bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real Time Small Angle X-Ray Scattering Measurements of Hips and ABS During Tensile Impact
Authors: Bubeck Robert A. , Blazy Joseph A. , Kramer Edward J. , Buckley Donald J. , Brown Hugh R. 
Published: March 2011

AbstractOne of the basic problems in the field of mechanical properties of polymers is the observation of the sequence of deformation events and the changes in microstructure associated with them during deformation at relatively high rates. Typically, well characterized polymer-samples are subjected to mechanical impact, and then various microscopy techniques are used to determine the deformation events (i.e., crazing, shear banding, cavitation) post mortem. Real time small angle X-ray scattering (RTSAXS) techniques, however, make possible the direct observation of scattering from crazes and voids while the deformation is in process. In this paper we report RTSAXS measurements, performed using intense synchrotron X-ray radiation, from a high impact polystyrene (HIPS) and an acrylonitrile butadiene styrene (ABS) copolymer during tensile impact. At a deformation rate of 4.2 cm/sec, (100 in./min), the ABS was found to absorb over ten times the impact energy of a HIPS sample. RTSAXS studies indicated: (1) that the ABS has a larger average craze fibril diameter than the HIPS (12.2nm vs. 8.7nm), (2) that localized shear occurs before crazing in the ABS, and (3) that the ABS sample generated 3.8 times the craze volume compared to the HIPS. The increase in craze volume alone, however, does not account for the greater toughness of the ABS, indicating the importance of the contribution of localized shear deformation to impact behavior.
Temperature Dependence of Stress Relaxation at the Copper/Polyimide Interface
Authors: Chen S. T. , Yang C. H. , Tong H. M. , Ho P. S. 
Published: March 2011

AbstractA Cu/polyimide thin film couple prepared on a thin quartz reed has been used to study interfacial stress relaxation during thermal cycling between room temperature and 400 °C. The polyimide thickness varies from 0 (no polyimide at all) to 10.5μm while the Cu thickness was fixed at 0.53μm. The average copper film stress has been calculated from the curvature of the quartz reed. The information clarifies the relation between the polyimide thickness and the average Cu film stress. The Cu/polyimide interfacial morphology after thermal cycling has also been examined using the cross sectional TEM technique. The results suggest that the interfacial stress is partially released through the deformation of polyimide near the Cu/polyimide interface.
Computer Simulation of Stress-Strain Behavior in Polymeric Materials
Authors: Cook Robert 
Published: March 2011

AbstractWe have developed a model of polymeric materials which includes many of the features of condensed-phase polymer chain dynamics, central among them chain relaxation by conformational motion. The model consists of a number of chains of particles which are connected by bonds with double-welled potentials to approximate the energetics of conformational motion. Interactions between particles on adjacent chains are modeled by shortrange repulsive potentials. We have examined the stress-strain behavior of the model using molecular dynamics simulations and find qualitative agreement with the observed experimental behavior of polymeric materials.
Pre-Yield Strain Hardening in Thermoplastics
Authors: Martin David C. 
Published: March 2011

AbstractSuccessive stress relaxation testing was used to investigate the strain hardening of polypropylene and polystyrene in the stage of deformation before yielding. By combining this information with that of a stress relaxation test it was possible to measure the change in flow stress with plastic strain or “workhardening” parameter K. K has been associated with the nucleation of “defects” of some sort which slow down the kinetics of the deformation process.Both polymers were found to strain harden in this deformation region. In polystyrene, the amount of time need to relax through a fixed stress increment reached a plateau at a point corresponding with visible crazing in the gage section of the sample. The workhardening parameter K was determined and found to decrease with stress. By plotting the rate of change of flow stress with total strain plots were obtained which avoided the use of strain, an ill-defined parameter in materials which change state during deformation. From these plots it was seen that polystyrene exhibits a well-defined linear region at small strain whereas polypropylene deviates from linearity immediately. Hardening of polystyrene was observed even in the linear response regime.
Reptation Analysis of Interdiffusing Chromophore-Labeled Polymers
Authors: Merrill W. W. , Tirrell M. , Prager S. 
Published: March 2011

