bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis by Sims and by Eels-Edx in a Stem of Sic Fibers Reinforced Composites
Authors: Lancin M. , Anxionnaz F. , Schuhmacher M. , Duone O. , Trebbia P. 
Published: March 2011

ABSTRACTA series of Nicalon SiC fibers (202) coated by CVD with C and SiC were analysed by Secondary Ion Mass Spectrometry (SIMS). Results (i) give the composition of the material, (ii) show its heterogeneity of composition, and (iii) demonstrate the limit of application of the method for the fibers analyses. SIMS and Electron Energy Loss Spectroscopy (EELS) analyses of one coated fiber segment were done. When elements are detected by both techniques, reasonable agreement is observed between the results. SiC - CVD deposits are not uniform: they are rich in carbon close to the fiber and tend towards stoechiometry after a few microns. The coated fibers are rich in oxygen and in free carbon. Analyses of a glass-ceramic matrix/ Nicalon SiC fiber (202) composite were performed using SIMS, EELS and Energy Dispersive X-Ray Spectroscopy (EDX).
The Temperature Dependence of Yield Stress and Fracture Toughness in Unstabilized Zirconia Crystals
Authors: Coyle T. W. , Ingel R. P. , Willging P. A. 
Published: March 2011

ABSTRACTThe flexural strength and the single edge notch beam fracture toughness of undoped ZrO2 crystals, grown by the skull melting technique, were examined from room temperature to 1400°C. On heating the toughness increased with test temperature to a maximum of 4.0 MPajm at 1225°C then gradually decreased to 2.6 MPa/m. Upon cooling after a 20 minute hold at 1250°C an increase in toughness to 5 MPa/m was observed at 1200°C; upon cooling to lower temperatures Kic gradually diminished. The loaddeflection curves for the flexural strength tests showed marked nonlinearity before failure for samples tested on cooling. The temperature dependence of the apparent yield stress suggests that initial yielding occurs by slip above 1200°C but that from 1200°C to 1050°C the observed yielding is due to stress induced tetragonal to monoclinic transformation.
Comparison of the Thermal Stabilities of Amorphous Hydrides Formed by Zr-Based Metallic Glasses
Authors: Cantrell J. S. , Bowman R. C. 
Published: March 2011

AbstractDifferential scanning calorimetry (DSC) and x-ray diffraction (XRD) measurements were performed on a-Zr2 PdHx, a-Zr3 RhHx, a-Zr76 Fe24 Hx, and a- Zr2NiHx to assess the effects of hydrogen on their thermal stabilities. Only exothermic DSC peaks were observed for the hydrogen-free glasses and are shown to correspond to the formation of crystalline intermetallic phases. On the other hand, heating of the amorphous hydrides gives decomposition reactions with the generation of ZrHx (1.5 <x < 2.0) and either free metal (e.g., Rh) or a Zr-depleted intermetallic (e.g., ZrPd). With the exception of the Zr2 PdHx samples, hydrogenation significantly decreases the thermal stabilities (i.e., the exothermic transitions occur at lower temperatures in the amorphous hydrides). Endothermic peaks, which are associated with hydrogen evolution from the glass, are observed when the hydrogen-to-metal ratios approach unity.
Electrochemical Study of the Passivation and Passive Film Breakdown of Mg70 Zn30 Metallic Glass
Authors: Hagans Patrick L. 
Published: March 2011

AbstractAnodic dc polarization measurements of glassy Mg70 Zn30 in pH=9.3 boric-borate electrolyte with and without the presence of Cl− were used to study both passive film formation and breakdown. In the absence of C− a single, broad passivation peak is observed which is very similar to that found with triply distilled Mg except that the large increase in peak potential and reduction in peak current density indicates that a more stable film has formed on Mg70 Zn30. Also observed with Mg70 Zn30 but not with Mg, Zn or other different types of crystalline Mg alloys is a large, narrow peak in the transpassive region (i.e., the region where the passive film begins to break down and/or O2 evolution commences). This process of breakdown of the passive film and further oxidation of the base metal is totally irreversible and is almost completely missing on the second and subsequent voltage sweeps. Although speculative in nature, existing evidence suggests that a phase transition has occurred within the passive film itself. In the presence of Cl− this process does not occur as passive film breakdown is initiated via a pitting mechanism at a potential nearly 2.5 Volts more negative than the onset of O2 evolution. Nevertheless, the onset of pitting is still 0.4 Volts more positive than that found for Mg indicating again that a much more protective film has formed on Mg70 Zn30
Fatigue Corrosion of Amorphous Fe75-xCrxB15 Si10 Wires
Authors: Le Anh , Kabacoff Lawrence T. , Martinez Nancy Y. 
Published: March 2011

