bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inertial Effects in the Dynamics of Martensitic Phase Boundaries
Authors: Truskinovsky Lev 
Published: March 2011

AbstractLocalized phase transitions, as well as shock waves, can be modeled by material discontinuities satisfying appropriate jump conditions. One can show that the classical system of Rankine-Hugoniot jump conditions is incomplete in the case of subsonic phase boundaries. The supplementary condition which generalizes the condition of phase equilibrium, can be obtained from the traveling wave solution of the truly dynamic system of equations describing the interface structure.
Shape Memory Behavior and Mechanical Properties of NiMn and Ni(Mn,X) Alloys
Authors: Yang W.S. , Mikkola D.E. 
Published: March 2011

AbstractPotential high transition temperature shape memory alloys based on NiMn have been studied with emphasis on the shape recovery, transformation temperatures and mechanical properties. Binary NiMn, which has been reported to be brittle, has a low shape recovery, but this can be increased with Al or Ti additions. Also, the transformation temperature can be changed and the room temperature ductility improved by ternary element additions. The various substitutional solute characteristics affecting the shape recovery, the transformation temperatures, and the ductility have been examined.
Orthorhombic Martensite, Intermetallic Precipitates and Retained Austenite in Ti-Rich Ti(Ni+Cu) Sputtered thin Films
Authors: Chang L. , Grummon D. S. 
Published: March 2011

AbstractPeriodic multilayered titanium-rich Ni-Ti thin films were prepared by magnetron sputtering from alternating Ni45Ti50Cu5 alloy and pure titanium targets, with an alloy-layerfl'i-layer thickness ratio of 9:1. The microstructure, martensite transformation behavior, and precipitate and defect structures were studied in films which had been annealed at 923K for one hour and furnace cooled at <20 K/min. Energy dispersive X-ray fluorescence measurements showed that the resulting films had a hyperstoichiometric titanium content of approximately 51 atomic percent. Ti2Ni precipitates were found in the annealed structures which were oriented with [1 1 0 ]Ti2Ni parallel to [110]B2 and (001)Ti2Ni parallel within +/− 10 to (001)B2. Differential scanning calorimetry (DSC) revealed an unusually low transformation enthalpy for the martensite reaction in the film (9.1 J/g as opposed to 20.7 J/g for the alloy sputtering target), and a significant fraction of residual B2 austenite was found at temperatures well below the nominal Mf. The martensite transformation was found to occur in two steps involving, on cooling, the initial formation of an orthorhombic martensite prior to transformation to the monoclinic martensite phase at low temperature.
Theory of Pre-Martensitic Effects in Alloys with ω- Transformation
Authors: Vul David A. 
Published: March 2011

AbstractIt is shown that the phonon dip in the longitudinal phonon branch L[111] in the metals Zr, Hf, Ti, Nb results in an oscillating component in static displacement field around a point defect. The oscillations have the wave vector 2/3(111) and occur in four rod-like shape regions along <111> directions. The value of the oscillations is much smaller then whole atomic displacements. Anomalies of the elastic diffuse scattering intensity from β-phase alloys based on the metals are explained as caused by the scattering on these distorted regions around solutes.
SMA and SME in Cu-Zn-Al Alloys: Local Studies inα, ε, T Space
Authors: Amengual A. , Isalgué A. , Lovey F.C. , Marco F. , Torra V. 
Published: March 2011

AbstractThe use of Cu-Zn-Al single crystals (electronic concentration e/a= 1.48) and of a high resolution equipment allows to study the evolution of one or few martensite domains. This kind of study proves the existence of intrinsic thermoelasticity, the differences between different friction processes (interface movements and nucleation) and also the coherence of the hysteresis loops obtained through mechanical stress or temperature. The different evolutions linked to the creation of dislocations or to the change of é precipitates can clearly be seen during the cycling. The observations allow to establish a model of the material behaviour consistent with experimental observation.
Effect of Superelastically Deforming NiTi Surface Microalloys on Fatigue Crack Nucleation in Copper.
Authors: Grummon D. S. , Nam S. , Chang L. 
Published: March 2011

