bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wear and Adhesion of thin Carbon Coatings
Authors: Wang Hsin-Fu , Nelson John C. , Lin Chien-Li , Hoehn Joel W. , Gerberich William W. 
Published: April 2011

AbstractThe ability of a hard coating to resist delamination in wear applications is found to depend on the substrate crystal orientation. A variety of alloys with and without a carbon coating were tested by microscratching with a diamond stylus. The hardness of the carbon coating was characterized by nanoindentation techniques before the microscratch tests. As the diamond passed from one crystal to another differing amounts of damage were observed for each crystal orientation. The width of the delaminated region was found to be dependent on the extent of the slip line fields in the substrate generated by the scratching. To eliminate the possibility of differing adhesion on different crystal faces, a nickel aluminide intermetallic with the two crystals rotated about the same pole was tested. In the uncoated state when scratched across the grain boundary the slip line fields were extensive for one crystal but limited for the other crystal. Similar fixed-load scratches on the carbon coating produced delamination on the easy slip orientation but only a slight deformation of the coating on the other crystal. The observed failure appears to be due to the deformation of the substrate and not inferior adhesion of the coating to the crystal face. This finding should have important ramifications in the design and failure analysis of systems, such as magnetic recording media, medical implants, etc.
Thin Film Adhesion Characterization by Microwedge Scratching of Precracked Fine Lines
Authors: de Boer M. P. , Huang H. , Gerberich W. W. 
Published: April 2011

AbstractA new procedure for obtaining accurate work of adhesion values for stiff films as thin as 0.5 µm or less is presented in this paper. The technique is based on fabrication of a two-dimensional test structure using a photolithographic alignment sequence. With precracks of variable length at the end of a fine line, a well known stress state is imposed before delamination. The test structure allows simple analytical equations to be applied to approximate the strain energy release rate, G. Finite element method is used to obtain more accurate values of G as well as of mode mixity. For short crack lengths, no buckling occurs, and the phase angle is near mode II. Kinking into the glass substrate is observed when the measured critical strain energy release rate, Gc, is greater than glass, but not when Gc is less than glass. When the precrack is lengthened, buckling may occur before delamination. In this case the phase angle has a large mode I component, and the crack remains in the interface even in the case of the strong interface.
Nonhydrostatic Stress Effects on Solid Phase Epitaxial Growth in Silicon
Authors: Carter William B. , Aziz Michael J. 
Published: April 2011

AbstractThe dependence of solid phase epitaxial growth in Si on uniaxial compression applied perpendicular to the amorphous-crystal interface is investigated. Long, thin pure Si bars of square cross section are ion-implanted to produce amorphous layers on the end faces. The bars are placed end-to-end and uniaxially loaded at temperature to partially regrow the amorphous layers. The resulting growth rates are measured ex situ by re-heating the samples on a hot stage and using time-resolved reflectivity to deduce interface depths. Preliminary results are that uniaxial compression is more effective than hydrostatic pressure for enhancing the growth rate, in qualitative but not quantitative agreement with previously made predictions.
Xps Study of Ni-Fe Manganite Thermistor Material
Authors: Braski D. N. , Osborne N. R. , Zurbuchen J. M. 
Published: April 2011

AbstractThe resistivity of the as-fabricated thermistor material, nickel-iron-manganite, changes during initial aging in the temperature range of 150-300ºC before becoming stable.X-ray photoelectron spectroscopy (XPS) was used to determine if any valency change or chemical shift of the cations or oxygen occurred during aging. The goal of the study was to identify any ionic changes that might affect thermistor stability. The only observed changes in 2p3/2 peaks due to aging were those related to Ni ions; the same peaks for Mn, Fe, and the 0-Is peak were unchanged. The changes in the Ni 2p3/2 peak may possibly be related to: (a) the migration of Ni2+ ions from octahedral to tetrahedral sites, (b) subtle changes in the energy states of Ni2+ which promoted a more stable ionic structure, or (c) the presence of Ni3+ ions, some of which revert to Ni2s+.
Compatibility of BaTiO3 and SrTiO3 with Shape Memory Alloy TiNi
Authors: Mercado Peter G. , Jardine A.Peter 
Published: April 2011

