bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toughening Effect and Oxidation Behavior of MoSi2 -ZrO2 Composites
Authors: Gong Karin , Yao Yiming , Sundberg Mats , Li Xin-Hai , Ström Erik , Li Changhai 
Published: June 2019

AbstractToughening effect of ZrO2-particles on MoSi2-based materials is one of the important toughening mechanism. In this work, the influence of particle size and volume percentage of unstabilized ZrO2-addition on toughening in MoSi2-matrix composites was studied. The measured data revealed that the fine particle size, < 1 ìm, with certain volume percentages around 20% have given more effective toughening results. The tested materials were prepared by two different sintering processes: pressure-less sintering (PLS) and PLS + Hipping sintering. The results on sintered density, RT-hardness and RT-toughness indicated that the PLS process could be a practical and economical method for producing MOSi2-ZrO2 composites in industry. Oxidation behavior of MoSi2-ZrO2 composites was also studied in the work. Clearly, the ZrO2-addition made the composites having a worse oxidation resistance than the monolithic MoSi2, which means that a low ZrO2-addition should be used in the composites, as far as an acceptable toughening effect was reached.
Control of the Si Vacancy Concentration and Arrangement in ReSi1.75 by Al and P Additions
Authors: Harada Shunta , Tanaka Katsushi , Kishida Kyosuke , Inui Haruyuki 
Published: June 2019

AbstractThe concentration and arrangement of Si vacancy in aluminum or phosphorus containing ReSi1.75 based silicides have been investigated. Both aluminum and phosphorus are substituted with silicon. In addition to the (001)C11b twins usually observed in binary ReSi1.75, planar defects are heterogeneously formed in both of the silicon substituted ternary alloys with small amount. By using the high resolution electron micrograph (HREM) technique, the planar defects are assigned as crystallographic shear (CS) planes lying on (109) C11b and (107) C11b in aluminum and phosphorus containing ReSi1.75, respectively. The CS vector in both ternary alloys is [100]C11b. Since the concentration of vacancies in the ReSi1.75 structure is changed by the introduction of these crystallographic shear, ternary alloys with silicon substituted by aluminum and phosphorus contain more or less amount of vacancies than the binary alloy, respectively. This implies us that concentration of Si vacancies changes so as to retain the average number of valence electron. We can control the concentration of Si vacancy in the ReSi1.75 based alloys.
Theoretical investigation of Pt monosilicide and several germanides: electronic structure, surface energetics, and work functions
Authors: Niranjan Manish K. , Kleinman Leonard , Demkov Alexander A. 
Published: June 2019

AbstractWe present a theoretical study of the electronic structure, surface energies and work functions of orthorhombic Pt monosilicide and germanides of Pt, Ni, Y and Hf within the framework of density functional theory (DFT). Our calculated bulk structures are within 1-2% of reported experimental values. Calculated work functsions for the (001) surfaces of PtSi, NiGe and PtGe are 5.12, 4.57 and 4.83 eV, respectively, suggesting that these metals and their alloys can be used as self-aligned contacts to p-type silicon and germanium. Work functions for Y and Hf germanides range from 2.4 to 4.3 eV making them a possible n-type contact material. In addition, we also report an ab-initio calculation of the Schottky-barrier height at the Si(001)/PtSi(001) interface. The p-type Schottky barrier height of 0.28 eV is found in good agreement with predictions of a simple metal induced gap states (MIGS) theory and available experiment. This low barrier suggests PtSi as a low contact resistance junction metal for silicon CMOS technology. We identify the growth conditions necessary to stabilize this orientation.
Magnetic Behavior due to Quenching Temperature in Co-based Heusler-type Alloys Co2MnZ (Z=Si, Ge, Sn)
Authors: Kikuchi Shigeyuki , Fujiwara Tetsuya , Ishibashi Hiroki , Kogachi Mineo 
Published: June 2019

AbstractMagnetic behavior in Co-based Heusler alloys Co2MnZ (Z=Si, Ge, Sn) is investigated as a function of quenching temperature. The mean magnetic moment decreases with increase in quenching temperature in Co2MnSi and Co2MnGe while it remains almost constant in Co2MnSn. Relation between the magnetic behavior and the atomic disorder is discussed.The results of the lattice constant and the electrical resistance measurements are also reported.
Effect of Ti3Si on Texture in Ti-Nb Based Shape Memory Alloys
Authors: Shimizu Ryutaro , Masumoto Kei , Fukui Yusuke , Inamura Tomonari , Wakashima Kenji , Hosoda Hideki , Miyazaki Shuichi 
Published: June 2019