AbstractAlloys based on near-equiatomic NiTi are capable of thermoelastic martensite transformations which give rise to shape memory and superelasticity (pseudoplasticity) effects. In particular, at temperatures above Ms and Af but below Md, NiTi alloys can deform by mechanisms of stressinduced martensite transformation and may display large anelastic strains which involve little or no deformation by slip. Under these conditions, the strain-controlled fatigue resistance of NiTi alloys may be exceptionally high [1]. In contrast, fcc metals like copper will, during strain controlled fatigue, eventuate severe plastic strain localization in the form of persistent slip bands (PSBs), whose behavior at free surfaces is intimately associated with fatigue crack initiation [2]. It is well known that fatigue crack initiation in fcc metals can be delayed by modifying surfacebreaking PSB structure or environment [3,4]. However, any attempt to strengthen the surface region in order to impede surface expression of persistent slip bands must contend with the large subsurface strain localizations enforced by the PSBs, which subject the film to strain cycling at roughly the characteristic PSB shear strain amplitude. Thermoelastic nickel-titanium alloys, capable of pseudoplastic straining, may be uniquely suited to the role of surface protection in situations where fatigue crack initiation is associated with PSB interaction with the external environment. In the present work, thin surface microalloys of NiTi, produced by ion sputtering, have been applied to polycrystalline copper fatigue specimens that were subsequently subjected to both monotonic loading, and fatigue under plastic strain control to produce mature PSB structures in the bulk material. Optical and scanning electron microscopy studies are described which assess the effect of the NiTi surface microalloy on the behavior of PSBs in the near surface region, and the attendant effect of the films on surface behavior of persistent slip bands. Although the results are incomplete with respect to the effects of the film on fatigue crack initiation, it has been shown for the first time that martensite transformation can be stress-induced (at temperatures above Ms) in a thin NiTi film on a plastically deforming substrate. This finding augurs well for the potential of such films to effectively suppress slip band penetration during low cycle fatigue.
Electric Transport Properties of a NiTi Shape Memory Alloy Under Applied Stress.
Authors: Airoldi G. , Riva G. , Ranucci T. , Vicentini B. 
Published: March 2011

AbstractIt is well known that mechanical properties of Shape Memory Alloys are strongly dependent upon the test temperature (T) respect to transformation temperatures: the stress-strain curves however hinder the true deformation processes acting.Electrical resistance(ER), a physical property sensibly affected by electronic structure modifications, traditionally used to follow the growth of thermal martensite, is here investigated to follow the modifications of a NiTi alloy, in an initial single phase structure, under applied stress. ER measurements are here detected with the aim to distinguish different deformation processes at four test temperatures Ti (i=1,..,4): in martensitic phase,either at T1 <Mf or at T2<As within the hysteresis cycle; in parent phase, either at Af<T3 or at Ms<T4 within the hysteresis cycle, where T2 = T4. Results are examined in comparison with previous obtained data and discussed at the light of imprinted deformation.
The Influence of Thermomechanical Treatment on R–Phase Transition and Shape Memory Effect
Authors: Jinfang Guo , Yuying Cheng , Ming Zhu , Long Shen , Guansen Yuan 
Published: March 2011

AbstractThis paper discussed the influence of cold working and annealing process on R–phase SME in an equiatomic TiNi alloy by means of tensile test, phase transformation, temperature measurement, and shape recovery examination. The results show that the increase in cold deformation of TiNi alloy got the increase in both tensile strength and R–phasc transition (TR–Ms). As R–phase becomes stable, the SME will be improved and the decay of memory effect will also be controlled at fatique test. The increase in annealing temperature got the decrease in R–phase transition range. In that case the stability of R–phase and the SME of the alloy also become bad. When annealing at 600°C, the recrystallization occurs no R–phase is found. Surely the SME of alloy becomes bad.
Material Characterization of Rapidly Solidified Ti-Ni-Cu Alloys
Authors: Furuya Y. , Matsumoto M. , Masumoto T. 
Published: March 2011

