bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Tempeature Ordered Compounds for Advanced AERO-Propulsion Applications
Authors: Anton D. L. , Shah D. M. 
Published: March 2011

ABSTRACTAdvanced aero-propulsion engine designs now being considered for implementation require structural materials with high temperature strength and creep properties above 1300°C, in excess of the range where nickel base superalloys are now being used. A number of ordered single phase compounds having melting points above 1500°C have been identified which both hold promise for engine applications and are representative of a number of different crystal structures such as B2, C15 (Laves), A15, C1 and DO19. Elevated temperature characterization has been conducted on these compounds which includes ductile/brittle transition temperature determination, minimum creep rate analysis, elastic modulus, tensile strength and cyclic oxidation testing. The results of these tests have led to insight in the processing methods required for these compounds and selection of compounds based on elemental constituents and crystal structure.
Deformation and its Structure in LloTi-Al-Nb Compound Alloys
Authors: Hahn Yoo-Dong , Whang Sung H. 
Published: March 2011

ABSTRACTThe ternary TiAl-Nb (Llo) alloys stabilized at 1000°C for a week were prepared into miniature specimens for compressive deformation tests. The specimens were deformed in uniaxial compression at room temperature as well as various high temperatures. The yield stress and fracture strain were determined with respect to Nb concentration, and as a function of temperature to investigate positive temperature dependence.Dislocation structures and other deformation structures of the deformed alloys were studied by TEM.
Accurate Determination of γ′ Solvus in Ni-Al-X Ternary Systems
Authors: Hong Yong Myong , Mishima Yoshinao , Suzuki Tomoo 
Published: March 2011

ABSTRACTAn attempt has been made to determine the γ/γ′ phase boundaries with particular emphasis on the γ′ solvus in ternary Ni-Al-X systems with X being one of the VA or VIA transition metal elements. It is shown that the γ′ solvus in each ternary system can be obtained as a surface with respect to composition and temperature by employing differential thermal analysis (DTA) as a key experimental technique with support from energy dispersive X-ray spectroscopy combined with scanning elecron microscope(SEM-EDX). Also shown is that the DTA results often provide useful information on the phase relation in the vicinity of γ and γ′ phase fields. In the Ni-Al-V ternary system, for example, the pseudo-binary constitution between Ni3Al and Ni3V is suggested. The results presented here are systematic and consistent and therefore are reliable as compared with the previous results reported fragmentarily.
The Tensile Properties and Microstructure of Ti-Tic Composites with Al Additions
Authors: Chen J. , Geng Z. , Chin B. A. 
Published: March 2011

ABSTRACTThe relationship between the tensile properties and microstructure of Ti-TiC composite materials with Al additions was investigated. Composites containing 40–50% TiC by volume were produced using standard casting procedures from the melt. Ultimate tensile strengths of 1113 MPa with 1–2 % ductility were found in these materials. Results show that the tensile properties are controlled by the size and distribution of TiC particles.
Reinforcement/Matrix Interaction in Sic Fiber-Reinforced Ni3a1 Matrix Composites
Authors: Yang J.-M. , Kao W. H. , Liu C. T. 
Published: March 2011

ABSTRACTThe interfacial reaction characteristics of two different types of SiC fibers with Ni3A1 (Ni-Al-Cr-Zr-B) matrix have been investigated. The microstructure and chemical compositions across the reaction zone have been analyzed quantitatively using microscopy and electron probe microanalysis. In both types of SiC/Ni3Al composites, it was found that Ni was the dominant diffusing species responsible for the overall reaction. The C-rich layer outside the SCS-6 fiber provided an incubation period, but could not stop the inward diffusion of Ni. It could, however, effectively stop the diffusion of Al, Zr and Cr. No significant increase in reaction zone thickness after exposure at temperatures below 900 °C for up to 100 hours was observed. When the C-rich layer was depleted, a rapid increase in reaction zone thickness and the formation of multilayer reaction products occurred. In the case of Sigma/Ni3A1 composite, extensive reaction between the fiber and the matrix occurred at all the temperatures studied. Diffusion barrier coating for both types of fibers is required to develop nickel aluminide matrix composites.
An Investigation of the Creep of Ni3Al(B, Hf) Single Crystals at Intermediate Temperatures
Authors: Hemker K. J. , Nix W. D. 
Published: March 2011

