bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of Boundary Free Tb-Dy-Fe Magnetostrictive Materials
Authors: Li Qiang , Chang Y.L. , Ouyang Shixi , Yuan R.Z. 
Published: April 2011

AbstractAs a promising candidate of advanced smart materials Tb-Dy-Fe system has been studied for many years. It is well known that the boundaries (which exist in polycrystal and grain oriented crystals of magnetostrictive materials) heavily hinder the motion of domain walls. Therefore to eliminating those boundaries will improve their magnetostrictive behaviors to a large extent. A single crystal growth method (which is called: growth with magnetic levitation cold crucible in CZ technique) has been successfully developed in our lab. since a few years ago. Now bulk cubic Laves phase RFe2 TbxDy1-xFe1.95–2.0 single crystals with boundary free structure can be prepared. Studies have been focused on comparing the performances of polycrystal, grains oriented crystal with a single crystal of the same composition. Some results indicate that λs and d33 performed by the single crystal are much higher than the two former materials under the same conditions.
Electrically-Induced Strains in Sn-Modified Lead Zirconate Titanate
Authors: Li Jie-Fang , Dai Xunhu , Forst Donald , Viehland Dwight 
Published: April 2011

AbstractIncommensuate antiferroelectric tin-modified lead zirconate titanate ceramics, PbNb0.02[(Zr1−x,Snx)1−yTiy]0.98O3, have been studied by Sawyer-Tower polarization and electrically-induced strain (ε-E) techniques. Sawyer-Tower polarization studies revealed antiferroelectric-ferroelectric (AFE-FE) P-E loops. Investigations then revealed that the electrically-induced strain associated with the AFE-FE transformation was not realized until field strengths significantly above that required for polarization saturation. It is believed that the electrically-induced strain is decoupled from the polarization due to AFEFE switching by the modulation of the phase of a <110> incommensurate structure. At field strengths above saturation, the commensurate rhombohedral ferroelectric state is believed to be induced from an incommensurate orthorhombic ferroelectric, and the electrically-induced strain is then realized.
Electro-Mechanical Properties of PbZrO3-PbTiO3 -Pb(Mn1/3Sb2/3)O3 Ceramics Under Vibration-Level Change
Authors: Takahashi Sadayuki , Sasaki Yasuhiro , Hirose Seiji , Uchino Kenji 
Published: April 2011

AbstractElectro-mechanical properties in the pseudo-ternary solid solution system of PbZrO3-PbTiO3- Pb(Mn1/3Sb2/3)O3 piezoelectric ceramics were studied by changing the vibration- level using a constant current / velocity driving method. The vibration velocity is proportional to the driving electric field under a relatively low field. The velocity, however, deviates from a linear relationship as electric field increases and converges on a certain value.The increase of the vibration-level is accompanied by a large amount of heat generation as well, and this heat generation sets a practical upper limit of the vibration-level. The heat generation is caused by a dissipated-vibration-energy which is represented as a function of vibration velocity and the constants depending on the materials and transducers.In these pseudo-ternary solid solution ceramics, the compositional ratio which shows excellent electro-mechanical properties under a relatively low vibration-level does not necessarily coincide with the compositional ratio which is excellent under a relatively high vibration-level.
Magnetostrictive Damping to Reduce Noise and Vibrations
Authors: Karimi A. , Giauque P. H. , Martin J. L. 
Published: April 2011

AbstractThe magnetomechanical damping capacity of cast and thermally sprayed Fe-Cr based alloys has been investigated using free and forced vibration techniques. The coatings were deposited using a vacuum plasma spraying method and the cast alloys were prepared in a high frequency furnace under an argon atmosphere. Three laboratory devices including a torsion pendulum, a resonant bar and a cantilever were used to cover a wide range of frequencies and amplitudes varying between f = 1Hz to 10 kHz, and ε = 10−6to 10−3. The damping capacity of the plasma sprayed coatings was found to be comparable to that of cast alloys. Appropriate heat treatments improved the damping capacity of both coatings and cast alloys by several times. The variation of the loss factor as function of the vibration amplitude showed a maximum, but versus frequency exhibited a slightly monotonous character. The magnetic domains were observed using the magneto-optical Kerr effect and their modification under heat treatments was associated with different values of the damping capacities.
Effects of the Multilayer Structure on the Responsivity of Pyroelectric Thin Film Detectors
Authors: Jianguo Zhu , Dingquan Xiao , Zhenghong Qian , Wen Zhang , Siaosong Du 
Published: April 2011

