bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Spatially Hybridized Charge Distribution and its Effect on Electron Transport in the Al-Cu-Ru-Si 1/1-Approximant ---Theoretical Basis for the Hume-Rothery rule---
Authors: Mizutani U. , Takeuchi T. , Banno E. , Fourneé V. , Takata M. , Sato H. 
Published: April 2011

AbstractThe origin of the pseudogap across the Fermi level was investigated by analyzing the electronic structure calculated in the framework of the LMTO-ASA method for the RT-type Al-Mg-Zn and MI-type Al-Cu-Ru-Si 1/1-approximants. The pseudogap in the former is proved to originate from the interaction of electronic states with the Brillouin zone planes associated with reciprocal lattice vectors matching with the Fermi sphere in the extended zone scheme. In the latter, the Fermi surface-Brillouin zone interaction coupled with the hybridization effect between the Al-3p and transition metal d-states produces a deep pseudogap at the Fermi level. The real-space charge distribution for electrons at the Fermi level is calculated for the Al-Cu-Ru-Si 1/1-approximant. The charge distribution thus obtained could explain not only the possession of a large resistivity of this approximant but also evidenced that the icosahedral clusters play a key role in reducing the electronic energy in favor of quasicrystalline and approximant phases.
Electrical Resistivity of an Al-Re-Si Cubic Approximant Phase and Role of Local Environment in Electronic Transport
Authors: Tamura Ryuji , Asao Takayuki , Tamura Mutsuhiro , Takeuchi Shin 
Published: April 2011

AbstractIn order to gain an insight into the role of the local atomic environment in the electronic transport of the icosahedral quasicrystal, the electrical resistivity of α-AlReSi, which is the (1/1,1/1,1/1) approximant of the icosahedral phase, has been investigated. Very high resistivity and its pronounced negative temperature dependence have been observed, indicating that the electronic states of the 1/1 cubic approximant are quite similar to those of icosahedral phases. In order to further elucidate which structural entity is responsible for such anomalous transport, a comparison of the electrical resistivity between (1/1,1/1,1/1) and (1/0,1/0,1/0) approximants has been made. The typical transport behavior of icosahedral phases which is also seen in 1/1 and higher-order approximants was not observed in any of the studied 1/0 cubic approximants. The result can be regarded as an implication that the intercluster distance between the TM clusters plays a significant role in the confinement of electronic states.
Crystal Structure of New Approximant Phase in Al-Fe-V-Si System
Authors: Ezersky Vladimir I. , Rochman Avi D. , Talianker Michael M. 
Published: April 2011

AbstractA model proposed for the atomic structure of the new hexagonal Al-Fe(V)-Si phase which was found in rapidly solidified Al-Fe(V)-Si alloys is discussed in terms of relation this phase to approximants. The structure of this new phase was described as hexagonal packing of double Mackay icosahedral units similar to those of which the cubic α-(AlFeSi) approximant phase is built up. On the basis of this model the experimental high resolution electron microscopic (HREM) images of the hexagonal phase were successfully interpreted. Like the á phase this structure is characterized by the local icosahedral ordering and can be regarded as an approximant.
Characterization of Ga-Mn Decagonal Quasicrystals in GaAs
Authors: Sun K. , Browning N. D. 
Published: April 2011

AbstractGa-Mn decagonal quasicrystals (DQC), as well as a Ga-Mn approximant and a normal crystal in GaAs are investigated by electron energy-loss spectroscopy (EELS) and energy dispersive X- ray spectroscopy (EDS) combined with Z-contrast imaging. Plasmon peak positions (Ep), full- width-half-maxima (FWHM) and Mn L3/L2ratios of these three phases are derived from their low-loss spectra and core-loss spectra respectively. Mn, Ga and As distributions in ion implanted GaAs layers are characterized by EDS at line-scan mode. These results show that the Ga-Mn DQC has higher Ep and FWHMs than those of its normal crystal counterpart, as well as all other reported QCs. The much larger L3/L2 intensity ratio of the Ga-Mn DQC over that of the Al-Mn icosahedral quasicrystals (IQC) may suggest Mn atoms in the Ga-Mn DQC have much larger local magnetic moments.
The Effect of Swift Heavy Ion Irradiation on Quasicrystals
Authors: Chatterjee Ratnamala , Kanjilal Aloke , Dunlop A. 
Published: April 2011