AbstractEffect of Ti3Si particles on recrystallization texture of Ti-Nb based superelastic alloys has been investigated using X-ray pole figure measurement and electron backscatter diffraction (EBSD) technique. The alloys used were Ti-24mol%Nb-3mol%Al-Xmol%Si (X=0~0.9, termed XSi) and Ti-24mol%Nb-3mol%Si alloy (termed 3Si). The apparent phase at room temperature was β-phase (bcc). Besides, (Ti, Nb)3Si particles with PTi3 type crystal structure were formed in the alloys with Si content higher than 0.7mol%. After the cold rolling of 99% reduction in thickness, a rolling texture of the β-phase was formed to be mainly {001}β<110>β regardless of the presence of the (Ti, Nb)3Si particles. After the solution treatment at 1273K, a recrystallization texture formed to be {112}β<110>β in all the alloys except for 3Si. The average grain size of the recrystallized alloys was 20~40μm. On the other hand, the solution treated 3Si exhibited the {001}β<110>βn texture and the average grain size of 3μm. It is concluded that the {001}β<110>β texture with fine grains of the solution treated 3Si is obtained by the suppression of grain boundary migration due to the existence of the (Ti, Nb)3Si particles.
Phase Constitution, Crystal Structures and Hardness of Ti60-xAu40Cox and Ti34-xAu44Co22+x (x=0, 2 and 4) Ternary Alloys
Authors: Tsugane Yasuhito , Inamura Tomonari , Wakashima Kenji , Hosoda Hideki 
Published: June 2019

AbstractIt was previously found that two B2 phases (matrix and precipitates) appeared in Ti-32mol%Au-18mol%Co superelastic alloy. In this study, each B2 single phase alloy was tried to be fabricated individually, and phase constitution, crystal structures and hardness were investigated. The chemical compositions were Ti60-xAu40Cox and Ti34-xAu44Co22+x (x=0, 2 and 4), and the alloys were fabricated by Ar-arc melting followed by a hot-forging at 1423K for 43.2ks and a solution treatment at 1173K for 3.6ks. It was found by X-ray diffraction analysis that Ti60-xAu40Cox (called Co-poor alloys) were composed of B19 (Ti, Co)Au and A15 Ti3Au two phases, instead of B2 single phase expected. It was also found that Ti34-xAu44Co22+x (called Co-rich alloys) were composed of C11b Ti(Au,Co)2 and C36 Co2(Ti,Au) two phases, instead of B2 single phase expected. These unexpected phase constitutions appeared in this work may be due to the difference in cooling rate and/or phase transformation from B2 to C11b. Lattice parameters of the obtained phases were precisely determined. The hardness of C11b Ti(Au,Co)2 and C36 Co2(Ti,Au) are HV480 and HV780, respectively. The hardness change of Co-rich alloys can be understood in terms of the volume fraction change of these phases.
Microstructures and Hydrogen Permeability of Nb-NiTi Eutectic Alloys Prepared by Directional Solidification
Authors: Yamaguchi Yuji , Kishida Kyosuke , Tokui Sho , Ishikawa Kazuhiro , Tanaka Katsushi , Aoki Kiyoshi , Inui Haruyuki 
Published: June 2019

AbstractThe Nb-NiTi eutectic alloys were directionally solidified (DS) in an optical floating zone furnace. Columnar grains of eutectic structures containing rod-shaped Nb in the NiTi matrix is observed in the DS ingots irrespective of the alloy composition. Well-aligned rod-type eutectic microstructures can be obtained for samples with a composition of Nb-41Ni-40Ti grown at relatively slow growth rates below 2.5mm/h. The hydrogen permeability along the direction parallel to the Nb rods of Nb-41Ni-40Ti DS alloy grown at 1mm/h is 2.60×10-8mol H2m-1 Pa-1/2 at 673K, which is over 20 times higher than that measured perpendicular to the Nb-rod direction. No hydrogen embrittlement is observed between 573 and 673K indicating that the eutectic structure itself is favorable in suppressing the hydrogen embrittlement of Nb.
High Temperature Mechanical Behavior of a Mo-Si-B Solid Solution Alloy
Authors: Jain Padam , Kumar K. S. 
Published: June 2019