ABSTRACTThis study was undertaken to characterize the intermediate temperature creep properties of Ni3Al. Itfocuses on the mechanisms controlling creep deformation and their relationship to the anomalous yielding behavior of this alloy. Constant stress creep tests were conducted for temperatures between 713–973 K, and the following observations were made. The creep curves exhibited two distinct regions. Primary creep was followed by inverse creep. Specimens cooled under constant stress strained an additional 20% during cooling. Temperature drop experiments indicate that Ni3Al is weakened by the addition of creep deformation.Glide on the primary octahedral plane appears to be exhausted during primary creep. Slip trace and TEM studies indicate that inverse creep is controlled by slip on the cube cross slip plane and a secondary octahedral plane. Primary octahedral slip is observed in the specimens that are cooled and deformed under constant stress.
Proton Irradiation-induced Disordering Reactions, Ductility and Strengthening of Ni3Al
Authors: Cheng J. , Lee C.-S. , Wagner C. N. J. , Ardell A. J. 
Published: March 2011

ABSTRACTOrdered Ni3Al containing 24 at.% Al was irradiated by 2 MeV protons at −45 °C to a fluence of 1.34 × 1016 H+/mm2. The induced microstructural changes were investigated by transmission electron microscopy, X-ray diffraction, scanning electron fractography and microhardness measurements. Proton irradiation produced a large volume fraction of small disordered zones residing in the ordered matrix. The morphology of the disordered zones bears some striking similarities to “tweed” microstructures. X-ray diffraction reveals distinct splitting of the higher order fundamental peaks toward low angles, and broadening of the displaced peaks, indicating that the zones observed are small clusters of tetragonally distorted disordered Ni3Al. The microhardness measurements suggest that the disordered zones strengthen the remaining ordered matrix considerably, most likely through a precipitation strengthening mechanism. The fractographic observations suggest that an increase in ductility accompanies disordering, as evidenced by the appearance of dimples, slip markings and river patterns on the fracture surface of the irradiated region of the sample.
Alloying Effect on the Microstructure and Property of Single Crystal Ni3Al Alloys
Authors: Jishan Zhang , Zhiya Zhang , Yajun Tang , Jinghua Zhang , Yang Yu , Yingao Li , Dongsheng Ding , Zhuangqi Hu 
Published: March 2011

ABSTRACTThe alloying effects of Cr, Zr, Ta, Nb and B on the microstructure and properties of single crystal Ni3Al alloys have been studied. The strength of the alloys has been improved markedly with promising plasticity. The 0.2% yield stress of some of these alloys is higher than that of IN713C, a typical cast nickel-base superalloy, in the temperature range from 25 to 950°C and some of them reach the strength level of advanced cast nickel-base alloys such as IN100 in the high temperature range. The creep strength of these alloys is also improved markedly. The single crystal Ni3Al alloy with a high Cr content ( 7 at-%) obviously shows an intermediate temperature low plasticity behavior. Although heat treatment can only slightly improve the strength, it can double the elongation of the alloy from 25% to 50%. In the Ni3Al monocrystal containing 1.2at%Zr there exist great amounts of the low melting point Ni5Zr-γ eutectics around the ordinary γ/γ′ eutectics. This makes it difficult to homogenize the coarse casting structures completely.
Study on Cast Ni3 Al-Base alloys
Authors: Yizhang Zhou , Tianxiang Zhang , Yingjie Tong , Bingda Zhang , Yaoxiao Zhu , Zhuangqi Hu 
Published: March 2011

ABSTRACTA series of cast Ni3Al-base alloys with the addition of alloying elements, such as Hf, Zr, Ti, Nb etc., have been studied, in which the total amount of Al and alloying elements substituting for Al was controlled in the range of 18 to 23 at%. It was found the alloying elements change remarkably the morphology, distribution and amount of γ phase as well as the morphology and size of primary γ′ intermetallic compound. The size of primary γ′ can be decreased to micron order. The brittle γ′-γ′ boundary (refer to primary γ′) can be substituted by tough γ′-γ-γ′ boundary. As a result, the mechanical properties of the cast Ni3Al-base alloys, especially high temperature ductility, can be enhanced. In addition, the effect of Cr is discussed when tested in air environment, and considered that chromium addition is not very effective to improve the high temperature embrittlement.
Deformation of a NI-AL-FE Gamma/Beta Alloy
Authors: Field R. D. , Krueger D. D. , Huang S. C. 
Published: March 2011

