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Sample records for memory alloy thin

  1. Novel tribological systems using shape memory alloys and thin films

    Science.gov (United States)

    Zhang, Yijun

    Shape memory alloys and thin films are shown to have robust indentation-induced shape memory and superelastic effects. Loading conditions that are similar to indentations are very common in tribological systems. Therefore novel tribological systems that have better wear resistance and stronger coating to substrate adhesion can be engineered using indentation-induced shape memory and superelastic effects. By incorporating superelastic NiTi thin films as interlayers between chromium nitride (CrN) and diamond-like carbon (DLC) hard coatings and aluminum substrates, it is shown that the superelasticity can improve tribological performance and increase interfacial adhesion. The NiTi interlayers were sputter deposited onto 6061 T6 aluminum and M2 steel substrates. CrN and DLC coatings were deposited by unbalanced magnetron sputter deposition. Temperature scanning X-ray diffraction and nanoindentation were used to characterize NiTi interlayers. Temperature scanning wear and scratch tests showed that superelastic NiTi interlayers improved tribological performance on aluminum substrates significantly. The two-way shape memory effect under contact loading conditions is demonstrated for the first time, which could be used to make novel tribological systems. Spherical indents in NiTi shape memory alloys and thin films had reversible depth changes that were driven by temperature cycling, after thermomechanical cycling, or one-cycle slip-plasticity deformation training. Reversible surface topography was realized after the indents were planarized. Micro- and nano- scale circular surface protrusions arose from planarized spherical indents in bulk and thin film NiTi alloy; line surface protrusions appeared from planarized scratch tracks. Functional surfaces with reversible surface topography can potentially result in novel tribological systems with reversible friction coefficient. A three dimensional constitutive model was developed to describe shape memory effects with slip

  2. A Homogenized Free Energy Model for Hysteresis in Thin-film Shape Memory Alloys

    National Research Council Canada - National Science Library

    Massad, Jordan E; Smith, Ralph C

    2004-01-01

    Thin-film shape memory alloys (SMAs) have become excellent candidates for microactuator fabrication in MEMS due to their capability to achieve very high work densities, produce large deformations, and generate high stresses...

  3. Synthesis and characterization of Cu–Al–Ni shape memory alloy multilayer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Cortés, J.F. [Dpt. Física Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain); San Juan, J., E-mail: jose.sanjuan@ehu.es [Dpt. Física Materia Condensada, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain); López, G.A.; Nó, M.L. [Dpt. Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco, Apdo. 644, 48080 Bilbao (Spain)

    2013-10-01

    Among active materials, shape memory alloys are well recognized for their work output density. Because of that, these alloys have attracted much attention to be used in micro/nano electromechanical systems. In the present work, the electron beam evaporation technique has been used to growth, by a multilayer method, two shape memory alloy thin films with different Cu–Al–Ni composition. Multilayers have been further thermally treated to produce the alloys by solid solution diffusion. The produced multilayers have been characterized and the presence of the martensite phase in the obtained thin films was studied. Furthermore, the influence of two different coatings onto the Si substrates, namely Si/SiO{sub 2} and Si/Si{sub 3}N{sub 4}, was investigated. Mechanically stable, not detaching from the substrates, Cu–Al–Ni shape memory alloy thin films, about 1 micrometre thick, showing a martensitic transformation have been produced. - Highlights: ► Multilayer thin films of Cu–Al–Ni shape memory alloys produced by e-beam evaporation. ► SiN{sub X} 200 nm thick coating is good for high quality Cu–Al–Ni shape memory thin films. ► Thermal treatment renders Cu–Al–Ni multilayer in homogeneous martensite thin film.

  4. Narrow thermal hysteresis of NiTi shape memory alloy thin films with submicrometer thickness

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Huilong; Hamilton, Reginald F., E-mail: rfhamilton@psu.edu; Horn, Mark W. [Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2016-09-15

    NiTi shape memory alloy (SMA) thin films were fabricated using biased target ion beam deposition (BTIBD), which is a new technique for fabricating submicrometer-thick SMA thin films, and the capacity to exhibit shape memory behavior was investigated. The thermally induced shape memory effect (SME) was studied using the wafer curvature method to report the stress-temperature response. The films exhibited the SME in a temperature range above room temperature and a narrow thermal hysteresis with respect to previous reports. To confirm the underlying phase transformation, in situ x-ray diffraction was carried out in the corresponding phase transformation temperature range. The B2 to R-phase martensitic transformation occurs, and the R-phase transformation is stable with respect to the expected conversion to the B19′ martensite phase. The narrow hysteresis and stable R-phase are rationalized in terms of the unique properties of the BTIBD technique.

  5. Shape memory alloys

    International Nuclear Information System (INIS)

    Kaszuwara, W.

    2004-01-01

    Shape memory alloys (SMA), when deformed, have the ability of returning, in certain circumstances, to their initial shape. Deformations related to this phenomenon are for polycrystals 1-8% and up to 15% for monocrystals. The deformation energy is in the range of 10 6 - 10 7 J/m 3 . The deformation is caused by martensitic transformation in the material. Shape memory alloys exhibit one directional or two directional shape memory effect as well as pseudoelastic effect. Shape change is activated by temperature change, which limits working frequency of SMA to 10 2 Hz. Other group of alloys exhibit magnetic shape memory effect. In these alloys martensitic transformation is triggered by magnetic field, thus their working frequency can be higher. Composites containing shape memory alloys can also be used as shape memory materials (applied in vibration damping devices). Another group of composite materials is called heterostructures, in which SMA alloys are incorporated in a form of thin layers The heterostructures can be used as microactuators in microelectromechanical systems (MEMS). Basic SMA comprise: Ni-Ti, Cu (Cu-Zn,Cu-Al, Cu-Sn) and Fe (Fe-Mn, Fe-Cr-Ni) alloys. Shape memory alloys find applications in such areas: automatics, safety and medical devices and many domestic appliances. Currently the most important appears to be research on magnetic shape memory materials and high temperature SMA. Vital from application point of view are composite materials especially those containing several intelligent materials. (author)

  6. RF magnetron sputtered TiNiCu shape memory alloy thin film

    International Nuclear Information System (INIS)

    Fu Yongqing; Du Hejun

    2003-01-01

    Shape memory alloys (SMAs) offer a unique combination of novel properties, such as shape memory effect, super-elasticity, biocompatibility and high damping capacity, and thin film SMAs have the potential to become a primary actuating mechanism for micro-actuators. In this study, TiNiCu films were successfully prepared by mix sputtering of a Ti 55 Ni 45 target with a separated Cu target. Crystalline structure, residual stress and phase transformation properties of the TiNiCu films were investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and curvature measurement methods. Effects of the processing parameters on the film composition, phase transformation and shape-memory effects were analyzed. Results showed that films prepared at a high Ar gas pressure exhibited a columnar structure, while films deposited at a low Ar gas pressure showed smooth and featureless structure. Chemical composition of TiNiCu thin films was dependent on the DC power of copper target. DSC, XRD and curvature measurement revealed clearly the martensitic transformation of the deposited TiNiCu films. When the free-standing film was heated and cooled, a 'two-way' shape-memory effect can be clearly observed

  7. Room temperature magnetocaloric effect in Ni-Mn-In-Cr ferromagnetic shape memory alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Akkera, Harish Sharma [Functionalnanomaterials Research Lab, Department of Physics, Indian Institute of Technology Roorkee, Uttarakhand-247667 (India); Singh, Inderdeep [Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Uttarakhand-24667 (India); Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in [Functionalnanomaterials Research Lab, Department of Physics, Indian Institute of Technology Roorkee, Uttarakhand-247667 (India)

    2017-02-15

    The influence of Cr substitution for In on the martensitic phase transformation and magnetocaloric effect (MCE) has been investigated in Ni-Mn-Cr-In ferromagnetic shape memory alloy (FSMA) thin films fabricated by magnetron sputtering. Temperature dependent magnetization (M-T) measurements demonstrated that the martensitic transformation temperatures (T{sub M}) monotonously increase with the increase of Cr content due to change in valence electron concentration (e/a) and cell volume. From the study of isothermal magnetization curves (M-H), magnetocaloric effect around the martensitic transformation has been investigated in these FSMA thin films. The magnetic entropy change ∆S{sub M} of 7.0 mJ/cm{sup 3}-K was observed in Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5} film at 302 K in an applied field of 2 T. Further, the refrigerant capacity (RC) was also calculated for all the films in an applied field of 2 T. These findings indicate that the Cr doped Ni-Mn-In FSMA thin films are potential candidates for room temperature micro-length-scale magnetic refrigeration applications. - Highlights: • The Cr content leads to an increase in the martensitic transformation temperature. • The ∆S{sub M} =7 mJ/cm{sup 3}-K at 302 K was observed in the Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5}. • The RC =39.2 mJ/K at 2 T was obtained in Ni{sub 51.1}Mn{sub 34.9}In{sub 9.5}Cr{sub 4.5} film.

  8. An analytical model for shape memory alloy fiber-reinforced composite thin-walled beam undergoing large deflection

    Directory of Open Access Journals (Sweden)

    Yongsheng Ren

    2015-03-01

    Full Text Available The structural model of the thin-walled laminated beams with integral shape memory alloy active fibers and accounting for geometrically nonlinear is presented in this article. The structural modeling is split into two parts: a two-dimensional analysis over the cross section and a geometrically nonlinear analysis of a beam along the beam span. The variational asymptotic method is used to formulate the force–deformation relationship equations taking into account the presence of active shape memory alloy fibers distributed along the cross section of the beam. The geometrically nonlinear governing equations are derived using variational principle and based on the von Kármán-type nonlinear strain–displacement relations. The equations are then solved using Galerkin’s method and an incremental Newton–Raphson method. The validation for the proposed model has been carried out by comparison of the present results with those available in the literature. The results show that significant extension, bending, and twisting coupled nonlinear deflections occur during the phase transformation due to shape memory alloy actuation. The effects of the volume fraction of the shape memory alloy fiber and ply angle are also addressed.

  9. Nonlinear dynamics and bifurcation characteristics of shape memory alloy thin films subjected to in-plane stochastic excitation

    International Nuclear Information System (INIS)

    Zhu, Zhi-Wen; Zhang, Qing-Xin; Xu, Jia

    2014-01-01

    A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters

  10. New Au–Cu–Al thin film shape memory alloys with tunable functional properties and high thermal stability

    International Nuclear Information System (INIS)

    Buenconsejo, Pio John S.; Ludwig, Alfred

    2015-01-01

    An Au–Cu–Al thin film materials library prepared by combinatorial sputter-deposition was characterized by high-throughput experimentation in order to identify and assess new shape memory alloys (SMAs) in this alloy system. Automated resistance measurements during thermal cycling between −20 and 250 °C revealed a wide composition range that undergoes reversible phase transformations with martensite transformation start temperatures, reverse transformation finish temperatures and transformation hysteresis ranging from −15 to 149 °C, 5 to 185 °C and 8 to 60 K, respectively. High-throughput X-ray diffraction analysis of the materials library confirmed that the phase-transforming compositions can be attributed to the existence of the β-AuCuAl parent phase and its martensite product. The formation of large amount of phases based on face-centered cubic (Au–Cu), Al–Cu and Al–Au is responsible for limiting the range of phase-transforming compositions. Selected alloys in this system show excellent thermal cyclic stability of the phase transformation. The functional properties of these alloys, combined with the inherent properties of Au-based alloys, i.e. aesthetic value, oxidation and corrosion resistance, makes them attractive as smart materials for a wide range of applications, including applications as SMAs for elevated temperatures in harsh environment

  11. Synthesis of shape memory alloys using electrodeposition

    Science.gov (United States)

    Hymer, Timothy Roy

    Shape memory alloys are used in a variety of applications. The area of micro-electro-mechanical systems (MEMS) is a developing field for thin film shape memory alloys for making actuators, valves and pumps. Until recently thin film shape memory alloys could only be made by rapid solidification or sputtering techniques which have the disadvantage of being "line of sight". At the University of Missouri-Rolla, electrolytic techniques have been developed that allow the production of shape memory alloys in thin film form. The advantages of this techniques are in-situ, non "line of sight" and the ability to make differing properties of the shape memory alloys from one bath. This research focused on the electrodeposition of In-Cd shape memory alloys. The primary objective was to characterize the electrodeposited shape memory effect for an electrodeposited shape memory alloy. The effect of various operating parameters such as peak current density, temperature, pulsing, substrate and agitation were investigated and discussed. The electrodeposited alloys were characterized by relative shape memory effect, phase transformation, morphology and phases present. Further tests were performed to optimize the shape memory by the use of a statistically designed experiment. An optimized shape memory effect for an In-Cd alloy is reported for the conditions of the experiments.

  12. A new mechanical characterization method for thin film microactuators and its application to NiTiCi shape memory alloy

    International Nuclear Information System (INIS)

    Seward, K P

    1999-01-01

    In an effort to develop a more full characterization tool of shape memory alloys, a new technique is presented for the mechanical characterization of microactuators and applied to SMA thin films. A test instrument was designed to utilize a spring-loaded transducer in measuring displacements with resolution of 1.5 pm and forces with resolution of 0.2 mN. Employing an out-of-plane loading method for freestanding SMA thin films, strain resolution of 30(mu)(epsilon) and stress resolution of 2.5 MPa were achieved. This new testing method is presented against previous SMA characterization methods for purposes of comparison. Four mm long, 2(micro)m thick NiTiCu ligaments suspended across open windows were bulk micromachined for use in the out-of-plane stress and strain measurements. The fabrication process used to micromachine the ligaments is presented step-by-step, alongside methods of fabrication that failed to produce testable ligaments. Static analysis showed that 63% of the applied strain was recovered while ligaments were subjected to tensile stresses of 870 MPa. In terms of recoverable stress and recoverable strain, the ligaments achieved maximum recovery of 700 MPa and 3.0% strain. No permanent deformations were seen in any ligament during deflection measurements. Maximum actuation forces and displacements produced by the 4 mm ligaments situated on 1 cm square test chips were 56 mN and 300(micro)m, respectively. Fatigue analysis of the ligaments showed degradation in recoverable strain from 0.33% to 0.24% with 200,000 cycles, corresponding to deflections of 90(micro)m and forces of 25 mN. Cycling also produced a wavering shape memory effect late in ligament life, leading to broad inconsistencies of as much as 35% deviation from average. Unexpected phenomena like stress-induced martensitic twinning that leads to less recoverable stress and the shape memory behavior of long life devices are addressed. Finally, a model for design of microactuators using shape memory

  13. Shape memory alloy engine

    International Nuclear Information System (INIS)

    Tanaka, M.

    1992-01-01

    This paper discusses a shape memory alloy engine, developed for the purpose of extracting the mechanical energy from a small difference in temperature. The engine is mainly composed of two pulleys (high temperature and low temperature) and single belt made of the nickel titanium shape memory alloy. The alloy memorizes a shape arcing in the direction opposite to the direction of the belt arc around the pulleys. When the temperature of the belt which is in contact with the high temperature pulley rises above the transformation temperature, a return to the memorized shape generates a force which rotates the pulleys. To make the heat transfer more effective, the engine was designed so that the lower part of the two pulleys are embedded in hot and cold water, respectively. To predict the performance of the shape memory alloy engine, the stress change of the shape memory alloy caused by temperature change has been also investigated with the bending stress test, and a torque loss of the engine system was measured. The predicted results were coincident with the output power experiment

  14. Shape memory effect alloys

    International Nuclear Information System (INIS)

    Koshimizu, S.

    1992-01-01

    Although the pseudo- or super-elasticity phenomena and the shape memory effect were known since the 1940's, the enormous curiosity and the great interest to their practical applications emerged with the development of the NITINOL alloy (Nickel-Titanium Naval Ordance Laboratory) by the NASA during the 1960's. This fact marked the appearance of a new class of materials, popularly known as shape memory effect alloys (SMEA). The objective of this work is to present a state-of-the-art of the development and applications for the SMEA. (E.O.)

  15. Microstructure of epitaxial thin films of the ferromagnetic shape memory alloy Ni{sub 2}MnGa

    Energy Technology Data Exchange (ETDEWEB)

    Eichhorn, Tobias

    2011-12-09

    This work is concerned with the preparation and detailed characterization of epitaxial thin films of the Heusler compound Ni{sub 2}MnGa. This multiferroic compound is of both technological and scientific interest due to the outstanding magnetic shape memory (MSM) behavior. Huge magnetic-field-induced strains up to 10 % have been observed for single crystals close to a Ni{sub 2}MnGa composition. The effect is based on a redistribution of crystallographic twin variants of tetragonal or orthorhombic symmetry. Under the driving force of the external magnetic field twin boundaries can move through the crystal, which largely affects the macroscopic shape. The unique combination of large reversible strain, high switching frequency and high work output makes the alloy a promising actuator material. Since the MSM effect results from an intrinsic mechanism, MSM devices possess great potential for implementation in microsystems, e.g. microfluidics. So far significant strains, in response to an external magnetic field, have been observed for bulk single crystals and foams solely. In order to take advantage of the effect in applications concepts for miniaturization are needed. The rather direct approach, based on epitaxial thin films, is explored in the course of this work. This involves sample preparation under optimized deposition parameters and fabrication of freestanding single-crystalline films. Different methods to achieve freestanding microstructures such as bridges and cantilevers are presented. The complex crystal structure is extensively studied by means of X-ray diffraction. Thus, the different crystallographic twin variants that are of great importance for the MSM effect are identified. In combination with microscopy the twinning architecture for films of different crystallographic orientation is clarified. Intrinsic blocking effects in samples of (100) orientation are explained on basis of the variant configuration. In contrast, a promising twinning microstructure

  16. Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

    Science.gov (United States)

    Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

    2005-01-01

    High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

  17. Influence of Thin-Film Adhesives in Pullout Tests Between Nickel-Titanium Shape Memory Alloy and Carbon Fiber-Reinforced Polymer Matrix Composites

    Science.gov (United States)

    Quade, Derek J.; Jana, Sadhan; McCorkle, Linda S.

    2018-01-01

    Strips of nickel-titanium (NiTi) shape memory alloy (SMA) and carbon fiber-reinforced polymer matrix composite (PMC) were bonded together using multiple thin film adhesives and their mechanical strengths were evaluated under pullout test configuration. Tensile and lap shear tests were conducted to confirm the deformation of SMAs at room temperature and to evaluate the adhesive strength between the NiTi strips and the PMC. Optical and scanning electron microscopy techniques were used to examine the interfacial bonding after failure. Simple equations on composite tensile elongation were used to fit the experimental data on tensile properties. ABAQUS models were generated to show the effects of enhanced bond strength and the distribution of stress in SMA and PMC. The results revealed that the addition of thin film adhesives increased the average adhesive strength between SMA and PMC while halting the room temperature shape memory effect within the pullout specimen.

  18. Solarbus Solar Array Innovative Light Weight Mechanical Architecture with Thin Lateral Panels Deployed with Shape Memory Alloy Regulator

    Science.gov (United States)

    D'Abrigeon, Laurent; Carpine, Anne; Laduree, Gregory

    2005-05-01

    The standard ALCATEL SOLAR ARRAY PLANAR CONCEPT on the TELECOM market today on flight is named SOLARBUS.This concept is:• 3 to 10 identical panels covered with Si Hi-η celltechnology.• A central mast constitute by 3 to 4 panels and 1yoke linked together by hinges and synchronizedby cables.• From 2 to 6 lateral panelsThis concept is able to fit with the customer requirements in order to have a competitive "global offer at system level" (mass to power ratio 48-50 W/Kg)But, for the near future, in line with the market trend, and based on the previous experience, an improvement of the SOLARBUS Solar Array concept in term of W/kg/€ is essential in order to maintain the competitiveness of the global ALCATEL offer at system level.In order to increase the W/Kg performance Alcatel has developed a new architecture named Lightweight Panel Structure (LPS). The objectives of this new structure are :• To decrease the kg/m2 ratio • To be compatible of all promising cells technology including Si Hi-n, GaAs, GaAs+ small reflectors. This new architecture is based on the fact that during the 3 major life phases of a Solar Array (Launch/Deployment/Deployed orbital life), the structural needs are more important for the central panels than for the lateral panels.So two different panels have been designed :• Central panels (named LPS1)• Lateral panels (named LPS2)The stowing configuration as been adapted : 2 thin lateral panels LPS2 between 2 structural central panels LPS1, and local bumpers to transfer the loads from LPS2 to LPS1.Also one of the more stringent loads applied to the panels are corresponding to deployment loads. In order to limit the mass of reinforcement of the panels, a deployment speed regulator shall be used. In the frame of the new generation of solar arrays, Alcatel has developed a new actuator based on shape memory alloy torsional rod. This light weight component is directly connected to heaters lines and is able to provide great actuation torque

  19. A bidirectional shape memory alloy folding actuator

    International Nuclear Information System (INIS)

    Paik, Jamie K; Wood, Robert J

    2012-01-01

    This paper presents a low-profile bidirectional folding actuator based on annealed shape memory alloy sheets applicable for meso- and microscale systems. Despite the advantages of shape memory alloys—high strain, silent operation, and mechanical simplicity—their application is often limited to unidirectional operation. We present a bidirectional folding actuator that produces two opposing 180° motions. A laser-patterned nickel alloy (Inconel 600) heater localizes actuation to the folding sections. The actuator has a thin ( < 1 mm) profile, making it appropriate for use in robotic origami. Various design parameters and fabrication variants are described and experimentally explored in the actuator prototype. (paper)

  20. Shape memory alloys – characterization techniques

    Indian Academy of Sciences (India)

    Abstract. Shape memory alloys are the generic class of alloys that show both thermal and mechan- ical memory. The basic physics involved in the shape memory effect is the reversible thermoelastic martensitic transformation. In general, there exists two phases in shape memory alloys, viz., a high- temperature phase or ...

  1. Shape memory alloys – characterization techniques

    Indian Academy of Sciences (India)

    Shape memory alloys are the generic class of alloys that show both thermal and mechanical memory. The basic physics involved in the shape memory effect is the reversible thermoelastic martensitic transformation. In general, there exists two phases in shape memory alloys, viz., a hightemperature phase or austenitic ...

  2. Effect of Cr addition on the structural, magnetic and mechanical properties of magnetron sputtered Ni-Mn-In ferromagnetic shape memory alloy thin films

    Energy Technology Data Exchange (ETDEWEB)

    Akkera, Harish Sharma [Indian Institute of Technology Roorkee, Functional Nanomaterials Research Lab, Department of Physics, Roorkee, Uttarakhand (India); Madanapalle Institute of Technology and Science, Department of Physics, Madanapalle, Chittoor, Andhra Pradesh (India); Kaur, Davinder [Indian Institute of Technology Roorkee, Functional Nanomaterials Research Lab, Department of Physics, Roorkee, Uttarakhand (India)

    2016-12-15

    The effect of Cr substitution for In on the structural, martensitic phase transformation and mechanical properties of Ni-Mn-In ferromagnetic shape memory alloy (FSMA) thin films was systematically investigated. X-ray diffraction results revealed that the Ni-Mn-In-Cr thin films possessed purely austenitic cubic L2{sub 1} structure at lower content of Cr, whereas higher Cr content, the Ni-Mn-In-Cr thin films exhibited martensitic structure at room temperature. The temperature-dependent magnetization (M-T) and resistance (R-T) results confirmed that the monotonous increase in martensitic transformation temperatures (T{sub M}) with the addition of Cr content. Further, the room temperature nanoindentation studies revealed the mechanical properties such as hardness (H), elastic modulus (E), plasticity index (H/E) and resistance to plastic deformation (H{sup 3}/E {sup 2}) of all the samples. The addition of Cr content significantly enhanced the hardness (28.2 ± 2.4 GPa) and resistance to plastic deformation H{sup 3}/E{sup 2} (0.261) of Ni{sub 50.4}Mn{sub 34.96}In{sub 13.56}Cr{sub 1.08} film as compared with pure Ni-Mn-In film. As a result, the appropriate addition of Cr significantly improved the mechanical properties with a decrease in grain size, which could be further attributed to the grain boundary strengthening mechanism. These findings indicate that the Cr-doped Ni-Mn-In FSMA thin films are potential candidates for microelectromechanical systems applications. (orig.)

  3. Simultaneous probing of phase transformations in Ni-Ti thin film shape memory alloy by synchrotron radiation-based X-ray diffraction and electrical resistivity

    Energy Technology Data Exchange (ETDEWEB)

    Braz Fernandes, F.M. [CENIMAT/I3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Mahesh, K.K., E-mail: kkmahesh@rediffmail.com [CENIMAT/I3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Martins, R.M.S. [CENIMAT/I3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), P.O. Box 510119, 01314 Dresden (Germany); IST/Instituto Tecnológico e Nuclear (IST/ITN), Universidade Técnica de Lisboa, EN10, 2696-953 Sacavém (Portugal); Centro de Física Nuclear da Universidade de Lisboa (CFNUL), Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); Silva, R.J.C. [CENIMAT/I3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Baehtz, C.; Borany, J. von [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf (HZDR), P.O. Box 510119, 01314 Dresden (Germany)

    2013-02-15

    Nickel–Titanium (Ni–Ti) thin film shape memory alloys (SMAs) have been widely projected as novel materials which can be utilized in microdevices. Characterization of their physical properties and its correlation with phase transformations has been a challenging issue. In the present study, X-ray beam diffraction has been utilized to obtain the structural information at different temperatures while cooling. Simultaneously, electrical resistivity (ER) was measured in the phase transformation temperature range. The variation of ER and integral area of the individual diffraction peaks of the different phases as a function of temperature have been compared. A mismatch between the conventional interpretation of ER variation and the results of the XRD data has been clearly identified. - Highlights: ► Phase transformation characterization of Ni–Ti thin film SMA has been carried out. ► Simultaneous monitoring of the XRD and ER with temperature is performed. ► The variation of ER and integral area of the diffraction peaks have been compared. ► A shift of the transformation temperatures obtained by two techniques is discussed.

  4. Shape memory alloy based motor

    Indian Academy of Sciences (India)

    (Duerig et al 1990) of the alloy. Unlike conventional materials, which show only, limited effect on stress–strain behaviour (Duerig et al 1990; Mellor 1989), SMA shows marked temperature dependence, because of reversible austenite to martensite transformation. The underlying phenomenon of the shape memory effect is ...

  5. Design optimization of shape memory alloy structures

    NARCIS (Netherlands)

    Langelaar, M.

    2006-01-01

    This thesis explores the possibilities of design optimization techniques for designing shape memory alloy structures. Shape memory alloys are materials which, after deformation, can recover their initial shape when heated. This effect can be used for actuation. Emerging applications for shape memory

  6. FABRICATION OF Cu-Al-Ni SHAPE MEMORY THIN FILM BY THERMAL EVOPRATION

    OpenAIRE

    Özkul, İskender; Canbay, Canan Aksu; Tekataş, Ayşe

    2017-01-01

    Among the functional, materials shape memory alloysare important because of their unique properties. So, these materials haveattracted more attention to be used in micro/nano electronic andelectromechanic systems. In this work, thermal evaporation method has been usedto produce CuAlNi shape memory alloy thin film. The produced CuAlNi thin filmhas been characterized and the presence of the martensite phase wasinvestigated and compared with the CuAlNi alloy sample. CuAlNi shape memoryalloy thin...

  7. Applications of shape memory alloys in Japan

    International Nuclear Information System (INIS)

    Asai, M.; Suzuki, Y.

    2000-01-01

    In Japan, a first application of shape memory TiNi alloy was a moving flap in an air-conditioner which was developed as sensing function of shape memory alloy at Matsushista Electric Industrial Co. Then, shape memory utilized in a coffee maker, an electric rice-cooker, a thermal mixing valve and etc. were commercialized in Japan. And brassiere wires, a guide wire for medical treatment, an antenna for portable telephone and others were commercialized utilizing superelasticity. At the same time with these commercial products, there was not only progress in fabrication technology to effect accurate transformation temperature, but also the discovery of small hysteresis alloy such as R-phase or TiNiCu alloy and low transformation temperature alloy such as TiNiFe, TiNiV and TiNiCo alloys. Therefore the shape memory alloy market has expanded widely to electric appliances, automobile, residence, medical care and other field today. (orig.)

  8. Hysteresis behaviour of thermoelastic alloys: some shape memory alloys models

    International Nuclear Information System (INIS)

    Lexcellent, C.; Torra, V.; Raniecki, B.

    1993-01-01

    The hysteretic behaviour of shape memory alloys (SMA) needs a more and more thin analysis because of its importance for technological applications. The comparison between different approaches allows to explicite the specifity of every model (macroscopic approach, micro-macro level, local description, phenomenological approach) and their points of convergence. On one hand, a thermodynamic treatment with a free energy expression as a mixing rule of each phase (parent or austenite phase and martensite) by adding a coupling term: the configurational energy, allowes modelling of material hysteresis loops. On the other hand, a phenomenological treatment based on a local investigation of two single crystals with a visualisation of microscopic parameters allows to perceive the phase transition mechanisms (nucleation, growth). All the obtained results show the importance of entropy production (or of the definition of the configurational energy term) for the correct description of hysteresis loops (subloops or external). (orig.)

  9. Development of an engineering model for ferromagnetic shape memory alloys

    International Nuclear Information System (INIS)

    Tani, Yoshiaki; Todaka, Takashi; Enokizono, Masato

    2008-01-01

    This paper presents a relationship among stress, temperature and magnetic properties of a ferromagnetic shape memory alloy. In order to derive an engineering model of ferromagnetic shape memory alloys, we have developed a measuring system of the relationship among stress, temperature and magnetic properties. The samples used in this measurement are Fe68-Ni10-Cr9-Mn7-Si6 wt% ferromagnetic shape memory alloy. They are thin ribbons made by rapid cooling in air. In the measurement, the ribbon sample is inserted into a sample holder winding consisting of the B-coil and compensation coils, and magnetized in an open solenoid coil. The ribbon is stressed with attachment weights and heated with a heating wire. The specific susceptibility was increased by applying tension, and slightly increased by heating below the Curie temperature

  10. Thermomechanical macroscopic model of shape memory alloys

    International Nuclear Information System (INIS)

    Volkov, A.E.; Sakharov, V.Yu.

    2003-01-01

    The phenomenological macroscopic model of the mechanical behaviour of the titanium nickelide-type shape memory alloys is proposed. The model contains as a parameter the average phase shear deformation accompanying the martensite formation. It makes i possible to describe correctly a number of functional properties of the shape memory alloys, in particular, the pseudoelasticity ferroplasticity, plasticity transformation and shape memory effects in the stressed and unstressed samples [ru

  11. Shape memory alloy consortium (SMAC)

    Science.gov (United States)

    Jacot, A. Dean

    1999-07-01

    The application of smart structures to helicopter rotors has received widespread study in recent years. This is one of the major thrusts of the Shape Memory Alloy Consortium (SMAC) program. SMAC includes 3 companies and 4 Universities in a cost sharing consortium funded under DARPA Smart Materials and Structures program. This paper describes the objective of the SMAC effort, and its relationship to a previous DARPA smart structure rotorcraft program from which it originated. The SMAC program includes NiTinol fatigue/characterization studies, SMA actuator development, and ferromagnetic SMA material development. The paper summarizes the SMAC effort, and includes background and details on Boeing's development of a SMA torsional actuator for rotorcraft applications. SMA actuation is used to retwist the rotorcraft blade in flight, and result in a significant payload increase for either helicopters or tiltrotors. This paper is also augmented by several other papers in this conference with specific results from other SMAC consortium members.

  12. Shape Memory Alloy Adaptive Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will demonstrate and scale up an innovative manufacturing process that yields aerospace grade shape memory alloy (SMA) solids and periodic...

  13. Characterization of Ni{sub 55.6}Mn{sub 11.4}Fe{sub 7.4}Ga{sub 25.6} high temperature shape memory alloy thin film

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H.B.; Liu, C.; Lei, Y.C. [National Key Laboratory Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001 (China); Cai, W. [National Key Laboratory Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: weicai@hit.edu.cn

    2008-10-06

    The Ni{sub 55.6}Mn{sub 11.4}Fe{sub 7.4}Ga{sub 25.6} high temperature shape memory alloy thin film was deposited onto silicon substrates by using radio-frequency (R.F.) magnetron sputtering technique. Surface morphology, crystallographic structure, martensitic transformation and microstructure were systematically investigated by means of scanning electron microscopy (SEM), atomic force microscope (AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that the film has columnar structure and an excellent surface quality. The film has seven-layered modulated orthorhombic structure with typical self-accommodated morphology at room temperature. The martensitic transformation start temperature of the film is up to 439 K, much higher than room temperature, displaying the promising application as high temperature actuator material.

  14. Fracture of Shape Memory Alloys

    OpenAIRE

    Miyazaki, Shuichi; Otsuka, Kazuhiro

    1981-01-01

    The initiation and the propagation of cracks during both quenching and deformation in polycrystalline Cu-Al-Ni alloys have been investigated under various conditions. The fracture surfaces of Ti-Ni and Cu-Al-Ni alloys were also observed by a scanning electron microscope. From these results, it was concluded that the brittleness of Cu-Al-Ni alloy and other β phase alloys are due to large elastic anisotropy and large grain sizes, while that the large ductility in Ti-Ni alloy being due to the sm...

  15. A jumping shape memory alloy under heat.

    Science.gov (United States)

    Yang, Shuiyuan; Omori, Toshihiro; Wang, Cuiping; Liu, Yong; Nagasako, Makoto; Ruan, Jingjing; Kainuma, Ryosuke; Ishida, Kiyohito; Liu, Xingjun

    2016-02-16

    Shape memory alloys are typical temperature-sensitive metallic functional materials due to superelasticity and shape recovery characteristics. The conventional shape memory effect involves the formation and deformation of thermally induced martensite and its reverse transformation. The shape recovery process usually takes place over a temperature range, showing relatively low temperature-sensitivity. Here we report novel Cu-Al-Fe-Mn shape memory alloys. Their stress-strain and shape recovery behaviors are clearly different from the conventional shape memory alloys. In this study, although the Cu-12.2Al-4.3Fe-6.6Mn and Cu-12.9Al-3.8Fe-5.6Mn alloys possess predominantly L2(1) parent before deformation, the 2H martensite stress-induced from L2(1) parent could be retained after unloading. Furthermore, their shape recovery response is extremely temperature-sensitive, in which a giant residual strain of about 9% recovers instantly and completely during heating. At the same time, the phenomenon of the jumping of the sample occurs. It is originated from the instantaneous completion of the reverse transformation of the stabilized 2H martensite. This novel Cu-Al-Fe-Mn shape memory alloys have great potentials as new temperature-sensitive functional materials.

  16. TiNi shape memory alloy coated with tungsten : A novel approach for biomedical applications

    NARCIS (Netherlands)

    Li, Huafang; Zheng, Yufeng; Pei, Y. T.; de Hosson, Jeff

    This study explores the use of DC magnetron sputtering tungsten thin films for surface modification of TiNi shape memory alloy (SMA) targeting for biomedical applications. SEM, AFM and automatic contact angle meter instrument were used to determine the surface characteristics of the tungsten thin

  17. Smart materials based on shape memory alloys: examples from Europe

    International Nuclear Information System (INIS)

    Gotthardt, R.; Scherrer, P.

    2000-01-01

    Shape memory alloys (SMAs) have become increasingly attractive as embedded actuators in polymers yielding adaptive composite structures. In particular, SMA-elements have been used to actively or passively control shape, elastic modules, internal stress level and damping capacity of such smart composites. In the passive approach, copper-base SMA-plates can be used as temperature-sensitive damping elements, an interesting solution to improve the vibrational behaviour of alpine skis for example. Active materials are obtained by the integration of pre-strained Ni-Ti-base thin wires in polymer matrix composites enabling control of the vibrational behaviour through the recovery-stress tuning technique. In this paper, some results of national research programmes in Belgium and Switzerland, mainly concerning the damping capacity, are shown and a new European project entitled ''adaptive composites with embedded shape memory alloy wires'' is presented in which partners from Belgium, Germany, Greece, Great Britain and Switzerland are collaborating. (orig.)

  18. Phase change memory based on SnSe4 alloy

    International Nuclear Information System (INIS)

    Karanja, J.M.; Karimi, P.M.; Njoroge, W.K.; Wamwangi, D.M.

    2013-01-01

    A phase change alloy has been synthesized and characterized. The reversible phase transitions between amorphous and crystalline states of SnSe 4 films have been studied using variable electrical pulses and X-ray diffraction. Temperature dependent sheet resistance measurements have shown two distinct resistivity states of more than two orders of magnitude. This high electrical contrast makes the alloy suitable for nonvolatile phase change memory applications. X-ray diffraction has attributed the large electrical contrast to an amorphous–crystalline phase transition. The nonvolatile memory cells have been fabricated using a simple sandwich structure (metal/chalcogenide thin film/metal). A threshold voltage of 3.71 V has been determined for this phase change random access memory cell. Memory switching was initiated using the voltage pulses of 3.71 V, 90 ns, 1.3 V and 26 μs, for the crystallization and amorphization process, respectively. - Highlights: ► Phase transition of SnSe 4 alloys with high set resistivity of 1.43 Ωm ► High transition temperatures of 174 °C ► Transition due to amorphous–crystalline changes ► Threshold switching at a high threshold voltage of 3.71 V

  19. Reversibility in martensitic transformation and shape memory in high Mn ferrous alloys

    International Nuclear Information System (INIS)

    Tomota, Y.

    2000-01-01

    The reversibility of austenite (γ : fcc) epsilon (ε : hcp) martensitic transformation and shape memory effect in high Mn ferrous alloys are discussed. A particular emphasis is put on the ε → γ reverse transformation behavior in two poly-crystalline alloys, Fe-24Mn and Fe-24Mn-6Si, where the latter exhibits excellent shape memory while the former shows poor memory although their forward γ → ε transformation behavior is quite similar. TEM in situ observations have revealed that the motion of Shockley partial dislocations during ε → γ reverse transformation is different from each other in these two alloys. The influence of alloying elements on the shape memory effect can be related to solid solution hardening of austenite, suggesting an important role of internal stress. The effect of training on enhancing the shape memory is explained by such an internal stress distribution associated with the formation of very thin, i.e., nano-scale ε/γ lamellae. (orig.)

  20. My Experience with Ti-Ni-Based and Ti-Based Shape Memory Alloys

    Science.gov (United States)

    Miyazaki, Shuichi

    2017-12-01

    The present author has been studying shape memory alloys including Cu-Al-Ni, Ti-Ni-based, and Ni-free Ti-based alloys since 1979. This paper reviews the present author's research results for the latter two materials since 1981. The topics on the Ti-Ni-based alloys include the achievement of superelasticity in Ti-Ni alloys through understanding of the role of microstructures consisting of dislocations and precipitates, followed by the contribution to the development of application market of shape memory effect and superelasticity, characterization of the R-phase and monoclinic martensitic transformations, clarification of the basic characteristics of fatigue properties, development of sputter-deposited shape memory thin films and fabrication of prototypes of microactuators utilizing thin films, development of high temperature shape memory alloys, and so on. The topics of Ni-free Ti-based shape memory alloys include the characterization of the orthorhombic phase martensitic transformation and related shape memory effect and superelasticity, the effects of texture, omega phase and adding elements on the martensitic transformation and shape memory properties, clarification of the unique effects of oxygen addition to induce non-linear large elasticity, Invar effect and heating-induced martensitic transformation, and so on.

  1. Effect of chemical treatment on surface characteristics of sputter deposited Ti-rich NiTi shape memory alloy thin-films

    International Nuclear Information System (INIS)

    Sharma, S.K.; Mohan, S.

    2014-01-01

    Graphical abstract: FTIR spectra recorded for sputter deposited (a) untreated and (b) chemically treated NiTi SMA thin-films. - Highlights: • The effect of chemical treatment on surface properties of NiTi films demonstrated. • Chemically treated films offer strong ability to form protective TiO 2 layer. • TiO 2 layer formation offer great application prospects in biomedical fields. - Abstract: NiTi thin-films were deposited by DC magnetron sputtering from single alloy target (Ni/Ti:45/55 at.%). The rate of deposition and thickness of sputter deposited films were maintained to ∼35 nm min −1 and 4 μm respectively. A set of sputter deposited NiTi films were selected for specific chemical treatment with the solution comprising of de-ionized water, HF and HNO 3 respectively. The influence of chemical treatment on surface characteristics of NiTi films before and after chemical treatment was investigated for their structure, micro-structure and composition using different analytical techniques. Prior to chemical treatment, the composition of NiTi films using energy dispersive X-ray dispersive spectroscopy (EDS), were found to be 51.8 atomic percent of Ti and 48.2 atomic percent of Ni. The structure and morphology of these films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD investigations, demonstrated the presence of dominant Austenite (1 1 0) phase along with Martensite phase, for untreated NiTi films whereas some additional diffraction peaks viz. (1 0 0), (1 0 1), and (2 0 0) corresponding to Rutile and Anatase phase of Titanium dioxide (TiO 2 ) along with parent Austenite (1 1 0) phase were observed for chemically treated NiTi films. FTIR studies, it can be concluded that chemically treated films have higher tendency to form metal oxide/hydroxide than the untreated NiTi films. XPS investigations, demonstrated the presence of Ni-free surface and formation of a protective metal oxide (TiO 2 ) layer on the surface of

  2. Thin-film cryogenic resistors from aluminium alloys

    Science.gov (United States)

    Tadros, N. N.; Holdeman, L. B.

    The temperature dependence of the resistances of thin films sputtered from three commercially available aluminium alloys (5052, 5086, 5456) has been measured in the temperature range 1.5-4.2 K. The 5052-alloy films had a positive temperature coefficient of resistance (TCR) throughout this temperature range, whereas films of the other two alloys had a negative TCR.

  3. Shape Memory Alloys (Part I: Significant Properties

    Directory of Open Access Journals (Sweden)

    I. Ivanic

    2014-09-01

    Full Text Available Shape memory alloys (SMAs belong to a group of functional materials with the unique property of “remembering” the shape they had before pseudoplastic deformation. Such an effect is based on crystallographic reversible thermo-elastic martensitic transformation. There are two crystal phases in SMAs: the austenite phase (stable at high temperature and the martensite phase (stable at low temperature. Austenite to martensite phase transformation can be obtained by mechanical (loading and thermal methods (heating and cooling. During martensitic transformation, no diffusive process is involved, only inelastic deformation of the crystal structure. When the shape memory alloy passes through the phase transformation, the alloy transforms from high ordered phase (austenite to low ordered phase (martensite. There are two types of martensite transformations. First is temperature-induced martensite, which is also called self-accommodating (twinned martensite. The second is stress-induced martensite, also called detwinned martensite. The entire austenite to martensite transformation cycle can be described with four characteristic temperatures: Ms – martensite start temperature, Mf – martensite finish temperature, As – austenite start temperature, and Af – austenite finish temperature. The main factors influencing transformation temperatures are chemical composition, heat treatment procedure, cooling speed, grain size, and number of transformation cycles. As a result of martensitic transformation in SMAs, several thermomechanical phenomena may occur: pseudoelasticity, shape memory effect (one-way and two-way SME and rubber-like behavior. Pseudoelasticity occurs when the SMA is subjected to a mechanical loading at a constant temperature above Af. The second thermomechanical behaviour that can be observed in SMA is the shape memory effect (SME, mainly one-way SME, which is the most commonly used SME. When the sample is subjected to a mechanical

  4. Combinatorial thin film materials science: From alloy discovery and optimization to alloy design

    International Nuclear Information System (INIS)

    Gebhardt, Thomas; Music, Denis; Takahashi, Tetsuya; Schneider, Jochen M.

    2012-01-01

    This paper provides an overview of modern alloy development, from discovery and optimization towards alloy design, based on combinatorial thin film materials science. The combinatorial approach, combining combinatorial materials synthesis of thin film composition-spreads with high-throughput property characterization has proven to be a powerful tool to delineate composition–structure–property relationships, and hence to efficiently identify composition windows with enhanced properties. Furthermore, and most importantly for alloy design, theoretical models and hypotheses can be critically appraised. Examples for alloy discovery, optimization, and alloy design of functional as well as structural materials are presented. Using Fe-Mn based alloys as an example, we show that the combination of modern electronic-structure calculations with the highly efficient combinatorial thin film composition-spread method constitutes an effective tool for knowledge-based alloy design.

  5. Shape Memory Alloy Isolation Valves: Public Quad Chart

    Science.gov (United States)

    2017-05-12

    NUMBER (Include area code) 12 May 2017 Briefing Charts 12 April 2017 - 12 May 2017 Shape Memory Alloy Isolation Valves: Public Quad Chart William...spacecraft (15+ yrs) • Shaped memory alloy isolation valves provide an intrinsically safe isolation system that increases lifetime >5x over SOTA and...Shape Memory Alloy Isolation Valves POC: W. Hargus, Ph.D., AFRL/RQRC B-52 Teardrop Antenna Depolymerization WC-130J Leading Edge Erosion Distribution

  6. Shape Memory Alloy-Based Periodic Cellular Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular structures...

  7. Shape Memory Alloy-Based Periodic Cellular Structures, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort will develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular structures...

  8. In situ characterization of local elastic properties of thin shape memory films by surface acoustic waves

    Czech Academy of Sciences Publication Activity Database

    Grabec, T.; Sedlák, Petr; Stoklasová, Pavla; Thomasová, M.; Shilo, D.; Kabla, M.; Seiner, Hanuš; Landa, Michal

    2016-01-01

    Roč. 25, č. 12 (2016), č. článku 127002. ISSN 0964-1726 R&D Projects: GA ČR GA14-15264S Institutional support: RVO:61388998 Keywords : thin films * shape memory alloys * surface acoustic waves Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.909, year: 2016

  9. Mechanism of improvement of shape memory effect by training in Fe-Mn-Si-based alloys

    International Nuclear Information System (INIS)

    Kajiwara, S.; Ogawa, K.

    2000-01-01

    High-resolution electron microscopy study has been made on the ''trained'' sample of an Fe-14Mn-6Si-9Cr-5Ni (mass %) alloy in order to know the mechanism of improvement of shape memory effect. High densities of extremely thin hcp martensite plates with uniform distribution are produced by ''training'', which is regarded as the key factor for improving shape memory effect. (orig.)

  10. Design of shape memory alloy (SMA) actuators

    CERN Document Server

    Rao, Ashwin; Reddy, J N

    2015-01-01

    This short monograph presents an analysis and design methodology for shape memory alloy (SMA) components such as wires, beams, and springs for different applications. The solid-solid, diffusionless phase transformations in thermally responsive SMA allows them to demonstrate unique characteristics like superelasticity and shape memory effects. The combined sensing and actuating capabilities of such materials allows them to provide a system level response by combining multiple functions in a single material system. In SMA, the combined mechanical and thermal loading effects influence the functionality of such materials. The aim of this book is to make the analysis of these materials accessible to designers by developing a "strength of materials" approach to the analysis and design of such SMA components inspired from their various applications with a review of various factors influencing the design process for such materials.

  11. Neutron irradiation effect on thermomechanical properties of shape memory alloys

    International Nuclear Information System (INIS)

    Abramov, V.Ya.; Ionajtis, R.R.; Kotov, V.V.; Loguntsev, E.N.; Ushakov, V.P.

    1996-01-01

    Alloys of Ti-Ni, Ti-Ni-Pd, Fe-Mn-Si, Mn-Cu-Cr, Mn-Cu, Cu-Al-Mn, Cu-Al-Ni systems are investigated after irradiation in IVV-2M reactor at various temperatures with neutron fluence of 10 19 - 10 20 cm -2 . The degradation of shape memory effect in titanium nickelide base alloys is revealed after irradiation. Mn-Cu and Mn-Cu-Cr alloys show the best results. Trends in shape memory alloy behaviour depending on irradiation temperature are found. A consideration is given to the possibility of using these alloys for components of power reactor control and protection systems [ru

  12. Shape Memory Alloys (Part II: Classification, Production and Application

    Directory of Open Access Journals (Sweden)

    I. Ivanic

    2014-09-01

    Full Text Available Shape memory alloys (SMAs have been extensively investigated because of their unique shape memory behaviour, i.e. their ability to recover their original shape they had before deformation. Shape memory effect is related to the thermoelastic martensitic transformation. Austenite to martensite phase transformation can be obtained by mechanical (loading and thermal methods (heating and cooling. Depending on thermomechanical conditions, SMAs demonstrate several thermomechanical phenomena, such as pseudoelasticity, superelasticity, shape memory effect (one-way and two-way and rubber-like behaviour. Numerous alloys show shape memory effect (NiTi-based alloys, Cu-based alloys, Fe-based alloys etc.. Nitinol (NiTi is the most popular and the most commonly used SMA due to its superior thermomechanical and thermoelectrical properties. NiTi alloys have greater shape memory strain and excellent corrosion resistance compared to Cu – based alloys. However, they are very costly. On the other hand, copper-based alloys (CuZn and CuAl based alloys are much less expensive, easier to manufacture and have a wider range of potential transformation temperatures. The characteristic transformation temperatures of martensitic transformation of CuAlNi alloys can lie between −200 and 200 °C, and these temperatures depend on Al and Ni content. Among the Cu – based SMAs, the most frequently applied are CuZnAl and CuAlNi alloys. Although CuZnAl alloys with better mechanical properties are the most popular among the Cu-based SMAs, they lack sufficient thermal stability, while CuAlNi shape memory alloys, in spite of their better thermal stability, have found only limited applications due to insufficient formability owing to the brittle γ2 precipitates. The most important disadvantage of polycrystalline CuAlNi alloys is a small reversible deformation (one-way shape memory effect: up to 4 %; two-way shape memory effect: only approximately 1.5 % due to intergranular

  13. Shape memory alloys as damping materials

    International Nuclear Information System (INIS)

    Humbeeck, J. van

    2000-01-01

    Shape memory alloys are gaining an increased interest as passive as well as active damping materials. This damping ability when applied in structural elements can lead to a better noise control, improved life time and even better performance of the envisaged tools. By passive damping, it is understood that the material converts a significant part of unwanted mechanical energy into heat. This mechanical energy can be a (resonance) vibration, impact loading or shock waves. This high damping capacity finds its origin in the thermoelastic martensitic phase due to the hysteretic mobility of martensite-variants or different phase interfaces. The damping capacity increases with increasing amplitude of the applied vibration or impact and is almost frequency independent. Special interest exists moreover for damping extreme large displacements by applying the mechanical hysteresis performed during pseudoelastic loading. This aspect is nowadays very strongly studied as a tool for protecting buildings against earthquakes in seismic active regions. Active damping can be obtained in hybrid composites by controlling the recovery stresses or strains of embedded shape memory alloy wires. This controls the internal energy fo a structure which allows controlled modal modification and tuning of the dynamical properties of structural elements. But also impact damage, acoustic radiation, dynamic shape control can be actively controlled. As a consequence improved fatigue-resistance, better performance and a longer lifetime of the structural elements can be obtained. (orig.)

  14. Estimation of Transformation Temperatures in Ti-Ni-Pd Shape Memory Alloys

    Science.gov (United States)

    Narayana, P. L.; Kim, Seong-Woong; Hong, Jae-Keun; Reddy, N. S.; Yeom, Jong-Taek

    2018-03-01

    The present study focused on estimating the complex nonlinear relationship between the composition and phase transformation temperatures of Ti-Ni-Pd shape memory alloys by artificial neural networks (ANN). The ANN models were developed by using the experimental data of Ti-Ni-Pd alloys. It was found that the predictions are in good agreement with the trained and unseen test data of existing alloys. The developed model was able to simulate new virtual alloys to quantitatively estimate the effect of Ti, Ni, and Pd on transformation temperatures. The transformation temperature behavior of these virtual alloys is validated by conducting new experiments on the Ti-rich thin film that was deposited using multi target sputtering equipment. The transformation behavior of the film was measured by varying the composition with the help of aging treatment. The predicted trend of transformational temperatures was explained with the help of experimental results.

  15. Metallic Thin-Film Bonding and Alloy Generation

    Science.gov (United States)

    Fryer, Jack Merrill (Inventor); Campbell, Geoff (Inventor); Peotter, Brian S. (Inventor); Droppers, Lloyd (Inventor)

    2016-01-01

    Diffusion bonding a stack of aluminum thin films is particularly challenging due to a stable aluminum oxide coating that rapidly forms on the aluminum thin films when they are exposed to atmosphere and the relatively low meting temperature of aluminum. By plating the individual aluminum thin films with a metal that does not rapidly form a stable oxide coating, the individual aluminum thin films may be readily diffusion bonded together using heat and pressure. The resulting diffusion bonded structure can be an alloy of choice through the use of a carefully selected base and plating metals. The aluminum thin films may also be etched with distinct patterns that form a microfluidic fluid flow path through the stack of aluminum thin films when diffusion bonded together.

  16. Magnetic Shape Memory Alloy Actuator for Instrument Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will develop a simple actuator based on magnetic shape memory alloy (MSMA), a novel new family of crystalline materials which exhibit strain deformation...

  17. Simulation of Dislocation and Transformation Plasticity in Shape Memory Alloys

    National Research Council Canada - National Science Library

    Volkov, Alexander

    1999-01-01

    A model of deformation of shape memory alloys has been developed. It takes into account deformation due to the phase transformation and plastic deformation, produced by an external stress or by inter-phase stresses...

  18. Shape Memory Alloy-Based Periodic Cellular Structures, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase II effort will continue to develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular...

  19. Nanostructured Shape Memory Alloys: Adaptive Composite Materials and Components

    National Research Council Canada - National Science Library

    Crone, Wendy C; Ellis, Arthur B; Perepezko, John H

    2007-01-01

    .... Both SMA-polymer and SMA-metal composites were created, as well as new fabrication strategies for producing NiTi and CuAlNi shape memory alloy particles with refined size which still display shape...

  20. Shape Memory Alloy-Based Periodic Cellular Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase II effort will continue to develop and demonstrate an innovative shape memory alloy (SMA) periodic cellular structural technology. Periodic cellular...

  1. Understanding the Shape-Memory Alloys Used in Orthodontics

    OpenAIRE

    Fernandes, Daniel J.; Peres, Rafael V.; Mendes, Alvaro M.; Elias, Carlos N.

    2011-01-01

    Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed...

  2. A novel fabrication method for nitinol shape memory alloys

    International Nuclear Information System (INIS)

    Rizvi, S.A.; Khan, T.I.

    2009-01-01

    Nitinol (NiTi) shape memory alloys are widely used in a variety of biomedical applications, such as dental implants, cervical and lumbar vertebral replacements, joint replacements and stents. In this study, commercially pure Ti and Ni foils approx. equal to 100 um thick were diffusion bonded in vacuum. The experimental conditions were optimized to achieve a near equiatomic composition to produce NiTi SMA thin foil of approx. 5-8 micron thick. The cross-sectional surfaces of joint were subjected to metallographic investigation using optical microscope after grinding, polishing and etching. Scanning electron microscope equipped with EDX system was utilized to characterize the bonded layer and compositional analysis. Differential scanning calorimetry (DSC) technique was employed to determine the shape memory effect. The samples were subjected to X-ray diffraction analysis in order to establish phase structures formed during the diffusion bonding stage. An ultra fast femto-second laser facility was utilized to ensure the production of complex shapes or patterns within micron scale. (author)

  3. The welding characteristics of Fe-based shape memory alloys

    International Nuclear Information System (INIS)

    Lin, H.C.; Lin, K.M.; Chuang, Y.C.; Chen, F.H.

    2000-01-01

    After TIG and laser welding, the microstructure, shape memory effect and chemical corrosion resistance of Fe-30Mn-6Si and Fe-30Mn-6Si-5Cr shape memory alloys have been investigated. Experimental results show that the welded zones exhibit dendrite structures. The as-welded alloys still have an excellent shape memory effect. The corrosion resistance of welded zones is found to be worse than that of the base-material for both Fe-30Mn-6Si and Fe-30Mn-6Si-5Cr alloys. The degradation of corrosion resistance is more obvious for laser-welded zone than that for TIG-welded zone. After annealing treatment of 1100 C x 2h for these welded alloys, the dendrite structures in the welded zones disappear and the corrosion resistance is improved. (orig.)

  4. Prospect of Ti-Ni shape memory alloy applied in reactor structures

    International Nuclear Information System (INIS)

    Duan Yuangang

    1995-01-01

    Shape memory effect mechanism, physical property, composition, manufacturing process and application in mechanical structure of Ti-Ni shape memory alloy are introduced. Applications of Ti-Ni shape memory alloy in reactor structure are prospected and some necessary technical conditions of shape memory alloy applied in the reactor structure are put forward initially

  5. Thermomechanical fatigue of shape memory alloys

    International Nuclear Information System (INIS)

    Lagoudas, D C; Kumar, P K; Miller, D A; Rong, L

    2009-01-01

    As shape memory alloys (SMAs) gain popularity as high energy density actuators, one characteristic that becomes particularly important is the thermomechanical transformation fatigue life, in addition to maximum transformation strain and stability of actuation cycles. In this paper, a novel test frame design and testing protocol are discussed, for investigating the thermally activated transformation fatigue characteristics of SMAs under various applied loads for both complete and partial phase transformation. A Ni 50 Ti 40 Cu 10 (at.%) SMA was chosen for this investigation and the effects of various heat treatments on the transformation temperatures and the transformation fatigue lives of actuators were studied. For selected heat treatments, the evolution of recoverable and irrecoverable strains up to failure under different applied stress levels was studied in detail. The influence of complete and partial transformation on the fatigue life is also presented. The irrecoverable strain accumulation as a function of the number of cycles to failure for different stress levels is presented by a relationship similar to the Manson–Coffin law for both partial and complete transformations

  6. Microplane modelling of shape memory alloys

    International Nuclear Information System (INIS)

    Kadkhodaei, M; Salimi, M; Rajapakse, R K N D; Mahzoon, M

    2007-01-01

    A three-dimensional (3D) constitutive model based on a statically constrained microplane theory with volumetric-deviatoric split is proposed for polycrystalline shape memory alloys (SMAs) under multiaxial loading paths. Microplane governing equations are 1D stress-strain relations for normal and shear stresses on each microplane, in which suitable relationships between the microscopic and macroscopic quantities are considered so that switching between elastic and inelastic local responses automatically occurs according to the macroscopic response of SMA without additional constraint. Shear stress on each microplane is expressed by the resultant shear component within the plane to overcome directional bias and to prevent the appearance of shear strain in a pure axial loading or axial strain in a pure shear loading while microplane formulations based on two shear directions may predict such impractical results. The behaviour of SMA under simple and complicated loadings has been studied. In nonproportional loading paths, the model shows interaction between stress components, as well as deviation from normality. Predicted results from the model are in good agreement with those of the existing theoretical and experimental investigations

  7. Application of Shape Memory Alloys in Seismic Isolation: A Review

    Directory of Open Access Journals (Sweden)

    Shaghayegh Alvandi

    2014-12-01

    Full Text Available In the last two decades, there has been an increasing interest in structural engineering control methods. Shape memory alloys and seismic isolation systems are examples of passive control systems that use of any one alone, effectively improve the seismic performance of the structure. Characteristics such as large strain range without any residual deformation, high damping capacity, excellent re-centering, high resistance to fatigue and corrosion and durability have made shape memory alloy an effective damping device or part of base isolators. A unique characteristic of shape memory alloys is in recovering residual deformations even after strong ground excitations. Seismic isolation is a device to lessen earthquake damage prospects. In the latest research studies, shape memory alloy is utilized in combination with seismic isolation system and their results indicate the effectiveness of the application of them to control the response of the structures. This paper reviews the findings of research studies on base isolation system implemented in the building and/or bridge structures by including the unique behavior of shape memory alloys. This study includes the primary information about the characteristic of the isolation system as well as the shape memory material. The efficiency and feasibility of the two mechanisms are also presented by few cases in point.

  8. Recent Progress on Modeling Slip Deformation in Shape Memory Alloys

    Science.gov (United States)

    Sehitoglu, H.; Alkan, S.

    2018-03-01

    This paper presents an overview of slip deformation in shape memory alloys. The performance of shape memory alloys depends on their slip resistance often quantified through the Critical Resolved Shear Stress (CRSS) or the flow stress. We highlight previous studies that identify the active slip systems and then proceed to show how non-Schmid effects can be dominant in shape memory slip behavior. The work is mostly derived from our recent studies while we highlight key earlier works on slip deformation. We finally discuss the implications of understanding the role of slip on curtailing the transformation strains and also the temperature range over which superelasticity prevails.

  9. Dissociation of dilute immiscible copper alloy thin films

    International Nuclear Information System (INIS)

    Barmak, K.; Lucadamo, G. A.; Cabral, C. Jr.; Lavoie, C.; Harper, J. M. E.

