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Sample records for memory alloy prepared

  1. Preparation of NiFe binary alloy nanocrystals for nonvolatile memory applications

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this work,an idea which applies binary alloy nanocrystal floating gate to nonvolatile memory application was introduced.The relationship between binary alloy’s work function and its composition was discussed theoretically.A nanocrystal floating gate structure with NiFe nanocrystals embedded in SiO2 dielectric layers was fabricated by magnetron sputtering.The micro-structure and composition deviation of the prepared NiFe nanocrystals were also investigated by TEM and EDS.

  2. Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting

    Science.gov (United States)

    Gustmann, T.; dos Santos, J. M.; Gargarella, P.; Kühn, U.; Van Humbeeck, J.; Pauly, S.

    2016-12-01

    Two shape-memory alloys with the nominal compositions (in wt.%) Cu-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr were prepared by selective laser melting (SLM). The parameters were optimised to identify the process window, in which almost fully dense samples can be obtained. Their microstructures were analysed and correlated with the shape-memory behaviour as well as the mechanical properties. Suction-cast specimens were also produced for comparison. Mainly, β 1' martensite forms in all samples, but 0.5 wt.% of Zr stabilises the Y phase (Cu2AlZr), and its morphology depends on the thermal history and cooling rate. After annealing, the Y phase is primarily found at the grain boundaries hampering grain coarsening. Due to the relative high cooling rates applied here, Zr is mostly dissolved in the martensite in the as-prepared samples and it has a grain-refining effect only up to a critical cooling rate. The Zr-containing samples have increased transformation temperatures, and the Y phase seems to be responsible for the jerky martensite-to-austenite transformation. All the samples are relatively ductile because they mostly fracture in a transgranular manner, exhibiting the typical double yielding. Selective laser melting allows the adjustment of the transformation temperatures and the mechanical properties already during processing without the need of a subsequent heat treatment.

  3. Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting

    Science.gov (United States)

    Gustmann, T.; dos Santos, J. M.; Gargarella, P.; Kühn, U.; Van Humbeeck, J.; Pauly, S.

    2017-03-01

    Two shape-memory alloys with the nominal compositions (in wt.%) Cu-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr were prepared by selective laser melting (SLM). The parameters were optimised to identify the process window, in which almost fully dense samples can be obtained. Their microstructures were analysed and correlated with the shape-memory behaviour as well as the mechanical properties. Suction-cast specimens were also produced for comparison. Mainly, β 1' martensite forms in all samples, but 0.5 wt.% of Zr stabilises the Y phase (Cu2AlZr), and its morphology depends on the thermal history and cooling rate. After annealing, the Y phase is primarily found at the grain boundaries hampering grain coarsening. Due to the relative high cooling rates applied here, Zr is mostly dissolved in the martensite in the as-prepared samples and it has a grain-refining effect only up to a critical cooling rate. The Zr-containing samples have increased transformation temperatures, and the Y phase seems to be responsible for the jerky martensite-to-austenite transformation. All the samples are relatively ductile because they mostly fracture in a transgranular manner, exhibiting the typical double yielding. Selective laser melting allows the adjustment of the transformation temperatures and the mechanical properties already during processing without the need of a subsequent heat treatment.

  4. On the preparation and characterization of thin NiTi shape memory alloy wires for MEMS

    Directory of Open Access Journals (Sweden)

    Ausonio Tuissi

    2013-01-01

    Full Text Available Shape memory alloy (SMA wires are employed as actuators in small devices for consumer electronics, valves and automotive applications. Because of the continued miniaturization of all the industrial products, nowadays the tendency is to produce MEMS (micro electromechanical systems. Among the most promising functional MEMS materials, the thin SMA wires that are offering a rapid actuating response with high power/weigh ratio of the material, are attracting a world wide interest. This paper is aimed at showing the production process and the characterizations of thin NiTi shape memory wires. The activity was focused on drawing procedure and on functional and TEM characterizations of the final products. In particular, it was evaluated the performance of the SMA wires for actuators in terms of functional fatigue and thermo-mechanical properties by means of an experimental apparatus design ad hoc for these specific tests.

  5. Shape Memory Alloy Actuator

    Science.gov (United States)

    Baumbick, Robert J. (Inventor)

    2002-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  6. Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Deexith Reddy

    2016-07-01

    Full Text Available Shape memory alloys (SMAs are metals that "remember" their original shapes. SMAs are useful for such things as actuators which are materials that "change shape, stiffness, position, natural frequency, and other mechanical characteristics in response to temperature or electromagnetic fields" The potential uses for SMAs especially as actuators have broadened the spectrum of many scientific fields. The study of the history and development of SMAs can provide an insight into a material involved in cutting-edge technology. The diverse applications for these metals have made them increasingly important and visible to the world. This paper presents the working of shape memory alloys , the phenomenon of super-elasticity and applications of these alloys.

  7. Oligocrystalline shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ueland, Stian M.; Chen, Ying; Schuh, Christopher A. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2012-05-23

    Copper-based shape memory alloys (SMAs) exhibit excellent shape memory properties in single crystalline form. However, when they are polycrystalline, their shape memory properties are severely compromised by brittle fracture arising from transformation strain incompatibility at grain boundaries and triple junctions. Oligocrystalline shape memory alloys (oSMAs) are microstructurally designed SMA structures in which the total surface area exceeds the total grain boundary area, and triple junctions can even be completely absent. Here it is shown how an oligocrystalline structure provides a means of achieving single crystal-like SMA properties without being limited by constraints of single crystal processing. Additionally, the formation of oSMAs typically involves the reduction of the size scale of specimens, and sample size effects begin to emerge. Recent findings on a size effect on the martensitic transformation in oSMAs are compared and a new regime of heat transfer associated with the transformation heat evolution in these alloys is discussed. New results on unassisted two-way shape memory and the effect of loading rate in oSMAs are also reported. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Preparation and Properties of the Ni2MnGa Magnetic Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    LIANG Ting; XU Hui-Bin; JIANG Cheng-Bao; GONG Sheng-Kai

    2000-01-01

    The polycrystalline Ni4s.2Mn22.4 Ga29.4 alloys were prepared by means of melting in argon arc furnace. X-ray diffraction pattern indicates a fcc cubic structure with a lattice parameter of 0.5822nm at room temperature.The phase transformation temperatures were: 1°C for martensite start temperature, -11°C for martensite finish temperature, 3°C for austenite start temperature and 11°C for austenite start temperature, respectively. The results showed that the effect of magnetic field on the strains increases with the decrease of temperature. A strain of 2.1×10-4 was obtained with an applied magnetic field of 5 kOe at -66°C

  9. Shape memory alloy actuator

    Science.gov (United States)

    Varma, Venugopal K.

    2001-01-01

    An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

  10. Shape memory alloy thaw sensors

    Science.gov (United States)

    Shahinpoor, Mohsen; Martinez, David R.

    1998-01-01

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.

  11. Shape memory alloy flexures

    Energy Technology Data Exchange (ETDEWEB)

    Bellouard, Yves; Clavel, Reymond

    2003-07-25

    Flexures are used in precision engineering where highly accurate, wear-free, smooth and repeatable motion is desired. Flexures are based on deformation of material to achieve a motion between elastically joined parts. They are used in a variety of precision mechanisms such as high-resolution balances or high accuracy optical positioning stages. Shape memory alloys (SMA) are an attractive option in designing flexures. Superelastic flexures can withstand larger deformations for the same weight as a conventional flexure. In addition, the damping properties of SMA, controllable through the phase transformation, offer new design opportunities for adaptive compliant mechanisms. The martensitic phase transformation can also be used to shift the natural frequency of flexures adding useful functionalities such as vibration rejection. This paper presents design principles of SMA flexures based on non-linear beam theory. Results show a good agreement between measured and predicted data. In addition, experimental results on phase transformation effects on damping behavior are also presented. Both, natural-frequency shift and increased damping were observed in bulk-micro machined flexures using the R-phase transformation. These results demonstrate the feasibility of natural-frequency-tunable flexures.

  12. Shape memory alloys. Ultralow-fatigue shape memory alloy films.

    Science.gov (United States)

    Chluba, Christoph; Ge, Wenwei; Lima de Miranda, Rodrigo; Strobel, Julian; Kienle, Lorenz; Quandt, Eckhard; Wuttig, Manfred

    2015-05-29

    Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle. Copyright © 2015, American Association for the Advancement of Science.

  13. Porous NiTi shape memory alloys prepared by thermal explosion method%热爆法制备多孔NiTi形状记忆合金

    Institute of Scientific and Technical Information of China (English)

    李强; 于景媛; 李晓东; 孙旭东; 白华; 李然

    2006-01-01

    Thermal explosion method was used to prepare porous NiTi shape memory alloy. The process of thermal explosion was investigated. The effect of process parameters on thermal explosion reaction and properties of products was analyzed. The results showed heating rate, green density, particle size of initial powder strongly affected combustion temperature, porosity and compressive strength of final products. The mechanism of thermal explosion and the microstructure of reacted products were studied by XRD and SEM photographs. The results showed the final products mainly comprised of NiTi, Ti2Ni and TiNi3 phases and theirstrength decreased with the increase of porosity.

  14. 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

  15. 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

  16. Ultralow-fatigue shape memory alloy films

    National Research Council Canada - National Science Library

    Chluba, C; Ge, W; Lima de Miranda, R; Strobel, J; Kienle, L; Quandt, E; Wuttig, M

    2015-01-01

    Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning...

  17. Applications of shape memory alloys in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Asai, M.; Suzuki, Y. [Furukawa Electric Co., Ltd., Yokohama, Kanagawa (Japan). R and D Labs.

    2000-07-01

    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 otherfield today. (orig.)

  18. Shape memory alloy based motor

    Indian Academy of Sciences (India)

    S V Sharma; M M Nayak; N S Dinesh

    2008-10-01

    Design and characterization of a new shape memory alloy wire based Poly Phase Motor has been reported in this paper. The motor can be used either in stepping mode or in servo mode of operation. Each phase of the motor consists of an SMA wire with a spring in series. The principle of operation of the poly phase motor is presented. The motor resembles a stepper motor in its functioning though the actuation principles are different and hence has been characterized similar to a stepper motor. The motor can be actuated in either direction with different phase sequencing methods, which are presented in this work. The motor is modelled and simulated and the results of simulations and experiments are presented. The experimental model of the motor is of dimension 150 mm square, 20 mm thick and uses SMA wire of 0·4 mm diameter and 125 mm of length in each phase.

  19. Rapidly solidified ferromagnetic shape memory alloys

    Science.gov (United States)

    Craciunescu, C. M.; Ercuta, A.; Mitelea, I.; Valeanu, M.; Teodorescu, V. S.; Lupu, N.; Chiriac, H.

    2008-05-01

    Ferromagnetic shape memory alloys have been manufactured by various techniques involving rapid solidification. Bulk alloys have been obtained by extracting the melted alloy in especially designed copper molds; glass coated wires have been obtained by drawing the melt from glass recipients followed by water cooling and ribbons have been fabricated by melt-spinning. Microstructural observations show particular solidification aspects of fractured areas, while ferromagnetic behavior has been detected in glass coated wires obtained by rapid solidification. The martensitic microstructure was observed on Co-Ni-Ga rapid solidified bulk alloys and Fe-Pd ribbons. The memory effect was detected using a Vibran system that allows the detection of the phase transition for the ribbons and by visual observation for other specimens. The conclusions of the observations are related to the comparison between the ferromagnetic behaviors of shape memory alloys solidified using different techniques.

  20. Shape Memory Alloy Rock Splitters (SMARS)

    Science.gov (United States)

    Benafan, Othmane (Inventor); Noebe, Ronald D. (Inventor)

    2017-01-01

    Shape memory alloys (SMAs) may be used for static rock splitting. The SMAs may be used as high-energy multifunctional materials, which have a unique ability to recover large deformations and generate high stresses in response to thermal loads.

  1. A lightweight shape-memory magnesium alloy.

    Science.gov (United States)

    Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Koike, Junichi

    2016-07-22

    Shape-memory alloys (SMAs), which display shape recovery upon heating, as well as superelasticity, offer many technological advantages in various applications. Those distinctive behaviors have been observed in many polycrystalline alloy systems such as nickel titantium (TiNi)-, copper-, iron-, nickel-, cobalt-, and Ti-based alloys but not in lightweight alloys such as magnesium (Mg) and aluminum alloys. Here we present a Mg SMA showing superelasticity of 4.4% at -150°C and shape recovery upon heating. The shape-memory properties are caused by reversible martensitic transformation. This Mg alloy includes lightweight scandium, and its density is about 2 grams per cubic centimeter, which is one-third less than that of practical TiNi SMAs. This finding raises the potential for development and application of lightweight SMAs across a number of industries.

  2. Mechanocaloric effects in Shape Memory Alloys

    OpenAIRE

    Manosa, Lluis; Planes, Antoni

    2016-01-01

    Shape memory alloys are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition gives rise to giant mechanocaloric effects. In non-magnetic shape memory alloys, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of allo...

  3. Medical applications of shape memory alloys

    Directory of Open Access Journals (Sweden)

    Machado L.G.

    2003-01-01

    Full Text Available Shape memory alloys (SMA are materials that have the ability to return to a former shape when subjected to an appropriate thermomechanical procedure. Pseudoelastic and shape memory effects are some of the behaviors presented by these alloys. The unique properties concerning these alloys have encouraged many investigators to look for applications of SMA in different fields of human knowledge. The purpose of this review article is to present a brief discussion of the thermomechanical behavior of SMA and to describe their most promising applications in the biomedical area. These include cardiovascular and orthopedic uses, and surgical instruments.

  4. Shape-Memory-Alloy Release Mechanism

    Science.gov (United States)

    Mckinnis, Darin

    1993-01-01

    Release-nut mechanism activated by electric current applied to shape-memory alloy. Separates attached objects quickly by remote control. Does not create hazard or cause damage. Shape-memory release-nut mechanism unaffected by moisture or vacuum. Requires sustained current lasting 5 seconds or longer, and insensitive to electromagnetic interference. Mechanism can be reused.

  5. 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.

  6. A NEW MODEL OF SHAPE MEMORY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    朱祎国; 吕和祥; 杨大智

    2002-01-01

    A new constitutive model of shape memory alloys ( SMAs ) based on Tanaka' s martensite fraction exponential expression is produced. This new model can present recoverable shape memory strain during different phase transformation, and reflect the action of martensite reorientation. Also it can overcome the defect of Tanaka's Model when the SMAs' microstructure is fully martensite . The model is very simple and suitable for using,and the correct behavior of the model is proved by test.

  7. Shape-Memory-Alloy Actuator For Flight Controls

    Science.gov (United States)

    Barret, Chris

    1995-01-01

    Report proposes use of shape-memory-alloy actuators, instead of hydraulic actuators, for aerodynamic flight-control surfaces. Actuator made of shape-memory alloy converts thermal energy into mechanical work by changing shape as it makes transitions between martensitic and austenitic crystalline phase states of alloy. Because both hot exhaust gases and cryogenic propellant liquids available aboard launch rockets, shape-memory-alloy actuators exceptionally suited for use aboard such rockets.

  8. Investigation of the Effect of Magnesium on the Microstructure and Mechanical Properties of NiTi Shape Memory Alloy Prepared by Self-Propagating High-Temperature Synthesis

    Science.gov (United States)

    Školáková, Andrea; Novák, Pavel; Salvetr, Pavel; Moravec, Hynek; Šefl, Václav; Deduytsche, Davy; Detavernier, Christophe

    2017-07-01

    This work aims to describe the effect of magnesium on the microstructure, phase composition, amount of undesirable Ti2Ni phase, martensitic transformation, mechanical properties, and corrosion resistance of NiTi alloy. To minimize the quantity of Ti2Ni phase, we use the magnesium as an element with high affinity to oxygen, because this phase is stabilized by oxygen. Various quantities of magnesium (1, 3, and 5 wt pct) were tested. Self-propagating high-temperature synthesis (SHS) was used as a production method of the alloys. The samples prepared by SHS were pulverized by a vibrating mill, and the obtained powders were used for consolidation by means of spark plasma sintering. Results showed a significant reduction of the content of undesirable Ti2Ni phase by the addition of magnesium. Further, magnesium increased corrosion resistance and yield strength.

  9. Precipitation Hardenable High Temperature Shape Memory Alloy

    Science.gov (United States)

    Noebe, Ronald Dean (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Crombie, Edwin A. (Inventor)

    2010-01-01

    A composition of the invention is a high temperature shape memory alloy having high work output, and is made from (Ni+Pt+Y),Ti(100-x) wherein x is present in a total amount of 49-55 atomic % Pt is present in a total amount of 10-30 atomic %, Y is one or more of Au, Pd. and Cu and is present in a total amount of 0 to 10 atomic %. The alloy has a matrix phase wherein the total concentration of Ni, Pt, and the one or more of Pd. Au, and Cu is greater than 50 atomic %.

  10. 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.

  11. Shape memory alloys – characterization techniques

    Indian Academy of Sciences (India)

    Jayagopal Uchil

    2002-05-01

    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 phase (A) and a low-temperature phase or martensitic phase (M). In addition, an intermediate R phase exists in some special cases. The M ↔ A transformation is associated with a recoverable strain of about 6.5–8% and the R ↔ A transformation is associated with a recoverable strain of about 1%. The former transformation has been widely used in the applications like antenna deployment of satellite, aerospace couplings, orthodontic arch wires, medical guide wires for diagnostic and therapeutic catheters and other industrial applications. Our group has been giving emphasis to the characterization techniques for R phase, using differential scanning calorimetry (DSC), electrical resistivity probe (ER) and thermomechanical analyzer (TMA). R phase is found to have attractive features like stability against thermal cycling, a small thermal hysteresis and a negligible strain recovery fatigue. DSC has been used successfully to characterize the recoverable strain parameters, apart from the determination of transformation temperatures. ER is used, for the systematic study of the dependence of various phases on heat-treatment temperatures. TMA has been effectively employed for the study of the mixed phases. A space-rotating platform is designed and fabricated, using an actuator of shape memory spring, for obtaining controlled rotations. The efficiency and the reliability of this actuator has been tested, over a million thermal cycles.

  12. 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

  13. 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...

  14. 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

  15. Mechanocaloric effects in shape memory alloys.

    Science.gov (United States)

    Mañosa, Lluís; Planes, Antoni

    2016-08-13

    Shape memory alloys (SMA) are a class of ferroic materials which undergo a structural (martensitic) transition where the associated ferroic property is a lattice distortion (strain). The sensitiveness of the transition to the conjugated external field (stress), together with the latent heat of the transition, gives rise to giant mechanocaloric effects. In non-magnetic SMA, the lattice distortion is mostly described by a pure shear and the martensitic transition in this family of alloys is strongly affected by uniaxial stress, whereas it is basically insensitive to hydrostatic pressure. As a result, non-magnetic alloys exhibit giant elastocaloric effects but negligible barocaloric effects. By contrast, in a number of magnetic SMA, the lattice distortion at the martensitic transition involves a volume change in addition to the shear strain. Those alloys are affected by both uniaxial stress and hydrostatic pressure and they exhibit giant elastocaloric and barocaloric effects. The paper aims at providing a critical survey of available experimental data on elastocaloric and barocaloric effects in magnetic and non-magnetic SMA.This article is part of the themed issue 'Taking the temperature of phase transitions in cool materials'.

  16. Fastening apparatus having shape memory alloy actuator

    Science.gov (United States)

    Mckinnis, Darin N. (Inventor)

    1992-01-01

    A releasable fastening apparatus is presented. The device includes a connecting member and a housing. The housing supports a gripping mechanism that is adapted to engage the connecting member. A triggering member is movable within the housing between a first position in which it constrains the gripping mechanism in locked engagement with the connecting member, and a second position in which the gripping mechanism is disengaged from the connecting member. A shaped memory alloy actuator is employed for translating the triggering member from its first to its second position. The actuator is designed to expand longitudinally when transitioned from a martensitic to an austenitic state.

  17. Porous NiTi alloy prepared from combustion synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Li Yonghua; Rong Lijian; Li Yiyi [Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research

    2002-07-01

    Porous NiTi shape memory alloy (SMA) is a promising biomaterial which can be used as replacement of hard tissue implant. It was prepared from elemental titanium and nickel powders by method of combustion synthesis. The phase composition, pore and fracture morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. Meanwhile the compressive mechanical property was also studied. The preliminary data indicated that porous NiTi SMA prepared from combustion synthesis had homogeneous pore distribution and proper mean pore size. The mechanical property of pure product depended strongly on preheating temperature during synthesis process. It has also good superelasticity. (orig.)

  18. 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.

  19. Constitutive Models for Shape Memory Alloy Polycrystals

    Science.gov (United States)

    Comstock, R. J., Jr.; Somerday, M.; Wert, J. A.

    1996-01-01

    Shape memory alloys (SMA) exhibiting the superelastic or one-way effects can produce large recoverable strains upon application of a stress. In single crystals this stress and resulting strain are very orientation dependent. We show experimental stress/strain curves for a Ni-Al single crystal for various loading orientations. Also shown are model predictions; the open and closed circles indicate recoverable strains obtained at various stages in the transformation process. Because of the strong orientation dependence of shape memory properties, crystallographic texture can be expected to play an important role in the mechanical behavior of polycrystalline SMA. It is desirable to formulate a constitutive model to better understand and exploit the unique properties of SMA.

  20. Shape-memory alloy micro-actuator

    Science.gov (United States)

    Busch, John D. (Inventor); Johnson, Alfred D. (Inventor)

    1991-01-01

    A method of producing an integral piece of thermo-sensitive material, which is responsive to a shift in temperature from below to above a phase transformation temperature range to alter the material's condition to a shape-memory condition and move from one position to another. The method is characterized by depositing a thin film of shape-memory material, such as Nickel titanium (Ni-Ti) onto a substrate by vacuum deposition process such that the alloy exhibits an amorphous non-crystalline structure. The coated substrate is then annealed in a vacuum or in the presence of an inert atmosphere at a selected temperature, time and cool down rate to produce an ordered, partially disordered or fully disordered BCC structure such that the alloy undergoes thermoelastic, martinsetic phase transformation in response to alteration in temperature to pass from a martinsetic phase when at a temperature below a phase transformation range and capable of a high level of recoverable strain to a parent austenitic phase in a memory shape when at a temperature above the phase transformation range. Also disclosed are actuator devices employing shape-memory material actuators that deform from a set shape toward an original shape when subjected to a critical temperature level after having been initially deformed from the original shape into the set shape while at a lower temperature. The actuators are mechanically coupled to one or more movable elements such that the temperature-induce deformation of the actuators exerts a force or generates a motion of the mechanical element(s).

  1. 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

  2. Nondestructive Evaluation of Ni-Ti Shape Memory Alloy

    Science.gov (United States)

    Meir, S.; Gordon, S.; Karsh, M.; Wiezman, A.; Ayers, R.; Olson, D. L.

    2011-06-01

    The nondestructive evaluation of nickel titanium (Ni-Ti) alloys for applications such as heat treatment for biomaterials applications (dental) and welding was investigated. Ni-Ti alloys and its ternary alloys are valued for mechanical properties in addition to the shape memory effect. Two analytical approaches were perused in this work. Assessment of the microstructure of the alloy that determines the martensitic start temperature (Ms) of Ni-Ti alloy as a function of heat treatment, and secondly, an attempt to evaluate a Friction Stir Welding, which involves thermo-mechanical processing of the alloy.

  3. Preparation and bioactivity of hydroxyapatite in medical NiTi-shaped memory alloy%医用镍钛形状记忆合金羟基磷灰石涂层的制备及其生物活性

    Institute of Scientific and Technical Information of China (English)

    尹燕; 马宝玉; 夏天东; 夏亚一; 达国祖

    2011-01-01

    背景:目前多采用等离子喷涂技术在钛及其合金表面涂覆羟基磷灰石涂层,制备成复合材料.但由于羟基磷灰石与钛合金基体的热膨胀系数相差较大,涂层在冷却过程中易产生脱落.目的:在医用镍钛形状记忆合金表面制备致密、均匀的羟基磷灰石生物陶瓷涂层,利用动物实验考查镍钛/羟基磷灰石涂层材料的生物相容性.方法:利用阴极旋转法在低温条件下从含钙、磷离子的电解水溶液中在镍钛形状记忆合金表面沉积了磷酸钙涂层,经碱处理获得羟基磷灰石涂层.分析工艺参数对涂层结构的影响.利用动物植入实验对该复合材料的生物活性进行研究,并与镍钛/羟基磷灰石与Ca3(PO3)2?2H2O混合涂层复合材料、医用镍钛形状记忆合金、医用钛合金进行对比.结果与结论:电化学沉积-碱处理方法适合在镍钛形状记忆合金表面制备羟基磷灰石生物活性陶瓷涂层,沉积电压、温度对涂层结构有强烈影响.4种不同材料植入动物体内后周围均出现不同程度的组织增生,在骨膜组织切片中都可见软骨细胞且有骨小梁形成,涂覆有羟基磷灰石涂层的植入材料组织反应较轻,相应的组织切片中所显示出的软骨细胞、骨小梁数量最多,分布均匀,表明羟基磷灰石涂层提高了医用镍钛形状记忆合金的生物活性.%BACKGROUND: At present, many plasma spraying technology in titanium and its surface of alloys coated hydroxyapatite (HA)coatings, and composite materials were prepared. However, the HA coating usually desquamated during the period of coolingdue to the different expansion coefficient between HA and titanium alloy substrate.OBJECTIVE: To prepare dense, uniform coating of HA bioceramic on the surface of medical niti -shaped memory alloy, and toinvestigate the biocompatibility of NiTi/HA composite by animal experiment.METHODS: HA coatings on the surface of NiTi-shaped memory alloy were

  4. 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.

  5. Shape memory alloys: New materials for future engineering

    Science.gov (United States)

    Hornbogen, E.

    1988-01-01

    Shape memory is a new material property. An alloy which experiences relative severe plastic deformation resumes its original shape again after heating by 10 to 100 C. Besides simple shape memory, in similar alloys there is the second effect where the change in shape is caused exclusively by little temperature change. In pseudo-elasticity, the alloy exhibits a rubber-like behavior, i.e., large, reversible deformation at little change in tension. Beta Cu and beta NiTi alloys have been used in practice. The probability is that soon alloys based on Fe will become available. Recently increasing applications for this alloy were found in various areas of technology, even medical technology. A review with 24 references is given, including properties, production, applications and fundamental principles of the shape memory effect.

  6. Ferrous polycrystalline shape-memory alloy showing huge superelasticity.

    Science.gov (United States)

    Tanaka, Y; Himuro, Y; Kainuma, R; Sutou, Y; Omori, T; Ishida, K

    2010-03-19

    Shape-memory alloys, such as Ni-Ti and Cu-Zn-Al, show a large reversible strain of more than several percent due to superelasticity. In particular, the Ni-Ti-based alloy, which exhibits some ductility and excellent superelastic strain, is the only superelastic material available for practical applications at present. We herein describe a ferrous polycrystalline, high-strength, shape-memory alloy exhibiting a superelastic strain of more than 13%, with a tensile strength above 1 gigapascal, which is almost twice the maximum superelastic strain obtained in the Ni-Ti alloys. Furthermore, this ferrous alloy has a very large damping capacity and exhibits a large reversible change in magnetization during loading and unloading. This ferrous shape-memory alloy has great potential as a high-damping and sensor material.

  7. An overview of constitutive models for shape memory alloys

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available The remarkable properties of shape memory alloys have facilitated their applications in many areas of technology. The purpose of this paper is to present an overview of thermomechanical behavior of these alloys, discussing the main constitutive models for their mathematical description. Metallurgical features and engineering applications are addressed as an introduction. Afterwards, five phenomenological theories are presented. In general, these models capture the general thermomechanical behavior of shape memory alloys, characterized by pseudoelasticity, shape memory effect, phase transformation phenomenon due to temperature variation, and internal subloops due to incomplete phase transformations.

  8. Evolution of Hydrogen Storage Alloys Prepared by Special Methods

    Institute of Scientific and Technical Information of China (English)

    Guo Hong; Zhang Ximin; Jing Hai; Li Chengdong; Xu Jun

    2004-01-01

    Microstructure characteristics and electrochemical properties of hydrogen storage alloys prepared by gas atomization, melt spinning and strip casting respectively were outlined.The advantages, disadvantages and research development of the above methods for preparing hydrogen storage alloys were explained.The strip casting is a new special means for preparing AB5 rare earth hydrogen storage alloys of high performance and low cost, and the study of the strip casting for preparing hydrogen storage alloys is presented specially.

  9. Control devices incorporated with shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    Xue Suduo; Li Xiongyan

    2007-01-01

    Shape Memory Alloy (SMA) is a type of material that offers some unique characteristics for use in devices for vibration control applications. Based on SMA's material properties, four types of control devices that incorporate NiTi SMA wires are introduced in this paper, which include three types of dampers (SMA damper, SMA-MR damper and SMA-friction damper) and one kind of isolation bearing (SMA-rubber bearing). Mechanical models of these devices and their experimental verifications are presented. To investigate the control performance of these devices, the SMA-MR damper and SMA-rubber bearing are applied to structures. The results show that the control devices could be effective in reducing the seismic response of structures.

  10. Transformation Volume Effects on Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Anna Kosogor

    2013-07-01

    Full Text Available It is generally accepted that the martensitic transformations (MTs in the shape memory alloys (SMAs are mainly characterized by the shear deformation of the crystal lattice that arises in the course of MT, while a comparatively small volume change during MT is considered as the secondary effect, which can be disregarded when the basic characteristics of MTs and functional properties of SMAs are analyzed. This point of view is a subject to change nowadays due to the new experimental and theoretical findings. The present article elucidates (i the newly observed physical phenomena in different SMAs in their relation to the volume effect of MT; (ii the theoretical analysis of the aforementioned volume-related phenomena.

  11. Rotor Embedded with Shape Memory Alloy Wires

    Directory of Open Access Journals (Sweden)

    K. Gupta

    2000-01-01

    Full Text Available In the present analysis, the fundamental natural frequency of a Jeffcott and a two-mass rotor with fibre reinforced composite shaft embedded with shape memory alloy (SMA wires is evaluated by Rayleigh's procedure. The flexibility of rotor supports is taken into account. The effect of three factors, either singly or in combination with each other, on rotor critical speed is studied. The three factors are: (i increase in Young's modulus of SMA (NITINOL wires when activated, (ii tension in wires because of phase recovery stresses, and (iii variation of support stiffness by three times because of activation of SMA in rotor supports. It is shown by numerical examples that substantial variation in rotor critical speeds can be achieved by a combination of these factors which can be effectively used to avoid resonance during rotor coast up/down.

  12. High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Biffi, C. A.; Tuissi, A.

    2014-10-01

    In this paper, an experimental study of laser micro-processing on a Cu-Zr-based shape memory alloy (SMA), which is suitable for high-temperature (HT) applications, is discussed. A first evaluation of the interaction between a laser beam and Zr50Cu28Ni7Co15 HT SMA is highlighted. Single laser pulses at various levels of power and pulse duration were applied to evaluate their effect on the sample surfaces. Blind and through microholes were produced with sizes on the order of a few hundreds of microns; the results were characterized from the morphological viewpoint using a scanning electron microscope. The high beam quality allows the holes to be created with good circularity and little melted material around the hole periphery. An analysis of the chemical composition was performed using energy dispersive spectroscopy, revealing that compositional changes were limited, while important oxidation occurred on the hole surfaces. Additionally, laser micro-cutting tests were also proposed to evaluate the cut edge morphology and dimensions. The main result of this paper concerned the good behavior of the material upon interaction with the laser beam, which suggests that microfeatures can be successfully produced in this alloy.

  13. Switchable Shape Memory Alloys (SMA) Thermal Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Shape memory alloys applies to a group of materials that demonstrate the ability to return to some previously defined shape when subjected to the appropriate thermal...

  14. Nonhysteretic superelasticity of shape memory alloys at the nanoscale.

    Science.gov (United States)

    Zhang, Zhen; Ding, Xiangdong; Sun, Jun; Suzuki, Tetsuro; Lookman, Turab; Otsuka, Kazuhiro; Ren, Xiaobing

    2013-10-04

    We perform molecular dynamics simulations to show that shape memory alloy nanoparticles below the critical size not only demonstrate superelasticity but also exhibit features such as absence of hysteresis, continuous nonlinear elastic distortion, and high blocking force. Atomic level investigations show that this nonhysteretic superelasticity results from a continuous transformation from the parent phase to martensite under external stress. This aspect of shape memory alloys is attributed to a surface effect; i.e., the surface locally retards the formation of martensite and then induces a critical-end-point-like behavior when the system is below the critical size. Our work potentially broadens the application of shape memory alloys to the nanoscale. It also suggests a method to achieve nonhysteretic superelasticity in conventional bulk shape memory alloys.

  15. 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...

  16. Effect of Trivalent Additions and Processing on Structural and Magnetic Transitions in Ni-Mn-Ga Ferromagnetic Shape Memory Alloys

    OpenAIRE

    R. P. Mathur; Singh, R. K.; Ray, S.; P. Ghosal; Chandrasekaran, V.

    2012-01-01

    Ferromagnetic shape memory Ni50Mn30Ga15Al5-xBx (x = 0, 1, and 4) alloys were prepared by vacuum arc melting and subsequent heat-treatment as well as by melt spinning to investigate the effect of trivalent element additions in ternary Ni-Mn-Ga alloys. The heat-treated alloys containing Al were reported to possess a modulated martensite structure, however alloy containing both Al and B showed a loss of modulated structure in martensite formed. The rapidly solidified alloys on the other hand sho...

  17. Mechanical Properties and Transformation Behavior of NiTiNb Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    Liu Wei; Zhao Xinqing

    2009-01-01

    NiTiNb shape memory alloys have attracted much attention in pipe coupling or sealing system because of their large transformation hysteresis upon a proper pre-deformation. In order to clarify the effects of adding Nb on the mechanical properties as well as the transformation behavior of NiTiNb shape memory alloys, Ni_(47)Ti_(44)Nb_9 and Ni_(49.8)Ti_(45.2)Nb_5 alloys with different microstructures but with similar martensitic transformation start temperature, are prepared. Comparative studies on the microstructures, mechanical properties and transformation characteristics are conducted by means of scanning electron microscopy (SEM), phase transformation measurements and mechanical property tests. It is found that Ni_(47)Ti_(44)Nb_9 and Ni49.8Ti45.2Nb5 alloys possess similar transformation hysteresis in the as-annealed state. However, the presence of Nb and its status exerts important effects on the mechanical properties, especially the yield strength and the yield behavior of the alloys. Ni_(49.8)Ti_(45.2)Nb_5 alloy exhibits remarkable increase in the yield strength than the Ni_(47)Ti_(44)Nb_9 alloy. The transformation hysteresis of both alloys under pre-deformation is characterized and the relative mechanism is discussed.

  18. Contribution to Shape Memory Alloys Actuated Systems Design

    Directory of Open Access Journals (Sweden)

    Daniel Amariei

    2009-10-01

    Full Text Available Even it has been recognized that Shape Memory Alloys have a significant potential for deployment actuators, the number of applications of SMA-based actuators to the present day is still quite small, due to the need of deep understanding of the thermomechanical behavior of SMA. SMAs offer attractive potentials such as: reversible strains of several percent, generation of high recovery stresses and high power / weight ratios. This paper tries to provide an overview of the shape memory functions. A table with property values for different properties of shape memory alloys is also included

  19. 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.

  20. Properties and Application of Iron-based Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Li Jian-chen; Jiang Qing; Dai Jun

    2005-01-01

    The properties of FeMnSiCrNi shape memory alloy were investigated. The results show that the best shape memory effect of Fel4Mn6Si9Cr5Ni alloy is 85%. The transformation amount of the ε→γ transformation is not complete after heating the alloy to 1000 K, As and Af points drop with increased transformation enthalpy ( △Hγ→ε) by thermal cycling and increased prestrain. The alloy shows also good creep and stress relaxation resistance. In addition, the alloy having a tensile force of 20 kN and a sealing pressure of 6 MPa can satisfy requirements for possible industrial application on pipe joints.

  1. Preparation of titanium/aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jecker, G.

    1984-03-20

    Alloys comprising titanium and aluminum, or titanium, aluminum and at least one of the metals M, wherein M is vanadium, zirconium, chromium, niobium, tantalum and/or iron, are facilely prepared by reducing an alkali metal fluotitanate, or coreducing admixture of an alkali metal fluotitanate and at least one halide of a metal M, with aluminum, in the presence of an alkali metal oxide reactive flux, either Na/sub 2/O and/or K/sub 2/O; next solubilizing with water the fluorine compounds of reduction/coreduction which are in admixture of reduction/coreduction with dispersion of the aforesaid metals in metallic state; separating said dispersion of metals in metallic state from said admixture of reduction/coreduction; and then alloying by melting and cooling said separated dispersion of metals in metallic state.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mc Schetky D, L. [Memry Corp., Brookfield, CT (United States)

    2000-07-01

    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.)

  3. Twice reverse shape memory effect in CuZnAl shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    李周; 汪明朴; 徐根应; 郭明星

    2004-01-01

    The variations of the shape memory effects in the Cu-13Zn-15Al(mole fraction, %) alloy upon successive heating (the rate of heating is 5 ℃/min) have been studied by means of p-T curve , shape memory effect measurement, optical metallographical observation and X-ray diffraction. The first abnormal reverse shape memory effect occurs when the tested alloy is heated to the temperature below 320 ℃; when it is heated to the temperature between 320 ℃ and 450 ℃, the forward shape memory effect occurs; in the two stages, the shape of the sample remains the same as that in the furnace when it is taken out from the furnace and air-cooled; when the tested alloy is heated to the temperature above 450 ℃, the shape of the sample remains unchanged during heating, but the second reverse shape memory effect occurs after it is air-quenched.

  4. 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.

  5. Structural Acoustic Response of Shape Memory Alloy Hybrid Composite Panels

    Science.gov (United States)

    Turner, Travis L.

    1996-01-01

    A method has been developed to predict the structural acoustic response of shape memory alloy hybrid composite panels subjected to acoustic excitation. The panel is modeled by a finite element analysis and the radiated field is predicted using Rayleigh's integral. Transmission loss predictions for the case of an aluminum panel excited by a harmonic acoustic pressure are shown to compare very well with a classical analysis. Predictions of the normal velocity response and transmitted acoustic pressure for a clamped aluminum panel show excellent agreement with experimental measurements. Predicted transmission loss performance for a composite panel with and without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss can be significantly increased with shape memory alloy reinforcement.

  6. 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...

  7. Periodic Cellular Structure Technology for Shape Memory Alloys

    Science.gov (United States)

    Chen, Edward Y.

    2015-01-01

    Shape memory alloys are being considered for a wide variety of adaptive components for engine and airframe applications because they can undergo large amounts of strain and then revert to their original shape upon heating or unloading. Transition45 Technologies, Inc., has developed an innovative periodic cellular structure (PCS) technology for shape memory alloys that enables fabrication of complex bulk configurations, such as lattice block structures. These innovative structures are manufactured using an advanced reactive metal casting technology that offers a relatively low cost and established approach for constructing near-net shape aerospace components. Transition45 is continuing to characterize these structures to determine how best to design a PCS to better exploit the use of shape memory alloys in aerospace applications.

  8. Fatigue Resistance of Liquid-assisted Self-repairing Aluminum Alloys Reinforced with Shape Memory Alloys

    Science.gov (United States)

    Wright, M. Clara; Manuel, Michele; Wallace, Terryl

    2013-01-01

    A self-repairing aluminum-based composite system has been developed using a liquid-assisted healing theory in conjunction with the shape memory effect of wire reinforcements. The metal-metal composite was thermodynamically designed to have a matrix with a relatively even dispersion of a low-melting eutectic phase, allowing for repair of cracks at a predetermined temperature. Additionally, shape memory alloy (SMA) wire reinforcements were used within the composite to provide crack closure. Investigators focused the research on fatigue cracks propagating through the matrix in order to show a proof-of-concept Shape Memory Alloy Self-Healing (SMASH) technology for aeronautical applications.

  9. Alloying and Casting Furnace for Shape Memory Alloys Project

    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...

  10. A rotating arm using shape-memory alloy

    Science.gov (United States)

    Jenkins, Phillip P.; Landis, Geoffrey A.

    1995-01-01

    NASA's Mars Pathfinder mission, to be launched in 1996, reflects a new philosophy of exploiting new technologies to reduce mission cost and accelerate the pace of space exploration. One of the experiments on board Pathfinder will demonstrate the first use in space of a multi-cycle, electrically-activated, shape-memory alloy (SMA) actuator. SMA's are metal alloys which, when heated, undergo a crystalline phase change. This change in phase alters the alloy lattice-constant, resulting in a change of dimension. Upon cooling, the alloy returns to its original lattice formation. Wire drawn from an SMA contracts in length when heated. The reversible change in length is 3 percent to 5 percent. The wire used in this actuator is a nickel-titanium alloy known as nitinol.

  11. Spooled packaging of shape memory alloy actuators

    Science.gov (United States)

    Redmond, John A.

    A vast cross-section of transportation, manufacturing, consumer product, and medical technologies rely heavily on actuation. Accordingly, progress in these industries is often strongly coupled to the advancement of actuation technologies. As the field of actuation continues to evolve, smart materials show significant promise for satisfying the growing needs of industry. In particular, shape memory alloy (SMA) wire actuators present an opportunity for low-cost, high performance actuation, but until now, they have been limited or restricted from use in many otherwise suitable applications by the difficulty in packaging the SMA wires within tight or unusually shaped form constraints. To address this packaging problem, SMA wires can be spool-packaged by wrapping around mandrels to make the actuator more compact or by redirecting around multiple mandrels to customize SMA wire pathways to unusual form factors. The goal of this dissertation is to develop the scientific knowledge base for spooled packaging of low-cost SMA wire actuators that enables high, predictable performance within compact, customizable form factors. In developing the scientific knowledge base, this dissertation defines a systematic general representation of single and multiple mandrel spool-packaged SMA actuators and provides tools for their analysis, understanding, and synthesis. A quasi-static analytical model distills the underlying mechanics down to the three effects of friction, bending, and binding, which enables prediction of the behavior of generic spool-packaged SMA actuators with specifiable geometric, loading, frictional, and SMA material parameters. An extensive experimental and simulation-based parameter study establishes the necessary understanding of how primary design tradeoffs between performance, packaging, and cost are governed by the underlying mechanics of spooled actuators. A design methodology outlines a systematic approach to synthesizing high performance SMA wire actuators

  12. Static critical phenomena in Co-Ni-Ga ferromagnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sethi, Brahmananda, E-mail: santra@iitg.ernet.in; Sarma, S., E-mail: santra@iitg.ernet.in; Srinivasan, A., E-mail: santra@iitg.ernet.in; Santra, S. B., E-mail: santra@iitg.ernet.in [Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039 (India)

    2014-04-24

    Ferromagnetic shape memory alloys are smart materials because they exhibit temperature driven shape memory effect and magnetic field induced strain. Thus two types of energy, i.e. thermal and magnetic, are used to control their shape memory behaviour. Study of critical phenomenon in such materials has received increased experimental and theoretical attention for better understanding of the magnetic phase transition behavior as well as further development of ferromagnetic shape memory materials. In the present study we report the preparation and characterization of bulk Co{sub 45}Ni{sub 25}Ga{sub 30} alloy, prepared by a sequence of arc melting technique followed by homogenization at 1150 °C for 24 hours and ice-water quenching. Structural and magnetic properties of the alloys were studied by means of X-ray diffraction and vibrating sample magnetometer in an applied field range of ±18 kOe equipped with a high temperature oven. We have determined the critical temperature T{sub C} (∼375.5 K) and the critical exponents viz; β=0.40, γ=1.68 and δ=5.2. Asymptotic critical exponents β, γ, and δ obey Widom scaling relation, γ+β=βδ, and the magnetization data satisfy the scaling equation of state for second-order phase transition in the asymptotic critical region.

  13. 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.)

  14. Inconvenient magnetocaloric effect in ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Khovaylo, Vladimir, E-mail: khovaylo@misis.ru [National University of Science and Technology “MISiS”, Moscow 119049 (Russian Federation)

    2013-11-15

    Highlights: ► Critical analysis of the available experimental results on isothermal magnetic entropy change in ferromagnetic shape memory alloys Ni–Mn–X (X = Ga, In, Sn, Sb) is given. ► Based on available in literature experimental data on total entropy change at martensitic transformation it is shown that the isothermal magnetic entropy change in Ni–Mn–X (X = Ga, In, Sn, Sb) should not greatly exceed 30 J/kg K. -- Abstract: Critical analysis available in the literature experimental results on magnetocaloric effect in ferromagnetic shape memory alloys Ni–Mn–X (X = Ga, In, Sn, Sb) is given. Based on a model developed by Pecharsky et al. [22], it is shown that the isothermal magnetic field-induced entropy change in the Ni–Mn–X alloys should not greatly exceed 30 J/kg K. Considering thermodynamics of temperature- and magnetic field-induced martensitic transformations, it is demonstrated that a contribution of the structural subsystem to the magnetocaloric effect in the Ni–Mn–X alloys studied so far is irreversible in magnetic fields below 5 T. This makes ferromagnetic shape memory alloys an inconvenient system for the practical application in modern magnetic refrigeration technology.

  15. Thermally driven phase transformation on shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mielke, A. [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany)]|[Humboldt-Universitaet, Berlin (Germany). Inst. fuer Mathematik; Petrov, A. [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany)

    2007-07-01

    This paper analyzes a model for phase transformation in shape-memory alloys induced by temperature changes and by mechanical loading. We assume that the temperature is prescribed and formulate the problem within the framework of the energetic theory of rate-independent processes. Existence and uniqueness results are proved. (orig.)

  16. Switchable Shape Memory Alloys (SMA) Thermal Materials Project

    Science.gov (United States)

    Falker, John; Zeitlin, Nancy; Williams, Martha; Fesmire, James

    2014-01-01

    Develop 2-way switchable thermal systems for use in systems that function in cold to hot temperature ranges using different alloy designs for SMA system concepts. In this project, KSC will specifically address designs of two proof of concept SMA systems with transition temperatures in the 65-95 C range and investigate cycle fatigue and "memory loss" due to thermal cycling.

  17. ESTIMATION OF LOCAL HYSTERETIC PROPERTIES FOR SHAPE MEMORY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The applicability of shape memory alloys (SMAs) in structural dynamics, particularly as hysteretic damping elements, is limited by the difficulties in modelling their deformation characteristics. At typical engineering design levels of loading SMAs exhibit pseudo-elastic properties. A combined experimental and simulation approach suitable for the characterisation of novel smart devices based on the pseudo-elastic effect is described.