ABSTRACTRoom temperature tensile tests were performed on annealed melt-spun ribbons of a 50Ni-20Al-30Fe alloy. The ribbons were found to possess a duplex structure consisting of fcc γ and B2 β grains and exhibited tensile elongations in excess of 10% while still maintaining good strength. The tested specimens were found to contain high dislocation densities in both the γ and β grains, with no indications of stress-induced martensite formation. Dislocation analysis revealed that the vast majority of dislocations in the β have <100> Burgers vectors; however, <111> dislocations were also observed. Slip transfer was often facilitated by specific orientation relationships between the γ and β grains.
Unlubricated Sliding Wear of Nickel Aluminides at Room Temperature and 400°C
Authors: Bonda N. Rao , Rigney D. A. 
Published: March 2011

ABSTRACTUnlubricated sliding tests were performed at room temperature and at 400°C on polycrystalline Ni3Al with and without boron and on IC218, an alloy containing nickel plus 8.94 Al, 7.55 Cr, 0.88 Zr, 0.015 B and 0.01 Hf (all in wt. %). A pjn/disk geometry was used with self-mated samples in air and vacuum (1.3×10-3 Pa). Normal load was 1.5 kg (14.7 N), sliding speeds were 15–19 mm/s and sliding distances were 145–175 m.It had been expected that materials with and without boron would behave differently during sliding because of their well-known differences in ductility and fracture resistance. However, sliding behavior was similar for materials with and without boron. Environmental effects were more dramatic. For tests in vacuum, the friction trace was very noisy and the average coefficient of friction varied erratically during most of each test. Wear debris ranged from 100 μm to 1 mm in size. Wear scars were smooth, but with signs of heavy deformation. All test materials exhibited smoother sliding behavior in air than in vacuum, but the wear rate was usually higher in air. Debris particles were finer, most of them were at least partially oxidized, and they included at least one ferromagnetic component, probably arising from selective oxidation. It is suggested that the increased wear rate in air is related to oxygen-enhanced fracture of these nickel aluminides.
The Effect of Cobalt on Martensitic Toughening Parameters in NiAl
Authors: Russell Scott M. , Law C. C. , Blackburn M. J. 
Published: March 2011

ABSTRACTThe martensitic transformation and the effect of cobalt additions on important martensitic toughening parameters are being studied as a means of toughening NiAl alloys. Cobalt additions to NiAl martensite are seen to lower the Ms temperature, reduce the transformation strain anisotropy, and reduce the transformation temperature hysteresis (an indicator of interfacial mobility). Optimization of these parameters should allow martensitic transformation toughening processes to aid in overcoming the ambient temperature brittleness of NiAl alloys.
The Deformation Microstructure in NI3Si Polycrystals Strained Over the Range of Temperature of Flow Stress Anomaly
Authors: Tounsia B. , Beauchamp P. , Mishima Y. , Suzuki T. , Veysslière P. 
Published: March 2011

ABSTRACTIn order to correlate the flow stress anomaly of Ni3Si with dislocation properties, a weakbeam study ofpolycrystalline samples deformed between ambient and the peak temperature was carried out. Samples with two extreme Ni/Si ratios were tested.The most frequently activated slip system changes progressively from octahedral to cubic with increasing temperature. The transformation of superdislocations into Kear-Wilsdorf configurations gives rise to screw dislocations that are rectilinear only after deformation at room temperature. The effect of temperature is to gradually promote bending of Kear-Wisdorf configurations in the cube plane, from a few nanometers at 230°C to several tenths of micrometers at intermediate temperature. Cube slip begins to be massively activated a little below the peak temperature. It is suggested that the flow stress anomaly is controlled by progressive exhaustion of octahedral slip by thermally-activated expansion of superdislocations on the cube cross-slip plane.
A Weak-Beam Study of the Microstructure of β-CUZN Deformed in the Domain of Flow Stress Anomaly
Authors: Dirras G. , Beauchamp P. , Veyssière P. 
Published: March 2011

ABSTRACTβ-brass single crystals oriented along <001> were deformed between room temperature and 300°C. The deformation microstructure and dissociation properties were studied by transmission electron microscopy under weak-beam imaging conditions.Whatever the deformation temperature, superdislocations with <111> Burgers vector and strong edge component dominate within the microstructure. In addition, below the temperature of the flow stress peak (≈ 250°C), the density of screw relative to mixed superdislocations decreases as straining temperature increases. Dissociation does not always occur on the slip plane neither does it proceed exclusively by glide, even in samples deformed at 100°C.
Fracture and Fractography of Ordered Ni4Mo
Authors: Kao H. P. , Brooks C. R. , Sanganeria M. 
Published: March 2011

