modulus at zero pressure estimated by the Birch-Murnaghan equation of state, the pressure between 4 and 10 GPa is 33 GPa larger than that at a pressure below 4 GPa. Considering previous experiments on magnetism at high pressure the Neel temperature at 4 GPa almost decreases to room temperature. These results suggest that the increase in the bulk modulus by 33 GPa can be attributed to the pressure-induced magnetic phase transition from anti-ferromagnetism to paramagnetism. Volume at zero pressure was estimated using the Birch-Murnaghan equation of state. The volume of FCC structure in the anti-ferromagnetic state was 1.17% larger than the volume in the paramagnetic state, namely, the spontaneous magnetostriction was 1.17%. Pressure-induced structural transition from FCC to HCP occurs with an increase in the pressure, especially at up to 5 GPa. The value of c/a is 1.62; this value almost corresponds to that of an ideal HCP structure. The bulk modulus of the HCP structure estimated by the Birch-Murnaghan equation of state is larger than that of the FCC structure, and the volume/atom ratio is smaller than that of the FCC structure. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2010.11.029

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Soldering processes involving the use of Pb have been known and practiced for more than 5000 years. In 2000, the European Union imposed a ban on the use of Pb because of the fact that Pb is poisonous to humans. Consequently, attempts are being made worldwide to develop a Pb-free solder. Among the various Pb-free solders, the Sn-0.75wt%Cu (Sn-0.75Cu) solder is the suitable one from the viewpoint of cost. Moreover, its acoustic properties are superior to those of the other Pb-free solders. However, the Sn-0.75Cu solder has a few disadvantages: its joining strength is lower than that of the other solders, and its melting temperature is higher than that of the Sn-37wt%Pb (Sn-Pb) solder. Therefore, we have attempted to decrease the melting temperature and improve the joining strength of Sn-0.75Cu to match those of the Sn Pb solder. It is well known that when Ga is added to a Sn-based alloy, the melting temperature of the alloy decreases. Moreover, Ga has superior wettability. Therefore, we added Ga to the Sn-0.75Cu solder in order to improve the joining strength and decrease the melting temperature of the solder. We observed that the melting temperature of Sn(95.3)CU(0.7)Ga(4) reduced to less than that of the Sn Pb solder. We also investigated the joining strength between the Ga-added solder and a Cu wire. We observed that the joining strength increased with an increase in Ga content, was the highest for Sn(97.3)Cu(0.7)Ga(2), and then decreased with an increase in Ga content. The peak joining strength of the Ga-added solder was almost 1.5 times that of the Sn-0.75Cu solder. However, the brittleness of the solder increased with an increase in the Ga content. This is a disadvantage of the addition of Ga to Sn.

DOI： 10.4028/www.scientific.net/DDF.312-315.518

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DOI： 10.1002/anie.201102228

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DOI： 10.1002/anie.201102228

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D0(3)-type Fe70Al30 shows a transition from ferromagnetism to spin glass with anomalous slow spin dynamics below 170 K. Furthermore, it shows a structural transition from D0(3) to body-centered cubic (BCC) at 823 K. In this article, the relationship between the magnetic properties, thermal expansion coefficient (TEC), and crystal structure transition of D0(3)-type Fe70Al30 is discussed. Below 170 K, TEC decreases with temperature, accompanied by a decrease in the Fe moments. In the ferromagnetic state between 170 K and the Curie temperature (T-C), TEC increases gradually with temperature. Above T-C, TEC increases rapidly. These temperature variations of TEC could be connected to the high-spin/low-spin transition and thermal spin fluctuations. During transition from D0(3) to disordered BCC at 823 K, TEC shows discontinuous behavior, similar to a first-order transformation. With further increase in temperature, TEC becomes constant. This implies that the phase transition from D0(3) to disordered BCC is accompanied by a change in spin fluctuation. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2009.12.045