AbstractPyroelectric thin film detectors have advantages of wavelength independent sensitivity, room temperature operation and direct incorporation with integrated circuit amplifiers. Pyroelectric thin films with good quality have be prepared by many advanced thin film technologies [1-2]. The responsivity of pyroelectric thin film detectors is dependent on the thermal properties of the substrate, on which pyroelectric thin film detectors are prepared. The heat conduction in the detectors was investigated using the one-dimensional heat flow equation and the expressions describing the detectors performance were derived for pyroelectric thin films detectors with multilayer structure. The numerical simulation showed that the pyroelectric thin film detectors need effective heat isolation. If the air gap could be the heat isolation layer, which is between the bottom electrode and substrate, the iesponsivity of detectors would be higher than that of detectors which have no heat isolation in certain modulation frequency range.
Recent Developments in High Temperature Shape Memory Alloys
Authors: Beyer Jeno , Mulder Jan.H. 
Published: April 2011

AbstractThe functional properties of Shape Memory Alloys (SMA's) are used succesfully at present in a variety of industrial and medical applications. The use of these materials in smart structures is now emerging in the field of aeronautic/space technology. Many applications require higher operating temperatures than available to date, or higher cooling rates and/or a higher number of cycles. For this purpose the properties and fabricability of commercial alloys as Ni-Ti-(X), Cu-Al-Ni or Cu-Zn-Al are being adjusted and improved. Other feasible alloys are being developed. The research and development is directed towards the control of the stress, strain, temperature and time dependence of shape memory properties for a stable in-service behaviour. In this paper the various approaches taken up in recent years by academic and industrial laboratories for developing high temperature SMA's are reviewed.
Development of NiAI(B2)-Base Shape Memory Alloys
Authors: Kainuma R. , Ono N. , Ishida K. 
Published: April 2011

AbstractThe basic concept underlying the alloy design and microstructural control method utilised in developing a new type ofβ(B2)+ γ (A1) two-phase ductile shape memory alloy in the Ni-Al base systems is briefly reviewed. The characteristic features of the shape memory effect (SME) in the Ni-Al-Fe and Ni-Al-Fe-Mn alloys are reported with particular reference to the transformation and deformation temperatures, the volume fractions of theγphase, the morphology of theβ + γstructure and the effect of cycling. Training by cycling treatment has a significant effect on the degree of shape recovery and pseudo-elasticity in theβ + γtwo-phase alloys. These duplexβ + γalloys also exhibit a combination of relatively high damping capacity and high yield strength. It is emphasized that these alloys could be expected to fill the need for a new group of shape memory alloys which operate at elevated temperatures over 100°C.
The Effects of La on Rapidly Solidified Al – 66 at.% NI
Authors: Sun Baode , Zhou Yaohe , Lin Hul , Lin Dongllang 
Published: April 2011

AbstractThis paper investigates the microstructure and ductility of Al - 66 at.% Ni by means of melt spinning technology combined with La microalloying. It shows that the Al - 66 at.% Ni without La exhibits coarse equiaxed martensite grains with Ni3Al precipitating at the grain boundaries (GBs). An addition of 0.05 wt.% La suppresses the precipitation of Ni3Al and a microstructure of complete martensite is obtained. When the amount of La is 0.2∼0.8 wt.%, a “supersaturated” single phase of B2 structure NiAl results. The elongation of Al - 66 at.% Ni without La is only 0.8%. When 0.05, 0.2, and 0.8 (wt.%) La are added to the alloy, their elongations can be as high as 2.6, 3.0, and 3.2% respectively. This shows that the elongation increases with increasing La content. The microstructural morphology and the ductility enhancement mechanism are discussed.
A Dye-Dispersed Liquid Crystal Smart Reflector
Authors: Chang Ching-Chao , Lonberg Franklin , Meyer Robert B. 
Published: April 2011

