bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Power Magnetostrictive Materials from Cryogenic Temperatures to 250 C
Authors: Clark Arthur E. 
Published: April 2011

AbstractThe rare earths, both in elemental form and in compounds, are widely known as possessing many extraordinary magnetic properties. In this paper, we focus on the huge magnetically induced displacements (magnetostrictions) based upon the element terbium. A proper balance of magnetic anisotropy and magnetostriction, plus a proper choice of crystal axes lead to materials which can switch large quantities of energy between the internal (magnetic) and external (mechanical) states with the application of small triggering magnetic fields. Power densities 2000 times those of conventional magnetostrictive materials and 10-20 times those of typical piezoceramics are available. These materials are particularly valuable for smart systems where large energy transduction is needed such as active structure stiffening and active vibration control.
Tem Study of Twinning and Magnetic Domains in Terfenol-D
Authors: Dooley Jennifer , Graef M. De 
Published: April 2011

AbstractThis paper reports the results of detailed TEM observations on [211] oriented single crystal samples of Terfenol-D. Domain structures are interpreted in terms of recent micromagnetic models developed by James and Kinderlehrer. Lorentz transmission electron microscopy was performed on a JOEL 120CX equipped with a low field objective lens. We also report for the first time energy-filtered magnetic domain images, recorded using a Gatan Imaging Filter on a JOEL 40000EX high resolution TEM. This observational mode allows for enhanced resolution and improved image contrast.
Pulsed Laser Deposition of ZnO Thin Films for Piezoelectric Applications
Authors: Donovan E.P. , Horwitz J.S. , Carosella C.A. , Auyeung R.C.Y. , Chrisey D.B. , Smits J.G. 
Published: April 2011

AbstractTransparent, insulating ZnO thin films have been deposited in-situ by pulsed laser deposition (PLD) from sintered targets. Films were deposited on substrates of fused quartz, <0001> A12O3, polycrystalline and textured (111) Au, at several substrate deposition temperatures (TSubstrate ≤ 700° C) and background oxygen pressures (P ≤ 300 mTorr). Film structure, morphology and electrical properties were characterized by X-ray diffraction, Rutherford backscattering spectrometry, optical properties were characterized by infrared transmission and reflection, and electrical resistivity was measured normal to the films. Films were crystalline, phase pure, and c-axis oriented. ZnO films deposited onto fused quartz and <0001> sapphire showed x-ray rocking curve full width at half maxima of 5° and 0.34°, respectively. The structure of ZnO films deposited on (111) textured Au was sensitive to the degree of texturing in the Au. The resistivity of PLD ZnO films was 61-63 kΩcm which was a factor of three improvement over sputter deposited films. Deposition of Au by both PLD and IBAD showed a negative correlation between the crystalline texturing and film adherence.
Influence of Mn Additions on the Thermoelastic and Pseudoelastic Behaviour of Cu-Ai-Ni Alloys
Authors: Morris M.A. , Lipe T. 
Published: April 2011

AbstractThe transformation properties of Cu-Al-Ni alloys modified by the additions of boron and manganese have been interpreted by studying the reversibility and stability of the martensitic transformation as a function of heat treatment and of manganese concentration between 2 and 4 wt%. The alloy containing 2% Mn exhibits a lack of thermoelasticity due to a decrease of the degree of B2 order and supression of DO3 order during quenching and the increase of both types of order during annealing. From the determination of the activation energies responsible for the martensitic and reverse transformations, we have deduced that, in both cases, the kinetics of the transformation are controlled by an atomic jump at the interface between the two phases.
The Interactive Response of Sma Springs which Control the Position of Dampers in Personal Environments™
Authors: Thoma Paul E. , Ivshin Yefim , Schachner Kurt D. 
Published: April 2011

AbstractPersonal Environments™ is a Johnson Controls, Inc. system for the control of indoor office environments. In this system, four SMA coiled extension springs interact to control the position of two dampers. Two opposing SMA springs connected to one damper control the percentage of primary conditioned air entering the system, and two opposing SMA springs connected to the second damper control the percentage of room air reentering the system.The interactive operation of the SMA springs is discussed and a model is presented on the interactive response of the SMA springs. The SMA spring transformation temperatures, force - strain relationship, and the experimentally measured interactive response to temperature are presented and discussed.
Intelligent Material Design Using Shape Memory Alloy
Authors: Furuya Yasiubumi 
Published: April 2011