ABSTRACTThe domain structure of the alloy Ni-20 at. % Mo depends upon the heat treatment below the critical temperature (868°C). Upon aging around 750–850°C, initially a very fine domain structure forms inside the a grains, which then coarsens, and then migration of these boundaries occurs with a coarser domains structure behind them. In the ordered condition, the alloy is very brittle. Fractographs are presented which correlate the fracture morphology to the microstructures of the ordered alloy, showing that fracture occurs along the migrated, former α grain boundaries.
Microstructures and Mechanical Properties of Dual Phase Alloys Consisting of the Intermetallic Phases Ti3 (Al, Si) and Ti5(Si, Al)3
Authors: Wu J. S. , Beaven P. A. , Wagner R. , Hartig Ch. , Seeger J. 
Published: March 2011

ABSTRACTAlloying additions of silicon to the intermetallic titanium-aluminide Ti4Al lead to two-phase microstructures consisting of α2-Ti3(Al, Si) and Ti5(Si, Al)3.Although details of the ternary Ti-Al-Si phase diagram are not available, theoretical analysis and experimental screening have indicated the existence of a eutectic line in the Ti-rich region of the Ti3Al + Ti5Si3 two-phase region. The eutectic alloys display dual phase structures with Ti3(Al, Si) being the matrix and Ti5(Si, Al)3 the second phase.In this paper the microstructures of the eutectic as well as hypoeutectic and hyper-eutectic alloys, which contain additionally primary Ti3(Al, Si) and Ti5(Si, Al)3 needles, respectively, are described. The influence of the particular microstructure on various temperature-dependent mechanical properties such as strength, ductility, creep and fracture behaviour has been investigated. Alloys with hypo-eutectic microstructures show promising high temperature mechanical properties.
Structural Modifications of Rigid-Rod Polymers
Authors: Arnold Fred E. 
Published: March 2011

ABSTRACTResearch in our laboratory on lyotropic liquid crystalline polymers has provided a series of high modulus, high tenacity materials derived from benzobisazole rigid-rod polymers. A number of different structural modifications on these systems have been carried out in our laboratory. This paper will be focused on those structural variations made by maintaining the para-ordered geometry while modifying the structure with pendent groups.
Orientability of Rigid Rodlike Molecules in Solution and Controlled Preparation of Model Systems
Authors: Odell Jeffrey A. , Keller Andrew , Atkins Edward D.T. , Nagy Miklos J. , Feijoo Jose Luis , Ungar Goran 
Published: March 2011

ABSTRACTA survey is presented of our works on orientability of poly(p-phenylene-benzbisthiazole) (PBT) as a model for rigid rods. It starts with the solid state with specific reference to diffraction by the individual molecule. It is followed by behaviour in semidilute solutions, demonstrating increase of orientability with increasing rod alignment, with vastly higher absolute values (as expressed by rotational diffusion coefficient) than anticipated from existing theory. The origin of the discrepancy, as identified by simulations, lies in the inappropriateness of the application of mean constraints, a recognition which should have wider implications. The relaxation from the highly oriented state, also in solution, has been followed and the elementary rotational jump of rods identified, with a new method relying on in situ (synchrotron) X-ray diffraction. As a separate line, we are announcing a new model system, ellipsoidal latices of predesigned axial ratios, with wide ranging potential for the study of rigid rod behaviour in polymer and colloid science.
Formation and Properties of Fiber and Film FROM PBZT
Authors: Chenevey Edwjard C. , Timmons William D. 
Published: March 2011

ABSTRACTBetween 1977 and 1985, the Air Force Materials Laboratory funded a series of contracts, whereby Hoechst Celanese Research, formerly the Celanese Research Company, demonstrated and developed processes for the formation of fibers and films from highly viscous, anisotropic dopes of PBZT polymer. Heat treatment of these products was found to have significant effects on the tensile properties, and comparisons will be shown between asspun fibers and ones heat-treated at up to 1335°F (725°C).In the later stages of the program, sufficient materials were produced to permit characterization of a broad range of properties. Some data on environmental resistance will be given. Fibers were incorporated into aerospace- grade epoxy resins for measurement of composite properties.In summary, the results show that PBZT can be processed into fibers and films with improved mechanical properties and environmental resistance compared to aramids. A high degree of orientation of the rigid-rod molecules can be achieved which provides outstanding axial properties but this results in deficiencies in transverse properties and composite compression strength.
An Integrated Laboratory Process for Preparing Rigid Rod Fibers from the Monomers
Authors: Ledbetter Harvey D. , Rosenberg Steven , Hurtig Carl W. 
Published: March 2011

