bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Path to Fluid Dynamics in Membranes
Authors: ten Bosch A. 
Published: April 2011

ABSTRACTAtomic scale dynamic theories and numerical simulation can explore atomistic processes but the relevant physics must fold atomistic understanding into a mesoscopic formulation in terms of average system properties. Transport equations for the density(or concentration), the flux and the pressure tensor are derived from a microscopic basis which mimics simulation by molecular dynamics. The validity of classical hydrodynamics is explored. The method includes interparticle interactions and small scale variations in time and space of relevance to modeling of membrane processes.
Observation of Deformation Substructure in Fatigued Intermetallic Alloys Using Magnetic Properties
Authors: Umakoshi Yukichi , Yasuda Hiroyuki Y. 
Published: April 2011

ABSTRACTMagnetic properties in ferromagnetic materials are very sensitive to lattice defects such as dislocations and planar faults. Dislocation substructures and planar faults in fatigued intermetallic compounds of Ni3Fe, Fe3Al and FeAl were observed using change in magnetic properties of spontaneous magnetization and high-field susceptibility. This magnetic technique was applied for the nondestructive evaluation of fatigue life.
Effects of Solidification Parameters on Lamellar Microstructures of Near Eutectic Cr-Cr3Si Alloys
Authors: Bei H. , George E. P. , Pharr G. M. 
Published: April 2011

ABSTRACTDirectional solidification of Cr-Cr3Si eutectic alloys has been carried out using a high temperature optical floating zone furnace. Uniform and well-aligned lamellar structures were obtained over a fairly wide range of intermediate growth rates but not at very low or very high growth rates where degenerate and cellular structures, respectively, were obtained. The lamellar spacing was found to increase with decreasing solidification rate, in agreement with the Jackson-Hunt theory. In addition, for a fixed growth rate, the lamellar spacing was found to increase with increasing rotation rate. Lamellar structures could also be produced at off-eutectic compositions, but only for a limited range of growth conditions. The Cr-rich lamellae are effective in stopping indention cracks nucleated in the brittle Cr3Si phase.
High Temperature Resistant Intermetallic Nial-Based Alloys with Refractory Metals Cr, Mo, Re - Structures - Properties - Applications -
Authors: Frommeyer G. , Rablbauer R. 
Published: April 2011

ABSTRACTThe stoichiometric intermetallic compound NiAl with B2 superlattice structure exhibits superior physical and high-temperature mechanical properties, and excellent oxidation resistance. The main disadvantages of polycrystalline NiAl are the lack in plasticity and fracture toughness below the brittle-to-ductile-transition temperature of about 550°C. Insufficient high-temperature strength and creep resistance occur at temperatures above 800°C. Despite these facts NiAl-based alloys are still considered as promising structural materials for high-temperature applications. The refractory metals Cr, Mo, and Re with b.c.c. and h.c.p. lattice structures form with NiAl quasi-binary eutectic systems, showing high melting temperatures and thermally stable microstructures. Elasticity, solid solution hardening, fibre reinforcement, and creep properties were investigated in view of the constitutional defect structure and microstructural features. Especially the fibre reinforced NiAl matrix composites possess optimum high-temperature strength up to 1200 °C, and improved creep resistance as well.
Observation of structural modulations and formation of H-carbides and ζ-silicides during α2 → γ transformation in fully lamellar γ-TiAl
Authors: Karadge M. , Gouma P. I. 
Published: April 2011