AbstractWe report a liquid crystal smart reflector, consisting of a cholesteric liquid crystal doped with dye. Light entering the liquid crystal is absorbed by the dye, generating heat which raises the average temperature of the liquid crystal. This in turn changes the pitch length of the cholesteric liquid crystal, causing an increase in its reflectivity, and thus reducing the amount of light absorbed by the dye molecules. A negative feedback stabilized condition is reached, in which the reflectivity is proportional to the incident light intensity. This effect is demonstrated both theoretically and experimentally.
Site Preference of Ternary Additions in Ni3Si
Authors: Sluiter M. , Kawazoe Y. 
Published: April 2011

AbstractThe site preference of Al and elements in the 3rd row of the periodic table in Ni3Si was studied in a systematic way by using electronic structure calculations based on the local density approximation. Alloying elements in this intermetallic may occupy exclusively the Ni or Si sublattices, or may exhibit no particular site preference. By performing the calculations both for spin-polarized and non-spin-polarized cases, it was found that magnetism affects the computed site substitution behavior of Mn, Fe, and Co in Ni3Si. In the case of Fe, e.g., a preference for the Ni sublattice is computed when magnetic effects are ignored, but when magnetic effects are accounted for it is found that Fe has no significant site preference Specific trends regarding the site preference across the transition metal series are shown and discussed.
Theoretical and Experimental Studies on the C15 Intermetallic Compound NbCr2
Authors: Chu F. , Thoma D. J. , He Y. , Mitchell T. E. , Chen S. P. , Petepezki J. H. 
Published: April 2011

AbstractThe electronic structure and total energy of the C15 NbCr2 phase have been calculated using the linear muffin-tin orbital (LMTO) method with the atomic sphere approximation (ASA). The total energy vs. volume curve, band structure, density of states and Fermi surface were obtained. The calculated results were used to examine several features of the C15 phase, including the elastic properties, phase formation and stability, and solubility range of the C15 phase. The theoretical results are compared to experimental studies on NbCr2 For example, the elastic moduli, phase stability, and homogeneity range have been determined with a variety of experimental techniques. Comparison of the experimental and theoretical results will be discussed.
Observation of Precipitation of the Intermetallic Phase Mg17Al12 In Mg-Al Alloys By 25Mg and 27Al Nmr
Authors: Bastow T. J. , Smith M.E. 
Published: April 2011

AbstractThe strength of the lightweight Mg(Al) alloys with Al concentration less than 10 wt% is due to controlled precipitation of the intermetallic phase Mg17Al12. This phase and its solid solution host have been characterised by 25Mg and 27Al NMR in terms of Knight shifts and nuclear quadrupole interactions for the distinguishable Mg and Al sites.
Alloying Effect on the Environmental Embrittlement of Ni3(Si,Ti) Alloys
Authors: Ma C. L. , Takasugi T. , Hanada S. 
Published: April 2011

AbstractThe effect of additions of chromium, manganese and iron on environmental embrittlement of the Ni3(Si,Ti) alloy is investigated by room temperature tensile tests in various kind of atmospheres (vacuum, air, distilled water and H2 gas) and at various strain rates. The observed tensile elongation and the associated fracture mode are very much dependent on atmospheres and strain rates. It is shown that additions of these transition elements to the Ni3(Si,Ti) alloy are effective in reducing the embrittlement particularly in air and distilled water, and their magnitude of reducing the embrittlement decreased in the order, chromium, manganese and iron. However, additions of these transition elements are only slightly effective in reducing the embrittlement in H2 gas. The beneficial effect of additions of these transition elements on environmental embrittlement of the Ni3(Si,Ti) alloy is discussed, based on some possible mechanisms.
Atomic Ordering and Lattice Site Location in Cubic (L12) Al3Ti-Based Alloys
Authors: Kim S. M. , Kogachi M. , Kameyama A. , Morris D. G. 
Published: April 2011

AbstractNeutron powder diffraction measurements have been carried out on cubic Al3TiX compounds (X = Cu, Cr, Mn, Fe and Ni) as a function of temperature from room temperature to 1200°C. The data were analysed by the Rietveld method in order to determine the ordering and lattice site location of the constituent atoms. All these intermetallic compounds were found to be highly ordered at room temperature, and a significant increase in disorder at higher temperatures was observed only in alloys containing Cr and Cu.
Disordering and Reordering Kinetics of a Fe–40A1 B2 Alloy
Authors: Gialanella S. , Baró M. D. , Lutterotti L. , Suriñach S. 
Published: April 2011