AbstractUnderstanding the dynamics of the microscopic mixing of polymer across an interface is crucial in determining the dependence of the fracture yield stress on healing time, and on the dynamics of polymer blending. Previous theoretical analyses of healing by Prager, Tirrell and Adolf [1,2,3] and Kim and Wool [4] have been helpful in interpreting the results of crack healing experiments. These models have asserted strict reptation dynamics and then postulated simple relationships between microstructure and fracture stress. The underlying microstructure can be probed directly by fluorescence measurements on interdiffusing chromophore-labeled polymers.
Small Angle Neutron Scattering Study of Micellization of a Charged Copolymer in Aqueous Solutions
Authors: Shih L. B. , Luccas M. H. , Chen S. H. , Lin T. L. 
Published: March 2011

AbstractWe present an asymototic analysis of small angle neutron scattering data of a comb-shaped charged copolymer, poly (1-octadecene-co-maleic anhydride), in D20. It is shown that at full ionization, the coRolymer self-asso iate to form cylindrical shape micelles with a radius 26Å and length 101 Å. The number of repeating units per micelle is calculated to be 200 and the hydration number 15 per repeating unit. The dimension of the cylinder remains approximately constant over the concentration range studied.
Application of SAS to Bulk Amorphous Polymers, Block Copolymers and Polymer Blends
Authors: Roe R. J. 
Published: March 2011

AbstractThis article discusses the application of small-angle neutron and X-ray scattering techniques to the study of bulk amorphous polymers, block copolymers and polymer blends. The subject matter discussed include density fluctuation in single component amorphous polymers, concentration fluctuation in compatible polymer blends and its interpretation in terms of the random phase approximation theory, analysis of the scattering from incompatible polymer blends as developed by Porod, determination of the phase boundary thickness, order-disorder transition in block copolymer, interpretation of the scattering from disordered block copolymer systems by means of the random phase approximation theory, characterization of ordered block copolymer structure, and the study of block copolymer micelles.
Nickel Base Metallic Glass Powders for Application as Plasma Sprayed Coatings
Authors: Panchanathan V. , Billerica N. , Tsai C.L. , Whang S. 
Published: March 2011

ABSTRACTNew nickel rich alloys containing molybdenum and chromium prepared as metallic powders are reported. Using standard plasma spray techniques, these powders (−170 mesh) can be deposited onto metallic substrates as dense, well bonded coatings having predominantly glassy structure. Such coatings exhibit high structural strength, hardness and good corrosion resistance in various corrosive media.
Casting of Laminated Ribbon using a Modified Melt-Spinning Technique
Authors: Raman R. V. , Witt A. F. 
Published: March 2011

ABSTRACTLaminated metal-metal and metal-semiconductor ribbons have been prepared by a modified melt-spinning technique. Characterization studies have been carried out on laminated Sn-Zn, Ge-Al, InSb-CuZr and some other materials. Characteristics of these ribbons and their potential applications will be described.
Comparison of the Quench Rates Attained in Gas Atomized Powders and Melt-Spun Ribbons of Co and Ni Base Superalloys : Influence on Resulting Microstructures
Authors: Duflos F. , Stohr J.F. 
Published: March 2011

ABSTRACTThe cooling rates during solidification of gas atomized Stellite 6 (S6) powders range from 103 K/s to 106 K/s for 400μm to 10 μm diameter powder particles respectively. The microstructures vary from equiaxed type in the coarser particles to fully dendritic, cellular and microcrystalline in the finer particles. In the case of melt spun ribbons, the variations in freezing rate along a cross section of the ribbon produce a change in the microstructure from microcrystalline at cooling rates greater than 107 K/s to cellular and finally dendritic at rates on the order of 106 K/s.
Cooling Rates and Fine Microstructures of Rsr and Argon Atomized Superalloy Powders
Authors: Cosandey F. , Kissinger R.D. , Tien J.K. 
Published: March 2011

ABSTRACTSuperalloy powders of an IN 792 plus Hf type alloy produced from Rapid Solidification (RSR) and Argon Atomized process (AA) techniques are analyzed and compared according to particle size. Characterization of powders include surface and interior morphology, particle size and void distribution, cooling microstructures, microcrystallinity, microsegretation and especially dendrite arm spacing and cooling rates. It is found that, for the alloy studied, RSR cooling rates are a factor of only two to four greater than those for AA, regardless of particle size.
Microsegregation of an Aluminum and Magnesium Alloy at High Solidification Rates
Authors: Masur L.J. , Burke J.T. , Kattamis T.Z. , Flemings M.C. 
Published: March 2011