  18. The Origin of Vibration Redemption Effect for Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Daniel Amariei

    2007-10-01

    Full Text Available Shape memory alloys (SMA components can affect through two mechanisms the vibrations of structures. The stresses from a SMA element that realize phase transformations, as a result of vibrations, have an effect on the frequency-amplitude characteristics. In addition, a dissipation of energy due to hysteresis in a SMA element can reduce the natural frequency and affect forced vibrations.

  19. Shape memory alloys: a state of art review

    Science.gov (United States)

    Naresh, C.; Bose, P. S. C.; Rao, C. S. P.

    2016-09-01

    Shape memory alloys (SMAs) are the special materials that have the ability to return to a predetermined shape when heated. When this alloy is in below transformation temperature it undergoes low yield strength and will deform easily into any new shape which it will retain, if this alloy is heated above its transformation temperature it changes its crystal lattice structure which returns to its real shape. SMAs are remarkably different from other materials are primarily due to shape memory effect (SME) and pseudoelasticity which are related with the specific way the phase transformation occurs, biocompatibility, high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. SMA are used in many applications such as aerospace, medical, automobile, tubes, controllers for hot water valves in showers, petroleum industry, vibration dampers, ball bearings, sensors, actuators, miniature grippers, micro valves, pumps, landing gears, eye glass frames, Material for helicopter blades, sprinklers in fine alarm systems packaging devices for electronic materials, dental materials, etc. This paper focuses on introducing shape memory alloy and their applications in past, present and in future, also revealed the concept and mechanism of shape memory materials for a particular requirement. Properties of SMAs, behaviour and characteristics of SMA, summary of recent advances and new application opportunities are also discussed.

  20. Obtaining shape memory alloy thin layer using PLD technique

    Directory of Open Access Journals (Sweden)

    Cimpoeşu N.

    2014-01-01

    Full Text Available Copper-based shape memory alloy (SMA was obtained through a classic melting method. The material was analyzed in heat treated and deformed states using scanning electrons microscopy (SEM, dilatometry (DIL, differential scanning calorimetry (DSC, dynamic mechanical analyzer (DMA and energy dispersive X-ray analyze (EDAX to establish the material microstructure, memory properties like martensitic transformation domain and rate or damping capacity. The material exhibits a good shape memory effect and high internal friction and it is proposed as target in a pulsed laser deposition (PLD process for obtaining thin films. The deposition process is described in this paper through presented experimental results on the layer.

  1. Characteristics of Anodized Layer in Investment Cast Ni50Ti50 Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Shimaa H. El-Hadad

    2014-01-01

    Full Text Available NiTi shape memory alloys are promising implant materials due to their shape memory effect and super elasticity. In the current study, some Ni50Ti50 (mass % SMAs samples were prepared by investment casting. These samples were then anodized and thermally treated to improve the surface properties. A fully saturated oxide layer was obtained. The structure and hardness properties of the anodized surfaces were then investigated. A hard porous layer with no free Ni atoms could be obtained which can be used as prebiomimetic surface for biological application.

  2. Two-stage Strain Recovery of Explosively Welded NiTi/NiTi Shape Memory Alloys Prestrained in Martensitic Phase

    Institute of Scientific and Technical Information of China (English)

    Yan Zhu; Cui Lishan; Zheng Yanjun

    2006-01-01

    The present work aimed to investigate the transformation behavior and strain recovery characteristics of Ni50.2Ti/Ni51Ti shape memory alloys (SMAs) prepared by explosive welding. The differential scanning calorimetry (DSC) results showed that the reverse transformation temperatures and the temperature range of NiTi-NiTi alloys increased with increasing prestrain level. Meanwhile, a two-stage strain recovery over a wide temperature range was obtained.

  3. 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.

  4. Thermal Arrest Memory Effect in Ni-Mn-Ga Alloys

    Directory of Open Access Journals (Sweden)

    A. Rudajevova

    2008-01-01

    Full Text Available Dilatation characteristics were measured to investigate the thermal arrest memory effect in Ni53.6Mn27.1Ga19.3 and Ni54.2Mn29.4Ga16.4 alloys. Interruption of the martensite-austenite phase transformation is connected with the reduction of the sample length after thermal cycle. If a total phase transformation took place in the complete thermal cycle following the interruption, then the sample length would return to its original length. Analysis of these results has shown that the thermal arrest memory effect is a consequence of a stress-focusing effect and shape memory effect. The stress-focusing effect occurs when the phase transformation propagates radially in a cylindrical sample from the surface, inward to the center. Evolution and release of the thermoelastic deformations in both alloys during heating and cooling are analyzed.

  5. Understanding the shape-memory alloys used in orthodontics.

    Science.gov (United States)

    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 to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA.

  6. Understanding the Shape-Memory Alloys Used in Orthodontics

    Science.gov (United States)

    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 to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA. PMID:21991455

  7. Properties of Porous TiNbZr Shape Memory Alloy Fabricated by Mechanical Alloying and Hot Isostatic Pressing

    Science.gov (United States)

    Ma, L. W.; Chung, C. Y.; Tong, Y. X.; Zheng, Y. F.

    2011-07-01

    In the past decades, systematic researches have been focused on studying Ti-Nb-based SMAs by adding ternary elements, such as Mo, Sn, Zr, etc. However, only arc melting or induction melting methods, with subsequent hot or cold rolling, were used to fabricate these Ni-free SMAs. There is no work related to powder metallurgy and porous structures. This study focuses on the fabrication and characterization of porous Ti-22Nb-6Zr (at.%) shape memory alloys produced using elemental powders by means of mechanical alloying and hot isostatic pressing. It is found that the porous Ti-22Nb-6Zr alloys prepared by the HIP process exhibit a homogenous pore distribution with spherical pores, while the pores have irregular shape in the specimen prepared by conventional sintering. X-ray diffraction analysis showed that the solid solution-treated Ti-22Nb-6Zr alloy consists of both β phase and α″ martensite phase. Morphologies of martensite were observed. Finally, the porous Ti-22Nb-6Zr SMAs produced by both MA and HIP exhibit good mechanical properties, such as superior superelasticity, with maximum recoverable strain of ~3% and high compressive strength.

  8. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations describing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA). The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper. The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect. Shape memory factor is redefined in order to make clear its physical meaning. A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test. It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA. A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy. It is expanded from one-dimension to three-dimension with assuming SMA as isotropic material. All material constants in the new constitutive equation can be determined from macroscopic experiments, which makes it more easily used in practical applications.

  9. A macro-mechanical constitutive model of shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    ZHOU Bo; LIU YanJu; LENG JinSong; ZOU GuangPing

    2009-01-01

    It is of practical interest to establish a precise constitutive model which includes the equations de-scribing the phase transformation behaviors and thermo-mechanical processes of shape memory alloy (SMA).The microscopic mechanism of super elasticity and shape memory effect of SMA is explained based on the concept of shape memory factor defined by the author of this paper.The conventional super elasticity and shape memory effect of SMA are further unified as shape memory effect.Shape memory factor is redefined in order to make clear its physical meaning.A new shape memory evolution equation is developed to predict the phase transformation behaviors of SMA based on the differential relationship between martensitic volume fraction and phase transformation free energy and the results of DSC test.It overcomes the limitations that the previous shape memory evolution equations or phase transformation equations fail to express the influences of the phase transformation peak temperatures on the phase transformation behaviors and the transformation from twinned martensite to detwinned martensite occurring in SMA.A new macro-mechanical constitutive equation is established to predict the thermo-mechanical processes realizing the shape memory effect of SMA from the expression of Gibbs free energy.It is expanded from one-dimension to three-dimension with assuming SMA as iso-tropic material.All material constants in the new constitutive equation can be determined from mac-roscopic experiments,which makes it more easily used in practical applications.

  10. Damping of High-temperature Shape Memory Alloys

    Science.gov (United States)

    Duffy, Kirsten P.; Padula, Santo A., II; Scheiman, Daniel A.

    2008-01-01

    Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf

  11. Grain Constraint and Size Effects in Shape Memory Alloy Microwires

    Science.gov (United States)

    Ueland, Stian Melhus

    Shape memory alloys exhibit interesting and useful properties, such as the shape memory effect and superelasticity. Among the many alloy families that have been shown to exhibit shape memory properties the ones based on copper are interesting because they are relatively inexpensive and show excellent properties when made as single crystals. However, the performance ofthese alloys is severely compromised by the introduction of grain boundaries, to the point where they are too poor for commercial applications. This thesis studies the mechanical properties of fine Cobased wires with a bamboo microstructure, i.e., where triple junctions are absent and grain boundaries run perpendicular to the wire axis. These microwires are not single crystals, but their microstructure is not as complex as that of polycrystals either: we call this new class of shape memory alloys oligocrystals. This thesis seeks to better understand the relationship between microstructure and properties in these alloys through a combination of mechanical testing, in situ experiments and modeling. First, in situ scanning electron microscopy, together with finite element modeling, is used to understand the role of grain constraint on the martensitic transformation. Grain constraints are observed to be much less severe in oligocrystalline wires as compared to polycrystals. Oligocrystalline microwires are then thermomechanically tested and shown to exhibit excellent properties that approach those of single crystals. Next, property evolution during cycling is investigated, revealing training effects as well as fatigue life and fracture. Finally, size effects in damping and transformation morphology are studied and it is shown that a transition from a many-domain to a single domain martensite morphology takes place when the wire diameter is decreased. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

  12. Structure evolution of Cu-based shape memory powder during mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructures of shape memory powders of Cu-Al-Ni prepared from pure powders of Cu, Al and Ni using the mechanical alloying(MA) technique were studied by means of hardness measurement, metallograph observation, XRD and SEM.The hardness reaches the peak as the increase in hardness due to plastic deformation and the decrease in hardness due to kinetic annealing reach a balance. The process of MA leads to the formation of a laminated structure, and the layer becomes thinner with an increase in milling time. The pre-alloyed shape memory powder can be formed by milling at 300 r/min for 50 h using a planetary ball mill.

  13. Platinum-Iridium Alloy Films Prepared by MOCVD

    Institute of Scientific and Technical Information of China (English)

    WEI Yan; CHEN Li; CAI Hongzhong; ZHENG Xu; YANG Xiya; HU Changyi

    2012-01-01

    Platinum-Iridium alloy films were prepared by MOCVD on Mo substrate using metal-acetylacetonate precursors.Effects of deposition conditions on composition,microstructure and mechanical properties were determined.In these experimental conditions,the purities of films are high and more than 99.0%.The films are homogeneous and monophase solid solution of Pt and Ir.Weight percentage of platinum are much higher than iridium in the alloy.Lattice constant of the alloy changes with the platinum composition.Iridium composition showing an up-down-up trend at the precursor temperature of 190~230℃ and the deposition temperature at 400~550℃.The hardness of Pt-Ir alloys prepared by MOCVD is three times more than the alloys prepared by casting.

  14. 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.

  15. Microstructure and high-temperature shape-memory effect in Ni54Mn25Ga21 alloy

    Institute of Scientific and Technical Information of China (English)

    MA Yun-qing; JIANG Cheng-bao; LI Yan; XU Hui-bin; WANG Cui-ping; LIU Xing-jun

    2006-01-01

    Ni54Mn25Ga21 alloy was prepared to investigate the microstructure, martensitic transformation and high-temperature shape-memory effect. Ni54Mn25Ga21 alloy exhibits single phase of non-modulated martensite with tetragonal structure at room temperature. Its martensitic start temperature Ms, martensitic finish temperature Mf on cooling, and austenitic start temperature As,austenitic finish temperature Af on heating are 260.2, 237.8, 262.5 and 287.8 ℃, respectively. The compressive strength and strain of Ni54Mn25Ga21 single crystal were measured to be 845 MPa and 20.5%, respectively, with compressive axis along the growth direction of the rods. An excellent shape-memory strain of 6.1%, which is the best performance among high-temperature shape-memory alloys up to the present, is obtained when prestrained to 8%.

  16. Design of shape memory alloy pipe couplers: modeling and experiments

    Science.gov (United States)

    Tabesh, Majid; Atli, Kadri C.; Rohmer, John; Franco, Brian E.; Karaman, Ibrahim; Boyd, James G.; Lagoudas, Dimitris C.

    2012-04-01

    Shape memory alloy (SMA) pipe couplers use the shape memory effect to apply a contact pressure onto the surface of the pipes to be coupled. In the current research, a SMA pipe coupler is designed, fabricated and tested. The thermally induced contact pressure depends on several factors such as the dimensions and properties of the coupler-pipe system. Two alloy systems are considered: commercially-available NiTiNb couplers and in-house developed NiTi couplers. The coupling pressure is measured using strain gages mounted on the internal surface of an elastic ring. An axisymmetric finite element model including SMA constitutive equations is also developed, and the finite element results are compared with the experimental results.

  17. 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.

  18. Characterization Results of a Novel Shape Memory Alloy

    Science.gov (United States)

    Collado, M.; Nava, N.; Herranz, S.; Ramiro, C.; San Juan, J. M.; Patti, S.; Lautier, J.-M.

    2012-07-01

    A novel Shape Memory Alloy (SMA) has been developed as an alternative to currently available alloys. This material, called SMARQ, shows a higher working range of temperatures with respect to the SMA materials used until now, mainly NiTi based alloys. SMARQ is a fully European material technology and production processes, which allows the manufacture of high quality products, with tuneable transformation temperatures up to 200oC. 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. 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 of space mechanisms and actuators, currently under development, will be summarized as part of this work, demonstrating the technology suitability for the development of space actuators.

  19. Low Temperature Shape Memory Alloys for Adaptive, Autonomous Systems Project

    Science.gov (United States)

    Falker, John; Zeitlin, Nancy; Williams, Martha; Benafan, Othmane; Fesmire, James

    2015-01-01

    The objective of this joint activity between Kennedy Space Center (KSC) and Glenn Research Center (GRC) is to develop and evaluate the applicability of 2-way SMAs in proof-of-concept, low-temperature adaptive autonomous systems. As part of this low technology readiness (TRL) activity, we will develop and train low-temperature novel, 2-way shape memory alloys (SMAs) with actuation temperatures ranging from 0 C to 150 C. These experimental alloys will also be preliminary tested to evaluate their performance parameters and transformation (actuation) temperatures in low- temperature or cryogenic adaptive proof-of-concept systems. The challenge will be in the development, design, and training of the alloys for 2-way actuation at those temperatures.

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

    OpenAIRE

    2006-01-01

    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 th...

  1. Dynamic Simulation for Hysteresis in Shape Memory Alloy under Tension

    Institute of Scientific and Technical Information of China (English)

    WANG Ping; ZHAO Jian-Bo; TANG Shao-Qiang

    2008-01-01

    We demonstrate that the Suliciu model is capable to model the hysteresis phenomenon observed experimentally in NiTi shape memory alloy micro-tubes.This model allows a class of stationary phase interfaces.By a series of fully dynamic numerical simulations that mimic quasi-static loading and unloading,the nominal stress-strain curve exhibits a big hysteresis loop,which quantitatively agrees with the experimental results.

  2. Flexible Robotic Spine Actuated by Shape Memory Alloy

    OpenAIRE

    2014-01-01

    A flexible robotic spine actuated by shape memory alloy (SMA) can achieve both bending motion and impact absorption, which will allow robots to realize a variety of postures. In this paper, the robotic spine is designed and simplified into a multi-segment dynamic model based on several verified assumptions. The SMA wire is modelled using the Seelecke-Muller-Acenbach theory. An iterative algorithm is developed to address the external forces distributed along the spine and compute the spine’s b...

  3. Shape Control of Solar Collectors Using Shape Memory Alloy Actuators

    Science.gov (United States)

    Lobitz, D. W.; Grossman, J. W.; Allen, J. J.; Rice, T. M.; Liang, C.; Davidson, F. M.

    1996-01-01

    Solar collectors that are focused on a central receiver are designed with a mechanism for defocusing the collector or disabling it by turning it out of the path of the sun's rays. This is required to avoid damaging the receiver during periods of inoperability. In either of these two cases a fail-safe operation is very desirable where during power outages the collector passively goes to its defocused or deactivated state. This paper is principally concerned with focusing and defocusing the collector in a fail-safe manner using shape memory alloy actuators. Shape memory alloys are well suited to this application in that once calibrated the actuators can be operated in an on/off mode using a minimal amount of electric power. Also, in contrast to other smart materials that were investigated for this application, shape memory alloys are capable of providing enough stroke at the appropriate force levels to focus the collector. Design and analysis details presented, along with comparisons to test data taken from an actual prototype, demonstrate that the collector can be repeatedly focused and defocused within accuracies required by typical solar energy systems. In this paper the design, analysis and testing of a solar collector which is deformed into its desired shape by shape memory alloy actuators is presented. Computations indicate collector shapes much closer to spherical and with smaller focal lengths can be achieved by moving the actuators inward to a radius of approximately 6 inches. This would require actuators with considerably more stroke and some alternate SMA actuators are currently under consideration. Whatever SMA actuator is finally chosen for this application, repeatability and fatigue tests will be required to investigate the long term performance of the actuator.

  4. Interfacial Modulus Mapping during Structural Transformation in Shape Memory Alloys

    Science.gov (United States)

    Wan, Jianfeng; Cui, Shushan; Zhang, Jihua; Rong, Yonghua

    2017-10-01

    Through the modified phase-field model the local soft mode mechanism of nucleation during martensitic transformation was confirmed in shape memory alloys. It was discovered that the modulus loss (8 pct) depended on the martensitic nucleation exceeding the loss (1 pct) during the martensitic growth. The elastic modulus and the stress across the martensite/parent interface differed from those across the martensitic twin boundary. The modulus losses in systems with three variants, two variants, and one variant were compared.

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

    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 Project

    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. Laser surface alloying fabricated porous coating on NiTi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Song; ZHANG Chun-hua; MAN Hau-chung; LIU Chang-sheng

    2007-01-01

    Laser surface alloying technique was applied to fabricate a metallic porous coating on a solid NiTi shape memory alloy. By laser surface alloying a 40%TiH2-60%NiTi powder mixture on the surface of NiTi alloy using optimized laser process parameters, a porous but crack-free NiTi layer can be fabricated on the NiTi substrate. The porous coating is metallurgically bonded to the substrate NiTi alloy. The pores are uniformly distributed and are interconnected with each other in the coating. An average pore size of less than 10 μm is achieved. The Ni content of the porous layer is much less than that of the original NiTi surface. The existence of the porous coating on the NiTi alloy causes a 37% reduction of the tensile strength and 55% reduction of the strain as compared with the NiTi alloy. Possible biomedical or other applications for this porous surface with good mechanical strength provided by the substrate are prospective.

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

    OpenAIRE

    2015-01-01

    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...

  9. Microfabricated Cantilevers Based on Sputtered Thin-Film Ni50Ti50 Shape Memory Alloy (SMA)

    Science.gov (United States)

    2015-08-01

    Memory Alloy ( SMA ) by Cory R Knick and Christopher J Morris Approved for public release; distribution unlimited...Microfabricated Cantilevers Based on Sputtered Thin-Film Ni50Ti50 Shape Memory Alloy ( SMA ) by Cory R Knick and Christopher J Morris Sensors...2014 – 05/2015 4. TITLE AND SUBTITLE Microfabricated Cantilevers Based on Sputtered Thin-Film Ni50Ti50 Shape Memory Alloy ( SMA ) 5a. CONTRACT NUMBER

  10. Production of NiTi shape memory alloys via electro-deoxidation utilizing an inert anode

    Energy Technology Data Exchange (ETDEWEB)

    Jiao Shuqiang, E-mail: sjiao@ustb.edu.c [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China)] [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom); Zhang Linlin; Zhu Hongmin [School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Fray, Derek J., E-mail: djf25@cam.ac.u [Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB2 3QZ (United Kingdom)

    2010-09-30

    NiTi shape memory alloys (SMA) with equiatomic composition of Ni and Ti were prepared by electro-deoxidation, in molten calcium chloride, at 950 {sup o}C. Constant voltage electro-deoxidation was conducted using a NiTiO{sub 3} cathode, and either a carbon anode or a novel CaRuO{sub 3}/CaTiO{sub 3} composite inert anode. Both anode materials successfully allowed NiTi shape memory alloy to be obtained. The primary difference is that molecular oxygen was produced on the inert anode, instead of environmentally undesired CO{sub 2} greenhouse gases on the carbon anode. Indeed, it was found that carbon could successfully be substituted with conductive calcium titanate-calcium ruthenate composites for electro-deoxidation. Furthermore, DSC was used to analyze the phase transformation of NiTi shape memory alloys, with results revealing the existence of reversible martensite-austenite phase transformations during the cooling and heating process.

  11. Thermally activated retainer means utilizing shape memory alloy

    Science.gov (United States)

    Grimaldi, Margaret E. (Inventor); Hartz, Leslie S. (Inventor)

    1993-01-01

    A retainer member suitable for retaining a gap filler placed in gaps between adjacent tile members is presented. One edge of the retainer member may be attached to the gap filler and another edge may be provided with a plurality of tab members which in an intermediate position do not interfere with placement or removal of the gap filler between tile members. The retainer member may be fabricated from a shape memory alloy which when heated to a specified memory temperature will thermally activate the tab members to predetermined memory positions engaging the tile members to retain the gap filler in the gap. This invention has particular application to the thermal tiles on space vehicles such as the Space Shuttle Orbiter.

  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. Effect of Trivalent Additions and Processing on Structural and Magnetic Transitions in Ni-Mn-Ga Ferromagnetic Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    R. P. Mathur

    2012-07-01

    Full Text Available Ferromagnetic shape memory Ni50Mn30Ga15Al5-xBx (x = 0, 1, and 4 alloys were prepared by vacuum arc melting and subsequent heat-treatment as well as by melt spinning to investigate the effect of trivalent element additions in ternary Ni-Mn-Ga alloys. The heat-treated alloys containing Al were reported to possess a modulated martensite structure, however alloy containing both Al and B showed a loss of modulated structure in martensite formed. The rapidly solidified alloys on the other hand showed the formation of a similar modulated structure without composition change in alloys containing Al and the alloys containing Al and B. In addition, the former showed a presence of an amorphous phase with latter showing crystalline boron rich phases. The magnetisation of the B containing alloys in both the processing technique was however very low, showing lower magnetic exchange interaction in such alloys.Defence Science Journal, 2012, 62(4, pp.252-260, DOI:http://dx.doi.org/10.14429/dsj.62.1279

  15. 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

    2016-11-29

    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.

  16. 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.

  17. 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

  18. Modeling of shape memory alloys and application to porous materials

    Science.gov (United States)

    Panico, Michele

    In the last two decades the number of innovative applications for advanced materials has been rapidly increasing. Shape memory alloys (SMAs) are an exciting class of these materials which exhibit large reversible stresses and strains due to a thermoelastic phase transformation. SMAs have been employed in the biomedical field for producing cardiovascular stents, shape memory foams have been successfully tested as bone implant material, and SMAs are being used as deployable switches in aerospace applications. The behavior of shape memory alloys is intrinsically complex due to the coupling of phase transformation with thermomechanical loading, so it is critical for constitutive models to correctly simulate their response over a wide range of stress and temperature. In the first part of this dissertation, we propose a macroscopic phenomenological model for SMAs that is based on the classical framework of thermodynamics of irreversible processes and accounts for the effect of multiaxial stress states and non-proportional loading histories. The model is able to account for the evolution of both self-accommodated and oriented martensite. Moreover, reorientation of the product phase according to loading direction is specifically accounted for. Computational tests demonstrate the ability of the model to simulate the main aspects of the shape memory response in a one-dimensional setting and some of the features that have been experimentally found in the case of multi-axial non-proportional loading histories. In the second part of this dissertation, this constitutive model has been used to study the mesoscopic behavior of porous shape memory alloys with particular attention to the mechanical response under cyclic loading conditions. In order to perform numerical simulations, the model was implemented into the commercial finite element code ABAQUS. Due to stress concentrations in a porous microstructure, the constitutive law was enhanced to account for the development of

  19. 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.

  20. Boriding of Binary Ni-Ti Shape Memory Alloys

    Science.gov (United States)

    Ucar, Nazim; Dogan, Sule; Karakas, Mustafa Serdar; Calik, Adnan

    2016-11-01

    Boriding of binary Ni-Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor-Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB2. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62×10-8 cm2 s-1.

  1. Several Issues in the Development of Ti-Nb-Based Shape Memory Alloys

    Science.gov (United States)

    Kim, Hee Young; Miyazaki, Shuichi

    2016-12-01

    Ni-free Ti-based shape memory alloys, particularly Ti-Nb-based alloys, have attracted increasing attraction since the early 2000s due to their wide application potentials in biomedical fields. Recently, there has been significant progress in understanding the martensitic transformation behavior of Ti-Nb-based alloys and many novel superelastic alloys have been developed. The superelastic properties of Ti-Nb-based alloys have been remarkably improved through the optimization of alloying elements and microstructure control. In this paper, in order to explore and establish the alloy design strategy, several important issues in the development of Ti-Nb-based shape memory alloys are reviewed. Particularly, the effects of alloying elements on the martensitic transformation temperature and the transformation strain are analyzed. The effects of omega phase and texture on the superelastic properties are also discussed.

  2. DSC study on temperature memory effect of NiTi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    N. LIU; W. M. HUANG

    2006-01-01

    A systematic study on the temperature memory effect (TME) in a polycrystalline NiTi shape memory alloy was presented. The investigation was carried out through a series of differential scanning calorimeter (DSC) tests. Two types of tests were conducted,namely single-step test and multi-step test. The influence of the step temperature on the peak/trough temperatures in the subsequent heating process and the associated energy absorption/release in the phase transformations was investigated. Using a simple theoretical model,the exact mechanism behind TME was studied.

  3. 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.

  4. 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.

  5. 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.

  6. Damping capacity in shape memory alloy honeycomb structures

    Science.gov (United States)

    Boucher, M.-A.; Smith, C. W.; Scarpa, F.; Miller, W.; Hassan, M. R.

    2010-04-01

    SMA honeycombs have been recently developed by several Authors [1, 2] as innovative cellular structures with selfhealing capability following mechanical indentation, unusual deformation (negative Poisson's ratio [3]), and possible enhanced damping capacity due to the natural vibration dissipation characteristics of SMAs under pseudoelastic and superelastic regime. In this work we describe the nonlinear damping effects of novel shape memory alloy honeycomb assemblies subjected to combine mechanical sinusoidal and thermal loading. The SMA honeycomb structures made with Ni48Ti46Cu6 are designed with single and two-phase polymeric components (epoxy), to enhance the damping characteristics of the base SMA for broadband frequency vibration.

  7. 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.

  8. Stability of the magnetomechanical problem in magnetic shape memory alloys

    Science.gov (United States)

    Chatzigeorgiou, George; Haldar, Krishnendu; Lagoudas, Dimitris C.

    2010-04-01

    In this work we study the unstable phenomena that occur on Magnetic Shape Memory Alloys (MSMAs) during compression tests. Solving the coupled magnetomechanical problem we observe that during the reorientation process the material presents strong non-uniformity, in the form of localized zones, in the distribution of the magnetic, the stress and the strain field. This non-uniformity is due to loss of ellipticity of the coupled problem during the martensitic reorientation and affects significantly the reorientation process. The identification of the stability conditions of the magnetomechanical problem is achieved by performing stability analysis.

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

    Energy Technology Data Exchange (ETDEWEB)

    Glendenning, R.W.; Enlow, R.L. [Otago Univ., Dunedin (New Zealand). Dept. of Math. and Stat.; Hood, J.A.A. [Dept. of Oral Sciences and Orthodontics, Univ. of Otago, Dunedin (New Zealand)

    2000-07-01

    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.)

  10. Application of Shape Memory Alloys in Facial Nerve Paralysis

    Directory of Open Access Journals (Sweden)

    M Vloeberghs

    2009-11-01

    Full Text Available The Facial Nerve can be damaged at a peripheral level by a stroke or, for example by trauma or infection within the faceor the ear. In these cases the facial muscles are paralysed with little or no chance of spontaneous recovery. This research focuses on the potential utilisation of a Shape Memory Alloy(SMA to replace the function of the Facial Nerve, which willallow in conjunction with passive reconstructive methods, a patient to regain limited but active movement of the mouthcorner. Paralysis of the mouth corner is a very disabling bothfunctionally and cosmetically, speech and swallowing are hampered and the patient loses saliva, with presents a social problem.

  11. A sharp interface evolutionary model for shape memory alloys

    Science.gov (United States)

    Knüpfer, Hans; Kružík, Martin

    2016-11-01

    We show the existence of an energetic solution to a quasistatic evolutionary model of shape memory alloys. Elastic behavior of each material phase/variant is described by polyconvex energy density. Additionally, to every phase boundary, there is an interface-polyconvex energy assigned, introduced by M. \\v{S}ilhav\\'{y}. The model considers internal variables describing the evolving spatial arrangement of the material phases and a deformation mapping with its first-order gradients. It allows for injectivity and orientation-preservation of deformations. Moreover, the resulting material microstructures have finite length scales.

  12. On phase transformation behavior of porous Shape Memory Alloys.

    Science.gov (United States)

    Liu, Bingfei; Dui, Guansuo; Zhu, Yuping

    2012-01-01

    This paper is concerned on the phase transformation mechanism of porous Shape Memory Alloys (SMAs). A unit-cell model is adopted to establish the constitutive relation for porous SMAs, the stress distributions, the phase distributions and the martensitic volume fractions for the model are then derived under both pure hydrostatic stress and uniaxial compression. Further, an example for the uniaxial response under compression for a porous Ni-Ti SMA material considering hydrostatic stress is supplied. Good agreement between the theoretical prediction of the proposed model and published experimental data is observed. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

  13. Fabrication of silicon-based shape memory alloy micro-actuators

    Science.gov (United States)

    Johnson, A. David; Busch, John D.; Ray, Curtis A.; Sloan, Charles L.

    1992-01-01

    Thin film shape memory alloy has been integrated with silicon in a new actuation mechanism for microelectromechanical systems. This paper compares nickel-titanium film with other actuators, describes recent results of chemical milling processes developed to fabricate shape memory alloy microactuators in silicon, and describes simple actuation mechanisms which have been fabricated and tested.

  14. 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......-tension of the springs. This article shows several experimental tests that allow one to obtain a general comprehension of the dynamical behaviour of SMA systems. Results show the general thermo-mechanical behaviour of SMA dynamical systems and the obtained conclusions can be applied in distinct situations as in rotor...

  15. Modeling of Functional Properties of Porous Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Volkov Aleksandr E.

    2015-01-01

    Full Text Available A model accounting for the microstructure of porous TiNi shape memory alloy samples fabricated by self-propagating high temperature synthesis has been proposed for simulation of their functional-mechanical properties. Structural elements of a porous sample have been approximated by curved beams. An analysis of shapes and sizes of pores and ligaments permitted to identify characteristic sizes of the beams. A mathematical object consisting of rigidly connected small curve beams has been considered. The stress-strain state of a beam was estimated by the classical methods of strength of materials. The microstructural model was used for calculation of the phase deformation of the shape memory material. Simulation of stress-strain curves and phase deformation of a porous TiNi sample on cooling and heating under a constant stress has shown a good correspondence between the experimental data and the results of modeling.

  16. Porous shape memory alloy scaffolds for biomedical applications: a review

    Energy Technology Data Exchange (ETDEWEB)

    Wen, C E; Xiong, J Y; Li, Y C; Hodgson, P D [Institute for Technology Research and Innovation, Deakin University, Waurn Ponds, VIC 3217 (Australia)

    2010-05-01

    The interest in using porous shape memory alloy (SMA) scaffolds as implant materials has been growing in recent years due to the combination of their unique mechanical and functional properties, i.e. shape memory effect and superelasticity, low elastic modulus combined with new bone tissue ingrowth ability and vascularization. These attractive properties are of great benefit to the healing process for implant applications. This paper reviews current state-of-the art on the processing, porous characteristics and mechanical properties of porous SMAs for biomedical applications, with special focus on the most widely used SMA nickel-titanium (NiTi), including (i) microstructural features, mechanical and functional properties of NiTi SMAs; (ii) main processing methods for the fabrication of porous NiTi SMAs and their mechanical properties and (iii) new-generation Ni-free, biocompatible porous SMA scaffolds.

  17. Phase transformation behaviors and shape memory effects of TiNiFeAl shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    Li Xiao; Fushun Liu; Huibin Xu

    2007-01-01

    Measurements of electrical resistivity, X-ray diffraction, and tensile test at room temperature and -196℃ were performed to investigate the effects of Al addition substituting Ni on the phase transformation behaviors, the mechanical properties, and the shape memory effects of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys. It is found that 1at% Al addition dramatically decreases the martensitic start transformation temperature and expands the transformation temperature range of R-phase for TiNiFeAl alloys. The results of tensile test indicate that 1at% Al improves the yield strength of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 alloys by 40% and 64%, but decreases the plasticity to 11% and 12% from 26% and 27% respectively. Moreover, excellent shape memory effect of 6.6% and 7.5% were found in Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.sAl1 alloys, which results from the stress-induced martensite transformation from the R-phase.

  18. Martensitic transformation of Ti50Ni30Cu20 alloy prepared by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Valeanu, M., E-mail: valeanu@infim.ro [National Institute of Materials Physics, 077125 Bucharest (Romania); Lucaci, M. [National Institute for Electrical Engineering ICPE-CA, 030138 Bucharest (Romania); Crisan, A.D.; Sofronie, M. [National Institute of Materials Physics, 077125 Bucharest (Romania); Leonat, L. [National Institute for Electrical Engineering ICPE-CA, 030138 Bucharest (Romania); Kuncser, V. [National Institute of Materials Physics, 077125 Bucharest (Romania)

    2011-03-31

    Research highlights: > Martensitic transformation sequence in Ti50Ni30Cu20 prepared high - energy milling. > Two transformations (B2-B19, B2-B19') are evidenced after 10 hours of milling. > B2-B19 transformation is not more observed after 20 hours of milling. > A longer milling process promotes the formation of the secondary Ti{sub 2}(NiCu) phase. - Abstract: Phase transformation behavior of Ti50Ni30Cu20 shape memory alloys prepared by powder metallurgy is analyzed with respect to the duration of mechanical alloying. The processed blends were studied by differential scanning calorimetry and room temperature X-ray diffraction. The martensitic transformations evidenced by thermal scans are discussed in correlation with the relative phase content obtained from the refinement of the X-ray diffraction patterns.

  19. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    Science.gov (United States)

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

    2005-01-01

    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.

  20. 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.

  1. Fatigue Crack Growth Fundamentals in Shape Memory Alloys

    Science.gov (United States)

    Wu, Y.; Ojha, A.; Patriarca, L.; Sehitoglu, H.

    2015-03-01

    In this study, based on a regression of the crack tip displacements, the stress intensity range in fatigue is quantitatively determined for the shape memory alloy Ni2FeGa. The results are compared to the calculated stress intensity ranges with a micro-mechanical analysis accounting for the transformation-induced tractions. The effective stress intensity ranges obtained with both methods are in close agreement. Also, the fatigue crack closure levels were measured as 30 % of the maximum load using virtual extensometers along the crack flanks. This result is also in close agreement with the regression and micro-mechanical modeling findings. The current work pointed to the importance of elastic moduli changes and the residual transformation strains playing a role in the fatigue crack growth behavior. Additional simulations are conducted for two other important shape memory alloys, NiTi and CuZnAl, where the reductions in stress intensity range were found to be lower than Ni2FeGa.

  2. 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.

  3. Effect of chemical component on shape memory effect of Fe-Mn-Si-Ni-C-RE shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    Naichao Si; Zhihong Jia; Longbiao Qi

    2004-01-01

    Effect of chemical component on shape memory effect (SME) of Fe-Mn-Si-Ni-C-RE shape memory alloys was studied by bent measurement, thermal cycle training, SEM etc. Results of study indicate that the alloys with high Mn content (25%) appeare better SME, especially in lower strain. SME improves evidently when Si is higher content, especially it′s range from 3% up to 4%.But brittleness of Fe-Mn-Si-Ni-C-RE alloy increases by increasing the Si content. SME of the alloy is weakening gradually as carbon content increases under small strain (3%). But in the condition of large strain (above 6%), SME of the alloy whose carbon content ranges from 0.1% to 0.12% shows small decreasing range, especially of alloy with the addition of compound RE.

  4. Effects of microstructure and deformation conditions on the hot formability of Ni-Ti-Hf shape memory alloys.

    Science.gov (United States)

    Kim, Jeoung Han; Park, Chan Hee; Kim, Seong Woong; Hong, Jae Keun; Oh, Chang-Seok; Jeon, Yeong Min; Kim, Kyong Min; Yeom, Jong Taek

    2014-12-01

    Ingots of Ni-Ti-Hf shape memory alloys were prepared by vacuum arc re-melting. Isothermal hot compression tests were conducted at temperatures ranging from 700 to 1000 degrees C and at strain rates from 10(-2) s(-1) to 1.0 s(-1). A decrease in the Ni content below 50.2 at.% significantly deteriorated the hot workability due to the formation of a brittle second phase. Also, the low Ni content alloy showed poor workability when the temperature exceeded 900 degrees C. Additional compression tests were conducted under various conditions to clarify the effects of the chemical composition, solidification anisotropy, and the strain rate.

  5. Effects of magnetic field on the shape memory behavior of single and polycrystalline magnetic shape memory alloys

    Science.gov (United States)

    Turabi, Ali Sadi

    Shape memory alloys and polymers have been extensively researched recently because of their unique ability to recover large deformations. Shape memory polymers (SMPs) are able to recover large deformations compared to shape memory alloys (SMAs), although SMAs have higher strength and are able to generate more stress during recovery. This project focuses on procedure for fabrication and Finite Element Modeling (FEM) of a shape memory composite actuator. First, SMP was characterized to reveal its mechanical properties. Specifically, glass transition temperature, the effects of temperature and strain rate on compressive response and recovery properties of shape memory polymer were studied. Then, shape memory properties of a NiTi wire, including transformation temperatures and stress generation, were investigated. SMC actuator was fabricated by using epoxy based SMP and NiTi SMA wire. Experimental tests confirmed the reversible behavior of fabricated shape memory composites. (Abstract shortened by ProQuest.).

  6. Preparation and properties of biomedical porous titanium alloys by gelcasting.

    Science.gov (United States)

    Yang, Donghua; Shao, Huiping; Guo, Zhimeng; Lin, Tao; Fan, Lianpeng

    2011-08-01

    Porous titanium alloys have been prepared by gelcasting in this study. The elastic solid green body was first polymerized and then vacuum sintered to porous titanium alloys with low contamination by controlling sintering conditions. The microstructure and the total porosity of the vacuum sintered porous Ti-Co and Ti-Mo alloys were analyzed by using scanning electron microscopy and x-ray diffraction. Moreover, compression and bending tests were conducted to investigate their mechanical properties. The results show that open and closed three-dimensional pore morphologies and total porosity ranging from 38.34% to 58.32% can be achieved. In contrast to porous Ti by gelcasting, the compression and bending strengths of porous titanium alloys were significantly increased by adding Mo and Co with Young's modulus ranging between 7-25 GPa, which is close to that of human cortical bone, therefore being suited for potential application in load-bearing implants.

  7. Two-way shape memory effect and its stability in Ti-Ni-Hf high temperature shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    MENG Xiang-long; WU Ye; CAI Wei; ZHAO Lian-cheng

    2005-01-01

    The two-way shape memory effect (TWSME) in a Ti36 Ni49 Hf15 high temperature shape memory alloy (SMA) was systematically studied by bending tests. In the TiNiHf alloy, the martensite deformation is an effective method to get two-way shape memory effect even with a small deformation strain. The results indicate that the internal stress field formed by the bending deformation is in the direction of the preferentially oriented martensite variants formed during the bending deformation. Upon cooling the preferentially oriented martensite variants form under such an oriented stress field, which should be responsible for the generation of the two-way shape memory effect.Proper training process benefits the formation of the oriented stress field, resulting in the improvement of the twoway shape memory effect. A maximum TWSME of 0.88 % is obtained in the present alloy.

  8. Thermal response of novel shape memory polymer-shape memory alloy hybrids

    Science.gov (United States)

    Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

    2014-03-01

    Shape memory polymers (SMP) and shape memory alloys (SMA) have both been proven important smart materials in their own fields. Shape memory polymers can be formed into complex three-dimensional structures and can undergo shape programming and large strain recovery. These are especially important for deployable structures including those for space applications and micro-structures such as stents. Shape memory alloys on the other hand are readily exploitable in a range of applications where simple, silent, light-weight and low-cost repeatable actuation is required. These include servos, valves and mobile robotic artificial muscles. Despite their differences, one important commonality between SMPs and SMAs is that they are both typically activated by thermal energy. Given this common characteristic it is important to consider how these two will behave when in close environmental proximity, and hence exposed to the same thermal stimulus, and when they are incorporated into a hybrid SMA-SMP structure. In this paper we propose and examine the operation of SMA-SMP hybrids. The relationship between the two temperatures Tg, the glass transition temperature of the polymer, and Ta, the nominal austenite to martensite transition temperature of the alloy is considered. We examine how the choice of these two temperatures affects the thermal response of the hybrid. Electrical stimulation of the SMA is also considered as a method not only of actuating the SMA but also of inducing heating in the surrounding polymer, with consequent effects on actuator behaviour. Likewise by varying the rate and degree of thermal stimulation of the SMA significantly different actuation and structural stiffness can be achieved. Novel SMP-SMA hybrid actuators and structures have many ready applications in deployable structures, robotics and tuneable engineering systems.

  9. 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.

  10. Pitting Corrosion of Cu-Zn-Al Shape Memory Alloy in Simulated Uterine Fluid

    Institute of Scientific and Technical Information of China (English)

    Bangyi CHEN; Chenghao LIANG; Daojun FU

    2005-01-01

    Electrochemical test technology and surface analysis method were employed to investigate the pitting corrosion of Cu-Zn-Al shape memory alloy in simulated uterine fluid. The results showed that the breakage of the breakingrenovating equilibrium of surface layers resulted in the pitting corrosion of Cu-Zn-Al shape memory alloy in simulated uterine fluid. The development of pitting corrosion was controlled by dissolution of surface layers. The critical pitting corrosion potential was 1.70 VsCE. The kinetics equation for the development of pitting corrosion for Cu-Zn-Al shape memory alloy in simulated uterine fluid was i0=465.68 t-0.5+1.5. Pitting appearances of pits could be two types: tortoise-shell, and anomaly abscess. Cl- ion facilitated the pitting corrosion of Cu-Zn-Al shape memory alloy by competing adsorption and concentrating on alloy surface at high positive potential.

  11. 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

    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...... 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...

  12. Evaluation of shape memory effect and damping characteristics of Cu–Al–Be–Mn shape memory alloys

    Directory of Open Access Journals (Sweden)

    A.G. Shivasiddaramaiah

    2016-09-01

    Full Text Available Among different shape memory alloys, copper (Cu based alloys were the most favourable alloys, because of their attaining price and good characteristic properties. In this present work different weight compositions of Cu–Al–Be–Mn shape memory alloys are considered and are in the range of 10–14 wt% of aluminium (Al, 0.4–0.5 wt% of beryllium (Be and 0.3–0.4 wt% of manganese (Mn and these alloys were synthesized by ingot metallurgy, which exhibits β-phase at higher temperatures, also demonstrates a shape memory effect (SME after quenching to room temperature. The Be, Mn and Al content was varied in different sets to study the shape memory effect and damping behaviour of the alloys by using differential scanning calorimetry and dynamic mechanical analyzer respectively. These alloys exhibit higher damping or internal friction in the martensitic condition and internal friction or damping peak in the transition zone.

  13. Structure of nanocomposites of Al–Fe alloys prepared by mechanical alloying and rapid solidification processing

    Indian Academy of Sciences (India)

    S S Nayak; B S Murty; S K Pabi

    2008-06-01

    Structures of Al-based nanocomposites of Al–Fe alloys prepared by mechanical alloying (MA) and subsequent annealing are compared with those obtained by rapid solidification processing (RSP). MA produced only supersaturated solid solution of Fe in Al up to 10 at.% Fe, while for higher Fe content up to 20 at.% the nonequilibrium intermetallic Al5Fe2 appeared. Subsequent annealing at 673 K resulted in more Al5Fe2 formation with very little coarsening. The equilibrium intermetallics, Al3Fe (Al13Fe4), was not observed even at this temperature. In contrast, ribbons of similar composition produced by RSP formed fine cellular or dendritic structure with nanosized dispersoids of possibly a nano-quasicrystalline phase and amorphous phase along with -Al depending on the Fe content in the alloys. This difference in the product structure can be attributed to the difference in alloying mechanisms in MA and RSP.

  14. Multiscale Characterization of Nickel Titanium Shape Memory Alloys

    Science.gov (United States)

    Gall, Keith

    Shape memory alloys were characterized by a variety of methods to investigate the relationship between microstructural phase transformation, macroscale deformation due to mechanical loading, material geometry, and initial material state. The major portion of the work is application of digital image correlation at several length scales to SMAs under mechanical loading. In addition, the connection between electrical resistance, stress, and strain was studied in NiTi wires. Finally, a new processing method was investigated to develop porous NiTi samples, which can be examined under DIC in future work. The phase transformation temperatures of a Nickel-Titanium based shape memory alloy (SMA) were initially evaluated under stress-free conditions by the differential scanning calorimetric (DSC) technique. Results show that the phase transformation temperature is significantly higher for transition from de-twinned martensite to austenite than from twinned martensite or R phase to austenite. To further examine transformation temperatures as a function of initial state a tensile test apparatus with in-situ electrical resistance (ER) measurements was used to evaluate the transformation properties of SMAs at a variety of stress levels and initial compositions. The results show that stress has a significant influence on the transformation of detwinned martensite, but a small influence on R phase and twinned martensite transformations. Electrical resistance changes linearly with strain during the transformations from both kinds of martensite to austenite. The linearity between ER and strain during the transformation from de-twinned martensite to austenite is not affected by the stress, facilitating application to control algorithms. A revised phase diagram is drawn to express these results. To better understand the nature of the local and global strain fields that accompany phase transformation in shape memory alloys (SMAs), here we use high resolution imaging together with image

  15. Dynamical Jumps in a Shape Memory Alloy Oscillator

    Directory of Open Access Journals (Sweden)

    H. S. Oliveira

    2014-01-01

    Full Text Available The dynamical response of systems with shape memory alloy (SMA elements presents a rich behavior due to their intrinsic nonlinear characteristic. SMA’s nonlinear response is associated with both adaptive dissipation related to hysteretic behavior and huge changes in properties caused by phase transformations. These characteristics are attracting much technological interest in several scientific and engineering fields, varying from medical to aerospace applications. An important characteristic associated with dynamical response of SMA system is the jump phenomenon. Dynamical jumps result in abrupt changes in system behavior and its analysis is essential for a proper design of SMA systems. This paper discusses the nonlinear dynamics of a one degree of freedom SMA oscillator presenting pseudoelastic behavior and dynamical jumps. Numerical simulations show different aspects of this kind of behavior, illustrating its importance for a proper understanding of nonlinear dynamics of SMA systems.