    2000-01-01

    The dissociation behavior of dilute, immiscible Cu-alloy thin films is found to fall into three broad categories that correlate most closely with the form of the Cu-rich end of the binary alloy phase diagrams. Available thermodynamic and tracer diffusion data shed further light on alloy behavior. Eight alloying elements were selected for these studies, with five elements from groups 5 and 6, two from group 8, and one from group 11 of the periodic table. They are respectively V, Nb, Ta, Cr, Mo, Fe, Ru, and Ag. The progress of precipitation in approximately 500-nm-thick alloy films, containing 2.5-3.8 at. % solute, was followed with in situ resistance and stress measurements as well as with in situ synchrotron x-ray diffraction. In addition, texture analysis and transmission electron microscopy were used to investigate the evolution of microstructure and texture of Cu(Ta) and Cu(Ag). For all eight alloys, dissociation occurred upon heating, with the rejection of solute and evolution of microstructure often occurring in multiple steps that range over several hundred degrees between approximately 100 and 900 degree sign C. However, in most cases, substantial reductions in resistivity of the films took place below 400 degree sign C, at temperatures of interest to copper metallization schemes for silicon chip technology. (c) 2000 American Institute of Physics

  10. Shape memory effects in a uranium + 14 at. % niobium alloy

    International Nuclear Information System (INIS)

    Vandermeer, R.A.; Ogle, J.C.; Snyder, W.B. Jr.

    1978-01-01

    There is a class of alloys that, on cooling from elevated temperatures, experience a martensitic phase change. Some of these, when stressed in the martensitic state to an apparently plastic strain, recover their predeformed shape simply by heating. This striking shape recovery is known as the ''shape memory effect'' (SME). Up to a certain limiting strain, epsilon/sub L/, 100% shape recovery may be accomplished. This memory phenomenon seems to be attributable to the thermoelastic nature of and deformational modes associated with the phase transformation in the alloy. Thus, shape recovery results when a stress-biased martensite undergoes a heat-activated reversion back to the parent phase from which it originated. There are uranium alloys that demonstrate SME-behavior. Uranium-rich, uranium--niobium alloys were the first to be documented; New experimental observations of SME in a polycrystalline uranium--niobium alloy are presented. This alloy can exhibit a two-way memory under cetain circumstances. Additional indirect evidence is presented suggesting that the characteristics of the accompanying phase transformation in this alloy meet the criteria or ''selection rules'' deemed essential for SME

  11. Fabrication Process and Reliability Evaluation of Shape Memory Alloy Composite

    International Nuclear Information System (INIS)

    Lee, Jin Kyung; Choi, Il Kook; Park, Young Chul; Lee, Kyu Chang; Lee, Joon Hyun

    2001-01-01

    Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and A16061 were used as reinforcing material and mix, respectively. In this study, TiNi/A16061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at the boundary between TiNi fiber and Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effect. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/A16061 shape memory alloy composite at high temperature

  12. Interface alloying in multilayer thin films using polarized neutron reflectometry

    International Nuclear Information System (INIS)

    Basu, Saibal

    2013-01-01

    Polarized Neutron Reflectometry (PNR) is an excellent tool to probe magnetic depth profile in multilayer thin film samples. In case of multilayer films with alternating magnetic and non-magnetic layers, PNR can provide magnetic depth profile at the interfaces with better than nanometer resolution. Using PNR and Xray Reflectometry (XRR) together one can obtain chemical composition and magnetic structure, viz. magnetic moment density at interfaces in multilayer films. We have used these two techniques to obtain kinetics of alloy formation at the interfaces and the magnetic nature of the alloy at the interfaces in several important thin films with magnetic/non-magnetic bilayers. These include Ni/Ti, Ni/Al and Si/Ni pairs. Results obtained from these studies will be presented in this talk. (author)

  13. Alloying and Casting Furnace for Shape Memory Alloys, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The concept in the proposed project is to create a melting, alloying and casting furnace for the processing titanium based SMA using cold crucible techniques. The...

  14. The industrial applications of shape memory alloys in North America

    International Nuclear Information System (INIS)

    Mc Schetky D, L.

    2000-01-01

    Literature in the recent past on shape memory effect alloys dwelt principally on the physical metallurgy, crystallography and kinetics of the shape memory phenomenon. By contrast, we now have books and conference proceedings devoted to the engineering aspects of SMAs, their technology and application. The dominant role SMAs now play in the field of medical and orthodontic devices is well documented and will be reviewed by others in this conference. In this paper we will discuss the commercial applications for shape memory alloy devices in the North American market; applications which are in many cases also produced in European countries and Japan. The early success of shape memory alloy couplings for joining tubing and pipe in the late 1960's was not followed by other large volume applications until the advent of shape memory eyeglass frames, brassiere underwires and cellular phone antennas. Many other applications have now evolved into mature markets and these will be reviewed. In addition to the many commercial applications cited, there are a number of other fields in which shape memory alloys are destined to play a major role; these include smart materials and adaptive structures, MEMS devices, infrastructure systems and electrical power generation and distribution. These applications are being developed with private and government funding and will also be briefly discussed. (orig.)

  15. Thermomechanical Methodology for Stabilizing Shape Memory Alloy (SMA) Response

    Science.gov (United States)

    Padula, Santo A., II (Inventor)

    2016-01-01

    Methods and apparatuses for stabilizing the strain-temperature response for a shape memory alloy are provided. To perform stabilization of a second sample of the shape memory alloy, a first sample of the shape memory alloy is selected for isobaric treatment and the second sample is selected for isothermal treatment. When applying the isobaric treatment to the first sample, a constant stress is applied to the first sample. Temperature is also cycled from a minimum temperature to a maximum temperature until a strain on the first sample stabilizes. Once the strain on the first sample stabilizes, the isothermal treatment is performed on the second sample. During isothermal treatment, different levels of stress on the second sample are applied until a strain on the second sample matches the stabilized strain on the first sample.

  16. First Principles Modelling of Shape Memory Alloys Molecular Dynamics Simulations

    CERN Document Server

    Kastner, Oliver

    2012-01-01

    Materials sciences relate the macroscopic properties of materials to their microscopic structure and postulate the need for holistic multiscale research. The investigation of shape memory alloys is a prime example in this regard. This particular class of materials exhibits strong coupling of temperature, strain and stress, determined by solid state phase transformations of their metallic lattices. The present book presents a collection of simulation studies of this behaviour. Employing conceptually simple but comprehensive models, the fundamental material properties of shape memory alloys are qualitatively explained from first principles. Using contemporary methods of molecular dynamics simulation experiments, it is shown how microscale dynamics may produce characteristic macroscopic material properties. The work is rooted in the materials sciences of shape memory alloys and  covers  thermodynamical, micro-mechanical  and crystallographical aspects. It addresses scientists in these research fields and thei...

  17. PROPERTY DATABASE FOR THE DEVELOPMENT OF SHAPE MEMORY ALLOY APPLICATIONS

    OpenAIRE

    Tang , W.; CederstrÖm , J.; SandstrÖm , R.

    1991-01-01

    Important points involving the selection of shape memory alloy (SMA) application projects are discussed. The development of a property database for SMA is initiated. Both conventional data as well as characteristics which are unique for SMA are stored. As an application example of the database SMA-SELECT, important properties for Ti-Ni alloys near equi-atomic composition, such as temperature window width for superelasticity (SE), stress rate, critical yield stress, and their interaction have ...

  18. Using Ternary Alloy Additions to Engineer Nitinol Shape Memory Alloys

    Data.gov (United States)

    National Aeronautics and Space Administration — Improving travel capabilities is essential in order to further investigative space exploration. For aerospace applications, weight savings is essential. Shape memory...

  19. Biocompatibility evaluation of nickel-titanium shape memory metal alloy

    OpenAIRE

    Ryhänen, J. (Jorma)

    1999-01-01

    Abstract The shape memory effect, superelasticity, and good damping properties, uncommon in other implant alloys, make the nickel-titanium shape memory metal alloy (Nitinol or NiTi) a fascinating material for surgical applications. It provides a possibility to make self-locking, self-expanding and self-compressing implants. The purpose of this work was to determine if NiTi is a safe material for surgical implant applications. The primary cytotoxicity and the corrosion rate of NiTi were...

  20. Effect of Al alloying on the martensitic temperature in Ti-Ta shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Alberto; Rogal, Jutta; Drautz, Ralf [Interdisciplinary Centre for Advanced Materials Simulation, Ruhr-Universitaet Bochum (Germany)

    2017-07-01

    Ti-Ta-based alloys are promising candidates as high temperature shape memory alloys (HTSMAs) for actuators and superelastic applications. The shape memory mechanism involves a martensitic transformation between the low-temperature α'' phase (orthorhombic) and the high-temperature β phase (body-centered cubic). In order to prevent the degradation of the shape memory effect, Ti-Ta needs to be alloyed with further elements. However, this often reduces the martensitic temperature M{sub s}, which is usually strongly composition dependent. The aim of this work is to analyze how the addition of a third element to Ti-Ta alloys affects M{sub s} by means of electronic structure calculations. In particular, it will be investigated how alloying Al to Ti-Ta alters the relative stability of the α'' and β phases. This understanding will help to identify new alloy compositions featuring both a stable shape memory effect and elevated transformation temperatures.

  1. Production and characterization of stainless steel based Fe-Cr-Ni-Mn-Si(-Co) shape memory alloys

    International Nuclear Information System (INIS)

    Otubo, J.

    1995-01-01

    It is well known that the Fe based alloys can exhibit shape memory effect due to the γ to ε martensitic transformation. The effect may not be as striking as observed in the NiTi alloy but it might become attractive from the practical point of view. In this work, two compositions of Fe-Cr-Ni-Mn-Si(-Co) stainless steel based shape memory alloy, prepared by the VIM technique, will be presented. The results are good with shape recovery of 95% for a pre-strain of 4% after some training cycles. In terms of workability the alloys produced are worse than the usual AISI304. However, adjusting the thermo-mechanical processing, it is perfectly possible to produce wire as thin as 1,20mm in dia. or down. (orig.)

  2. Performance characteristics of shape memory alloy and its applications for fusion technology

    International Nuclear Information System (INIS)

    Nishikawa, Masahiro; Watanabe, Kenji

    1987-01-01

    As a shape memory alloy, Au-Cd alloy was found in 1951. Thereafter, also in In-Tl alloy, shape memory effect was found. The U.S. Naval Ordinance Laboratory developed Ni-Ti alloy, and published in 1965 as NITINOL. As Cu group shape memory alloys, there are Cu-Zn-Al alloy, Cu-Al-Be alloy and Cu-Al-Ni alloy. Recently, iron group shape memory alloy was published. In 1975, 'Shape memory effect and its application' symposium, in 1978, 'NITINOL heat engine international conference', and in 1982 and 1986, 'Martensite transformation international conference' were held, and the method of the proper use of shape memory alloys and the problems of the alloys themselves such as fatigue have been gradually clarified. In this report, the fundamental action characteristics of shape memory alloys are discribed from the viewpoint of the application, and the possibility of applying these characteristics to nuclear fusion devices and the advantage obtained as the result are explained. Shape memory effect and pseudo-elasticity, reversible shape memory effect, the thermodynamic behavior of shape memory alloys, transformation temperature range and using temperature range and so on are described. (Kako, I.)

  3. Laser welding of Ti-Ni type shape memory alloy

    International Nuclear Information System (INIS)

    Hirose, Akio; Araki, Takao; Uchihara, Masato; Honda, Keizoh; Kondoh, Mitsuaki.

    1990-01-01

    The present study was undertaken to apply the laser welding to the joining of a shape memory alloy. Butt welding of a Ti-Ni type shape memory alloy was performed using 10 kW CO 2 laser. The laser welded specimens showed successfully the shape memory effect and super elasticity. These properties were approximately identical with those of the base metal. The change in super elasticity of the welded specimen during tension cycling was investigated. Significant changes in stress-strain curves and residual strain were not observed in the laser welded specimen after the 50-time cyclic test. The weld metal exhibited the celler dendrite. It was revealed by electron diffraction analysis that the phase of the weld metal was the TiNi phase of B2 structure which is the same as the parent phase of base metal and oxide inclusions crystallized at the dendrite boundary. However, oxygen contamination in the weld metal by laser welding did not occur because there was almost no difference in oxygen content between the base metal and the weld metal. The transformation temperatures of the weld metal were almost the same as those of the base metal. From these results, laser welding is applicable to the joining of the Ti-Ni type shape memory alloy. As the application of laser welding to new shape memory devices, the multiplex shape memory device of welded Ti-50.5 at % Ni and Ti-51.0 at % Ni was produced. The device showed two-stage shape memory effects due to the difference in transformation temperature between the two shape memory alloys. (author)

  4. A thermodynamically consistent model of shape-memory alloys

    Czech Academy of Sciences Publication Activity Database

    Benešová, Barbora

    2011-01-01

    Roč. 11, č. 1 (2011), s. 355-356 ISSN 1617-7061 R&D Projects: GA ČR GAP201/10/0357 Institutional research plan: CEZ:AV0Z20760514 Keywords : slape memory alloys * model based on relaxation * thermomechanic coupling Subject RIV: BA - General Mathematics http://onlinelibrary.wiley.com/doi/10.1002/pamm.201110169/abstract

  5. Phase stability of CuAlMn shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Zárubová, Niva; Novák, Václav

    2004-01-01

    Roč. 378, - (2004), s. 216-221 ISSN 0921-5093 Institutional research plan: CEZ:AV0Z1010914 Keywords : CuAlMn * shape memory alloys * martensitic transformation * - stress -strain tests * tension-compression cycling * history dependent phenomena Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.445, year: 2004

  6. Thermomechanical Modeling of Shape Memory Alloys and Applications

    Science.gov (United States)

    Lexcellent, C.; Leclercq, S.

    The aim of the present paper is a general macroscopic description of the thermomechanical behavior of shape memory alloys (SMA). We use for framework the thermodynamics of irreversible processes. This model is efficient for describing the behavior of "smart" structures as a bronchial, a tentacle element and an prosthesis hybrid structure made of Ti Ni SMA wires embedded in a resin epoxy matrix.

  7. Nanoscale shape-memory alloys for ultrahigh mechanical damping.

    Science.gov (United States)

    San Juan, Jose; Nó, Maria L; Schuh, Christopher A

    2009-07-01

    Shape memory alloys undergo reversible transformations between two distinct phases in response to changes in temperature or applied stress. The creation and motion of the internal interfaces between these phases during such transformations dissipates energy, making these alloys effective mechanical damping materials. Although it has been shown that reversible phase transformations can occur in nanoscale volumes, it is not known whether these transformations have a sample size dependence. Here, we demonstrate that the two phases responsible for shape memory in Cu-Al-Ni alloys are more stable in nanoscale pillars than they are in the bulk. As a result, the pillars show a damping figure of merit that is substantially higher than any previously reported value for a bulk material, making them attractive for damping applications in nanoscale and microscale devices.

  8. Shape memory alloys: metallurgy, biocompatibility, and biomechanics for neurosurgical applications.

    Science.gov (United States)

    Hoh, Daniel J; Hoh, Brian L; Amar, Arun P; Wang, Michael Y

    2009-05-01

    SHAPE MEMORY ALLOYS possess distinct dynamic properties with particular applications in neurosurgery. Because of their unique physical characteristics, these materials are finding increasing application where resiliency, conformation, and actuation are needed. Nitinol, the most frequently manufactured shape memory alloy, responds to thermal and mechanical stimuli with remarkable mechanical properties such as shape memory effect, super-elasticity, and high damping capacity. Nitinol has found particular use in the biomedical community because of its excellent fatigue resistance and biocompatibility, with special interest in neurosurgical applications. The properties of nitinol and its diffusionless phase transformations contribute to these unique mechanical capabilities. The features of nitinol, particularly its shape memory effect, super-elasticity, damping capacity, as well as its biocompatibility and biomechanics are discussed herein. Current and future applications of nitinol and other shape memory alloys in endovascular, spinal, and minimally invasive neurosurgery are introduced. An understanding of the metallurgic properties of nitinol provides a foundation for further exploration of its use in neurosurgical implant design.

  9. The response of macrophages to a Cu-Al-Ni shape memory alloy.

    Science.gov (United States)

    Colić, Miodrag; Tomić, Sergej; Rudolf, Rebeka; Anzel, Ivan; Lojen, Gorazd

    2010-09-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but little is known about their biocompatibility. The aim of this work was to study the response of rat peritoneal macrophages (PMØ) to a Cu-Al-Ni SMA in vitro, by measuring the functional activity of mitochondria, necrosis, apoptosis, and production of proinflammatory cytokines. Rapidly solidified (RS) thin ribbons were used for the tests. The control alloy was a permanent mold casting of the same composition, but without the shape memory effect. Our results showed that the control alloy was severely cytotoxic, whereas RS ribbons induced neither necrosis nor apoptosis of PMØ. These findings correlated with the data that RS ribbons are significantly more resistant to corrosion compared to the control alloy, as judged by the lesser release of Cu and Ni in the conditioning medium. However, the ribbons generated intracellular reactive oxygen species and upregulated the production of IL-6 by PMØ. These effects were almost completely abolished by conditioning the RS ribbons for 5 weeks. In conclusion, RS significantly improves the corrosion stability and biocompatibility of Cu-Al-Ni SMA. The biocompatibility of this functional material could be additionally enhanced by conditioning the ribbons in cell culture medium.

  10. Formability of Annealed Ni-Ti Shape Memory Alloy Sheet

    Science.gov (United States)

    Fann, K. J.; Su, J. Y.; Chang, C. H.

    2018-03-01

    Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its application, this study attempts to investigate the strength and cold formability of its sheet blank, which is annealed at various temperatures, by hardness test and by Erichsen-like cupping test. As a result, the higher the annealing temperature, the lower the hardness, the lower the maximum punch load as the sheet blank fractured, and the lower the Erichsen-like index or the lower the formability. In general, the Ni-Ti sheet after annealing has an Erichsen-like index between 8 mm and 9 mm. This study has also confirmed via DSC that the Ni-Ti shape memory alloy possesses the austenitic phase and shows the superelasticity at room temperature.

  11. Cold Forming of Ni-Ti Shape Memory Alloy Sheet

    Science.gov (United States)

    Fann, Kaung-Jau; Su, Jhe-Yung

    2018-03-01

    Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its further application, this study attempts to investigate the feasibility of cold forming its sheet blank especially under a bi-axial tensile stress state. Not only experiments but also a Finite Element Analysis (FEA) with DEFORM 2D was conducted in this study. The material data for FEA was accomplished by the tensile test. An Erichsen-like cupping test was performed as well to determine the process parameter for experiment setup. As a result of the study, the Ni-Ti shape memory alloy sheet has a low formability for cold forming and shows a relative large springback after releasing the forming load.

  12. Shape memory characteristics of sputter-deposited Ti-Ni thin films

    International Nuclear Information System (INIS)

    Miyazaki, Shuichi; Ishida, Akira.

    1994-01-01

    Ti-Ni shape memory alloy thin films were deposited using an RF magnetron sputtering apparatus. The as-sputtered films were heat-treated in order to crystallize and memorize. After the heat treatment, the shape memory characteristics have been investigated using DSC and thermomechanical tests. Upon cooling the thin films, the solution-treated films showed a single peak in the DSC curve indicating a single stage transformation occurring from B2 to the martensitic phase, while the age-treated films showed double peaks indicating a two-stage transformation, i.e., from B2 to the R-phase, then to the martensitic phase. A perfect shape memory effect was achieved in these sputter-deposited Ti-Ni thin films in association both with the R-phase and martensitic transformations. Transformation temperatures increased linearly with increasing applied stress. The transformation strain also increased with increasing stress. The shape memory characteristics were strongly affected by heat-treatment conditions. (author)

  13. The two way memory effect in TiNi alloys

    Energy Technology Data Exchange (ETDEWEB)

    Filip, P.; Mazanec, K. [Technical Univ. of Ostrava (Czech Republic). Inst. of Materials Engineering

    1996-08-01

    The two way memory effect (TWME) in shape memory alloys represents a reversible spontaneous shape changes during cooling and heating processes. This is a consequence of reversible phase transformations observed without application of any external stresses. The TWME is usually obtained after a thermomechanical treatment often called training. The different opinions were published concerning the influence of R-phase formation in TiNi based alloys on the stability of TWME. Stachowiak and McCormick have stated that the formation of R-phase diminishes the extent of obtained reversible strain as well as the stability of TWME. In contrast to this conclusion, the authors observed enhanced stability of TWME in the cases when the R-phase formation precedes the martensitic transformation B2 {yields} B19{prime}. Repeating the heating cycles at loading of the memory materials, the complex degradation mechanisms of TiNi alloys occurs. The dislocation generation in the matrix of TiNi alloys (work hardening) strongly influences the maximum level of generated stresses and the extent of reversible strain. As a contribution to the explanation of physical principles of TWME, the present paper is devoted to the study of substructure after so called hard training at which the specimens are deformed ({var_epsilon} = 4%) and cyclically heated and cooled down at constrained conditions.

  14. Cavitation erosion of Ti-Ni shape memory alloy deposited coatings and Fe base shape memory alloy solid

    International Nuclear Information System (INIS)

    Hattori, Shuji; Fujisawa, Seiji; Owa, Tomonobu

    2007-01-01

    In this study, cavitation erosion tests were carried out by using thermal spraying and deposition of Ti-Ni shape memory alloy for the surface coating. The results show the test speciment of Ti-Ni thermal spraying has many initial defects, so that the erosion resistance is very low. The erosion resistance of Ti-Ni deposit is about 5-10 times higher than that of SUS 304, thus erosion resistance of Ti-Ni deposit is better than that of Ti-Ni thermal spraying. The cavitation erosion tests were carried out by using Fe-Mn-Si with shape memory and gunmetal with low elastic modulus. The erosion resistance of Fe-Mn-Si shape memory alloy solid is about 9 times higher than that of SUS 304. The erosion resistance of gunmetal is almost the same as SUS 304, because the test specimen of gunmetal has many small defects on the original surface. (author)

  15. Deposition of Chitosan Layers on NiTi Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Kowalski P.

    2015-04-01

    Full Text Available The NiTi shape memory alloys have been known from their application in medicine for implants as well as parts of medical devices. However, nickel belongs to the family of elements, which are toxic. Apart from the fact that nickel ions are bonded with titanium into intermetallic phase, their presence may cause allergy. In order to protect human body against release of nickel ions a surface of NiTi alloy can be modified with use of titanium nitrides, oxides or diamond-like layers. On the one hand the layers can play protective role but on the other hand they may influence shape memory behavior. Too stiff or too brittle layer can lead to limiting or completely blocking of the shape recovery. It was the reason to find more elastic covers for NiTi surface protection. This feature is characteristic for polymers, especially, biocompatible ones, which originate in nature. In the reported paper, the chitosan was applied as a deposited layer on surface of the NiTi shape memory alloy. Due to the fact that nature of shape memory effect is sensitive to thermo and/or mechanical treatments, the chitosan layer was deposited with use of electrophoresis carried out at room temperature. Various deposition parameters were checked and optimized. In result of that thin chitosan layer (0.45µm was received on the NiTi alloy surface. The obtained layers were characterized by means of chemical and phase composition, as well as surface quality. It was found that smooth, elastic surface without cracks and/or inclusions can be produced applying 10V and relatively short deposition time - 30 seconds.

  16. Relationship between microstructure, cytotoxicity and corrosion properties of a Cu-Al-Ni shape memory alloy.

    Science.gov (United States)

    Colić, Miodrag; Rudolf, Rebeka; Stamenković, Dragoslav; Anzel, Ivan; Vucević, Dragana; Jenko, Monika; Lazić, Vojkan; Lojen, Gorazd

    2010-01-01

    Cu-Al-Ni shape memory alloys (SMAs) have been investigated as materials for medical devices, but their biomedical application is still limited. The aim of this work was to compare the microstructure, corrosion and cytotoxicity in vitro of a Cu-Al-Ni SMA. Rapidly solidified (RS) thin ribbons, manufactured via melt spinning, were used for the tests. The control alloy was a permanent mould casting of the same composition, but without shape memory effect. The results show that RS ribbons are significantly more resistant to corrosion compared with the control alloy, as judged by the lesser release of Cu and Ni into the conditioning medium. These results correlate with the finding that RS ribbons were not cytotoxic to L929 mouse fibroblasts and rat thymocytes. In addition, the RS ribbon conditioning medium inhibited cellular proliferation and IL-2 production by activated rat splenocytes to a much lesser extent. The inhibitory effects were almost completely abolished by conditioning the RS ribbons in culture medium for 4 weeks. Microstructural analysis showed that RS ribbons are martensitic, with boron particles as a minor phase. In contrast, the control Cu-Al-Ni alloy had a complex multiphase microstructure. Examination of the alloy surfaces after conditioning by energy dispersive X-ray and Auger electron spectroscopy showed the formation of Cu and Al oxide layers and confirmed that the metals in RS ribbons are less susceptible to oxidation and corrosion compared with the control alloy. In conclusion, these results suggest that rapid solidification significantly improves the corrosion stability and biocompatibility in vitro of Cu-Al-Ni SMA ribbons.

  17. Biomedical Applications of Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Lorenza Petrini

    2011-01-01

    behaviors, due to the peculiar crystallographic structure of the alloys, assure the recovery of the original shape even after large deformations and the maintenance of a constant applied force in correspondence of significant displacements. These properties, joined with good corrosion and bending resistance, biological and magnetic resonance compatibility, explain the large diffusion, in the last 20 years, of SMA in the production of biomedical devices, in particular for mini-invasive techniques. In this paper a detailed review of the main applications of NiTi alloys in dental, orthopedics, vascular, neurological, and surgical fields is presented. In particular for each device the main characteristics and the advantages of using SMA are discussed. Moreover, the paper underlines the opportunities and the room for new ideas able to enlarge the range of SMA applications. However, it is fundamental to remember that the complexity of the material and application requires a strict collaboration between clinicians, engineers, physicists and chemists for defining accurately the problem, finding the best solution in terms of device design and accordingly optimizing the NiTi alloy properties.

  18. Role of alloying additions on the properties of Cu–Al–Mn shape memory alloys

    International Nuclear Information System (INIS)

    Dasgupta, Rupa; Jain, Ashish Kumar; Kumar, Pravir; Hussain, Shahadat; Pandey, Abhishek

    2015-01-01

    Highlights: • Cu based SMAs with high transition temperature could be made using LM route. • The properties depend on alloying composition. • Property characterisation establishes feasibility of making SMAs. - Abstract: The effect of alloying seven different elements [Zn, Si, Fe, Ni, Mg, Cr and Ti] on the microstructure, hardness, phase precipitation and transformation temperature in a Cu–12.5Al–5Mn alloy with a view to possible improvements as a result of these additions is the focus of the reported study. The base alloy has been chosen keeping in mind its ability to exhibit shape memory properties and improved ductility over other Cu-based SMAs. The objective was to ascertain changes or improvements attained due to the individual tertiary additions. The samples were prepared through liquid metallurgy route using pure copper, aluminum, manganese and the respective quaternary alloying elements in right quantities to weigh 1000 g of the alloy in total and were melted together. Samples from the cast alloys were subject to homogenisation treatment at 200 °C for 2 h in a muffle furnace and furnace cooled. Samples from the homogenised alloys were heated and held for 2 h at 920 °C followed by ice quenching to obtain the desired martensitic structure for shape memory behaviour. The alloys in the cast, homogenised and quenched conditions were metallographically polished to observe the martensitic phase formation mainly in quenched samples which is a pre requisite for exhibiting shape memory properties in these alloys. X-ray Diffraction studies were carried out on the cast and quenched samples using Cu Kα target; and the phases identified indicate martensitic phase precipitation; however in some cases the precipitation is incomplete. Differential Scanning Calorimetric [DSC] studies were carried out on quenched samples from room temperature to 600 °C maintaining a constant rate of 10 °C/min. Results indicate clear transformation peaks in all the samples which

  19. Role of alloying additions on the properties of Cu–Al–Mn shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dasgupta, Rupa, E-mail: rupadasgupta@ampri.res.in; Jain, Ashish Kumar; Kumar, Pravir; Hussain, Shahadat; Pandey, Abhishek

    2015-01-25

    Highlights: • Cu based SMAs with high transition temperature could be made using LM route. • The properties depend on alloying composition. • Property characterisation establishes feasibility of making SMAs. - Abstract: The effect of alloying seven different elements [Zn, Si, Fe, Ni, Mg, Cr and Ti] on the microstructure, hardness, phase precipitation and transformation temperature in a Cu–12.5Al–5Mn alloy with a view to possible improvements as a result of these additions is the focus of the reported study. The base alloy has been chosen keeping in mind its ability to exhibit shape memory properties and improved ductility over other Cu-based SMAs. The objective was to ascertain changes or improvements attained due to the individual tertiary additions. The samples were prepared through liquid metallurgy route using pure copper, aluminum, manganese and the respective quaternary alloying elements in right quantities to weigh 1000 g of the alloy in total and were melted together. Samples from the cast alloys were subject to homogenisation treatment at 200 °C for 2 h in a muffle furnace and furnace cooled. Samples from the homogenised alloys were heated and held for 2 h at 920 °C followed by ice quenching to obtain the desired martensitic structure for shape memory behaviour. The alloys in the cast, homogenised and quenched conditions were metallographically polished to observe the martensitic phase formation mainly in quenched samples which is a pre requisite for exhibiting shape memory properties in these alloys. X-ray Diffraction studies were carried out on the cast and quenched samples using Cu Kα target; and the phases identified indicate martensitic phase precipitation; however in some cases the precipitation is incomplete. Differential Scanning Calorimetric [DSC] studies were carried out on quenched samples from room temperature to 600 °C maintaining a constant rate of 10 °C/min. Results indicate clear transformation peaks in all the samples which

  20. Modeling of mechanical properties for ferrous shape memory alloy

    International Nuclear Information System (INIS)

    Wada, Manabu; Ide, Yusuke; Mizote, Shinichiro; Naoi, Hisashi; Tsukimori, Kazuyuki

    2002-08-01

    In order to acquire technical data that are necessary for manufacture and design of the simulation test device for analyzing the core mechanics of Fast Breeder Reactor, ferrous shape memory alloy of Fe-28%Mn-6%Si-5%Cr is melted, forged and heat-treated. The microstructures are austenite. The specimens are deformed of up to 16% work-strain by tensile and compressive test, resulting in appearance of epsilon-martensite that is induced by stress. Then, heating at 673K for 10 minutes causes austenitic transformation from epsilon-martensite and shape memory strains are measured. We also investigate shape memory character of specimens, which are given, so called 'training treatment' of 5% pre-strain and recovery heat treatment. As a result, there is little difference between tensile and compressive test without training treatment and shape memory strain is 2% after being given 5% work-strain and recovery heat treatment. On the other hand, training treatment is remarkable and shape memory strain reaches to 3.7% after 5% work-strain. We analyze shape recovery character of this alloy specimen at three-point bending by using finite element method, and indicate possibility that its deformation behavior can be estimated from mechanical properties' data obtained at tensile and compressive test. (author)

  1. Three-Dimensional Cellular Structures Enhanced By Shape Memory Alloys

    Science.gov (United States)

    Nathal, Michael V.; Krause, David L.; Wilmoth, Nathan G.; Bednarcyk, Brett A.; Baker, Eric H.

    2014-01-01

    This research effort explored lightweight structural concepts married with advanced smart materials to achieve a wide variety of benefits in airframe and engine components. Lattice block structures were cast from an aerospace structural titanium alloy Ti-6Al-4V and a NiTi shape memory alloy (SMA), and preliminary properties have been measured. A finite element-based modeling approach that can rapidly and accurately capture the deformation response of lattice architectures was developed. The Ti-6-4 and SMA material behavior was calibrated via experimental tests of ligaments machined from the lattice. Benchmark testing of complete lattice structures verified the main aspects of the model as well as demonstrated the advantages of the lattice structure. Shape memory behavior of a sample machined from a lattice block was also demonstrated.

  2. Magnetic shape-memory alloys: thermomechanical modelling and analysis

    Czech Academy of Sciences Publication Activity Database

    Roubíček, Tomáš; Stefanelli, U.

    2014-01-01

    Roč. 26, č. 6 (2014), s. 783-810 ISSN 0935-1175 R&D Projects: GA ČR GAP201/10/0357 Institutional support: RVO:61388998 Keywords : magnetic shape-memory alloys * martensitic phase transformation * ferro/paramagnetic phase transformation Subject RIV: BA - General Mathematics Impact factor: 1.779, year: 2014 http://link.springer.com/article/10.1007/s00161-014-0339-8#

  3. The role of adaptive martensite in magnetic shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Niemann, R.; Rößler, U.K.; Gruner, M.E.; Heczko, Oleg; Schultz, L.; Fähler, S.

    2012-01-01

    Roč. 14, č. 8 (2012), s. 562-581 ISSN 1438-1656 Grant - others:AVČR(CZ) M100100913 Institutional research plan: CEZ:AV0Z10100520 Keywords : Ni-Mn-Ga * magnetic shape memory alloy * ferromagnetic martensite * modulated structure * adaptive phase * mobility of twin boundary Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.608, year: 2012

  4. Orthodontic applications of a superelastic shape-memory alloy model

    International Nuclear Information System (INIS)

    Glendenning, R.W.; Enlow, R.L.

    2000-01-01

    During orthodontic treatment, dental appliances (braces) made of shape memory alloys have the potential to provide nearly uniform low level stresses to dentitions during tooth movement over a large range of tooth displacement. In this paper we model superelastic behaviour of dental appliances using the finite element method and constitutive equations developed by F. Auricchio et al. Results of the mathematical model for 3-point bending and several promising 'closing loop' designs are compared with laboratory results for the same configurations. (orig.)

  5. Miniature High Force, Long Stroke Linear Shape Memory Alloy Actuators, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Shape Memory Alloys (SMAs) are metal alloys (Nickel-Titanium, for example) that change shape when heated. When drawn and processed in wire form, the shape change is...

  6. Miniature High Force, Long Stroke Linear Shape Memory Alloy Actuators, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Shape Memory Alloys (SMAs) are metal alloys (of Nickel-Titanium, for example) that can change their shape when heated. When drawn and processed in wire form, the...

  7. Temperature compensation in piezoelectric energy harvesters using shape memory alloys

    Science.gov (United States)

    Rhimi, Mohamed; Lajnef, Nizar

    2011-04-01

    Harvested vibration energy is typically considered as an alternative power source for sensors' networks for health and usage monitoring in civil and mechanical structures. The longevity, and hence the efficacy, of these sensors is severely limited by the levels of generated power. Piezoelectric vibration harvesters have been widely used given their energy conversion ability and relatively high mechanical to electrical coupling properties. Several techniques can be applied to improve these properties and to cancel external environmental effects such as temperature variations. In this paper, the temperature compensation of the response characteristics of a bimorph cantilever Lead zirconate titanate (PZT) piezoelectric beam, through a combination with shape memory alloys, is studied. A mathematical model, based on onedimensional linear piezoelectricity equations and one dimensional constitutive behavior of shape memory alloys, is derived. The model describes the effect of temperature deviations on the theoretical harvestable energy levels as well as the compensation methodology. Proof of concept experimental results are also presented. The voltage response transfer functions are measured at different temperatures to show the induced effect by shape memory alloys.

  8. Memory and threshold switching in thin film PMMA polymer

    International Nuclear Information System (INIS)

    Rabah, K.V.O.

    1995-05-01

    Threshold switching between two impedance states have been observed at room temperature in a polymethylmethacrylate (PMMA) thin film sandwiched between two evaporated Al-metal electrodes. The cell's I-V characteristics were found to exhibit memory property. (author). 19 refs, 4 figs

  9. Developing prospects of NiAlMn high temperature shape memory alloy

    International Nuclear Information System (INIS)

    Zou Min

    1999-01-01

    The reason and information on high temperature shape memory alloy research are introduced briefly Also, referring to some experimental reports on NiAlMn high temperature shape memory alloy, it is pointed out that ductility and memory property of this alloy can be improved by adapting proper composition and procedure to control its microstructure. Meanwhile, the engineering details must be considered when NiAlMn high temperature shape memory alloy being developed so as to resolve the problems of its practical use

  10. Powder-metallurgy preparation of NiTi shape-memory alloy using mechanical alloying and spark-plasma sintering.

    Czech Academy of Sciences Publication Activity Database

    Novák, P.; Moravec, H.; Vojtěch, V.; Knaislová, A.; Školáková, A.; Kubatík, Tomáš František; Kopeček, Jaromír

    2017-01-01

    Roč. 51, č. 1 (2017), s. 141-144 ISSN 1580-2949 R&D Projects: GA ČR(CZ) GA14-03044S Institutional support: RVO:61389021 ; RVO:68378271 Keywords : mechanical alloying * spark plasma sintering * NiTi * shape memory alloy Subject RIV: JG - Metallurgy; JG - Metallurgy (FZU-D) OBOR OECD: Materials engineering ; Materials engineering (FZU-D) Impact factor: 0.436, year: 2016 https://www.researchgate.net/publication/313900224_Powder-metallurgy_preparation_of_NiTi_shape-memory_alloy_using_mechanical_alloying_and_spark-plasma_sintering

  11. Characterization and design of antagonistic shape memory alloy actuators

    International Nuclear Information System (INIS)

    Georges, T; Brailovski, V; Terriault, P

    2012-01-01

    Antagonistic shape memory actuators use opposing shape memory alloy (SMA) elements to create devices capable of producing differential motion paths and two-way mechanical work in a very efficient manner. There is no requirement for additional bias elements to ‘re-arm’ the actuators and allow repetitive actuation. The work generation potential of antagonistic shape memory actuators is determined by specific SMA element characteristics and their assembly conditions. In this study, the selected SMA wires are assembled in antagonistic configuration and characterized using a dedicated test bench to evaluate their stress–strain characteristics as a function of the number of cycles. Using these functional characteristics, a so-called ‘working envelope’ is built to assist in the design of such an actuator. Finally, the test bench is used to simulate a real application of an antagonistic actuator (case study). (paper)

  12. Deformation and Failure Mechanisms of Shape Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Daly, Samantha Hayes [Univ. of Michigan, Ann Arbor, MI (United States)

    2015-04-15

    The goal of this research was to understand the fundamental mechanics that drive the deformation and failure of shape memory alloys (SMAs). SMAs are difficult materials to characterize because of the complex phase transformations that give rise to their unique properties, including shape memory and superelasticity. These phase transformations occur across multiple length scales (one example being the martensite-austenite twinning that underlies macroscopic strain localization) and result in a large hysteresis. In order to optimize the use of this hysteretic behavior in energy storage and damping applications, we must first have a quantitative understanding of this transformation behavior. Prior results on shape memory alloys have been largely qualitative (i.e., mapping phase transformations through cracked oxide coatings or surface morphology). The PI developed and utilized new approaches to provide a quantitative, full-field characterization of phase transformation, conducting a comprehensive suite of experiments across multiple length scales and tying these results to theoretical and computational analysis. The research funded by this award utilized new combinations of scanning electron microscopy, diffraction, digital image correlation, and custom testing equipment and procedures to study phase transformation processes at a wide range of length scales, with a focus at small length scales with spatial resolution on the order of 1 nanometer. These experiments probe the basic connections between length scales during phase transformation. In addition to the insights gained on the fundamental mechanisms driving transformations in shape memory alloys, the unique experimental methodologies developed under this award are applicable to a wide range of solid-to-solid phase transformations and other strain localization mechanisms.

  13. Properties and medical applications of shape memory alloys.

    Science.gov (United States)

    Tarniţă, Daniela; Tarniţă, D N; Bîzdoacă, N; Mîndrilă, I; Vasilescu, Mirela

    2009-01-01

    One of the most known intelligent material is nitinol, which offers many functional advantages over conventional implantable alloys. Applications of SMA to the biomedical field have been successful because of their functional qualities, enhancing both the possibility and the execution of less invasive surgeries. The biocompatibility of these alloys is one of their most important features. Different applications exploit the shape memory effect (one-way or two-way) and the super elasticity, so that they can be employed in orthopedic and cardiovascular applications, as well as in the manufacture of new surgical tools. Therefore, one can say that smart materials, especially SMA, are becoming noticeable in the biomedical field. Super elastic NiTi has become a material of strategic importance as it allows to overcome a wide range of technical and design issues relating to the miniaturization of medical devices and the increasing trend for less invasive and therefore less traumatic procedures. This paper will consider just why the main properties of shape memory alloys hold so many opportunities for medical devices and will review a selection of current applications.

  14. Design and development of novel antibacterial Ti-Ni-Cu shape memory alloys for biomedical application

    Science.gov (United States)

    Li, H. F.; Qiu, K. J.; Zhou, F. Y.; Li, L.; Zheng, Y. F.

    2016-11-01

    In the case of medical implants, foreign materials are preferential sites for bacterial adhesion and microbial contamination, which can lead to the development of prosthetic infections. Commercially biomedical TiNi shape memory alloys are the most commonly used materials for permanent implants in contact with bone and dental, and the prevention of infections of TiNi biomedical shape memory alloys in clinical cases is therefore a crucial challenge for orthopaedic and dental surgeons. In the present study, copper has been chosen as the alloying element for design and development novel ternary biomedical Ti‒Ni‒Cu shape memory alloys with antibacterial properties. The effects of copper alloying element on the microstructure, mechanical properties, corrosion behaviors, cytocompatibility and antibacterial properties of biomedical Ti‒Ni‒Cu shape memory alloys have been systematically investigated. The results demonstrated that Ti‒Ni‒Cu alloys have good mechanical properties, and remain the excellent shape memory effects after adding copper alloying element. The corrosion behaviors of Ti‒Ni‒Cu alloys are better than the commercial biomedical Ti‒50.8Ni alloys. The Ti‒Ni‒Cu alloys exhibit excellent antibacterial properties while maintaining the good cytocompatibility, which would further guarantee the potential application of Ti‒Ni‒Cu alloys as future biomedical implants and devices without inducing bacterial infections.

  15. Shape Memory Alloy Actuator Design: CASMART Collaborative Best Practices

    Science.gov (United States)

    Benafan, Othmane; Brown, Jeff; Calkins, F. Tad; Kumar, Parikshith; Stebner, Aaron; Turner, Travis; Vaidyanathan, Raj; Webster, John; Young, Marcus L.

    2011-01-01

    Upon examination of shape memory alloy (SMA) actuation designs, there are many considerations and methodologies that are common to them all. A goal of CASMART's design working group is to compile the collective experiences of CASMART's member organizations into a single medium that engineers can then use to make the best decisions regarding SMA system design. In this paper, a review of recent work toward this goal is presented, spanning a wide range of design aspects including evaluation, properties, testing, modeling, alloy selection, fabrication, actuator processing, design optimization, controls, and system integration. We have documented each aspect, based on our collective experiences, so that the design engineer may access the tools and information needed to successfully design and develop SMA systems. Through comparison of several case studies, it is shown that there is not an obvious single, linear route a designer can adopt to navigate the path of concept to product. SMA engineering aspects will have different priorities and emphasis for different applications.

  16. Compositional trends and magnetic excitations in binary and ternary Fe–Pd–X magnetic shape memory alloys

    International Nuclear Information System (INIS)

    Gruner, Markus Ernst; Hamann, Sven; Brunken, Hayo; Ludwig, Alfred; Entel, Peter

    2013-01-01

    Highlights: ► We discuss compositional trends in Fe–Pd–Cu and Fe–Pd–Mn magnetic shape memory alloys. ► We combine density functional theory and combinatorial thin film experiments. ► Magnetic excitations contribute decisively to the structural transformation behavior. -- Abstract: High throughput thin film experiments and first-principles calculations are combined in order to get insight into the relation between finite temperature transformation behavior and structural ground state properties of ternary Fe–Pd–X alloys. In particular, we consider the binding surface, i.e., the energy of the disordered alloy calculated along the Bain path between bcc and fcc which we model by a 108 atom supercell. We compare stoichiometric Fe 75 Pd 25 with ternary systems, where 4.6% of the Fe atoms were substituted by Cu and Mn, respectively. The computational trends are related to combinatorial experiments on thin film libraries for the systems Fe–Pd–Mn and Fe–Pd–Cu which reveal a systematic evolution of the martensitic start temperature with composition within the relevant concentration range for magnetic shape memory (MSM) applications. Our calculations include atomic relaxations, which were shown to be relevant for a correct description of the structural properties. Furthermore, we find that magnetic excitations can substantially alter the binding surface. The comparison of experimental and theoretical trends indicates that, both, compositional changes and magnetic excitations contribute significantly to the structural stability which may thus be tailored by specifically adding antiferromagnetic components

  17. Solid state thin film battery having a high temperature lithium alloy anode

    Science.gov (United States)

    Hobson, David O.

    1998-01-01

    An improved rechargeable thin-film lithium battery involves the provision of a higher melting temperature lithium anode. Lithium is alloyed with a suitable solute element to elevate the melting point of the anode to withstand moderately elevated temperatures.

  18. Implement of Shape Memory Alloy Actuators in a Robotic Hand

    Directory of Open Access Journals (Sweden)

    Daniel Amariei

    2006-10-01

    Full Text Available This paper was conceived to present the ideology of utilizing advanced actuators to design and develop innovative, lightweight, powerful, compact, and as much as possible dexterous robotic hands. The key to satisfying these objectives is the use of Shape Memory Alloys (SMAs to power the joints of the robotic hand. The mechanical design of a dexterous robotic hand, which utilizes non-classical types of actuation and information obtained from the study of biological systems, is presented in this paper. The type of robotic hand described in this paper will be utilized for applications requiring low weight, power, compactness, and dexterity.

  19. Thermo-Mechanical Methodology for Stabilizing Shape Memory Alloy Response

    Science.gov (United States)

    Padula, Santo

    2013-01-01

    This innovation is capable of significantly reducing the amount of time required to stabilize the strain-temperature response of a shape memory alloy (SMA). Unlike traditional stabilization processes that take days to weeks to achieve stabilized response, this innovation accomplishes stabilization in a matter of minutes, thus making it highly useful for the successful and practical implementation of SMA-based technologies in real-world applications. The innovation can also be applied to complex geometry components, not just simple geometries like wires or rods.

  20. Applications of the directional solidification in magnetic shape memory alloys

    Science.gov (United States)

    Huang, Y. J.; Liu, J.; Hu, Q. D.; Liu, Q. H.; Karaman, I.; Li, J. G.

    2016-03-01

    A zone melting liquid metal cooling (ZMLMC) method of directional solidification was applied to prepare highly-oriented Ni52Fe17Ga27Co4 magnetic shape memory alloys. At high temperature gradient and low growth velocity, the well-developed preferred orientation for coarse columnar crystals was obtained. Such a structure leads to a large complete pseudoelastic recovery of 5% at 348 K. Moreover, the pseudoelastic behaviours and the kinetics of the martensitic transformation (MT) are significantly affected by the intersection angle between the loading direction and the grain boundaries.

  1. Characterization of shape memory alloys for safety mechanisms.

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, Jarred T.; Buchheit, Thomas Edward; Massad, Jordan Elias

    2008-03-01

    Shape memory alloys (SMAs) are metals that exhibit large recoverable strains and exert large forces with tremendous energy densities. The behavior of SMAs is thermomechanically coupled. Their response to temperature is sensitive to their loading condition and their response to loading is sensitive to their thermal condition. This coupled behavior is not to be circumvented, but to be confronted and understood, since it is what manifests SMA's superior clamping performance. To reasonably characterize the coupled behavior of SMA clamping rings used in safety mechanisms, we conduct a series of experiments on SMA samples. The results of the tests will allow increased fidelity in modeling and failure analysis of parts.

  2. Shape memory alloy heat engines and energy harvesting systems

    Science.gov (United States)

    Browne, Alan L; Johnson, Nancy L; Keefe, Andrew C; Alexander, Paul W; Sarosi, Peter Maxwell; Herrera, Guillermo A; Yates, James Ryan

    2013-12-17

    A heat engine includes a first rotatable pulley and a second rotatable pulled spaced from the first rotatable pulley. A shape memory alloy (SMA) element is disposed about respective portions of the pulleys at an SMA pulley ratio. The SMA element includes first spring coil and a first fiber core within the first spring coil. A timing cable is disposed about disposed about respective portions of the pulleys at a timing pulley ratio, which is different than the SMA pulley ratio. The SMA element converts a thermal energy gradient between the hot region and the cold region into mechanical energy.

  3. Coupled magnetoelastic waves in ferromagnetic shape-memory alloys

    Science.gov (United States)

    Bar'Yakhtar, V. G.; Danilevich, A. G.; L'Vov, V. A.

    2011-10-01

    The theory of the spectra of coupled magnetoelastic waves in ferromagnetic shape-memory alloys (FSMA) is developed. The possibility of an abnormally strong coupling of spin waves with the soft elastic mode at approaching the martensitic transformation (MT) temperature is disclosed. In particular the magnetoelastic waves in Ni-Mn-Ga single crystals are considered. A considerable (by an order of magnitude) reduction of the shear elastic modulus and an appropriate lowering of the transversal velocity of sound in the applied magnetic field are predicted. Optimum conditions for the experimental observation of the predicted effects are specified.

  4. Uncertainty analysis of a one-dimensional constitutive model for shape memory alloy thermomechanical description

    DEFF Research Database (Denmark)

    Oliveira, Sergio A.; Savi, Marcelo A.; Santos, Ilmar F.

    2014-01-01

    The use of shape memory alloys (SMAs) in engineering applications has increased the interest of the accuracy analysis of their thermomechanical description. This work presents an uncertainty analysis related to experimental tensile tests conducted with shape memory alloy wires. Experimental data...

  5. Experimental analyses of dynamical systems involving shape memory alloys

    DEFF Research Database (Denmark)

    Enemark, Søren; Savi, Marcelo A.; Santos, Ilmar F.

    2015-01-01

    The use of shape memory alloys (SMAs) in dynamical systems has an increasing importance in engineering especially due to their capacity to provide vibration reductions. In this regard, experimental tests are essential in order to show all potentialities of this kind of systems. In this work, SMA...... springs are incorporated in a dynamical system that consists of a one degree of freedom oscillator connected to a linear spring and a mass, which is also connected to the SMA spring. Two types of springs are investigated defming two distinct systems: a pseudoelastic and a shape memory system....... The characterisation of the springs is evaluated by considering differential calorimetry scanning tests and also force-displacement tests at different temperatures. Free and forced vibration experiments are made in order to investigate the dynamical behaviour of the systems. For both systems, it is observed...

  6. Ageing and memory effects in a mechanically alloyed nanoparticle system

    International Nuclear Information System (INIS)

    Osth, Michael; Herisson, Didier; Nordblad, Per; De Toro, Jose A.; Riveiro, Jose M.

    2007-01-01

    Ageing and memory experiments have been performed to explore the non-equilibrium dynamics of the mechanically alloyed nanoparticle system Fe 30 Ag 40 W 30 , which comprises a heterogeneous ensemble of magnetic particles with average moment ∼ 10 2 μ B dispersed in a metallic non-magnetic matrix. This system has earlier, from critical slowing down analysis, been reported to enter a spin glass like state at low temperatures [J. A. de Toro et al., Phys. Rev. B 69, (2004) 224407]. The wait time dependence of the magnetic relaxation observed after the application of a weak magnetic field and the memory of the thermal history in the low temperature phase recorded on continuous heating in a weak applied field show similar features as observed in corresponding experiments on canonical spin glasses

  7. Texture memory and strain-texture mapping in a NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Ye, B.; Majumdar, B. S.; Dutta, I.

    2007-01-01

    The authors report on the near-reversible strain hysteresis during thermal cycling of a polycrystalline NiTi shape memory alloy at a constant stress that is below the yield strength of the martensite. In situ neutron diffraction experiments are used to demonstrate that the strain hysteresis occurs due to a texture memory effect, where the martensite develops a texture when it is cooled under load from the austenite phase and is thereafter ''remembered.'' Further, the authors quantitatively relate the texture to the strain by developing a calculated strain-texture map or pole figure for the martensite phase, and indicate its applicability in other martensitic transformations

  8. Vibration control of a flexible rotor suspended by shape memory alloy wires

    DEFF Research Database (Denmark)

    Alves, Marco Túlio Santana; Steffen Jr., Valder; Castro dos Santos, Marina

    2018-01-01

    The present contribution is devoted to the study of the influence of shape memory alloys on the dynamic behavior of flexible rotors. In this sense, a suspension composed by pseudoelastic shape memory alloy wires that are connected to a rotor-bearing test rig was designed. To evaluate...... a phase transformation. The constitutive model used to describe the shape memory alloy behavior is a modified version of the Brinson model for the one-dimensional case. To provide all thermomechanical properties of shape memory alloy wire, a complete characterization process was performed. Due...... to numerical reasons, the size of the model of the rotating system was reduced. Finally, numerical and experimental results demonstrate the success of shape memory alloy applied to the suspension of rotating machines as an interesting alternative for vibration control....

  9. Characterization of mechanical properties of pseudoelastic shape memory alloys under harmonic excitation

    Science.gov (United States)

    Böttcher, J.; Jahn, M.; Tatzko, S.

    2017-12-01

    Pseudoelastic shape memory alloys exhibit a stress-induced phase transformation which leads to high strains during deformation of the material. The stress-strain characteristic during this thermomechanical process is hysteretic and results in the conversion of mechanical energy into thermal energy. This energy conversion allows for the use of shape memory alloys in vibration reduction. For the application of shape memory alloys as vibration damping devices a dynamic modeling of the material behavior is necessary. In this context experimentally determined material parameters which accurately represent the material behavior are essential for a reliable material model. Subject of this publication is the declaration of suitable material parameters for pseudoelastic shape memory alloys and the methodology of their identification from experimental investigations. The used test rig was specifically designed for the characterization of pseudoelastic shape memory alloys.

  10. Effect of Ternary Addition of Iron on Shape Memory Characteristics of Cu-Al Alloys

    Science.gov (United States)

    Raju, T. N.; Sampath, V.

    2011-07-01

    The effect of alloying Cu-Al alloys with Fe on their transformation temperatures and shape memory properties was investigated by differential scanning calorimetry and bend test. It was found that the minor additions of iron resulted in change of transformation temperatures and led to excellent shape memory properties of the alloys. Since the transformation temperatures are high, they are an ideal choice for high-temperature applications.

  11. Ductile shape memory alloys of the Cu-Al-Mn system

    International Nuclear Information System (INIS)

    Kainuma, R.; Takahashi, S.; Ishida, K.

    1995-01-01

    Cu-Al-Mn shape memory alloys with enhanced ductility have been developed by decreasing the degree of order in the β parent phase. Cu-Al-Mn alloys with Al contents lower than 18% exhibit good ductility with elongations of about 15% and excellent cold-workability arising from a lower degree of order in the Heusler (L21) β 1 parent phase, without any loss in their shape memory behavior. In this paper the mechanical and shape memory characteristics, such as the cold-workability, the Ms temperatures, the shape memory effect and the pseudo-elasticity of such ductile Cu-Al-Mn alloys are presented. (orig.)

  12. Shape memory effect and superelasticity of titanium nickelide alloys implanted with high ion doses

    International Nuclear Information System (INIS)

    Pogrebnjak, A D; Bratushka, S N; Beresnev, V M; Levintant-Zayonts, N

    2013-01-01

    The state of the art in ion implantation of superelastic NiTi shape memory alloys is analyzed. Various technological applications of the shape memory effect are outlined. The principles and techiques of ion implantation are described. Specific features of its application for modification of surface layers in surface engineering are considered. Key properties of shape memory alloys and problems in utilization of ion implantation to improve the surface properties of shape memory alloys, such as corrosion resistance, friction coefficient, wear resistance, etc. are discussed. The bibliography includes 162 references

  13. Shape memory and superelastic behavior of Ti-7.5Nb-4Mo-1Sn alloy

    International Nuclear Information System (INIS)

    Zhang, D.C.; Lin, J.G.; Jiang, W.J.; Ma, M.; Peng, Z.G.

    2011-01-01

    Research highlights: → A Ti-based shape memory alloy, Ti-7.5Nb-4Mo-1Sn, was designed. → The martensitic transformation start temperature of the alloy, M s , is 261 K. → The alloy exhibits good shape memory and superelastic behaviors. → The alloy also shows a good superelastic stability at room temperature. → The Ti-5Mo-7.5Nb-1Sn alloy has a potential application as a biomedical material. -- Abstract: In the present work, a Ti-based shape memory alloy with the composition of Ti-7.5Nb-4Mo-1Sn was designed based on the d-electron orbit theory. The shape memory and superelastic behavior of the alloy were investigated. It is found that the martensitic transformation temperature of the alloy is near 261 K. The tensile and the thermal cycling testing results show that the alloy exhibits the stable shape memory effect and superelasticity at room temperature. The maximum recovered strain of the alloy is 4.83%.

  14. A Shape Memory Alloy Application for Compact Unmanned Aerial Vehicles

    Directory of Open Access Journals (Sweden)

    Salvatore Ameduri

    2016-05-01

    Full Text Available Shape memory alloys materials, SMA, offer several advantages that designers can rely on such as the possibility of transmitting large forces and deformations, compactness, and the intrinsic capability to absorb loads. Their use as monolithic actuators, moreover, can lead to potential simplifications of the system, through a reduction of number of parts and the removal of many free play gaps among mechanics. For these reasons, technological aerospace research is focusing on this kind of technology more and more, even though fatigue life, performance degradation, and other issues are still open. In the work at hand, landing gear for unmanned aerial vehicles, UAV, is presented, integrated with shape memory alloys springs as actuation devices. A conceptual prototype has been realized to verify the system ability in satisfying specs, in terms of deployment and retraction capability. Starting from the proposed device working principle and the main design parameters identification, the design phase is faced, setting those parameters to meet weight, deployment angle, energy consumption, and available room requirements. Then, system modeling and performance prediction is performed and finally a correlation between numerical and experimental results is presented.

  15. Modeling the Cyclic Behavior of Shape Memory Alloys

    Science.gov (United States)

    Waimann, Johanna; Junker, Philipp; Hackl, Klaus

    2017-06-01

    The phenomenon of functional fatigue occurs during cyclic loading of pseudoelastic shape memory alloys. We model this effect by considering an irreversible martensitic volume fraction in addition to the reversible amounts of austenite and martensite based on variational principles. The inclusion of irreversible martensitic volume fractions coincides with experimental observations and enables the model to be easily calibrated without any fitting functions. In our previous studies, we modeled the polycrystalline material structure by static discretization of a relatively large number of randomly chosen grain orientations, which required much numerical effort. In contrast, we now apply a dynamic representation of the orientation distribution function to the modeling of functional fatigue which has proven to be beneficial regarding the numerical performance. To this end, we take into account an averaged grain orientation parameterized by three Euler angles that serve as additional internal variables. This results in an extremely reduced numerical effort. The model derivation is given along with the numerical implementation and computer experiments on the cyclic behavior of shape memory alloys.

  16. Recentering Shape Memory Alloy Passive Damper for Structural Vibration Control

    Directory of Open Access Journals (Sweden)

    Hui Qian

    2013-01-01

    Full Text Available This paper presents a preliminary study on the evaluation of an innovative energy dissipation system with shape memory alloys (SMAs for structural seismic protection. A recentering shape memory alloy damper (RSMAD, in which superelastic nitinol wires are utilized as energy dissipation components, is proposed. Improved constitutive equations based on Graesser and Cozzarelli model are proposed for superelastic nitinol wires used in the damper. Cyclic tensile-compressive tests on the damper with various prestrain under different loading frequencies and displacement amplitudes were conducted. The results show that the hysteretic behaviors of the damper can be modified to best fit the needs for passive structural control applications by adjusting the pretension of the nitinol wires, and the damper performance is not sensitive to frequencies greater than 0.5 Hz. To assess the effectiveness of the dampers for structural seismic protection, nonlinear time history analysis on a ten-story steel frame with and without the dampers subjected to representative earthquake ground motions was performed. The simulation results indicate that superelastic SMA dampers are effective in mitigating the structural response of building structures subjected to strong earthquakes.

  17. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    International Nuclear Information System (INIS)

    Krishnan, V.B.; Singh, J.D.; Woodruff, T.R.; Vaidyanathan, R.; Notardonato, W.U.

    2004-01-01

    Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed

  18. Functional Characterization of a Novel Shape Memory Alloy

    Science.gov (United States)

    Collado, M.; Cabás, R.; San Juan, J.; López-Ferreño, I.

    2014-07-01

    A novel shape memory alloy (SMA) has been developed as an alternative to currently available alloys. This alloy, commercially known by its proprietary brand SMARQ, shows a higher working range of temperatures with respect to the SMA materials used until now in actuators, limited to environment temperatures below 90 °C. SMARQ is a high temperature SMA (HTSMA) based on a fully European material technology and production processes, which allows the manufacture of high quality products, with tuneable transformation temperatures up to 200 °C. Both, material and production processes have been evaluated for its use in space applications. A full characterization test campaign has been completed in order to obtain the material properties and check its suitability to be used as active material in space actuators. In order to perform the functional characterization of the material, it has been considered as the key element of a basic SMA actuator, consisting in the SMA wire and the mechanical and electrical interfaces. The functional tests presented in this work have been focused on the actuator behavior when heated by means of an electrical current. Alloy composition has been adjusted in order to match a transition temperature (As) of +145 °C, which satisfies the application requirements of operating temperatures in the range of -70 and +125 °C. Details of the tests and results of the characterization test campaign, focused in the material unique properties for their use in actuators, will be presented in this work. Some application examples in the field of space mechanisms and actuators, currently under development, will be summarized as part of this work, demonstrating the technology suitability as active material for space actuators.