AbstractThe effect of pure electronic excitations (by ∼ 835 MeV Kr irradiation) on a stable icosahedral quasicrystal is compared with the effect of electronic excitations combined with the nuclear collisions (by 100 MeV Ni irradiation) occurring in a similar quasicrystal. The critical stopping power was kept at 1300 eV/Å for both the experiments. Under the pure electronic excitations, the R(φ)/R(0) [ratio of resistance at fluence φ and the resistance on the same piece with zero fluence) of quasicrystal goes through oscillatory changes, until at ∼ 1 × 1012 ions/cm2where this ratio drops considerably. The ex-situ XRD on the irradiated sample does show the evidence of degradation of the structure. In contrast, the Ni- irradiated sample shows an increase in resistivity after a critical fluence of 2.5 × 1013 ions/cm2, which remains constant for higher fluences. Corresponding defect annihilation effects are observed in the XRD of Ni- irradiated samples.
Dislocation Dynamics in Icosahedral Al-Pd-Mn Single Quasicrystals
Authors: Messerschmidt Ulrich , Bartsch Martin , Geyer Bert , Ledig Lars , Feuerbacher Michael , Wollgarten Markus , Urban Knut 
Published: April 2011

AbstractThe paper reviews results from in situ straining experiments on Al-Pd-Mn single quasicrystals in a high-voltage electron microscope. Slip planes were determined from the orientation and width of slip traces. Dislocations are generated by a specific cross slip mechanism. On some slip traces, dislocations move at two distinctly different velocities. A stress exponent was determined on a single dislocation by observing its displacement under decreasing load. The in situexperiments reveal the behaviour of individual dislocations in a temperature range where the deformation of bulk specimens is strongly affected by recovery.
First Results on the Electronic Distributions of Zn-Mg-Y Alloys as Investigated by Soft X-ray Spectroscopies
Authors: Esther Belin-Ferré , Vincent Fournée , Anne Sadoc , Marie Françoise Fontaine , Zoltan Dankhazi , Herbert Müller , Pang Tsai An 
Published: April 2011

AbstractWe report our first results on the electronic structure of icosahedral Zn55Mg35Y10as compared to hexagonal Zn65Mg28Y7and to the conventional Zn2Mg alloy. The occupied Mg 3s,d, and Mg 3p on the one hand and empty Mg p, Zn d-s and Y d-s states on the other hand have been investigated using soft X-ray emission and photoabsorption spectroscopy, respectively. The various sub-bands presented for Mg are adjusted in the binding energy scale whereas for the other elements they are plotted in the X-ray transition energy scale. We observe that the metallic character of the samples progressively decreases when going from the pure metals to the icosahedral compound.
Formation of Icosahedral Quasicrystals in Mg-Al-X (X=Transition Metal) Ternary Systems
Authors: Koshikawa Naokiyo , Yoda Shinichi , Edagawa Keiichi , Takeuchi Shin 
Published: April 2011

AbstractFormation of icosahedral quasicrystalline phase (i-phase) was investigated for Mg-Al-X (X=Co, Ni, Cu, Rh, Ag, Pt and Au) ternary systems. A Mackay-icosahedron (MI) type i-phase was found to form in the Mg-Al-Rh system at the composition Mg8Al68Rh24. The i-phase has the F-type ordered structure and the quasilattice constant is 0.447nm. Differential thermal analysis (DTA) studies showed that the i-phase has a high stability. On the other hand, the formation of a Frank-Kasper (FK) type i-phase was found in the Mg-Al-Pt system at the composition Mg45Al42Pt13. The conditions necessary for the formation of the i-phases are discussed in terms of the atomic radius ratio and the electronegativity as well as the electron-per-atom ratio.
Short Range Chemical Ordering in Bulk Metallic Glasses
Authors: Sterne P. A. , Asoka-Kumar P. , Hartley J. H. , Howell R. H. , Nieh T.G. , Flores K. M. , Suh D. , Dauskardt R. H. 
Published: April 2011

AbstractWe provide direct experimental evidence for a non-random distribution of atomic constituents in Zr-based multi-component bulk metallic glasses using positron annihilation spectroscopy. The Ti content around the open-volume regions is significantly enhanced at the expense of Cu and Ni, indicating that Cu and Ni occupy most of the volume bounded by their neighboring atoms while Ti and Zr are less closely packed and more likely to be associated with open-volume regions. Temperature-dependent measurements indicate the presence of at least two different characteristic sizes for the open volume regions. Measurements on hydrogen- charged samples show that the larger open-volume regions can be filled by hydrogen up to a critical density. Beyond this critical density, local atomic-scale open-volume damage is created in the sample to accommodate additional hydrogen. The onset of this local damage in positron annihilation data coincides with the onset of volume expansion in X-ray diffraction data.
In-Situ Observations of Shear Band Development during Deformation of a Bulk Metallic Glass
Authors: El-Deiry Paul A. , Vinci Richard P. , Barbosa Nicholas , Hufnagel T. C. 
Published: April 2011