  16. 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.

  17. Shape memory alloy heat engines and energy harvesting systems

    Energy Technology Data Exchange (ETDEWEB)

    Browne, Alan L; Johnson, Nancy L; Shaw, John Andrew; Churchill, Christopher Burton; Keefe, Andrew C; McKnight, Geoffrey P; Alexander, Paul W; Herrera, Guillermo A; Yates, James Ryan; Brown, Jeffrey W

    2014-09-30

    A heat engine includes a first rotatable pulley and a second rotatable pulley 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 a first wire, a second wire, and a matrix joining the first wire and the second wire. The first wire and the second wire are in contact with the pulleys, but the matrix is not in contact with the pulleys. A timing cable is 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.

  18. Application Of Shape Memory Alloy In Harvesto-Absorber System

    Directory of Open Access Journals (Sweden)

    Kęcik Krzysztof

    2015-09-01

    Full Text Available This paper presents a conception of the harvester-absorber system consisting of two parts. The first is the pendulum attached to the main system (oscillator, which is suspended on the linear damper and the nonlinear spring made of shape memory alloy. The spring is modelled as a polynomial function based on Landau–Ginzburg theory of phase transitions (similar as ferroelectric and ferromagnets. The obtained results show, that SMA element can increase harvesting energy level, while the absorber effect can be impaired (but not loss. Additionally, introducing SMA element causes changes in dynamics, introduces a new unstable solutions and bifurcations. The analysis was done by classical integration and continuation solution methods.

  19. Shape memory alloy actuated adaptive exhaust nozzle for jet engine

    Science.gov (United States)

    Song, Gangbing (Inventor); Ma, Ning (Inventor)

    2009-01-01

    The proposed adaptive exhaust nozzle features an innovative use of the shape memory alloy (SMA) actuators for actively control of the opening area of the exhaust nozzle for jet engines. The SMA actuators remotely control the opening area of the exhaust nozzle through a set of mechanism. An important advantage of using SMA actuators is the reduction of weight of the actuator system for variable area exhaust nozzle. Another advantage is that the SMA actuator can be activated using the heat from the exhaust and eliminate the need of other energy source. A prototype has been designed and fabricated. The functionality of the proposed SMA actuated adaptive exhaust nozzle is verified in the open-loop tests.

  20. Simulation of grain size effects in nanocrystalline shape memory alloys

    Science.gov (United States)

    Ahluwalia, Rajeev; Quek, Siu Sin; Wu, David T.

    2015-06-01

    Recently, it has been demonstrated that martensitic transformation in nanocrystalline shape memory alloys can be suppressed for small grain sizes. Motivated by these results, we study the grain size dependence of martensitic transformations and stress-strain response of nanocrystalline shape memory alloys within the framework of the Ginzburg-Landau (GL) theory. A GL model for a square to rectangle transformation in polycrystals is extended to account for grain boundary effects. We propose that an inhibition of the transformation in grain boundary regions can occur, if the grain boundary energy of the martensite is higher than that of the austenite phase. We show that this inhibition of transformation in grain boundary regions has a strong influence on domain patterns inside grains. Although the transformation is inhibited only at the grain boundaries, it leads to a suppression of the transformation even inside the grains as grain size is decreased. In fact, below a critical grain size, the transformation can be completely suppressed. We explain these results in terms of the extra strain gradient cost associated with grain boundaries, when the transformation is inhibited at grain boundaries. On the other hand, no significant size effects are observed when transformation is not inhibited at grain boundaries. We also study the grain size dependence of the stress strain curve. It is found that when the transformation is inhibited at grain boundaries, a significant reduction in the hysteresis associated with stress-strain curves during the loading-unloading cycles is observed. The hysteresis for this situation reduces even further as the grain size is reduced, which is consistent with recent experiments. The simulations also demonstrate that the mechanical behavior is influenced by inter-granular interactions and the local microstructural neighbourhood of a grain has a stronger influence than the orientation of the grain itself.

  1. Shape memory alloy resetable spring lift for pedestrian protection

    Science.gov (United States)

    Barnes, Brian M.; Brei, Diann E.; Luntz, Jonathan E.; Strom, Kenneth; Browne, Alan L.; Johnson, Nancy

    2008-03-01

    Pedestrian protection has become an increasingly important aspect of automotive safety with new regulations taking effect around the world. Because it is increasingly difficult to meet these new regulations with traditional passive approaches, active lifts are being explored that increase the "crush zone" between the hood and rigid under-hood components as a means of mitigating the consequences of an impact with a non-occupant. Active lifts, however, are technically challenging because of the simultaneously high forces, stroke and quick timing resulting in most of the current devices being single use. This paper introduces the SMArt (Shape Memory Alloy ReseTable) Spring Lift, an automatically resetable and fully reusable device, which couples conventional standard compression springs to store the energy required for a hood lift, with Shape Memory Alloys actuators to achieve both an ultra high speed release of the spring and automatic reset of the system for multiple uses. Each of the four SMArt Device subsystems, lift, release, lower and reset/dissipate, are individually described. Two identical complete prototypes were fabricated and mounted at the rear corners of the hood, incorporated within a full-scale vehicle testbed at the SMARTT (Smart Material Advanced Research and Technology Transfer) lab at University of Michigan. Full operational cycle testing of a stationary vehicle in a laboratory setting confirms the ultrafast latch release, controlled lift profile, gravity lower to reposition the hood, and spring recompression via the ratchet engine successfully rearming the device for repeat cycles. While this is only a laboratory demonstration and extensive testing and development would be required for transition to a fielded product, this study does indicate that the SMArt Lift has promise as an alternative approach to pedestrian protection.

  2. Performance of a base isolator with shape memory alloy bars

    Institute of Scientific and Technical Information of China (English)

    Fabio Casciati; Lucia Faravelli; Karim Hamdaoui

    2007-01-01

    A new and innovative base isolation device is introduced in this paper based on extensive research carried out by the authors and their co-workers.A prototype of the device was built and experimentally tested on the shaking table.The new base isolation device consists of two disks,one vertical cylinder with an upper enlargement sustained by three horizontal cantilevers,and at least three inclined shape memory alloy(SMA) bars.The role of the SMA bars is to limit the relative motion between the base and the superstructure,to dissipate energy by their super-elastic constitutive law and to guarantee the re-centring of the device.To verify the expected performance,a prototype was built and tested under sinusoidal waves of displacement of increasing frequency with different amplitudes.It is shown that the main feature of the proposed base isolation device is that for cyclic loading,the super-elastic behavior of the alloy results in wide load-displacement loops,where a large amount of energy is dissipated.

  3. 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.

  4. Boriding of binary Ni-Ti shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ucar, Nazim; Dogan, Sule [Suleyman Demirel Univ., Isparta (Turkey). Physics Dept.; Karakas, Mustafa Serdar [Cankaya Univ., Ankara (Turkey). Materials Science and Engineering Dept.; Calik, Adnan [Suleyman Demirel Univ., Isparta (Turkey). Manufacturing Engineering Dept.

    2016-07-01

    Boriding of binary Ni-Ti shape memory alloys was carried out in a solid medium at 1273 K for 2, 4, 6, and 8 h using the powder pack method with proprietary Ekabor-Ni powders. Characterization of the boride layer formed on the surface of alloys was done by optical microscopy and scanning electron microscopy. The presence of boride, silicide, and borosilicide phases in the boride layers was confirmed by X-ray diffraction analysis. The thickness and microhardness of the boride layers increased with increasing boriding time. Hardness profiles showed a rapid decrease in hardness moving from the boride layer to the main structure. The high hardness of the boride layer was attributed mainly to the formation of TiB{sub 2}. A parabolic relationship was observed between layer thickness and boriding time, and the growth rate constant for the boriding treatment was calculated as 0.62 x 10{sup -8} cm{sup 2}s{sup -1}.

  5. Damping performance of Cu-Zn-Al shape memory alloys in engineering structures

    Institute of Scientific and Technical Information of China (English)

    司乃潮; 孙克庆; 孙少纯; 刘海霞

    2004-01-01

    The stress strain curves of two CuZnAl shape memory alloys which have the martensitic transformation temperatures of 50 ℃ and -10 ℃ respectively, were measured by using electronic material tester after treated by different heat-treatment conditions. The results show that the area enclosed by hysteresis loop of the CuZnAl shape memory alloy in martensitic state is much larger than that of the alloy in austenitic state with super-elasticity at room temperature. Therefore, the former has better vibration attenuation effect. After being oil-quenched, waterquenched, and step-quenched, the CuZnAl alloy takes on more stable shape memory effect, better super-plasticity and superelasticity (pseudoelasticity). A CuZnAl shape memory alloy damper was designed, produced and installed to a 2-layer frame structure. In addition, the vibration experiments were made by dynamic data collecting analysis meter. The velocity of vibration attenuation of frame structure with CuZnAl shape memory alloy damper is much faster than that without it. And with the help of CuZnAl shape memory alloy damper, the attenuation period reduces to 1/10 of the original.

  6. Microstructure and Shape Memory Behavior of Ti-Nb Shape Memory Alloy Thin Film

    Science.gov (United States)

    Meng, X. L.; Sun, B.; Sun, J. Y.; Gao, Z. Y.; Cai, W.; Zhao, L. C.

    2017-06-01

    Ti-Nb shape memory alloy (SMA) thin film is a promising candidate applied as microactuator in biomedical field. In this study, the microstructure and shape memory behavior of Ti-Nb SMA thin films in different heat treatment conditions have been investigated. Fine ω phases embedded in the β phase matrix suppress the martensitic transformation of the films. As a result, the as-deposited and most of the annealed films consist of the β and α″ dual phases. The annealed Ti-Nb thin film shows excellent superelasticity effect when deformed above the reverse martensitic transformation temperature, that is 3.5% total recovery strain can be obtained when 4% pre-strain is loaded.

  7. Nanocrystallization of the Ti50Ni48Co2 Shape Memory Alloy by Thermomechanical Treatment

    Science.gov (United States)

    Mohammad Sharifi, E.; Karimzadeh, F.; Kermanpur, A.

    2015-01-01

    The microstructural evolution during nanostructuring of the Ti50Ni48Co2 shape memory alloy by thermomechanical processing is investigated. The high purity ingots were fabricated by a copper boat vacuum induction melting technique. The differential scanning calorimetry measurements showed that the homogenized Ti50Ni48Co2 specimen have two-stage transformation during cooling including the austenite to R phase and the R phase to martensite. The homogenized specimens were then hot rolled and annealed to prepare the initial microstructure. Thereafter, annealed specimens were subjected to cold rolling with various thickness reductions up to 70 %. Transmission electron microscopy revealed that the severe cold rolling led to the formation of a mixed microstructure consisting of amorphous and nanocrystalline phases in Ti50Ni48Co2 alloy. After annealing at 400 °C, the amorphous phase formed in the 70 % cold-rolled specimen was completely crystallized and an entire nanocrystalline structure with the grain size between 10 and 60 nm was achieved. The nanocrystalline Ti50Ni48Co2 alloy exhibited about 12 % of recoverable strain and very high plateau stress (about 730 MPa) which was significantly higher than that of the coarse-grained state.

  8. Fabrication and modeling of shape memory alloy springs

    Science.gov (United States)

    Heidari, B.; Kadkhodaei, M.; Barati, M.; Karimzadeh, F.

    2016-12-01

    In this paper, shape memory alloy (SMA) helical springs are produced by shape setting two sets of NiTi (Ti-55.87 at% Ni) wires, one of which showing shape memory effect and another one showing pseudoelasticity at the ambient temperature. Different pitches as well as annealing temperatures are tried to investigate the effect of such parameters on the thermomechanical characteristics of the fabricated springs. Phase transformation temperatures of the products are measured by differential scanning calorimetry and are compared with those of the original wires. Compression tests are also carried out, and stiffness of each spring is determined. The desired pitches are so that a group of springs experiences phase transition during loading while the other does not. The former shows a varying stiffness upon the application of compression, but the latter acts as passive springs with a predetermined stiffness. Based on the von-Mises effective stress and strain, an enhanced one-dimensional constitutive model is further proposed to describe the shear stress-strain response within the coils of an SMA spring. The theoretically predicted force-displacement responses of the produced springs are shown to be in a reasonable agreement with the experimental results. Finally, effects of variations in geometric parameters on the axial force-displacement response of an SMA spring are investigated.

  9. Applications of shape memory alloys for neurology and neuromuscular rehabilitation.

    Science.gov (United States)

    Pittaccio, Simone; Garavaglia, Lorenzo; Ceriotti, Carlo; Passaretti, Francesca

    2015-05-27

    Shape memory alloys (SMAs) are a very promising class of metallic materials that display interesting nonlinear properties, such as pseudoelasticity (PE), shape memory effect (SME) and damping capacity, due to high mechanical hysteresis and internal friction. Our group has applied SMA in the field of neuromuscular rehabilitation, designing some new devices based on the mentioned SMA properties: in particular, a new type of orthosis for spastic limb repositioning, which allows residual voluntary movement of the impaired limb and has no predetermined final target position, but follows and supports muscular elongation in a dynamic and compliant way. Considering patients in the sub-acute phase after a neurological lesion, and possibly bedridden, the paper presents a mobiliser for the ankle joint, which is designed exploiting the SME to provide passive exercise to the paretic lower limb. Two different SMA-based applications in the field of neuroscience are then presented, a guide and a limb mobiliser specially designed to be compatible with diagnostic instrumentations that impose rigid constraints in terms of electromagnetic compatibility and noise distortion. Finally, the paper discusses possible uses of these materials in the treatment of movement disorders, such as dystonia or hyperkinesia, where their dynamic characteristics can be advantageous.

  10. Applications of Shape Memory Alloys for Neurology and Neuromuscular Rehabilitation

    Directory of Open Access Journals (Sweden)

    Simone Pittaccio

    2015-05-01

    Full Text Available Shape memory alloys (SMAs are a very promising class of metallic materials that display interesting nonlinear properties, such as pseudoelasticity (PE, shape memory effect (SME and damping capacity, due to high mechanical hysteresis and internal friction. Our group has applied SMA in the field of neuromuscular rehabilitation, designing some new devices based on the mentioned SMA properties: in particular, a new type of orthosis for spastic limb repositioning, which allows residual voluntary movement of the impaired limb and has no predetermined final target position, but follows and supports muscular elongation in a dynamic and compliant way. Considering patients in the sub-acute phase after a neurological lesion, and possibly bedridden, the paper presents a mobiliser for the ankle joint, which is designed exploiting the SME to provide passive exercise to the paretic lower limb. Two different SMA-based applications in the field of neuroscience are then presented, a guide and a limb mobiliser specially designed to be compatible with diagnostic instrumentations that impose rigid constraints in terms of electromagnetic compatibility and noise distortion. Finally, the paper discusses possible uses of these materials in the treatment of movement disorders, such as dystonia or hyperkinesia, where their dynamic characteristics can be advantageous.

  11. Modeling of thermomechanical response of porous shape memory alloys

    Science.gov (United States)

    Lagoudas, Dimitris C.; Entchev, Pavlin B.; Vandygriff, Eric L.; Qidwai, Muhammad A.; DeGiorgi, Virginia G.

    2000-06-01

    Shape memory alloys (SMAs) have emerged as a class of materials with unique thermal and mechanical properties that have found numerous applications in various engineering areas. While the shape memory and pseudoelasticity effects have been extensively studied, only a few studies have been done on the high capacity of energy dissipation of SMAs. Because of this property, SMAs hold the promise of making high-efficiency damping devices that are superior to those made of conventional materials. In addition to the energy absorption capability of the dense SMA material, porous SMAs offer the possibility of higher specific damping capacity under dynamic loading conditions, du to scattering of waves. Porous SMAs also offer the possibility of impedance matching by grading the porosity at connecting joints with other structural materials. As a first step, the focus of this work, is on establishing the static properties of porous SMA material. To accomplish this, a micromechanics-based analysis of the overall behavior of porous SMA is carried out. The porous SMA is modeled as a composite with SMA matrix, which is modeled using an incremental formulation, and pores as inhomogeneities of zero stiffness. The macroscopic constitutive behavior of the effective medium is established using the incremental More-Tanaka averaging method for a random distribution of pores, and a FEM analysis of a unit cell for a periodic arrangement of pores. Results form both analyses are compared under various loading conditions.

  12. Study on hemocompatibility and corrosion behavior of ion implanted TiNi shape memory alloy and Co-based alloys.

    Science.gov (United States)

    Liang, Chenghao; Huang, Naibao

    2007-10-01

    Biomedical TiNi shape memory alloy and Co-based alloys were ion implanted, and corrosion resistance and hemocompatibility of these had been investigated with electrochemical method, dynamic clotting time, and hemolysis rate tests. The results indicated that the electrochemical stability and anodic polarization behavior of the materials were improved significantly after ion implantation. When TiNi, Co-based alloys were implanted Mo + C and Ti + C, respectively, the corrosion potentials were enhanced more than 200 mV, passive current densities decreased, and passive ranges were broadened. Dynamic clotting time of the ion implanted substances was prolonged and hemolysis rate decreased. All the results pointed out that corrosion resistance and hemocompatibility of the alloys were improved by ion implantation, and effects of dual implantation was better than that of C single implantation. X-ray diffraction analysis of the alloys after dual implantation revealed that TiC, Mo(2)C, Mo(9)Ti(4), and Mo appeared on the surface of TiNi alloy, and CoC(x), Co(3)Ti, TiC, and TiO on the surface of Co-based alloys. These phases dispersing on the alloy surface formed amorphous film, prevented dissolving of alloy elements and improved the corrosion resistance and hemocompatibility of the alloys.

  13. Precipitation-Strengthened, High-Temperature, High-Force Shape Memory Alloys

    Science.gov (United States)

    Noebe, Ronald D.; Draper, Susan L.; Nathal, Michael V.; Crombie, Edwin A.

    2008-01-01

    Shape memory alloys (SMAs) are an enabling component in the development of compact, lightweight, durable, high-force actuation systems particularly for use where hydraulics or electrical motors are not practical. However, commercial shape memory alloys based on NiTi are only suitable for applications near room temperature, due to their relatively low transformation temperatures, while many potential applications require higher temperature capability. Consequently, a family of (Ni,Pt)(sub 1-x)Ti(sub x) shape memory alloys with Ti concentrations ranging from about 15 to 25 at.% have been developed for applications in which there are requirements for SMA actuators to exert high forces at operating temperatures higher than those of conventional binary NiTi SMAs. These alloys can be heat treated in the range of 500 C to produce a series of fine precipitate phases that increase the strength of alloy while maintaining a high transformation temperature, even in Ti-lean compositions.

  14. Microwave-Assisted Preparation of High Entropy Alloys

    Directory of Open Access Journals (Sweden)

    Paolo Veronesi

    2015-10-01

    Full Text Available Microwaves at the ISM (Industrial, Scientific and Medical, reserved internationally frequency of 2450 or 5800 MHz have been used to prepare FeCoNiCuAl, FeCrNiTiAl and FeCoCrNiAl2.5 high entropy alloys by direct heating of pressed mixtures of metal powders. The aim of this work is to explore a new microwave-assisted near-net-shape technology, using a powder metallurgy approach for the preparation of high entropy alloys, able to overcome the limits of current melting technologies (defects formation or solid state ones (time demanding. High entropy alloy compositions have been selected so as to comprise at least one ferromagnetic element and one highly reactive couple, like Ni-Al, Ti-Al, Co-Al or Fe-Al. Results show that direct microwave heating of the powder precursors occurs, and further heating generation is favored by the ignition of exothermal reactions in the load. Microwaves have been applied both for the ignition and sustaining of such reactions, showing that by the proposed technique, it is possible to control the cooling rate of the newly-synthesized high entropy alloys. Results showed also that microwave heating in predominant magnetic field regions of the microwave applicator is more effective at controlling the cooling rate. The herein proposed microwave-assisted powder metallurgy approach is suitable to retain the shape of the load imparted during forming by uniaxial pressing. The homogeneity of the prepared high entropy alloys in all cases was good, without the dendritic segregation typical of arc melting, even if some partially-unreacted powders were detected in the samples.

  15. Vacuum Plasma Spray Formed High Transition Temperature Shape Memory Alloys Project

    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...

  16. High Work Output Ni-Ti-Pt High Temperature Shape Memory Alloys and Associated Processing Methods

    Science.gov (United States)

    Noebe, Ronald D. (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Garg, Anita (Inventor)

    2009-01-01

    According to the invention, compositions of Ni-Ti-Pt high temperature, high force, shape memory alloys are disclosed that have transition temperatures above 100 C.; have narrow hysteresis; and produce a high specific work output.

  17. 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...

  18. 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...... 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...

  19. Numerical Analysis of Thermo-Mechanical Coupling in Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    S. Hashemi

    2016-01-01

    Full Text Available The phase transformation phenomenon due to the crystallographic change of shape memory alloys subjected to mechanical or thermal loading is very complicated. Regarding the thermo-mechanical coupling effects in shape memory alloys, in case of high  loading rates, heat generation/absorption during the forward/reverse transformation, will lead in temperature-dependent variation and consequently affects its mechanical behavior. In this paper, a numerical algorithm based on the finite element method is proposed to investigate complex mechanical, thermal, and coupled behavior of shape memory alloys, including both exclusive behaviours of these alloys, that are superelasticity and shape memory effect. Several key examples are simulated and discussed to assess the efficiency and accuracy of proposed algorithm.

  20. Medical application of NiTi shape memory alloy in China

    Energy Technology Data Exchange (ETDEWEB)

    Chu, Y. [Nonferrous Metals Society of China (NFSOC), Beijing, BJ (China); Dai, K. [Ninth People' s Hospital, Shanghai, SH (China); Zhu, M.; Mi, X. [General Research Inst. for Nonferrous Metals, Beijing, BJ (China)

    2000-07-01

    In the present paper, a general review of clinical application of NiTi shape memory alloy in bone implantation, orthodontics and interventional treatment in China is given with some of typical topics introduced in detail. (orig.)

  1. Relationship between phase composition and corrosion resistanceof Ni-Ti-Nb based shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The stability and microstructure of Ni-Ti-Nb based shape memory alloys were investigated after alloyed with elements Zr, Cr and V. In artificial seawater (3.5%NaCl) and physiological solution (5%NaCl+0.1%H2O2), the results show that the alloying elements influence the corrosion behavior of Ni-Ti-Nb alloys. Generally, Zr improves the corrosion resistance of Ni-Ti-Nb alloy, Cr reduces its corrosion resistance and V does not change the property. In order to investigate the reason of the difference,the relation of the phase components and corrosion resistance of Ni-Ti-Nb based shape memory alloys were studied by element analysis and SEM.

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

    Directory of Open Access Journals (Sweden)

    Sakib Tanvir

    2015-08-01

    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.

  3. 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.

  4. Two- way Shape Memory Effect in a Ti-Ni-Nb Shape Memory Alloy with Wide Hysteresis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A two-way shape memory effect (TWSME) in the Ti46.3Ni44.7Nb9 alloy has been systematically investigated by means of bending test and transmission electron microscopy (TEM) observations. Based on the analysis of the microstructure after training, the mechanism of TWSME in the Ti46.3Ni44.7Nb9 alloy has been discussed.

  5. 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.

  6. The Effect of Stress Ageing on the Properties of Shape Memory Alloys

    OpenAIRE

    A. Michael

    1995-01-01

    The performance characteristics of shape memory alloys operating in an overtemperature shut-off valve at a temperature of 95°C for up to 2000 hours are presented. Alloys of NiTi, Cu-Al-Ni and Cu-Zn-Al have been characterised under these ageing conditions. The effect of altering the processing parameters, viz solution treatment temperature, quenching technique and training procedure were examined. All alloys show degradation of the memory behaviour but results are presented which demonstrate t...

  7. 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 dedi

  8. Texture development and anisotropic behaviour in a Ti-45Ni-5Cu (AT.%) shape memory alloy

    NARCIS (Netherlands)

    Zhao, Lie

    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 an

  9. Alloying effect on K-shell fluorescence parameters of porous NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cengiz, E., E-mail: erhan_cengiz@ktu.edu.tr [Karadeniz Technical University, Science Faculty, Department of Physics, 61080 Trabzon (Turkey); Ozkendir, O.M. [Mersin University, Tarsus Faculty of Technology, Tarsus (Turkey); Kaya, M. [Adiyaman University, Department of Material Science Engineering, 02040 Adiyaman (Turkey); Tirasoglu, E. [Karadeniz Technical University, Science Faculty, Department of Physics, 61080 Trabzon (Turkey); Karahan, I.H. [Mustafa Kemal University, Faculty of Arts and Sciences, Department of Physics, Antakya, Hatay (Turkey); Kimura, S.; Hajiri, T. [UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585 (Japan)

    2014-01-01

    Highlights: • The K{sub α,β} shell production cross-sections and K{sub β}/K{sub α} intensity ratios of porous NiTi SMAs were determined by ED-XRF. • To analyze the changes in the structures due to the preheating and solution heat treatment processes, XRD and XPS measurements were also performed. • The deviations between the experimental and theoretical were interpreted to charge transfer phenomena. - Abstract: The K{sub α,β} shell production cross-sections and K{sub β}/K{sub α} intensity ratios of porous Ni −49 at% Ti shape memory alloys were determined using energy dispersive X-ray fluorescence (EDXRF) technique. Also, the alloying effect on the K shell fluorescence parameters was investigated. The samples were excited by 59.5 keV γ-rays from an {sup 241}Am annular radioactive source. The K X-rays emitted by the samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The structure analyses of the samples were also made using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The deviations between the present results and theoretical values, calculated for pure Ti and Ni, were attributed to charge transfer phenomena and/or rearrangement of valance shell electrons and porosity.

  10. Effect of solution hardening on the shape memory effect of Fe-Mn based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzaki, K.; Natsume, Y.; Maki, T. [Kyoto Univ. (Japan). Dept. of Materials Science and Engineering; Tomota, Y. [Ibaraki Univ., Hitachi (Japan)

    1995-10-01

    Fe-high Mn-Si alloys, which undergo {gamma} (fcc) to {var_epsilon} (hcp) martensitic transformation, exhibit a pronounced shape memory effect. The origin of shape memory effect of these alloys is the reversion of stress-induced {var_epsilon} martensite. A shape change must hence be accomplish3ed by stress-induced martensitic transformation without permanent slip in austenite ({gamma}) in order to obtain a good shape memory effect. It is clear that the intrusion of permanent slip can be suppressed by increasing the strength of austenite and by decreasing the applied stress required for a shape change due to stress-induced martensitic transformation. It has been reported that the addition of the interstitial elements of C and N as well as the substitutional elements of Mo and V increases the 0.2% proof stress of austenite in Fe-high Mn alloys. However, there have been few studies on the effect of these alloying elements on the shape memory effect of Fe-high Mn based alloys. In the present study, it was aimed to improve the shape memory effect of Fe-high Mn based alloys by the strengthening of austenite through solution hardening due to C and Mo.

  11. Potential High-Temperature Shape-Memory Alloys Identified in the Ti(Ni,Pt) System

    Science.gov (United States)

    Noebe, Ronald D.; Biles, Tiffany A.; Garg, Anita; Nathal, Michael V.

    2004-01-01

    "Shape memory" is a unique property of certain alloys that, when deformed (within certain strain limits) at low temperatures, will remember and recover to their original predeformed shape upon heating. It occurs when an alloy is deformed in the low-temperature martensitic phase and is then heated above its transformation temperature back to an austenitic state. As the material passes through this solid-state phase transformation on heating, it also recovers its original shape. This behavior is widely exploited, near room temperature, in commercially available NiTi alloys for connectors, couplings, valves, actuators, stents, and other medical and dental devices. In addition, there are limitless applications in the aerospace, automotive, chemical processing, and many other industries for materials that exhibit this type of shape-memory behavior at higher temperatures. But for high temperatures, there are currently no commercial shape-memory alloys. Although there are significant challenges to the development of high-temperature shape-memory alloys, at the NASA Glenn Research Center we have identified a series of alloy compositions in the Ti-Ni-Pt system that show great promise as potential high-temperature shape-memory materials.

  12. Thermodynamic assessment of the stabilization effect in deformed shape memory alloy martensite

    Energy Technology Data Exchange (ETDEWEB)

    Kato, Hiroyuki, E-mail: hkato@eng.hokudai.ac.jp [Division of Mechanical and Space Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Yasuda, Yohei, E-mail: yasuda-yoh@mech-me.eng.hokudai.ac.jp [Division of Mechanical and Space Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Sasaki, Kazuaki, E-mail: kazki@eng.hokudai.ac.jp [Division of Mechanical and Space Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan)

    2011-06-15

    When a martensitic shape memory alloy is deformed, the reverse transformation occurs at higher temperature than that of undeformed martensite. This is a typical case of the stabilization effect of martensite that is commonly observed in shape memory alloys. Regarding previous results measured by electric resistance and/or dilatometoric methods in NiTi and CuAlNi shape memory alloys, this study has performed calorimetric measurement in these alloys in order to re-examine the stabilization effect in terms of thermodynamics. Experimental evidence for appreciable changes in the reverse transformation temperature due to variant change of the martensite is presented. The elastic energy stored in the deformed martensite and the irreversible energy dissipated during the reverse transformation are estimated from the transformation temperatures, the stress-strain curves of the martensite and the latent heat of transformation. The temperatures of the reverse martensitic transformation have been related to these energies in explicit form.

  13. Reinforcement of bulk Y-Ba-Cu-O superconductors by using Fe-Mn-Si-Ni shape memory alloy rings

    Science.gov (United States)

    Seki, H.; Honma, Y.; Nomura, M.; Nakayama, C.; Koshizuka, N.; Maruyama, T.; Murakami, M.

    Bulk Y-Ba-Cu-O superconductors are brittle ceramics and their tensional strengths are very low. Therefore, reinforcement of the bulk superconductor is needed for practical applications. Pre-compression load has been shown to be effective in enforcing the bulk superconductors. Fe-Mn-Si alloys exhibit shape-memory effects and the size change due to the shape recovery is large. Therefore, the Fe-Mn-Si shape memory alloy rings will function as effective reinforcement material for the bulk superconductors. We prepared Y-Ba-Cu-O bulk superconductors with top-seeded melt-growth process and the Ni added Fe-Mn-Si (Fe-Mn-Si-Ni) alloy ring which exhibited better shape memory performances than Ni-free Fe-Mn-Si alloys. The ring was extended by inserting a steel rod and heated to 623K. The amount of shape recovery strain was about 2%. Based on these results, the TSMG-processed bulk YBa- Cu-O superconductor 39.0 mm in diameter was inserted into the Fe-Mn-Si-Ni ring whose inner diameter was 39.3 mm at room temperature. With heating to 623K, the Fe-Mn-Si-Ni ring shrank and firmly encapsulated the bulk Y-Ba-Cu-O superconductor. Cracking was not observed in the bulk superconductor. It was interesting to note that the trapped magnetic field of the Y-Ba-Cu-O superconductor at 77K was increased from 2,550 G to 3,795 G through Fe-Mn-Si-Ni ring reinforcement. These results clearly show that the reinforcement treatment with Fe-Mn-Si-Ni alloy ring or pre-compression load is effective in improving the field trapping ability in addition to thee improvement of the mechanical properties.

  14. Preparation of Mg-Li alloys by electrolysis in molten salt at low temperature

    Institute of Scientific and Technical Information of China (English)

    Mi Lin Zhang; Yong De Yan; Zhi Yao Hou; Lu An Fan; Zeng Chen; Ding Xiang Tang

    2007-01-01

    A new technology for preparation of low cost Mg-Li alloys was studied. The alloys were prepared by electrolysis in molten were investigated, and optimal electrolysis parameters were obtained. Mg-Li alloys with low lithium content (about 25%) were prepared by the unique method of a higher post-thermal treatment temperature after electrolysis at low temperature. The results showed that the electrolysis can be carried out at low temperature, which resulted in reducing preparation cost due to energy saving.The new technology for the preparation of Mg-Li alloy by electrolysis in molten salt was proved to be feasible.

  15. Shape memory alloy wire for self-sensing servo actuation

    Science.gov (United States)

    Josephine Selvarani Ruth, D.; Dhanalakshmi, K.

    2017-01-01

    This paper reports on the development of a straightforward approach to realise self-sensing shape memory alloy (SMA) wire actuated control. A differential electrical resistance measurement circuit (the sensorless signal conditioning (SSC) circuit) is designed; this sensing signal is directly used as the feedback for control. Antagonistic SMA wire actuators designed for servo actuation is realized in self-sensing actuation (SSA) mode for direct control with the differential electrical resistance feedback. The self-sensing scheme is established on a 1-DOF manipulator with the discrete time sliding mode controls which demonstrates good control performance, whatever be the disturbance and loading conditions. The uniqueness of this work is the design of the generic electronic SSC circuit for SMA actuated system, for measurement and control. With a concern to the implementation of self-sensing technique in SMA, this scheme retains the systematic control architecture by using the sensing signal (self-sensed, electrical resistance corresponding to the system position) for feedback, without requiring any processing as that of the methods adopted and reported previously for SSA techniques of SMA.

  16. Transformation reversibility in Fe-Mn-Si shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tsuzaki, K. [Kyoto Univ. (Japan). Dept. of Mater. Sci. and Eng.; Natsume, Y. [Kyoto Univ. (Japan). Dept. of Mater. Sci. and Eng.; Maki, T. [Kyoto Univ. (Japan). Dept. of Mater. Sci. and Eng.

    1995-12-01

    The change of the surface relief associated with stress-induced epsilon martensite before and after the reverse transformation in an Fe-33%Mn-6%Si alloy (Ms=264K) has been investigated. The permanent strain of a 2.7% tensile-strained specimen was 1.1% after the reverse transformation. In this specimen, a large part of surface relief still remained after heating to 623K (above Af). When five training cycles of 2.5% straining at room temperature and heating at 623K were applied, the permanent strain became negligible and the surface relief vanished well. TEM observations showed that usual permament slip deformation hardly occurred in the interior of an austenite grain in a 3.8% tensile-strained specimen where the permanent strain after the reversion was 2%. These results indicate that the permanent strain in the shape memory behavior is mainly attributed to the lack of transformation reversibility, i.e., the lack of reversible movement of Shockley partial dislocations. The conditions for the reversibility were discussed and the importance of the back stress formed by the forward transformation was pointed out. The effects of traning were also briefly discussed. (orig.).

  17. 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.

  18. 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.

  19. A novel inertial energy harvester using magnetic shape memory alloy

    Science.gov (United States)

    Askari Farsangi, Mohammad Amin; Sayyaadi, Hassan; Zakerzadeh, Mohammad Reza

    2016-10-01

    This paper studies the output voltage from a novel inertial energy harvester using magnetic shape memory alloys (MSMAs). The MSMA elements are attached to the root of a cantilever beam by means of two steps. In order to get electrical voltage, two coils are wound around the MSMAs and a shock load is applied to a tip mass at the end of the beam to have vibration in it. The beam vibration causes strain in the MSMAs along their longitudinal directions and as a result the magnetic flux alters in the coils. The change of magnetic flux in the surrounding coil produces an AC voltage. In order to predict the output voltage, the nonlinear governing equations of beam motion based on Euler-Bernoulli model and von Kármán theory are derived. A thermodynamics-based constitutive model is used to predict the nonlinear strain and magnetization response of the MSMAs. Also, the induced voltage during martensite variant reorientation in MSMAs is investigated with the help of Faraday’s law of induction. Finally, the effect of different parameters including bias magnetic field, pre-strain and number of MSMA elements are investigated in details. The results show that this novel energy harvester has the capability of using as an alternative to the current piezoelectric and magnetostrictive ones for harvesting energy from ambient vibration.

  20. Electro-mechanical behavior of a shape memory alloy actuator

    Science.gov (United States)

    Pausley, Matthew E.; Furst, Stephen J.; Talla, Vamsi; Seelecke, Stefan

    2009-03-01

    This paper presents experimental study and numerical simulation of the electro-thermo-mechanical behavior of a commercially available Flexinol shape memory alloy (SMA) wire [1]. Recently, a novel driver device has been presented [2], which simultaneously controls electric power and measures resistance of an SMA wire actuator. This application of a single wire as both actuator and sensor will fully exploit the multifunctional nature of SMA materials and minimize system complexity by avoiding extra sensors. Though the subject is not new [3-6], comprehensive resistance data under controlled conditions for time-resolved and hysteresis-based experiments is not readily available from the literature. A simple experimental setup consisting of a Flexinol wire mounted in series with the tip of a compliant cantilever beam is used to systematically study the SMA behavior. A Labview-based data acquisition system measures actuator displacement and SMA wire stress and resistance and controls the power passed through the SMA actuator wire. The experimental setup is carefully insulated from ambient conditions, as the thermal response of a 50-micron diameter Flexinol wire is extremely sensitive to temperature fluctuation due to convective heat transfer. Actuator performance is reported for a range of actuation frequencies and input power levels. The effect of varying actuator pre-stress is reported as well. All of the experimental data is compared with simulated behavior that is derived from a numerical model for SMA material [7-10].

  1. 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.

  2. 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.

  3. 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.

  4. Shape-Memory-Alloy-Based Deicing System Developed

    Science.gov (United States)

    1996-01-01

    Ice buildup on aircraft leading edge surfaces has historically been a problem. Most conventional deicing systems rely either on surface heating to melt the accreted ice or pneumatic surface inflation to mechanically debond the ice. Deicers that rely solely on surface heating require large amounts of power. Pneumatic deicers usually cannot remove thin layers of ice and lack durability. Thus, there is a need for an advanced, low-power ice protection system. As part of the NASA Small Business and Innovation Research (SBIR) program, Innovative Dynamics, Inc., developed an aircraft deicing system that utilizes the properties of Shape Memory Alloys (SMA). The SMA-based system has achieved promising improvements in energy efficiency and durability over more conventional deicers. When they are thermally activated, SMA materials change shape; this is analogous to a conventional thermal expansion. The thermal input is currently applied via conventional technology, but there are plans to implement a passive thermal input that is supplied from the energy transfer due to the formation of the ice itself. The actively powered deicer was tested in the NASA Lewis Icing Research Tunnel on a powered rotating rig in early 1995. The system showed promise, deicing both rime and glaze ice shapes as thin as 1/8 in. The first prototype SMA deicer reduced power usage by 45 percent over existing electrothermal systems. This prototype system was targeted for rotorcraft system development. However, there are current plans underway to develop a fixed-wing version of the deicer.

  5. Modiolus-hugging intracochlear electrode array with shape memory alloy.

    Science.gov (United States)

    Min, Kyou Sik; Jun, Sang Beom; Lim, Yoon Seob; Park, Se-Ik; Kim, Sung June

    2013-01-01

    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.

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

    Science.gov (United States)

    Min, Kyou Sik; Lim, Yoon Seob; Park, Se-Ik; Kim, Sung June

    2013-01-01

    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. PMID:23762181

  7. MOSFET Switching Circuit Protects Shape Memory Alloy Actuators

    Science.gov (United States)

    Gummin, Mark A.

    2011-01-01

    A small-footprint, full surface-mount-component printed circuit board employs MOSFET (metal-oxide-semiconductor field-effect transistor) power switches to switch high currents from any input power supply from 3 to 30 V. High-force shape memory alloy (SMA) actuators generally require high current (up to 9 A at 28 V) to actuate. SMA wires (the driving element of the actuators) can be quickly overheated if power is not removed at the end of stroke, which can damage the wires. The new analog driver prevents overheating of the SMA wires in an actuator by momentarily removing power when the end limit switch is closed, thereby allowing complex control schemes to be adopted without concern for overheating. Either an integral pushbutton or microprocessor-controlled gate or control line inputs switch current to the actuator until the end switch line goes from logic high to logic low state. Power is then momentarily removed (switched off by the MOSFET). The analog driver is suited to use with nearly any SMA actuator.

  8. 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.

  9. A Gradient-Based Constitutive Model for Shape Memory Alloys

    Science.gov (United States)

    Tabesh, Majid; Boyd, James; Lagoudas, Dimitris

    2017-06-01

    Constitutive models are necessary to design shape memory alloy (SMA) components at nano- and micro-scales in NEMS and MEMS. The behavior of small-scale SMA structures deviates from that of the bulk material. Unfortunately, this response cannot be modeled using conventional constitutive models which lack an intrinsic length scale. At small scales, size effects are often observed along with large gradients in the stress or strain. Therefore, a gradient-based thermodynamically consistent constitutive framework is established. Generalized surface and body forces are assumed to contribute to the free energy as work conjugates to the martensite volume fraction, transformation strain tensor, and their spatial gradients. The rates of evolution of these variables are obtained by invoking the principal of maximum dissipation after assuming a transformation surface, which is a differential equation in space. This approach is compared to the theories that use a configurational force (microforce) balance law. The developed constitutive model includes energetic and dissipative length scales that can be calibrated experimentally. Boundary value problems, including pure bending of SMA beams and simple torsion of SMA cylindrical bars, are solved to demonstrate the capabilities of this model. These problems contain the differential equation for the transformation surface as well as the equilibrium equation and are solved analytically and numerically. The simplest version of the model, containing only the additional gradient of martensite volume fraction, predicts a response with greater transformation hardening for smaller structures.

  10. 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.

  11. Microstructure and thermal expansion properties of invar-type Cu-Zn-Al shape memory alloys

    Science.gov (United States)

    Wang, J. J.; Omori, T.; Sutou, Y.; Kainuma, R.; Ishida, K.

    2004-10-01

    The effects of grain size, volume fraction of the α (fcc) phase in the β (bcc) matrix, and thermal stability on low thermal expansion (LTE) properties of Cu-Zn-Al shape memory (SM) alloys induced by cold rolling were investigated by dilatometry, optical microscopy, differential scanning calorimetry, and electrical conductivity measurements. The alloys with the larger grains showed a superior two-way memory (TWM) effect, wider LTE temperature intervals with excellent thermal stability under 80°C. The α+β two-phase alloys also exhibited a good combination of cold workability and LTE properties. These results suggest that the Cu-Zn-Al alloys with high electrical conductivity of about 20% International Annealed Copper Standard (%IACS) have high potential as a new class of Invar alloys that can be applied in various fields.

  12. Relationship between mechanical property and microstructure of NiTi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    LIU; Mei-rong; GAO; Bao-dong; FENG; Zhao-wei; WANG; Jiang-bo

    2005-01-01

    The relationship between mechanical property and microstructure of NiTi shape memory alloy has been studied. It was founded that with increasing prestrain the memory recovery rate decreased, but the recovery stress and the recovery strain increased first and then decreased. The recovery stress and the recovery strain reached maximum at about 11% prestrain. The TEM(Transmission Electron Microscope) results of the alloy indicated that the microstructures with different prestrain of the alloy had obvious characters. At 9% prestrain, the martensite anamorphosis of the alloy still presented self-cooperation configuration, and some martensites have become thick obvi ously because of tropism. When the prestrain was 11%, the martensite anamorphosis has become completely thick and tropism became consistent. As the prestrain increased to 13%, the microstructures of the alloy have become disordered, the tropism became inconsistent and the interface became blurry.

  13. Shape memory effect in Fe-Mn-Ni-Si-C alloys with low Mn contents

    Energy Technology Data Exchange (ETDEWEB)

    Min, X.H., E-mail: MIN.Xiaohua@nims.go.jp [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Sawaguchi, T.; Ogawa, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Maruyama, T. [Awaji Materia Co., Ltd. 2-3-13, Kanda ogawamachi, Chiyoda, Tokyo 101-0052 (Japan); Yin, F.X. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Tsuzaki, K. [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Ibaraki 305-0047 (Japan)

    2011-06-15

    Highlights: {yields} A class of new Fe-Mn-Ni-Si-C shape memory alloys with low Mn contents has been designed. {yields} A Mn content for the onset of the {alpha}' martensite is less than 13 mass%, and the {epsilon} martensite still exists in the alloy with a 9 mass% Mn. {yields} The shape recovery strain decreases considerably when the Mn content is reduced from 13 to 11 mass%. {yields} The sudden decrease in the shape recovery strain is mainly caused by the formation of {alpha}' martensite. - Abstract: An attempt was made to develop a new Fe-Mn-Si-based shape memory alloy from a Fe-17Mn-6Si-0.3C (mass%) shape memory alloy, which was previously reported to show a superior shape memory effect without any costly training treatment, by lowering its Mn content. The shape memory effect and the phase transformation behavior were investigated for the as-solution treated Fe-(17-2x)Mn-6Si-0.3C-xNi (x = 0, 1, 2, 3, 4) polycrystalline alloys. The shape recovery strain exceeded 2% in the alloys with x = 0-2, which is sufficient for an industrially applicable shape memory effect; however, it suddenly decreased in the alloys between x = 2 and 3 although the significant shape recovery strain still exceeded 1%. In the alloys with x = 3 and 4, X-ray diffraction analysis and transmission electron microscope observation revealed the existence of {alpha}' martensite, which forms at the intersection of the {epsilon} martensite plates and suppresses the crystallographic reversibility of the {gamma} austenite to {epsilon} martensitic transformation.

  14. Potential High-Temperature Shape-Memory-Alloy Actuator Material Identified

    Science.gov (United States)

    Noebe, Ronald D.; Gaydosh, Darrell J.; Biles, Tiffany A.; Garg, Anita

    2005-01-01

    Shape-memory alloys are unique "smart materials" that can be used in a wide variety of adaptive or "intelligent" components. Because of a martensitic solid-state phase transformation in these materials, they can display rather unusual mechanical properties including shape-memory behavior. This phenomenon occurs when the material is deformed at low temperatures (below the martensite finish temperature, Mf) and then heated through the martensite-to-austenite phase transformation. As the material is heated to the austenite finish temperature Af, it is able to recover its predeformed shape. If a bias is applied to the material as it tries to recover its original shape, work can be extracted from the shape-memory alloy as it transforms. Therefore, shape-memory alloys are being considered for compact solid-state actuation devices to replace hydraulic, pneumatic, or motor-driven systems.