AbstractThe ordered structure of Fe–40A1 B2 powders was completely disordered by high energy ball-milling. The defect structures of the powders disordered to different extents were characterized using X-Ray diffraction. A significant lattice expansion was observed, which we tried to relate to the high concentration of point defects introduced into the material as a consequence of milling.A complete reordering was accomplished by heating up the specimens under an inert Ar atmosphere. We followed the kinetics of the disorder to order transformation by Differential Scanning Calorimetry and Thermogravimetric Magnetic Measurements. The two techniques allowed us to identify the temperature range and the apparent activation energy of the process. As expected, a decrease in the magnetic moment of the originally disordered powders as a consequence of the reordering treatments was also observed.
Screw Dipoles Acting as Strong Locks in Ni3Al
Authors: Karnthaler H. P. , Rentenberger C. , Yu H. 
Published: April 2011

AbstractSingle crystalline specimens of L12 ordered binary Ni3A1 and Ni3(A1,B) with single slip [123] and multiple slip [001] orientations were deformed in compression within the anomalous temperature regime. In all cases the TEM investigations show that dipoles of locked screws are a dominant feature of the dislocation structure. This is of special interest since screw dipoles are not observed in disordered fee structures. The results indicate that screws interact and form long sessile dipoles even when their height is much larger (= factor of 10) than that given by the passing stress. The minimum height of the screw dipoles is about 16±4 nm and seems to be given when the interaction stress corresponds to the saturation stress. In the dipoles the locked screws are very difficult to unlock since the external stress is screened to a large extent. Therefore the deformation has to occur by the movement of edge segments. It is suggested that based on this exhaustion of the screws steady state conditions do not always apply on a local scale.
Yield Stress Reversibility and the Operation of Frank-Read Sources in Li2 Alloys in the Anomalous Regime For (111) Slip
Authors: Ezz S. S. , Hirsch P. B. 
Published: April 2011

AbstractThe yield stress τy at small strains (≈ 0.01%) is strain rate independent, and has the same anomalous temperature dependence as that of the 0.2% strain. τy is considered to be the stress at which Frank-Read sources operate in a virgin crystal. For successful operation, τy must exceed the stress τs at which screws propagate dynamically through the crystal, and the source dislocation must pass rapidly through the unstable Frank - Read configuration. This can be achieved by the bowing edge dislocation overcoming local obstacles before reaching that configuration. Loops elongated along the screw direction are expected to be formed in the microstrain region. Under certain conditions such loops are unstable on unloading, thereby generating long edge dislocations which can operate successfully as sources at low but not at high temperatures, explaining the reversibility phenomenon.
A New Interpretation of Stress Relaxations in Ni3(Al,Hf) Single Crystals.
Authors: Bonneville J. , Spätig P. , Martin J.-L. 
Published: April 2011

AbstractA technique of repeated stress relaxations is used to characterise the strain hardening rate (K) and the mobile dislocation density (ρm) in the flow strength anomaly domain of Ni3(Al,Hf) single crystals. It is shown that there is no independent means for measuring both effects but that reasonable assumptions about the strain hardening rate lead to determine the variation of ρm during relaxation. Preliminary results indicate that during relaxation ρm decreases more rapidly with strain (stress) when the temperature is raised.
Influence of Dislocation Mobility on Room and High Temperature Ductility of <100>-Oriented Nial Single Crystals
Authors: Morris M. A. , Perez J. P. , Darolia R. 
Published: April 2011