ABSTRACTResults are presented of an on-going study of structure and solute redistribution in ribbon cast Al-Cu and Mg-Zn alloys. Regions found in these ribbons are (1) an apparently chemically homogeneous coarse-grained zone adjacent the chill, (2) a transition cellular region, and (3) a dendritic zone, usually equiaxed. In both alloys, structure in the equiaxed region becomes coarser with increasing distance from the chill. In Mg-Zn alloys, the amount of nonequilibrium second phase increases essentially linearly with distance in the cellular and dendritic regions. Scanning transmission electron microscopy can accurately measure solute distribution across rapidly solidified cells or dendrites, but the possibility of surface compositional changes during specimen preparation must be recognized.
Microstructures of Glassy and Metastable Crystalline Phases Formed From FE-C- Ternary Alloys
Authors: Hornbogen Erhard , Schmidt Ingo 
Published: March 2011

ABSTRACTFe-C-base alloys were rapidly cooled from the liquid and then reheated from ambient temperature. In addition to the transitional elements (V,Cr,Mo,W), B was added as third element to substitute C. A systematic approach to the understanding of phases and microstructures, which form under these conditions is the purpose of this work. This includes the considerations of forming ability and thermal stability of metallic glasses. Three aspects require attention: a) absolute stability of the glass phase, b) relative stability i.e. the difference of Free Energy between the amorphous and particular crystalline phases, c) kinetic stability based on the rate and mechanisms of crystallization reactionsincluding the rate determing diffusion process. Light and electron microscopy and electron diffraction were used for the analysis of the structure of the alloys.
The Variation of Magnetic Properties of Fe-Based Amorphous Alloys Along the Ribbon Length
Authors: Sato Takashi , Ozawa Tsutomu , Yamada Toshio , Matsumoto Ryutaro 
Published: March 2011

ABSTRACTThe variation of ac magnetic properties along the length of melt-spun Fe-based amorphous ribbons was examined in relation to the variations of the roller surface temperature and the ribbon thickness. The results indicated that the lengthwise variation of magnetic properties strongly depends both on the roller surface temperature and the ribbon thickness. The critical cooling rates at which core loss begins to increase were determined from the relationship between core loss and cooling rate. For ribbons cast at lower cooling rate than critical cooling rate, the finedomain patterns were usually observed on the free surface. From the disappearance of the fine-domain pattern and the remarkable decrease of core loss by removal of the surface layers, it is ascertained that the surface layers deteriorate magnetic properties.
Thermodynamic Properties of Dilute Solutions of Hydrogen in Glassy PD.80SI.20
Authors: Finocchiaro R.S. , Tsai C.L. , Giessen B.C. 
Published: March 2011

ABSTRACTEquilibrium vapor pressures of dilute solutions of hydrogen in glassy Pd.80Si.20 have been measured from 10–90°C and at hydrogen pressures P of 1–100 torr. Under these conditions the ratio of hydrogen to alloy, x as determined by a volumetric method, reaches a maximum value of 0.0070. Over this range of x, the system exhibits a positive deviation from Sieverts' Law; isotherms were analyzed in terms of Lacher's modified statistical mechanical theory of hydrogen in palladium. The data were used to calculate relative partial molar enthalpies, excess entropies, and excess free energies for the formation of the solid solutions. The thermodynamic properties were found to vary with hydrogen content over the composition range studied.
Catalytic Hydrogenation with Amorphous and Crystalline Pd8 0Si2 0
Authors: Giessen Bill C. , Mahmoud Sabri S. , Forsyth David A. , Hediger Markus 
Published: March 2011

ABSTRACTSeveral metallic glasses in the form of ribbons were screened for activity as hydrogenation catalysts. Pd80Si20 and (Ni50Fe50)80B20 showed activity in reducing cyclohexene. Pd 80 Si20 was further examined for differences between the glassy and crystalline phases in the selectivity shown during hydrogenation reactions of n-hexenes, phenylethyne, α-pinene, and cyclododecene. No significant differences were found for catalytic selectivity in regard to cis-trans isomerization, double bond migration, and stereochemistry of addition under the reaction conditions used. Minor differences were observed in hydrogen-deuterium exchange.
Microstructures of Rapidly Solidified Fe-Al-Zr Alloys
Authors: Patel A. N. , Vassamillet L. F. , Clauer A. H. 
Published: March 2011