AbstractRecently, shape memory alloy(SMA) is regarded as one promising material element natively with intelligent functions. I introduce the fundamental design concept and several trials for developing intelligent(smart) materials and structures by using shape memory alloy. Moreover, I introduce our recent works and point out the necessity for developing fundamental techniques to realize the intelligent materials using SMA.
Thermal and X-Ray Diffraction Studies of Doped and Undoped Single Crystal and Polycrystalline BaTiO3
Authors: Carreiro L.G. , Marzik J.V. , Deb K.K 
Published: April 2011

AbstractCalorimetric changes in a series of pure and doped single crystal and polycrystalline BaTiO3were studied using differential scanning calorimetry over the temperature range of-110°C to 200°BC. The dopants, oxides of niobium and iron were varied from 0.5 to 8 mole percent, and strontium was varied from 5 to 35 mole percent. Endotherms were observed corresponding to three crystallographic transitions. The highest observed thermal transition corresponds to a tetragonal to cubic crystallographic transition and is also associated with the Curie temperature in these materals. Two additional endothermic transitions were also observed, an intermediatetemperature orthorhombic to tetragonal transition, and a low-temperature rhombohedral to orthorhombic transition. The three dopants decreased the crystallographic transition temperatures and Curie temperature as the dopant concentration was increased. X-ray diffraction was used to identify phases present and to determine the extent of solid solution. It is expected that these materials will display improved infrared detection as well as opto-electronic properties.
Piezoelectric-Ceramic Cylinder Type Vibratory Gyroscope
Authors: Yoshida T. 
Published: April 2011

AbstractA new equivalent circuit for the vibratory gyroscope and an analyzing and controlling method for the vibration mode axis of the vibrator have been studied. The vibrator of this gyroscope consists of a piezoelectric-ceramic cylinder. On its outer cylindrical surface, interdigital electrodes are formed. And these electrodes are used for poling, AC excitation as well as detection. In order to prevent some deviation of the performance of the gyroscope due to the adhesion process, these electrodes are directly printed on the cylinder surface.By changing the electrodes pattern and making a groove on the surface of the vibrator, the vibration mode axis can be easily controlled. Optimum design suited for demanded specifications can then be obtained.
Mechanical Properties of a β Containing Ti-Al-Cr-Alloy at Ambient and Elevated Temperatures
Authors: Chen W. R. , Wang J. , Zhang B. , Wan X. , Chen W. J. 
Published: April 2011

AbstractThe mechanical properties of a β-containing Ti-Al-Cr alloy were investigated at ambient and elevated temperatures. The results show that the Ti-Al-Cr alloy containing the β phase has a very high tensile strength but a poor ductility at ambient temperature, and that higher ductility is obtained at high temperatures. The temperature dependence of mechanical properties is found to be sensitive to the strain rate during the test. Fractography shows that the fracture mode changes from fully brittle to ductile-brittle mixture with the increased temperature. All the results suggest that the triple-phased TiAl alloys (α2+β+γ) may have the combined mechanical properties of the dual-phased T13Al ((α2+β) and dual-phased TiAl (α2+γ) alloys.
Investigation of a New Type of Al3Ti-Based Ll2 Alloy With Second Phase Precipitation
Authors: Hu Gengxiang , Sun Jian , Weng Xiaojun , Li Tong , Chen Shipu 
Published: April 2011

AbstractSince the L12 structured Al3Ti alloy exists only in a narrow compositional range, further alloying of the single phase Ll2 alloy to improve its property seems hardly successful. Developing two-phase or multiphase Al3Ti alloys may be an effective approach for strengthening and toughening. In this article, a new type of Al3Ti-based alloy which has a Ll2 matrix with precipitates of a second phase is reported. The quaternary alloys based on Al67Mn8Ti25, and modified with Nb additions, consist of an Ll2 matrix and DO22 second phase particles in the annealed state, but the second phase can be dissolved by solution treatment and precipitated during high temperature aging. Remarkable strenghtening and promising compressive ductility were exhibited by the experimental alloy. The influence of composition on the microstructure and properties of the alloys are reported also.
Structural Phase Stability of ThSb Under Pressure
Authors: Palanivel B. , Kalpana G. , Rajagopalan M. 
Published: April 2011