AbstractThe dislocation configurations produced by room and high temperature compression of <100> oriented single crystals of binary NiAl and in those containing iron and hafnium additions have been analysed and compared to those obtained by hardness indentation and TEM insitu tensile tests. Kinking occurs during room temperature compression such that <100> dislocations are activated in all cases but the iron-containing alloy also exhibited a large density of <111> screw dislocations. The latter however, appear immobile when they are created by hardness indentations of thin foils, while only pile-ups of <100> segments can propagate. Similarly, although different slip systems are present after high temperature compression, only <100> dislocation segments have been confirmed to be mobile after room temperature hardness indentation of these predeformed thin foils. The improvement in ductility observed at room temperature in the predeformed specimens of the binary and the iron containing alloys has been attributed to the increased production of these mobile <100> dislocations.
Local Electronic Structure and Cohesion of Grain Boundaries in Ni3Al
Authors: Muller D. A. , Subramanian S. , Sass S. L. , Silcox J. , Batson P. E. 
Published: April 2011

AbstractOne of the fundamental questions concerning Ni3Al is why doping with boron improves the room temperature ductility of the polycrystalline material. Boron is thought to prevent environmental embrittlement and increase the cohesive strength of grain boundaries since it changes the fracture mode from intergranular to transgranular. This change in cohesive energy must be reflected in the bonding changes at the grain boundary which can be probed using spatially resolved electron energy loss spectroscopy (EELS). We have examined grain boundaries in both undoped and boron doped Ni0.76Al0.24using EELS, EDX and ADF imaging in a UHV STEM. Ni-enrichment is seen in a 0.5–1 nm wide region at large angle grain boundaries, both in the absence and presence of B. EELS shows that B segregation can vary along the interface. The Ni L2, 3core edge fine structure which is sensitive to the filling of the Ni d-band, shows only the boron rich regions of the grain boundary to have a bonding similar to that of the bulk material. These results demonstrate that boron segregation increases the cohesive energy and hence improves the fracture resistance of the grain boundary, by making the bonding at boundaries similar to that in the bulk. The measured changes in d band filling may also affect the local solubility of hydrogen.
The Effect of Nitrogen on the Oxidation of TiAl
Authors: Dettenwanger Franz , Schumann E. , RÜhle M. , Rakowski J. , Meier G. H. 
Published: April 2011

AbstractTi-50(at.%)Al samples were oxidized at 900°C in air for 1 hour and studied by electron microscopy. The application of electron spectroscopic imaging with energy filtered TEM permitted the imaging of the distribution of the relevant elements (Ti, Al, O, N) within the oxide scale. With this method the formation of TiN in the inner part of the scale could be shown. The oxidation in air lead to an alternating scale containing TiN and alumina near the metal/scale interface. The formation of an aluminum-depleted second metallic phase in the metal beneath the oxide scale was observed.
A Non-Linear Behavior Model for SiC/SiC Composites
Authors: Kibler J.J. , Jones M.L. , Yen C.F. 
Published: April 2011

ABSTRACTAn interactive analytical model has been developed for modeling the behavior of Continuous Fiber reinforced Ceramic matrix Composites (CFCC). The model integrates a large number of micromechanics solutions to problems associated with the microstructure of CFCC materials into an easy to use tool for predicting properties, strengths, and stress states for these materials in unidirectional and laminated forms. Particulate reinforcement and voids can be included in the material description. Inherent in the code is a model for handling the accumulation of micro cracks within the matrix as loading is increased, resulting in a nonlinear stress-strain response of the composite. Sufficient material characteristics are retained within the model to enable sensitivity studies to identify principal causes for material behavior.
A Numerical Analysis of Fracture and High Temperature Creep Characteristics of Composites with Discontinuous Ductile Reinforcements
Authors: Biner S. B. 
Published: April 2011

ABSTRACTThe role of the material parameters on the fracture and creep behavior of discontinuous ductile fiber reinforced brittle matrix composite system was numerically investigated. For simulation of fracture behavior, the ductile fibers were modeled using a constitutive relationship that accounts for strength degradation resulting from nucleation and growth of the voids. The matrix is assumed to be elastic and fails according to requirements of a stress criterion. Results indicate that the contribution of ductile reinforcement to the work of fracture value (toughness) of the composite increases with less exhaustion of its work hardening capacity before the onset of matrix failure. At creep regime, for rigidly bonded interfaces, the creep rate of the composite is not significantly influenced by the material properties of the ductile reinforcing phase due to development of large hydrostatic stress and constrained deformation in the reinforcement. Significant increases in room temperature fracture toughness can be achieved without extensively sacrificing the creep strength by ductile discontinuous reinforcements.