AbstractMaterial properties of of rapidly solidified(RS),Ti5øNi5ø-xCux(X=O-2Oat%) alloys,i.e., thermoelasatic transformation temperature,transformation strain vs. temperature hysteresis, strength.ductility,themal fatigue resistance and corrosion resistance etc. were investigated. Specimens of thin ribbon were prepared by using melt-spinning machine with single Cu rolls at the cooling rate of about 40 m/sec. In the range of Cu content over lOat%,rapidly solidified (RS)ribbons were producible as a very thin plate and showed high ductility(i.e.180° bending). From the measurements of transformation strain vs. temperature hysteresis under small stress a bout 60MPa,transformation strain shows the maximum at Cu=5at%,and its transformtion temperature range nΔ(=Af-Mf) decreased with increasing Cu content to minimum value of 6.5K at Cu=17 at%. Thermal fatigue resistance was improved very much about ten times,futhermore,corrosion resistance was also improved over 100 times as much as conventionally processed(i.e. melting→ mechanically worked) material. It can be concluded that the functional superioity of RS meltspun Ti5øNi5ø-xCux ribbon exists in the range of Cu content over 10 at%. The reason of abovementioned remarkable improvements of material properties of RS TiNiCu alloys is discussed by relating with the observed unique fine columnar microstructures having strong crystal anisotropy and homogeneouss smooth surface.
From a Seed to a Need: the Growth of Shape Memory Applications in Europe.
Authors: Humbeeck Ir. J. Van 
Published: March 2011

AbstractA more systematic marketing research approach has finally revealed good ideas anticipating a market need for the use of shape memory alloys. The success of those new ideas, prototypes and applications are analysed in terms of “the value of the function”, defined as the importance of the function divided by the cost of providing the function. A high importance and/or a low cost of the function are thus the basic requirements for the successful introduction of shape memory applications. Attention is also paid to the way how the 4 P's, product, price, place, promotion (the marketing mix) are applied by the European companies. Those different items will be illustrated on the basis of some small-, medium- and largescale applications, used in different markets. “to the point research”, fundamental and applied, on material properties as well as on manufacturing (cost reduction) is being discussed as the key factor to increase the function value.
The Interior of the Pseudoelastic Hysteresis
Authors: Fu Senlin , Müller Ingo , Xu Huibin 
Published: March 2011

AbstractAn interesting problem within the research on shape memory is provided by the investigation of the pseudo-elastic hysteresis loop that accompanies the strain-induced austenitic-martensitic phase transition. Miller [1] suggested by thermodynamic arguments that the size of that loop should be related to the coherency energy at interfaces between martensite and austenite. That proposition received a boost when Müller & Xu [2] showed that the same thermodynamic arguments predicted the onset of internal yield and recovery inside the hysteresis loop on a well-definqd line of unstable phase equilibrium. Recently Fu, Müller and Xu [3] have reported results with improved specimens and methods of observation that may help to understand the nature of metastability inside the hysteresis loop.
Aging Effects of Cu-Zn-Al Shape Memory Alloys Studied by the Alchemi Measurements
Authors: Shimizu K. , Nakata Y. , Yamamoto O. 
Published: March 2011

AbstractThe aging effects of two kinds of Cu-Zn-Al shape memory alloys (Cu-ll.4 Zn-18.7A1 (A) and Cu-ll.2Zn-17.lAl (B) in at%) have been examined by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atom location by channeling enhanced microanalysis (ALCHEMI). In the directly quenched (D.Q.) state, alloy A was the parent phase, Ms being 253 K, and alloy B was the martensite phase. The alloy B was subjected another quenching treatment as follows: It was once quenched into an oil bath at 423 K and held for 300 s, followed by quenching into iced water (step quench (S.Q.) ). The D.Q. alloy B did not exhibit the reverse transformation because of a stabilization of the martensbite phase, but the S.Q. alloy B did and its As temperature of the reverse transformation was raised with the progress of aging at the martensitic state. Fraction of Zn atoms at the Cu(2) site examined by the ALCHEMI measurements was almost the same in the parent phase of D.Q. alloy A and its aged one, indicating no change in Cu and Zn atom sites, while it was gradually decreased in S.Q. alloy B with the progress of aging. The fraction of Zn atoms in D.Q. alloy B was much lower than those in the S.Q. alloy B and its aged one. TEM observation of the S.Q. alloy B revealed that stacking faults as the lattice invariant shear in the M18R martensites decreased in the density with the progress of aging. The decrease in the fraction of Zn atoms and in the density of stacking faults well corresponds to the increase in As temperature, and thus the martensite stabilization was attributed to a disordering between Cu and Zn atoms and to an annihilation of stacking faults.
Two - Step Martensitic Transformations in TiNi(10% Cu) Shape Memory Alloys
Authors: Moberly Warren J. , Duerig T.W. , Proft J.L. , Sinclair R. 
Published: March 2011

AbstractThird element additions to TiNi provide a wide range of modifications of its shape memory properties. The advantages of Cu additions are to provide a more narrow hysteresis, less sensitivity to the Ti::Ni(+Cu) ratio of the temperature at which martensite starts to form (Ms), a larger strength differential between the austenite and martensite phases, and superior fatigue resistance. The substitution of a few atomic percent Cu for Ni does not significantly alter the crystal structure of either the cubic B2 austenite nor the monoclinic B19ʹ martensite phases; however, the addition of greater than 10% Cu results in an orthorhombic B19 martensite phase. For the case of 10% Cu, a two-step martensitic transformation occurs upon cooling, with the cubic austenite transforming to the orthorhombic B19 martensite and subsequently to the monoclinic B19ʹ martensite. As a result of this two-step crystallographic transformation, material properties such as resistivity and shape change also exhibit a two-step transformation.In situ transmission electron microscopy heating and cooling experiments are used to observe the two-step martensitic transformation and to establish an orientation relationship between the B19 orthorhombic and the B19ʹ monoclinic structures. Strain vs temperature Ms tests establish the relative shape changes associated with both the cubic-to-orthorhombic transformation and the orthorhombic-to-monoclinic transformation. Similar Ms tests, where an applied load is removed during the transformation, establishes a crystallographic dependence between the two shape changes. Whereas binary TiNi is "trained" to undergo a specific shape change, this ternary TiNiCu alloy has a "natural" direction associated with the second step of its shape change.
Aging Effects in Ni-36% Al Shape Memory Alloy
Authors: Angst David R. , Kao Ming-Yuan , McKinney Bryan L. 
Published: March 2011

AbstractSamples of Ni-36 at% Al which were hot rolled, then solutionized at 1230°C and quenched, exhibited reversible transformations between the low-temperature, martensitic phase and the high temperature, austenitic phase. The initial peak transformation temperatures on heating (AP), cooling (MP), and the heats of transformation (ΔH) determined by differential scanning calorimetry (DSC) were ∼121°C, 119°C and 4 J/g, respectively for the as-solutionized material.Decreases in transformation temperatures and heats after aging at 350°C were also determined using differential scanning calorimetry (DSC), and microhardness testing (DPH). The DPH values plotted against age time showed two distinct peaks, a result similar to precipitation hardening in other Al alloys.
Ordered Structure of Copolyesters Having Mesogenic Components
Authors: Niki Akihiro , Hasegawa Hirokazu , Hashimoto Takeji 
Published: March 2011

AbstractOrdered structures of the multiblock copolyesters composed of p-quarterphenyl (DHQ, rigid segments) and poly(ethylene adipate) (flexible segments) were investigated by means of WAXD and SAXS. It was found that only the DHQ segments crystallize but the poly(ethylene adipate) segments hardly crystallize which make this copolyester a good thermoplastic elastomer. The copolyesters exhibit microphase separation above the melting temperature of the DHQ segments.
Study of the Reduction of Turbulent Drag by Photon Correlation Spectroscopy
Authors: Tong P. , Goldburg W. I. , Huang J. S. 
Published: March 2011

AbstractTurbulent drag reduction in a dilute polymer solution has been studied using the technique of photon-correlation homodyne spectroscopy to measure velocity differences in a concentric cylinder cell, in which the inner cylinder rotates. A large anisotropic suppression of turbulent velocity differences is found in the bulk region of the turbulent fluid. The suppression effect occurs at various length scales up to ∼ 1 mm, which is far beyond the Kolmogorov dissipation length ℓd (∼ 0.04 mm). The large-scale velocity fluctuations are suppressed, but their statistical properties remain unchanged. The small-scale fluctuations, on the other hand, are damped out much more strongly, resulting in a different functional form for the velocity density function. The latter observation is consistent with the notion that the polymer-turbulence interaction causes a truncation of the turbulent energy cascade at small scales.
Colloidal Dynamics from Forced Rayleigh Scattering
Authors: Gochanour C. , Mazur S. , Wolfe M.S. 
Published: March 2011