AbstractThe electronic structure and high pressure structural phase transition in thorium antimonide have been investigated using the tight binding LMTO method. We have calculated the total energies by reducing the cell volume for NaCl as well as CsCl structures using TBLMTO method. The total energy calculations reveal that ThSb undergoes a structural transition from NaCl to CsCl structure at 78 kbar. The calculated value of equilibrium cell volume and the cell volume at which phase transition occurs are found to have a good agreement with the experimental results.
Counteracting Effects of Boron and Hydrogen on Ductility In Ni3Al
Authors: Chaki T. K. 
Published: April 2011

AbstractA minute amount of boron doping in polycrystalline Ni3Al can suppress embrit-tlement due to environmental moisture. However, B is ineffective in suppressing hydrogen embrittlement due to cathodic charging. A mechanism is proposed to explain this seemingly contradictory dichotomy. Grain boundaries in B-free Ni3Al contain crack-like microcavities, to the tips of which atomic hydrogen, generated by the reaction of moisture with Al, can diffuse and cause embrittlement. In B-doped Ni3Al interstitial B atoms interact with Ni atoms and reduce the strength of directional bonding between Ni and Al atoms, such that the atoms can relax easily to close up the microcavities, thereby reducing environmental embrittlement. In the presence of a large amount of hydrogen, introduced by cathodic charging, microcracks can be nucleated in B-doped Ni3Al by hydrogen-enhanced dislocation activity, and then hydrogen embrittlement can proceed by enhanced plasticity at the crack tips.
Deformation Behavior of An O + β0 Processed Ti-21 Ai-23Nb Alloy at High Temperatures
Authors: Seetharaman Venkat 
Published: April 2011

AbstractA hot workability study was conducted on an orthorhombic Ti-21AI-23Nb alloy using isothermal, constant velocity compression tests, over the temperature range 900–1155°C and nominal strain rate range 0.001 to 1.0 s−1. Three different microstructures corresponding to (a) hot rolled and mill annealed, (b) β0 -heat treated, and (c) β0 solution treated and direct aged conditions were examined. These microstructures varied from a relatively coarse distribution of O-phase precipitates in a matrix of transformed βO to the metastable retained βO. Flow stress displayed a sharp dependence on temperature, strain rate and on the initial structure. While uniform plastic flow was obtained at high temperatures and for structures containing primary O, βO-heat treated structures led to pronounced flow softening. Strong yield point phenomena and serrated flow were observed in selected test conditions and for microstructures containing high volume fractions of metastable βO. These flow instabilities resulting from Luder band propagation and dynamic strain aging are interpreted in terms of dislocation interactions in supersaturated βO.
Mechanical Behavior and Oxidation Properties of Molybdenum-Modified Cr3Si/Cr5Si3 Intermetallics
Authors: Nazmy M. , Noseda C. , Sauthoff G. , Zeumer B. , Anton D. 
Published: April 2011

AbstractA series of two-phase chromium silicide base intermetallics have been investigated with respect to creep behavior and oxidation resistance. The first results of these investigations are reported. Good oxidation resistance has been demonstrated in one composition, which was due to the formation of the protective vitrious SiO2 layer, while the chromium oxide layer is very helpful at the intermediate temperature range.
Pseudo-Twinning in A Deformed Nb-15Al-25Ti B2 Alloy
Authors: Yang S.-S. , Hou D.-H. , Shyue J. , Wheeler R. , Fraser H. L. 
Published: April 2011

AbstractAn alloy with nominal composition of Nb-15Al-25Ti (in at.%) has been developed for high temperature structural applications. This alloy exhibits a B2 ordered structure in the as-cast form [1]. In addition to dislocation slip, pseudo-twinning occurs in this B2 alloy when deformed in compression at room temperature at a strain rate of ∼ 10−4 sec−1 to 3% strain. The pseudo-twinning plane has been deduced to be the {112} planes, which is similar to that in twinning of bcc metals. The mechanism of deformation pseudo-twinning in this B2 alloy is found to be analogous to the normal twinning mechanism in bcc metals, involving glide of partial dislocations with Burgers vector (b) given by b=l/6<111= on {112} planes. This pseudo-twinning mechanism causes a phase transformation from the B2 to an ordered orthorhombic structure.
Stucture of 1/2<110> Dislocations In γ-Tial by High Resolution Tem and Embedded Atom Method Modelling
Authors: Simmons J. P. , Mills M. J. , Rao S. I. 
Published: April 2011