AbstractMeasurements have been made of the corrosion and fatigue properties of metallic glass wires of composition Fe75-xCrxB15Si10 (X = 5, 8, 11) in air, deionized water, 3.5 w/o NaCl and 1.0 N H2SO4. A clear inverse relationship was observed between the corrosion rate and the number of cycles to failure. Fatigue limits were observed for those cases where spontaneous passivation occurs (all compositions in air and deionized water, and 8 and 11 a/o Cr in chloride solution). It was found that the mechanism for the fatigue failure of specimens which spontaneously passivate differs from that of metallic glasses in an acidified chloride environment where active/passive behavior is observed. A model is proposed to explain this observation.
Confined Gas Atomization: The Role of the Melt Delivery Tube in Particle Size Control
Authors: Raman R. V. 
Published: March 2011

AbstractGas atomization is one of the key processes used for the production of rapidly solidified materials. The unique feature of the gas atomization process is its capability to form spherical powders of multicomponent alloys containing reactive elements. Spherically shaped powder is specified in the secondary processing operations used in a number of applications. This requirement has resulted from the higher flow rate, better packing density, and lower surface area obtained in spherical particles compared to irregularly shaped particles.
Stabilization of Metallic Glasses by Irradiation with Picosecond Laser Pulses.
Authors: Radliński A. P. , Calka A. , Davies B. Luther 
Published: March 2011

IntroductionGlassy metallic alloys are usually formed by bringing a small amount of the melt mechanically into good thermal contact with a heat conducting medium. Cooling rates of the order of 106K/sec can thereby be obtained. Despite the extensive use of laser treatment in many areas of technology the idea of using ultra short laser pulses to increase the cooling rate by many orders of magnitude is relatively new. The rates obtainable in metals as a result of laser irradiation have been estimated to be of the order of 1010 K/sec (for nanosecond laser pulses) in the critical temperature region of high nucleation rate and low viscosity. Some less sophisticated estimates for laser annealing of silicon with picosecond pulses yield values of 1012 – 1013 K/sec.. The recent measurements of the surface colour temperature in laser irradiated metals suggest cooling rates of the order of 1010K/sec in both nanosecond and picosecond regimes.
Nucleation During the Solidification of Atomized Droplets Catalyzed by Spherically-Shaped Oxide Particles
Authors: Libera Matthew R. , Olson Gregory B. , Sande John B. Vander 
Published: March 2011

AbstractNucleation temperatures are calculated for the case of solidification in atomized metal droplets where spherical substrate particles act as nucleation catalysts. Following the method of Fletcher, the effect of substrate size on catalytic potency is illustrated, and the model is applied to the nucleation of bcc solid from pure, liquid iron containing oxide substrate particles as catalysts. Supercooling data from the literature are used to determine wetting angles for alumina, silica, and rare-earth oxide. Oxide particle-size distributions are then used to predict the supercooling behavior of atomized liquid droplets based on the probability that a given size of droplet will contain a particular size of substrate particle. A transition size regime is found separating droplet sizes undergoing very small and very large supercoolings, respectively. This is discussed in terms of the types and number densities of inclusions present during atomization of the melt.
Nonequilibrium Interface Kinetics During Rapid Solidification
Authors: Aziz Michael J. 
Published: March 2011

AbstratThe deviations from local equilibrium at a rapidly moving solid-liquid interface are well documented. The fraction of solute atoms in the liquid at the interface that joins the crystal during rapid solidification approaches unity and the interface temperature drops. Experimental and theoretical work on impurity incorporation and interfacial undercooling is reviewed. Past and future experiments to test the theories are discussed.
Grain Growth Behavior of a Rapidly Solidified Fe-10Cr-8A1 Alloy
Authors: Maloney M. J. , Garratt-Reed A. J. , Yurek G. J. 
Published: March 2011