  19. Fabrication of TiNi powder by mechanical alloying and shape memory characteristics of the sintered alloy

    International Nuclear Information System (INIS)

    Terayama, Akira; Kyogoku, Hideki; Komatsu, Shinichiro; Sakamura, Masaru

    2006-01-01

    This paper presents the fabrication condition of TiNi alloy powder by mechanical alloying and shape memory characteristics of the sintered alloy. The effect of mechanical alloying condition on the characteristics of mechanically alloyed powder (MA powder) was investigated. Also, the difference in sintering behavior between the MA powder and the elementally mixed powders by V-blender and the shape memory characteristics of the sintered alloys were also examined. The MA powder was fabricated by milling using a planetary ball mill in a rotational speed between 200 and 500 min -1 for various milling times in an atmosphere of Ar gas. These two of powders prepared in different processes were sintered using a pulse-current pressure sintering equipment at various sintering temperatures. The powder agglomerated and its particle size became larger with an increase in milling time. The mixture of Ti and Ni powders changed into an amorphous state by processing for 3.6 ks over 300 min -1 . The sintered alloy of the MA powder showed more uniform phase of TiNi than that of the elementally mixed powders sintered in a same manner, however, the former showed a lower density than the latter due to a larger particle size of the MA powder of before-sintering. It was found from the measurement of the transformation temperature of the sintered alloy of the MA powder using DSC that the alloy has shape memory characteristics, and the transformation temperatures of the alloy are higher than those of the alloy of the elementally mixed powders due to waste of Ni powder. (author)

  20. Radioactive material package closures with the use of shape memory alloys

    International Nuclear Information System (INIS)

    Koski, J.A.; Bronowski, D.R.

    1997-11-01

    When heated from room temperature to 165 C, some shape memory metal alloys such as titanium-nickel alloys have the ability to return to a previously defined shape or size with dimensional changes up to 7%. In contrast, the thermal expansion of most metals over this temperature range is about 0.1 to 0.2%. The dimension change of shape memory alloys, which occurs during a martensite to austenite phase transition, can generate stresses as high as 700 MPa (100 kspi). These properties can be used to create a closure for radioactive materials packages that provides for easy robotic or manual operations and results in reproducible, tamper-proof seals. This paper describes some proposed closure methods with shape memory alloys for radioactive material packages. Properties of the shape memory alloys are first summarized, then some possible alternative sealing methods discussed, and, finally, results from an initial proof-of-concept experiment described

  1. Thermomechanical behavior of Fe-Mn-Si-Cr-Ni shape memory alloys modified with samarium

    International Nuclear Information System (INIS)

    Shakoor, R.A.; Khalid, F. Ahmad

    2009-01-01

    The deformation and training behavior of Fe-14Mn-3Si-10Cr-5Ni (wt.%) shape memory alloys containing samarium addition has been studied in the iron-based shape memory alloys. It is noticed that thermomechanical treatment (training) has significant influence on proof stress, critical stress and shape memory behavior of the alloys. The improvement in shape memory behavior can be attributed to the decrease in the proof stress and critical stress which facilitates the formation of ε (hcp martensite). It is also observed that alloy 2 containing samarium undergoes less softening as compared to alloy 1 with training which inhibits the formation of α (bcc martensite) and thus enhances the shape memory behavior. The excessive thermomechanical treatment with increase in the training cycle has led to the formation of α (bcc martensite) along with ε (hcp martensite) in the alloy 1 which appeared to have decline in the shape memory effect. This has been demonstrated by the examination of microstructure and identification of α (bcc martensite) martensite in the alloy 1 as compared to alloy 2

  2. Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar; Savi, Marcelo A.

    2015-01-01

    hysteretic stress-strain relations which may be utilized for damping purposes. These ideas are tested in this study on a dedicated test-rig, consisting of a rigid shaft and disc held vertically by passive magnetic bearings, where the damping is low. The bearing housings is flexibly supported by shape memory......tor-bearing systems have critical speeds and to pass through them is an ongoing challenge in the field of mechanical engineering. The incorporation of shape memory alloys in rotating systems has an increasing importance to improve system performance and to avoid potential damaging situations when...... passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with temperature variations and thus they may change system dynamics. Shape memory alloys also exhibit...

  3. Improvement of shape memory effect in Fe-Mn-Si alloy by slight tantalum addition

    International Nuclear Information System (INIS)

    Yang, Cheng-Hsiu; Lin, Hsin-Chih; Lin, Kun-Ming

    2009-01-01

    The effects of slight tantalum (Ta) addition on the microstructures, precipitates, martensitic transformation and shape memory performance of Fe-30Mn-6Si-based alloys were investigated. Experimental results show that the slight Ta addition will increase the c/a ratio of ε martensite, reduce the M s temperature and improve the alloy's shape recovery ability. After TMT at 650 deg. C, the alloy's M s temperature is reduced and lots of (Fe, Mn) 3 Si and TaC precipitates form. The effective nuclei and well-aligned precipitates within the grain interior after TMT will improve significantly the alloy's shape memory performance.

  4. Electromagnetic heating of a shape memory alloy translator

    Science.gov (United States)

    Giroux, E.-A.; Maglione, M.; Gueldry, A.; Mantoux, J.-L.

    1996-03-01

    The active part of a linear translator is a shape memory alloy (SMA) made of nickel and titanium (NiTi) wire which is to be thermally cycled. We have achieved heating using electromagnetic radiation with a magnetic sheath and low-frequency waves at 8 kHz and without magnetic sheath and radio frequency waves at 28 MHz. The heating is equivalent for these two arrangements. In vitro experiments have been confirmed by computer simulations of the radiation distribution within the implant. We thus show that electromagnetic radiation could specifically heat a NiTi wire inside a stainless steel tube without heating the tube. An application could be a femoral prosthesis for the lengthening of the bone.

  5. Using Shape Memory Alloys: A Dynamic Data Driven Approach

    KAUST Repository

    Douglas, Craig C.

    2013-06-01

    Shape Memory Alloys (SMAs) are capable of changing their crystallographic structure due to changes of either stress or temperature. SMAs are used in a number of aerospace devices and are required in some devices in exotic environments. We are developing dynamic data driven application system (DDDAS) tools to monitor and change SMAs in real time for delivering payloads by aerospace vehicles. We must be able to turn on and off the sensors and heating units, change the stress on the SMA, monitor on-line data streams, change scales based on incoming data, and control what type of data is generated. The application must have the capability to be run and steered remotely as an unmanned feedback control loop.

  6. Development of Shape Memory Alloys- Challenges and Solutions

    Science.gov (United States)

    Benafan, Othmane

    2016-01-01

    Shape memory alloys (SMAs) are a unique class of multifunctional materials that have the ability to recover large deformations or generate high stresses in response to thermal, mechanical andor electromagnetic stimuli. These abilities have made them a viable option for actuation systems in aerospace, medical, and automotive applications, amongst others. However, despite many advantages and the fact that SMA actuators have been developed and used for many years, so far they have only found service in a limited range of applications. In order to expand their applications, further developments are needed to increase their reliability and stability and to address processing, testing and qualification needed for large-scale commercial application of SMA actuators. In this seminar, historical inhibitors of SMA applications and current research efforts by NASA Glenn Research Center and collaborators will be discussed. Relationships between fundamental physicalscientific understanding, and the direct transition to engineering and design of mechanisms using these novel materials will be highlighted. Examples will be presented related to targeted alloy development, microstructural control, and bulk-scale testing as a function of stresses, temperatures and harsh environments. The seminar will conclude with a summary of SMA applications under development and current advances.

  7. Vacuum Arc Melting Processes for Biomedical Ni-Ti Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Tsai De-Chang

    2015-01-01

    Full Text Available This study primarily involved using a vacuum arc remelting (VAR process to prepare a nitinol shape-memory alloy with distinct ratios of alloy components (nitinol: 54.5 wt% to 57 wt%. An advantage of using the VAR process is the adoption of a water-cooled copper crucible, which effectively prevents crucible pollution and impurity infiltration. Optimising the melting production process enables control of the alloy component and facilitates a uniformly mixed compound during subsequent processing. This study involved purifying nickel and titanium and examining the characteristics of nitinol alloy after alloy melt, including its microstructure, mechanical properties, phase transition temperature, and chemical components.

  8. Effects of surface damage on twinning stress and the stability of twin microstructures of magnetic shape memory alloys

    International Nuclear Information System (INIS)

    Chmielus, Markus; Witherspoon, Cassie; Ullakko, Kari; Muellner, Peter; Schneider, Rainer

    2011-01-01

    Research highlights: → Electropolishing reduces residual stresses in surfaces of magnetic shape-memory alloys and reduces the twinning stress. → Mechanical polishing and grinding produces a layer of defects on surfaces and increases the twinning stress of magnetic shape-memory alloys. → Defects localized near the surface (surface damage) increase the twinning stress and smoothen the stress-strain curve. → Defects localized near the surface create a stable and dense twin microstructure with mobile twins which extend throughout the entire crystal. → A stable dense twin microstructure provides the basis for fatigue-resistant magnetic shape-memory alloys. - Abstract: Twinning is the primary deformation mechanism in magnetic shape memory alloys (MSMAs). Obstacles such as inclusions, precipitates and defects hinder or even prevent twin boundary motion in the bulk of Ni-Mn-Ga MSMA single crystals. Here, we study the effect of surface damage on the mechanical properties and twin structure of Ni-Mn-Ga single crystals. Any methods that produce defects may be considered for modifying the near-surface microstructure. In this study deformations were produced by grinding and mechanical polishing using abrasive particles. The amount of damage was characterized with X-ray diffraction: damage causes peak broadening. Deformation and damage localized near the surface increases the twinning stress. Surface damage stabilizes a densely twinned microstructure. The twins are thin but extend over the entire sample and allow a large strain to be accommodated at moderate stress. This effect is critical for preventing damage accumulation in high-cycle magnetomechanical actuation and for achieving high dynamic performance.

  9. Structural properties of calcogenic thin films and alloys subjected to synchrotron light

    International Nuclear Information System (INIS)

    Moura, P.R.; Almeida, D.P.; Lima, J.C. de; Campos, C.E.M.; Ponciano, C.R.

    2009-01-01

    Results on structural characterization of Sb 50 Te 50 and Te 24 In 38 Sb 38 alloys prepared as powder and after deposited as a thin films are presented. For that x ray diffraction and energy dispersive X-ray fluorescence were used. The nanocrystalline phases Sb 2 Te 2 and Sb 24 Te 9 were nucleated in both Sb 50 Te 50 and Te 24 In 38 Sb 38 alloys, respectively. The thin films of both binary and ternary alloys are mainly amorphous. According to X-ray fluorescence results the chemical composition inside the ultraviolet irradiated region on one of the binary thin film become different than that outside irradiation marks, suggesting Sb migration. (author)

  10. Stresses related to the shape memory effect in Fe-Mn-Si-based shape memory alloys

    International Nuclear Information System (INIS)

    Caenegem, N. van; Duprez, L.; Verbeken, K.; Segers, D.; Houbaert, Y.

    2008-01-01

    The shape memory behaviour of two Fe-Mn-Si-based alloys has been investigated. Two compositions were studied, i.e. Fe29Mn7Si and Fe29Mn7Si5Cr (numbers indicate mass%). Characterizations of the martensitic transformation and the different structural constituents were performed using optical microscopy and X-ray diffraction methods. Transformation temperatures were determined by thermodilatometry on undeformed and deformed samples. The shape recovery was quantified by means of bending tests and dilatometry experiments on compressed samples. A procedure was designed to measure the recovery stresses caused by the dimensional changes of the sample due to the shape memory effect. The recovery stress is defined as the stress that is generated when the recovery of deformation is impeded under constraint. The mechanical results are discussed on the basis of the underlying transformation and deformation processes

  11. Near Net Shape Fabrication Technology for Shape Memory Alloy Components Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This STTR Phase I effort proposes to develop an innovative, affordable processing route for larger-sized shape memory alloy (SMA) components. Despite significant...

  12. Shape Memory Alloy Cryogenic Transfer Coupling for Space Depot Docking Operations

    Data.gov (United States)

    National Aeronautics and Space Administration — The technical objective of the proposed effort is to establish the feasibility of using shape memory alloy (SMA) actuators for selected components of the automatic...

  13. Vacuum Plasma Spray Formed High Transition Temperature Shape Memory Alloys, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Smart materials control of aero-surfaces based on shape memory alloys (SMA) is seeing increased use for improving of future subsonic fixed wing aircraft aero-surface...

  14. Processing and Characterization of NiTi Shape Memory Alloy Particle Reinforced Sn-In Solders

    National Research Council Canada - National Science Library

    Chung, Kohn C

    2006-01-01

    .... In previous work, it was proposed that reinforcement of solder by NiTi shape memory alloy particles to form smart composite solder reduces the inelastic strain of the solder and hence, may enhance...

  15. Near Net Shape Fabrication Technology for Shape Memory Alloy Components, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This STTR Phase I effort proposes to develop an innovative, affordable processing route for larger-sized shape memory alloy (SMA) components. Despite significant...

  16. Stress Relaxation Of Superelastic Shape Memory Alloy Under Bending And Torsional Load

    Directory of Open Access Journals (Sweden)

    Sakib Tanvir

    2017-04-01

    Full Text Available Stress Relaxation of Superelastic Shape memory NiTi Alloy under bending and torsion is uncommon in literature. Therefore experimental set up has been devised and test results are obtained for superelastic SMA.Unlike the other common engineering materials superelastic SMA it gives dramatic reduction in stress. In this paper therefore results of stress relaxation of superelastic shape memory alloy under bending and torsion are presented graphically and interpreted in terms of stress induced martensitic transformation.

  17. Shape memory alloy seals for geothermal applications. Final report. Report ESG-82-14

    Energy Technology Data Exchange (ETDEWEB)

    Friske, Warren H.; Schwartzbart, Harry

    1982-07-30

    A novel temperature-actuated seal for geothermal applications is under development. This program uses the shape memory property of nickel-titanium (Nitinol) alloys to achieve an improved seal in geothermal downhole pumps. Nitinol flange face seals and pump shaft seals have been designed, fabricated, and tested. It has been demonstrated that the shape memory effect of Nitinol alloys can be utilized to activate and maintain a leaktight seal in geothermal environments.

  18. Bio-inspired Miniature Suction Cups Actuated by Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Hu Bing-Shan

    2009-09-01

    Full Text Available Wall climbing robots using negative pressure suction always employ air pumps which have great noise and large volume. Two prototypes of bio-inspired miniature suction cup actuated by shape memory alloy (SMA are designed based on studying characteristics of biologic suction apparatuses, and the suction cups in this paper can be used as adhesion mechanisms for miniature wall climbing robots without air pumps. The first prototype with a two-way shape memory effect (TWSME extension TiNi spring imitates the piston structure of the stalked sucker; the second one actuated by a one way SMA actuator with a bias has a basic structure of stiff margin, guiding element, leader and elastic element. Analytical model of the second prototype is founded considering the constitutive model of the SMA actuator, the deflection of the thin elastic plate under compound load and the thermo-dynamic model of the sealed air cavity. Experiments are done to test their suction characteristics, and the analytical model of the second prototype is simulated on Matlab/simulink platform and validated by experiments.

  19. The W alloying effect on thermal stability and hardening of nanostructured Cu–W alloyed thin films

    Science.gov (United States)

    Zhao, J. T.; Zhang, J. Y.; Hou, Z. Q.; Wu, K.; Feng, X. B.; Liu, G.; Sun, J.

    2018-05-01

    In order to achieve desired mechanical properties of alloys by manipulating grain boundaries (GBs) via solute decoration, it is of great significance to understand the underlying mechanisms of microstructural evolution and plastic deformation. In this work, nanocrystalline (NC) Cu–W alloyed films with W concentrations spanning from 0 to 40 at% were prepared by using magnetron sputtering. Thermal stability (within the temperature range of 200 °C–600 °C) and hardness of the films were investigated by using the x-ray diffraction, transmission electron microscope (TEM) and nanoindentation, respectively. The NC pure Cu film exhibited substantial grain growth upon all annealing temperatures. The Cu–W alloyed films, however, displayed distinct microstructural evolution that depended not only on the W concentration but also on the annealing temperature. At a low temperature of 200 °C, all the Cu–W alloyed films were highly stable, with unconspicuous change in grain sizes. At high temperatures of 400 °C and 600 °C, the microstructural evolution was greatly controlled by the W concentrations. The Cu–W films with low W concentration manifested abnormal grain growth (AGG), while the ones with high W concentrations showed phase separation. TEM observations unveiled that the AGG in the Cu–W alloyed thin films was rationalized by GB migration. Nanoindentation results showed that, although the hardness of both the as-deposited and annealed Cu–W alloyed thin films monotonically increased with W concentrations, a transition from annealing hardening to annealing softening was interestingly observed at the critical W addition of ∼25 at%. It was further revealed that an enhanced GB segregation associated with detwinning was responsible for the annealing hardening, while a reduced solid solution hardening for the annealing softening.

  20. The W alloying effect on thermal stability and hardening of nanostructured Cu-W alloyed thin films.

    Science.gov (United States)

    Zhao, J T; Zhang, J Y; Hou, Z Q; Wu, K; Feng, X B; Liu, G; Sun, J

    2018-05-11

    In order to achieve desired mechanical properties of alloys by manipulating grain boundaries (GBs) via solute decoration, it is of great significance to understand the underlying mechanisms of microstructural evolution and plastic deformation. In this work, nanocrystalline (NC) Cu-W alloyed films with W concentrations spanning from 0 to 40 at% were prepared by using magnetron sputtering. Thermal stability (within the temperature range of 200 °C-600 °C) and hardness of the films were investigated by using the x-ray diffraction, transmission electron microscope (TEM) and nanoindentation, respectively. The NC pure Cu film exhibited substantial grain growth upon all annealing temperatures. The Cu-W alloyed films, however, displayed distinct microstructural evolution that depended not only on the W concentration but also on the annealing temperature. At a low temperature of 200 °C, all the Cu-W alloyed films were highly stable, with unconspicuous change in grain sizes. At high temperatures of 400 °C and 600 °C, the microstructural evolution was greatly controlled by the W concentrations. The Cu-W films with low W concentration manifested abnormal grain growth (AGG), while the ones with high W concentrations showed phase separation. TEM observations unveiled that the AGG in the Cu-W alloyed thin films was rationalized by GB migration. Nanoindentation results showed that, although the hardness of both the as-deposited and annealed Cu-W alloyed thin films monotonically increased with W concentrations, a transition from annealing hardening to annealing softening was interestingly observed at the critical W addition of ∼25 at%. It was further revealed that an enhanced GB segregation associated with detwinning was responsible for the annealing hardening, while a reduced solid solution hardening for the annealing softening.

  1. Effect of plastic strain on shape memory characteristics in sputter-deposited Ti-Ni thin films

    International Nuclear Information System (INIS)

    Nomura, K.

    1995-01-01

    The plastic strain which is introduced during cooling and heating under a constant stress has an influence upon the transformation and deformation characteristics of sputter-deposited Ti-Ni shape memory alloy thin films. With increasing the accumulated plastic strain, Ms rises and recovery strain increases. The changes in such characteristics are due to the internal stress field that is formed by plastic deformation. However, the change in Ms in Ti-50.5at%Ni is larger than that in Ti-48.9at%Ni, although the plastic strain in the former is lower than that in the latter. In order to understand this point, the effective internal stresses were estimated in both alloys; the internal stress in the former is more effectively created by the introduction of plastic strain than in the latter. (orig.)

  2. Phases stability of shape memory alloys Cu based under irradiation

    International Nuclear Information System (INIS)

    Zelaya, Maria Eugenia

    2006-01-01

    The effects of irradiation on the relative phase stability of phases related by a martensitic transformation in copper based shape memory alloys were studied in this work.Different kind of particles and energies were employed in the irradiation experiments.The first kind of irradiation was performed with 2,6 MeV electrons, the second one with 170 keV and 300 keV Cu ions and the third one with swift heavy ions (Kr, Xe, Au) with energies between 200 and 600 MeV.Stabilization of the 18 R martensite in Cu-Zn-Al-Ni induced by electron irradiation was studied.The results were compared to those of the stabilization induced by quenching and ageing in the same alloy, and the ones obtained by irradiation in 18 R-Cu-Zn-Al alloys.The effects of Cu irradiation over b phase were analyzed with several electron microscopy techniques including: scanning electron microscopy (S E M), high resolution electron microscopy (H R E M), micro diffraction and X-ray energy dispersive spectroscopy (E D S). Structural changes in Cu-Zn-Al b phase into a closed packed structure were induced by Cu ion implantation.The closed packed structures depend on the irradiation fluence.Based on these results, the interface between these structures (closed packed and b) and the stability of disordered phases were analyzed. It was also compared the evolution of long range order in the Cu-Zn-Al and in the Cu-Zn-Al-Ni b phase as a function of fluence.The evolution of the g phase was also compared. Both results were discussed in terms of the mobility of irradiation induced point defects.Finally, the effects induced by swift heavy ions in b phase and 18 R martensite were studied. The results of the irradiation in b phase were qualitatively similar to those produced by irradiation with lower energies. On the contrary, nano metric defects were found in the irradiated 18 R martensite.These defects were characterized by H R E M.The characteristic contrast of the defects was associated to a local change in the

  3. The effects of. gamma. -irradiation on Ti-Ni shape-memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Guilin; Xu Feng; Liu Wenhong; Hu Wenxiang; Yu Fanghua; Zhang Yiping (Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Nuclear Research); Wang Jingcheng; Shao Zichang (Shanghai Iron and Steel Research Inst, SH (China))

    1992-04-01

    Because gamma irradiation provides a means of introducing lattice defects into crystalline solids in a controlled fashion, it can be used to study the influence of lattice defects on the physical properties of solids such as shape-memory alloys (SMAs). The study described here shows that gamma irradiation can be used to ameliorate the performance of SMAs and to understand the mechanism of the shape memory further in these alloys. In particular it shows the effect of gamma irradiation on the martensitic transformation temperatures of Ti-Ni alloys. (UK).

  4. Nonlinear angle control of a sectioned airfoil by using shape memory alloys

    Directory of Open Access Journals (Sweden)

    Abreu G.

    2014-01-01

    Full Text Available The present work illustrates an application of shape memory alloys and nonlinear controller applied to the active angular control of a sectioned airfoil. The main objective of the proposed control system is to modify the shape of the profile based on a reference angle. The change of the sectioned airfoil angle is resultant by the effect of shape memory of the alloy due to heating of the wire caused by an electric current that changes its temperature by Joule effect. Considering the presence of plant’s nonlinear effects, especially in the mathematical model of the alloy, this work proposes the application of an on-off control system.

  5. Shape memory effect of Fe-14% Mn-6% Si-9% Cr-6% Ni alloy polycrystals

    International Nuclear Information System (INIS)

    Inagaki, Hirosuke

    1992-01-01

    Factors affecting the shape memory effect in Fe-14% Mn-6% Si-9% Cr-6% Ni alloy polycrystals were studied in detail. It was found that the shape memory effect in this alloy was most influenced by the amount of deformation. With increasing amount of deformation, the shape memory effect diminished appreciably. Although the fraction of the initial dimensional change that could be restored was about 45% in the specimen strained by 4%, only 21% of the initial dimensional change was recovered in the specimen strained by 9%. Temperatures of deformation were found to be also an important factor that affected the shape memory effect. The maximum shape memory effect was observed in the specimens strained at temperatures between the M s and M d temperatures. In this alloy, however, specimens strained at temperatures below the M s temperature indicated a relatively large shape memory effect, too. It was further found that the shape memory effect was appreciably intensified by repeated straining and annealing, especially when straining was performed at 500deg C. It was suggested that the shape memory effect in Fe base alloys was strongly influenced by the dislocation substructure present in the starting material. (orig.) [de

  6. Design optimization of shape memory alloy active structures using the R-phase transformation

    NARCIS (Netherlands)

    Langelaar, M.; Van Keulen, F.

    2007-01-01

    This article illustrates the opportunities that combining computational modeling and systematic design optimization techniques offer to facilitate the design process of shape memory alloy (SMA) structures. Focus is on shape memory behavior due to the R-phase transformation in Ni-Ti, for which a

  7. Experimental characterization of shape memory alloy actuator cables

    Science.gov (United States)

    Biggs, Daniel B.; Shaw, John A.

    2016-04-01

    Wire rope (or cables) are a fundamental structural element in many engineering applications. Recently, there has been growing interest in stranding NiTi wires into cables to scale up the adaptive properties of NiTi tension elements and to make use of the desirable properties of wire rope. Exploratory experiments were performed to study the actuation behavior of two NiTi shape memory alloy cables and straight monofilament wire of the same material. The specimens were held under various dead loads ranging from 50 MPa to 400 MPa and thermally cycled 25 times from 140°C to 5°C at a rate of 12°C/min. Performance metrics of actuation stroke, residual strain, and work output were measured and compared between specimen types. The 7x7 cable exhibited similar actuation to the single straight wire, but with slightly longer stroke and marginally more shakedown, while maintaining equivalent specific work output. This leads to the conclusion that the 7x7 cable effectively scaled up the adaptive properties the straight wire. Under loads below 150 MPa, the 1x27 cable had up to double the actuation stroke and work output, but exhibited larger shakedown and poorer performance when loaded higher.

  8. A cycloidal wobble motor driven by shape memory alloy wires

    Science.gov (United States)

    Hwang, Donghyun; Higuchi, Toshiro

    2014-05-01

    A cycloidal wobble motor driven by shape memory alloy (SMA) wires is proposed. In realizing a motor driving mechanism well known as a type of reduction system, a cycloidal gear mechanism is utilized. It facilitates the achievement of bidirectional continuous rotation with high-torque capability, based on its high efficiency and high reduction ratio. The applied driving mechanism consists of a pin/roller based annular gear as a wobbler, a cycloidal disc as a rotor, and crankshafts to guide the eccentric wobbling motion. The wobbling motion of the annular gear is generated by sequential activation of radially phase-symmetrically placed SMA wires. Consequently the cycloidal disc is rotated by rolling contact based cycloidal gearing between the wobbler and the rotor. In designing the proposed motor, thermomechanical characterization of an SMA wire biased by extension springs is experimentally performed. Then, a simplified geometric model for the motor is devised to conduct theoretical assessment of design parametric effects on structural features and working performance. With consideration of the results from parametric analysis, a functional prototype three-phase motor is fabricated to carry out experimental verification of working performance. The observed experimental results including output torque, rotational speed, bidirectional positioning characteristic, etc obviously demonstrate the practical applicability and potentiality of the wobble motor.

  9. Bioinspired Soft Actuation System Using Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Matteo Cianchetti

    2014-07-01

    Full Text Available Soft robotics requires technologies that are capable of generating forces even though the bodies are composed of very light, flexible and soft elements. A soft actuation mechanism was developed in this work, taking inspiration from the arm of the Octopus vulgaris, specifically from the muscular hydrostat which represents its constitutive muscular structure. On the basis of the authors’ previous works on shape memory alloy (SMA springs used as soft actuators, a specific arrangement of such SMA springs is presented, which is combined with a flexible braided sleeve featuring a conical shape and a motor-driven cable. This robot arm is able to perform tasks in water such as grasping, multi-bending gestures, shortening and elongation along its longitudinal axis. The whole structure of the arm is described in detail and experimental results on workspace, bending and grasping capabilities and generated forces are presented. Moreover, this paper demonstrates that it is possible to realize a self-contained octopus-like robotic arm with no rigid parts, highly adaptable and suitable to be mounted on underwater vehicles. Its softness allows interaction with all types of objects with very low risks of damage and limited safety issues, while at the same time producing relatively high forces when necessary.

  10. Shape Memory Alloy (SMA)-Based Launch Lock

    Science.gov (United States)

    Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph

    2014-01-01

    Most NASA missions require the use of a launch lock for securing moving components during the launch or securing the payload before release. A launch lock is a device used to prevent unwanted motion and secure the controlled components. The current launch locks are based on pyrotechnic, electro mechanically or NiTi driven pin pullers and they are mostly one time use mechanisms that are usually bulky and involve a relatively high mass. Generally, the use of piezoelectric actuation provides high precession nanometer accuracy but it relies on friction to generate displacement. During launch, the generated vibrations can release the normal force between the actuator components allowing shaft's free motion which could result in damage to the actuated structures or instruments. This problem is common to other linear actuators that consist of a ball screw mechanism. The authors are exploring the development of a novel launch lock mechanism that is activated by a shape memory alloy (SMA) material ring, a rigid element and an SMA ring holding flexure. The proposed design and analytical model will be described and discussed in this paper.

  11. Modiolus-Hugging Intracochlear Electrode Array with Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Kyou Sik Min

    2013-01-01

    Full Text Available In the cochlear implant system, the distance between spiral ganglia and the electrodes within the volume of the scala tympani cavity significantly affects the efficiency of the electrical stimulation in terms of the threshold current level and spatial selectivity. Because the spiral ganglia are situated inside the modiolus, the central axis of the cochlea, it is desirable that the electrode array hugs the modiolus to minimize the distance between the electrodes and the ganglia. In the present study, we propose a shape-memory-alloy-(SMA- embedded intracochlear electrode which gives a straight electrode a curved modiolus-hugging shape using the restoration force of the SMA as triggered by resistive heating after insertion into the cochlea. An eight-channel ball-type electrode array is fabricated with an embedded titanium-nickel SMA backbone wire. It is demonstrated that the electrode array changes its shape in a transparent plastic human cochlear model. To verify the safe insertion of the electrode array into the human cochlea, the contact pressures during insertion at the electrode tip and the contact pressures over the electrode length after insertion were calculated using a 3D finite element analysis. The results indicate that the SMA-embedded electrode is functionally and mechanically feasible for clinical applications.

  12. Martensitic phase transformation in shape-memory alloys

    International Nuclear Information System (INIS)

    Golestaneh, A.A.

    1979-01-01

    Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M → P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M → P → M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface

  13. Martensitic phase transformation in shape-memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Golestaneh, A A

    1979-01-01

    Isothermal studies are described of the shape-recovery phenomenon, stress-strain behavior, electrical resistivity and thermo-electric power associated with the martensite-parent phase reaction in the Ni-Ti shape-memory alloys. The energy-balance equation that links the reaction kinetics with the strain energy change during the cooling-deforming and heating cycle is analyzed. The strain range in which the Clausius-Clapeyron equation satisfactorily describes this reaction is determined. A large change in the Young's modulus of the specimen is found to be associated with the M ..-->.. P reaction. A hysteresis loop in the resistivity-temperature plot is found and related to the anomaly in the athermal resistivity changes during cyclic M ..-->.. P ..-->.. M transformation. An explanation for the resistivity anomaly is offered. The M structure is found to be electrically negative relative to the P structure. A thermal emf of greater than or equal to 0.12 mV is found at the M-P interface.

  14. Thermal responses of shape memory alloy artificial anal sphincters

    Science.gov (United States)

    Luo, Yun; Takagi, Toshiyuki; Matsuzawa, Kenichi

    2003-08-01

    This paper presents a numerical investigation of the thermal behavior of an artificial anal sphincter using shape memory alloys (SMAs) proposed by the authors. The SMA artificial anal sphincter has the function of occlusion at body temperature and can be opened with a thermal transformation induced deformation of SMAs to solve the problem of severe fecal incontinence. The investigation of its thermal behavior is of great importance in terms of practical use in living bodies as a prosthesis. In this work, a previously proposed phenomenological model was applied to simulate the thermal responses of SMA plates that had undergone thermally induced transformation. The numerical approach for considering the thermal interaction between the prosthesis and surrounding tissues was discussed based on the classical bio-heat equation. Numerical predictions on both in vitro and in vivo cases were verified by experiments with acceptable agreements. The thermal responses of the SMA artificial anal sphincter were discussed based on the simulation results, with the values of the applied power and the geometric configuration of thermal insulation as parameters. The results obtained in the present work provided a framework for the further design of SMA artificial sphincters to meet demands from the viewpoint of thermal compatibility as prostheses.

  15. Hydrodynamic characterization of a passive shape memory alloy valve

    Science.gov (United States)

    Waddell, A. M.; Punch, J.; Stafford, J.; Jeffers, N.

    2014-07-01

    Next generation high-performance electronics will have large heat fluxes (>102 W/cm2) and an alternative approach to traditional air cooling is required. An attractive solution is micro-channel cooling and micro-valves will be required for refined flow control in the supporting micro-fluidic systems. A NiTi Shape Memory Alloy (SMA) micro-valve design was hydrodynamically characterized in this work to obtain the valve loss coefficient (K) from pressure measurements. The hydrodynamic characterization was important as in the flow regime of the micro-fluidic system K is sensitive to Reynolds number (Re) and geometry. Static replicas of the SMA valve geometry were studied for low Reynolds numbers (110 - 220) in a 1x1 mm CSA miniature channel. The loss coefficients were found to be sensitive to flow rate and decreased rapidly with an increase in Re. The SMA valve was compared to a similar gate micro-valve and loss across both valves was of the same order of magnitude. The valve loss coefficients obtained in this work are important parameters in the modeling and design of micro-fluidic cooling systems.

  16. On the Fracture Response of Shape Memory Alloy Actuators

    Science.gov (United States)

    Jape, Sameer; Parrinello, Antonino; Baxevanis, Theocharis; Lagoudas, Dimitris C.

    In this paper, the effect of global thermo-mechanically-induced phase transformation on the driving force for crack growth in polycrystalline shape memory alloys is analyzed in an infinite center-cracked plate subjected to thermal actuation under isobaric, plane strain, mode I loading. Finite element calculations are carried out to determine the mechanical fields near the static crack and the crack-tip energy release rate using the virtual crack closure technique. Analysis of the static crack shows that, as compared to constant mechanical loading, the energy release rate during cooling increases by approximately an order of magnitude. This increase is attributed to the stress redistribution at the crack-tip induced by global phase transformation during cooling. Crack growth during actuation is assumed to occur when the crack-tip energy release rate reaches a material specific critical value. Fracture toughening behavior is observed during crack growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving crack tip. Lastly, the effect of crack configuration on fracture toughness enhancement in the large-scale transformation problem is studied. Numerical results for static cracks in compact tensile and three-point bending SMA specimens are reported and a comparison of fracture toughening during thermal actuation in the semi-infinite crack configuration with the compact tensile and three-point bending geometries is presented.

  17. Pseudo-creep in Shape Memory Alloy Wires and Sheets

    Science.gov (United States)

    Russalian, V. R.; Bhattacharyya, A.

    2017-10-01

    Interruption of loading during reorientation and isothermal pseudoelasticity in shape memory alloys with a strain arrest ( i.e., holding strain constant) results in a time-dependent evolution in stress or with a stress arrest ( i.e., holding stress constant) results in a time-dependent evolution in strain. This phenomenon, which we term as pseudo-creep, is similar to what was reported in the literature three decades ago for some traditional metallic materials undergoing plastic deformation. In a previous communication, we reported strain arrest of isothermal pseudoelastic loading, isothermal pseudoelastic unloading, and reorientation in NiTi wires as well as a rate-independent phase diagram. In this paper, we provide experimental results of the pseudo-creep phenomenon during stress arrest of isothermal pseudoelasticity and reorientation in NiTi wires as well as strain arrest of isothermal pseudoelasticity and reorientation in NiTi sheets. Stress arrest in NiTi wires accompanied by strain accumulation or recovery is studied using the technique of multi-video extensometry. The experimental results were used to estimate the amount of mechanical energy needed to evolve the wire from one microstructural state to another during isothermal pseudoelastic deformation and the difference in energies between the initial and the final rest state between which the aforementioned evolution has occurred.

  18. Hydrodynamic characterization of a passive shape memory alloy valve

    International Nuclear Information System (INIS)

    Waddell, A M; Punch, J; Stafford, J; Jeffers, N

    2014-01-01

    Next generation high-performance electronics will have large heat fluxes (>10 2 W/cm 2 ) and an alternative approach to traditional air cooling is required. An attractive solution is micro-channel cooling and micro-valves will be required for refined flow control in the supporting micro-fluidic systems. A NiTi Shape Memory Alloy (SMA) micro-valve design was hydrodynamically characterized in this work to obtain the valve loss coefficient (K) from pressure measurements. The hydrodynamic characterization was important as in the flow regime of the micro-fluidic system K is sensitive to Reynolds number (Re) and geometry. Static replicas of the SMA valve geometry were studied for low Reynolds numbers (110 – 220) in a 1x1 mm CSA miniature channel. The loss coefficients were found to be sensitive to flow rate and decreased rapidly with an increase in Re. The SMA valve was compared to a similar gate micro-valve and loss across both valves was of the same order of magnitude. The valve loss coefficients obtained in this work are important parameters in the modeling and design of micro-fluidic cooling systems.

  19. Role of samarium additions on the shape memory behavior of iron based alloys

    International Nuclear Information System (INIS)

    Shakoor, R.A.; Khalid, F. Ahmad; Kang, Kisuk

    2011-01-01

    Research highlights: → The effect of samarium contents on shape memory behavior has been studied. → Addition of samarium increases the strength, c/a ratio and ε (hcp martensite). → Addition of samarium retards the nucleation of α (bcc martensite). → Improvement in shape memory effect with the increase in samarium contents. - Abstract: The effect of samarium contents on shape memory behavior of iron based shape memory alloys has been studied. It is found that the strength of the alloys increases with the increase in samarium contents. This effect can be attributed to the solid solution strengthening of austenite by samarium addition. It is also noticed that the shape memory effect increases with the increase in samarium contents. This improvement in shape memory effect presumably can be regarded as the effect of improvement in strength, increase in c/a ratio and obstruction of nucleation of α in the microstructure.

  20. Aging response of shape memory behavior in γ-MnCu alloys

    International Nuclear Information System (INIS)

    Tsuchiya, K.; Kawabata, O.; Umemoto, M.; Sato, H.; Marukawa, K.

    2000-01-01

    An effect of aging on shape memory behavior was investigated for Mn - 15 at % Cu alloy. It was revealed that aging of the alloy at 693 K significantly improves both shape memory effect (SME) and reversible shape memory effect (RSME). The reason of improved SME can be attributed to the decrease in the axial ratio, c/a, of fct martensite phase at room temperature. The enhancement of RSME might be related to the formation of Mn-rich zones associated with a higher antiferromagnetic ordering temperature. (orig.)

  1. Self-positioned thin Pb-alloy base electrode Josephson junction

    International Nuclear Information System (INIS)

    Kuroda, K.; Sato, K.

    1986-01-01

    A self-positioned thin (SPOT) Pb-alloy base electrode Josephson junction is developed. In this junction, a 50-nm thick Pb-alloy base electrode is restricted within the junction region on an Nb underlayer using a self-alignment technique. The grain size reduction and the base electrode area restriction greatly improve thermal cycling stability, where the thermal cycling tests of 4000 proposed junctions (5 x 5 μm 2 ) showed no failures after 4000 cycles. In addition, the elimination of insulator layer stress on the Pb-alloy base electrode rectifies the problem of size effect on current density. The Nb underlayers also serve to isolate the Pb-alloy base electrodes from the resistors

  2. Synthesis and evaluation of ageing effect on Cu–Al–Be–Mn quaternary Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    A.G. Shivasiddaramiah

    2016-09-01

    Full Text Available Copper based shape memory alloy exhibits high transformation temperature and ability to differ the achieved properties through alloying additions. A quaternary Cu–Al–Be–Mn shape memory alloys of 0.2–0.4 wt% of manganese, 0.4–0.5 wt% of Beryllium and 10–14 wt% of aluminium with remaining copper, showing β-phase at higher temperature and show shape memory effect when quenching to lower temperatures, SMA's were prepared by induction melting. The objective is to study the effect of thermal ageing at different temperatures Af (above austenitic phase finish temperature and at different time on shape memory effect and transformation temperatures. The aged specimens or SMA's were studied by DSC, OM and hardness measurements. The results from this study help to find the applications in different thermal conditions.

  3. Cu-based shape memory alloys with enhanced thermal stability and mechanical properties

    International Nuclear Information System (INIS)

    Chung, C.Y.; Lam, C.W.H.

    1999-01-01

    Cu-based shape memory alloys were developed in the 1960s. They show excellent thermoelastic martensitic transformation. However the problems in mechanical properties and thermal instability have inhibited them from becoming promising engineering alloys. A new Cu-Zn-Al-Mn-Zr Cu-based shape memory alloy has been developed. With the addition of Mn and Zr, the martensitic transformation behaviour and the grain size ca be better controlled. The new alloys demonstrates good mechanical properties with ultimate tensile strenght and ductility, being 460 MPa and 9%, respectively. Experimental results revealed that the alloy has better thermal stability, i.e. martensite stabilisation is less serious. In ordinary Cu-Zn-Al alloys, martensite stabilisation usually occurs at room temperature. The new alloy shows better thermal stability even at elevated temperature (∝150 C, >A f =80 C). A limited small amount of martensite stabilisation was observed upon ageing of the direct quenched samples as well as the step quenched samples. This implies that the thermal stability of the new alloy is less dependent on the quenching procedure. Furthermore, such minor martensite stabilisation can be removed by subsequent suitable parent phase ageing. The new alloy is ideal for engineering applications because of its better thermal stability and better mechanical properties. (orig.)

  4. A Review of TiNiPdCu Alloy System for High Temperature Shape Memory Applications

    Science.gov (United States)

    Khan, M. Imran; Kim, Hee Young; Miyazaki, Shuichi

    2015-06-01

    High temperature shape memory alloys (HTSMAs) are important smart materials and possess a significant potential to improve many engineering systems. Many TiNi-based high temperature ternary alloy systems have been reported in literature including TiNiPd, TiNiPt, TiNiZr, TiNiAu, TiNiHf, etc. Some quaternary additions of certain elements in the above systems have been successful to further improve many important shape memory and mechanical properties. The success criteria for an HTSMA become strict in terms of its cyclic stability, maximum recoverable strain, creep resistance, and corrosion resistance at high temperatures. TiNiPdCu alloy system has been recently proposed as a promising HTSMA. Unique nanoscaled precipitates formed in TiNiPdCu-based HTSMAs are found to be stable at temperatures above 773 K, while keeping the benefits of ease of fabrication. It is expected that this alloy system possesses significant potential especially for the high temperature shape memory applications. Till now many research reports have been published on this alloy system. In the present work, a comprehensive review of the TiNiPdCu system is presented in terms of thermomechanical behavior, nanoscale precipitation mechanism, microstructural features, high temperature shape memory and mechanical properties, and the important parameters to control the high temperature performance of these alloys.

  5. Evaluation on microscopic damage and fabrication process of shape memory alloy

    International Nuclear Information System (INIS)

    Lee, Jin Kyung; Choi, Il Kook; Park, Young Chul; Lee, Kyu Chang; Lee, Jun Hyun

    2002-01-01

    Shape memory alloy has been used to improve the tensile strength of composite by the occurrence of compressive residual stress in matrix using its shape memory effect. In order to fabricate shape memory alloy composite, TiNi alloy and Al6061 were used as reinforcing material and matrix, respectively. In this study, TiNi/Al6061 shape memory alloy composite was made by using hot press method. However, the specimen fabricated by this method had the bonding problem at tile boundary between TiNi fiber anti Al matrix when the load was applied to it. A cold rolling was imposed to the specimen to improve the bonding effort. It was found that tensile strength of specimen subjected to cold rolling was more increased than that of specimen which did not underwent cold rolling. In addition, acoustic emission technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite at high temperature.

  6. Empirical Study of the Multiaxial, Thermomechanical Behavior of NiTiHf Shape Memory Alloys

    Science.gov (United States)

    Shukla, Dhwanil; Noebe, Ronald D.; Stebner Aaron P.

    2013-01-01

    An empirical study was conducted to characterize the multiaxial, thermomechanical responses of new high temperature NiTiHf alloys. The experimentation included loading thin walled tube Ni(sub 50.3)Ti(sub 29.7)Hf(sub 20) alloy samples along both proportional and nonproportional axial-torsion paths at different temperatures while measuring surface strains using stereo digital image correlation. A Ni(sub 50.3)Ti(sub 33.7)Hf(sub 16) alloy was also studied in tension and compression to document the effect of slightly depleting the Hf content on the constitutive responses of NiTiHf alloys. Samples of both alloys were made from nearly texture free polycrystalline material processed by hot extrusion. Analysis of the data shows that very small changes in composition significantly alter NiTiHf alloy properties, as the austenite finish (Af) temperature of the 16-at Hf alloy was found to be approximately 60 C less than the 20-at Hf alloy (approximately 120 C vs. 180 C). In addition, the 16-at Hf alloy exhibited smaller compressive transformation strains (2 vs. 2.5 percent). Multi-axial characterization of the 20-at % Hf alloy showed that while the random polycrystal transformation strains in tension (4 percent) and compression (2.5 percent) are modest in comparison with binary NiTi (6 percent, 4 percent), the torsion performance is superior (7 vs. 4 shear strain width to the pseudoelastic plateau).

  7. Shape memory alloy wire-based smart natural rubber bearing

    International Nuclear Information System (INIS)

    Hedayati Dezfuli, F; Shahria Alam, M

    2013-01-01

    In this study, two types of smart elastomeric bearings are presented using shape memory alloy (SMA) wires. Due to the unique characteristics of SMAs, such as the superelastic effect and the recentering capability, the residual deformation in SMA-based natural rubber bearings (SMA-NRBs) is significantly reduced whereas the energy dissipation capacity is increased. Two different configurations of SMA wires incorporated in elastomeric bearings are considered. The effect of several parameters, including the shear strain amplitude, the type of SMA, the aspect ratio of the base isolator, the thickness of SMA wire, and the amount of pre-strain in the wires on the performance of SMA-NRBs is investigated. Rubber bearings are composed of natural rubber layers bonded to steel shims as reinforcement. Results show that ferrous SMA wire, FeNiCuAlTaB, with 13.5% superelastic strain and a very low austenite finish temperature (−62 °C), is the best candidate to be used in SMA-NRBs subjected to high shear strain amplitudes. In terms of the lateral flexibility and wire strain level, the smart rubber bearing with a cross configuration of SMA wires is more efficient. Moreover, the cross configuration can be implemented in high-aspect-ratio elastomeric bearings since the strain induced in the wire does not exceed the superelastic range. When cross SMA wires with 2% pre-strain are used in a smart NRB, the dissipated energy is increased by 74% and the residual deformation is decreased by 15%. (paper)

  8. Vibration improved the fluidity of aluminum alloys in thin wall ...

    African Journals Online (AJOL)

    Misrun is a term used to describe the incomplete filling of the mould cavity. It is a major defect in the investment casting process when used to produce turbine blades, impellers and impulse blades for turbo pumps which have complex profiles, thin walls and sharp edges. From the casting engineering point of view, poor ...

  9. Preparation and characterization of nanodiamond cores coated with a thin Ni-Zn-P alloy film

    International Nuclear Information System (INIS)

    Wang Rui; Ye Weichun; Ma Chuanli; Wang Chunming

    2008-01-01

    Nanodiamond cores coated with a thin Ni-Zn-P alloy film were prepared by an electroless deposition method under the conditions of tin chloride sensitization and palladium chloride activation. The prepared materials were analyzed by Fourier transform infrared (FTIR) spectrometry and X-ray diffraction (XRD). The nanostructure of the materials was then characterized by transmission electron microscopy (TEM). The alloy film composition was characterized by Energy Dispersive X-ray (EDX) analysis. The results indicated the approximate composition 49.84%Ni-37.29%Zn-12.88%P was obtained

  10. Nonlinear dynamics of a pseudoelastic shape memory alloy system - theory and experiment

    DEFF Research Database (Denmark)

    Enemark, Søren; A Savi, M.; Santos, Ilmar

    2014-01-01

    In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping...... capabilities and varying stiffness. Besides, these properties depend on the temperature and pretension conditions. Because of these capabilities, shape memory alloys are interesting in relation to engineering design of dynamic systems. A theoretical model based on a modification of the 1D Brinson model...... was established. Basically, the hardening and the sub-loop behaviour were altered. The model parameters were extracted from force–displacement tests of the spring at different constant temperatures as well as from differential scanning calorimetry. Model predictions were compared with experimental results of free...

  11. Shape memory alloy fixator system for suturing tissue in minimal access surgery.

    Science.gov (United States)

    Xu, W; Frank, T G; Stockham, G; Cuschieri, A

    1999-01-01

    A new technique for suturing human tissue is described in which tissue closure is achieved by means of small fixators made from shape memory alloy. The aim of the development is to provide an alternative to thread suturing in minimal access surgery, which is quicker and requires less skill to achieve the required suturing quality. The design of the fixators is described in terms of the thermal shape recovery of shape memory alloy and a novel form of finite element analysis, which uses a nonlinear elastic element for the material property. Thermal analysis of the fixators and surrounding tissue is used to predict the temperature distribution during and after the application of electric current heating. This was checked in an in vitro experiment, which confirmed that deployment caused no detectable collateral damage to surrounding tissue. In vivo animal studies on the use of the shape memory alloy fixator for suturing tissue are ongoing to establish safety and healing effects.

  12. A Constitutive Description for Shape Memory Alloys with the Growth of Martensite Band

    Directory of Open Access Journals (Sweden)

    Weiguo Li

    2014-01-01

    Full Text Available Based on the experimental results and the finite element analysis, a constitutive model is proposed for two phase shape memory alloys by introducing a compensative volumetric strain into a constrained relationship between the two phases, accounting for the reduced constraint due to the growth of martensite band. The pseudoelasticity of NiTi shape memory alloy micro-tube, subjected to pure tension, is analyzed and compared with the experimental results. It can be seen that the pseudoelastic behavior, especially the phenomena of a stress drop during tension processes, can be well described with the proposed model. The proposed model separates the complicated constitutive behavior of a shape memory alloy (SMA into simple responses arising respectively from its two phases, taking into account laminar microstructure, the thickness of martensite phase and the interaction between the two phases, and provides an easy but comprehensive method for the description of the constitutive behavior of SMAs under complex thermomechanical loading.

  13. The pseudoelasticity and the shape memory effect in CoNiAl alloys

    Czech Academy of Sciences Publication Activity Database

    Kopeček, Jaromír; Jarošová, Markéta; Jurek, Karel; Heczko, Oleg

    2014-01-01

    Roč. 21, č. 1 (2014), s. 43-48 ISSN 1335-0803 R&D Projects: GA ČR(CZ) GA101/09/0702; GA ČR GAP107/10/0824; GA ČR(CZ) GAP107/11/0391; GA AV ČR IAA100100920 Institutional support: RVO:68378271 Keywords : shape memory alloys * co-alloys * metallography * martensitic transition * stress induced martensite Subject RIV: BM - Solid Matter Physics ; Magnetism

  14. Formation of titanium oxide coatings on NiTi shape memory alloys by selective oxidation

    International Nuclear Information System (INIS)

    Pohl, M.; Glogowski, T.; Kuehn, S.; Hessing, C.; Unterumsberger, F.

    2008-01-01

    Materials used for medical devices that are in contact with human tissue must have good corrosion resistance and biocompatibility. NiTi shape memory alloys (SMAs) are often used in medical applications due to their special functional and mechanical properties (shape memory effect, pseudo elasticity). Because of the high Ni content in nearly stoichiometric NiTi SMAs, the possibility of Ni being released needs to be considered as Ni may cause problems in the human body. SMAs exhibit a high intrinsic corrosion resistance because of the thermodynamic stability of Ni (thermodynamic reason) and the low degree of disorder in a thin protective TiO 2 -layer (kinetic reason). While therefore there is no need to be concerned too much about a normal corrosive attack in the human body, it has to be kept in mind that in medical applications, these materials represent one part of a tribological system where wear processes need to be considered. The formation of a uniform TiO 2 -layer can be beneficial in this respect. The selective oxidation of Ti to TiO 2 on the surface is a promising method to decrease the Ni release significantly. This can be achieved by controlling the partial pressure of oxygen during a controlled oxidation process. The atmosphere must be adjusted so that TiO 2 is stable while NiO cannot yet form. The result of a selective oxidation is a TiO 2 -layer that has an excellent degree of purity and represents a safe barrier against Ni emission

  15. Thin wall ductile iron casting as a substitute for aluminum alloy casting in automotive industry

    Directory of Open Access Journals (Sweden)

    M. Górny

    2009-01-01

    Full Text Available In paper it is presented thin wall ductile iron casting (TWDI as a substitute of aluminium alloy casting. Upper control arm made of ductile iron with wall thickness ranging from 2 – 3.7 mm was produced by inmold process. Structure, mechanical properties and computer simulations were investigated. Structural analysis of TWDI shows pearlitic-ferritic matrix free from chills and porosity. Mechanical testing disclose superior ultimate tensile strength (Rm, yield strength (Rp0,2 and slightly lower elongation (E of TWDI in comparison with forged control arm made of aluminium alloy (6061-T6. Moreover results of computer simulation of static loading for tested control arms are presented. Analysis show that the light-weight ductile iron casting can be loaded to similar working conditions as the forged Al alloy without any potential failures.

  16. Experimental study and theoretical simulation of the cross hardening effect in shape memory alloys

    Science.gov (United States)

    Movchan, A. A.; Sil'chenko, A. L.; Kazarina, S. A.

    2017-10-01

    The shapes and the relative position of martensitic inelasticity and forward transformation diagrams are experimentally studied. The strain dependences of the stress in loading under martensitic inelasticity conditions after an experiment on the accumulation of the forward transformation-induced strain at a constant or variable stress are investigated on titanium nickelide samples. It is found that the hardening of the martensite part of the representative volume of a shape memory alloy (titanium nickelide) after forward transformation under a nonmonotonically changing stress can be nonuniform. The cross hardening phenomenon is theoretically described in terms of the model of nonlinear deformation of a shape memory alloy during phase and structural transformations.

  17. Modelling, characterisation and uncertainties of stabilised pseudoelastic shape memory alloy helical springs

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar; Savi, M. A.

    2016-01-01

    The thermo-mechanical behaviour of pseudoelastic shape memory alloy helical springs is of concern discussing stabilised and cyclic responses. Constitutive description of the shape memory alloy is based on the framework developed by Lagoudas and co-workers incorporating two modifications related...... the global spring behaviour in spite of complex stress–strain distributions. The experiments are carried out considering different deflection amplitudes, frequencies and ambient temperatures, which influence the spring behaviour to different extents. The model is fitted against a calibration data set...

  18. Modification of Ni-Mn-Ga ferromagnetic shape memory alloy by addition of rare earth elements

    International Nuclear Information System (INIS)

    Tsuchiya, Koichi; Tsutsumi, Akinori; Ohtsuka, Hideyuki; Umemoto, Minoru

    2003-01-01

    Effect of addition of rare earth elements, such as, Nd, Sm and Tb, was investigated on various properties of Ni-Mn-Ga ferromagnetic shape memory alloys (SMAs). The solubility of the rare earth in the L2 1 phase was found to be very low, most likely less than 0.1 mol%. Insolvable rare earth segregated into subgrain boundaries or grain boundaries to form precipitates. Phase transformation behavior and the structure of martensite phase exhibit a similar dependence on valence electron concentration to those in ternary Ni-Mn-Ga alloys. It was revealed that the addition of rare earth significantly improves the compressive ductility of the alloy

  19. Investigations of binary and ternary phase change alloys for future memory applications

    International Nuclear Information System (INIS)

    Rausch, Pascal

    2012-01-01

    The understanding of phase change materials is of great importance because it enables us to predict properties and tailor alloys which might be even better suitable to tackle challenges of future memory applications. Within this thesis two topics have been approached: on the one hand the understanding of the alloy In 3 Sb 1 Te 2 and on the other hand the so called resistivity drift of amorphous Ge-Sn-Te phase change materials. The main topic covers an in depth discussion of the ternary alloy In 3 Sb 1 Te 2 . At first glance, this alloy does not fit into the established concepts of phase alloys: e.g. the existence of resonant bonding in the crystalline phase is not obvious and the number of p-electrons is very low compared to other phase change alloys. Furthermore amorphous phase change alloys with high indium content are usually not discussed in literature, an exception being the recent work by Spreafico et al. on InGeTe 2 . For the first time a complete description of In 3 Sb 1 Te 2 alloy is given in this work for the crystalline phase, amorphous phase and crystallization process. In addition comparisons are drawn to typical phase change materials like Ge 2 Sb 2 Te 5 /GeTe or prototype systems like AgInTe 2 and InTe. The second topic of this thesis deals with the issue of resistivity drift, i.e. the increase of resistivity of amorphous phase change alloys with aging. This drift effect greatly hampers the introduction of multilevel phase change memory devices into the market. Recently a systematic decrease of drift coefficient with stoichiometry has been observed in our group going from GeTe over Ge 3 Sn 1 Te 4 to Ge 2 Sn 2 Te 4 . These alloys are investigated with respect to constraint theory.

  20. Shape memory alloys for vibration isolation and damping

    Science.gov (United States)

    Machado, Luciano G.

    This work investigates the use of shape memory alloys (SMAs) for vibration isolation and damping of mechanical systems. The first part of this work evaluates the nonlinear dynamics of a passive vibration isolation and damping (PVID) device through numerical simulations and experimental correlations. The device, a mass connected to a frame through two SMA wires, is subjected to a series of continuous acceleration functions in the form of a sine sweep. Frequency responses and transmissibility of the device as well as temperature variations of the SMA wires are analyzed for the case where the SMA wires are pre-strained at 4.0% of their original length. Numerical simulations of a one-degree of freedom (1-DOF) SMA oscillator are also conducted to corroborate the experimental results. The configuration of the SMA oscillator is based on the PVID device. A modified version of the constitutive model proposed by Boyd and Lagoudas, which considers the thermomechanical coupling, is used to predict the behavior of the SMA elements of the oscillator. The second part of this work numerically investigates chaotic responses of a 1-DOF SMA oscillator composed of a mass and a SMA element. The restitution force of the oscillator is provided by an SMA element described by a rate-independent, hysteretic, thermomechanical constitutive model. This model, which is a new version of the model presented in the first part of this work, allows smooth transitions between the austenitic and the martensitic phases. Chaotic responses of the SMA oscillator are evaluated through the estimation of the Lyapunov exponents. The Lyapunov exponent estimation of the SMA system is done by adapting the algorithm by Wolf and co-workers. The main issue of using this algorithm for nonlinear, rate-independent, hysteretic systems is related to the procedure of linearization of the equations of motion. The present work establishes a procedure of linearization that allows the use of the classical algorithm. Two

  1. Knowledge and method base for shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Welp, E.G.; Breidert, J. [Ruhr-University Bochum, Institute of Engineering Design, 44780 Bochum (Germany)

    2004-05-01

    It is often impossible for design engineers to decide whether it is possible to use shape memory alloys (SMA) for a particular task. In case of a decision to use SMA for product development, design engineers normally do not know in detail how to proceed in a correct and beneficial way. In order to support design engineers who have no previous knowledge about SMA and to assist in the transfer of results from basic research to industrial practice, an essential knowledge and method base has been developed. Through carefully conducted literature studies and patent analysis material and design information could be collected. All information is implemented into a computer supported knowledge and method base that provides design information with a particular focus on the conceptual and embodiment design phase. The knowledge and method base contains solution principles and data about effects, material and manufacturing as well as design guidelines and calculation methods for dimensioning and optimization. A browser-based user interface ensures that design engineers have immediate access to the latest version of the knowledge and method base. In order to ensure a user friendly application, an evaluation with several test users has been carried out. Reactions of design engineers from the industrial sector underline the need for support related to knowledge on SMA. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [German] Fuer Konstrukteure ist es haeufig schwierig zu entscheiden, ob sich der Einsatz von Formgedaechtnislegierungen (FGL) fuer eine bestimmte Aufgabe eignet. Fuer den Fall, dass FGL fuer die Produktentwicklung genutzt werden sollen, besitzen Ingenieure zumeist nur unzureichende Detailkenntnisse, um Formgedaechtnislegierungen richtig und in vorteilhafter Weise anwenden zu koennen. Zur Unterstuetzung von Konstrukteuren, die ueber kein Vorwissen und keine Erfahrungen zu FGL verfuegen und zum Transfer von Forschungsergebnissen in die industrielle Praxis, ist eine

  2. Effect of surface oxidation on thermomechanical behavior of NiTi shape memory alloy wire

    Science.gov (United States)

    Ng, Ching Wei; Mahmud, Abdus Samad

    2017-12-01

    Nickel titanium (NiTi) alloy is a unique alloy that exhibits special behavior that recovers fully its shape after being deformed to beyond elastic region. However, this alloy is sensitive to any changes of its composition and introduction of inclusion in its matrix. Heat treatment of NiTi shape memory alloy to above 600 °C leads to the formation of the titanium oxide (TiO2) layer. Titanium oxide is a ceramic material that does not exhibit shape memory behaviors and possess different mechanical properties than that of NiTi alloy, thus disturbs the shape memory behavior of the alloy. In this work, the effect of formation of TiO2 surface oxide layer towards the thermal phase transformation and stress-induced deformation behaviors of the NiTi alloy were studied. The NiTi wire with composition of Ti-50.6 at% Ni was subjected to thermal oxidation at 600 °C to 900 °C for 30 and 60 minutes. The formation of the surface oxide layers was characterized by using the Scanning Electron Microscope (SEM). The effect of surface oxide layers with different thickness towards the thermal phase transformation behavior was studied by using the Differential Scanning Calorimeter (DSC). The effect of surface oxidation towards the stress-induced deformation behavior was studied through the tensile deformation test. The stress-induced deformation behavior and the shape memory recovery of the NiTi wire under tensile deformation were found to be affected marginally by the formation of thick TiO2 layer.