AbstractMulti phase alloys at the Mo-rich end of the Mo-Si-B system have drawn recent attention because of their high temperature performance capabilities. Previous studies on two- and three-phase alloys have confirmed the central role of the Mo-rich solid solution phase in affecting creep resistance and low-temperature toughness in these multiphase alloys. Thus, it is important to understand the intrinsic mechanical response of the matrix solid solution. In this study, compression and tensile tests were conducted over a nominal strain rate regime spanning 10-4 s-1 to 10-7 s-1 and temperature ranging from 1000°C to 1300°C in vacuum on a Mo-Si-B solid solution alloy (Mo-3Si-1.3B in at.%) that contained a low fraction (~5 %) of the T2 phase. The microstructure of the deformed specimens was examined to elucidate the underlying deformation mechanisms.
Pseudoelastic Behavior of Fe3Ga Single Crystals with D03 Structure
Authors: Yasuda Hiroyuki Y. , Aoki Mitsuhiro , Fukushima Kouki , Umakoshi Yukichi 
Published: June 2019

AbstractPseudoelastic behavior of Fe3Ga single crystals regardless of a thermoelastic martensitic transformation was investigated focusing on the dislocation structure and the phase constituent. Large pseudoelasticity of 5 % recoverable strain appeared in Fe3Ga single crystals sufficiently annealed in the D03 single-phase region. In the crystals, uncoupled and paired 1/4[111] superpartial dislocations moved dragging the nearest-neighbor (NN) and next-nearest neighbor (NNN) anti-phase boundaries (APBs) during loading, respectively. During unloading, these APBs pulled back the superpartials resulting in large pseudoelasticity, which is similar to D03-ordered Fe3Al crystals. The dislocation configuration was closely related to the ordered domain structure developed in the D03 phase. Moreover, the precipitation of the thermally stable L12 phase was so slow that the metastable D03 phase developed even if the crystals were annealed in the (a+ L12) and (D03+ L12) phase fields in Fe-Ga equilibrium phase diagram. The metastable D03 phase also demonstrated large pseudoelasticity of which recovery ratio was above 80 %. On the other hand, if the L12 phase precipitated by long time annealing in the (a+ L12) region, the reversible motion of 1/4[111] superpartials was suppressed by the L12 phase resulting in a decrease in recovery ratio. In addition, the crystals aged in the (a+ D03) phase region showed small strain recovery.
Texture Formation in High Niobium Containing TiAl Alloys
Authors: Stark Andreas , Bartels Arno , Schimansky Frank-Peter , Clemens Helmut 
Published: June 2019

AbstractTexture formation was studied in high Nb bearing g-TiAl based alloys with compositions of Ti-45Al-(5,7.5,10)Nb-(0,0.5)C (compositions are in atomic percent). In order to start with texture-free material hot-isostatically pressed powder compounds were used. The deformation was performed either in uniaxial compression or by hot rolling. After compression at 700 °C and 800 °C fiber textures with <110> and <302> components occur. These deformation textures can be verified by computer simulations using a yield surface model of g-TiAl. With higher deformation temperatures the <110> fiber vanishes and new accumulations of orientations are formed, which are due to dynamic recrystallization.Hot rolling was performed at temperatures in the upper part of the (a+g) phase field and, therefore, with more than 50% a-phase existing. The co-deformation of a- and g-phase during rolling leads to correlated components in the independently measured textures of both phases. The texture of the g-phase shows a maximum of orientation around the Goss2 component and the texture of the a-phase exhibits an orientation maximum around the transversal component. The correlation is the Blackburn orientation relation, although the textures are not caused by phase transformations, but by co-deformation. Hot rolling with many passes and reheating between the passes lead to the formation of a cube component with an alignment of the c-axes in transverse direction. In general, this is a typical recrystallization-induced component in hot rolled TiAl.
Effect of SPS processing temperature on the microstructure and properties of a Ti49Al47Cr2Nb2 alloy
Authors: Couret Alain , Molénat Guy , Galy Jean , Thomas Marc 
Published: June 2019

AbstractThe sintering of TiAl alloys by the Spar Plasma Sintering (SPS) technique is investigated in the present paper. Compactions are conducted between 1100°C and 1225°C on a Ti49Al47Cr2Nb2 powder. Single phased and lamellar microstructures are generated at low and high temperatures, respectively. The former exhibits enhanced tensile properties at room temperature but at the expense of a limited creep resistance. On the other hand, the latter suffers from a poor ductility.The deformation systems which are activated are determined by post-mortem transmission electron microscopy. The behavior of the single phased-alloy is analyzed in terms of the Hall-Petch law.
Development of Dual Multi-Phase Intermetallic Alloys Composed of Geometrically Close Packed Ni3X(X:Al and V) Structures
Authors: Takasugi Takayuki , Kaneno Yasuyuki 
Published: June 2019