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We have investigated the thermal expansion properties, crystal structures, and magnetism of Fe(1-x)Ga(x) alloys with 27.5 < X < 37.5. Fe-Ga alloys with BCC structures can be obtained by quenching from high temperatures, and these alloys exhibit ferromagnetism. As the temperature increases, BCC Fe-Ga alloys undergo crystal structural transformation from the BCC to the FCC structure, accompanied by volume expansion. With a further increase in temperature, these alloys undergo structural transformation from the FCC to a hexagonal phase (D0(19)). The transformation from the FCC to the D019 phase is accompanied by a decrease in volume per atom of the alloys, in spite of an increase in the temperature. The Curie temperature of FCC Fe-Ga alloys is higher than that of BCC Fe-Ga alloys, and D019 show the nonmagnetic in present work. Considering from the above-mentioned results, the anomalous volume behavior accompanying the crystal structure transformation can be related to the contribution of magnetism in FCC Fe-Ga alloys. In a previous report, an FCC structure was obtained by carrying out long-time annealing at 550 degrees C. However, in this study, the FCC structure is obtained from the BCC structure as the temperature increases smoothly at a rate of 5 degrees C/min. Moreover, the Fe(62.5)Ga(37.5) alloy undergoes a structural transformation from the BCC to an unknown high-temperature phase. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2009.11.026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

It is well known that duplex stainless steels having refined grain, structure exhibit superplasticity. In this paper, the diffusion of boron in the superplastic duplex stainless steels has been investigated. Boron diffuses through the interior of the grains in superplastic duplex stainless steels. On the other hand, in case of normal duplex stainless steel having the same chemical concentration, boron mainly diffuses along the grain boundaries and does not diffuse through the interior of the grains. Investigations using Auger electron microscopy for super plastic duplex stainless steels revealed, the Cr concentration is much higher than Fe concentration in boron diffused areas. These results indicate that superplasticity activates diffusion into the interiors of grains. Further, it seems that boron preferentially reacts with Cr rather than Fe. Moreover the distribution of Fe and Cr is changed by the diffusion of boron.

DOI： 10.1007/s11669-009-9611-1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

The pressure-volume relationship of Fe72Pt28 alloy was investigated at 300, 500, 700, 900, 1100, and 1300 K by performing energy-dispersive X-ray diffraction measurements using a white X-ray beam produced from synchrotron radiation at the High Energy Accelerator Organization, Japan. The pressure-volume relationship measurements were performed only along the decreasing the pressure path. Below 700 K and 3.5 GPa, the compressibility of Fe72Pt28 alloy increased with the pressure. Above 900 K, the pressure-volume relationship was almost linear. Further the temperature-volume relationship at high pressures was linear. An abrupt decrease in the volume or a thermal expansion coefficient anomaly, which was observed in the case of Fe69Ni31 alloy in previous experiments, was not observed in the case of Fe72Pt28 alloy,

DOI： 10.1088/1742-6596/215/1/012014

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：TRANS TECH PUBLICATIONS LTD  

Recrystallization processing of cold-rolled copper after isothermal annealing was investigated using high-resolution electron backscattered diffraction pattern analysis. The fiber texture is obtained by cold rolling with the rolled direction oriented along {111}, and the transverse and nominal directions have a random orientation. An isothermal recrystallization process at 150 degrees C was investigated. Initially, rotations of the orientations occur from {111} to {100} and then small misfit angle boundaries decreased. Accompanying this change, the fiber-shaped grains change to a round shape grain and their sizes decrease. Considering these tendencies, we determined that rotation at subgrain boundaries is activated by isothermal annealing and subboundaries grow the boundary misfit angle >15 degrees. With further annealing, those grains surrounded by grain boundaries greater than 15 degrees expanded. The rolling, transverse, and nominal orientations rotate {100}. Subsequently, a twin boundary appeared, and the fraction of twin boundaries increased.

DOI： 10.4028/www.scientific.net/DDF.297-301.359

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We have investigated the effect of superplastic carburizing on the texture of duplex stainless (DS) alloy. The diffusion velocity of carbon in the superplastic DS alloy is much higher than that in non-superplastic DS alloy that has the same chemical composition. In carburized layer, the segregation of Cr can be observed and Cr-carbides precipitate at the grain boundary, in particularly, the triple-point intersection of grain boundaries. The precipitation of Cr-carbides in stainless alloys is disadvantageous because it causes a decrease in its corrosion resistance. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2008.11.051