AbstractWe have studied the development of shear band structure in a Zr57Ti5Cu20Ni8Al10 bulk metallic glass during deformation. In order to investigate the relationship between shear band development and serrated flow, we performed uniaxial compression tests in an environmental scanning electron microscope (ESEM). During the deformation, load-time data and surface images were simultaneously recorded. In the stress-time data, stress drops or “serrated flow” appear to correlate to new shear band formation. The majority of the shear bands we observed were at an angle of 45° with respect to the compression axis. In addition, we measured shear offset as a function of position along the shear band. We observed two different offset behaviors: Consistent offset along the length of a shear band, and offset that is localized into part of the band. The localized offset behavior could be evidence for dislocation-like displacement increments, or could be the result of a transition in the failure mode.
On the High Temperature Creep and Relaxation Behaviour of Zr-based Bulk Metallic Glasses
Authors: Daniel B. S. S. , Heilmaier M. , Reger-Leonhard A. , Eckert J. , Schultz L. 
Published: April 2011

AbstractCreep tests under constant load as well as constant true strain rate were carried out at near the glass transition temperatures (Tg) to study the time dependent flow behaviour of a Zr-based bulk metallic glass (BMG). The strain rate - stress relation over a wide strain rate-range (10-7 to 10-2 s-1) was established for different temperatures. The high temperature deformation behaviour is explained on the basis of stress induced creation of free volume versus diffusion controlled annihilation processes. It was found that the creep kinetics near Tg is controlled by the mobility of atoms with an activation energy value Q =410kJ/mol.
Effect of Preparation on Glass Formation and Magnetic Properties of Nd-Fe-Co-Al-B Alloys
Authors: Kumar G. , Eckert J. , Xing L.Q. , Güth A. , Roth S. , Löser W. , Ram S. 
Published: April 2011

AbstractThe effect of alternative preparation methods (copper mold casting, melt spinning, and mechanical attrition) on amorphization and properties of Nd57Fe20Co5Al10B8 and Nd40Fe40Co5Al8B7 alloys has been investigated. For all differently prepared samples an amorphous phase is formed upon solidification or solid sate reaction. However, the samples prepared by different processing routes exhibit different transformation behavior in thermal analysis. The cast Nd57Fe20Co5Al10B8 rod exhibits crystallization at 790 K followed by melting at 810 K. Neither appreciable endothermic reaction due to a glass transition nor a supercooled liquid region have been observed. Mechanically alloyed powders and ball-milled prealloys reveal two exothermic DSC peaks in the range of 650-850 K. The J-H hysteresis loops of samples synthesized by different routes show that the unique atomic order responsible for hard magnetic properties can only be accessed at moderate cooling rate of the melt as realized in copper mold casting. Rapidly quenched ribbons, mechanically alloyed powders and ball-milled ingots do not show hard magnetic properties at room temperature. These results indicate that amorphous samples with different local atomic order can be prepared by different processing routes.
Preparation and Mechanical Properties of Hafnium-based Bulk Metallic Glasses
Authors: Gu Xiaofeng , Xing Li-qian , Hufnagel T. C. 
Published: April 2011

AbstractWe have prepared bulk metallic glasses of composition (HfxZr1-x)52.5Cu17.9Ni14.6Al10Ti5 (with x=0-1) by an arc melting/suction casting method. The density of these alloys increases by nearly 67% with increasing Hf content, which is advantageous for their potential use as kinetic energy armor-piercing projectile materials. The glass transition temperature and the melting temperature increase linearly with increasing Hf content. The reduced glass transition temperature (Tg/Tm) decreases from 0.64 (x=0) to 0.62 (x=1), indicating reduced glass-forming ability for the Hf- based alloy. The fracture strength in uniaxial compression at quasi-static strain rates also increases with increasing Hf content, reaching ∼ 2.2 GPa for Hf52.5Cu17.9Ni14.6Al10Ti5.
Thermal Expansion of Glass-Forming Zr-based Alloys in the Melt, the Undercooled Liquid and the Different Solid States
Authors: Samwer K. , Damaschke B. , Krause M. , Ryder P. 
Published: April 2011