AbstractThin film layers of shape memory alloys and ferroelectric ceramics can produce a family of ‘smart’ heterostructures capable of performing both sensing and actuating functions. The compatibility of sol-gel processed BaTiO3 (BTO) and SrTiO3 (STO) thin films with shape memory effect TiNi substrates were investigated. Important issues in the synthesis of these active structures are the ability to generate the appropriate crystalline phases of each material while producing defect-free homogeneous high quality films.
Porous TiNi Synthesis from Elemental Powders
Authors: Hey Janet C. , Jardine A. Peter 
Published: April 2011

AbstractThe shape memory alloy TiNi is produced by either Vacuum Induction Melting (VIM) or by Vacuum Arc Remelting (VAR) of pure metal ingots for actuator applications. Powder metallurgy techniques provide an alternative fabrication route for their use in passive damping applications where porosity and deviations in chemical homogeneity can be tolerated. In this study TiNi compacts were cold pressed from the blended elemental powders and sintered in vacuum for varying times at temperatures from 800°C to 1000°C. Two heating rates were used, 5 K/min. and 10 K/min. A TiNi microstructure could be produced after annealing at 1000°C for 6 h., although some TiNi3 was still observed. Sintering above 900°C produced porous microstructures with green densities approaching 3.5 gm/cm3.
The Dynamics of SAW Streaming and its Application to Fluid Devices
Authors: Shiokawa Showko , Matsui Yoshikazu 
Published: April 2011

AbstractVarious liquid motions such as streaming and droplet formation on the surface of surface acoustic wave (SAW) propagating substrate are called SAW streaming. In this paper, the liquid dynamic motions excited by the SAW fabricated on 128° rot. Y-X LiNb03 at the frequency of 50 MHz with various pulse widths are demonstrated. The SAW streaming system are also tested for use as a micropump. Theoretically, SAW streaming force can be derived based on the acoustic streaming theory. The calculated SAW streaming force is found to be very large and strong enough to expel a droplet from a liquid surface.Nonlinear behavior in a water drop vibration induced by the SAW streaming force is also experimentally investigated as a model of inverse bubble oscillation. We succeed in detecting the transformation of the water drop vibration with a single pulse frequency spectrum to 1/2 and its harmonics.
The Effects of Processing Variables on Reaction Synthesis of Fe-A1 Alloys
Authors: Joslin D. L. , Easton D. S. , Liu C. T. , David S. A. 
Published: April 2011

AbstractThe effects of alloy composition and reaction atmosphere on reaction synthesis of binary Fe-Al alloys were studied. Reactions were observed in an open (air) furnace, under static vacuum (in an evacuated quartz tube) and in a dynamic vacuum furnace. High-speed videotapes of reaction syntheses of compacts formed from 45-μm Fe and 10-μm Al powders reacted in air and under static vacuum revealed that an unusual “two-stage” reaction exists in this system under these conditions. The first stage of the two-stage reaction lasts several seconds and starts at around 650°C. The second stage begins at about 900°C, reaching temperatures between 1250 and 1350°C. The progress of the reaction to the second stage is sensitive to the alloy composition and reaction environment. The reaction behavior is explained in terms of thermodynamics and heat transfer, which control the delicate balance between heat accumulation and heat loss during reaction synthesis.
High Temperature Mechanical Behavior of Nb5Si3/Nb Laminates
Authors: Provancher William , Ghosh Amit K. 
Published: April 2011

AbstractTwo phase alloys based on the intermetallic system Nb5Si3/Nb system provide potentially superior combination of strength and toughness over their monolithic counterparts at high temperatures. To gain fundamental knowledge of the mechanical behavior of these materials, initial focus has been on the mechanical behavior of Nb5Si3/Nb laminates and composites at elevated temperatures. In this study, laminates have been fabricated at 32 at% Si with Nb, and a total laminate thickness of 2.1mm. Tests are being conducted on notched and unnotched tensile specimens. The unnotched specimens provide the overall strength and ductility of the laminate and a basis for comparison with notched specimens which provide information on crack propagation and ductile phase toughening effects. Results from samples with a variety of laminate spacings are being explored, and preliminary data will be presented.
Chemisorption of Moisture-Induced Hydrogen and the Embrittlement Effects in Transition Metal Aluminides
Authors: Wang Jian-Sheng 
Published: April 2011