AbstractA rapidly solidified Fe-10Cr-8Al alloy that contained a dispersion of very fine MnS and Al203 particles was produced by a gas atomization/twin-roll quenching technique. The RS particulates were consolidated by hot isostatic pressing, and the consolidated alloy was hot forged, and then hot and cold rolled. Grain growth took place during primary recrystallization of the alloy; however, once primary recrystallization was complete, the dispersion of second phase particles was effective in pinning alloy grain boundaries.
Microstructure of Metastable Metallic Alloy Films Produced by Laser Breakdown Chemical Vapor Deposition and Ion Implantation
Authors: Henon S. K. , Jervis T. R. , Nastasi M. 
Published: March 2011

AbstractThin films produced by laser breakdown chemical vapor deposition from nickel and iron carbonyls and by implanting Ni foils with varying levels of C have been characterizea by transmission electron microscopy. Decomposition of Ni(CO)4 produces polycrystalline films of fcc Ni and metastable ordered nexaogonal Ni3C. This metastable phase is identical to that produced by gas carburization, rapid solidification of Ni-C melts, and ion implantation ot C into Ni at low;co ncentrations. Increasing the H2 content in the gas mixture during laser deposition reduces the grain size of the films significantly witn grain sizes smaller than 10 nanometers produced. Laser uecomposition of Fe(CO)5 produces films with islands of fcc gamma-Fe and finely dispersed metastable Fe3C (Cementite). In addition, the ferrous oxides Fe2O3 and Fe3O4 were found in these samples. Implants of C into pure Ni foils at 77°K and at a concentration of 35 at.% produced amorphous layers. Implants at the same dose at room temperature did not proouce amorphous layers.
Microstructure & Phase Transformation in Rapidly Solidified V-Ga Alloys
Authors: Park M. W. , Whang S. H. , Karmarkar S. , Divecha D. 
Published: March 2011

AbstractThe A15 Phase forming V-Ga alloys were processed into ribbons and foils by rapid solidification techniques. Microstructures and phase transformation in these alloys by rapid solidification and succeeding heat treatment were investigated by x-ray diffraction and TEM. It is shown that equilibrium A15 phases can readily be suppressed by rapid quenching in these alloys. A significant grain refinement resulting from the rapid solidification also was observed. Microhardnesses of these alloys as a function of Ga concentration were determined.
Microstructure of Rapidly Solidified W-Ni Alloys
Authors: Vujic Dinko , Whang Sung H. , Cytron Sheldon 
Published: March 2011

AbstractBinary W-Ni alloys of four different compositions were rapidly quenched into thin foils. Microstructures and hardnesses of the as-quenched alloys were studied by TEM and hardness measurements. The results from the microstructural study show that the W grains and particles undergo extensive refinement and that the grain size is much smaller than that obtained in conventional alloys. In addition, the formation of WNi and W2Ni, the low melting temperature intermetallic compounds in the W-Ni system, was readily suppressed by rapid quenching. The hardness increase in rapidly solidified W-Ni alloys appears to have originated from the microstructural refinement.
Microstructure and Wear Behavior of Laser Processed Co-Cr-W/Steel Surface Alloys
Authors: Xiaoping Jiang , Zhuangqi Hu , Yunlong Ge , Ming Jiang , Changxu Shih 
Published: March 2011

AbstractSurface alloys with various compositions of Co, Cr and W on 20CrMo steel have been processed by controlling the ratio of thickness of plasma sprayed Co-Cr-W coating to laser melting depth. A formula has been suggested to evaluate the contents of surface alloying elements. With increasing the contents of Co, Cr and W in the surface alloy system, two hardness peaks occur at about 17Co7Cr3W and 52Co22CrgW corresponding to microstructure of M and γ-Co + M23C6 respectively. Wear experiments in media of air, 1N H2SO4 and 1% NaCl indicate that 17Co7Cr3W surface alloy has higher wear resistance in air, while 52Co22Cr9W better in the corrosive media under high load. In any case, wear resistance of the above two surface alloys are much better than that of plasma sprayed coating of Co-Cr-W.
Melt-Spun Permanent Magnet Alloy with Enhanced Isotropic Remanence
Authors: Kadin A. M. , McCallum R. W. , Clemente G. B. , Keem J. E. 
Published: March 2011