AbstractThe thermal expansion coefficients of glass-forming Zr-based alloys were measured in the melt, the undercooled liquid and the glassy/crystalline state. Due to the high reactivity of the liquid material the experiments were performed containerlessly in an electrostatic levitator. We used an optical method where the samples were imaged with a high-resolution CCD- camera and the volume of the samples was evaluated by digital image processing. The coefficients of thermal expansion in the liquid and in the solid state could be determined from the volume versus temperature curves. The results can be compared with measurements in the electromagnetic levitation facility TEMPUS performed under microgravity conditions in the mission MSL-1 and ground based DMA-measurements. The thermal expansion data can be interpreted in terms of the free volume model.
Glass and Quasicrystal Formation in a Zr-based Multicomponent Alloy
Authors: Kühn U. , Eckert J. , Mattern N. , Schultz L. 
Published: April 2011

AbstractThe phase formation of a Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5alloy has been investigated upon cooling from the melt at different quenching rates as well as upon annealing of as-cast specimens. The different samples are characterized by x-ray diffraction, transmission electron microscopy and differential scanning calorimetry. Rapid quenching using the melt spinning technique results in amorphization. Slower cooling as realized upon copper mold casting leads to an icosaheadral quasicrystalline phase coexisting with a small amount of amorphous phase. The primarily formed quasicrystals have a grain size of about 1 νm. Upon annealing, the amorphous phase formed upon melt spinning precipitates quasicrystals in the first step of a series of transformations to the crystalline equilibrium compounds. The quasicrystals formed by annealing do not exceed a size of 5 to 10 nm.
Self-diffusion in Zr55Al10Ni10Cu25 and Pd40Cu30Ni10P20 Bulk Metallic Glass
Authors: Nakajima H. , Kojima T. , Nonaka K. , Zhang T. , Inoue A. , Nishiyama N. 
Published: April 2011

AbstractSelf-diffusion coefficients of Ni in Zr55Al10Ni10Cu25and of Ni and Pd inPd40Cu30Ni10P20 bulk metallic glass below and above the glass transition temperature Tg have been measured with an ion-beam sputter-sectioning technique using the radioactive isotope 63Ni and 103Pd. The diffusion coefficients in the supercooled liquid region are much higher than those extrapolated from low temperature data in the amorphous region. The temperature dependence of the diffusion coefficients exhibits non-Arrhenius behaviour in the supercooled liquid phase. Such a deviation from the Arrhenius plots is interpreted by a cooperation of moving tracer atom with the surrounding atoms. The difference of the diffusion behaviour in between Zr-Al-Ni-Cu and Pd-Cu-Ni-P glasses is attributed to the different structural stability of both glasses.
Controlled Crystallization of Metallic Glasses Through Joule Heating
Authors: Knobel Marcelo , Piccin Rafael , da Silva Fábio C.S. , Filho Walter J. Botta , Yavari Alain Reza 
Published: April 2011

AbstractThis work reviews the basic aspects of an alternative thermal treatment of metallic glasses by Joule heating, which explores the heat produced by an electrical current flowing through samples. The advantages of this annealing method are discussed, and a brief description of available models in a variety of materials is given. The experimental procedures are discussed in detail, with emphasis in a new variant of Joule heating, known as “linear varying current Joule heating”. This method allows one to precisely monitor the structural transformations that take place during annealing, by interrupting the thermal treatment at any desired point, leading to samples with controlled micro and/or nanostructures. Some examples of Joule heating curves in novel bulk amorphous samples are shown, to illustrate the excellent perspectives of this annealing technique.
Effect of Boron on Crystallization Process, Forming Ability and Magnetic Properties of Amorphous Fe91−xZr5BxNb4 Alloy
Authors: Yao B. , Hu X. , Si L , Tan H , Li Y. 
Published: April 2011

AbstractEffects of boron (B) on crystallization, glass forming ability (GFA) and magnetic properties of amorphous Fe91−xZr5BxNb4 (FZBN) were studied in the B content ranging from 0 to 36 at%. The amorphous FZBN crystallizes to μ-Fe in primary crystallization mode at B≤ 20 at% and to Fe-Zr-B-Nb cubic phase with lattice constant of 1.0704 nm and μFe in eutectic mode in the range from 22 at% to 30 at% B. The change of crystallization mode is accompanied by the sharp enhance of glass transition and crystallization temperatures. The GFA of FZBN alloys changes with B content and reaches the largest near 27.5 at % B. Curie temperature (Tc) and magnetization at room-temperature (MRT) and 78K (M78K) for the amorphous FZBN increase with increasing B content. However, the change laws of the Tc and the magnetizations are somewhat different in the composition ranges of 5 to 20 at% B and 22.5 at% to 30 at% B.
Domain Structure and Thermal Dependence of the Coercive Field in Nanocrystalline FeZrBCu
Authors: Hernando A. , Arcas J. 
Published: April 2011