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In this study, we have attempted the solid-phase welding of superplastic duplex stainless steel (SPDSS) with carbon steel that has a carbon content of 0.43 wt% (S45C). The welding was performed at 1373 K. The ultimate tensile strength of the welded specimen increases with the welding time and becomes approximately the same as that of S45C for a welding time above 220 s. And the carbon contents of the interface between both materials change. The carbon content of S45C decreases, while that of SPDSS increases in the region near the interface. Considering from these result, the carbon in S45C diffuses into SPDSS. Then we have investigated cyclic fatigue fracture of the welded specimen. The crack initiates in the decarburized layer of the S45C section of the interface. When the crack propagates the interface, the crack extended drastically. Cyclic fatigue fracture property is similar to that of low carbon steel that has a carbon content of 0.1 wt%. On the basis of these results, we can conclude that SPDSS can be suitably used for solid-phase welding of carbon steel in a short-duration. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2008.10.036

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Fe50Ni37Mn13, which is a ferromagnetic alloy with FCC crystal structure, has been reported to show the Invar effect below the Curie temperature; however, this alloy shows a typical anti-Invar effect above the Curie temperature. In this paper, we discuss the pressure dependence of the temperature variation of the alternative current (AC) susceptibility at a frequency of 1 kHz for Fe50Ni37Mn13 at various pressures up to 7.5 GPa above 77 K; we then compare the results with those for Fe68.1Ni31.9, which were obtained in a previous study. Fe50Ni37Mn13 was in a ferromagnetic state throughout the entire pressure range measured. T-C decreases in inverse proportion to the increasing pressure; dT(C)/dp and dln T-C/dp for Fe50Ni37Mn13 are -26 K GPa(-1) and -0.07 GPa(-1), respectively. Further, the temperature variation of the shape of the chi'-T curve for different pressures indicates continuous combining of magnetic interactions occurs at high pressures. These results are similar to those obtained for Fe68.1Ni31.9. (C) 2008 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2008.09.041

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In the present study, quench tests were carried out to characterize the fracture behavior of advanced pore-free SiC with damage tolerance during thermal shock. The residual strength of specimens after the quench tests was also measured. It is found that the critical temperature difference and the decrease in residual strength of this material are larger than those of conventional SiC. This is because the fracture is dominated only by flaw size since the wake zone is not generated during thermal shock with high strain rate. The critical temperature difference as well as the crack propagation is calculated with the aid of the unified theory of thermal shock.

DOI： 10.1299/kikaia.74.1156

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The pressure variations of the magnetic property of amorphous La(Fe0.85Al0.15)(13) alloy have been investigated by ac susceptibility measurements under high pressures up to 7.3 GPa, in the temperature range between 5 and 330 K. With increasing pressure, the Curie temperature decreased, and a new high-pressure magnetic phase came to appear in the low-temperature region below 50 K. Further increasing pressure, the ferromagnetic state disappeared and then the new high-pressure magnetic phase only remained. These pressure variations of the magnetic properties in amorphous La(Fe0.85Al0.15)(13) alloy are quiet different from La(Fe0.85Al0.15)(13) compound, but similar to those of Invar alloys. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2007.01.049

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We have investigated the variations in the crystal structure of Fe(69)Ni(31) Invar alloys under high pressures below 6.5 GPa and high temperatures below 1300 K using energy dispersive x-ray diffraction. The crystal structure is stabilized as a face-centered-cubic (fcc) lattice structure over the entire investigated range. However, the volume of the fcc in Fe(69)Ni(31) shows an abrupt decrease at 1300 K above 2 GPa and at 1100 K above 3 GPa with increasing pressure. These results show that a pressure-induced phase transition to a low-volume state occurs under high-temperature and high-pressure conditions. We consider this transition would be that from the high-spin state to the low-spin state, which has been speculated in some previous theoretical studies.