ABSTRACTThe present paper illustrates the experimentally observed microstructures related to α2 → γ + Ti2AlC (H-carbide) and Ti5Si3 (ζ silicide) phase transformations in fully lamellar Ti-46Al-2Cr-3Nb-0.2W-0.2Si-0.1C alloy. These transformations were observed by in-situ heat treatments in the TEM at temperatures up to 800°C and by post heat treatment examination in a high-resolution transmission electron microscope. α2 dissolution was observed to start both inside the lath and at the α2/γ interface. H-type carbides were observed to nucleate inside the α2 lath, which explains the appearance of long arrays of well-aligned structures along prior α2 laths in creep-deformed samples. ζ silicide precipitates nucleate at the α2/γ interface, this growth occurs epitaxially along the pre-existing <0001>α2 direction. Modulated structures were observed during the α2 → H, newly formed γ and at the α2 / ζ interface. All these modulated structures consist of regular arrangement of stacking faults and dislocations.
Precipitation Phenomena and Strain Hardening of Intermetallic Titanium Aluminides
Authors: Müllauer J. , Appel F. 
Published: April 2011

ABSTRACTIn two-phase titanium aluminide alloys, the implementation of precipitation reactions is a widely utilized concept to control the microstructure and strengthen the material. A study has been made on the influence of carbide and boride precipitates on dislocation mobility and strengthening at 300 K. Compression tests were carried out for characterizing the mechanisms determining flow stress and dislocation glide resistance. The interaction mechanisms between the precipitates and dislocations were assessed by thermodynamic glide parameters and transmission electron microscopy. It has been shown that small titanium boride precipitates and carbide precipitates of perovskite type act as long-range dislocation glide obstacles. The interaction between the dislocations and the borides and carbides mainly leads to an athermal stress contribution. However, the dislocation-particle interactions are quite different. Small groups of borides are encircled by dislocations. This gives rise to the formation of loop structures the density of which increases with strain. On the contrary, the carbide precipitates are shearable and can be overcome without Orowan looping. This different behaviour is also reflected in the work hardening characteristics. Whereas the work hardening coefficient of the boron doped material increases with increasing B-concentration, it is independent of concentration in the case of the carbon-doped material.
Microstructure and Oxidation of a Cast Nickel Aluminide Alloy
Authors: Lee D. Y. , Santella M. L. , Anderson I. M. , Pharr G. M. 
Published: April 2011

ABSTRACTSpecimens of the cast Ni3Al alloy IC221M were annealed in air at 900°C to examine the effects of oxidation and thermal aging on the microstructure. The alloy is comprised of a dendritically solidified γ-γ′ matrix containing γ+Ni5Zr eutectic colonies in the interdendritic regions. Microstructures of aged specimens were examined by optical microscopy and energy dispersive X-ray (EDX) spectrum imaging in the scanning electron microscope (SEM). Two primary changes in the microstructures were observed: (1) there is considerable homogenization of the cast microstructures with aging, and (2) the volume fraction of the γ+Ni5Zr eutectic decreases. Oxidation products were identified using x-ray diffraction and EDX spectrum imaging with multivariate statistical analysis (MSA). During the initial stages of oxidation, the first surface oxide to form is mostly NiO with small amounts of Cr2O3, ZrO2, NiCr2O4, and θ-Al2O3. Initially, oxidation occurs primarily in the interdendritic regions due to microsegregation of alloying elements during casting. With further aging, a continuous film of α-Al2O3forms immediately beneath the surface that eventually evolves into a double layer of α-Al2O3and NiAl2O4. Although these oxides are constrained to the near surface region, others penetrate to greater depths facilitated by oxidation of the γ+Ni5Zr eutectic colonies. These oxides appear in the microstructure as long, thin spikes of ZrO2surrounded by a thin sheath of Al2O3.
Microstructures and Tensile Properties of Cold-rolled Thin Foils of Binary Ni-Al γ/γ' Alloys
Authors: Li Dingqiang , Demura Masahiko , Kishida Kyosuke , Suga Yozo , Hirano Toshiyuki 
Published: April 2011