  15. Shape memory behavior of single and polycrystalline nickel rich nickel titanium alloys

    Science.gov (United States)

    Kaya, Irfan

    NiTi is the most commonly used shape memory alloy (SMA) and has been widely used for bio-medical, electrical and mechanical applications. Nickel rich NiTi shape memory alloys are coming into prominence due to their distinct superelasticity and shape memory properties as compared to near equi-atomic NiTi shape memory alloys. Besides, their lower density and higher work output than steels makes these alloys an excellent candidate for aerospace and automotive industry. Shape memory properties and phase transformation behavior of high Ni-rich Ni54Ti46 (at.%) polycrystals and Ni-rich Ni 51Ti49 (at.%) single-crystals are determined. Their properties are sensitive to heat treatments that affect the phase transformation behavior of these alloys. Phase transformation properties and microstructure were investigated in aged Ni54Ti46 alloys with differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) to reveal the precipitation characteristics and R-phase formation. It was found that Ni54Ti46 has the ability to exhibit perfect superelasticity under high stress levels (~2 GPa) with 4% total strain after 550°C-3h aging. Stress independent R-phase transformation was found to be responsible for the change in shape memory behavior with stress. The shape memory responses of [001], [011] and [111] oriented Ni 51Ti49 single-crystals alloy were reported under compression to reveal the orientation dependence of their shape memory behavior. It has been found that transformation strain, temperatures and hysteresis, Classius-Clapeyron slopes, critical stress for plastic deformation are highly orientation dependent. The effects of precipitation formation and compressive loading at selected temperatures on the two-way shape memory effect (TWSME) properties of a [111]- oriented Ni51Ti49 shape memory alloy were revealed. Additionally, aligned Ni4Ti3 precipitates were formed in a single crystal of Ni51Ti49 alloy by aging under applied compression stress along the

  16. INFLUENCE OF PROCESSING ON SHAPE MEMORY EFFECT OF Fe-Mn-Si-Ni-C-RE SHAPE MEMORY ALLOY

    Institute of Scientific and Technical Information of China (English)

    N.C. Si; Z.H. Jia; L.B. Qi

    2003-01-01

    Effect of carbon, compound RE, quenching temperature, pre-strain and recovery temperature on shape memory effect (SME) of Fe-Mn-Si-Ni-C-RE shape memory alloy was studied by bent measurement, thermal cycle training, SEM etc. It was shown that the grains of alloys addition with .compound RE became finer and SME increased evidently. SME of the alloy was weakening gradually as carbon content increased under small strain (3%o). But in the condition of large strain (more than 6%), SME of the alloy whose carbon content range from 0.1% to 0.12% showed small decreasing range, especially of alloy with the addition of compound RE. Results were also indicated that SME was improved by increasing quenching temperature (>1000℃). The amount of thermal induced martensite increased and the relative shape recovery ratio could be increased to more than 40% after 3-4 times thermal training. The relative shape recovery ratio decreased evidently depending on rising of pre-strain. Furthermore, because speed of martensite transition was extremely great under higher tempering temperature (more than 450℃), ε→γtransition completed in 1os meanwhile the relative shape recovery ratio of the alloy increased rapidly.

  17. 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.

  18. Solid state amorphisation in binary systems prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, G., E-mail: gemagonz@ivic.v [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of); Sagarzazu, A. [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of); Bonyuet, D. [Instituto de Investigacion en Biomedicina y Ciencias Aplicadas, Universidad de Oriente, Cumana (Venezuela, Bolivarian Republic of); D' Angelo, L. [UNEXPO, Universidad Experimental Politecnica Luis Caballero Mejias, Dpto. Ing. Mecanica (Venezuela, Bolivarian Republic of); Villalba, R. [Lab. Ciencia e Ing. de Materiales, Instituto Venezolano de Investigaciones Cientificas, IVIC, Caracas (Venezuela, Bolivarian Republic of)

    2009-08-26

    In the present work a detailed study of amorphisation in different systems prepared by mechanical alloying under the same experimental conditions was carried out, milling up to 50 and 100 h in some cases. The systems studied were: AlTi, AlNi, AlFe, FeNi, FeCo, NiMo, NiW, NiCo, MoW, CoMo. These systems were chosen to study the effect of Al-transition metal, transition metal-transition metal and also systems with large and small negative heat of mixing, different and similar crystal structures, atomic sizes and diffusion coefficients. Calculations based on the Miedema model for alloy formation and amorphisation on all the alloys studied were performed. The experimental results from X-ray diffraction and transmission electron microscopy showed that the systems based on Fe (FeNi, FeCo and FeAl) did not amorphised, even after milling for 100 h, and formed a stable solid solution with a nanometric grain size of 7 nm. The systems NiMo, NiW, MoW and CoMo (systems with small negative heat of mixing), showed amorphisation after 50 h of milling. NiAl and TiAl form an intermediate amorphous phase after around 20 h of milling and with further milling they recrystallize into a fcc solid solution. Agreement between the theoretical calculations based on the Miedema model and the experimental results was found in most of the systems.

  19. Effect of heat treatment on Fe-B-Si-Nb alloy powder prepared by mechanical alloying

    Directory of Open Access Journals (Sweden)

    Rodrigo Estevam Coelho

    2005-06-01

    Full Text Available The effect of heat treatment on crystallization behavior of Fe73.5B15Si10Nb1.5 alloy powder prepared by mechanical alloying was studied. The powder samples were prepared by mechanical alloying (MA and for different milling times (1, 5, 25, 70 and 100 hours. Crystalline powders of iron, boron, silicon and niobium were sealed with tungsten carbide balls in a cylindrical vial under nitrogen atmosphere. The ball-to-powder weight ratio was 20 to 1. A Fritsch Pulverizette 5 planetary ball mill was used for MA the powders at room temperature and at 250 rpm. To study the microstructural evolution, a small amount of powder was collected after different milling times and examined by X-ray diffraction, using CuKalpha radiation (lambda = 0.15418 nm. The crystallization behavior was studied by differential thermal analysis, from 25 up to 1000 °C at a heating rate of 25 °C min-1.

  20. Improving Robustness of Tuned Vibration Absorbers Using Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Mohammad H. Elahinia

    2005-01-01

    Full Text Available A conventional passive tuned vibration absorber (TVA is effective when it is precisely tuned to the frequency of a vibration mode; otherwise, it may amplify the vibrations of the primary system. In many applications, the frequency often changes over time. For example, adding or subtracting external mass on the existing primary system results in changes in the system’s natural frequency. The frequency changes of the primary system can significantly degrade the performance of TVA. To cope with this problem, many alternative TVAs (such as semiactive, adaptive, and active TVAs have been studied. As another alternative, this paper investigates the use of Shape Memory Alloys (SMAs in passive TVAs in order to improve the robustness of the TVAs subject to mass change in the primary system. The proposed SMA-TVA employs SMA wires, which exhibit variable stiffness, as the spring element of the TVA. This allows us to tune effective stiffness of the TVA to adapt to the changes in the primary system's natural frequency. The simulation model, presented in this paper, contains the dynamics of the TVA along with the SMA wire model that includes phase transformation, heat transfer, and the constitutive relations. Additionally, a PID controller is included for regulating the applied voltage to the SMA wires in order to maintain the desired stiffness. The robustness analysis is then performed on both the SMA-TVA and the equivalent passive TVA. For our robustness analysis, the mass of the primary system is varied by ± 30% of its nominal mass. The simulation results show that the SMA-TVA is more robust than the equivalent passive TVA in reducing peak vibrations in the primary system subject to change of its mass.

  1. Thermoelectric control of shape memory alloy microactuators: a thermal model

    Science.gov (United States)

    Abadie, J.; Chaillet, Nicolas; Lexcellent, Christian; Bourjault, Alain

    1999-06-01

    Microtechnologies and microsystems engineering use new active materials. These materials are interesting to realize microactuators and microsensors. In this category of materials, Shape Memory Alloys (SMA) are good candidates for microactuation. SMA wires, or thin plates, can be used as active material in microfingers. These microstructures are able to provide very important forces, but have low dynamic response, especially for cooling, in confined environment. The control of the SMA phase transformations, and then the mechanical power generation, is made by the temperature. The Joule effect is an easy and efficiency way to heat the SMA wires, but cooling is not so easy. The dynamic response of the actuator depends on cooling capabilities. The thermal convection and conduction are the traditional ways to cool the SMA, but have limitations for microsystems. We are looking for a reversible way of heating and cooling SMA microactuators, based on the thermoelectric effects. Using Peltier effect, a positive or a negative electrical courant is able to pump or produce heat, in the SMA actuator. A physical model based on thermal exchanges between a Nickel/Titanium (NiTi) SMA, and Bismuth/Telluride (Te3Bi2) thermoelectric material has been developed. For simulation, we use a numerical resolution of our model, with finite elements, which takes into account the Peltier effect, the Joule effect, the convection, the conduction and the phase transformation of the SMA. We have also developed the corresponding experimental system, with two thermoelectric junctions, where the SMA actuator is one of the element of each junction. In this paper, the physical model and its numerical resolution are given, the experimental system used to validate the model is described, and experimental results are shown.

  2. Improved Damage Resistant Composite Materials Incorporating Shape Memory Alloys

    Science.gov (United States)

    Paine, Jeffrey S. N.; Rogers, Craig A.

    1996-01-01

    Metallic shape memory alloys (SMA) such as nitinol have unique shape recovery behavior and mechanical properties associated with a material phase change that have been used in a variety of sensing and actuation applications. Recent studies have shown that integrating nitinol-SMA actuators into composite materials increases the composite material's functionality. Hybrid composites of conventional graphite/epoxy or glass/epoxy and nitinol-SMA elements can perform functions in applications where monolithic composites perform inadequately. One such application is the use of hybrid composites to function both in load bearing and armor capacities. While monolithic composites with high strength-to-weight ratios function efficiently as loadbearing structures, because of their brittle nature, impact loading can cause significant catastrophic damage. Initial composite failure modes such as delamination and matrix cracking dissipate some impact energy, but when stress exceeds the composite's ultimate strength, fiber fracture and material perforation become dominant. One of the few methods that has been developed to reduce material perforation is hybridizing polymer matrix composites with tough kevlar or high modulus polyethynylene plies. The tough fibers increase the impact resistance and the stiffer and stronger graphite fibers carry the majority of the load. Similarly, by adding nitinol-SMA elements that absorb impact energy through the stress-induced martensitic phase transformation, the composites' impact perforation resistance can be greatly enhanced. The results of drop-weight and high velocity gas-gun impact testing of various composite materials will be presented. The results demonstrate that hybridizing composites with nitinol-SMA elements significantly increases perforation resistance compared to other traditional toughening elements. Inspection of the composite specimens at various stages of perforation by optical microscope illustrates the mechanisms by which

  3. Cyclic response of shape memory alloy smart composite beams

    Science.gov (United States)

    Friend, Clifford M.; Morgan, Neil B.

    1994-09-01

    'Smart' structure are an emerging technology which will provide the possibility of engineering structures with enhanced functionality for a wide range of applications. In most current Smart Structural Concepts a mechatronic or 'Frankenstein' approach is adopted where separate sensors, signal processing and actuators are 'bolted-together' to produce a 'Smart' system response. In the majority of these concepts the sensors and actuators are integrated within the host structure itself, and many of the sensor and actuator materials are familiar from other more conventional sensing/actuation applications. Amongst the materials used/proposed for actuators are Shape- Memory Alloys (SMAs) since these materials offer a range of attractive properties, including the possibility of high strain/stress actuation. The literature-base on the integration of SMA actuators into composite structures is not extensive. However, their use has been investigated for vibration [1], acoustic radiation [1,2], damage [3], buckling [1,2], and shape [1] control. An interesting feature of this work has been a heavy bias towards modelling, with only limited attempts to experimentally verify the calculated results. Previous work has also failed to produce a systematic database on one other key issue. This is the durability of SPA hybrid composites. The present work was therefore undertaken to provide a preliminary appraisal of the durability issues associated with the use of SMA hybrid composites. This work addressed a number of issues including (i) the effect of actuator fraction on strain outputs, (ii) the effect of actuator fraction and maximum strain on the cyclic stability of shape changes, and (iii) the effect of these variables on damage accumulation within the hybrid structures.

  4. Synthesis, characterization, and microwave absorption properties of Fe-40 wt%Ni alloy prepared by mechanical alloying and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jun [College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China); Feng Yongbao, E-mail: fengyongbao@163.com [College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China); Qiu Tai [College of Materials Science and Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009 (China)

    2011-12-15

    Fe-40 wt%Ni alloys with granular shape and flake shape were prepared by a mechanical alloying (MA) and annealing method. The phase composition and morphology of the FeNi alloys, electromagnetic parameters, and microwave absorbing properties of the silicone rubber composite absorbers filled with the as-prepared FeNi alloy particles were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and vector network analyzer. The XRD results indicate that the crystalline structures of the Fe-40 wt%Ni alloys prepared by both one-step and two-step MA processes are face-centered cubic (fcc) Ni (Fe) solid solutions, and the structures can be retained after annealing at 600 deg. C for 2 h. SEM images show that the FeNi alloy powders for one-step process have a granular shape; however the particles turned into flake form when they were sequentially milled with absolute ethyl alcohol. With the increase in thickness of composite absorber, the reflection loss (RL) decreases, and the peak for minimum reflection loss shifts towards the lower frequency range. Compared to the absorbers filled with the granular FeNi alloy, the absorbers filled with flaky FeNi alloys possess higher complex permittivities and permeabilities and have a lower RL and peak frequency under the same thickness. Microwave absorbing materials with a low reflection loss peak in the range of 1-4 GHz are obtained, and their microwave absorbing properties can be adjustable by changing their thicknesses. - Highlights: > We prepare face-centered cubic (FCC) Ni (Fe) solid solutions by mechanical alloying and annealing. > Shape of FeNi alloy powder changes from granular to flaky after wet-milling. > Absorbers containing flaky FeNi alloys possess higher electromagnetic parameters. > MAMs with low reflection loss peak in the range of 1-4 GHz are obtained. > Microwave absorbing properties can be adjustable by modifying the thickness of the absorbers.

  5. 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.

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

    Science.gov (United States)

    Li, Weiguo; Shen, Xueliang; Peng, Xianghe

    2014-01-20

    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.

  7. Effect of heat treatment on transformation behavior of Ti-Ni-V shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    He Zhirong, E-mail: hezhirong01@163.com [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China); Liu Manqian [School of Materials Science and Engineering, Shaanxi University of Technology, Hanzhong 723003 (China)

    2011-08-25

    Highlights: {yields} New shape memory alloy (SMA) - Ti-50.8Ni-0.5V SMA. {yields} The evolution laws of transformation types of annealed Ti-50.8Ni-0.5V SMA. {yields} The evolution laws of transformation types of aged Ti-50.8Ni-0.5V SMA. {yields} The effect laws of annealing on transformation temperature and hysteresis of the alloy. {yields} The effect laws of aging on transformation temperature and hysterises of the alloy. - Abstract: Effects of annealing and aging processes on the transformation behaviors of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of differential scanning calorimetry (DSC). The A {yields} R/R {yields} A (A - parent phase, R - R phase) type one-stage reversible transformation occurs in 350-400 deg. C annealed alloy, the A {yields} R {yields} M/M {yields} R {yields} A (M - martensite) type two-stage transformation occurs in 450-500 deg. C annealed alloy, the A {yields} R {yields} M/M {yields} A type transformation occurs in 550 deg. C annealed alloy, and A {yields} M/M {yields} A type transformation occurs in the alloy annealed at above 600 deg. C upon cooling/heating. The transformation type of 300 deg. C aged alloy is A {yields} R/R {yields} A, and that of 500 deg. C aged alloy is A {yields} R {yields} M/M {yields} A, while that of 400 deg. C aged alloy changes from A {yields} R/R {yields} A to A {yields} R {yields} M/M {yields} R {yields} A with increasing aging time. The effects of annealing and aging processes on R and M transformation temperatures and temperature hysteresis are given. The influence of annealing and aging temperature on transformation behaviors is stronger than that of annealing and aging time.

  8. Formation Mechanism of Curved Martensite Structures in Cu-based Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The curved martensite structures have been observed in CuZnAl-based shape memory alloys by both transmission electron microscope and optical microscope. It was found that the curved martensite structures observed in as-solution treated, as-aged and as-trained alloys usually occurred around dislocation tangles or precipitate, at the plate boundary or grain boundary, and when the growing plates collided with each other or alternate mutually.

  9. The Effects of Grain Size on the Martensitic Transformation in Copper-Zinc-Aluminum Shape Memory Alloys.

    Science.gov (United States)

    1982-12-01

    production or nearly so. In the medical arts these alloys are being exploited for their SME properties as orthodontic appliances, intercranial aneurism...treatment is applicable to the Cu-Zn-Al alloys. 60 LIST OF REFERENCES 1. Wayman, C. M., "Some Applications of Shape Memory Alloys," Journal of Metals, pp

  10. Corrosion resistance of benzotriazole passivated Cu-Zn-Al shape memory alloy in artificial Ringer's solution

    Institute of Scientific and Technical Information of China (English)

    LIANG Chenghao; CHEN Bangyi; CHEN Wan; WANG Hua

    2005-01-01

    The corrosion resistance of the Cu-Zn-Al shape memory alloy passivated by benzotriazole was investigated by salt spraying test and electrochemical methods in artificial Ringer's solution. The results showed that after benzotriazole passivation, the corrosion resistance of the Cu-Zn-Al shape memory alloy was improved evidently. The anodic polarization current density of the passivated alloy decreased, the mass loss reduced, the anodic passivation accelerated, the anodic active dissolution was inhibited effectively, and the surface tarnishing was restrained. Infrared reflection spectrum test showed that Cu(Ⅰ)-benzoaiazole or Cu(Ⅱ)-benzotriazole complex layer was formed on the surface of the Cu-Zn-Al shape memory alloy after passivation. This layer appeared plane, well adhesion, and presented homogeneous golden metallic luster. The corrosion resistance of the Cu-Zn-Al shape memory alloy passivated by benzotriazole is improved for the formation of an electrochemical stable baffle layer on passivated surface. This layer separates the metal substrate from the outside corrosion medium effectively and retards the corrosion process of dezincification.

  11. A free-cutting and ductile CuAlMnZnTiB shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    刘娜; 李周; 李灵; 刘斌; 李擎天; 徐根应

    2015-01-01

    The mechanical properties and cutting performance of the designed CuAlMnZnTiB shape memory alloy were studied by tensile test and microstructure observation. Using X-ray diffractometry, differential scanning calorimetry (DSC) and semi-quantitative shape memory effect test, the microstructure and shape memory effect were analyzed. It is found that lots ofβ phase and fewα phase are formed in the quenching of Cu-7.5Al-9.7Mn-3.4Zn-0.3Ti-0.14B (mass fraction, %) alloy, a great deal of martensite and fewα phase are formed in the aging alloy, while the annealing alloy is composed of a great deal ofα phase and fewβ phase. The tensile strength and elongation of the annealed alloy are 649 MPa and 17.1%, respectively. Some tiny and dispersion distributed second phase particles are generated in Ti and B precipitates, greatly improving the alloy machinability.

  12. Topology Optimization of Shape Memory Alloy Actuators using Element Connectivity Parameterization

    DEFF Research Database (Denmark)

    Langelaar, Matthijs; Yoon, Gil Ho; Kim, Yoon Young

    2005-01-01

    This paper presents the first application of topology optimization to the design of shape memory alloy actuators. Shape memory alloys (SMA’s) exhibit strongly nonlinear, temperature-dependent material behavior. The complexity in the constitutive behavior makes the topology design of SMA structures......-independent constitutive model of SMA’s is employed which allows efficient adjoint sensitivity analysis. The effectiveness of the proposed technique is illustrated by several numerical examples.In terms of computation time, the I-ECP method, a newly-developed version of ECP, is much more efficient because the degrees...

  13. 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...... are compared with numerical simulations obtained from a constitutive model with internal constraints employed to describe the thermomechanical behavior of SMAs. The idea is to evaluate if the numerical simulations are within the uncertainty range of the experimental data. Parametric analysis is also developed...

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

    OpenAIRE

    Abreu G.; Maestá M.; Faria C.; Lopes V.

    2014-01-01

    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 o...

  15. 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...... resulting in 1.3% residual standard deviation relative to the full range force. Compared to the validation data set, the errors are below 10% relative to the full range of the complex modulus. Uncertainty analysis of the model parameters using a Markov chain Monte Carlo technique shows low to high parameter...

  16. A Model to Describe the Magnetomechanical Behavior of Martensite in Magnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Zaoyang Guo

    2014-01-01

    Full Text Available A model to describe the constitutive behavior of magnetic shape memory alloy composed with pure martensite is proposed based on the analysis of variants reorientation. A hyperbolic tangent expression is given to describe the variants transition during magnetic and mechanical loading process. The main features of magnetic shape memory alloy, such as pseudoelastic and partially pseudoelastic behavior as well as minor hysteretic loops, can be successfully replicated with the proposed model. A good agreement is achieved between calculated results and experimental data for NiMnGa single crystal.

  17. Microstructural Analysis of Ti-Based Shape Memory Alloys Following the Electrochemical Corrosion in Artificial Saliva

    Science.gov (United States)

    Baciu, C.; Baciu, E. R.; Cimpoeșu, R.; Levente, C. G.; Bosinceanu, D. G.; Baciu, M.; Bejinariu, C.

    2017-06-01

    The investigations carried out aimed to highlight the structural modifications occurred in the Ti-based shape memory alloys subject to electrocorrosion in Afnor artificial saliva. The behavior to corrosion was highlighted by fast electrochemical tests, mainly by dynamic potentiometry. From the microstructural analysis we noticed that the specimens of the two Ti-based shape memory alloys show traces of “pitting” corrosion on their surface of diverse sizes, a fact that will raise issues in terms of cytotoxicity due to the corrosion products released.

  18. Microstructures and properties of welded joint of TiNi shape memory alloy and stainless steel

    Institute of Scientific and Technical Information of China (English)

    邱小明; 孙大谦; 李明高; 刘卫红

    2004-01-01

    The fracture characteristics of the joint were analyzed by means of scanning electron microscope(SEM).Microstructures of the joint were examined by means of optical microscope, SEM and an image analyzer. The results show that the tensile strength of the inhomogeneous joint of TiNi shape memory alloy and stainless steel is lower than that of the homogeneous joint and a plastic field appears in the heat affected zone on the side of TiNi shape memory alloy. Because TiNi shape memory alloy and stainless steel melted, a brittle as-cast structure was formed in the weld. The tensile strength and the shape memory effect of the inhomogeneous joint are strongly influenced by the changes of composition and structure of the joint. Measures should be taken to reduce the base metal melting and prevent the weld metal from the invasion by O for improving the properties of the TiNi shape memory alloy and stainless steel inhomogeneous joint.

  19. Effects of Ta Addition on NiTi Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The effect of Ta addition on the martensitic transformation characteristics and the X-ray visibility on NiTi shape memory alloy have been studied in (Ni51Ti49)1-xTax system. It was found that the transformation temperatures of the Ni51Ti49 binary alloy increased drastically by an addition of 0~4 at. pct Ta, but only slightly when the concentration exceeded 4 at. pct; the addition of Ta greatly decreases the sensitivity of the martensitic transformations to the variation in the Ni-Ti ratio. The addition of Ta to the NiTi binary alloy can improve its X-ray visibility.

  20. Martensitic transformation and related magnetic effects in Ni-Mn-based ferromagnetic shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    Wang Dun-Hui; Han Zhi-Da; Xuan Hai-Cheng; Ma Sheng-Can; Chen Shui-Yuan; Zhang Cheng-Liang; Du You-Wei

    2013-01-01

    Ferromagnetic shape memory alloys,which undergo the martensitic transformation,are famous multifunctional materials.They exhibit many interesting magnetic properties around the martensitic transformation temperature due to the strong coupling between magnetism and structure.Tuning magnetic phase transition and optimizing the magnetic effects in these alloys are of great importance.In this paper,the regulation of martensitic transformation and the investigation of some related magnetic effects in Ni-Mn-based alloys are reviewed based on our recent research results.

  1. Phase Transformation and Thermal Stability of Aged Ti-Ni-Hf High Temperature Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    Xianglong MENG; Wei CAI; K.T.Lau; L.M.Zhou; Liancheng ZHAO

    2006-01-01

    The use of Ni-rich TiNiHf alloys as high temperature shape memory alloys(SMAs)through aging has been presented. For Ni-rich Ti80-xNixHf20 alloys, their phase transformation temperatures are averagely increased more than 100 K by aging at 823 K for 2 h. Especially for the alloys with Ni-content of 50.4 at. pct and 50.6 at. pct, their martensitic transformation start temperatures(Ms)are more than 473 K after aging. TEM observation confirmed that some fine particles precipitate from the matrix during aging. The aged Ni-rich TiNiHf SMAs show the better thermal stability of phase transformation temperatures than the solutiontreated TiNiHf alloys. The fine particles precipitated during aging should be responsible for the increase of phase transformation temperatures and its high stability.

  2. Microstructure and Shape Memory Effect of Cu-26.1Zn-4.8Al Alloy

    Institute of Scientific and Technical Information of China (English)

    CHENG Xiaomin; HUANG Feng; LI Na; WU Xingwen

    2008-01-01

    The influence of processing parameters on the microstructure and shape memory effect of Cu-26.1Zn-4.8Al alloy was investigated. The treated specimens were characterized by metallography, X-ray diffraction (XRD) and transmission electron microscopy (TEM) to explain the mechanism of shape memory effect in Cu-26.1Zn-4.8Al alloy. The results reveal that the shape memory effect is markedly increased by appropriate quenching and ageing process. XRD shows that γ-phase precipitates from martensite when aged at higher temperature and γ precipitates impair the shape memory effect. TEM analysis indicate that the substructure of plate-like martensite consists of twins and stacking faults.

  3. Fixation of external drainage device with injectable shape-memory alloy clips.

    Science.gov (United States)

    Olson, Jeffrey L; Erlanger, Michael

    2013-09-01

    To describe a novel surgical technique and novel surgical instrumentation for fixating an extraocular drainage device used for glaucoma-filtering surgery. The technique was performed in a laboratory setting using ex-vivo porcine eyes. We describe the surgical technique of using injectable, 25-gauge shape-memory clip system to fixate an Ahmed drainage device. The use of an injectable, shape-memory alloy clip provides the advantages of rapid, easy deployment and decreased risk of late suture failure. Importantly, the injectable, shape-memory clips can be used in surgical situations where suturing is difficult and time intensive, such as those encountered during glaucoma drainage device placement. The use of an injectable, shape-memory alloy clip is a promising new surgical tool and technique for fixating an extraocular drainage device used for glaucoma surgery.

  4. Functional and structural fatigue of titanium tantalum high temperature shape memory alloys (HT SMAs)

    Energy Technology Data Exchange (ETDEWEB)

    Niendorf, T., E-mail: Thomas.Niendorf@iwt.tu-freiberg.de [Institute of Materials Engineering, Technische Universität Bergakademie Freiberg, 09599 Freiberg (Germany); Krooß, P. [Lehrstuhl für Werkstoffkunde (Materials Science), University of Paderborn, 33098 Paderborn (Germany); Batyrsina, E. [Institut für Werkstoffkunde (Materials Science), Leibniz Universität Hannover, 30823 Garbsen (Germany); Paulsen, A.; Motemani, Y.; Ludwig, A.; Buenconsejo, P.; Frenzel, J.; Eggeler, G. [Institut für Werkstoffe, Ruhr-Universität Bochum, 44801 Bochum (Germany); Maier, H.J. [Institut für Werkstoffkunde (Materials Science), Leibniz Universität Hannover, 30823 Garbsen (Germany)

    2015-01-03

    Due to their high work output and good mechanical properties, actuators made from shape memory alloys (SMAs) are used in numerous applications. Unfortunately, SMAs such as nickel–titanium (Ni–Ti) can only be employed at temperatures up to about 100 °C. Lately, high-temperature shape memory alloys (HT SMAs) have been introduced to overcome this limitation. Ternary systems based on Ni–Ti have been intensively characterized and alloys are available that can operate at elevated temperatures. However, these alloys either contain substantial amounts of expensive noble elements like platinum and palladium, or the materials are brittle. The titanium–tantalum (Ti–Ta) system has been developed to overcome these issues. Binary Ti–Ta provides relatively high M{sub S} temperature combined with excellent workability, but it suffers from fast cyclic degradation. By alloying with third elements this drawback can be overcome: The ternary Ti–Ta–Al alloy shows overall promising properties as will be shown in the present work. In-situ thermo-mechanical cycling experiments were conducted and allowed for evaluation of the factors affecting the functional and structural fatigue of this alloy. Functional fatigue is dominated by ω-phase evolution, while structural fatigue is triggered by an interplay of ω-phase induced embrittlement and deformation constraints imposed by unsuitable texture. In addition, a concept for fatigue life extension proposed very recently for binary Ti–Ta, is demonstrated to be also applicable for the ternary Ti–Ta–Al.

  5. EFFECTS OF HEAT TREATMENT ON THE MICROSTRUCTURE OF Cu-Zn-Al (RE) SHAPE MEMORY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    N.C.Si; S.C.Sun

    2001-01-01

    The effects of heat treatment on the Cu-Zn-Al shape memory alloys with mixed REwere researched with the help of X-ray diffraction and transmission electron micro-scope (TEM).The results show that the shape memory alloys with martensite can beproduced by adding mixed RE and heat treatment processes holding at 820C -880Cfor 15min,quenching into oil,aging at 150C for 15min,and then holding in waterat 50C for 10min.The alloys have the lowest transformation thermal hysteresis.Among the four experimental heat treatment processes the gradationally quenchingmakes the alloy have the highest transformation temperature and quenching into oilor water at room temperature makes the alloy have the largest thermal hysteresis.Mi-crostructure examination shows that aging at 2000C could destroy the substructuresin lathy martensites in the alloy and form a lot of dislocations,and aging at 250℃could cause the bainite transformation in the alloy.

  6. Magnetic Properties and Phase Diagram of Ni50Mn_{50-x}Ga_{x/2}In_{x/2} Magnetic Shape Memory Alloys

    Science.gov (United States)

    Xu, Xiao; Yoshida, Yasuki; Omori, Toshihiro; Kanomata, Takeshi; Kainuma, Ryosuke

    2016-12-01

    Ni50Mn50- x Ga x/2In x/2 magnetic shape memory alloys were systematically prepared, and the magnetic properties as well as the phase diagram, including atomic ordering, martensitic and magnetic transitions, were investigated. The B2- L21 order-disorder transformation showed a parabolic-like curve against the Ga+In composition. The martensitic transformation temperature was found to decrease with increasing Ga+In composition and to slightly bend downwards below the Curie temperature of the parent phase. Spontaneous magnetization was investigated for both parent and martensite alloys. The magnetism of martensite phase was found to show glassy magnetic behaviors by thermomagnetization and AC susceptibility measurements.

  7. Effect of Training on Two-way Shape Memory Effect and Its Stability in a Ti-Ni-Hf High Temperature Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Xianglong MENG; Wei CAI; K.T. LAU; L.M. ZHOU; Liancheng ZHAO

    2003-01-01

    The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36Ni49Hf15 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.

  8. Orthopedic implant prepared by shape memory alloy in treatment of violence-induced bone injury and fracture healing%形状记忆合金材料制备的骨科内植物治疗暴力骨损伤与骨折愈合

    Institute of Scientific and Technical Information of China (English)

    原黎君

    2012-01-01

    BACKGROUND: With the elevation of opposability and intensity of athletic competition, participants were affected by varied internal and external violence. Shape memory alloy, as a novel internal fixation material in the department of orthopedics, has obtained good outcomes in clinical therapy.OBJECTIVE: To introduce therapeutic mechanisms of shape memory alloy, and to analyze the fracture-related outcomes. METHODS: The author retrieved China National Knowledge Infrastructure from 1980 to 2011 and PubMed from 1980 to 2011. The key words were "memory alloy, bone, internal fixation, treatment". The mechanism and outcomes of shape memory alloy on fracture were summarized.RESULTS AND CONCLUSION: A total of 138 articles were retrieved, and 29 articles were included in accordance with inclusion criteria and exclusion criteria. The therapeutic mechanisms of shape memory alloy were summarized, including material feature, working principle and clinical application of different instruments, clinical therapeutic measures and outcomes of fracture at different sites. Results indicated that shape memory alloy has many advantages of bone internal fixation materials, is a novel perfect material, but still has a certain operation risk. It is important to choose specialized internal fixation material for therapeutic outcomes in accordance with the anatomic morphological features of fracture site, requirement of special functions, shape, size and metal property of internal fixation material.%背景:随着体育竞赛对抗性和竞争激烈性的提高,运动参与者受内外部暴力影响的因素越来越多.而形状记忆合金作为一种新型的骨科内固定材料在临床治疗方面取得了良好效果.目的:介绍形状记忆合金的治疗机制,并对骨折相关疗效进行阐述.方法:由第一作者用计算机检索中国期刊全文数据库(CNKI:1980/2011)和pubMed (1980/2011)数据库,检索词分别为"记忆合金,骨,内固定,治疗"和"memory alloy

  9. A new look at biomedical Ti-based shape memory alloys.

    Science.gov (United States)

    Biesiekierski, Arne; Wang, James; Gepreel, Mohamed Abdel-Hady; Wen, Cuie

    2012-05-01

    Shape memory alloys (SMAs) are materials that exhibit a distinct thermomechanical coupling, one that gives rise to a wide variety of applications across a broad range of fields. One of the most successful roles is in the construction of novel medical implants. Unfortunately, concerns have been raised about the biocompatibility of the most popular SMA, nitinol (NiTi), due to the known toxic, allergenic and carcinogenic properties of nickel. Given the unique capabilities of SMAs, it is apparent that there is a need for a new class of alloys - alloys that exhibit the full range of shape memory abilities yet are also free of any undesirable side effects. This article reviews the literature surrounding SMAs and identifies the metals Ti, Au, Sn, Ta, Nb, Ru and Zr as candidates for the production of thoroughly biocompatible SMAs. Hf and Re are also promising, though more research is necessary before a definitive statement can be made. Further, the Ti-(Ta,Nb)-(Zr,Hf) alloy system is particularly suited for orthopaedic implants due to a reduced Young's modulus. However, concerns over this system's shape memory properties exist, and should be taken into consideration. Alternate alloy systems that demonstrate higher bulk moduli may still be considered, however, if they are formed into a porous structure. Due to the nature of the alloying components, blended elemental powder metallurgy is recommended for the manufacture of these alloys, particularly due to the ease with which it may be adapted to the formation of porous alloys. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  10. Microstructure, Compression Property and Shape Memory Effect of Equiatomic TaRu High Temperature Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Xin GAO; Yufeng ZHENG; Wei CAI; Su ZHANG; Liancheng ZHAO

    2004-01-01

    The microstructure, phase transformation, compression property and strain recovery characteristics of equiatomic TaRu super high temperature shape memory alloy have been studied by optical microscope, XRD, DTA, compression tests and TEM observations. When cooling the alloy specimen from high temperature to the room temperature,β(parent phase)→β′(interphase) →β"(martensite) two-step phase transformations occur. The microstructure at room temperature show regularly arranged band morphology, with the monoclinic crystal structure. The twinning relationship between the martensite bands is determined to be (101) of Type I. Reorientation and coalescence of the martensite bands inside the variant happened during compression at room temperature. The β′→β reversible transformation contributes mainly the shape memory effect, with the maximum completely recovery strain of 2%.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tobe, H. [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Kim, H.Y., E-mail: heeykim@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Inamura, T.; Hosoda, H. [Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Nam, T.H. [School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Miyazaki, S., E-mail: miyazaki@ims.tsukuba.ac.jp [Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of); Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia)

    2013-11-15

    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.

  12. Accumulative Roll Bonding and Post-Deformation Annealing of Cu-Al-Mn Shape Memory Alloy

    Science.gov (United States)

    Moghaddam, Ahmad Ostovari; Ketabchi, Mostafa; Afrasiabi, Yaser

    2014-12-01

    Accumulative roll bonding is a severe plastic deformation process used for Cu-Al-Mn shape memory alloy. The main purpose of this study is to investigate the possibility of grain refinement of Cu-9.5Al-8.2Mn (in wt.%) shape memory alloy using accumulative roll bonding and post-deformation annealing. The alloy was successfully subjected to 5 passes of accumulative roll bonding at 600 °C. The microstructure, properties as well as post-deformation annealing of this alloy were investigated by optical microscopy, scanning electron microscopy, x-ray diffraction, differential scanning calorimeter, and bend and tensile testing. The results showed that after 5 passes of ARB at 600 °C, specimens possessed α + β microstructure with the refined grains, but martensite phases and consequently shape memory effect completely disappeared. Post-deformation annealing was carried out at 700 °C, and the martensite phase with the smallest grain size (less than 40 μm) was obtained after 150 s of annealing at 700 °C. It was found that after 5 passes of ARB and post-deformation annealing, the stability of SME during thermal cycling improved. Also, tensile properties of alloys significantly improved after post-deformation annealing.

  13. 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.

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

    Science.gov (United States)

    Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard

    2015-10-01

    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.

  15. 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.

  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

    2014-01-01

    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 fi

  17. A high-rate shape memory alloy actuator for aerodynamic load control on wind turbines

    NARCIS (Netherlands)

    Lara-Quintanilla, A.; Hulskamp, A.W.; Bersee, H.E.N.

    2013-01-01

    This paper discusses the development of a high rate shape memory alloy (SMA) driven actuator. The concept of the actuator was developed to act as aerodynamic load control surface on wind turbines. It was designed as a plate or beam-like structure with prestrained SMA wires embedded off its neutral a

  18. Multistage Development of Müller-Achenbach model for Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Simin A. Oshkovr

    2008-01-01

    Full Text Available This research focused on the conceptual development of constitutive Müller-Achenbach model and proceeds to construct a model based on phase transition under changing temperature and load for variants of martensite in shape memory alloy CuAlNi (Copper-aluminum-nickel. Problem statement: Motivation of this research is rare information of a variant of martensite phase (M++ and prediction of the shape recovery of shape memory alloy in this stage of transformation. Approach: The mathematical equations proposed a prediction of stability of Austenite phases and extend it to multistage martensitic phase transformation. These phase transformations occurred by loading on the material. Equations described free energy landscape in CuAlNi shape memory alloys at low (260K and high temperature (440K. The model evaluated the free energy due to the phase transformation between the austenite and multistage martensitic structures. Results: Results for M++ phase showed decrease in temperature from 440K to 260K presented decrease in stress approximately from 1 kN to 0.4kN and free energy from 5 kJ/kg to 0.1 kJ/kg. Equations have been solved and plotted by software programmed in MATLAB. Conclusions/Recommendations: The model which has derived focused on homogeneous shape memory alloys, but future performance requirements will most likely be met with heterogeneous materials. Therefore, simulation models for heterogeneous materials must be developed.

  19. DSC-Analysis of thermomechanically treated TiNi shape memory alloy

    NARCIS (Netherlands)

    Beyer, J.; Besselink, P.A.; Aartsen, A.J.

    1985-01-01

    The martensitic transformation behaviour, after thermomechanical treatment of the TiNi-alloy with two-way shape memory, have been studied by differential scanning calorimetry. The results are correlated with electrical resistivity and electron microscopical observations. One heating and cooling cycl

  20. Study of Friction at the Mesoscale using Nitinol Shape Memory Alloy

    CERN Document Server

    Peters, R D

    2003-01-01

    Elastic and dissipative properties of a NiTi shape memory alloy have been studied in both the martensite and austenite phases, using the free-decay of a vibrating Nitinol wire. The influence of air was estimated from a martensite measurement in vacuum.

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

    DEFF Research Database (Denmark)

    Karagiannis, Dimitrios; Stamatelos, Dimtrios; Kappatos, Vassilios;

    2016-01-01

    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...

  2. Development of a Flapping Wing Design Incorporating Shape Memory Alloy Actuation

    Science.gov (United States)

    2010-03-01

    Hong Wang , Chen-Hsien Fan. “Optimal Design of Rotary Manipulators Using Shape Memory Alloy Wire Actuated Flexures,” Sensors & Actuators A: Physical... Chih -Ming Ho. “Unsteady Aerodynamics and Flow Control for Flapping Wing Flyers,” Progress in Aerospace Sciences, 39: 635-681 (November 2003

  3. 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

  4. Preparation and characterization of electroplated amorphous gold-nickel alloy film for electrical contact applications

    Energy Technology Data Exchange (ETDEWEB)

    Togasaki, Norihiro [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Okinaka, Yutaka [Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Homma, Takayuki [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Osaka, Tetsuya [Department of Applied Chemistry, Waseda University, Okubo, Shinjuku, Tokyo 169-8555, Japan and Advanced Research Institute for Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan)]. E-mail: osakatet@waseda.jp

    2005-11-10

    A process for electroplating amorphous gold-nickel alloy with the atomic ratio of unity was developed. The plating bath was prepared by adding potassium cyanoaurate(I) into a known plating bath which produces amorphous nickel-tungsten alloy. At a sufficiently high gold concentration, the alloy deposit did not contain any tungsten. The amorphous nature of the Au-Ni alloy produced in the new bath was confirmed by using TEM and THEED. Hardness, resistivity, and contact resistance of this new alloy were determined, and the results are discussed for applications as an electrical contact material.

  5. Preparation and research on poisoning resistant Zr-Co based hydrogen storage alloys

    Institute of Scientific and Technical Information of China (English)

    LI Hualing; WANG Shumao; JIANG Lijun; ZHANG Lidong; LIU Xiaopeng; LI Zhinian

    2008-01-01

    At present,all hydrogen storage alloys are poisoned by hydrogen mixed with CO,CO2,etc,which decreases the hydrogen storage property sharply.Zr-Co based hydrogen storage alloys with good poisoning resistance were prepared by alloying,fluorinating,and electroless plating.The experiment results show that the poisoning resistance of the Zr-Co based alloy was improved remarkably after the treatments.The poisoning resistance mechanism of the Zr-Co based hydrogen storage alloys was analyzed.

  6. Shape memory characteristics of Ti-Ni alloys with several specimen sizes from micrometer to millimeter

    Science.gov (United States)

    Miyazaki, Shuichi; Kitamura, Kazuhiro; Nomura, Kuniaki; Fang, Dong; Tobushi, Hisaaki

    1996-02-01

    Ti-Ni shape memory alloys with nearly equiatomic compositions were made by three types of production methods, i.e., rolling, drawing and sputtering methods. These methods were used for making thin plates 0.1 mm thick, thick and thin wires 1.0 mm and 0.08 mm in diameter, and thin films 0.007 mm thick, respectively. These specimens were annealed at 673 K, 773 K, and 873 K in order to investigate the affect of annealing temperature on the shape memory characteristics in each specimen. The shape memory characteristics were compared among these specimens in order to investigate the effect of the production method.

  7. Applications and development of shape-memory and superelastic alloys in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Takaoka, S.; Horikawa, H. [Furukawa Electric Co., Ltd., Hiratsuka (Japan); Kobayashi, J. [Japan Association of Shape Memory Alloys, Yokohama (Japan); Shimizu, K. [Kanazawa Inst. of Tech., Matsutou (Japan)

    2002-07-01

    The present situation of the applications and development of shape memory and superelastic alloys in Japan will collectively be introduced. Of many shape memory alloys, TiNi alloy systems have mostly been used for the applications from the point of view of fatigue and corrosion characteristics. Shape memory effect has been utilized for mainly thermal actuators with the form of coil springs. The effect associated with the B2 to R-phase transformation and its reversion exhibits recoverable strain of approximately 1%, and after a million thermal cycles the recovery characteristics are not affected. Thus, the effect is widely utilized as sensor flap of the air conditioner, water flow control valve, underfloor vent, automatic oil volume adjusting equipment for Shinkansen and water mixing valve. Another effect associated with the B2 to orthorhombic transformation and its reversion, as in TiNiCu alloys containing Cu more than 8%, can be applied to actuators required for 10,000 to 50,000 times life, and thus it is utilized as rice cooker, coffee maker and anti-scald valve. In Japan, however, the TiNi shape memory alloy systems are mainly used for applications using the superelasticity, like a rubber material. The superelasticity associated with the B2 to monoclinic stress-induced transformation and its reversion upon un-loading has been utilized as brassiere wire, eye glasses flame, antenna core wire for cellular phone and fishing wire, and that associated with the B2 to orthorhombic stress-induced transformation and its reversion upon un-loading has been as orthodontic wire, because the TiNiCu alloy wire exhibits smaller stress hysteresis than that of usual TiNi alloy wire. The TiNi shape memory alloy systems are now developed to make various shapes, such as tapes, foils and tubes, and the alloys with those shapes are examined to apply to medical uses, such as guide wire for catheter and catheter tube itself, and to any other uses. The development in Japan is rapidly

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

    Energy Technology Data Exchange (ETDEWEB)

    Rynko, Ramona; Marquardt, Axel; Pauksen, Alexander; Frenzel, Jan; Somsen, Christoph; Eggeler, Gunther [Bochum Univ. (Germany). Inst. for Materials

    2015-04-15

    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{sub 70}Ta{sub 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{sup -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.

  9. Shape memory alloy actuation effect on subsonic static aeroelastic deformation of composite cantilever plate

    Science.gov (United States)

    Hussein, A. M. H.; Majid, D. L. Abdul; Abdullah, E. J.

    2016-10-01

    Shape memory alloy (SMA) is one of the smart materials that have unique properties and used recently in several aerospace applications. SMAs are metallic alloys that can recover permanent strains when they are heated above a certain temperature. In this study, the effects of SMA actuation on the composite plate under subsonic aeroelastic conditions are examined. The wind tunnel test is carried out for two configurations of a cantilever shape memory alloy composite plate with a single SMA wire fixed eccentrically. Strain gage data for both bending and torsional strain are recorded and demonstrated during the aeroelastic test for active and non-active SMA wire in two locations. The cyclic actuation of the SMA wire embedded inside the composite plate is also investigated during the aeroelastic test. The results show reduction in both bending and torsional strain of the composite plate after activation of the SMA wire during the wind tunnel test.

  10. Spray Forming of NiTi and NiTiPd Shape-Memory Alloys

    Science.gov (United States)

    Mabe, James; Ruggeri, Robert; Noebe, Ronald

    2008-01-01

    In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

  11. 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.

  12. The Investigation of a Shape Memory Alloy Micro-Damper for MEMS Applications

    Directory of Open Access Journals (Sweden)

    Chongdu Cho

    2007-09-01

    Full Text Available Some shape memory alloys like NiTi show noticeable high damping property inpseudoelastic range. Due to its unique characteristics, a NiTi alloy is commonly used forpassive damping applications, in which the energy may be dissipated by the conversion frommechanical to thermal energy. This study presents a shape memory alloy based micro-damper, which exploits the pseudoelasticity of NiTi wires for energy dissipation. Themechanical model and functional principle of the micro-damper are explained in detail.Moreover, the mechanical behavior of NiTi wires subjected to various temperatures, strainrates and strain amplitudes is observed. Resulting from those experimental results, thedamping properties of the micro-damper involving secant stiffness, energy dissipation andloss factor are analyzed. The result indicates the proposed NiTi based micro-damper exhibitsgood energy dissipation ability, compared with conventional materials damper.

  13. Spray Forming of NiTi and NiTiPd Shape-Memory Alloys

    Science.gov (United States)

    Mabe, James; Ruggeri, Robert; Noebe, Ronald

    2008-01-01

    In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior could be developed in the deposited materials and the investigation proved that VPS forming could be a means to directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.

  14. 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.

  15. TiNi Shape Memory Alloy Foams Synthesized by Spacer Sintering and their Properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Titanium (Ti) andnickel (Ni) elemental powders were blended by ball milling and the ball milled powders were employed to fabricate TiNi shape memory alloy (SMA) foams by spacer sintering. Effect of ball milling time on phase constitutes of the sintered TiNi alloy foams was studied by X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) was used to characterize the porous structure, and compressive tests were carried out to evaluate the mechanical properties ofthe foams. Results indicate that porosities of the TiNi alloy foams can be controlled by using the spacer sintering method, and the porosities show a significant effect on the mechanical properties and shape memory effect (SME).

  16. Influence of process factors on shape memory effect of CuZnAl alloys

    Institute of Scientific and Technical Information of China (English)

    LIU Hai-xia; SI Nai-chao; XU Gui-fang

    2006-01-01

    Thermal cycle training of CuZnAI shape memory alloys with different transformation temperatures was carried out. The influence of different pre-strains, heat treatments and media on the shape memory effect(SME) of CuZnAl alloys with different transformation temperatures was studied by means of scanning electron microscopy(SEM) and X-ray diffractometry(XRD).Experimental results show that despite respective variation in heat treatment, medium and cycling number, the recovery rate always decreases as pre-strain increases. The decline is obvious when pre-strain is less than 2.6% but not so sharp when pre-strain exceeds 2.6%. Larger pre-strain results in more than one slip system and causes intercutting of the martensite strips among martensitic variants, then leads to the decline of SME. The SME of alloys with transformation temperatures below 347 K is larger than that of alloys beyond 361 K by 20%-40%. The recovery rate of two-step aged alloy is higher than that of step-quenched alloy by 20%-25%.During thermal cycling, the recovery rate in oil is better than that in water.

  17. Production of Ni{sub 100-x-y}Mn{sub x}Ga{sub y} magnetic shape memory alloys by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Hatchard, T D; Thorne, J S; Dunlap, R A [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, B3H 3J5 (Canada); Farrell, S P [Defence R and D Canada-Atlantic, PO Box 1012, 9 Grove Street, Dartmouth, Nova Scotia, B2Y 3Z7 (Canada)], E-mail: hatchard@dal.ca

    2008-11-05

    Powdered samples of a variety of compositions of the off-stoichiometric magnetic shape memory alloy Ni{sub 2}MnGa have been prepared by mechanical alloying from elemental precursors. As-milled powders are highly disordered and show very weak ferromagnetic order. Annealing produces a well-ordered L2{sub 1} Heusler phase with high saturation magnetization. Annealing results in a consistent loss of Ga of about 1-4 at.% (of total sample composition). Structural and magnetic properties of a range of compositions have been measured and are reported in the present work. A magnetically oriented metal-polymer composite has been prepared by mixing the powdered sample in epoxy and curing under an externally applied magnetic field. The magnetic anisotropy energy of the composite sample has been measured and found to be about 20% of the value expected for a single crystal of similar composition. Possibilities for increasing the magnetic anisotropy of metal-polymer composites are discussed. Results are discussed in terms of the effects of structural and chemical order on the resulting magnetic properties in the context of a model based on indirect exchange interactions.

  18. Characterization of NiTi shape memory alloys using dual kriging interpolation

    Energy Technology Data Exchange (ETDEWEB)

    Trochu, F.; Sacepe, N.; Volkov, O.; Turenne, S. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Mechanical Engineering

    1999-12-15

    A large number of industrial applications could benefit from the remarkable properties of shape memory alloys (SMA). The development of a general material law is the first important step before reliable design calculations of shape memory devices can be carried out. This paper presents a new phenomenological constitutive law based on dual kriging, which is a powerful mathematical tool used here as interpolation method to simulate the macroscopic mechanical behavior of shape memory alloys. From a set of experimental strain-temperature curves at constant loads, two deformation surfaces are constructed in the stress, strain and temperature space which describe the cooling and heating behaviors of the material for any stress. The response of a specimen subjected to complex thermomechanical loading can be calculated by dual kriging form a general 3-dimensional parametric solid constructed inside the hysteretic domain delimited by the main cooling and heating deformation surfaces. This approach presents the advantage of yielding immediately the explicit equation of any partial cycle inside the main hysteretic domain, thus yielding a general material law for shape memory alloys. Preliminary validation for a set of simple examples demonstrates the potential of this new model that includes in a single formulation superelasticity, rubber-like behavior and shape memory effect. (orig.)

  19. Surface corrosion enhancement of passive films on NiTi shape memory alloy in different solutions.

    Science.gov (United States)

    Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Limin, Dong

    2016-06-01

    The corrosion behaviors of NiTi shape memory alloy in NaCl solution, H2SO4 solution and borate buffer solution were investigated. It was found that TiO2 in passive film improved the corrosion resistance of NiTi shape memory. However, low corrosion resistance of passive film was observed in low pH value acidic solution due to TiO2 dissolution. Moreover, the corrosion resistance of NiTi shape memory alloy decreased with the increasing of passivated potential in the three solutions. The donor density in passive film increased with the increasing of passivated potential. Different solutions affect the semiconductor characteristics of the passive film. The reducing in the corrosion resistance was attributed to the more donor concentrations in passive film and thinner thickness of the passive film.

  20. Factors Affecting Transformation Temperatures in Fe-Mn-Si-Cr-Ni Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The effects of prestrain and annealing temperature on phase transformation temperatures in Fe14Mn5Si8Cr4Ni shape memory alloy have been studied. The results showed that when the annealing temperature was 673 K, both the Af and the Ms temperatures increased appreciably as the prestrain increased, the As temperature increased slightly with increasing prestrain; the resistivity difference at 303 K between the heating and cooling curve also increased with increasing prestrain, which agreed with the recovery strain. The shape memory effect in Fe-Mn-Si-Cr-Ni shape memory alloy is caused by the stress-induced γ → ε martensite transformation and its reverse transformation. When the prestrain was 10%, the Ms temperature decreased remarkably as the annealing temperature increased.

  1. Identification of epsilon martensite in a Fe-based shape memory alloy by means of EBSD.

    Science.gov (United States)

    Verbeken, K; Van Caenegem, N; Raabe, D

    2009-01-01

    Ferrous shape memory alloys (SMAs) are often thought to become a new, important group of SMAs. The shape memory effect in these alloys is based on the reversible, stress-induced martensitic transformation of austenite to epsilon martensite. The identification and quantification of epsilon martensite is crucial when evaluating the shape memory behaviour of this material. Previous work displayed that promising results were obtained when studying the evolution of the amount of epsilon martensite after different processing steps with Electron BackScatter Diffraction (EBSD). The present work will discuss in detail, on the one hand, the challenges and opportunities arising during the identification of epsilon martensite by means of EBSD and, on the other hand, the possible interpretations that might be given to these findings. It will be illustrated that although the specific nature of the austenite to epsilon martensite transformation can still cause some points of discussion, EBSD has a high potential for identifying epsilon martensite.

  2. Reverse Shape Memory Effect Related to α → γ Transformation in a Fe-Mn-Al-Ni Shape Memory Alloy

    Science.gov (United States)

    Peng, Huabei; Huang, Pan; Zhou, Tiannan; Wang, Shanling; Wen, Yuhua

    2017-05-01

    In this study, we investigated the shape memory behavior and phase transformations of solution-treated Fe43.61Mn34.74Al13.38Ni8.27 alloy between room temperature and 1173 K (900 °C). This alloy exhibits the reverse shape memory effect resulting from the phase transformation of α (bcc) → γ (fcc) between 673 K and 1073 K (400 °C and 800 °C) in addition to the shape memory effect resulting from the martensitic reverse transformation of γ' (fcc) → α (bcc) below 673 K (400 °C). There is a high density of hairpin-shaped dislocations in the α phase undergoing the martensitic reverse transformation of γ' → α. The lath γ phase, which preferentially nucleates and grows in the reversed α phase, has the same crystal orientation with the reverse-transformed γ' martensite. However, the vermiculate γ phase, which is precipitated in the α phase between lath γ phase, has different crystal orientations. The lath γ phase is beneficial to attaining better reverse shape memory effect than the vermiculate γ phase.

  3. Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

    Institute of Scientific and Technical Information of China (English)

    Gheorghe Gurau; Carmela Gurau; Vedamanickam Sampath; Leandru Gheorghe Bujoreanu

    2016-01-01

    Low-costiron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure tor-sion (HSHPT) process on the microstructural evolution of an Fe–Mn–Si–Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations charac-teristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence ofε-martensite with an HCP crystal structure andγ-phase with an FCC structure.

  4. Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

    Science.gov (United States)

    Gurau, Gheorghe; Gurau, Carmela; Sampath, Vedamanickam; Bujoreanu, Leandru Gheorghe

    2016-11-01

    Low-cost iron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion (HSHPT) process on the microstructural evolution of an Fe-Mn-Si-Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ɛ-martensite with an HCP crystal structure and γ-phase with an FCC structure.

  5. Electrochemical behavior of YAG laser-welded NiTi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    YAN Xiao-jun; YANG Da-zhi; LIU Xiao-peng

    2006-01-01

    Electrochemical behaviors of laser-welded Ti-50.6%Ni(mole fraction) shape memory alloy and the base metal in 0.9% NaCl solution were investigated by electrochemical techniques as corrosion potential measurement, linear and potentiodynamic polarization. The results indicate that the laser-welded NiTi alloy is less susceptible to pitting and crevice corrosion than the base metal, which is demonstrated by the increase in polarization resistance(Rp) and pitting potential(ψpit) and decrease in corrosion current density(Jcorr) and mean difference between ψpit and ψprot values. It is confirmed by scanning electron microscope micrographs that pits could be observed on the surface of base metal but not on the surface of laser-welded alloy after potentiodynamic tests. An improvement of corrosion resistance of laser-welded NiTi alloy could be attributed to almost complete dissolution of inclusions upon laser welding.

  6. Electrochemical behavior of Ti-Ni shape memory alloy in fibrinogen solution

    Institute of Scientific and Technical Information of China (English)

    梁成浩; 郭海霞; 陈邦义

    2004-01-01

    Electrochemical behaviors of Ti-Ni shape memory alloy in fibrinogen solution were studied by electrochemical techniques. The results indicate that the addition of the fibrinogen has no obvious effect on the corrosion potential, but decreases the pitting potential markedly and increases the passive current densities. The analysis of energy-dispersive X-ray for samples adsorbing fibrinogen exhibits that the elements of O, C and N exist on the surface of Ti-Ni alloy. Furthermore, the scanning electron microscope micrographs confirm that the configuration of the adsorbing fibrinogen concentrating on surface defects is like cluster and the fibrinogen adsorption concentration is 96.67 mg/m2 through ultroviolet ray absorption method. Fibrinogen combined with Ti-Ni alloy surface by complex band and its electrochemical transfer accelerated the corrosion of alloy.

  7. Investigation of influence of preparation and heat treatment on deformation behaviour of the alloy NiTi after ECAE

    Energy Technology Data Exchange (ETDEWEB)

    Kocich, Radim, E-mail: r.kocich@seznam.cz [Department of Material Forming, VSB TU Ostrava, 17.listopadu 15, 70833 Ostrava-Poruba (Czech Republic); Szurman, Ivo; Kursa, Miroslav [Department of Non Ferrous Metals, Refining and Recycling, VSB TU Ostrava, 17.listopadu 15, 70833 Ostrava-Poruba (Czech Republic); Fiala, Jaroslav [Department of Materials Engineering, VSB TU Ostrava, 17.listopadu 15, 70833 Ostrava-Poruba (Czech Republic)

    2009-06-25

    The work objective was focused on investigation of deformation behaviour of NiTi-based shape memory alloys with respect to technology of their preparation. Deformation behaviour was assessed by unconventional forming methods, particularly by equal channel angular extrusion (ECAE)-but in combination with preceding rotary forging (swaging). Classical light microscopy, as well as X-ray diffraction, was used for evaluation of structural framework of castings and of material after forming. It was established that the alloy Ni50.6-Ti (at.%) after ECAE and re-crystallisation annealing shows bi-modal distribution of mosaic blocks, i.e. mosaic blocks larger than 10 {mu}m and blocks smaller than 10 {mu}m. For determination of re-crystallisation temperature in deformed materials 7 modes of heat treatment were applied. It was proven that the temperature of 600 deg. C was the starting temperature that initiated re-crystallisation.

  8. Modeling and cyclic behavior of segmental bridge column connected with shape memory alloy bars

    Science.gov (United States)

    Roh, Hwasung; Reinhorn, Andrei M.; Lee, Jong Seh

    2012-09-01

    This paper examines the quasi-static cyclic behavior, lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy (SMA) link-bars. Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column, including a modified four-spring model prepared for the SMA bars. The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars. A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system, considering the residual stress of the martensitic SMA bars. The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical. When large diameter NiTi superelastic SMA bars are incorporated into the column system, the cyclic response varies substantially. The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column. Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.

  9. Composition-structure-function diagrams of Ti-Ni-Au thin film shape memory alloys.

    Science.gov (United States)

    Buenconsejo, Pio John S; Ludwig, Alfred

    2014-12-08

    Ti-Ni-Au thin film materials libraries were prepared from multilayer precursors by combinatorial sputtering. The materials libraries were annealed at 500, 600, and 700 °C for 1 h and then characterized by high-throughput methods to investigate the relations between composition, structure and functional properties. The identified relations were visualized in functional phase diagrams. The goal is to identify composition regions that are suitable as high temperature shape memory alloys. Phase transforming compositions were identified by electrical resistance measured during thermal cycles in the range of -20 and 250 °C. Three phase transformation paths were confirmed: (1) B2-R, (2) B2-R-B19', and (3) B2-B19. For the materials library annealed at 500 °C only the B2-R transformation was observed. For the materials libraries annealed at 600 and 700 °C, all transformation paths were observed. High transformation temperatures (M(s) ≈ 100 °C) were only obtained by annealing at 600 or 700 °C, and with compositions of Ti ≈ 50 at. % and Au > 20 at. %. This is the composition range that undergoes B2-B19 transformation. The phase transformation behaviors were explained according to the compositional and annealing temperature dependence of phase/structure formation, as revealed by X-ray diffraction analysis of the materials libraries.

  10. Factors influencing martensite transitions in Fe-based shape memory alloys

    Directory of Open Access Journals (Sweden)

    Mihalache Elena

    2015-01-01

    Full Text Available Fe-14Mn-6Si-9Cr-5Ni (mass % shape memory alloy (SMA specimens were obtained by powder metallurgy in as-blended state (0_MA and with particle volume fractions of 10 and 20 % MA’d powders, respectively. After hot rolling and solution treatment, between 973 and 1373 K, the specimens were pre-strained up to 4 %, on a tensile testing machine. The influences of: (i MA’d fractions, (ii solution treatment temperature and (iii pre-straining degree were analysed by X-ray diffraction (XRD, optical (OM and scanning electron (SEM microscopy. In this purpose, the gauges of pre-strained specimens were cut and metallographically prepared. Dynamic mechanical analysis (DMA was employed to emphasize the reverse transformation, during heating, of thermally induced martensite, obtained after solution treatment. The results proved that, as an effect of PM-MA processing, mechanical properties were improved, the amount of stress induced martensite increased and the reverse martensitic transformation was enhanced.

  11. An extended thermo-mechanically coupled algorithm for simulation of superelasticity and shape memory effect in shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    S. HASHEMI; H. AHMADIAN; S. MOHAMMADI

    2015-01-01

    Thermo-mechanical coupling in shape memory alloys is a very complicated phenomenon. The heat generation/absorption during forward/reverse transformation can lead to temperature-dependent variation of its mechanical behavior in the forms of superelasticity and shape memory effect. However, unlike the usual assumption, slow loading rate cannot guarantee an isothermal process. A two-dimensional thermo-mechanically coupled algorithm is proposed based on the original model of Lagoudas to efficiently model both superelasticity and shape memory effects and the influence of various strain rates, aspect ratios and boundary conditions. To implement the coupled model into a finite element code, a numerical staggered algorithm is employed. A number of simulations are performed to verify the proposed approach with available experimental and numerical data and to assess its efficiency in solving complex SMA problems.

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

    Directory of Open Access Journals (Sweden)

    Jungkyu ePark

    2015-03-01

    Full Text Available 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.

  13. Behavior and effect of Ti{sub 2}Ni phase during processing of NiTi shape memory alloy wire from cast ingot

    Energy Technology Data Exchange (ETDEWEB)

    Bhagyaraj, J. [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208 016 (India); Ramaiah, K.V.; Saikrishna, C.N.; Bhaumik, S.K. [Council of Scientific and Industrial Research, Materials Science Division, CSIR – National Aerospace Laboratories, Bangalore 560 017 (India); Gouthama, E-mail: gouthama@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208 016 (India)

    2013-12-25

    Highlights: •Ti{sub 2}Ni second phase particles forms in different sizes and shapes in cast ingot. •TEM evidences showed shearing/fragmentation of Ti{sub 2}Ni during processing. •Matrix close to Ti{sub 2}Ni experienced severe plastic deformation lead to amorphisation. •Ti{sub 2}Ni interfaces were mostly faceted and assist in nucleation of martensite. •Heterogeneity of microstructure observed near to and away from Ti{sub 2}Ni. -- Abstract: Binary NiTi alloy is one of the commercially successful shape memory alloys (SMAs). Generally, the NiTi alloy composition used for thermal actuator application is slightly Ti-rich. In the present study, vacuum arc melted alloy of 50.2Ti–Ni (at.%) composition was prepared and characterized using optical, scanning and transmission electron microcopy. Formation of second phase particles (SPPs) in the cast alloy and their influence on development of microstructure during processing of the alloy into wire form has been investigated. Results showed that the present alloy contained Ti{sub 2}Ni type SPPs in the matrix. In the cast alloy, the Ti{sub 2}Ni particles form in varying sizes (1–10 μm) and shapes. During subsequent thermo-mechanical processing, these SPPs get sheared/fragmented into smaller particles with low aspect ratio. The presence of SPPs plays a significant role in refinement of the microstructure during processing of the alloy. During deformation of the alloy, the matrix phase around the SPPs experiences conditions similar to that observed in severe plastic deformation of metallic materials, leading to localized amorphisation of the matrix phase.

  14. Characterization of Ternary NiTiPt High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Rios, Orlando; Noebe, Ronald; Biles, Tiffany; Garg, Anita; Palczer, Anna; Scheiman, Daniel; Seifert, Hans Jurgen; Kaufman, Michael

    2005-01-01

    Pt additions substituted for Ni in NiTi alloys are known to increase the transformation temperature of the alloy but only at fairly high Pt levels. However, until now only ternary compositions with a very specific stoichiometry, Ni50-xPtxTi50, have been investigated and then only to very limited extent. In order to learn about this potential high-temperature shape memory alloy system, a series of over twenty alloys along and on either side of a line of constant stoichiometry between NiTi and TiPt were arc melted, homogenized, and characterized in terms of their microstructure, transformation temperatures, and hardness. The resulting microstructures were examined by scanning electron microscopy and the phase compositions quantified by energy dispersive spectroscopy."Stoichiometric" compositions along a line of constant stoichiometry between NiTi to TiPt were essentially single phase but by any deviations from a stoichiometry of (Ni,Pt)50Ti50 resulted in the presence of at least two different intermetallic phases, depending on the overall composition of the alloy. Essentially all alloys, whether single or two-phase, still under went a martensitic transformation. It was found that the transformation temperatures were depressed with initial Pt additions but at levels greater than 10 at.% the transformation temperature increased linearly with Pt content. Also, the transformation temperatures were relatively insensitive to alloy stoichiometry within the range of alloys examined. Finally, the dependence of hardness on Pt content for a series of Ni50-xPtxTi50 alloys showed solution softening at low Pt levels, while hardening was observed in ternary alloys containing more than about 10 at.% Pt. On either side of these "stoichiometric" compositions, hardness was also found to increase significantly.

  15. Amorphous TM1−xBx alloy particles prepared by chemical reduction (invited)

    DEFF Research Database (Denmark)

    Linderoth, Søren; Mørup, Steen

    1991-01-01

    Amorphous transition-metal boron (TM-B) alloy particles can be prepared by chemical reduction of TM ions by borohydride in aqueous solutions. ln the last few years systematic studies of the parameters which control the composition, and, in turn, many of the properties of the alloy particles, have...... been performed and are reviewed in the present paper. The most important preparation parameters which influence the composition are the concentration of the borohydride solution and the pH of the TM salt solution. By controlling these parameters it is possible to prepare amorphous alloy samples...

  16. Nanoscale design of Ni-Al shape memory alloys.

    Science.gov (United States)

    Subramaniyan, Arun K; Sun, C T

    2009-02-25

    Nanoscale design of Ni-Al alloys was performed to optimize the phase transformation behavior. The distribution of nickel and aluminum atoms was identified as a key parameter in the phase transformation process. A design criterion based on thermal expansion asymmetry was proposed. The effectiveness of the design criterion was validated using molecular dynamics simulations.

  17. On the Driving Forces of Magnetically Induced Martensitic Transformation in Directionally Solidified Polycrystalline Ni-Mn-In Meta-Magnetic Shape Memory Alloy with Structural Anisotropy

    Science.gov (United States)

    Hu, Qiaodan; Zhou, Zhenni; Yang, Liang; Huang, Yujin; Li, Jun; Li, Jianguo

    2017-08-01

    The magnetic anisotropy energy (MAE) in the ferromagnetic shape memory alloys (FSMAs) provides the driving forces to obtain large magnetic field induced strain (MFIS) by rearranging the martensitic variants. However, to date, no significant MAE was observed in the new class of Ni-Mn-Z (Z = In, Sn, Sb) metamagnetic shape memory alloys (MSMAs). Here, we report a significant magnetic anisotropy in Ni48Mn35In17 Heusler alloy with a [110]A fiber texture prepared by the directional solidification. In this case, when the applied magnetic field is along the [110]A direction, a larger magnetization change is obtained compared with that of the randomly oriented samples, which increases the driving forces for the magnetically induced martensitic transformation (MIMT). In contrast, along the [110]A direction, the magnetocaloric effect (MCE) is enhanced by 60 pct, the MFIS is improved by 20 pct, and the critical field for the MFIS is reduced by 0.5 T. Such a peculiar magnetic behavior could be well explained by a proposed model on the viewpoint of the transformation of ferromagnetic austenite phase. Furthermore, considering the thermodynamics aspects, we demonstrate that two main magnetic energies of the Zeeman energy and the MAE in the MSMAs assist each other to promote the MIMT, instead of opposing each other in the FSMAs. This discovery of the strong magnetic anisotropy in highly textured polycrystals provides a feasible route to enhance the MIMT, and new insights to design and prepare the Ni-Mn-based Heusler alloys for practical applications.

  18. Micro pulling down growth of very thin shape memory alloys single crystals

    Science.gov (United States)

    López-Ferreño, I.; Juan, J. San; Breczewski, T.; López, G. A.; Nó, M. L.

    Shape memory alloys (SMAs) have attracted much attention in the last decades due to their thermo-mechanical properties such as superelasticity and shape memory effect. Among the different families of SMAs, Cu-Al-Ni alloys exhibit these properties in a wide range of temperatures including the temperature range of 100-200∘C, where there is a technological demand of these functional materials, and exhibit excellent behavior at small scale making them more competitive for applications in Micro Electro-Mechanical Systems (MEMS). However, polycrystalline alloys of Cu-based SMAs are very brittle so that they show their best thermo-mechanical properties in single-crystal state. Nowadays, conventional Bridgman and Czochralski methods are being applied to elaborate single-crystal rods up to a minimum diameter of 1mm, but no works have been reported for smaller diameters. With the aim of synthesizing very thin single-crystals, the Micro-Pulling Down (μ-PD) technique has been applied, for which the capillarity and surface tension between crucible and the melt play a critical role. The μ-PD method has been successfully applied to elaborate several cylindrical shape thin single-crystals down to 200μm in diameter. Finally, the martensitic transformation, which is responsible for the shape memory properties of these alloys, has been characterized for different single-crystals. The experimental results evidence the good quality of the grown single-crystals.

  19. Formation of the Nanocrystalline Structure in an Equiatomic NiTi Shape-Memory Alloy by Thermomechanical Processing

    Science.gov (United States)

    Mohammad Sharifi, E.; Kermanpur, A.; Karimzadeh, F.; Esmaili, A.

    2014-04-01

    The microstructural evolution during cold rolling followed by annealing of an equiatomic NiTi shape-memory alloy was investigated. The high purity Ni50Ti50 alloy was cast by a copper boat vacuum induction-melting technique. The as-cast ingots were then homogenized, hot rolled, and annealed to prepare the suitable initial microstructure. Thereafter, annealed specimens were cold rolled up to 70 % thickness reduction at room temperature. Post-deformation annealing was conducted at 400 °C for 1 h. The microstructure was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and differential scanning calorimetry techniques. The initial microstructure was free from segregation and Ti- or Ni-rich precipitates and was composed of coarse grains with an average size of 50 μm. The cold rolling of NiTi alloy resulted in a partial amorphization and the deformation-induced grain refinement. A nanocrystalline structure with the grain size of about 20-70 nm was formed during the post-deformation annealing.

  20. Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

    Science.gov (United States)

    Nicholson, D. E.; Padula, S. A., II; Noebe, R. D.; Benafan, O.; Vaidyanathan, R.

    2014-12-01

    Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance.

  1. Martensitic Transformation and Magnetic-Field-Induced Strain in Magnetic Shape Memory Alloy NiMnGa Melt-Spun Ribbon

    Institute of Scientific and Technical Information of China (English)

    Shihai GUO; Yanghuan ZHANG; Jianliang LI; Baiyun QUAN; Yan QI; Xinlin WANG

    2005-01-01

    A magnetic shape memory alloy with nonstoichiometric Ni5oMn27Ga23 was prepared by using melt-spinning technology. The martensitic transformation and the magnetic-field-induced strain (MFIS) of the polycrystalline melt-spun ribbon were investigated. The experimental results showed that the melt-spun ribbons underwent thermal-elastic martensitic transformation and reverse transformation in cooling and heating process and exhibited typical thermoelastic shape memory effect. However the start temperature for martensitic transformation decreased from 286 K for as-cast alloy to 254 K for as-quenched ribbon and Curie temperature remains approximately constant. A particular internal stress induced by melt-spinning resulted in the formation of a texture structure in the ribbons, which made the ribbons obtain larger martensitic transformation strain and MFIS. The internal stress was released substantially after annealing, which resulted in a decrease of MFIS of the ribbons.

  2. Characterization of the Ni-45wt% Ti shape memory alloy rapidly solidified; Caracterizacao da liga Ni-45wt%Ti com efeito de memoria de forma solidificadas rapidamente

    Energy Technology Data Exchange (ETDEWEB)

    Anselmo, G.C.S.; Castro, W.B. de; Araujo, C.J. de, E-mail: walman@dem.ufcg.edu.b [Universidade Federal de Campina Grande (UAEM/UFCG), PB (Brazil). Unidade Academica de Engenharia Mecanica

    2010-07-01

    One important challenge of microsystems design is the implementation of miniaturized actuation principles efficient at the micro-scale. Shape memory alloys (SMAs) have early on been considered as a potential solution to this problem as these materials offer attractive properties like a high-power to weight ratio, large deformation and the capability to be processed at the micro-scale. shape memory characteristics of Ni-45wt%Ti alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray. In these experiments particular attention has been paid to change the velocity of cooling wheel from 30 to 50 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on martensitic transformation behaviors and structure are discussed. (author)

  3. Phase change memory based on SnSe{sub 4} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Karanja, J.M.; Karimi, P.M.; Njoroge, W.K. [Physics Department, Kenyatta University, P.O. Box 43844, Nairobi (Kenya); Wamwangi, D.M., E-mail: Daniel.Wamwangi@wits.ac.za [School of Physics, University of the Witwatersrand, Private Bag 3, 2050 (South Africa)

    2013-01-01

    A phase change alloy has been synthesized and characterized. The reversible phase transitions between amorphous and crystalline states of SnSe{sub 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{sub 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.

  4. An Implicit Algorithm for the Numerical Simulation of Shape-Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Becker, R; Stolken, J; Jannetti, C; Bassani, J

    2003-10-16

    Shape-memory alloys (SMA) have the potential to be used in a variety of interesting applications due to their unique properties of pseudoelasticity and the shape-memory effect. However, in order to design SMA devices efficiently, a physics-based constitutive model is required to accurately simulate the behavior of shape-memory alloys. The scope of this work is to extend the numerical capabilities of the SMA constitutive model developed by Jannetti et. al. (2003), to handle large-scale polycrystalline simulations. The constitutive model is implemented within the finite-element software ABAQUS/Standard using a user defined material subroutine, or UMAT. To improve the efficiency of the numerical simulations, so that polycrystalline specimens of shape-memory alloys can be modeled, a fully implicit algorithm has been implemented to integrate the constitutive equations. Using an implicit integration scheme increases the efficiency of the UMAT over the previously implemented explicit integration method by a factor of more than 100 for single crystal simulations.

  5. Optimizing Magnetocaloric Properties of Heusler-Type Magnetic Shape Memory Alloys by Tuning Magnetostructural Transformation Parameters

    Science.gov (United States)

    Huang, Lian; Qu, Yuhai; Cong, Daoyong; Sun, Xiaoming; Wang, Yandong

    2017-08-01

    Heusler-type magnetic shape memory alloys show a magnetostructural transformation from the low-magnetization phase to the high-magnetization phase upon the application of external magnetic fields. As a result, these alloys exhibit fascinating multifunctional properties, such as magnetic shape memory effect, magnetocaloric effect, magnetoresistance, and magnetic superelasticity. All these functional properties are intimately related to the coupling of the structural and magnetic transitions. Therefore, deliberate tuning of the magnetostructural transformation parameters is essential for obtaining optimal multifunctional properties. Here, we show that by tuning the magnetostructural transformation parameters, we are able to achieve a variety of novel magnetocaloric properties with different application potentials: (1) large magnetic entropy change of 31.9 J kg-1 K-1 under a magnetic field of 5 T; (2) giant effective magnetic refrigeration capacity (251 J kg-1) with a broad operating temperature window (33 K) under a magnetic field of 5 T; (3) large reversible field-induced entropy change (about 15 J kg-1 K-1) and large reversible effective magnetic refrigeration capacity (77 J kg-1) under a magnetic field of 5 T. The balanced tuning of magnetostructural transformation parameters of magnetic shape memory alloys may provide an instructive reference to the shape memory and magnetic refrigeration communities.

  6. Phase diagram of FeNiCoAlTaB ferrous shape memory alloy on aging time

    Directory of Open Access Journals (Sweden)

    Zhijian Zhou

    2017-04-01

    Full Text Available Ferrous shape memory alloy, Fe41Ni28Co17Al11.5Ta2.5B0.05, has shown large superelastic strain and strength in previous study. In the fabrication of this alloy, aging process is crucial for the formation of shape memory effect/superelasticity. However, its phase evolution on aging time is not clearly known. In this study, we systematically studied the phase diagram of this alloy on aging time. It is found that the unaged alloy shows a strain glass transition. With the aging time proceeding, the martensitic transformation gradually emerges. The phase diagram can be explained by the formation of coherent precipitates induced by aging. The heterogeneous strain between coherent precipitates and matrix is the driving force responsible for the emerging martensitic transformation. The generic explanation is supposed to be useful in martensitic transformation engineering for developing novel shape memory alloys from non-transforming materials.

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

    Directory of Open Access Journals (Sweden)

    Jaromir Kopecek

    2014-01-01

    Full Text Available The cobalt alloys (close to the CoNiAl stoichiometry are the less known shape memory alloys. Such behavior is consequence of the martensitic transformation. The pseudoelasticity is caused by the stress-induced martensitic transformation above the equilibrium martensite start temperature from high temperature cubic phase (austenite to lower symmetry phase (martensite. In CoNiAl the pseudoelastic behavior can be obtained by the high temperature annealing. In presented work the effect of the annealing temperature on both pseudoelastic behavior and microstructure was investigated.

  8. Theoretical description of magnetocaloric effect in the shape memory alloy exhibiting metamagnetic behavior

    Energy Technology Data Exchange (ETDEWEB)

    L' vov, Victor A. [Institute of Magnetism, Kyiv 03142 (Ukraine); Taras Shevchenko National University, Kyiv 01601 (Ukraine); Kosogor, Anna, E-mail: annakosogor@gmail.com [Institute of Magnetism, Kyiv 03142 (Ukraine); National University of Science and Technology ‘MISiS’, Moscow 119049 (Russian Federation); Barandiaran, Jose M. [BCMaterials and University of Basque Country, UPV/EHU, Bilbao 48080 (Spain); Chernenko, Volodymyr A. [BCMaterials and University of Basque Country, UPV/EHU, Bilbao 48080 (Spain); Ikerbasque, Basque Foundation for Science, Bilbao 48013 (Spain)

    2016-01-07

    A simple thermodynamic theory is proposed for the quantitative description of giant magnetocaloric effect observed in metamagnetic shape memory alloys. Both the conventional magnetocaloric effect at the Curie temperature and the inverse magnetocaloric effect at the transition from the ferromagnetic austenite to a weakly magnetic martensite are considered. These effects are evaluated from the Landau-type free energy expression involving exchange interactions in a system of a two magnetic sublattices. The findings of the thermodynamic theory agree with first-principles calculations and experimental results from Ni-Mn-In-Co and Ni-Mn-Sn alloys, respectively.

  9. Martensitic Transformation of TiNi Shape Memory Alloy Fiber Reinforced Ni Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Lishan CUI; Yan LI; Yan jun ZHENG; Huibin XU

    2003-01-01

    In this paper, a TiNi shape memory alloy fiber Ni matrix composite was fabricated by an electroplating method using TiNialloy as the cathode and Ni as the anode. The constrained martensitic transformation behaviors of the TiNi alloy were studiedby differential scanning calorimeter (DSC), and the results showed that two endothermic peaks appear on the DSC heatingcurves and the reverse transformation temperatures increase with increasing prestrain levels. Moreover, comparing to the freetransformation, the temperature window of the constrained reverse transformation is widely expanded due to the influence ofrecovery stress.

  10. 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).

  11. The stabilization of martensite in Cu-Zn-Al-Ti-B shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Romero, R.; Stipcich, M. [Univ. Nacional del Centro de la Provincia de Buenos Aires, Tandil (AR). Inst. de Fisica de Materiales Tandil (IFIMAT); Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (Argentina)

    2001-11-01

    Recent studies on aging effects in the martensite phase have shown that the addition of Ti-B to Cu-Zn-Al shape memory alloy has a notable influence on stabilization characteristics of this alloy. The overall process is delayed and the stabilization magnitude is significantly diminished. In an attempt to understand this effect the experimental results are analyzed within a cluster rearrangement model. The characteristic energy values are determined and compared with those obtained in single crystal experiments. The obtained results suggest the formation of vacancy-Ti complexes that increase the average vacancy migration energy for about 25%. (orig.)

  12. Tribological characteristics of ceramic conversion treated NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ju, X; Dong, H [Department of Metallurgy and Materials, School of Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2007-09-21

    NiTi shape memory alloys are very attractive for medical implants and devices (such as orthopaedic and orthodontic implants) and various actuators. However, wear is a major concern for such applications and a novel surface engineering process, ceramic conversion treatment, has recently been developed to address this problem. In this study, the tribological characteristics of ceramic conversion treated NiTi alloy have been systematically investigated under dry unidirectional wear, reciprocating-corrosion wear and fretting-corrosion wear condition. Based on the experimental results, the wear behaviour under different conditions is compared and wear mechanisms involved are discussed.

  13. An Experimental Study on Rate-sensitive Tensile Deformation Behaviour of Fe-based Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Iwamoto Takeshi

    2015-01-01

    Full Text Available Recently, it is attempted to apply high manganese steel including Fe-based shape memory alloy to vibration dampers. Especially, the alloy indicates a special characteristic as a well-known shape memory effect. By coupling between this effect and its plastic deformation, it can be considered that its deformation behaviour at higher deformation rate becomes quite complicated and still unclear. In this study, tensile tests of Fe-based shape memory alloy at different rate of deformation are conducted by using two different testing apparatuses such as the conventional material testing machine and impact testing machine based on the split Hopkinson pressure bar technique. In the tests, temperature rise is captured during the quasi-static deformation. After the quasi-static test, the recovery strain due to shape memory effect is measured by heating up the deformed specimens to Af temperature. Finally, the rate sensitivity of the alloy is discussed including the recovery strain.

  14. Transformation Temperatures, Shape Memory and Magnetic Properties of Hafnium Modified Ti-Ta Based High Temperature Shape Memory Alloys

    Science.gov (United States)

    Khan, W. Q.; Wang, Q.; Jin, X.

    2017-02-01

    In this study the modification effect of Hf content on the shape memory properties and magnetic permeability of a 75.5-77Ti-20Ta-3-4.5Hf alloy system has been systematically studied by DSC, three-point bend test, vector network analyzer and XRD. The martensitic transformation temperature, heat of reaction and recovery strain increases with the increase of hafnium and tantalum content. A stable high temperature shape memory effect was observed (Ms = 385-390 °C) during the two thermal cycles between 20 °C and 725 °C. Transformation temperatures and heats of reaction were determined by DSC measurements. Recovery strain was determined by three-point bend testing. Also an alloy, 70Ti-26Ta-4Hf, with higher tantalum content was produced to observe the effect of Ta on the shape memory properties. Permeability increases gradually from 1.671 to 1.919 with increasing content of hafnium modification and remains stable in the frequency range of 450 MHz to 1 GHz.

  15. Relationship among grain size, annealing twins and shape memory effect in Fe-Mn-Si based shape memory alloys

    Science.gov (United States)

    Wang, Gaixia; Peng, Huabei; Zhang, Chengyan; Wang, Shanling; Wen, Yuhua

    2016-07-01

    In order to clarify the relationship among grain size, annealing twins and the shape memory effect in Fe-Mn-Si based shape memory alloys, the Fe-21.63Mn-5.60Si-9.32Cr-5.38Ni (weight %) alloy with a grain size ranging from 48.9 μm-253.6 μm was obtained by adjusting the heating temperature or heating time after 20% cold-rolling. The densities of grain boundaries and annealing twins increase with a decrease in grain size, whereas the volume fraction and width of stress-induced ɛ martensite after 9% deformation at Ms + 10 K decrease. This result indicates that grain refinement raises the constraint effects of grain boundaries and annealing twins upon martensitic transformation. In this case, the ability to suppress the plastic deformation and facilitate the stress-induced ɛ martensite transformation deteriorates after grain refinement owing to the enhancement of the constraint effects. It is demonstrated by the result that the difference at Ms + 10 K between the critical stress for plastic yielding and that for inducing martensitic transformation is smaller for the specimen with a grain size of 48.9 μm than for the specimen with a grain size of 253.6 μm. Therefore, the shape memory effect declined by decreasing the grain size.

  16. 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.

  17. Quenching effects in Cu-Al-Mn shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Obrado, E.; Manosa, L.; Planes, A. [Barcelona Univ. (Spain). Dept. d' Estructura i Constituents de la Materia; Romero, R.; Somoza, A. [IFIMAT, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, 7000 Tandil, and Comision de Investigaciones Cientificas de la Provincia de Buenos Aires, Buenos Aires (Argentina)

    1999-12-15

    In this paper the effect of quenching from different temperatures (T{sub q}) in a Cu-Al-Mn alloy is studied. This alloy system, which displays an L2{sub 1} ordered structure, transforms martensitically at an intermediate temperature T{sub M}, and undergoes a spin freezing process at a lower temperature T{sub f}. Positron annihilation measurements have shown that after the quench, an excess of vacancies is retained in the system, depending on T{sub q}. In addition, both T{sub M} and T{sub f} have been found to be sensitive to T{sub q}. This has been attributed to frozen-in disorder induced by the quench. Experimental results have been interpreted in terms of the growth of magnetic clusters, quenched-in vacancies and atomic disorder. (orig.)

  18. Metallographic preparation of Zn-21Al-2Cu alloy for analysis by electron backscatter diffraction (EBSD).

    Science.gov (United States)

    Rodríguez-Hernández, M G; Martínez-Flores, E E; Torres-Villaseñor, G; Escalera, M Dolores

    2014-08-01

    Samples of Zn-21Al-2Cu alloy (Zinalco) that will be heavily deformed were prepared using five different manual mechanical metallographic methods. Samples were analyzed before tensile testing using the orientation imaging microscopy-electron backscatter diffraction (OIM-EBSD) technique. The effect of type and particle size during the final polishing stages for this material were studied in order to identify a method that produces a flat, damage free surface with a roughness of about 50 nm and clean from oxide layers, thereby producing diffraction patterns with high image quality (IQ) and adequate confidence indexes (CI). Our results show that final polishing with alumina and silica, as was previously suggested by other research groups for alloys that are difficult to prepare or alloys with low melting point, are not suitable for manual metallographic preparation of this alloy. Indexes of IQ and CI can be used to evaluate methods of metallographic preparation of samples studied using the OIM-EBSD technique.

  19. Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

    Science.gov (United States)

    Atli, K. C.; Karaman, I; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2010-01-01

    A Ti(50.5)Ni(24.5)Pd25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti(50.5)Ni(24.5)Pd25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

  20. Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

    Science.gov (United States)

    Atli, K. C.; Karaman, I; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2010-01-01

    A Ti(50.5)Ni(24.5)Pd25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti(50.5)Ni(24.5)Pd25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

  1. Electrolytic Passivation of Nitinol Shape Memory Alloy in Different Electrolytes

    Institute of Scientific and Technical Information of China (English)

    SU Xiang-dong; WANG Tian-min; HAO Wei-chang; HE Li

    2006-01-01

    The corrosion behavior of the nitinol alloy was studied in various corrosion media of different Cl- ion concentrations. The results demonstrate that the Cl- ion concentration has significant influences on the corrosion behavior of the nitinol alloy. In order to enhance the corrosion resistance, protective films were generated on the surface of the nitinol alloy by means of the electrochemical passivation method, for which five different electrolytic solutions were investigated. The surface analysis indicates full growth of all samples passivated in the different electrolytic solutions with layers, however, showing different morphological features. Without any defects like micro-cracks and pores, the surface of the samples passivated in the molybdate solution turns out smoother and denser than those passivated in other solutions. It is shown that the electro-chemical passivation will reduce Ni content but increase Ti content in the surface, reaching the Mole ratio of Ti:Ni = 9.01:1 on the outermost surface. Potentiodynamic polarization test demonstrates that the samples electrochemically passivated in the molybdate solution present a significant increase in breakdown potential due to titanium enrichment on the outermost surface.

  2. Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.

  3. Electrochemical preparation of La-Co-Fe alloy films in dimethylsulfoxide (DMSO)

    Institute of Scientific and Technical Information of China (English)

    袁定胜; 黄开胜; 刘冠昆; 童叶翔; 沙励嫦

    2001-01-01

    Potentiostatic and pulse electrolysis techniques were used to prepare La-Co-Fe alloy films using ethylenediamine (EN) as complexant. Surfaces of alloy films obtained by these two techniques are smooth, adhesive, compact and metallic luster. The contents of La in alloy films obtained by potentiostatic electrolysis technique are in the range of 13.23%~47.67%. The contents of La in alloy films deposited by pulse electrolysis technique are in the range of 10.67%~16.29%.

  4. ON DEVELOPMENT OF OPTIMAL METALLURGICAL PROCESS FOR PREPARATION OF A NEW GENERATION OF INTERMETALLIC ALLOYS

    Directory of Open Access Journals (Sweden)

    Viliam Hrnčiar

    2009-06-01

    Full Text Available Intermetallic TiAl based alloys are used in extreme conditions, e.g. high temperature, aggressive atmosphere and combined high temperature mechanical loading. The contribution deals with development and optimization of plasma melting metallurgical process in new developed crystallizer with rotational and axial movement of melt, for preparation of new intermetallic alloys based on Ti-(45-48Al-(1-10Ta (at.%. The melting process parameters and their influence to final microstructure and properties of alloys are discussed. The aim of this work is to produce alloys with lower number of technological steps necessary to achieve chemical composition, homogeneity and purity as well.

  5. Microestrutural evolution in a CuZnAl shape memory alloy: kinetics and morphological aspects

    Directory of Open Access Journals (Sweden)

    R.A. Sanguinetti Ferreira

    2000-10-01

    Full Text Available The microstructural evolution of the CuZnAl shape memory alloys was studied by indirect techniques relating to the atomic migration rate of grain boundaries. Addition elements were used in a Cu-15,5Zn-8,0Al alloy to provide a comparison with the same alloy without microelement additions. The alloys were melted in an induction furnace of 24 kVA. After casting, the bulk samples of the alloys were homogenized. Then they were solution treated and hot-rolled followed by water-quenching to initiate the recrystallization. Finally, annealing produced at different temperature ranges was made in different samples in order to establish a law for the grain growth. Following the heat treatments, all annealed samples were examined by statistical metallography and the grain sizes were measured. After measurements, the same empirical law of grain growth was found for the different alloys and the ln [D-Do] x 1/T diagrams were plotted in order to establish the kinetic behavior. Based on the estimated values of the activation energy, important conclusions were obtained concerning the addition elements.

  6. Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

    Directory of Open Access Journals (Sweden)

    Miaolei Zhou

    Full Text Available As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

  7. Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

    Science.gov (United States)

    Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

    2014-01-01

    As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

  8. 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.

  9. 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

  10. LOW VELOCITY RESPONSE CHARACTERISTICS OF COMPOSITE PLATE WITH EMBEDDED SHAPE MEMORY ALLOY

    Institute of Scientific and Technical Information of China (English)

    WuYongdong; ZhongWeifang; LiangYide

    2004-01-01

    This paper analyzes the characteristics of utilizing shape memory effect (SME) of shape memory alloy (SMA) in improving the low velocity impact resistance performance of composite plate by using finite element method. The constitutive relation for SMA hybrid composite plates is presented. The analytic model of finite element for SMA composite plate subjected to low velocity impact is established. The modified Hertz's contact law is used to determine the impact contact force. The computing procedures for solving the finite element equation using Newmark direct integration method are given. The numerical modelling results show that the SMA can effectively improve the low velocity impact resistance performance of composite plate.