ABSTRACTRapidly quenched short fibers of Fe–8Al and Fe– 8Al–XZr (X = 0.1, 0.2, 0.4, and 1) alloys were produced by the Pendant Drop Melt Extraction Process, (PDME) to explore the feasibility of producing intermediate temperature, oxidation resistant iron base alloys. The fibers had a diameter of 20 to 50 μm and ranged in length from 2–5 mm. The cooling rate was insufficient to retain zirconium in solution in the Zr-containing alloys, resulting in precipitates of the type Fex(Zr,Al) having differing compositions at the grain boundaries and within the matrix. No precipitates were observed in the FeAl alloys. The precipitates were uniform in distribution and size (nominally 0.1 to 0.3 μm diameter). Grain boundary precipitation and precipitate size both decreased with decreasing Zr contents.
Mechanical Properties of (Fe100−XMX)83B17 Metallic Glasses
Authors: Hunger Gerhard , Mordike Barry L. 
Published: March 2011

ABSTRACTThe mechanical properties hardness, tensile strength and fracture toughness of (Fe100−x Mx )83B17 glasses were measured for different alloying con en s and heat treatments. In the as quenched state the hardness is influenced mainly by changes in the metal-metalloid bonding. The fracture toughness is dependent on the alloying elements as well as the actual state of the glass. Heat treatment of the glass thus hardly influences the hardness whereas the toughness decreases strongly and significant changes in the fracture surface occur. Calorimetric observations suggest that structural relaxation is the primary reason for this behaviour although some effect of annealing out of internal stresses must be present.
Ostwald Ripening in Two Phase Mixtures With Application to Rapid Solidification
Authors: Voorhees P. W. , Glicksman M. E. 
Published: March 2011

ABSTRACTRapid solidification invariably results in fine-scale microstructures with concomitant fine-scale segregation. These microstructures, which are produced relatively far from equilibrium, have large. specific surface energies and tend to coarsen rapidly. Experiments were carried out on highly supercooled bulk specimens of elemental P4 in which the average temperature of rapidly solidified 2-phase mixtures was accurately monitored over time. A continuous rise in temperature toward the bulk melting point is always measured, independent of the volume fraction of solid produced at recalescence. New theoretical work outlined here shows that this temperature rise can be associated with the Ostwald ripening of the as-solidified solid-plusliquid mixture. The new theory permits calculation of coarsening rates after recalescence and the distribution of dendritic particle sizes as a function of time. Implications for establishing limiting dendritic particle sizes are discussed.
FCC and BCC Solidification Products in a Rapidly Solidified Austenitic Steel.
Authors: Kelly Thomas F. , Vander Sande John B. , Cohen Morris 
Published: March 2011

ABSTRACTThe microstructures and local composition variations in centrifugally atomized high-sulfur stainless steel powder are investigated. Both fcc and bcc are found to be primary solidification phases in the as-solidified powder of this nominally austenitic steel where the smaller powder particles (≲ 70 micron diameter) tend to be bcc.Cellular solidification structures, with sulfide precipitates (100 to 200 nm diameter in size) at the cell walls, are observed in both fcc and bcc particles. The bcc structure, however, has many small sulfide precipitates (10 to 20 nm diameter) in the cell interior with few larger sulfide precipitates at the cell walls. The small precipitates, observed only in the bcc structures, form on cooling from a supersaturated solid solution that results from reduced solute partitioning during solidification. Partitioning of chromium and nickel is minimal in these cellular structures. A non-cellular bcc structure is also observed with small sulfide precipitates throughoutthe entire structure. This non-cellular bcc structure results from smooth-front massive solidification. Analysis of the nucleation process for solidification indicates that a transition from fcc nucleation to bcc nucleation occurs with increasing wetting angle in heterogeneous nucleation. Thus bcc should nucleate in the smaller droplets of a liquid dispersion where catalytic surfaces of low potentcy (large wetting angle) tend to be the only heterogeneous nucleants available.
Superconducting Properties and Flux Pinning in Liquid Quenched Nb-Ga Alloys
Authors: Clemente Gregory B. , Habbal F. , Bevk J. 
Published: March 2011