DOI： 10.1103/PhysRevB.77.064429

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Currently, chemical pretreatment and electroless plating are used to fabricate Cu films on perfluoroalkoxy vinyl ether (PFA) copolymer. In order to reduce the wastage of water during chemical pretreatment and electroless plating, we have investigated the fabrication of Cu films by a dry process as an alternative. In the present report, we have investigated the fabrication of Cu film on the PFA by using a conventional RF sputter deposition apparatus. An Ar ion sputter-etching pretreatment is performed on the PFA prior to sputter deposition; however, it does not significantly influences the peel strength and grain size. The grain size of Cu influences its resistivity in the present experiments. The resistivity increases with decreasing grain size. This result is explained by considering the scattering of conduction electrons at the grain boundaries. Further, substrate temperatures obviously influence the grain size of Cu and the peel strength between Cu and PFA. in particular, for substrate temperatures above 150 degrees C, the grain size and peel strength increase drastically. We can use the Cu film fabricated on the PFA substrate above 150 degrees C as a seed layer for CUSO4 electroplating. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmatprotec.2007.04.114

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ceramic Society of Japan  

It had been well known that the fracture of SiC manufactured by conventional reaction sintering method was caused by one of the pores in that. However, according to the recent studies, pore free SiC so called APF-SiC was developed by improvement of reaction sintering method. As the result, the strength and the damage tolerance ability rise and then the cause of fracture of APF-SiC changed from pores to something else. Therefore we have investigated fracture surface of APF-SiC by using FE-SEM and EDS in order to demonstrate the cause of fracture. As the result, we found the inclusion that consisted of allotropes of Carbon covered with very thin SiO2 and SiN layer. And the size of the inclusion is ten times larger than that of SiC grain. Considering from present results, the inclusion is the one of the cause of fracture of APF-SiC.

DOI： 10.2109/jcersj2.116.126

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Language：Japanese   Publisher：The Society of Materials Science, Japan  

Sphere indentation tests were performed to clarify damage properties on surface of Advanced Pore-Free SiC (APF-SiC) with excellent damage tolerance. The ring crack initiation strength properties were discussed from fracture mechanics viewpoint based on FEM analysis and detailed observations of growth behaviors of the ring crack and the cone crack. As compared to conventional SiC, the initiation strength was nearly equal to regardless of sphere sizes. However, its scatter was increased with increasing sphere sizes. Clusters are formed by uniting some in multi-micro cracks which occur near surface with increasing the contact load, one of that from which the ring crack occurs. Therefore, the strength and the scatter are controlled by the cluster size and its distribution, and the size depends on the generating crack density. It can be explained by the mechanics model which is expressed by the relationship between strength ratio and crack density based on the energy equilibrium theory.

DOI： 10.2472/jsms.57.1138

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Other Link： https://jlc.jst.go.jp/DN/JALC/00321386593?from=CiNii

Language：Japanese   Publisher：山陽放送学術文化財団  

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Magnetic properties of a Co52.5Fe38Cr9.5 Invar alloy have been investigated under high-pressure by ac susceptibility measurements. With increasing pressure, ferromagnetic ground state disappeared and new high-pressure magnetic states came to appear. Further increasing pressure up to 4.6 GPa, the high-pressure magnetic states vanished and no magnetic signal observed in the investigation range 5-300 K. These pressure variations of magnetic phases are similar to Fe based Invar alloy. So far considering from the series of our experimental results, it is concluded that the moment-volume instability in Invar alloys are associated with a several magnetically ordered phases that exist in low volume side of ground state. These facts support some theoretical model for the origin of Invar effect. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2006.09.080

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We have performed AC susceptibility measurements at various frequencies for high-pressure magnetic phases in Fe68.1Ni31.9 and Co52.5Fe38Cr9.5 Invar alloys. In the high-pressure magnetic phases of both alloys, chi'-T curve shows a cusp, and the peak temperature of the cusp (T-P) shifts to lower temperature side with decreasing frequency. The orders of the magnitude of the frequency shift of T-P are similar to those of the spin glass phases and smaller than that of the super parramagnetism. In addition, the frequency dependences of T-P almost follow with Vogel-Fulcher law. These results are corresponding to the previous report for the spin glass phases. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2006.10.653

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Advanced Pore-Free SiC (APF-SiC) with super-high strength is expected to be used as engineering structural materials since it has damage tolerance ability by preceding failure of metallic silicon particles In the present study, thermal shock tests of this material were carried out to characterize the fracture behavior. The residual strength after thermal shock was also measured. It is found that the critical temperature difference ΔT_c of this material is larger than that of conventional SiC due to smaller size of pre-existing flaws. As the result, the validity of the Griffith's theory was experimentally confirmed. In addition, the damage tolerance behavior in thermal-shocked materials is not observed because the metallic silicon particles may he failed by thermal shock.