AbstractRapid solidification onto a copper quench surface (melt-spinning) has been used to fabricate a high-performance permanent magnet alloy (Ovonic Hi-Rem™) based on the Nd-Fe-B class of materials. Crucial idditions of alloying elements are combined with careful control over quench parameters to yield a random assembly of microcrystallites, with macrosconically isotropic magnetic properties including values of remanent induction that can exceed 10 kG and maximum energy products greater than 20 MGOe. These values exceed those expected from conventional randomly oriented magnets. The enhanced magnetic performance is related to results of x-ray diffraction and electron microscopy.
Magnetic Percolation in New Crystalline FCC Fe-Cu Alloys
Authors: Chien C. L. , Liou S. H. , Xiao Gang , Gatzke M. A. 
Published: March 2011

AbstractMagnetic percolation has rarely been realized in Fe-based binary alloys either because Fe does not retain its moment in the dilute limit or because the solubility is too low. By using a vapor quenching method, which in our case is highrate sputtering, we have succeeded in making new metastable crystalline alloys of fcc FexCu1−x which do not appear in the equilibrium phase diagram. These alloys spanning the percolation threshold allow magnetic percolation phenomena on an fcc lattice to be observed by SQUID magnetometry and Mössbauer spectroscopy. Above xc, the magnetic ordering temperature varies as (x−xc)γ with xc = 0.185 and γ = 0.63. Below xc, spin glass ordering has been observed.
Reversible Structural Relaxation in Fe-Ni-B-Si Metallic Glasses
Authors: Brüning R. , Altounian Z. , Ström-Olsen J. O. 
Published: March 2011

AbstractReversible structural relaxation has been studied in (Fe1-xNix)80B10Si10 by differential scanning calorimetry and X-ray diffraction. It is found that surface crystallization plays a major role in inhibiting reversibility. In consequence previously published data have presented a misleading picture about the composition dependence of the reversible effect in Fe-Ni-B-Si, which simply increases monotonically with Ni composition. There is no evidence that chemical short range order plays any role in reversibility.
Comparison of Miogtiwiures and Magnetic Properties of Melt Spun and Plasmla Sprayed Alloys of Fe-Rare Earti-B
Authors: Anderson C. D. , Overfelt R. A. , Flanagan W. F. 
Published: March 2011

AbstractSamples of Fe76RE16B8 have been prepared by melt spinning and plasma deposition. The samples were fully saturated by cooling fran 350°C in a 5 kOe field. The room temperature coercivities of these samples are reported and correlated to the microstructures revealed by scanning electron microscopy. Subsequent heat treatments are shown to either increase or decrease the intrinsic coercivities depending upon the solidification rate that each sample experienced.
Structural Relaxation and Interdiffusion in Amorphous Fe-Ti Compositionally Modulated Films
Authors: Chason Eric H. , Mizoguchi Tadashi 
Published: March 2011

AbstractInterdiffusion and structural relaxation in amorphous compositionally modulated films of Fe-Ti have been measured simultaneously. Interdiffusivity is determined by the change in X-ray modulation peak intensity upon annealing and structural relaxation is determined by the shift in X-ray peak position corresponding to the densification. The relaxation kinetics of the densification are explained by the free volume model of structural relaxation. The relaxation kinetics of the inverse diffusivity are shown to be the same as for viscosity relaxation.
Deformation-Induced Amorphization of Crystalline Particles in a Cu-Ti Metallic Glass
Authors: Kamenetzky Eduardo A. , Asikenazy Philip D. , Tanner Lee E. , Johnson William L. 
Published: March 2011

AbstractCrystalline particles and grains embedded in Cu35Ti65 glass ribbons have been amorphized by isothermal cold rolling. The structural evolution has been studied by X-ray diffraction and TEM techniques. Initial particle morphologies are spherulitic and spherical, the latter with sizes ranging between 10 and 100 nm. The new amorphous phase seems to nucleate at crystalline-amorphous matrix interfaces. Initially there is a well defined interface between the new and the existing amorphous phases but it disappears as rolling progresses. Crystallites on a nanoscale still present in the final stages of particle amorphization have been observed by convergent beam electron diffraction. After sufficient deformation the consolidated ribbon becomes completely glassy. A morphological description of the transformation process in terms of crystal destabilization and solid-state particle melting is presented.
Kinetics and Mechanisms of Formation of Al-Ni Intermetallics
Authors: Patchett J. A. , Abbaschian G. J. 
Published: March 2011