ABSTRACTThree single crystal plates of γ/γ' Ni-Al two-phase alloys with near cube, Goss and intermediate orientations between cube and Goss were cold-rolled to 300 μm-thick foils with 83% reduction. Tensile tests of the foils were performed at room temperature to study the effect of rolling microstructures and textures on the mechanical properties. The fracture strength of all the foils was very high, 1.4–1.7 GPa, having a small initial normal direction (ND) dependence and a small difference between rolling direction (RD) and transverse direction (TD). The foils fabricated from initial cube and intermediate orientations showed necking and a small fracture elongation when tensile-tested along RD, while the foil fabricated from initial Goss orientation did not show necking and fracture elongation. All the foils showed small fracture elongations due to shear band formation when tensile-tested along TD.
The Effects of Substitutional Additions on Creep Behavior of Tetragonal and Hexagonal Nb-Silicides
Authors: Bewlay B. P. , Briant C. L. , Sylven E. T. , Jackson M. R. 
Published: April 2011

ABSTRACTNb-silicide based in-situ composites combine a ductile Nb-based solid solution with high-strength silicides, and they show great promise for aircraft engine applications. The Nb-silicide controls the high-temperature creep behavior of the composite. Previous work has shown that the silicide composition has an important effect on the creep rate, with particular attention on the role of Ti and Hf additions. The aim of the present study is to understand the effects of the substitutional elements on the stability of the silicide phase, ordering in the crystal lattice, including the hP16-tI32 transition, and the creep behavior of the monolithic phases. To pursue this goal monolithic alloys with a range of compositions were prepared and the creep rates were measured at temperatures of 1100–1350°C. The stress sensitivities of the creep rates of the monolithic phases were also determined.
Fe tracer diffusion in L10 ordered FePt
Authors: Nosé Y. , Ikeda T. , Nakajima H. , Tanaka K. , Numakura H. 
Published: April 2011

ABSTRACTTracer diffusion coefficient of 59Fe in FePt with the tetragonal L10 ordered structure has been measured by an ion-beam sputter-sectioning technique in the temperature range from 1173 to 1374 K. Anisotropy in diffusion has been studied using single-variant single-crystal specimens. The diffusion coefficient in the direction perpendicular to [001] axis (in the a-axis direction), Da, is larger than that in the [001] (c-axis) direction, Dc, as expected from the atomic arrangement of the L10 ordered structure. The ratio of the diffusion coefficients, Da/Dc, is 1.33.6 for Fe42Pt58 and smaller at higher temperatures. The activation energy for the diffusion is 259 ± 1 kJ/mol for Da and 309 ± 18 kJ/mol for Dc, while the pre-exponential factor is and , respectively in Fe42Pt58.
Defect Structures of Intermetallic FeRh Alloys Induced by High-Speed Deformation
Authors: Kibata Yasunori , Hori Fuminobu , Oshima Ryuichiro , Komatsu Masao , Kiritani Michio 
Published: April 2011

ABSTRACTIn order to study the role of vacancy-type defects in the unique deformati on-induced phase transition mechanisms of B2-L10 and B2-A1 of intermetallic compound Fe-Rh alloys, high-speed impact compression deformation has been carried out. Induced phases and substructures were examined by XRD and TEM. The relation between the phase transitions and vacancy-type defects was investigated by the positron annihilation Coincidence Doppler Broadening (CDB) method. The results showed that intermixed phases of L10 and A1 were always formed in the B2 phase, and the vacancy concentrations were rather decreased in the specimens deformed by higher strain rates, suggesting that vacancies were more consumed by the phase transition to A1 structure.
The Effects of Ternary Elemental Additions on the Structure and Magnetic Properties of Nanocrystalline Feco Powders
Authors: Baker I. , Quiller R. G. , Robson M. , Wu D. 
Published: April 2011