AbstractColloidal suspensions are remarkable analogues of molecular fluids. In particular, at high volume fraction (Φv) they share two characteristic features with super-cooled molecular liquids: the appearance of two distinct modes of translational motion (fast and slow diffusive modes), and a critical retardation of the latter as Φv approaches random close packing (a colloidal “glass transition”). These phenomena have been studied extensively by photon correlation spectroscopy (PCS) [1-4] and are the subject of many theoretical analyses [5-12]. This paper concerns the use of forced Rayleigh scattering (FRS) to address questions not resolved by existing data or theory. We report: 1) properties of a hydrophobic silica colloid bearing photoactive azo-dye groups suitable for FRS studies, and 2) preliminary results from FRS measurements which reveal some unanticipated features regarding the transition from short-time to long-time self-diffusion at small k.
The Use of Mechanical Property Measurements to Characterize Gels and Gelation Processes
Authors: Yang Y. , Ichise N. , Li Z. , Yuan Q. , Mark J. E. , Chan E. K. M. , Alamo R. G. , Mandelkern L. 
Published: March 2011

AbstractThere are a variety of gels (highly swollen solids) that are of considerable interest to polymer scientists, materials scientists, and ceramists. One type consists of typical organic polymers such as polyethylene or polystyrene, in networks which are formed by means of physical cross links, such as crystallites or physical aggregates. Such gels are thermoreversible in that liquefaction occurs upon heating. Another type consists of chain-like structures permanently bonded into covalent networks. These permanently branched and cross-linked chains can be either organic (phenol-formaldehyde resins, epoxies, etc.), or inorganic [silica (SiO2), titania (TiO2), zirconia (ZrO2), etc.] Both the organic and inorganic covalent types have been used to prepare aerogels, and the inorganic ones are now much used to prepare high-tech ceramics by the new sol-gel route.In the case of the thermoreversible, organic polymer gels, moduli can be measured as a function of concentration, temperature, and structural characteristics of the polymer (molecular weight, molecular weight distribution, and nature and degree of any chain branching). Such equilibrium results give information on the nature of the gels, including the influence of morphology, and the presence of dangling-chain irregularities. Measurements carried out as a function of time, for example, on polyethylene homopolymers and copolymers, can give information about their gelation kinetics.In the case of the ceramic materials, the evolution of the shear modulus with time is very useful in establishing induction times, rates of gelation, and aging effects. Correlation of such information with results of scattering studies can give much insight into the nature of the sol-gel process.
Sol-Gel Diagram of Silica-Siloxane Mixtures. Percolation Approach
Authors: Cohen-Addad J.P. 
Published: March 2011

AbstractThe property of elasticity and the effect of swelling of mechanically induced silica-siloxane mixtures are interpreted within a percolation framework. This approach is illustrated by varying the specific amount of adsorbed polymer upon the silica surface of aggregates.
Structure of The Diblock Co-Polywer Aggregates in Solution
Authors: Huang J. S. , Fetters L. J. , Sung J. , Lin H. Y. , Richter D. , Hadjichristidis N. , Farago B. , Gast A. P. 
Published: March 2011

AbstractWe have employed a variety of scattering techniques to study the structure of diblock copolymer aggregates in solution The system of interest is an anionically prepared poly(styrene-isoprene) diblock copolymer (PS-PI) with well defined molecular weight and composition. When the diblock copolymer is added to decane, which dissolves the polyisoprene but not the polystyrene, we observe that polymeric micelles form at concentrations above a critical micellar concentration. The aggregation number is determined by light scattering and neutron scattering to be roughly 120. The micellar aggregate consists of a spherical polystyrene core with a mean radius of 105 A surrounded by a PI corona. The size distribution is quite narrow (<10%). The PS core is swollen with the solvent by roughly a factor of 2 in volume. By combining dynamic light scattering and SANS, we determined the thickness of the corona to be 50 A, which is 70% larger than the radius of gyration of a free PI chain of the same molecular weight in a good solvent. Furthermore, SANS measurements suggest that the aggregates form an ordered phase at the nominal cross-over concentration as it is expected for a highly functionalized star-branched macromolecules in solution.