  3. A review on shape memory alloys with applications to morphing aircraft

    OpenAIRE

    Barbarino, S; Saavedra Flores, E I; Ajaj, R M; Dayyani, I; Friswell, M I

    2014-01-01

    Shape memory alloys (SMAs) are a unique class of metallic materials with the ability to recover their original shape at certain characteristic temperatures (shape memory effect), even under high applied loads and large inelastic deformations, or to undergo large strains without plastic deformation or failure (super-elasticity). In this review, we describe the main features of SMAs, their constitutive models and their properties. We also review the fatigue behavior of SMAs and some methods ado...

  4. Verbal memory impairments in schizophrenia associated with cortical thinning

    Directory of Open Access Journals (Sweden)

    S. Guimond

    2016-01-01

    Full Text Available Verbal memory (VM represents one of the most affected cognitive domains in schizophrenia. Multiple studies have shown that schizophrenia is associated with cortical abnormalities, but it remains unclear whether these are related to VM impairments. Considering the vast literature demonstrating the role of the frontal cortex, the parahippocampal cortex, and the hippocampus in VM, we examined the cortical thickness/volume of these regions. We used a categorical approach whereby 27 schizophrenia patients with ‘moderate to severe’ VM impairments were compared to 23 patients with ‘low to mild’ VM impairments and 23 healthy controls. A series of between-group vertex-wise GLM on cortical thickness were performed for specific regions of interest defining the parahippocampal gyrus and the frontal cortex. When compared to healthy controls, patients with ‘moderate to severe’ VM impairments revealed significantly thinner cortex in the left frontal lobe, and the parahippocampal gyri. When compared to patients with ‘low to mild’ VM impairments, patients with ‘moderate to severe’ VM impairments showed a trend of thinner cortex in similar regions. Virtually no differences were observed in the frontal area of patients with ‘low to mild’ VM impairments relative to controls. No significant group differences were observed in the hippocampus. Our results indicate that patients with greater VM impairments demonstrate significant cortical thinning in regions known to be important in VM performance. Treating VM deficits in schizophrenia could have a positive effect on the brain; thus, subgroups of patients with more severe VM deficits should be a prioritized target in the development of new cognitive treatments.

  5. Thermal Stability of Copper-Aluminum Alloy Thin Films for Barrierless Copper Metallization on Silicon Substrate

    Science.gov (United States)

    Wang, C. P.; Dai, T.; Lu, Y.; Shi, Z.; Ruan, J. J.; Guo, Y. H.; Liu, X. J.

    2017-08-01

    Copper thin films with thickness of about 500 nm doped with different aluminum concentrations have been prepared by magnetron sputtering on Si substrate and their crystal structure, microstructure, and electrical resistivity after annealing at various temperatures (200°C to 600°C) for 1 h or at 400°C for different durations (1 h to 11 h) investigated by grazing-incidence x-ray diffraction (GIXRD) analysis, scanning electron microscopy (SEM), and four-point probe (FPP) measurements. Cu-1.8Al alloy thin film exhibited good thermal stability and low electrical resistivity (˜5.0 μΩ cm) after annealing at 500°C for 1 h or 400°C for 7 h. No copper silicide was observed at the Cu-Al/Si interface by GIXRD analysis or SEM for this sample. This result indicates that doping Cu thin film with small amounts of Al can achieve high thermal stability and low electrical resistivity, suggesting that Cu-1.8Al alloy thin film could be used for barrierless Cu metallization on Si substrate.

  6. Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kosogor, Anna [National University of Science and Technology “MISiS,” Moscow 119049 (Russian Federation); Institute of Magnetism, 36-b, Vernadsky Str., Kyiv 03142 (Ukraine); Donetsk Institute for Physics and Engineering, Kyiv 03028 (Ukraine); L' vov, Victor A. [Institute of Magnetism, 36-b, Vernadsky Str., Kyiv 03142 (Ukraine); Faculty of Radiophysics, Electronics and Computer Systems, Taras Shevchenko University, Glushkov Str. 4G, Kyiv 01601 (Ukraine); Departament de Fisica, Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca (Spain); Cesari, Eduard [Departament de Fisica, Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, 07122 Palma de Mallorca (Spain)

    2015-10-07

    In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.

  7. Effects of annealing temperature in a metal alloy nano-dot memory

    International Nuclear Information System (INIS)

    Lee, Jung Min; Lee, Gae Hun; Song, Yun Heub; Bea, Ji Cheol; Tanaka, Tetsu

    2011-01-01

    The annealing temperature dependence of the capacitance-voltage (C-V) characteristic has been studied in a metal-oxide semiconductor structure containing FePt nano-dots. Several in-situ annealing temperatures from 400 to ∼700 .deg. C in a high vacuum ambience (under 1 x 10 -5 Pa) were evaluated in view of the cell's characteristics and its reliability. Here, we demonstrate that the annealing temperature is significant for memory performance in an alloy metal nano-dot structure. A higher in-situ temperature provides better retention and a more reliable memory window. In the sample with an in-situ annealing condition of 700 .deg. C for 30 min, a memory window of 9.2 V at the initial stage was obtained, and a memory window of 6.2 V after 10 years was estimated, which is reliable for a non-volatile memory. From these results, the annealing condition for an alloy metal nano-dot memory is one of the critical parameters for the memory characteristics, and should be optimized for better memory performance.

  8. Study of Cu-Al-Ni-Ga as high-temperature shape memory alloys

    Science.gov (United States)

    Zhang, Xin; Wang, Qian; Zhao, Xu; Wang, Fang; Liu, Qingsuo

    2018-03-01

    The effect of Ga element on the microstructure, mechanical properties and shape memory effect of Cu-13.0Al-4.0Ni- xGa (wt%) high-temperature shape memory alloy was investigated by optical microscopy, SEM, XRD and compression test. The microstructure observation results showed that the Cu-13.0Al-4.0Ni- xGa ( x = 0.5 and 1.0) alloys displayed dual-phase morphology which consisted of 18R martensite and (Al, Ga)Cu phase, and their grain size was about several hundred microns, smaller than that of Cu-13.0Al-4.0Ni alloy. The compression test results proved that the mechanical properties of Cu-13.0Al-4.0Ni- xGa alloys were improved by addition of Ga element owing to the grain refinement and solid solution strengthening, and the compressive fracture strains were 11.5% for x = 0.5 and 14.9% for x = 1.0, respectively. When the pre-strain was 8%, the shape memory effect of 4.2 and 4.6% were obtained for Cu-13.0Al-4.0Ni-0.5 Ga and Cu-13.0Al-4.0Ni-1.0 Ga alloys after being heated to 400 °C for 1 min.

  9. Effect of Nb content on deformation behavior and shape memory properties of Ti–Nb alloys

    International Nuclear Information System (INIS)

    Tobe, H.; Kim, H.Y.; Inamura, T.; Hosoda, H.; Nam, T.H.; Miyazaki, S.

    2013-01-01

    Highlights: ► Reorientation of martensite variants occurred by the deformation of the {1 1 1} type I and 〈2 1 1〉 type II twins. ► Magnitude of twinning shear in Ti–20Nb is larger than that in Ti–23Nb. ► Ti–20Nb exhibited a higher stress for the reorientation of martensite variants when compared with Ti–23Nb. -- Abstract: Deformation behavior and shape memory properties of Ti–(20, 23) at.% Nb alloys in a single α″ martensite state were investigated. The Ti–20Nb alloy exhibited a higher stress for the reorientation of martensite variants when compared with the Ti–23Nb alloy. The recovery strain due to the shape memory effect in the Ti–20Nb alloy was smaller than that in the Ti–23Nb alloy. Transmission electron microscope (TEM) observation revealed that the reorientation of martensite variants occurred by the deformation of {1 1 1} type I and 〈2 1 1〉 type II twins. The Nb content dependence of the deformation behavior and shape memory properties was discussed considering the magnitude of twinning shear of the twins

  10. Rhenium Alloys as Ductile Substrates for Diamond Thin-Film Electrodes.

    Science.gov (United States)

    Halpern, Jeffrey M; Martin, Heidi B

    2014-02-01

    Molybdenum-rhenium (Mo/Re) and tungsten-rhenium (W/Re) alloys were investigated as substrates for thin-film, polycrystalline boron-doped diamond electrodes. Traditional, carbide-forming metal substrates adhere strongly to diamond but lose their ductility during exposure to the high-temperature (1000°C) diamond, chemical vapor deposition environment. Boron-doped semi-metallic diamond was selectively deposited for up to 20 hours on one end of Mo/Re (47.5/52.5 wt.%) and W/Re (75/25 wt.%) alloy wires. Conformal diamond films on the alloys displayed grain sizes and Raman signatures similar to films grown on tungsten; in all cases, the morphology and Raman spectra were consistent with well-faceted, microcrystalline diamond with minimal sp 2 carbon content. Cyclic voltammograms of dopamine in phosphate-buffered saline (PBS) showed the wide window and low baseline current of high-quality diamond electrodes. In addition, the films showed consistently well-defined, dopamine electrochemical redox activity. The Mo/Re substrate regions that were uncoated but still exposed to the diamond-growth environment remained substantially more flexible than tungsten in a bend-to-fracture rotation test, bending to the test maximum of 90° and not fracturing. The W/Re substrates fractured after a 27° bend, and the tungsten fractured after a 21° bend. Brittle, transgranular cleavage fracture surfaces were observed for tungsten and W/Re. A tension-induced fracture of the Mo/Re after the prior bend test showed a dimple fracture with a visible ductile core. Overall, the Mo/Re and W/Re alloys were suitable substrates for diamond growth. The Mo/Re alloy remained significantly more ductile than traditional tungsten substrates after diamond growth, and thus may be an attractive metal substrate for more ductile, thin-film diamond electrodes.

  11. An investigation of shape memory alloys as actuating elements in aerospace morphing applications

    DEFF Research Database (Denmark)

    Karagiannis, Dimitrios; Stamatelos, Dimtrios; Kappatos, Vasileios

    2017-01-01

    Two innovative actuating concepts for aerospace morphing applications, based on Shape Memory Alloys (SMAs), are proposed. The first concept investigates a composite plate incorporating embedded SMA wires. A Nonlinear Auto Regressive with eXogenous excitation (NARX) model is proposed for controlling...

  12. Auxetic shape memory alloy cellular structures for deployable satellite antennas: design, manufacture and testing

    Directory of Open Access Journals (Sweden)

    Di Maio D.

    2010-06-01

    Full Text Available We describe the production development and experimental tests related to an hybrid honeycomb-truss made of shape memory alloy (Ni48Ti46Cu6, and used as a demonstrator for a deployable antenna in deep-space missions. Specific emphasis is placed on the modal analysis techniques used to test the lightweight SMA structure.

  13. Modelling of shape memory alloy oscillator and its application to middle ear structural reconstruction

    Science.gov (United States)

    Rusinek, Rafal; Rekas, Joanna

    2018-01-01

    The paper presents numerical research of a reconstructed middle ear system using the element made of shape memory alloy. The material is modelled based on a hysteretic nonlinear theory where strain rate is taken into account. Bifurcation analysis of the system reveals different kinds of solutions starting from regular and ending with chaotic vibrations depending on external excitation.

  14. IN SITU neutron diffraction study of stresses generated by shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Šittner, Petr; Lukáš, Petr; Novák, Václav; Neov, Dimitar; Ceretti, M.

    2001-01-01

    Roč. 9, - (2001), s. 143-150 ISSN 1023-8166 R&D Projects: GA AV ČR IAA1048107; GA ČR GV202/97/K038 Institutional research plan: CEZ:AV0Z1010914 Keywords : IN SITU neutron diffraction * shape memory alloy * martensitic transformation compression - test Subject RIV: BM - Solid Matter Physics ; Magnetism

  15. Neutron diffraction analysis of solid phases transforming in CuAlZnMn shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Neov, Dimitar; Lukáš, Petr; Černík, M.; Šittner, P.

    2001-01-01

    Roč. 2001, - (2001), s. 251-254 [Conference on applied crystallography (CAC) /18./. Katowice, 04.09.2000-07.09.2000] R&D Projects: GA AV ČR IAA1048107 Institutional research plan: CEZ:AV0Z1048901 Keywords : neutron diffraction * shape memory alloy Subject RIV: BM - Solid Matter Physics ; Magnetism

  16. Temperature dependence of magnetic susceptibility in the vicinity of martensitic transformation in ferromagnetic shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Zablotskyy, Vitaliy A.; Pérez-Landazábal, J.I.; Recarte, V.; Gómez-Polo, C.

    2010-01-01

    Roč. 22, č. 31 (2010), 316004/1-316004/7 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100520 Keywords : shape memory alloys * magnetic susceptibility * martensitic transition * magnetic domains Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.332, year: 2010

  17. Nonlinear dynamics of a pseudoelastic shape memory alloy system—theory and experiment

    International Nuclear Information System (INIS)

    Enemark, S; F Santos, I; A Savi, M

    2014-01-01

    In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping capabilities and varying stiffness. Besides, these properties depend on the temperature and pretension conditions. Because of these capabilities, shape memory alloys are interesting in relation to engineering design of dynamic systems. A theoretical model based on a modification of the 1D Brinson model was established. Basically, the hardening and the sub-loop behaviour were altered. The model parameters were extracted from force–displacement tests of the spring at different constant temperatures as well as from differential scanning calorimetry. Model predictions were compared with experimental results of free and forced vibrations of the system setup under different temperature conditions. The experiments give a thorough insight into dynamic systems involving pseudoelastic shape memory alloys. Comparison between experimental results and the proposed model shows that the model is able to explain and predict the overall nonlinear behaviour of the system. (paper)

  18. Development of elastic properties of Cu-based shape memory alloys during martensitic transformation

    Czech Academy of Sciences Publication Activity Database

    Novák, Václav; Landa, Michal; Šittner, Petr

    2004-01-01

    Roč. 115, - (2004), s. 363 ISSN 1155-4339 Institutional research plan: CEZ:AV0Z1010914 Keywords : Cu-based shape memory alloy s * elastic properties * elastic constants * modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.294, year: 2004

  19. Shape recovery mechanism observed in single crystals of shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Seiner, Hanuš; Sedlák, Petr; Landa, Michal

    2008-01-01

    Roč. 81, č. 6 (2008), s. 537-551 ISSN 0141-1594 Institutional research plan: CEZ:AV0Z20760514 Keywords : shape memory alloy s * shape recovery process * martensitic microstructure * non-classical boundaries Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.201, year: 2008

  20. Entropy change linked to the martensitic transformation inmetamagnetic shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Recarte, V.; Pérez-Landazábal, J.I.; Sánchez-Alarcos, V.; Zablotskyy, Vitaliy A.; Cesari, E.; Kustov, S.

    2012-01-01

    Roč. 60, 6-7 (2012), s. 3168-3175 ISSN 1359-6454 Institutional support: RVO:68378271 Keywords : metamagnetic shape memory alloys (MSMAs) * martensitic phase transformation * thermodynamics * transformation entropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.941, year: 2012

  1. Review of properties of magnetic shape memory (MSM) alloys and MSM actuator designs

    International Nuclear Information System (INIS)

    Gabdullin, N; Khan, S H

    2015-01-01

    Magnetic shape memory alloys are a new group of ''smart'' materials that exhibit large strain of 6-12% when subjected to magnetic fields. This indicates their enormous potential to be used in different electromagnetic (EM) devices such as actuators, sensors, energy harvesters and dampers. Shape change in MSM materials is controlled by magnetic field and doesn't involve phase transformation, allowing it to overcome a number of disadvantages of conventional shape memory alloys (SMAs). MSM devices are capable of producing large force and stroke output in considerably small dimensions. At the same time they can have fast response and potentially very long lifetime. This paper discusses different modern designs and approaches to MSM actuator design with their advantages and disadvantages. An overview on characteristics of MSM alloys is also presented in order to highlight how different properties of the material influence the total output of a device

  2. Apparatus and Method for Low-Temperature Training of Shape Memory Alloys

    Science.gov (United States)

    Swanger, A. M.; Fesmire, J. E.; Trigwell, S.; Gibson, T. L.; Williams, M. K.; Benafan, O.

    2015-01-01

    An apparatus and method for the low-temperature thermo-mechanical training of shape memory alloys (SMA) has been developed. The experimental SMA materials are being evaluated as prototypes for applicability in novel thermal management systems for future cryogenic applications. Alloys providing two-way actuation at cryogenic temperatures are the chief target. The mechanical training regimen was focused on the controlled movement of rectangular strips, with S-bend configurations, at temperatures as low as 30 K. The custom holding fixture included temperature sensors and a low heat-leak linear actuator with a magnetic coupling. The fixture was mounted to a Gifford-McMahon cryocooler providing up to 25 W of cooling power at 20 K and housed within a custom vacuum chamber. Operations included both training cycles and verification of shape memory movement. The system design and operation are discussed. Results of the training for select prototype alloys are presented.

  3. The effect of thermomechanical training on the microstructures of Fe-Mn-Si shape memory alloy

    International Nuclear Information System (INIS)

    Wang, D.F.; Chen, Y.R.; Gong, F.Y.; Liu, D.Z.; Liu, W.X.

    1995-01-01

    The shape memory effect and the microstructures of Fe-30Mn-6Si(wt%) alloy subjected to different training treatments have been studied in present paper. It has been found that the recovery strain increases significantly through the training treatment of 4% tensile pre-strain followed by recovery annealing at 700 C (treatment A) while the recovery strain decreases after the training treatment of 4% tensile pre-strain plus recovery annealing at 300 C (treatment B). The microstructures of the alloy after the above training treatments were investigated by TEM. It was found that the treatment A favoured the formation of oriented dislocations and stacking faults which results in the improvement of shape memory effect in Fe-Mn-Si alloy. (orig.)

  4. Apparatus and method for low-temperature training of shape memory alloys

    Science.gov (United States)

    Swanger, A. M.; Fesmire, J. E.; Trigwell, S.; Gibson, T. L.; Williams, M. K.; Benafan, O.

    2015-12-01

    An apparatus and method for the low-temperature thermo-mechanical training of shape memory alloys (SMA) has been developed. The experimental SMA materials are being evaluated as prototypes for applicability in novel thermal management systems for future cryogenic applications. Alloys providing two-way actuation at cryogenic temperatures are the chief target. The mechanical training regimen was focused on the controlled movement of rectangular strips, with S-bend configurations, at temperatures as low as 30 K. The custom holding fixture included temperature sensors and a low heat-leak linear actuator with a magnetic coupling. The fixture was mounted to a Gifford-McMahon cryocooler providing up to 25 W of cooling power at 20 K and housed within a custom vacuum chamber. Operations included both training cycles and verification of shape memory movement. The system design and operation are discussed. Results of the training for select prototype alloys are presented.

  5. A new method to determinate phase transformation in shape memory alloys: infrared thermography

    International Nuclear Information System (INIS)

    Bubulinca, C.; Balandraud, X.; Grediac, M.; Plaiasu, G. A.; Abrudeanu, M.; Stanciu, S.

    2013-01-01

    In this article it is presented a shape memory alloy case, based on copper, namely Cu-Zn-Al, which is subjected to periodic mechanical traction. Traction is performed in conditions of normal temperature and pressure. The purpose of this article it is to study stress induced phase transformation. All tests are performed in same conditions. Transformation on which is based this effect occurs in two ways: by applying a stress or temperature variation. In this article it is studied stress induced phase transformation. The method to analyze the microstructure of an shape memory alloy (SMA) is relatively new and it is based on tracking the evolution of temperature. After thermal analysis we can decide in which state is one alloy without any other supplier measures (differential scanning calorimetric or electrical resistivity). If our specimen will producing thermal energy when specimen is tensile he is austenitic. If absorbing heat during the first deformation is in martensitic state. (authors)

  6. Microstructural evolution in a Ti-Ta high-temperature shape memory alloy during creep

    International Nuclear Information System (INIS)

    Rynko, Ramona; Marquardt, Axel; Pauksen, Alexander; Frenzel, Jan; Somsen, Christoph; Eggeler, Gunther

    2015-01-01

    Alloys based on the titanium-tantalum system are considered for application as high-temperature shape memory alloys due to their martensite start temperatures, which can surpass 200 C. In the present work we study the evolution of microstructure and the influence of creep on the phase transformation behavior of a Ti 70 Ta 30 (at.%) high-temperature shape memory alloy. Creep tests were performed in a temperature range from 470 to 530 C at stresses between 90 and 150 MPa. The activation energy for creep was found to be 307 kJ mol -1 and the stress exponent n was determined as 3.7. Scanning and transmission electron microscopy investigations were carried out to characterize the microstructure before and after creep. It was found that the microstructural evolution during creep suppresses subsequent martensitic phase transformations.

  7. Void formation in NiTi shape memory alloys by medium-voltage electron irradiation

    International Nuclear Information System (INIS)

    Schlossmacher, P.; Stober, T.

    1995-01-01

    In-situ electron irradiation experiments of NiTi shape memory alloys, using high-voltage transmission electron microscopes, result in amorphization of the intermetallic compound. In all of these experiments high-voltages more than 1.0 MeV had to be applied in order to induce the crystalline-to-amorphous transformation. To their knowledge no irradiation effects of medium-voltage electrons of e.g. 0.5 MeV have been reported in the literature. In this contribution, the authors describe void formation in two different NiTi shape memory alloys, resulting from in-situ electron irradiation, using a 300 kV electron beam in a transmission electron microscope. First evidence is presented that void formation is correlated with the total oxygen content of the alloys

  8. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...... driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen...

  9. Recovery stress and shape memory stability in Ni-Ti-Cu thin wires at high temperatures

    Czech Academy of Sciences Publication Activity Database

    Molnár, Peter; Van Humbeeck, J.

    2011-01-01

    Roč. 102, č. 11 (2011), s. 1362-1368 ISSN 1862-5282 Institutional research plan: CEZ:AV0Z10100520 Keywords : shape memory alloys * recovery stress * Ni-Ti-Cu * stress relaxation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.830, year: 2011 http://www.ijmr.de/directlink.asp?MK110596

  10. Factors influencing shape memory effect and phase transformation behaviour of Fe-Mn-Si based shape memory alloys

    International Nuclear Information System (INIS)

    Li, H.; Dunne, D.; Kennon, N.

    1999-01-01

    The objective of this research work was to investigate the factors influencing the shape memory effect and phase transformation behaviour of three Fe-Mn-Si based shape memory alloys: Fe-28Mn-6Si, Fe-13Mn-5Si-10Cr-6Ni and Fe-20Mn-6Si-7Cr-1Cu. The research results show that the shape memory capacity of Fe-Mn-Si based shape memory alloys varies with annealing temperature, and this effect can be explained in terms of the effect of annealing on γ ε transformation. The nature and concentration of defects in austenite are strongly affected by annealing conditions. A high annealing temperature results in a low density of stacking faults, leading to a low nucleation rate during stress induced γ→ε transformation. The growth of ε martensite plates is favoured rather than the formation of new ε martensite plates. Coarse martensite plates produce high local transformation strains which can be accommodated by local slip deformation, leading to a reduction in the reversibility of the martensitic transformation and to a degradation of the shape memory effect. Annealing at low temperatures (≤673 K) for reasonable times does not eliminate complex defects (dislocation jogs, kinks and vacancy clusters) created by hot and cold working strains. These defects can retard the movement and rearrangement of Shockley partial dislocations, i.e. suppress γ→ε transformation, also leading to a degradation of shape memory effect. Annealing at about 873 K was found to be optimal to form the dislocation structures which are favourable for stress induced martensitic transformation, thus resulting in the best shape memory behaviour. (orig.)

  11. Thermomechanical treatment and deformation behavior of iron based shape memory alloys

    International Nuclear Information System (INIS)

    Shakoor, R.A.; Khalid, F.A.; Draper, P.H.

    2007-01-01

    The thermomechanical treatment (training) and deformation behavior of iron based shape memory alloys have been studied. The thermomechanical treatment results in improvement of shape memory effect. This improvement in shape memory effect can be attributed to the formation of lamellar structure of (lambda)/(epsilon) and to an increase in the volume fraction of epsilon martensite (epsilon). It is also found that excessive training may result in the nucleation of bcc martensite (alpha) along with epsilon martensite (epsilon) which degrades the shape memory effect. Also the shape memory effect decreases with the increase in amount of strain, which presumably can be regarded as the effect of increasing tendency of deformation to occur through slip and formation of (alpha) which reduces the reversibility of (epsilon) into (lambda). (author)

  12. Properties and structure of oxide layers on thin coating of titanium alloy

    Directory of Open Access Journals (Sweden)

    Jan Krčil

    2015-12-01

    Full Text Available Present work discusses issues of growth and characterization of a thin oxide layer formed on the surface of a titanium-niobium alloy. An oxide layer on the surface of titanium alloys introduces a corrosion resistance and also a bio-compatibility, which is required for a medical application. Although this oxide layer is a result of a spontaneous passivation, for the practical applications it is necessary to control the growth of oxides. In this work the oxide layer was formed on the PVD coating from Ti39Nb alloy which was sputtered on three different base materials: CP Ti grade 2, stainless steel AISI 316LVM and titanium alloy Ti–6Al–4V ELI. The oxide layer was created by a thermal oxidation at 600 °C for three different oxidation periods: 1, 4 and 8 hours. After the oxidation process the influence of oxidation characteristics and base materials on the thickness and properties of oxide layer was studied. There was observed a change of color and surface roughness. The oxide layer surface as well as the layer thickness was observed by SEM. The influence of the substrate material under the coating on the oxide layer should be more investigated in the future.

  13. Modeling solid-state dewetting of a single-crystal binary alloy thin films

    Science.gov (United States)

    Khenner, Mikhail

    2018-01-01

    Dewetting of a binary alloy thin film is studied using a continuum many-parameter model that accounts for the surface and bulk diffusion, the bulk phase separation, the surface segregation, and the particle formation. An analytical solution is found for the quasistatic equilibrium concentration of a surface-segregated atomic species. This solution is factored into the nonlinear and coupled evolution partial differential equations (PDEs) for the bulk composition and surface morphology. The stability of a planar film surface with respect to small perturbations of shape and composition is analyzed, revealing the dependence of the particle size on major physical parameters. The computations show various scenarios of the particle formation and the redistribution of the alloy components inside the particles and on their surface. In most situations, for the alloy film composed initially of 50% A and 50% B atoms, core-shell particles are formed, and they are located atop a wetting layer that is modestly rich in the B phase. Then the particle shell is the nanometric segregated layer of the A phase, and the core is the alloy that is modestly rich in the A phase.

  14. Characterization of thin Zn-Ni alloy coatings electrodeposited on low carbon steel

    International Nuclear Information System (INIS)

    El Hajjami, A.; Gigandet, M.P.; De Petris-Wery, M.; Catonne, J.C.; Duprat, J.J.; Thiery, L.; Raulin, F.; Pommier, N.; Starck, B.; Remy, P.

    2007-01-01

    The characteristics of initial layer formation in alkaline bath for Zn-Ni (12-15%) alloy electrodeposition on low carbon steel plates are detected in a nanometric thickness range by electron probe microanalysis (EPMA), with both bulk sample and thin film on substrate correction procedure, glow discharge optical emission spectroscopy (GDOES) and gracing incidence X-ray diffraction (GIXRD). The Zn-Ni coatings were elaborated using either intensiostatic or potentiostatic mode. A preferential deposition of Ni, in the initial thin layer, is detected by these analyses; according to EPMA and GDOES measurements, a layer rich in nickel at the interface substrate/deposit is observed (90 wt.% Ni) and approved by GIXRD; the thin layer of Ni formed in the first moments of electrolysis greatly inhibits the Zn deposition. The initial layer depends upon the relative ease of hydrogen and metal discharge and on the different substrate surfaces involved. The electrodeposition of zinc-nickel alloys in the first stage is a normal phenomenon of codeposition, whereby nickel - the more noble metal - is deposited preferentially

  15. Soft magnetic properties and damping parameter of (FeCo-Al alloy thin films

    Directory of Open Access Journals (Sweden)

    Isao Kanada

    2017-05-01

    Full Text Available For high frequency device applications, a systematic study of the soft magnetic properties and magnetization dynamics of (FeCo-Al alloy thin films has been carried out. A low effective damping parameter αeff of 0.002 and a high saturation magnetization of about 1,800 emu/cc are obtained at y=0.2∼0.3 for (Fe1-yCoy98Al2 alloy thin films deposited onto fused silica and MgO(100 at an ambient temperature during deposition. Those films are of the bcc structure with the orientation normal to the film plane. They possess a columnar structure, grown along the film normal. The column width is found to be about 20 nm for y=0.25. It is concluded that the (FeCo-Al thin films with a damping parameter as low as 0.002 and high saturation magnetization of about 1,800 emu/cc have been successfully fabricated, and that they are potential for future high frequency device applications.

  16. Formation and structure of V-Zr amorphous alloy thin films

    KAUST Repository

    King, Daniel J M

    2015-01-01

    Although the equilibrium phase diagram predicts that alloys in the central part of the V-Zr system should consist of V2Zr Laves phase with partial segregation of one element, it is known that under non-equilibrium conditions these materials can form amorphous structures. Here we examine the structures and stabilities of thin film V-Zr alloys deposited at room temperature by magnetron sputtering. The films were characterized by X-ray diffraction, transmission electron microscopy and computational methods. Atomic-scale modelling was used to investigate the enthalpies of formation of the various competing structures. The calculations confirmed that an amorphous solid solution would be significantly more stable than a random body-centred solid solution of the elements, in agreement with the experimental results. In addition, the modelling effort provided insight into the probable atomic configurations of the amorphous structures allowing predictions of the average distance to the first and second nearest neighbours in the system.

  17. Laser deposition rates of thin films of selected metals and alloys

    DEFF Research Database (Denmark)

    Cazzaniga, Andrea Carlo; Canulescu, Stela; Schou, Jørgen

    Thin films of Cu, Zn and Sn as well as mixtures of these elements have been produced by Pulsed Laser Deposition (PLD). The deposition rate of single and multicomponent metallic targets was determined. The strength of PLD is that the stoichiometry of complex compounds, even of complicated alloys...... or metal oxides, can be preserved from target to film. We apply this technique to design films of a mixture of Cu, Zn and Sn, which are constituents of the chalcogenide CZTS, which has a composition close to Cu2ZnSnS4. This compound is expected to be an important candidate for absorbers in new solar cells...... for alloys of the different elements as well as compounds with S will be presented....

  18. Shape recovery characteristics of biaxially prestrained Fe-Mn-Si-based shape memory alloy

    International Nuclear Information System (INIS)

    Wada, M.; Naoi, H.; Yasuda, H.; Maruyama, T.

    2008-01-01

    Fe-Mn-Si-based shape memory alloy has already been used practically for steel pipe joints. In most of the applications including the steel pipe joints, it is possible to estimate the reduction of diameter from the experimental data of the shape recovery after uniaxial stretching of the alloy materials. However, studies on shape recovery effects after biaxial stretching are important for the extensive applications of the alloy. In this study, we investigated the shape recovery strain after uniaxial and biaxial stretching and the microstructures of the alloy in order to see the effects of uniaxial and biaxial prestrain on the stress-induced martensitic transformation. Amounts of shape recovery strain in the biaxially prestrained specimens are smaller than those in the uniaxially prestrained specimens. Transmission electron microscopy revealed that reverse transformations of stress-induced martensitic ε-phase are prevented by slip bands formed at the same time in the biaxially prestrained specimens, but not in the uniaxially prestrained specimens. The technological data and interpretations presented in this study should be useful in forming design guidelines for promoting the extensive applications of Fe-Mn-Si-based shape memory alloy

  19. Thermoelastic martensite and shape memory effect in ductile Cu-Al-Mn alloys

    Science.gov (United States)

    Kainuma, R.; Takahashi, S.; Ishida, K.

    1996-08-01

    Ductile shape memory (SM) alloys of the Cu-AI-Mn system have been developed by controlling the degree of order in the β phase. Additions of Mn to the binary Cu-Al alloy stabilize the β phase and widen the single-phase region to lower temperature and lower Al contents. It is shown that Cu-Al-Mn alloys with low Al contents have either the disordered A2 structure or the ordered L21 structure with a lower degree of order and that they exhibit excellent ductility. The disordered A2 phase martensitically transforms to the disordered Al phase with a high density of twins. The martensite phase formed from the ordered L21 phase has the 18R structure. The SM effect accompanies both the A2 → Al and L21 → 18R martensitic transformations. These alloys exhibit 15 pct strain to failure, 60 to 90 pct rolling reduction without cracking, and 80 to 90 pct recovery from bend test in the martensitic condition. Experimental results on the microstructure, crystal structure, mechanical properties, and shape memory behavior in the ductile Cu-AI-Mn alloys are presented and discussed.

  20. Investigation of interfacial shear stresses, shape fixity, and actuation strain in composites incorporating shape memory polymers and shape memory alloys

    Science.gov (United States)

    Park, Jungkyu; Headings, Leon; Dapino, Marcelo; Baur, Jeffery; Tandon, Gyaneshwar

    2015-03-01

    Shape memory composites (SMCs) based on shape memory alloys (SMAs) and shape memory polymers (SMPs) allow many design possibilities due to their controllable temperature-dependent mechanical properties. The complementary characteristics of SMAs and SMPs can be utilized in systems with shape recovery created by the SMA and shape fixity provided by the SMP. In this research, three SMC operating regimes are identified and the behavior of SMC structures is analyzed by focusing on composite shape fixity and interfacial stresses. Analytical models show that SMPs can be used to adequately fix the shape of SMA actuators and springs. COMSOL finite element simulations are in agreement with analytical expressions for shape fixity and interfacial stresses. Analytical models are developed for an end-coupled linear SMP-SMA two-way actuator and the predicted strain is shown to be in good agreement with experimental test results.

  1. Superelastic and shape memory properties of TixNb3Zr2Ta alloys.

    Science.gov (United States)

    Zhu, Yongfeng; Wang, Liqiang; Wang, Minmin; Liu, Zhongtang; Qin, Jining; Zhang, Di; Lu, Weijie

    2012-08-01

    The microstructure and phase constitutions of TixNb3Zr2Ta alloys (x=35, 31, 27, 23) (wt%) were studied. With a lower niobium content the grain size of β phase in TixNb3Zr2Ta alloys increased significantly, and the TixNb3Zr2Ta system was more likely to form α″ phase and even α phase. Tensile tests showed that UTS of TixNb3Zr2Ta alloys improved as the Nb content was decreased. Cyclic loading-unloading tensile tests were carried on TixNb3Zr2Ta alloys. Ti23Nb3Zr2Ta and Ti27Nb3Zr2Ta alloys featured the best superelasticity among the alloys studied. The pseudoelastic strain ratio of Ti35Nb3Zr2Ta alloy decreased a lot as the cycle number increased. Ti31Nb3Zr2Ta alloy showed only minimum superelasticity. This is because Ti23Nb3Zr2Ta and Ti27Nb3Zr2Ta alloys had higher yield strength than Ti31Nb3Zr2Ta did, which allowed martensite phase to be induced. On the contrary, Ti31Nb3Zr2Ta alloy exhibited better shape memory property than Ti27Nb3Zr2Ta, Ti23Nb3Zr2Ta and Ti35Nb3Zr2Ta titanium alloys. β phase, α phase and α″ phase were found in Ti23Nb3Zr2Ta alloy by TEM observation. The dislocation density of α phase was much lower than that of β phase due to their crystal structure difference. This may explained why Ti23Nb3Zr2Ta with α phase possessed higher tensile strength. The incomplete shape recovery of Ti23Nb3Zr2Ta alloy after unloading resulted from two sources. Plastic deformation occurred in β phase, α phase and even α″ phase under dislocation slip mechanism, and incomplete decomposition of α″ martensitic phase resulted in unrecovered strain as well. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Size effects on magnetic actuation in Ni-Mn-Ga shape-memory alloys.

    Science.gov (United States)

    Dunand, David C; Müllner, Peter

    2011-01-11

    The off-stoichiometric Ni(2)MnGa Heusler alloy is a magnetic shape-memory alloy capable of reversible magnetic-field-induced strains (MFIS). These are generated by twin boundaries moving under the influence of an internal stress produced by a magnetic field through the magnetocrystalline anisotropy. While MFIS are very large (up to 10%) for monocrystalline Ni-Mn-Ga, they are near zero (textiles, foams and composites). Various strategies are proposed to accentuate this geometric effect which enables large MFIS in polycrystalline Ni-Mn-Ga by matching grain and sample sizes.

  3. Martensitic transformations and morphology studies of NiTi shape memory alloy

    Science.gov (United States)

    Murari, M. S.; Pattabi, Manjunatha

    2017-05-01

    The forward transformation temperatures Martensite Start (Ms) and Martensite Finish (Mf) during cooling, reverse transformation temperatures Austenite Start (As) and Austenite Finish (Af) during heating are very sensitive to the thermal and mechanical history of the Shape Memory Alloy (SMA). Heat treatments, cold and hot roll, thermal and mechanical cycling have great influence on the transformation temperatures. Different characterizing techniques like Differential Scanning Calorimeter (DSC), X-Ray Diffractometer (XRD), Electrical Resistivity (ER) and Thermo Mechanical Analyzer (TMA) were employed to study the phase transformation temperatures of NiTi alloy. The microstructure of the samples was studied with Atomic Force Microscope (AFM), Optical Microscope (OM) and Field Emission Scanning Electron Microscope (FESEM).

  4. A simple method to treat an ingrowing toenail with a shape-memory alloy device.

    Science.gov (United States)

    Ishibashi, Masaya; Tabata, Nobuko; Suetake, Takaki; Omori, Toshihiro; Sutou, Yuji; Kainuma, Ryosuke; Yamauchi, Kiyoshi; Ishida, Kiyohito

    2008-01-01

    An ingrowing toenail has no definitive treatment. Previously, effective methods were complicated but easy ones had less effect. We show both an easy and an effective way with Cu-Al-Mn-based shape-memory alloys (SMAs). They have a characteristic shape which patients themselves can detach easily without any pain. But they also have enough corrective force. Cu-based SMAs cost much less than Ni-Ti-based alloys. Despite not being appropriate for all cases of ingrowing toenails, it is an easy, effective and less costly alternative.

  5. Alloy-dependent deformation behavior of highly ductile nanocrystalline AuCu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lohmiller, Jochen [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Spolenak, Ralph [Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Gruber, Patric A., E-mail: patric.gruber@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2014-02-10

    Nanocrystalline thin films on compliant substrates become increasingly important for the development of flexible electronic devices. In this study, nanocrystalline AuCu thin films on polyimide substrate were tested in tension while using a synchrotron-based in situ testing technique. Analysis of X-ray diffraction profiles allowed identifying the underlying deformation mechanisms. Initially, elastic and microplastic deformation is observed, followed by dislocation-mediated shear band formation, and eventually macroscopic crack formation. Particularly the influence of alloy composition, heat-treatment, and test temperature were investigated. Generally, a highly ductile behavior is observed. However, high Cu concentrations, annealing, and/or large plastic strains lead to localized deformation and hence reduced ductility. On the other hand, enhanced test temperature allows for a delocalized deformation and extended ductility.

  6. Rapid precision casting for complex thin-walled aluminum alloy parts

    Directory of Open Access Journals (Sweden)

    Xuanpu DONG

    2004-11-01

    Full Text Available Based on Vacuum Differential Pressure Casting (VDPC precision forming technology and the Selective Laser Sintering (SLS Rapid Prototyping (RP technology, a rapid manufacturing method called Rapid Precision Casting (RPC process from computer three-dimensional solid models to metallic parts was investigated. The experimental results showed that the main advantage of RPC was not only its ability to cast higher internal quality and more accurate complex thin-walled aluminum alloy parts, but also the greatly-reduced lead time cycle from Selective Laser Sintering(SLS plastic prototyping to metallic parts. The key forming technology of RPC for complex thin-walled metallic parts has been developed for new casting production and Rapid Tooling (RT, and it is possible to rapidly manufacture high-quality and accurate metallic parts by means of RP in foundry industry.

  7. Finite element analysis of Al 2024/Cu-Al-Ni shape memory alloy composites with defects/cracks

    Science.gov (United States)

    Kotresh, M.; Benal, M. M., Dr; Siddalinga Swamy, N. H., Dr

    2018-02-01

    In this work, a numerical approach to predict the stress field behaviour of defect/crack in shape memory alloy (SMA) particles reinforced composite known as the adaptive composite is presented. Simulation is based on the finite element method. The critical stress field approach was used to determine the stresses around defect/crack. Thereby stress amplification issue is being resolved. In this paper, the effect volume % of shape memory alloy and shape memory effect of reinforcement for as-cast and SME trained composites are examined and discussed. Shape memory effect known as training is achieved by pre-straining of reinforcement particles by equivalent changes in their expansion coefficients.

  8. Fabrication of Ti-Ni-Cu shape memory alloy powders by ball milling method

    International Nuclear Information System (INIS)

    Kang, S.; Nam, T.

    2001-01-01

    Ti-Ni and Ti-Ni-Cu shape memory alloy powders have been fabricated by ball milling method, and then alloying behavior and transformation behavior were investigated by means of optical microscopy, electron microscopy, X-ray diffraction and differential scanning calorimetry. As milled Ti-Ni powders fabricated with milling time less than 20 hrs was a mixture of pure elemental Ti and Ni, and therefore it was unable to obtain alloy powders because the combustion reaction between Ti and Ni occurred during heat treatment. Since those fabricated with milling time more than 20 hrs was a mixture of Ti-rich and Ni-rich Ti-Ni solid solution, however, it was possible to obtain alloy powders without the combustion reaction during heat treatment. Clear exothermic and endothermic peaks appeared in the cooling and heating curves, respectively in DSC curves of 20 hrs and 30 hrs milled Ti-Ni powders. On the other hand, in DSC curves of 1 hr, 10 hrs, 50 hrs and 100 hrs, the thermal peaks were almost discernible. The most optimum ball milling time for fabricating Ti-Ni alloy powders was 30 hrs. Ti-40Ni-10Cu(at%) alloy powders were fabricated successfully by ball milling conditions with rotating speed of 100 rpm and milling time of 30 hrs. (author)

  9. Simulation of the plastic deformation of shape-memory alloys

    International Nuclear Information System (INIS)

    Likhachev, V.A.; Puschtschajenko, O.V.

    1997-01-01

    On the basis of the structural analytical theory of durability a mathematical model is developed which describes mechanical properties of shape memory metals. The influence of dislocation glide on martensitic nonelasticity is investigated. Results of numerical modeling show, that within the framework of the model such shape memory phenomena, as pseudo-elasticity in martensite and austenite, deformation cycles (also in a incomplete temperature interval) or the two-way effect can be well described. The two-way effect was simulated assuming inheritence of the effective fields strain in martensite and austenite. (orig.)

  10. In vitro corrosion behaviour of Ti-Nb-Sn shape memory alloys in Ringer's physiological solution.

    Science.gov (United States)

    Rosalbino, F; Macciò, D; Scavino, G; Saccone, A

    2012-04-01

    The nearly equiatomic Ni-Ti alloy (Nitinol) has been widely employed in the medical and dental fields owing to its shape memory or superelastic properties. The main concern about the use of this alloy derives form the fact that it contains a large amount of nickel (55% by mass), which is suspected responsible for allergic, toxic and carcinogenic reactions. In this work, the in vitro corrosion behavior of two Ti-Nb-Sn shape memory alloys, Ti-16Nb-5Sn and Ti-18Nb-4Sn (mass%) has been investigated and compared with that of Nitinol. The in vitro corrosion resistance was assessed in naturally aerated Ringer's physiological solution at 37°C by corrosion potential and electrochemical impedance spectroscopy (EIS) measurements as a function of exposure time, and potentiodynamic polarization curves. Corrosion potential values indicated that both Ni-Ti and Ti-Nb-Sn alloys undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Ti-18Nb-5Sn alloy. Significantly low anodic current density values were obtained from the polarization curves, indicating a typical passive behaviour for all investigated alloys, but Nitinol exhibited breakdown of passivity at potentials above approximately 450 mV(SCE), suggesting lower corrosion protection characteristics of its oxide film compared to the Ti-Nb-Sn alloys. EIS studies showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The obtained EIS spectra were analyzed using an equivalent electrical circuit representing a duplex structure oxide film, composed by an outer and porous layer (low resistance), and an inner barrier layer (high resistance) mainly responsible for the alloys corrosion resistance. The resistance of passive film present on the metals' surface

  11. Investigations of binary and ternary phase change alloys for future memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Rausch, Pascal

    2012-09-13

    The understanding of phase change materials is of great importance because it enables us to predict properties and tailor alloys which might be even better suitable to tackle challenges of future memory applications. Within this thesis two topics have been approached: on the one hand the understanding of the alloy In{sub 3}Sb{sub 1}Te{sub 2} and on the other hand the so called resistivity drift of amorphous Ge-Sn-Te phase change materials. The main topic covers an in depth discussion of the ternary alloy In{sub 3}Sb{sub 1}Te{sub 2}. At first glance, this alloy does not fit into the established concepts of phase alloys: e.g. the existence of resonant bonding in the crystalline phase is not obvious and the number of p-electrons is very low compared to other phase change alloys. Furthermore amorphous phase change alloys with high indium content are usually not discussed in literature, an exception being the recent work by Spreafico et al. on InGeTe{sub 2}. For the first time a complete description of In{sub 3}Sb{sub 1}Te{sub 2} alloy is given in this work for the crystalline phase, amorphous phase and crystallization process. In addition comparisons are drawn to typical phase change materials like Ge{sub 2}Sb{sub 2}Te{sub 5}/GeTe or prototype systems like AgInTe{sub 2} and InTe. The second topic of this thesis deals with the issue of resistivity drift, i.e. the increase of resistivity of amorphous phase change alloys with aging. This drift effect greatly hampers the introduction of multilevel phase change memory devices into the market. Recently a systematic decrease of drift coefficient with stoichiometry has been observed in our group going from GeTe over Ge{sub 3}Sn{sub 1}Te{sub 4} to Ge{sub 2}Sn{sub 2}Te{sub 4}. These alloys are investigated with respect to constraint theory.

  12. Superhydrophobic nanostructured ZnO thin films on aluminum alloy substrates by electrophoretic deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ying; Sarkar, D.K., E-mail: dsarkar@uqac.ca; Chen, X-Grant

    2015-02-01

    Graphical abstract: - Highlights: • Fabrication of superhydrophobic ZnO thin films surfaces by electrophoretic deposition process on aluminum substrates. • Effect of bath temperature on the physical and superhydrophobic properties of thin films. • The water contact angle of 155° ± 3 with roll off property has been observed on the film that was grown at bath temperatures of 50 °C. • The activation energy for electrophoretic deposition of SA-functionalized ZnO nanoparticle is calculated to be 0.50 eV. - Abstract: Superhydrophobic thin films have been fabricated on aluminum alloy substrates by electrophoretic deposition (EPD) process using stearic acid (SA) functionalized zinc oxide (ZnO) nanoparticles suspension in alcohols at varying bath temperatures. The deposited thin films have been characterized using both X-ray diffraction (XRD) and infrared (IR) spectroscopy and it is found that the films contain low surface energy zinc stearate and ZnO nanoparticles. It is also observed that the atomic percentage of Zn and O, roughness and water contact angle of the thin films increase with the increase of the deposited bath temperature. Furthermore, the thin film deposited at 50 °C, having a roughness of 4.54 ± 0.23 μm, shows superhydrophobic properties providing a water contact angle of 155 ± 3° with rolling off properties. Also, the activation energy of electrophoretic deposition of stearic-acid-functionalized ZnO nanoparticles is calculated to be 0.5 eV.

  13. Modeling and Application of Process Damping in Milling of Thin-Walled Workpiece Made of Titanium Alloy

    Directory of Open Access Journals (Sweden)

    Xin Li

    2015-01-01

    Full Text Available The modeling as well as application of process damping in milling of thin-walled workpiece made of titanium alloy is investigated. Titanium alloy used commonly in aviation industry is one typical difficult-to-machine material. Chatter usually occurs in cutting of titanium alloy, which results in poor surface quality and damaged tool. Thus, chatter is one important restriction for the quality and efficiency of titanium alloy manufacture, especially for the thin-walled workpiece made of titanium alloy due to poor structural stiffness. Process damping results from interference between flank face and machined surface, which is critical but usually ignored in chatter analysis for difficult-to-machine material. The paper presents one nonlinear dynamic model considering process damping for milling of thin-walled workpiece made of titanium alloy and designs antivibration clearance angle to suppress chatter based on the model. The experimental and computational results indicate that the presented methods for chatter stability analysis are reasonable, and the antivibration clearance angle designed is effective in suppressing chatter and improving machining quality.

  14. An model for the analysis of shape memory alloy fiber-composites

    Science.gov (United States)

    Kohlhaas, Benedikt; Klinkel, Sven

    2015-02-01

    This contribution deals with a computational model for a shape memory alloy fiber composite. Three main topics have been considered within the presented model. First, a 1D fiber model is derived which accounts for all relevant nonlinear material phenomena of shape memory alloys. These are pseudoelasticity in the high temperature range and pseudoplasticity in the low temperature range. The latter is closely connected to the shape memory effect. The constrained and two-way shape memory effect are captured as well. Second, the shape memory fiber model is implemented into the finite element method. Two different structural elements are derived which lead to two different discretization schemes. A non-conform meshing concept and a conform meshing concept are presented. Randomly oriented and distributed fibers are considered. Both schemes are compared within the paper. Third, an ansatz is presented. The computational homogenization process makes the detailed description of the complicated fiber-structure on macro-level dispensable. The micro-structure is considered in a representative volume element. It captures the main characteristics of the multi-functional composite. Finally, numerical examples present the capability of the formulation.

  15. Vibration Control of a Flexible Rotor Using Shape Memory Alloy Wires

    DEFF Research Database (Denmark)

    Alves, Marco Túlio Santana; Enemark, Søren; Steffen Jr, Valdar

    2015-01-01

    In the present contribution, a theoretical model of a test rig containing a flexible rotor is simulated considering pseudoelastic SMA (Shape Memory Alloy) wires connected to a bearing in order to dissipate energy and consequently reduce vibration. SMAs have characteristics of shape memory...... of rotor and SMA wires are coupled. The chosen constitutive model that governs the SMA behaviour is a modified version of the model by Brinson for the one-dimensional case. Both transient and steady-state tests arenumerically simulated. The first one, a run-up test, is performed only at room temperature...

  16. Design of a Shape Memory Alloy deployment hinge for reflector facets

    Science.gov (United States)

    Anders, W. S.; Rogers, C. A.

    1991-01-01

    A design concept for a Shape Memory Alloy (SMA) actuated hinge mechanism for deploying segmented facet-type reflector surfaces on antenna truss structures is presented. The mechanism uses nitinol, a nickel-titanium shape memory alloy, as a displacement-force micro-actuator. An electrical current is used to resistively heat a 'plastically' elongated SMA actuator wire, causing it to contract in response to a thermally-induced phase transformation. The resulting tension creates a moment, imparting rotary motion between two adjacent panels. Mechanical stops are designed into the device to limit its range of motion and to establish positioning accuracy at the termination of deployment. The concept and its operation are discussed in detail, and an analytical dynamic simulation model is presented. The model has been used to perform nondimensionalized parametric design studies.

  17. Nanoparticles from Cu-Zn-Al shape memory alloys physically synthesized by ion milling deposition

    Energy Technology Data Exchange (ETDEWEB)

    Pavon, Luis Alberto Lopez [Universidad Autonoma de Nuevo Leon (UANL), Nuevo Leon (Mexico); Cuellara, Enrique Lopez; Castro, Alejandro Torres; Cruza, Azael Martinez de la [Universidad Autonoma de Nuevo Leon (CIIDIT/UANL), Nuevo Leon (Mexico). Centro de Innovacion, Investigacion y Desarrollo en Ingenieria y Tecnologia; Ballesteros, Carmen [Universidad Carlos III de Madrid, Madrid (Spain). Departamento de Fisica; Araujo, Carlos Jose de [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Departamento de Engenharia Mecanica

    2012-05-15

    In this research, an ion milling equipment was used to elaborate nanoparticles from Cu-Zn-Al alloys with shape memory effect. Two different compositions were used, target A: 75.22Cu-17.12Zn-7.66Al at % with an Ms of -9 deg C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 degree C. Nanoparticles were characterized by High Resolution Transmission Electron Microscopy, Electron Diffraction and Energy Dispersive X-ray Spectroscopy. The obtained nanoparticles showed a small dispersion, with a size range of 3.2-3.5 nm. Their crystal structure is in good agreement with the bulk martensitic structure of the targets. In this sense, results on morphology, composition and crystal structure have indicated that it is possible to produce nanoparticles of CuZnAl shape memory alloys with martensitic structure in a single process using Ion Milling. (author)

  18. Efficiency of Energy Harvesting in Ni-Mn-Ga Shape Memory Alloys

    Science.gov (United States)

    Lindquist, Paul; Hobza, Tony; Patrick, Charles; Müllner, Peter

    2018-03-01

    Many researchers have reported on the voltage and power generated while energy harvesting using Ni-Mn-Ga shape memory alloys; few researchers report on the power conversion efficiency of energy harvesting. We measured the magneto-mechanical behavior and energy harvesting of Ni-Mn-Ga shape memory alloys to quantify the efficiency of energy harvesting using the inverse magneto-plastic effect. At low frequencies, less than 150 Hz, the power conversion efficiency is less than 0.1%. Power conversion efficiency increases with (i) increasing actuation frequency, (ii) increasing actuation stroke, and (iii) decreasing twinning stress. Extrapolating the results of low-frequency experiments to the kHz actuation regime yields a power conversion factor of about 20% for 3 kHz actuation frequency, 7% actuation strain, and 0.05 MPa twinning stress.

  19. Shape memory alloy Co-Ni-Al as complex multiferroic

    Czech Academy of Sciences Publication Activity Database

    Kopeček, Jaromír; Jarošová, Markéta; Jurek, Karel; Drahokoupil, Jan; Kratochvílová, Irena; Fekete, Ladislav; Bodnárová, Lucie; Seiner, Hanuš; Sedlák, Petr; Landa, Michal; Šepitka, J.; Lukeš, J.; Kopecký, Vít; Heczko, Oleg

    2012-01-01

    Roč. 19, č. 2 (2012), s. 114-115 ISSN 1211-5894. [Struktura 2012. Kolokvium Krystalografické společnosti. 11.06.2012-14.06.2012, Klatovy] R&D Projects: GA ČR(CZ) GA101/09/0702; GA ČR GAP107/10/0824; GA ČR(CZ) GAP107/11/0391; GA AV ČR IAA100100920 Institutional support: RVO:68378271 ; RVO:61388998 Keywords : Co-alloys * metallography * EBSD method * martensite Subject RIV: JG - Metallurgy http://www. xray .cz/ms/bul2012-2/sessionc.pdf

  20. The tensile behavior of Ti36Ni49Hf15 high temperature shape memory alloy

    International Nuclear Information System (INIS)

    Wang, Y.Q.; Zheng, Y.F.; Cai, W.; Zhao, L.C.

    1999-01-01

    Recently, ternary Ti-Ni-Hf alloys have attracted great interest in the field of high temperature shape memory materials research and development. Extensive studies have been made on its manufacture process, constitutional phases, phase transformation behavior, the structure, substructure and interface structure of martensite and the precipitation behavior during ageing. Yet up to date there is no report about the fundamental mechanical properties of Ti-Ni-Hf alloys, such as the stress-strain data, the variation laws of the yield strength and elongation with the temperature. In the present study, tensile tests at various temperatures are employed to investigate the mechanical behavior of Ti-Ni-Hf alloy with different matrix structures, from full martensite to full parent phase structure, with the corresponding deformation mechanism discussed

  1. Martensitic Transformation and Superelasticity in Fe-Mn-Al-Based Shape Memory Alloys

    Science.gov (United States)

    Omori, Toshihiro; Kainuma, Ryosuke

    2017-12-01

    Ferrous shape memory alloys showing superelasticity have recently been obtained in two alloy systems in the 2010s. One is Fe-Mn-Al-Ni, which undergoes martensitic transformation (MT) between the α (bcc) parent and γ' (fcc) martensite phases. This MT can be thermodynamically understood by considering the magnetic contribution to the Gibbs energy, and the β-NiAl (B2) nanoprecipitates play an important role in the thermoelastic MT. The temperature dependence of critical stress for the MT is very small (about 0.5 MPa/°C) due to the small entropy difference between the parent and martensite phases in the Fe-Mn-Al-Ni alloy, and consequently, superelasticity can be obtained in a wide temperature range from cryogenic temperature to about 200 °C. Microstructural control is of great importance for obtaining superelasticity, and the relative grain size is among the most crucial factors.

  2. Formation of two-way shape memory effect in rapid-quenched TiNiCu alloys

    International Nuclear Information System (INIS)

    Shelyakov, A.V.; Bykovsky, Yu.A.; Matveeva, N.M.; Kovneristy, Yu.K.

    1995-01-01

    Recently we have developed a number of devices for an optical radiation control based on the shape memory effect. A blind of rapid-quenched TiNiCu alloy having a two-way shape memory in bending was used as a basic element. So far as the rapid quenched alloy used is amorphous in initial state, it needs thermal annealing to form shape memory. This paper describes procedure of thermo-mechanical treatment, that allows to form desired two-way shape memory immediately during thermal annealing of amorphous alloy without training. It was shown that degree of two-way shape recovery depends critically on initial strain, temperature and duration of the annealing. It was experimentally determined optimum parameters of thermo-mechanical treatment to achieve maximum two-way shape memory. (orig.)

  3. Stress evolution during and after sputter deposition of thin Cu Al alloy films

    Science.gov (United States)

    Pletea, M.; Wendrock, H.; Kaltofen, R.; Schmidt, O. G.; Koch, R.

    2008-06-01

    The stress evolution during and after sputter deposition of thin Cu-Al alloy films containing 1 and 2 at.% Al onto oxidized Si(100) substrates has been studied up to thicknesses of 300 nm by means of in situ substrate curvature measurements. In order to correlate stress and morphology, the microstructure was investigated by focused ion beam microscopy, scanning electron microscopy, and atomic force microscopy. The evolution of the stress and microstructure of the Cu-Al alloy films is similar to that for sputtered pure Cu films. Film growth proceeds in the Volmer-Weber mode, typical for high mobility metals. It is characterized by nucleation, island, percolation, and channel stages before the films become continuous, as well as lateral grain growth in the compact films. With increasing Al content the overall atom mobility and, thus, the average grain size of the alloy films are reduced. Increase of the sputter pressure from 0.5 to 2 Pa leads to films with larger grain size, rougher surface morphology and higher electrical resistivity.

  4. Numerical simulation for mold-filling of thin-walled aluminum alloy castings in traveling magnetic field

    Directory of Open Access Journals (Sweden)

    Shiping WU

    2004-11-01

    Full Text Available The numeical simulation for mold-filling of thin-walled aluminum alloy castins in horizontal traveling magnetic field is performed. A force model of Al alloy melt in the traveling magnetic field is founded by analyzing traveling magnetic field carefully. Numerical model of Al alloy mold-filling is founded based on N-S equation, which was suitable for traveling magnetic field. By using acryl glass mold with indium as alloy melt, the experiment testiied the filling state of alloy in traveling magnetic field. The results of numerical simulation indicate that the mold-filling ability of gallium melt increases continually with the incease of the input ampere turns.