ABSTRACTPowders of near-equiatomic Fe and Co were mechanically milled with additions of Zr, C, Ni, Cu and/or B for 60 hr using stainless steel balls in a Svegari attritor operated at 1300 r.p.m. under argon. The milled powders were examined before and after annealing at 600 °C. The morphologies and sizes of the powders were examined using a scanning electron microscope. The grain sizes were characterized from the widths of X-ray diffraction peaks obtained using a computer-controlled x-ray diffractometer and the lattice parameters were determined. The resulting magnetic properties were measured using a vibrating sample magnetometer.
Phase Transformation of Ti-Ni Containing Platinum-Group Metals
Authors: Hosoda Hideki , Tsuji Masahiro , Mimura Motoki , Takahashi Yohei , Wakashima Kenji , Yamabe-Mitarai Yoko 
Published: April 2011

ABSTRACTSince the maximum shape recovery temperature of the binary Ti-Ni alloys is limited to be around 400K, the increase in martensitic transformation temperature (Ms) of Ti-Ni should be done by alloying for the demand of high temperature applications. Although most of additional elements are known to decrease Ms of Ti-Ni, substitutional elements having large atomic size are expected to increase Ms. In this study, phase constitution, phase transformation temperature, lattice parameter of B2 phase and Vickers hardness were investigated for Ti-Ni alloys containing several platinum-group metals (PGM). The alloy systems investigated were the pseudobinary systems of TiNi-TiRh, TiNi-TiIr and TiNi-TiPt where the PGM atoms substitute for the Ni-sites of TiNi. The phase transformation and phase constitution were assessed by differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). It was found by XRD that TiNi can contain a large amount of the PGMs as Ti(Ni, Rh), Ti(Ni, Ir) and Ti(Ni, Pt). Lattice parameters monotonously increase with increasing amount of PGMs. With increasing Pt content, Ms slightly decreases when less than 10mol%Pt while continuously increases as the rate of 26K/mol%Pt when more than 10mol%Pt. On the other hand, Ms decreases and then disappears with increasing Rh or Ir content. Hardness ranges from HV180 to HV570 and the maximum values in the pseudobinary systems lie around 20–30mol%PGM, suggesting solid solution hardening caused by the substitution of PGMs.
Reversible Hydrogen Absorption/Desorption and Related Lattice Deformation of Ti3Al Based Alloys in the Ti-Al-Nb System
Authors: Ito Kazuhiro , Zhang Lanting T. , Okabe Yoshiharu , Vasudevan Vijay K. , Yamaguchi Masaharu 
Published: April 2011

ABSTRACTHydrogen absorption/desorption of Ti3Al-based alloys with α2 single-phase, β0 single-phase and β/O two-phase microstructures was investigated to obtain systematic understanding microstructure effects. On exposing all the alloys to hydrogen, β (βH) and γ (γH) hydrides are formed. The βH and γH have bcc and bct (close to fcc) based structures, respectively. The hydrogen/metal ratio of the γH is larger than that of βH. Thus, solute hydrogen in Ti3Al based alloys stabilizes the bcc-based phase just like Nb, regardless of their original structure before hydrogenation. On the other hand, reversible hydrogen absorption/desorption around 100°C and related reversible βH-γH transformation was observed in β/O two-phase (Ti,Nb)3Al and α2-Ti3Al alloys, but not obviously observed in a β0-(Ti,Nb)3Al alloy. In forming the βH, the expansion of the β0 and β phases occurred isotropically keeping their structures B2 and bcc, respectively. In contrast, the O and α2 phases expanded in anisotropic manner. The lattice deformation for the βH→γH transformation can be described similarly to those for the O→βH and α2→βH transformations. Such lattice deformation in anisotropic manner most likely agrees with that observed in a martensitic displacive transformation, because of the surface relief observed on the γH after the βH→γH transformation in the β0-(Ti,Nb)3Al alloy and many twins formed during the α2→βH transformation in the α2-Ti3Al alloy. Mechanisms of the reversible βH-γH transformation in the β/O two-phase (Ti,Nb)3Al and α2-Ti3Al alloys was proposed on the basis of similarities in the lattice deformation and ordering of hydrogen atoms required for the βH-γH, O-βH and α2-βH transformations.
Plastic Deformation Behavior of Al5Ti3 Single-Phase Single Crystals
Authors: Nakano Takayoshi , Hayashi Koutaro , Nagasawa Yosuke , Umakoshi Yukichi 
Published: April 2011