AbstractHigh Resolution TEM (HRTEM) observations of a dislocation in γ-TiAl are compared directly with atomistic calculations of dislocation structures performed with atomistic potentials in order to obtain an estimate of the Complex Stacking Fault Energy (γcsf). A value of between 470 and 620 mJ/M2 was obtained. HRTEM observations are presented of a Ti-52AI sample, containing a dislocation with Burgers vector 1/2<110> and 60° line orientation. This image is matched against images simulated from the outputs of Embedded Atom Method (EAM) simulations, using potentials that were fit to bulk γ-TiAl properties. Two atomistic simulation methods were employed in order to give the range of values for γcsf. In the first of these methods, three EAM potentials were used to simulate the stress-free core structure. These were fit so as to produce three different values of γcsf, all other properties being roughly the same as the literature values for γ-TiAI. All of these potentials produced cores that were more extended than the experimental observation. Thus a value of 470 mJ/M2, being the highest value of γcsf obtainable for the EAM potentials, is reported as a low limit estimate of γcsf for γ-TiAl. An upper limit estimate of the value of γcsf was obtained by applying an external ‘Escaig’ stress that forced the Shockley partials to further constrict, simulating the effect of an increase in γcsf, The preliminary value calculated from this procedure was 620 mJ/M2.
Phase Transformations in the Fe-Al System Studied by “In-Situ” Tem Heating
Authors: Korner A. 
Published: April 2011

AbstractThe domain structure and the evolution of antiphase boundaries (APBs) have been investigated in Fe-Al by means of “in-situ” transmission electron microscopy (TEM) heating experiments. Single crystals with composition Fe22.1at%Al and Fe25.6at%Al have been used.The grown-in structure of the Fe22.1at%al single crystal is composed of DO3 ordered particles embedded in the disorderd ±-matrix. A bimodal distribution of the particles was found. Small ordered particles are in between the large precipitates which are surrounded by particle-free zones. Numerous of this large ordered precipitates contain APBs. Crossing the transition temperature to the disordered phase, the small particles dissolve into the ±-matrix and the large particles start to shrink by dissolving.The single crystal with composition Fe25.6at%Al was found to be completely DO3 ordered. The grown-in domains are separated by APBs of type a′0/2〈100〉. At temperatures far below the transition temperature to the B2 phase no significant change in the APB and domain structure has been detected. In contrast, a remarkable evolution in the APB structure has been observed approaching the transition temperature. Coarsening of the domains has been found. Furthermore, APBs of B2-type (a′0/4〈lll〉 shear) are dragged out by dislocation motion. B2- and DC3-type APBs react and junctions are formed. With increasing annealing time, the density of B2-type boundaries increases. The TEM image is dominated by B2-type boundaries linked by the D03-type boundaries. The DO3 superlattice spots are clearly excited approaching the transition temperature to B2. Above the transition temperature, the DO3 spots disappear completely and the diffraction pattern reveals B2 long range order.
The Influence of Short Range Order on the Energetics of Ni-Rich Nial Alloys
Authors: Wang Yang , Stocks G. M. , Nicholson D.M.C. , Shelton W. A. , Hines E. L. , Szotek Z. , Temmerman W. M. 
Published: April 2011

AbstractTotal energy calculations for Ni-rich ß′-phase NiAl have been performed using the large system multiple scattering (LSMS) method. The large samples used to model the alloys involved up to 128 atoms per cell, and were constructed to have the experimental short range order (SRO) parameters. Both short range ordering and charge transfer effects are automatically taken into account in the calculation. The calculated formation energies of both stoichiometric and non-stoichiometric compounds are in excellent agreement with experiment.
Atomistic Studies of Grain Boundaries in NiAl
Authors: Yan M. , Chen S. P. , Vitek V. 
Published: April 2011