AbstractDual multi-phase intermetallic alloys composed of Ni3Al (L12)+Ni3V (D022) phases were developed, based on the Ni3Al-Ni3Ti-Ni3V pseudo-ternary alloy system. High-temperature tensile deformation, fracture behavior, and compression and tension creep were investigated using polycrystalline and single crystalline materials. The alloys with such a novel microstructure show extremely high yield and tensile strength with good temperature retention, and also reasonable tensile ductility. Also, creep test conducted at high temperature showed extremely low creep rate and long creep rupture time. The obtained results are promising for the development of a new-type of high-temperature structural material exceeding conventional superalloys.
Microstructures and Mechanical Properties of in-situ V-V3B2 Composites
Authors: Xie Sujing , George Easo P. 
Published: June 2019

AbstractA series of binary V-B alloys, with compositions spanning the eutectic, were produced by arc melting and drop casting. Microstructural examination revealed that the fully eutectic structure occurs at V-11B rather than V-15B as reported in the V-B phase diagram (all compositions in at.%). The V-11B eutectic was directionally solidified in an optical floating zone furnace, resulting in a composite microstructure consisting of a V matrix and flake or trigonal shaped V3B2 phase. The boride flake spacing (ë) decreases with increasing growth rate (R), following the relation ë2.56R=C, where C is a constant. TEM observations showed that the orientation relationship between the V and V3B2 phases is given by: [001]V // [001]V3B2 and (100)V // (100)V3B2. The growth direction and the V/V3B2 interface are parallel to the [001] direction and (100) planes in the two phases, respectively. Tensile tests were used to investigate the temperature dependence of the strength and ductility of the composite. At temperatures to 600°C, the yield strength of the eutectic is about 140 MPa higher than that of a commonly used vanadium solid-solution alloy, V-4Cr-4Ti. Surprisingly, the eutectic shows 5% tensile ductility at room temperature which increases to 10% as the test temperature is raised to 800°C.
Deformation Behavior of ReCr Sigma Phase Diffusion Barrier on Ni-based Superalloy
Authors: Miura Seiji , Ohkubo Kenji , Mohri Tetsuo , Yoshioka Takayuki , Narita Toshio 
Published: June 2019

AbstractIn order to attain a better oxidation resistance of Ni-based superalloys for high performance engines, a ReCr-based sigma-phase diffusion barrier coating between the MCrAlY bond coat (Al reservoir) layer and a Ni-based superalloy substrate has been proposed to suppress the diffusion of Al and other elements. The deformation behavior of TMS82+ superalloy specimens with coating layers composed of an Al-rich surface layer (corresponding to a bond coat) and a ReCr sigma-phase inner layer is investigated. In-situ observation of the bending tests using a Laser scanning confocal microscopy revealed that the crack formation in the Al-rich surface layer(s) on the tension side of the bend specimen occurs at an early stage of bending. On the other hand, small cracks in the sigma-phase layer under the Al-rich surface layer(s) are formed at the slip traces in the Ni-based superalloy single crystal substrate. This suggests a good adhesion between the sigma-phase and the Ni-based superalloy. At the compression side, in both the Al-rich surface layer(s) and the sigma-phase layer no cracking was observed until the Al-rich surface layer(s) shows buckling.
Thermo-Mechanical Modelling of Pebble Beds in Fusion Blankets and its Implementation by a Return-Mapping Algorithm
Authors: Gan Yixiang , Kamlah Marc 
Published: June 2019

AbstractIn this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered.Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importance with respect to the application of pebble beds in fusion blankets [1]. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis.The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made.
Structural Study of SiC Nanoparticles Grown by Inductively Coupled Plasma and Laser Pyrolysis for Nanostructured Ceramics Elaboration
Authors: Leconte Yann , Leparoux Marc , Portier Xavier , Herlin-Boime Nathalie , Siegmann Stephan , Rohr Lukas , Reynaud Cecile 
Published: June 2019

AbstractRefractory carbide nanostructured ceramics as SiC constitute interesting materials for high temperature applications and particularly for fourth generation nuclear plants. To elaborate such nanomaterials, weighable amounts of SiC nanopowders have to be synthesized first with an accurate control of the grain size and stoichiometry. The inductively coupled plasma and the laser pyrolysis techniques, respectively developed at EMPA Thun and CEA Saclay, allow meeting these requirements. Both techniques are able to produce dozens of grams per hour of silicon carbide nanopowders. The particle size can be adjusted down to around 20 nm for the plasma synthesis and even down to 5-10 nm for the laser pyrolysis. The stoichiometry Si/C can be tuned by the addition of methane into the plasma and acetylene for the laser process.
Microstructure and Mechanical Properties of n-Irradiated Fe-Cr Model Alloys
Authors: Matijasevic Milena , Al Mazouzi Abderrahim 
Published: June 2019

AbstractHigh chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement.In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160°C to 300°C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300°. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening.