bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strength and Toughness of MG-PSZ and Y-TZP Materials at Cyrogenic Temperatures
Authors: Veitch S. , Marmach M. , Swain M. V. 
Published: March 2011

ABSTRACTThe influence of temperature between R.T. and liquid nitrogen (−196°C) on the strength and toughness of three grades of Mg-PSZ and a 3 mol% Y-TZP material have been investigated. The toughness of the Mg-PSZ materials passes through a maximum at the Ms temperature, whereas the strength increases monotonically with decreasing temperature regardless of Ms. The Y-TZP material exhibits increasing toughness with decreasing temperature but the strength passes through a maximum at -80°C. The results are discussed in terms of transformation and R-curve limited strength of transformation toughened ceramics. For Mg-PSZ materials it is suggested that the critical stress to initiate a non reversible transformation on the tensile surface is responsible for microcracking and ensueing R-curve development.
Strengthening Mechanism in Consolidated Amorphous Alloys
Authors: Otooni M. A. 
Published: March 2011

AbstractSeveral samples of consolidated amorphous alloys have been studied by using High Resolution Electron Microscopy (HREM), Differential Scanning Calorimetry (DSC), Microdiffraction (MD), and Energy Dispersive X-Ray Diffraction Analysis (EDXD). The phenomenon of plastic deformation at consolidated particulate interfaces has been examined. Two simultaneous processes have been identified occurring at these boundaries, namely, accelerated nucleation and growth of the deformed zone and the the formation of dislocation microstructures (dislocation networks). It has been observed that both type and the density of microstructures depend on the mode of consolidation. Post consolidation processing, annealing, affects density and the directional distribution of defects in the plastic zone. Microstructural examination of the consolidated mass has revealed two major factors important in the strengthening mechanism: (1) presence of a plastically deformed and pressureinduced nucleated zone; (2) presence of a system of dislocation networks in the compacted particulates. Based on these observations, it has been concluded that the stored strain energies in the plastically deformed zones provides the necessary activation energy for dislocation motions from one particulate to the next. These observations have been employed in developing a quasi-quantative model to explain the strengthening mechanism in consolidated amorphous alloys.
Effects of Microadditions of Cerium on Annealing Embrittlement in FeBSi Glasses
Authors: Kroeger D. M. , Mckamey C. G. , Scarbrough J. O. 
Published: March 2011

AbstractMicroadditions of cerium retard annealing embrittlement in some but not all metallic glass compositions in the FeBSi system. Effects on embrittlement of doping with both cerium and oxygen have been determined for a series of compositions, FexB13 Si87-x. For X > 80, cerium retards annealing embrittlement and oxygen promotes it, suggesting that the beneficial effect of cerium additions results from gettering of impurities. The results indicate that for those compositions in the FeBSi system with the highest values of the saturation magnetization, Ms, microadditions of cerium can prevent annealing embrittlement until the onset of crystallization.
High-Performance Light-Weight Allovs by Rapid Solidification Processing
Authors: Kim Nack J. , Das S. K. 
Published: March 2011

AbstractThere exists a great need for the development of high-performance light-weight alloys for aerospace application. Application of rapid solidification processing (RSP) has shown a strong potential for the improvement of properties of existing alloys and also for the development of novel alloy systems with superior properties. The present paper reviews the Allied-Signal's activities in the development of high-performance lightweight alloys by RSP. Examples include (i) high temperature aluminum alloys, (ii) aluminum-lithium alloys and (iii) corrosion resistant magnesium alloys.
The Effect of Solidification Rate on the Formability of Nickel Aluinide Containing Iron and Boron
Authors: Carro G. , Flanagan W. F. 
Published: March 2011

AbstractIt has been repcrted that rapid solidification insproves the ductility of certain nickel aluminides. This work. was devised to test whether it gives addittinal improvement in a nickel aluminide containing both Fe and B. Small samples were solidified in free-fall or splat-quenced after free-fall. Their uicrostructure has been characterized, and the results of preliminary tests, which give a quantitative measure of mechanical properties, are discussed.
Microstructure in Rapidly Quenched Al-Ti,Al-B and Al-Ti-B Alloys
Authors: Majumdar A. , Mair R. H. , Muddle B. C. 
Published: March 2011

AbstractRapidly quenched ribbons (˜50m thickness) of Al-5wt.%Ti, Al-lwt.%B and a range of Al-Ti-B alloys have been produced by melt spinning under He atmosphere and the microstructures of the ribbons, following solidification and post-solidification heat treatment, characterized using analytical electron microscopy. In the Al-5Ti alloy, the coarse equilibrium primary phase (b.c.t. Al3 Ti) that is observed following conventional casting is replaced by fine (0.1–0. 2μm), cuboidal particles of a metastable cubic (Ll2) Al3Ti in melt-spun ribbon. These metastable particles form directly from the melt and act as nucleation sites for the solid solution which subsequently forms. A refined microstructure with an average grain size of 1–2μm results. A supersaturation of Ti is retained in matrix solid solution following solidification and a variety of solid state precipitate forms, including fine dispersions of coherent, metastable Al3 Ti particles, is observed to emerge during post-solidification heat treatment. For the Al-1B alloy, the coarse distribution of primary AlB2 particles in a chill-cast ingot is replaced by a fine, uniform dispersion of the metastable boride, α-AlB12, in the melt-spun ribbon. Attempts to induce a refined boride dispersion in melt-spun Al-Ti-B alloys have proved largely unsuccessful.
Microstructure and Properties of Rapidly Solidified Complex Titanium Alloys
Authors: Munroe P. R. , Woodfield A. P. , Loretto M. H. 
Published: March 2011

AbstractRapidly solidified titanium alloys containing carbon and erbium have been examined microstructurally in the as-quenched and aged conditions. Studies show that cubic erbia forms initially, but prolonged aging results in the formation of trigonal erbia. The formation of this phase is enhanced by the presence of carbon.
Amorphous Transition Metal-Rare Earth Alloy Films for Magneto-Optic Recording
Authors: Luborsky Fred E. 
Published: March 2011

AbstractThis paper reviews the history of the development of films for use in magneto-optic recording. A discussion of why these early attempts with films of MnBi and Europium compounds were abandoned is given. The current work on amorphous transition metal-rare earth alloys is then reviewed. The origins of the necessary perpendicular magnetic anisotropy are discussed. The ideal combination of properties desired are: a high room temperature coercivity, a large temperature coefficient of coercivity, a large perpendicular anisotropy constant, large Ms, thermal and environmental stability, and, depending on whether a reflection or absorption mode of operation will be used, a large Kerr rotation with large reflectivity or a large Faraday rotation with a small specific absorption. These factors, their control, bow they influence the recording performance and the limits on performance of these amorphous films are discussed.
Dynamics of Rapid Solidification in Silicon
Authors: Peercy P. S. , Thompson Michael O. , Tsao J. Y. 
Published: March 2011

AbstractReal-time techniques were used to study rapid melt and solidification dynamics in silicon. In crystalline Si, the interface response function was characterized and found to be asymmetric for large deviations from the melting temperature, which will require reevaluation of conventional transition state treatments of melt and solidification. In amorphous Si, the mechanism of explosive crystallization was studied. The explosive transformation is mediated by a buried liquid layer, and detailed measurements have led to the suggestion that polycrystalline Si nucleates at the moving liquid-amorphous interface. For certain conditions, this process could yield fine-grained polycrystalline Si; for other conditions it permits epitaxial regrowth from the underlying crystalline Si for maximum melt thickness much less than the original amorphous layer thickness.
Deposition, Characterization, and Magneto-Optical Properties of Amorphous TbFe Alloys
Authors: Chakravartty D. , Mansuripur M. , Ruane M. F. 
Published: March 2011

AbstractAmorphous films of TbxFe1-x are prepared by simultaneous RF bias sputtering onto various substrates and the hysteresis loops of the resulting samples are obtained both by magneto-optical and VSM loop tracers. The coercivities of the samples deposited in the same run but onto different substrates are observed to be somewhat different and these differences are discussed in light of the current understanding of the deposition process.
Interdiffusion in Amorphous Compositionally Modulated Ni-Zr Thin Films
Authors: Atzmon M. , Spaepen F. 
Published: March 2011

AbstractWe report measurements of interdiffusion in compositionally modulated amorphous Ni-Zr films. We show the dependence of the diffusion coefficient on the modulation wavelength and correlate it with the thermodynamic properties of the Ni-Zr system. A bulk interdiffusion coefficient is extrapolated from the data. Our values for the interdiffusivity in Ni55Zr45 are about three orders of magnitude lower than those obtained by other authors for similar alloys. Possible explanations are suggested.
The Structural and Mechanical Properties of a Cu60 Zr40 (at %) Alloy Processed by High Velocity Injection (HVT)
Authors: Hays C. C. , Naugle D. G. 
Published: March 2011

AbstractIn the HVI process, alloys are arc-melted in a watercooled copper crucible and injected (at high velocities) into a circular channel by a gas/vacuum coupled pressure gradient. The molten jet rapidly solidifies, as it is in good thermal contact with the circular walls of the copper channel. This process (melting and injection) is carried out in the inert protective atmospheres (helium). The samples produced are in the form of cylindrical rods with large length to diameter ratios (40:1). The samples exhibit a good surface finish and are of high density. Results presented in this paper show that amorphous samples can be produced using the HVI process.
On the Formation of Rapidly Quenched Ti-Pd and Pd-Si Alloys: A Comparison with Mechanically Alloyed Materials
Authors: Politis C. , Thompson J. R. 
Published: March 2011

AbstractWe have investigated the formation of amorphous and microcrystalline alloys of Pd-Si and Ti-Pd. In order to allow comparison of the two methods, both liquid quenching (LQ) for rapid solidification and mechanical alloying (MA) techniques were employed. Characterization of the materials was obtained through X-ray diffraction and differential thermal analysis (DTA).Both the LQ and MA syntheses yielded amorphous Pd80Si20alloys, with very similar X-ray line widths and crystallization temperaiures. However, the MA alloys contained as minority component a second phase, indexed to Pd3Si.Quite different results were obtained for the Ti-Pd alloys. LQ splats containing 42, 66, and 80 at % Ti were not amorphous but microcrystalline, as might be expected from the very similar atomic radii of Ti and Pd. In contrast, a broad range of amorphicity, from approximately 42 to 85 at % Ti, was found in the MA synthesized materials. Overall, these results show that the two methods, LQ and MA, differ in the mechanisms of amorphization. This conclusion is further supported by additional MA and LQ experiments on ternary Ti-Pd-Cu alloys.
Annealing of Cold Worked Hypostoichiometric Ni3Al Alloys Using Positron Lifetime Spectroscopy
Authors: Usmar S. G. , Lynn K. G. 
Published: March 2011

AbstractHypostoichiometric Ni3Al alloys of composition 76.2 Ni:23.8 Al containing impurity levels of boron and hafnium (supplied by Oak Ridge National Laboratory) were either cold rolled or pressed. Rolled and pressed samples were deformed by 20% and 10% thickness reductions, respectively. Samples were annealed isochronally at approximately 50ºC intervals up to 1050ºC. Two major annealing stages were apparent in all three alloys studied. These could be attributed to vacancy migration to sinks and annealingof dislocations and(or) recrystallization. The onset of vacancy migration occurred at approximately 200ºC in all three alloys. Annealing of dislocations started at 650ºC to 700ºC and was complete at 1000ºC for alloys which contained boron and or hafnium impurities. In the pure alloy the onset of dislocation annealing occurred at 800ºC and was incomplete at the highest (1050ºC) annealing temperatures reached.
Microstructures of Rapidly Solidified Ti-15Al-11Mo Alloy
Authors: Jackson A. G. , Teal K. , Froes F. H. 
Published: March 2011

AbstractThe microstructural development in a Ti3Al alloy modified with an addition ofil w/o Mo has been studied. Under equilibrium conditions (arcmelted) a two phase ordered hexagonal and ordered bcc structure is present. Evidence of omega phase was alsoobserved. By rapid solidification the hexagonal structure is suppressed, which contrastswith the behavior of a Ti3Al alloy modified with a similar amount of Nb. The mechanism by which the phases present form is discussed in terms of the atomic movements required.
Lattice Location of Ta in Ni3Ai by Ion Channeling and Nuclear Reaction Analysis
Authors: Lin H. , Sehberling L. E. , Lyman P. F. , Pope D. P. 
Published: March 2011

AbstractWe have investigated the lattice location of Ta in Ni3Al using Rutherford backscattering with channeling, and nuclear reaction analysis. An 8 MeV 4He ion beam was directed along the < 100> crystallographic axis of the Ni75Al24Ta single crystal. A silicon surface barrier detector was used to analyze 4He ions backscattered from Ni and Ta atoms. Neutrons generated from Al by the 27Al(4He,n)30P reaction were detected by a large volume liquid scintillator placed outside of the scattering chamber. Essentially all of the Ta atoms were found to be substitutional, as determined by the Ta channeling minimum yield. A comparison of the width of the channeling angular scan for Al, Ni and Ta indicated that the Ta atoms are predominantly distributed on the Ni sites. This result is in conflict with expectations based on the ternary phase diagram.
Effects of Fe and Mn Additions on the Ductility and Fracture of Ni3Al
Authors: Dimiduk Dennis M. , Weddington Vicky L. , Lipsitt Harry A. 
Published: March 2011

AbstractRecent studies suggested that additions of either Fe or Mn to polycrystalline Ni3Al without boron, result in a ductile alloy. In the present study the effects of Fe and Mn additions on the strength and ductility of Ni3Al were investigated at 25°C, 600°C in air and at 600°C in vacuum. Metallographic examination showed that with 4 at.% solute a single phase structure existed but at higher solute levels the alloys were two phase. Single phase materials tested in bending showed virtually no plastic strain and low bend strengths at all temperatures. The two phase materials tested at 25°C and 600°C in vacuum showed marked ductility. However, the same alloys tested at 600°C in air exhibited brittle failure. These results suggest that Fe and Mn have no effect on the high temperature dynamic environmental embrittlement known to occur in Ni3Al.
Creep Deformation of Ta Modified Gamma Prime Single Crystals
Authors: Anton D.L. , Pearson D.D. , Snow D.B. 
Published: March 2011

AbstractThe role of substitutional element alloying of single phase γ' has become of primary interest to alloy designers who would like to exploit its low density and excellent oxidation resistance. Current γ' alloys have not shown sufficient strength to be useful in a creep limited environment. In order to maximize the potential of single phase γ' alloys and to more fully understand the creep strengthening mechanisms in two phase Ni-base superalloys, it has become necessary to clarify the role of Al-substitution elements. Ta is a potent strengthening element in γ' as well as imparting beneficial surface stability to superalloys; its effect on the creep properties of Ni3Al is the subject of this paper. The 1300°C isotherm of the Ni-Al-Ta system was determined in order to establish the γ' single phase field. Comrpositions were fabricated having chemistries which systematically varied both the Al:Ta ratio at Ni=75% and Ni:(AI+Ta) ratio at Ta=6%. Creep tests were conducted on <001> oriented single crystals at 760, 871 and 982°C. Electron microscopy was used to characterize the nature of slip deformation, confirm phase purity and to determine the existence of tetragonal distortions in these crystals. In this manner the strengthening due to Ta was examined in the absence of grain boundary effects. These γ' mono—crystals did not display classical creep response. Incubation creep was observed in all of the specimens tested. Surprisingly, the maximum incubation time was found to occur in the high ratio Ni:(Al+Ta) compounds, where less than 0.5% creep strain was obtained after 200 hours at stress. After incubation, either tertiary creep leading to failure, or apparently classic primary, secondary and tertiary creep ensued. In addition extremely long elongations, to 85%, were measured.
Effects of Mo and Ti Additions on The High Temperature Compressive Properties of Iron Aluminides Near Fe3Al
Authors: Diehm R. S. , Mikkola D. E. 
Published: March 2011

AbstractHot compression testing has been used to examine the effects of Mo and Ti additions on the yield strength and rate of work hardening for cast alloys near Fe3Al. A few powder processed materials have also been studied. Significant improvements in high temperature compressive properties on alloying have been related to increases in the DO3→B2 transition temperature and the associated changes in the nature of the dislocations involved in the deformation processes.
Evaluation of Multicomponent Nickel Base LI2 and Other Intermetallic Alloys as High Temperature Structural Materials
Authors: Shah D. M. , Duhl D. N. 
Published: March 2011

AbstractMulticomponent nickel base intermetallics with the L12 structure were evaluated as high temperature structural materials. The compounds were based on the γ' composition of PWA 1480, a high strength single crystal nickel base superalloy. The best balance of properties in the compound was achieved with <111> oriented single crystals but no significant advantage could be demonstrated over the precipitation hardened superalloys. Insufficient impact resistance was a major deficiency of the L12 compounds. Other nickel base intermetallics were also evaluated but showed little advantage over superalloys.
Reaction Chemistry and Thermodynamics of the Ni-Al and Fe-Al Systems
Authors: Santandrea Robert P. , Behrens Robert G. , King Mary A. 
Published: March 2011

AbstractThe reaction chemistry of the Fe-Al and Ni-Al systems was studied using differential scanning calorimetry (DSC). Experimentally measured heats of reaction and compositions of reaction products were characterized in terms of sample heating rates, reaction temperature, shape and size of aluminum powder, and sample preparation. Standard enthalpies of formation were derived from DSC results. Reaction products were identified by x-ray powder diffraction techniques.
Rapidly Solidified Binary Tial Alloys
Authors: Huang S. C. , Hall E. L. , Gigliotti M. F. X. 
Published: March 2011

AbstractMelt spinning has been carried out on binary TiAl alloys at three Ti/Al ratios. Antiphase domains were observed in one ribbon specimen, but no significant disordering was induced by the rapid solidification as indicated by X-ray and electron diffraction analyses. Bending tests of both the ribbons and the consolidated counterparts showed a decrease in ductility with increasing Al concentration. This compositional effect can be correlated with the TiAl tetragonality (the c/a ratio) as well as the grain structure.
Order—Disorder Behavior of Grain Boundaries in a two Dimensional Mcdel Ordered Alloy
Authors: Farkas Diana , Jang Ho 
Published: March 2011

AbstractThe order-disorder behavior of a Σ = 5 grain boundary was investigated using a two dimensional latice gas model and the cluster variation method. It is found that a disordered layer forms in the grain boundary region at temperatures significantly below theorder—disorder temperature for the bulk. Under certain assumptions for the pair interaction energies the model predicts grain boundary compositions different from the bulk.
On the use of Positron Annihilation Spectroscopy in the Study of a Nonuniform Spatial Distribution of Metallurgical Defects
Authors: Schaffer James P. 
Published: March 2011

ABSTRACTMost of the Interpretation of positron annihilation results to date have been done within the context of the simple trapping model which assumes a uniform spatial distribution of defects within the specimen examined. While this assumption is often justifiable there are numerous metallurgical defect configurations which are markedly nonuniform. In this work some of the appropriate trapping models which have previously appeared in the literature will be briefly reviewed. Additional models which are currently being developed will be presented and the series of experiments which are being used to test the trapping models will be described.
Charging Microscopy of Semi-Insulating Gallium Arsenide
Authors: Sheu T.C. , Myhajlenko S. , Edwards J.L. , Roedel R.J. , Krause S.J. 
Published: March 2011

ABSTRACTThe recent demonstration of “charging microscopy” to reveal resistivity variations in semi-insulating GaAs has generated interest in using the scanning electron microscope (SEM) as a contactless characterization technique for GaAs wafers. Resistivity variations give rise to a surface potential and secondary electron (SE) contrast, or “charging microscopy”, when viewing a wafer in the SEM. In this work we have shown that operating conditions may play a significant role in the SE image. Varying accelerating voltage from 5 to 35 keV gave rise to minor changes in the SE image, but varying beam current from 2×10−11A to 2×10−6A resulted in dramatic changes in the SE image, with two image contrast reversals occurring. The explanation for these changes in the SE image are unclear, but factors that are involved include surface and bulk conductivity, beam induced dielctric relaxation, and the sample-detector geometry.
Periodic {001} Walls of Defects in Proton-Irradiated Cu and Ni
Authors: Ehrhart P. , Jäger W. , Schilling W. , Dworschak F. , Gadalla Afaf A. , Tsukuda N. 
Published: March 2011

ABSTRACTThe evolution of the defect structure in 3 MeV-proton irradiated Cu and Ni has been investigated by transmission electron microscopy and by differential dilatometry. The proton irradiations were performed at T≦100°C up to irradiation doses of 2 dpa. An efficient loss of selfinterstitial atoms at dislocations and a consequently high average concentration of vacancies in clusters is observed starting from rather low fluences. In addition an ordering of the defects in the form of periodic {001} walls with a typical periodicity length of ≈ 60 nm is observed for all equivalent {001} planes. The walls consist of high local concentrations of dislocations, dislocation loops and stacking-fault tetrahedra. The observed formation of periodic arraysof defect walls is considered as an example for a possibly general microstructural phenomenon in metals under irradiation.