AbstractBased on simple thermodynamic models free energies of chemisorption of water vapor in transition metal aluminides and enthalpies and entropies of formation of solid solutions of hydrogen in the aluminides are derived. Susceptibilities of the aluminides to moisture-induced embrittlement are evaluated with these thermodynamic properties and compared with the susceptibilities to hydrogen-induced embrittlement.
Deformation of C15 Laves Phase Alloys
Authors: Chu F. , Pope D.P 
Published: April 2011

AbstractDetails of the structure and previous work on the deformation of C15 Laves phases are reviewed. The phase diagram of the Hf-V-Nb system, some metallurgical and physical properties, mechanical behavior, and the deformation mechanisms of HfV2+Nb (C15 HfV2+Nb and V-rich bcc solution) are presented based on our previous work. Theoretical approaches to understanding the results of these studies are discussed.
Dislocation Dynamics and Yield Stress Anomalies in Intermetallic Alloys
Authors: Caillard Daniel 
Published: April 2011

AbstractMany intermetallic alloys with L12, L10and BCC related structures exhibit yield-stress anomalies, which have strong influence on their mechanical properties at intermediate temperatures. A short review is made of the anomalous glide systems in various intermetallics. They are shown to exhibit several common characteristics, which allow it to classify them into three groups with possibly similar dislocation mechanisms. In the second half, the well-known case of octahedral glide in Ni3Al is considered again, and a new model is proposed, based on the formation and the unlocking process of incomplete Kear-Wilsdorf locks by a double cross-slip mechanism. This model is supported by several microscopic and macroscopic observations including “in situ” straining experiments in a TEM. It accounts for the positive temperature dependence of the yield-stress with fairly good orders-of-magnitude estimates of the stress. It also explains satisfactorily the small stress-strain rate sensitivity and the transient effects.
Reaction Process of αəγ Massive Transformation in Ti-Rich TiAl Alloy
Authors: Kumagai T. , Abe E. , Takeyama M. , Nakamura M. 
Published: April 2011

AbstractReaction sequence of the massive transformation from the high-temperature α-Ti phase to the γ-TiAl phase (αm) in a Ti-48at.% Al alloy has been examined in terms of optical and transmission electron microscopes. Both transformed and untransformed regions were macroscopically observed in the sample quenched from the high-temperature α phase field, when the sample was held there for a extended period of time prior to quenching. The transformed region consists of randomly oriented fine α single phase grains, in which many thermal anti-phase domains (TAPDs), together with a number of stacking faults were observed. In contrast, the untransformed region comprises extremely fine lamellae of the α and α2-Ti3Al phases, and the α plates were found to run through the TAPDs caused by α ə α2 ordering. Subsequent aging at 1273K causes the microstructure change in the untransformed region from α2/γ lamellae to γ/γ lamellae spontaneously and expands the γm region. These observations suggest that the α ə γm transformation proceeds through formation of fine γ plates.
1200 K Compressive Properties of N-Containing Nial
Authors: Whittenberger J. Daniel , Noebe R. D. , Wheeler D. R. 
Published: April 2011

AbstractAs part of a series of experiments to understand the role of N on the strength of NiAl, a heat of NiAl was enriched with N by melting and atomization to powder in a nitrogen atmosphere. Following consolidation of the powder by hot extrusion, 1200 K compressive properties were measured in air. Within the range of strain rates examined, 10−3 to 10−9 s−1, the strength of the N-enriched NiAl was greater than that of a simple 15 µm grain size polycrystalline, binary NiAl alloy. For the most part the overall improvement in strength is ascribed to the fine grain size of the N-doped NiAl rather than the alloy chemistry; however, the alloy displayed a complex behavior exhibiting both weakening effects as well as strengthening ones.
Gamma Titanium Aluminide Alloys
Authors: Yamaguchi M. , Inui H. , Kishida K. , Matsumoro M. , Shirai Y. 
Published: April 2011