  5. Assessment of Shape Memory Alloys - From Atoms To Actuators - Via In Situ Neutron Diffraction

    Science.gov (United States)

    Benafan, Othmane

    2014-01-01

    As shape memory alloys (SMAs) become an established actuator technology, it is important to identify the fundamental mechanisms responsible for their performance by understanding microstructure performance relationships from processing to final form. Yet, microstructural examination of SMAs at stress and temperature is often a challenge since structural changes occur with stress and temperature and microstructures cannot be preserved through quenching or after stress removal, as would be the case for conventional materials. One solution to this dilemma is in situ neutron diffraction, which has been applied to the investigation of SMAs and has offered a unique approach to reveal the fundamental micromechanics and microstructural aspects of bulk SMAs in a non-destructive setting. Through this technique, it is possible to directly correlate the micromechanical responses (e.g., internal residual stresses, lattice strains), microstructural evolutions (e.g., texture, defects) and phase transformation properties (e.g., phase fractions, kinetics) to the macroscopic actuator behavior. In this work, in situ neutron diffraction was systematically employed to evaluate the deformation and transformation behavior of SMAs under typical actuator conditions. Austenite and martensite phases, yield behavior, variant selection and transformation temperatures were characterized for a polycrystalline NiTi (49.9 at. Ni). As the alloy transforms under thermomechanical loading, the measured textures and lattice plane-level variations were directly related to the cyclic actuation-strain characteristics and the dimensional instability (strain ratcheting) commonly observed in this alloy. The effect of training on the shape memory characteristics of the alloy and the development of two-way shape memory effect (TWSME) were also assessed. The final conversion from a material to a useful actuator, typically termed shape setting, was also investigated in situ during constrained heatingcooling and

  6. Fabrication of Pb (Zr, Ti) O3 Thin Film for Non-Volatile Memory Device Application

    International Nuclear Information System (INIS)

    Mar Lar Win

    2011-12-01

    Ferroelectric lead zirconate titanate powder was composed of mainly the oxides of titanium, zirconium and lead. PZT powder was firstly prepared by thermal synthesis at different Zr/Ti ratios with various sintering temperatures. PZT thin film was fabricated on SiO2/Si substrate by using thermal evaporation method. Physical and elemental analysis were carried out by using SEM, EDX and XRD The ferroelectric properties and the switching behaviour of the PZT thin films were investigated. The ferroelectric properties and switching properties of the PZT thin film (near morphotropic phase boundary sintered at 800 C) could function as a nonvolatile memory.

  7. Effect of titanium addition on shape memory effect and recovery stress of training-free cast Fe–Mn–Si–Cr–Ni shape memory alloys

    International Nuclear Information System (INIS)

    Wang, Gaixia; Peng, Huabei; Sun, Panpan; Wang, Shanling; Wen, Yuhua

    2016-01-01

    The shape memory effect and recovery stress of cast Fe–17.2Mn–5.28Si–9.8Cr–4.57Ni (18Mn) and Fe–17.5Mn–5.29Si–9.68Cr–4.2Ni–0.09Ti (18Mn–Ti) alloys have been investigated by optical microscopy, scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and resistivity–temperature curves. The cast 18Mn and 18Mn–Ti alloys solidified as the ferritic mode for which liquid phase fully transforms into primary δ ferrite. The role of titanium is to indirectly refine the austenite through refining the primary δ ferrite. In this case, the austenitic grains of the cast 18Mn alloy were much bigger than that of the cast 18Mn–Ti alloy, although the two alloys underwent δ→γ phase transformation. Grain refinement suppresses the stress-induced ε martensitic transformation, and thus the shape memory effect of the cast 18Mn–Ti alloy is worse than that of the cast 18Mn alloy. On the contrary, the maximum recovery stress and the recovery stress at room temperature are higher for the cast 18Mn–Ti alloy annealed at 1073 K for 30 min than for the cast 18Mn alloy annealed at 973 K for 30 min, because grain refinement suppresses the relaxation of recovery stress caused by the plastic deformation and the stress-induced ε martensitic transformation during cooling process. It is difficult to obtain the training-free cast Fe–Mn–Si based shape memory alloys with excellent shape memory effect and high recovery stress only by grain refinement.

  8. Deployable auxetic shape memory alloy cellular antenna demonstrator: design, manufacturing and modal testing

    International Nuclear Information System (INIS)

    Jacobs, S; Coconnier, C; DiMaio, D; Scarpa, F; Martinez, J; Toso, M

    2012-01-01

    This work describes the design, manufacturing and testing of a deployable antenna for deep-space missions based on a hybrid honeycomb truss made of shape memory alloy (SMA). The deployable characteristics are enhanced by the equivalent auxetic (negative Poisson’s ratio) behaviour of the cellular configuration. Specific emphasis is placed on the modal analysis techniques used to test the lightweight SMA structure. (paper)

  9. Contribution of Shape Memory Alloys Elements in Designing Underwater Smart Structures

    Directory of Open Access Journals (Sweden)

    Daniel Amariei

    2007-10-01

    Full Text Available Shape memory alloys (SMA have generated a lot of new ideas in engineering. Application is however so far limited to clamps and springs. With respect to smart structures sensing as well as control has to be included. While sensing looks to be relatively feasible control is the big challenge. This paper describes some related a smart structure idea using SMAs and discusses the challenges which need to be solved before these ideas can be realised.

  10. From canonical Hamiltonian to Port-Hamiltonian modeling application to magnetic shape memory alloys actuators.

    OpenAIRE

    Calchand, Nandish; Hubert, Arnaud; Le Gorrec, Yann; Maschke, Bernhard

    2011-01-01

    International audience; This paper presents the modelling of an actuator based on Magnetic Shape Memory Alloys (MSMA). The actuation principle relies on the ability of the material to change its shape under the application of a magnetic field. Previous models proposed by authors were based on canonical (symplectic) Hamiltonian modeling and thermodynamics of irreversible processes. These models, though physically cogent, are non-minimal differential algebraic dynamical models and hence less ad...

  11. Thermo-mechanical response and fatigue behavior of shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya [Tokyo Univ. (Japan). Dept. of Mechanical Engineering

    1998-11-01

    Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

  12. Recent activities of association of shape memory alloys (ASMA) in Japan

    International Nuclear Information System (INIS)

    Kobayashi, J.; Yamauchi, K.; Miyashita, T.; Ohkata, I.; Narumi, S.; Suzuki, Y.

    1995-01-01

    The Association of Shape Memory Alloys(ASMA) was established in 1983 and systematic surveys on the Ni-Ti and Cu based SMAs were carried out until 1986. The ASMA is now reorganized as a private association. In this paper, we briefly introduce several SMA products of the member companies and present a couple of products, a static rock breaking system and a thermostatic mixing valve in detail. (orig.)

  13. Biomechanical study of posterior wall acetabular fracture fixation using acetabular tridimensional memory alloy-fixation system.

    Science.gov (United States)

    Xin-wei, Liu; Shuo-gui, Xu; Chun-cai, Zhang; Qing-ge, Fu; Pan-feng, Wang

    2010-05-01

    We developed the acetabular tridimensional memory alloy-fixation system (ATMFS), which is made of NiTi shape memory alloy, according to the specific mechanical properties of biological memory material, nitinol alloy and measured distribution of contact area and pressure between the acetabulum and the femoral head of cadaveric pelvis. Six formalin-preserved cadaveric pelvis were used for this investigation. Pressure-sensitive film was used to measure contact area and pressure within the anterior, superior, and posterior regions of the acetabulum. The pelvis were loaded under the following four conditions: (1) intact; (2) following a creation posterior wall fracture defect; (3) following reduction and standard internal fixation with reconstruction plate; (4) following reduction and internal fixation with a new shape memory alloy device named ATMFS. A posterior wall fracture was created along an arc of 40-90 degrees about the acetabular rim. Creation of a posterior wall defect resulted in increased load in the superior acetabulum (1422N) as compared to the intact condition (762N, P=0.007). Following reduction and internal fixation, the load distributed to the superior acetabulum (1486N) was not statistically different from the defect condition. Following the fixation with ATMFS, the load seen at the superior region of the actabulum (936N) was less than fixation with reconstruction plate and was not different from intact state (P=0.4). These data indicate that the use of ATMFS as a fracture internal fixation device resulted a partial restoration of joint loading parameters toward the intact state. ATMFS fixation may result in a clinical benefit. Copyright 2010 Elsevier Ltd. All rights reserved.

  14. Integration of Shape Memory Alloys into Low-Damped Rotor-Bearing Systems

    DEFF Research Database (Denmark)

    Enemark, Søren

    2015-01-01

    to use passive adaptive control through smart materials. Shape Memory Alloys (SMAs) are interesting candidates in that relation, because of their highly temperature sensitive stiffness and mechanical hysteresis, which can be used for damping purposes. The thesis focuses on three main aspects related...... properties. Different element geometries are investigated with focus on helical springs. Several spring models are presented, which use different levels of approximations to the mechanical stress state. The models are compared to experimental results covering different levels of temperature, deformation...

  15. Ni4Ti3 precipitate structures in Ni-rich NiTi shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Holec, David; Bojda, Ondřej; Dlouhý, Antonín

    2008-01-01

    Roč. 481, Sp. Iss. (2008), s. 462-465 ISSN 0921-5093. [ESOMAT 2006. Bochum, 10.09.2006-15.09.2006] R&D Projects: GA ČR(CZ) GA106/05/0918 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Ni4Ti3 precipitates * Multi-step martensitic transformations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.806, year: 2008

  16. Well-posedness of a thermo-mechanical model for shape memory alloys under tension

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel; Stefanelli, U.

    2010-01-01

    Roč. 44, č. 6 (2010), s. 1239-1253 ISSN 0764-583X R&D Projects: GA ČR GAP201/10/2315 Institutional research plan: CEZ:AV0Z10190503 Keywords : shape memory alloys * thermo-mechanics * well-posedness * hysteresis operator Subject RIV: BA - General Mathematics Impact factor: 1.202, year: 2010 http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8129335

  17. Ageing effects in a Cu-Al-Ni shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Daříček, Tomáš; Lašek, Jiří; Zárubová, Niva; Novák, Václav; Bartuška, Pavel

    2001-01-01

    Roč. 11, - (2001), s. Pr8-179-Pr8-184 ISSN 1155-4339 R&D Projects: GA AV ČR IAA1010909; GA AV ČR IAA1010817 Institutional research plan: CEZ:AV0Z1010914 Keywords : Cu-Al-Ni alloy * shape memory * martensitic transformation * resistometry Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.401, year: 2001

  18. Thermo-mechanical response and fatigue behavior of shape memory alloy

    International Nuclear Information System (INIS)

    Kusagawa, Masaki; Asada, Yasuhide; Nakamura, Toshiya

    1998-01-01

    Mechanical, thermo-mechanical and fatigue behaviors of Ni-Ti-Nb shape memory alloy (SMA) have been studied to prepare material data for a design purpose. Presented are testing devices, testing procedure and test results of monotonic tensile, recovery of inelastic deformation due to post heating (thermo-mechanical recovery) and fatigue for future use of the SMA as a structural material of nuclear incore structures. (orig.)

  19. A microscopically motivated constitutive model for shape memory alloys: Formulation, analysis and computations

    Czech Academy of Sciences Publication Activity Database

    Frost, Miroslav; Benešová, B.; Sedlák, P.

    2016-01-01

    Roč. 21, č. 3 (2016), s. 358-382 ISSN 1081-2865 R&D Projects: GA ČR GA13-13616S; GA ČR GAP201/10/0357 Institutional support: RVO:61388998 Keywords : shape memory alloys * constitutive model * generalized standard materials * dissipation * energetic solution Subject RIV: BA - General Mathematics Impact factor: 2.953, year: 2016 http://mms.sagepub.com/content/21/3/358

  20. Ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory

    International Nuclear Information System (INIS)

    Han, Jinhua; Wang, Wei; Ying, Jun; Xie, Wenfa

    2014-01-01

    An ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory was demonstrated, with discrete distributed gold nanoparticles, tetratetracontane (TTC), pentacene as the floating-gate layer, tunneling layer, and active layer, respectively. The electron traps at the TTC/pentacene interface were significantly suppressed, which resulted in an ambipolar operation in present memory. As both electrons and holes were supplied in the channel and trapped in the floating-gate by programming/erasing operations, respectively, i.e., one type of charge carriers was used to overwrite the other, trapped, one, a large memory window, extending on both sides of the initial threshold voltage, was realized

  1. Effect of tellurium on machinability and mechanical property of CuAlMnZn shape memory alloy

    International Nuclear Information System (INIS)

    Liu Na; Li Zhou; Xu Genying; Feng Ze; Gong Shu; Zhu Lilong; Liang Shuquan

    2011-01-01

    Highlights: → A novel free-machining Cu-7.5Al-9.7Mn-3.4Zn-0.3Te (wt.%) shape memory alloy has been developed. → The size of dispersed particles with richer Te is 2-5 μm. → The CuAlMnZnTe alloy has good machinability which approached that of BZn15-24-1.5 due to the addition of Te. → Its shape memory property keeps the same as that of CuAlMnZn alloy with free Te. → The CuAlMnZn shape memory alloy with and without Te both have good ductile as annealed at 700 deg. C for 15 min. - Abstract: The microstructure transition, shape memory effect, machinability and mechanical property of the CuAlMnZn alloy with and without Te have been studied using X-ray diffraction analysis, chips observation and scanning electron microscopy (SEM), tensile strength test and differential scanning calorimeter (DSC), and semi-quantitative shape memory effect (SME) test. The particles with richer Te dispersedly distributed in grain interior and boundary with size of 2-5 μm. After the addition of Te, the CuAlMnZnTe alloy machinability has been effectively increased to approach that of BZn15-24-1.5 and its shape memory property remains the same as the one of CuAlMnZn alloy. The CuAlMnZn shape memory alloys with and without Te both have good ductility as annealed at 700 deg. C for 15 min.

  2. Experimental evaluation of shape memory alloy actuation technique in adaptive antenna design concepts

    Science.gov (United States)

    Kefauver, W. Neill; Carpenter, Bernie F.

    1994-01-01

    Creation of an antenna system that could autonomously adapt contours of reflecting surfaces to compensate for structural loads induced by a variable environment would maximize performance of space-based communication systems. Design of such a system requires the comprehensive development and integration of advanced actuator, sensor, and control technologies. As an initial step in this process, a test has been performed to assess the use of a shape memory alloy as a potential actuation technique. For this test, an existing, offset, cassegrain antenna system was retrofit with a subreflector equipped with shape memory alloy actuators for surface contour control. The impacts that the actuators had on both the subreflector contour and the antenna system patterns were measured. The results of this study indicate the potential for using shape memory alloy actuation techniques to adaptively control antenna performance; both variations in gain and beam steering capabilities were demonstrated. Future development effort is required to evolve this potential into a useful technology for satellite applications.

  3. Origin of anomalous cryogenic magnetic behavior in a Ni-Mn-based magnetic shape memory alloy

    Science.gov (United States)

    Sun, X. M.; Cong, D. Y.; Liss, K.-D.; Qu, Y. H.; Ma, L.; Suo, H. L.; Wang, Y. D.

    2017-03-01

    The origin of the anomalous low-temperature staircase-like magnetization behavior in magnetic shape memory alloys, which has been commonly observed in a large variety of materials, has been remaining a mystery since it was discovered. Here, we elucidate the underlying mechanism for such anomalous magnetic behavior via tracing the structural evolution during applying magnetic fields at 4 K in an archetypal Ni-Mn-based magnetic shape memory alloy, by in-situ neutron diffraction technique. We found that it is the magnetic-field-induced structural transformation occurring at this extremely low temperature (far below martensitic transformation temperature) that is responsible for the anomalous low-temperature magnetic behavior. It is believed that this transformation proceeds by a succession of discrete steps, accounting for the abrupt jumps on the magnetization curve. The present study provides deep insights into the interplay between magnetism and structure in magnetic shape memory alloys, and it is also instructive for understanding the anomalous staircase-like magnetization behavior in other materials undergoing a magnetostructural transition.

  4. Shape memory behavior of high strength NiTiHfPd polycrystalline alloys

    International Nuclear Information System (INIS)

    Karaca, H.E.; Acar, E.; Ded, G.S.; Basaran, B.; Tobe, H.; Noebe, R.D.; Bigelow, G.; Chumlyakov, Y.I.

    2013-01-01

    Systematic characterization of the shape memory properties of a quaternary Ni 45.3 –Ti 29.7 –Hf 20 –Pd 5 (at.%) polycrystalline alloy was performed in compression after selected aging treatments. Precipitation characteristics were revealed by transmission electron microscopy. The effects of aging temperature and time on transformation temperatures, recoverable and residual strains, and temperature and stress hystereses were determined by differential scanning calorimetry, constant-load thermal cycling experiments and isothermal strain cycling (superelasticity) tests. The crystal structure and lattice parameters of the transforming phases were determined from X-ray diffraction analysis. It was revealed that precipitation hardening significantly improved the shape memory properties of the NiTiHfPd alloy. Under optimum aging conditions, shape memory strains of up to 4% under 1 GPa were possible, and superelasticity experiments resulted in full strain recovery without any plastic deformation, even at stress levels as high as 2 GPa. The NiTiHfPd polycrystalline alloy exhibited very high damping capacity/absorbed energy (30–34 J cm −3 ) and work output (30–35 J cm −3 ), which were attributed to the ability to operate at high stress levels without significant plastic deformation and to a high mechanical hysteresis (>900 MPa) at temperatures ranging from 20 °C to 80 °C

  5. Computational design of precipitation-strengthened titanium-nickel-based shape memory alloys

    Science.gov (United States)

    Bender, Matthew D.

    Motivated by performance requirements of future medical stent applications, experimental research addresses the design of novel TiNi-based, superelastic shape-memory alloys employing nanoscale precipitation strengthening to minimize accommodation slip for cyclic stability and to increase output stress capability for smaller devices. Using a thermodynamic database describing the B2 and L21 phases in the Al-Ni-Ti-Zr system, Thermo-Calc software was used to assist modeling the evolution of phase composition during 600°C isothermal evolution of coherent L21 Heusler phase precipitation from supersaturated TiNi-based B2 phase matrix in an alloy experimentally characterized by atomic-scale Local Electrode Atom Probe (LEAP) microanalysis. Based on measured evolution of the alloy hardness (under conditions stable against martensitic transformation) a model for the combined effects of solid solution strengthening and precipitation strengthening was calibrated, and the optimum particle size for efficient strengthening was identified. Thermodynamic modeling of the evolution of measured phase fractions and compositions identified the interfacial capillary energy enabling thermodynamic design of alloy microstructure with the optimal strengthening particle size. Extension of alloy designs to incorporate Pt and Pd for reducing Ni content, enhancing radiopacity, and improving manufacturability were considered using measured Pt and Pd B2/L2 1 partitioning coefficients. After determining that Pt partitioning greatly increases interphase misfit, full attention was devoted to Pd alloy designs. A quantitative approach to radiopacity was employed using mass attenuation as a metric. Radiopacity improvements were also qualitatively observed using x-ray fluoroscopy. Transformation temperatures were experimentally measured as a function of Al and Pd content. Redlich-Kister polynomial modeling was utilized for the dependence of transformation reversion Af temperature on B2 matrix phase

  6. Biocompatibility of nanoactuators: stem cell growth on laser-generated nickel-titanium shape memory alloy nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Barcikowski, Stephan, E-mail: s.barcikowski@lzh.de; Hahn, Anne [Laser Zentrum Hannover e.V. (Germany); Guggenheim, Merlin; Reimers, Kerstin [Medical School Hannover, Department of Plastic, Hand and Reconstructive Surgery (Germany); Ostendorf, Andreas [Laser Zentrum Hannover e.V. (Germany)

    2010-06-15

    Nanoactuators made from nanoparticulate NiTi shape memory alloy show potential in the mechanical stimulation of bone tissue formation from stem cells. We demonstrate the fabrication of Ni, Ti, and NiTi shape memory alloy nanoparticles and their biocompatibility to human adipose-derived stem cells. The stoichiometry and phase transformation property of the bulk alloy is preserved during attrition by femtosecond laser ablation in liquid, giving access to colloidal nanoactuators. No adverse effect on cell growth and attachment is observed in proliferation assay and environmental electron scanning microscopy, making this material attractive for mechanical stimulation of stem cells.

  7. Biocompatibility of nanoactuators: stem cell growth on laser-generated nickel-titanium shape memory alloy nanoparticles

    Science.gov (United States)

    Barcikowski, Stephan; Hahn, Anne; Guggenheim, Merlin; Reimers, Kerstin; Ostendorf, Andreas

    2010-06-01

    Nanoactuators made from nanoparticulate NiTi shape memory alloy show potential in the mechanical stimulation of bone tissue formation from stem cells. We demonstrate the fabrication of Ni, Ti, and NiTi shape memory alloy nanoparticles and their biocompatibility to human adipose-derived stem cells. The stoichiometry and phase transformation property of the bulk alloy is preserved during attrition by femtosecond laser ablation in liquid, giving access to colloidal nanoactuators. No adverse effect on cell growth and attachment is observed in proliferation assay and environmental electron scanning microscopy, making this material attractive for mechanical stimulation of stem cells.

  8. In Situ Neutron Diffraction Study of NiTi-21Pt High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Benafan, O.; Gaydosh, D. J.; Noebe, R. D.; Qiu, S.; Vaidyanathan, R.

    2016-12-01

    In situ neutron diffraction was used to investigate the microstructural features of stoichiometric and Ti-rich NiTiPt high-temperature shape memory alloys with target compositions of Ni29Ti50Pt21 and Ni28.5Ti50.5Pt21 (in atomic percent), respectively. The alloys' isothermal and thermomechanical properties (i.e., moduli, thermal expansion, transformation strains, and dimensional stability) were correlated to the lattice strains, volume-averaged elastic moduli, and textures as determined by neutron diffraction. In addition, the unique aspects of this technique when applied to martensitic transformations in shape memory alloys are highlighted throughout the paper.

  9. Studies on nonvolatile resistance memory switching in ZnO thin films

    Indian Academy of Sciences (India)

    Six decades of research on ZnO has recently sprouted a new branch in the domain of resistive random access memories. Highly resistive and c-axis oriented ZnO thin films were grown by us using d.c. discharge assisted pulsed laser deposition on Pt/Ti/SiO2/Si substrates at room temperature. The resistive switching ...

  10. Ferroelectric Thin Films Basic Properties and Device Physics for Memory Applications

    CERN Document Server

    Okuyama, Masanori

    2005-01-01

    Ferroelectric thin films continue to attract much attention due to their developing, diverse applications in memory devices, FeRAM, infrared sensors, piezoelectric sensors and actuators. This book, aimed at students, researchers and developers, gives detailed information about the basic properties of these materials and the associated device physics. All authors are acknowledged experts in the field.

  11. Formation of Ti-Ta-based surface alloy on TiNi SMA substrate from thin films by pulsed electron-beam melting

    Science.gov (United States)

    Meisner, L. L.; Markov, A. B.; Ozur, G. E.; Rotshtein, V. P.; Yakovlev, E. V.; Meisner, S. N.; Poletika, T. M.; Girsova, S. L.; Semin, V. O.; Mironov, Yu P.

    2017-05-01

    TiNi shape memory alloys (SMAs) are unique metallic biomaterials due to combination of superelastisity and high corrosion resistance. Important factors limiting biomedical applications of TiNi SMAs are a danger of toxic Ni release into the adjacent tissues, as well as insufficient level of X-ray visibility. In this paper, the method for fabrication of protective Ni-free surface alloy of thickness ∼1 μm of near Ti70Ta30 composition on TiNi SMA substrate has been successfully realized. The method is based on multiple alternation of magnetron co-deposition of Ti70Ta30 thin (50 nm) films and their liquid-phase mixing with the TiNi substrate by microsecond low-energy, high current electron beam (≤15 keV, ∼2 J/cm2) using setup RITM-SP (Microsplav, Russia). It was found by AES, XRD, SEM/EDS and HRTEM/EDS examinations, that Ti-Ta surface alloy has an increased X-ray visibility and gradient multiphase amorphous-nanocrystalline structure containing nanopores.

  12. Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

    International Nuclear Information System (INIS)

    Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

    2015-01-01

    Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications

  13. Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Czarnowska, Elżbieta [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Borowski, Tomasz [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Sowińska, Agnieszka [Children' s Memorial Health Institute, Pathology Department, Al. Dzieci Polskich 20, 04-730 Warsaw (Poland); Lelątko, Józef [Silesia University, Faculty of Computer Science and Materials Science, 75 Pułku Piechoty 1A, 41-500 Chorzów (Poland); Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland); Wierzchoń, Tadeusz, E-mail: twierz@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska 141, 02-507 Warsaw (Poland)

    2015-04-15

    Highlights: • Low temperature plasma nitriding process of NiTi shape memory alloy is presented. • The possibility of treatment details of sophisticated shape. • TiN surface layer has diffusive character. • TiN surface layer increases corrosion resistance of NiTi alloy. • Produced TiN layer modify the biological properties of NiTi alloy. - Abstract: NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

  14. Texture development and anisotropic behaviour of a TI-44.2NI4.9CU (AT.%) shape memory alloy

    NARCIS (Netherlands)

    Zhao, L.

    1997-01-01

    The objective of this work was to determine the relationship between texture development and anisotropy of shape memory properties. A commercial Ti-45Ni-5Cu (at.%) shape memory alloy was selected. Textures were developed by controlling rolling parameters, such as rolling temperature, intermediate

  15. A review on shape memory alloys with applications to morphing aircraft

    Science.gov (United States)

    Barbarino, S.; Saavedra Flores, E. I.; Ajaj, R. M.; Dayyani, I.; Friswell, M. I.

    2014-06-01

    Shape memory alloys (SMAs) are a unique class of metallic materials with the ability to recover their original shape at certain characteristic temperatures (shape memory effect), even under high applied loads and large inelastic deformations, or to undergo large strains without plastic deformation or failure (super-elasticity). In this review, we describe the main features of SMAs, their constitutive models and their properties. We also review the fatigue behavior of SMAs and some methods adopted to remove or reduce its undesirable effects. SMAs have been used in a wide variety of applications in different fields. In this review, we focus on the use of shape memory alloys in the context of morphing aircraft, with particular emphasis on variable twist and camber, and also on actuation bandwidth and reduction of power consumption. These applications prove particularly challenging because novel configurations are adopted to maximize integration and effectiveness of SMAs, which play the role of an actuator (using the shape memory effect), often combined with structural, load-carrying capabilities. Iterative and multi-disciplinary modeling is therefore necessary due to the fluid-structure interaction combined with the nonlinear behavior of SMAs.

  16. A review on shape memory alloys with applications to morphing aircraft

    International Nuclear Information System (INIS)

    Barbarino, S; Saavedra Flores, E I; Ajaj, R M; Dayyani, I; Friswell, M I

    2014-01-01

    Shape memory alloys (SMAs) are a unique class of metallic materials with the ability to recover their original shape at certain characteristic temperatures (shape memory effect), even under high applied loads and large inelastic deformations, or to undergo large strains without plastic deformation or failure (super-elasticity). In this review, we describe the main features of SMAs, their constitutive models and their properties. We also review the fatigue behavior of SMAs and some methods adopted to remove or reduce its undesirable effects. SMAs have been used in a wide variety of applications in different fields. In this review, we focus on the use of shape memory alloys in the context of morphing aircraft, with particular emphasis on variable twist and camber, and also on actuation bandwidth and reduction of power consumption. These applications prove particularly challenging because novel configurations are adopted to maximize integration and effectiveness of SMAs, which play the role of an actuator (using the shape memory effect), often combined with structural, load-carrying capabilities. Iterative and multi-disciplinary modeling is therefore necessary due to the fluid–structure interaction combined with the nonlinear behavior of SMAs. (topical review)

  17. Alloying process of sputter-deposited Ti/Ni multilayer thin films

    International Nuclear Information System (INIS)

    Cho, H.; Kim, H.Y.; Miyazaki, S.

    2006-01-01

    Alloying process of a Ti/Ni multilayer thin film was investigated in detail by differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The Ti/Ni multilayer thin film was prepared by depositing Ti and Ni layers alternately on a SiO 2 /Si substrate. The number of each metal layer was 100, and the total thickness was 3 μm. The alloy composition was determined as Ti-51 at.%Ni by electron probe micro analysis (EPMA). The DSC curve exhibited three exothermic peaks at 621, 680 and 701 K during heating the as-sputtered multilayer thin film. In order to investigate the alloying process, XRD and TEM observation was carried out for the specimens heated up to various temperatures with the heating rate same as the DSC measurement. The XRD profile of the as-sputtered film revealed only diffraction peaks of Ti and Ni. But reaction layers of 3 nm in thickness were observed at the interfaces of Ti and Ni layers in cross-sectional TEM images. The reaction layer was confirmed as an amorphous phase by the nano beam diffraction analysis. The XRD profiles exhibited that the intensity of Ti diffraction peak decreased in the specimen heat-treated above 600 K. The peak from Ni became broad and shifted to lower diffraction angle. The amorphous layer thickened up to 6 nm in the specimen heated up to 640 K. The diffraction peak corresponding to Ti-Ni B2 phase appeared and the peak from Ni disappeared for the specimen heated up to 675 K. The Ti-Ni B2 crystallized from the amorphous reaction layer. After further heating above the third exothermic peak, the intensity of the peak from the Ti-Ni B2 phase increased, the peak from Ti disappeared and the peaks corresponding to Ti 2 Ni appeared. The Ti 2 Ni phase was formed by the reaction of the Ti-Ni B2 and Ti

  18. Experimental Studies on Dynamic Vibration Absorber using Shape Memory Alloy (NiTi) Springs

    International Nuclear Information System (INIS)

    Kumar, V. Raj; Kumar, M. B. Bharathi Raj; Kumar, M. Senthil

    2011-01-01

    Shape memory alloy (SMA) springs have been used as actuators in many applications although their use in the vibration control area is very recent. Since shape memory alloys differ from conventional alloy materials in many ways, the traditional design approach for springs is not completely suitable for designing SMA springs. Some vibration control concepts utilizing unique characteristics of SMA's will be presented in this paper.A dynamic vibration absorber (DVA) using shape memory alloy (SMA) actuator is developed for attenuation of vibration in a cantilever beam. The design procedure of the DVA is presented. The system consists of a cantilever beam which is considered to generate the real-time vibration using shaker. A SMA spring is used with a mass attached to its end. The stiffness of the SMA spring is dynamically varied in such a way to attenuate the vibration. Both simulation and experimentation are carried out using PID controller. The experiments were carried out by interfacing the experimental setup with a computer using LabVIEW software, Data acquisition and control are implemented using a PCI data acquisition card. Standard PID controllers have been used to control the vibration of the beam. Experimental results are used to demonstrate the effectiveness of the controllers designed and the usefulness of the proposed test platform by exciting the structure at resonance. In experimental setup, an accelerometer is used to measure the vibration which is fed to computer and correspondingly the SMA spring is actuated to change its stiffness to control the vibration. The results obtained illustrate that the developed DVA using SMA actuator is very effective in reducing structural response and have great potential to be an active vibration control medium.

  19. Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Yamabe-Mitarai, Yoko; Takebe, Wataru; Shimojo, Masayuki

    2017-12-01

    To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti-(50 - x)Pt- xPd-5Zr alloys ( x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti-50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was < 1% and a large irrecoverable strain was obtained. The shape recovery was explained by the austenite strength. The training effect was also investigated.

  20. Thermal processing of polycrystalline NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Frick, Carl P.; Ortega, Alicia M.; Tyber, Jeffrey; Maksound, A.El.M.; Maier, Hans J.; Liu Yinong; Gall, Ken

    2005-01-01

    The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.% Ni in hot-rolled and cold-drawn states. In particular, we examine microstructure, transformation temperatures as well as mechanical behavior in terms of both uniaxial monotonic testing and instrumented Vickers micro-indentation. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress-induced martensite and resistance to plastic flow in NiTi, all of which are critical for optimizing the mechanical properties. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. The subsequent cold-drawing-induced a high density of dislocations and martensite. Heat treatments were carried out on hot-rolled, as well as, hot-rolled then cold-drawn materials at various temperatures for 1.5 h. Transmission Electron Microscopy observations revealed that Ti 3 Ni 4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti 3 Ni 4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi. Instrumented micro-indention tests revealed that Martens (Universal) Hardness values are more dependent on the resistance to dislocation

  1. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen......Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...

  2. InAs quantum dot morphology after capping with In, N, Sb alloyed thin films

    Energy Technology Data Exchange (ETDEWEB)

    Keizer, J. G.; Koenraad, P. M. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, NL-5600 MB Eindhoven (Netherlands); Ulloa, J. M.; Utrilla, A. D. [Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politecnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2014-02-03

    Using a thin capping layer to engineer the structural and optical properties of InAs/GaAs quantum dots (QDs) has become common practice in the last decade. Traditionally, the main parameter considered has been the strain in the QD/capping layer system. With the advent of more exotic alloys, it has become clear that other mechanisms significantly alter the QD size and shape as well. Larger bond strengths, surfactants, and phase separation are known to act on QD properties but are far from being fully understood. In this study, we investigate at the atomic scale the influence of these effects on the morphology of capped QDs with cross-sectional scanning tunneling microscopy. A broad range of capping materials (InGaAs, GaAsSb, GaAsN, InGaAsN, and GaAsSbN) are compared. The QD morphology is related to photoluminescence characteristics.

  3. Fabrication of Si3N4 thin films on phynox alloy substrates for electronic applications

    Science.gov (United States)

    Shankernath, V.; Naidu, K. Lakshun; Krishna, M. Ghanashyam; Padmanabhan, K. A.

    2018-04-01

    Thin films of Si3N4 are deposited on Phynox alloy substrates using radio frequency magnetron sputtering. The thickness of the films was varied between 80-150 nm by increasing the duration of deposition from 1 to 3 h at a fixed power density and working pressure. X-ray diffraction patterns reveal that the Si3N4 films had crystallized inspite of the substrates not being heated during deposition. This was confirmed using selected area electron diffraction and high resolution transmission electron microscopy also. It is postulated that a low lattice misfit between Si3N4 and Phynox provides energetically favourable conditions for ambient temperature crystallization. The hardness of the films is of the order of 6 to 9 GPa.

  4. Coercivity of domain wall motion in thin films of amorphous rare earth-transition metal alloys

    Science.gov (United States)

    Mansuripur, M.; Giles, R. C.; Patterson, G.

    1991-01-01

    Computer simulations of a two dimensional lattice of magnetic dipoles are performed on the Connection Machine. The lattice is a discrete model for thin films of amorphous rare-earth transition metal alloys, which have application as the storage media in erasable optical data storage systems. In these simulations, the dipoles follow the dynamic Landau-Lifshitz-Gilbert equation under the influence of an effective field arising from local anisotropy, near-neighbor exchange, classical dipole-dipole interactions, and an externally applied field. Various sources of coercivity, such as defects and/or inhomogeneities in the lattice, are introduced and the subsequent motion of domain walls in response to external fields is investigated.

  5. The role of memory in the relationship between attention toward thin-ideal media and body dissatisfaction.

    Science.gov (United States)

    Jiang, Michelle Y W; Vartanian, Lenny R

    2016-03-01

    This study examined the causal relationship between attention and memory bias toward thin-body images, and the indirect effect of attending to thin-body images on women's body dissatisfaction via memory. In a 2 (restrained vs. unrestrained eaters) × 2 (long vs. short exposure) quasi-experimental design, female participants (n = 90) were shown images of thin models for either 7 s or 150 ms, and then completed a measure of body dissatisfaction and a recognition test to assess their memory for the images. Both restrained and unrestrained eaters in the long exposure condition had better recognition memory for images of thin models than did those in the short exposure condition. Better recognition memory for images of thin models was associated with lower body dissatisfaction. Finally, exposure duration to images of thin models had an indirect effect on body dissatisfaction through recognition memory. These findings suggest that memory for body-related information may be more critical in influencing women's body image than merely the exposure itself, and that targeting memory bias might enhance the effectiveness of cognitive bias modification programs.

  6. Effects of Palladium Content, Quaternary Alloying, and Thermomechanical Processing on the Behavior of Ni-Ti-Pd Shape Memory Alloys for Actuator Applications

    Science.gov (United States)

    Bigelow, Glen

    2008-01-01

    The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently driving research in high-temperature shape memory alloys (HTSMA) having transformation temperatures above 100 C. One of the basic high temperature systems under investigation to fill this need is NiTiPd. Prior work on this alloy system has focused on phase transformations and respective temperatures, no-load shape memory behavior (strain recovery), and tensile behavior for selected alloys. In addition, a few tests have been done to determine the effect of boron additions and thermomechanical treatment on the aforementioned properties. The main properties that affect the performance of a solid state actuator, namely work output, transformation strain, and permanent deformation during thermal cycling under load have mainly been neglected. There is also no consistent data representing the mechanical behavior of this alloy system over a broad range of compositions. For this thesis, ternary NiTiPd alloys containing 15 to 46 at.% palladium were processed and the transformation temperatures, basic tensile properties, and work characteristics determined. However, testing reveals that at higher levels of alloying addition, the benefit of increased transformation temperature begins to be offset by lowered work output and permanent deformation or "walking" of the alloy during thermal cycling under load. In response to this dilemma, NiTiPd alloys have been further alloyed with gold, platinum, and hafnium additions to solid solution strengthen the martensite and parent austenite phases in order to improve the thermomechanical behavior of these materials. The tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared and discussed. In addition, the benefits of more advanced thermomechanical processing or training on the dimensional stability of

  7. Study of Ti-Ni-Nb shape memory alloys with a wide hysteresis

    International Nuclear Information System (INIS)

    Zhao, L.C.

    2000-01-01

    It has been shown that TiNiNb shape memory alloys exhibit a wide transformation hysteresis compared to TiNi binary alloys (about 145 C versus 30 C). This wide hysteresis has important engineering utility. The present paper was undertaken to review of the microstructure, mechanical behavior, deformation-induced martensitic transformation and the effect of deformation on the stability of martensite and its reverse transformation in TiNiNb alloys. Simultaneously, the strain recovery characteristic and interface structure of martensite were explained, and the mechanism for increasing martensite stability by deformation was discussed. In addition, the microstructure and interface structure inside the stress-induced martensite (SIM) variants were evaluated. It is found that the morphology and substructure of SIM depend on deformation condition. The tensile deformation at parent phase condition has great influence on the substructure and interface structure of SIM variants. The most distinctive substructural feature of the stress-induced martensite is the presence of the various secondary twins. Based on the analysis of the stability and shape memory effect of various kinds of martensite, the concept of stability of deformed stress-induced martensite was proposed and explained by the mechanism for the formation of several secondary deformation twins. (orig.)

  8. Gating System Design for Casting thin Aluminium Alloy (Al-Si Plates

    Directory of Open Access Journals (Sweden)

    Victor ANJO

    2013-11-01

    Full Text Available The main problems caused by improper gating are entrained aluminium oxide films, cuts and washes, low casting yield and entrapped gas. This study describes the design of a gating system to produce thin Aluminium cast alloy plates of different sizes and thicknesses of 4mm, 6mm, 8mm, and 10mm using the non-pressurized gating with ratio of 1:4:4 and green sand moulding technique. The gating design was based on the laws of fluid mechanics and empirical rules of gating for non ferrous metals. The equipments used for this experiment includes; a coal fired crucible furnace and an X-Ray machine. Materials used include; silica sand, clay, wood, glue and Aluminium alloy scraps. The experimental procedure involved: the gating design calculations, construction of wooden pattern and gating; using the wooden pattern and gating to produce the mould cavities and gating; melting, melt treatment and pouring of melt in the sand mould to produce the casting. The plate castings after removal from mould were visually examined for surface defects and after fettling and cleaning X-Ray radiography was used to find the internal soundness of the castings. From the results obtained in the experiment, it was found that there were no internal defects and quality castings were produced.

  9. Laser-induced diffusion decomposition in Fe–V thin-film alloys

    Energy Technology Data Exchange (ETDEWEB)

    Polushkin, N.I., E-mail: nipolushkin@fc.ul.pt [Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa (Portugal); Instituto de Ciência e Engenharia de Materiais e Superfícies, 1049-001 Lisboa (Portugal); Duarte, A.C.; Conde, O. [Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa (Portugal); Instituto de Ciência e Engenharia de Materiais e Superfícies, 1049-001 Lisboa (Portugal); Alves, E. [Associação Euratom/IST e Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa (Portugal); Barradas, N.P. [Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela LRS (Portugal); García-García, A.; Kakazei, G.N.; Ventura, J.O.; Araujo, J.P. [Departamento de Física, Universidade do Porto e IFIMUP, 4169-007 Porto (Portugal); Oliveira, V. [Instituto de Ciência e Engenharia de Materiais e Superfícies, 1049-001 Lisboa (Portugal); Instituto Superior de Engenharia de Lisboa, 1959-007 Lisboa (Portugal); Vilar, R. [Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa (Portugal); Instituto de Ciência e Engenharia de Materiais e Superfícies, 1049-001 Lisboa (Portugal)

    2015-05-01

    Highlights: • Irradiation of an Fe–V alloy by femtosecond laser triggers diffusion decomposition. • The decomposition occurs with strongly enhanced (∼4 orders) atomic diffusivity. • This anomaly is associated with the metallic glassy state achievable under laser quenching. • The ultrafast diffusion decomposition is responsible for laser-induced ferromagnetism. - Abstract: We investigate the origin of ferromagnetism induced in thin-film (∼20 nm) Fe–V alloys by their irradiation with subpicosecond laser pulses. We find with Rutherford backscattering that the magnetic modifications follow a thermally stimulated process of diffusion decomposition, with formation of a-few-nm-thick Fe enriched layer inside the film. Surprisingly, similar transformations in the samples were also found after their long-time (∼10{sup 3} s) thermal annealing. However, the laser action provides much higher diffusion coefficients (∼4 orders of magnitude) than those obtained under standard heat treatments. We get a hint that this ultrafast diffusion decomposition occurs in the metallic glassy state achievable in laser-quenched samples. This vitrification is thought to be a prerequisite for the laser-induced onset of ferromagnetism that we observe.

  10. Enhanced photomechanical response of a Ni-Ti shape memory alloy coated with polymer-based photothermal composites

    Science.gov (United States)

    Perez-Zúñiga, M. G.; Sánchez-Arévalo, F. M.; Hernández-Cordero, J.

    2017-10-01

    A simple way to enhance the activation of shape memory effects with light in a Ni-Ti alloy is demonstrated. Using polydimethylsiloxane-carbon nanopowder (PDMS+CNP) composites as coatings, the one-way shape memory effect (OWSME) of the alloy can be triggered using low power IR light from a laser diode. The PDMS+CNP coatings serve as photothermal materials capable to absorb light, and subsequently generate and dissipate heat in a highly efficient manner, thereby reducing the optical powers required for triggering the OWSME in the Ni-Ti alloy. Experimental results with a cantilever flexural test using both, bare Ni-Ti and coated samples, show that the PDMS+CNP coatings perform as thermal boosters, and therefore the temperatures required for phase transformation in the alloy can be readily obtained with low laser powers. It is also shown that the two-way shape memory effect (TWSME) can be set in the Ni-Ti alloy through cycling the TWSME by simply modulating the laser diode signal. This provides a simple means for training the material, yielding a light driven actuator capable to provide forces in the mN range. Hence, the use of photothermal coatings on Ni-Ti shape memory alloys may offer new possibilities for developing light-controlled smart actuators.

  11. Functional Performances of CuZnAl Shape Memory Alloy Open-Cell Foams

    Science.gov (United States)

    Biffi, C. A.; Casati, R.; Bassani, P.; Tuissi, A.

    2018-01-01

    Shape memory alloys (SMAs) with cellular structure offer a unique mixture of thermo-physical-mechanical properties. These characteristics can be tuned by changing the pore size and make the shape memory metallic foams very attractive for developing new devices for structural and functional applications. In this work, CuZnAl SMA foams were produced through the liquid infiltration of space holder method. In comparison, a conventional CuZn brass alloy was foamed trough the same method. Functional performances were studied on both bulk and foamed SMA specimens. Calorimetric response shows similar martensitic transformation (MT) below 0 °C. Compressive response of CuZnAl revealed that mechanical behavior is strongly affected by sample morphology and that damping capacity of metallic foam is increased above the MT temperatures. The shape memory effect was detected in the CuZnAl foams. The conventional brass shows a compressive response similar to that of the martensitic CuZnAl, in which plastic deformation accumulation occurs up to the cellular structure densification after few thermal cycles.

  12. A Constitutive Model for Superelastic Shape Memory Alloys Considering the Influence of Strain Rate

    Directory of Open Access Journals (Sweden)

    Hui Qian

    2013-01-01

    Full Text Available Shape memory alloys (SMAs are a relatively new class of functional materials, exhibiting special thermomechanical behaviors, such as shape memory effect and superelasticity, which enable their applications in seismic engineering as energy dissipation devices. This paper investigates the properties of superelastic NiTi shape memory alloys, emphasizing the influence of strain rate on superelastic behavior under various strain amplitudes by cyclic tensile tests. A novel constitutive equation based on Graesser and Cozzarelli’s model is proposed to describe the strain-rate-dependent hysteretic behavior of superelastic SMAs at different strain levels. A stress variable including the influence of strain rate is introduced into Graesser and Cozzarelli’s model. To verify the effectiveness of the proposed constitutive equation, experiments on superelastic NiTi wires with different strain rates and strain levels are conducted. Numerical simulation results based on the proposed constitutive equation and experimental results are in good agreement. The findings in this paper will assist the future design of superelastic SMA-based energy dissipation devices for seismic protection of structures.

  13. Sign reversal of transformation entropy change in Co2Cr(Ga,Si) shape memory alloys

    International Nuclear Information System (INIS)

    Xu, Xiao; Omori, Toshihiro; Kainuma, Ryosuke; Nagasako, Makoto; Kanomata, Takeshi

    2015-01-01

    In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co 2 Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy

  14. Seismic performance assessment of knee bracing equipped with shape memory alloys

    Directory of Open Access Journals (Sweden)

    Mussa Mahmoudi

    2016-09-01

    Full Text Available According to current seismic design codes, the serviceability of the building is not necessary after the sever earthquakes but the life safety is important. It is caused to reduce the cost of construction. In recent years, the researchers have proposed the new methods and materials to improve the purposes of seismic design and to reduce the cost of construction. For example, the use of materials such as shape memory alloys (SMA with high elastic property and low residual strain was suggested. In this study the use of these alloys is evaluated for steel knee bracing. The result showed that the structures with SMA remain survival during the sever earthquakes with low retrofitting.

  15. An informatics approach to transformation temperatures of NiTi-based shape memory alloys

    International Nuclear Information System (INIS)

    Xue, Dezhen; Xue, Deqing; Yuan, Ruihao; Zhou, Yumei; Balachandran, Prasanna V.; Ding, Xiangdong; Sun, Jun; Lookman, Turab

    2017-01-01

    The martensitic transformation serves as the basis for applications of shape memory alloys (SMAs). The ability to make rapid and accurate predictions of the transformation temperature of SMAs is therefore of much practical importance. In this study, we demonstrate that a statistical learning approach using three features or material descriptors related to the chemical bonding and atomic radii of the elements in the alloys, provides a means to predict transformation temperatures. Together with an adaptive design framework, we show that iteratively learning and improving the statistical model can accelerate the search for SMAs with targeted transformation temperatures. The possible mechanisms underlying the dependence of the transformation temperature on these features is discussed based on a Landau-type phenomenological model.

  16. Study on properties of stress relaxation for NiTiNb shape memory alloy

    International Nuclear Information System (INIS)

    Zhou Xuchang; Mo Huaqiang; Zeng Guangting; Shen Baoluo; Huo Yongzhong

    2002-01-01

    Stress relaxation tests at high temperature are performed for NiTiNb shape memory alloy to obtain the properties of stress relaxation. The relaxation curve fitted with the expression, which is deduced based on the relation between the relaxation and the creep. With the aid of experimental data, relaxation characteristic coefficient and remaining stress ratio are obtained, which characterize the relaxation behavior. The results of the study show that stress relaxation would be more evident with the higher temperature and/or greater initial stress. NiTiNb alloy has good relaxation resistance in the temperature range 300-400 degree C and the initial stress range 260-360 MPa. NiTiNb has better properties to resist relaxation than NiTiFe, therefore it is more applicable to work at high temperature

  17. Effect of grain size on superelasticity in Fe-Mn-Al-Ni shape memory alloy wire

    Directory of Open Access Journals (Sweden)

    T. Omori

    2013-09-01

    Full Text Available Effects of grain size on superelastic properties in Fe-34Mn-15Al-7.5Ni alloy wires with a ⟨110⟩ fiber-texture were investigated by cyclic tensile tests. It was confirmed that the critical stress for induced martensitic transformation and the superelastic strain are functions of relative grain size d/D (d: mean grain diameter, D: wire diameter, and that the critical stress is proportional to (1–d/D2 as well as in Cu-based shape memory alloys. A large superelastic strain of about 5% was obtained in the specimen with a large relative grain size over d/D = 1.

  18. Modelling and experimental investigation of geometrically graded NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Shariat, Bashir S; Liu, Yinong; Rio, Gerard

    2013-01-01

    To improve actuation controllability of a NiTi shape memory alloy component in applications, it is desirable to create a wide stress window for the stress-induced martensitic transformation in the alloy. One approach is to create functionally graded NiTi with a geometric gradient in the actuation direction. This geometric gradient leads to transformation load and displacement gradients in the structure. This paper reports a study of the pseudoelastic behaviour of geometrically graded NiTi by means of mechanical model analysis and experimentation using three types of sample geometry. Closed-form solutions are obtained for nominal stress–strain variation of such components under cyclic tensile loading and the predictions are validated with experimental data. The geometrically graded NiTi samples exhibit a distinctive positive stress gradient for the stress-induced martensitic transformation and the slope of the stress gradient can be adjusted by sample geometry design. (paper)

  19. Preparation and evaluation of ageing effect of Cu-Al-Be-Mn shape memory alloys

    Science.gov (United States)

    Shivasiddaramaiah, A. G.; Mallik, U. S.; Mahato, Ranjit; Shashishekar, C.

    2018-04-01

    10-14 wt. % of aluminum, 0.3-0.6 wt. % of beryllium and 0.1-0.4 wt. % of manganese and remaining copper melted in the induction furnace through ingot metallurgy. The prepared SMAs are subjected to homogenization. It was observed that the samples exhibits β-phase at high temperature and shape memory effect after going through step quenching to a low temperature. Scanning Electron Microscope, DSC, bending test were performed on the samples to determine the microstructure, transformation temperatures and shape memory effect respectively. The alloy exhibit good shape memory effect, up to around 96% strain recovery by shape memory effect. The ageing is performed on the specimen prepared according to ASTM standard for testing micro-hardness and tensile test. Precipitation hardening method was employed to age the samples and they were aged at different temperature and at different times followed by quenching. Various forms of precipitates were formed. It was found that the formation rate and transformation temperature increased with ageing time, while the amount of precipitate had an inverse impact on strain recovery by shape memory effect. The result expected is to increase in mechanical properties of the material such as hardness.

  20. Resonant ultrasound spectroscopy - a tool to probe magneto-elastic properties of ferromagnetic shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Seiner, Hanuš; Sedlák, Petr; Kopeček, Jaromír; Kopecký, Vít; Landa, Michal

    2013-01-01

    Roč. 86, č. 2 (2013), s. 1-5 ISSN 1434-6028 R&D Projects: GA ČR(CZ) GA101/09/0702; GA ČR GAP107/10/0824; GA ČR(CZ) GAP107/11/0391 Institutional support: RVO:68378271 ; RVO:61388998 Keywords : elastic properties of ferromagnetic martensite * ferromagnetic shape memory alloys * Resonant ultrasound spectroscopy * Ni-Mn-Ga Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.463, year: 2013

  1. Magnetic Shape Memory Alloys as smart materials for micro-positioning devices

    Directory of Open Access Journals (Sweden)

    A. Hubert

    2012-10-01

    Full Text Available In the field of microrobotics, actuators based on smart materials are predominant because of very good precision, integration capabilities and high compactness. This paper presents the main characteristics of Magnetic Shape Memory Alloys as new candidates for the design of micromechatronic devices. The thermo-magneto-mechanical energy conversion process is first presented followed by the adequate modeling procedure required to design actuators. Finally, some actuators prototypes realized at the Femto-ST institute are presented, including a push-pull bidirectional actuator. Some results on the control and performances of these devices conclude the paper.

  2. Oxidation behavior of TiNi shape memory alloy at 450-750 deg. C

    International Nuclear Information System (INIS)

    Xu, C.H.; Ma, X.Q.; Shi, S.Q.; Woo, C.H.

    2004-01-01

    The isothermal oxidation behavior of a commercial TiNi shape memory alloy (SMA) in pure oxygen over the temperature range of 450-750 deg. C was studied. The oxidation products were identified by X-ray diffraction (XRD). Characterization of the specimens after oxidation was conducted using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The oxidation kinetics at different temperature was studied, according to parabolic and logarithmic laws. The mechanism and activation energy of oxidation were discussed based on the oxidation kinetics. The spallation of the multi-layer scale formed during oxidation was analyzed by growth induced thermal stresses

  3. X-ray diffraction studies of NiTi shape memory alloys

    OpenAIRE

    E. Łągiewka; Z. Lekston

    2007-01-01

    Purpose: The purpose of this paper is to present the results of the investigations of phase transitions of TiNiCo and Ni-rich NiTi shape memory alloys designed for medical applications.Design/methodology/approach: Temperature X-ray diffraction (TXRD), differential scanning calorimetry (DSC), electrical resistivity (ER) and the temperature shape recovery measurements in three-point bending ASTM 2082-01 tests were used.Findings: It has been found in this work that ageing after solution treatme...

  4. Martensitic transformation in nanostructured TiNi shape memory alloy formed via severe plastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, K. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan)]. E-mail: tsuchiya@pse.tut.ac.jp; Inuzuka, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Tomus, D. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Hosokawa, A. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Nakayama, H. [Department of Mechanical Engineering, University of Washington (United States); Morii, K. [Research and Development Laboratory, Daido Steel, Co., Ltd. (Japan); Todaka, Y. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan); Umemoto, M. [Department of Production Systems Engineering, Toyohashi University of Technology (Japan)

    2006-11-25

    Martensitic transformation and mechanical behavior was investigated on TiNi shape memory alloy subjected to severe plastic deformation by cold rolling. Transmission electron microscopy revealed the sample to be a mixture of nanocrystalline and amorphous material after 40% cold rolling. Diffrential scaning calorimetry measurements and X-ray diffractometry suggested that the martensitic transformation was suppressed when the thickness reduction was over 25%. The pseudoelastic stress-strain curves of nanocrystalline/amorphous TiNi are characterized by the absence of a stress-plateau and by small hysteresis.

  5. Internal stresses in steel plate generated by shape memory alloy inserts

    Czech Academy of Sciences Publication Activity Database

    Malard, B.; Pilch, Jan; Šittner, Petr; Davydov, V.; Sedlák, Petr; Konstantinidis, K.; Hughes, D. J.

    2012-01-01

    Roč. 60, č. 3 (2012), s. 1378-1394 ISSN 1359-6454 R&D Projects: GA ČR GAP108/10/1296 Grant - others:SMARTNETS(XE) FP7-NMP2-2011-262806 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20760514 Keywords : shape memory alloy * NiTi * residual stress * neutron diffraction * strain scanning Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.941, year: 2012 http://www.sciencedirect.com/science/article/pii/S1359645411007294

  6. Thermomechanical behavior of an Fe-based shape memory alloy: transformation conditions and hystereses

    International Nuclear Information System (INIS)

    Tanaka, K.; Nishimura, F.; Tobushi, H.; Oberaigner, E.R.; Fischer, F.D.

    1995-01-01

    Transformation/thermomechanical behavior in an Fe-9%Cr-5%Ni-14%Mn-6%Si polycrystalline shape memory alloy during thermomechanical loading is investigated. The transformation lines in the stress-temperature plane are strongly influenced by the parameters characterizing the thermomechanical loading. The transformation start condition, the martensite start stress and the austenite start temperature, is carefully measured to compare the results with the other experimental and theoretical observations. The stress-strain-temperature hysteresis loops, full and sub, are determined during cyclic loading. (orig.)

  7. Electron energy-loss spectroscopy study of NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Yang, Z.Q.; Schryvers, D.

    2008-01-01

    Electron energy loss spectroscopy (EELS) investigations were carried out on NiTi shape memory alloys. The composition of lens-shaped precipitates is determined to be Ni 4 Ti 3 by model-based EELS quantification, and the Ni-depleted zone in the B2 matrix surrounding the Ni 4 Ti 3 precipitates was quantified. The Young's modulus Y m of the B2 matrix with 51 at.% Ni and the Ni 4 Ti 3 precipitates was evaluated to be about 124 and 175 GPa, respectively. The intensity of the Ni L 3 edge for the precipitate is slightly higher than that for the B2 phase

  8. Investigation on thermo-mechanical behavior of shape memory alloy actuator

    Directory of Open Access Journals (Sweden)

    Kurzawa Milena

    2017-12-01

    Full Text Available The paper presents the design procedure and elaborated software for designing calculation of the shape memory alloy (SMA actuator. The thermo-mechanical behavior of a linear SMA actuator has been studied. The experimental set-up was especially designed to perform the thermo-mechanical characterization of SMA wires. The stroke (s - temperature (T hysteresis characteristics have been determined. The cycle of heating and cooling has been performed under a constant load. The model for the SMA actuator s - T behavior has been proposed and successfully implemented. The selected results and conclusions have been presented. The concept proposal of the linear actuator using the SMA wire has been given.

  9. The preparation of oriented samples of ferromagnetic shape memory alloy CoNiAl

    Czech Academy of Sciences Publication Activity Database

    Kopeček, Jaromír; Jurek, Karel; Jarošová, Markéta; Drahokoupil, Jan; Sedláková, Silvia; Šittner, Petr; Novák, Václav

    2010-01-01

    Roč. 7, č. 1 (2010), 012013/1-012013/8 ISSN 1757-8981. [European Workshop on Modern Developments and Applications in Microbeam Analysis /11./. Gdansk, 10.05.2009-14.05.2009] R&D Projects: GA AV ČR IAA200100902; GA AV ČR(CZ) IAA200100627; GA ČR(CZ) GA101/09/0702 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z10100521 Keywords : shape memory alloys * cobalt * metallography * crystal growth * scanning electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism

  10. Response of a Shape Memory Alloy Beam Model under Narrow Band Noise Excitation

    Directory of Open Access Journals (Sweden)

    Gen Ge

    2014-01-01

    Full Text Available To describe the hysteretic nonlinear characteristic of the strain-stress relation of shape memory alloy (SMA, a Van-der-Pol hysteretic cycle is applied to simulate the hysteretic loops. Then, the model of a simply supported SMA beam subject to transverse narrow band noise excitation with nonlinear damping was proposed. The deterministic and the stochastic responses are studied, respectively, applying the multiple scale method. The stability of the steady state responses is analyzed by Floquet theory and the moment method. The numerical simulation results quite agree with the theoretical analysis.

  11. Review on structural fatigue of NiTi shape memory alloys: Pure mechanical and thermo-mechanical ones

    Directory of Open Access Journals (Sweden)

    Guozheng Kang

    2015-11-01

    Full Text Available Structural fatigue of NiTi shape memory alloys is a key issue that should be solved in order to promote their engineering applications and utilize their unique shape memory effect and super-elasticity more sufficiently. In this paper, the latest progresses made in experimental and theoretical analyses for the structural fatigue features of NiTi shape memory alloys are reviewed. First, macroscopic experimental observations to the pure mechanical and thermo-mechanical fatigue features of the alloys are summarized; then the state-of-arts in the mechanism analysis of fatigue rupture are addressed; further, advances in the construction of fatigue failure models are provided; finally, summary and future topics are outlined.

  12. Sn-Sb-Se based binary and ternary alloys for phase change memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Kyung-Min

    2008-10-28

    In this work, the effect of replacing Ge by Sn and Te by Se was studied for a systematic understanding and prediction of new potential candidates for phase change random access memories applications. The temperature dependence of the electrical/structural properties and crystallization kinetics of the Sn-Se based binary and Sn-Sb-Se based ternary alloys were determined and compared with those of the GeTe and Ge-Sb-Te system. The temperature dependence of electrical and structural properties were investigated by van der Pauw measurements, X-ray diffraction, X-ray reflectometry. By varying the heating rate, the Kissinger analysis has been used to determine the combined activation barrier for crystallization. To screen the kinetics of crystallization, a static laser tester was employed. In case of binary alloys of the type Sn{sub x}Se{sub 1-x}, the most interesting candidate is SnSe{sub 2} since it crystallizes into a single crystalline phase and has high electrical contrast and reasonably high activation energy for crystallization. In addition, the SnSe{sub 2}-Sb{sub 2}Se{sub 3} pseudobinary alloy system also might be sufficient for data retention due to their higher transition temperature and activation energy for crystallization in comparison to GeTe-Sb{sub 2}Te{sub 3} system. Furthermore, SnSe{sub 2}-Sb{sub 2}Se{sub 3} pseudobinary alloys have a higher crystalline resistivity. The desired rapid crystallization speed can be obtained for Sn{sub 1}Sb{sub 2}Se{sub 5} and Sn{sub 2}Sb{sub 2}Se{sub 7} alloys. (orig.)

  13. Examination of temperature-induced shape memory of uranium--5.3-to 6.9 weight percent niobium alloys

    International Nuclear Information System (INIS)

    Hemperly, V.C.