AbstractThe effects of cooling rate and composition on the nucleation and growth kinetics of NiAl, Ni2Al3, and NiAl3 intermetallics were studied for alloys containing 25 and 31.5 ht.% Ni. Fgr the former composition, the peritectic regction Ni Al + Liquid → NiAl3 was studied over cooling rates from 20 to 105 K/s. For the latter composhtion, the reaction NiAl + Liquid → Ni2Al3 was studied at cooling rates ranging form 10 to 600 K/sec. The amounis of constituent phases are shown to depend on the cooling rate, and for the peritectic phases, on the surface area of the primary phase. The nucleation of Ni2Al3 and NiAl3, and the ordering of the aluminum-rich NiAl were also examines uding trans ission electron microscopy. Cooling the NiAl + liquid below the peritectic temperature results in a metastable extension of NiAl with a high dislocation and stacking fault density, followed by the epitaxial nucleation and almost dislocation-free growth of Ni2Al3 In contrast, the nucleation of the NiAl3 on Ni2Al3 occurs directly witgoud the formationof an intermediate region.
Long—Range Ordering in Rapidly Quenched Llo TiAl Compound Alloys
Authors: Whang S.H. , Li Z.X. , Vujic D. 
Published: March 2011

AbstractRapid solidification has an effect on lattice parameters and long&range order parameter in L1o TiAl compound alloys. In these compounds rapid quenching from the liquid state significantly decreases the long—range order parameter while the tetragonal distortion c/a decreases as a result of rapid quenching. The lattice parameter change due to rapid quenching becomes pronounced with increasing aluminum concentration beyond the stoichiometric alloy composition. The recovery from the disordered state and the relaxation from the tetragonal distortion were found to be two different kinetic processes.The long—range ordering requires low temperature and long annealing time in comparison with high temperature and short annealing time for the recovery of the tetragonal distortion.
Two—Phase Nickel Aurunides
Authors: Khadkikar P. S. , Veduia K. , Shabel B. S. 
Published: March 2011

AbstractThe as—extruded microstructures of two alloys in the two phase field consisting of Ni3Al and NiAl in the Ni—Al phase diagram exhibit fibrous morphologyand consist of Ll2 Ni3Al and B2 NiAl. These as—extruded microstructures can be modified dramatically by suitable heat treatments. Martensite plus NiAl or martensite plus Ni3Al microstructures are obtained upon quenching from1523 K. Aging of martensite at 873 K results in the recently identified phase Ni5Al3 whereas aging at 1123 K reverts the microstructures to Ni Al plui NAl. The microstructures with predominantly martensite or Ni5Al3 phases are brittle in tension at room temperature. The latter microstructure does not deformplastically even in compression at room temperature. However, some promise of room temperature tensile ductility is indicated by the Ni3Al plus NiAl phase mixtures.
Creep in Ternary B2 Aluminides and Other Intermetallic Phases
Authors: Jung I. , Rudy M. , Sauthoff G. 
Published: March 2011

AbstractThis paper examines the possibilities for obtaining a high creep resistance in intermetallic phases. In a first section, the creep mechanisms are discussed with respect to the effects of stress, temperature and composition in the light of recent experimental results on the creep behaviour of the B2 phase (Fe,Ni) Al between 650 °C and 1100 °C. The familiar models for describing the creep of conventional disordered alloys apply to intermetallic phases, too, and describe the observed behaviour in a quantitative way. In the second section the creep of various ordered bcc phases - (Fe,Ni)Al and (Co,Ni)Al with B2 structure and the Heusler-type Ni2AlTi with L21structure - and ordered fcc phases - Ni3Al with L12structure, Fe3AlC and Ni3AlC with E21structure and NbAl3with DO22structure - are examined. Large increases in creep strength are possible by the transition to phases with more complex structures as well as by appropriate alloying. Much further work is necessary for making more reliable predictions on the obtainable creep strengths.
Antiphase Domains, Disordered Films and the Ductility of Ordered Alloys Based on Ni3Ai
Authors: Cahn R. W. 
Published: March 2011

AbstractIn elements and intermetallic compounds alike, tensile ductility is favoured by a small spacing of obstacles to dislocation movement, whether these obstacles be grain boundaries or other structural features. The evidence for this generalisation is reviewed.Antiphase domains (APD) form only when Tt is below the freezing temperature, Tf: this isa rule which has not hitherto been recognized. In Ni-Al, Tt < Tf when the Al content is less than ≈23.5at.%. APD's can serve as heterogeneous nuclei where films of disordered (γ) phase deposit. Domains, especially if decorated by γ films, are associated with enhanced ductility, and there is circumstantial evidence that the ductility is indeed caused by these microstructural features.