AbstractExtensive progress and improvements have been made in the science and technology of gamma titanium aluminide alloys within the last decade. In particular, our understanding of their microstructural characteristics and property/microstructurc relationships has been substantially deepened. Based on these achievements, various engineering two-phase gamma alloys have been developed and their mechanical and chemical properties have been assessed. Aircraft and automotive industries arc pursuing their introduction for various structural components. At the same time, recent basic studies on the mechanical properties of two-phase gamma alloys, in particular with a controlled lamellar structure have provided a considerable amount of fundamental information on the deformation and fracture mechanisms of the two-phase gamma alloys. The results of such basic studies are incorporated in the recent alloy and microstructure design of two-phase gamma alloys. In this paper, such recent advances in the research and development of the two-phase gamma alloys and industrial involvement are summarized.
Strain Hardening by High Density SISFs During Low Cycle Fatigue in Ni3(Al,Zr) Single Crystal
Authors: Gu Yuefeng , Liu Yi , Guo Jianting , Lin Dongliang 
Published: April 2011

AbstractStress response and its correlation with dislocation substructures in Ni3(Al,Zr) single crystal fatigued at room temperature have been studied. Cyclic strain hardening was found to be asymmetric and increased with increasing applied cyclic strain. Transmission Electron Microscope (TEM) observation showed that there are a profusion superlattic intrinsic stacking faults (SISFs) in fatigued Ni3(Al,Zr) single crystal samples. The cyclic strain hardening and stress asymmetry are explained by the movement of the SISF.
In-SituHeating Observations on Superlattice Dislocation in A Ni3(Al, Zr) Single Crystal
Authors: Liu Yi , Gu Yuefeng , Lin Dongliang , Chen Shipu , Zhao Xiaoning , Hong Jianming 
Published: April 2011

AbstractThe TEM weak-beam technique has been used to investigate the behavior of dissociated superlattice dislocation in Ni3Al single crystal as a function of temperature. The observed dislocation with the Burgers vector of [110] partly dissociated on the (001) plane forming Kear-Wilsdorf (KW) lock. The dissociated pair did not indicate significant variation of separation in the temperature range from room temperature to 773K. but turned to form a jog at 773K. At 898K, which is near the peak temperature, the dissociated segment constricted completely. The experimental observations are discussed.
Formation and Growth of Antiphase Domains During Recrystallization of Cold-Rolled Cu3Au
Authors: Yang Rui , Cahn Robert W. 
Published: April 2011

AbstractAn experimental study by TEM was made of the morphology of the antiphase domains formed when heavily rolled Q13AU is annealed at a temperature slightly below the critical temperature for ordering, Tc. Domains are formed at the advancing grain boundary with extremely small size and grow as recrystallization proceeds. From an early stage, domain walls show a preference for (100) orientation. The key question is raised whether domain formation during recrystallization entails the presence of a disordered zone at a moving grain boundary near Tc, and the conclusion is that such a zone is probably present. A provisional theory is constructed for the genesis of domains during recrystallization, taking into account the dragging force which newly formed domains exert on a moving grain boundary thereby diminishing the effective driving force for grain boundary motion, and a critical domain size is estimated which should completely inhibit grain-boundary motion. The intriguing fact that no domains at all are formed during the recrystallization of strongly ordered intermetallics such as Ni3Al is briefly discussed and a reason is proposed.
Determination of Site-Occupancies in Aluminide Intermetallics by Alchemi
Authors: Anderson I. M. , Duncan A. J. , Bentley J. 
Published: April 2011

AbstractThe site-distributions of Fe in four B2-ordered NiAl-based alloys with Fe concentrations of 10%, 2%, and 0.5% have been determined by ALCHEMI (atom-location by channeling-enhanced microanalysis). Site-distributions have been extracted with standard errors between ∼1.5% (10% Fe concentration) and ∼6% (0.5% Fe concentration). The results show that Fe has no strong site-preference in NiAl and tends to reside on the site of the stoichiometrically deficient host element.An improved ALCHEMI analysis procedure is outlined. The analysis explicidy addresses the phenomenon of ionization delocalization, which previously complicated the determination of site-distributions in aluminide intermetallics, leading to inaccurate and oftentimes nonphysical results. The improved ALCHEMI analysis also addresses the presence of anti-site defects. The data acquisition conditions have been optimized to minimize the sources of statistical and systematic error. This optimized procedure should be suitable for all analyses of B2-ordered alloys. Several analyses at different channeling orientations show that the extracted site-occupancies are robust as long as the data are acquired at orientations that are remote from any major pole of the crystal.
Normal and Anomalous Yield Stresses in a Tial Single Crystal and the Dominating Dislocation Mechanisms.
Authors: Bird N. , Taylor G. , Sun Y. Q. 
Published: April 2011

AbstractSingle crystal γ-TiAl with axial orientation [3 16 15] has been tested in compression between 4K and 1048K and the dislocation structures observed in TEM. The slip plane was found to be (111) over the entire temperature range tested. Three regimes exist in the variation of the yield stress with temperature, whereas the dislocation substructures are of two types, dominated by 30° 1/3[112] and 1/2 < 110] dislocations respectively. The anomalous yield stress is associated with 1/2 < 110] dislocations undergoing frequent cross-slip off the (111) plane.
Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B
Authors: Ezz S. S. , Sun Y. Q. , Hirsch P. B. 
Published: April 2011

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.
Dislocation Annihilation in L12 Alloys
Authors: Shi Xiaoli , Saada Georges , Lem Patrick VeyssiÈre 
Published: April 2011

AbstractA transmission electron microscope (TEM) study of dislocation reactions that take place during the first few percents of permanent strain at room temperature is presented. The nature of the dipolar segments, a noticeable feature within the deformation microstructure, is elucidated. It is determined that antiphase boundary (APB) tube formation is unlikely to stem from the annihilation between a mobile superdislocation and an immobilized Kear-Wilsdorf (KW) configuration, at variance from what has been expected so far. A clear relationship between APB tubes and superlattice stacking fault (SSF) dipoles is pointed out.
Temperature Dependence of Dislocation Mobility in Ni3Al
Authors: Nadgorny Edward M. , Iunin Yu. L. 
Published: April 2011

AbstractThe stress and temperature dependence of the dislocation velocity v(σ, T) has been studied experimentally in Ni3AI single crystals. The mobility of individual dislocations was measured by the stress pulse-etching technique at temperatures between 77 and 873 K at the resolved shear stresses between 25 and 150 MPa over a range of dislocation velocities from 3×l0−7 to 3×10−5 m/s. Fresh dislocations were introduced and revealed by a selective etchant on {001} surfaces of electropolished specimens annealed at 1473 K for 120 hours in argon. The specimens were deformed in three point bending around <110> bending axis at a constant temperature. The dislocation arrays moved in two acting <110> {111} primary glide systems. The motion occurred over a range of applied stresses close to the macroscopical yield stresses y The dislocation velocity decreased as temperature increased, in perfect analogy to the experimental data on y obtained before 1 on the same Ni3Al.. No detectable violation of the Schmid law was observed. The stress dependence of the dislocation velocity was rather steep resulting in a relatively large activation area of A=100-200b2. Such an activation area is greater than that one could expect in a kink-mode crystal with predominant Peierls mechanism for dislocation motion, although it is considerably less than A measured in other materials controlled by local obstacles.
Microstructure/Property Studies Supporting Development of Low Cost Processes for TiAl Automotive Valves
Authors: Jones P. E. , Porter W. J. , Keller M. M. , Eylon D. 
Published: April 2011

AbstractLightweight gamma titanium aluminide automotive valves may significantly improve engine performance and fuel economy. However, low cost mass production processes must be developed to realize these gains. Permanent mold casting processes and low cost heat treatments are being developed to enable commercial introduction of TiAl automotive valves. Microstructural development, tensile, creep, and high cycle fatigue properties of permanent mold Ti-47Al-2Nb-1.75Cr (at%) castings are compared with investment castings of similar size. A recommendation is made to use as-HIP castings for components not designed to damage tolerant criteria. This work was performed as part of a vertically integrated team effort to transfer aerospace TiAl technology to the automotive market.
Growth and Facet Orientations in Single-Phase TiAl Single Crystals
Authors: Mahapatra R. , Lin H. , Pope D. P. , Chou Y. T. 
Published: April 2011

AbstractSingle crystals of single-phase TiAl alloy (Ti-56 at. % Al) have been grown at lOmm/h solidification rate in an ASGAL FZ-SS35W Optical Floating Zone Furnace. The orientations of the resulting single crystals have been determined using the Laue X-ray diffraction, and Electron Backscattering Pattern (EBSP) methods. A correlation between orientations of the crystal growth and grown-in facets has been established.