ABSTRACTAl5Ti3 single-phase single crystals with the stoichiometric composition of Ti-62.5at.%Al were obtained by the floating zone method and subsequent heat treatment at 750°C for 48h. The crystals contain no L10 phase, but compose of anti-phase domains (APD) surrounded by the anti-phase boundary (APB) on the basis of the Al5Ti3 long-period superstructure.Orientation dependence of plastic deformation behavior and operative slip system were examined in compression in a wide temperature range between RT and 750°C using the single-phase single crystals in comparison with Al-rich TiAl single crystals with the L10 matrix and Al5Ti3 precipitates. In the wide crystal orientation area, {111)<110] ordinary slip appeared independent of the tested temperature, while {111)<101] superlattice slip was operative only at around [001] and [110] axes. This is because the critical resolved shear stress (CRSS) for the ordinary slip is lower than that for the superlattice slip and that for the ordinary slip in other Al-rich TiAl crystals containing L10. This implies that existence of the L10 matrix with the Al5Ti3 phase must be closely related to strengthening for the ordinary slip, similarity in Ni-base super-alloys consisting of the Ni-based matrix and L12 precipitates. The CRSS for both slips gradually decreased or was kept constant with temperature, showing no remarkable anomalous strengthening.In this paper, deformation mechanism in Al5Ti3 single-phase single crystals will be discussed focusing on condition of the Al5Ti3 superstructure.
Formation and Characterisation of Periodically Structured B2-Aluminides Thin Films by Laser Interference Irradiation
Authors: Liu K. W. , Mücklich F. 
Published: April 2011

ABSTRACTB2-aluminide thin films can be used as protective layers to prevent mechanical, thermal and chemical impact on the main components and as intermediate thermal or diffusion barrier layers for semiconductor contacts. Laser irradiation can induce phase transformation due to thermal interaction with sample surface. Moreover, with laser interference, the laser power can be distributed periodically on interference points or lines. The scale of the pattern, sub-micrometer to dozens of micrometer, can be varied easily to the typical scale of grain sizes. In this work, B2-structured NiAl and RuAl thin films with periodic pattern are prepared from corresponding elemental bi-films by laser interference irradiation. The micro-nano-structured surface constitutes of a line-like pattern with a period of about 5 micrometer. There occur melting and re-solidification processes during laser interaction with sample surface. The line-like patterns possess fine grains with a size of about 20 nm in Ni/Al and 5 nm in Ru/Al bi-films. The appearance of B2-structured NiAl and RuAl phases are confirmed by TEM. It is proposed that the phase transformation from initial metastable solid solution to the B2 phases can be induced by laser irradiation.
Amorphization of C15 Laves RFe2 compounds by hydrogen absorption
Authors: Aoki K. , Dilixiati M. , Ishikawa K. 
Published: April 2011

ABSTRACTC15 Laves RFe2 (R= Y, Ce, Sm, Gd, Tb, Dy, Ho and Er) compounds were thermally analyzed to elucidate conditions of hydrogen-induced amorphization (HIA), i.e. amorphization of intermetallics by hydrogen absorption, using a pressure scanning differential calorimeter (PDSC) in a hydrogen atmosphere of 1.0 MPa. As the temperature increases, hydrogen absorption in the crystalline state, HIA, precipitation of RH2 in the amorphous phase and decomposition of the remaining amorphous phase into RH2+oc-Fe occur exothermally for RFe2 (R=Y, Sm, Gd, Tb, Dy and Ho). HIA and precipitation of ErH2 occur simultaneously in ErFe2. On the contrary, hydrogen absorption of CeFe2 always leads to HIA, i.e. no hydrogen absorbed crystalline phase is formed. The mechanism of HIA in the C15 Laves phases RFe2 is discussed on the basis of the experimental results.
A Cr(IV) based 1212-type cuprate
Authors: Ruiz-Bustos Rocío , Aguirre Myriam H. , Alario-Franco M.Á. 
Published: April 2011