AbstractNanocrystalline Fe85Zr7B6Cu2 and Fe87.2Zr7.4B4.3Cu1.1 (at. %) samples have been obtained by annealing Melt-spun ribbons for 1hr at various temperatures in the range 593K to 953K. Structural characterization by means of X-ray diffraction and thermomagnetic analyses reveal the manifestations of Fe nanocrystals embedded in an amorphous matrix. The coercive field has been measured by a Förster coercimeter at temperatures ranging between 50 K and 300 K, and the room temperature domain structure has been monitored by magneto-optical Kerr effect. Both, the as cast as well as the sample annealed above 813K display soft magnetic properties at room temperature, exhibiting a coercive field below 10 A/m, and wide regular domains. In contrast, the samples annealed at 750 K, corresponding to the beginning of the crystallization process, undergo a magnetic hardening, showing higher coercive fields (up to 150 A/m for Fe87.2Zr7.4B4.3Cu1.1) and a dull domain pattern. When these magnetically harder samples are cooled, their coercivity is reduced. Thus, the magnetic hardening is attributed to the exchange decoupling between crystallites, due to the proximity of the Curie temperature of the amorphous phase.
Transmission Electron Microscopy Investigations of an As-Processed Yttria-Stablilized zirconia on Platinum Aluminide Bond Coat
Authors: Yang Judith C. , Nuhfer Noel T. 
Published: April 2011

ABSTRACTWe examined an as-processed yttria-stabilized zirconia (YSZ) on platinum aluminide bond coat (BC), produced by electron beam physical vapor deposition, with transmission electron microscopy, including energy dispersive X-ray spectroscopy and hollow-cone diffraction. Columnar α-Al2O3 grains (∼100nm) formed at the interface between the BC and YSZ. A thin intermix (∼50nm) region was observed between the α-Al2O3 and YSZ. Hollow cone diffraction showed that the α-Al2O3 grains and the small-grained (∼10nm) YSZ near the α-Al2O3 are randomly oriented, without preferential texturing. No evidence of spinel formation was noted.
Recent Advances in Development and Processing of Titanium Aluminide Alloys
Authors: Appel Fritz , Clemens Helmut , Oehring Michael 
Published: April 2011

ABSTRACTIntermetallic titanium aluminides are one of the few classes of emerging materials that have the potential to be used in demanding high-temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel-base superalloys currently in use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. Some of these concerns are addressed in the present paper through specific comments on the physical metallurgy and technology of gamma TiAl-base alloys. Particular emphasis is placed on recent developments of TiAl alloys with enhanced high-temperature capability.
Refinement of Crystallographic Parameters in Refractory Metal Disilicides
Authors: Tanaka K. , Nawata K. , Inui H. , Yamaguchi M. , Koiwa M. 
Published: April 2011

ABSTRACTThe crystallographic structures of seven refractory metal (Ti, V, Cr, Nb, Mo, Ta and W) disilicides with the C11b, C40 and C54 structures have been refined through analysis of single-crystal X-ray diffraction data. Crystallographic parameters refined are lattice constants, atomic parameters and the space group of the C40 disilicides. In most of previous studies, silicon atoms have been considered to locate at the ideal positions so that the refractory metal atoms are perfectly six-fold coordinated in RSi2 layers prevailing in all the three structures. The present analysis shows that the silicon atoms are displaced from the ideal positions. The magnitude of such displacement is found to be closely related to the interatomic distance in these pseudo-hexagonally arranged RSi2 layers. The space group of three of the four C40 disilicides, VSi2, CrSi2 and TaSi2, is determined to be P6422, which is of chirality with respect to that (P6222) assigned in the previous studies.
Effect of E21-Fe3AlC Precipitation on Mechanical Properties of γ -Austenite Stabilized by Addition of Mn and Co
Authors: Miura Seiji , Ishii Hiroaki , Mohri Tetsuo 
Published: April 2011

ABSTRACTEffects of Co addition on the phase relation and mechanical properties of an E21-Fe3AlC phase in the Fe-Mn-Al-C system are investigated. The relation between the γ-austenite and E21 phases is the same with Co-free alloys. Two kinds of precipitation processes of E21 phase from γ-austenite matrix are observed: a fine E21 phase precipitation and a cellular structure formation from grain boundaries. The cellular structure formation is explained in relation to the lattice mismatch evaluated by XRD.The lattice mismatch is estimated to be ∼3%, rather higher than that of γ/γ′ in Ni-based superalloys, and the volume fraction of the E21-Fe3AlC phase precipitated in the γ-austenite phase is as large as 30%. The micro-vickers hardness increases with increasing Al or C, caused by the increase in the volume fraction of the E21-Fe3AlC phase.