  11. Experimental Study on Characteristics of NiMnGa Magnetically Controlled Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Fengxiang WANG; Wenjun LI; Qingxin ZHANG; Chenxi LI; Xinjie WU

    2006-01-01

    The static and dynamic magnetic controlling characteristics of NiMnGa magnetically controlled shape memory alloy (MSMA) were experimentally studied. The results show that the characteristics of induced strain with respect to the magnetic field are nonlinear with saturation nature, and dependent on the temperature as well as the load applied to the MSMA. The magnetic shape memory effect can be observed only in complete martensite phase at room temperature. The magnetic permeability of MSMA is not constant and reduces with the increment of magnetic field. The relative saturation magnetic permeability of MSMA is about 1.5.

  12. 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)

  13. Performance of Integrated Fiber Optic, Piezoelectric, and Shape Memory Alloy Actuators/Sensors in Thermoset Composites

    Science.gov (United States)

    Trottier, C. Michael

    1996-01-01

    Recently, scientists and engineers have investigated the advantages of smart materials and structures by including actuators in material systems for controlling and altering the response of structural environments. Applications of these materials systems include vibration suppression/isolation, precision positioning, damage detection and tunable devices. Some of the embedded materials being investigated for accomplishing these tasks include piezoelectric ceramics, shape memory alloys, and fiber optics. These materials have some benefits and some shortcomings; each is being studied for use in active material design in the SPICES (Synthesis and Processing of Intelligent Cost Effective Structures) Consortium. The focus of this paper concerns the manufacturing aspects of smart structures by incorporating piezoelectric ceramics, shape memory alloys and fiber optics in a reinforced thermoset matrix via resin transfer molding (RTM).

  14. Load carrying capacity of RCC beams by replacing steel reinforcement bars with shape memory alloy bars

    Science.gov (United States)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2016-04-01

    In this paper the structural behavior of reinforced concrete (RC) beams with smart rebars under two point loading system has been numerically studied, using Finite Element Method. The material used in this study is Super-elastic Shape Memory Alloys (SE SMAs) which contains nickel and titanium. In this study, different quantities of steel and SMA rebars have been used for reinforcement and the behavior of these models under two point bending loading system is studied. A comparison of load carrying capacity for the model between steel reinforced concrete beam and the beam reinforced with S.M.A and steel are performed. The results show that RC beams reinforced with combination of shape memory alloy and steel show better performance.

  15. Modeling of effects of matrix on actuation characteristics of embedded shape memory alloy wires

    Institute of Scientific and Technical Information of China (English)

    CUI Xiao-long; ZHENG Yan-jun; CUI Li-shan

    2005-01-01

    Effects of matrix properties on the actuation characteristics of embedded shape memory alloy wires were studied. The coefficient of thermal expansion and the modulus of matrix have significant effect on the maximum recovery stress. The thermal strain rate of the SMA wires upon heating is more sensitive to the matrix properties than the stress rate does. Additional fibers embedded in the matrix have significant effect on the stress distribution between the SMA wires and the matrix, and thus affect the interface quality significantly. Fibers with negative thermal expansion coefficient are beneficial to the interface between shape memory alloy wires and the epoxy matrix. All conclusions based on the numerical modeling can find experimental supports.

  16. Investigation of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    Science.gov (United States)

    Davis, Brian A.

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical model. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. Excellent agreement is achieved between the predicted and measured results, thereby quantitatively validating the numerical tool.

  17. Attractors for a Three-Dimensional Thermo-Mechanical Model of Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    Pierluigi COLLI; Michel FR(E)MOND; Elisabetta ROCCA; Ken SHIRAKAWA

    2006-01-01

    In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global attractor. More precisely,we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the non-autonomous case by the limiting global attractor.

  18. 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.

  19. Investigation on actuation and thermo-mechanical behaviour of Shape Memory Alloy spring using hot water

    Science.gov (United States)

    Chouhan, Priya; Nath, Tameshwer; Lad, B. K.; Palani, I. A.

    2016-09-01

    In this paper, hot water is used as an actuation media for Shape memory alloy and its impact on the morphology of structure of Nitinol Shape Memory Alloy (SMA), is presented. With hot water actuation as the temperature reaches 70-80°C, spring gets fully compressed for the first few cycles followed by a displacement loss in actuation. This actuation loss is then studied with different characterization methods such as Thermo Gravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). With SEM results, it can be inferred that the energy source is not deteriorating the structure. Results observed from TGA shows high oxygen content at lower temperature limits with hot water actuation which suggest the need of conducting experiments in inert atmosphere. As a possible mechanism, a new actuation medium is introduced and various results can be seen in the paper discussed below.

  20. Variational prediction of the mechanical behavior of shape memory alloys based on thermal experiments

    Science.gov (United States)

    Junker, Philipp; Jaeger, Stefanie; Kastner, Oliver; Eggeler, Gunther; Hackl, Klaus

    2015-07-01

    In this work, we present simulations of shape memory alloys which serve as first examples demonstrating the predicting character of energy-based material models. We begin with a theoretical approach for the derivation of the caloric parts of the Helmholtz free energy. Afterwards, experimental results for DSC measurements are presented. Then, we recall a micromechanical model based on the principle of the minimum of the dissipation potential for the simulation of polycrystalline shape memory alloys. The previously determined caloric parts of the Helmholtz free energy close the set of model parameters without the need of parameter fitting. All quantities are derived directly from experiments. Finally, we compare finite element results for tension tests to experimental data and show that the model identified by thermal measurements can predict mechanically induced phase transformations and thus rationalize global material behavior without any further assumptions.

  1. Topology Optimization of Shape Memory Alloy Actuators using Element Connectivity Parameterization

    DEFF Research Database (Denmark)

    Langelaar, Matthijs; Yoon, Gil Ho; Kim, Yoon Young

    2005-01-01

    This paper presents the first application of topology optimization to the design of shape memory alloy actuators. Shape memory alloys (SMA’s) exhibit strongly nonlinear, temperature-dependent material behavior. The complexity in the constitutive behavior makes the topology design of SMA structures...... intractable by the conventional element density-based topology optimization. Therefore, in the present study, the recently developed element connectivity parameterization (ECP) formulation is applied, which offers important advantages for complex nonlinear topology optimization problems. A history......) stiffness matrix of continuum finite elements. Therefore, any finite element code, including commercial codes, can be readily used for the ECP implementation. The key ideas and characteristics of these methods will be presented in this paper....

  2. [Design and biomechanical analysis of nickel-titanium open shape memory alloy artificial vertebral body].

    Science.gov (United States)

    Liu, Hui; Lian, Kejian; Liao, Lijun; Zhai, Wenliang; Ding, Zhenqi

    2010-10-01

    To design an open shape memory alloy artificial vertebral body that can be used to reconstruct the vertebral body in spine diseases, such as thoracic-lumbar spine tumors, burst fracture of the vertebrae, kyphosis and scoliosis, and to evaluate the biomechanical stability of lumbar functional segment unit after insertion with the shape memory alloy artificial vertebral body. The open shape memory alloy artificial vertebral body with nickel-titanium (NiTi) alloy was made. Eight fresh spine specimens (T14-L5) from normal adult porcine were used to detect the range of motion (ROM) in 4 models and were divided into 4 groups: intact vertebrae served as group A; pedicle screw fixation of T15, L1, L3, and L4 was given in group B; after total resection of L2, it was reconstructed by open shape memory alloy artificial vertebral body combined with pedicle screw fixation of T15, L1, L3, and L4 in group C; and after total resection of L2, it was reconstructed by titanium cage vertebral body combined with pedicle screw fixation of T15, L1, L3, and L4 in group D. The three-dimensional ROM of flexion, extension, left/right lateral bending, and left/right rotation in T15-L1, L1-3, and L3,4 segments were detected in turn by the spinal three-dimensional test machine MTS-858 (load 0-8 N x m). Compared with group A, groups B, C, and D had good stability in flexion, extension, left/right lateral bending, and left/right rotation, showing significant differences (P 0.05). Group C had less degree of motion in T15-L1 and L3,4 segments than group D, showing significant differences (P 0.05). The open shape memory alloy artificial vertebral body has a reasonable structure and good biomechanical stability, it can be used to stabilize the spinal segment with pedicle screw fixation.

  3. Preparation and Characterization of Novel Porous Fe-Si Alloys

    Institute of Scientific and Technical Information of China (English)

    WANG Jiefeng; HE Yuehui; JIANG Yao; GAO Hanyan; YANG Junsheng; GAO Lin

    2016-01-01

    Porous Fe-Si alloys with different nominal compositions ranging from Fe-10wt% Si to Fe-50wt% Si were fabricated through a reactive synthesis of Fe and Si elemental powder mixtures. The effects of Si contents on the pore structure of porous Fe-Si alloy were investigated in detail. The results showed that the open porosity, gas permeability and maximum pore size of the porous Fe-Si alloys increased with increasing Si contents, indicating that the porosity and pore size can be tailored by changing the Si contents. The pore structure parameter including the open porosity, gas permeability, maximum pore size obeyed the Hagen-Poiseuille formula with the constant G=0.035 m-1Pa-1s-1 for the reactively synthesized porous Fe-Si alloys. The mechanical property of the porous Fe-Si alloys showed applicability in the ifltration industries.

  4. Kinetic arrest behavior in martensitic transformation of NiCoMnSn metamagnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Umetsu, R.Y., E-mail: rieume@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Ito, K.; Ito, W. [Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba, Sendai 980-8579 (Japan); Koyama, K. [High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kanomata, T. [Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537 (Japan); Ishida, K.; Kainuma, R. [Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba, Sendai 980-8579 (Japan)

    2011-02-03

    Research highlights: > NiMnZ (Z = Ga, Al, In, Sn, Sb) Heusler alloys are now very attractive because of their unique physical properties, such as, magnetic shape memory effect, magnetic field-induced phase transition, inverse magnetocaloric effect, magnetoresistance effect and the giant magnetothermal conductivity. > In our previous investigations for the NiCoMnSn alloy, the behavior of the shape recovery due to the magnetic field induced reverse transformation has been reported. However, the detailed investigations on the magnetic properties such as metamagnetic behavior have not been made. > In our present manuscript, we show the experimental results of the magnetic properties under the magnetic fields up to 12 T for NiCoMnSn alloy. We demonstrated the kinetic arresting behavior of the martensitic transformation under the high magnetic fields and thermodynamically discussed it. In addition, we analyzed the structure of the martensitic phase with a long period stacking structure and showed a lattice change between the before and the after the martensitic transformation. We believe that these results are high importance for understanding the interesting physical properties of the Ni-based ferromagnetic shape memory alloys and its applications. - Abstract: High-field magnetic measurements were carried out in order to investigate behaviors of field-induced reverse martensitic transformation and kinetic arrest of NiCoMnSn metamagnetic shape memory alloy. In the thermomagnetization curves, it was confirmed that the reverse martensitic transformation temperature decreases 67 K by applying magnetic field of 5 T, while in the magnetic field cooling process under 5 T, martensitic transformation does not occur down to low temperatures. Equilibrium magnetic field, defined from the critical magnetic fields of the metamagnetic evidence in the magnetization curves, exhibits almost constant below about 100 K, suggesting that the entropy change becomes zero, which is considered

  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. Effect of selenium addition on the GeTe phase change memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Vinod, E.M., E-mail: vinuem@gmail.com [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India); Singh, A.K.; Ganesan, R. [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India); Sangunni, K.S., E-mail: sangu@physics.iisc.ernet.in [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India)

    2012-10-05

    Highlights: Black-Right-Pointing-Pointer Selenium is used as an additive to GeTe phase change materials. Black-Right-Pointing-Pointer Crystalline structure of GeTe alloys does not affect up to 0.20 at.% of Se. Black-Right-Pointing-Pointer The possibility of Se occupying Ge vacancy sites in GeTe structure is explained. Black-Right-Pointing-Pointer Ge-Se and GeTe{sub 2} bonds increase with increase of Se concentration. Black-Right-Pointing-Pointer T{sub m} is reduced in 0.50 at.% Se alloy, which can reduce RESET current requirements. - Abstract: Compositional dependent investigations of the bulk GeTe chalcogenides alloys added with different selenium concentrations are carried out by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), electron probe micro-analyzer (EPMA) and differential scanning calorimetry (DSC). The measurements reveal that GeTe crystals are predominant in alloys up to 0.20 at.% of Se content indicating interstitial occupancy of Se in the Ge vacancies. Raman modes in the GeTe alloys changes to GeSe modes with the addition of Se. Amorphousness in the alloy increases with increase of Se and 0.50 at.% Se alloy forms a homogeneous amorphous phase with a mixture of Ge-Se and Te-Se bonds. Structural changes are explained with the help of bond theory of solids. Crystallization temperature is found to be increasing with increase of Se, which will enable the amorphous stability. For the optimum 0.50 at.% Se alloy, the melting temperature has reduced which will reduce the RESET current requirement for the phase change memory applications.

  7. TEM observation of oxidation of CuZnAlMnNi shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The atmospheric oxidation of a quenched CuZnAlMnNi alloy after ion-polishing was examined by transmission electron microscopy (TEM). It was found that a lot of oxide grains with various sizes yield homogeneously on the surface of the alloy after exposure at room temperature for 90 d. The grains mainly form along the planes of stacking fault, meanwhile, they can also be observed at the stacking fault tetrahedrals or around the dislocation lines. The formarion of the oxides gives rise to the reduction of the stacking faults, and even complete disappearance in some zones,which is partly responsible for the decrement of shape memory. effect (SME) of the alloy quenched during long-term holding at room temperature.

  8. Investigation on microstructure and martensitic transformation of neodymium-added NiTi shape memory alloys

    Science.gov (United States)

    Maashaa, Dovchinvanchig; Dorj, Ulzii-Orshikh; Lee, Malrey; Lee, Min Hi; Zhao, Chunwang; Dashjav, Munguntsetseg; Woo, Seon-Mi

    2016-10-01

    The effect of rare earth element neodymium (Nd) addition on the microstructure and martensitic transformation behavior of Ni50Ti50-xNdx (x = 0, 0.1, 0.3, 0.5 and 0.7 at.%) shape memory alloy was investigated by scanning electronic microscope, X-ray diffraction and differential scanning calorimetry. The results show that the microstructure of Ni-Ti-Nd ternary alloy consists of NiNd phase, NiTi2 and the NiTi matrix. A one-step martensitic transformation is observed in the alloys. The martensitic transformation temperature Ms increases sharply increasing 0.1-0.7 at.% Nd content is added.

  9. Characterization of Polylactide Layer Deposited on Ni-Ti Shape Memory Alloy

    Science.gov (United States)

    Goryczka, Tomasz; Szaraniec, Barbara

    2014-07-01

    Polylactide (PLA) thin layer was deposited on the surface of the as-quenched NiTi shape memory alloy. First, NiTi alloy was quenched from the 850°C, then its surface was covered with PLA. Deposited PLA is in an amorphous state, whereas the as-quenched NiTi alloy stays in the B2 structure. PLA deposition caused smoothing of the surface and changed its hydrophilic character to hydrophobic one. In general, procedure of PLA deposition does not influence the course of the reversible martensitic transformation. After deformation of NiTi sample covered with PLA up to 4%, its surface does not reveal any cracks and still remains continuous.

  10. Influence of crystalline orientation on the thermal-energy convertion efficiency in shape memory alloys

    Directory of Open Access Journals (Sweden)

    Cortés-Pérez J.

    2014-01-01

    Full Text Available A theoretical study about the influence of crystalline orientation on the energy conversion efficiency of two shape memory alloys is present. The study consider single crystal samples in simple tension. The results showed higher properties for of the NiTi than Cu-Al-Be, especially in the temperature-increment (ΔT necessary for get a conversion energy cycle. However, the study showed a crystalline orientation favorable for Cu-Al-Be.

  11. 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.

  12. 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.

  13. Point defects behavior in beta Cu-based shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Romero, R.; Somoza, A. [Univ. Nacional del Centro de la Provincia de Buenos Aires, Tandil (Argentina). IFIMAT

    1999-12-15

    A summary of positron annihilation spectroscopy data relating to the point defect behavior after quenching and to thermal equilibrium in {beta}-phase Cu-based shape memory alloys Cu-Zn-Al and Cu-Al-Be is presented. Particular attention is given to the initial concentration of quenched-in vacancies as a function of the quenching temperature, migration of the retained point defects with aging temperature and time, and the vacancy formation and migration energies. (orig000.

  14. Surface Characterization of Laser Surface Melted NiTi Shape Memory Alloy in Hanks' Solution

    Institute of Scientific and Technical Information of China (English)

    CUIZhen-duo; ZHUSheng-li; MANHauchung; YANGXian-jin

    2004-01-01

    The surface of Ti-50.8Ni at% shape memory alloy was melted by an Nd-YAG laser. The Ti/Ni and Ti4+/ Tiatomic concentration ratios at the surface were changed significantly. The Ni ion release rate of the laser melted surface was much lower than that of the mechanical polished samples. A calcium-phosphorous layer with high Ca/P ratio was detected after immersion in Hanks' solution.

  15. Surface Characterization of Laser Surface Melted NiTi Shape Memory Alloy in Hanks' Solution

    Institute of Scientific and Technical Information of China (English)

    CUI Zhen-duo; ZHU Sheng-li; MAN Hauchung; YANG Xian-jin

    2004-01-01

    The surface of Ti-50.8Ni at% shape memory alloy was melted by an Nd-YAG laser. The Ti/Ni and Ti4+/Ti atomic concentration ratios at the surface were changed significantly. The Ni ion release rate of the laser melted surface was much lower than that of the mechanical polished samples. A calcium-phosphorous layer with high Ca/P ratio was detected after immersion in Hanks' solution.

  16. Thermomechanical Modeling of Shape Memory Alloys with Rate Dependency on the Pseudoelastic Behavior

    Directory of Open Access Journals (Sweden)

    Jin-Ho Roh

    2014-01-01

    Full Text Available The loading-rate dependency on the pseudoelastic behaviors of shape memory alloy (SMA wires is experimentally and numerically investigated. The results are analyzed to estimate the parameters for a thermomechanical constitutive model of SMA wire with strain-rate dependency of the hysteresis behavior. An analytical model of SMAs is developed by using nonconstant parameters during various strain rates. Numerical simulations are performed to demonstrate the accuracy of the improved model.

  17. Constitutive modelling of magnetic shape memory alloys with discrete and continuous symmetries.

    Science.gov (United States)

    Haldar, K; Lagoudas, D C

    2014-09-08

    A free energy-based constitutive formulation is considered for magnetic shape memory alloys. Internal state variables are introduced whose evolution describes the transition from reference state to the deformed and transformed one. We impose material symmetry restrictions on the Gibbs free energy and on the evolution equations of the internal state variables. Discrete symmetry is considered for single crystals, whereas continuous symmetry is considered for polycrystalline materials.

  18. Low Velocity Impact Response Analysis of Shape Memory Alloy Reinforced Composite Beam

    Institute of Scientific and Technical Information of China (English)

    WU Yongdong; ZHONG Weifang; WU Guorong; ZOU Jing

    2005-01-01

    The low velocity impact responses of shape memory alloy ( SMA ) reinforced composite beams were analyzed by employing the finite element method. The finite element dynamic equation was solved by the Newmark direct integration method, the impact contact force was determined using the Hertzian contact law, and the influence of SMA fibers on stiffness matrix is studied. Numerical results show that the SMA fibers can effectively improve the low velocity impact response property of composite beam.

  19. Phase transformation behavior of a TiNiCu shape memory alloy electrolytically charged with hydrogen

    Institute of Scientific and Technical Information of China (English)

    WU Jihong; ZU Xiaotao; WANG Zhiguo; LIU Yanzhang

    2005-01-01

    The transformation behavior of a TiNiCu shape memory alloy electrolytically charged with hydrogen was investigated by means of different scanning calorimetry (DSC), optical microscope and X-ray diffraction (XRD). The results showed that inter- and inner-granular hydrides formed after charging with hydrogen, and the hydrides suppressed martensitic transformation. The electrolytically charged hydrogen can be easily released by heat treatment and the transformation occurred again, which was verified by the DSC and XRD experiments.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu Na [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Li Zhou, E-mail: lizhou6931@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Changsha, 410083 (China); Xu Genying; Feng Ze; Gong Shu; Zhu Lilong; Liang Shuquan [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China)

    2011-10-15

    Highlights: {yields} A novel free-machining Cu-7.5Al-9.7Mn-3.4Zn-0.3Te (wt.%) shape memory alloy has been developed. {yields} The size of dispersed particles with richer Te is 2-5 {mu}m. {yields} The CuAlMnZnTe alloy has good machinability which approached that of BZn15-24-1.5 due to the addition of Te. {yields} Its shape memory property keeps the same as that of CuAlMnZn alloy with free Te. {yields} 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 {mu}m. 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.

  1. Reversible Martensitic Transformation under Low Magnetic Fields in Magnetic Shape Memory Alloys

    Science.gov (United States)

    Bruno, N. M.; Wang, S.; Karaman, I.; Chumlyakov, Y. I.

    2017-01-01

    Magnetic field-induced, reversible martensitic transformations in NiCoMnIn meta-magnetic shape memory alloys were studied under constant and varying mechanical loads to understand the role of coupled magneto-mechanical loading on the transformation characteristics and the magnetic field levels required for reversible phase transformations. The samples with two distinct microstructures were tested along the [001] austenite crystallographic direction using a custom designed magneto-thermo-mechanical characterization device while carefully controlling their thermodynamic states through isothermal constant stress and stress-varying magnetic field ramping. Measurements revealed that these meta-magnetic shape memory alloys were capable of generating entropy changes of 14 J kg−1 K−1 or 22 J kg −1 K−1, and corresponding magnetocaloric cooling with reversible shape changes as high as 5.6% under only 1.3 T, or 3 T applied magnetic fields, respectively. Thus, we demonstrate that this alloy is suitable as an active component in near room temperature devices, such as magnetocaloric regenerators, and that the field levels generated by permanent magnets can be sufficient to completely transform the alloy between its martensitic and austenitic states if the loading sequence developed, herein, is employed. PMID:28091551

  2. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    Science.gov (United States)

    La Roca, P.; Baruj, A.; Sade, M.

    2016-12-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  3. Dynamic mechanical analyze of superelastic CuMnAl shape memory alloy

    Science.gov (United States)

    (Dragoș Ursanu, A. I.; Stanciu, S.; Pricop, B.; Săndulache, F.; Cimpoeșu, N.

    2016-08-01

    A new shape memory alloy was obtain from high purity Cu, Mn and Al elements using a induce furnace. The intelligent material present negative transformation temperatures and an austenite like state at room temperature. The austenite state of CuMnAl shape memory alloy present superelasticity property. Five kilograms ingot was obtain of Cu10Mn10Al alloy. From the base material (melted state) were cut samples with 6 mm thickness using a mechanical saw. After an homogenization heat treatment the samples were hot rolled through four passes with a reduction coefficient of 20%. Experimental lamellas were obtained with 1.5 mm thickness and 90x10 mm length and width. After the hot rolled treatment the materials were heat treated at 800°C for 20 minutes and chilled in water. Four samples, one just laminated and three heat treated by aging, were analyzed with a Netzsch DMA equipment to establish the elastic modulus and the internal friction values of the materials. Metallic materials microstructure was analyzed using a scanning electron microscope Vega Tescan LMH II type. After the aging heat treatment a decrease of internal friction is observed on the entire analyze range which is assigned to formation of Al-based precipitates that block the internal movement of the alloy characteristic phases.

  4. 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.

  5. Reversible Martensitic Transformation under Low Magnetic Fields in Magnetic Shape Memory Alloys.

    Science.gov (United States)

    Bruno, N M; Wang, S; Karaman, I; Chumlyakov, Y I

    2017-01-16

    Magnetic field-induced, reversible martensitic transformations in NiCoMnIn meta-magnetic shape memory alloys were studied under constant and varying mechanical loads to understand the role of coupled magneto-mechanical loading on the transformation characteristics and the magnetic field levels required for reversible phase transformations. The samples with two distinct microstructures were tested along the [001] austenite crystallographic direction using a custom designed magneto-thermo-mechanical characterization device while carefully controlling their thermodynamic states through isothermal constant stress and stress-varying magnetic field ramping. Measurements revealed that these meta-magnetic shape memory alloys were capable of generating entropy changes of 14 J kg(-1) K(-1) or 22 J kg (-1) K(-1), and corresponding magnetocaloric cooling with reversible shape changes as high as 5.6% under only 1.3 T, or 3 T applied magnetic fields, respectively. Thus, we demonstrate that this alloy is suitable as an active component in near room temperature devices, such as magnetocaloric regenerators, and that the field levels generated by permanent magnets can be sufficient to completely transform the alloy between its martensitic and austenitic states if the loading sequence developed, herein, is employed.

  6. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    Science.gov (United States)

    La Roca, P.; Baruj, A.; Sade, M.

    2017-03-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  7. Reversible Martensitic Transformation under Low Magnetic Fields in Magnetic Shape Memory Alloys

    Science.gov (United States)

    Bruno, N. M.; Wang, S.; Karaman, I.; Chumlyakov, Y. I.

    2017-01-01

    Magnetic field-induced, reversible martensitic transformations in NiCoMnIn meta-magnetic shape memory alloys were studied under constant and varying mechanical loads to understand the role of coupled magneto-mechanical loading on the transformation characteristics and the magnetic field levels required for reversible phase transformations. The samples with two distinct microstructures were tested along the [001] austenite crystallographic direction using a custom designed magneto-thermo-mechanical characterization device while carefully controlling their thermodynamic states through isothermal constant stress and stress-varying magnetic field ramping. Measurements revealed that these meta-magnetic shape memory alloys were capable of generating entropy changes of 14 J kg-1 K-1 or 22 J kg -1 K-1, and corresponding magnetocaloric cooling with reversible shape changes as high as 5.6% under only 1.3 T, or 3 T applied magnetic fields, respectively. Thus, we demonstrate that this alloy is suitable as an active component in near room temperature devices, such as magnetocaloric regenerators, and that the field levels generated by permanent magnets can be sufficient to completely transform the alloy between its martensitic and austenitic states if the loading sequence developed, herein, is employed.

  8. Recent breakthrough development of the magnetic shape memory effect in Ni Mn Ga alloys

    Science.gov (United States)

    Söderberg, O.; Ge, Y.; Sozinov, A.; Hannula, S.-P.; Lindroos, V. K.

    2005-10-01

    Magnetic shape memory (MSM) alloys or ferromagnetic shape memory alloy (FSMA) materials discovered by Ullakko et al (1996 Appl. Phys. Lett. 69 1966-8) have received increasing interest, since they can produce a large strain with rather high frequencies without a change in the external temperature. These materials have potential for actuator and sensor applications. MSM materials exhibit giant magnetic field induced strain (MFIS) based on the rearrangements of the crystallographic domains (twin variants). The magnetization energy of the material is lowered when such twin variants that have the easy axis of magnetization along the field start to grow due to twin boundary motion. Currently, the best working MSM materials are the near-stoichiometric Ni2MnGa Heusler alloys in which the properties are highly composition dependent. Their modulated martensitic structures, 5M and 7M, show 6% or 10% response respectively in a magnetic field less than 800 kA m-1. The MSM service temperature of the 5M alloys is between 150 and 333 K, and the optimal frequency region is up to 500 Hz. The fatigue life of the MSM elements has been shown to be at least 50 × 106 shape change cycles. This paper reviews the research work carried out at Helsinki University of Technology on MSM materials since 1998.

  9. 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.

  10. Artificial trachea reconstruction with two-stage approach using memory-alloy mesh

    Institute of Scientific and Technical Information of China (English)

    赵凤瑞; 张银合; 刘世民; 余建军

    2003-01-01

    @@ Artificial tracheal prosthesis is now a challenge to the entire surgical field all over the world. Previously, all kinds of prosthesis were "inner stent" that could not be integrated with native trachea. Since there is an interface between smooth surface of the prosthesis and living tissues, and the inner side of the prosthesis is not covered with living membrane, infections always happen around the prosthesis. We then developed a new technique, which combined memory-alloy mesh with traditional operative procedures. Memory-alloy mesh is extensible, flexible and can maintain the shape of a tube. It has very good compatibility with tissues and no antigenicity. Thus, it is the most desirable material nowadays that can be found to make the frame of an artificial trachea by using a two-stage approach. That is imbedding a pre-shaped memory-alloy mesh under skin or endothelium (pleura or peritoneum), and then making the "sandwich" pedicle skin and muscle flap to a pedicled artificial trachea anastomosed with native trachea. After a two-year experimental study, a patient received the artificial trachea replacement on April 18, 2002, with a good result.

  11. Shake table tests and analytical simulations of a steel structure with shape memory alloy dampers

    Science.gov (United States)

    Parulekar, Y. M.; Kiran, A. Ravi; Reddy, G. R.; Singh, R. K.; Vaze, K. K.

    2014-12-01

    This study uses the pseudoelastic properties of Ni-Ti shape memory alloy wires for attenuation of the seismic response of a steel structure and evaluates its effectiveness and applicability in seismic response control. In this paper, shake table tests, carried out on a model of a steel structure with and without wire-based shape memory alloy dampers, are discussed in detail. Shake table tests, comprised of free vibration tests and spectrum compatible time history tests, were carried out. The former were used for the evaluation of the frequency and damping, and the later were used to prove the efficacy of the shape memory alloy dampers. Further analytical simulations are carried out using detailed time history analysis utilizing a thermomechanical model of an SMA and taking into account the residual martensite accumulation, which is irreversibly due to cyclic forward/reverse martensitic transformation. Moreover, a simple iterative response spectrum (IRS) method with equivalent damping and stiffness is also used to evaluate the response of the structure with SMA dampers, and it is proved that the method can be conservatively used by designers.

  12. Miniaturized Rotary Actuators Using Shape Memory Alloy for Insect-Type MEMS Microrobot

    Directory of Open Access Journals (Sweden)

    Ken Saito

    2016-03-01

    Full Text Available Although several types of locomotive microrobots have been developed, most of them have difficulty locomoting on uneven surfaces. Thus, we have been focused on microrobots that can locomote using step patterns. We are studying insect-type microrobot systems. The locomotion of the microrobot is generated by rotational movements of the shape memory alloy-type rotary actuator. In addition, we have constructed artificial neural networks by using analog integrated circuit (IC technology. The artificial neural networks can output the driving waveform without using software programs. The shape memory alloy-type rotary actuator and the artificial neural networks are constructed with silicon wafers; they can be integrated by using micro-electromechanical system (MEMS technology. As a result, the MEMS microrobot system can locomote using step patterns. The insect-type MEMS microrobot system is 0.079 g in weight and less than 5.0 mm in size, and its locomotion speed is 2 mm/min. The locomotion speed is slow because the heat of the shape memory alloy conducts to the mechanical parts of the MEMS microrobot. In this paper, we discuss a new rotary actuator compared with the previous model and show the continuous rotation of the proposed rotary actuator.

  13. 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.

  14. Titanium-nickel shape memory alloy foams for bone tissue engineering.

    Science.gov (United States)

    Xiong, J Y; Li, Y C; Wang, X J; Hodgson, P D; Wen, C E

    2008-07-01

    Titanium-nickel (TiNi) shape memory alloy (SMA) foams with an open-cell porous structure were fabricated by space-holder sintering process and characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The mechanical properties and shape memory properties of the TiNi foam samples were investigated using compressive test. Results indicate that the plateau stresses and elastic moduli of the foams under compression decrease with the increase of their porosities. The plateau stresses and elastic moduli are measured to be from 1.9 to 38.3 MPa and from 30 to 860 MPa for the TiNi foam samples with porosities ranged from 71% to 87%, respectively. The mechanical properties of the TiNi alloy foams can be tailored to match those of bone. The TiNi alloy foams exhibit shape memory effect (SME), and it is found that the recoverable strain due to SME decreases with the increase of foam porosity.

  15. Preparation of semi-solid billet of magnesium alloy and its thixoforming

    Institute of Scientific and Technical Information of China (English)

    JIANG Ju-fu; LUO Shou-jing

    2007-01-01

    Preparation of semi-solid billet of magnesium alloy and thixoforming was investigated by applying equal channel angular extrusion to magnesium alloy. The results show that mechanical properties of AZ91D alloy at room temperature, such as yield strength(YS), ultimate tensile strength(UTS) and elongation, are enhanced greatly by four-pass equal channel angular extrusion(ECAE) at 573 K and microstructure of AZ91D alloy is refined to the average grain size of 20 μm. Through using ECAE as strain induced step in SIMA and completing melt activated step by semi-solid isothermal treatment, semi-solid billet with fine spheroidal grains of 25 μm can be prepared successfully. Compared with common SIMA, thixoformed satellite angle frame components using semi-solid billet prepared by new SIMA have higher mechanical properties at room temperature and high temperature of 373 K.

  16. 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.

  17. Reconciling viability and cost-effective shape memory alloy options – A review of copper and iron based shape memory metallic systems

    Directory of Open Access Journals (Sweden)

    Kenneth Kanayo Alaneme

    2016-09-01

    Full Text Available Shape memory alloys (SMAs are group of alloys that display anthropomorphic characteristics. These alloys recover their pre-deformed morphology when heated above their transition temperatures after being deformed in their lower temperature phase (martensitic phase. This unique material behavior is explored in industrial and technological applications where capacity for strain recovery is a key design parameter. Copper and iron based SMAs are largely viewed as potential cost effective substitute to Ni–Ti SMAs judging from their promising shape memory properties, damping capacity and other functional properties. Despite their outstanding potentials, the susceptibility of copper based SMAS to phase stabilization, transition hysteresis, aging and brittleness creates doubt on the possibility of transiting from the realm of potential to functional long term use in engineering applications. On the other hand the low percentage shape recovery in the Fe based SMAs also creates a gap between the theory and potential use of these alloys. This paper takes a critical look at the science of shape memory phenomena as applicable to copper and iron based SMA systems. It also covers the limitations of these systems, the effect of processing parameters on these alloys, proposed solutions to limitations associated with this group of shape memory alloys and thoughts for future consideration.

  18. Development of laminated nanocomposites on the bases of magnetic and non-magnetic shape memory alloys: Towards new tools for nanotechnology

    Energy Technology Data Exchange (ETDEWEB)

    Irzhak, Artemy [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Koledov, Viktor [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation); Zakharov, Dmitry, E-mail: dmitry.zakharov@misis.ru [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Lebedev, Gor [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Mashirov, Alexey; Afonina, Veronika; Akatyeva, Kristina; Kalashnikov, Vladimir [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation); Sitnikov, Nikolay [National Research Nuclear University “MEPhI”, Moscow (Russian Federation); Tabachkova, Natalia [National University of Science and Technology “MISiS”, Moscow (Russian Federation); Shelyakov, Alexander [National Research Nuclear University “MEPhI”, Moscow (Russian Federation); Shavrov, Vladimir [Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow (Russian Federation)

    2014-02-15

    Highlights: ► New results on the recently developed shape memory nanocomposites are reported. ► Impact of FIB fabrication method on shape memory properties was studied. ► Shape memory effect for Ti{sub 2}NiCu sample prepared by FIB vanishes at thickness between 70 nm and 170 nm. ► Ni{sub 2}MnGa-based magnetic microcomposite was fabricated and tested for the first time. -- Abstract: New composite functional material with shape memory effect (SME) has recently been proposed and tested for actuation on microscale. The composite nanotweezers have been designed and tested in manipulation of nano-objects. This report presents the new experiments on shape memory alloy’s (SMAs) properties on submicron scale of dimensions and the development of the technology of nanomanipulation on their bases. The minimal thickness of shape memory layer that undergoes SME was experimentally estimated for Ti{sub 2}NiCu alloy. Impact of the focused ion beam modification of SMA superficial layer on the shape memory properties of micro-sized samples is discussed. Composite actuator of Ni–Mn–Ga magnetic SMA with the size of 20 × 4 × 2 μm{sup 3} was fabricated for the first time and its thermal actuation was experimentally demonstrated ( (http://www.smwsm.org/microactuators/NiMnGa.html))

  19. Magnetostriction of heavily deformed Fe–Co binary alloys prepared by forging and cold rolling

    Energy Technology Data Exchange (ETDEWEB)

    Yamaura, Shin-ichi, E-mail: yamaura@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Nakajima, Takashi [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577 (Japan); Satoh, Takenobu; Ebata, Takashi [Tohoku Steel, Co., Ltd., 23 Nishigaoka, Murata, Murata-machi, Shibata 989-1393 (Japan); Furuya, Yasubumi [North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813 (Japan)

    2015-03-15

    Highlights: • The as-forged Fe{sub 25}Co{sub 75} alloy shows the magnetostriction of 108 ppm. • The as-cold rolled Fe{sub 25}Co{sub 75} alloy shows the magnetostriction of 140 ppm. • Magnetostriction of Fe–Co alloy reached the maximum in a single bcc state. • Fcc phase is harmful to the increase in magnetostriction of Fe–Co alloy. • Fcc phase precipitation in Fe–Co alloy can be suppressed by cold rolling. - Abstract: Magnetostriction of Fe{sub 1−x}Co{sub x} (x = 50–90 at%) alloys prepared by forging and subsequent cold-rolling was studied as functions of alloy compositions and thermomechanical treatments. Magnetostriction of the as-forged Fe{sub 25}Co{sub 75} alloy was 108 ppm and that of the as-cold rolled Fe{sub 25}Co{sub 75} alloy measured parallel to the rolling direction (RD) was 128 ppm. The cold-rolled Fe{sub 25}Co{sub 75} alloy possessed a nearly {1 0 0}<0 1 1> texture, leading to the maximum magnetostriction of 140 ppm when measured at an angle of 45° to RD. Moreover, the fully annealed Fe{sub 25}Co{sub 75} and Fe{sub 20}Co{sub 80} alloys were gradually cold rolled and magnetostriction were measured. Results showed that the magnetostriction of those cold-rolled alloys drastically increased with increasing reduction rate. According to the XRD and TEM observations, intensity of the fcc peak gradually decreased with increasing reduction rate and that the alloys became to be in a bcc single state at a reduction rate higher than 90%, leading to a drastic increase in magnetostriction.

  20. Preparation of casting alloy ZL101 with coarse aluminum-silicon alloy

    Institute of Scientific and Technical Information of China (English)

    YOU Jing; WANG Yao-wu; FENG Nai-xiang; YANG Ming-sheng

    2008-01-01

    The coarse Al-Si alloy produced by carbothermal reduction of aluminous ore contains 55% Al, 25% Si and some impurities. The main impurities are slag and iron. The process of manufacturing casting Al-Si alloy ZL101 with the coarse Al-Si alloy was studied. The phase constitution and microstructure of the coarse Al-Si alloy, slag and ZL101 were examined by X-ray diffractometry and scanning electron microscopy. The results show that the content of silicon and iron in the casting alloy reduces with the increase of the dosage of purificant and manganese, but increases with the rise of filtering temperature. It is found that casting Al-Si alloy conforming to industrial standard can be produced after refining by using purificant, and removing iron by using manganese and added magnesium.

  1. Characterization of Sputtered Nickel-Titanium (NiTi) Stress and Thermally Actuated Cantilever Bimorphs Based on NiTi Shape Memory Alloy (SMA)

    Science.gov (United States)

    2015-11-01

    Actuated Cantilever Bimorphs Based on NiTi Shape Memory Alloy ( SMA ) by Merric D Srour, Cory R Knick, and Christopher J Morris...Actuated Cantilever Bimorphs Based on NiTi Shape Memory Alloy ( SMA ) by Merric D Srour, Cory R Knick, and Christopher J Morris Sensors and...Shape Memory Alloy ( SMA ) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Merric D Srour, Cory R Knick, and

  2. THE APPLICATION OF SHAPE MEMORY ALLOY ENCIRCLED FIXER TO BONE FRACTURE%形状记忆合金环抱器在骨折中的应用

    Institute of Scientific and Technical Information of China (English)

    刘宝荣; 康亦锋

    2002-01-01

    Objective:To evaluate the effect of encircled fixer of shape memory alloy on bone fracture. Methods:A total of twenty patients with eighteen males and two females was studied. There were three patients with fractares in the upper one third of thighbone, five with fractures in the middle part of thighbone, six with humeral fractures, three with collarbone fractures,one with ulna fracture and two with thighbone fractures as complication of artificial hipbone arthroplasty. After exposure and fixation of fracture ends, prepared encircled fixer was inserted into 0~4℃ normal reline(NS) to lower its temperature, then pulled out with a clamp. Encircled fixer was put on the tersile side of the fractured bone(center pointed to fracture line), restored and stabilized after raising temperature in 40℃ NS. Results: Encircled fixers of shape memory alloy were used to treat twenty patients with bone fracture.Clinical concrescence was obtained in 1.5 to 3 months after operation,and the joint gained its normal function without complication. Conclusion:Encircled fixer of shape memory alloy has features as exerting vertical pressure continoulsy, little stress shield effect and convenient manipulation, especially adapt to stem fracture after artificial arthroplasty.

  3. 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.

  4. In vitro investigation of NiTiW shape memory alloy as potential biomaterial with enhanced radiopacity.

    Science.gov (United States)

    Li, Huafang; Cong, Ying; Zheng, Yufeng; Cui, Lishan

    2016-03-01

    In the present study, a novel kind of NiTiW shape memory alloy with chemical composition of Ni43.5Ti45.5W11 (at.%) has been successfully developed with excellent X-ray radiopacity by the introduction of pure W precipitates into the NiTi matrix phase. Its microstructure, X-ray radiopacity, mechanical properties, corrosion resistance in simulated body fluid, hemocompatibility and in vitro cytocompatibility were systematically investigated. The typical microstructural feature of NiTiW alloy at room temperature was tiny pure W particles randomly distributing in the NiTi matrix phase. The presence of W precipitates was found to result in enhanced radiopacity and microhardness of NiTiW alloy in comparison to that of NiTi binary alloy. NiTiW alloy exhibits excellent shape memory effect, and a maximum shape recovery ratio of about 30% was obtained with a total prestrain of 8% for the NiTiW alloy sample. In the electrochemical test, NiTiW alloy presented an excellent corrosion resistance in simulated body fluid, comparable to that of NiTi alloy. Hemocompatibility tests indicated that the NiTiW alloy has quite low hemolysis (lower than 0.5%) and the adherent platelet showed round shape without pseudopod. Besides, in vitro cell viability tests demonstrated that the cell viability is all above 90%, and the cells spread well on the NiTiW alloy, having polygon or spindle healthy morphology. The hemocompatibility tests, in vitro cell viability tests and morphology observation indicated that the NiTiW shape memory alloys have excellent biocompatibility. The excellent X-ray radiopacity makes the NiTiW alloys show obvious advantages in orthopedic, stomatological, neurological and cardiovascular domains where radiopacity is quite important factor in order to guarantee successful implantation. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, D. N.; Priolkar, K. R., E-mail: krp@unigoa.ac.in [Department of Physics, Goa University, Taleigao Plateau, Goa 403 206 (India); Emura, S. [Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Nigam, A. K. [Tata Institute of Fundamental Research, Dr. Homi Bhabha Road, Colaba, Mumbai 400 005 (India)

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  6. Preparation of cast aluminum alloy-mica particle composites

    Science.gov (United States)

    Deonath, MR.; Bhat, R. T.; Rohatgi, P. K.

    1980-01-01

    A method for making aluminum-mica particle composites is presented in which mica particles are stirred in molten aluminum alloys followed by casting in permanent molds. Magnesium is added either as an alloying element or in the form of pieces to the surface of the alloy melts to disperse up to 3 wt% mica powders in the melts and to obtain high recoveries of mica in the castings. The mechanical properties of the aluminum alloy-mica composite decrease with increasing mica content; however, even at 2.2% it has a tensile strength of 14.22 kg/sq mm with 1.1% elongation, a compression strength of 42.61 kg/sq mm, and an impact strength of 0.30 kgm/sq cm. Cryogenic and self-lubricating bearing are mentioned applications.

  7. Preparation of cast aluminum alloy-mica particle composites

    Science.gov (United States)

    Deonath, MR.; Bhat, R. T.; Rohatgi, P. K.

    1980-01-01

    A method for making aluminum-mica particle composites is presented in which mica particles are stirred in molten aluminum alloys followed by casting in permanent molds. Magnesium is added either as an alloying element or in the form of pieces to the surface of the alloy melts to disperse up to 3 wt% mica powders in the melts and to obtain high recoveries of mica in the castings. The mechanical properties of the aluminum alloy-mica composite decrease with increasing mica content; however, even at 2.2% it has a tensile strength of 14.22 kg/sq mm with 1.1% elongation, a compression strength of 42.61 kg/sq mm, and an impact strength of 0.30 kgm/sq cm. Cryogenic and self-lubricating bearing are mentioned applications.

  8. Constitutive modeling of shape memory alloys at finite strain

    Energy Technology Data Exchange (ETDEWEB)

    Pethoe, A. [Technical Univ. Budapest (Hungary). Dept. of Applied Mechanics

    2001-07-01

    A new model which is able to reproduce the basic responses of shape memory materials on both micro- and macrostructural aspects is presented. The model is based on a local finite strain continuum description and uses a multiplicative decomposition of the total deformation gradient which involves elastic, plastic and microstructurally given phase transitional parts. For the elastic behavior of the material a coupled hyper-hypoelastic model is used based on a recently developed logarithmic rate. A complex constitutive equation is presented which consists of the kinetics of phase change process given by thermodynamical basis. Finally a simple one dimensional example is also shown. (orig.)

  9. [Study of blood compatibility on TiO2 coated biomedical Ni-Ti shape memory alloy].

    Science.gov (United States)

    Gao, Shuchun; Zhai, Yuchun; Hu, Jinling

    2011-10-01

    We coated a thin TiO2 film on the surface of Ni-Ti shape memory alloy by activated sputter method in the present work. The blood platelet adherence and antithrombogenicity of the TiO2-coated Ni-Ti alloy were evaluated. The results showed that the platelets on the TiO2-coated Ni-Ti alloy were fewer than those on 316L stainless steel, and no agglomeration or distortion for the platelets on the coated alloy was found, which means less probability of blood coagulation for the alloy. The coagulation time on the coated Ni-Ti shape memory alloy was longer than that on the 316L. Compared with that on the 316L stainless steel, the TiO2 coated Ni-Ti shape memory alloy showed better blood compatibility, indicating that the Ni-Ti alloy with TiO2 coating is a kind of ideal biomedical materials with high clinical value.

  10. Phase transition, structure and shape memory effect of Ni47Ti43Hf10 alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A Ni47Ti43Hf10 high temperature shape memory alloy is fabricated. The martensitic transformation temperature (TT) is obtained by differential scanning calorimetry and four-probe electrical resistivity measurements. The effect of thermal cycling is investigated and it is found that the TT tends to be stable quickly, which is of benefit to practical applications. The martensite structure is determined to be B19′ monoclinic by X-ray diffraction and transmission electron microscopy. One-way and two-way (which is seldom reported before) shape memory properties are studied by tensile and bending tests. The cycling number of two-way shape memory effect is tested for more than 20000 times.

  11. A review of modeling techniques for advanced effects in shape memory alloy behavior

    Science.gov (United States)

    Cisse, Cheikh; Zaki, Wael; Ben Zineb, Tarak

    2016-10-01

    micro, micro-macro and macro scales focusing pseudoelastic and shape memory effects. The paper reviews and discusses various techniques used in the literature for modeling complex behaviors observed in shape memory alloys (SMAs) that go beyond the core pseudoelastic and shape memory effects. These behaviors, which will be collectively referred to herein as ‘secondary effects’, include mismatch between austenite and martensite moduli, martensite reorientation under nonproportional multiaxial loading, slip and transformation-induced plasticity and their influence on martensite transformation, strong thermomechanical coupling and the influence of loading rate, tensile-compressive asymmetry, and the formation of internal loops due to incomplete phase transformation. In addition, because of their importance for practical design considerations, the paper discusses functional and structural fatigue, and fracture mechanics of SMAs.

  12. 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.

  13. Experimental Validation of Condition Monitoring for Electrically Activated Shape Memory Alloys for an Unlocking Device

    Science.gov (United States)

    Rathmann, Christian; Theren, Benedict; Fleczok, Benjamin; Kuhlenkötter, Bernd

    2017-06-01

    Shape memory alloys (SMA) belong to the group functional materials which can be activated thermally. Along with a phase transformation, they can remember a previously imprinted shape and have a special resistance behavior. Therefore, they can also be used as a sensor and may be capable of detecting various system states in technical systems. This paper makes a contribution by evaluating the measurability of measured variables by SMA elements. Furthermore, it investigates the technically relevant states of “blockade” and “activation” of electrically activated shape memory actuators. It develops and validates an algorithm which is able to detect a possible “blockade”. Moreover, this work presents a hardware concept for a condition monitoring system of shape memory actuators.

  14. A new antibacterial titanium-copper sintered alloy: preparation and antibacterial property.

    Science.gov (United States)

    Zhang, Erlin; Li, Fangbing; Wang, Hongying; Liu, Jie; Wang, Chunmin; Li, Muqin; Yang, Ke

    2013-10-01

    Copper element was added in pure titanium by a powder metallurgy to produce a new antibacterial titanium-copper alloy (Ti-Cu alloy). This paper reported the very early stage results, emphasizing on the preparation, mechanical property and antibacterial activity. The phase constitution was analyzed by XRD and the microstructure was observed under SEM equipped with EDS. The hardness, the compressive strength and the corrosion resistance of Ti-Cu alloy were tested in comparison with cp-Ti. The antibacterial property of the Ti-Cu alloy was assessed by two methods: agar diffusion assay and plate-count method, in which Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were used. XRD and SEM results showed that Ti2Cu phase and Cu-rich phase were synthesized in the Ti-Cu sintered alloy, which significantly increases the hardness and the compressive strength compared with cp-Ti and slightly improves the corrosion resistance. No antibacterial activity was detected by the agar diffusion assay on the Ti-Cu alloy, but the plate-count results indicated that the Ti-Cu alloy exhibited strong antibacterial property against both bacteria even after three polishing treatments, which demonstrates strongly that the whole alloy is of antibacterial activity. The antibacterial mechanism was thought to be in associated with the Cu ion released from the Ti-Cu alloy. © 2013.

  15. Characterization of Transformation-Induced Defects in Nickel Titanium Shape Memory Alloys

    Science.gov (United States)

    Bowers, Matthew L.

    Shape memory alloys have remarkable strain recovery properties that make them ideal candidates for many applications that include devices in the automotive, aerospace, medical, and MEMS industries. Although these materials are widely used today, their performance is hindered by poor dimensional stability resulting from cyclic degradation of the martensitic transformation behavior. This functional fatigue results in decreased work output and cyclic accumulation of permanent strain. To date, few studies have taken a fundamental approach to investigating the interaction between plasticity and martensite growth and propagation, which is vitally important to mitigating functional fatigue in future alloy development. The current work focuses on understanding the interplay of these deformation mechanisms in NiTi-based shape memory alloys under a variety of different thermomechanical test conditions. Micron-scale compression testing of NiTi shape memory alloy single crystals is undertaken in an effort to probe the mechanism of austenite dislocation generation. Mechanical testing is paired with post mortem defect analysis via diffraction contrast scanning transmission electron microscopy (STEM). Accompanied by micromechanics-based modeling of local stresses surrounding a martensite plate, these results demonstrate that the previously existing martensite and resulting austenite dislocation substructure are intimately related. A mechanism of transformation-induced dislocation generation is described in detail. A study of pure and load-biased thermal cycling of bulk polycrystalline NiTi is done for comparison of the transformation behavior and resultant defects to the stress-induced case. Post mortem and in situ STEM characterization demonstrate unique defect configurations in this test mode and STEM-based orientation mapping reveals local crystal rotation with increasing thermal cycles. Changes in both martensite and austenite microstructures are explored. The results for

  16. Characterization of Stoichiometric and Aging Effects on NiTiHf High Temperature Shape Memory Alloys

    Science.gov (United States)

    Coughlin, Daniel Robert

    NiTiHf ternary alloys exhibit attractive high temperature shape memory alloy (HTSMA) properties. Material properties include moderate transformation strain, relatively high transformation temperature, stable pseudoelastic (PE) behavior, and very small irrecoverable strain during load biased tests. The addition of Hf is more attractive than Pt and Pd due to the fact that Hf has a lower cost. Four NiTiHf alloys with different chemical compositions spanning stoichiometry were used to analyze microstructure and mechanical behavior. Research will mainly be focused on the Ni-rich alloys based on that the Ni-lean alloys do not exhibit the previously mentioned HTSMA material properties. The alloys analyzed all had 20(at.)% Hf with varying Ti concentrations (29(at.)%, 29.7(at.)%, 30(at.)%, and 30.5(at.)%). All of the alloys were formed by induction melting, homogenized at 1050C for 72hrs, and then hot extruded with a diameter reduction of 7:1 at a temperature of 900C. In addition to the homogenized and extruded condition, several short-term aging cycles above 400C were completed on each of the alloys. Certain microstructure and mechanical properties are obtained when Hf is added to NiTi and a proper aging cycle is used. Results from isothermal compression tests that were executed above the austenite finish temperature determined that the Ni-rich NiTiHf alloys exhibited all the necessary properties to be considered for HTSMA applications. The test temperature range of the isothermal compression tests were chosen to characterize the transition from PE behavior to austenite plasticity and to examine the deformation behavior of the B2 phase at high temperatures. Results from compression tests showed a strengthening effect when the test temperature was increased through the PE test region. The strengthening effect is due to the yield stress and plasticity being related to the stress induced martensite that is created during the compression test executed above the austenite

  17. Superelasticity of NiTi Shape Memory Alloy Thin Films

    Institute of Scientific and Technical Information of China (English)

    Zhenyu YUAN; Dong XU; Zhican YE; Bingchu CAI

    2005-01-01

    The superelastic properties of NiTi thin films prepared with sputtering were studied. To characterize their superelasticity, tensile and bulging and indentation tests were performed. The measured mechanisms using these three methods were compared, and the factors that influence superelasticity were described.

  18. Influence of Tin Additions on the Phase-Transformation Characteristics of Mechanical Alloyed Cu-Al-Ni Shape-Memory Alloy

    Science.gov (United States)

    Saud, Safaa N.; Hamzah, E.; Abubakar, T.; Bakhsheshi-Rad, H. R.; Mohammed, M. N.

    2016-10-01

    The influence of the addition of Sn to Cu-Al-Ni alloy as a fourth element with different percentages of 0.5, 1.0, and 1.5 wt pct on the microstructure, phase-transformation temperatures, mechanical properties, and corrosion behaviors was investigated. The modified and unmodified alloys were fabricated by mechanical alloying followed by microwave sintering. The sintered and homogenized alloys of Cu-Al-Ni- xSn shape-memory alloys had a refined particle structure with an average particle size of 40 to 50 µm associated with an improvement in the mechanical properties and corrosion resistance. With the addition of Sn, the porosity density tends to decrease, which can also lead to improvements in the properties of the modified alloys. The minimum porosity percentage was observed in the Cu-Al-Ni-1.0 wt pct Sn alloy, which resulted in enhancing the ductility, strain recovery, and corrosion resistance. Further increasing the Sn addition to 1.5 wt pct, the strength of the alloy increased because the highest volume fraction of precipitates was formed. Regarding the corrosion behavior, addition of Sn up to 1 wt pct increased the corrosion resistance of the base SMA from 2.97 to 19.20 kΩ cm2 because of formation of a protective film that contains hydrated tin oxyhydroxide, aluminum dihydroxychloride, and copper chloride on the alloy. However, further addition of Sn reduced the corrosion resistance.

  19. Martensitic transition, inverse magnetocaloric effect and shape memory characteristics in Mn48-xCuxNi42Sn10 Heusler alloys

    Science.gov (United States)

    Liu, Changqin; Li, Zhe; Zhang, Yuanlei; Liu, Yang; Sun, Junkun; Huang, Yinsheng; Kang, Baojuan; Xu, Kun; Deng, Dongmei; Jing, Chao

    2017-03-01

    In this paper, we have systematically prepared a serials of polycrystalline Mn48-xCuxNi42Sn10 alloys (x=0, 1, 3, 5, 6, 8, 10 and 12) and investigated the influence of the Cu doping on martensitic transition (MT) as well as magnetic properties. Experimental results indicate that the MT temperature and the martensite Curie temperature (TcM) shift to high temperature with increasing the substitution of Cu (from Mn rich alloy to Ni rich alloy), while the austenite Curie temperature (TcA) is almost unchanged. It was found that the structures undergo L21 and 4O with the increasing of Cu concentration near room temperature. Therefore, the magnetostructural transition can be tuned by appropriate Cu doping in these alloys. Moreover, we mainly studied the multiple functional properties for inverse magnetocaloric effect and shape memory characteristics associated with the martensitic transition. A large positive isothermal entropy change of Mn48Ni42Sn10 was obtained, and the maximum transition entropy change achieves about 48 J/kg K as x=8. In addition, a considerable temperature-induced spontaneous strain with the value of 0.16% was obtained for Mn48Ni42Sn10 alloys.

  20. PREPARATION OF SEMI-SOLID AlSi7Mg ALLOY SLURRY

    Institute of Scientific and Technical Information of China (English)

    Z.D. Zhao; W.M. Mao

    2008-01-01

    In this article, semi-solid AlSi7Mg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the microstructure of the AlSi7Mg alloy slurry were studied. The results showed that the semi-solid AlSi7Mg alloy slurry, 127 mm in diameter, could be prepared by using the low superheat pouring and weak electromagnetic stirring technology and this new technology could save energy and make the pouring process convenient. When the liquid AlSi7Mg alloy was poured at 650°C or 630°C, the solidified microstructure of the AlSi7Mg alloy slurry, prepared by weak electromagnetic stirring, was remarkably improved when compared with that of the slurry prepared without stirring. The primary α-Al grains appeared rosette-like or spherical. When the pouring temperature was decreased, the shape of the primary α-Al grains gradually changed from dendritic-like grains to spherical grains. When the pouring temperature was appropriately increased, that is, raised to a certain superheat, the pouring processbecame easier and an ideal spherical microstructure of the AlSiTMg alloy slurry, prepared by weak electromagnetic stirring, could also be obtained. In this experiment,when the stirring power was 0.36 kW, the optimized pouring temperature parameter was 630°C. When the AISiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring, the pouring temperature was 630°C. Increasing the stirring power appropriately could gain better spherical primary α-Al grains, but if the stirring power was increased to a certain value, the shape of the primary α-Al grains did not improve further. In this experiment, the optimized stirring power parameter was 0.36 kW.

  1. New bulk glassy alloys in Cu-Zr-Ag ternary system prepared by casting and milling

    Science.gov (United States)

    Janovszky, D.; Tomolya, K.; Sveda, M.; Solyom, J.; Roosz, A.

    2009-01-01

    The thermal stability, crystallization behaviour and glass forming ability of Cu-Zr-Ag system have been investigated on the basis of a ternary phase diagram. We altered the concentration of the alloys from the Cu58Zr42 to the concentration of the deep eutectic point of the Cu-Zr-Ag ternary system and we calculated the glass forming ability parameters. This paper summerises the results of the procedure during which Cu-Zr-Ag amorphous alloys with different Ag content (0-25%) were prepared by casting and ball-milling. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mold. The supercooled liquid region (ΔTx) exceeded 75K. Following the characterization of the cast alloys, master alloys of identical composition were milled in a Fritsch Pulverisette 2 ball-mill. The powders, milled for various periods of time were analysed by XRD in order to define the amorphous fraction.

  2. Comportamento termomecânico de compósitos ativos preparados com nanocompósitos epóxi/argila organofílica e fios de liga Ni-Ti com memória de forma Thermomechanical behavior of active composites prepared with epoxy/organoclay nanocomposites and Ni-Ti shape memory alloy wires

    Directory of Open Access Journals (Sweden)

    Artur S. C. Leal

    2012-01-01

    Full Text Available Neste trabalho, nanocompósitos epóxi/argila organofílica foram selecionados como matriz por apresentarem valores de temperatura de transição vítrea (Tg e estabilidade térmica suficientemente alta para que fios de uma liga com memória de forma (LMF possam ser incorporados. Para tanto, quatro frações volumétricas de fios LMF de Ni-Ti (1,55, 2,56, 3,57 e 4,54% foram embebidas na matriz epoxídica diglicidil éter do bisfenol-A (DGEBA, reticulada com a amina aromática 4,4’-diamino difenil sulfona (DDS contendo 1 pcr da argila bentonita purificada organofiliada (APOC. A formação do nanocompósito foi confirmada por análise de difração de raio X, enquanto a transformação de fase dos fios de Ni-Ti foi determinada por análise dinâmico-mecânica (DMA. As amostras dos compósitos ativos preparados a partir da matriz de nanocompósito e fios de Ni-Ti foram caracterizadas principalmente por DMA. De acordo com os resultados obtidos foi constatada uma recuperação do módulo de armazenamento do compósito ativo durante o aquecimento na faixa de transformação de fase dos fios de Ni-Ti quando a fração volumétrica foi mantida em torno de 3,5%.In this work, epoxy/organoclay nanocomposites were selected as matrix for presenting high enough glass transition temperature (Tg and thermal stability values in order to be incorporated in shape memory alloys (SMA. Four volume fractions of SMA wires containing Ni-Ti (1.55, 2.56, 3.57 and 4.54% were embedded in diglycidyl ether of bisphenol A (DGEBA, cured with the aromatic amine 4,4’-diamino diphenyl sulfone (DDS and containing 1 phr of purified organobentonite (APOC. The formation of nanocomposite was confirmed by X ray diffraction analysis, while the phase transformation of Ni-Ti wires was determined by dynamic mechanical analysis (DMA. Samples of the active composites prepared from nanocomposite matrix and Ni-Ti wires were mainly characterized by DMA. A recovery of the storage modulus of

  3. Research on Semisolid Microstructural Evolution of 2024 Aluminum Alloy Prepared by Powder Thixoforming

    OpenAIRE

    Pubo Li; Tijun Chen; Suqing Zhang; Renguo Guan

    2015-01-01

    A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 bulk alloy, prepared by cold pressing of atomized alloy powders to clarify the mechanisms of how the consolidated powders evolve into small and spheroidal primary...

  4. Preparation of Al-Sr Master Alloy in Aluminum Electrolysis Cell

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Al-Sr master alloy was prepared by using liquid aluminum cathode and a mixture of Na3AlF6- SrCO3 as the basic molten salt electrolyte in a laboratory electrolysis cell.The effects of electrolyte composition,electrolysis temperature,cathodic current density and the electrolytic duration on Sr content of Al-Sr alloy were studied.Through laboratory experiments,the parameters for smooth electrolytic reaction were proposed.

  5. Phase Development and Crystallization Kinetics of NiTi Prepared by Mechanical Alloying

    Institute of Scientific and Technical Information of China (English)

    Xunyong JIANG; Xueping GAO; Deying SONG

    2003-01-01

    NiTi alloy is produced by mechanical alloying(MA). It becomes amorphous after milling for enough time, such as 100 h in this paper. DSC measurement shows that the crystallization temperature is 676 K for the amorphous powder. Activation energy of crystallization is 199.98 kJ/mol for MA powder, which is lower than that of amorphous prepared by magnetron sputtering.Avrami parameter of crystallization is 1.07.

  6. Thermodynamic constitutive model for load-biased thermal cycling test of shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Young, Sung, E-mail: ysy@kut.ac.kr [Korea University of Technology and Education, Chonan (Korea, Republic of); Nam, Tae-Hyun, E-mail: tahynam@gnu.ac.kr [School of Materials Science and Engineering and ERI, Gyeongsang National University, 900 Gazwadong, Jinju, Gyeongnam 660-701 (Korea, Republic of)

    2013-12-15

    Graphical abstract: - Highlights: • Thermodynamic calculation model for martensitic transformation of shape memory alloy was proposed. • Evolution of the self-accommodation was considered independently by a rate-dependent kinetic equation. • Finite element calculation was conducted for B2–B19′ transformation of Ti–44.5Ni–5Cu–0.5 V (at.%). • Three-dimensional numerical results predict the macroscopic strain under bias loading accurately. - Abstract: This paper presents a three-dimensional calculation model for martensitic phase transformation of shape memory alloy. Constitutive model based on thermodynamic theory was provided. The average behavior was accounted for by considering the volume fraction of each martensitic variant in the material. Evolution of the volume fraction of each variant was determined by a rate-dependent kinetic equation. We assumed that nucleation rate is faster for the self-accommodation than for the stress-induced variants. Three-dimensional finite element analysis was conducted and the results were compared with the experimental data of Ti–44.5Ni–5Cu–0.5 V (at.%) alloy under bias loading.

  7. Preparation of biomimetic hydrophobic coatings on AZ91D magnesium alloy surface

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The hydrophobic coating has been a promising technology for improving surface performance. The surface performance of magnesium alloy has been limited in application. Furthermore, the hydrophobic of magnesium alloy is rarely investigated because magnesium alloy is an active metal alloy. In this paper, inspired by microstructure character of typical plant leaf surface such as lotus, the biomimetic hydrophobic coatings on AZ91D magnesium alloy surface were prepared by means of wet-chemical combining electroless. The samples were immersed into AgNO3 solution in wet-chemical method firstly. Then, biomimetic hydrophobic coatings were prepared by electroless after wet-method pretreatment. The microstructure was observed by SEM and the contact angles were measured by contact angle tester. The results indicated that the biomimetic hydrophobic coatings with uniform crystalline and dense structure could be obtained on AZ91D magnesium alloy surface. The results of contact angle revealed that the biomimetic nano-composite coatings were hydrophobic. The wet-chemical method treatment on the AZ91D magnesium alloy substrate provided a rough microstructure, thus improving adhesion of the coating and the substrate.

  8. Sintering and Cold Swaging of Tungsten Heavy Alloys Prepared from Various Grades of W Powder

    Science.gov (United States)

    Eroglu, S.

    2017-10-01

    In the present work, sintering and cold swaging of 92.5W-5.25Ni-2.25Fe heavy alloys prepared from various grades of W powder were investigated. The mean particle sizes of the W powder grades were 3.4 µm, 10.5 µm, and 28.0 µm. It was observed that linear shrinkage decreased with increasing W particle size. The sintering behavior of the alloys was discussed in terms of liquid capillarity and W particle size. The alloy prepared from the 28.0-µm grade W powder exhibited incomplete densification. This alloy could not be swaged because of the poor mechanical properties. The alloys of the other grades were fully densified. They exhibited better ductility and swageability. The alloy of the 10.5-µm grade W powder had good mechanical properties (e.g., tensile strength 1300 MPa, hardness 38 HRC after 10% cold swaging) that were equivalent to those of the alloy of the fine-grade W powder (3.4 µm).

  9. 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.

  10. Non-alloyed Ni3Al based alloyspreparation and evaluation of mechanical properties

    Directory of Open Access Journals (Sweden)

    J. Malcharcziková

    2013-07-01

    Full Text Available The paper reports on the fabrication and mechanical properties of Ni3Al based alloy, which represents the most frequently used basic composition of nickel based intermetallic alloys for high temperature applications. The structure of the alloy was controlled through directional solidification. The samples had a multi-phase microstructure. The directionally solidified specimens were subjected to tensile tests with concurrent measurement of acoustic emission (AE. The specimens exhibited considerable room temperature ductility before fracture. During tensile testing an intensive AE was observed.

  11. Preparation of Ti-based amorphous brazing alloy

    Institute of Scientific and Technical Information of China (English)

    ZOU Jia-sheng; JIANG Zhi-guo; XU Zhi-rong; CHEN Guang

    2006-01-01

    A new kind of amorphous active brazing alloy foil with the composition of Ti40Zr25Ni15Cu20 was successfully synthesized using melt spinning in roll forging machine in argon atmosphere. The amorphous structure and composition were examined by X-ray diffraction, differential thermal analysis and energy dispersive X-ray detector. The results show that the Ti40Zr25Ni15Cu20 amorphous alloy foil has excellent wettability on Si3N4 ceramic and demonstrate a strong glass forming ability. The reduced glass transition temperature (Trg) and the temperature interval of supercooled liquid region before crystallization are 0.76 and 78 K, respectively.

  12. Sample preparation of metal alloys by electric discharge machining

    Science.gov (United States)

    Chapman, G. B., II; Gordon, W. A.

    1976-01-01

    Electric discharge machining was investigated as a noncontaminating method of comminuting alloys for subsequent chemical analysis. Particulate dispersions in water were produced from bulk alloys at a rate of about 5 mg/min by using a commercially available machining instrument. The utility of this approach was demonstrated by results obtained when acidified dispersions were substituted for true acid solutions in an established spectrochemical method. The analysis results were not significantly different for the two sample forms. Particle size measurements and preliminary results from other spectrochemical methods which require direct aspiration of liquid into flame or plasma sources are reported.

  13. A Generic Metallographic Preparation Method for Magnesium Alloys

    Science.gov (United States)

    2013-05-01

    structure in castings. Immerse sample 5–15 s. For higher Al content, use 20-g tartaric acid . 16: 100-ml water 2–11-g citric acid For Mg, Mg-Cu...and Mg die-casting alloys. Immerse sample about 30 s. 17: 100-ml water 5–10-g citric acid For Mg-Mn wrought alloys and solution-treated castings...speed and direction, cycle time, lubricating fluid selection, sample down force, and water rinse. The use of the AD-5 fluid dispenser facilitates

  14. Parametric analysis of a shape memory alloy actuated arm

    Science.gov (United States)

    Wright, Cody; Bilgen, Onur

    2016-04-01

    Using a pair of antagonistic Shape Memory Allow (SMA) wires, it may be possible to produce a mechanism that replicates human musculoskeletal movement. The movement of interest is the articulation of the elbow joint actuated by the biceps brachii muscle. In an effort to understand the bio-mechanics of the arm, a single degree of freedom crankslider mechanism is used to model the movement of the arm induced by the biceps brachii muscle. First, a purely kinematical analysis is performed on a rigid body crank-slider. Force analysis is also done modeling the muscle as a simple linear spring. Torque, rocking angle, and energy are calculated for a range of crank-slider geometries. The SMA wire characteristics are experimentally determined for the martensite detwinned and full austenite phases. Using the experimental data, an idealized actuator characteristic curve is produced for the SMA wire. Kinematic and force analyses are performed on the nonlinear wire characteristic curve and a linearized wire curve; both cases are applied to the crankslider mechanism. Performance metrics for both cases are compared, followed by discussion.

  15. 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.

  16. Ingredient Losses during Melting Binary Ni-Ti Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    S.K. Sadrnezhaad; S. Badakhshan Raz

    2005-01-01

    Losses of the alloying elements during vacuum induction melting of the binary NiTi alloys were evaluated by visual observation and chemical analysis of the NiTi melted specimens and the scalp formed on the internal surface of the crucible. The results indicated that the major sources of the losses were (a) evaporation of the metals, (b) formation of the NiTi scalp and (c) the sprinkling drops splashed out of the melt due to the exothermic reactions occurring between Ni and Ti to form the NiTi parent phase. Quantitative evaluations were made for the metallic losses by holding the molten alloy for 0.5, 3, 5, 10 and 15 min at around 100℃ above the melting point inside the crucible.Chemical analysis showed that there existed an optimum holding time of 3 min during which the alloying elements were only dropped to a predictable limit. Microstructure, chemical composition, shape memory and mechanical properties of the cast metal ingots were determined to indicate the appropriate achievements with the specified 3 min optimum holding time.

  17. Effect of Al addition on properties of TiNiFe shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    XIAO Li; LIU Fu-shun; XU Hui-bin

    2006-01-01

    A little amount of aluminum substituting for Ni was added to Ti50Ni48Fe2 and Ti50Ni47.5Fe2.5 alloys to improve the mechanical properties, especially the yield stress of the TiNiFe alloys. The martensitic transformation temperature and mechanical properties of Ti50Ni48-xFe2Alx and Ti50Ni47.5-xFe2.5Alx (x=0, 0.5, 1) alloys were examined, and it was revealed that 0.5% and 1%(mole fraction) aluminum addition lead to about 10℃ and 60-80 ℃ martensitic transformation temperature (MS) decrease, respectively. 1%(mole fraction) aluminum addition enhances remarkably the yield stresses of Ti50Ni47Fe2Al1 and Ti50Ni46.5Fe2.5Al1 to 560 and 580 MPa, respectively. The systemic microstructure analysis indicates that the second phase Ti2Ni at the grain boundaries plays an important role in improving the mechanical properties of TiNiFe shape memory alloys.

  18. Characterisation and modelling of vacancy dynamics in Ni–Mn–Ga ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Merida, D., E-mail: david.merida@ehu.es [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); García, J.A. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); BC Materials (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain); Sánchez-Alarcos, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Pérez-Landazábal, J.I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Institute for Advanced Materials (INAMAT), Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

    2015-08-05

    Highlights: • We study the dynamics of vacancies for three different Ni–Mn–Ga alloy samples. • The formation and migration energies have been obtained experimentally. • The entropic factor and the distance a vacancy has to reach a sink are measured. • We present a theoretical model to explain the dynamics of vacancies. • Results are applicable for any thermal treatment and extensible to other alloys. - Abstract: The dynamics of vacancies in Ni–Mn–Ga shape memory alloys has been studied by positron annihilation lifetime spectroscopy. The temperature evolution of the vacancy concentration for three different Ni–Mn–Ga samples, two polycrystalline and one monocrystalline, have been determined. The formation and migration energies and the entropic factors are quite similar in all cases, but vary slightly according to composition. However, the number of jumps a vacancy has to overtake to reach a sink is five times higher in the single crystal. This is an expected result, due to the role that surfaces and grain boundaries should play in balancing the vacancy concentration. In all cases, the initial vacancy concentration for the samples quenched from 1173 K lies between 1000 ppm and 2000 ppm. A phenomenological model able to explain the dynamics of vacancies has been developed in terms of the previous parameters. The model can reproduce the vacancy dynamics for any different kind of thermal history and can be easily extended to other alloys.

  19. Correlation between liquid structure and γ2-phase precipitation of Cu-Al-Ni shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    潘学民; 边秀房; 孙景芹; 王伟民

    2002-01-01

    Cu71Al25Ni4 (mole fraction,%) shape memory alloy ribbons exhibit a good shape memory effect, which were prepared by melt-spinning technique. The microstructure of the as-spun ribbons was identified by D/Max-rA X-ray diffractometer. The order degree of martensite increases with decreasing liquid quenching temperature at the same quenching rate. The liquid structure of Cu75Al25 and Cu71Al25Ni4 was investigated using X-ray diffraction method. The distinct pre-peaks have been found in front of main peaks of the structure factors. The pre-peak increases intensity with decreasing temperature or adding Ni. Gaussian peaks decomposing radial distribution function (RDF) indicated that Cu-Al distance is anomalously short. These results suggest that a strong interaction between Cu and Al is favorable to form β-phase-like clusters, which leads to chemical medium-range ordering in melt. This promotes formation of order martensite and suppresses γ2-phase precipitation.

  20. 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

  1. CuZrAl amorphous alloys prepared by casting and milling

    Science.gov (United States)

    Tomolya, K.; Janovszky, D.; Sveda, M.; Hegman, N.; Solyom, J.; Roosz, A.

    2009-01-01

    Several preparation methods are available for the production of amorphous alloys. During the experiment described in this paper (Cu58Zr42)100-xAlx (x = 0-14,8; in at%) amorphous alloys were prepared by casting and ball-milling. The ingots were produced by arc melting. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mould. The microstructures of these samples were defined by SEM. The amorphous samples were analysed by DSC and the activation energy of the crystallization processes was calculated from the measured temperatures. The master alloys of identical composition were milled by ball-mill for different periods of time. The powders were analysed by XRD in order to define the amorphous fractions.

  2. Preparation of three-dimensional shaped aluminum alloy foam by two-step foaming

    Energy Technology Data Exchange (ETDEWEB)

    Shang, J.T. [Key laboratory of MEMS of Ministry of Education, Southeast University, Nanjing 210096 (China)], E-mail: Jshang@seu.edu.cn; Xuming, Chu; Deping, He [School of Materials Science and Engineering, Southeast University, Nanjing 210096 (China)

    2008-06-25

    A novel method, named two-step foaming, was investigated to prepare three-dimensional shaped aluminum alloy foam used in car industry, spaceflight, packaging and related areas. Calculations of thermal decomposition kinetics of titanium hydride showed that there is a considerable amount of hydrogen releasing when the titanium hydride is heated at a relatively high temperature after heated at a lower temperature. The hydrogen mass to sustain aluminum alloy foam, having a high porosity, was also estimated by calculations. Calculations indicated that as-received titanium hydride without any pre-treatment can be used as foaming agents in two-step foaming. The processes of two-step foaming, including preparing precursors and baking, were also studied by experiments. Results showed that, low titanium hydride dispersion temperature, long titanium hydride dispersion time and low precursors porosity are beneficial to prepare three-dimensional shaped aluminum alloy foams with uniform pores.

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

    Science.gov (United States)

    Zablotskii, V; Pérez-Landazábal, J I; Recarte, V; Gómez-Polo, C

    2010-08-11

    Temperature dependences of low-field quasistatic magnetic susceptibility in the vicinity of martensitic transitions in an NiFeGa alloy are studied both by experiment and analytically. Pronounced reversible jumps of the magnetic susceptibility were observed near the martensitic transition temperature. A general description of the temperature dependences of the susceptibility in ferromagnetic austenite and martensite phases and the susceptibility jump at the transition is suggested. As a result, the main factors governing the temperature dependences of the magnetic susceptibility in the magnetic shape memory alloys are revealed. The magnetic susceptibility jump value is found to be related to changes of: (i) magnetic anisotropy; (ii) magnetic domain wall geometrical constraints (those determined by the alignment and size of twin variants) and (iii) mean magnetic domain spacing.

  4. 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.

  5. Anodic Fabrication of Ti-Ni-O Nanotube Arrays on Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Qiang Liu

    2014-04-01

    Full Text Available Surface modification with oxide nanostructures is one of the efficient ways to improve physical or biomedical properties of shape memory alloys. This work reports a fabrication of highly ordered Ti-Ni-O nanotube arrays on Ti-Ni alloy substrates through pulse anodization in glycerol-based electrolytes. The effects of anodization parameters and the annealing process on the microstructures and surface morphology of Ti-Ni-O were studied using scanning electron microscope and Raman spectroscopy. The electrolyte type greatly affected the formation of nanotube arrays. A formation of anatase phase was found with the Ti-Ni-O nanotube arrays annealed at 450 °C. The oxide nanotubes could be crystallized to rutile phase after annealing treatment at 650 °C. The Ti-Ni-O nanotube arrays demonstrated an excellent thermal stability by keeping their nanotubular structures up to 650 °C.

  6. Effect of Laser Welding Parameters on Formation of NiTi Shape Memory Alloy Welds

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available In this work experimental trials of welding of NiTi flat plates with 2.0 mm thickness were conducted using a 4.5 kW continuous wave (CW Nd:YAG laser. The influences of laser output power, welding speed, defocus amount and side-blow shielding gas flow rate on the morphology, welding depth and width, and quality of the welded seam were investigated. Meanwhile, the effects of heat input on the mechanical and functional properties of welded joints were studied. The results show that laser welding can take better formation in NiTi alloys. The matching curves with laser power and welding speed affecting different formation of welds were experimentally acquired, which can provide references for laser welding and engineering application of NiTi alloy. The heat input has obvious effects on the ultimate tensile strength (UTS and shape memory behavior of the welded joints.

  7. Electro-thermomechanical properties of superelasticity in single crystals shape memory alloys

    Directory of Open Access Journals (Sweden)

    Cezar Henrique Gonzalez

    2010-06-01

    Full Text Available In this work, superelastic behavior of single crystals shape memory alloys has been investigated by the electric resistivity (ER measure technique coupled simultaneously during traction tests. Samples in austenitic phase were submitted to stress induced martensite (SIM under several conditions such as: different temperatures, different deformation rate, throughout successive martensitic transformations and different crystallographic orientation axes. ER vs. deformation curves presented a linear relation without hysteresis and independence on temperature. In the case on the increasing of deformation rate, these curves show a little hysteresis due to adiabatic transformations. For samples submitted to successive transformations, ER curves showed changes with induced martensite types. In samples of the same alloy with different crystallographic orientations was observed that single variant martensite nucleation presented distinct values, this characterizes martensite electric resistivity anisotropy.

  8. AlCu alloy films prepared by the thermal diffusion technique

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, A.I., E-mail: oliva@mda.cinvestav.mx [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Departamento de Fisica Aplicada, Km. 6 Antigua Carretera a Progreso, CP 97310, Merida Yucatan (Mexico); Corona, J.E.; Sosa, V. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Departamento de Fisica Aplicada, Km. 6 Antigua Carretera a Progreso, CP 97310, Merida Yucatan (Mexico)

    2010-07-15

    100-nm thick films of Al{sub 1-x}Cu{sub x} alloys were prepared on glass substrates by thermal diffusion technique. The Cu atomic concentration was varied from 10% to 90%. Alloys were prepared at different temperatures into a vacuum oven with Argon atmosphere. Two thermal processes were used: i) heating the film at 400 deg. C in a single step, and ii) heating the films in sequential steps at 100, 200, 300 and 400 deg. C. Morphology, electrical resistivity, and crystalline orientation of the alloys were studied. The electrical resistivity and surface roughness of the alloys were found to depend strongly on the atomic composition and the diffusion temperature. However, we did not find differences between samples prepared under the two thermal processes. Alloys prepared with x = 0.6 and x = 0.1-0.3 as Cu at concentration exhibited values on electrical resistivity and surface roughness lower than pure Al. Different phases of the Al{sub 1} {sub -} {sub x}Cu{sub x} films were observed as a function of Cu concentration showing a good agreement with the AlCu phase diagram.

  9. Preparation of PdCu Alloy Nanocatalysts for Nitrate Hydrogenation and Carbon Monoxide Oxidation

    Directory of Open Access Journals (Sweden)

    Fan Cai

    2016-06-01

    Full Text Available Alloying Pd with Cu is important for catalytic reactions such as denitrification reaction and CO oxidation reaction, but understanding of the catalyst preparation and its correlation with the catalyst’s activity and selectivity remains elusive. Herein, we report the results of investigations of the preparation of PdCu alloy nanocatalysts using different methods and the catalytic properties of the catalysts in catalytic denitrification reaction and CO oxidation reaction. PdCu alloy nanocatalysts were prepared by conventional dry impregnation method and ligand-capping based wet chemical synthesis method, and subsequent thermochemical activation as well. The alloying characteristics depend on the bimetallic composition. PdCu/Al2O3 with a Pd/Cu ratio of 50:50 was shown to exhibit an optimized hydrogenation activity for the catalytic denitrification reaction. The catalytic activity of the PdCu catalysts was shown to be highly dependent on the support, as evidenced by the observation of an enhanced catalytic activity for CO oxidation reaction using TiO2 and CeO2 supports with high oxygen storage capacity. Implications of the results to the refinement of the preparation of the alloy nanocatalysts are also discussed.

  10. Cytocompatibility evaluation of NiMnSn meta-magnetic shape memory alloys for biomedical applications.

    Science.gov (United States)

    Guiza-Arguello, Viviana R; Monroe, James A; Karaman, Ibrahim; Hahn, Mariah S

    2016-07-01

    Recently, magnetic shape memory alloys (MSMAs) have emerged as an interesting extension to conventional shape memory alloys (SMAs) due to their capacity to undergo reversible deformation in response to an externally applied magnetic field. Meta-magnetic SMAs (M-MSMAs) are a class of MSMAs that are able to transform magnetic energy to mechanical work by harnessing a magnetic-field induced phase transformation, and thus have the capacity to impose up to 10 times greater stress than conventional MSMAs. As such, M-MSMAs may hold substantial promise in biomedical applications requiring extracorporeal device activation. In the present study, the cytotoxicity and ion release from an Ni50 Mn36 Sn14 atomic percent composition M-MSMA were evaluated using NIH/3T3 fibroblasts. Initial studies showed that the viability of cells exposed to NiMnSn ion leachants was 60 to 67% of tissue culture polystyrene (TCP) controls over 10 to 14 days of culture. This represents a significant improvement in cytocompatibility relative to NiMnGa alloys, one of the most extensively studied MSMA systems, which have been reported to induce 80% cell death in only 48 h. Furthermore, NiMnSn M-MSMA associated cell viability was increased to 80% of TCP controls following layer-by-layer alloy coating with poly(allylamine hydrochloride)/poly(acrylic acid) [PAH/PAA]. Ion release measures revealed that the PAH/PAA coatings decreased total Sn and Mn ion release by 50% and 25%, respectively, and optical microscopy evaluation indicated that the coatings reduced NiMnSn surface oxidation. To our knowledge, this study presents the first cytotoxicity evaluation of NiMnSn M-MSMAs and lays the groundwork for their further biological evaluation. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 853-863, 2016.

  11. MICROSTRUCTURAL AND TEXTURE STUDY IN Fe43.5Mn34Al15Ni7.5 SHAPE MEMORY ALLOY

    Directory of Open Access Journals (Sweden)

    Juan M. Vallejos

    2016-03-01

    Full Text Available Fe alloy 43.5Mn34Al15Ni7.5 recently discovered, has pseudoplastic behavior in a wide temperature range. This characteristic is attractive for automobile, space, cryogenic and seismic applications. Currently there is no comprehensive analysis of the phases generated by heat treatments in the alloy and the influence of textures in shape memory properties. generated in the alloy with heat treatment and the influence of the textures on the properties of shape memory. The material studied was hot rolled at a temperature of 1000 ° C and then heat treated at different temperatures in order to analyse the phases present, microstructure and crystal orientations. The studies show that the martensitic phase (γ is achieved with quenching in water at temperatures over 1200ºC. Furthermore, heat treatments above 1000ºC generate grain sizes in α phase close to a millimeter. This grains growth would improve pseudoelastic properties of the alloy.

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

    DEFF Research Database (Denmark)

    Kappatos, Vasileios; Karagiannis, Dimitrios; Stamatelos, Dimtrios

    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...... a single-cycle/multi-cycle loading conditions of the SMA wires. The second actuating concept studies a novel rib configuration, which incorporates a compliant mechanism for enabling aerofoil's Leading Edge (LE) morphing. Different rib-compliant mechanism concepts are designed and analysed. The most...

  13. 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.

  14. QUANTITATIVE CHARACTERIZATION OF STRESS-STRAIN HYSTERESIS LOOPS OF Cu-Zn-Al SHAPE MEMORY ALLOY

    Institute of Scientific and Technical Information of China (English)

    Y.F. Guo; Y.Z. Huo; G.T. Zeng; X.T. Zu

    2001-01-01

    A six-parameter mathematical model was introduced to simulate the stress-strain hysteresis and the inner hysteresis of polycrystalline shape memory alloys (SMAs). By comparing with experiments of Cu-Zn-Al SMA, it was shown that the model could be used to calculate the stress-strain relations with rather good accuracy. Moreover,it was found that the six parameters introduced in this paper represented the characteristics of the stress-strain hysteresis of polycrystalline SMA and can be used to characterize the hysteresis quantitatively.

  15. R-phase transformation of aged Ti-Ni shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    GONG Chang-wei; WANG Yi-nong; YANG Da-zhi; LIU Xiao-peng

    2005-01-01

    Ti-50.6Ni(molar fraction, %) shape memory alloy solution treated at 850℃ for 1h followed by ageing treatment at 450℃ for 3h was studied with differential scanning calorimetry(DSC), X-ray diffractometry(XRD) and transmission electron microscopy(TEM). DSC measurement reveals two separate transformation peaks. XRD and TEM demonstrate that a three-stage transformation occurs. The Ti3Ni4 precipitates are coherent with the R-phase. The crystal structure of R-phase was analyzed by two diffraction patterns method. The diffraction patterns of R-phase were obtained in detail from the same region.

  16. Seismic Response Control of Offshore Platform Structures with Shape Memory Alloy Dampers

    Institute of Scientific and Technical Information of China (English)

    LI Hong-nan; HE Xiao-yu; HUO Lin-sheng

    2005-01-01

    In this study, the seismic response control of offshore platform structures with Shape Memory Alloy (SMA) dampers is investigated. A new SMA damper and its restoring force model are introduced for the calculation of seismic response reduction. Based on an actual platform structure and its mechanical model, the parameters which may affect the rate of shock absorption are analyzed, such as the number, position and characteristics of the SMA dampers andthe condition of the site where the platform is located. The results show that the SMA damper is an effective control device for offshore platforms and satisfactory control can be achieved by proper selection of the parameters.

  17. Annealing-induced evolution of transformation characteristics in TiNi shape memory alloys

    Science.gov (United States)

    Wang, Z. G.; Zu, X. T.; Feng, X. D.; Zhu, S.; Zhou, J. M.; Wang, L. M.

    2004-11-01

    The effect of annealing on transformation characteristics of TiNi shape memory alloys (SMAs) was investigated by differential scanning calorimetry (DSC) and the evolution of the microstructure was studied using positron annihilation technology (PAT) and transmission electron microscopy (TEM). The results showed that transformation characteristics depend on the annealing temperature. The R-phase transformation appeared at low annealing temperature. The R-phase disappeared and austensite transformed into martensite directly as the annealing temperature exceeded 550 °C. With increasing annealing temperature, the vacancy cluster and dislocation related positron lifetime decreased. Changes in transformation characteristics can be attributed to the evolution of the microstructrue of the TiNi specimen.

  18. MARTENSITE AND REVERSE TRANSFORMATION IN PRESTRAINED TiNi SHAPE MEMORY ALLOY THIN FILM

    Institute of Scientific and Technical Information of China (English)

    X.P. Liu; M.Z. Cao; R. Yang

    2003-01-01

    The effect of pre-strain on phase transformation of TiNi shape memory alloy film was studied by differential scanning calorimeter measurement (DSC). Compared with un deformed TiNi film, the reverse transformation of pre-strained specimens was elevated to a higher temperature on the first heating, but martensite and reverse transforma tion on subsequent thermal cycles occurred at a lower temperature. The evolution of transformation behavior in pre-strained TiNi film was related to the change of elastic strain energy, irreversible energy and internal stress field.

  19. Active Vibration Control of Elastic Beam by Means of Shape Memory Alloy Layers

    Science.gov (United States)

    Chen, Q.; Levy, C.

    1996-01-01

    The mathematical model of a flexible beam covered with shape memory alloy (SMA) layers is presented. The SMA layers are used as actuators, which are capable of changing their elastic modulus and recovery stress, thus changing the natural frequency of, and adjusting the excitation to, the vibrating beam. The frequency factor variation as a function of SMA Young's modulus, SMA layer thickness and beam thickness is discussed. Also control of the beam employing an optimal linear control law is evaluated. The control results indicate how the system reacts to various levels of excitation input through the non-homogeneous recovery shear term of the governing differential equation.

  20. Application of Laguerre based adaptive predictive control to Shape Memory Alloy (SMA) Actuator.

    Science.gov (United States)

    Kannan, S; Giraud-Audine, C; Patoor, E

    2013-07-01

    This paper discusses the use of an existing adaptive predictive controller to control some Shape Memory Alloy (SMA) linear actuators. The model consists in a truncated linear combination of Laguerre filters identified online. The controller stability is studied in details. It is proven that the tracking error is asymptotically stable under some conditions on the modelling error. Moreover, the tracking error converge toward zero for step references, even if the identified model is inaccurate. Experimental results obtained on two different kind of actuator validate the proposed control. They also show that it is robust with regard to input constraints.

  1. [Design of minimally invasive surgery wrist institution actuated by shape memory alloy].

    Science.gov (United States)

    Zhang, Zhenhua; Cao, Tong; Chen, Hua; Liu, Da; Shi, Zhenyun; Ma, Chen

    2013-06-01

    The rapid development of minimally invasive surgery technology requires higher flexibility of surgical treatment and small volume of medical instrument. This paper proposed a new type of minimally invasive surgery wrist institution actuated by TiNi shape memory alloy (SMA) wire. The wrist institution has some advantages such as compact structure, flexible function, light weight, big movement space, and high output position precision. The paper briefly introduces the properties of TiNi SMA and describes the configuration of wrist institution. We also carried out mechanism simulation analysis to the mechanics model and set up kinematics equations, and finally presented the workspace of the institution.