AbstractThis paper presents the results of atomistic studies of grain boundaries in NiAl B2 alloy. The interatomic forces are described by Finnis-Sinclair type N-body potentials, and are fitted to properties of NiAl. The results show that the structure, energy and cohesive strength of a grain boundary depend strongly on its chemistry, and a grain boundary possessing more Al is the weakest. Energies of antisite defects at the grain boundary ∑5 {210} are also calculated, and the results suggest that Al has much larger tendency to segregate at a grain boundary than Ni does.
Subboundary Characterization and Creep Deformation in Investment Cast Ti-48Al-2Nb-2Cr
Authors: Jin Zhe , Bieler Thomas R. 
Published: April 2011

AbstractSubgrain boundaries (subboundaries) in a creep deformed investment cast Ti-48Al-2Nb-2Cr specimen were characterized. A multi-stress drop test was performed at temperature 765 °C and stresses from 276 MPa to 103 MPa. The stress exponent n = 7. Subboundaries were observed both in equiaxed γ grains and within γ laths in lamellar grains. Dislocations within the subboundaries are characterized to be ordinary 1/2<110] dislocations. Subboundaries are found to occur on many crystallographic planes and no preferred crystallographic planes are found for subboundary formation in the crept TiAl specimen. Misorientations across the subboundaries are less than 1°. Analysis of subboundary formation mode indicates that the creep deformation in TiAl is pure metal type.
Creep of Particle-Reinforced NiAl Intermetallics: New Materials For Up to 1400°C
Authors: Arzt E. , Grahle P. 
Published: April 2011

AbstractThe intermetallic compound NiAl is a promising high temperature material as it possesses a favorable combination of advantageous properties (high melting point, low density, high thermal conductivity, good oxidation resistance). However its creep resistance is far inferior to that of advanced superalloys. We have developed new powder-metallurgical NiAl alloys, where the creep strength is raised by incorporating fine yttria dispersoids. The materials are produced by mechanical alloying and subsequent coarse-grain recrystallization at temperatures close to the solidus temperature. The resulting alloys show exceptional creep strength up to 1400 °C, thereby exeeding the temperature capability of superalloys significantly. The creep properties are in agreement with our recently developed model for “detachment-controlled creep”, in which the release of dislocations from incoherent particles determines the creep rate. In addition, the brittleness problem at room temperature can be moderately alleviated by incorporating coarse ductile phases such as Mo. While the particles raise the critical stress intensity factor, they do not improve the room temperature tensile ductility.
Wear of Ductile-Phase Toughened NiAl
Authors: Kennedy F.E. , Baker I. , Johnson B.J. 
Published: April 2011

AbstractThe purpose of this work was to study the effect of ductile phases on the wear of brittle intermetallic compounds. The material system of interest was NiAl with an incorporated ductile Fe phase. Three different compositions were studied: Fe10Ni45Al45, Fe30Ni35Al35, and Fe44Ni28Al28, each after two different heat treatments. Their wear behavior in unlubricated sliding against zirconia was investigated using pin-on-disk tests at room temperature in air. Hardness and fracture toughness tests were run for the same materials to clarify the relationship between wear and deformation. Results for the ductile-phase toughened materials were compared with results of similar tests for unalloyed NiAl.
NiAl-Base Composite Containing High Volume Fraction of Aln Particulate for Advanced Engines
Authors: Hebsur Mohan G. , Whittenberger J. D. , Lowell C. E. , Garg A. 
Published: April 2011

AbstractCryomilling of prealloyed NiAl containing 53 at. % AJ was carried out to achieve high nitrogen levels. The consolidation of cryomilled powder by extrusion or hot pressing/hot isostatic pressing resulted in a fully dense NiAl-base composite containing 30 vol. % of inhomogeneously distributed, nanosized AlN particulate. The NiAl-30AlN composite exhibited the highest compression yield strengths at all temperatures between 300 and 1300 K as compared with other compositions of NiAl-AlN composite. The NiAl-30AlN specimens tested under compressive creep loading between 1300 and 1500 K also exhibited the highest creep resistance with very little surface oxidation indicating also their superior elevated temperature oxidation resistance. In the high stress exponent regime, the strength is proportional to the square root of the AlN content and in the low stress exponent regime, the influence of AlN content on strength appears to be less dramatic. The specific creep strength of this material at 1300 K is superior to a first generation Ni-base single crystal superalloy. The improvements in elevated temperature creep strength and oxidation resistance have been achieved without sacrificing the room temperature fracture toughness of the NiAl-base material. Based on its attractive combination of properties, the NiAl-30AlN composite is a potential candidate for advanced engine applications.