    1976-01-01

    The uranium-niobium alloy system was examined in the range of 5.3-to-6.9 weight percent niobium with respect to shape memory, mechanical properties, metallography, Coefficients of linear thermal expansion, and differential thermal analysis. Shape memory increased with increasing niobium levels in the study range. There were no useful correlations found between shape memory and the other tests. Coefficients of linear thermal expansion tests of as-quenched 5.8 and 6.2 weight percent niobium specimens, but not 5.3 and 6.9 weight percent niobium specimens, had a contraction component on heating, but the phenomenon was not a contributor to shape memory

  14. Characteristics of Reduced Graphene Oxide Quantum Dots for a Flexible Memory Thin Film Transistor.

    Science.gov (United States)

    Kim, Yo-Han; Lee, Eun Yeol; Lee, Hyun Ho; Seo, Tae Seok

    2017-05-17

    Reduced graphene oxide quantum dot (rGOQD) devices in formats of capacitor and thin film transistor (TFT) were demonstrated and examined as the first trial to achieve nonambipolar channel property. In addition, through a gold nanoparticle (Au NP) layer embedded between the rGOQD active channel and dielectric layer, memory capacitor and TFT performances were realized by capacitance-voltage (C-V) hysteresis and gate program, erase, and reprogram biases. First, capacitor structure of the rGOQD memory device was constructed to examine memory charging effect featured in hysteretic C-V behavior with a 30 nm dielectric layer of cross-linked poly(vinyl alcohol). For the intervening Au NP charging layer, self-assembled monolayer (SAM) formation of the Au NP was executed to utilize electrostatic interaction by a dip-coating process under ambient environments with a conformal fabrication uniformity. Second, the rGOQD memory TFT device was also constructed in the same format of the Au NPs SAMs on a flexible substrate. Characteristics of the rGOQD TFT output showed novel saturation curves unlike typical graphene-based TFTs. However, The rGOQD TFT device reveals relatively low on/off ratio of 10 1 and mobility of 5.005 cm 2 /V·s. For the memory capacitor, the flat-band voltage shift (ΔV FB ) was measured as 3.74 V for ±10 V sweep, and for the memory TFT, the threshold voltage shift (ΔV th ) by the Au NP charging was detected as 7.84 V. In summary, it was concluded that the rGOQD memory device could accomplish an ideal graphene-based memory performance, which could have provided a wide memory window and saturated output characteristics.

  15. Effect of Thermomechanical Processing on the Microstructure, Properties, and Work Behavior of a Ti50.5 Ni29.5 Pt20 High-Temperature Shape Memory Alloy

    Science.gov (United States)

    Noebe, Ronald; Draper, Susan; Gaydosh, Darrell; Garga, Anita; Lerch, Brad; Penney, Nicholas; Begelow, Glen; Padula, Santo, II; Brown, Jeff

    2006-01-01

    TiNiPt shape memory alloys are particularly promising for use as solid state actuators in environments up to 300 C, due to a reasonable balance of properties, including acceptable work output. However, one of the challenges to commercializing a viable high-temperature shape memory alloy (HTSMA) is to establish the appropriate primary and secondary processing techniques for fabrication of the material in a required product form such as rod and wire. Consequently, a Ti(50.5)Ni(29.5)Pt20 alloy was processed using several techniques including single-pass high-temperature extrusion, multiple-pass high-temperature extrusion, and cold drawing to produce bar stock, thin rod, and fine wire, respectively. The effects of heat treatment on the hardness, grain size, room temperature tensile properties, and transformation temperatures of hot- and cold-worked material were examined. Basic tensile properties as a function of temperature and the strain-temperature response of the alloy under constant load, for the determination of work output, were also investigated for various forms of the Ti(50.5)Ni(29.5)Pt20 alloy, including fine wire.

  16. Nonlinear finite element formulation for analyzing shape memory alloy cylindrical panels

    International Nuclear Information System (INIS)

    Mirzaeifar, R; Shakeri, M; Sadighi, M

    2009-01-01

    In this paper, a general incremental displacement based finite element formulation capable of modeling material nonlinearities based on first-order shear deformation theory (FSDT) is developed for cylindrical shape memory alloy (SMA) shells. The Boyd–Lagoudas phenomenological model with polynomial hardening in conjunction with 3D incremental convex cutting plane explicit algorithm is implemented for preparing the SMA constitutive model in the finite element formulation. Several numerical examples are presented for demonstrating the performance of the proposed formulation in stress, deflection and phase transformation analysis of pseudoelastic behavior of shape memory cylindrical panels with various boundary conditions. Also, it is shown that the presented formulation can be implemented for studying plates and beams with rectangular cross section

  17. Characterization of Magnetoelastic Coupling in Ferromagnetic Shape Memory Alloys Using Neutron Diffraction

    Science.gov (United States)

    Pramanick, Abhijit; Wang, Xun-Li

    2013-01-01

    Ferromagnetic shape memory alloys (FSMA) are a new class of smart materials with unique properties and applications. The shape memory properties of FSMAs are due to a strong coupling between their elastic and magnetic properties. Understanding the physical origins of magnetoelastic coupling is therefore critical for future materials development and device design. To this end, a thorough study is required of the atomistic and microscopic structural arrangements and how these structural arrangements are related to the orientation of the magnetic moments. The different characterization techniques developed recently to probe these features are reviewed. A special emphasis is placed on in situ techniques such as neutron diffraction through which the microscopic origins of the collective material behavior could be ascertained.

  18. Relationship between thermomechanical treatment, microstructure and α' martensite in stainless Fe-based shape memory alloys

    International Nuclear Information System (INIS)

    Otubo, J.; Mei, P.R.; Shinohara, A.H.; Suzuki, C.K.

    1999-01-01

    This work presents some preliminary results relating training treatment, training temperature and the formation of α' martensite to the shape recovery effect of stainless shape memory alloys. For the composition tested, the sample shows some mechanical memory (constant tensile stress at 4% strain and constant yield stress throughout the training cycles) with a very good shape recovery (95% after 4% tensile strain) at a training temperature of 873 K. Its residual strain is related to the generation of perfect dislocations only. For the sample trained at 723 K, the residual strain could be attributed to incomplete reversion of stress-induced ε martensite, in part due to the blocking effect of α' martensite and also to the generation of perfect dislocations. The influence of α' martensite on shape recovery is relative and is dependent on training temperature, and the preferential growth of α' martensite is shown to occur for large grain size. (orig.)

  19. Thermomechanical response of NiTi shape-memory nanoprecipitates in TiV alloys

    Science.gov (United States)

    Maisel, S. B.; Ko, W.-S.; Zhang, J.-L.; Grabowski, B.; Neugebauer, J.

    2017-08-01

    We study the properties of NiTi shape-memory nanoparticles coherently embedded in TiV matrices using three-dimensional atomistic simulations based on the modified embedded-atom method. To this end, we develop and present a suitable NiTiV potential for our simulations. Employing this potential, we identify the conditions under which the martensitic phase transformation of such a nanoparticle is triggered—specifically, how these conditions can be tuned by modifying the size of the particle, the composition of the surrounding matrix, or the temperature and strain state of the system. Using these insights, we establish how the transformation temperature of such particles can be influenced and discuss the practical implications in the context of shape-memory strengthened alloys.

  20. Additive Manufacturing of NiTiHf High Temperature Shape Memory Alloy

    Science.gov (United States)

    Benafan, Othmane; Bigelow, Glen S.; Elahinia, Mohammad; Moghaddam, Narges Shayesteh; Amerinatanzi, Amirhesam; Saedi, Soheil; Toker, Guher Pelin; Karaca, Haluk

    2017-01-01

    Additive manufacturing of a NiTi-20Hf high temperature shape memory alloy (HTSMA) was investigated. A selective laser melting (SLM) process by Phenix3D Systems was used to develop components from NiTiHf powder (of approximately 25-75 m particle fractions), and the thermomechanical response was compared to the conventionally vacuum induction skull melted counterpart. Transformation temperatures of the SLM material were found to be slightly lower due to the additional oxygen pick up from the gas atomization and melting process. The shape memory response in compression was measured for stresses up to 500 MPa, and transformation strains were found to be very comparable (Up to 1.26 for the as-extruded; up to 1.52 for SLM).

  1. Effect of vacuum annealing on evaporated pentacene thin films for memory device applications

    International Nuclear Information System (INIS)

    Gayathri, A.G.; Joseph, C.M.

    2016-01-01

    Graphical abstract: Switching of ITO/pentacene/Al thin films for different annealing temperatures. - Highlights: • Memory device performance in pentacene improved considerably with annealing. • ON/OFF ratio of the pentacene device increases due to annealing. • Threshold voltage reduces from 2.55 V to 1.35 V due to annealing. • Structure of pentacene thin films is also dependent on annealing temperature. - Abstract: Thin films of pentacene were deposited thermally onto glass substrates and annealed at 323 K, 373 K, 423 K, 473 K and 523 K in high vacuum. Effect of annealing on the morphological and structural properties of these films was studied. X-ray diffraction patterns confirmed the crystalline nature of the films. Electrical studies for the use as write once read many (WORM) memory devices were done for the vacuum deposited pentacene thin films on indium tin oxide coated glass. Due to annealing, a sharp increase in the ON/OFF ratio of current and a decrease in threshold voltage were observed at around 373 K. This device showed a stable switching with an ON/OFF current ratio as high as 10 9 and a switching threshold voltage of 1.35 V. The performance of the device degraded above 423 K due to the changes in the crystallinity of the film.

  2. Effect of Aging Treatment on the Compressibility and Recovery of NiTi Shape Memory Alloys as Static Seals

    Science.gov (United States)

    Lu, Xiaofeng; Li, Gang; Liu, Luwei; Zhu, Xiaolei; Tu, Shan-Tung

    2017-07-01

    The improvement of the compressibility and recovery of the gaskets can decrease the leakage occurrence in bolted flange connections. In this study, the effect of aging treatment on the compressibility and recovery of NiTi shape memory alloys is investigated as static seals together with thermal analysis. The experimental results indicate that different phase transformations of NiTi alloys are exhibited in the DSC curves during aging treatment. The recovery coefficient of NiTi alloys aged at 500 °C for 2 h is quite low accompanied with a large residual strain. With increasing aging time at the aging temperature of 400 °C, the residual strain and area of hysteresis loop of NiTi alloys are both increased, whereas the recovery coefficient is decreased. Since the deformation associates the phase transformation behavior, aging treatment could improve the compressibility and recovery of NiTi alloys as static seals.

  3. Development of stainless steel shape memory alloys; Desenvolvimento de acos inoxidaveis com efeito de memoria de forma

    Energy Technology Data Exchange (ETDEWEB)

    Otubo, J.; Mei, P.R. [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica; Koshimizu, S. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1995-12-31

    It is presented in this work, pioneer in Brazil, the development of two stainless steel shape memory alloys assisted by non thermo-elastic martensitic transformation. In terms of shape recovery, the results obtained are very promising comparable to the best results in the literature with 95 % shape recovery after pre-strain of 4 % when subjected do thermo-mechanical training cycle. The stainless steel character and the shape recovery of almost 4 % of the alloys promote it to practical applications such as for pipe fittings or satellite solar panel release mechanism. Consideration about the alloys processing, mechanical and microstructural properties will also be presented 28 refs., 7 figs., 2 tabs.

  4. Dependence of the organic nonvolatile memory performance on the location of ultra-thin Ag film

    International Nuclear Information System (INIS)

    Jiao Bo; Wu Zhaoxin; He Qiang; Mao Guilin; Hou Xun; Tian Yuan

    2010-01-01

    We demonstrated organic nonvolatile memory devices based on 4,4',4''-tris[N-(3-methylphenyl)-N-phenylamino] triphenylamine (m-MTDATA) inserted by an ultra-thin Ag film. The memory devices with different locations of ultra-thin Ag film in m-MTDATA were investigated, and it was found that the location of the Ag film could affect the performance of the organic memory, such as ON/OFF ratio, retention time and cycling endurance. When the Ag film was located at the ITO/m-MTDATA interface, the largest ON/OFF ratio (about 10 5 ) could be achieved, but the cycling endurance was poor. When the Ag film was located in the middle region of the m-MTDATA layer, the ON/OFF ratios came down by about 10 3 , but better performance of cycling endurance was exhibited. When the Ag film was located close to the Al electrode, the ON/OFF ratios and the retention time of this device decreased sharply and the bistable phenomenon almost disappeared. Our works show a simple approach to improve the performance of organic memory by adjusting the location of the metal film.

  5. Thin PZT-Based Ferroelectric Capacitors on Flexible Silicon for Nonvolatile Memory Applications

    KAUST Repository

    Ghoneim, Mohamed T.

    2015-04-24

    A flexible version of traditional thin lead zirconium titanate ((Pb1.1Zr0.48Ti0.52O3)-(PZT)) based ferroelectric random access memory (FeRAM) on silicon shows record performance in flexible arena. The thin PZT layer requires lower operational voltages to achieve coercive electric fields, reduces the sol-gel coating cycles required (i.e., more cost-effective), and, fabrication wise, is more suitable for further scaling of lateral dimensions to the nano-scale due to the larger feature size-to-depth aspect ratio (critical for ultra-high density non-volatile memory applications). Utilizing the inverse proportionality between substrate\\'s thickness and its flexibility, traditional PZT based FeRAM on silicon is transformed through a transfer-less manufacturable process into a flexible form that matches organic electronics\\' flexibility while preserving the superior performance of silicon CMOS electronics. Each memory cell in a FeRAM array consists of two main elements; a select/access transistor, and a storage ferroelectric capacitor. Flexible transistors on silicon have already been reported. In this work, we focus on the storage ferroelectric capacitors, and report, for the first time, its performance after transformation into a flexible version, and assess its key memory parameters while bent at 0.5 cm minimum bending radius.

  6. Phase transformation, oxidation and shape memory properties of Ti–50Au–10Zr alloy for high temperature applications

    International Nuclear Information System (INIS)

    Wadood, A.; Hosoda, H.; Yamabe-Mitarai, Y.

    2014-01-01

    Highlights: • Ti–50Au–10Zr exhibited better thermo-mechanical and shape memory properties than Ti–50Au. • Improvement was related to solid solution and precipitation strengthening. • No oxidation problem as oxidation was observed at 100 K higher than A f . • TMA was used not only for thermo-mechanical but also for shape memory and oxidation. - Abstract: In this study, we investigated the phase transformation, oxidation and high temperature mechanical and shape memory properties of Ti–50Au–10Zr (all compositions in atomic%) alloy. Thermo-mechanical analyzer (TMA) was used not only for phase transformation but also for the measurement of shape memory effect and oxidation behavior in air environment. Ti–50Au–10Zr exhibited lower martensitic transformation temperature of 758 K than TiAu stoichiometric alloy exhibiting 870 K since Zr addition stabilizes B2 parent phase. Oxidation was initiated at 873 K that was about 100 K higher than the austenite finish temperature, indicating no such oxidation problems for practical use. Shape memory effect was improved by partial substitution of Ti with Zr in Ti–50Au–10Zr alloy. Compression test of Ti–50Au–10Zr revealed high compressive strength of 1239 MPa of martensite at 691 K (=M f − 50 K) and 924 MPa of B2 parent phase at 834 K (=A f + 50 K) in comparison with Ti–50Au. It is concluded that Zr is effective to improve the mechanical and shape memory properties of TiAu alloy, and that Ti–50Au–10Zr shape memory alloy has potential for high temperature (∼650–850 K) practical applications

  7. Modeling and numerical analysis of a three-dimensional shape memory alloy shell structure

    Science.gov (United States)

    Zhao, Pengtao; Qiu, Jinhao; Ji, Hongli; Wang, Mingyi; Nie, Rui

    2012-04-01

    In this paper, modeling and numerical analysis of a three dimensional shell structure made of shape memory alloy (SMA) are introduced. As a new smart material, SMA material has been applied in many fields due to two significant macroscopic phenomena which are called the shape memory effect (SME) and pseudoelasticity. The material of SMA exhibits two-way shape memory effect (TWSME) after undergoing especial heat treatment and thermo-mechanical training. This work investigates the numerical simulation and application of the SMA component: SMA strip, which has been pre-curved in the room temperature. The component is expected to extend upon heating and shorten on cooling along the curve. Hence the shape memory effect can be used to change the shape of the structure. The return mapping algorithm of the 3-D SMA thermomechanical constitutive equations based on Boyd-Lagoudas model is used in the finite element analysis to describe the material features of the SMA. In this paper, the ABAQUS finite element program has been utilized with a user material subroutine (UMAT) which is written in the FORTRAN code for the modeling of the SMA strip. The SMA component which has a certain initial transformation strain can emerge considerable deflection during the reverse phase transformation inducing by the temperature.

  8. Aggregation in thin-film silver: Induced by chlorine and inhibited by alloying with two dopants

    International Nuclear Information System (INIS)

    Koike, Katsuhiko; Shimada, Koichi; Fukuda, Shin

    2009-01-01

    The Ag aggregation mechanism triggered by chlorine (Cl) is discussed. The frontier orbital theory by K. Fukui is applied in order to determine the growing point in the silver (Ag) cluster. Ag in the thin-film silver would grow to Ag n Cl and stack, triggered by Cl from the outside according to the mechanism described. This would lead to an aggregate with a high Ag density. It is suggested that this would be the generating mechanism of the silver-gray aggregate consisting mostly of Ag, which is generated by exposing it to Cl. Two tactics in order to prevent restrain aggregation induced by Cl according to the mechanism are proposed. Tactic 1 is a restraining of structure change to a plane in the process of Ag 6 Cl + Ag → Ag 7 Cl. Tactic 2 is the trapping of Cl before it generates a bond to Ag. The ability of the two combined dopants with the abilities of tactics 1 and 2, such as in an Ag alloy including palladium and copper (APC), and including neodymium and gold (ANA) is expected to be very high. The aggregation resistance of an Ag alloy including two dopants is evaluated by a salt water immersion test. The APC and ANA demonstrated a very high resistance to Cl, because of the combination of the dopants working with tactic 1 (Pd, Au) and tactic 2 (Cu, Nd). The multilayer sputter coating with an ANA layer demonstrated a very interesting profile where the light transmittance and the electrical sheet resistance are almost the same as the multilayer sputter coating with a pure Ag. The multilayer sputter coating with AIS also demonstrates a very interesting profile, where the light transmittance is higher than the multilayer sputter coating with a pure Ag.

  9. Complete Status Report Documenting Development of Friction Stir Welding for Joining Thin Wall Tubing of ODS Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hoelzer, David T. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Bunn, Jeffrey R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gussev, Maxim N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    The development of friction stir welding (FSW) for joining thin sections of the advanced oxide dispersion strengthened (ODS) 14YWT ferritic alloy was initiated in Fuel Cycle Research and Development (FCRD), now the Nuclear Technology Research and Development (NTRD), in 2015. The first FSW experiment was conducted in late FY15 and successfully produced a bead-on-plate stir zone (SZ) on a 1 mm thick plate of 14YWT (SM13 heat). The goal of this research task is to ultimately demonstrate that FSW is a feasible method for joining thin wall (0.5 mm thick) tubing of 14YWT.

  10. Interplay of structural instability and lattice dynamics in Ni{sub 2}MnAl shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mehaddene, T.

    2007-02-12

    The work presented here is devoted to investigate the interplay of lattice dynamics and structural instability in Ni{sub 2}MnAl shape memory alloys. Inelastic neutron scattering is used to get more insight on the dynamic precursors of structural instability in Ni{sub 2}MnAl. Differential Scanning Calorimetry was used to characterise the martensitic transition in Ni{sub 2}MnAl alloys. Effects of composition and heat treatments have been investigated. The measured martensitic transition temperature in Ni-Mn-Al alloys depends linearly on the valence electron concentration. Two single crystals with different compositions have been succesfully grown using the Czochralski technique. Acoustic and optical phonon modes have been measured at room temperature in the high symmetry directions of the cubic B2 phase. The force constants have been fitted to the measured data using the Born-von Karman model. The character of the phonon softening measured in Ni{sub 2}MnAl corresponds to the pattern of atomic displacements of the modulations 2M, 10M, 12M and 14M observed in bulk and thin-films of Ni{sub 2}MnAl. The effect of the composition on the lattice instability has been investigated by measuring normal modes of vibration in two different crystals, Ni{sub 51}Mn{sub 18}Al{sub 31} and Ni{sub 53}Mn{sub 22}Al{sub 25}, with e/a ratios of 7.29 and 7.59 respectively. The stabilisation of a single L2{sub 1} phase in Ni{sub 2}MnAl by annealing a Ni{sub 51}Mn{sub 18}Al{sub 31} single crystal at 673 K during 45 days has been attempted. Despite of the long-time annealing, a single L2{sub 1} phase could not be stabilised because of either a slow diffusion kinetics or the establishment of an equilibrium between the L2{sub 1} and the B2 phases. Phonon measurements of the TA{sub 2}[{xi}{xi}0] branch in the annealed sample revealed a substantial effect. The wiggle, associated with the anomalous softening, is still present but the degree of softening is smaller below 673 K and changes

  11. A study on the electrodeposition of NiFe alloy thin films using chronocoulometry and electrochemical quartz crystal microgravimetry

    CERN Document Server

    Myung, N S

    2001-01-01

    Ni, Fe and NiFe alloy thin films were electrodeposited at a polycrystalline Au surface using a range of electrolytes and potentials. Coulometry and EQCM were used for real-time monitoring of electroplating efficiency of the Ni and Fe. The plating efficiency of NiFe alloy thin films was computed with the aid of ICP spectrometry. In general, plating efficiency increased to a steady value with deposition time. Plating efficiency of Fe was lower than that of Ni at -0.85 and -1.0 V but the efficiency approached to the similar plateau value to that of Ni at more negative potentials. The films with higher content of Fe showed different stripping behavior from the ones with higher content of Ni. Finally, compositional data and real-time plating efficiency are presented for films electrodeposited using a range of electrolytes and potentials.

  12. Tensile-compressive asymmetry influence on shape memory alloy system dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Savi, Marcelo A. [Universidade Federal do Rio de Janeiro, COPPE - Department of Mechanical Engineering, P.O. Box 68.503, 21.941.972 Rio de Janeiro (Brazil)], E-mail: savi@mecanica.ufrj.br; Sa, Milton A.N. [Universidade Federal do Rio de Janeiro, COPPE - Department of Mechanical Engineering, P.O. Box 68.503, 21.941.972 Rio de Janeiro (Brazil); Paiva, Alberto [Universidade Federal Fluminense, Escola de Engenharia Industrial e Metalurgica de Volta Redonda, 27.255.250 Volta Redonda, RJ (Brazil)], E-mail: paiva@lavi.coppe.ufrj.br; Pacheco, Pedro M.C.L. [CEFET/RJ - Department of Mechanical Engineering, 20.271.110 Rio de Janeiro, RJ (Brazil)], E-mail: calas@cefet-rj.br

    2008-05-15

    The remarkable properties of shape memory alloys (SMAs) are attracting much technological interest in several science and engineering fields, varying from medical to aerospace applications. Hysteretic response of these systems is one of their essential characteristics being related to the martensitic phase transformation. The dynamical response of systems with SMA actuators presents a rich behavior due to their intrinsic nonlinear characteristic. Since experimental results show that SMAs present an asymmetric behavior when subjected to tensile or compressive loads, it is important to evaluate the influence of this kind of behavior in the nonlinear dynamics of mechanical systems with SMA devices. This article discusses the nonlinear dynamics of shape memory alloy systems, considering the influence of tensile-compressive asymmetry in the thermomechanical behavior of SMAs. An iterative numerical procedure based on the operator split technique, the orthogonal projection algorithm and the fourth-order Runge-Kutta method is developed to deal with nonlinearities in the formulation. A numerical investigation is carried out showing some qualitative results such as chaotic-like response and multi-stability behavior for a single degree of freedom SMA oscillator.

  13. An improved tuned mass damper (SMA-TMD) assisted by a shape memory alloy spring

    International Nuclear Information System (INIS)

    Mishra, Sudib K; Gur, Sourav; Chakraborty, Subrata

    2013-01-01

    The tuned mass damper (TMD) is a well acclaimed passive control device for vibration control of structures. However, the requirement of a higher mass ratio restricts its applicability for seismic vibration control of civil engineering structures. Improving the performance of TMDs has been attempted by supplementing them with nonlinear restoring devices. In this regard, the ability of shape memory alloy (SMA) in dissipating energy through a hysteretic phase transformation of its microstructure triggered by cyclic loading is notable. An improved version of TMD assisted by a nonlinear shape memory alloy (SMA) spring, referred as SMA-TMD, is studied here for seismic vibration mitigation. Extensive numerical simulations are conducted based on nonlinear random vibration analysis via stochastic linearization of the nonlinear force–deformation hysteresis of the SMA. A design optimization based on minimizing the root mean square displacement of the main structure is also carried out to postulate the optimal design parameters for the proposed system. The viability of the optimal design is verified with respect to its performance under recorded earthquake motions. Significant improvements of the control efficiency and a reduction of the TMD displacement at a much reduced mass ratio are shown to be achieved in the proposed SMA-TMD over those in the linear TMD. (paper)

  14. Working principle of bio-inspired shape memory alloy composite actuators

    International Nuclear Information System (INIS)

    Smith, Colin; Villanueva, Alex; Joshi, Keyur; Tadesse, Yonas; Priya, Shashank

    2011-01-01

    Recently, bio-inspired shape memory alloy composite (BISMAC) actuators have been shown to mimic the deformation characteristics of natural jellyfish medusa. In this study, a constant cross-section BISMAC actuator was characterized in terms of bending deflection and force in conjunction with microscopy to understand its deformation mechanism. The actuator showed bending deflection of 111% with respect to the active length along with a blocking force of 0.061 N. The resulting energy density of the composite actuator was 4929 J m −3 at an input voltage and current level of 12 V and 0.7 A, respectively. For a dry-state actuator, this performance is extremely high and represents an optimum combination of force and deflection. Experiments reveal that BISMAC's performance is related to the moment induced from tip attachment of the shape memory alloy (SMA) rather than to friction within the composite structure. A physics-based model of BISMAC structure is presented which shows that the actuator is highly sensitive to the distance between the SMA wire and the incompressible component. While SMA has both stress and strain limitations, the limiting factor in BISMAC actuators is dependent on separation distance. The limiting factor in BISMAC's suitability for mimicking the performance of medusa was experimentally found to be related to the maximum 4% strain of the SMA and not its force generation. (fast track communication)

  15. Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

    Science.gov (United States)

    Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

    2018-01-01

    Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

  16. A comprehensive energy approach to predict fatigue life in CuAlBe shape memory alloy

    Science.gov (United States)

    Sameallah, S.; Legrand, V.; Saint-Sulpice, L.; Kadkhodaei, M.; Arbab Chirani, S.

    2015-02-01

    Stabilized dissipated energy is an effective parameter on the fatigue life of shape memory alloys (SMAs). In this study, a formula is proposed to directly evaluate the stabilized dissipated energy for different values of the maximum and minimum applied stresses, as well as the loading frequency, under cyclic tensile loadings. To this aim, a one-dimensional fully coupled thermomechanical constitutive model and a cycle-dependent phase diagram are employed to predict the uniaxial stress-strain response of an SMA in a specified cycle, including the stabilized one, with no need of obtaining the responses of the previous cycles. An enhanced phase diagram in which different slopes are defined for the start and finish of a backward transformation strip is also proposed to enable the capture of gradual transformations in a CuAlBe shape memory alloy. It is shown that the present approach is capable of reproducing the experimental responses of CuAlBe specimens under cyclic tensile loadings. An explicit formula is further presented to predict the fatigue life of CuAlBe as a function of the maximum and minimum applied stresses as well as the loading frequency. Fatigue tests are also carried out, and this formula is verified against the empirically predicted number of cycles for failure.

  17. Surface characterizations of laser modified biomedical grade NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Pequegnat, A. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Michael, A., E-mail: a2michae@uwaterloo.ca [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Wang, J. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Lian, K. [Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4 (Canada); Zhou, Y. [Centre for Advanced Materials Joining (CAMJ), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Centre for Bioengineering and Biotechnology (CBB), University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Khan, M.I. [Department of Materials Science and Engineering, University of Toronto, 184 College Street, Suite 140, Toronto, ON M5S 3E4 (Canada); Smarter Alloys, Inc., MaRS Centre, South Tower, 101 College Street, Suite 200, Toronto, ON M5G 1L7 (Canada)

    2015-05-01

    Laser processing of shape memory alloys (SMAs) promises to enable the multifunctional capabilities needed for medical device applications. Prior to clinical implementation, the surface characterisation of laser processed SMA is essential in order to understand any adverse biological interaction that may occur. The current study systematically investigated two Ni-49.8 at.% Ti SMA laser processed surface finishes, including as-processed and polished, while comparing them to a chemically etched parent material. Spectrographic characterisation of the surface included; X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and Raman spectroscopy. Corrosion performance and Ni ion release were also assessed using potentiodynamic cyclic polarization testing and inductively coupled plasma optical emission spectroscopy (ICP-OES), respectively. Results showed that surface defects, including increased roughness, crystallinity and presence of volatile oxide species, overshadowed any possible performance improvements from an increased Ti/Ni ratio or inclusion dissolution imparted by laser processing. However, post-laser process mechanical polishing was shown to remove these defects and restore the performance, making it comparable to chemically etched NiTi material. - Highlights: • Laser processed NiTi shape memory alloy surfaces were systematically characterized. • Chemistry, oxide thickness, composition, microstructure, and roughness were identified. • Localized superficial defects dictated corrosion and Ni ion release performance. • Mechanical polishing restored corrosion performance. • Bulk material corrosion performance was unaffected by pulsed laser process.

  18. Phenomenological Model for Phase Transformation Characteristics of Textured Shape Memory Alloys

    Science.gov (United States)

    Chatziathanasiou, Dimitris; Chemisky, Yves; Meraghni, Fodil; Chatzigeorgiou, George; Patoor, Etienne

    In the present study, a new transformation criterion that includes the effect of tension-compression asymmetry and texture-induced anisotropy is proposed and combined with a thermodynamical model to describe the thermomechanical behavior of polycrystalline shape memory alloys. An altered Prager criterion has been developed, introducing a general transformation of the axes in the stress space. A convexity analysis of such criterion is included along with an identification strategy aimed at extracting the model parameters related to tension-compression asymmetry and anisotropy. These are identified from a numerical simulation of a SMA polycrystal, using a self-consistent micromechanical model previously developed by Patoor et al. (Patoor, E., Eberhardt, A., Berveiller, M., 1996. Micromechanical Modelling of Superelasticity in Shape Memory Alloys. Journal de Physique IV 6, C1 277) for several loading cases on isotropic, rolled and drawn textures. Transformation surfaces in the stress and transformation strain spaces are obtained and compared with those predicted by the micromechanical model. The good agreement obtained between the macroscopic and the microscopic polycrystalline simulations states that the proposed criterion and transformation strain evolution equation can capture phenomenologically the effects of texture on anisotropy and asymmetry in SMAs.

  19. Oxidation Kinetics of a NiPtTi High Temperature Shape Memory Alloy

    Science.gov (United States)

    Smialek, James L.; Humphrey, Donald L.; Noebe, Ronald D.

    2007-01-01

    A high temperature shape memory alloy (HTSMA), Ni30Pt50Ti, with an M(sub s) near 600 C, was isothermally oxidized in air for 100 hr over the temperature range of 500 to 900 C. Parabolic kinetics were confirmed by log-log and parabolic plots and showed no indication of fast transient oxidation. The overall behavior could be best described by the Arrhenius relationship: k(sub p) = 1.64 x 10(exp 12)[(-250 kJ/mole)/RT] mg(sup 2)/cm(sup 4)hr. This is about a factor of 4 reduction compared to values measured here for a binary Ni47Ti commercial SMA. The activation energy agreed with most literature values for TiO2 scale growth measured for elemental Ti and other NiTi alloys. Assuming uniform alloy depletion of a 20 mil (0.5 mm) dia. HTSMA wire, approx. 1 percent Ti reduction is predicted after 20,000 hr oxidation at 500 C, but becomes much more serious at higher temperatures.

  20. Restoration properties of neutron irradiated Ti-Ni shape memory alloys

    International Nuclear Information System (INIS)

    Hoshiya, Taiji; Takada, Fumiki; Omi, Masao; Goto, Ichiro; Ando, Hiroei

    1992-01-01

    Transformation properties and deformation behavior of Ti-Ni shape memory alloys which were irradiated at 323 and 520 K up to a maximum fast neutron fluence of 10 25 m -2 and subsequently annealed above 523 K, were examined by electrical resistance measurements and tensile tests. When irradiation was performed at 323 K, M s temperature of irradiated specimens abruptly decreased at a dose over 10 -2 dpa. This shows that the irradiation has a great influence on transformation properties of specimens. After post-irradiation annealing above 523 K, the M s temperature of specimens which were irradiated with a dose of 10 -1 dpa, increased to that of unirradiated ones. When irradiation was performed at 520 K, the decrease in M s temperature was negligibly small regardless of the magnitude of damage. It is clear that at irradiation temperature of 520 K the irradiation has no influence on transformation properties of Ti-Ni alloys. In the Ti-Ni alloys two conflicting processes take place during irradiation: disordering and ordering. The migration of vacancies is enhanced by thermal activation and ordering becomes predominant over the disordering and restoration phenomena occur. The phenomena can be described as a function of temperature, displacement and displacement rate by the theory of order-disorder transformation under irradiation. It is confirmed that the threshold temperature at which the restoration phenomena take place is about 520 K. (author)

  1. Nanostructured thin film formation on femtosecond laser-textured Ti-35Nb-xZr alloy for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Yong-Hoon [Department of Dental Materials and Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Choe, Han-Cheol, E-mail: hcchoe@chosun.ac.kr [Department of Dental Materials and Research Center of Nano-Interface Activation for Biomaterials, School of Dentistry, Chosun University, Gwangju (Korea, Republic of); Brantley, William A. [Division of Restorative and Prosthetic Dentistry and Primary Care, College of Dentistry, Ohio State University, Columbus, OH (United States)

    2011-05-31

    The aim of this study was to investigate the nanostructured thin film formation on femtosecond (FS) laser-textured Ti-35Nb-xZr alloy for biomedical applications. The initial surface roughening treatment involved irradiation with the FS laser in ambient air. After FS laser texturing, nanotubes were formed on the alloy surface using a potentiostat and a 1 M H{sub 3}PO{sub 4} solution containing 0.8 wt.% NaF with an applied cell voltage of 10 V for 2 h. The surface phenomena were investigated by FE-SEM, EDS, XRD, XPS and a cell proliferation test. It was found that nanostructured Ti-35Nb-xZr alloys after FS laser texturing had a hybrid surface topography with micro and nano scale structures, which should provide very effective osseointegration.

  2. Continuous AFM observation of martensitic transformation and its reversion in training cycles of Fe-Mn-Si based shape memory alloys

    International Nuclear Information System (INIS)

    Liu, D.Z.; Kikuchi, T.; Kajiwara, S.; Shinya, N.

    2000-01-01

    The effect of thermomechanical treatment (so-called ''training'') cycles on stress-induced martensitic transformation and its reversion has been studied by atomic force microscopy (AFM) to make clear the origin of improvement of shape memory effect (SME) due to training in Fe-Mn-Si based shape memory alloys (SMAs). It was found that training cycles make martensite plates tend to grow on the primary shear system, i.e., on the most favorable shear system for the fcc to hcp martensitic transformation. In addition, training cycles lead to a more uniform distribution of thin martensite plates in a grain. Martensitic plates with the above characteristics are easier to be reverted back to parent phase when heated, and then nearly perfect SME is obtained. AFM observation shows that the key factor to realize perfect SME in Fe-Mn-Si based SMAs is to produce the uniform distribution of thin martensite plates on the primary shear system when deformed by external stress. (orig.)

  3. Oxide Scales Formed on NiTi and NiPtTi Shape Memory Alloys

    Science.gov (United States)

    Smialek, James L.; Garg, Anita; Rogers, Richard B.; Noebe, Ronald D.

    2011-01-01

    Ni-49Ti and Ni-30Pt-50Ti (at.%) shape memory alloys were oxidized isothermally in air over the temperature range of 500 to 900 C. The microstructure, composition, and phase content of the scales were studied by SEM, EDS, XRD, and metallography. Extensive plan view SEM/EDS identified various features of intact or spalled scale surfaces. The outer surface of the scale was a relatively pure TiO2 rutile structure, typified by a distinct highly striated and faceted crystal morphology. Crystal size increased significantly with temperature. Spalled regions exhibited some porosity and less distinct features. More detailed information was obtained by correlation of SEM/EDS studies of 700 C/100 hr cross-sections with XRD analyses of serial or taper-polishing of plan surfaces. Overall, multiple layers exhibited graded mixtures of NiO, TiO2, NiTiO3, Ni(Ti) or Pt(Ni,Ti) metal dispersoids, Ni3Ti or Pt3Ti depletion zones, and substrate, in that order. The NiTi alloy contained a 3 at.% Fe impurity that appeared in embedded localized Fe-Ti-rich oxides, while the NiPtTi alloy contained a 2 v/o dispersion of TiC that appeared in lower layers. The oxidation kinetics of both alloys (in a previous report) indicated parabolic growth and an activation energy (250 kJ/mole) near those reported in other Ti and NiTi studies. This is generally consistent with TiO2 existing as the primary scale constituent, as described here.

  4. Microstructure and properties of Cu–Al–Fe high-temperature shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuiyuan, E-mail: yangshuiyuan@xmu.edu.cn; Su, Yu; Wang, Cuiping; Liu, Xingjun, E-mail: lxj@xmu.edu.cn

    2014-07-01

    Highlights: • Three-phase microstructure is observed for x = 0 both under the quenched and aged states. • Two-phase microstructure is observed for x = 1 both under the quenched and aged states. • Only martensite exists for x = 2 after quenching, whereas γ{sub 1}(Cu{sub 9}Al{sub 4}) phase appears after aging. • High martensitic transformation temperatures (>450 °C) are obtained for all studied alloys. • The alloy for x = 1 after aging still remains relatively good recovery strain and ratio. - Abstract: The microstructure, martensitic transformation, mechanical and shape memory properties of Cu{sub 84−x}Al{sub 11+x}Fe{sub 5} (x = 0, 1, 2) alloys under the quenched and aged states were investigated. The results show that x = 0 and 1 under the quenched state exhibit a mixture of primary β{sup ′}{sub 1} and little γ{sup ′}{sub 1} martensites, and x = 2 only shows dominant γ{sup ′}{sub 1} martensite. Small amounts of α(Cu) and Fe(Al,Cu) phases are observed for x = 0, whereas only tiny Fe(Al,Cu) phase exists for x = 1. After aging, all alloys have a mixture of β{sup ′}{sub 1} and γ{sup ′}{sub 1} martensites, and the snowflake-shaped γ{sub 1} (Cu{sub 9}Al{sub 4}) precipitate is present for x = 2. The recovery strain and ratio for x = 0 and 2 remarkably decrease after aging due to the precipitations. However, the recovery strain of x = 1 after aging still linearly increases with the increase of the pre-strain, up to a maximum value of 1.6%.

  5. Structural and optical properties of (Ag,Cu)(In,Ga)Se2 polycrystalline thin film alloys

    International Nuclear Information System (INIS)

    Boyle, J. H.; Shafarman, W. N.; Birkmire, R. W.; McCandless, B. E.

    2014-01-01

    The structural and optical properties of pentenary alloy (Ag,Cu)(In,Ga)Se 2 polycrystalline thin films were characterized over the entire compositional range at a fixed (Cu + Ag)/(In + Ga) ratio. Films deposited at 550 °C on bare and molybdenum coated soda-lime glass by elemental co-evaporation in a single-stage process with constant incident fluxes exhibit single phase chalcopyrite structure, corresponding to 122 spacegroup (I-42d) over the entire compositional space. Unit cell refinement of the diffraction patterns show that increasing Ag substitution for Cu, the refined a o lattice constant, (Ag,Cu)-Se bond length, and anion displacement increase in accordance with the theoretical model proposed by Jaffe, Wei, and Zunger. However, the refined c o lattice constant and (In,Ga)-Se bond length deviated from theoretical expectations for films with mid-range Ag and Ga compositions and are attributed to influences from crystallographic bond chain ordering or cation electronegativity. The optical band gap, derived from transmission and reflection measurements, widened with increasing Ag and Ga content, due to influences from anion displacement and cation electronegativity, as expected from theoretical considerations for pseudo-binary chalcopyrite compounds.

  6. Titanium Alloys Thin Sheet Welding with the Use of Concentrated Solar Energy

    Science.gov (United States)

    Pantelis, D. I.; Kazasidis, M.; Karakizis, P. N.

    2017-12-01

    The present study deals with the welding of titanium alloys thin sheets 1.3 mm thick, with the use of concentrated solar energy. The experimental part of the work took place at a medium size solar furnace at the installation of the Centre National de la Recherche Scientifique, at Odeillo, in Southern France, where similar and dissimilar defect-free welds of titanium Grades 4 and 6 were achieved, in the butt joint configuration. After the determination of the appropriate welding conditions, the optimum welded structures were examined and characterized microstructurally, by means of light optical microscopy, scanning electron microscopy, and microhardness testing. In addition, test pieces extracted from the weldments were tested under uniaxial tensile loading aiming to the estimation of the strength and the ductility of the joint. The analysis of the experimental results and the recorded data led to the basic concluding remarks which demonstrate increased hardness distribution inside the fusion area and severe loss of ductility, but adequate yield and tensile strength of the welds.

  7. Gilbert damping constant of FePd alloy thin films estimated by broadband ferromagnetic resonance

    Directory of Open Access Journals (Sweden)

    Kawai T.

    2014-07-01

    Full Text Available Magnetic relaxation of FePd alloy epitaxial thin films with very flat surfaces prepared on MgO(001 substrate are measured by in-plane broadband ferromagnetic resonance (FMR. Magnetic relaxation is investigated as Δω for FMR absorption peak by frequency sweep measurements. ΔH is calculated by using the measured Δω. Gilbert damping constant, α, is estimated by employing a straight line fitting of the resonant frequency dependence of ΔH. The α value for an FePd film deposited at 200 ˚C, which shows disordered A1 structure, is 0.010 and ΔH0, which is frequency independent part of ΔH, is 10 Oe. The α value for a film annealed at 400 ˚C, which shows partially L10 ordered structure (S=0.32, is 0.013, which is slightly larger than that for the disorder A1 structure film. However, ΔH0 for the annealed film is 85 Oe, which is much larger than that for the film with disordered structure. The results show that the magnetic relaxation of the 400 ˚C annealed film is mainly dominated by ΔH0, which is related with magnetic in-homogeneity caused by the appearance of perpendicular anisotropy of partially ordered phase.

  8. Exploring Cd-Zn-O-S alloys for improved buffer layers in thin-film photovoltaics

    Science.gov (United States)

    Varley, J. B.; Lordi, V.; He, X.; Rockett, A.

    2017-07-01

    To compete with existing and more mature solar cell technologies such as crystalline Si, thin-film photovoltaics require optimization of every aspect in the device heterostructure to reach maximum efficiencies and cost effectiveness. For absorbers like CdTe, Cu(In ,Ga )Se 2 (CIGSe), and Cu2ZnSn(S ,Se ) 4 (CZTSSe), improving the n -type buffer layer partner beyond conventional CdS is one avenue that can reduce photocurrent losses and improve overall performance. Here, we use first-principles calculations based on hybrid functionals to explore alloys spanning the Cd-, Zn-, O-, and S-containing phase space to identify compositions that may be superior to common buffers like pure CdS or Zn(O,S). We address issues highly correlated with device performance such as lattice-matching for improved buffer-absorber epitaxy and interface quality, dopability, the band gap for reduced absorption losses in the buffer, and the conduction-band offsets shown to facilitate improved charge separation from photoexcited carriers. We supplement our analysis with device-level simulations as parameterized from our calculations and real devices to assess our conclusions of low-Zn and O content buffers showing improved performance with respect to CdS buffers.

  9. Optimation of Sputtering Process Parameters on the Deposition of Nitride Titanium Thin Layer on Aluminum Alloys

    International Nuclear Information System (INIS)

    Tjipto Sujitno; Agus Santoso; Wiryoadi; Sayono; Bambang Siswanto; Lely Susita RM

    2002-01-01

    Research on the optimization of sputtering process parameters on the deposition of nitride titanium thin layer on aluminum alloys has been carried out. The aim of this research is to get the optimum conditions of the process parameters. The parameters of the process are ratio of sputter gas (Ar) and dopant (Nitrogen) gas, time of the process (t), temperature (T), electrode distance, electrode voltage and vacuum conditions of the process. In this experiment the electrode distance and electrode voltage are constants i.e.: 4 cm, 1.5 kV and 2.0 x 10 -1 torr, respectively. To examine the results, it was characterized its hardness, wear and corrosion resistance. It's found that optimum conditions was achieved at the ratio of Ar:N 2 = 5:7, t = 3 hours, T= 100 o C and vacuum conditions 2 x 10 -2 torr. At the optimum conditions, the hardness increases from 120.33 KHN to 149.59 KHN or there is an increasing in hardness in order of 24.32 %, the wear resistance increases from 1 x 10 -4 g/minutes to 6 x 10 -5 g/minutes or there is an increasing in wear resistance in order of 40.00 %, and the corrosion resistance in diluted sea water 1000 times media increases from 6.22 mpy to 0.68 mpy or there is an increasing in corrosion resistance in order of 811.76 %. (author)

  10. Embedded Shape Memory Alloy Particles for the Self-Sensing of Fatigue Crack Growth in an Aluminum Alloy

    Science.gov (United States)

    Leser, William Paul

    Future aerospace vehicles will be built using novel materials for mission conditions that are difficult to replicate in a laboratory. Structural health monitoring and condition-based maintenance will be critical to ensure the reliability of such vehicles. A multi-functional aluminum alloy containing embedded shape memory alloy (SMA) particles to detect fatigue crack growth is proposed. The regions of intensified strain near the tip of a growing fatigue crack cause the SMA particles to undergo a solid-to-solid phase transformation from austenite to martensite, releasing a detectable and identifiable acoustic emission (AE) signal that can be used to locate the crack in the affected component. This study investigates the AE response of two SMA systems, Ni-Ti, and Co-Ni-Al. Tensile (Ni-Ti) and compressive (Co-Ni-Al) tests were conducted to study the strain-induced transformation response in both of the alloy systems. It was found that the critical stress for transformation in both SMA systems was easily identified by a burst of AE activity during both transformation and reverse transformation. AE signals from these experiments were collected for use as training data for a Bayesian classifier to be used to identify transformation signals in a Al7050 matrix with embedded SMA particles. The Al/SMA composite was made by vacuum hot pressing SMA powder between aluminum plates. The effect of hot pressing temperature and subsequent heat treatments (solutionizing and peak aging) on the SMA particles was studied. It was found that, at the temperatures required, Co-Ni-Al developed a second phase that restricted the transformation from austenite to martensite, thus rendering it ineffective as a candidate for the embedded particles. Conversely, Ni-Ti did survive the embedding process and it was found that the solutionizing heat treatment applied after hot pressing was the main driver in determining the final transformation temperatures for the Ni-Ti particles. The effect of hot

  11. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    International Nuclear Information System (INIS)

    Albuquerque, Victor Hugo C. de; Melo, Tadeu Antonio de A; Gomes, Rodinei M.; Lima, Severino Jackson G. de; Tavares, Joao Manuel R.S.

    2010-01-01

    Research highlights: → This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. → The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. → Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. → First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. → The results are of relevant value to enhance the understanding of the CuAlBe alloy. - Abstract: This work is a study of the influence of grain size and temperature on the toughness of CuAlBe shape memory alloys with (CuAlBeNbNi) and without NbNi (CuAlBe) grain refiner elements. The toughness analysis was based on the V-notch Charpy impact test under temperatures of -150, -100, -50, 0, 50, 100 and 150 deg. C. A statistical analysis of the results led to the conclusion that the toughness of both alloys was influenced by temperature and grain size. The CuAlBeNbNi alloy absorbed higher impact energy than the CuAlBe alloy showing that the refining elements improved the toughness of the alloy. To confirm and complement these findings, the fracture surfaces were evaluated by stereomicroscopy. Smooth homogeneous surfaces and rough heterogonous surfaces were detected for the CuAlBeNbNi and CuAlBe alloys, respectively. Predominately brittle zones were confirmed by scanning electron microscopy in both alloys. Furthermore, to determine the phase transformation temperatures and the associated microstructures, the alloys were assessed by conventional differential scanning calorimetry (DSC) and DSC with optical microscopy.

  12. Grain size and temperature influence on the toughness of a CuAlBe shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, Victor Hugo C. de, E-mail: victor.albuquerque@fe.up.pt [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Melo, Tadeu Antonio de A, E-mail: tadeu@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Gomes, Rodinei M., E-mail: gomes@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Lima, Severino Jackson G. de, E-mail: jackson@lsr.ct.ufpb.br [Universidade Federal da Paraiba (UFPB), Departamento de Engenharia Mecanica (DEM), Laboratorio de Solidificacao Rapida LSR, Cidade Universitaria, S/N 58059-900 Joao Pessoa, PB (Brazil); Tavares, Joao Manuel R.S., E-mail: tavares@fe.up.pt [Faculdade de Engenharia da Universidade do Porto (FEUP), Departamento de Engenharia Mecanica (DEMec)/Instituto de Engenharia Mecanica e Gestao Industrial INEGI, Rua Dr. Roberto Frias, S/N 4200-465 Porto (Portugal)

    2010-11-25

    Research highlights: {yields} This work evaluated the capacity of a CuAlBe alloy to absorb energy until rupture. {yields} The V-notch Charpy test was adopted at -150, -100, -50, 0, 50, 100 and 150 deg. C. {yields} Charpy tests were complemented by DSC, DSC with optical microscope and by SEM. {yields} First work to analyze the toughness of a CuAlBe alloy based on the Charpy test. {yields} The results are of relevant value to enhance the understanding of the CuAlBe alloy. - Abstract: This work is a study of the influence of grain size and temperature on the toughness of CuAlBe shape memory alloys with (CuAlBeNbNi) and without NbNi (CuAlBe) grain refiner elements. The toughness analysis was based on the V-notch Charpy impact test under temperatures of -150, -100, -50, 0, 50, 100 and 150 deg. C. A statistical analysis of the results led to the conclusion that the toughness of both alloys was influenced by temperature and grain size. The CuAlBeNbNi alloy absorbed higher impact energy than the CuAlBe alloy showing that the refining elements improved the toughness of the alloy. To confirm and complement these findings, the fracture surfaces were evaluated by stereomicroscopy. Smooth homogeneous surfaces and rough heterogonous surfaces were detected for the CuAlBeNbNi and CuAlBe alloys, respectively. Predominately brittle zones were confirmed by scanning electron microscopy in both alloys. Furthermore, to determine the phase transformation temperatures and the associated microstructures, the alloys were assessed by conventional differential scanning calorimetry (DSC) and DSC with optical microscopy.

  13. The effect of addition of various elements on properties of NiTi-based shape memory alloys for biomedical application

    Science.gov (United States)

    Kök, Mediha; Ateş, Gonca

    2017-04-01

    In biomedical applications, NiTi and NiTi-based alloys that show their shape memory effects at body temperature are preferred. In this study, the purpose is to produce NiTi and NiTi-based alloys with various chemical rates and electron concentrations and to examine their various physical properties. N45Ti55, Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Sn, Co) alloys were produced in an arc melter furnace in this study. After the homogenization of these alloys, the martensitic phase transformation temperatures were determined with differential-scanner calorimeter. The transformation temperature was found to be below the 37 ° C (body temperature) in Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co) alloys; and the transformation temperature of the N45Ti55, Ni48Ti51Sn alloys was found to be over 37 ° C . Then, the micro and crystal structure analyses of the alloys were made, and it was determined that Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co) alloys, which were in austenite phase at room temperature, included B2 (NiTi) phase and Ti2Ni precipitation phase, and the alloys that were in the martensite phase at room temperature included B19ı (NiTi) phase and Ti2Ni phase. The common phase in both alloy groups is the Ti2Ni phase, and this type of phase is generally seen in NiTi alloys that are rich in titanium (Ti-rich).

  14. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    Science.gov (United States)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  15. Enhanced stress corrosion cracking resistance and electrical conductivity of a T761 treated Al-Zn-Mg-Cu alloy thin plate

    Science.gov (United States)

    Chen, Xu; Zhai, Sudan; Gao, Di; Liu, Ye; Xu, Jing; Liu, Yang

    2018-01-01

    The stress corrosion cracking (SCC) behavior, electrical conductivity and mechanical properties of an Al-Zn-Mg-Cu alloy pre-stretched thin plate for wing skin were researched in this paper. The microstructures and SCC fracture surfaces of the alloy treated at different conditions were characterized by transmission electron microscopy, optical microscopy and scanning electron microscopy. Results indicated that with the increasing of aging temperature, the electrical conductivity and the elongation increased greatly, while the strength decreased gradually which were closely associated with the type and morphology of the precipitates. Compared with the T6 treated alloy, the SCC resistance of the T761 treated Al-Zn-Mg-Cu alloy was improved greatly. The SCC behavior of the T6 treated alloy was dominated by anodic dissolution theory, whereas the hydrogen induced cracking controlled the fracture behavior of the T761 treated alloy which was influenced by the morphology of grain boundary precipitates in this investigated alloy.

  16. NiTi thin films on a flexible substrate : Fabrication & Characterization

    NARCIS (Netherlands)

    Kotnur, V.G.

    2015-01-01

    NiTi (Nickel Titanium) is a shape memory alloy (SMA) known for shape memory effect and superelasticity. The shape memory effect and superelasticity allows NiTi to be strained reversibly unto 6-8%. NiTi thin films are of technological interest as actuator materials in microelectromechanical systems

  17. Moessbauer study of the ageing effects on the structure of CuZnSn shape memory alloy

    International Nuclear Information System (INIS)

    Frackowiak, J.E.; Dutkiewicz, J.; Morgiel, J.

    1986-01-01

    Using the 119 Sn Moessbauer spectroscopy the study of ageing effects on the structure of a CuZnSn shape memory alloy was performed. Two stages of ageing at 200 0 C were observed. The first stage is connected with formation of DO 3 structure and the second stage with precipitation of α and γ phases. (Auth.)

  18. Development, Integration, and Testing of a Nano-Satellite Coupling Mechanism Using Shape Memory Alloy for an Interference Joint

    Science.gov (United States)

    2012-12-01

    symmetric to cambered. The medical field uses SMA for stents, filters, orthodontic wires , and for minimally invasive surgery. The oil industry uses SMA...Shape Memory Alloy, SMA, Nickel Titanium, NiTi, Nichrome wire , press-fit, interference joint, austenite, twinned martensite, detwinned martensite...13  C.  COMPARE DEVELOPED DEVICES ................................................. 14  1.  Nichrome Burn Wire

  19. Finding the energy source for self-propagating high-temperature synthesis production of NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Novák, P.; Školáková, A.; Pignol, D.; Průša, F.; Salvetr, P.; Kubatík, Tomáš František; Perriere, L.; Karlík, M.

    2016-01-01

    Roč. 181, September (2016), s. 295-300 ISSN 0254-0584 Institutional support: RVO:61389021 Keywords : NiTi * Shape memory alloys * Powder metallurgy * Microstructure Subject RIV: JG - Metallurgy Impact factor: 2.084, year: 2016 http://www.sciencedirect.com/science/article/pii/S025405841630476X

  20. The influence of imposed strain on the development of microstructure and transformation characteristics of Ni-Ti shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Kocich, R.; Krusa, M.; Szurman, I.; Dlouhý, Antonín

    2011-01-01

    Roč. 509, č. 6 (2011), s. 2716-2722 ISSN 0925-8388 Institutional research plan: CEZ:AV0Z20410507 Keywords : intermetallics * metals and alloys * shape memory Subject RIV: JG - Metallurgy Impact factor: 2.289, year: 2011

  1. Effect of magnetostatic interactions on twin boundary motion in Ni-Mn-Ga magnetic shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Vokoun, David; Kopecký, Vít; Beleggia, M.

    2015-01-01

    Roč. 6, Jul (2015), s. 1000204 ISSN 1949-307X R&D Projects: GA ČR GA15-00262S Institutional support: RVO:68378271 Keywords : magnetism in solids * demagnetization factors * magnetostatic interactions * shape memory alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.978, year: 2015

  2. Modeling of Stress Development During Thermal Damage Healing in Fiber-reinforced Composite Materials Containing Embedded Shape Memory Alloy Wires

    NARCIS (Netherlands)

    Bor, Teunis Cornelis; Warnet, Laurent; Akkerman, Remko; de Boer, Andries

    2010-01-01

    Fiber-reinforced composite materials are susceptible to damage development through matrix cracking and delamination. This article concerns the use of shape memory alloy (SMA) wires embedded in a composite material to support healing of damage through a local heat treatment. The composite material

  3. Neutron diffraction studies of the stress effect on texture transformations in NiTi shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Šittner, Petr; Neov, Dimitar; Lukáš, Petr; Toebbens, D. M.

    2004-01-01

    Roč. 12, - (2004), s. 115-120 ISSN 1023-8166 R&D Projects: GA AV ČR IAA1048107; GA ČR GA106/01/0396 Institutional research plan: CEZ:AV0Z1010914; CEZ:AV0Z1048901 Keywords : shape memory alloy * martensitic transformation * texture * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism

  4. Co and In doped Ni-Mn-Ga magnetic shape memory alloys: a thorough structural, magnetic and magnetocaloric study

    Czech Academy of Sciences Publication Activity Database

    Fabbrici, S.; Porcari, G.; Cugini, F.; Solzi, M.; Kamarád, Jiří; Arnold, Zdeněk; Cabassi, R.; Albertini, F.

    2014-01-01

    Roč. 16, č. 4 (2014), s. 2204-2222 ISSN 1099-4300 Institutional support: RVO:68378271 Keywords : magnetic shape memory materials * magnetocaloric effect * multifunctional Heusler alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.502, year: 2014

  5. Application of Taguchi method to optimization of surface roughness during precise turning of NiTi shape memory alloy

    Science.gov (United States)

    Kowalczyk, M.

    2017-08-01

    This paper describes the research results of surface quality research after the NiTi shape memory alloy (Nitinol) precise turning by the tools with edges made of polycrystalline diamonds (PCD). Nitinol, a nearly equiatomic nickel-titanium shape memory alloy, has wide applications in the arms industry, military, medicine and aerospace industry, and industrial robots. Due to their specific properties NiTi alloys are known to be difficult-to-machine materials particularly by using conventional techniques. The research trials were conducted for three independent parameters (vc, f, ap) affecting the surface roughness were analyzed. The choice of parameter configurations were performed by factorial design methods using orthogonal plan type L9, with three control factors, changing on three levels, developed by G. Taguchi. S/N ratio and ANOVA analyses were performed to identify the best of cutting parameters influencing surface roughness.

  6. Atom redistribution and multilayer structure in NiTi shape memory alloy induced by high energy proton irradiation

    Science.gov (United States)

    Wang, Haizhen; Yi, Xiaoyang; Zhu, Yingying; Yin, Yongkui; Gao, Yuan; Cai, Wei; Gao, Zhiyong

    2017-10-01

    The element distribution and surface microstructure in NiTi shape memory alloys exposed to 3 MeV proton irradiation were investigated. Redistribution of the alloying element and a clearly visible multilayer structure consisting of three layers were observed on the surface of NiTi shape memory alloys after proton irradiation. The outermost layer consists primarily of a columnar-like TiH2 phase with a tetragonal structure, and the internal layer is primarily comprised of a bcc austenite phase. In addition, the Ti2Ni phase, with an fcc structure, serves as the transition layer between the outermost and internal layer. The above-mentioned phenomenon is attributed to the preferential sputtering of high energy protons and segregation induced by irradiation.

  7. Fabrication of SLM NiTi Shape Memory Alloy via Repetitive Laser Scanning

    Science.gov (United States)

    Khoo, Zhong Xun; Liu, Yong; Low, Zhi Hong; An, Jia; Chua, Chee Kai; Leong, Kah Fai

    2018-01-01

    Additive manufacturing has the potential to overcome the poor machinability of NiTi shape-memory alloy in fabricating smart structures of complex geometry. In recent years, a number of research activities on selective laser melting (SLM) of NiTi have been carried out to explore the optimal parameters for producing SLM NiTi with the desired phase transformation characteristics and shape-memory properties. Different effects of energy density and processing parameters on the properties of SLM NiTi were reported. In this research, a new approach—repetitive laser scanning—is introduced to meet these objectives as well. The results suggested that the laser absorptivity and heat conductivity of materials before and after the first scan significantly influence the final properties of SLM NiTi. With carefully controlled repetitive scanning process, the fabricated samples have demonstrated shape-memory effect of as high as 5.11% (with an average value of 4.61%) and exhibited comparable transformation characteristics as the NiTi powder used. These results suggest the potential for fabricating complex NiTi structures with similar properties to that of the conventionally produced NiTi parts.

  8. Atomically Thin Ordered Alloys of Transition Metal Dichalcogenides: Stability and Band Structures

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Jacobsen, Karsten Wedel; Thygesen, Kristian Sommer

    2016-01-01

    We explore the possibility of modulating the electronic band edges of the transition metal dichalcogenides (TMD) via alloying of different semiconductors within the same group (intra-group alloying). The stability of the ordered alloys is assessed from the calculated mixing enthalpy which is found...