  2. Variable area nozzle for gas turbine engines driven by shape memory alloy actuators

    Science.gov (United States)

    Rey, Nancy M. (Inventor); Miller, Robin M. (Inventor); Tillman, Thomas G. (Inventor); Rukus, Robert M. (Inventor); Kettle, John L. (Inventor); Dunphy, James R. (Inventor); Chaudhry, Zaffir A. (Inventor); Pearson, David D. (Inventor); Dreitlein, Kenneth C. (Inventor); Loffredo, Constantino V. (Inventor)

    2001-01-01

    A gas turbine engine includes a variable area nozzle having a plurality of flaps. The flaps are actuated by a plurality of actuating mechanisms driven by shape memory alloy (SMA) actuators to vary fan exist nozzle area. The SMA actuator has a deformed shape in its martensitic state and a parent shape in its austenitic state. The SMA actuator is heated to transform from martensitic state to austenitic state generating a force output to actuate the flaps. The variable area nozzle also includes a plurality of return mechanisms deforming the SMA actuator when the SMA actuator is in its martensitic state.

  3. 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.

  4. The shape memory alloy actuator controlled by the Sun’s radiation

    Science.gov (United States)

    Riad, Amine; Alhamany, Abdelilah; Benzohra, Mouna

    2017-07-01

    Shape memory alloys (SMAs) have many thermo-mechanical characteristics which can return to their original value once exposed to a specific temperature. These materials are able to change their mechanical features such as shape, displacement or frequency in response to stress or heating; this may be useful for actuators in many fields such as aircraft, robotics and microsystems. In order to know the effect of the Sun’s radiation on SMAs we have conducted a numerical study that simulates a SMA actuator.

  5. Active Vibration Control of Elastic Beam by Means of Shape Memory Alloy Layers

    Science.gov (United States)

    Chen, Q.; Levy, C.

    1996-01-01

    The mathematical model of a flexible beam covered with shape memory alloy (SMA) layers is presented. The SMA layers are used as actuators, which are capable of changing their elastic modulus and recovery stress, thus changing the natural frequency of, and adjusting the excitation to, the vibrating beam. The frequency factor variation as a function of SMA Young's modulus, SMA layer thickness and beam thickness is discussed. Also control of the beam employing an optimal linear control law is evaluated. The control results indicate how the system reacts to various levels of excitation input through the non-homogeneous recovery shear term of the governing differential equation.

  6. Shape Memory Titanium Nickel Alloy Clip for Female Sterilization——Clinical and Experimental Study

    Institute of Scientific and Technical Information of China (English)

    薛培; 杨诞华

    1994-01-01

    From May 1982 to Dec 1987, a new shape memory titanium nickel alloy clips was employed for female sterilization by minilaparotomy in 1002 cases. This clip was noncorrasive and had high histocompatibility. The clip was designed to open in ice water at 4℃ and to close at 30℃ spontaneously,. It was placed vertically over the isthmus 3cm away from the uterine comus avoiding blood vessels in the mesosalpinx.Clip application was painless without complications. On follow-up, only 6.3% had

  7. 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.

  8. Magnetic domain evolution with applied field in a Ni-Mn-Ga magnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ge Yanling [Laboratory of Materials Science, Helsinki University of Technology, P.O. Box 6200, FI-02015 TKK (Finland)]. E-mail: Yanling.Ge@tkk.fi; Heczko, Oleg [Laboratory of Materials Science, Helsinki University of Technology, P.O. Box 6200, FI-02015 TKK (Finland); Soederberg, Outi [Laboratory of Materials Science, Helsinki University of Technology, P.O. Box 6200, FI-02015 TKK (Finland); Hannula, Simo-Pekka [Laboratory of Materials Science, Helsinki University of Technology, P.O. Box 6200, FI-02015 TKK (Finland)

    2006-06-15

    The evolution of a magnetic domain pattern with an applied field in two perpendicular directions was studied in a Ni-Mn-Ga magnetic shape memory alloy by means of optical and scanning electron microscopy (SEM). The optical contrast of magnetic domains arises from surface undulation. This surface relief is coherent at the (1 0 1) twin boundary. However, the surface relief causes the trace of the (0 1 1) twin boundary to follow a zigzag pattern. These optical observationre confirmed by SEM Type II magnetic contrast.

  9. 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.

  10. 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....... In the second, the unbalancedrotor runs at the first critical speed and two cases are considered: i) room temperature; ii) time-varying temperature.The results from these evaluations show that SMA can be an interesting alternative for vibration control in rotating machinery....

  11. Phase diagram kinetics for shape memory alloys: a robust finite element implementation

    Science.gov (United States)

    Gao, Xiujie; Qiao, Rui; Brinson, L. Catherine

    2007-12-01

    A physically based one-dimensional shape memory alloy (SMA) model is implemented into the finite element software ABAQUS via a user interface. Linearization of the SMA constitutive law together with complete transformation kinetics is performed and tabulated for implementation. Robust rules for transformation zones of the phase diagram are implemented and a new strategy for overlapping transformation zones is developed. The iteration algorithm, switching point updates and solution strategies are developed and are presented in detail. The code is validated via baseline simulations including the shape memory effect and pseudoelasticity and then further tested with complex loading paths. A hybrid composite with self-healing function is then simulated using the developed code. The example demonstrates the usefulness of the methods for the design and simulation of materials or structures actuated by SMA wires or ribbons.

  12. 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.

  13. 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).

  14. PtxGd alloy formation on Pt(111): Preparation and structural characterization

    Science.gov (United States)

    Ulrikkeholm, Elisabeth T.; Pedersen, Anders F.; Vej-Hansen, Ulrik G.; Escudero-Escribano, Maria; Stephens, Ifan E. L.; Friebel, Daniel; Mehta, Apurva; Schiøtz, Jakob; Feidenhansl', Robert K.; Nilsson, Anders; Chorkendorff, Ib

    2016-10-01

    PtxGd single crystals have been prepared in ultra high vacuum (UHV). This alloy shows promising catalytic properties for the oxygen reduction reaction. The samples were prepared by using vacuum deposition of a thick layer of Gd on a sputter cleaned Pt(111) single crystal, resulting in a ∼63 nm thick alloy layer. Subsequently the surfaces were characterized using X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED), ion scattering spectroscopy (ISS) and temperature programmed desorption (TPD) of CO. A Pt terminated alloy was observed upon annealing the sample to 600 ∘C. The LEED and synchrotron XRD experiments have shown that a slightly compressed (2 × 2) alloy appear. The alloy film followed the orientation of the Pt(111) substrate half the time, otherwise it was rotated by 30∘. The TPD spectra show a well-defined peak shifted down 200 ∘C in temperature. The crystal structure of the alloy was investigated using ex-situ X-ray diffraction experiments, which revealed an in-plane compression and a complicated stacking sequence. The crystallites in the crystal are very small, and a high degree of twinning by merohedry was observed.

  15. Electrolytic preparation of Al-Ca master alloy on liquid Al cathode

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    As a newly developing superplastic aluminum alloy, Al-Ca alloy has been widely used in industry, however thetechnology for preparing Al-Ca master alloy and its influencing factors need to be further studied. Therefore the Al-Camaster alloy was prepared by using liquid aluminum cathode and a mixture of 80%CaC12-18% KC1-2%CaF2 as the moltensalt electrolysis in a laboratory electrolyte cell; the effects of electrolysis temperature, cathodic current density and electrolytic duration on current efficiency and Ca content of Al-Ca alloy as well were studied. Through laboratory experiments, the parameters for smooth electrolytic reaction were proposed. The proper electrolysis technology is as follows:with the 80%CaCl2-18%KCl-2%CaF2 electrolyte, the electrolytic temperature is 973 K and the cathodic current densityis 0.8 A/cm2, the electrolysis can go on smoothly and a calcium content of 17.5%(mass fraction) can be obtained. Withthe increase of electrolysis duration, the calcium content in the alloy increasas whereas the current efficiency decreases

  16. Effect of Y addition on the martensitic transformation and shape memory effect of Ti-Ta high-temperature shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, X.H. [National Key Laboratory Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Sui, J.H., E-mail: suijiehe@hit.edu.cn [National Key Laboratory Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhang, X.; Tian, X.H.; Cai, W. [National Key Laboratory Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2012-10-25

    Highlights: Black-Right-Pointing-Pointer We added the rare earth element Y into Ti-Ta alloys for the first time. Black-Right-Pointing-Pointer The addition of Y results in a change in the microstructure. Black-Right-Pointing-Pointer The reverse martensitic transformation finish temperature is increased by addition of Y. Black-Right-Pointing-Pointer The addition of Y also enhances the shape memory effect of Ti-Ta alloys. - Abstract: The effect of Y addition on the microstructure, martensitic transformation and shape memory effect of Ti-30Ta alloy was investigated. The Y addition results in a change of the microstructure. The reverse martensitic transformation finish temperature (A{sub f}) increases 30 K with the 0.5 at.% Y addition. It is found that the shape memory effect with the maximum recovery strain of 4.32% is obtained in the (Ti-30Ta){sub 99.5}Y{sub 0.5} alloy, which is also higher than that of Ti-30Ta alloy.

  17. 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.)

  18. Characterization of Cu-Zn Alloy Nanocrystalline Powders Prepared by Wire Electrical Explosion

    Institute of Scientific and Technical Information of China (English)

    WANG Qun; YANG Hai-Bin; GUO Wei-Li; ZOU Guang-Tian

    2000-01-01

    Nanocrystalline powders of Cu-Zn alloy in size ranging from 10 to 140nm was prepared from α-Cu-Zn alloy wire containing 39.8at.% Zn by an electrical explosion method. The particles are identified from x-ray diffraction as a mixture of the α,β,γ, and ε phases of Cu-Zn alloy. Most of the particles are hexagonal in shape, with only a small part being spherical and cubic. The composition of Zn in the explosion products varied from 6.9 to 45.2 at.% in different particles as determined by energy dispersive x-ray spectrometer. A possible mechanism for the formation of the alloy nanocrystalline powders is proposed, in which a redistribution process occurred caused by strong collision and diffusion between the two kinds of atoms during the powder formation.

  19. Narrowing of hysteresis of cubic-tetragonal martensitic transformation by weak axial stressing of ferromagnetic shape memory alloy

    Science.gov (United States)

    Kosogor, Anna

    2016-06-01

    An influence of axial mechanical stress on the hysteresis of martensitic transformation and ordinary magnetostriction of ferromagnetic shape memory alloy has been described in the framework of a Landau-type theory of phase transitions. It has been shown that weak stress can noticeably reduce the hysteresis of martensitic transformation. Moreover, the anhysteretic deformation can be observed when the applied mechanical stress exceeds a critical stress value. The main theoretical results were compared with recent experimental data. It is argued that shape memory alloys with extremely low values of shear elastic modulus are the candidates for the experimental observation of large anhysteretic deformations.

  20. Microstructural Evolution and Functional Properties of Fe-Mn-Al-Ni Shape Memory Alloy Processed by Selective Laser Melting

    Science.gov (United States)

    Niendorf, Thomas; Brenne, Florian; Krooß, Philipp; Vollmer, Malte; Günther, Johannes; Schwarze, Dieter; Biermann, Horst

    2016-06-01

    In the current study, a Fe-Mn-Al-Ni shape memory alloy is processed by additive manufacturing for the first time. Microstructural evolution upon processing is strongly affected by thermal gradients and solidification velocity and, thus, by processing parameters and the actual specimen geometry. By single-step solutionizing heat treatment pronounced grain growth is initiated leading to microstructures showing good reversibility. The compressive stress-strain response revealed maximum reversible pseudo-elastic strain of about 7.5 pct. Critical steps toward further optimization of additively manufactured Fe-Mn-Al-Ni shape memory alloys are discussed.

  1. Transformation-induced plasticity in high-temperature shape memory alloys: a one-dimensional continuum model

    Science.gov (United States)

    Sakhaei, Amir Hosein; Lim, Kian-Meng

    2016-07-01

    A constitutive model based on isotropic plasticity consideration is presented in this work to model the thermo-mechanical behavior of high-temperature shape memory alloys. In high-temperature shape memory alloys (HTSMAs), both martensitic transformation and rate-dependent plasticity (creep) occur simultaneously at high temperatures. Furthermore, transformation-induced plasticity is another deformation mechanism during martensitic transformation. All these phenomena are considered as dissipative processes to model the mechanical behavior of HTSMAs in this study. The constitutive model was implemented for one-dimensional cases, and the results have been compared with experimental data from thermal cycling test for actuator applications.

  2. Microstructural Evolution of Semisolid 6063 Aluminum Alloy Prepared by Recrystallization and Partial Melting Process

    Science.gov (United States)

    Wang, Yongfei; Zhao, Shengdun; Zhang, Chenyang

    2017-08-01

    Radial forging (RF) was proposed as a novel deformation method to prepare semisolid 6063 aluminum alloy in the recrystallization and partial melting (RAP) process. The effects of area reduction rate, isothermal holding temperature and time on the microstructural evolution of RF-deformed 6063 aluminum alloy were investigated. Results showed that RF can be successfully introduced in RAP process to prepare large semisolid 6063 aluminum alloy bar. With the increase of the area reduction rate, the average grain size firstly decreased and then no significant change occurred. Meanwhile, the spheroidization degree of solid grains firstly increased rapidly, and then increased slowly. The effects of isothermal holding temperature and time are similar, with the increase of the isothermal holding temperature or time, the average grain size initially decreased but then increased; and the spheroidization degree of solid grains gradually increased. High-quality semisolid 6063 aluminum alloy can be prepared with 70% area reduction rate and subsequent semisolid isothermal treatment (SSIT) at 630 °C for 10 min. The coarsening rate constant was 5185.2 µm3/s at 630 °C. Additionally, a strong deformation texture was created in the RF-deformed alloy with 70% area reduction rate, which was transformed to a weakened texture following the SSIT process.

  3. Electro-thermomechanical characterization of Ti-Ni shape memory alloy thin wires

    Directory of Open Access Journals (Sweden)

    Nascimento Maria Marony Sousa Farias

    2006-01-01

    Full Text Available The use of shape memory alloys (SMA as smart structures and other modern applications require a previous evaluation of its performance under load as well as a training procedure. In general, these requirements lead to the design and assembly of a specific test bench. In this work, an experimental set-up was specially designed to perform the electro-thermomechanical characterization of SMA wires. This apparatus was used to determine the strain-temperature (epsilon - T and electrical resistance-temperature (R - T hysteretic characteristics curves of a Ti-Ni shape memory wire (90 mm in length and 150 µm in diameter under mechanical load. The SMA wire is loaded by means of constant weights and a controlled system for injection of electrical power allows performing the heating-cooling cycles. The obtained hysteretic epsilon - T and R - T characteristics curves for some levels of applied loads are used to determine important shape memory parameters, like martensitic transformation temperatures, temperature hysteresis, temperature slopes and shape memory effect under load. These parameters were in accord with the ones found in literature for the studied SMA wires.

  4. Perspectives on the exploitation of CuZnAl alloys, FeMnSi-based alloys and ZrO{sub 2}-containing shape-memory ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, T.Y. [Shanghai Jiao Tong Univ. (St. Helena). School of Materials Science and Engineering

    2002-07-01

    Cu-Zn-Al alloys possess advantages for exploitation such as low cost, easy fabrication and excellent shape memory effect (SME). The deficiencies of Cu-Zn-Al shape memory alloys, i.e. the appearance of the stabilization of martensite, degradation of SME in prolonged application and the rather low fatigue life, can be overcome by various processing such as immediate up-quenching, alloying addition for retarding the incubation of bainite formation and grain refinement. Fe-Mn-Si based alloys are one-way shape memory material with high strength, high action temperatures, good workability and low cost. Addition of nitrogen or rare earth (RE) elements can considerably strengthen the austenite and lower the Neel temperature in Fe-Mn-Si alloys. Partial replacement of Mn with Cr and addition of RE elements to Fe-Mn-Si may reduce its stacking fault energy. Nitrogen and RE elements also lower the M{sub s} temperature of Fe-Mn-Si and Fe-Mn-Si-Cr, stabilizing the austenite after shape recovery. The newly developed Fe-25Mn-6Si-5Cr-0.14N alloy possesses not only a complete shape memory recovery with a recoverable strain of 3% through only one cycle of training, but also the nice corrosion resistance in aqueous solution of NaOH and NaCl. The SME of Fe-Mn-Si-RE is superior to that of Fe-Mn-Si, e.g. its recoverable strain is about two-fold larger than that of Fe-Mn-Si when the pre-strain {epsilon}>3%. The exploitation of the Fe-Mn-Si-Cr-N and Fe-Mn-Si-RE alloys as coupling materials seems to be foresighted. Studies on (8{proportional_to}12)mol%CeO{sub 2}-(0.25{proportional_to}0.75)mol%Y{sub 2}O{sub 3}-ZrO{sub 2} with various grain size and density after different sintering processes show that 8mol%CeO{sub 2}-0.5mol%Y{sub 2}O{sub 3}-ZrO{sub 2} fabricated by sintering at 1773 K for 6 hours exhibits best SME, i.e. a complete shape memory recovery and a recoverable strain of 1.2% at high temperatures (above 773 K). The shape memory ceramics 8Ce-0.5Y-TZP is worthy to be developed. (orig.)

  5. Effect of Heat-Treatment on the Phases of Ni-Mn-Ga Magnetic Shape Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Huq, Ashfia [ORNL; Ari-Gur, Pnina [Western Michigan University; Kimmel, Giora [University of the Negev; Richardson, James W [Argonne National Laboratory (ANL); Sharma, Kapil [Indian Institute of Technology, Kanpur

    2009-01-01

    The Heusler alloys Ni50Mn25+xGa25-x display magnetic shape memory effect (MSM) with very fast and large reversible strain under magnetic fields. This large strain and the speed of reaction make MSM alloys attractive as smart materials. Our crystallographic investigation of these alloys, focused on non-stoichiometric composition with excess of manganese. Using neutron diffraction, we revealed the necessary processing parameters to achieve and preserve the homogeneous metastable one-phase martensitic structure that is needed for an MSM effect at room temperature.

  6. Phase Transformation Behaviors and Effects of Terbium in Polycrystalline Ni-Mn-Ga Magnetic Shape Memory Alloys

    Institute of Scientific and Technical Information of China (English)

    赵增祺; 熊玮; 吴双霞; 王新林

    2004-01-01

    The phase transformation behaviors of two kinds of magnetic shape memory alloys Ni50Mn25+xGa25-x and Ni50Mn29Ga21-xTbx were studied. When the composition of Ni in these alloys was constant, increasing Mn and reducing Ga contents make martensitic transformation temperatures rise obviously. Simultaneously, thermal hysteresis of phase transformation reduce but Curie temperature unalters. When terbium was added, phase transformation temperature went up further and Curie temperature kept constant. The alloys still show strong ferromagnetism and properties of thermoelastic martensite phase transformation.

  7. Structural Characterization of Cu- 13.58%Al- 3.94%Ni (wt. % shape memory alloy elaborated by fusion

    Directory of Open Access Journals (Sweden)

    Necib K.

    2010-06-01

    Full Text Available This work concerns the structural characterization of Cu -13.58% Al- 3.94% Ni (wt. % shape memory alloy elaborated by fusion using various techniques such as microscopy (OM and SEM, dilatometry and diffractometry (XRD. A particular attention is lent to the thermo elastic transformation may occur depending on the content of alloying and heat treatments' adopted. In this context, measurements of transformation temperatures were carried out. The microscopy is used for the characterization of alloy after different heat treatments adopted taking into account also the chemical composition. X-rays diffraction is used in order to access information on the different phases obtained and identify some types of martensite formed after quenching of alloy. The transformation temperatures are measured by the dilatometric analysis technique. This allows studying the structural evolution that occurs during heating and cooling of the alloy studied.

  8. 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.

  9. Studies on Preparation of Co-Bi Alloy Films by Electrodeposition From Nonaqueous Medium

    Institute of Scientific and Technical Information of China (English)

    LI Gao-ren; TONG Ye-xiang; LIU Guan-kun

    2003-01-01

    Cyclic voltammetry and potentiostatic electrolysis were used to investigate the preparation of Co-Bi alloy films in a LiClO4-DMSO system. The experimental results indicate that the Co-Bi alloy films containing 14.35%-29.77% Co can be prepared via potentionstatic electrolysis on Cu substrates, at deposition potential -1.10--1.65 V(vs. SCE) and by controlling the system composition and deposition condition. They are uniform gray films with a metallic luster and they are adhered firmly to the Cu substrate. The films were analyzed by EDS, SEM and XRD. After heat treatment of crystallization at 275 ℃ for 1 h, the alloy phase of Co-Bi can be confirmed via the XRD pattern.

  10. Preparation of Dy-Bi alloy films by electrodeposition in organic bath

    Institute of Scientific and Technical Information of China (English)

    LI Gaoren; TONG Yexiang; LIU Guankun

    2004-01-01

    The cyclic voltammetry and potentiostatic electrolysis were used to investigate the preparing of Dy-Bi alloy films in LiCl-DMSO (dimethylsulfoxide) system. The effects of several factors including the potential of deposition, concentrations of main salts, and the concentration ratio of DyCl3 to Bi(NO3)3 were studied. Dy-Bi alloy films containing 4.82%-80.62% (mass fraction) dysprosium were prepared in DyCl3-Bi(NO3)3-LiCl-DMSO system by controlling the system composition and deposition conditions. The films are gray, uniform, metallic luster and adhere firmly to the copper substrates analyzed by SEM (scanning electron microscope), EDS (X-ray energy dispersive analysis), and XRD (X-ray diffraction). After heat treatment at 718 K for l h, the alloy phase of Dy-Bi was found in XRD patterns.

  11. Role of Si in Improving the Shape Recovery of FeMnSiCrNi Shape Memory Alloys

    Science.gov (United States)

    Maji, Bikas C.; Krishnan, Madangopal; Gouthama; Ray, R. K.

    2011-08-01

    The effect of Si addition on the microstructure and shape recovery of FeMnSiCrNi shape memory alloys has been studied. The microstructural observations revealed that in these alloys the microstructure remains single-phase austenite ( γ) up to 6 pct Si and, beyond that, becomes two-phase γ + δ ferrite. The Fe5Ni3Si2 type intermetallic phase starts appearing in the microstructure after 7 pct Si and makes these alloys brittle. Silicon addition does not affect the transformation temperature and mechanical properties of the γ phase until 6 pct, though the amount of shape recovery is observed to increase monotonically. Alloys having more than 6 pct Si show poor recovery due to the formation of δ-ferrite. The shape memory effect (SME) in these alloys is essentially due to the γ to stress-induced ɛ martensite transformation, and the extent of recovery is proportional to the amount of stress-induced ɛ martensite. Alloys containing less than 4 pct and more than 6 pct Si exhibit poor recovery due to the formation of stress-induced α' martensite through γ- ɛ- α' transformation and the large volume fraction of δ-ferrite, respectively. Silicon addition decreases the stacking fault energy (SFE) and the shear modulus of these alloys and results in easy nucleation of stress-induced ɛ martensite; consequently, the amount of shape recovery is enhanced. The amount of athermal ɛ martensite formed during cooling is also observed to decrease with the increase in Si.

  12. Grain-size effect in micromechanical modelling of hysteresis in shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Stupkiewicz, Stanislaw; Petryk, Henryk [Institute of Fundamental Technological Research (IPPT), Warsaw (Poland)

    2010-10-15

    Size effects in pseudoelastic polycrystalline shape memory alloys are studied by considering a representative spherical laminated domain (subgrain) and its interfacial energy at three scales: at the subgrain boundaries, at the austenite-martensite interfaces, and at the twin boundaries. Two sources of interfacial energy are accounted for, namely the atomic-scale energy of twin and phase boundaries and the elastic strain energy at microstructured interfaces, the latter being predicted theoretically. The evolution of microstructure of the representative domain is determined using the incremental energy minimization rule applied to the sum of the increments in the Helmholtz free energy and rate-independent dissipation. The size-dependent part of dissipation is estimated by assuming that negative increments in interfacial energy, associated with annihilation of interfaces, cannot be reverted back into the bulk free energy and are thus dissipated. Simple analytic formula for the interfacial energy dissipated in a complete forward-reverse transformation cycle is derived and combined with a micromechanical model of a polycrystalline NiTi shape memory alloy. A numerical example illustrating size-dependent hysteresis in the stress-induced martensitic transformation is presented. (orig.)

  13. Force-displacement characteristics of simply supported beam laminated with shape memory alloys

    Institute of Scientific and Technical Information of China (English)

    Zhi-Qiang Wu; Zhen-Hua Zhang

    2011-01-01

    As a preliminary step in the nonlinear design of shape memory alloy (SMA) composite structures,the forcedisplacement characteristics of the SMA layer are studied.The bilinear hysteretic model is adopted to describe the constitutive relationship of SMA material.Under the assumption that there is no point of SMA layer finishing martensitic phase transformation during the loading and unloading process,the generalized restoring force generated by SMA layer is deduced for the case that the simply supported beam vibrates in its first mode.The generalized force is expressed as piecewise-nonlinear hysteretic function of the beam transverse displacement.Furthermore the energy dissipated by SMA layer during one period is obtained by integration,then its dependencies are discussed on the vibration amplitude and the SMA's strain (Ms-Strain) value at the beginning of martensitic phase transformation.It is shown that SMA's energy dissipating capacity is proportional to the stiffness difference of bilinear model and nonlinearly dependent on Ms-Strain.The increasing rate of the dissipating capacity gradually reduces with the amplitude increasing.The condition corresponding to the maximum dissipating capacity is deduced for given value of the vibration amplitude.The obtained results are helpful for designing beams laminated with shape memory alloys.

  14. Micromechanics of composites with shape memory alloy fibers in uniform thermal fields

    Science.gov (United States)

    Birman, Victor; Saravanos, Dimitris A.; Hopkins, Dale A.

    1995-01-01

    Analytical procedures are developed for a composite system consisting of shape memory alloy fibers within an elastic matrix subject to uniform temperature fluctuations. Micromechanics for the calculation of the equivalent properties of the composite are presented by extending the multi-cell model to incorporate shape memory alloy fibers. A three phase concentric cylinder model is developed for the analysis of local stresses which includes the fiber, the matrix, and the surrounding homogenized composite. The solution addresses the complexities induced by the nonlinear dependence of the in-situ martensite fraction of the fibers to the local stresses and temperature, and the local stresses developed from interactions between the fibers and matrix during the martensitic and reverse phase transformations. Results are presented for a nitinol/epoxy composite. The applications illustrate the response of the composite in isothermal longitudinal loading and unloading, and in temperature induced actuation. The local stresses developed in the composite under various stages of the martensitic and reverse phase transformation are also shown.

  15. Differences of transformation behavior between Ni-rich TiNi shape memory films and alloys

    Institute of Scientific and Technical Information of China (English)

    贺志荣; 周敬恩

    2002-01-01

    The differences of transformation behavior between Ni-rich TiNi shape memory film (SMF) and shape memory alloy (SMA) age-treated at 773K after solution-treatment at 973K have been investigated, using Ti-51.5Ni thin film and Ti-51.5Ni bulk alloy as examples, by differential scanning calorimetry (DSC), SEM and EDX. It is found that the age-treated Ni-rich TiNi SMF and SMA are of the same types of transformation, i.e., A→R→M (during cooling), and M→A (during heating) (A: parent phase; R: R-phase; M: martensite); the transformation temperature of the TiNi SMF is lower than that of the SMA, but the SMFs hysteresis is larger. The transformation heat of the TiNi SMF and SMA is nearly the same. The reason that TiNi SMFs strain is sensitive to temperature is not hysteresis, but its thickness is thinner, and the temperature is easy to distribute homogeneously.

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

    Directory of Open Access Journals (Sweden)

    Luis Alberto López Pavón

    2012-06-01

    Full Text Available 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 °C and target B: 76.18Cu-15.84Zn-7.98Al with an Ms of 20 °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.

  17. An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.

    Science.gov (United States)

    Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

    2013-01-30

    The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

  18. Microstructure and transformation behavior of Ni50Ti45Ta5 shape memory alloy

    Institute of Scientific and Technical Information of China (English)

    宫长伟; 王轶农; 杨大智

    2004-01-01

    The microstructure and transformation behavior of Ni50 Ti45 Ta5 shape memory alloy were investigated using optical microscope, EPMA, X-ray diffraction and DSC methods. The microstructures are primary NiTi dendrite and net-like eutectic. The room temperature phases of this alloy are B2 austenite with lattice parameter a=0. 302 5nm, B19' martensite with lattice parameters a=0. 290 nm, b=0. 412 nm and c=0. 473 nm, β= 98.2° and a body center cubic β-Ta with lattice parameter a' =0. 330 4 nm. A maximal shape memory recovery strain of 5.6% is obtained after deformation to 6.4%. The reverse transformation temperatures increase and the forward transformation temperatures decrease in the first heating/cooling cycle after deformation. The reverse transformation heat also increases with increasing deformation. The phenomenon disappears in the second heating/cooling cycle. It is closely related to the variation of elastic energy and irreversible energies during deformation.

  19. Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

    Science.gov (United States)

    Davis, Brian; Turner, Travis L.; Seelecke, Stefan

    2005-01-01

    Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons within the beam structures. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical analysis/design tool. The experimental investigation is refined by a more thorough test procedure and incorporation of higher fidelity measurements such as infrared thermography and projection moire interferometry. The numerical results are produced by a recently commercialized version of the constitutive model as implemented in ABAQUS and are refined by incorporation of additional measured parameters such as geometric imperfection. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. The results demonstrate the effectiveness of SMAHC structures in controlling static and dynamic responses by adaptive stiffening. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

  20. Effects of grain size on the martensitic phase transformation of nanocrystalline Ni/Al shape memory alloys

    OpenAIRE

    Morrison, Keith; Cherukara, Mathew; Kim, Hojin; Strachan, Alejandro

    2014-01-01

    Shape memory alloys (SMAs) owe their distinct properties to a diffusion less martensitic phase transformation from a high temperature, high symmetry phase (austenite) to a low temperature (martensite) phase upon cooling or strain. Their shape memory and pseudoelastic properties make SMAs useful as active components in microdevices, medical implants and for vibrational damping. Despite their widespread application, the miniaturization limit of SMAs is not known. In this study, we use large-sca...

  1. 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.

  2. Indentation response of a NiTi shape memory alloy: modeling and experiments

    Directory of Open Access Journals (Sweden)

    C. Maletta

    2012-07-01

    Full Text Available The indentation response of a pseudoelastic nickel-titanium based shape memory alloy (SMA has been analyzed. Indentation tests have been carried out at room temperature using a spherical diamond tip and indentation loads in the range 50-500 mN in order to promote a large stress-induced transformation zone in the indentation region and, consequently, to avoid local effects due to microstructural variations. The measured load-displacement data have been analyzed to obtain information on the pseudoelastic response of the alloy. To aid this analysis numerical simulations were performed, by using a commercial finite element (FE software code and a special constitutive model for SMAs, so as to understand better the microstructural evolution occurring during the indentation process. Finally, the FE model has been used to analyze the effects of temperature on the indentation response of the alloy. This analysis revealed a marked variation of both the maximum and residual penetration depths with increasing test temperature.

  3. Phase transformation kinetics and microstructure of NiTi shape memory alloy: effect of hydrostatic pressure

    Indian Academy of Sciences (India)

    CENGIZ TATAR; ZÜLKÜF YILDIRIM

    2017-08-01

    The effect of hydrostatic pressure on the behaviour of reverse and forward transformation temperatures andphysical properties of NiTi shape memory alloy has been investigated. The transformation temperatures and physical properties of the alloy change with applied pressure. It has been clearly seen from differential scanning calorimetry that with theincrease of applied pressure, while $A_{\\rm s}$, $A_{\\rm f}$ and $M_{\\rm f}$ transformation temperatures decrease, Ms value increases. Moreover, it is obvious that with the increase of applied pressure, Gibbs free energy increases by 5.2883 J, while elastic energy increases by 1.4687 J. In addition, entropy of the alloys decreases by 0.2335 J (g $^{\\circ}$C)$^{−1}$ with applied pressure. Additionally, it is evident from the scanning electron microscopy images of the samples that there is an obvious difference in the grain sizes of the unpressured sample and the samples on which pressure is applied, the sizes being 10–100 and 30–150 $\\mu$m, respectively.

  4. Fabrication of NiTi shape memory alloy by Micro-FAST

    Directory of Open Access Journals (Sweden)

    Huang Kunlan

    2015-01-01

    Full Text Available A NiTi shape memory alloy, known as nitinol, has been intensively studied for last five decades. The NiTi alloy with large size is commonly produced by vacuum sintering, thermal explosion mode of self-propagating high-temperature synthesis (TE-SHS and spark plasma sintering (SPS. These methods are, however, rarely utilized for the forming of miniature and micro-sized components and have their own limits and disadvantages, such as long process chains and low efficiency with the processes. In the study reported in this paper, an innovation in rapid powder consolidation technology, called Micro-FAST (combining micro-forming and electric-current activated sintering techniques (FAST is introduced for the forming of micro-components in which the loose powders are loaded directly into the die, followed by electric-sintering. In the study, Φ4.0 mm × 4.0 mm miniature cylinders were formed with pre-alloyed NiTi powders. Sintered sample with relative density of 98.65% has been fabricated at a sintering temperature of 1150 °C in a relatively short cycle time (119.5 s. Based on the results of SEM and XRD, it was found that the densified samples with Ni3Ti, NiTi and NiTi2 phases were produced.

  5. Mathematical Modeling and Control of Nonlinear Oscillators with Shape Memory Alloys

    Science.gov (United States)

    Bendame, Mohamed

    Shape memory alloys (SMAs) belong to an interesting type of materials that have attracted the attention of scientists and engineers over the last few decades. They have some interesting properties that made them the subject of extensive research to find the best ways to utilize them in different engineering, biomedical, and scientific applications. In this thesis, we develop a mathematical model and analyze the behavior of SMAs by considering a one degree of freedom nonlinear oscillator consisting of a mass connected to a fixed frame through a viscous damping and a shape memory alloy device. Due to the nonlinear and dissipative nature of shape memory alloys, optimal control and Lyapunov stability theories are used to design a controller to stabilize the response of the one degree of freedom nonlinear oscillator. Since SMAs exist in two phases, martensite and austenite, and their phase transformations are dependent on stress and temperature, this work is presented in two parts. The first part deals with the nonlinear oscillator system in its two separate phases by considering a temperature where the SMA exists in only one of the phases. A model for each phase is developed based on Landau-Ginzburg-Devonshire theory that defines the free energy in a polynomial form enabling us to describe the SMAs shape memory effect and pseudoelasticity. However, due to the phenomenon of hysteresis in SMAs, the response of the nonlinear oscillator with a SMA element, in either phase, is chaotic and unstable. In order to stabilize the chaotic behavior, an optimal linear quadratic regulator controller is designed around a stable equilibrium for the martensitic and the austenitic phases. The closed-loop response for each phase is then simulated and computational results are presented. The second part of the thesis deals with the entire system in its dynamics by combining the two phases and taking into account the effect of temperature on the response of the system. Governing equations

  6. Design and modeling of a novel fibrous shape memory alloy (SMA) actuator

    Science.gov (United States)

    Shahinpoor, Mohsen; Wang, Guoping

    1994-05-01

    Presented is a novel design of a composite linear actuator utilizing a parallel array of contractile shape-memory alloy (SMA) wires. The fiber bundle of SMA wires is either circumscribed inside a helical compression spring with flat heads or are in parallel with a number of helical compression springs, end-capped by two parallel circular plates with embedded electrodes to which the ends of the SMA wires are secured. Thus, the wires can be electrically heated and subsequently contracted to compress the helical compression spring. Upon cooling the SMA wires expand and allow the helical compression spring to tightly stretch them to their initial length. Design details are first fully described. Steps involved in the fabrication of a number of these composite SMA actuators are then elaborated on. A number of interesting heat transfer phenomena are observed. In essence the dynamic behavior of the actuator depends on the interaction between the current supplied to the wires and the rate of heat transfer from the wires due to convection and radiation. A design model is finally presented for the dynamic response of contractile fiber bundles embedded in or around elastic springs that are either linear helical compression springs, hyperelastic springs such as rubberlike materials, or nonlinear springs such as air. The fiber bundle is assumed to consist of a parallel array of contractile fibers made from contractile shape-memory alloy (SMA) wires. The proposed model considers the temperature- induced contraction of the fibers due to resistive heating of the shape-memory wires. Results of both dynamic computer simulation and dynamics of a prototype model built in our laboratory indicate a fairly good comparison.

  7. Control of equiaxed grains in a complicated Cu-Ni based alloy prepared by centrifugal casting

    Directory of Open Access Journals (Sweden)

    Luo Zongqiang

    2011-02-01

    Full Text Available A complicated Cu-Ni based alloy was developed to fabricate wear-resisting bush for high temperature application. The concern focuses on the control of equiaxed grains in the developed alloy ingot prepared by centrifugal casting. The results show that the equiaxed grains are determined by the pouring temperature of the melt, the cooling rate and the rotation speed of the mold. With the decrease in pouring temperature, the fraction of the equiaxed grains in the transverse section of the ingot increases and the average length of columnar grain decreases. When the pouring temperature is confined below 1,250℃, complete equiaxed grains can be obtained. Based on the optimal centrifugal casting processing, the tensile strength of the developed alloy ingot with complete equiaxed grains reaches to 810 MPa and 435 MPa at room temperature and 500℃, respectively, which is 14% and 110% higher than that of common commercial QAl10-4-4 alloy. The wear rate of the developed alloy is 7.0 × 10-8 and 3.8 × 10-7 mm3•N-1•mm-1 at room temperature and 500℃, respectively, which is 5 times and 39 times lower than that of QAl10-4-4 alloy.

  8. The New Heat Treatment Technology of A356 Aluminium Alloy Prepared by Ptc

    Science.gov (United States)

    Zhang, Lianyong; Jiang, Yanhua; Ma, Zhuang; Wang, Wenkui

    Phase Transition Cooling (PTC), using the absorbed latent heat during the melting of phase transition cooling medium to cool and solidify alloys in the process of casting, is a new casting technology. Specimens of A356 casting aluminum alloy were prepared by this method in the paper. The new heat treatment process (cast and then aging directly without solid solution) of A356 alloy was performed. For comparison, the conventional T6 heat treatment (solution and then aging treatment) was performed too. The mechanical properties of A356 alloy with different heat treatments were measured by tensile strength testing methods and microstructures of the alloy with different heat treatment process were investigated by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-rays diffraction (XRD) and transmission electron microscopy (TEM) too. The results show that ultimate tensile strength (UTS) of A356 alloy with the new heat treatment process is much higher than that with conventional heat treatment while the elongations with the two heat treatment processes are very close. This is due to the grain refinement obtained after PTC processing.

  9. 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.

  10. Magnetoresistance in ferromagnetic shape memory alloy NiMnFeGa

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Z.H.; Ma, X.Q. [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China); Zhu, Z.Y.; Luo, H.Z.; Liu, G.D.; Chen, J.L. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Wu, G.H., E-mail: ghwu@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Zhang Xiaokai; Xiao, John Q. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2011-08-15

    The magnetoresistance (MR){l_brace}=[R(H)-R(0)]/R(0){r_brace} properties in ferromagnetic shape memory alloy of NiMnFeGa ribbons and single crystals, and NiFeGa ribbons have been investigated. It is found that the NiMnFeGa melt-spun ribbon exhibited GMR effect, arising from the spin-dependent scattering from magnetic inhomogeneities consisting of antiferromagnetically coupled Mn atoms in B2 structure. In the absence of these magnetic inhomogeneities, Heusler alloys seem to show a common linear MR behavior at around 0.8T{sub C}, regardless of sample structures. This may be explained by the s-d model. At low temperatures, conventional AMR behaviors due to the spin-orbital coupling are observed. This is most likely due to the diminished MR from s-d model because of much less spin fluctuation, and is not associated with martensite phase. MR anomaly at intermediate field ({rho}{sub perpendicular} >{rho}{sub ||}) is also observed in single crystal samples, which may be related to unique features of Heusler alloys. - Highlights: > NiMnFeGa melt-spun ribbon exhibited GMR effect with a large negative MR up to -13%. > GMR behavior is arising from the spin-dependent scattering from magnetic inhomogeneities. > In the absence of these magnetic inhomogeneities, Heusler alloys seem to show a common linear MR behavior at around 0.8T{sub C}. > Conventional AMR behaviors due to the spin-orbital coupling are observed in NiMnFeGa single crystal and Ni{sub 2}FeGa ribbon samples at low temperatures.

  11. Microstructure of cryogenically treated martensitic shape memory nickel-titanium alloy

    Directory of Open Access Journals (Sweden)

    Thilla Sekar Vinothkumar

    2015-01-01

    Full Text Available Context: Recent introduction of shape memory (SM nickel-titanium (NiTi alloy into endodontics is a major breakthrough. Although the flexibility of these instruments was enhanced, fracture of rotary endodontic instruments during instrumentation is an important challenge for the operator. Implementation of supplementary manufacturing methods that would improve the fatigue life of the instrument is desirable. Aim: The purpose of this study was to investigate the role of dry cryogenic treatment (CT conditions on the microstructure of martensitic SM NiTi alloy. Materials and Methods: Experiments were conducted on Ni-51 wt% Ti-49 wt% SM alloy. Five cylindrical specimens and five sheet specimens were subjected to different CT conditions: Deep CT (DCT 24 group: −185°C; 24 h, DCT 6 group: −185°C; 6 h, shallow CT (SCT 24 group: −80°C, 24 h, SCT 6 group: −80°C, 6 h and control group. Microstructure of surface was observed on cylindrical specimens with an optical microscope and scanning electron microscope at different magnifications. Subsurface structure was analyzed on sheet specimens using X-ray diffraction (XRD. Results: Microstructures of all SM NiTi specimens had equiaxed grains (approximately 25 μm with well-defined boundaries and precipitates. XRD patterns of cryogenically treated specimens revealed accentuation of austenite and martensite peaks. The volume of martensite and its crystallite size was relatively more in DCT 24 specimen. Conclusions: DCT with 24 h soaking period increases the martensite content of the SM NiTi alloy without altering the grain size.

  12. Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aluminum-silicon-titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite-alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al-Si-Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al-Si-Ti master alloys.

  13. Improvement in the Mechanical Properties of High Temperature Shape Memory Alloy (Ti50Ni25Pd25) by Copper Addition

    National Research Council Canada - National Science Library

    Rehman, Saif ur; Khan, Mushtaq; Khan, A. Nusair; Jaffery, Syed Husain Imran; Ali, Liaqat; Mubashar, Aamir

    2015-01-01

      High temperature shape memory alloys Ti50Ni25Pd25 and Ti50Ni20Pd25Cu5 were developed, characterized, and tensile tested in both martensite ( [subscript]Mf[/subscript] - 50°C) and austenite ( [subscript]Af[/subscript] + 50°C) phases...

  14. 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

  15. Modeling of Stress Development During Thermal Damage Healing in Fiber-reinforced Composite Materials Containing Embedded Shape Memory Alloy Wires

    NARCIS (Netherlands)

    Bor, T.C.; Warnet, L.; Akkerman, R.; Boer, de A.

    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 co

  16. 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.

  17. The Effects of Different Electrode Types for Obtaining Surface Machining Shape on Shape Memory Alloy Using Electrochemical Machining

    Science.gov (United States)

    Choi, S. G.; Kim, S. H.; Choi, W. K.; Moon, G. C.; Lee, E. S.

    2017-06-01

    Shape memory alloy (SMA) is important material used for the medicine and aerospace industry due to its characteristics called the shape memory effect, which involves the recovery of deformed alloy to its original state through the application of temperature or stress. Consumers in modern society demand stability in parts. Electrochemical machining is one of the methods for obtained these stabilities in parts requirements. These parts of shape memory alloy require fine patterns in some applications. In order to machine a fine pattern, the electrochemical machining method is suitable. For precision electrochemical machining using different shape electrodes, the current density should be controlled precisely. And electrode shape is required for precise electrochemical machining. It is possible to obtain precise square holes on the SMA if the insulation layer controlled the unnecessary current between electrode and workpiece. If it is adjusting the unnecessary current to obtain the desired shape, it will be a great contribution to the medical industry and the aerospace industry. It is possible to process a desired shape to the shape memory alloy by micro controlling the unnecessary current. In case of the square electrode without insulation layer, it derives inexact square holes due to the unnecessary current. The results using the insulated electrode in only side show precise square holes. The removal rate improved in case of insulated electrode than others because insulation layer concentrate the applied current to the machining zone.

  18. Confined martensitic phase transformation kinetics and lattice dynamics in Ni–Co–Fe–Ga shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cong, Daoyong; Rule, Kirrily Clair; Li, Wen-Hsien; Lee, Chi-Hung; Zhang, Qinghua; Wang, Haoliang; Hao, Yulin; Wang, Yandong; Huang, E-Wen (UST - China); (NCU-Taiwan); (Beijing Inst. Tech.); (Chinese Aca. Sci.); (ANSTO); (NCTU)

    2016-09-02

    Here we describe insights into the phase transformation kinetics and lattice dynamics associated with the newly discovered confined martensitic transformation, which are of great significance to the in-depth understanding of the phase transformation behavior responsible for the rich new physical phenomena in shape memory alloys and could shed light on the design of novel multifunctional properties through tuning the confined martensitic transformation.

  19. Development of a Nano-Satellite Micro-Coupling Mechanism with Characterization of a Shape Memory Alloy Interference Joint

    Science.gov (United States)

    2010-12-01

    3 Endothermic for martensite to austenite transformation. Exothermic for austenite to martensite transformation. 4 Note that the...original work by definition . Unique contributions to the related art of coupling devices and shape memory alloys are as follows: 1) A zero impact

  20. The behavior of concrete cylinders confined by shape memory alloy wires

    Science.gov (United States)

    Choi, Eunsoo; Nam, Tae-hyun; Cho, Sung-Chul; Chung, Young-Soo; Park, Taehyo

    2008-12-01

    The purpose of this study was to propose a new method to confine concrete cylinders or reinforced concrete columns using martensitic or austenitic shape memory alloy (SMA) wires. The prestrained martensitic SMA wire was wrapped around a concrete cylinder then heated by a heating jacket. In the process, the confining stress around the cylinder was developed in the SMA wire due to the shape memory effect, which can increase the strength and ductility of the cylinder under axial compressive load. For austenitic shape memory wires, the wires were prestrained as they were wrapped around the concrete cylinders on which post-tensioning stress was generated. In this study, martensitic and austenitic SMA wires of 1.0 mm in diameter were used for the confinement. Recovery tests were conducted on the martensitic wire to assess the recovery stress. Also, a superelastic behavior test was performed for the austenitic wire. The confinement by martensitic SMA wires increased the strength slightly and greatly increased the ductility compared to the strength and ductility of plain concrete cylinders. The austenitic SMA wires showed a similar effect on concrete cylinders to that of the martensitic wires. This study showed the potential of the SMA wire jacketing method to retrofit reinforced concrete columns and protect them from seismic risks.