ABSTRACTBy means of high pressure and high temperature we have prepared a new material similar to the classic YBa2Cu3O7 (Ybacuo) superconductor but having chromium in the so-called charge reservoir layer: CrSr2YCu2O8. It has been characterised by different techniques such as X-ray diffraction, TEM, ED, EDS, and magnetic susceptibility. The new material is isostructural with the Ru equivalent compound (RuSr2YCu2O8). An antiferromagnetic transition is observed on cooling below 130 K. The as prepared material is not superconducting down to 4 K.
Stabilization of beta-SrAl2O4 with Eu Prepared by Spray Pyrolysis
Authors: Shi W.S. , Yamada H. , Nishikubo K. , Kusaba H. , Xu C.N. 
Published: April 2011

ABSTRACTThe effect of doping europium on the structure of strontium aluminate (SrAl2O4:Eu) synthesized by spray pyrolysis was studied. Results revealed that all of the as-sprayed samples were a mixture structure of monoclinic and hexagonal phases. However, the structural behaviors of the SrAl2O4:Eu post-calcinated at 1300°C in reducing ambient for 2hrs strongly depended on the europium concentrations. As increase of the europium concentrations, a characteristic of hexagonal phase could be observed from the post-annealed samples. Up to 12 percent of strontium were replaced by the europium, the structure of the post-annealed sample achieved a pure hexagonal phase. The mechanism of the phase dependence of the SrAl2O4:Eu on europium concentration was discussed.
Nuclear and Magnetic Structures of K2NiF4-type Iron(III) Oxide Halides
Authors: Hector Andrew L. , MacDonald Alexander I. , Price Daniel J. , Weller Mark T. 
Published: April 2011

ABSTRACTK2NiF4-type iron(III) oxides show a very common form of magnetic ordering, XY antiferromagnetic ordering within the layers combined with layer stacking based on alignment of spins in alternate layers. The Ising antiferromagnet Ca2MnO4 has been reported to have a doubled c-axis (ca 24Å) in the magnetic structure and we have found a similar stacking in the XY antiferromagnet Sr2FeO3F. We show here that this unusual c-axis doubling is related to the exposure of the material to air and suggest that in both Sr2FeO3F and Ca2MnO4 it may be related to the occupation of interstitial sites.
Synthesis and Characterization of Neutral and Cationic Layered Materials Based on Heavier Group 14 Metals: BING-5, -6, -9, -10
Authors: Tran Dat T. , Zavalij Peter Y. , Oliver Scott R. J. 
Published: April 2011

ABSTRACTOur research involves the solvothermal synthesis and characterization of new 3D open-framework and low dimensional inorganic materials. We focus on heavier group 14 elements to prepare structures that are analogous to aluminosilicate zeolites, but the main emphasis is to obtain cationic materials, a feat not possible with silicon oxides. We have successfully synthesized a series of novel compounds with Pb as building block: a cationic layered lead fluoride material (BING-5, Pb3F5NO3); a neutral, layered lead phenylphosphonate pyridine (BING-6); and a layered lead metamethylphenyl-phosphonate (BING-9). A molecular solid, tetrafluorodipyridine-germanium (BING-10) was also obtained. These structures are characterized by a variety of solid state techniques, including: powder X-Ray diffraction (PXRD), thermogravimetric analysis (TGA), UV-Vis spectroscopy and NMR. Our BING-5 material can exchange its interlayer NO3- for a variety of other anions. It is also stable to 450°C, which is far superior to organic resins that are still the standard for anion-exchange.