  9. Effect of W Contents on Martensitic Transformation and Shape Memory Effect in Co-Al-W Alloys

    Science.gov (United States)

    Yang, X.; Qian, B. N.; Peng, H. B.; Wu, B. J.; Wen, Y. H.

    2018-04-01

    To clarify the effect of W contents on the shape memory effect (SME) in the Co-Al alloys and its influencing mechanism, the SME, martensitic transformation, and deformation behavior were studied in the Co-7Al-xW ( x = 0, 4, 6, 9 wt pct) alloys. The results showed that the additions of W all deteriorated the SME in Co-7Al alloy when deformed at room temperature. However, when deformed in liquid nitrogen, the SME in Co-7Al alloy could be remarkably improved from 43 to 78 pct after the addition of 4 pct W, above which the SME decreased rapidly with the increase of W content although the yield strength of the parent phase rose due to the solution strengthening of W. The deterioration in SME induced by the excessive addition of W could be ascribed to its resulting significant drop of the start temperature of martensitic transformation.

  10. Effect of Isothermal Ageing on Structural and Magnetic Properties of Ni47Mn40Sn13 Ferromagnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    A. Ghotbi varzaneh

    2015-12-01

    Full Text Available In this investigation, Ni47Mn40Sn13 ferromagnetic shape memory alloy was prepared by mechanical alloying. The metal powders were ball milled in argon atmosphere for 20 hours. X-ray diffraction pattern confirmed formation of crystalline structure of Heusler alloy. As-milled powder samples were sealed in quartz tubes under high vacuum and subjected to heat treatments at 950°C for different time durations. Then, the effect of isothermal ageing on structural, magnetic and electrical properties of samples was investigated. Results of electrical resistance displayed a metal-like behavior around martensitic transformation. The results showed that 16 hours of annealing was the optimal time for producing this alloy which could be an appropriate candidate for magnetic refrigerant.

  11. The study of mechanical properties and reactive stresses in the i-Ni-Nb shape memory alloys

    International Nuclear Information System (INIS)

    Popov, N.N.; Sysoeva, T.I.; Lar'kin, V.F.; Vedernikova, I.I.; Prokoshkin, S.D.

    2007-01-01

    One investigated into the effect of the induced deformation value, rate and temperature, of the thermal treatment procedure and of the chemical composition on the mechanical properties and the development of the reactive stresses in Ti-Ni-Nb system shape memory alloys. One showed the effect of the material composition and of the deformation temperature on the mechanical features of the investigated alloys. One determined the temperature and deformation conditions ensuring the maximum level of the reactive stresses in the alloys. One revealed the dependence of the maximum reactive stress value on the austenite mechanical features, namely, on its yield limit. One chose Ti-Ni-Nb alloy compositions applicable in the pipeline thermomechanical connections [ru

  12. Effect of Si on the reversibility of stress-induced martensite in Fe-Mn-Si shape memory alloys

    International Nuclear Information System (INIS)

    Stanford, N.; Dunne, D.P.

    2010-01-01

    Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a-vis shape memory. This paper examines the effect of Si on the morphology and the crystallography of the martensite in the Fe-Mn-Si system. It is concluded that the addition of Si increases the c/a ratio of the martensite, reduces the transformation volume change and decreases the atomic spacing difference between the parallel close-packed directions in the austenite-martensite interface (habit) plane. It is proposed that, in addition to austenite strengthening, Si enhances reversibility by reducing the volume change and the interfacial atomic mismatch between the martensite and the austenite. Although shape memory is improved, transformation reversibility remains limited by the necessary misfit dislocations that accommodate the atomic spacing differences in the interface.

  13. Microstructure evolution and coercivity enhancement in Nd-Fe-B thin films diffusion-processed by R-Al alloys (R=Nd, Pr)

    Science.gov (United States)

    Xie, Yigao; Yang, Yang; Zhang, Tongbo; Fu, Yanqing; Jiang, Qingzheng; Ma, Shengcan; Zhong, Zhenchen; Cui, Weibin; Wang, Qiang

    2018-05-01

    Diffusion process by Nd-Al and Pr-Al alloys was compared and investigated in Nd-Fe-B thin films. Enhanced coercivity 2.06T and good squareness was obtained by using Pr85Al15 and Nd85Al15 alloys as diffusion sources. But the coercivity of diffusion-processed thin films by Pr70Al30 and Pr55Al45 alloys decreased to 2.04T and 1.82T. High ambient coercivity of 2.26T was achieved in diffusion-processed thin film by Nd70Al30 leading to an improved coercivity thermal stability because Nd2Fe14B grains were enveloped by Nd-rich phase as seen by transmission electron microscopy Nd-loss image. Meanwhile, microstructure-dependent parameters α and Neff were improved. However, high content of Al in diffusion-processed thin film by Nd55Al45 lead to degraded texture and coercivity.

  14. Fabrication and AE characteristics of TiNi/A16061 shape memory alloy composite

    International Nuclear Information System (INIS)

    Park, Young Chul; Lee, Jin Kyung

    2004-01-01

    TiNi/A16061 Shape Memory Alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which underwent pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/A16061 SMA composite

  15. Confinement of NORMAL- AND HIGH-STRENGTH CONCRETE by Shape Memory Alloy (SMA) Spirals

    Science.gov (United States)

    Gholampour, A.; Ozbakkaloglu, T.

    2018-01-01

    This paper presents the results of an experimental study on the axial compressive behaviour of normal- and high-strength concrete (NSC and HSC) confined by shape memory alloy (SMA) spirals. A spiral pitch space of 36 and 20 mm was used for SMA confinement of NSC and HSC columns, respectively. The confining pressure was applied on the concrete cylinders by SMA spirals that were prestrained at 0, 5.5, and 9.5%. The compression test results on the SMA-confined specimens indicate that the prestrain level of SMA significantly affects the axial compressive behaviour of both NSC and HSC. An increase in the level of prestrain leads to an increase in the peak axial stress and corresponding strain of SMA-confined concrete.

  16. Shape Memory Alloy Research and Development at NASA Glenn - Current and Future Progress

    Science.gov (United States)

    Benafan, Othmane

    2015-01-01

    Shape memory alloys (SMAs) are a unique class of multifunctional materials that have the ability to recover large deformations or generate high stresses in response to thermal, mechanical and or electromagnetic stimuli. These abilities have made them a viable option for actuation systems in aerospace, medical, and automotive applications, amongst others. However, despite many advantages and the fact that SMA actuators have been developed and used for many years, so far they have only found service in a limited range of applications. In order to expand their applications, further developments are needed to increase their reliability and stability and to address processing, testing and qualification needed for large-scale commercial application of SMA actuators.

  17. Adaptive online inverse control of a shape memory alloy wire actuator using a dynamic neural network

    International Nuclear Information System (INIS)

    Mai, Huanhuan; Liao, Xiaofeng; Song, Gangbing

    2013-01-01

    Shape memory alloy (SMA) actuators exhibit severe hysteresis, a nonlinear behavior, which complicates control strategies and limits their applications. This paper presents a new approach to controlling an SMA actuator through an adaptive inverse model based controller that consists of a dynamic neural network (DNN) identifier, a copy dynamic neural network (CDNN) feedforward term and a proportional (P) feedback action. Unlike fixed hysteresis models used in most inverse controllers, the proposed one uses a DNN to identify online the relationship between the applied voltage to the actuator and the displacement (the inverse model). Even without a priori knowledge of the SMA hysteresis and without pre-training, the proposed controller can precisely control the SMA wire actuator in various tracking tasks by identifying online the inverse model of the SMA actuator. Experiments were conducted, and experimental results demonstrated real-time modeling capabilities of DNN and the performance of the adaptive inverse controller. (paper)

  18. Nonlinear Analysis of Actuation Performance of Shape Memory Alloy Composite Film Based on Silicon Substrate

    Directory of Open Access Journals (Sweden)

    Shuangshuang Sun

    2014-01-01

    Full Text Available The mechanical model of the shape memory alloy (SMA composite film with silicon (Si substrate was established by the method of mechanics of composite materials. The coupled action between the SMA film and Si substrate under thermal loads was analyzed by combining static equilibrium equations, geometric equations, and physical equations. The material nonlinearity of SMA and the geometric nonlinearity of bending deformation were both considered. By simulating and analyzing the actuation performance of the SMA composite film during one cooling-heating thermal cycle, it is found that the final cooling temperature, boundary condition, and the thickness of SMA film have significant effects on the actuation performance of the SMA composite film. Besides, the maximum deflection of the SMA composite film is affected obviously by the geometric nonlinearity of bending deformation when the thickness of SMA film is very large.

  19. Laser actuated shape memory alloy mobile micro-robot: initial results

    Science.gov (United States)

    van den Broek, Peter-Jan; Potsaid, Benjamin; Bellouard, Yves; Wen, John T.

    2007-10-01

    Mobile micro-robots are needed for micro positioning, manipulation or manufacturing small components, or sensing in chemical and biological environments. The design of mobile micro-robots poses challenges in terms of fabrication, actuation and sensing. Current approaches require complex assembly or sophisticated MEMS processes, to obtain actuators with a high energy density. Furthermore, the energy source for locomotion has either to be carried onboard (which by itself poses additional miniaturization challenges) or be remotely located so that the energy is transferred through tethered cables or wirelessly. In this paper, we propose a radically different approach: the micro-robot consists of a single piece of shape memory alloy (SMA) suitably shaped to perform inchworm-like locomotion, and remotely actuated by a laser beam. We report the modeling and design of an SMA inchworm like micro-robot, and the first experimental results.

  20. Shape memory alloy-based small crawling robots inspired by C. elegans

    Energy Technology Data Exchange (ETDEWEB)

    Yuk, Hyunwoo; Kim, Daeyeon; Shin, Jennifer H [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of); Lee, Honggu; Jo, Sungho, E-mail: shjo@kaist.ac.kr, E-mail: j_shin@kaist.ac.kr [Department of Computer Science, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon (Korea, Republic of)

    2011-12-15

    Inspired by its simple musculature, actuation and motion mechanisms, we have developed a small crawling robot that closely mimics the model organism of our choice: Caenorhabditis elegans. A thermal shape memory alloy (SMA) was selected as an actuator due to the similarities of its properties to C. elegans muscles. Based on the anatomy of C. elegans, a 12-unit robot was designed to generate a sinusoidal undulating motion. Each body unit consisting of a pair of SMA actuators is serially connected by rigid links with an embedded motion control circuit. A simple binary operation-based motion control mechanism was implemented using a microcontroller. The assembled robot can execute C. elegans-like motion with a 0.17 Hz undulation frequency. Its motion is comparable to that of a real worm.

  1. Tuning the vibration of a rotor with shape memory alloy metal rubber supports

    Science.gov (United States)

    Ma, Yanhong; Zhang, Qicheng; Zhang, Dayi; Scarpa, Fabrizio; Liu, Baolong; Hong, Jie

    2015-09-01

    The paper describes a novel smart rotor support damper with variable stiffness made with a new multifunctional material - the shape memory alloy metal rubber (SMA-MR). SMA-MR gives high load bearing capability (yield limit up to 100 MPa and stiffness exceeding 1e8 N/m), high damping (loss factor between 0.15 and 0.3) and variable stiffness (variation of 2.6 times between martensite and austenite phases). The SMA-MR has been used to replace a squeeze film damper and combined with an elastic support. The mechanical performance of the smart support damper has been investigated at room and high temperatures on a rotor test rig. The vibration tuning capabilities of the SMA-MR damper have been evaluated through FEM simulations and experimental tests. The study shows the feasibility of using the SMA-MR material for potential applications of active vibration control at different temperatures in rotordynamics systems.

  2. A 3D finite strain phenomenological constitutive model for shape memory alloys considering martensite reorientation

    Science.gov (United States)

    Arghavani, J.; Auricchio, F.; Naghdabadi, R.; Reali, A.; Sohrabpour, S.

    2010-06-01

    Most devices based on shape memory alloys experience both finite deformations and non-proportional loading conditions in engineering applications. This motivates the development of constitutive models considering finite strain as well as martensite variant reorientation. To this end, in the present article, based on the principles of continuum thermodynamics with internal variables, a three-dimensional finite strain phenomenological constitutive model is proposed taking its basis from the recent model in the small strain regime proposed by Panico and Brinson (J Mech Phys Solids 55:2491-2511, 2007). In the finite strain constitutive model derivation, a multiplicative decomposition of the deformation gradient into elastic and inelastic parts, together with an additive decomposition of the inelastic strain rate tensor into transformation and reorientation parts is adopted. Moreover, it is shown that, when linearized, the proposed model reduces exactly to the original small strain model.

  3. Quantification of parameter uncertainty for robust control of shape memory alloy bending actuators

    International Nuclear Information System (INIS)

    Crews, John H; McMahan, Jerry A; Smith, Ralph C; Hannen, Jennifer C

    2013-01-01

    In this paper, we employ Bayesian parameter estimation techniques to derive gains for robust control of smart materials. Specifically, we demonstrate the feasibility of utilizing parameter uncertainty estimation provided by Markov chain Monte Carlo (MCMC) methods to determine controller gains for a shape memory alloy bending actuator. We treat the parameters in the equations governing the actuator’s temperature dynamics as uncertain and use the MCMC method to construct the probability densities for these parameters. The densities are then used to derive parameter bounds for robust control algorithms. For illustrative purposes, we construct a sliding mode controller based on the homogenized energy model and experimentally compare its performance to a proportional-integral controller. While sliding mode control is used here, the techniques described in this paper provide a useful starting point for many robust control algorithms. (paper)

  4. Adaptive proportional–integral–derivative tuning sliding mode control for a shape memory alloy actuator

    International Nuclear Information System (INIS)

    Tai, Nguyen Trong; Ahn, Kyoung Kwan

    2011-01-01

    In this paper, a novel adaptive sliding mode control with a proportional–integral–derivative (PID) tuning method is proposed to control a shape memory alloy (SMA) actuator. The goal of the controller is to achieve system robustness against the SMA hysteresis phenomenon, system uncertainties and external disturbances. In the controller, the PID controller is employed to approximate the sliding mode equivalent control along the direction that makes the sliding mode asymptotically stable. Due to the system nonlinearity, the PID control gain parameters are systematically computed online according to the adaptive law. To improve the transient performance, the initial PID gain parameters are optimized by the particle swarm optimization (PSO) method. Simulation and experimental results demonstrate that the controller performs well for the desired trajectory tracking, and the hysteresis phenomenon is compensated for completely. The control results are also compared with the optimized PID controller

  5. Preliminary investigation of fabrication composite structures by using shape memory alloys

    Science.gov (United States)

    Klein, W.; Dudek, O.

    2017-09-01

    The paper shows method of smart forming composite structures and fundamentals of propose fabrication technology. The presented method is based on innovative 3D printing technics with SMA (Shape Memory Alloy) fibres application. The SMA fibres layout cause an eccentric axial load after thermal activation. The result of this process is composite structures deflection in a predictable direction. The technology demonstrator sample was fabricated as well as numerical simulations were performed in aim of proof of concept. The identification process was developed to determine the layout of SMA fibres. The simulations were performed in MATLAB and ANSYS environment, where the genetic algorithm was used to identify geometrical parameters. The MAC (Modal Assurance Criterion) criterion was used to compare nodal solution with the predefined shape pattern. The simulation results shows possibilities of forming composite structures on the example of deflected beam.

  6. Wear Properties of Porous NiTi Orthopedic Shape Memory Alloy

    Science.gov (United States)

    Wu, Shuilin; Liu, Xiangmei; Yeung, K. W. K.; Xu, Z. S.; Chung, C. Y.; Chu, Paul K.

    2012-12-01

    Porous NiTi shape memory alloy (SMA) scaffolds have great potential to be used as orthopedic implants because of their porous structure and superior physical properties. Its metallic nature provides it with better mechanical properties and Young's modulus close to that of natural bones. Besides allowing tissue ingrowth and transfer of nutrients, porous SMA possesses unique pseudoelastic properties compatible to natural hard tissues like bones and tendons, thus expediting in vivo osseointegration. However, the nickel release from debris and the metal surface may cause osteocytic osteolysis at the interface between the artificial implants and bone tissues. Subsequent mobilization may finally lead to implant failure. In this study, the wear properties of porous NiTi with different porosities processed at different treatment temperatures are determined. The results of the study show that the porosity, phase transformation temperature, and annealing temperature are major factors influencing the wear characteristics of porous NiTi SMA.

  7. Numerical Study of the Plasticity-Induced Stabilization Effect on Martensitic Transformations in Shape Memory Alloys

    Science.gov (United States)

    Junker, Philipp; Hempel, Philipp

    2017-12-01

    It is well known that plastic deformations in shape memory alloys stabilize the martensitic phase. Furthermore, the knowledge concerning the plastic state is crucial for a reliable sustainability analysis of construction parts. Numerical simulations serve as a tool for the realistic investigation of the complex interactions between phase transformations and plastic deformations. To account also for irreversible deformations, we expand an energy-based material model by including a non-linear isotropic hardening plasticity model. An implementation of this material model into commercial finite element programs, e.g., Abaqus, offers the opportunity to analyze entire structural components at low costs and fast computation times. Along with the theoretical derivation and expansion of the model, several simulation results for various boundary value problems are presented and interpreted for improved construction designing.

  8. On the driving force for crack growth during thermal actuation of shape memory alloys

    Science.gov (United States)

    Baxevanis, T.; Parrinello, A. F.; Lagoudas, D. C.

    2016-04-01

    The effect of thermomechanically induced phase transformation on the driving force for crack growth in polycrystalline shape memory alloys is analyzed in an infinite center-cracked plate subjected to a thermal actuation cycle under mechanical load in plain strain. Finite element calculations are carried out to determine the mechanical fields near the static crack and the crack-tip energy release rate using the virtual crack closure technique. A substantial increase of the energy release rate - an order of magnitude for some material systems - is observed during the thermal cycle due to the stress redistribution induced by large scale phase transformation. Thus, phase transformation occurring due to thermal variations under mechanical load may result in crack growth if the crack-tip energy release rate reaches a material specific critical value.

  9. Design and testing of shape memory alloy actuation mechanism for flapping wing micro unmanned aerial vehicles

    Science.gov (United States)

    Kamaruzaman, N. F.; Abdullah, E. J.

    2017-12-01

    Shape memory alloy (SMA) actuator offers great solution for aerospace applications with low weight being its most attractive feature. A SMA actuation mechanism for the flapping micro unmanned aerial vehicle (MAV) is proposed in this study, where SMA material is the primary system that provides the flapping motion to the wings. Based on several established design criteria, a design prototype has been fabricated to validate the design. As a proof of concept, an experiment is performed using an electrical circuit to power the SMA actuator to evaluate the flapping angle. During testing, several problems have been observed and their solutions for future development are proposed. Based on the experiment, the average recorded flapping wing angle is 14.33° for upward deflection and 12.12° for downward deflection. This meets the required design criteria and objective set forth for this design. The results prove the feasibility of employing SMA actuators in flapping wing MAV.

  10. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    Science.gov (United States)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  11. Impact of Different Electrical Time-Based Activations on NiTi Shape Memory Alloys

    Science.gov (United States)

    Fleczok, Benjamin; Rathmann, Christian; Otibar, Dennis; Weirich, Antonia; Kuhlenkötter, Bernd

    2017-06-01

    The use of NiTi shape-memory alloys (SMA) in actuators bears significant advantages for designing robust, simple and lightweight applications. The SMA effect is based on a phase transformation of the atomic lattice in response to stress, strain and temperature. The resulting crystallographic configurations lead to a complex behavior revealing different electrical and mechanical characteristics. In view of the impact of thermo-mechanical cyclization on the operational lifetime, this paper investigates the influences of different types of electrical activation. For this purpose, six current curves with six samples each are compared to a reference activation with regard to the operational lifetime. The chosen time of activation is 1 second in accordance with an industrially relevant cycle of technical actuators. Based on the results of these investigations, recommendations of the activation type shall be developed for the operational lifetime of NiTi-SMA.

  12. Low carbon content NiTi shape memory alloy produced by electron beam melting

    Directory of Open Access Journals (Sweden)

    Otubo Jorge

    2004-01-01

    Full Text Available Earlier works showed that the use of electron beam melting is a viable process to produce NiTi shape memory alloy. In those works a static and a semi-dynamic processes were used producing small shell-shaped and cylindrical ingots respectively. The main characteristics of those samples were low carbon concentration and good composition homogeneity throughout the samples. This paper presents the results of scaling up the ingot size and processing procedure using continuous charge feeding and continuous casting. The composition homogeneity was very good demonstrated by small variation in martensitic transformation temperatures with carbon content around 0.013wt% compared to 0.04 to 0.06wt% of commercial products.

  13. Nitride coating enhances endothelialization on biomedical NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, 077125 Magurele-Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Marx, Philippe [AMF Company, Route de Quincy, 18120 Lury-sur-Arnon (France); Gordin, Doina-Margareta; Gloriant, Thierry [INSA Rennes, UMR CNRS 6226 ISCR, 20 Avenue des Buttes de Coësmes, 35708 Rennes Cedex 7 (France)

    2016-05-01

    Surface nitriding was demonstrated to be an effective process for improving the biocompatibility of implantable devices. In this study, we investigated the benefits of nitriding the NiTi shape memory alloy for vascular stent applications. Results from cell experiments indicated that, compared to untreated NiTi, a superficial gas nitriding treatment enhanced the adhesion of human umbilical vein endothelial cells (HUVECs), cell spreading and proliferation. This investigation provides data to demonstrate the possibility of improving the rate of endothelialization on NiTi by means of nitride coating. - Highlights: • Gas nitriding process of NiTi is competent to promote cell spreading. • Surface nitriding of NiTi is able to stimulate focal adhesion formation and cell proliferation. • Similar expression pattern of vWf and eNOS was exhibited by bare and nitrided NiTi. • Gas nitriding treatment of NiTi shows promise for better in vivo endothelialization.

  14. Shape Memory Alloy connectors for Ultra High Vacuum applications: a breakthrough for accelerator technologies

    CERN Document Server

    AUTHOR|(CDS)2091326; Garion, Cedric

    Beam-pipe coupling in particle accelerators is nowadays provided by metallic flanges that are tightly connected by several screws or heavy collars. Their installation and dismounting in radioactive areas contribute to the radiation doses received by the technical personnel. Owing to the increased proton-beam intensity and luminosity of the future High-Luminosity LHC (HL-LHC), radioactivity in some specific zones will be significantly higher than in the present LHC; the presence of the technical staff in these areas will be strictly controlled and minimized. Remote interventions are being considered, too. Shape Memory Alloys (SMAs) offer a unique possibility to generate tight connections and fast clamping/unclamping by remotely changing the temperature of the junction unit. In fact, SMAs exhibit unique strain and stress recovery capabilities which are related to reversible phase transition mechanisms, induced thermally or mechanically. In this PhD work, a novel Ultra-High Vacuum (UHV) coupling system based on ...

  15. Visible microactuation of a ferromagnetic shape memory alloy by focused laser beam

    International Nuclear Information System (INIS)

    Hu, Zhibin; Tamang, Rajesh; Varghese, Binni; Sow, Chorng-Haur; Rajini Kanth, B; Mukhopadhyay, P K

    2012-01-01

    We used a focused laser beam to achieve large amplitude and localized controlled actuation in a microstructure made of a ferromagnetic shape memory alloy. Significant deformation (18 µm) was achieved at low laser power (20 mW) and the amplitude of actuation could be linearly controlled with the laser power. The rapid mechanical actuation shows no apparent sign of fatigue even after a million continuous oscillatory cycles. As a possible mechanism, we propose that the deformation of structure was induced by a combination of the thermal effect and the magnetic field of the incident laser light. This is possibly the first such reported visual evidence of microactuation of materials due to the optomagnetic field. (fast track communication)

  16. Numerical simulation of superelastic shape memory alloys subjected to dynamic loads

    International Nuclear Information System (INIS)

    Cismaşiu, Corneliu; Amarante dos Santos, Filipe P

    2008-01-01

    Superelasticity, a unique property of shape memory alloys (SMAs), allows the material to recover after withstanding large deformations. This recovery takes place without any residual strains, while dissipating a considerable amount of energy. This property makes SMAs particularly suitable for applications in vibration control devices. Numerical models, calibrated with experimental laboratory tests from the literature, are used to investigate the dynamic response of three vibration control devices, built up of austenitic superelastic wires. The energy dissipation and re-centering capabilities, important features of these devices, are clearly illustrated by the numerical tests. Their sensitivity to ambient temperature and strain rate is also addressed. Finally, one of these devices is tested as a seismic passive vibration control system in a simplified numerical model of a railway viaduct, subjected to different ground accelerations

  17. Direct observation of hierarchical nucleation of martensite and size-dependent superelasticity in shape memory alloys.

    Science.gov (United States)

    Liu, Lifeng; Ding, Xiangdong; Li, Ju; Lookman, Turab; Sun, Jun

    2014-02-21

    Martensitic transformation usually creates hierarchical internal structures beyond mere change of the atomic crystal structure. Multi-stage nucleation is thus required, where nucleation (level-1) of the underlying atomic crystal lattice does not have to be immediately followed by the nucleation of higher-order superstructures (level-2 and above), such as polysynthetic laths. Using in situ transmission electron microscopy (TEM), we directly observe the nucleation of the level-2 superstructure in a Cu-Al-Ni single crystal under compression, with critical super-nuclei size L2c around 500 nm. When the sample size D decreases below L2c, the superelasticity behavior changes from a flat stress plateau to a continuously rising stress-strain curve. Such size dependence definitely would impact the application of shape memory alloys in miniaturized MEMS/NEMS devices.

  18. Coupling of metals and biominerals: characterizing the interface between ferromagnetic shape-memory alloys and hydroxyapatite.

    Science.gov (United States)

    Allenstein, Uta; Selle, Susanne; Tadsen, Meike; Patzig, Christian; Höche, Thomas; Zink, Mareike; Mayr, Stefan G

    2015-07-22

    Durable, mechanically robust osseointegration of metal implants poses one of the largest challenges in contemporary orthopedics. The application of biomimetic hydroxyapatite (HAp) coatings as mediators for enhanced mechanical coupling to natural bone constitutes a promising approach. Motivated by recent advances in the field of smart metals that might open the venue for alternate therapeutic concepts, we explore their mechanical coupling to sputter-deposited HAp layers in a combined experimental-theoretical study. While experimental delamination tests and comprehensive structural characterization, including high-resolution transmission electron microscopy, are utilized to establish structure-property relationships, density functional theory based total energy calculations unravel the underlying physics and chemistry of bonding and confirm the experimental findings. Experiments and modeling indicate that sputter-deposited HAp coatings are strongly adherent to the exemplary ferromagnetic shape-memory alloys, Ni-Mn-Ga and Fe-Pd, with delamination stresses and interface bonding strength exceeding the physiological scales by orders of magnitude.

  19. Discrete memory schemes for finite strain thermoplasticity and application to shape memory alloys

    International Nuclear Information System (INIS)

    Favier, D.; Guelin, P.; Pegon, P.; Nowacki, W.K.

    1987-01-01

    A theory of finite strain plasticity has been proposed: The scheme of pure hysteresis with mixed transport has been extended to the case of non-rotational kinematics. Secondly, the simple shear case has been studied, taking into account Drucker's recent analysis regarding the 'appropriate simple idealizations for finite plasticity'. Illustrations are provided for general stress/strain paths. Also a new theory of isotropic hyperelasticity has been proposed. The 'reversible' relative Cauchy stress tensor (of type (1,1) and weight one) is defined in the dragged along coordinates as a tensorial isotropic function of the Almansi tensor and of its invariants (through the partial derivatives of the actual scalar density of elastic energy per unit extent of dragged along coordinates). The correspondance between strain and stress paths is then defined in a general form which is particularly convenient for the study of first order effects, limit behaviours, coupling and second order effects. Illustrations are provided. The addition of the pure hysteresis stress contribution σ a and of the reversible contribution σ rev leads to a scheme of 'superelasticity' departure to obtain a provisional scheme of shape memory effects. Some remarks are given regarding some of the possible generalizations of the scheme. (orig./GL)

  20. Internal stresses in steel plate generated by shape memory alloy inserts

    International Nuclear Information System (INIS)

    Malard, B.; Pilch, J.; Sittner, P.; Davydov, V.; Sedlák, P.; Konstantinidis, K.; Hughes, D.J.

    2012-01-01

    Graphical abstract: Display Omitted Highlights: ► Thermoresponsive internal stresses introduced into steel by embedding SMA inclusions. ► Neutron strain scanning on steel plate coupons with NiTi inserts at 21 °C and 130 °C. ► Internal stress field in steel evaluated directly from strains and by FE simulation. ► Internal stress generation by SMA insert resistant to thermal and mechanical fatigue. - Abstract: Neutron strain scanning was employed to investigate the internal stress fields in steel plate coupons with embedded prestrained superelastic NiTi shape memory alloy inserts. Strain fields in steel were evaluated at T = 21 °C and 130 °C on virgin coupons as well as on mechanically and thermally fatigued coupons. Internal stress fields were evaluated by direct calculation of principal stress components from the experimentally measured lattice strains as well as by employing an inverse finite element modeling approach. It is shown that if the NiTi inserts are embedded into the elastic steel matrix following a carefully designed technological procedure, the internal stress fields vary with temperature in a reproducible and predictable way. It is estimated that this mechanism of internal stress generation can be safely applied in the temperature range from −20 °C to 150 °C and is relatively resistant to thermal and mechanical fatigue. The predictability and fatigue endurance of the mechanism are of essential importance for the development of future smart metal matrix composites or smart structures with embedded shape memory alloy components.

  1. Nano-hardness, wear resistance and pseudoelasticity of hafnium implanted NiTi shape memory alloy.

    Science.gov (United States)

    Zhao, Tingting; Li, Yan; Liu, Yong; Zhao, Xinqing

    2012-09-01

    NiTi shape memory alloy was modified by Hf ion implantation to improve its wear resistance and surface integrity against deformation. The Auger electron spectroscopy and x-ray photoelectron spectroscopy results indicated that the oxide thickness of NiTi alloy was increased by the formation of TiO₂/HfO₂ nanofilm on the surface. The nano-hardness measured by nano-indentation was decreased even at the depth larger than the maximum reach of the implanted Hf ion. The lower coefficient of friction with much longer fretting time indicated the remarkable improvement of wear resistance of Hf implanted NiTi, especially for the sample with a moderate incident dose. The formation of TiO₂/HfO₂ nanofilm with larger thickness and decrease of the nano-hardness played important roles in the improvement of wear resistance. Moreover, Hf implanted NiTi exhibited larger pseudoelastic recovery strain and retained better surface integrity even after being strained to 10% as demonstrated by in situ scanning electron microscope observation. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  2. Compact tension testing of martensitic/pseudoplastic NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gollerthan, S. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany)], E-mail: susanne.gollerthan@rub.de; Herberg, D. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany); Baruj, A. [TEMADI, Centro Atomico Bariloche, 8400 S.C. Bariloche (Argentina); Eggeler, G. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany)

    2008-05-25

    NiTi shape memory alloys show unique properties such as pseudoelasticity and the one-way effect, both based on a martensitic phase transformation between a high temperature phase (B2) and a low temperature phase (B19'). When a martensitic, pseudoplastic alloy is subjected to a stress, favourably oriented martensite variants grow. In the present work we study how pseudoplasticity affects the mechanical behaviour of fracture mechanics compact tension (CT) specimens. For this purpose we have scaled down CT specimens of type ASTM Standard E399. We use a smaller specimen for two reasons. (1) NiTi is more expensive than, e.g. structural steel and there is a need to economise specimen material. (2) And more importantly, we need specimen thicknesses which are transparent to high-energy synchrotron radiation because we aim at characterizing microstructural and crystallographic changes in front of cracks. The present work reports mechanical results from fracture mechanics testing of a martensitic, pseudoplastic microstructure. We use approaches from linear elastic fracture mechanics to determine critical stress intensity factors and to obtain estimates on the dimensions of pseudoplastic zones in front of crack tips in martensitic NiTi.

  3. Towards High-Frequency Shape Memory Alloy Actuators Incorporating Liquid Metal Energy Circuits

    Science.gov (United States)

    Hartl, Darren; Mingear, Jacob; Bielefeldt, Brent; Rohmer, John; Zamarripa, Jessica; Elwany, Alaa

    2017-12-01

    Large shape memory alloy (SMA) actuators are currently limited to applications with low cyclic actuation frequency requirements due to their generally poor heat transfer rates. This limitation can be overcome through the use of distributed body heating methods such as induction heating or by accelerated cooling methods such as forced convection in internal cooling channels. In this work, a monolithic SMA beam actuator containing liquid gallium-indium alloy-filled channels is fabricated through additive manufacturing. These liquid metal channels enable a novel multi-physical thermal control system, allowing for increased heating and cooling rates to facilitate an increased cyclic actuation frequency. Liquid metal flowing in the channels performs the dual tasks of inductively heating the surrounding SMA material and then actively cooling the SMA via forced internal fluid convection. A coupled thermoelectric model, implemented in COMSOL, predicts a possible fivefold increase in the cyclic actuation frequency due to these increased thermal transfer rates when compared to conventional SMA forms having external heating coils and being externally cooled via forced convection. The first ever experimental prototype SMA actuator of this type is described and, even at much lower flow rates, is shown to exhibit a decrease in cooling time of 40.9%.

  4. Determination of strain fields in porous shape memory alloys using micro-computed tomography

    Science.gov (United States)

    Bormann, Therese; Friess, Sebastian; de Wild, Michael; Schumacher, Ralf; Schulz, Georg; Müller, Bert

    2010-09-01

    Shape memory alloys (SMAs) belong to 'intelligent' materials since the metal alloy can change its macroscopic shape as the result of the temperature-induced, reversible martensite-austenite phase transition. SMAs are often applied for medical applications such as stents, hinge-less instruments, artificial muscles, and dental braces. Rapid prototyping techniques, including selective laser melting (SLM), allow fabricating complex porous SMA microstructures. In the present study, the macroscopic shape changes of the SMA test structures fabricated by SLM have been investigated by means of micro computed tomography (μCT). For this purpose, the SMA structures are placed into the heating stage of the μCT system SkyScan 1172™ (SkyScan, Kontich, Belgium) to acquire three-dimensional datasets above and below the transition temperature, i.e. at room temperature and at about 80°C, respectively. The two datasets were registered on the basis of an affine registration algorithm with nine independent parameters - three for the translation, three for the rotation and three for the scaling in orthogonal directions. Essentially, the scaling parameters characterize the macroscopic deformation of the SMA structure of interest. Furthermore, applying the non-rigid registration algorithm, the three-dimensional strain field of the SMA structure on the micrometer scale comes to light. The strain fields obtained will serve for the optimization of the SLM-process and, more important, of the design of the complex shaped SMA structures for tissue engineering and medical implants.

  5. Investigation of resistive switching in barium strontium titanate thin films for memory applications

    International Nuclear Information System (INIS)

    Shen, Wan

    2010-01-01

    Resistive random access memory (RRAM) has attracted much attention due to its low power consumption, high speed operation, non-readout disturbance and high density integration potential and is regarded as one of the most promising candidates for the next generation non-volatile memory. The resistive switching behavior of Mn-doped BaSrTiO 3 (BST) thin films with different crystalline properties was investigated within this dissertation. The laser fluence dependence was checked in order to optimize the RRAM properties. Although the film epitaxial quality was improved by reducing the laser energy during deposition process, the yields fluctuated and only 3% RRAM devices with highest epitaxial quality of BST film shows resistive switching behavior instead of 67% for the samples with worse film quality. It gives a clue that the best thin film quality does not result in the best switching performance, and it is a clear evidence of the importance of the defects to obtain resistive switching phenomena. The bipolar resistive switching behavior was studied with epitaxial BST thin films on SRO/STO. Compared to Pt top electrode, the yield, endurance and reliability were strongly improved for the samples with W top electrode. Whereas the samples with Pt top electrode show a fast drop of the resistance for both high and low resistance states, the devices with W top electrode can be switched for 10 4 times without any obvious degradation. The resistance degradation for devices with Pt top electrode may result from the diffusion of oxygen along the Pt grain boundaries during cycling whereas for W top electrode the reversible oxidation and reduction of a WO x layer, present at the interface between W top electrode and BST film, attributes to the improved switching property. The transition from bipolar to unipolar resistive switching in polycrystalline BST thin films was observed. A forming process which induces a metallic low resistance state is prerequisite for the observation of

  6. Investigation of resistive switching in barium strontium titanate thin films for memory applications

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Wan

    2010-11-17

    Resistive random access memory (RRAM) has attracted much attention due to its low power consumption, high speed operation, non-readout disturbance and high density integration potential and is regarded as one of the most promising candidates for the next generation non-volatile memory. The resistive switching behavior of Mn-doped BaSrTiO{sub 3} (BST) thin films with different crystalline properties was investigated within this dissertation. The laser fluence dependence was checked in order to optimize the RRAM properties. Although the film epitaxial quality was improved by reducing the laser energy during deposition process, the yields fluctuated and only 3% RRAM devices with highest epitaxial quality of BST film shows resistive switching behavior instead of 67% for the samples with worse film quality. It gives a clue that the best thin film quality does not result in the best switching performance, and it is a clear evidence of the importance of the defects to obtain resistive switching phenomena. The bipolar resistive switching behavior was studied with epitaxial BST thin films on SRO/STO. Compared to Pt top electrode, the yield, endurance and reliability were strongly improved for the samples with W top electrode. Whereas the samples with Pt top electrode show a fast drop of the resistance for both high and low resistance states, the devices with W top electrode can be switched for 10{sup 4} times without any obvious degradation. The resistance degradation for devices with Pt top electrode may result from the diffusion of oxygen along the Pt grain boundaries during cycling whereas for W top electrode the reversible oxidation and reduction of a WO{sub x} layer, present at the interface between W top electrode and BST film, attributes to the improved switching property. The transition from bipolar to unipolar resistive switching in polycrystalline BST thin films was observed. A forming process which induces a metallic low resistance state is prerequisite for the

  7. Smart surgical needle actuated by shape memory alloys for percutaneous procedures

    Science.gov (United States)

    Konh, Bardia

    Background: Majority of cancer interventions today are performed percutaneously using needle-based procedures, i.e. through the skin and soft tissue. Insufficient accuracy using conventional surgical needles motivated researchers to provide actuation forces to the needle's body for compensating the possible errors of surgeons/physicians. Therefore, active needles were proposed recently where actuation forces provided by shape memory alloys (SMAs) are utilized to assist the maneuverability and accuracy of surgical needles. This work also aims to introduce a novel needle insertion simulation to predict the deflection of a bevel tip needle inside the tissue. Methods: In this work first, the actuation capability of a single SMA wire was studied. The complex response of SMAs was investigated via a MATLAB implementation of the Brinson model and verified via experimental tests. The material characteristics of SMAs were simulated by defining multilinear elastic isothermal stress-strain curves. Rigorous experiments with SMA wires were performed to determine the material properties as well as to show the capability of the code to predict a stabilized SMA transformation behavior with sufficient accuracy. The isothermal stress-strain curves of SMAs were simulated and defined as a material model for the Finite Element Analysis of the active needle. In the second part of this work, a three-dimensional finite element (FE) model of the active steerable needle was developed to demonstrate the feasibility of using SMA wires as actuators to bend the surgical needle. In the FE model, birth and death method of defining boundary conditions, available in ANSYS, was used to achieve the pre-strain condition on SMA wire prior to actuation. This numerical model was validated with needle deflection experiments with developed prototypes of the active needle. The third part of this work describes the design optimization of the active using genetic algorithm aiming for its maximum flexibility

  8. Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud, E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

    2015-05-29

    Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

  9. Structure and properties of nitrided surface layer produced on NiTi shape memory alloy by low temperature plasma nitriding

    Science.gov (United States)

    Czarnowska, Elżbieta; Borowski, Tomasz; Sowińska, Agnieszka; Lelątko, Józef; Oleksiak, Justyna; Kamiński, Janusz; Tarnowski, Michał; Wierzchoń, Tadeusz

    2015-04-01

    NiTi shape memory alloys are used for bone and cardiological implants. However, on account of the metallosis effect, i.e. the release of the alloy elements into surrounding tissues, they are subjected to various surface treatment processes in order to improve their corrosion resistance and biocompatibility without influencing the required shape memory properties. In this paper, the microstructure, topography and morphology of TiN surface layer on NiTi alloy, and corrosion resistance, both before and after nitriding in low-temperature plasma at 290 °C, are presented. Examinations with the use of the potentiodynamic and electrochemical impedance spectroscopy methods were carried out and show an increase of corrosion resistance in Ringer's solution after glow-discharge nitriding. This surface titanium nitride layer also improved the adhesion of platelets and the proliferation of osteoblasts, which was investigated in in vitro experiments with human cells. Experimental data revealed that nitriding NiTi shape memory alloy under low-temperature plasma improves its properties for bone implant applications.

  10. Effect of Contact Temperature Rise During Sliding on the Wear Resistance of TiNi Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    S.K. Roy Chowdhury

    2013-03-01

    Full Text Available The high wear resistance of TiNi shape memory alloys has generally been attributed to its pseudoelastic nature. In the present work the hardening effect due to its phase transformation from martensite to austenite due to frictional heating during sliding has been considered. Based on existing constitutive models that represent the experimental results of TiNi shape memory alloys a theoretical model of the dependence of wear-resistance on the contact temperature rise has been developed. The analysis was further extended to include the operating and surface roughness parameters. The model essentially indicates that for these alloys wear decreases with the rise in contact temperature over a wide range of load, speed and surface roughness combination during sliding. This means that the wear resistance of these alloys results from the very cause that is normally responsible for the increased wear and seizure of common engineering materials. Preliminary wear tests were carried out with TiNi alloys at varying ambient temperature and varying load-speed combinations and the results agree well with the theoretical predictions.

  11. Effect of micro-arc oxidation surface modification on the properties of the NiTi shape memory alloy.

    Science.gov (United States)

    Xu, J L; Zhong, Z C; Yu, D Z; Liu, F; Luo, J M

    2012-12-01

    In this paper, the effects of micro-arc oxidation (MAO) surface modification (alumina coatings) on the phase transformation behavior, shape memory characteristics, in vitro haemocopatibility and cytocompatibility of the biomedical NiTi alloy were investigated respectively by differential scanning calorimetry, bending test, hemolysis ratio test, dynamic blood clotting test, platelet adhesion test and cytotoxicity testing by human osteoblasts (Hobs). The results showed that there were no obvious changes of the phase transformation temperatures and shape memory characteristics of the NiTi alloy after the MAO surface modification and the coating could withstand the thermal shock and volume change caused by martensite-austenite phase transformation. Compared to the uncoated NiTi alloys, the MAO surface modification could effectively improve the haemocopatibility of the coated NiTi alloys by the reduced hemolysis ratio, the prolonged dynamic clotting time and the decreased number of platelet adhesion; and the rough and porous alumina coatings could obviously promote the adherence, spread and proliferation of the Hobs with the significant increase of proliferation number of Hobs adhered on the surface of the coated NiTi alloys (P < 0.05).

  12. Shape memory alloy actuated accumulator for ultra-deepwater oil and gas exploration

    Science.gov (United States)

    Patil, Devendra; Song, Gangbing

    2016-04-01

    As offshore oil and gas exploration moves further offshore and into deeper waters to reach hydrocarbon reserves, it is becoming essential for the industry to develop more reliable and efficient hydraulic accumulators to supply pressured hydraulic fluid for various control and actuation operations, such as closing rams of blowout preventers and controlling subsea valves on the seafloor. By utilizing the shape memory effect property of nitinol, which is a type of shape memory alloy (SMA), an innovative SMA actuated hydraulic accumulator prototype has been developed and successfully tested at Smart Materials and Structure Laboratory at the University of Houston. Absence of gas in the developed SMA accumulator prototype makes it immune to hydrostatic head loss caused by water depth and thus reduces the number of accumulators required in deep water operations. Experiments with a feedback control have demonstrated that the proposed SMA actuated accumulator can provide precisely regulated pressurized fluids. Furthermore the potential use of ultracapacitors along with an embedded system to control the electric power supplied to SMA allows this accumulator to be an autonomous device for deployment. The developed SMA accumulator will make deepwater oil extraction systems more compact and cost effective.

  13. Investigation of shape memory alloy honeycombs by means of a micromechanical analysis

    International Nuclear Information System (INIS)

    Freed, Yuval; Aboudi, Jacob; Gilat, Rivka

    2008-01-01

    Shape memory alloy (SMA) honeycombs are promising new smart materials which may be used for light-weight structures, biomedical implants, actuators and active structures. In this study, the behavior of several SMA honeycomb structures is investigated by means of a continuum-based thermomechanically coupled micromechanical analysis. To this end, macroscopic inelastic stress–strain responses of several topologies are investigated, both for pseudoelasticity and for shape memory effect. It was found that the triangular topology exhibits the best performance. In addition, the initial transformation surfaces are presented for all possible combinations of applied in-plane stresses. A special two-phase microstructure that is capable of producing an overall negative coefficient of thermal expansion is suggested and studied. In this configuration, in which one of the phases is a SMA, residual strains are being generated upon recovery. Here, the negative coefficient of thermal expansion appears to be associated with a larger amount of residual strain upon recovery. Furthermore, a two-dimensional SMA re-entrant topology that generates a negative in-plane Poisson's ratio is analyzed, and the effect of the full thermomechanical coupling is examined. Finally, the response of a particular three-dimensional microstructure is studied

  14. Superelasticity and Shape Memory Behavior of NiTiHf Alloys

    Science.gov (United States)

    Sehitoglu, H.; Wu, Y.; Patriarca, L.; Li, G.; Ojha, A.; Zhang, S.; Chumlyakov, Y.; Nishida, M.

    2017-06-01

    The NiTiHf high-temperature shape memory alloys represent a significant advancement in extending the functionality of binary NiTi to elevated temperatures above 100 °C. Despite this potential, the previous results in the literature point to a disappointingly low shape memory strains with addition of Hf. On the other hand, based on theoretical analysis using the lattice constants, the transformation strains should increase substantially with increase in Hf content. The present paper addresses this discrepancy, and using atomistic simulations, determination of twinning modes in martensite with transmission electron microscopy, digital image measurements of habit plane orientation, and strains in single-crystal specimens show that the experimental transformation strains in NiTiHf indeed increase with increasing Hf to unprecedented strain levels near 20%. The Hf contents considered were in the range 6.25-25 at.%, and NiTi (0% Hf) results are provided as the baseline. The current work represents more than 60 experiments representing an extremely thorough study on single crystals and polycrystals.

  15. Electro-bending characterization of adaptive 3D fiber reinforced plastics based on shape memory alloys

    Science.gov (United States)

    Ashir, Moniruddoza; Hahn, Lars; Kluge, Axel; Nocke, Andreas; Cherif, Chokri

    2016-03-01

    The industrial importance of fiber reinforced plastics (FRPs) is growing steadily in recent years, which are mostly used in different niche products, has been growing steadily in recent years. The integration of sensors and actuators in FRP is potentially valuable for creating innovative applications and therefore the market acceptance of adaptive FRP is increasing. In particular, in the field of highly stressed FRP, structural integrated systems for continuous component parts monitoring play an important role. This presented work focuses on the electro-mechanical characterization of adaptive three-dimensional (3D)FRP with integrated textile-based actuators. Here, the friction spun hybrid yarn, consisting of shape memory alloy (SMA) in wire form as core, serves as an actuator. Because of the shape memory effect, the SMA-hybrid yarn returns to its original shape upon heating that also causes the deformation of adaptive 3D FRP. In order to investigate the influences of the deformation behavior of the adaptive 3D FRP, investigations in this research are varied according to the structural parameters such as radius of curvature of the adaptive 3D FRP, fabric types and number of layers of the fabric in the composite. Results show that reproducible deformations can be realized with adaptive 3D FRP and that structural parameters have a significant impact on the deformation capability.

  16. Training and two-way shape memory in NiTi alloys: influence on thermal parameters

    International Nuclear Information System (INIS)

    Lahoz, R.; Puertolas, J.A.

    2004-01-01

    The two-way shape memory effect (TWSME) was studied in a near equiatomic commercial alloy. A training procedure based on a constant load applied in the temperature range of the parent → martensite transformation was carried out on NiTi wires. The efficiency of the method was determined from deformation-temperature measurements by MTA at different training stress and number of cycles. A maximum of two shape memory strain was obtained for a stress training of 115 MPa, independently of number of training cycles. A correlation was established between the TWSME arisen and the permanent strain generated during the training. The A s and A f transitions present a positive shift and the M s and M f a negative one with increasing training stress. All the transitions temperatures decrease with the training cycling. In the trained material, the P→M and M→P temperatures and the latent heat of these conversions undergoes a strong decrease with increasing training stress, with a strong asymmetry between the forward and the reversed transitions. The changes of these thermal parameters as a function of the training parameters were studied on a thermodynamic frame

  17. Comparing the cyclic behavior of concrete cylinders confined by shape memory alloy wire or steel jackets

    International Nuclear Information System (INIS)

    Park, Joonam; Choi, Eunsoo; Kim, Hong-Taek; Park, Kyoungsoo

    2011-01-01

    Shape memory alloy (SMA) wire jackets for concrete are distinct from conventional jackets of steel or fiber reinforced polymer (FRP) since they provide active confinement which can be easily achieved due to the shape memory effect of SMAs. This study uses NiTiNb SMA wires of 1.0 mm diameter to confine concrete cylinders with the dimensions of 300 mm × 150 mm (L × D). The NiTiNb SMAs have a relatively wider temperature hysteresis than NiTi SMAs; thus, they are more suitable for the severe temperature-variation environments to which civil structures are exposed. Steel jackets of passive confinement are also prepared in order to compare the cyclic behavior of actively and passively confined concrete cylinders. For this purpose, monotonic and cyclic compressive loading tests are conducted to obtain axial and circumferential strain. Both strains are used to estimate the volumetric strains of concrete cylinders. Plastic strains from cyclic behavior are also estimated. For the cylinders jacketed by NiTiNb SMA wires, the monotonic axial behavior differs from the envelope of cyclic behavior. The plastic strains of the actively confined concrete show a similar trend to those of passive confinement. This study proposed plastic strain models for concrete confined by SMA wire or steel jackets. For the volumetric strain, the active jackets of NiTiNb SMA wires provide more energy dissipation than the passive jacket of steel

  18. On the Fracture Toughness and Stable Crack Growth in Shape Memory Alloys Under Combined Thermomechanical Loading

    Science.gov (United States)

    Jape, Sameer Sanjay

    Advanced multifunctional materials such as shape memory alloys (SMAs) offer unprecedented improvement over conventional materials when utilized as high power output solid-state actuators in a plethora of engineering applications, viz. aerospace, automotive, oil and gas exploration, etc., replacing complex multi-component assemblies with compact single-piece adaptive components. These potential applications stem from the material's ability to produce large recoverable actuation strains when subjected to combined thermomechanical loads, via a diffusionless solid-to-solid phase transition between high-temperature cubic austenite and low-temperature monoclinic martensite crystalline phases. To ensure reliable design, functioning and durability of SMA-based actuators, it is imperative to develop a thorough scientific knowledge base and understanding about their fracture properties i.e. crack-initiation and growth during thermal actuation, vis-a-vis the phase transformation metrics (i.e. transformation strains, hysteresis, and temperatures, critical stresses for phase transformation, etc.) and microstructural features (grain size, precipitates, and texture). Systematic experimental and analytical investigation of SMA fracture response based on known theories and methodologies is posed with significant challenges due to the inherent complexity in SMA thermomechanical constitutive response arising out of the shape memory and pseudoelastic effects, martensite detwinning and variant reorientation, thermomechanical coupling, and transformation induced plasticity (TRIP). In this study, a numerical analysis is presented that addresses the fundamental need to study fracture in SMAs in the presence of aforementioned complexities. Finite element modeling with an energetics based fracture toughness criterion and SMA thermomechanical behavior with nonlinearities from thermomechanical coupling and TRIP was conducted. A specific analysis of a prototype boundary value fracture problem

  19. Engineering Design Tools for Shape Memory Alloy Actuators: CASMART Collaborative Best Practices and Case Studies

    Science.gov (United States)

    Wheeler, Robert W.; Benafan, Othmane; Gao, Xiujie; Calkins, Frederick T; Ghanbari, Zahra; Hommer, Garrison; Lagoudas, Dimitris; Petersen, Andrew; Pless, Jennifer M.; Stebner, Aaron P.; hide

    2016-01-01

    The primary goal of the Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART) is to enable the design of revolutionary applications based on shape memory alloy (SMA) technology. In order to help realize this goal and reduce the development time and required experience for the fabrication of SMA actuation systems, several modeling tools have been developed for common actuator types and are discussed herein along with case studies, which highlight the capabilities and limitations of these tools. Due to their ability to sustain high stresses and recover large deformations, SMAs have many potential applications as reliable, lightweight, solid-state actuators. Their advantage over classical actuators can also be further improved when the actuator geometry is modified to fit the specific application. In this paper, three common actuator designs are studied: wires, which are lightweight, low-profile, and easily implemented; springs, which offer actuation strokes upwards of 200 at reduced mechanical loads; and torque tubes, which can provide large actuation forces in small volumes and develop a repeatable zero-load actuation response (known as the two-way shape memory effect). The modeling frameworks, which have been implemented in the design tools, are developed for each of these frequently used SMA actuator types. In order to demonstrate the versatility and flexibility of the presented design tools, as well as validate their modeling framework, several design challenges were completed. These case studies include the design and development of an active hinge for the deployment of a solar array or foldable space structure, an adaptive solar array deployment and positioning system, a passive air temperature controller for regulation flow temperatures inside of a jet engine, and a redesign of the Corvette active hatch, which allows for pressure equalization of the car interior. For each of the presented case studies, a prototype or proof

  20. Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni50.3Ti34.7Zr15 shape memory alloy

    International Nuclear Information System (INIS)

    Evirgen, A.; Karaman, I.; Pons, J.; Santamarta, R.; Noebe, R.D.

    2016-01-01

    The microstructure and shape memory characteristics of the Ni 50.3 Ti 34.7 Zr 15 shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure–property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformation–precipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni 50.3 Ti 34.7 Zr 15 alloy.

  1. Crystallization characteristic and scaling behavior of germanium antimony thin films for phase change memory.

    Science.gov (United States)

    Wu, Weihua; Zhao, Zihan; Shen, Bo; Zhai, Jiwei; Song, Sannian; Song, Zhitang

    2018-04-19

    Amorphous Ge8Sb92 thin films with various thicknesses were deposited by magnetron sputtering. The crystallization kinetics and optical properties of the Ge8Sb92 thin films and related scaling effects were investigated by an in situ thermally induced method and an optical technique. With a decrease in film thickness, the crystallization temperature, crystallization activation energy and data retention ability increased significantly. The changed crystallization behavior may be ascribed to the smaller grain size and larger surface-to-volume ratio as the film thickness decreased. Regardless of whether the state was amorphous or crystalline, the film resistance increased remarkably as the film thickness decreased to 3 nm. The optical band gap calculated from the reflection spectra increases distinctly with a reduction in film thickness. X-ray diffraction patterns confirm that the scaling of the Ge8Sb92 thin film can inhibit the crystallization process and reduce the grain size. The values of exponent indices that were obtained indicate that the crystallization mechanism experiences a series of changes with scaling of the film thickness. The crystallization time was estimated to determine the scaling effect on the phase change speed. The scaling effect on the electrical switching performance of a phase change memory cell was also determined. The current-voltage and resistance-voltage characteristics indicate that phase change memory cells based on a thinner Ge8Sb92 film will exhibit a higher threshold voltage, lower RESET operational voltage and greater pulse width, which implies higher thermal stability, lower power consumption and relatively lower switching velocity.

  2. A correlative experimental and ab initio approach to improve the fracture behavior of Mo thin films by alloying with Cu

    Science.gov (United States)

    Jörg, Tanja; Music, Denis; Cordill, Megan J.; Franz, Robert; Köstenbauer, Harald; Linke, Christian; Winkler, Jörg; Schneider, Jochen M.; Mitterer, Christian

    2017-09-01

    The effect of Cu alloying on the deformation behavior of Mo thin films is investigated as a feasible concept to overcome their poor ductility, which severely limits performance in flexible electronics. 50 nm thick Mo1-xCux films (with 0 ≤ x ≤ 0.51) were sputter-deposited on polyimide substrates and subjected to uniaxial tensile loading while measuring their electrical resistance in situ. A significant ductility enhancement is experimentally observed with increasing Cu content. This can be rationalized by considering the associated changes in bond character as the Cu additions weaken the covalent and hence shear resistant contribution to the overall bond character.

  3. Formation of SmFe5(0001) ordered alloy thin films on Cu(111) single-crystal underlayers

    International Nuclear Information System (INIS)

    Yabuhara, Osamu; Ohtake, Mitsuru; Nukaga, Yuri; Futamoto, Masaaki; Kirino, Fumiyoshi

    2010-01-01

    SmFe 5 (0001) single-crystal thin films are prepared by molecular beam epitaxy employing Cu(111) single-crystal underlayers on MgO(111) substrates. The Cu atoms diffuse into the Sm-Fe layer and substitute the Fe sites in SmFe 5 structure forming an alloy compound of Sm(Fe,Cu) 5 . The Sm(Fe,Cu) 5 film is more Cu enriched with increasing the substrate temperature. The Cu underlayer plays an important role in assisting the formation of the ordered phase.

  4. Anomalous Hall effect in ion-beam sputtered Co2FeAl full Heusler alloy thin films

    Science.gov (United States)

    Husain, Sajid; Kumar, Ankit; Akansel, Serkan; Svedlindh, Peter; Chaudhary, Sujeet

    2017-11-01

    Investigations of temperature dependent anomalous Hall effect and longitudinal resistivity in Co2FeAl (CFA) thin films grown on Si(1 0 0) at different substrate temperature Ts are reported. The scaling of the anomalous Hall conductivity (AHC) and the associated phenomenological mechanisms (intrinsic and extrinsic) are analyzed vis-à-vis influence of Ts. The intrinsic contribution to AHC is found to be dominating over the extrinsic one. The appearance of a resistivity minimum at low temperature necessitates the inclusion of quantum corrections on account of weak localization and electron-electron scattering effects whose strength reduces with increase in Ts. The study establishes that the optimization of Ts plays an important role in the improvement of atomic ordering which indicates the higher strength of spin-orbit coupling and leads to the dominant intrinsic contribution to AHC in these CFA full Heusler alloy thin films.

  5. Protection of molybdenum and molybdenum - alloy thin films against low - temperature oxidation

    International Nuclear Information System (INIS)

    Schintlmeister, A.; Wilhartitz, P.

    2001-01-01

    Molybdenum is an interesting functional material for thin film applications like electrical connections in thin film transistor flat panel displays (TFT-FPD) or thin film solar cells (CIS). Despite its advantageous properties, the use of pure molybdenum has been restricted mainly because of its low stability against corrosion in moist air even at room temperature. In this paper it is described how thin films ( 2 . (author)

  6. Bioactive (Si, O, N)/(Ti, O, N)/Ti composite coating on NiTi shape memory alloy for enhanced wear and corrosion performance

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Tao, E-mail: taosun@hotmail.com.hk [Institute of Microelectronics, Agency for Science, Technology and Research - A*STAR, Singapore 117685 (Singapore); Xue, Ning [Institute of Microelectronics, Agency for Science, Technology and Research - A*STAR, Singapore 117685 (Singapore); Liu, Chao, E-mail: msm-liu@126.com [School of Electronics Science, Northeast Petroleum University, Daqing 163318 (China); Wang, Chao [Institute of Microelectronics, Agency for Science, Technology and Research - A*STAR, Singapore 117685 (Singapore); He, Jin, E-mail: jin.he@whu.edu.cn [Institute of Microelectronics, Agency for Science, Technology and Research - A*STAR, Singapore 117685 (Singapore); School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2015-11-30

    Graphical abstract: - Highlights: • A novel (Si, O, N)/(Ti, O, N)/Ti composite coating was fabricated on NiTi shape memory alloy via PIIID followed by magnetron sputtering. • The multifunctional protective coating is capable of improving bioactivity, wear and corrosion resistance. • The potential mechanisms behind the improved bioactivity, wear and corrosion resistance were discussed. - Abstract: In this investigation, (Si, O, N)/(Ti, O, N)/Ti composite coating was synthesized on a NiTi shape memory alloy (SMA) substrate (50.8 at.% Ni) via plasma immersion ion implantation and deposition (PIIID) followed by magnetron sputtering, with the aim of promoting bioactivity and biocompatibility of NiTi SMAs. Nano featured (Si, O, N)/(Ti, O, N)/Ti coating was approximate 0.84 ± 0.05 μm in thickness, and energy dispersive X-ray (EDX) spectroscopy showed that Ni element was depleted from the surface of coated samples. X-ray diffraction (XRD) did not identify the phase composition of the (Si, O, N)/(Ti, O, N)/Ti coating, probably due to its thin thickness and poor crystalline resulting from low-temperature coating processes (<200 °C). X-ray photoelectron spectroscopy (XPS) analyses confirmed that a Ni-free surface was formed and Si element was incorporated into the composite coating via the magnetron sputtering process. Additionally, phase transformation behaviors of uncoated and coated NiTi SMA samples were characterized using differential scanning calorimetry (DSC). Wear and corrosion resistance of uncoated and coated NiTi SMA samples were evaluated using ball-on-disc tests and potentio-dynamic polarization curves, respectively. The (Si, O, N)/(Ti, O, N)/Ti coated NiTi SMA samples showed enhanced wear and corrosion resistance. Furthermore, the (Si, O, N)/(Ti, O, N)/Ti composite coating facilitated apatite formation in simulated body fluid (SBF) and rendered NiTi SMA bioactivity.