ABSTRACTThe preparation of small, representative research samples of polymers for evaluation in the form of a fiber has been a continuing problem because of the several complex and interrelated steps in going from the monomer to the polymer to the fiber. Such complexity can be magnified in the preparation of rigid rod polymers likecis-PBO, i.e., poly[benzo(1,2-d:5,4-d')-bisoxazole-2,6-diyl-1,4-phenylene]. PBO is a member of the group of high performance polymers generically labeled the PBZ family. With these polymers the additional factors of unreliable mixing, high viscosity, varying morphology, poor solubility, extended polymerization times, etc., present formidable experimental problems. especially when only small quantities of monomers are available.A new laboratory process has been developed to overcome the difficulties enumerated above so that a dehydrohalogenated monomer mixture in an appropriate solvent can be polymerized rapidly with molecular weight control. The polymer is degassed and otherwise conditioned for spinning, transferred to the spin pump with controlled morphological change, and subjected to dry-jet wet spinning to prepare a fiber representative of the polymer. The spinning operation incorporates features characteristic of both solution processing and thermoplastic extrusion.Typical fibers of cis-PBO prepared by the process are described.
Mechanical Behavior of Rigid Rod Polymeric Fibers
Authors: Allen Steven R. , Farris Richard J. 
Published: March 2011

ABSTRACTPoly-(p-phenylene benzobisthiazole) fibers provide a model system for the evaluation of structure-property relationships in extended-chain polymeric fibers. Owing to the poorly developed lateral order in as-spun fibers, the enhancement of structural perfection and of mechanical properties may be examined through heat treatment processing more readily than with more crystalline fibers. High tensile modulus (to 300 GPa) and high tensile strength (3 GPa) have been obtained from heat treatment processing of the fibers. The development of tensile modulus and tensile strength depends directly on the enhancement of overall axial molecular orientation. Tensile strength is additionally dominated by the development of stronger lateral molecular interaction. The mechanical properties mimic the inherent chain anisotropy arising from strong primary bonding along the chain and much weaker secondary interactions between chains. Tensile to shear moduli ratios of 200:1, tensile to shear strength ratios of 50:1 and tensile to compressive strength ratios of 10:1 are observed.
Theoretical Predictions for Side-Chain Liquid-Crystal Polymers and Comparison to Experiment
Authors: Dowell F. 
Published: March 2011

ABSTRACTThis paper presents results from a unique microscopic molecular theory for side-chain liquid-crystalline polymers (LCPs) in the nematic (N) and multiple smectic-A (SA) LC phases and the isotropic (I) liquid phase. There are no ad hoc or arbitrarily adjustable parameters in this theory. The agreement between the theoretical and experimental values for various properties (including transition temperatures and quadratic characteristic radii) is very good (relative deviations between 0% and less than 6.2%). The theoretical results also show--for the first time--that the N and I phases for these LCPs involve the packing of plate-like sections of backbones and side chains and that the local bilayer SA phase involves packing of side-chains within a plate-like section. This type of packing is predicted to be typical for side-chain LCPs. This theory can predict-- for the first time--whether the side chains of a molecule pack on the same or alternating opposite sides of the backbone and whether side chains on different molecules interdigitate (overlap) with each other.
An Exact Method to Determine the Chain Axis Orientation Distribution in High Performance Fibers from a Single Inter-Chain Reflection
Authors: Saraf Ravi F. , Watson T.J. 
Published: March 2011

ABSTRACTAn exact pole inversion method is used to calculate the complete chain-axis orientation distribution from a single inter-chain reflection. A brief outline of the formulation and computation method is given. This method is demonstrated by comparing the measured chain-axis distribution from a (002) reflection of oriented polyethylene samples, to the calculated distribution from (110) and (200) reflections of the same sample. The error in the Hermans Orientation function is less than 0.5% for the two samples tested.