ABSTRACTNb75−xGa25+xtapes (1≤ x ≤ 6) were prepared by liquid quenching technique in an argon atmosphere. The transition temperature Tc, upper critical field Hc2 and critical current density Jc were measured in both as-quenched and annealed samples. The values of Tc (onset) ranged from 16.5 to 18.0K in the asquenched samples and increased upon annealing up to 20.0 K. Similar increase was also observed in the values of Hc2 (4.2 K) from ∼190 kOe to values higher than the attainable field of 220 kOe. For annealed samples near stoichiometric composition, Hc2 was estimated to be higher than 300 kOe. The critical current densities of these tapes are relatively low [Jc (4.2 K) ≤ 2 × 104A/cm2] compared to other melt-quenched A-15 compounds. Flux pinning force, FP, does not obey a single scaling law. The existence of two peaks in FP at low temperatures and of only one peak at 13.4 K for 1 ≤ x ≤ 4 is discussed in terms of the microstructural characteristics of the samples.
Structure/Property Relationships and Applications of Rapidly Solidified Aluminum Alloys
Authors: Adam C. M. 
Published: March 2011

ABSTRACTDuring the last five years Pratt & Whitney Aircraft has developed rapid solidification powder metallurgy and consolidation techniques to produce advanced aluminum alloys. A centrifugal rotary atomization device with forced high velocity helium convective cooling has been developed to pilot-plant stage, to produce aluminum alloys of novel compositions for advanced gas turbine engine applications. Rapidly solidified aluminum alloys solidify as spherical droplets up to 100 μm diameter with cooling rates of 105 — 106 K/sec, and demonstrate new microstructural features which have been exploited to develop elevated temperature mechanical properties. Alloys have been developed for 400 — 500°F fan and compressor applications that have traditionally used titanium alloys, and this paper reviews the microstructural evolution of rapidly solidified structures during thermomechanical processing.
Microstructure and Properties of Fine Grained Supersaturated Fe-C Alloys
Authors: Mordike B. L. , Bergmann H. W. 
Published: March 2011

ABSTRACTRapidly quenched tapes of Fe-C-X alloys (X=Cr, Mn,Ni, Co, Al, Si) were produced by melt spinning. The hardness, ductility, grain size and micro and lattice structure were determined. The system Fe 2.1C 13 Cr was chosen for further study. The transformation (isothermal and continious) characteristics were determined for the as quenched and reaustinitized states. The results can be presented in the form of TTT diagrams and hardness measurements
Surface Alloying of Iron Alloys by Laser Beam Melting
Authors: Mordike Barry L. , Bergmann Hans W. 
Published: March 2011

ABSTRACTThe surface heat treatment of iron alloys using high power lasers is reported. The essential features e.g. epitaxial growth, homogeneity etc. are discussed. The results are tabulated for the technically important alloys. The possibilities of laser hardening are demonstrated by four examples.
Production and Properties of Amorphous Layers on Metal Substrates by Laser and Electron Beam Melting
Authors: Bergmann H.W. , Mordike B.L. 
Published: March 2011

ABSTRACTVarious techniques of laser glazing are presented. Rules are given for the choise of systems which are suitable for producing amorphous surface layers. Methods of demonstrating the existence of a truly amorphous layer are discussed. Two examples are given: I) electron beam glazing of Ni-Nb coated single crystals 2) laser beam glazing of Fe-B coated Fe-Cr-C cold working steel.
Laser Surface Treatment of Aerospace Steels
Authors: Christodoulou G. , Henry P. , Steen W.M. , West D.R.F. 
Published: March 2011

ABSTRACTAn investigation is reported of the laser surface melting of four alloy steels with carbon contents ranging up to 1 wt%. Studies were made of the profiles, microstructures and hardnesses of zones produced using a laser power of 1.7 kW and a range of traverse speeds and beam diameters. The observed zone profiles were correlated with calculations from a three-dimensional, moving source, heat transfer model. In the high carbon steels, the shallow laser melted zones contained substantial amounts of retained austenite.