DOI： 10.1299/jsmemecjo.2007.1.0_647

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AC susceptibility measurements in mechanically alloyed (MA) Ni-20 at% Mn were made under hydrostatic pressures up to 7.5 GPa. The results were compared with a bulk alloy made by the conventional method of melting. The Curie temperature decreased with pressure at the rate of -6.9 and -8.0 K/GPa in MA and the bulk alloy, respectively. The transition temperature to the reentrant spin glass state increased at the rate of 1.2 and 1.7 K/GPa in MA and the bulk alloy, respectively. The results were explained by assuming a Gaussian distribution of concentration fluctuation. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2005.06.006

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Pressure dependence of the irradiation-induced ferromagnetism recently found in Fe-Ni invar alloys was investigated under hydrostatic pressures up to 7.5 GPa. A rectangular sheet of Fe-30.2 at% Ni invar alloy was irradiated with 80 MeV Xe ions. The range was much smaller than the thickness of the sample. The Curie temperature of the irradiated part increased by 63 K, and the absolute value of the pressure coefficient, dT(C)/dp was smaller than that of non-irradiated part. The relation p approximate to (T(Co) - T(c))(n) holds with n = 2 for both non-irradiated and irradiated part. The itinerant character was not so much modified by irradiation. (C) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2005.02.065

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Pressure variations of the magnetic state in Fe65Ni27Mn8 and disordered Fe72.8Pt27.2 Invar alloys have been investigated by ac susceptibility measurements under high pressure up to 7.5 GPa. In both alloys, the ferromagnetic state vanished and high-pressure magnetic states came to appear with increasing pressure. In addition, we observed the pressure-induced phase transition from the high-pressure magnetic phase to nonmagnetic state in disordered Fe72.8Pt27.2. These results are corresponding to the previous theoretical studies.

DOI： 10.1103/PhysRevB.72.214404

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The crystal structure of ordered and disordered Fe-Pt Invar alloys has been investigated under high pressures up to 13 GPa in the temperature range of 12-300 K by in situ angle dispersive X-ray diffraction using synchrotron radiation. An FCC structure was confirmed to be stable in whole pressure range, and pressure-induced lattice softening was observed. The relationship between the pressure-induced magnetic phase transition and the lattice softening was discussed in connection with a recent band calculation. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.07.006

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The magnetic properties of an ordered Fe72.8Pt27.2 Invar alloy have been investigated under high pressures up to 7.5 GPa by AC susceptibility measurements in the temperature range from 4.2 to 430 K. The Curie temperature decreased with increasing pressure and then the ferromagnetic state vanished above 6.5 GPa. A new high-pressure magnetic phase appeared at 3.5 GPa in the low temperature range below 40 K, which is quiet different from the high-pressure phase observed in disordered Fe-Pt and Fe-Ni Invar alloys. The transition temperature to this new phase increased with pressure and the new phase became more stable. This tendency resembles to the feature expected by a recent theoretical calculation. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0304-8853(03)00648-6

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The magnetic properties of an FCC Fe68.1Ni31.9 Invar alloy have been investigated under high pressure up to 7.7 GPa by AC susceptibility measurements in the temperature range from 4.2 to 400 K. Up to 5.5 GPa, the Curie temperature (T-C) decreased linearly with increasing pressure. Above 3.5 GPa, a reentrant spin glass-like phase was observed clearly in the low-temperature region below 50 K. Above 5.5 GPa, ferromagnetic (FM) phase began to collapse with increasing pressure, and then at 7.7 GPa, FM phase disappeared, while the spin glass-like phase was still seen. Our results dearly show the pressure induced magnetic phase transition from the FM phase to the spin glass-like high-pressure magnetic phase. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(03)00287-7

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To investigate the magnetic properties of disordered Fe70Pt30 Invar alloy under high pressure, measurements of the real part of the AC susceptibility (chi) were made under pressure up to 7.5 GPa in the temperature range 4.2-385 K using a cubic anvil high-pressure apparatus. The Curie temperature (T-C) decreased with increasing pressure, and then, two new high-pressure magnetic phases appeared. These results show that the ferromagnetism of Fe-Pt Invar alloy becomes weaker, and the antiferromagnetic interaction becomes dominant with increasing pressure. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(02)01342-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Measurements of the temperature dependence of the AC susceptibility were made for Fe-Ni Invar mechanical alloys under hydrostatic pressures up to 1.5 GPa. The Curie temperatures decreased linearly with pressure. The rate of decrease became larger for specimens annealed at higher temperatures. The temperature of annealing after ball milling has been directly related to the extent of the chemical concentration fluctuation, and the extent becomes smaller for specimens annealed at higher temperature. This tendency can be explained by assuming a Gaussian distribution function.