  7. Grain size effect on the structural parameters of the stress induced epsilonhcp: martensite in iron-based shape memory alloy

    Directory of Open Access Journals (Sweden)

    Fabiana Cristina Nascimento

    2008-03-01

    Full Text Available The aim of this work was to study the effect of austenitic grain size (GS reduction on the structural parameters of the epsilonhcp - martensite in stainless shape memory alloy (SMA. Rietveld refinement data showed an expansion in c-axis and a reduction in a and b-axis with thermo-mechanical cycles for all samples analyzed. Samples with 75 < GS (µm < 129 were analyzed. It was also observed an increase of the unit cell volume in this phase with GS reduction. The smallest grain size sample (GS = 75 µm presented a c/a ratio of 1.649, and approximately 90% of total shape memory recovery.

  8. Infrared thermography videos of the elastocaloric effect for shape memory alloys NiTi and Ni2FeGa

    Directory of Open Access Journals (Sweden)

    Garrett J. Pataky

    2015-12-01

    Full Text Available Infrared thermogrpahy was utilized to record the temperature change during tensile loading cycles of two shape memory alloy single crystals with pseudoelastic behavior. During unloading, a giant temperature drop was measured in the gage section due to the elastocaloric effect. This data article provides a video of a [001] oriented Ni2FeGa single crystal, including the corresponding stress–strain curve, shows the temperature drop over one cycle. The second video of a [148] oriented NiTi single crystal depicts the repeatability of the elastocaloric effect by showing two consecutive cycles. The videos are supplied in this paper. For further analysis and enhanced discussion of large temperature change in shape memory alloys, see Pataky et al. [1

  9. Influence of aging and thermomechanical cycling on the magnetostriction and magnetic shape memory effect in martensitic alloy

    International Nuclear Information System (INIS)

    L’vov, Victor A; Kosogor, Anna; Barandiaran, Jose M; Chernenko, Volodymyr A

    2015-01-01

    An influence of internal stress created by the crystal defects on the magnetically induced reorientation (MIR) of martensite variants in the ferromagnetic shape memory alloy (FSMA) has been analyzed. Using the internal stress conception, a noticeable influence of the spatial reconfiguration of crystal defects on the ordinary magnetostriction of FSMA and magnetic shape memory (MSM) effect has been predicted. It has been shown that the defect reconfiguration, which stabilizes the martensitic phase during martensite aging, increases the shear elastic modulus. The increase of shear modulus reduces the magnetostriction value and in this way suppresses the MSM effect. The magneto-thermo-mechanical training of aged alloys destabilizes the martensitic phase, restores the initial magnetostriction value, and promotes the MSM effect. (paper)

  10. Martensitic transformation and shape memory effect in NiTi alloy covered by chitosan/silver layer

    Directory of Open Access Journals (Sweden)

    Goryczka Tomasz

    2015-01-01

    Full Text Available The NiTi shape memory alloy was covered with chitosan/silver layer. Coatings were deposited at room temperature using combination of processing parameters such as deposition voltage and amount of silver in colloidal suspension. Structure of layers was studied by means of X-ray diffraction. Quality of the coatings was evaluated basing on observations done in scanning electron microscopy. Transformation behaviour of coated samples was studied with use of differential scanning calorimeter. The covered sample revealed presence of the reversible martensitic transformation and ability to deformation (in bending mode up to 8%. Forward martensitic transformation, in as-received NiTi alloy and in alloy after layer deposition occurred in two steps B2-R-B19’. After deformation quality of the chitosan/silver layer remained unchanged.

  11. Bond-length strain in buried Ga1-xInxAs thin-alloy films grown coherently on InP(001)

    International Nuclear Information System (INIS)

    Woicik, J.C.; Gupta, J.A.; Watkins, S.P.; Crozier, E.D.

    1998-01-01

    The bond lengths in a series of strained, buried Ga 1-x In x As thin-alloy films grown coherently on InP(001) have been determined by high-resolution extended x-ray absorption fine-structure measurements. Comparison with a random-cluster calculation demonstrates that the external in-plane epitaxial strain imposed by pseudomorphic growth opposes the natural bond-length distortions due to alloying.copyright 1998 American Institute of Physics

  12. Adhesion enhancement of diamond-like carbon thin films on Ti alloys by incorporation of nanodiamond particles

    International Nuclear Information System (INIS)

    Zhang, C.Z.; Tang, Y.; Li, Y.S.; Yang, Q.

    2013-01-01

    Coating adherent diamond-like carbon (DLC) thin films directly on Ti alloys is technologically difficult. This research incorporates nanodiamond particles to form a diamond/DLC composite interlayer to enhance the adhesion of DLC thin films on Ti6Al4V substrates. Initially, nanodiamond particles were deposited on Ti6Al4V substrates by microwave plasma enhanced chemical vapor deposition from a methane–hydrogen gas mixture. A DLC thin film was then deposited, on top of the nanodiamond particles, by direct ion beam deposition. Scanning electron microscopy, Atomic force microscopy, X-ray Diffraction and Raman spectroscopy were used to characterize the microstructure and chemical bonding of the deposited particles and films, and Rockwell indentation testing was used to evaluate the adhesion of the deposited films. The results indicate that the pre-deposited nanodiamond particles significantly enhance the interfacial adhesion between the DLC thin film and the Ti6Al4V substrate, possibly by enhanced interfacial bonding, mechanical interlocking, and stress relief. - Highlights: ► Nanodiamond particles were deposited on Ti6Al4V before DLC deposition. ► Diamond/DLC composite film was formed by incorporation of nanodiamond particles. ► Greatly enhanced adhesion of diamond/DLC composite film on Ti6Al4V was achieved. ► Enhanced adhesion is by increased interfacial bonding and mechanical interlocking

  13. Adhesion enhancement of diamond-like carbon thin films on Ti alloys by incorporation of nanodiamond particles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, C.Z.; Tang, Y. [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada S7N 5A9 (Canada); Li, Y.S. [Plasma Physics Laboratory, University of Saskatchewan, 116 Science Place, Saskatoon, SK, Canada S7N 5E2 (Canada); Yang, Q., E-mail: qiaoqin.yang@usask.ca [Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada S7N 5A9 (Canada)

    2013-01-01

    Coating adherent diamond-like carbon (DLC) thin films directly on Ti alloys is technologically difficult. This research incorporates nanodiamond particles to form a diamond/DLC composite interlayer to enhance the adhesion of DLC thin films on Ti6Al4V substrates. Initially, nanodiamond particles were deposited on Ti6Al4V substrates by microwave plasma enhanced chemical vapor deposition from a methane–hydrogen gas mixture. A DLC thin film was then deposited, on top of the nanodiamond particles, by direct ion beam deposition. Scanning electron microscopy, Atomic force microscopy, X-ray Diffraction and Raman spectroscopy were used to characterize the microstructure and chemical bonding of the deposited particles and films, and Rockwell indentation testing was used to evaluate the adhesion of the deposited films. The results indicate that the pre-deposited nanodiamond particles significantly enhance the interfacial adhesion between the DLC thin film and the Ti6Al4V substrate, possibly by enhanced interfacial bonding, mechanical interlocking, and stress relief. - Highlights: ► Nanodiamond particles were deposited on Ti6Al4V before DLC deposition. ► Diamond/DLC composite film was formed by incorporation of nanodiamond particles. ► Greatly enhanced adhesion of diamond/DLC composite film on Ti6Al4V was achieved. ► Enhanced adhesion is by increased interfacial bonding and mechanical interlocking.

  14. Memory and Electrical Properties of (100-Oriented AlN Thin Films Prepared by Radio Frequency Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Maw-Shung Lee

    2014-01-01

    Full Text Available The (100-oriented aluminum nitride (AlN thin films were well deposited onto p-type Si substrate by radio frequency (RF magnetron sputtering method. The optimal deposition parameters were the RF power of 350 W, chamber pressure of 9 mTorr, and nitrogen concentration of 50%. Regarding the physical properties, the microstructure of as-deposited (002- and (100-oriented AlN thin films were obtained and compared by XRD patterns and TEM images. For electrical properties analysis, we found that the memory windows of (100-oriented AlN thin films are better than those of (002-oriented thin films. Besides, the interface and interaction between the silicon and (100-oriented AlN thin films was serious important problem. Finally, the current transport models of the as-deposited and annealed (100-oriented AlN thin films were also discussed. From the results, we suggested and investigated that large memory window of the annealed (100-oriented AlN thin films was induced by many dipoles and large electric field applied.

  15. Direct observation of magnetic domains by Kerr microscopy in a Ni-Mn-Ga magnetic shape-memory alloy

    Czech Academy of Sciences Publication Activity Database

    Perevertov, Oleksiy; Heczko, Oleg; Schaefer, R.

    2017-01-01

    Roč. 95, č. 14 (2017), s. 1-5, č. článku 144431. ISSN 2469-9950 R&D Projects: GA ČR GA15-00262S Institutional support: RVO:68378271 Keywords : shape memory * magnetic domains * Kerr microscopy * N-Mn-Ga alloy Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

  16. On the influence of heterogeneous precipitation on martensitic transformations in a Ni-rich NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Allafi, J. K.; Eggeler, G.; Dlouhý, Antonín; Schmahl, W.; Somsen, Ch.

    378 A, 1-2 (2004), s. 148-151 ISSN 0921-5093. [European Symposium on Martensitic Transformations. Royal Agricultural College, Cirencester, 17.08.2003-22.08.2003] R&D Projects: GA AV ČR IBS2041001 Institutional research plan: CEZ:AV0Z2041904 Keywords : shape memory alloys * martensitic transformations * precipitation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.445, year: 2004

  17. Load partion in NiTi shape memory alloy polycrystals investigated by in-situ neutron diffraction and micromechanics modelling

    Czech Academy of Sciences Publication Activity Database

    Šittner, Petr; Novák, Václav; Lukáš, Petr; Lugovyy, Dmytro; Neov, Dimitar

    404-407, - (2002), s. 829-834 ISSN 0255-5476 R&D Projects: GA AV ČR IAA1048107; GA ČR GV202/97/K038 Institutional research plan: CEZ:AV0Z1010914 Keywords : shape memory alloy * neutron diffraction * martensitic transformation * NiTi * micromechanics modelling * load partition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.613, year: 2002

  18. Reactive Stresses in Ni49Fe18Ga27Co6 Shape-Memory-Alloy Single Crystals

    Science.gov (United States)

    Averkin, A. I.; Krymov, V. M.; Guzilova, L. I.; Timashov, R. B.; Soldatov, A. V.; Nikolaev, V. I.

    2018-03-01

    The reactive stresses induced in Ni49Fe18Ga27Co6-alloy single crystals during martensitic transformations with a limited possibility of shape-memory-strain recovery have been experimentally studied. The data on these crystals are compared with the results obtained previously for Cu-Al-Ni, Ni-Ti, and Ni‒Fe-Ga crystals. The potential of application of the Ni49Fe18Ga27Co6 single crystals in designing drives and power motors is demonstrated.

  19. Precipitation of Ni4Ti3-variants in a polycrystalline Ni-rich NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Bojda, Ondřej; Eggeler, G.; Dlouhý, Antonín

    2005-01-01

    Roč. 53, č. 1 (2005), s. 99-104 ISSN 1359-6462 R&D Projects: GA ČR(CZ) GA106/05/0918 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Ni4Ti3 precipitation * Transmission electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.228, year: 2005

  20. Shape Memory Alloys for Monitoring Minor Over-Heating/Cooling Based on the Temperature Memory Effect via Differential Scanning Calorimetry: A Review of Recent Progress

    Science.gov (United States)

    Wang, T. X.; Huang, W. M.

    2017-12-01

    The recent development in the temperature memory effect (TME) via differential scanning calorimetry in shape memory alloys is briefly discussed. This phenomenon was also called the thermal arrest memory effect in the literature. However, these names do not explicitly reveal the potential application of this phenomenon in temperature monitoring. On the other hand, the standard testing process of the TME has great limitation. Hence, it cannot be directly applied for temperature monitoring in most of the real engineering applications in which temperature fluctuation occurs mostly in a random manner within a certain range. However, as shown here, after proper modification, we are able to monitor the maximum or minimum temperature in either over-heating or over-cooling with reasonable accuracy.

  1. Designing a New Ni-Mn-Sn Ferromagnetic Shape Memory Alloy with Excellent Performance by Cu Addition

    Directory of Open Access Journals (Sweden)

    Kun Zhang

    2018-02-01

    Full Text Available Both magnetic-field-induced reverse martensitic transformation (MFIRMT and a high working temperature are crucial for the application of Ni-Mn-Sn magnetic shape memory alloys. Here, by first-principles calculations, we demonstrate that the substitution of Cu for Sn is effective not only in enhancing the MFIRMT but also in increasing martensitic transformation, which is advantageous for its application. Large magnetization difference (ΔM in Ni-Mn-Sn alloy is achieved by Cu doping, which arises from the enhancement of magnetization of austenite due to the change of Mn-Mn interaction from anti-ferromagnetism to ferromagnetism. This directly leads to the enhancement of MFIRMT. Meanwhile, the martensitic transformation shifts to higher temperature, owing to the energy difference between the austenite L21 structure and the tetragonal martensite L10 structure increases by Cu doping. The results provide the theoretical data and the direction for developing a high temperature magnetic-field-induced shape memory alloy with large ΔM in the Ni-Mn-Sn Heusler alloy system.

  2. Structural, topographical and magnetic evolution of RF-sputtered Fe-Ni alloy based thin films with thermal annealing

    International Nuclear Information System (INIS)

    Lisha, R; Geetha, P; Anantharaman, M R; Hysen, T; Avasthi, D K; Ramanujan, R V

    2014-01-01

    Metglas 2826 MB having a nominal composition of Fe 40 Ni 38 Mo 4 B 18 is an excellent soft magnetic material and finds application in sensors and memory heads. However, the thin-film forms of Fe 40 Ni 38 Mo 4 B 18 are seldom studied, although they are important in micro-electro-mechanical systems/nano-electro-mechanical systems devices. The stoichiometry of the film plays a vital role in determining the structural and magnetic properties of Fe 40 Ni 38 Mo 4 B 18 thin films: retaining the composition in thin films is a challenge. Thin films of 52 nm thickness were fabricated by RF sputtering technique on silicon substrate from a target of nominal composition of Fe 40 Ni 38 Mo 4 B 18 . The films were annealed at temperatures of 400 °C and 600 °C. The micro-structural studies of films using glancing x-ray diffractometer (GXRD) and transmission electron microscope (TEM) revealed that pristine films are crystalline with (FeNiMo) 23 B 6 phase. Atomic force microscope (AFM) images were subjected to power spectral density analysis to understand the probable surface evolution mechanism during sputtering and annealing. X-ray photoelectron spectroscopy (XPS) was employed to determine the film composition. The sluggish growth of crystallites with annealing is attributed to the presence of molybdenum in the thin film. The observed changes in magnetic properties were correlated with annealing induced structural, compositional and morphological changes. (papers)

  3. Sn buffered by shape memory effect of NiTi alloys as high-performance anodes for lithium ion batteries

    International Nuclear Information System (INIS)

    Hu Renzong; Zhu Min; Wang Hui; Liu Jiangwen; Liuzhang Ouyang; Zou Jin

    2012-01-01

    By applying the shape memory effect of the NiTi alloys to buffer the Sn anodes, we demonstrate a simple approach to overcome a long-standing challenge of Sn anode in the applications of Li-ion batteries – the capacity decay. By supporting the Sn anodes with NiTi shape memory alloys, the large volume change of Sn anodes due to lithiation and delithiation can be effectively accommodated, based on the stress-induced martensitic transformation and superelastic recovery of the NiTi matrix respectively, which leads to a decrease in the internal stress and closing of cracks in Sn anodes. Accordingly, stable cycleability (630 mA h g −1 after 100 cycles at 0.7C) and excellent high-rate capabilities (478 mA h g −1 at 6.7C) were attained with the NiTi/Sn/NiTi film electrode. These shape memory alloys can also combine with other high-capacity metallic anodes, such as Si, Sb, Al, and improve their cycle performance.

  4. Microstructure, elastic deformation behavior and mechanical properties of biomedical β-type titanium alloy thin-tube used for stents.

    Science.gov (United States)

    Tian, Yuxing; Yu, Zhentao; Ong, Chun Yee Aaron; Kent, Damon; Wang, Gui

    2015-05-01

    Cold-deformability and mechanical compatibility of the biomedical β-type titanium alloy are the foremost considerations for their application in stents, because the lower ductility restricts the cold-forming of thin-tube and unsatisfactory mechanical performance causes a failed tissue repair. In this paper, β-type titanium alloy (Ti-25Nb-3Zr-3Mo-2Sn, wt%) thin-tube fabricated by routine cold rolling is reported for the first time, and its elastic behavior and mechanical properties are discussed for the various microstructures. The as cold-rolled tube exhibits nonlinear elastic behavior with large recoverable strain of 2.3%. After annealing and aging, a nonlinear elasticity, considered as the intermediate stage between "double yielding" and normal linear elasticity, is attributable to a moderate precipitation of α phase. Quantitive relationships are established between volume fraction of α phase (Vα) and elastic modulus, strength as well as maximal recoverable strain (εmax-R), where the εmax-R of above 2.0% corresponds to the Vα range of 3-10%. It is considered that the "mechanical" stabilization of the (α+β) microstructure is a possible elastic mechanism for explaining the nonlinear elastic behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. The effect of applied stress on the shape memory behavior of TiNi-based alloys with different consequences of martensitic transformations

    International Nuclear Information System (INIS)

    Meisner, L.L.; Sivokha, V.P.

    2004-01-01

    The development of plastic deformation and shape memory behavior of the Ti 49.5 Ni 50.5 , Ti 50 Ni 34 Pt 16 , Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloys are studied. The alloys differ by consequences of martensitic transformations (MT). It is found that the behavior of both accumulated and returned strain components exhibit some features in the alloys under consideration. The strain-temperature diagrams of the Ti 49.5 Ni 50.5 alloy with the B2↔B19' MT are of the one-step form. There are three stages on the strain-stress curves of this alloy depending on value of the applied mechanical torque. The regularity of plastic behavior of the Ti 50 Ni 34 Pt 16 alloy with the B2↔B19 transformation is similar to that of the Ti 49.5 Ni 50.5 alloy. The strain-stress diagram has three stages. However, there is a significant difference in the shape memory behavior of this alloy. The shape-memory behavior of the Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloy corresponds to the two-stage nature of its B2↔B19↔B19' MT. The deformation mechanisms for these stages have their features in contrast to those of the foregoing alloys. The strain and temperature parameters of the shape memory effect and plastic behavior of the TiNi-based alloys are also examined

  6. The Microstructures and Electrical Resistivity of (Al, Cr, TiFeCoNiOx High-Entropy Alloy Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Chun-Huei Tsau

    2015-01-01

    Full Text Available The (Al, Cr, TiFeCoNi alloy thin films were deposited by PVD and using the equimolar targets with same compositions from the concept of high-entropy alloys. The thin films became metal oxide films after annealing at vacuum furnace for a period; and the resistivity of these thin films decreased sharply. After optimum annealing treatment, the lowest resistivity of the FeCoNiOx, CrFeCoNiOx, AlFeCoNiOx, and TiFeCoNiOx films was 22, 42, 18, and 35 μΩ-cm, respectively. This value is close to that of most of the metallic alloys. This phenomenon was caused by delaminating of the alloy oxide thin films because the oxidation was from the surfaces of the thin films. The low resistivity of these oxide films was contributed to the nonfully oxidized elements in the bottom layers and also vanishing of the defects during annealing.

  7. Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kun [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Huang, Xu [Memry Corporation, Bethel, CT 06801 (United States); Gibson, Des [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of the West of Scotland, Paisley PA1 2BE (United Kingdom); Zheng, Yang; Liu, Jiao; Sun, Lu [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Fu, Yong Qing, E-mail: richard.fu@northumbria.ac.uk [Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom)

    2017-08-31

    Highlights: • The corrosion resistance of Ni-Ti-Nb shape memory thin films is investigated. • Modified surface oxide layers improve the corrosion resistance of Ni-Ti-Nb films. • Further Nb additions reduce the potential corrosion tendency of the films. - Abstract: Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb{sub 2}O{sub 5}. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (E{sub corr}) and lower corrosion current densities (i{sub corr}) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of E{sub corr} and i{sub corr} was found among the Ni-Ti-Nb films.

  8. Ceramic tantalum oxide thin film coating to enhance the corrosion and wear characteristics of Ti−6Al−4V alloy

    Energy Technology Data Exchange (ETDEWEB)

    Rahmati, B., E-mail: r.bijan@yahoo.com [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Sarhan, Ahmed A.D., E-mail: ah_sarhan@um.edu.my [Department of Mechanical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia); Basirun, W. Jeffrey [Department of Chemistry, University of Malaya, 50603 Kuala Lumpur (Malaysia); Abas, W.A.B.W. [Department of Biomedical Engineering, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2016-08-15

    In this research, an attempt is made to study the corrosion and wear behavior of TaO{sub 2} thin film coating deposited onto Ti−6Al−4V alloy with the highest adhesion (was achieved in the author's previous experiments using Taguchi statistical method) which leads to increase corrosion resistance, decrease debris generation and improve durability. Accordingly, pure tantalum (Ta) was deposited onto Ti−6Al−4V substrate surface as intermetallic layer then to form a TaO{sub 2} thin film, Ta was deposited onto the sample surface in the presence of oxygen by using physical vapor deposition magnetron sputtering (PVDMS). Corrosion testing was carried out in fetal bovine serum (FBS). The corrosion test in FBS medium confirmed that the corrosion resistance of the TaO{sub 2} – coated Ti−6Al−4V alloys was significantly higher than the uncoated Ti−6Al−4V substrate due to the decrease in corrosion current density (I{sub corr}) for the coated substrate with high thin-film adhesion. Wear testing was carried out on uncoated and coated Ti−6Al−4V substrates in the presence of FBS medium under 15 N load (natural walking load) at 1.09 m/s (simulated medium walking speed). The tests revealed that the specific wear ratio of TaO{sub 2} coating was significantly lower than the uncoated substrate wear ratio. The average friction coefficients obtained were 0.183 and 0.152 for uncoated substrate and TaO{sub 2} thin film coating, respectively. So, due to the noticeable corrosion and wear resistance characteristics of the TaO{sub 2} coating, it is suggested for hip joint implant. - Highlights: • The TaO{sub 2} coating has been created onto the Ti−6Al−4V surface by using PVDMS method. • The TaO{sub 2} coating has been formed on the Ti−6Al−4V sample at the highest adhesion. • The corrosion resistance of the coated Ti−6Al−4V substrate has been improved. • The wear resistance of the coated Ti−6Al−4V substrate has been increased. • The durability

  9. Electrochemical Properties of Ni 47 Ti 49 Co 4 Shape Memory Alloy in Artificial Urine for Urological Implant

    KAUST Repository

    Ahmed, Rasha A.

    2015-09-02

    © 2015 American Chemical Society. The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications.

  10. Picosecond laser pulse-driven crystallization behavior of SiSb phase change memory thin films

    International Nuclear Information System (INIS)

    Huang Huan; Li Simian; Zhai Fengxiao; Wang Yang; Lai Tianshu; Wu Yiqun; Gan Fuxi

    2011-01-01

    Highlights: → We reported crystallization dynamics of a novel SiSb phase change material. → We measured optical constants of as-deposited and irradiated SiSb areas. → Optical properties of as-deposited and irradiated SiSb thin film were compared. → Crystallization of irradiated SiSb was confirmed by using AFM and micro-Raman spectra. → The heat conduction effect of lower metal layer of multi-layer films was studied. - Abstract: Transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse was studied using time-resolved reflectivity measurements. The ps laser pulse-crystallized domains were characterized by atomic force microscope, Raman spectra and ellipsometrical spectra measurements. A reflectivity contrast of about 15% can be achieved by ps laser pulse-induced crystallization. A minimum crystallization time of 11 ns was achieved by a low-fluence single ps laser pulse after pre-irradiation. SiSb was shown to be very promising for fast phase change memory applications.

  11. The microstructure investigation of GeTi thin film used for non-volatile memory

    International Nuclear Information System (INIS)

    Shen Jie; Liu Bo; Song Zhitang; Xu Cheng; Liang Shuang; Feng Songlin; Chen Bomy

    2008-01-01

    GeTi thin film has been found to have the reversible resistance switching property in our previous work. In this paper, the microstructure of this material with a given composition was investigated. The film was synthesized by magnetron sputtering and treated by the rapid temperature process. The results indicate a coexist status of amorphous and polycrystalline states in the as-deposited GeTi film, and the grains in the film are extremely fine. Furthermore, not until the film annealed at 600 deg. C, can the polycrystalline state be detected by X-ray diffraction. Based on the morphological analysis, the sputtered GeTi has the column growth tendency, and the column structure vanishes with the temperature increasing. The microstructure and thermal property analysis indicate that GeTi does not undergo evident phase change process during the annealing process, which makes the switching mechanism of GeTi different from that of chalcogenide memory material, the most widely used phase change memory material

  12. Development and Testing of a Shape Memory Alloy-Driven Composite Morphing Radiator

    Science.gov (United States)

    Walgren, P.; Bertagne, C.; Wescott, M.; Benafan, O.; Erickson, L.; Whitcomb, J.; Hartl, D.

    2018-01-01

    Future crewed deep space missions will require thermal control systems that can accommodate larger fluctuations in temperature and heat rejection loads than current designs. To maintain the crew cabin at habitable temperatures throughout the entire mission profile, radiators will be required to exhibit turndown ratios (defined as the ratio between the maximum and minimum heat rejection rates) as high as 12:1. Potential solutions to increase radiator turndown ratios include designs that vary the heat rejection rate by changing shape, hence changing the rate of radiation to space. Shape memory alloys exhibit thermally driven phase transformations and thus can be used for both the control and actuation of such a morphing radiator with a single active structural component that transduces thermal energy into motion. This work focuses on designing a high-performance composite radiator panel and investigating the behavior of various SMA actuators in this application. Three designs were fabricated and subsequently tested in a relevant thermal vacuum environment; all three exhibited repeatable morphing behavior, and it is shown through validated computational analysis that the morphing radiator concept can achieve a turndown ratio of 27:1 with a number of simple configuration changes.

  13. Large scale testing of nitinol shape memory alloy devices for retrofitting of bridges

    International Nuclear Information System (INIS)

    Johnson, Rita; Emmanuel Maragakis, M; Saiid Saiidi, M; Padgett, Jamie E; DesRoches, Reginald

    2008-01-01

    A large scale testing program was conducted to determine the effects of shape memory alloy (SMA) restrainer cables on the seismic performance of in-span hinges of a representative multiple-frame concrete box girder bridge subjected to earthquake excitations. Another objective of the study was to compare the performance of SMA restrainers to that of traditional steel restrainers as restraining devices for reducing hinge displacement and the likelihood of collapse during earthquakes. The results of the tests show that SMA restrainers performed very well as restraining devices. The forces in the SMA and steel restrainers were comparable. However, the SMA restrainer cables had minimal residual strain after repeated loading and exhibited the ability to undergo many cycles with little strength and stiffness degradation. In addition, the hysteretic damping that was observed in the larger ground accelerations demonstrated the ability of the materials to dissipate energy. An analytical study was conducted to assess the anticipated seismic response of the test setup and evaluate the accuracy of the analytical model. The results of the analytical simulation illustrate that the analytical model was able to match the responses from the experimental tests, including peak stresses, strains, forces, and hinge openings

  14. Development of Miniature Stewart Platform Using TiNiCu Shape-Memory-Alloy Actuators

    Directory of Open Access Journals (Sweden)

    Alaa AbuZaiter

    2015-01-01

    Full Text Available A Stewart platform is a parallel manipulator robot that is able to perform three linear movements, lateral, longitudinal, and vertical, and three rotations, pitch, yaw, and roll. This paper reports a 30 mm × 30 mm × 34 mm miniscale Stewart platform using TiNiCu shape-memory-alloy (SMA actuators. The proposed Stewart platform possesses various advantages, such as large actuation force and high robustness with a simple mechanical structure. This Stewart platform uses four SMA actuators and four bias springs and performs a linear z-axis movement and tilting motions. The SMA actuators are activated by passing a current through the SMA wires using a heating circuit that generates a pulse width modulation (PWM signal. This signal is varied to control the level of the displacement and tilting angle of the platform. The tilting direction depends on the SMA actuator that is activated, while all four SMA actuators are activated to achieve the linear z-axis movement. Each SMA actuator exerts a maximum force of 0.6 N at PWM duty cycle of 100%. The fabricated miniature Stewart platform yields a full actuation of 12 mm in the z-axis at 55°C, with a maximum tilting angle of 30° in 4 s.

  15. The elastocaloric effect of Ni50.8Ti49.2 shape memory alloys

    Science.gov (United States)

    Zhou, Min; Li, Yushuang; Zhang, Chen; Li, Shaojie; Wu, Erfu; Li, Wei; Li, Laifeng

    2018-04-01

    Solid-state cooling technologies are considered as possible alternatives for vapor compression cooling systems. The elastocaloric cooling (whose caloric effects are driven by uniaxial stress) technology, as an efficient and clean solid-state cooling technology, is receiving a great deal of attention very recently. Herein, a NiTi-based elastocaloric bulk material was reported. A large coefficient-of-performance of the material (COPmater) of 4.5 was obtained, which was even higher than that of other NiTi bulk materials. The temperature changes (ΔT) increased with increasing applied strain (ɛ), and reached 18 K upon loading and  -11 K upon unloading when the ɛ value increased to 4%. The high temperature changes were attributed to the large stress-induced entropy changes (the maximum ΔS σ value was 37 J kg-1 K-1). The temperature changes decreased with loading-unloading tensile cycles, and stabilized at 6.5 K upon loading and  -6 K upon unloading after tens of mechanical cycles. The Ni50.8Ti49.2 shape memory alloy showed great promise for application in solid-state refrigeration (or as heat pumps).

  16. Damping Characteristics of Inherent and Intrinsic Internal Friction of Cu-Zn-Al Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Shyi-Kaan Wu

    2017-09-01

    Full Text Available Damping properties of the inherent and intrinsic internal friction peaks (IFPT + IFI of Cu-xZn-11Al (x = 7.0, 7.5, 8.0, 8.5, and 9.0 wt. % shape memory alloys (SMAs were investigated by using dynamic mechanical analysis. The Cu-7.5Zn-11Al, Cu-8.0Zn-11Al, and Cu-8.5Zn-11Al SMAs with ( IF PT + IF I β 3 ( L 2 1 → γ 3 ′ ( 2 H peaks exhibit higher damping capacity than the Cu-7.0Zn-11Al SMA with a ( IF PT + IF I β 3 ( L 2 1 → γ 3 ′ ( 2 H peak, because the γ 3 ′ martensite phase possesses a 2H type structure with abundant movable twin boundaries, while the β 3 ′ phase possesses an 18R structure with stacking faults. The Cu-9.0Zn-11Al SMA also possesses a ( IF PT + IF I β 3 ( L 2 1 → γ 3 ′ ( 2 H peak but exhibits low damping capacity because the formation of γ phase precipitates inhibits martensitic transformation. The Cu-8.0Zn-11Al SMA was found to be a promising candidate for practical high-damping applications because of its high (IFPT + IFI peak with tan δ > 0.05 around room temperature.

  17. An Introduction to a Porous Shape Memory Alloy Dynamic Data Driven Application System

    KAUST Repository

    Douglas, Craig C.

    2012-06-02

    Shape Memory Alloys are capable of changing their crystallographic structure due to changes of temperature and/or stress. Our research focuses on three points: (1) Iterative Homogenization of Porous SMAs: Development of a Multiscale Model of porous SMAs utilizing iterative homogenization and based on existing knowledge of constitutive modeling of polycrystalline SMAs. (2) DDDAS: Develop tools to turn on and off the sensors and heating unit(s), to monitor on-line data streams, to change scales based on incoming data, and to control what type of data is generated. The application must have the capability to be run and steered remotely. (3) Modeling and applications of porous SMA: Vibration isolation devices with SMA and porous SMA components for aerospace applications will be analyzed and tested. Numerical tools for modeling porous SMAs with a second viscous phase will be developed.The outcome will be a robust, three-dimensional, multiscale model of porous SMA that can be used in complicated, real-life structural analysis of SMA components using a DDDAS framework.

  18. Pre-stressing piezoelectric actuators by using superelastic shape memory alloys

    International Nuclear Information System (INIS)

    Schiedeck, Florian; Mojrzisch, Sebastian; Wallaschek, Jorg

    2010-01-01

    This work investigates and describes the use of superelastic shape memory alloys (SMAs) for pre-stressing piezoelectric actuators. The nonlinear, hysteretic stress-strain diagram of superelastic SMAs is characterized by two stress plateaus over strains of up to 8% during loading and unloading. In this range of strain, the stress is nearly constant, which yields a theoretical stiffness of 0. A superelastic SMA that is used for pre-stressing will be stretched by the piezoceramic in the range of per mill (one-tenth of a percent), which leads to minor hysteretic loops. The effective stiffness when cycling these minor loops is very small compared to conventional steel - large strokes close to the nominal displacement of the unloaded piezoelectric ceramic are reachable. This theory was experimentally proven with a piezoelectric multilayer actuator using replacable pre-stressing elements. The investigations have confirmed that the use of a superelastic SMA leads to a larger stroke in comparison to the use of steel elements.

  19. Superelastic cycling of Cu–Al–Ni shape memory alloy micropillars

    International Nuclear Information System (INIS)

    San Juan, J.; Nó, M.L.; Schuh, C.A.

    2012-01-01

    Superelastic nanocompression tests are performed on different micropillars milled by focused ion beam from [0 0 1]-oriented single crystals of Cu–Al–Ni shape memory alloys. Over hundreds of cycles such micropillars exhibit reproducible superelastic behavior with complete recovery at stresses around 300 MPa and stress-induced transformation strains above 5%. Upon cycling, the critical stress to induce the transformation decreases, and the transformation strain increases, both signatures of a training effect which is analyzed here in terms of the microscopic mechanisms controlling the nucleation, growth and recovery of the martensite plates. The mechanical hysteresis is characterized through the energy dissipated during closed superelastic cycles, and its evolution during cycling is discussed. The superelastic cycling of the micropillars is also found to depend on the strain rate. The highest strain rate studied here, 10 −1 s −1 , is found to impinge upon the nucleation and growth kinetics of γ 3 ′ and β 3 ′ martensites, with the result that the mechanical hysteresis and transformation strain are reduced. Finally, specific cycling tests have been conducted at increasing maximum loads to analyze the limit for plastic deformation of the micropillar, which happens between 500 and 700 MPa.

  20. Deformation of the UI-14at%Nb shape memory alloy: experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Field, Robert D [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Mc Cabe, Rodney J [Los Alamos National Laboratory; Clarke, Amy J [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tupper, Catherine N [Los Alamos National Laboratory

    2010-12-22

    U-14at%Nb is a shape memory effect (SME) alloy that undergoes deformation by the motion of complex twins and twin related lath boundaries up to the limit of SME deformation ({approx}7%). All of the twins present in the as-transformed martensite and active during SME deformation are derived from those of the orthorhombic alpha-U phase, modified for the monoclinic distortion of the alpha martensite phase. In the SME regime a simple Bain strain model qualitatively predicts variant selection, texture development in polycrystalline samples, and stress-strain behavior as a function of parent phase orientation in single crystal micropillars. In the post-SME regime, unrecoverable deformation occurs by a combination of slip and twinning, with the first few percent of strain in tension apparently governed by a twin species specifically associated with the monoclinic distortion (i.e. not present in the orthorhombic alpha-U phase). The situation in compression is more complicated, with a combination of slip and twinning systems believed responsible for deformation. A review of the Bain strain model for SME deformation will be presented in conjunction with experimental data. In addition, results from modeling of post-SME behavior using the Visco-Plastic Self-Consistent (VPSC) model will be compared to experimental texture measurements.

  1. A general method for the design and fabrication of shape memory alloy active spring actuators

    International Nuclear Information System (INIS)

    Follador, M; Cianchetti, M; Arienti, A; Laschi, C

    2012-01-01

    Shape memory alloys have been widely proposed as actuators, in fields such as robotics, biomimetics and microsystems: in particular spring actuators are the most widely used, due to their simplicity of fabrication. The aim of this paper is to provide a general model and the techniques for fabricating SMA spring actuators. All the steps of the design process are described: a mechanical model to optimize the mechanical characteristic for a given requirement of force and available space, and a thermal model for the estimation of the electrical power needed for activation. The parameters of both models are obtained by experimental measurements, which are described in the paper. The models are then validated on springs manufactured manually, showing also the fabrication process. The design method is valid for the dimensioning of SMA springs, independently from the external ambient conditions. The influence on the actuator bandwidth was investigated for different working environments, providing numerical indications for the utilization in underwater applications. The spring characteristics can be calculated by the mechanical model with an accuracy of 5%. The thermal model allows one to calculate the current needed for activation under different ambient conditions, in order to guarantee activation in the specific loading conditions. Moreover, two solutions were found to reduce the power consumption by more than 40% without a dramatic reduction of bandwidth. (paper)

  2. Nonlinear thermal stability of geometrically imperfect shape memory alloy hybrid laminated composite plates

    Science.gov (United States)

    Asadi, Hamed; Eynbeygi, Mehdi; Wang, Quan

    2014-07-01

    The instability of geometrically imperfect shape memory alloy (SMA) fibers reinforced with hybrid laminated composite (SMAHC) plates and subjected to a uniform thermal loading is analytically investigated. The material properties of the SMAHC plates are assumed to be functions of temperature. Nonlinear equations of the plates’ thermal stability are derived based on a higher order shear deformation theory incorporating von Karman geometrical nonlinearity via stationary potential energy. The structural recovery stress, which is generated by martensitic phase transformation of the prestrained SMA fibers, is calculated based on the one-dimensional thermodynamic constitutive model by Brinson. Adopting the Galerkin procedure, the governing nonlinear partial differential equations are converted into a set of nonlinear algebraic equations, in which systems of equations are solved by introducing an analytical approach. Closed-form formulations are presented to determine the load-deflection path and critical buckling temperature of the plate. Based on the developed closed-form solutions, ample numerical results are presented to provide an insight into the effects of the volume fraction, prestrain, location and orientation of the SMA fibers, composite plate geometry, geometrical imperfection and temperature dependence on the stability of the SMAHC plates. It is shown that a proper application of SMA fibers results in a considerable delay of the thermal bifurcation and controllable thermal post-buckling deflection of the SMAHC plate.

  3. A new isolation device using shape memory alloy and its application for long-span structures

    Science.gov (United States)

    Ding, Youliang; Chen, Xin; Li, Aiqun; Zuo, Xiaobao

    2011-06-01

    The key points to consider in determining the effectiveness of using structural isolation with shape memory alloys (SMA) are the constitutive model, the SMA isolation device and the analysis method. In this paper, a simplified constitutive model based on the classic theory of plasticity is proposed to simulate the behavior of the superelasticity of the SMA, in which the martensite volume fraction is considered as one of the state variables. Comparisons between simulation results and experimental results are made and indicate that the proposed constitutive model yields stress-strain curves that are in good agreement with the experimental ones. Thus, the proposed model can correctly simulate the yield mechanism and energy dissipation capacity of the SMA. Next, in order to make full use of the superelasticity of SMA, a new SMA isolator composed of pre-tensioned SMA bars is presented. Then, a finite element analytical model is established to simulate the behavior of the SMA isolator according to its configuration and simplified constitutive model. Finally, a simplified design method for long-span structures installed with SMA isolators is proposed, which is further used to investigate the isolation effects of a space grid structure. Results show that the SMA isolator can reduce the seismic responses of the structure effectively, which indicates the effectiveness of the proposed SMA isolation method.

  4. Plastic and transformation interactions of pores in shape memory alloy plates

    Science.gov (United States)

    Zhu, Pingping; Stebner, Aaron P.; Brinson, L. Catherine

    2014-10-01

    A three-dimensional constitutive model for shape memory alloys (SMAs) is developed along the lines of the Stebner-Brinson (SB) implementation of the Panico-Brinson model. Plastic kinematic hardening behavior is simulated in addition to elastic deformation and phase transformation. A series of finite element simulations is carried out using this model to investigate the localization effects of the stress and strain field on NiTi plates with structured arrays of pores. The application of this model on porous architectures provides insight into how geometric features influence the mechanics of the structure. The incorporation of plastic deformation shows a marked decrease in the maximum stress levels; these results are more consistent with experimental data as compared to the original SB model. Furthermore, the new results demonstrate that clustered pores lead to more distributed stresses and transformation compared to a dispersed configuration of pores, indicating the importance of pore geometry in determining the stress and strain distribution. The improved model provides a practical tool toward design and optimization of porous SMA structures.

  5. Compliant liquid column damper modified by shape memory alloy device for seismic vibration control

    International Nuclear Information System (INIS)

    Gur, Sourav; Mishra, Sudib Kumar; Bhowmick, Sutanu; Chakraborty, Subrata

    2014-01-01

    Liquid column dampers (LCDs) have long been used for the seismic vibration control of flexible structures. In contrast, tuning LCDs to short-period structures poses difficulty. Various modifications have been proposed on the original LCD configuration for improving its performance in relatively stiff structures. One such system, referred to as a compliant-LCD has been proposed recently by connecting the LCD to the structure with a spring. In this study, an improvement is attempted in compliant LCDs by replacing the linear spring with a spring made of shape memory alloy (SMA). Considering the dissipative, super-elastic, force-deformation hysteresis of SMA triggered by stress-induced micro-structural phase transition, the performance is expected to improve further. The optimum parameters for the SMA-compliant LCD are obtained through design optimization, which is based on a nonlinear random vibration response analysis via stochastic linearization of the force-deformation hysteresis of SMA and dissipation by liquid motion through an orifice. Substantially enhanced performance of the SMA–LCD over a conventional compliant LCD is demonstrated, the consistency of which is further verified under recorded ground motions. The robustness of the improved performance is also validated by parametric study concerning the anticipated variations in system parameters as well as variability in seismic loading. (paper)

  6. Study of shape memory alloy fibers for the development of artificial myocardium.

    Science.gov (United States)

    Hassoulas, Ioannis A; Ladopoulos, Vlassios S; Kalogerakos, Paris-Dimitrios K

    2010-01-01

    Circulatory support devices are employed to treat heart failure. Such a device could be made from shape memory alloy (SMA) fibers. These Ni-Ti fibers contract when electric current flows through them, thus resembling artificial muscles. An artificial myocardium device made from SMA fibers can directly compress the epicardial surface of a failing heart, thus contributing to the pumping action. Unlike modern mechanical circulatory support devices, there is no blood-contacting surface to provoke thromboembolism, hemorrhage, inflammatory response or hemolysis. The experimental setup permitted a detailed study of a sample SMA fiber with great accuracy while the ambient temperature was controlled to resemble that of the human body. The current profile through the fiber was controlled (current shaping, CS) by a microcontroller and a portable computer. Parameters such as strain, contraction and relaxation velocities and the effect of ambient temperature were measured. The contraction and relaxation velocities were measured after applying various effective currents. It was found that the contraction velocity could be manipulated to reach that of the healthy myocardium through CS. On the other hand, the relaxation velocity was independent of the contraction velocity. A cardiac assist device can be made from SMA fibers. More studies need to be conducted in this direction.

  7. A validated model for induction heating of shape memory alloy actuators

    Science.gov (United States)

    Saunders, Robert N.; Boyd, James G.; Hartl, Darren J.; Brown, Jonathan K.; Calkins, Frederick T.; Lagoudas, Dimitris C.

    2016-04-01

    Shape memory alloy (SMA) actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. One disadvantage of these thermally driven actuators is their slow cyclic time response compared to conventional actuators. Induction heating has recently been proposed to quickly heat SMA components. However efforts to date have been purely empirical. The present work approachs this problem in a computational manner by developing a finite element model of induction heating in which the time-harmonic electromagnetic equations are solved for the Joule heat power field, the energy equation is solved for the temperature field, and the linear momentum equations are solved to find the stress, displacement, and internal state variable fields. The combined model was implemented in Abaqus using a Python script approach and applied to SMA torque tube and beam actuators. The model has also been used to examine magnetic flux concentrators to improve the induction systems performance. Induction heating experiments were performed using the SMA torque tube, and the model agreed well with the experiments.

  8. A validated model for induction heating of shape memory alloy actuators

    International Nuclear Information System (INIS)

    Saunders, Robert N; Boyd, James G; Hartl, Darren J; Lagoudas, Dimitris C; Brown, Jonathan K; Calkins, Frederick T

    2016-01-01

    Shape memory alloy (SMA) actuators deliver high forces while being compact and reliable, making them ideal for consideration in aerospace applications. One disadvantage of these thermally driven actuators is their slow cyclic time response compared to conventional actuators. Induction heating has recently been proposed to quickly heat SMA components. However efforts to date have been purely empirical. The present work approachs this problem in a computational manner by developing a finite element model of induction heating in which the time-harmonic electromagnetic equations are solved for the Joule heat power field, the energy equation is solved for the temperature field, and the linear momentum equations are solved to find the stress, displacement, and internal state variable fields. The combined model was implemented in Abaqus using a Python script approach and applied to SMA torque tube and beam actuators. The model has also been used to examine magnetic flux concentrators to improve the induction systems performance. Induction heating experiments were performed using the SMA torque tube, and the model agreed well with the experiments. (paper)

  9. Exploiting NiTi shape memory alloy films in design of tunable high frequency microcantilever resonators

    Science.gov (United States)

    Stachiv, I.; Sittner, P.; Olejnicek, J.; Landa, M.; Heller, L.

    2017-11-01

    Shape memory alloy (SMA) films are very attractive materials for microactuators because of their high energy density. However, all currently developed SMA actuators utilize martensitic transformation activated by periodically generated heating and cooling; therefore, they have a slow actuation speed, just a few Hz, which restricts their use in most of the nanotechnology applications such as high frequency microcantilever based physical and chemical sensors, atomic force microscopes, or RF filters. Here, we design tunable high frequency SMA microcantilevers for nanotechnology applications. They consist of a phase transforming NiTi SMA film sputtered on the common elastic substrate material; in our case, it is a single-crystal silicon. The reversible tuning of microcantilever resonant frequencies is then realized by intentionally changing the Young's modulus and the interlayer stress of the NiTi film by temperature, while the elastic substrate guarantees the high frequency actuation (up to hundreds of kHz) of the microcantilever. The experimental results qualitatively agree with predictions obtained from the dedicated model based on the continuum mechanics theory and a phase characteristic of NiTi. The present design of SMA microcantilevers expands the capability of current micro-/nanomechanical resonators by enabling tunability of several consecutive resonant frequencies.

  10. Shape memory alloy resistance behaviour at high altitude for feedback control

    Science.gov (United States)

    Ng, W. T.; Sedan, M. F.; Abdullah, E. J.; Azrad, S.; Harithuddin, A. S. M.

    2017-12-01

    Many recent aerospace technologies are using smart actuators to reduce the system's complexity and increase its reliability. One such actuator is shape memory alloy (SMA) actuator, which is lightweight, produces high force and large deflection. However, some disadvantages in using SMA actuators have been identified and they include nonlinear response of the strain to input current, hysteresis characteristic that results in inaccurate control and less than optimum system performance, high operating temperatures, slow response and also high requirement of electrical power to obtain the desired actuation forces. It is still unknown if the SMA actuators can perform effectively at high altitude with low surrounding temperature. The work presented here covers the preliminary process of verifying the feasibility of using resistance as feedback control at high altitude for aerospace applications. Temperature and resistance of SMA actuator at high altitude is investigated by conducting an experiment onboard a high altitude balloon. The results from the high altitude experiment indicate that the resistance or voltage drop of the SMA wire is not significantly affected by the low surrounding temperature at high altitude as compared to the temperature of SMA. Resistance feedback control for SMA actuators may be suitable for aerospace applications.

  11. Fracture mechanics and microstructure in NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gollerthan, S. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany); Young, M.L. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany)], E-mail: marcus.young@rub.de; Baruj, A.; Frenzel, J. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany); Schmahl, W.W. [Institut fuer Geologie, Mineralogie und Geophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Department of Earth and Environmental Sciences, Materials Research, LMU Munich (Germany); Eggeler, G. [Institut fuer Werkstoffe, Ruhr-Universitaet Bochum, Universitaetsstrasse 150, D-44801 Bochum (Germany)

    2009-02-15

    Crack extension under static loading in pseudoplastic and pseudoelastic binary NiTi shape memory alloy (SMA) compact tension (CT) specimens was examined. Two material compositions of 50.3 at.% Ni (martensitic/pseudoplastic) and 50.7 at.% Ni (austenitic/pseudoelastic) were investigated. The SMAs were characterized using differential scanning calorimetry to identify the phase transformation temperatures and tensile testing to characterize the stress-strain behavior. A miniature CT specimen was developed, which yields reliable critical fracture mechanics parameters. At 295 K, cracks propagate at similar stress intensities of 30{+-}5MPa{radical}(m) into martensite and pseudoelastic austenite. Integrating the miniature CT specimen into a small test device which can be fitted into a scanning electron microscope shows that this is due to cracks propagating into regions of detwinned martensite in both materials. Investigating a pseudoelastic miniature CT specimen in a synchrotron beam proves that martensite forms in front of the crack in the center of the CT specimen, i.e. under plane strain conditions.

  12. A biomimetic robotic jellyfish (Robojelly) actuated by shape memory alloy composite actuators

    International Nuclear Information System (INIS)

    Villanueva, Alex; Smith, Colin; Priya, Shashank

    2011-01-01

    An analysis is conducted on the design, fabrication and performance of an underwater vehicle mimicking the propulsion mechanism and physical appearance of a medusa (jellyfish). The robotic jellyfish called Robojelly mimics the morphology and kinematics of the Aurelia aurita species. Robojelly actuates using bio-inspired shape memory alloy composite actuators. A systematic fabrication technique was developed to replicate the essential structural features of A. aurita. Robojelly's body was fabricated from RTV silicone having a total mass of 242 g and bell diameter of 164 mm. Robojelly was able to generate enough thrust in static water conditions to propel itself and achieve a proficiency of 0.19 s -1 while the A. aurita achieves a proficiency of around 0.25 s -1 . A thrust analysis based on empirical measurements for a natural jellyfish was used to compare the performance of the different robotic configurations. The configuration with best performance was a Robojelly with segmented bell and a passive flap structure. Robojelly was found to consume an average power on the order of 17 W with the actuators not having fully reached a thermal steady state.

  13. The specific heat of Cu-Al-Ni shape memory alloys

    International Nuclear Information System (INIS)

    Ruiz-Larrea, I.; Lopez-Echarri, A.; Bocanegra, E.H.; No, M.L.; San Juan, J.M.

    2006-01-01

    The specific heat of Cu 81.8 Al 13.7 Ni 4.5 (AK10) shape memory alloy has been studied by means of conventional DSC and adiabatic calorimetry techniques. The transformation temperatures and the shape of the calorimetric curves obtained by adiabatic calorimetry do not show any noticeable dependence on the temperature measurement rates, contrarily to what is observed by other calorimetric techniques. The dynamical character of the various experimental methods together with the influence of the latent heat associated to the first order character of these phase transitions are discussed. The specific heat of AK10 has been measured from 50 to 350 K which covers the phase transformation temperature range. The forward and reverse martensitic transformation peaks were found at 299.5 and 304.6 K, showing a thermal hysteresis of 5.1 deg. C. The C p accuracy can be estimated in 0.1% of C p and permits a reliable assignment of the following values to the phase transition thermodynamic functions: ΔH = 7.4 ± 0.2 J/g and ΔS = 0.025 ± 0.001 J/gK

  14. Standardization of shape memory alloy test methods toward certification of aerospace applications

    Science.gov (United States)

    Hartl, D. J.; Mabe, J. H.; Benafan, O.; Coda, A.; Conduit, B.; Padan, R.; Van Doren, B.

    2015-08-01

    The response of shape memory alloy (SMA) components employed as actuators has enabled a number of adaptable aero-structural solutions. However, there are currently no industry or government-accepted standardized test methods for SMA materials when used as actuators and their transition to commercialization and production has been hindered. This brief fast track communication introduces to the community a recently initiated collaborative and pre-competitive SMA specification and standardization effort that is expected to deliver the first ever regulatory agency-accepted material specification and test standards for SMA as employed as actuators for commercial and military aviation applications. In the first phase of this effort, described herein, the team is working to review past efforts and deliver a set of agreed-upon properties to be included in future material certification specifications as well as the associated experiments needed to obtain them in a consistent manner. Essential for the success of this project is the participation and input from a number of organizations and individuals, including engineers and designers working in materials and processing development, application design, SMA component fabrication, and testing at the material, component, and system level. Going forward, strong consensus among this diverse body of participants and the SMA research community at large is needed to advance standardization concepts for universal adoption by the greater aerospace community and especially regulatory bodies. It is expected that the development and release of public standards will be done in collaboration with an established standards development organization.

  15. Pressure controlled clamp using shape memory alloy for minimal vessel invasion in blood flow occlusion.

    Science.gov (United States)

    Zhang, Ye; Kanetaka, Hiroyasu; Sano, Yuya; Kano, Mitsuhiro; Kudo, Tadaaki; Sato, Takumi; Shimizu, Yoshinaka

    2013-01-01

    Vessel damage after clamping may affect the success of surgical operations. A new pressure controlled clamp (SMA clamp) was designed using super elastic property of shape memory alloy (SMA) to realize atraumatic vessel occlusion. The ability and biological effect of the SMA clamp to control pressure was investigated in vivo. The loading-displacement curves of the SMA clamps (experimental group) and conventional clamp (control group) by occlusion of pig carotid arteries were evaluated using a clamping-pressure analyzing system. To investigate macroscopically and histologically the vessel damage of the SMA and conventional clamps, pig carotid arteries were stained with Evan's blue and its histological sections were stained with Elastica Massion after clamping for fifteen minutes. Constant value was shown in the loading-displacement curve of SMA clamp. In the control group, damaged area stained with Evan's blue in the vessel wall showed enlargement with the pressure increasing. Less areas in experimental groups are observed than that in the control group. Histological section in the experimental group showed no obvious except a slight compressive damage in the tunica intima. In the control group, vessel wall showed irreversible damages. This experiment indicated that the SMA clamp, which has a unique mechanical property, can be used without vessels damage. This pressure controlled clamp can be a selection in clinical apparatus to improve surgical safety.

  16. Hysteresis Modeling of Magnetic Shape Memory Alloy Actuator Based on Krasnosel'skii-Pokrovskii Model

    Directory of Open Access Journals (Sweden)

    Miaolei Zhou

    2013-01-01

    Full Text Available As a new type of intelligent material, magnetically shape memory alloy (MSMA has a good performance in its applications in the actuator manufacturing. Compared with traditional actuators, MSMA actuator has the advantages as fast response and large deformation; however, the hysteresis nonlinearity of the MSMA actuator restricts its further improving of control precision. In this paper, an improved Krasnosel'skii-Pokrovskii (KP model is used to establish the hysteresis model of MSMA actuator. To identify the weighting parameters of the KP operators, an improved gradient correction algorithm and a variable step-size recursive least square estimation algorithm are proposed in this paper. In order to demonstrate the validity of the proposed modeling approach, simulation experiments are performed, simulations with improved gradient correction algorithm and variable step-size recursive least square estimation algorithm are studied, respectively. Simulation results of both identification algorithms demonstrate that the proposed modeling approach in this paper can establish an effective and accurate hysteresis model for MSMA actuator, and it provides a foundation for improving the control precision of MSMA actuator.

  17. Frontiers of Theoretical Research on Shape Memory Alloys: A General Overview

    Science.gov (United States)

    Chowdhury, Piyas

    2018-03-01

    In this concise review, general aspects of modeling shape memory alloys (SMAs) are recounted. Different approaches are discussed under four general categories, namely, (a) macro-phenomenological, (b) micromechanical, (c) molecular dynamics, and (d) first principles models. Macro-phenomenological theories, stemming from empirical formulations depicting continuum elastic, plastic, and phase transformation, are primarily of engineering interest, whereby the performance of SMA-made components is investigated. Micromechanical endeavors are generally geared towards understanding microstructural phenomena within continuum mechanics such as the accommodation of straining due to phase change as well as role of precipitates. By contrast, molecular dynamics, being a more recently emerging computational technique, concerns attributes of discrete lattice structures, and thus captures SMA deformation mechanism by means of empirically reconstructing interatomic bonding forces. Finally, ab initio theories utilize quantum mechanical framework to peek into atomistic foundation of deformation, and can pave the way for studying the role of solid-sate effects. With specific examples, this paper provides concise descriptions of each category along with their relative merits and emphases.

  18. Finite-strain micromechanical model of stress-induced martensitic transformations in shape memory alloys

    International Nuclear Information System (INIS)

    Stupkiewicz, S.; Petryk, H.

    2006-01-01

    A micromechanical model of stress-induced martensitic transformation in single crystals of shape memory alloys is developed. This model is a finite-strain counterpart to the approach presented recently in the small-strain setting [S. Stupkiewicz, H. Petryk, J. Mech. Phys. Solids 50 (2002) 2303-2331]. The stress-induced transformation is assumed to proceed by the formation and growth of parallel martensite plates within the austenite matrix. Propagation of phase transformation fronts is governed by a rate-independent thermodynamic criterion with a threshold value for the thermodynamic driving force, including in this way the intrinsic dissipation due to phase transition. This criterion selects the initial microstructure at the onset of transformation and governs the evolution of the laminated microstructure at the macroscopic level. A multiplicative decomposition of the deformation gradient into elastic and transformation parts is assumed, with full account for the elastic anisotropy of the phases. The pseudoelastic behavior of Cu-Zn-Al single crystal in tension and compression is studied as an application of the model

  19. Modeling of thermo-mechanical fatigue and damage in shape memory alloy axial actuators

    Science.gov (United States)

    Wheeler, Robert W.; Hartl, Darren J.; Chemisky, Yves; Lagoudas, Dimitris C.

    2015-04-01

    The aerospace, automotive, and energy industries have seen the potential benefits of using shape memory alloys (SMAs) as solid state actuators. Thus far, however, these actuators are generally limited to non-critical components or over-designed due to a lack of understanding regarding how SMAs undergo thermomechanical or actuation fatigue and the inability to accurately predict failure in an actuator during use. The purpose of this study was to characterize the actuation fatigue response of Nickel-Titanium-Hafnium (NiTiHf) axial actuators and, in turn, use this characterization to predict failure and monitor damage in dogbone actuators undergoing various thermomechanical loading paths. Calibration data was collected from constant load, full cycle tests ranging from 200-600MPa. Subsequently, actuator lifetimes were predicted for four additional loading paths. These loading paths consisted of linearly varying load with full transformation (300-500MPa) and step loads which transition from zero stress to 300-400MPa at various martensitic volume fractions. Thermal cycling was achieved via resistive heating and convective cooling and was controlled via a state machine developed in LabVIEW. A previously developed fatigue damage model, which is formulated such that the damage accumulation rate is general in terms of its dependence on current and local stress and actuation strain states, was utilized. This form allows the model to be utilized for specimens undergoing complex loading paths. Agreement between experiments and simulations is discussed.

  20. Development and experimental evaluation of a novel annuloplasty ring with a shape memory alloy core

    Science.gov (United States)

    Purser, Molly Ferris

    A novel annuloplasty ring with a shape memory alloy core has been developed to facilitate minimally invasive mitral valve repair. In its activated (austenitic) phase, this prototype ring provides comparable mechanical properties as commercial semi-rigid rings. In its pre-activated (martensitic) phase, this ring is flexible enough to be introduced through an 8 mm trocar and easily manipulated with robotic instruments within the confines of a left atrial model. The core is constructed of 0.508 mm diameter NiTi, which is maintained below its M s temperature (24°C) during deployment and suturing. After suturing, the stiffener is heated to its Af temperature (37°C, normal human body temperature) enabling the NiTi to retain its optimal geometry and stiffness characteristics indefinitely. The NiTi core is shape set in a furnace to the appropriate size and optimal geometry during fabrication. The ring is cooled in a saline bath prior to surgery, making it compliant and easy to manipulate. Evaluation of the ring included mechanical testing, robotic evaluation, static pressure testing, dynamic flow testing and fatigue testing. Experimental results suggest that the NiTi core ring could be a viable alternative to flexible bands in robot-assisted mitral valve repair.