DOI： 10.1088/0953-8984/14/44/429

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Magnetization measurements have been carried out for disordered Fe72Pt28, Fe66Pd34, and Fe68Pd32 Invar alloys under high pressure using a technique combining a pressure-clamp-type Drickamer cell and a pulse magnet. In Fe72Pt28 at room temperature, the magnetization decreased rapidly with increasing pressure up to 2.5 GPa, but above 2.5 GPa the rate of decrease became small and remained at a small value up to 5.6 GPa. In Fe-Pd Invar alloys at room temperature, the magnetization decreased linearly with increasing pressure. But, at 4.2 K, the change of magnetization with pressure was small in Fe66Pd34, which means that Fe66Pd34 behaves as a strong ferromagnet.

DOI： 10.1088/0953-8984/14/44/371

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：Japan Society of High Pressure Science and Technology  

DOI： 10.4131/jshpreview.27.224

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Cu/AlN composites used as electronic devices have a problem with thermal stress. The thermal stress has an effect on residual strength of the composites. Here we report the residual strength of the Cu/AlN composites subjected to cyclic thermal loadings. We perform finite element analysis, cyclic thermal loading tests and residual strength on the Cu/AlN composites. The results reveal that microscopic damage of AlN substrates reduce the residual strength of the Cu/AlN composites.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study, thermal fatigue lifetimes of S45C/Cu/Si_3N_4 composites subjected to cyclic thermal loadings were evaluated. First, S45C/Cu/Si_3N_4 composites with interlayer thicknesses of 150 and 200 μm were prepared. Next, thermal fatigue tests were carried out at temperature differences of 275 K and 575 K. The cycles to failure of the composites were evaluated and a model for predicting thermal fatigue life was proposed. In addition, the suitability of theoretical model was considered. The results revealed that temperature difference of cyclic thermal loading and thickness of Cu interlayer have effects on thermal fatigue lifetimes.

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The mechanical strength properties of ceramic/metal substrates exposed to cyclic thermal loadings were studied in order to discuss the effects of the number of thermal loadings on the residual strength of the substrates. First, thermal stress analysis was performed using the finite element method for an examination of the thermal stress behaviors during the cyclic thermal loading processes. Next, test samples of Cu/AIN substrates, including brazing filler metals of AgCuTi, were prepared by brazing in a vacuum furnace. Thirdly, thermal cycling tests with cycle numbers of 25,50 and 100 were conducted on the test samples. Finally, four-point bending tests were conducted on the thermally-loaded samples to evaluate residual strength. The results showed that residual strength increased after 25 thermal cycles. In contrast, thermal cycling with 25-100 cycles resulted in a reduction of residual strength. These behaviors were discussed in terms of residual stress relaxation and a mechanism for the microscopic damage of sintered materials with polycrystalline structures.

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Porous ceramics is expected to be applied as cleanup filter under high temperature environment since it has high damage tolerance ability. We have investigated effect of damage tolerance ability on fundamental fracture properties by carrying out 4-point bending test under loading rates. As the result, at above loading rate of 0.5mm/min, strengths increased with increasing loading rate. Because it is only depended at slow crack growth of one of the flaws in this material. In contrast, at the loading rates below 0.5mm/min, strengths also increased. It is considered that resistance to crack growth increased due to release of accumulated internal energy since grain boundary markedly fails with decreasing loading rate. These phenomenon was explained by unified strength estimation method considering effect loading rate.

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Event date： 2019.10

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：English  

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Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (invited, special)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (invited, special)  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Public lecture, seminar, tutorial, course, or other speech  

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Presentation type：Oral presentation (general)  

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Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Presentation type：Oral presentation (general)  

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Language：English   Presentation type：Poster presentation  

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